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Columns & Departments<br />
COLUMNS<br />
4 Front Page<br />
Don Nelson,<br />
Publisher<br />
The buzz surrounding MEMS.<br />
12 Micromachining<br />
Alan Richter,<br />
Senior Edi<strong>to</strong>r<br />
Strategies for effectively boring<br />
microholes.<br />
15 L<strong>as</strong>er Points<br />
Ronald D. Schaeffer,<br />
Pho<strong>to</strong>Machining Inc.<br />
Fac<strong>to</strong>rs <strong>to</strong> weigh before<br />
purch<strong>as</strong>ing a l<strong>as</strong>er.<br />
17 Down Sizing<br />
Dennis Spaeth,<br />
Electronic Media Edi<strong>to</strong>r<br />
Microturbine research<br />
recharged.<br />
19 Me<strong>as</strong>urement Matters<br />
Susan Woods,<br />
Contributing Edi<strong>to</strong>r<br />
Gaging surface roughness<br />
with scanning white light<br />
interferometry.<br />
22 About Tooling<br />
Hugh McAllister,<br />
Chardon Tool<br />
Conventional machines can<br />
run single-crystal-diamond<br />
<strong>to</strong>ols.<br />
52 L<strong>as</strong>t Word<br />
Phillip M. Leopold,<br />
Medical Murray Inc.<br />
Thoughts from a medical<br />
manufacturing pioneer.<br />
DEPARTMENTS<br />
6 Tech News<br />
48 Products/Services<br />
50 Research Roundup<br />
51 Advertisers Index<br />
On <strong>MICROmanufacturing</strong>.com<br />
From μTube:<br />
5-axis micromilling<br />
Microlution’s new 5100-S 5-axis CNC micromilling machine is a<br />
vertical bridge-style machining center with a trunnion-style confi<br />
guration. Visit our Web site for a video over<strong>view</strong> of the machine.<br />
Grinding machine<br />
Highlights of Rollomatic USA’s new GrindSmart Nano6, designed<br />
<strong>to</strong> manufacture cutting <strong>to</strong>ols with diameters from 0.01mm <strong>to</strong><br />
2.0mm.<br />
Robot router<br />
A video from Micromagic Systems, a U.K. animatronics and robotics<br />
company, shows a hexapod CNC router that could potentially<br />
put a whole new face on micromachining.<br />
3-D microfabrication<br />
Researchers at the École Polytechnique de Montréal, Canada,<br />
have developed a 3-D microfabrication technique that uses ultraviolet<br />
light <strong>to</strong> cure a liquid polymer material <strong>as</strong> it is dispensed.<br />
6<br />
17<br />
12<br />
micromanufacturing.com | 1
Features<br />
36<br />
WINTER 2009 • Volume 2 • Issue 4 2 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
COVER STORY:<br />
25 New Directions<br />
William Leven<strong>to</strong>n<br />
New design strategies facilitate<br />
MEMS production.<br />
30 Taking Form<br />
Lowell Thom<strong>as</strong> and<br />
Luke Volpe,<br />
Dynamics Research Corp.,<br />
Metrigraphics Div.<br />
Electroforming use grows <strong>as</strong><br />
complex electronic devices<br />
shrink.<br />
36 Clean Machining<br />
Joel C<strong>as</strong>sola<br />
Clean rooms being used more<br />
for micromachining.<br />
40 Good Vibration<br />
(Control)<br />
Bill Kennedy,<br />
Contributing Edi<strong>to</strong>r<br />
Countering vibration in small<br />
and large machine <strong>to</strong>ols for<br />
micromachining.<br />
30<br />
40<br />
ON THE COVER<br />
Microvision Inc.’s MEMS scanning<br />
mirror is used in the<br />
company’s new hand-held l<strong>as</strong>er<br />
bar-code scanner. Additional<br />
information can be found at<br />
www.microvisin.com.<br />
Cover design: Tom Wright.<br />
www.micromanufacturing.com<br />
Main Offi ce<br />
40 Skokie Blvd.<br />
Ste. 450<br />
Northbrook, IL 60062<br />
(847) 714-0048<br />
micromanufacturing@jwr.com<br />
Staff<br />
Publisher<br />
Don Nelson<br />
(847) 714-0173<br />
dnelson@jwr.com<br />
Edi<strong>to</strong>rial Direc<strong>to</strong>r<br />
Alan Rooks<br />
(847) 714-0174<br />
arooks@jwr.com<br />
Senior Edi<strong>to</strong>rs<br />
Alan Richter Daniel McCann<br />
(847) 714-0175 (847) 714-0177<br />
alanr@jwr.com dmccann@jwr.com<br />
Electronic Media Edi<strong>to</strong>r<br />
Dennis Spaeth<br />
(847) 714-0176<br />
dspaeth@jwr.com<br />
Contributing Edi<strong>to</strong>rs<br />
Bill Kennedy<br />
(724) 537-6182<br />
billk@jwr.com<br />
Ad Production Manager<br />
Julie Distenfi eld<br />
(847) 714-0179<br />
julied@jwr.com<br />
Art Direc<strong>to</strong>r<br />
Gina Moore<br />
(847) 714-0178<br />
ginam@jwr.com<br />
Administrative Assistant<br />
Pat Jones<br />
patj@jwr.com<br />
Circulation<br />
Synergy Direct Inc.<br />
(866) 207-1448<br />
andrea@sdicirc.com<br />
Advertising Sales<br />
Scott Beller (E<strong>as</strong>t)<br />
(847) 714-0183<br />
scottb@jwr.com<br />
Bob West (South, West)<br />
(770) 730-9763<br />
microm_bobwest@msn.com<br />
Jody Nelson (Midwest, Int’l)<br />
(847) 714-0170<br />
jodyn@jwr.com<br />
®<br />
Susan Woods<br />
susanw@jwr.com
IMTS.com
FRONTpage Don Nelson<br />
Publisher<br />
MEMS devices: widely used, little known<br />
4 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Amicroelectromechanical-system device<br />
probably saved my life 15 years ago. At<br />
the very le<strong>as</strong>t, MEMS technology prevented<br />
me from sustaining m<strong>as</strong>sive injuries.<br />
I w<strong>as</strong> driving an au<strong>to</strong>mobile involved in<br />
a head-on collision with a car heading the<br />
wrong way on an exit ramp. Both vehicles<br />
were traveling at 45 mph. My car had an airbag<br />
system that incorporated a MEMS accelerometer,<br />
a type of sensor. When these<br />
sensors experience rapid deceleration, they<br />
signal a control unit <strong>to</strong> deploy the airbag—a<br />
sequence that l<strong>as</strong>ts less than 60 milliseconds.<br />
My airbag worked perfectly.<br />
Th e upshot of the s<strong>to</strong>ry is that I spent 6<br />
hours in the hospital, for observation, w<strong>as</strong><br />
discharged and home in time for dinner. Th e<br />
other driver, whose car w<strong>as</strong>n’t equipped with<br />
an airbag, spent 4 days in the hospital’s intensive<br />
care unit followed by 6 weeks recovering<br />
from extensive external and internal injuries.<br />
Many people have had their lives saved<br />
by airbags, which became standard equipment<br />
on vehicles because relatively low-cost<br />
MEMS accelerometers made them aff ordable.<br />
And many, many more people have benefi<br />
ted from and had their lives enriched by<br />
MEMS devices without realizing they exist.<br />
Few know that the technology underlies<br />
the operation of inkjet printer heads; bar<br />
code scanners; smart phones, such <strong>as</strong> Apple’s<br />
iPhone (an accelerometer transforms the<br />
screen from portrait <strong>to</strong> landscape <strong>view</strong> when<br />
the user turns the phone sideways); microphones;<br />
televisions; lap<strong>to</strong>p computers; GPS<br />
navigation systems; and Nintendo’s Wii.<br />
Experts predict MEMS applications will<br />
grow signifi cantly in the coming years.<br />
An industry analyst from Yole Développement<br />
SARL who spoke at a recent conference<br />
sponsored by the MEMS Industry Group<br />
projected that worldwide sales of MEMS devices<br />
would rise from $6.9 billion in 2009 <strong>to</strong><br />
$13.2 billion in 2013.<br />
Before an uptick can occur, though, the<br />
companies that buy MEMS devices will need<br />
relief from current economic conditions. A<br />
representative from the market research fi rm<br />
Gartner Inc. <strong>to</strong>ld conference attendees that,<br />
in 2009, he expects revenues for the au<strong>to</strong>motive<br />
and consumer product sec<strong>to</strong>rs—two<br />
major industries served by MEMS suppliers—<strong>to</strong><br />
be down 30.1 percent and 19.9 percent,<br />
respectively.<br />
To fulfi ll its potential, the MEMS industry<br />
will also have <strong>to</strong> change some of the ways<br />
it conducts business and brings product <strong>to</strong><br />
market. For one, it will need <strong>to</strong> improve design<br />
processes, which is the subject of this issue’s<br />
cover s<strong>to</strong>ry. It will also have <strong>to</strong> develop<br />
m<strong>as</strong>s-fabrication processes for MEMS. And,<br />
according <strong>to</strong> the Yole analyst, suppliers must<br />
decre<strong>as</strong>e the time and expense of commercializing<br />
MEMS devices. On average, it takes<br />
4 years <strong>to</strong> bring a MEMS product <strong>to</strong> market—at<br />
a cost of $45 million.<br />
Th e ongoing “microsizing” of consumer<br />
products and medical devices will be a prime<br />
driver of MEMS growth. Maximizing profi tability<br />
will necessitate fi nding new applications<br />
for existing technologies.<br />
“We are experiencing a technology convergence<br />
in MEMS,” said MEMS Industry<br />
Group Managing Direc<strong>to</strong>r Karen Lightman.<br />
“Sensors made for au<strong>to</strong>mobiles—extremely<br />
complex systems requiring the highest levels<br />
of safety and reliability—are being used for<br />
health-care devices, such <strong>as</strong> heart moni<strong>to</strong>rs,<br />
and 3-D motion tracking. MEMS-b<strong>as</strong>ed energy<br />
harvesters (clean, renewable alternatives<br />
<strong>to</strong> batteries for powering small systems) are<br />
being utilized in consumer and industrial<br />
systems, and they may one day be used in<br />
more energy-effi cient, or even all-electric,<br />
au<strong>to</strong>mobiles.”<br />
Assuming that day comes, the general<br />
public may come <strong>to</strong> understand—and appreciate—the<br />
benefi ts of MEMS technology <strong>as</strong><br />
much <strong>as</strong> I do. µ<br />
Publisher<br />
<strong>MICROmanufacturing</strong><br />
Telephone: (847) 714-0173<br />
E-mail: dnelson@jwr.com
TECHnews<br />
L<strong>as</strong>er technique<br />
promises improved<br />
artifi cial implants<br />
Purdue University researchers are developing<br />
technologies <strong>to</strong> make artifi cial<br />
implants that can be manufactured 10<br />
times f<strong>as</strong>ter, l<strong>as</strong>t three times longer and<br />
cost less than those made with current<br />
technologies.<br />
Conventional manufacturing of orthopedic<br />
implants typically involves coating<br />
the surface of milled or molded titanium<br />
parts with a polymer material that adjoins<br />
the patient’s natural bone or tissue cells,<br />
said Dr. Yung Shin, professor of mechanical<br />
engineering and direc<strong>to</strong>r of Purdue’s<br />
Center for L<strong>as</strong>er-B<strong>as</strong>ed Manufacturing.<br />
The polymer’s life expectancy of about<br />
10 years requires some patients <strong>to</strong> undergo<br />
several implant procedures during<br />
their lives.<br />
Shin and his team of researchers are<br />
working <strong>to</strong> improve implant longevity by<br />
using continuous fi ber l<strong>as</strong>ers <strong>to</strong> melt and<br />
combine titanium and ceramic (trical-<br />
6 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
cium phosphate or hydroxyapatite) powders,<br />
which are then deposited in layers<br />
<strong>to</strong> form the implants. The highest proportion<br />
of TCP is present in the implant’s<br />
porous, outermost layer, which makes<br />
direct contact with the patient’s bones.<br />
“Titanium and other metals do not<br />
match either the stiffness or the nature of<br />
bones, so you have <strong>to</strong> coat it with something<br />
that does,” Shin said. “However,<br />
Purdue University<br />
Purdue researchers are using continuous fiber l<strong>as</strong>ers <strong>to</strong> make hip implants via layer<br />
deposition of melted titanium and ceramic powders.<br />
if you deposit TCP on metal, you don’t<br />
want an abrupt change of materials because<br />
that causes differences in thermal<br />
expansion and chemical composition,<br />
which results in cracks. One way <strong>to</strong> correct<br />
this is <strong>to</strong> change the composition<br />
gradually, so you don’t have a sharp<br />
boundary.”<br />
Since TCP degrades at a much slower<br />
rate than polymer materials, Shin estimates<br />
the TCP-coated devices can l<strong>as</strong>t at<br />
le<strong>as</strong>t 30 years, or three times longer than<br />
current implants.<br />
The l<strong>as</strong>er deposition process also enables<br />
the researchers <strong>to</strong> make cus<strong>to</strong>m<br />
parts with complex shapes. “Medical im-<br />
aging scans could just be sent <strong>to</strong> the labora<strong>to</strong>ry,<br />
w<strong>here</strong> the l<strong>as</strong>er deposition would<br />
create the part from images,” Shin said.<br />
“Instead of taking 30 days like it does<br />
now, because you have <strong>to</strong> make a mold<br />
fi rst, we could do it in 3 days. You reduce<br />
both the cost and production time.”<br />
Though Shin and his team of researchers<br />
are still refi ning their l<strong>as</strong>er-b<strong>as</strong>ed<br />
technology, he said it should be ready for<br />
commercialization in 2 years.<br />
Researchers devise<br />
microreac<strong>to</strong>r from<br />
fused silica<br />
Cornell University researchers used<br />
high-purity fused silica <strong>to</strong> fabricate a<br />
microreac<strong>to</strong>r capable of withstanding<br />
temperatures of 1, 100° C. An initial application<br />
for the device, which h<strong>as</strong> an area<br />
of less than 3 sq. cm, is detecting athletes’<br />
use of performance-enhancing drugs.<br />
While such testing <strong>to</strong>day is widely<br />
conducted with larger-scale technology,<br />
shrinking its size <strong>to</strong> microdimensions<br />
can cut testing time by three times (down<br />
<strong>to</strong> 10 minutes) and reduce the amount of<br />
chemical preparation needed for analysis,<br />
said Tom Brenna, Ph.D., a professor<br />
in Cornell’s Division of Nutritional Sciences,<br />
who coordinated the project.<br />
“Th e reac<strong>to</strong>r that is currently used<br />
commercially is a fi xed ceramic tube<br />
with an internal diameter of 500μm and<br />
a length of about 12", ” Brenna said. To<br />
conduct steroid doping tests, the tube<br />
(containing steroid molecules) is placed<br />
in a 6"-long furnace, which subjects the<br />
steroid <strong>to</strong> temperatures of about 1,000°<br />
C. Th e combustion reaction prepares<br />
the steroids for stable iso<strong>to</strong>pe analysis,<br />
allowing testers <strong>to</strong> distinguish between<br />
naturally occurring and synthetic<br />
tes<strong>to</strong>sterone.<br />
As Brenna and his team of researchers<br />
set out <strong>to</strong> minimize the size of the<br />
microreac<strong>to</strong>rs <strong>to</strong> reduce cycle time, they<br />
realized the conventional ceramic composition<br />
wouldn’t work. “As we reduced<br />
dimensions, the materials and components<br />
we had available became very<br />
fragile and were not suited for routine<br />
use,” Brenna said. “Th at’s why we went
<strong>to</strong> microfabrication.”<br />
Th ey decided <strong>to</strong> make the microreac<strong>to</strong>r<br />
from split, 1mm-thick wafers of<br />
high-purity fused silica, which can accommodate<br />
the required temperatures.<br />
“Fused silica is gl<strong>as</strong>s—silicon dioxide,”<br />
said Herbert J. Tobi<strong>as</strong>, Ph.D., technical<br />
lead for microfabricating the device.<br />
“Usually gl<strong>as</strong>s is doped with materials<br />
that make its melting point low, so the<br />
more pure it is the higher temperature it<br />
can withstand.”<br />
Th e Cornell researchers designed<br />
each half of the wafer with an input<br />
channel leading <strong>to</strong> a series of high-temperature<br />
coiled channels (10μm wide),<br />
w<strong>here</strong> combustion takes place, and an<br />
output channel. Th ey used pho<strong>to</strong>lithography<br />
<strong>to</strong> create a pattern for the reac<strong>to</strong>r<br />
channels, which were wet-etched in<strong>to</strong><br />
the wafers.<br />
Th e researchers have successfully<br />
Cornell University<br />
Fabricated with high-purity fused silica, the<br />
microreac<strong>to</strong>r is capable of withstanding<br />
temperatures of 1,100° C.<br />
tested the microreac<strong>to</strong>r and are fi netuning<br />
the device <strong>to</strong> further reduce testing<br />
time. Th ey’re also talking with manufacturers<br />
interested in m<strong>as</strong>s producing<br />
the device.<br />
“Th e big innovation for us w<strong>as</strong> not<br />
simply designing it the way we did,<br />
because many people have made <strong>to</strong>rtuous<br />
[channel] paths like we did for various<br />
applications,” Brenna said. “Th e key<br />
w<strong>as</strong> <strong>to</strong> make it in a material that will<br />
happily withstand 1,000° C for an extended<br />
time. And this fused silica really<br />
does the job.”<br />
Mobile surface<br />
analysis system<br />
for micromachining<br />
Microdynamics Inc. recently added<br />
the μQC inspection microscope <strong>to</strong> its<br />
line of surface analysis products.<br />
Me<strong>as</strong>uring 8.5" wide × 4.5" long ×<br />
3.7" high, the 4.8-lb. device is a noncontact,<br />
vertical scanning interferometer<br />
adaptable <strong>to</strong> a variety of applications,<br />
including micromachining, said John<br />
Beardon, president and chief technical<br />
offi cer of Woods<strong>to</strong>ck, Ga.-b<strong>as</strong>ed<br />
Microdynamics.<br />
Parts <strong>to</strong> be me<strong>as</strong>ured are usually<br />
micromanufacturing.com | 7
TECHnews<br />
placed inside stationary interferometer<br />
systems. But the mobile, computer-controlled<br />
μQC [Quality Control] is designed<br />
for added fl exibility.<br />
“Th e μQC can be mounted on an X,<br />
Y or Z axis, on translational stages, on a<br />
CMM or attached <strong>to</strong> a robot,” Beardon<br />
said. “It can be oriented in any three-dimensional<br />
space. Because of its unique<br />
counterbalance system, we can use it<br />
upside down or sideways. And with the<br />
borescope interferometer attachment,<br />
we can me<strong>as</strong>ure the wall surface roughness<br />
in a bore <strong>as</strong> small <strong>as</strong> 6mm in diameter<br />
and 50mm deep.”<br />
Th e modular μQC consists of an interferometer<br />
attached <strong>to</strong> a vertical scanning<br />
axis with 20mm of travel. Th e μQC<br />
houses the linear mo<strong>to</strong>r drive, the encoder,<br />
servo controller, camera and an<br />
USB interface.<br />
“We’ve built a shutter in<strong>to</strong> the interferometer<br />
and that allows you <strong>to</strong> close<br />
off the reference surface, giving you a<br />
higher contr<strong>as</strong>t image,” Beardon said.<br />
Th e μQC can present images in 2-D or<br />
3-D graphics, with magnifi cations of 2×,<br />
4×, 10×, 20× and 40×.<br />
“Th e μQC can resolve better than<br />
20nm and return data in roughly 30 <strong>to</strong><br />
40 seconds,” Beardon said. “If you’re using<br />
a 4× interferometer module, that image<br />
is roughly 1.5mm wide × 1mm high.”<br />
Th e μQC is capable of analyzing<br />
the surfaces of large engine blocks and<br />
MEMs with equal e<strong>as</strong>e. Th e device costs<br />
about $25,000. For more information, go<br />
<strong>to</strong> www.microdynamics.net.<br />
8 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
New green l<strong>as</strong>er<br />
for miniature projec<strong>to</strong>rs<br />
In mid-2010, Tokyo-b<strong>as</strong>ed QD L<strong>as</strong>er<br />
Inc. plans <strong>to</strong> commercialize a green l<strong>as</strong>er<br />
for use in mobile projec<strong>to</strong>rs that can be<br />
mounted on mobile phones and lap<strong>to</strong>p<br />
computers.<br />
Developed in collaboration with Prof.<br />
Y<strong>as</strong>uhiko Arakawa of the University of<br />
Tokyo’s Institute for Nano Quantum<br />
Information Electronics, the l<strong>as</strong>er mea-<br />
sures 5.6mm in diameter and consumes<br />
little power, since it can operate at up <strong>to</strong><br />
60°C without the need for cooling.<br />
According <strong>to</strong> QD L<strong>as</strong>er, its green l<strong>as</strong>er<br />
is the world’s fi rst <strong>to</strong> incorporate<br />
quantum dot semiconduc<strong>to</strong>r crystals.<br />
Th e company grows the quantum<br />
dot crystals by directing a<strong>to</strong>m beams<br />
of indium and arsenic on<strong>to</strong> a gallium<br />
arsenide substrate in a vacuum.<br />
After a two-dimensional InAs crystal<br />
forms on the substrate, strain en-<br />
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The µQC can be affixed<br />
<strong>to</strong> parts and provides<br />
both low and high<br />
resolutions, presented<br />
in 2-D or 3-D graphics,<br />
with magnifications of<br />
2×, 4×, 10×, 20× and<br />
40×.
TECHnews<br />
ergy from the lattice mismatch between InAs and GaAs<br />
causes tiny islands of 3-D crystals <strong>to</strong> form. Th e crystals,<br />
20nm in diameter and 5nm in height, are quantum dots.<br />
Key <strong>to</strong> the production of the green l<strong>as</strong>er is the application of<br />
distributed feedback (DFB) l<strong>as</strong>er technology, which is used in<br />
high-reliability optical<br />
communications<br />
<strong>to</strong> create a quantum<br />
dot semiconduc<strong>to</strong>r<br />
crystal l<strong>as</strong>er<br />
with a wavelength<br />
of 1064nm. DFB l<strong>as</strong>ers<br />
oscillate in a<br />
single mode <strong>as</strong> the<br />
active region of the<br />
QD L<strong>as</strong>er<br />
QD L<strong>as</strong>er Inc.’s quantum dot l<strong>as</strong>er can be<br />
used in mobile projec<strong>to</strong>rs.<br />
semiconduc<strong>to</strong>r l<strong>as</strong>er<br />
is structured using<br />
diff raction gratings,<br />
w<strong>here</strong> only wave-<br />
lengths in the interval of the diff raction gratings are amplifi ed.<br />
Th e pho<strong>to</strong>n stream is subsequently fi ltered through a nonlinear<br />
crystal via a process called second-harmonic generation,<br />
which is a nonlinear optical procedure that transforms<br />
two pho<strong>to</strong>ns in<strong>to</strong> one—with twice the frequency and half the<br />
wavelength of the original pho<strong>to</strong>ns. In the c<strong>as</strong>e of the green<br />
l<strong>as</strong>er, the pho<strong>to</strong>ns have a wavelength of 532nm.<br />
QD l<strong>as</strong>er noted that the conversion of the 1064nm quantum<br />
dot l<strong>as</strong>er from electricity <strong>to</strong> light is effi cient and results in<br />
reduced power consumption.<br />
Cimatron issues white paper<br />
on micromilling<br />
Cimatron Technologies Inc., a provider of integrated CAD/<br />
CAM solutions for mold, <strong>to</strong>ol and die makers <strong>as</strong> well <strong>as</strong> part<br />
manufacturers, h<strong>as</strong> issued a white paper for moldmakers seeking<br />
practical tips <strong>to</strong> overcome the challenges of micromilling.<br />
“With submicron <strong>to</strong>lerances and <strong>to</strong>ol tips that can hardly<br />
be seen by the naked eye, micromilling presents moldmakers<br />
with numerous challenges,” said the Novi, Mich.-b<strong>as</strong>ed<br />
Subscribe<br />
now<br />
company.<br />
The white paper, titled “Capitalizing on the Growing Demand<br />
for Micro-Milling,” offers tips <strong>to</strong> help moldmakers.<br />
Topics include:<br />
■ Micromilling machining requirements—machine geometry,<br />
machine construction, guide-way system, drive and motion<br />
technology, spindle, <strong>to</strong>ol holder and spindle interface, CNC<br />
technology, auxiliary components, machine requirements.<br />
■ Micromilling CAD/CAM requirements—data translation,<br />
tight <strong>to</strong>lerances, machining strategies, <strong>to</strong>ol motion, multi-axis.<br />
To download a copy of the white paper, visit: http://<strong>to</strong>olingtimes.com/MMGuide_Register.htm.<br />
µ<br />
Want a free subscription <strong>to</strong><br />
<strong>MICROmanufacturing</strong>?<br />
Fill out and return the card on page 9 or 43.<br />
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micromanufacturing.com | 11
MICROmachining<br />
Avoiding bad breaks when boring<br />
12 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
T<strong>here</strong>’s a b<strong>as</strong>ic misconception about applying<br />
micro boring bars <strong>to</strong> fi nish small<br />
holes: the <strong>to</strong>ols won’t work.<br />
“Yes, they will,” said Duane Drape, national<br />
sales manager for HORN USA Inc. Th e<br />
Franklin, Tenn., <strong>to</strong>olmaker off ers <strong>to</strong>ols in its<br />
Supermini line <strong>as</strong> small <strong>as</strong> 0.17mm (0.0067")<br />
for boring a hole with a 0.2mm (0.0079")<br />
minimum bore diameter at a maximum<br />
DOC of 0.02mm (0.0008").<br />
“Th e maximum DOC doesn’t necessarily<br />
mean you remove that much s<strong>to</strong>ck. It just<br />
1 2<br />
4<br />
HORN<br />
A microboring sequence (clockwise from upper<br />
left): HORN’s Supermini boring bars are for<br />
finishing holes with a minimum bore diameter<br />
down <strong>to</strong> 0.2mm.<br />
means that’s the maximum clearance of the<br />
<strong>to</strong>ol,” Drape noted, adding that a larger DOC<br />
can be taken when boring various softer materials,<br />
including pl<strong>as</strong>tics, aluminum and even<br />
titanium.<br />
Th ese micro boring bars are typically for<br />
Swiss-style machines, w<strong>here</strong> the <strong>to</strong>ol remains<br />
stationary and the workpiece rotates, but<br />
they can also be applied <strong>as</strong> rotating <strong>to</strong>ols in<br />
machining centers. Either way, the machine<br />
must be stable.<br />
Th e <strong>to</strong>ols must also be positioned on cen-<br />
3<br />
terline. Setting a boring bar above centerline<br />
creates more cutting force and, t<strong>here</strong>fore,<br />
puts more pressure on the delicate micro<strong>to</strong>ol,<br />
reducing <strong>to</strong>ol life and potentially causing it<br />
<strong>to</strong> break. A <strong>to</strong>ol set above centerline can also<br />
hinder chip evacuation. When set below centerline,<br />
the noncutting portion of the <strong>to</strong>ol<br />
may rub, causing the <strong>to</strong>ol <strong>to</strong> break. (See diagram<br />
on page 46.)<br />
HORN designs and grinds a micro boring<br />
<strong>to</strong>ol’s primary and secondary relief angles<br />
b<strong>as</strong>ed on it being on centerline. Th erefore,<br />
altering a <strong>to</strong>ol’s centerline placement diminishes<br />
its eff ectiveness. “It completely changes<br />
how the <strong>to</strong>ol w<strong>as</strong> designed <strong>to</strong> be cutting,”<br />
Drape said.<br />
Th ese problems are also evident when a<br />
boring bar is positioned above or below centerline<br />
and then manually rotated down or<br />
up in<strong>to</strong> the centerline position. As the fi gures<br />
on page 46 show, a boring <strong>to</strong>ol with a positive<br />
chip rake cuts more effi ciently than one with<br />
a neutral rake. “It must be a very positive,<br />
free-cutting geometry,” Drape said, “which<br />
means the <strong>to</strong>p rake angle will not be zero.” He<br />
added that a sharp cutting edge also provides<br />
free cutting because the <strong>to</strong>ol experiences less<br />
pressure. However, a sharp edge is more susceptible<br />
<strong>to</strong> chipping when bouncing occurs.<br />
Fortunately, <strong>to</strong>olmakers generally design<br />
the holders that accept the boring bar, or insert,<br />
<strong>to</strong> au<strong>to</strong>matically position the <strong>to</strong>ol on centerline.<br />
“Our <strong>to</strong>olholder completely takes care<br />
of it, ” Drape said. “It’s built in<strong>to</strong> the polygon<br />
shape of our clamp.” According <strong>to</strong> Drape, an<br />
insert that’s removed from a HORN holder<br />
and placed back in the holder will have less<br />
than a 5μm (0.0002") variation on centerline.<br />
If adjustments are needed for microhole applications,<br />
HORN off ers microadjustment<br />
cartridges <strong>to</strong> adjust the center height within<br />
tenths when a boring <strong>to</strong>ol is running on the<br />
back <strong>to</strong>ol block of a Swiss-style machine.<br />
When the <strong>to</strong>ol is running in the main <strong>to</strong>ol<br />
slide, the programmer can position the slide<br />
at any point <strong>to</strong> allow microadjustment of the<br />
centerline because the main <strong>to</strong>ol slide moves<br />
up and down linearly unlike a turret, which rotates.<br />
Normally, this slide is used for OD work,<br />
but if the end user performs microboring, this
Prevent <strong>to</strong>ol snapping through chip control<br />
EFFECTIVE CHIP EVACUATION is critical when boring<br />
microholes because chips clogging a bore can cause the tiny<br />
boring bars <strong>to</strong> snap. Pacifi c Precision Inc. experienced that<br />
when boring a 1mm-dia., 5mm-deep hole in a titanium part.<br />
The San Dim<strong>as</strong>, Calif., parts manufacturer produces medical<br />
and dental implants and performs general machining.<br />
Pacifi c Precision uses micro boring bars on its Citizen Swissstyle<br />
machines and previously applied fl ood coolant <strong>to</strong> clear<br />
chips. “We<br />
were breaking<br />
and snapping <strong>to</strong>ols in<br />
small, deep bores because of<br />
The Utilis Multidec Microbore <strong>to</strong>ol from<br />
Genevieve Swiss h<strong>as</strong> a multifaceted neck <strong>to</strong><br />
reduce vibration and is secured by hand with a finepitch<br />
threaded nut.<br />
slide allows him <strong>to</strong> position the <strong>to</strong>ol closer <strong>to</strong> the part for a<br />
more stable application.<br />
Genevieve Swiss Industries Inc., Westfi eld, M<strong>as</strong>s., also offers<br />
a holder that au<strong>to</strong>matically aligns a boring bar’s cutting<br />
edge on center, including its smallest one—a 0.42mm-dia.<br />
(0.016") <strong>to</strong>ol for a 0.5mm (0.02") minimum bore diameter.<br />
Manufactured by Utilis, the<br />
Multidec Microbore boring<br />
bars from Genevieve<br />
Swiss have an angled back<br />
end that locates within 5μm<br />
(0.0002") against a positive<br />
location pin in the Microbore<br />
holder. A fi ne-pitch<br />
threaded and knurled nut<br />
Genevieve Swiss Industries Inc.<br />
A multifaceted neck helps<br />
prevent micro boring <strong>to</strong>ols from<br />
chattering.<br />
Genevieve Swiss<br />
applies suffi cient force<br />
against the snap ring collar<br />
on the boring bar, and the<br />
system provides an axial and<br />
radial location repeatability of ±10μm (0.0004"), according <strong>to</strong><br />
the company.<br />
“You don’t have <strong>to</strong> worry about snapping the micro<strong>to</strong>ol<br />
when tightening the nut, ” said Scott Laprade, marketing manager<br />
for Genevieve Swiss. “Finger tightening is all it requires.”<br />
To minimize harmful harmonic vibration, the Microbore<br />
<strong>to</strong>ols have a multifaceted neck, w<strong>here</strong> every facet is a different<br />
thickness. “Th at prevents the bar from chattering,”<br />
Laprade said. In addition <strong>to</strong> front boring <strong>to</strong>ols, the line includes<br />
<strong>to</strong>ols for back boring, drilling and boring, internal<br />
By Alan Richter,<br />
Senior Edi<strong>to</strong>r<br />
chip control,” said Jouni Levanen, the company’s plant manager.<br />
He added that vibration and the resulting chatter were also<br />
causing <strong>to</strong>ol breakage.<br />
A boring bar no larger than 0.8mm is required for the 1mm<br />
hole <strong>to</strong> provide clearance for the chips and oil. “An oil-b<strong>as</strong>ed<br />
coolant seems <strong>to</strong> work best with titanium,” Levanen said. “Also,<br />
we need <strong>to</strong> use oil because of the revolving bushings on the<br />
machines.”<br />
The company tried various boring <strong>to</strong>ols and found that Utilis<br />
Multidec Microbore through-coolant <strong>to</strong>ols from Genevieve<br />
Swiss Industries Inc. worked from the get-go.<br />
The machines can provide a through-coolant pressure<br />
up <strong>to</strong> 2,000 psi, but the typical range is from 800 <strong>to</strong> 1,200<br />
psi. “That’s effective for evacuating chips,” Levanen said. In<br />
addition, the boring bars’ multifaceted neck cut the chatter. “We<br />
have not had any vibration issues with Utilis.”<br />
—A. Richter<br />
micromanufacturing.com | 13
MICROmachining<br />
Micro boring <strong>to</strong>ols<br />
usually are used<br />
on Swiss-type<br />
machines.<br />
14 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Genevieve Swiss<br />
grooving, boring and undercutting, profi ling, chamfering<br />
and threading.<br />
Another critical boring bar geometry is the lead off the<br />
front cutting edge, which reduces cutting pressure. HORN<br />
provides an 8° lead <strong>to</strong> enable free cutting, Drape explained. A<br />
smaller angle, such <strong>as</strong> 5°, provides a slightly stronger cutting<br />
edge but also creates more pressure, w<strong>here</strong><strong>as</strong> one that’s 15°<br />
provides freer cutting but exerts more pressure on the <strong>to</strong>ol’s<br />
corner radius.<br />
Th e corner radius for HORN’s 0.17mm boring bar is<br />
0.02mm (0.0008"), which Drape called a true radius with a<br />
controllable dimension rather than a chamfer. To achieve the<br />
required surface requirements on that radius without having<br />
excessive peaks and valleys, Drape said micrograin carbide<br />
is required for the <strong>to</strong>ol’s substrate, which isn’t coated for the<br />
company’s smallest boring bars.<br />
On the other hand, Genevieve Swiss typically off ers micro<br />
boring bars coated with Utilis’ HX coating, which is similar<br />
<strong>to</strong> titanium aluminum nitrite but in a submicron-layer form.<br />
“Because the coating layer is so thin, it doesn’t incre<strong>as</strong>e the<br />
corner radii on the <strong>to</strong>ols,” Laprade said. He noted that<br />
uncoated <strong>to</strong>ols are also available.<br />
Sometimes a boring <strong>to</strong>ol begins its life coated and fi nishes<br />
it without one on the cutting edge. For instance, Doug<br />
Day, CNC specialist at Tomak Precision, Lebanon, Ohio, applies<br />
coated <strong>to</strong>ols <strong>to</strong> bore stainless steel, cobalt and titanium,<br />
among other materials, and then manually regrinds them for<br />
an aluminum or br<strong>as</strong>s job. “A coating is not necessary then,”<br />
continued on page 46
LASERpoints By Ronald D. Schaeffer,<br />
Pho<strong>to</strong>Machining Inc.<br />
Cost considerations when buying a l<strong>as</strong>er<br />
Over the p<strong>as</strong>t few years, the federal government<br />
h<strong>as</strong> off ered companies purch<strong>as</strong>ing<br />
capital equipment some pretty good<br />
incentives—like accelerated depreciation.<br />
Now may be the time <strong>to</strong> buy that l<strong>as</strong>er micromachining<br />
system you’ve always wanted!<br />
Before giving a thumbs up or down <strong>to</strong> acquiring<br />
a l<strong>as</strong>er, though, t<strong>here</strong> are some important<br />
cost fac<strong>to</strong>rs <strong>to</strong> consider. Among<br />
them is operating cost. Th e informa-<br />
tion that follows will give you an idea<br />
of the annual costs of operating a l<strong>as</strong>er.<br />
Capitalization. At minimum, a typical<br />
precision l<strong>as</strong>er will cost $250,000 and may<br />
run over $500,000. Expect <strong>to</strong> pay, on average,<br />
about $350,000 for a good machine. Of<br />
course, much depends on the system chosen<br />
and its level of au<strong>to</strong>mation.<br />
In order <strong>to</strong> determine the average annual<br />
operating cost for a l<strong>as</strong>er, let’s choose a<br />
$350,000 model. We will combine this fi gure<br />
with the expenditures discussed below.<br />
Facilities preparation. Th is cost can vary<br />
widely, depending on w<strong>here</strong> in the facility you<br />
locate the l<strong>as</strong>er.<br />
I know of one company that bought a l<strong>as</strong>er<br />
and installed it in an area that experienced intense<br />
fl oor vibrations caused by a big mo<strong>to</strong>r<br />
running nearby. Instead of moving the l<strong>as</strong>er,<br />
the owner tried <strong>to</strong> isolate it from the rest of<br />
the building. He removed a section of the existing<br />
fl oor, placed the l<strong>as</strong>er in it and built a<br />
room around it. Th is cost tens of thousands<br />
of dollars, and the l<strong>as</strong>er could not be used for<br />
several months.<br />
Local ordinances may also come in<strong>to</strong> play.<br />
For instance, California h<strong>as</strong> much more stringent<br />
requirements than good old “Live Free<br />
or Die” New Hampshire (w<strong>here</strong> this writer<br />
lives). At minimum, t<strong>here</strong> must be electrical<br />
preparations and, perhaps, some arrangements<br />
made for cooling water.<br />
Be prepared <strong>to</strong> address safety issues. Everyone<br />
thinks of eye safety when considering<br />
l<strong>as</strong>ers, but t<strong>here</strong> are other matters <strong>to</strong> think<br />
about. For instance, most l<strong>as</strong>ers require a<br />
high-voltage power supply, which can be extremely<br />
dangerous for someone unfamiliar<br />
with using such equipment. Th ere also are<br />
material-handling issues and the need <strong>to</strong> remove<br />
debris, smoke and effl uent. W<strong>as</strong>te removal,<br />
depending on the type and how much<br />
is generated, can be a major issue.<br />
Here’s another consideration—one I always<br />
emph<strong>as</strong>ize: If you want the l<strong>as</strong>er <strong>to</strong>ol<br />
<strong>to</strong> perform optimally, house it in a temperature-<br />
and humidity-controlled environment.<br />
Failure <strong>to</strong> do so is <strong>as</strong>king for trouble. Temperature<br />
and humidity can infl uence processing<br />
results. It’s also important <strong>to</strong> ensure the<br />
work environment is clean. It can cost lots of<br />
money <strong>to</strong> replace optics and other sensitive<br />
components damaged by dirt.<br />
Facility-preparation costs can run anyw<strong>here</strong><br />
from $10,000 <strong>to</strong> $100,000. Let’s pick a<br />
conservative fi gure: $20,000.<br />
Operating expenses. Th ese normally include<br />
electricity, water, consumables (optics,<br />
fi lters, etc.), maintenance fees and service expenses<br />
for after-warranty work. Most l<strong>as</strong>er<br />
micromachining work can be done with a<br />
sealed CO 2 , diode-pumped solid-state or<br />
fi ber l<strong>as</strong>er. Operating expenses for these l<strong>as</strong>ers<br />
are fairly low compared <strong>to</strong> excimer l<strong>as</strong>ers,<br />
for instance.<br />
micromanufacturing.com | 15
LASERpoints<br />
Th e hourly operating cost varies according<br />
<strong>to</strong> usage level. For example, the<br />
more the l<strong>as</strong>er <strong>to</strong>ol runs, the more electricity<br />
is consumed and the higher the<br />
utility cost. Some usage-related operating<br />
expenses are amortized over time, such<br />
<strong>as</strong> maintenance and refurbishment costs.<br />
Th e operating cost for a l<strong>as</strong>er running<br />
one shift per day, 5 days a week, will<br />
probably be $20 <strong>to</strong> $30 per hour. If used<br />
more—i.e., <strong>to</strong> make more parts—the<br />
cost can drop <strong>to</strong> $10 per hour. (Note:<br />
L<strong>as</strong>ers can run about 20, 000 hours before<br />
they require major servicing.)<br />
Let’s fi gure operating costs at $10<br />
per hour and <strong>as</strong>sume the l<strong>as</strong>er runs 40<br />
hours per week. Th e yearly cost would<br />
be $20,800 ($400 × 52).<br />
Salaries. Th is expense also depends<br />
on the l<strong>as</strong>er <strong>to</strong>ol’s usage. At minimum,<br />
an engineer needs <strong>to</strong> oversee the l<strong>as</strong>er,<br />
whether he runs it or not. An engineer<br />
typically is responsible for programming<br />
and maintenance, while an opera<strong>to</strong>r<br />
runs most of the jobs.<br />
Figure on minimal annual salaries of<br />
$50,000 for the engineer and $30,000<br />
for the opera<strong>to</strong>r. When you add insurance,<br />
taxes, benefi ts, supplies and so<br />
forth, the real costs for the engineer<br />
and opera<strong>to</strong>r are $65,000 and $38,000,<br />
Find It Online<br />
For advice on choosing a shop <strong>to</strong> perform<br />
l<strong>as</strong>er work, read Ron’s column in the Fall<br />
issue of <strong>MICROmanufacturing</strong> or online<br />
at www.micromanufacturing.com (under<br />
“Articles”).—Ed.<br />
Want a free subscription <strong>to</strong><br />
<strong>MICROmanufacturing</strong>?<br />
16 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
respectively. Add 30 percent <strong>to</strong> those<br />
numbers if your company is located in a<br />
major metropolitan area.<br />
Let’s <strong>as</strong>sume the engineer devotes<br />
25 percent of his time <strong>to</strong> l<strong>as</strong>er operations<br />
and the opera<strong>to</strong>r 80 percent. Th e<br />
costs would be $16,250 for the engineer<br />
($65,000 × 0.25) and $30,400 for the<br />
opera<strong>to</strong>r ($38,000 × 0.80), for a <strong>to</strong>tal of<br />
$46,650.<br />
If you want the l<strong>as</strong>er<br />
<strong>to</strong>ol <strong>to</strong> perform<br />
optimally, house it in<br />
a temperature- and<br />
humidity-controlled<br />
environment.<br />
To that amount, you need <strong>to</strong> add<br />
overhead and indirect expenditures<br />
such <strong>as</strong> managers’ salaries, common<br />
corporate are<strong>as</strong> and a host of other expenses.<br />
Th is fi gure varies from one<br />
company <strong>to</strong> the next, of course, but 50<br />
percent is a good rule of thumb. To fi nd<br />
the yearly labor expense for one-shift<br />
operation of a l<strong>as</strong>er, multiply $46,650 ×<br />
1.50, which comes <strong>to</strong> $69,975.<br />
If you amortize your capitalization<br />
and facility-preparation costs ($350,000<br />
+ $20,000 = $370,000) over a 5-year depreciation<br />
schedule, the cost per year is<br />
$74,000 ($370,000 ÷ 5). If you add salaries<br />
($69,975) and operating expenses<br />
($20,800), the <strong>to</strong>tal cost <strong>to</strong> own and operate<br />
a l<strong>as</strong>er <strong>to</strong>ol for a year is approximately<br />
$164,775 ($74,000 + $69,975 +<br />
Fill out and return the card on page 9 or 43.<br />
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$20,800). Th at breaks down <strong>to</strong> about<br />
$13,700 monthly.<br />
Worth the cost?<br />
If a company consistently needs l<strong>as</strong>er<br />
work done in volume, it often will buy<br />
a machine. Th is is not always the c<strong>as</strong>e,<br />
though. Many large companies contract<br />
work <strong>to</strong> small l<strong>as</strong>er shops. Th ey outsource<br />
the job because a smaller company<br />
often can perform the work more<br />
cheaply, due <strong>to</strong> having lower overhead<br />
and specialized expertise that would be<br />
expensive for a large company <strong>to</strong> acquire.<br />
Having said that, I know of many<br />
companies that must own a l<strong>as</strong>er because<br />
their cus<strong>to</strong>mers—usually in the<br />
defense sec<strong>to</strong>r—dictate that all processing<br />
be done in-house. In these c<strong>as</strong>es,<br />
the numbers are skewed by the value of<br />
the <strong>to</strong>tal job.<br />
Another re<strong>as</strong>on <strong>to</strong> acquire a l<strong>as</strong>er<br />
<strong>to</strong>ol is turnaround time. Quick-turn<br />
shops can charge higher prices, and<br />
they make bigger profi ts.<br />
Yet another re<strong>as</strong>on <strong>to</strong> buy is if the user<br />
needs <strong>to</strong> integrate a l<strong>as</strong>er in<strong>to</strong> a production<br />
line so that a process can run uninterrupted<br />
from start <strong>to</strong> fi nish.<br />
In c<strong>as</strong>es w<strong>here</strong> t<strong>here</strong>’s no requirement<br />
<strong>to</strong> buy a l<strong>as</strong>er, however, the question<br />
usually comes down <strong>to</strong>, “Do I have<br />
enough business <strong>to</strong> warrant a monthly<br />
outlay of nearly $14,000?” µ<br />
About the author: Ron Schaeffer is CEO<br />
of Pho<strong>to</strong>Machining Inc., a high-precision<br />
l<strong>as</strong>er job shop and systems integra<strong>to</strong>r<br />
in Pelham, N.H. E-mail: rschaeffer@<br />
pho<strong>to</strong>machining.com.<br />
Subscribe<br />
now
Downsizing By Dennis Spaeth,<br />
Electronic Media Edi<strong>to</strong>r<br />
Microturbines headed back <strong>to</strong> the future<br />
Nobody’s talking about generating 1.21<br />
gigawatts of power <strong>as</strong> w<strong>as</strong> required in<br />
the “Back <strong>to</strong> the Future” movie, but microturbine<br />
research is headed back <strong>to</strong> w<strong>here</strong> it<br />
w<strong>as</strong> in early 2007. Dr. Alan Epstein, one of the<br />
prime movers behind the micro-engine project<br />
at the M<strong>as</strong>sachusetts Institute of Technology,<br />
expected <strong>to</strong> have a micro-engine<br />
producing power by the late spring of that<br />
year, and a fully integrated device ready for<br />
commercialization within 5 years.<br />
In the interim, however, the research hit<br />
a wall at MIT and h<strong>as</strong> moved <strong>to</strong> the University<br />
of Maryland in College Park, Md. Dr.<br />
Reza Ghodssi, a member of the MIT team<br />
from 1997 <strong>to</strong> 2000 and now the Herbert<br />
Rabin Distinguished Professor and Direc<strong>to</strong>r<br />
of the Institute for Systems Research with the<br />
A. James Clark School of Engineering at the<br />
University of Maryland, continued <strong>to</strong> work<br />
on such a device—though with one major<br />
diff erence: Ghodssi is using stainless steel ball<br />
bearings <strong>to</strong> support the ro<strong>to</strong>r <strong>as</strong> opposed <strong>to</strong><br />
air bearings.<br />
And Ghodssi seems confi dent a fully integrated<br />
microturbine will be ready <strong>to</strong> demonstrate<br />
within 4 <strong>to</strong> 5 years.<br />
To truly appreciate this feat, we need <strong>to</strong><br />
go back <strong>to</strong> 1995. Th at’s when it occurred <strong>to</strong><br />
Epstein, now retired, that if a large turbine<br />
could power a city, then a tiny turbine should<br />
be able <strong>to</strong> supply enough electrical power<br />
for one person’s needs. It w<strong>as</strong>, if you will, his<br />
“fl ux capaci<strong>to</strong>r” moment.<br />
Main pho<strong>to</strong> courtesy of Siemens AG; inset pho<strong>to</strong>s courtesy Reza Ghodssi, Matthew McCarthy, C. Mike Waits, Mustafa Beyaz, Brendan Hanrahan, University of Maryland<br />
In 1995, while pondering how a large turbine could power an entire city, such <strong>as</strong> the one above, produced by Siemens AG, Dr. Alan Epstein<br />
first thought about creating a microturbine <strong>to</strong> meet one person’s needs. A cross section of the microturbine (left inset) created at the<br />
University of Maryland reveals the location of the micro ball bearings, which are contained in a notch in the edge of the turbine below the<br />
ro<strong>to</strong>rs (right inset).<br />
micromanufacturing.com | 17
Downsizing<br />
With a team of researchers, the professor<br />
in MIT’s Department of Aeronautics<br />
and Astronautics set out <strong>to</strong><br />
develop a tiny turbine, which Epstein<br />
theorized could have a thrust-<strong>to</strong>-weight<br />
ratio of 100:1. Perhaps with his own<br />
nod <strong>to</strong> the “Back <strong>to</strong> the Future” movie<br />
franchise, he playfully observed in a<br />
May 23, 1997, issue of Science that it<br />
would be theoretically possible <strong>to</strong> use<br />
some 1,400 microturbines <strong>to</strong> levitate a<br />
skateboard.<br />
By early 2007, t<strong>here</strong> were no levitating<br />
skateboards, but the MIT team had<br />
used silicon wafer technology <strong>to</strong> construct<br />
a pro<strong>to</strong>type microturbine one<br />
layer at a time.<br />
“We showed that we could run this<br />
[device] at high temperatures,” said<br />
Stuart Jacobson, the former deputy<br />
direc<strong>to</strong>r of the MIT micro-engine<br />
project. “We burned inside the combustion<br />
chamber, [and] the device sped<br />
up <strong>as</strong> you would expect when you’re<br />
putting a high-temperature g<strong>as</strong> through<br />
the turbine. And that b<strong>as</strong>ically showed<br />
the next step—that we could integrate<br />
the turbine machinery, the bearings<br />
and the combustion chamber in a<br />
single device. And that’s w<strong>here</strong> things<br />
sort of closed out.” Funding from the<br />
U.S. Army Research Labora<strong>to</strong>ry came<br />
<strong>to</strong> an end.<br />
While the team didn’t run in<strong>to</strong> any<br />
“show s<strong>to</strong>ppers,” noted Jacobson, the<br />
vital question that remained unanswered<br />
w<strong>as</strong> whether the device could<br />
be manufactured at yield levels that<br />
would allow it <strong>to</strong> be sold at a re<strong>as</strong>onable<br />
price.<br />
Want a free subscription <strong>to</strong><br />
<strong>MICROmanufacturing</strong>?<br />
18 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Ghodssi credits the MIT project<br />
for sparking the creation of the annual<br />
Power MEMS Conference and generating<br />
a body of knowledge, technology<br />
and b<strong>as</strong>ic science that benefi ts similar<br />
research elsew<strong>here</strong>—including his own.<br />
“When I went <strong>to</strong> Maryland,” Ghodssi<br />
recalled, “I realized that from my p<strong>as</strong>t<br />
work [at MIT and during his m<strong>as</strong>ter’s<br />
research at the University of Wisconsin-<br />
Madison] that a lot of the diffi culties of<br />
developing the microturbine really lie<br />
in the complexity of the fabrication because<br />
the scales are so rigid. To meet<br />
the specs, you need a perfect fabrication<br />
process that by itself is very complex<br />
because you have multilayer fi lms<br />
coming <strong>to</strong>gether.<br />
“So I decided <strong>to</strong> take an in-between<br />
approach,” Ghodssi continued.<br />
“I thought about using stainless steel<br />
ball bearings on a small scale.” Th ough<br />
doing so produces a slower device, the<br />
simplicity appears <strong>to</strong> have paid off . In<br />
the University of Maryland MEMS Sensors<br />
and Actua<strong>to</strong>rs Lab, Ghodssi said<br />
the microturbine h<strong>as</strong> reached speeds up<br />
<strong>to</strong> 95,000 rpm.<br />
“If you can reach 150,000 rpm,” he<br />
added, “you can start generating electricity.”<br />
And Ghodssi said he expects <strong>to</strong><br />
do that very soon.<br />
Using 285μm-dia. stainless steel ball<br />
bearings e<strong>as</strong>es fabrication because the<br />
spinning plates sit on ball bearings.<br />
“You don’t have <strong>to</strong> fi t them in place and<br />
hold them with pressurized air,” <strong>as</strong> with<br />
the MIT device, he noted.<br />
A critical breakthrough for the use of<br />
ball bearings, said Ghodssi, came from<br />
Fill out and return the card on page 9 or 43.<br />
Or, subcribe online at www.micromanufacturing.com<br />
Dr. C. Mike Waits (currently at the<br />
Army Research Lab in Adelphi, Md.),<br />
who introduced the idea of supporting<br />
the microturbine with a planar-contact<br />
encapsulated ball bearing.<br />
With this encapsulated approach,<br />
the University of Maryland team no<br />
longer had <strong>to</strong> worry about handling<br />
the ball bearings one by one using tweezers.<br />
Ghodssi said encapsulating them<br />
made the fabrication process much<br />
more robust from a manufacturing<br />
standpoint.<br />
Ghodssi said he hopes <strong>to</strong> have a microgenera<strong>to</strong>r<br />
ready <strong>to</strong> add <strong>to</strong> the microturbine<br />
within the next year. Th e goal in<br />
the next 2 <strong>to</strong> 3 years is <strong>to</strong> integrate the<br />
microgenera<strong>to</strong>r with an off -the-shelf<br />
micro-engine.<br />
“So once the device is working,” observed<br />
Ghodssi, “it will be robust and<br />
reproducible.”<br />
And once that moment arrives, the<br />
microturbine could power anything<br />
from unmanned aerial vehicles <strong>to</strong> any<br />
number of digital devices used by U.S.<br />
troops, who could then do away with<br />
about 20 lbs. of lithium-ion and other<br />
batteries that they now must carry in<strong>to</strong><br />
battle.<br />
Asked whether the current microturbine<br />
device, which me<strong>as</strong>ures 23mm<br />
× 23mm × 1.5mm, could get smaller,<br />
Ghodssi noted that t<strong>here</strong> are 150μmdia.<br />
ball bearings available. But fi rst he<br />
wants <strong>to</strong> prove the existing device can<br />
work.<br />
Now, if only we could hop in the<br />
DeLorean, we could fi nd out what<br />
happens! µ<br />
Subscribe<br />
now
MEASUREMENT matters By Susan Woods,<br />
Contributing Edi<strong>to</strong>r<br />
Understanding scanning white<br />
light interferometry<br />
Scanning white light interferometry<br />
(SWLI) is a versatile technology<br />
that provides a noncontact, 3-D<br />
method of me<strong>as</strong>uring surface roughness.<br />
Th e interference microscopy<br />
technology combines an interferometer<br />
and microscope in<strong>to</strong> one instrument.<br />
Illumination from a white light<br />
beam p<strong>as</strong>ses through a fi lter and then a<br />
microscope objective lens <strong>to</strong> the sample<br />
surface. Th e objective lens is coupled<br />
with a beam splitter so some of<br />
the light is refl ected from a reference<br />
mirror. Th e light refl ecting back from<br />
the surface recombines with the reference<br />
beam. Th e recombined beams<br />
create bright and dark bands called<br />
“fringes,” which make up the interferogram.<br />
Fringes represent the object’s<br />
<strong>to</strong>pography.<br />
Th e pattern of these fringes is captured<br />
on a CCD camera array for software<br />
analysis. By obtaining several<br />
frames of intensity information for<br />
each point, the system can recreate the<br />
sample surface. Th e frames are p<strong>as</strong>sed<br />
through an algorithm <strong>to</strong> convert those<br />
intensity signals in<strong>to</strong> height information.<br />
Microscope-b<strong>as</strong>ed white light optical<br />
profi lers are capable of me<strong>as</strong>uring<br />
a variety of surface types, including<br />
ground and polished surfaces, steps<br />
and fi lms. Th ey do this by mapping<br />
surface heights that range from subnanometers<br />
<strong>to</strong> microns across are<strong>as</strong><br />
that range from microns <strong>to</strong> millimeters<br />
in a single me<strong>as</strong>urement. Th is rapidly<br />
provides surface roughness, shape and<br />
waviness data.<br />
When the required me<strong>as</strong>urement<br />
are<strong>as</strong> are larger than the fi eld of <strong>view</strong>, a<br />
stitching procedure can be employed<br />
that involves a number of partially<br />
overlapping me<strong>as</strong>urements being combined<br />
in<strong>to</strong> one surface profi le. Stitching,<br />
however, requires that regions<br />
overlap, with the overlapping data<br />
aligning adjacent me<strong>as</strong>urements. Be-<br />
cause overlap regions are me<strong>as</strong>ured<br />
more than once, overall me<strong>as</strong>urement<br />
time incre<strong>as</strong>es.<br />
Th e primary applications for SWLI<br />
are surface me<strong>as</strong>urement of MEMS<br />
(microelectromechanical systems) and
MEASUREMENT matters<br />
semiconduc<strong>to</strong>rs. Other applications include<br />
me<strong>as</strong>uring machined surfaces,<br />
microfl uidic devices, optics and fi bers,<br />
ceramics, gl<strong>as</strong>s, paper, thin fi lms and<br />
polymers.<br />
“Anyw<strong>here</strong> w<strong>here</strong> it is important<br />
<strong>to</strong> understand vertical features over<br />
a small lateral scale is w<strong>here</strong> it h<strong>as</strong> a<br />
great application,” said Eric Felkel, product<br />
manager, Zygo Corp., Middlefi eld,<br />
Conn., a manufacturer of 3-D noncontact<br />
optical me<strong>as</strong>uring instruments.<br />
SWLI optical profi lers are used in<br />
development and production environments.<br />
“It is an instrument that works<br />
well in the research lab, the failure analysis<br />
lab [and] in production manufacturing,”<br />
Felkel added.<br />
While other metrology solutions<br />
provide either high resolution or<br />
high speed, SWLI off ers both. It combines<br />
noncontact me<strong>as</strong>urement, repeatable<br />
3-D surface me<strong>as</strong>urement, high<br />
speeds and subnanometer resolution.<br />
SWLI is employed for surfaces with<br />
average roughness down <strong>to</strong> 0.1nm R a<br />
and peak-<strong>to</strong>-valley heights up <strong>to</strong> several<br />
millimeters, and repeatability can be<br />
0.1nm or better. (While the upper<br />
peak-<strong>to</strong>-valley height limit would most<br />
often be applicable <strong>to</strong> macro applications,<br />
it can be useful in certain micro<br />
applications.)<br />
Pros and cons<br />
SWLI off ers many advantages over<br />
other methods, such <strong>as</strong> stylus profi<br />
lometry and a<strong>to</strong>mic force microscopy<br />
(AFM). Two principle advantages are<br />
SWLI’s high-speed and noncontact capabilities.<br />
Th e user can rapidly acquire a<br />
3-D rendered surface <strong>to</strong> make me<strong>as</strong>urements<br />
immediately.<br />
On the other hand, “AFM is a very<br />
high-resolution technique, but it takes<br />
a lot of time <strong>to</strong> perform. It requires a<br />
very knowledgeable user,” said Patrick<br />
O’Hara, president and CEO of Ambios<br />
Technology Inc., Santa Cruz, Calif.,<br />
a supplier of surface metrology<br />
instruments.<br />
And stylus profi lometry is a contact<br />
technique, which may not be desired.<br />
“When you drag a stylus across the sur-<br />
20 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Zygo<br />
Shown me<strong>as</strong>uring a MEMS device, the NewView 7300 white light optical profiler from Zygo<br />
characterizes and quantifies surface roughness, critical dimensions and other <strong>to</strong>pographical<br />
features without sample preparation.<br />
Light source<br />
Filter<br />
Field of <strong>view</strong> multiplier (FOV)<br />
Aperture<br />
s<strong>to</strong>p<br />
Field<br />
s<strong>to</strong>p<br />
Interferometer objective<br />
(Mirau type)<br />
Reference mirror<br />
A schematic showing how SWLI works.<br />
face and it <strong>to</strong>uches the part, it h<strong>as</strong> the<br />
potential <strong>to</strong> damage or even destroy the<br />
surface you are interested in characterizing,”<br />
Felkel said.<br />
Another benefi t of SWLI is that it is<br />
an area-b<strong>as</strong>ed technique, w<strong>here</strong>in the<br />
sensor images the interference signal<br />
from an area of the part and communicates<br />
that signal <strong>to</strong> the camera. Other<br />
Camera<br />
Beam<br />
splitter<br />
Transla<strong>to</strong>r<br />
Veeco Metrology<br />
<strong>to</strong>pography techniques<br />
only sense the surface at<br />
a single point or along<br />
a single line. “You are<br />
looking at an area fi eld<br />
of <strong>view</strong> that is determined<br />
by the magnifi cation<br />
of the microscope<br />
objective being used,”<br />
Felkel said. “You can<br />
look at low-frequency<br />
structures, such <strong>as</strong> surface<br />
form, waviness<br />
and steps, with a lowmagnifi<br />
cation lens and<br />
then switch <strong>to</strong> higher<br />
magnifi cation and look<br />
at high-frequency features<br />
that contribute <strong>to</strong><br />
roughness. Other ways<br />
of performing this type<br />
of surface characterization<br />
are not area-b<strong>as</strong>ed,<br />
such <strong>as</strong> a triangulation sensor or a line<br />
scanner.”<br />
When compared <strong>to</strong> techniques such<br />
<strong>as</strong> video microscopy, SWLI is advantageous<br />
because it does not depend on<br />
part color <strong>to</strong> obtain high-quality data.<br />
Even if the surface being me<strong>as</strong>ured refl<br />
ects a small amount of light, that refl<br />
ected light interferes with the light
that refl ects off of the reference surface.<br />
Th is interference signal is what defi nes<br />
the surface me<strong>as</strong>urement data. Because<br />
SWLI uses the interference signal <strong>to</strong><br />
me<strong>as</strong>ure the height of the surface—and<br />
not simply a raw camera image like a<br />
video system—it is possible <strong>to</strong> me<strong>as</strong>ure<br />
structures that visibly have little color<br />
contr<strong>as</strong>t, but are e<strong>as</strong>y <strong>to</strong> see by their<br />
<strong>to</strong>pography.<br />
L<strong>as</strong>tly, SWLI is an e<strong>as</strong>y-<strong>to</strong>-learn technique<br />
and does not require sample<br />
preparation. “It is <strong>as</strong> simple <strong>as</strong> putting<br />
the sample under the microscope, focusing<br />
and me<strong>as</strong>uring,” said Greg Maksinchuk,<br />
marketing product manager,<br />
Veeco Metrology Group, Tucson, Ariz.,<br />
a provider of metrology and process<br />
equipment.<br />
Th e principle disadvantage of SWLI,<br />
or any optical technique, is that it depends<br />
on the optical properties of the<br />
medium through which it is looking,<br />
whether it’s gl<strong>as</strong>s, air or, for semiconduc<strong>to</strong>r<br />
manufacturing, thin fi lms.<br />
“Each of those dielectric thin fi lms<br />
h<strong>as</strong> it own optical properties,” O’Hara<br />
said. “Th is can produce anomalous results,<br />
such <strong>as</strong> inaccurate fi lm thickness<br />
or step me<strong>as</strong>urements, due <strong>to</strong> the diff erent<br />
optical properties of the fi lms. Most<br />
instrument manufacturers have proprietary<br />
methods of overcoming these<br />
anomalies, but the ambiguity remains.<br />
However, AFM or stylus profi lometry<br />
provides an unambiguous me<strong>as</strong>ure of<br />
the <strong>to</strong>p surface or the step.”<br />
Also, SWLI is typically focused on<br />
the part’s vertical resolution, or <strong>to</strong>pography,<br />
and less on lateral resolution,<br />
such <strong>as</strong> the part’s geometric dimensions.<br />
SWLI <strong>to</strong>ols do focus on high<br />
lateral resolution, but if the user is primarily<br />
interested in lateral information,<br />
other less-expensive me<strong>as</strong>urement<br />
methods are available.<br />
New developments<br />
While me<strong>as</strong>uring thin fi lms can be<br />
a challenge, one of the most important<br />
improvements <strong>to</strong> SWLI technology is<br />
its ability <strong>to</strong> me<strong>as</strong>ure surface <strong>to</strong>pography<br />
in the presence of an optical fi lm.<br />
“If the surface you are me<strong>as</strong>uring h<strong>as</strong> a<br />
transparent fi lm on it, you have two interference<br />
signals because you see the<br />
<strong>to</strong>p and bot<strong>to</strong>m of the fi lm,” Felkel said,<br />
adding that now SWLI can be used <strong>to</strong><br />
me<strong>as</strong>ure the <strong>to</strong>p and bot<strong>to</strong>m of the fi lm<br />
and its thickness.<br />
And manufacturers are improving<br />
this process <strong>to</strong> work with thinner and<br />
Will your parts<br />
fit in<strong>to</strong> this box?<br />
Parts that small need <strong>to</strong> be of the highest quality for reliability,<br />
yet they present significant challenges <strong>to</strong> achieving accurate<br />
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thinner fi lms. “We work along two different<br />
paths,” Felkel said. “We develop<br />
software that can identify these interference<br />
signals <strong>as</strong> they get closer and<br />
closer <strong>to</strong>gether, and we design imaging<br />
systems <strong>to</strong> resolve these interference<br />
signals with higher fi delity.”<br />
continued on page 47<br />
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micromanufacturing.com | 21
ABOUT<strong>to</strong>oling<br />
SCD <strong>to</strong>ols: not just for specialized machines<br />
22 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Single-crystal-diamond <strong>to</strong>ols are routinely<br />
used <strong>to</strong> cut optical-quality components<br />
on special turning machines. But they also<br />
can run on conventional machine <strong>to</strong>ols—<br />
often <strong>to</strong> great advantage.<br />
Th e main re<strong>as</strong>ons are that many of <strong>to</strong>day’s<br />
CNC machining centers and lathes incorporate<br />
ultraprecision ball bearing spindles,<br />
which couple with high-speed servodrives.<br />
And, control of axes motion h<strong>as</strong> improved,<br />
thanks <strong>to</strong> linear mo<strong>to</strong>rs and submicron-positioning<br />
feedback systems. Augmenting these<br />
improvements are ongoing CAD/CAM software<br />
developments that help the end user<br />
take full advantage of a machine’s enhanced<br />
capabilities.<br />
Cutting <strong>to</strong>ols have evolved, <strong>to</strong>o. Th ere are<br />
literally thousands of ways geometries, wearresistant<br />
coatings, substrates and other <strong>to</strong>ol<br />
elements can be combined <strong>to</strong> optimize performance.<br />
Most of these <strong>to</strong>ols eff ectively remove<br />
material, have acceptable wear life and<br />
meet the user’s surface-fi nish requirements.<br />
But t<strong>here</strong> are applications w<strong>here</strong> no other<br />
cutting <strong>to</strong>ol material can duplicate the results<br />
achievable with single-crystal diamond.<br />
Like the name suggests, SCD is a solid<br />
crystal made from tightly packed carbon<br />
a<strong>to</strong>ms. Using special equipment and techniques,<br />
SCDs are shaped in<strong>to</strong> <strong>to</strong>ols whose<br />
cutting edges have no apparent chips at mag-<br />
Single-crystal diamond vs. other cutting <strong>to</strong>ol materials<br />
Surface fi nish Mirror fi nish: R a<br />
0.5µin. or better<br />
All images: Chardon Tool<br />
Prior <strong>to</strong> milling this copper, high-pressure manifold<br />
with a diamond-tipped carbide insert, shop<br />
personnel hand-lapped the sealing surfaces with<br />
a series of fine abr<strong>as</strong>ives. One SCD <strong>to</strong>ol can cut<br />
hundreds of parts, saving many hours of laborintensive<br />
processing.<br />
nifi cation up <strong>to</strong> 1,200× and exhibit extremely<br />
good wear resistance. Additionally, an SCD<br />
can be vacuum-brazed <strong>to</strong> almost any carbide<br />
insert.<br />
To use or not<br />
Choosing whether or not <strong>to</strong> apply SCD<br />
<strong>to</strong>ols depends on a number of fac<strong>to</strong>rs. Th e<br />
following questions and answers are intended<br />
SCD 1 PCD 2 PCD Coating WC 3 PCBN 4<br />
Depends on PCD<br />
grade: R a 2µin <strong>to</strong><br />
32µin.<br />
R a 16 <strong>to</strong> 32 µin. R a 16 <strong>to</strong> 32 µin. Depends on PCBN<br />
grade: R a 1µin <strong>to</strong> 32<br />
µin.<br />
Accuracy Submicron 2µm <strong>to</strong> 5µm 2µm <strong>to</strong> 5µm 2µm <strong>to</strong> 10µm 2µm <strong>to</strong> 5µm<br />
Wear resistance<br />
(compared <strong>to</strong> WC)<br />
50× <strong>to</strong> 1000× 10× <strong>to</strong> 100× 5× <strong>to</strong> 50× 1× 10× <strong>to</strong> 50×<br />
Workpiece materials Aluminum, br<strong>as</strong>s,<br />
bronze, copper,<br />
crystalline materials<br />
(including silicon, zinc<br />
selenide and germanium),<br />
graphite, metalmatrix<br />
composites,<br />
nickel and polymers<br />
Aluminum, br<strong>as</strong>s,<br />
bronze, copper,<br />
fi berboard, fi bergl<strong>as</strong>s,<br />
graphite, graphite<br />
composites, Kevlar,<br />
metal-matrix composites<br />
and polymers<br />
1 Single-crystal diamond. 2 Polycrystalline diamond. 3 Tungsten carbide. 4 Polycrystalline cubic boron nitride.<br />
Aluminum, br<strong>as</strong>s,<br />
bronze, copper,<br />
graphite, graphite<br />
composites, metalmatrix<br />
composites,<br />
and polymers<br />
Aluminum, br<strong>as</strong>s,<br />
bronze, copper, c<strong>as</strong>t<br />
iron, fi berboard,<br />
fi bergl<strong>as</strong>s, graphite,<br />
Kevlar, polymers, steel,<br />
titanium and wood<br />
Chilled c<strong>as</strong>t iron,<br />
hardened <strong>to</strong>ol and<br />
mold steels
<strong>to</strong> help you decide if an SCD <strong>to</strong>ol is<br />
right for your application.<br />
When should I use SCD <strong>to</strong>ols?<br />
When superior surface fi nish, part precision<br />
and long <strong>to</strong>ol life are required.<br />
Depending on the machine <strong>to</strong>ol, it’s<br />
possible <strong>to</strong> achieve a surface fi nish of<br />
R a 0.5μin. or better with an SCD. Th e<br />
structure of diamond is such that it can<br />
be sharpened <strong>to</strong> an almost perfect cutting<br />
edge. Th is unique property lets it<br />
produce mirror-like fi nishes. Diamond<br />
is also the hardest and most abr<strong>as</strong>ionresistant<br />
substance known, allowing<br />
it <strong>to</strong> outl<strong>as</strong>t carbide <strong>to</strong>ols by 1,000:1 in<br />
certain applications.<br />
How do I know if my machine <strong>to</strong>ol<br />
is rigid enough for SCD <strong>to</strong>ols? Spindles<br />
should run quietly and be free from<br />
vibration. Slideways and lead screws<br />
must have minimal slop and backl<strong>as</strong>h.<br />
Most modern CNC machines meet<br />
these requirements, making them suitable<br />
<strong>to</strong> run SCD <strong>to</strong>ols. Styles are available<br />
for turning, facing, grooving,<br />
milling, spot facing, fl ycutting, boring<br />
and trepanning.<br />
What kind of materials can I ma-<br />
The shop that made this aluminum airframe<br />
c<strong>as</strong>ting w<strong>as</strong> hand lapping the part’s difficult<strong>to</strong>-reach<br />
locating pads. Each surface had<br />
<strong>to</strong> be inspected. The company installed<br />
a diamond-tipped insert in<strong>to</strong> its existing<br />
<strong>to</strong>oling and facemilled the part. This<br />
eliminated all hand work, and the process<br />
is now so repeatable that quality-control<br />
requirements are met with batch checks.<br />
chine? Just about any nonferrous<br />
metal—including aluminum, copper<br />
and br<strong>as</strong>s—<strong>as</strong> well <strong>as</strong> pl<strong>as</strong>tics and many<br />
kinds of crystals. SCD is not suitable for<br />
By Hugh McAllister,<br />
Chardon Tool<br />
metals that contain iron.<br />
What kind of feeds and speeds<br />
should I use? In general, SCD <strong>to</strong>ols are<br />
for fi ne fi nishing, so light cuts are the<br />
micromanufacturing.com | 23
24 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
ABOUT<strong>to</strong>oling<br />
rule. Depths of cut range from 0.0001" <strong>to</strong> 0.001". Feed rates<br />
depend on the <strong>to</strong>ol tip radius and desired surface fi nish. A<br />
good starting point for the feed is 0.400 ipm. Due <strong>to</strong> the cutting<br />
edge’s sharpness, cutting speed is not overly important.<br />
However, 1,000 sfm is a good initial speed.<br />
What about coolant? Users can opt for spray mist or<br />
microdrop lubrication. If fl ood coolant is used, it should<br />
be fi ne-fi ltered <strong>to</strong> remove swarf and fi nes that can become<br />
trapped between the cutting edge and workpiece surface.<br />
Th ese particles can chip the cutting edge or degrade the<br />
surface fi nish.<br />
Is an SCD <strong>to</strong>ol expensive? Th e initial cost is signifi cantly<br />
higher than for a normal cutting <strong>to</strong>ol. A typical diamondtipped<br />
insert sells for approximately $300. However, utilizing<br />
SCD <strong>to</strong>ols can often eliminate costly, time-consuming lapping,<br />
polishing, honing and buffi ng of parts that have stringent<br />
requirements for<br />
geometric-form accuracy<br />
and surface fi nish.<br />
Moreover, SCD <strong>to</strong>ols<br />
can be resharpened<br />
many times, and at a<br />
relatively low cost.<br />
What else do I need<br />
<strong>to</strong> know before cutting<br />
with SCD? Because of<br />
its extreme hardness,<br />
SCD is brittle. Care<br />
must be taken when<br />
handling <strong>to</strong>ols. Don’t<br />
<strong>to</strong>uch the cutting edge<br />
with fi ngers, dirty chip<br />
brushes or rags. When<br />
not in use, the <strong>to</strong>ols<br />
should be kept in their<br />
protective packaging.<br />
Workholding and<br />
An end user w<strong>as</strong> machining this<br />
housing for an underwater camera on<br />
a conventional CNC lathe. The domes<br />
were hand-polished <strong>to</strong> make them<br />
optically clear. The end user installed<br />
a diamond <strong>to</strong>ol <strong>to</strong> make several fine<br />
finishing cuts, a move that eliminated<br />
the labor-intensive polishing process.<br />
<strong>to</strong>olholding devices should be rigid and tight. Vibration is one<br />
of the main causes of excessive SCD wear and poor cutting<br />
performance.<br />
When possible, use a noncontact <strong>to</strong>ol-presetting system. If<br />
that’s not possible, place a pl<strong>as</strong>tic shim between the diamond<br />
and the surface of the preset device <strong>to</strong> avoid hard contact.<br />
SCD isn’t for everyone or every job, of course. Th e machine<br />
<strong>to</strong>ol must be in good condition, the workpiece material<br />
must be of good quality and the opera<strong>to</strong>r needs <strong>to</strong> be<br />
trained on <strong>to</strong>ol usage. But when mirror-like fi nishes and submicron<br />
accuracies are required, an SCD might be the <strong>to</strong>ol <strong>to</strong><br />
turn <strong>to</strong>. µ<br />
About the author: Hugh McAllister is sales engineer at Chardon<br />
(Ohio) Tool, a producer of diamond <strong>to</strong>ols for ultraprecision<br />
machining applications. Telephone: (440) 286-6440. E-mail:<br />
hmcallister@chardon<strong>to</strong>ol.com. Web site: www.chardon<strong>to</strong>ol.com.
New Directions<br />
MEMS suppliers adopt new design strategies<br />
Cover S<strong>to</strong>ry<br />
Microelectromechanical systems are very<br />
small, which is one re<strong>as</strong>on they’re a big<br />
challenge <strong>to</strong> design. Designers are meeting the<br />
challenge in a variety of ways, including application<br />
of new engineered materials, software <strong>to</strong>ols<br />
and testing techniques.<br />
What’s more, designers are employing strategies<br />
<strong>to</strong> expedite the process of producing new<br />
MEMS devices, such <strong>as</strong> minimizing component<br />
By William Leven<strong>to</strong>n<br />
interactions, making use of generic designs and<br />
modifying existing MEMS designs <strong>to</strong> improve<br />
manufacturability.<br />
Some MEMS designers are also benefi ting<br />
from a broader <strong>view</strong> of what can be a narrowly<br />
focused process. Th ese designers are paying attention<br />
<strong>to</strong> critical are<strong>as</strong> like <strong>as</strong>sembly and packaging,<br />
<strong>as</strong> well <strong>as</strong> reaching out for important input<br />
from colleagues outside the design offi ce.<br />
Microvision Inc.<br />
micromanufacturing.com | 25
New Directions continued<br />
Material advances<br />
Perhaps nothing affecting MEMS<br />
design is experiencing more rapid<br />
and profound change than materials.<br />
New engineered silicon-on-insula<strong>to</strong>r<br />
materials include through-silicon vi<strong>as</strong><br />
(TSVs) <strong>to</strong> significantly reduce device<br />
footprints. TSVs connect <strong>to</strong> external<br />
devices via solder bumps, eliminating<br />
the need <strong>to</strong> make electrical connections<br />
with wires and bond pads that can clutter<br />
chips, explained David Buckley, vice<br />
president of sales and marketing for Micralyne<br />
Inc., a MEMS foundry in Edmon<strong>to</strong>n,<br />
Alberta.<br />
Micralyne also works with proprietary<br />
engineered materials known <strong>as</strong> Glancing<br />
Angle Deposition fi lms. GLAD is a<br />
patented, thin-fi lm fabrication process<br />
developed by Micralyne and the GLAD<br />
Labora<strong>to</strong>ry at the University of Alberta.<br />
GLAD diff ers from traditional thin fi lm<br />
deposition techniques by using highly<br />
oblique deposition angles that produce<br />
tilted-column nanostructures on substrates.<br />
By creating millions of these<br />
columns on a substrate, GLAD greatly<br />
incre<strong>as</strong>es the active surface area, making<br />
it more sensitive and, t<strong>here</strong>by, incre<strong>as</strong>ing<br />
its ability <strong>to</strong> detect various substances.<br />
Th is can be an advantage in life sciences<br />
26 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
and other applications, Buckley noted.<br />
MEMS material options have also expanded<br />
<strong>to</strong> include silicon carbide and<br />
diamond, which can withstand higher<br />
temperatures than regular silicon, according<br />
<strong>to</strong> Keith Ortiz, manager of MEMS<br />
technologies for Sandia National Labora<strong>to</strong>ries<br />
in Albuquerque, N.M. Th is makes<br />
them suitable for devices such <strong>as</strong> sensors<br />
that me<strong>as</strong>ure temperatures in the hot<br />
compartments of jet engines.<br />
On the downside, Ortiz added, sili-<br />
HT Micro Analytical Inc.<br />
HT Micro impact switch device, a p<strong>as</strong>sive omnidirectional acceleration switch that me<strong>as</strong>ures<br />
2mm × 2mm × 1mm, w<strong>as</strong> developed in conjunction with the U.S. Army for fuzing<br />
applications.<br />
No software t<strong>as</strong>k is more<br />
important <strong>to</strong> the MEMS<br />
design process than<br />
simulation.<br />
con carbide and diamond are less reactive<br />
than silicon, making them diffi cult <strong>to</strong><br />
etch during a MEMS-fabrication process.<br />
As for metals, MEMS designers are<br />
moving away from traditional monolithic<br />
materials and <strong>to</strong>ward alloys, noted Paul<br />
Rubel, vice president of design and product<br />
development for Innovative Micro<br />
Technology (IMT), which off ers contract<br />
MEMS manufacturing and design<br />
services in Santa Barbara, Calif. Unlike<br />
monolithic materials, gold, copper and<br />
nickel alloys off er long-term resistance<br />
<strong>to</strong> creep, <strong>as</strong> well <strong>as</strong> greater conductivity<br />
and hardness, added Rubel.<br />
At HT MicroAnalytical Inc., Albuquerque,<br />
an electrodeposition process is<br />
used <strong>to</strong> produce metal alloys for MEMS<br />
devices. Research h<strong>as</strong> shown that electrodeposition<br />
can alter the microstructures<br />
of materials in order <strong>to</strong> change mechanical<br />
characteristics such <strong>as</strong> yield strength<br />
and fatigue resistance, said Todd Christenson,<br />
HT Micro’s vice president and<br />
chief technology offi cer.<br />
Christenson said that one metal alloy<br />
produced in this manner offers yield<br />
strength of more than 1GPa and can handle<br />
more than 10 million cycles at a stress<br />
of more than 1,000 MPa. HT Micro uses<br />
the alloy <strong>to</strong> make microminiature fl exures<br />
for impact switches.<br />
In addition <strong>to</strong> metals and silicon,<br />
MEMS designers are taking advantage of<br />
the special properties of polymers. For example,<br />
Rubel said designers are beginning<br />
<strong>to</strong> use polyimides for structural components<br />
of complex 3-D MEMS devices that<br />
would be more diffi cult <strong>to</strong> make using silicon<br />
or metal. In addition, he said, SU-8 is<br />
becoming more common in the fabrication<br />
of MEMS parts. Th is pho<strong>to</strong>-imageable<br />
polymer becomes a hard, gl<strong>as</strong>s-like<br />
structure once cured, making it an eff ective<br />
structural material.<br />
Other polymers have what it takes <strong>to</strong><br />
be good actua<strong>to</strong>r materials.<br />
Electro-active polymers can undergo<br />
large amounts of deformation, making<br />
them suitable for artifi cial muscle actua<strong>to</strong>rs,<br />
according <strong>to</strong> Dan Popa, an <strong>as</strong>sistant<br />
professor of electrical engineering at Th e<br />
University of Tex<strong>as</strong> at Arling<strong>to</strong>n.<br />
Another new actua<strong>to</strong>r material is PZT,<br />
or lead zirconate titanate. A piezoelectric<br />
material, PZT changes shape when an external<br />
electric fi eld is applied. For microactua<strong>to</strong>r<br />
use, PZT off ers high precision<br />
and force output but very small displacement,<br />
Popa said. It also allows conversion<br />
of displacement in<strong>to</strong> voltage for energyharvesting<br />
applications.<br />
Software and MEMS design<br />
Like their counterparts in other fi elds,<br />
MEMS designers rely heavily on software<br />
for a variety of crucial t<strong>as</strong>ks. Among<br />
other things, the latest MEMS software<br />
can help engineers optimize designs <strong>to</strong><br />
achieve their goals.<br />
“If you have a device that heats something,<br />
[software] can help you fi gure out
w<strong>here</strong> <strong>to</strong> place the heater <strong>to</strong> get maximum<br />
effi ciency,” said Mary Ann Maher, CEO<br />
of SoftMEMS LLC, a MEMS software<br />
developer in Santa Clara, Calif.<br />
No software t<strong>as</strong>k is more important <strong>to</strong><br />
the MEMS design process than simulation,<br />
which is complicated by the fact that<br />
even relatively simple MEMS designs can<br />
involve a number of diff erent physical domains.<br />
MEMS designers deal with these<br />
situations by using so-called “multiphysics”<br />
simulation software from companies<br />
such <strong>as</strong> ANSYS, Comsol, Coven<strong>to</strong>r and<br />
IntelliSense.<br />
SoftMEMS LLC<br />
MEMS Xplorer from SoftMEMS is said <strong>to</strong><br />
have an intuitive user interface and provides<br />
MEMS-specific capabilities that reduce m<strong>as</strong>k<br />
layout time.<br />
If you start by trying <strong>to</strong><br />
do everything at once,<br />
you’ll get really confused,<br />
so start with a simple<br />
model.<br />
Even with this special software, however,<br />
it can be diffi cult <strong>to</strong> perform a multiphysics<br />
simulation. In some c<strong>as</strong>es, “you<br />
would need a Cray computer <strong>to</strong> do all the<br />
calculations,” IMT’s Rubel said. To simplify<br />
the process, designers sometimes<br />
break up the job in<strong>to</strong> smaller t<strong>as</strong>ks. When<br />
designing some electromagnetic devices,<br />
for example, IMT does separate magnetic<br />
simulations and then inputs that data in<strong>to</strong><br />
actua<strong>to</strong>r simulations.<br />
“If you start by trying <strong>to</strong> do everything<br />
at once, you’ll get really confused.<br />
Start with a simple model,” advised Micralynes’<br />
Buckley, who defi nes a simple<br />
model <strong>as</strong> one that takes in<strong>to</strong> account just<br />
one <strong>as</strong>pect of the design. MEMS devices<br />
are essentially “big mechanical structures<br />
made very small,” he added, so one way<br />
<strong>to</strong> start is by performing a relatively sim-<br />
ple mechanical analysis of the structure<br />
using fi nite element analysis (FEA). Th e<br />
mechanical analysis can be followed by<br />
separately modeling other physical <strong>as</strong>pects<br />
of the design. Finally, all the separate<br />
models can be combined in<strong>to</strong> the<br />
multiphysics model.<br />
To simplify matters further, MEMS designers<br />
may choose not <strong>to</strong> start with FEA,<br />
which can involve complex meshing and<br />
yield detailed simulation results. Instead,<br />
University of Tex<strong>as</strong>’ Popa said, designers<br />
can make “lumped model approximations”<br />
that don’t involve FEA. Lumped<br />
models break complex systems in<strong>to</strong> discrete<br />
components and approximate the<br />
behavior of the components. Th ese approximations<br />
can then be tied <strong>to</strong>gether<br />
<strong>to</strong> show how the entire system will work.<br />
The important difference between<br />
lumped model approximations and FEA<br />
is the number of nodes in the models.<br />
For example, an FEA model of a cantilever<br />
might have 100 or even 1,000 nodes,<br />
micromanufacturing.com | 27
New Directions continued<br />
Popa said. In such c<strong>as</strong>es, “if you wanted<br />
<strong>to</strong> look at 1,000 cantilevers with FEA, it<br />
would be prohibitively complicated and<br />
time consuming.” By contr<strong>as</strong>t, he noted,<br />
a lumped model can approximate a cantilever<br />
with just one node, greatly simplifying<br />
the t<strong>as</strong>k of studying the behavior of<br />
1,000 cantilevers at the same time.<br />
Physical testing<br />
Whatever method is employed,<br />
the key <strong>to</strong> a good simulation<br />
is using accurate material<br />
properties. But in many c<strong>as</strong>es,<br />
obtaining these properties is not<br />
simply a matter of looking them<br />
up somew<strong>here</strong>.<br />
“In the MEMS industry, t<strong>here</strong><br />
are a lot of thin fi lms and other<br />
materials being used that may<br />
not be well characterized,” Soft-<br />
MEMS’ Maher said. “So designers<br />
need good test structures <strong>to</strong><br />
make sure they’re putting accurate<br />
material information in<strong>to</strong><br />
their simulations.”<br />
Test structures help designers evaluate<br />
both the structural behavior and the reliability<br />
of new materials. Th ese test structures<br />
are much simpler than the MEMS<br />
devices being designed. For example,<br />
Rubel said, a designer might make a cantilever<br />
beam out of a certain material and<br />
then subject it <strong>to</strong> electrostatic force <strong>to</strong> see<br />
how much the beam deforms. Creating a<br />
simple beam <strong>to</strong> obtain this information<br />
is much e<strong>as</strong>ier and f<strong>as</strong>ter than building a<br />
pro<strong>to</strong>type of the entire device in order <strong>to</strong><br />
run the test.<br />
Testing also can be the best way <strong>to</strong> ob-<br />
28 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
tain other types of information critical <strong>to</strong><br />
MEMS design. Consider a designer who<br />
must determine the damping eff ects in<br />
an impact switch in order <strong>to</strong> produce a<br />
certain response time. One way <strong>to</strong> get the<br />
information is <strong>to</strong> use a computer simulation.<br />
But modeling an entire complex<br />
device structure “can take a long time,”<br />
Christenson said.<br />
So instead of going through a lengthy<br />
simulation process, he and his colleagues<br />
Micralyne Inc.<br />
Shown is a MEMS optical mirror produced by Micralyne using<br />
Micragem, which is a four-m<strong>as</strong>k lithography MEMS process. The<br />
starting point is a 500µm-thick gl<strong>as</strong>s wafer.<br />
at HT Micro create cells w<strong>here</strong> they use<br />
tests <strong>to</strong> obtain empirical information<br />
about damping behavior. If the fabrication<br />
process is relatively short and simple, test<br />
cells can yield key design data f<strong>as</strong>ter than<br />
simulation, he said.<br />
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In addition <strong>to</strong> proximity<br />
effects, the MEMS<br />
designer may fail <strong>to</strong><br />
account for the impact of<br />
<strong>as</strong>sembly and packaging.<br />
Similarly, Micralyne uses simple “short<br />
loop” experiments <strong>to</strong> help eliminate<br />
uncertainties. For example, suppose a<br />
MEMS design calls for an embedded<br />
structure 1.5μm wide, with an accuracy<br />
of ±50nm. To see if this design is manufacturable,<br />
Buckley said, “you can run the<br />
full fab process, which may take 8 weeks.<br />
Or you can just do one layer <strong>to</strong> see if you<br />
can hit those <strong>to</strong>lerances, which may take<br />
2 days and allows you <strong>to</strong> provide rapid<br />
feedback <strong>to</strong> the designer.”<br />
Simplifying the process<br />
Just <strong>as</strong> MEMS devices can be<br />
complex, so can the processes<br />
used <strong>to</strong> design and manufacture<br />
them. But t<strong>here</strong> are steps<br />
designers can take <strong>to</strong> simplify<br />
these processes, t<strong>here</strong>by saving<br />
time and money—not <strong>to</strong><br />
mention trouble. For instance,<br />
they can minimize or eliminate<br />
component interactions such <strong>as</strong><br />
pneumatic cross-talk so that the<br />
components can be considered<br />
independent of each other, which simplifi<br />
es design.<br />
At IMT, complications result when<br />
cus<strong>to</strong>mers insist on the use of materials<br />
and processes that are unfamiliar <strong>to</strong><br />
the company. Th ese cus<strong>to</strong>mers would be<br />
better off opting for one of IMT’s many<br />
“platforms,” which are generic or b<strong>as</strong>e<br />
MEMS designs, suggested Rubel. “Even<br />
though we may not have designed a particular<br />
product for a cus<strong>to</strong>mer before, we<br />
can use one of our platforms <strong>as</strong> a b<strong>as</strong>is<br />
for creating the product, taking a general<br />
architecture and adapting it <strong>to</strong> what<br />
the cus<strong>to</strong>mer wants,” he said. “To adapt<br />
Subscribe<br />
now
The tiny swimmer<br />
A “MICROSWIMMER” RESEMBLING a tiny fi sh w<strong>as</strong> this year’s<br />
winner in the novel design category of the 5th annual MEMS<br />
University Alliance Design Competition, sponsored by Sandia<br />
National Labora<strong>to</strong>ries. About the diameter of a human hair, the<br />
microswimmer h<strong>as</strong> an aluminum tail that moves back and forth<br />
when heated and cooled by bursts of microwave radiation.<br />
In the future, a medical device like the microswimmer could<br />
be used <strong>to</strong> travel in the human bloodstream, according <strong>to</strong> Tom<br />
Zipperian, Sandia senior microfabrication manager.<br />
The novel design category is for innovative designs that take<br />
advantage of the strengths of the Sandia Ultra-planar Multi-level<br />
MEMS Technology 5 (SUMMiT V) fabrication process, which<br />
that platform makes the design simpler,<br />
incre<strong>as</strong>es the probability of success and<br />
signifi cantly reduces costs.”<br />
By choosing a platform, MEMS designers<br />
also can make their devices e<strong>as</strong>ier<br />
<strong>to</strong> fabricate, because platforms are b<strong>as</strong>ed<br />
on products that have already been successfully<br />
manufactured. Th is allows IMT<br />
<strong>to</strong> take advantage of previously acquired<br />
manufacturing knowledge, Rubel noted.<br />
A broader <strong>view</strong><br />
MEMS devices are aff ected by many<br />
external fac<strong>to</strong>rs, both in production and<br />
in use, so designers must be sure not <strong>to</strong><br />
focus on a device operating in isolation.<br />
Such an approach fails <strong>to</strong> account for fac<strong>to</strong>rs<br />
like electrostatic eff ects or energy<br />
loss, which can be caused by wiring or<br />
other devices that are in close proximity<br />
<strong>to</strong> a MEMS device.<br />
Designers “have <strong>to</strong> simulate the environment<br />
of the device in addition <strong>to</strong> the<br />
device itself,” Maher said, adding that<br />
new software <strong>to</strong>ols allow designers <strong>to</strong><br />
evaluate so-called “proximity eff ects” on<br />
MEMS devices.<br />
In addition <strong>to</strong> proximity eff ects, the<br />
MEMS designer may fail <strong>to</strong> account for<br />
the impact of <strong>as</strong>sembly and packaging.<br />
According <strong>to</strong> some estimates, <strong>as</strong>sembly<br />
and packaging can account for up <strong>to</strong> 90<br />
percent of the cost of a MEMS device.<br />
Th ey also can have a signifi cant eff ect on<br />
the behavior of a device. “You may have<br />
a product that works great when it’s not<br />
packaged, but won’t work when it is packaged,”<br />
Popa said.<br />
Still, he added, the traditional approach<br />
is <strong>to</strong> deal with <strong>as</strong>sembly and packaging<br />
after the pro<strong>to</strong>type is created. But he said<br />
these two processes should be considered<br />
early in the design ph<strong>as</strong>e.<br />
New software can help designers do<br />
just that. In the p<strong>as</strong>t, separate software<br />
<strong>to</strong>ols were used <strong>to</strong> design the MEMS device,<br />
the device packaging and the accompanying<br />
electronics. While this allowed<br />
designers <strong>to</strong> optimize their particular<br />
parts of the system, “they couldn’t really<br />
see how <strong>to</strong> optimize the whole system,”<br />
Maher said.<br />
So SoftMEMS developed software that<br />
brings simulation up <strong>to</strong> the system level,<br />
linking FEA with electronics and packaging<br />
design. Th is allows people in diff erent<br />
are<strong>as</strong> <strong>to</strong> work <strong>to</strong>gether on a co-design,<br />
which can reduce design time and overall<br />
system costs, Maher said.<br />
Collaborative software <strong>to</strong>ols may be<br />
helpful, but they can’t take the place of<br />
an old-f<strong>as</strong>hioned meeting, according <strong>to</strong><br />
one industry observer.<br />
“Early in the design process, it’s imperative<br />
that you bring the whole team <strong>to</strong>gether,”<br />
said Roger Grace, a Florida-b<strong>as</strong>ed<br />
MEMS marketing consultant. In addition<br />
<strong>to</strong> the designers, the MEMS team<br />
includes those responsible for packaging,<br />
testing and manufacturing the device.<br />
During the meeting, all the attendees<br />
should provide their own special design<br />
input. For example, Grace said, “the<br />
testing people might tell the designers,<br />
‘If we’re going <strong>to</strong> test this thing, we need<br />
these kinds of pads on these devices.’ Or<br />
the packaging people might provide practical<br />
footprints for the design.”<br />
Of course, communication should be a<br />
continuing process throughout the design<br />
ph<strong>as</strong>e. But according <strong>to</strong> Grace, “the kickoff<br />
meeting is important, so everybody is<br />
on notice at the outset that this project is<br />
a team eff ort.” µ<br />
manufactures MEMS devices with fi ve levels of polysilicon.<br />
SUMMiT V w<strong>as</strong> used <strong>to</strong> make parts for the contest entrants.<br />
Sandia’s MEMS experts and university professors re<strong>view</strong>ed the<br />
designs and picked the winner.<br />
Contestants must come from schools that are members<br />
of the MEMS University Alliance, which is open <strong>to</strong> all U.S.<br />
institutions of higher learning. The alliance provides cl<strong>as</strong>sroom<br />
teaching materials and re<strong>as</strong>onably priced licenses for the use of<br />
Sandia’s SUMMiT V <strong>to</strong>ols. This makes it possible for universities<br />
lacking their own microfabrication facilities <strong>to</strong> offer a MEMS<br />
curriculum.<br />
—W. Leven<strong>to</strong>n<br />
Contribu<strong>to</strong>rs<br />
Roger Grace Associates<br />
(239) 596-8738<br />
www.rgrace.com<br />
HT MicroAnalytical Inc.<br />
(505) 341-0466<br />
www.htmicro.com<br />
Innovative Micro Technology (IMT)<br />
(805) 681-2800<br />
www.imtmems.com<br />
Micralyne Inc.<br />
(780) 431-4400<br />
www.micralyne.com<br />
Sandia National Labora<strong>to</strong>ries<br />
(505) 845-0011<br />
www.sandia.gov<br />
SoftMEMS LLC<br />
(408) 426-4301<br />
www.softmems.com<br />
University of Tex<strong>as</strong>, Arling<strong>to</strong>n<br />
Au<strong>to</strong>mation & Robotics<br />
Research Institute<br />
(817) 272-5900<br />
www.arri.uta.edu<br />
About the author:<br />
William Leven<strong>to</strong>n is<br />
a New Jersey-b<strong>as</strong>ed<br />
freelance writer.<br />
Telephone: (609)<br />
926-6447. E-mail:<br />
wleven<strong>to</strong>n@verizon.net.<br />
micromanufacturing.com | 29
Taking Form<br />
Electroforming use grows <strong>as</strong> complex electronic devices shrink<br />
30 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
By Lowell Thom<strong>as</strong> and Luke Volpe, Dynamics Research Corp., Metrigraphics Division<br />
As the drive <strong>to</strong> build smaller and more complex<br />
electromechanical devices (microdevices)<br />
continues, design engineers struggle<br />
<strong>to</strong> bridge the gap between traditional micromachining<br />
techniques, such <strong>as</strong> milling, l<strong>as</strong>er<br />
cutting and EDMing, and MEMS (microelectromechanical<br />
systems) technology.<br />
Specifi cally, design engineers are discovering<br />
that many products now in the design stage<br />
are <strong>to</strong>o small <strong>to</strong> be machined with traditional<br />
All images provided by Metrigraphics<br />
Four-layer micro induction coil with 12.5µm lines<br />
and spaces, 7µm-thick gold traces and 10µm-thick<br />
polyimide dielectric between traces.<br />
techniques and are not candidates for MEMS<br />
technology because of size, cost or material<br />
limitations.<br />
A combination of two mature technologies—electrochemical<br />
metal deposition and<br />
micron-level pho<strong>to</strong>lithography—have enabled<br />
the manufacture of 3-D microstructures that<br />
bridge the gap between traditional machining<br />
techniques and MEMS technology.<br />
Th e term “electroforming,” <strong>as</strong> used in this article,<br />
refers <strong>to</strong> the electrochemical deposition of<br />
a variety of conductive metals, including gold,<br />
copper, nickel and nickel/cobalt, in<strong>to</strong> a prefabricated<br />
mold, usually an ultraviolet-imagable<br />
pho<strong>to</strong>resist. Th e technology forms freestanding<br />
or linked multilevel microstructures, sometimes<br />
referred <strong>to</strong> <strong>as</strong> 3-D micros, with microsized<br />
features.<br />
With its ability <strong>to</strong> create ultrafi ne features,<br />
electroforming h<strong>as</strong> replaced EDMing and conventional<br />
machining in some applications. However,<br />
the strength of this new technology is not<br />
in replacing other techniques but in enabling<br />
new part designs.<br />
Th is article discusses electroforming technology<br />
and limitations, specifi c application are<strong>as</strong><br />
and development trends.<br />
Technology’s foundation<br />
As stated, electroforming creates 3-D structures<br />
by electrochemically depositing a metal<br />
in<strong>to</strong> a pho<strong>to</strong>resist mold. B<strong>as</strong>ic process steps are<br />
<strong>as</strong> follows (see illustration on page 32):<br />
1. A carrier plate is prepared by sputter<br />
depositing a thin (less than 5,000 angstroms)<br />
adhesive/conductive seed metal<br />
layer on<strong>to</strong> a gl<strong>as</strong>s blank, or other suitable<br />
b<strong>as</strong>e material.<br />
2. A pho<strong>to</strong>resist mold of the intended structure<br />
is created. Th e mold is formed by depositing<br />
and imaging the X- and Y-plane<br />
features of the intended structure in<strong>to</strong><br />
a UV-sensitive pho<strong>to</strong>resist on the seed<br />
metal coated gl<strong>as</strong>s carrier.<br />
3. Th e desired metal is electrochemically<br />
deposited in<strong>to</strong> the pho<strong>to</strong>resist mold prepared<br />
in step 2 above.<br />
4. Th e pho<strong>to</strong>resist mold is removed from<br />
the gl<strong>as</strong>s carrier plate.<br />
5. Finally, the completed electroformed<br />
microstructure is removed from the carrier<br />
plate.<br />
Multilayer structures are formed by repeating<br />
the above steps. Th is process is capable of creating<br />
3-D microstructures with features—posts,<br />
channels and grooves—<strong>as</strong> small <strong>as</strong> 0.005mm.<br />
Funnel-shaped through-holes <strong>as</strong> small <strong>as</strong><br />
0.001mm in diameter are possible.<br />
Th e X- and Y-plane dimensions are controlled<br />
by the pho<strong>to</strong>resist process. Th e Z-axis dimensions,<br />
such <strong>as</strong> post and wall heights, channel<br />
depths and wall profi les, are controlled and<br />
restricted by the pho<strong>to</strong>resist <strong>as</strong>pect ratio. Th e
<strong>as</strong>pect ratio is equal <strong>to</strong> the maximum<br />
height (Z dimension) divided by the minimum<br />
feature width (X or Y dimension).<br />
For example, a 0.010mm-dia. ×<br />
0.030mm-high post would have an <strong>as</strong>pect<br />
ratio of 3:1. Maximum X and Y dimensions<br />
can be 25mm, and generally are<br />
less than 1mm or 2mm.<br />
Th e current generation of 3-D microstructures<br />
made by microforming fall in<strong>to</strong><br />
the dimensional realm described above<br />
and are used for a variety of applications,<br />
including medical devices, magnetic induction<br />
coils for RF coupling, data transfer,<br />
microfl uidic molds and integrated<br />
circuit manufacturing.<br />
To date, electroforming h<strong>as</strong> been successfully<br />
implemented in many applications,<br />
enabling the development of<br />
diverse structures not possible with other<br />
micromanufacturing technologies. (See<br />
Figures 1, 2 and 3 for examples of electroformed<br />
devices and features.)<br />
However, current electroforming technology<br />
faces challenges in terms of minimum<br />
structure size, maximum structural<br />
<strong>as</strong>pect ratio, number of possible layers,<br />
fl exibility issues related <strong>to</strong> multilayer devices<br />
and manufacturing cost. Future<br />
applications could also require dielectric<br />
coatings or interlayers not currently available.<br />
(Note: Dielectric isolation h<strong>as</strong> always<br />
been required for 3-D microstructures<br />
used in electrical applications. Current<br />
challenges in applying dielectric coatings<br />
on microstructures include coating uniformity<br />
and the inability <strong>to</strong> coat the structure’s<br />
carrier side. As structures become<br />
smaller, it will be essential <strong>to</strong> uniformly<br />
overcoat the entire 3-D structure.)<br />
Pho<strong>to</strong>resist<br />
Several pho<strong>to</strong>resist materials exist that<br />
are capable of resolving 0.010mm structural<br />
features with <strong>as</strong>pect ratios of 3:1 (5:1<br />
<strong>as</strong>pect ratio structures are possible with<br />
some restrictions). Pho<strong>to</strong>resist materials<br />
that allow higher <strong>as</strong>pect ratios for smaller<br />
feature sizes could improve the functionality<br />
of existing devices and enable new<br />
applications.<br />
Figure 1: RF coupling device. Figure 2: Funnel-shaped orifice hole.<br />
Future device-design engineers will<br />
be looking <strong>to</strong> build structures with minimum<br />
feature sizes in the 0.002mm <strong>to</strong><br />
0.005mm range with 5:1 <strong>to</strong> 10:1 <strong>as</strong>pect<br />
ratios.<br />
Once the electroformed metal deposition<br />
h<strong>as</strong> been completed, the pho<strong>to</strong>resist<br />
mold must be chemically removed,<br />
a process known <strong>as</strong> stripping, or dissolving.<br />
Removability h<strong>as</strong> a signifi cant eff ect<br />
micromanufacturing.com | 31
Taking Form continued<br />
on minimum aperture, or blind-hole size,<br />
<strong>as</strong> well <strong>as</strong> on isolated cavities in multilevel<br />
structures. As blind-holes and isolated<br />
cavities become smaller, the ability<br />
of solvent chemistry <strong>to</strong> penetrate holes<br />
and cavities becomes an issue.<br />
Some pho<strong>to</strong>resists are available that<br />
can resolve higher <strong>as</strong>pect ratios, but, <strong>to</strong><br />
date, these materials are limited by solubility<br />
characteristics, or stripping issues.<br />
However, most manufacturers of pho<strong>to</strong>resists<br />
are developing solutions <strong>to</strong> these<br />
challenges.<br />
Imaging method<br />
Th e imaging method (UV) also h<strong>as</strong> a<br />
signifi cant eff ect on <strong>as</strong>pect ratio and feature<br />
characteristics, such <strong>as</strong> wall angle<br />
and uniformity. Th ere are two traditional<br />
imaging methods.<br />
Th e predominant method is contact<br />
printing. With this approach, a pho<strong>to</strong>graphic<br />
m<strong>as</strong>k containing multiple, reverse-polarity<br />
images of the structure <strong>to</strong><br />
be built is placed in intimate contact with<br />
the pho<strong>to</strong>resist-coated carrier plate. Th e<br />
carrier plate/pho<strong>to</strong>resist/m<strong>as</strong>k stack is<br />
exposed <strong>to</strong> a collimated UV light source.<br />
Depending on the type of resist used, the<br />
UV-exposed pho<strong>to</strong>resist will either be<br />
cross linked or made soluble so the retained<br />
pho<strong>to</strong>resist will form the desired<br />
mold cavity.<br />
Th is system is economical, relatively<br />
e<strong>as</strong>y <strong>to</strong> use and can create a full sheet of<br />
hundreds—possibly thousands—of mold<br />
cavities with a single exposure. However,<br />
UV intensity variation over the m<strong>as</strong>k area<br />
and defects caused by m<strong>as</strong>k contact with<br />
the pho<strong>to</strong>resist can reduce product yield.<br />
Th e second method is projection-imaging<br />
stepping (repeating). Devices made<br />
with this method are used extensively<br />
in the integrated-circuit and fl at-panel<br />
display industries. Th ese systems use<br />
a single-structure image m<strong>as</strong>k at some<br />
magnifi cation that is projected through<br />
a reduction lens on<strong>to</strong> and in<strong>to</strong> the pho<strong>to</strong>resist<br />
plane (b<strong>as</strong>e carrier plate coated<br />
with pho<strong>to</strong>resist).<br />
Th e UV source is positioned behind<br />
the single-image m<strong>as</strong>k with a shutter<br />
mechanism between them. Every time<br />
the shutter opens, a single unit structure<br />
is exposed. When the shutter is closed, an<br />
interferometer-controlled, movable stage<br />
repositions the b<strong>as</strong>e carrier plate.<br />
32 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
2.a<br />
2.b<br />
2.c<br />
Second-level m<strong>as</strong>k<br />
2.d<br />
Second-level<br />
pho<strong>to</strong>resist mold<br />
2.e<br />
2.f<br />
Precision electroforming process<br />
Gl<strong>as</strong>s Carrier<br />
Th e advantages of this system are that<br />
higher-resolution, concentrated UV<br />
power permits deeper exposure, result-<br />
Unexposed pho<strong>to</strong>resist<br />
Seed metal<br />
UV expose First-level pho<strong>to</strong> m<strong>as</strong>k<br />
Imaged pho<strong>to</strong>resist<br />
Gl<strong>as</strong>s Carrier<br />
First-level<br />
electroplated metal<br />
Gl<strong>as</strong>s Carrier<br />
Gl<strong>as</strong>s Carrier<br />
Seed metal<br />
Second-level seed metal<br />
Pho<strong>to</strong>resist mold<br />
UV expose Second-level imaged<br />
pho<strong>to</strong>resist<br />
Second-level seed metal<br />
Second-level electroplated metal<br />
Gl<strong>as</strong>s Carrier<br />
Gl<strong>as</strong>s Carrier<br />
Completed second-level electroformed microstucture<br />
before being removed from gl<strong>as</strong>s carrier<br />
Figure 3: Monofilament/microlens holder.<br />
ing in a higher <strong>as</strong>pect-ratio capability<br />
and greater image-<strong>to</strong>-image consistency<br />
for UV exposures. Th e system is also
The quest for smaller microelectronic devices<br />
ONE OF THE CRITICAL ISSUES in the<br />
quest for smaller, more complex medical<br />
and telecommunication devices is the<br />
integrated circuit chip interconnect system.<br />
Because of size, biocompatibility and<br />
fl exibility requirements, traditional<br />
fl ex circuit and PC board technologies<br />
are typically not suitable for these devices.<br />
The current generation of<br />
medically implantable telemetric and<br />
telecommunication microdevices<br />
are b<strong>as</strong>ed on extreme-resolution,<br />
microfl exible-interconnect (ERMF)<br />
circuits. This technology depends on<br />
micropho<strong>to</strong>lithography, thin-fi lm sputterdeposited<br />
b<strong>as</strong>e metals, electrochemically<br />
deposited metal (usually noble) traces,<br />
biocompatible polyimide substrates and<br />
dielectric interlayers.<br />
Minimum signal trace and space<br />
dimensions are 3µm <strong>to</strong> 5µm. For<br />
applications requiring signifi cant current<br />
density, high-<strong>as</strong>pect ratio trace cross<br />
sections allow higher current-carrying<br />
capacity and minimize overall circuit area.<br />
ERMF circuits may have a single<br />
conduc<strong>to</strong>r level or <strong>as</strong> many <strong>as</strong> six<br />
conduc<strong>to</strong>r levels, depending on device<br />
complexity.<br />
To date, ERMF circuits have been<br />
successfully used in several intrusive<br />
and implantable medical applications,<br />
such <strong>as</strong> ultr<strong>as</strong>onic angiopl<strong>as</strong>ty probes,<br />
blood glucose moni<strong>to</strong>ring systems and<br />
developmental retinal implants.<br />
Other, more complex ERMF circuitb<strong>as</strong>ed<br />
medical devices are being<br />
developed, such <strong>as</strong> permanently<br />
implanted RF coupling (data transfer)<br />
moni<strong>to</strong>ring systems and more complex<br />
cardiac moni<strong>to</strong>ring probes.<br />
The success of these and other<br />
still unidentifi ed medical and<br />
telecommunication applications may<br />
depend on yet unresolved or identifi ed<br />
ERMF manufacturing issues. These issues<br />
relate <strong>to</strong> materials and manufacturing<br />
technology.<br />
Liquid-state polyimide is generally<br />
considered the material of choice for<br />
ERMF circuits. This material, when<br />
c<strong>as</strong>t and completely cured, typically<br />
h<strong>as</strong> adequate dielectric strength in<br />
thicknesses above 0.015mm. As the<br />
circuits become more complex and<br />
require more trace layers, the fl exibility<br />
of the stack can become an issue. One<br />
possible solution includes improving the<br />
intrinsic dielectric properties of the cured<br />
polyimide, allowing for thinner dielectric<br />
interlayers. Thinner dielectric layers<br />
will improve the fl exibility of the cured<br />
material.<br />
One method of manufacturing utilizes<br />
UV pho<strong>to</strong>-imagable polyimide <strong>to</strong> create<br />
via holes. This process can create an<br />
entire sheet of hundreds, possibly<br />
thousands, of holes with a one-pho<strong>to</strong><br />
process. Using this process, however,<br />
imaged via hole wall angles may be<br />
diffi cult <strong>to</strong> control and the process can<br />
produce random, poor or nonexistent<br />
continuity interlayer interconnects.<br />
Current ERMF manufacturing processes<br />
specify l<strong>as</strong>er drilling <strong>to</strong> create via holes.<br />
This process creates clean, slag-free holes<br />
<strong>as</strong> small <strong>as</strong> 0.015mm in diameter with<br />
cured and planarized deposited polyimide<br />
predrilling. L<strong>as</strong>er-drilled holes also have<br />
positively tapered wall angles that ensure<br />
complete metal coverage and reliable<br />
continuity. However, this process may not<br />
be cost effective without semi-au<strong>to</strong>mated<br />
or fully au<strong>to</strong>mated equipment.<br />
Investments in manufacturing<br />
development are being evaluated that<br />
could help ERMF technology reach its<br />
full potential. The following issues are<br />
currently under evaluation:<br />
■ The standard 6-sq.-in. panel size<br />
restricts high-volume production; 12-sq.in.<br />
or round panels will be required.<br />
■ Chemical mechanical planarization<br />
will be required <strong>to</strong> guarantee fl atness<br />
and planarity on each layer of multilayer<br />
structures. This process is only suitable<br />
with l<strong>as</strong>er via drilling.<br />
■ I/O bonding pads must<br />
accommodate processes such <strong>as</strong> pickand-place<br />
<strong>as</strong>sembly and fl ip chip/solder<br />
refl ow.<br />
■ The circuit-manufacturing process<br />
must be au<strong>to</strong>mated <strong>to</strong> reduce the cost<br />
per circuit for high-volume manufacturing<br />
operations.<br />
— L. Thom<strong>as</strong> and L. Volpe<br />
micromanufacturing.com | 33
Taking Form continued from page 32<br />
suitable for high-volume manufacturing.<br />
Its main disadvantage is that it requires<br />
a major capital investment. State-of-theart<br />
projection steppers cost $1 million<br />
and up, but some used equipment may<br />
be available now, or in the future, at signifi<br />
cantly lower cost.<br />
Any discussion relating <strong>to</strong> high-<strong>as</strong>pect-ratio<br />
imaging systems would be incomplete<br />
without mention of LIGA, a<br />
process named for the German acronym<br />
for lithographie, galvanoformung and abformung<br />
(lithography, electroplating and<br />
molding). LIGA is b<strong>as</strong>ed on synchrotron,<br />
hard X-ray exposure of polymethyl methacrylate<br />
(PMMA). Although this system<br />
can resolve extremely high-<strong>as</strong>pect-ratio<br />
images (50:1 and greater), t<strong>here</strong> are a limited<br />
number of synchrotron beam lines<br />
available and these are extremely costly<br />
<strong>to</strong> operate. (Synchrotron radiation is<br />
electromagnetic radiation accelerated <strong>to</strong><br />
speeds approaching that of light.)<br />
Such systems cost hundreds of millions<br />
of dollars, depending on the <strong>to</strong>tal<br />
size and number of beam lines. Th ere are<br />
only four synchrotrons in the U.S., and<br />
they are all <strong>as</strong>sociated with large institutions,<br />
such <strong>as</strong> national labora<strong>to</strong>ries and<br />
large universities.<br />
On a more practical level, continuing<br />
labora<strong>to</strong>ry testing of newly developed<br />
pho<strong>to</strong>resist materials will enable higher<br />
<strong>as</strong>pect ratios using more conventional exposure<br />
and developing techniques.<br />
Multilevel stacking<br />
B<strong>as</strong>ed on recent trends, future 3-D<br />
microstructures will become more complex,<br />
requiring multilayer structures. Th e<br />
current multilevel stack limit is between<br />
three and fi ve levels, depending on the<br />
criticality of individual stack thickness<br />
and fl atness specifi cations, minimum<br />
feature size and <strong>as</strong>pect ratio. (See Figures<br />
4 and 5 for examples of multilayer<br />
structures.)<br />
Th e critical issues in the stacking process<br />
are previous-layer uniformity, pho<strong>to</strong>resist<br />
coating uniformity and precision<br />
of m<strong>as</strong>k alignment <strong>to</strong> the previously electroformed<br />
layer.<br />
Plating uniformity is a key part of this<br />
process. Plating uniformity is a function<br />
of the anode and cathode positional relationship<br />
(in this system, the cathode is<br />
the sheet of 3-D structures being built)<br />
34 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Figure 4: Two-level, magnetically activated switching device. The cross-section of the three<br />
serpentine springs is 0.050mm × 0.050 mm.<br />
Figure 5: Positive-locking, two-level contact interconnect.<br />
Figure 6: Two-level solid gold implantable<br />
capillary device.<br />
and current density uniformity.<br />
Th e geometry of the structure being<br />
plated determines current density uniformity.<br />
Practically all 3-D microstructures<br />
have varying geometric (X- and<br />
Y-plane) shapes and sizes. Th is X- and<br />
Y-plane variation is unique <strong>to</strong> each particular<br />
microstructure pattern.<br />
Unfortunately, one of the<br />
significant causes of nonuniform<br />
plating is pattern<br />
geometry variation. All microstructure-plating<br />
layers and<br />
thicknesses have some nonuniformity,<br />
the overriding<br />
multiple-level structure limitation.<br />
Nonuniform electrodeposited<br />
thicknesses cause<br />
imprecise alignment, and<br />
nonuniform plating in subsequent<br />
layers exaggerates<br />
the problem. As the number<br />
of required structural layers<br />
incre<strong>as</strong>es, structural geometries<br />
become dis<strong>to</strong>rted and<br />
overall thickness <strong>to</strong>lerances cannot be<br />
maintained.<br />
A planarizing technology called chemical<br />
mechanical planarization (CMP)<br />
combines chemical etching and abr<strong>as</strong>ive<br />
polishing. It allows dissimilar materials,<br />
such <strong>as</strong> an electrochemically deposited<br />
metal and pho<strong>to</strong>resist, <strong>to</strong> be planarized,<br />
or polished, <strong>to</strong> microfl atness. Th is planarization<br />
process addresses the multilevel<br />
limiting issues stated above. CMP is<br />
a mature technology but is used sparingly<br />
in multilevel microstructure manufacturing<br />
because of cost.<br />
As the demand for higher volume<br />
and more complex multilevel devices incre<strong>as</strong>es,<br />
chemical mechanical planarization<br />
will be required. In-house CMP<br />
continued on page 51
ICOMM<br />
5 th INTERNATIONAL CONFERENCE ON<br />
2010<br />
MICROMANUFACTURING
Clean Machining<br />
Clean room use growing <strong>to</strong> optimize specialized processes<br />
36 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
By Joel C<strong>as</strong>sola<br />
Clean Air Products<br />
Various types of clean rooms are available, including soft-sided, hard-walled and modular styles. Shown is the Series 591 portable clean<br />
room from Clean Air Products. The free-standing, modular, prefabricated clean rooms are available from Cl<strong>as</strong>s 100,000 <strong>to</strong> Cl<strong>as</strong>s 10 and<br />
feature open spans from 6’ <strong>to</strong> 34’.<br />
With incre<strong>as</strong>ing frequency, access <strong>to</strong> controlled<br />
environments for attenuating<br />
temperature, humidity, dust, dirt, particulates<br />
and microorganisms is essential for shops competing<br />
for high-end micromanufacturing jobs.<br />
His<strong>to</strong>rically, clean rooms were used primarily for<br />
cleaning, <strong>as</strong>sembly and packaging operations.<br />
Today, they are also being used <strong>to</strong> control potential<br />
contamination and improve accuracy within<br />
molding, machining and inspection operations.<br />
Th e following “cr<strong>as</strong>h course” on clean rooms<br />
is b<strong>as</strong>ed on inter<strong>view</strong>s with two clean room suppliers<br />
and three micromanufacturers that have<br />
installed them.<br />
When and why are clean rooms used for<br />
micromachining? Th e naïveté of this question<br />
made some of our respondents laugh. Clean<br />
rooms are typically used <strong>to</strong> keep the controlled<br />
environments cleaner than surrounding are<strong>as</strong>,<br />
and temperature and humidity within acceptable<br />
ranges. Th e room or enclosure may protect parts<br />
from the incursion of dust being blown from<br />
other parts with an air hose at nearby machining<br />
operations. As a result, most clean rooms<br />
are under positive pressure.<br />
However, the question is actually not <strong>as</strong> naïve<br />
<strong>as</strong> it sounds, because sometimes clean rooms<br />
and equipment enclosures are designed <strong>to</strong> keep
things in—such <strong>as</strong> dust from exotic work<br />
materials, chemical fumes and the like.<br />
Th ese rooms rely on negative pressure.<br />
Ambient temperature may be controlled<br />
because it aff ects dimensional control<br />
of molded and machined parts. For<br />
example, a 7° C shift in temperature can<br />
cause a <strong>to</strong>ol <strong>to</strong> grow or shrink by 0.01mm.<br />
Th at’s not much by conventional standards<br />
but poses real problems for parts<br />
manufactured <strong>to</strong> micron <strong>to</strong>lerances.<br />
Humidity can promote bacterial<br />
growth, cause parts <strong>to</strong> corrode or impede<br />
subsequent bonding operations.<br />
One manufacturer inter<strong>view</strong>ed strives<br />
<strong>to</strong> control humidity around his milling<br />
equipment <strong>to</strong> within 10 <strong>to</strong> 15 percent and<br />
may even put off some sensitive manufacturing<br />
operations during hot and humid<br />
summer days.<br />
Some clean rooms control electrostatic<br />
discharge, which can zap electronics by<br />
overloading tiny circuits with heavy transient<br />
charges, burning them out.<br />
Th e driver behind all of these considerations<br />
is the need <strong>to</strong> meet incre<strong>as</strong>ingly<br />
stringent cleanliness and precision requirements<br />
for a growing list of industries.<br />
All of the respondents agreed that<br />
most OEMs producing pristine or sterile<br />
products demand exceptionally clean<br />
parts, even though these OEMs may be<br />
cleaning, <strong>as</strong>sembling, fi lling and packaging<br />
the end product in their own clean<br />
room. Th ey appreciate, if not insist on,<br />
their suppliers having clean rooms so<br />
they don’t have <strong>to</strong> be <strong>as</strong> concerned about<br />
extraneous contamination entering their<br />
own processes.<br />
What types of manufacturers require<br />
clean rooms? Our respondents<br />
were happy <strong>to</strong> inform us that clean<br />
rooms are a growth business. Medical<br />
device, electronics, defense and aerospace<br />
component manufacturers are all<br />
big users. Th e trend <strong>to</strong>ward marrying a<br />
wide range of electromechanical devices<br />
(for instance, tiny windshield wiper mo<strong>to</strong>rs)<br />
with computer chips is currently<br />
driving a lively interest in clean rooms for<br />
both parts manufacturing and <strong>as</strong>sembly<br />
operations <strong>to</strong> ensure that the electronics<br />
are not compromised by the incursion<br />
of particles created during conventional<br />
manufacturing.<br />
Can clean rooms make a contribution<br />
<strong>to</strong> micromachining operations?<br />
Defi nitely. For example, the need <strong>to</strong> con-<br />
Keeping clean<br />
THE PART MANUFACTURERS inter<strong>view</strong>ed<br />
for this article offered the following<br />
perspectives on keeping their operations<br />
clean and under control.<br />
Made in a Cl<strong>as</strong>s 10,000 clean<br />
room. Albright Technologies, Leominster,<br />
M<strong>as</strong>s., built a Cl<strong>as</strong>s 10,000 clean room<br />
primarily <strong>to</strong> control particulates and<br />
temperature during proprietary silicone<br />
molding and inspection processes for<br />
implantable microscale drug-delivery<br />
devices. A half-million devices can be<br />
manufactured from just one pound of<br />
material.<br />
David Comeau, Albright’s president,<br />
said designing and building his fi xedwall<br />
clean room cost about $150,000.<br />
The company decided <strong>to</strong> build the<br />
Cl<strong>as</strong>s 10,000 clean room instead of<br />
a Cl<strong>as</strong>s 100,000 room, which would<br />
have been adequate, because the cost<br />
difference w<strong>as</strong> not substantial. While the<br />
company w<strong>as</strong> designing and installing<br />
its clean room, it also obtained ISO<br />
13485 certifi cation for medical device<br />
manufacturing.<br />
Micromachining in clean rooms.<br />
ARC Technologies, White Bear Lake,<br />
Minn., machines microparts for the<br />
aerospace and scientifi c instruments<br />
industries in a cl<strong>as</strong>s 10,000 clean room.<br />
Advanced Research Corp. Vice<br />
trol thermal growth of the part or <strong>to</strong>oling<br />
is a critical fac<strong>to</strong>r when microparts<br />
have dimensions that must be held within<br />
microns. MicroEDMs and conventional<br />
machine <strong>to</strong>ols may have special enclosures<br />
that do a good job of controlling<br />
President Marlow Roberts said the biggest<br />
issue is temperature consistency. “If you<br />
are holding 2µm <strong>to</strong>lerances or ultrahighprecision<br />
pitching accuracies, you need<br />
temperature consistency throughout. If<br />
you use long cutting processes at varying<br />
temperatures, [the workpiece] grows<br />
or shrinks, so how do you know w<strong>here</strong><br />
you’re at?”<br />
The company operates a small hole<br />
popper (Sodick AE05 microEDM). Even<br />
though the system h<strong>as</strong> its own enclosure<br />
with environmental controls, external<br />
temperature control is important <strong>to</strong><br />
ensure that parts can be me<strong>as</strong>ured away<br />
from the machine under comparable<br />
thermal conditions.<br />
Near-clean room controls. Micro<br />
Precision Parts Manufacturing of<br />
Vancouver, British Columbia, does not<br />
have a certifi ed clean room, but many<br />
systems are in place <strong>to</strong> control dust<br />
and dirt (air fi ltration and sticky mats),<br />
humidity and temperature.<br />
Company president Steve Cot<strong>to</strong>n said<br />
that since a single speck of dust can ruin<br />
the fi nish on medical microparts, the<br />
parts are vacuum cleaned using a 30µm<br />
fi lter and wrapped in a lint-free material<br />
prior <strong>to</strong> shipping.<br />
Albright Technologies<br />
—Joel C<strong>as</strong>sola<br />
Albright<br />
Technologies built a<br />
Cl<strong>as</strong>s 10,000 clean<br />
room <strong>to</strong> control<br />
particulates and<br />
temperature during<br />
silicone molding<br />
and inspection<br />
processes.<br />
temperature. However, this equipment—<br />
enclosure and all—may also be housed<br />
in a clean room that maintains temperature<br />
within ±1° C so that inspection<br />
equipment will me<strong>as</strong>ure the parts under<br />
thermal conditions comparable <strong>to</strong> those<br />
micromanufacturing.com | 37
Clean Machining continued<br />
under which they were manufactured.<br />
Even builders of conventional products<br />
like mo<strong>to</strong>rcycles are insisting that critical<br />
components for their fuel-injection systems<br />
be machined and packaged in clean<br />
rooms so that t<strong>here</strong> is no danger that a<br />
particle of dust will plug a critical orifi ce.<br />
How are clean rooms cl<strong>as</strong>sifi ed?<br />
Clean rooms are typically cl<strong>as</strong>sifi ed according<br />
<strong>to</strong> the number and size of particles<br />
within a given volume of air. Th e two most<br />
common standards are the now-defunct<br />
U.S. Federal Standard 209E and<br />
ISO14644-1, which replaced it. Th e 209E<br />
standard w<strong>as</strong> cancelled by the General<br />
Services Administration of the U.S. Department<br />
of Commerce on Nov. 29, 2001,<br />
but is still widely used.<br />
The old Federal standard had six<br />
cl<strong>as</strong>ses for clean rooms: 100,000, 10,000,<br />
1,000, 100, 10 and 1, with one being the<br />
cleanest. Th e ISO Cl<strong>as</strong>ses 8 through 3<br />
correspond <strong>to</strong> these, with cl<strong>as</strong>ses 2 and 1<br />
being even cleaner.<br />
Th e lower-number cl<strong>as</strong>ses are typically<br />
found in industries like silicon chip and<br />
pharmaceutical manufacturing. Clean<br />
rooms used by micromanufacturers are<br />
most frequently Cl<strong>as</strong>s 8 or Cl<strong>as</strong>s 7. Th e<br />
cl<strong>as</strong>sifi cation only tells part of the s<strong>to</strong>ry,<br />
however, because t<strong>here</strong> are many other<br />
features of a clean room’s design that<br />
have little if anything <strong>to</strong> do with its cl<strong>as</strong>s.<br />
What are the key components of<br />
clean room and temperature control<br />
systems? Th e key component of a clean<br />
room is the fi ltration system (otherwise<br />
called a fan/fi lter, OPA fi lter or HEPA<br />
fi lter). Th is primary system may be used<br />
in conjunction with a wide range of additional<br />
systems, such <strong>as</strong> dehumidifi ers,<br />
air conditioning and bag-in/bag-out fi lters<br />
that make it e<strong>as</strong>y <strong>to</strong> remove dangerous<br />
contaminants and incinerate them.<br />
Soft-sided clean rooms are like tents<br />
with open bot<strong>to</strong>ms. Positive pressure prevents<br />
particles from entering the room.<br />
Th ey can be purch<strong>as</strong>ed for about $40 per<br />
square foot. Hard-walled clean rooms<br />
range from $120 <strong>to</strong> $200-plus per square<br />
foot, depending on the room’s cl<strong>as</strong>s and<br />
the complexity of its particle fi ltration<br />
system and other environmental controls.<br />
Modular clean rooms cost less and<br />
can be dis<strong>as</strong>sembled and moved. Th ey are<br />
treated <strong>as</strong> equipment, not construction,<br />
so they depreciate f<strong>as</strong>ter. Conventionally<br />
38 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Advanced Research Corp. machines aerospace and scientific instrument microparts<br />
in a cl<strong>as</strong>s 10,000 clean room. The company operates an enclosed small hole popper<br />
(microEDM) with its own environmental controls. Still, external temperature control is<br />
important <strong>to</strong> ensure that parts me<strong>as</strong>ured away from the machine are under comparable<br />
thermal conditions.<br />
Albright Technologies<br />
Albright Technologies' shop supervisor,<br />
Jim Smith, "gowns up" before entering the<br />
company's Cl<strong>as</strong>s 10,000 clean room.<br />
ARC<br />
constructed clean rooms typically cost<br />
more, but they allow for the greatest degree<br />
of design fl exibility.<br />
Operating costs include such things<br />
<strong>as</strong> power for various electromechanical<br />
systems, materials (fi ltration, cleaning,<br />
gowns, mats, etc.), maintenance and<br />
staff training.<br />
Clean rooms frequently require certifi -<br />
cation. Some clean room manufacturers<br />
off er this service; however, independent<br />
consultants, such <strong>as</strong> those who perform<br />
ISO certification audits, are a better<br />
choice for those who wish <strong>to</strong> avoid the<br />
appearance of a confl ict of interest. Moni<strong>to</strong>ring<br />
devices may be installed in clean<br />
rooms <strong>to</strong> provide ongoing verifi cation<br />
that the desired standards are being met.<br />
Does having a clean room help solicit<br />
micromachining jobs? Maybe.<br />
It stands <strong>to</strong> re<strong>as</strong>on that having a clean<br />
room could open the door <strong>to</strong> new jobs.<br />
However, the manufacturers consulted<br />
said that their decision <strong>to</strong> install a clean<br />
room had little <strong>to</strong> do with impressing<br />
prospective cus<strong>to</strong>mers and more <strong>to</strong> do
with optimizing specialized processes<br />
the companies had developed for making<br />
high-value-added products. To them<br />
it w<strong>as</strong> an essential ingredient, so they did<br />
not hesitate <strong>to</strong> build what they needed.<br />
In other c<strong>as</strong>es, OEMs that want <strong>to</strong><br />
minimize sources of contamination often<br />
drive the micromanufacturer’s decision <strong>to</strong><br />
build a clean room. Manufacturers that<br />
adopt a “build it and they will come” attitude<br />
may have a hard time justifying the<br />
expense if they don’t come.<br />
How <strong>to</strong> avoid grief<br />
All of our respondents agreed that the<br />
three most important fac<strong>to</strong>rs in developing<br />
a successful clean room operation for<br />
micromanufacturing are:<br />
1. Know the requirements. Understand<br />
completely the requirements of<br />
your cus<strong>to</strong>mers and your processes and<br />
design and operate your clean room accordingly.<br />
Find out exactly which environmental<br />
fac<strong>to</strong>rs need <strong>to</strong> be controlled<br />
and <strong>to</strong> what degree. Some manufacturers<br />
Contribu<strong>to</strong>rs<br />
MICROMANUFACTURERS<br />
Albright Technologies Inc.<br />
(978) 466-5870<br />
www.albright1.com<br />
ARC Technologies<br />
(651) 789-9000<br />
www.arcnano.com<br />
Micro Precision Parts<br />
Manufacturing Ltd.<br />
(250) 752-5401<br />
www.precisionmicromachining.com<br />
CLEAN ROOM SUPPLIERS<br />
Clean Air Products<br />
(763) 425-9122<br />
www.cleanairproducts.com<br />
Starrco<br />
(800) 325-4259, x305<br />
www.starrco.com<br />
inter<strong>view</strong> their cus<strong>to</strong>mer’s cus<strong>to</strong>mer <strong>to</strong><br />
get a more accurate idea of the requirements.<br />
One manufacturer estimated the<br />
cost of change orders at $1,500 each. So,<br />
getting the specs right the fi rst time can<br />
be a real money saver.<br />
2. Develop a mindset. Th e people<br />
who work in clean rooms are themselves<br />
a major source of contamination. Workers<br />
must develop a mindset embracing<br />
the strict disciplines governing dress, behavior<br />
and part handling. Th is requires<br />
thorough training at the outset and con-<br />
tinual reinforcement of correct practices.<br />
3. Fill it. Have a realistic plan for acquiring<br />
a suffi cient amount of work <strong>to</strong><br />
keep your clean room operating profi tably.<br />
An unused room—regardless of how<br />
clean it is—is a money w<strong>as</strong>ter. µ<br />
About the author: Joel C<strong>as</strong>sola is a<br />
freelance journalist and Web content<br />
consultant with more than 25 years of<br />
experience reporting on manufacturing<br />
systems and software. E-mail: joel.<br />
c<strong>as</strong>sola@gmail.com.<br />
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micromanufacturing.com | 39
Good vibration<br />
(control)<br />
Small vs. large machines: different approaches <strong>to</strong> countering vibration<br />
40 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Machine <strong>to</strong>ol builders off er a growing selection<br />
of machining centers that make parts<br />
with microscale features and <strong>to</strong> submicron accuracies.<br />
Th e machines come in a variety of sizes,<br />
from half-<strong>to</strong>n and smaller units with 4"×4"×4"<br />
work volumes <strong>to</strong> 5-<strong>to</strong>n and larger machines<br />
with work capacities of 20"×20"×20" and greater.<br />
All the machine confi gurations are seen <strong>to</strong> be<br />
eff ective in making very small parts. Th e level at<br />
which that production is achieved, however, differs<br />
somewhat in relation <strong>to</strong> machine size. While<br />
the smaller machines typically are less costly and<br />
more energy-effi cient than the larger units, the<br />
greater table capacity of the larger, more expensive<br />
machines enables them <strong>to</strong> create microfeatures<br />
on larger parts.<br />
One of the key diff erences among the machines<br />
is the type of operations they perform<br />
and how they counter negative machining infl<br />
uences, such <strong>as</strong> vibration and heat. Th e more<br />
m<strong>as</strong>sive components of the bigger machines<br />
permit operations such <strong>as</strong> hard milling and<br />
rigid tapping, but require additional features <strong>to</strong><br />
control machining forces. Th e small machines’<br />
more compact constituents, <strong>as</strong> well <strong>as</strong> the min-<br />
By Bill Kennedy, Contributing Edi<strong>to</strong>r<br />
imal cutting forces generated by the small cutting<br />
<strong>to</strong>ols they employ, serve <strong>to</strong> signifi cantly<br />
reduce the need <strong>to</strong> quell vibration with sheer<br />
structural m<strong>as</strong>s.<br />
Critical m<strong>as</strong>s?<br />
Microlution Inc., Chicago, off ers two smallscale<br />
micro machine <strong>to</strong>ols. Its 3-axis, 363-S<br />
vertical machining center h<strong>as</strong> a 2"×2"×2" work<br />
envelope, a 2-sq.-ft. footprint and weighs about<br />
1,000 lbs.; the work volume of its new 4,600lb.,<br />
3.4'×5.4' footprint, 5-axis 5100s VMC is<br />
4"×4"×4".<br />
According <strong>to</strong> Andrew Honegger, vice president<br />
of Microlution, t<strong>here</strong> is nothing in<strong>here</strong>ntly<br />
wrong with the traditional idea that greater<br />
m<strong>as</strong>s improves the vibration characteristics of<br />
a machine <strong>to</strong>ol. “M<strong>as</strong>s does a good job of eliminating<br />
vibration,” he said. Th e diff erence really<br />
is in the application. A larger machine <strong>to</strong>ol<br />
may be able <strong>to</strong> handle larger <strong>to</strong>ols and workpieces,<br />
but “the diff erence in our line of thinking<br />
is that we are designing machine <strong>to</strong>ols that<br />
are specifi cally geared <strong>to</strong>ward only the small<br />
<strong>to</strong>ols and small parts. Th at is w<strong>here</strong> the design<br />
A<strong>to</strong>metric Kern Precision<br />
Small machines, like the 900-lb. G-4 Utra from A<strong>to</strong>mectric, rely on their compact design and low cutting forces <strong>to</strong> prevent vibration. Large<br />
machines, such <strong>as</strong> Kern’s 17, 600-lb. Nano VMC, rely on their m<strong>as</strong>sive b<strong>as</strong>es.
constraints change a bit.” All Microlution<br />
machines are designed for cutters<br />
¼" (6.35mm) in diameter and smaller.<br />
Gary Zurek, president of Kern Precision<br />
Inc., Webster, M<strong>as</strong>s., agreed that the<br />
miniscule-part focus of the smaller machines<br />
may minimize the need for a m<strong>as</strong>sive<br />
machine b<strong>as</strong>e. “On the other hand,”<br />
he said, “I would argue that [with any machine]<br />
traveling at 1 <strong>to</strong> 2 Gs over 2" t<strong>here</strong><br />
will be vibration, and somehow these vibrations<br />
must be addressed.”<br />
As result, some of Kern’s machines for<br />
medium- <strong>to</strong> small-part machining are<br />
far from small. Th e company’s 17,600-lb.<br />
Pyramid Nano VMC h<strong>as</strong> a 9.3'×10.5' footprint,<br />
h<strong>as</strong> travels of 19.6"×19.6"×15.7" in<br />
the X, Y and Z axes, and can handle <strong>to</strong>ols<br />
from 50μm <strong>to</strong> 18mm in diameter. Th e<br />
machine’s polymer-concrete-fi lled b<strong>as</strong>e<br />
and frame absorb up <strong>to</strong> 10 times more vibration<br />
than c<strong>as</strong>t iron, improving <strong>to</strong>ol life<br />
and imparting surface fi nishes fi ner than<br />
0.05μm R a, according <strong>to</strong> the company.<br />
Th e machine’s size also facilitates the use<br />
of hydrostatic drives, which also dampen<br />
vibration. Kern’s two smaller machines,<br />
the Micro and EVO, incorporate similar<br />
polymer-concrete b<strong>as</strong>es but are targeted<br />
<strong>to</strong>ward small and micro part production.<br />
Conversely, builders of small machines<br />
say their equipment is designed <strong>to</strong> be<br />
proportional <strong>to</strong> the size of the parts they<br />
are making.<br />
“We <strong>to</strong>ok a lot of eff ort <strong>to</strong> make our<br />
machines squat and s<strong>to</strong>ut, a structure that<br />
is <strong>as</strong> re<strong>as</strong>onably compact <strong>as</strong> possible,” said<br />
Th om<strong>as</strong> N. Lindem, president of A<strong>to</strong>metric<br />
Inc., Rockford, Ill. “We thought if<br />
we scaled it appropriately <strong>to</strong> the parts, it<br />
didn’t have <strong>to</strong> be an extremely heavy machine<br />
<strong>to</strong> be stiff .” A<strong>to</strong>metric’s G-4 Ultra<br />
I would argue that with<br />
any machine traveling<br />
at 1 <strong>to</strong> 2 Gs over 2"<br />
t<strong>here</strong> will be vibration,<br />
and somehow these<br />
vibrations must be<br />
addressed.<br />
micromachining centers have a work<br />
area of 4"×4"×4" (with an 8" stroke available),<br />
a 2.3-sq.-ft. footprint and weigh<br />
about 900 lbs.<br />
Structural elements<br />
Regarding the role structural materials<br />
play in vibration damping, Lindem said he<br />
and his father, A<strong>to</strong>metric founder Th om<strong>as</strong><br />
J. Lindem, previously designed large machine<br />
<strong>to</strong>ols at Ingersoll Milling Machine<br />
Co., w<strong>here</strong> they utilized c<strong>as</strong>t iron, welded<br />
steel, granite and synthetic-granite b<strong>as</strong>es.<br />
Th e diff erent materials, he said, “all have<br />
their advantages and disadvantages. I’m<br />
not advocating one over the other; they<br />
all make excellent systems, but for all of<br />
Kern Precision<br />
Although they may be less<br />
space- and energy-efficient<br />
than small machine <strong>to</strong>ols,<br />
larger multiplatform machining<br />
centers have the <strong>to</strong>rque <strong>to</strong><br />
perform operations like rigid<br />
tapping and microdrilling, <strong>as</strong><br />
illustrated in this 10mm-thick<br />
cutaway titanium part. The<br />
angled holes are tapped<br />
with a M3×0.5 thread, and<br />
taper from a maximum OD<br />
of 2.5mm <strong>to</strong> a section just<br />
0.9mm long and 0.1mm in<br />
diameter near the part’s b<strong>as</strong>e.<br />
them you have <strong>to</strong> look at all their characteristics.<br />
Granite is a great natural dampener,<br />
but thick steel also h<strong>as</strong> some very<br />
well known stiff ness and frequencies, and<br />
we are using a heavy steel b<strong>as</strong>e.”<br />
According <strong>to</strong> Lindem, a key consideration<br />
in controlling vibration and maintaining<br />
machining accuracy is keeping<br />
what he calls the “force loop” <strong>as</strong> small <strong>as</strong><br />
possible. Th e force loop, he explained,<br />
consists of a circle or square drawn<br />
through the workpiece, fixture, table<br />
and machine b<strong>as</strong>e, around the structure<br />
of the axes and through the spindle and<br />
the <strong>to</strong>ol. “Th e goal is <strong>to</strong> make those distances<br />
<strong>as</strong> short <strong>as</strong> possible,” he said. If the<br />
same part is machined in a larger force<br />
loop, any element of defl ection will tend<br />
<strong>to</strong> incre<strong>as</strong>e vibration exponentially. Th at<br />
incre<strong>as</strong>e in vibration can be estimated<br />
by cubing the distances within the force<br />
loop. Lindem added that in many graniteb<strong>as</strong>e<br />
machines, the force loop is actually<br />
contained in the unit’s steel structure; in<br />
that c<strong>as</strong>e, a larger steel structure mounted<br />
on granite can develop more vibration<br />
than an all-steel structure that is smaller<br />
and more compact.<br />
micromanufacturing.com | 41
42 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
Microlution<br />
The Microlution 5100s 5-axis<br />
micromachining center h<strong>as</strong> a 3.4'×5.4'<br />
footprint and a work volume of 4"×4"×4".<br />
Makino<br />
A small V-22 VMC from Makino machined<br />
a mold for 5mm×5mm medical staples in<br />
hardened 420 stainless steel (50 <strong>to</strong> 52 HRC).<br />
Each staple required 0.10mm corner radii.<br />
Good vibration (control) continued<br />
Mark Jackson, <strong>as</strong>sociate professor in<br />
the Department of Mechanical Engineering<br />
Technology at the Purdue University<br />
College of Technology, agreed that<br />
the small-machine concept makes sense<br />
with respect <strong>to</strong> controlling vibration. For<br />
example, he said t<strong>here</strong> is a signifi cant<br />
amount of work being done with Swissstyle<br />
lathes <strong>to</strong> machine medical parts,<br />
such <strong>as</strong> bone screws, from metal workpieces.<br />
“But they are still using existing<br />
techniques, which may not be appropriate<br />
for machining certain geometries,” he<br />
said. “Th ere is a need for dedicated machine<br />
<strong>to</strong>ols that not only consistently produce<br />
those features but don’t suff er from<br />
vibration or thermal changes that [lessen]<br />
the ability <strong>to</strong> consistently control the size<br />
of very small parts.”<br />
When small parts are produced on<br />
large machines, he said, “chatter occurs<br />
because the machine <strong>to</strong>ol is far <strong>to</strong>o big;<br />
the size of the machine is disproportionate<br />
<strong>to</strong> the size of the components. You<br />
have a huge m<strong>as</strong>s moving around, and the<br />
vibrations have <strong>to</strong> go somew<strong>here</strong>. Th ey<br />
are regenerated and actually replicated<br />
on the surface of the part.”<br />
Scaling down machine <strong>to</strong>ols may require<br />
an approach very diff erent from<br />
simply downsizing the equipment, Jackson<br />
said. “We came up with a pro<strong>to</strong>type<br />
tetrahedral machine <strong>to</strong>ol that had three<br />
A<strong>to</strong>metric<br />
The rotary axes of the<br />
G-4 Ultra micromachining<br />
center from A<strong>to</strong>metric are<br />
shown machining a 0.35"-<br />
cubed demonstration part<br />
from ½"-dia. bar s<strong>to</strong>ck.<br />
machined balls on the surface, connected<br />
via hollow columns <strong>to</strong> a fourth ball at<br />
the <strong>to</strong>p of the vertex. Th e tetrapod, actually<br />
a truncated pyramid, is the most<br />
stable shape in nature. We fi ll those columns<br />
with oil, water or solids <strong>to</strong> tune the<br />
machine <strong>to</strong>ol and damp out certain frequencies<br />
of vibration. All the vibrations<br />
attenuate <strong>to</strong>wards the center of each circular<br />
ball.”<br />
Not exciting<br />
Another important step in controlling<br />
vibration, said Bill Howard, VMC product<br />
manager for Makino USA Inc., M<strong>as</strong>on,<br />
Ohio, is minimizing self-excitation between<br />
adjacent machine components.<br />
For example, although Makino’s Hyper<br />
2J micromachining center is the company’s<br />
smallest VMC, the machine h<strong>as</strong> an<br />
8"×6"×6" work volume, a 6'×8' footprint<br />
and weighs 11,000 lbs. To minimize selfgenerated<br />
vibration, it is essential <strong>to</strong> ensure<br />
tight alignment and fi t between the<br />
machine’s drive elements and its b<strong>as</strong>ic<br />
structure. “Two metal surfaces rubbing<br />
against each other, even if they are<br />
ground, are still going <strong>to</strong> have potential<br />
<strong>to</strong> vibrate or oscillate against each other,”<br />
Howard said.<br />
To control that tendency, the ways of<br />
the Hyper 2J, the V-22 VMC (slightly<br />
larger and more production-oriented<br />
continued on page 45
Good vibration (control)<br />
continued from page 42 Contribu<strong>to</strong>rs<br />
than the Hyper 2J) and other of the company’s<br />
machines feature guideways lined<br />
with Tercite, a self-lubricating, thermopl<strong>as</strong>tic<br />
bearing material. According <strong>to</strong><br />
Howard, the stiff , rigid material is handscraped<br />
<strong>to</strong> maximize accuracy and create<br />
pockets that evenly distribute lubrication<br />
between machine components. Th e lining<br />
also provides a cushion between the<br />
diff erent elements of the machine <strong>to</strong>ol.<br />
Th e cutting process itself can excite vibration.<br />
Microlution’s Honegger pointed<br />
out that when machines use micro cutting<br />
<strong>to</strong>ols, “typically the cutting forces are<br />
a lot smaller, so the input that is causing<br />
the vibration h<strong>as</strong> a much lower magnitude.”<br />
In addition, small-diameter <strong>to</strong>ols<br />
generally are applied at much higher<br />
spindle speeds than larger <strong>to</strong>ols. Th e<br />
higher-frequency vibrations the small<br />
<strong>to</strong>ols produce are e<strong>as</strong>ier <strong>to</strong> control because<br />
vibration-damping mechanisms are<br />
correlated <strong>to</strong> the frequencies, according<br />
<strong>to</strong> Honegger.<br />
“Th e higher the frequency, the e<strong>as</strong>ier<br />
it is <strong>to</strong> damp, <strong>as</strong> long <strong>as</strong> you are careful<br />
Makino<br />
A small V-22 VMC from Makino equipped<br />
with a 0.050mm-dia. drill machined 61<br />
individual 0.002"-dia. microholes in<strong>to</strong> a flat,<br />
0.020"-thick, 303 stainless steel workpiece.<br />
about structural resonances. M<strong>as</strong>s is definitely<br />
an eff ective vibration-elimination<br />
mechanism, but b<strong>as</strong>ed on the type of<br />
input that we have from small <strong>to</strong>ols, you<br />
don’t need <strong>as</strong> much of it.”<br />
It appears that both small and large<br />
machine <strong>to</strong>ols for micromachining<br />
can effectively control vibration and<br />
other machining forces. What users<br />
have <strong>to</strong> decide, then, is what will the machine<br />
be used for, how fl exible it needs<br />
<strong>to</strong> be and if the added fl exibility is worth<br />
the added cost. µ<br />
A<strong>to</strong>metric Inc.<br />
(815) 986-7352<br />
www.a<strong>to</strong>metric.com<br />
Mark Jackson<br />
Purdue University<br />
jacksomj@purdue.edu<br />
Kern Precision Inc.<br />
(508) 943-7202<br />
www.kernprecision.com<br />
Makino Inc.<br />
(513) 573-7200<br />
www.makino.com<br />
Microlution Inc.<br />
(773) 282-6495<br />
www.microlution-inc.com<br />
About the author: Bill Kennedy is a<br />
contributing edi<strong>to</strong>r <strong>to</strong> <strong>MICROmanufacturing</strong><br />
and Cutting Tool Engineering magazines.<br />
Telephone: (724) 537-6182; E-mail:<br />
billk@jwr.com.<br />
micromanufacturing.com | 45
MICROmachining<br />
continued from page 14<br />
he said. “I push them <strong>as</strong> much <strong>as</strong> I can<br />
by reusing them.”<br />
Th e chips a boring bar produces<br />
need <strong>to</strong> be evacuated from the hole,<br />
which is typically a blind-hole in Swissstyle<br />
machining. Th at’s because parts<br />
are produced from a continuous piece<br />
of bar s<strong>to</strong>ck unless work is being performed<br />
on the subspindle. Flood coolant<br />
is one method of chip removal, but<br />
through-the-<strong>to</strong>ol coolant is generally<br />
preferred, which is available on even the<br />
smallest <strong>to</strong>ols. “Th e 0.42mm <strong>to</strong>ol h<strong>as</strong> a<br />
coolant delivery port that is EDMed,”<br />
Laprade said. “It doesn’t actually go<br />
The chips a boring bar<br />
produces need <strong>to</strong> be<br />
evacuated from the hole,<br />
which is typically a<br />
blind-hole in Swiss-style<br />
machining.<br />
through the bar itself but comes out at<br />
the b<strong>as</strong>e of the neck and coolant e<strong>as</strong>ily<br />
penetrates the hole.”<br />
Th rough-coolant pressure ranges<br />
from about 100 <strong>to</strong> 2,000 psi. Th at’s the<br />
c<strong>as</strong>e at Tomak Precision, w<strong>here</strong> Day<br />
prefers through-coolant but normally<br />
applies fl ood coolant for the fi rst piece.<br />
When Tomak Precision expanded<br />
by purch<strong>as</strong>ing a small machine shop a<br />
few years ago, it acquired two Citizen<br />
Swiss-style machines. It also acquired<br />
a need for new <strong>to</strong>ols. “Swiss machining<br />
w<strong>as</strong> new <strong>to</strong> us, so small <strong>to</strong>oling w<strong>as</strong><br />
needed,” Day said, noting that he needs<br />
<strong>to</strong>ols <strong>as</strong> small <strong>as</strong> 0.039" for boring a<br />
0.050" hole.<br />
He came across information about<br />
the Utilis Multidec boring bars from<br />
Genevieve Swiss at a machine show<br />
and decided <strong>to</strong> try them. Today, Tomak<br />
uses four diff erent styles of the boring<br />
<strong>to</strong>ols.<br />
Day found <strong>to</strong>ol life <strong>to</strong> be good, even<br />
when boring titanium. “I ran a 1,600piece<br />
titanium job, and I used two<br />
46 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
The importance of proper center height for a boring bar<br />
inserts for the whole run,” he said. Th at<br />
required boring a hole at an angle<br />
with a slight counterbore before the diameter<br />
stepped down <strong>to</strong> 0.088". Tolerance<br />
w<strong>as</strong> 0.002". “We held a 31-rms<br />
fi nish,” Day said. “Th e part requirement<br />
w<strong>as</strong> 63 rms.”<br />
Day noted that the feeds for microboring<br />
range from 0.0004 <strong>to</strong> 0.005 ipr<br />
with a DOC from 0.002" <strong>to</strong> 0.025".<br />
Taking a single boring p<strong>as</strong>s is preferred.<br />
“I normally try <strong>to</strong> drill <strong>as</strong> close<br />
<strong>to</strong> nominal <strong>as</strong> I can,” he said. “With<br />
though-coolant, I can drill a lot f<strong>as</strong>ter<br />
than I can bore.” µ<br />
About the author: Alan Richter is senior<br />
edi<strong>to</strong>r of <strong>MICROmanufacturing</strong>. Telephone:<br />
(847) 714-0175. E-mail: alanr@jwr.com.<br />
Force<br />
Force<br />
A positive chip rake boring bar set<br />
on centerline provides the most<br />
efficient cutting. The positive rake<br />
reduces cutting force and heat.<br />
Chips are pulled from the inner<br />
wall for the best evacuation, and<br />
<strong>to</strong>ol life is optimal.<br />
A neutral rake boring bar set on<br />
centerline requires more cutting<br />
force. Chips are moderately<br />
controlled but may poorly<br />
evacuate. Tool life is slightly<br />
reduced because of incre<strong>as</strong>ed<br />
heat.<br />
Force<br />
Force<br />
A positive rake boring bar set<br />
above centerline and rotated down<br />
<strong>to</strong> achieve centerline. The effective<br />
rake is neutral, requiring more<br />
cutting force. Chips are moderately<br />
controlled but could have<br />
evacuation trouble. The incre<strong>as</strong>ed<br />
heat slightly reduces <strong>to</strong>ol life.<br />
A neutral rake boring bar set<br />
above centerline and rotated<br />
down <strong>to</strong> achieve centerline. The<br />
effective rake is negative, requiring<br />
incre<strong>as</strong>ed force <strong>to</strong> shear the<br />
material. The chip is pushed back<br />
in the part’s wall, causing poor chip<br />
evacuation. The incre<strong>as</strong>ed heat<br />
shortens <strong>to</strong>ol life.<br />
Force<br />
A positive rake boring bar set<br />
below centerline and rotated up <strong>to</strong><br />
achieve centerline. The effective<br />
positive rake improves chip flow<br />
except clearance is sacrificed,<br />
causing the <strong>to</strong>ol <strong>to</strong> rub and<br />
bounce. The result is excessive<br />
chatter, heat and premature <strong>to</strong>ol<br />
failure.<br />
Force<br />
A neutral rake boring bar set<br />
below centerline and rotated up <strong>to</strong><br />
achieve centerline. The effective<br />
positive rake improves chip flow<br />
except clearance is sacrificed,<br />
causing the <strong>to</strong>ol <strong>to</strong> rub and<br />
bounce. The result is excessive<br />
chatter, heat and premature <strong>to</strong>ol<br />
failure.<br />
Contribu<strong>to</strong>rs<br />
Genevieve Swiss<br />
Genevieve Swiss Industries Inc.<br />
(413) 562-4800<br />
www.genswiss.com<br />
HORN USA Inc.<br />
(888) 818-HORN<br />
www.hornusa.com<br />
Pacifi c Precision Inc.<br />
(909) 599-8471<br />
www.pacifi cprecisioninc.com<br />
Tomak Precision<br />
(513) 932-7941<br />
www.<strong>to</strong>mak.com
MEASUREMENT matters<br />
continued from page 21 30.0<br />
A specifi c example of a recent development<br />
in SWLI is the TTM (transmissive<br />
media module) from Veeco<br />
0<br />
Metrology for me<strong>as</strong>uring through<br />
microdevice packaging and other trans- 20μm<br />
parent media. “We have added the<br />
capability <strong>to</strong> look through transpar- 40μm<br />
ent materials, like gl<strong>as</strong>s in environmental<br />
chambers, <strong>to</strong> me<strong>as</strong>ure a part that is 60μm<br />
under temperature control or humidity<br />
changes,” Maksinchuk said. “You can 80μm<br />
do me<strong>as</strong>urements in real time while the<br />
device is being exposed <strong>to</strong> a harsh envi-<br />
0<br />
ronment.” Applications include corrosion<br />
studies and MEMS devices used in extreme<br />
environments.<br />
As for future developments, Felkel mentioned energy applications,<br />
such <strong>as</strong> solar panels. SWLI would be used <strong>to</strong> help<br />
control the manufacturing process. “Th e solar panel itself can<br />
be <strong>as</strong> big <strong>as</strong> your desk, but [SWLI would me<strong>as</strong>ure] the busbars<br />
and fi ngers; those are things that you want <strong>to</strong> know the<br />
profi le of <strong>to</strong> understand how much material you are putting<br />
down and <strong>to</strong> control the process,” he said.<br />
In the area of MEMS applications, t<strong>here</strong> is interest in effi -<br />
ciently making very bright LEDs. “A lot of that comes down<br />
<strong>to</strong> <strong>to</strong>pography-b<strong>as</strong>ed features,” Felkel added. “Th ese include<br />
roughness and the height of various layers <strong>as</strong> you stack the<br />
LEDs.” µ<br />
About the author: Susan Woods is a regular contribu<strong>to</strong>r <strong>to</strong><br />
<strong>MICROmanufacturing</strong> and Cutting Tool Engineering magazines.<br />
E-mail: susanw@jwr.com.<br />
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This image illustrates the<br />
remarkably high Z-axis<br />
resolution offered by the<br />
SWLI technique. These<br />
terraces represent single<br />
a<strong>to</strong>mic steps in the HOPG<br />
(Highly Ordered Pyrolytic<br />
Graphite) crystal lattice.<br />
The a<strong>to</strong>mic terraces, or<br />
plateaus, are only a few<br />
angstroms high.<br />
micromanufacturing.com | 47
PRODUCTS/services<br />
MICROEDM. Sarix SA’s MACHline micro<br />
electrical discharge machines feature<br />
the Twin Axis system, which allows<br />
multiple operations <strong>to</strong> be performed on<br />
one machine. These operations include<br />
electrical discharge drilling, sinker EDMing,<br />
wire electrode grinding, 3-D electrical<br />
discharge milling, l<strong>as</strong>er ablation and 3-D<br />
scope me<strong>as</strong>uring. The machine’s large<br />
work envelope permits microscale features<br />
<strong>to</strong> be produced on large parts. All X-, Y-<br />
and Z-axis travels are 100mm. Accuracy is<br />
±2µm.<br />
+41 91 785 81 71<br />
www.sarix.com<br />
MICROBELLOWS. Cus<strong>to</strong>m-designed<br />
microbellows from Servometer Precision<br />
Manufacturing Group LLC can be <strong>as</strong><br />
small <strong>as</strong> 0.5mm in diameter. Composed<br />
of electrodeposited nickel, the devices<br />
can be used <strong>as</strong> metallic hermetic seals,<br />
volume compensa<strong>to</strong>rs, pressure and<br />
temperature sensors and connec<strong>to</strong>rs.<br />
Pressure-responsive applications include<br />
use <strong>as</strong> precision springs, electrical contacts<br />
and flexible microcouplings. The devices<br />
can operate in temperatures from -423°<br />
<strong>to</strong> 350° F.<br />
(973) 785-4630<br />
www.servometer.com<br />
48 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
LINEAR STAGES. Aerotech Inc. offers<br />
ANT130-L long-travel, direct-drive<br />
linear stages for alignment, inspection,<br />
positioning and me<strong>as</strong>urement stations.<br />
The low-profile stages employ a centerdriven,<br />
noncogging, noncontact linear<br />
mo<strong>to</strong>r and encoder <strong>as</strong> the driving element.<br />
Peak unloaded acceleration is 1G and<br />
maximum velocity is 350 mm/sec. The<br />
stages provide 1nm resolution, 50nm<br />
repeatability, 250nm accuracy and 3nm<br />
in-position stability. Eight models are<br />
available, with travels ranging from 35mm<br />
<strong>to</strong> 160mm.<br />
(412) 963-7470<br />
www.aerotech.com<br />
SWISS-STYLE MACHINING. American<br />
Swiss Products Co. Inc. turns parts<br />
with diameters down <strong>to</strong> 0.0025" and<br />
<strong>to</strong>lerances <strong>as</strong> tight <strong>as</strong> 0.0001" on Swissstyle<br />
machines. The ISO-certified company<br />
offers small-run, complex parts <strong>as</strong> well <strong>as</strong><br />
long-run, less-complex parts. Secondary<br />
and finishing operations include broaching,<br />
drilling, grinding, knurling, l<strong>as</strong>er etching,<br />
milling and threading. Industries served<br />
include aerospace, au<strong>to</strong>motive, electronics<br />
and medical.<br />
(800) 805-9855<br />
www.americanswiss.com<br />
MEASUREMENT CENTER. Micro-Vu<br />
Corp.’s Vertex 120 me<strong>as</strong>urement center<br />
features servo-staging, high-resolution<br />
encoders, 12:1 programmable zoom<br />
and programmable lighting. Systems<br />
include InSpec metrology software with<br />
point-and-click programming, proprietary<br />
edge-learning algorithms, instant reports<br />
and geometric dimensioning and<br />
<strong>to</strong>lerancing (GD&T). With vision and <strong>to</strong>uch<br />
technologies, the machine can be used<br />
in medical, watchmaking, electronics,<br />
microEDM and l<strong>as</strong>er applications. The<br />
company reports the Vertex 120 provides<br />
results in seconds.<br />
(707) 838-6272<br />
www.microvu.com<br />
MICRODRILLS. A<strong>to</strong>m Precision of<br />
America Inc.’s Neo-Pro-series solid-carbide<br />
microdrills are for multiple-hole drilling in<br />
a range of steels. The <strong>to</strong>ols are available<br />
in short-, standard- and long-flute lengths.<br />
Diameters range from 0.03mm <strong>to</strong> 3mm,<br />
in 0.01mm increments. The drills feature<br />
wide chip pockets <strong>to</strong> enhance chip<br />
evacuation when high-speed and highfeed<br />
drilling. According <strong>to</strong> the company,<br />
the slight hones on drills larger than<br />
1.6mm in diameter extend <strong>to</strong>ol life.<br />
(317) 889-1072<br />
www.a<strong>to</strong>mprecision.com
ULTRASHORT-PULSE LASER. Norman<br />
Noble Inc. introduces the Noble<br />
UltraLight athermal, ultr<strong>as</strong>hort-pulse<br />
l<strong>as</strong>er for machining intricate features<br />
without producing a heat-affected zone<br />
in materials ranging from bioabsorbable<br />
polymers <strong>to</strong> shape-memory metals and<br />
exotic alloys. With its ability <strong>to</strong> machine<br />
athermally, the l<strong>as</strong>er can reduce or<br />
eliminate the need for deburring and other<br />
post-processing procedures, according<br />
<strong>to</strong> the company. Applications include the<br />
manufacture of drug delivery systems,<br />
catheters, valves and needles.<br />
(800) 474-4322<br />
www.nnoble.com<br />
PROTOTYPING SERVICES. FineLine<br />
Pro<strong>to</strong>typing offers an array of pro<strong>to</strong>typing<br />
services, including stereolithography of<br />
large and small 3-D objects. The parts are<br />
<strong>as</strong> small <strong>as</strong> the head of a pin. A range of<br />
material and finish options are available.<br />
Other services include SLArmor, which<br />
involves finishing a ceramic-filled epoxy<br />
material with a metal coating, microfluidic<br />
device fabrication and selective l<strong>as</strong>er<br />
sintering for production of limited-volume<br />
end use parts.<br />
(919) 781-7702<br />
www.finelinepro<strong>to</strong>typing.com<br />
MICROMACHINING SERVICES. Johnson<br />
Matthey Medical provides products<br />
for orthopedic, endoscopy, cardiology,<br />
neurology and implant applications. The<br />
company machines, draws, rolls and forms<br />
platinum, Nitinol and specialty metals.<br />
Micromachining capabilities include wire<br />
EDMing, grinding, milling, turning, coating<br />
and electroplating. The company can CNC<br />
mill and turn parts <strong>as</strong> small <strong>as</strong> 0.1" and<br />
drill holes <strong>as</strong> small <strong>as</strong> 0.012" <strong>to</strong> <strong>to</strong>lerances<br />
of ±0.0005". Grinding is used for tube<br />
and wire components, with diameters <strong>to</strong><br />
0.005" and <strong>to</strong>lerances <strong>to</strong> ±0.0002".<br />
(800) 442-1405<br />
www.jmmedical.com<br />
MACHINING CENTER. Mori Seiki USA<br />
Inc.’s NN1000 is a 5-axis machine <strong>to</strong>ol for<br />
specialty mold production. The machine<br />
utilizes diamond milling or scribing <strong>to</strong>ols<br />
and can machine features in the micron<br />
range with nanometer-level surface<br />
finishes. The maximum standard spindle<br />
speed is 56,000 rpm; higher speeds<br />
are optional. Symmetric DCG (Driven<br />
at the Center of Gravity) construction<br />
enables feeds of up <strong>to</strong> 4,500 mm/min.<br />
and minimizes thermal deformation. The<br />
machine features 1nm control resolution.<br />
(847) 593-5400<br />
www.moriseikius.com<br />
WATERJET MACHINES. Finecut AB, along<br />
with Sweden AB, offers Fine Abr<strong>as</strong>ive<br />
Waterjet (FAW) machines for micro<br />
applications. With a kerf width of 0.3mm,<br />
the waterjets deliver the abr<strong>as</strong>ive via water<br />
or air and provide cutting jet diameters<br />
from 50µm <strong>to</strong> 300µm. The machines<br />
provide a standard feed rate of 20 m/min.<br />
(double that in f<strong>as</strong>t-feed mode). The b<strong>as</strong>ic<br />
machine features an enc<strong>as</strong>ed stand-alone<br />
unit with a dedicated CNC operating panel<br />
and display screen.<br />
+46 70 6763355<br />
www.finecut.se<br />
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membrane that is moved in and out of<br />
the beam by noncontact electromagnetic<br />
techniques, which reduce shock, vibration<br />
and wear. The noncontact flexure closes<br />
at a position slightly away from the pole,<br />
essentially floating in air <strong>to</strong> eliminate any<br />
potential vibration or bounce. The units can<br />
be used in clean rooms.<br />
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micromanufacturing.com | 49
RESEARCHroundup<br />
Geometry and Surface Damage in<br />
MicroEDMing of Microholes<br />
Bülent Ekmekci, Atakan Sayar, Tahsin Tecelli Öpöz and<br />
Abdulkadir Erden<br />
Scientists investigated the link between<br />
microEDM pulse energy and its effect on<br />
the geometry and subsurface damage <strong>to</strong><br />
blind microholes. They used a tungstencarbide<br />
electrode at various pulses and<br />
a hydrocarbon-b<strong>as</strong>ed dielectric liquid <strong>to</strong><br />
machine microholes in pl<strong>as</strong>tic mold steel<br />
samples. Researchers found that the heatdamaged<br />
segments were composed of<br />
three distinct layers, each “relatively thick”<br />
and each at a different drilling depth. Even<br />
low-pulse energies caused crack formation<br />
in some sections of the microholes. They<br />
also observed that during machining, an<br />
electrically conductive bridge between the<br />
workpiece material and debris particles can<br />
form at the end tip; this leads <strong>to</strong> electric<br />
discharges between piled segments of<br />
debris particles and the electrode during<br />
discharging. The researchers concluded that<br />
the cracking mechanism when microEDMing<br />
microholes differs from the surface cracks<br />
caused by conventional EDMing.<br />
Journal of Micromechanics and<br />
Microengineering, 2009. The full study is<br />
available for purch<strong>as</strong>e at www.journals.iop.org.<br />
Analyzing the Performance of<br />
Diamond-Coated Microendmills<br />
C.D. Torres, P.J. Heaney, A.V. Sumant, M.A. Hamil<strong>to</strong>n,<br />
R.W. Carpick and F.E. Pfefferkorn<br />
Scientists detailed a new method <strong>to</strong><br />
improve <strong>to</strong>ol life and cutting performance<br />
of 300µm-dia., tungsten-carbide<br />
microendmills by applying thin (less than<br />
30nm), fine-grained diamond (FGD) and<br />
nanocrystalline diamond (NCD) coatings<br />
using the hot-filament chemical vapor<br />
deposition process. They evaluated the<br />
diamond-coated <strong>to</strong>ols by comparing their<br />
performance in dry slot milling of 6061-T6<br />
aluminum against uncoated tungstencarbide<br />
microendmills. Overall, diamondcoated<br />
<strong>to</strong>ols showed improvement in<br />
<strong>to</strong>ol integrity (corners remained intact), a<br />
lower wear rate, no observable adhesion<br />
of aluminum <strong>to</strong> the diamond and a<br />
reduction in cutting forces (greater than 50<br />
percent). While about 80 percent of the<br />
<strong>to</strong>ols coated with the larger FGD coatings<br />
failed during testing due <strong>to</strong> delamination,<br />
only 40 percent of the NCD <strong>to</strong>ols had<br />
50 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
delamination problems. Also, the NCD<br />
films proved more robust; they were able<br />
<strong>to</strong> continue <strong>to</strong>ol operations even after the<br />
coating had been compromised.<br />
International Journal of Machine Tool and<br />
Manufacture, 2009. The full study is available<br />
for purch<strong>as</strong>e at www.sciencedirect.com.<br />
Surface Emitting Microl<strong>as</strong>er B<strong>as</strong>ed on<br />
2-D Pho<strong>to</strong>nic Crystal Rod Lattices<br />
Lydie Ferrier, Ounsi El Daif, Xavier Letartre, Pedro Rojo<br />
Romeo, Christian Se<strong>as</strong>sal, Radoslaw Mazurczyk and<br />
Pierre Vik<strong>to</strong>rovitch<br />
Researchers investigated optical properties<br />
of a 2-D pho<strong>to</strong>nic crystal (2-D PC)<br />
rod lattice under stimulated emission.<br />
They reported that, for the first time,<br />
stimulated emission around 1.5µm w<strong>as</strong><br />
demonstrated in the structures. They<br />
also showed that the use of rods allows<br />
for the control of the emitting area of a<br />
Bloch mode l<strong>as</strong>er, through carrier-induced<br />
refractive index change. According <strong>to</strong><br />
the researchers, the l<strong>as</strong>er wavelength is<br />
sensitive <strong>to</strong> the device’s environment,<br />
“opening the way <strong>to</strong> a new type of<br />
integrated op<strong>to</strong>fluidic device w<strong>here</strong> liquid<br />
can flow through the resona<strong>to</strong>r itself,<br />
reinforcing the sensitivity of the sensors.”<br />
Optics Express, 2009. The full study is available<br />
<strong>to</strong> download at www.opticsinfob<strong>as</strong>e.org.<br />
Microstructuring of Gl<strong>as</strong>s with<br />
Features Less than 100µm by<br />
ECDMing<br />
Xuan Doan Cao, Bo Hyun Kim and Chong Nam Chu<br />
Researchers investigated the fe<strong>as</strong>ibility of<br />
using electrochemical discharge machining<br />
(ECDMing) <strong>to</strong> improve the machining of<br />
3-D microstructures of gl<strong>as</strong>s. In ECDMing,<br />
voltage is applied <strong>to</strong> generate a g<strong>as</strong> film<br />
and sparks on an electrode; however, a<br />
high voltage produces poor machining<br />
resolution. To obtain a stable g<strong>as</strong> film over<br />
the entire <strong>to</strong>ol surface at a low voltage,<br />
scientists used a new mechanical contact<br />
detec<strong>to</strong>r, which is b<strong>as</strong>ed on a load cell.<br />
Also, the immersion depth of the electrode<br />
in the electrolyte w<strong>as</strong> reduced <strong>as</strong> much<br />
<strong>as</strong> possible. The researchers were able<br />
<strong>to</strong> fabricate various microstructures less<br />
than 100µm in size, such <strong>as</strong> 60µm-dia.<br />
microholes and a 10µm-thin wall.<br />
Precision Engineering, 2009. The full study is<br />
available for purch<strong>as</strong>e at www.sciencedirect.<br />
com.<br />
The Microchannel of Microfluidic<br />
Chip Fabrication by Micropowder<br />
Bl<strong>as</strong>ting<br />
Chiung Fang Huang, Yung Kang Shen, Yi Lin, Chi Wei Wu<br />
Micropowder bl<strong>as</strong>ting involves high-speed<br />
g<strong>as</strong> flow combined with microparticles<br />
delivered <strong>to</strong> the substrate via a specialized<br />
nozzle. A study used various-sized<br />
aluminum-oxide powders (Al203 ) with<br />
a novel m<strong>as</strong>king technique <strong>to</strong> make<br />
channels in a microfluidic chip made<br />
from soda gl<strong>as</strong>s 2,000µm wide and<br />
1,631µm deep. The m<strong>as</strong>king technology<br />
involved two combined polymers: the<br />
el<strong>as</strong>tic and thermal-curable polydimethyl<br />
siloxane, for its erosion resistance;<br />
and the brittle epoxy resin SU-8, for its<br />
pho<strong>to</strong>sensitivity. In evaluating the process,<br />
the scientists discussed a number of<br />
parameters, including micropowder<br />
impact pressure, the distance between<br />
nozzle and substrate, micropowder size<br />
and micropowder impact time. Results<br />
showed that micropowder size w<strong>as</strong> the<br />
most important fac<strong>to</strong>r for achieving the<br />
desired depth of channel in the chip. The<br />
microchannel’s surface roughness w<strong>as</strong><br />
5µm Ra <strong>to</strong> 6µm Ra .<br />
Advanced Materials Research, 2009. The full<br />
study is available for purch<strong>as</strong>e www.scientifi c.<br />
net/orderpaper/70645.<br />
3-D Microfabrication of Materials by<br />
Fem<strong>to</strong>second L<strong>as</strong>ers for Pho<strong>to</strong>nics<br />
Applications<br />
Saulius Juodkazis, Vygant<strong>as</strong> Mizeikis and Hiroaki<br />
Misawa<br />
Researchers re<strong>view</strong>ed fem<strong>to</strong>second<br />
l<strong>as</strong>er fabrication of 3-D structures for<br />
pho<strong>to</strong>nics. In particular, they discuss: the<br />
production of pho<strong>to</strong>nic crystal structures<br />
by direct l<strong>as</strong>er writing and holographic<br />
recording by multiple-beam interference<br />
techniques, the physical mechanisms<br />
<strong>as</strong>sociated with structure formation and<br />
post fabrication, and the advantages<br />
and limitations of various fem<strong>to</strong>second<br />
l<strong>as</strong>er microfabrication techniques for<br />
the preparation of pho<strong>to</strong>nic crystals and<br />
elements of microelectromechanical and<br />
micro-op<strong>to</strong>fluidic systems.<br />
Journal of Applied Physics, 2009. The full study<br />
is available for purch<strong>as</strong>e at www.commerce.<br />
aip.org/cart.do.<br />
µ
Taking Form continued from page 34<br />
capability may become a necessity for<br />
companies involved in 3-D microstructure<br />
manufacturing.<br />
Material variation<br />
Th e most common electrochemically<br />
deposited metals are gold, nickel, nickel/<br />
cobalt and copper. Some combinations<br />
of these metals work well, such <strong>as</strong> copper<br />
and gold or nickel/cobalt and gold.<br />
Overplating the entire 3-D structure is<br />
problematic but possible, depending on<br />
the overcoat material. Gold over copper<br />
or nickel is possible. Platinum, palladium<br />
and rhodium are desirable overplating<br />
materials but can present plating issues<br />
related <strong>to</strong> the specifi c plating bath.<br />
Magnetic metal deposition baths are<br />
available and may be considered for those<br />
applications requiring magnetic proper-<br />
ADindex<br />
ties. However, complex and exotic solutions<br />
like this make the plating process<br />
more diffi cult.<br />
Future 3-D microstructure applications<br />
will likely require at le<strong>as</strong>t one of<br />
the above metal or coating options. For<br />
example, pure gold overplatings may be<br />
essential on copper-b<strong>as</strong>ed RF coupling<br />
devices w<strong>here</strong> biocompatibility is an issue.<br />
Similarly, dielectric overplating will be essential<br />
in applications w<strong>here</strong> controlled<br />
dielectric characteristics are critical. (See<br />
Figure 6 on page 34 for an example of a<br />
device that h<strong>as</strong> been overplated.)<br />
Th e enabling technologies mentioned<br />
previously are expected <strong>to</strong> make electroforming<br />
an even more commercially viable<br />
process. For example, projection imaging<br />
will enable the creation of electroformed<br />
features with resolutions of less than 1μm<br />
and <strong>as</strong>pect ratios of 10:1 or higher. Chem-<br />
ADVERTISER NAME PAGE # CONTACT NAME CONTACT PHONE CONTACT E-MAIL / WEB SITE<br />
Accumold 5 Aaron Johnson 515-964-5741 ajohnson@accu-mold.com / www.accu-mold.com<br />
Brush Research Mfg. Co. Inc. 7 Michael Miller 323-261-2193 sales@brushresearch.com / www.brushresearch.com<br />
Chardon Tool 13 Hugh McAllister 440-286-6440 hmcallister@chardon<strong>to</strong>ol.com / www.chardon<strong>to</strong>ol.com<br />
Excalibur Tool Inc. 39 Dan Wayman 541-862-2939 dansonly@earthlink.net / www.excalibur-<strong>to</strong>ol.com<br />
FineLine Pro<strong>to</strong>typing 27 Rob Connelly 919 781-7702 rob@finelinepro<strong>to</strong>typing.com / www.finelinepro<strong>to</strong>typing.com<br />
Harvey Tool Co. LLC Cover 4 Peter P. Jenkins 800-645-5609 pjenkins@harvey<strong>to</strong>ol.com / www.harvey<strong>to</strong>ol.com<br />
HORN USA Cover 2 Sebrina Carter 888-818-HORN sales@hornusa.com / www.hornusa.com<br />
ICOMM/4M 2010 35 Frank Pfefferkorn 608-263-2668 pfefferk@engr.wisc.edu<br />
ical mechanical polishing will support<br />
smaller multilayer structures and enable<br />
precision alignments of less than 1μm.<br />
Electroforming h<strong>as</strong> already had a<br />
positive impact in several critical applications,<br />
such <strong>as</strong> semi-intrusive and<br />
permanent medical implants, telemetry<br />
and telecommunication devices and military<br />
devices. As the technology is developed<br />
further, it will enhance the use of<br />
3-D microstructures in existing applications<br />
and enable penetration in<strong>to</strong> new<br />
applications. µ<br />
About the authors: Lowell Thom<strong>as</strong><br />
is senior staff engineer and Luke Volpe<br />
is direc<strong>to</strong>r of engineering (retired) for<br />
Dynamics Research Corp., Metrigraphics<br />
Division, Wilming<strong>to</strong>n, M<strong>as</strong>s. Telephone:<br />
(978) 658-6100. Web site: www.drc.com/<br />
metrigraphics.<br />
IMTS 2010 - Intl. Mfg. Technology Show 3 Jessica Aybar 703-827-5288 jaybar@am<strong>to</strong>nline.org / www.imts.com<br />
MachineTools.com Inc. 39 785-965-2659 info@machine<strong>to</strong>ols.com / www.machine<strong>to</strong>ols.com<br />
Micro Waterjet LLC 11 Coni Chamley 704-948-1223 cchamley@daetwyler.com / www.microwaterjet.com<br />
Microcut 8 Joe Dennehy 781-582-8090 info@microcutusa.com / www.microcutusa.com<br />
Performance Micro Tool 23 David Bur<strong>to</strong>n 866-PERFORM info@pmtnow.com / www.pmtnow.com<br />
Sandvik Coromant Co. Cover 3 Björn Roodzant 800-SANDVIK bjorn.roodzant@sandvik.com / www.sandvik.coromant.com/us<br />
Schütte TGM LLC 14 David Brigham 517-782-2938 davidtgm@acd.net / www.schuttetgm.com<br />
Society of Manufacturing Engineers 47 Marci Shannon 313-271-1500 mshannon@sme.org / www.sme.org<br />
Tungsten Toolworks 41 John Forrest 800-564-5832 john@<strong>to</strong>olalliance.com / www.tungsten<strong>to</strong>olworks.com<br />
U.S. Pho<strong>to</strong>nics Inc. 31 Kevin Whitworth 417-863-9027 info@uspho<strong>to</strong>nics.net / www.uspho<strong>to</strong>nics.net<br />
U.S. Union Tool Inc. 24 Jonathon Hay 714-521-6242 jon.hay@usunion<strong>to</strong>ol.com / www.usunion<strong>to</strong>ol.com<br />
VIEW Micro-Metrology 19 Tim Sladden 585-544-0450 ext. 460 tsladden@<strong>view</strong>mm.com / www.<strong>view</strong>mm.com<br />
Virtual Industries Inc. 33 Tom Mealey 719-572-5566 tmealey@virtual-ii.com / www.virtual-ii.com<br />
Xact Wire EDM 45 Michael Ra<strong>as</strong>ch 262-549-9005 mra<strong>as</strong>ch@xactedm.com / www.xactedm.com<br />
Carl Zeiss IMT Corp. 21 Cus<strong>to</strong>mer Service 800-327-9735 imt@zeiss.com / www.zeiss.com/imt<br />
The Advertisers Index is provided <strong>as</strong> a courtesy <strong>to</strong> advertisers. Every effort is made <strong>to</strong> avoid errors, but should one occur, <strong>MICROmanufacturing</strong> is not responsible.<br />
<strong>MICROmanufacturing</strong> (ISSN: 1938-2170) is published quarterly. Copyright 2009 by M2 Media Company, 40 Skokie Blvd., Suite 450, Northbrook, IL 60062-7903. All rights reserved. Postage paid at Northbrook,<br />
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following procedures described <strong>here</strong>in. Postm<strong>as</strong>ter: Send address changes <strong>to</strong> <strong>MICROmanufacturing</strong>, P.O. Box 2747, Orlando, FL 32802-2747. Produced in the U.S.A.<br />
micromanufacturing.com | 51
LASTword By Phillip M. Leopold,<br />
Medical Murray Inc.<br />
Thoughts from a medical<br />
micromanufacturing pioneer<br />
52 | WINTER 2009 | <strong>MICROmanufacturing</strong><br />
My son, Andy, and I bought Medical<br />
Murray Inc. in 1996. We design,<br />
develop and manufacture molded medical<br />
devices especially for minimally inv<strong>as</strong>ive<br />
treatments in three major are<strong>as</strong>—v<strong>as</strong>cular,<br />
surgical and urological.<br />
Medical Murray, headquartered in Barring<strong>to</strong>n,<br />
Ill., began <strong>as</strong> a mechanical consulting<br />
engineering company, with maybe a fourth of<br />
its business in the medical arena. We knew<br />
from the start that we were going <strong>to</strong> go 100<br />
percent in<strong>to</strong> medical devices. We both recognized<br />
that t<strong>here</strong> w<strong>as</strong> a growing emph<strong>as</strong>is<br />
[in the medical arena] <strong>to</strong> make things smaller<br />
and saw the potential for using molding <strong>to</strong> do<br />
that. We specialize in making cus<strong>to</strong>m catheter<br />
systems and components, complex disposables<br />
and implantable devices.<br />
Th e biggest challenge in working at the<br />
microlevel is <strong>to</strong> get the molds <strong>to</strong> the needed<br />
precision, because the devices are so tiny.<br />
One of the fi rst things we did w<strong>as</strong> <strong>to</strong> build an<br />
injection molding machine that incorporates<br />
a linear mo<strong>to</strong>r, which w<strong>as</strong> fairly new at that<br />
time. We designed the machine so that a very<br />
small volume of pl<strong>as</strong>tic would melt, which we<br />
could precisely control <strong>as</strong> it w<strong>as</strong> injected in<strong>to</strong><br />
the mold. In fact, the machine can be fi lled<br />
with 3 grams of material, so high-cost materials<br />
can be molded with minimal loss.<br />
Another important feature of the machine<br />
is its ability <strong>to</strong> inject pl<strong>as</strong>tic very f<strong>as</strong>t. Th is allows<br />
thin are<strong>as</strong> of the mold <strong>to</strong> fi ll before the<br />
melted pl<strong>as</strong>tic solidifi es. Th e linear mo<strong>to</strong>r<br />
moves the injection ram at the rate of 1 meter<br />
per second. By comparison, typical hydraulic<br />
presses move at 0.2 m/sec. and ballscrewdriven<br />
electric presses move at 0.4 m/sec.<br />
When making devices that go in<strong>to</strong> people’s<br />
bodies, you avoid rigid materials; you want<br />
something soft. For the most part, the materials<br />
used are polyurethane or silicone rubber.<br />
Th e primary ticket <strong>to</strong> the medical device<br />
game is the ISO 13485 medical quality certifi -<br />
cation. We don’t distribute products <strong>to</strong> the end<br />
user, so we don’t have <strong>to</strong> be registered by the<br />
U.S. Food and Drug Administration.<br />
Many manufacturers interested in entering<br />
the medical device industry <strong>as</strong>k how much<br />
volume t<strong>here</strong> is and how much money they<br />
can make. Th ey see that the fi eld is growing<br />
and the work is remaining in the country—at<br />
le<strong>as</strong>t for high-end products like complex catheters<br />
that cost from $100 <strong>to</strong> $1,000 or more.<br />
Getting those types of products made off -<br />
shore can’t be justifi ed because of the high<br />
transfer and training cost, and because their<br />
volume is fairly small—maybe a few thousand<br />
a month. And while traditionally t<strong>here</strong> have<br />
been pretty high margins in the fi eld, some of<br />
those margins are needed <strong>to</strong> help cover quality<br />
systems and <strong>as</strong>sociated liability issues.<br />
Many of the companies interested in the<br />
medical device industry don’t realize how<br />
long it takes <strong>to</strong> get a job from concept <strong>to</strong> production.<br />
We have several products now in<br />
production that we fi rst started working on 8<br />
years ago. We have <strong>as</strong> many <strong>as</strong> 30 <strong>to</strong> 40 diff erent<br />
projects in varying stages of development<br />
going on at any one time. Some might be on<br />
hold because we’re waiting for FDA approval<br />
or for some testing <strong>to</strong> come back; others are<br />
active because we’re making parts for a project’s<br />
next round of testing, and so on. About<br />
10 percent of product concepts make it <strong>to</strong><br />
fi nal production, so it’s important <strong>to</strong> have different<br />
projects in diff erent stages of development<br />
in order <strong>to</strong> stay busy.<br />
It can be diffi cult <strong>to</strong> get on a big medical<br />
company’s approved-vendor list. As in any<br />
other industry, the larger companies don’t<br />
want 500 vendors for a part. Th ey want one<br />
or two that are qualifi ed and that they can<br />
work with. It’s rare that an OEM will switch<br />
vendors because of all that’s involved in getting<br />
the vendor qualifi ed, the parts certifi ed<br />
and conducting the requisite biocompatibility<br />
testing.<br />
Th e best strategy for getting on OEMs’<br />
vendor lists is <strong>to</strong> be available and help them<br />
solve a problem that had been insurmountable.<br />
You make contact with people t<strong>here</strong> so<br />
they know you and come <strong>to</strong> you when they<br />
need help. And then—<strong>as</strong> one of their “go<strong>to</strong>”<br />
sources—they’ll call on you again <strong>to</strong> help<br />
them on other projects. µ
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