LTCC PROCESSING INSTRUCTIONS For Ferro A6 and L8 Tape

1.1 UNREEL TAPE
LTCC PROCESSING INSTRUCTIONS
For Ferro A6 and L8 Tape
FERRO Tape is commonly removed from its polyester backing film at the first stage of
processing. However, it is also possible with FERRO Tape to retain the backing film on the tape
until the lamination stage of processing is reached. If the tape is removed from the backing film,
this should be carried out in clean, dust free conditions. There is no requirement for the material
to be aged prior to further processing for stabilization purposes, and heat treatment should be
avoided, since it provides no benefit and may be detrimental to the materials further
performance.
1.2 BLANK TAPE TO SIZE
The FERRO Tape may be blanked using standard techniques such as hot knife, die cutting, or
lasering. Blanked tape should be used as soon as possible after blanking, and preferably within
2 weeks.
The lead free, non toxic nature of the FERRO Tape facilitates disposal of scrap tape.
1.3 FRAME AND REGISTER
Registration holes are commonly added to the material during blanking, or may be subsequently
punched, drilled or lasered into the unfired tape.
FERRO Tape may also be mounted onto support frames using rubber cements or similar
adhesives.
Cross plying of the FERRO Tape is not necessary.
1.4 PUNCH VIAS/CAVITIES
Vias may be formed in the FERRO Tape using mechanical punches, drills or lasers. Via
diameters as small as 2 mil (50 μm) have been demonstrated in the FERRO A6-5-M tape, but
for production purposes, a minimum via diameter of 4 mil (100 μm) is suggested. Maximum via
diameters of up to 25 mil (625μm) have been demonstrated. Ferro recommends either a USHIO
or Baccini punch.

1.5 FILL VIAS
STENCILS
At Ferro Electronic Materials, 3 mil thick brass stencils are used on an AMI printer, MP9156, to
fill vias. The brass is punched on a Ushio MP7150 punch using tight tolerance dies with 5μm
clearance and brass bottomed strippers. The brass is lightly oiled before punching and usually
is punched twice to ensure good cone-free holes.
The punched brass is mounted in a 12” x 12” frame on a stainless steel 325 mesh screen. First,
the brass is cut to size and glue is spread on one side around the edge of the brass in a band
about 1/2-inch wide. The brass is then pressed into the center of the bottom of the screen and
weights are put on the screen to ensure good contact of the brass and screen while the glue
dries.
After the glue has dried, the screen mesh is cut away from on top of the stencil. Some thin tape,
such as Scotch tape, can be used to smooth the cut edge of the screen.
PRINTER
The printer used at Ferro Electronic Materials has a porous stone base through which a vacuum
can be pulled. A backing paper is always used between the stone and the tape layer.
The printer parameters are important. These are:
PRINTING
Squeegee 90 durometer, diamond 3/8 inches.
Squeegee Set in the squeegee “down position” with the screen removed. The printer
Pressure stage with paper and tape in place is positioned under the squeegee and
the squeegee pressure adjusted to 7.5 psi.
Downstop This can be left open.
Squeegee Set to 0.6 inches per second in both directions.
Speed
Print Mode Use print/print mode, i.e., print in both directions for each filling of vias.
Vacuum Use 20-25 inches Hg. It is important that areas of the stone outside the
tape and backing paper are covered to prevent vacuum leakage. Mylar
can be used for this.
Snap-Off With stencil in place, bring the screen slowly down until the vacuum just
pulls it on to the stone with tape and backing paper on it. Then use this as
zero set-point and make snap-off at 25 mils.
Vias are filled using the print/print printer mode. After printing, the paper must stay in place
beneath the tape during the drying stage to ensure good vias. So carefully lift the paper and
tape together from the printer stone stage and place in drying oven. Dry for 30 minutes at 70°C.
Then pull tape from the paper. Only a very minor amount of paste will remain on the paper. Via
filling is typically accomplished using modified on or off contact printing with metal or plastic

ased stencils. A vacuum pull through is typically used on the printing stage, and backing paper
is typically used for backing the film during the via filling operation. Purpose built bladder type
via filling equipment may also be used with the FERRO Tape and Via fill paste systems. Precise
via filling conditions will depend on the number, size and mix of vias to be filled, and should be
determined experimentally.
1.6 DRY
After completion of via filling the parts should be dried (backing paper still supporting the tape)
in conventional drying ovens at a maximum temperature of 70°C for 20 to 30 minutes.
1.7 PRINT CONDUCTORS
Conductors are printed onto the tape using conventional screen printing techniques and
recommended screens (see individual product data sheets). Conductor prints may be dried in
conventional drying ovens at a maximum temperature of 70°C for 10 minutes.
1.8 DRY
Dry in conventional drying ovens at a maximum temperature of 70°C for 10 to 20 minutes.
1.9 PRINT RESISTORS
All co-fireable resistors are printed onto the unfired tape using #325 screens. Target dried
thickness is 25-28 μm. The resistors should be dried in conventional drying ovens at a
maximum temperature of 70°C for 10 minutes.
1.10 DRY
Dry in conventional drying ovens at a maximum temperature of 70°C for 10 to 20 minutes.
1.11 STACK LAYERS
All layers should be inspected for visual acceptance and collated.
1.12 INSERTS FOR CAVITY FORMATION
Some general guidelines are offered in “Ferro LTCC Handling and Design Recommendations.”
These must be followed for best results.
There are four principal types of cavity.
1. Cavity with vertical walls but closed at bottom.
2. Cavity with stepped walls, closed at bottom.
3. Through cavity.

4. Through cavity with stepped walls.
One other type of cavity has been produced and is a major problem to control. This cavity has a
floor that is not at the bottom of the laminate, i.e. the cavity bottom is only supported where it
joins the walls.
At Ferro Electronic Materials the preferred approach to cavity formation is to punch the cavity
layers before any metallization steps (vias, conductors, resistors). Because punching is used
cavity geometries are limited to rectangular shapes with rounded corners.
It must be recognized that removal of much of a tape layer for cavities can seriously weaken the
green sheet and cause difficulties during subsequent processing. One approach to overcome
this problem is to punch the tape cavities after metallization. Frames for this have been
produced by UHT. Results using this method at Ferro Electronic Materials have not been good
because alignment of vias were never as good as with the single punching step.
PROCESS STEPS
1. Punch each layer of tape. This punching will make both via holes and cut out the
cavity.
2. Fill vias.
3. Print conductors.
4. Print cofiring resistors.
5. Stack layers on registration fixture.
6. Put inserts in cavities (see below for inserts). Do not use top plate.
7. Vacuum bag.
8. Laminate.
9. Remove from vacuum bag and remove from registration fixture.
10. Remove inserts.
11. Trim part to size.
12. Fire.
Some of the above steps may not be necessary, e.g. some layers may have no vias.
INSERTS
Inserts are essential to prevent the cavities from distortion during lamination. At its simplest this
distortion will result in rounded cavity wall edges. At the most extreme, cavities will tend to close
up and the bottom of the cavity will lift.
The through cavities are easiest to deal with. Here inserts can be made from hard materials that
can be machined to give a good fit.
With other types of cavity the Ferro Electronic Materials preferred material for inserts is Silastic
J RTV from Dow Corning. These inserts are made by preparing a dummy part with cavities but

no metallization, etc. Only minimum pressure is used to laminate this dummy part to avoid any
cavity distortion. With Ferro Tape, 1000 psi has typically been used.
Once the dummy laminate has been prepared, the Silastic J is cast in the cavities and allowed
to cure. After curing, the inserts are removed and cleaned and are then ready for use.
Other materials that can be used for inserts are pieces of latex and other soft rubber. Latex
must be accurately cut to size however.
STEPPED WALLS
It is important to understand that a major problem can arise with stepped walls. This occurs if
inserts are too stiff and do not compress enough during the lamination step. Consequently the
steps can receive greater or lesser pressure than the bulk of the laminate and during firing
shrink at a different rate.
A similar effect can occur with cavity bottoms if a top plate is used on the registration fixture that
over compresses Silastic J or latex.
1.13 LAMINATION
Lamination may be carried out in either isostatic or uniaxial laminators. However, lamination is
critical in achieving consistent green density, and hence consistent shrinkage, hermeticity and
electrical performance, and Ferro strongly recommends the use of isostatic lamination, which
has been demonstrated to give the most consistent results.
Recommended lamination conditions are a pressure of 3000 psi, a temperature of 70°C with a
10 minute dwell time –no pressure followed by a lamination time of 10 minutes.
Ferro will provide Lamination Pressure vs. Lamination Density curves for each lot of Ferro Tape
as a reference guide for processing.
1.14 BURN-OUT / FIRING
Organic burn out may be combined with the firing operation in both box and tunnel furnaces, or
may be performed as a separate step.
The unfired laminates are heated, on their setters, at a rate of 2°C/minute to peak temperature
of 450°C, which should be maintained for a minimum of 2 hours, to ensure complete
combustion of all organics. This burn out procedure should be considered a starting point,
although it should be more than adequate for most requirements; fine tuning of the burnout
procedure will depend on part size, number of layers, and amount of metallization.

For A6 Tape use the following profile:
Ramp for 450°C to 850°C at 6-8C per minute followed by a 10 minute dwell at 850C. The air
flow should be set at 100 SCFH. It is critical that A6 see 850C for a minimum of 10 minutes
A6 Tape Burn out & Firing Profile
TemperatureC
900
800
700
600
500
400
300
200
100
25C
Standard Bakeout and Firing Profile for Ferro A6S Tape System
450C
0
0 100 200 300 400 500 600 700
450C
Time in Minutes
850C
Firing Profile is 6C - 8C per minute from 450C-850C with a minimum 10 minute soak
Bakeout Profile is 2C per minute from 250C to 450C with a 2 hour soak
For L8 Tape choose from the following profiles:
Box- Ramp for 450°C to 850°C at 4- 8C per minute followed by a 30 minute dwell at 850C
Belt- 16’ (7) Zone furnace with a 0.5” /minute belt speed and a set point of 850C –see L8
Belt profile below –contact Ferro for specific Zone air flow and temperature settings
25C

L8 Tape Burn out & Firing Profile Box Furnace
Temperature C
900
800
700
600
500
400
300
200
100
0
Standard Bakeout and Firing Profile for Ferro L8- Box Kiln
Firing Ramp Rate is 4C - 8C per minute from 450C - 850C with a 30 minute soak
Bakeout Profile is 1C* per minute from 25C to 450C with a 2 hour soak
* Bakeout ramp adjusted to 1C /min for Thicker Parts > 50-mils
0 100 200 300 400 500 600
Time in Minutes
450C
Parts less than 50 mils can generally use a 2C ramp for Bakeout depending
upon metal loading
L8 Tape Burn out & Firing Profile Belt Furnace
Temperature C
900
800
700
600
500
400
300
200
100
L8 Belt Profile
0
0 50 100 150 200 250 300 350 400 450
Time Minutes

1.15 FIRING
RECOMMENDED SETTTERS
Fused quartz for either L8 or A6 . Bare alumina setters are ok for L8 but should not be used for
A6M. In some cases Zirconia felt is better for full coverage ground plane metallization parts to
improve air flow and reduce hot spots and ultimately warpage.
RECOMMENDED SUPPLIERS
Fused Quartz GE 124, 16 micro inch surface: Behm Quartz Industries,
www.behmquartz.com 800.543.7875
Zirconia Felt: Zicar Fibrous Ceramics, Part No. ZYF-50, Tel: 800.245.2562
Alumina Setters, 96% Alumina, Coorstek www.coorstek.com
1.16 CLEANING
There is no cleaning solution for tape. Particulates are typically removed with an anti-static
brush. We recommend using only reagent grade acetone for cleaning fired parts.

LTCC DESIGN
RECOMMENDATIONS
2.1 CONDUCTOR LAYOUT
Conductor width and spacing
A B C
preferred 30 mils 20 mils 10 mils
possible 4 mils 4 mils 4 mils
Product Resistance normalized
to 25.4 microns
(mΩ/sq.)
A6 & L8 All Au
FX 30-025

L8 All Ag
CN33- 498 Ag

2.2 GROUND AND POWER PLANES
IC Bonding Fingers
FEATURE SURFACE PLANE BURIED PLANES
SOLID GROUND/POWER
PLANE
COMPLETE COVERAGE 100 MIL WIDE STRIPS MAX
GRID SIZE 10 MIL CONDUCTOR 10 MIL CONDUCTOR
15 MIL SPACING
15 MIL SPACING
CASTELLATION N/A AT EDGES OF PART OR
AT CAVITY WALL
CASTELLATION
N/A ENDS >10 MILS FROM
CLEARANCE
EDGE OR WALL
GROUNDING
N/A ENDS EXTEND >10 MILS
CASTELLATION
PAST EDGE
FEED THROUGH
CLEARANCE
20 MILS ALL SIDES 20 MILS ALL SIDES
TAPE LAYERS ABOVE OR OFFSET SPACE AND OFFSET SPACE AND
BELOW GRID PLANES LINES BY 12 MILS
LINES BY 12 MILS
X-Y
X-Y

2.3 CAVITIES

2.4 ELECTRICAL VIAS
Electrical via to edge of substrate.
Via
A
Recommended
Thickness
Diameter
Min
Punch Method
2 mil >10 mil 25 mil Punch
4-10 20 mil Punch
10 mil 25 mil Punch
4-10 20 mil Punch
10 mil 25 mil Punch
4-10 20 mil Punch

2.6 THERMAL VIAS
Product
Dimensions of Thermal Via and Catch Pad
Thermal Conductivity
(W/m-k)
Thermal
Resistance
A6
CN 30-078 (Au) >50

Thermal Hexagonal Via Pattern: Six mil vias only
Thermal Rectangular Via Pattern: 6 or 10 mil vias

2.7 RESISTORS
Technical Specification 87 Series Resistor System For A6 Tape
Tolerance Hot TCR Cold TCR
Resistor Type Ohms/square Specification (ppm/°C) (ppm/°C)
FX 87-011 Buried 10 ±30% - -
FX 87-011 Surface 10 ±30% - -
FX 87-101 Surface 100 ±30% ±450 ±450
FX 87-101 Buried 100 ±30% ±450 ±450
FX 87-102 Surface 1000 ±30% ±200 ±200
FX 87-102 Buried 1000 ±30% ±200 ±200
FX 87-103 Surface 10,000 ±30% ±200 ±200
FX 87-103 Buried 10,000 ±30% ±200 ±200
Resistor Layout and Probe Area Layout

Resistor to conductor termination overlaps for surface and buried resistors
Minimum Spacing Maximum Spacing
Layout
(mils)
(mils)
A 10 15
B 15 20
C 10 10

2.7 Resistors-cont.
Ohms
120
100
80
60
40
20
0
Blending of the 87 Series
Blend curve for 87-101Series Resistor Material with
% Additions of 87-011 (40 x 40 mil resistor)
0 20 40 60 80 100
Percent by weight of 87-011