UNCLASSIFIED AD NUMBERE I I Il Lab. Project IED-20 Final Report ABSTRACT The relative deterioration of noble metal platings for electric contacts by marine atmospheres has been determined

UNCLASSIFIED

AD NUMBER

AD830116

NEW LIMITATION CHANGE

TOApproved for public release, distributionunlimited

FROMDistribution authorized to DoD only;Administrative/Operational Use; APR 1968.Other requests shall be referred to USNaval Applied Science Lab., Brooklyn, NY11251.

AUTHORITY

Naval Applied Science Lab. ltr dtd 28 Oct1970

THIS PAGE IS UNCLASSIFIED

Lab. Project IED-20Final Report

Investigation of T'latings

of

Electrical Contacts

0

Albert Glowasky

Physical Sciences Division

U. S. NAVAL APPLIED SCIENCE LABORATORYBROOKLYN, NEW YORK

have prior approval of the U. S. Naval Applied Science Laboratory

INVESTIGATION OF PLATINGSQF

ELECTRICAL CONTACTS

8 April 1968


Albert Glowasky

PHYSICAL SCIENCES DIVISIONJ.M. McGREEVY, HEAD

Approved: Approved: _ _ _ _ _

K.CA t T.T.McGILLIGUDDY, CAPTAII USNT Comanding Officer and Director

U.S. NAVAL APPLIED SCIENCE LABORATORYFLUSHING AND WASHINGTON AVENUES

BROOKLYN, NEW YORK, 11251

Each transmittal of this document outside the Department of Defense musthave prior approval of the Naval Applied Science Laboratory.

E Il I I


ABSTRACT

The relative deterioration of noble metal platings for electric contacts by marineatmospheres has been determined in the interests of improving the reliability ofelectrical connections and conserving precious metals. As part of a cooperativeeffort with EIA, P-5.1 Committee Research Laboratories, this Laboratory investi-gated the effects of marine and laboratory salt spray atmospheres on variouscontact platings in order to determine optimum platings. Emphasis is given tothe effect of silver underplating. Work described includes establishment ofexperimental techniques, equipment development, the marine exposure site atFt. Tilden, N.Y., the lboratory salt spray environment and procedures. Theresults with the various platings were summarized and show that nickel under-plating is undesirable, 30 millionths of gold over 100 millionths of silver issuperior and 30 millionths of gold over 100millionths of copper is adequatefor Naval applications in a marine atmosphere.

2


SUMMARY

The increasing usage of separable connectors in large quantities for electricaland-electronic communications has pointed up a need for study of contactmaterials having high reliability and low contact resistance especially whenexposed to a marine environment as required for Naval use. A search of theliterature reveals little information on the properties and performance ofelectroplated contact metals when exposed to marine environmental contaminants.The Naval Applied Science Laboratory in cooperation with the Bell TelephoneLaboratories, Murray Hill, N.J. and the Electronic Industries AssociationP-5.1.4 Committee on Contact Plating formulated a program for determiningoptimum contact platings for application in a marine environment.

MIL-C-26636 size #16 and #20 pin and socket contacts were electroplated withgold over silver, gold over nickel, gold over copper, rhodium over nickel andrhodium over silver. Plated contacts were wired and assembled in a modifiedlouvered Stevenson Sc-een and installed at the NASL marine environmental siteat Ft. Tilden, N.Y. mounted on a supporting structure facing the ocean withoutobstruction, approximately 300 feet from the shore line and 40 feet aboveM.L.W. A second group of size #20 plated contacts were wired and assembled.on a stainless steel stand and installed in the NASL salt spray environment.

Analysis of tarnish films deposited on exposed copper plates during theexposure period at the Ft. Tilden test site indicated a suitable marineenvironment free of sulphide contamination.

Twenty-two months of marine exposure at Ft. Tilden, N.Y. produced no appreciablechange in the resistances of gold over silver and gold over copper platedelectrical contacts. The resistances of the gold over nickel and rhodium overnickel plated contacts more than doubled within 400 hours of salt spray fogexposure and then proceeded to increase exponentially thereafter.

The results indicated that nickel underplating is undesirable, 30 millionthsof gold over 100 millionths of silver is superior and 30 millionths of goldover 100 millionths of copper is adequate for Naval applications in a marineatmosphere.

The adequacy of gold over copper plating indicates that conservation of precioussilver and substantial savings can be accomplished through the use of electricalcontacts without silver underplating.

3

Lab. Project IED-20

Final Report

TABLE OF CONTENTS

Page No.

ABSTRACT 2

SUMMARY 3

ADMINISTRATIVE INFORMATION 5

ACKNOWLEDGMENTS 5

OBJECT 5

INTRODUCTION 5

APPROACH 6

PROCEDURE 8

RESULTS 10

CONCLUSION 13

RECOMMENDATIONS 14

TABLES

1 - Thickness Measurements of Plated Contacts (4 pp)2 - Summary of Contact Resistance Measurements taken at Ft. Tilden,

N.Y. Exposure Site (4 pp)3 - Summary of Contact Resistance Measurements taken at NASL Salt

Spray Exposure Environment (2 pp)

FIGURES

1 - Plating Schedule2 - Photo L 21039-1, Preconditioning, Reciprocating Insertion and

Withdrawal Mechanism3 - Photo L 21039-2, Electrical Contacts Wired Fixtures Assembled on Stand4 - Photo L 21039-3, Complete Wired Assembly With Keithley Model 502A

Milliohmeter and 10 Position Switch5 - Photo L 21039-4, Marine Environment Exposure Site at Ft. Tilden, N.Y.

Showing Stevenson Screen With Glass Wool Filter6 - Photo L 21039-5, Marine Environment Exposure Site at Ft. Tilden, N.Y.

Showing Stevenson Screen With Stainless Steel Mesh Screen Filter7 - Photo L 21039-6 NASL Salt Spray Exposure Environment

APPENDIX

A - Bibliography on Platings of Electrical contacts (2 pp)

4

Lab. Project IED-20

Final Report

ADMINISTRATIVE INFORMATION

Ref: (a) NASL Technical Director's Memo of,5 Oct i965(b) NASL Technical Director's Memo 901C:JMR-3920 of 21 Apr 1966(c) NASL Project IED-20 Program Summary dated 1 May 1966(d) Lab. Project IED-20, Technical Memo 1, Investigation of Platings on

Electrical Contacts of 8 Jul 1966(e) Lab. Project IED-20, Status Report No. 2; NASL Annual In-House

Independent Exploratory Development Program Report for PeriodEnding 31 Dec 1966

1. As directed by references (a) and(b) and in accordance with the objectivesset forth in reference (c), the Naval Applied Science Laboratory conducted astudy to develop techniques to determine the efficacy of various types ofelectroplatings on electrical contacts under marine and laboratory salt sprayenvironmental exposure for Naval use. The work reported herein was formerlycovered by Subproject SF 021-02-02, Task 9633.

ACKNOWLEDGMENTS

2. This work was performed by A. Glowasky under the general supervision ofG.J. Thompson, Head, Electrical Branch. The technical assistance rendered byR.G. Baker of Bell Telephone Laboratories, C. Stuart of Amphenol Corp., A. Nashof Burndy Corp., R. Tweed of Nu-Line Industries and S. Weiss of Elco Corp., isacknowledged.

OBJECT

3. The objective of this investigation is to develop techniques to determinethe efficacy of various types-of contact platings, to investigate the effects "of laboratory developed salt spray environment as compared with those causedby marine environment and to determine optimum contact platings for Navalapplications.

INTRODUCTION

4. Reliability studies have shown that electrical connectors produce thelargest portion of failures in electrical and electronic circuits. Physicalsize- limitations in low power circuits, which is the area of concern, generallyrestrict connector improvements to contact configurations, surfaces andmaterials. Currently, improvements are concentrated on noble metal electro-platings of electrical contacts and are based on incomplete information onelectrical performance and durability. In these attempts at improvement, suchplatings as 0.000030 inch gold over 0.00020 inch silver and up to 0.0015 inchhard gold are specified in various military and industrial procurement documents.Suitable evidence of material with minimum thicknesses for reliable wear andlow contact resistance, particularly at low voltage levels, and capable ofoperation under industrial and especially marine environments, has not beenfirmly established. The requirements for commercial applications may be met

5


without the use of silver underplating, a feature tentatively considered necessaryfor inhibiting corrosion in a marine atmosphere. Evidence was needed to demon-strate whether or not this feature is necessary for Naval application. For thesereasons the Electronic Industries Association, P-5.1 Committee on ElectricalContacts, in which this Laboratory participated, formulated a program for deter-mining optimum contact platings. This Laboratory conducted the investigationon contact platings in a marine atmosphere for Naval application. This reportpresents the design of the planned experiment to establish the plating require-ments for a marine environment. A detailed description of the methodology andtechniques essential to cooperating laboratories in correlating their work.The results compiled from field and laboratory environments are analyzed andrecommendations are made.

APPROACH

5. The Navy's interest in the electroplating of electrical contacts is uniquein that it concerns performance under a marine corrosion environment. The NavalApplied Science Laboratory in cooperation with Electronics Industry AssociationP-5.1.4 Committee on Electrical Contact Platings formulated plans for a programto determine the optimum plating for such contacts and this required the develop-ment of experimental techniques, equipment and procedures that would be employedby all participating laboratories regardless of the environment with which eachwas concerned.

6. The committee established the following guide lines and objectives for itsprogram:

a. The primary aim was confined to electroplatings of electrical contactsand not contact geometry or contact life.

b. The development of methodology to determine the efficacy of varioustypes of platings.

c. Investigation of exposure sites and their relationship to the applica-tion environments namely:

1. Industrial - Urban2. Sulfurous3. Elevated temperature4. Marine

In addition NASL agreed to conduct an investigation of the effect of laboratorysalt spray on the plating of electrical contacts. It was important to selectfor study, one type of basic metal for the contact preferably from one manu-facturer and one geometry of contact. This eliminated as many variables aspossible from the experiment to facilitate correlation between cooperatinglaboratories. While it is recognized that investigation of wear and possible

6


advantages of lubrication should be considered for future study when results haveestablished one or several good finishes for each environment, these will not becovered as part of this program.

7. The study under marine corrosion environment and laboratory salt spray con-ditions was undertaken-by the Naval Applied Science Laboratory. The environ-mental study utilizing industrial-urban atmosphere was assigned to Bell TelephoneLaboratories while the sulfurous atmosphere was assigned to Burndy ResearchDivision.

8. In order to keep the size of the exploratory program manageable while pro-viding the maximum amount of useful information with the minimum number of speci-mens, it was agreed to study the following nine combinations of platings onsize #16 and size #20 MIL-C-26636 type pin and socket contacts.

a. Gold over Silver:

(1) Gold 30x10-6 inches over Silver 10Ox10 -6 inches

(2) Gold lOOxl1- 6 inches over Silver 100x10-6 inches

(3) Gold 50x10-6 inches over Silver 200x10-6 inches

b. Gold over Nickel:

(1) Gold 30xlO -6 inches over Nickel 10Ox10-6 inches

(2) Gold 100x10"6 inches over Nickel lOOxlO "6 inches

c. Gold over Copper:

(1) Gold 30x10-6 inches over Copper 100x10- 6 inches

(2) Gold 10Ox10-6 inches over Copper lOOxlO - 6 inches

d. Rhodium over Nickel:

(1) Rhodium 20 to 30xi0-6 inches over Bright Nickel lOOxlO' 6 inches

e. Rhodium over Silver:

(1) Rhodium 20 to 30x10"6 inches over Silver 100x10- 6 inches

9. Amphenol Corporation furnished a sufficient number of size #16 and #20 unplatedpin and socket contacts manufactured from their leaded copper full hard alloy 126.for the study.

7


10. Nu-Line Industries plated all the contacts in accordance with Bell TelephoneLabs requirements indicated in BTL Specification WL-2250.101, Issue 8 forElectroplated Finishes.

11. Upon receipt of all the electroplated contacts at NASL, no effort was madeto chemically or otherwise clean them since they were to be handled in thenormal manner as would electroplated contacts received from any contact manu-facturer. However, precautionary measures were taken to avoid further contamina-tion of the specimens by crimping and wiring them in a clean controlled atmosphereroom with the technicians using disposable vinyl examination gloves when handlingthe electroplated contacts and their related components.

PROCEDURI

12. Approximately 14 specimen contacts were withdrawn from each size and typeof plating for plating thickness measurements. These were first measured withthe Betascope using the Beta Ray method and then sectioned for verificationmeasurement with a toolmaker's microscope.

13. Twenty plated contacts were allotted for each size and type of contact foreach environment as indicated in Figure 1. Each pin and socket contact wascrimped to two separate conductors (one current lead and the other a voltagelead). A Buchanan MS3191-1 crimping tool with a MS3191-20A positioner for thetwo size #24 wires and a MS3191-16A positioner for the two size #22 wires wasutilized to perform all the crimping of the respective 2 wire conductors toeach plated contact. The best combination of conductors was experimentallydetermined to be two #22 strandedwires for the size #16 contact and two #24stranded wires for the size #20 contact. Navy Type E MIL-W-16878/4A 7 strand,white teflon insulated wire was used throughout. The opposite ends of the twowires emanating from each pin and socket contact were soldered into a 50 contactAmphenol connector pt. No. 57-20500. Ten such pin and socket contacts wiredwith forty conductors were soldered to each Amphenol 50 contact connector. Tenof these contacts were mated once-prior to installation in the field environmentwhile the remaining ten contacts were mated 100 times at a rate not exceedingone engagement every five minutes. This relatively long interval betweenengagements avoids possible overheating and relieves stresses of the contactsurfaces. The mating of the contacts was accomplished by a specially designedreciprocating merhanism as shown in Figure 2, which was automated to permit10 pin and socket contacts to be mated repetitively once every five minuteswith a mating cycle of insertion and withdrawal of 10 seconds. Ten wired matedcontacts were connected into a 10 position transfer switch through which theirresistances were measured-by a Keithley Model 502A Milliohmeter. During cycling,resistance measurements were made on the contacts after every 25th cycle ofengagement, utilizing a 4 wire contact measuring circuit.

14. Each group of 10 wired pin and socket contacts was then mounted in a plasticfixture. These fixtures measured 2 3/4" wide x 2 1/2" high x 4" long and wereconstructed of 1/4" thick epoxy glass, assembled with stainless steel non-magnetic

8


screws. Thirty-six such fixture assemblies were prepared for the 9 differenttypes of electroplated contacts, namely 18 fixtures of size #20 contacts and18 fixtures of size #16 contacts. All 36 wired fixtures were mounted on astainless steel stand measuring 15" wide x 19" long x 12 5/8" high. Wiredfixtures are shown in-Figure 3. The complete wired assembly was shock mountedon 4 layers 1/4" thick isomode pads. This was done to avoid mechanical dis-turbance of any films that would form in the contact area. The assembly washoused in a louvered aluminum shelter, 30" x 30" x 19" similar to a StevensonScreen and mounted on an aluminum base 36" x 48" x 1/4" thick. One inch thickglass wool filters behind the louvers permitted a free circulation of air butrestricted dust particles from contaminating the contact specimens. Theenclosure was hinged to the base plate to permit periodic examinations of thecontacts. The electrical contact terminations in the 36 fifty contact Amphenolconnectors were mounted on a stainless steel terminal rack in front of theexposure housing as shown in Figure 4 and protected by an aluminum cover sealedto the base by a neoprene gasket. In addition numbered electrolytic copperpanels 1/2" x 1" x 1/32" thick prepared by Bell Telephone Laboratories weremounted elong side the stainless steel stand with glass thread as shown inFigures 3 and 4. These copper panels were removed at monthly intervals andreturned to Bell Telephone Laboratories where the amount and types of tarnishfilms were analyzed. By exposing a set of these panels at the start of thisstudy and measuring the tarnish rate, it is possible to compare the corrosivenessof the environment of this study with that of another no matter when they arestarted. This technique also allows the study of climatic variations fromyear-to-year.

15. Upon completion of the assembly, the entire shelter was transported to theMarine field exposure site at Ft. Tilden, N.Y. and shock mounted on 5 layersof 1/4" isomode lads, two feet above ground on a special supporting structurefacing the ocean without obstruction approximately 300 feet from the shore lineand 40 feet above M.L.W. as shown in Figure 5.

16. Periodic resistance measurements were recorded on all 360 plated specimencontacts mounted within the modified Stevenson Screen enclosure at the marineexposure site during the 22 month exposure period.

17. Aftar 17 months of exposure from January 1966 to June 1967, there wasample evidence of salt spray corrosion to components of the external supportingstructure, however, no salt spray corrosion was noted within the StevensonScreen enclosure. It therefore appeared evident that the salt laden atmospheremust have consisted of salt and moisture in such particulate form and size asto have been prevented by the glass wool filter from entering the enclosureholding the specimens. These filters were therefore replaced with type 316stainless steel wire screening 0.009" diam. wire, 18x18 mesh which then permitteda freer entry of the salt laden marine atmosphere but prevented insects anddebris entering the contact specimen area as shown in Figure 6.

F9

Lab. Project IED-20

Final Report

18. A similar stainless steel stand was assembled with only 18 fixtures of 10wired contacts each of size #20 contacts. For each type of plating, 10 of thesecontacts were mated only once while the remaining 10 contacts were mated 100times. These contacts were wired identically to those installed at the exposuresite at Ft. Tilden, N.Y.

19. The completed assembly was shock mounted on 4 layers of 1/4" isomode padsonto a 1/4" stainless steel base and installed in a modified laboratory saltspray environment as shown in Figure 7.

20. This assembly of 180 plated contacts was then subjected to the salt sprayfog (corrosion) utilizing a 5% salt solution as outlined in method 101C ofMIL-STD-202C. In order to utilize maximum corrosion time, the contacts weresubjected to the salt spray fog corrosion for 64 hours, rinsed and washed intap water for several hours, then dried for 24 hours after which time contactresistance measurements were recorded. The electrical contacts were againsubmitted to the salt spray fog corrosion for another 48 hours, rinsed andwashed in tap water, dried and contact resistance measurements recorded. Thiswas all accomplished in a 7 day period. This procedure was repeated continuouslyuntil the electrical contacts were subjected to a total of 4000 salt spray foghours with electrical contact resistances being recorded at the end of eachsalt spray corrosion period.

RESULTS

21. The unplated contacts furnished by Amphenol Corp. were plated by Nu-LineIndustries in accordance with the plating schedule indicated in Figure 1.Results of these platings shown in Table I indicate a wide variation in platingthickness for each plating requirement. These variations were recognized andtolerated because they are representative of the present state-of-the-art ofplating. The uniformity of plating is difficult to control because of variablesin plating solutions, temperatures, current density, cleanliness and quantity ofcontacts involved.

22. The resistance measurements of the plated contacts which were precondi-tioned for 100 cycles showed only slight variation in contact resistance duringthe insertion and withdrawal matings. There was no significant difference inthe average contact resistance of the contacts that were mated 100 times asopposed to those that were mated only once, but with one exception. The contactsthat were plated with rhodium over nickel and were mated 100 times showed anaverage contact resistance approximately 30% higher than the contacts thatwere mated only once.

23. The data on the amount of tarnish films found on the copper panels exposedat the Ft. Tilden exposure site given below are in Angstroms and should only beconsidered significant to the nearest 100 X for this purpose. The compositionand thickness of the films of these panels was determined by the cathodic reduc-tion method.

10


Cuprous CupricRemoval oxide * oxideDate Panel No. Xngstroms Angstroms

2/8/66 1 173 03/10/66 2 625 604/11/66 3 565 1185/12/66 4 520 1076/9/66 5 577 1497/7/66 6 657 1498/11/66 7 692 3289/7/66 8 857 8310/14/66 9 1695 11311/16/66 10 1775 17912/15/66 11 2363 02/15/67 12 2929 03/27/67 13 4427 04/20/67 14 5630 05/18/67 15 5096 06/21/67 16 6138 0

It is known that corrosion films do not form uniformly over the entire surfaceof the panel. However, in order to report an apparent thickness, one must assumeuniformity of tarnish films, because of the possibility of slightly differentrates of formation on an individual panel. Seeming anomalies such as panels 2and 3 can occur and should not be of concern. There is no indication of anysulphide tarnish films which indicates a suitable marine environment free ofsulphide contamination.

24. The data obtained at the Ft. Tilden site have been summarized in Table 2.The data taken for the Laboratory Salt Spray conditions have been summarizedin Table 3. Seventeen months of sea side exposure, from January 1966 toJune 1967 produced-no appreciable change in contact resistance according to themeasurements shown in Table 2. Examination of the interior of the screenedarea showed no visual evidence of salt corrosion.Tests were then made byswabbing all interior surfaces with sterile cotton swabs wetted with distilledwater. These were chemically analyzed for presence of sodium chloride witha silver nitrate solution. Results showed that there was n6 sodium chloridepresent within the screened enclosure. There was however ample visual evidenceof salt spray corrosion to components of the external supporting structure. Itwas therefore concluded that the salt laden atmosphere consisted of salt andmoisture in such particulate form and size that it had been prevented fromentering the specimen enclosure by the glass wool filters shown in Figure 5.These filters were therefore replaced with a stainless steel mesh screenfilter shown in Figure 6 in order to permit the salt laden marine atmosphereto come in contact with the plated specimen contacts. Subsequent measurementsmade during the period June 1967 to November 1967 indicate a slight increase in

11


resistance of the gold over nickel and rhodium over nickel plated specimenswhile no significant change was noted in the gold over silver and gold overcopper plated specimens as shown in Table 2.

25. The resistance of the gold over nickel and rhodium over nickel platedspecimens more than doubled within the first 400 hours of exposure to LaboratorySalt Spray. After 400 hours, this increase became exponential with time. Underthe same conditions the gold over silver and gold over copper plated specimensshowed no significant increase in resistance for the entire 4000 hours ofexposure.

26. Prior to the removal of the glass wool filters from the Stevenson Screenenclosure in June 1967 there was noted only copper oxide corrosion of the smallcopper monitoring panels. However after the glass wool filters were replacedwith the stainless steel mesh screen filters there was definite visualevidence of green (copper chloride) corrosion indicating the presence of salt.

12

L I

Lab. Project IED-20

Final Report

CONCLUSIONS

27. The copper corrosion panels data show no indications of atmosphericsulphide, while there is ample evidence of salt spray corrosion of the structurefittings indicating that the site is suitable for marine exposure withoutindustrial atmospheric contamination.

28. The absence of salt spray corrosion within the Stevenson Screen enclosurewith glass wool filters for the 17 month exposure period to June 1967 wasinvestigated by swabbing all interior surfaces with sterile cotton swabs wettedwith distilled water. A chemical analysis of these swabs with silver nitratesolution showed no trace of sodium chloride. An analysis of the copper corro-sion panels during this same period also indicated the absence of sodiumchloride corrosion. However with the replacement of the glass wool filterswith the stainless steel mesh screen filter, there was definite visual evidenceof salt spray corrosion within the enclosure and by the green corrosion depositson the copper corrosion panels. It was therefore concluded that the salt ladenatmosphere consisted of salt and moisture in such particulate form and size soas to be prevented from entering the specimen enclosure by the glass wool filters.

29. The 100 cycles of insertion and withdrawal preconditioning did not signifi-cantly affect the contact resistance of the gold palted specimens.

30. The results of exposure of plated contacts at the Ft. Tilden, N.Y. marineenvironment and in the Laboratory Salt Spray environment indicated that nickelunderplating is undesirable because of the relatively high increase in resistancein the contacts with gold over nickel and rhodium over nickel underplating.There was no significant increase in resistance in the gold over silver and goldover copper plated contacts, therefore while 30 millionths of gold over 100millionths of silver is superior, 30 millionths of gold over 100 millionths ofcopper is adequate for Naval applications in a marine atmosphere. Conclusionsas to the adequacy of these gold platings are made with due regard to the inhereiitvariations in such platings produced by even the best current commercial practice,As Table 1 shows there are overall variations in gold thicknesses ranging fromabout 80 percent above the nominal to 50 percent below the nominal 30 millionthsof an inch. The stable contact resistances maintained in corrosive atmospheresby specimens with the gold platings overlaying substrates susceptible to saltcorrosion indicates that these platings were non-porous. The conclusions as tothe adequacy of platings are therefor conditional on the plating quality orporosity as well as the actual thickness as represented by the lower limit inthe variation of plating thickness shown in the report.

31. The results have shown that although there was evidence of salt spraycorrosion within the Stevenson Screen enclosure after the installation of thestainless steel mesh screen from June to November 1967, there was no significantchange in the resistances of the various plated contacts and therefore therecan be no correlation between the results obtained at the Marine exposure atFt. Tilden and at the Laboratory Salt Spray environment at this time.

13

Lab. Project IED-20

Final Report

RECOMMENDATIONS

32. In view of the adequate performance of the gold over copper plated con-tacts in a marine and laboratory salt spray environment, it is recommendedthat silver underplating no longer be required for Naval applications. Undernormal conditions of actual use as represented by the repeated matings describedin this investigation the plating of 30 millionths of gold over 100 millionthsof copper is recommended.

33. Although a comparison of the results of exposure of the contacts to amarine environment and laboratory salt spray does not indicate the degree ofacceleration of corrosion attributable to the laboratory salt spray, the poorperformance of nickel underplated contacts under laboratory salt spray indi-cates a possible source of failure. It is therefore recommended that nickelunderplating be avoided, where possible, for Naval shipboard applications.

34. It is recommended that the methods and procedures adopted for thisinvestigation be-used as guide lines in the study of plating of electricalcontacts under, Industrial-Urban, Sulfurous and Elevated Temperature environ-ments so that the results of all investigations can be correlated.

35. In a marine environment where salt spray atmosphere corrosion is to bestudied, it is recommended that a modified Stevenson Screen enclosure withtype 316 stainless steel mesh screen filter be utilized in lieu of glasswool filter in order to permit the passage of salt laden atmosphere whichhas been shown to be in particulate form.

14

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US. NAVAL APPLIED SCIENCE LABORATORY LAB PROJECT IFD 20

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U.S. NAVAL APPLIED SCIENCE LABORATORY Lab. Project IED-20

Final Report

APPENDIX A

BIBLIOGRAPHY ON PLATINGS OF ELECTRICAL CONTACTS

1. R. Holm, Electric Contact Handbook 3rd Edition, Springer-Verlag, Berlin 1958

2. T. F. Egan and A. Mendizza, Creeping Silver Sulphide, Bell TelephoneLaboratories, Jou, Electrochem. Soc. Vol. 107, No, 4, April 1960

3. K. G. Compton and R. G. Baker, The use of Electroplated Metals in StaticContacts, Engineering Seminar on Electrical Contacts, Pennsylvania StateUniversity, June 1960

4. B. E. Blake, Summary Report of the ASTM Section G Contact Field Tests,Section G ASTM Committee B-4 Sub Committee IV, 1963

S. R. E. Tweed, Manufacturing Methods for Electroplating Silver, Gold andRhodium on Electrical Connector Contacts, Nu-Line Industries, August 1963

6. W. H. Graft, H. G. Hamre and B. P. Lathan, Plating Requirements for Multi-Pin Connectors, Illinois Research Institute, October 1963

7. R. G. Baker, Studies of Static Low Voltage Contacts at the Bell TelephoneLaboratories, Murray Hill, N. J., 2nd International Conference on ElectricalContacts, Graz, Austria 1964

8. H. S. Swan and J. M. Davis, Problems With Electrical Connectors, NASATechnical Memorandum, NASA TMX-1083, March 1965

9. R. V. Chiarenzelli, Air Pollution Effects on Contact Materials, IBM,Poughkeepsie, N.Y., Engineering Seminar on Electrical Contacts, Universityof Maine, June 1965

10. The Connector Controversy, Electronic Products Forum, October 1965

11. H. Musnitsky, Platings: A Prime Problem, Electronic Products Forum,October 1965

12. H.S. Swan and J. M. Davis, Problems With Electrical Connectors, ASD-QA-09-65-5 Class III, 14th Annual Wire and Cable Symposium, Atlantic City,N.J., December 1965

13. NAVAPLSCIENLAB, Investigation of Platings on Electrical Contacts,Lab. Project IED-20, Technical Memorandum 1, 8 July 1966

14. M. Antler, Current Topics in the Surface Chemistry of Electric Contacts,IEEE Transactions, Vol PMP-2, No. 3, September 1966

A-1

U.S. NAVAL APPLIED SCIENCE LABORATORY Lab. Project IED-20Final Report

APPENDIX A (CONT'D)

15. H. B. Ulsh, Current Ideas in the Philosophy of Testing Electrical Contacts,IEEE Transactions, Vol. PMP-2, No. 3, September 1966

16. J. B. P. Williamson, Recent Studies on the Physics of Electrical ConnectorSurfaces, IEEE Transactions, Vol. PMP-2, No. 3, September 1966

17. A. Mendizza, The Standard Salt-Spray Test - Is It A Valid Acceptance Test,Bell Telephone Labs Monograph 2807i June 1957

18. R. F. Snowball, J. B. P. Williamson and R. C. Hack, Ingress of ReactantsBetween Contacting Surfaces, Burndy Research Report No. 40, May 1966

19. Burndy Research Division, Inhibition of Corrosion and Wear of Gold PlatedContacts, January 1967

20. M. Antler and J. Gilbert, The Effects of Air Pollution on ElectricContacts 56th meeting of APCA, June 1963

A-2

UNCLASSIFIED

Security Classification

DOCUMENT CONTROL DATA - R & D(Security classification of title, body of abstract and indexing annotation muvt be entered when the overall report is classified)

i. ORIGINATING ACTIVITY (Corporate author) 20. REPORT SECURITY CLASSIFICATIONU.S. Naval Applied Science LaboratoryI UNCLASSIFIED

Flushing and Washington Avenues zb. GOUP

Brooklyn,, New York 112513. REPORT TITLE

Investigation of Platings of Electrical Contacts

4. DESCRIPTIVE NOTES (Type of report and.incluaive dates)

Final ReportS AU THO1IS) (Flret name, 'middle initial, last name)

Albert Glowasky

6. REPORT DATE 70. TOTAL NO. OF PAGES 17b. NO. OF REFS

8 April 1968 33 20Sa. CONTRACT OR GRANT NO. 98. ORIGINATOR'S REPORT NUMSER(S)

6. PROJECT NO. IED-20 Final Report

C. 9b. OTHER REPORT NOIS? (Any other nuabere that may be assignedthis report)

d.

10. DISTRIBUTION STATEMENT

Each transmittal of this doclment outside the Department of Defense musthave prior approval of the Naval Applied Science Laboratory.

II. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY

U.S. Naval Applied Science LaboratoryFlushing and Washington AvenuesBrooklyn, New York 11251

15. ABSTRACT

Deterioration of noble metal plated electric contacts by marine atmospheres has beendetermined in the interests of improving reliability and c onserving precious metals.EIA, P-5.1 Committee Research Laboratories mith this Laboratory investigated effectsof marine and laboratory salt spray atmospheres on plated contacts to determineoptimum platings. Work described includes establishment of experimental techniques,equipment development, marine exposure site at Ft. Tilden, N.Y., laboratory saltspray environment and procedures. Results indicate nickel underplating is undesir-

able, 0.000030w of gold over 0.0001000 of silver is superior and 0.0000300 of goldover 0.000100" of copper is adequate for Naval applications in a marine atmosphere.

DD.'R..1473 (PAGE W UNCLASSIFIEDS/N 0101 -807-6611 Security Classification

A- 31408

UNCLASSIFIEDSecurity Classification ________

14. KYWRSLINK A LINK 8 LINK C

ROLE_ WT ROLE WT ROLE WT

Electrical ContactsElectrical ConnectorsComponent FailuresMetal Plated ContactsMarine AtmosphereSalt Spray AtmosphereContact Platings

DD FN0 *.1473 (BC)UNCLASSIFPIEDS/N 0101-807-6821 Security Classification A- 31409

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UNCLASSIFIED AD NUMBERE I I Il Lab. Project IED-20 Final Report ABSTRACT The relative deterioration of noble metal platings for electric contacts by marine atmospheres has been determined