download

Evaluating the reliability of optical connectors 

Report 1 


Yuichi Aoki Technical Development Headquarters, Reliability Research Section 

Kishichi Sasaki Reliability Center for Electronic Components of Japan, Environmental Testing Laboratory 

Kiyoyuki Mutaguchi Japan Aviation Electronics Industry, Limited, Connector Division 

W 

e performed the High Temperature Storage Test (Damp Heat) and the 

Temperature Cycling Test on optical connectors in conformance to 

the Telcordia standards. During these reliability tests, automatic 

measurements of the optical characteristics of the specimens were carried 

out and physical changes were compared. During the evaluation following 

the tests, we checked for physical changes in the tips of the optical connectors. 

We found pistoning changes occurring on the tips of the connectors, especially 

during the Temperature Cycling Test. However, these pistoning changes caused 

almost no perceptible changes in optical characteristics. The ferrule tips were 

distorted after 2000 hours at 85°C and 85 percent relative humidity, exhibited 

flattening distortion. 

1 

Introduction 

Next-generation technology infrastructure using optical fiber has been on the march 

toward achieving widespread use during recent years. Acceptance of this technology has 

resulted in demand for lower cost and miniaturized optical components, but such 

improvements must be based on information from reliability testing assuring that quality 

can be maintained. Testing to evaluate reliability of optical components is generally 

performed in conformance to the Telcordia standards. *1 These standards include 

requirements for simultaneously measuring optical characteristics of multiple specimens 

during environmental testing. 1) Measurement methods are not affected by measurement 

margin of error when measuring with the connectors either connected or disconnected. 

Additionally, automatic measuring is capable of efficiently gathering data at short 

measurement intervals. MTF (Mean Time to Failure) calculations are easy to perform using 

this system, for which published examples are available. 2,3) This report will focus on optical 

connectors, which exhibit the basic characteristics of optical components. We shall also 

consider the results of reliability testing that incorporates automatic measuring in 

conformance to the Telcordia standards. 

Fig.1 Overview of optical components 

- 1 - 

Espec Technology Report No20


2 

The Telcordia standards that require simultaneously measuring optical characteristics of 

multiple specimens are mainly concerned with passive optical components. In this report 

the term "passive optical components" refers to such items as fiber, connectors, 

switches, couplers, attenuators, and all types of filters. Table 1 shows reliability tests for 

typical optical components. 

3 

Test standards for passive optical components 

Table 1 Telcordia test standards 

Standard Title 

GR-326-CORE 

Generic Requirements for Single-Mode Optical Connectors and 

Jumper Assemblies 

GR-1209-CORE Generic Requirements for Passive Optical Components 

GR-1221-CORE 

Generic Reliability Assurance Requirements for Passive Optical 

Components 

Structure of optical connectors and factors affecting their reliability 

Optical connectors are 

used to connect optical 

fiber. Photo 1 shows 

some typical 

connectors. Fig.2 

shows the composition 

of the optical 

connectors used in these tests. 

The fiber is inserted into the housing, which is called a zirconia ferrule, and the fiber is 

held in place with a hardening epoxy adhesive. The adhesive used for the connectors is 

Epo-Tek353ND (Epoxy Technology, Inc.). The degradation of this adhesive is a crucial 

element leading to the loss of the reliability of the optical connectors. A major factor 

producing degradation is the absorption of humidity, which causes degradation to occur 

over time. 1~5) Photo 1 Optical connectors 

The High Temperature Storage Test (Damp Heat) is used to evaluate 

humidity-induced degradation. As Fig.2 shows, adhesive degradation resulted in 

pistoning changes to the ferrule tip on the end of the optical connectors. A significant 

amount of pistoning causes such problems as an increase in air layers and an increase in 

leakage of insertion light. These problems result in an increase in optical loss. 

The Temperature Cycling Test was also run to evaluate the progression of cracking 

caused by micro-cracks in the fiber. 

- 2 - 



Fig.2 Structure of optical connectors and factors affecting their reliability 

4 

Environmental test system for optical components 

An environmental test system for optical components was developed to be used in this 

research for testing the reliability of passive optical components. Photo 2 shows the 

system, and Fig.3 shows a block diagram of the system. 

This measurement system selects the light source wavelength using an optical switch 

selector, and is capable of measuring a maximum of 170 channels simultaneously for 

multiple specimens during environmental testing. This capability puts the system in 

conformance to the requirements of the Telcordia standards. The system is capable of 

measuring insertion loss, *4 return loss, *5 and PDL (Polarization Dependent Loss). *6 

Photo 2 Environmental Test System 

- 3 - 



5 

Test method 

Fig.3 System block diagram 

The High Temperature Storage Test (Damp Heat) and the Temperature Cycling Test 

were run using optical connectors as specimens. Table 2 shows the test conditions, and 

Table 3 shows the specimens. The test conditions complied with the 

Telcordia-GR-1221-CORE standards. The specimens consisted of single mode *7 SC and FC 

connectors. As seen in Fig.4, the specimens were connected in groups of three optical 

connectors with fiber and with the measurement points n = 5 (groups). The 

measurement system was used to measure insertion loss and return loss. Table 4 shows 

the measurement conditions. 

The test specimens were measured after each 1000 hours of the High Temperature 

Storage Test (Damp Heat) and after the completion of the Temperature Cycling Test. A 

Ferrule Tip Condition Surveyor (Direct Optical Research Company) was used to measure 

ferrule tip curvature radius, *8 eccentricity, *9 and pistoning. Failure was determined using 

the Telcordia-GR-1221-CORE evaluation standards shown in Table 5. 

The Temperature Cycling Test was not effective for determining degradation, since 

changes occurred in both insertion loss and return loss in the optical fiber temperature 

characteristics in this test. The PVC sheath *10 coating in particular exhibited major 

changes at low temperatures, and so the test was run using Hytrel ® core *11 , which 

exhibited minimal loss at low temperatures as seen in Fig.5. 

- 4 - 



Table 2 Reliability test conditions 

Test items Test Conditions 

High 

Temperature 

Storage Test 

(Damp Heat) 

Temperature 

Cycling Test 

85°C, 85%rh, 

2000 h 

-40°C ←→ 85°C, 

1 hour each, 500 

cycles 

Fig.4 Test method 

Table 4 Measurement conditions 

Items Details 

Measurement items 

Insertion loss and 

return loss 

Light source 

wavelength 

1310 nm, 1550 nm 

Light source power 1 mW 

6 

Measurement 

intervals 

Test results 

Every 10 to 15 min. 

Specimens 

No. of 

specimens 

Evaluation 

method 

- 5 - 

Table 3 Specimens 

FC connectors, SC connectors 

(single mode) 

n = 5 

Insertion loss and return loss 

(optical component 

environmental test system) 

Tip condition measurement 

(pistoning, eccentricity, and 

curvature radius) 

Fig.5 Fiber temperature 

characteristics 

Table 5 Evaluation standards 

(from Telcordia GR-1221-CORE) 

Requirement Objective 

Insertion 

loss 

change 

0.3dB 0.2dB 

Return 

loss 

change 

6-1 Test results from the High Temperature Storage Test (Damp Heat) 

5dB 2dB 

Fig.6 shows the measurement results for the light source wavelength of 1310 nm for the 

first 1000 hours of the 2000-hour High Temperature Storage Test (Damp Heat). After 

1000 hours and again after 2000 hours, we verified that fluctuation did not exceed any 

evaluation standards. In addition, identical trends were exhibited for both light source 

wavelengths, 1310 nm and 1550 nm. No major difference was seen between the FC 

connectors and the SC connectors. 



Test time (h) 

(a) SC connector insertion loss 

Test time (h) 

(c) FC connector insertion loss 

- 6 - 

Test time (h) 

(b) SC connector return loss 

Test time (h) 

(d) FC connector return loss 

Fig.6 Results of the High Temperature Storage Test (Damp Heat) 

(light source wavelength: 1310 nm) 

6-2 Results of the Temperature Cycling Test 

Almost no differences were seen between the FC connectors and the SC connectors in 

the Temperature Cycling Test. Fig.7 shows partial measurement results for the SC 

connectors. Some insertion loss change and return loss change was seen following 

temperature changes in the temperature chamber during the Temperature Cycling Test, 

but these changes did not exceed the evaluation standard limits. The changes included 

insertion loss occurring at low temperatures, but no major fluctuation was seen at high 

temperatures. Return loss, however, tended to increase at high temperatures. Looking at 

the return loss changes over the long term confirms that as soon as return loss increases, 

the fluctuation stabilizes. This is thought to indicate that return loss quality stabilizes due 

to the adhesion of the connectors over time. 



(a) Insertion loss 

(b) Return loss 

Fig.7 Results of the Temperature Cycling Test 

(SC connectors; light source wavelength, 1310 nm) 

6-3 Pistoning measurement results 

Measurement results for the ferrule tip surfaces did not indicate major changes in 

eccentricity and curvature radius, but the measurements confirmed that changes 

occurred in pistoning compared to the initial values. 

Fig.8 shows pistoning measurements after 1000 and 2000 hours of the High 

Temperature Storage Test (Damp Heat), and after 500 cycles of the Temperature Cycling 

Test. This report represents the direction of pistoning as a negative value. In the IEC, the 

standard for tolerance is recommended as -50 to 100 nm, and this level is exceeded, but 

the insertion loss and return loss measurements did not exhibit conspicuous fluctuation. 

On the other hand, optical connectors with powerful insertion light may be subject to 

influence by pistoning. Because of this, we face the challenge of investigating the 

relationship between pistoning and optical characteristics in such areas as manufacturing 

conditions. 

In this research, more pistoning occurred in the Temperature Cycling Test than in the 

High Temperature Storage Test (Damp Heat), regardless of whether the type of fiber 

coating included Hytrel ® core or the PVC sheath. The cause for the increased pistoning is 

thought to include stress in the direction of the pistoning from contraction and peeling of 

the adhesive. This, in turn, is thought to be possibly caused by the effects of humidity and 

the re-hardening of the adhesive at the test temperature (85°C) for reliability testing. 

- 7 - 



Test time (h) 

(85°C, 85%rh, PVC sheath coating) 

Test cycles 

(-40/85°C, 1 hour each, PVC sheath coating) 

Test cycles 

(-40/85°C, 1 hour each, Hytrel ® core) 

Fig.8 Changes in pistoning 

- 8 - 



6-4 Observation of the tip shape 

Fig.9 shows the results of observations made on the shape of the ferrule tip before and 

after the High Temperature Storage Test (Damp Heat). After 2000 hours at 85°C and 85 

percent relative humidity, the surface of the ferrule tip showed signs of pitting and was 

rougher than before testing. This roughness did not appear on the surface of the tip after 

the Temperature Cycling Test, leading to the conclusion that the roughness was caused 

by humidity. Fig.10 shows a three-dimensional computer graphics rendition of the shape 

of the tip. After 2000 hours at 85°C and 85 percent relative humidity, the ferrule tip 

exhibited flattening distortion. However, pistoning measurements with the Ferrule Tip 

Condition Surveyor measured the position of the apex of the tip from the sphericity of the 

ferrule tip, and, using that position as a standard, calculated the amount of pistoning. 

Accordingly, if the position of the tip section differs from these measurements, the 

amount of pistoning could be greater than that calculated. 

(a) Initial period 

(b) After testing 

Fig.9 Ferrule tip observation (85°C, 85%rh, 2000 h) 

(Initial period) (-40 /85°C, 500 cycles) (85°C, 85%rh, 2000 h) 

Fig.10 Three-dimensional shape of the ferrule tip 

- 9 - 



7 

The optical characteristics of the optical connectors reviewed for this study were 

automatically measured during the High Temperature Storage Test (Damp Heat) (at 

85°C and 85 percent relative humidity for 1000 hours) and the Temperature Cycling Test 

(at 85°C / -40°C for 500 cycles of one hour each). We obtained the following results. 

(1)No changes occurred in optical characteristics, but pistoning increased in the 

connectors. 

(2)Increased pistoning of the ferrule tips was observed in both the Temperature Cycling 

Test and the High Temperature Storage Test (Damp Heat), but the major changes 

occurred in the Temperature Cycling Test. 

(3)The post-test condition of the ferrule tips after testing at 85°C and 85 percent relative 

humidity for 2000 hours exhibited flattening distortion. This result could indicate that 

the actual pistoning was greater than the calculated amount. 

8 

Conclusion 

Topics for future discussion 

Many aspects of the relationship between pistoning and optical characteristics have yet 

to be confirmed, and topics such as manufacturing conditions also require research. 

[Terminology] 

*1.Telcordia 

The breakup of the American communications giant AT&T (Bell Telephone) created 

seven regional telephone providers (the so-called "Baby Bells") and established a 

research and development company initially called Bellcore. Later, when this 

subsidiary was sold to a company unrelated to the original Bell, the company became 

known as Telcordia Technologies. In the field of communications in the U.S., the 

Telcordia standards are widely referenced as the baseline standards for this field. 

*2.SC connectors, and *3. FC connectors 

Both of these optical connectors are zirconia ferrule (refer to Fig.2 above) connectors 

developed in Japan that are widely used throughout the world. The stationary part of 

the SC connector is made of plastic, and can be connected by merely being pressed 

on. The stationary part of the FC connector, though, is made of metal and must be 

attached with screws. 

*4.Insertion loss 

The transmission loss occurring when light passes through the part. This value 

compares the insertion light with the outgoing light, and is expressed in decibels. 

*5.Return loss 

This value compares the insertion light power and the reflected light power of the 

reflected light returning inside the part. This value is expressed in decibels. 

- 10 - 



*6. PDL (Polarization Dependent Loss) 

The PDL value measures the change occurring in insertion loss caused by 

polarization. Polarization is a condition of deviation in the vibrational direction of 

light. 

*7. Single mode 

Single mode is a condition which provides light with a single pathway of propagation. 

This mode contrasts with multi-mode, which consists of multiple pathways of light 

propagation. Due to the mode-dispersed loss occurring in multi-mode, single mode 

is used for long-distance transmission. 

*8. Curvature radius 

The length (in mm) of the radius of a circle from a circumference projected from a 

curved surface. 

*9. Eccentricity 

The length (in µm) of the deviation between the center of the ferrule and the center 

of the core of the optical fiber. 

*10.PVC sheath 

This polyvinyl chloride (PVC) sheath, referred to as optical fiber cable, has a 

protective fiber coating. This type of sheath is mainly used indoors. 

*11.Hytrel ® core 

Hytrel ® is a polyester elastomer made of thermoplastic resin that was developed by 

the Dupont Corporation. This substance is an engineering plastic with superb 

features such as strength and heat characteristics. Hytrel ® core is a fiber optic 

stranded conductor coated with this elastomer. 

[Bibliography] 

1) "Generic Reliability Assurance Requirements for Passive Optical Components", 

Telcordia GR-1221-CORE Issue 2, 1999 

2) T. Tomasi, I. De Munari, V. Lista, L. Gherardi, A. Righetti, M. Villa: "Passive optical 

components: from degradation data to reliability assessment-preliminary results", 

Microelectronics Reliability 42, p.1333-1338, 2002 

3) A. Piccirillo, G. Zaffiro, T. Tambosso, G. Gallo: "Reliability of Optical Branching 

Devices", IEEE (Institute of Electrical and Electronics Engineers), Journal of Selected 

Topics in Quantum Electronics, Vol.5 No.5, 1999 

4) F. Caloz, D. Ernst, P. Rossini, L. Gherardi, L. Grassi, J. Arnaud: "Reliability of optical 

connectors - Humidity behavior of the adhesive", Microelectronics Reliability 42, 

p.1323-1328, 2002 

5) Tetso Kumazawa, Makoto Shimaoka, Kazuyuki Fukuda: "Moisture Absorbency of 

Optical Components Resin Adhesive" Journal of Japan Institute of Electronics 

Packaging, Vol.4, No.7, p.621- 624, 2001 

- 11 - 


Measuring conductivity of proton conductive membranes in the direction of thickness 

Report 2 

Measuring conductivity of proton conductive membranes in the 

direction of thickness 

Shuhua Ma, Akiko Kuse Technical Development Headquarters, Espec Corp. 

Zyun Siroma, Kazuaki Yasuda National Institute of Advanced Industrial Science and Technology (AIST) 

P 

roton conductive membrane is generally evaluated by measuring its 

conductivity along the planes of the membrane. However, in view of the 

possibility of this membrane exhibiting anisotropy in the direction of 

membrane thickness compared to measuring along the longitudinal and 

transversal planes, the need to measure its conductivity in the direction of 

thickness has recently been receiving greater attention. The research work 

for this report is aimed at finding a way to stably and precisely measure the 

conductivity of a Nafion ®1) membrane in the direction of thickness. 

Measurements can be conducted with either 2- or 4-probe methods, but 

measuring with 2 probes is much easier than with 4, and this method yields 

more stable results as fewer inconsistencies occur with multiple specimens. 

This report presents the results with the 2-probe method for membrane 

conductivity measurements with an emphasis on the effect of interface 

complexity between membrane and electrodes and the feasibility of using 

this method for measurements. 

1 

Polymer electrolyte membrane fuel cells (PEFCs) are promising energy systems for use 

as automotive power supplies and for stationary as well as portable applications, due to 

their low operating temperature, high energy density, and acceptable levels of 

miniaturization. Since it is one of the most important criteria, proton conductivity is 

always used to evaluate the practicability of newly-developed membranes as well as the 

cell performance of the perfluorosulfonic acid (PFSA) polymer membrane often used with 

PEFC. 2) 

Introduction 

Compared to the conductivity in the direction of thickness, the resistance measured in 

along the plane reaches as high as 1000Ω, which features a large cell constant *1 (L/A in 

σ=L/(R·A)). The four-probe method *2 yields narrower data dispersion and smaller 

relative errors, thus this method is commonly used to measure the proton conductivity of 

the PFSA membrane *3 along the plane. 

- 12 - 



However, it is highly likely that treatments the membrane undergoes in the 

manufacturing and processing processes, such as stretching and hot-press, will change 

not only its crystalline structure and dimensional stability in the longitudinal, transverse, 

and thickness directions but also exert some influence on its proton conductivity. There 

is a high probability of anisotropy3) in the proton conductivity of the membrane. On the 

other hand, PFSA membranes are being used in the direction of thickness for the solid 

polymer electrolyte fuel cells, and an anisotropically conductive membrane that was 

newly-developed must also be evaluated in various directions. Therefore, a reliable 

measuring technique with high stability, reproducibility and accuracy is required to 

evaluate proton conductivity in the direction of thickness of the membrane. The research 

for this report focuses on developing a stable and precise method of measuring 

conductivity in the direction of thickness for the proton-conductive polymer electrolyte 

membrane. 4) 

Measurements in the direction of thickness can be conducted with 2-probe *4 and 

4-probe methods, but measuring with two probes is much easier than with four, and 

results are more stable as there are fewer inconsistencies with multiple specimens. This 

report presents the results obtained using the 2-probe method for conductivity 

measurements of ion exchange membranes. 

2 

Experimental method 

2-1 Equipment and materials 

Table 1 lists the equipment and materials used in this research. 

Table 1 Equipment and materials 

Equipment/materials Manufacturer 

Impedance gain/phase 

analyzer 

- 13 - 

Model/registered 

product name 

Solartron Instruments SI 1260 

Electrochemical interface Solartron Instruments SI 1287 

Temperature & humidity 

chamber 

Ion exchange membrane 

ESPEC Corporation PL-1KPH 

E. I. du Pont de Nemours 

and Company 

Nafion ® 117 



2-2 Specimen preparation 

MEA specimens were made by hot-pressing electrodes to a Nafion ® 117 membrane. In a 

preliminary test, measurements were made with two kinds of MEAs. One type of MEA 

specimen was produced by hot-pressing two Pt foil electrodes, coated with Nafion ® 

solution on one side each, to a membrane. The other MEA specimen was produced by 

hot-pressing two Pt foil electrodes to a membrane without using the Nafion ® coatings. 

Results showed good reproducibility with the Nafion ® -coated specimen, therefore, in this 

report specimens were prepared by coating a Nafion ® solution onto one surface of the 

electrodes for voltage impression unless otherwise specified. 

For 2-probe measurements in the direction of thickness, specimens were prepared by 

hot-pressing a Nafion ® membrane sandwiched into electrodes consisting of two pieces of 

metal sheets (5 mm x 5 mm x 10 to 20µm) or carbon papers (5 mm x 5 mm x 190µm) 

situated opposite each other. On one face of the metal sheets, a coating was applied with 

5 µl of 5 wt. % Nafion ® dispersion solution in lower aliphatic alcohols followed by vacuum 

drying one hour at room temperature. No coating was used on the carbon paper 

electrodes. Photo 1 shows the configuration of the membrane/electrode assembly 

(MEA *5 ) used in this report for the 2-probe measurements in the direction of thickness. 

The assembly is made of platinized Pt black sheets and Nafion ® 117 membrane. 

Photo.1 MEA of Pt black/Nafion ® 117 for 2-probe measurements in 

the direction of thickness 

For 4-probe measurements in the direction of thickness, the specimens were prepared 

by sandwiching and hot-pressing platinum wire electrodes between three Nafion ® 

membranes and then, as with the specimens for the 2-probe measurements, 

hot-pressing metal sheets that had been coated with Nafion ® solution and vacuum-dried 

onto both outside faces of the assembly. 

- 14 - 



Since 4-probe measurements in the surface direction obtained results with better 

reproducibility, these measurements were used as comparison reference against the 

measurements in the direction of thickness of the membrane. The specimens for 4-probe 

surface direction measurements were prepared by press-fitting metal sheets to both 

ends of the Nafion ® membrane and vertically piercing into the membrane near the center 

with platinum wires. 

Fig. 1 (a) and (b) respectively show schematics of the specimens for the 2-probe and 

4-probe measurements in the direction of thickness, while (c) shows the same for the 

4-probe surface direction measurements. 

Fig.1 Sample arrangements for (a) the 2-probe method, (b) the 4-probe 

method in the direction of thickness, and (c) the 4-probe method in 

the surface direction 

2-3 Conductivity Measurements 

A specimen fixed to a measuring cell was placed inside a temperature and humidity 

chamber under constant temperature and humidity (80°C, 30 to 90% rh). AC impedance 

measurements were taken using a computer-controlled Solartron Instruments model 

1260 impedance gain/phase analyzer and a computer-controlled 1287 electrochemical 

interface, and Cole-Cole (Z’-Z’’) and Bode (log|Z|-log Frequency and theta-log 

Frequency) plots were obtained. The frequency limits of the sinusoidal signals were 

typically set between 5 MHz and 0.01 Hz, with an oscillation of 10 mV. Assuming a circuit 

equivalent to the one shown in Fig.3, a best-fitting curve was overlaid onto the 

measurements taken by the 2-probe method. Conductivity was calculated from the 

obtained membrane resistance, Rbulk, using the following formula. 

…(1) 

Where σ is conductivity (Scm-1 ), L is membrane thickness (cm), A is electrode area 

(cm2 ), and R is resistance (Ω). 

- 15 - 



Equipment connection for the impedance gain/phase analyzer (IGPA), the 

electrochemical interface (EI) and the membrane/electrode assembly (MEA) was shown 

in Fig. 2 for 2-probe conductivity measurements used in this report. 

3 

Fig.2 Connections for impedance measured by the 2-probe method, with an 

IGPA in combination with potentiostat/galvanostat (electrochemical 

interface) mode. 

Results and observations 

3-1 Humidity dependency of resistance and capacity components of impedance 

In the Cole-Cole plot obtained from the 2-probe measurements, two loops appeared. 

They were named loop 1 and loop 2 in order of descending frequency and were treated as 

RY parallel circuits. The resistance and capacity components obtained from the fit were 

R1, R2, Y1 and Y2 (Y is a constant phase element and substituted for the equivalent 

capacity component in the fitting process). Fig. 3 shows a diagram of the equivalent 

circuit. 

Fig.3 Equivalent circuit for the membrane/electrode interface studied 

- 16 - 



Measurements were taken at an ambient temperature of 80°C using 4 types of 

electrodes made of gold, platinum, platinum black and carbon paper. Fig. 4 shows the 

humidity dependency of Rbulk (membrane resistance), R1, Y1, R2, and Y2 using the various 

electrode materials. 

As ambient relative humidity during measuring increased, Rbulk, R1, and R2 decreased. 

This phenomenon indicates that the conductivity of proton-conductive polymer materials 

such as Nafion ® depend on their water content. In particular, minimum resistance was 

obtained for R1 and R2 when using the platinum black electrode with higher active 

surface area, suggesting that both loop 1 and loop 2 with R/Y parallel connections are 

strongly correlated to the interface between membrane and electrode. With capacitance 

components of Y1 and Y2, regular increases in electrical capacity were found to 

correspond to increases in ambient humidity. Increases in this electrical capacity can be 

considered to result from improved contact between membrane and electrode concurrent 

to the hygroscopic swelling of the moisture-absorbent membrane. Types and surface 

morphology of electrode materials also notably affect interface resistance and capacity 

due to their varied surface area and differences in membrane contact. However, with Rbulk 

membrane resistance, equivalent measurement values have been obtained for various 

electrode materials with no major influence based on material types found. Therefore, it 

can be concluded that membrane resistance (Rbulk) can be separated from interface 

elements (R1, Y1, R2, and Y2) regardless of electrode materials used, since the 

multi-layer complexity of contact of the interface between membrane and electrodes, 

e.g., multiple semicircles in Cole-Cole plot, can be removed by equivalent circuit fitting. 

- 17 - 



Fig. 4 Dependence on relative humidity of various electric elements in 

equivalent circuits at 80°C 

- 18 - 



3-2 Conductivity 

Conductivity was calculated using Rbulk from Fig. 4 (a) and formula 1. Fig. 5 shows the 

conductivity values measured at an ambient temperature of 80°C and various humidity 

levels. For comparison, the results from 4-probe measurements in surface direction were 

also plotted. As shown in Fig. 5, conductivity results using 2-probe measurements in the 

direction of thickness were similar to those using 4-probe measurements in the surface 

direction for all electrode materials, demonstrating the validity of using the 2-probe 

method in the direction of thickness. 

4 

Fig. 5 Comparison of conductivity results at 80°C using the 2-probe 

Method in the direction of thickness and the 4-probe method in 

the surface direction. 

Conclusions 

Conductivity of Nafion ® membranes in the direction of thickness was measured using the 

2-probe AC impedance method. These experiments confirm that equivalent circuit fitting 

can separate membrane resistance from the interface components. Moreover, good 

contact at the interface between the membrane and electrode can be attained by coating 

the electrode with Nafion ® solution, and conductivity results are similar to results using 

4-probe measurements in the surface direction. These experiments demonstrate the 

validity and feasibility of using the 2-probe method for measuring in the direction of 

thickness. 

- 19 - 



[Terminology] 

*1.Cell constant 

Typically, electrical conductivity of a material can be expressed as 

σ=L/(A·R)=k/R, where L is the length (cm) of the material in electronic flow, A is 

the sectional area (cm2 ) across the flow of the material, R is the measured resistance 

(Ω), and k=L/A, the proportionality factor, is called the cell constant. The electrical 

conductivity of the material is in direct proportion to the reciprocal of the measured 

resistance between the electrodes by the scale factor, k, which represents the 

influence of the dimensions of the measuring cell. 

*2.Conductivity measurement using the 4-probe method 

As one method for measuring the electrical conductivity of materials, the 4-probe 

method possesses much higher measurement precision than the 2-probe method. 

Two terminals are used to conduct a current through the sample, and another two 

terminals measure the potential drop across the sample. 

*3.Proton-conductive membrane 

When potential difference exists in a conductor, electrical charges move in the 

direction required to weaken the difference. The property of this conductor is called 

its electrical conduction. When protons exist in the conductor as the main current 

carriers, the material is referred to as proton conduction, and the quality or power of 

the conduction is called proton conductivity. Some membrane materials, typically 

consisting of such as inorganic compounds of ceramics and/or glass, organic 

polymer compounds, and inorganic/organic hybrid materials, exhibit high H + ion 

conduction. Proton exchange membranes based on fluorinated polymers as typified 

by Nafion ® have been widely used in solid polymer electrolyte fuel cells (PEFCs) due 

to their high proton conductivity (to 0.1 Scm-1 ) and chemical stability. 

*4.Conductivity measurement using the 2-probe method 

As the simplest and most straightforward method for measuring electrical 

conductivity, the 2-probe method uses only two terminals that share the functions 

of both introduction of current (I) and measurement of voltage (V) across the 

sample. The electrical conductivity of a specimen can be calculated with the formula 

of σ=(I·L)/(V·A), provided that sectional area (A) and length (L) of the specimen are 

measured. 

*5.Membrane electrode assembly (MEA) 

An electrode layer composed of platinum black or platinum-supporting carbon and a 

porous supporting collector layer composed of carbon paper or carbon cloth 

arranged in succession on both sides of a cation exchange membrane, with the 

assembly unified by hot-pressing, is called a membrane electrode assembly (MEA). 

[Bibliography] 

1)http://www.fuelcells.dupont.com/ 

2)Y. Sone, et al., J. Electrochem. Soc., 143, p.1254, 1996 

3)K. M. Cable et al., Chem. Mater., 7, p.1601, 1995 

4)A. Kuse, S. Ma, A. Mizugaki, H. Okuda, Z. Siroma, T. Ioroi, K. Yasuda, Y. Miyazaki; 

11th FCDIC Fuel Cell Symposium Proceedings, p.262, 2004 

- 20 - 


New product focus: Ultra View Temperature (& Humidity) Chamber 

Topic 1 


Toshimi Ishida, 

Takehiko Umehara, 

1 

Introduction 

Environmental Test Business Headquarters, Business Control Department, 

Product Planning Group 

Environmental Test Business Headquarters, Development & Design Department, 

Product Development Group 

The Ultra View Temperature (& Humidity) Chamber is based on the overwhelmingly 

popular Espec Platinous K series of environmental test chambers that has become 

established as our flagship product line. The new chambers are equipped with large glass 

viewing windows that enable the user to visually inspect the condition of specimens 

during tests. We are pleased to offer these products that we have developed to meet this 

basic need of our customers. 

When large viewing glass windows were provided on temperature and humidity 

chambers in the past, the design imposed limits on product performance, but this new 

chamber utilizes multilayer deposit metal electro-coated (EC) glass panes, enabling these 

models to maintain performance at the highest level. 

Potential market applications for these chambers include testing a wide variety of 

products such as automotive parts, household appliances, display devices ranging from 

cellular telephones to LCD monitors, and all types of information technology equipment. 

Display devices in particular are now being rushed to market as quickly as possible. 

Providing the ability to visually confirm the changes induced by temperature and humidity 

to these products fills a basic need of our customers for visual observation and inspection. 

Naturally, this advantage is not limited to display devices, but can also be applied to a 

wide range of product testing. 

Photo 1 Ultra View Temperature (& Humidity) Chamber 

- 21 - 



2 

Product features 

The features offered with these new chambers include full visibility from a widely 

expanded viewing area, anti-fogging viewing window panes, markedly improved 

performance, improved reliability of the viewing glass, and greatly improved ease of use. 

2-1 Full visibility 

The glass viewing windows provide full visibility from a widely expanded viewing area, 

offering a better view of the chamber interior and maintaining adequate light. 

Table 1 Viewing window effective size 

New product Established Espec products 

Type 2 470×720 310×650 

Type 3 570×820 410×750 

Type 4 970×970 810×900 

Effective viewing dimensions W×H (mm) 

These new chambers use twin type fluorescent lighting attached to the upper section of 

the chamber door, maintaining good lighting inside the test area. Conventional halogen 

lighting gives off a yellow hue that provides an unnatural tint to the specimens from the 

lighting, but the twin type fluorescent lighting utilized in the new test chamber makes it 

possible to reproduce natural colors. As an additional benefit, replacement parts can be 

obtained at reasonable prices. 

Table 2 Twin type fluorescent bulbs 

(1 bulb for types 2 and 3; 2 bulbs for type 4) 

Type 3 Type 4 

Lighting at the center 

of the chamber 

650 lux 1000 lux 

 

In Japan, domestic regulations for safety and health require businesses to provide the 

following lighting levels for workers in the workplace (excluding special types of work). 

Table 3 Lighting and illumination standards 

Workplace Standard 

Fine work 300 lux min. 

Normal work 150 lux min. 

Simple rough work 70 lux min. 

- 22 - 



2-2 Anti-fogging viewing window panes 

Environmental test chamber not only requires interior lighting and the effective visibility 

noted on the previous page, the chamber must also prevent the glass panes from fogging 

up due to the temperature and humidity conditions inside the chamber. Fogging occurs 

when the moisture in the air condenses on the surface of the glass. The conventional 

method of preventing fogging was to install a heater to warm the surface of the glass, but 

this approach required maintaining the glass surface temperature above the dew-point 

temperature, which was not economical. Also, during tests using such conditions as high 

temperature and low humidity, a heater is not required to maintain the glass surface 

temperature above the dew-point temperature. These new chambers prevent fogging on 

the glass surface using a heater control inside the glass, so instead of merely applying 

constant heat to the glass, only the minimum amount of heat required is used, thus 

conserving energy. (Patent pending) 

Glass using conventional heat-reflecting film or incorporating heating wires required the 

chamber design to incorporate upper and lower heat limits that were suited to the 

thermal limits of the glass panes. When reach-in ports were added to provide a means of 

operating the specimens, the glass surface in the vicinity of the reach-in ports tended to 

fog up, and localized hot spots occurred. This fogging was caused by not being able to 

place heaters near the reach-in ports (due to the processing on the glass for the ports) so 

that the heater current did not flow near the reach-in ports, resulting in a difference in 

current density in the vicinity of the reach-in ports. These new chambers are designed so 

that the current density is the same in all areas of the glass, including the areas around 

the reach-in ports, with no unevenness in current. Even when reach-in ports must be 

provided, there is no fogging on the surface of the glass, and the specimens can be clearly 

observed and operated. (Fig.1) (Patent pending) 

 

Fig.1 Current flow with viewing window reach-in ports in glass doors 

- 23 - 



2-3 Markedly improved performance 

Using conventional heat-reflecting film or incorporating heating wires in the glass panes 

required design limits on the performance of the chambers, but by utilizing glass 

reinforced with layers of deposit metal film, performance can be markedly upgraded. This 

design permits a wide temperature range, from –40°C to +120°C. 

Table 4 Comparison of lowest and highest achievable temperatures 

Lowest achievable emperature Highest achievable temperature 

New chambers -40°C *1 +120°C *2 

Established chambers -20°C to -35°C +80°C to +100°C 

*1 This performance table conforms to JTM K01-1998. 

*2 With the optional “viewing window reach-in ports”, the limit is +100°C. 

Expanding this temperature range makes it possible to apply the following types of test 

conditions as well. 

 

(1)LCD device environmental tests 

Storage (at high temperature) test: +30 to +100°C 

Storage (at low temperature) test*: -50 to 0°C 

Damp heat, steady state test: +40°C, 93%rh to +85°C, 93%rh; 85°C, 85%rh 

Composite temperature/humidity cyclic test: +25°C, 93%rh to +65°C, 93%rh; 

-10°C 

Standards: IEC61747-5 (JIS C60068-2-38), EIAJ ED-2531A 

(2)Automotive parts environmental tests 

High Temperature, Low Temperature Test: +120°C to –40°C 

High Temperature Exposure Test: +120°C 

Low Temperature Exposure Test: -30°C 

Standards: JIS D 0204, 0208 

(3)PDP environmental tests 

High Temperature (storage): +30 to +100°C 

Low Temperature (storage)*: -50 to 0°C 

High Temperature, High Humidity (constant): +40 to +60°C, 85% or 93%rh 

Low Temperature Operation: -20 to 0°C 

(*The Ultra View Temperature (& Humidity) Chamber is compatible down to 

-40°C.) 

To meet the demand for these standards, Espec has utilized glass reinforced with deposit 

metal, broadly extending the temperature range from –40°C to +120°C. 

The new chambers offer a greatly extended range of control for humidity as well as for 

temperature. 

- 24 - 



Fig.2 Temperature and humidity control range 

The new chambers also offer improvement in the temperature heat-up time and 

pull-down time. 

Table 5 Comparison of temperature heat-up time and pull-down time 

New chambers 

Established 

chambers 

Temperature heat-up time Temperature pull-down time 

50 minute max. 

(-40°C to +120°C) 


(-35°C to +100°C) 

- 25 - 


(+20°C to –40°C) 


(+20°C to –35°C) 

2-4 Improved reliability of the viewing window glass 

Glass using heat reflective film suffers deterioration of the film with long-term use, 

resulting in impaired visibility. Glass incorporating heating wires can suffer wire breakage 

leading to fogging of the glass surface. Utilizing glass reinforced with deposit metal film 

has eliminated these defects, providing solidly improved reliability. 

2-5 Greatly improved ease of use 

Not only responding to the need for visual inspection, we at Espec have responded to the 

desire to touch, operate, and measure the specimens by offering optional “reach-in ports” 

on the viewing window (one each on the right and left sides, for a total of two ports). 

Conventional reach-in ports had screw-on covers, requiring extra time and effort to open 

and close. There was also a danger of scratching the glass around the reach-in ports when 

opening and closing the screw-on covers, and finding where the covers were put after 

they had been removed could cause problems for the operator. 

These new chambers have incorporated one-touch swing covers for the reach-in ports. 

These covers are easy to open and close, and the operator never has to look for the 

covers. (Photo 2) 



 

Photo 2 Opening and closing the reach-in port on the viewing window 

- 26 - 



When the job requires continual work using the hands inside the reach-in ports, the 

releasing hinges allow for completely removing the covers. 

→ → 

Photo 3 Removing the reach-in port covers on the viewing window 

Interior lighting (fluorescent) is built into the upper section of the door. The bulbs can be 

easily replaced with no halt in testing. A dew condensation tray is also built into the lower 

section of the door to prevent water dripping onto the floor when the door is opened. 

Photo 4 Removing the interior lighting cover 

- 27 - 



3 

Table 6 shows the main specifications of the new chambers. 

Table 6 Main specifications 

Model PWL-2KP PWL-3KP PWL-4KP PWU-2KP PWU-3KP PWU-4KP 

Power supply 

Temperature (& humidity) 

control system 

- 28 - 

200V AC 3Ф 3W 50/60Hz, 

220V AC 3Ф 3W 60Hz, 

380V AC 3Ф 4W 50 Hz 

Balanced temperature and humidity 

Balanced temperature control (BTC) 

control (BTHC) 

Working temperature range 0 to +40°C 

Temperature range -40 to +120°C 

Humidity range 20 to 98%rh ---------- 

Temperature 

-40 to 

+100°C 

±0.3°C 

fluctuation +100.1 to 

+120°C 

±0.5°C 

Humidity fluctuation ±2.5%rh ---------- 

Performance 

*1 

Temperature 

-40 to 

+100°C 

±0.5°C ±1.0°C ±0.5°C ±1.0°C 

uniformity +100.1 to 

+120°C 

±0.75°C ±1.5°C ±0.75°C ±1.5°C 

Humidity uniformity ±3.0%rh ±5.0%rh ---------- 

Temperature 

heat-up time 

Within 50 min from -40 to +120°C 

Temperature 

pull-down time 

Within 60 min from +20 to -40°C 

Effective viewing dimensions 

(W×H mm) 

Dimension 

*2 

Specifications 

Test area dimensions 

(W×H×Dmm) 

Outer dimensions 

(W×H×D mm) 

470x720 570x820 970x970 470x720 570x820 970x970 

500× 

705× 

600 

910× 

1590× 

1039 

600× 

850× 

800 

1010× 

1690× 

1239 

1000× 

1000× 

800 

1410× 

1970× 

1239 

500× 

705× 

600 

910× 

1590× 

1039 

600× 

850× 

800 

1010× 

1690× 

1239 

1000× 

1000× 

800 

1410× 

1970× 

1239 

Loading capacity (L) 225 408 800 225 408 800 

Weight (kg) 310 370 560 300 360 550 

* 1:・Performance values are given for +23°C ambient temperature and no specimens 

inside chamber. 

・Temperature/Humidity fluctuation and uniformity are based on JTM (Standard of 

Testing Machinery Association of Japan) K 01-1998. 

・Loading capacity is given for an effective area up to 1/6 the distance from walls in 

all direction. 

* 2: Excluding projections. 



4 

Conclusion 

The new Ultra View Temperature (& Humidity) Chamber was designed to respond to the 

basic need during environmental tests and evaluation tests to see, touch, operate, and 

measure the specimens being tested. 

To meet the special needs presented by the current trend of increasingly complex 

functions combined with miniaturization, finer tolerances, lighter weight, and the 

environmentally friendly materials required by current products, all of which are impacted 

by the increasing demand for speeding up the product development cycle, we at Espec 

are committed to meeting our customers’ needs for all kinds of tests needed for 

development, evaluation and reliability for all our customers’ new products. 

・For further information 

Please feel free to contact the Espec International Operations Center or drop in to your 

nearest overseas dealer for further information or to request a catalog regarding the 

Ultra View Temperature (& Humidity) Chamber. 

- 29 -

download

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?