Investigation of electroplated electrical contacts

The relative deterioration by marine atmospheres of noble metal platings for electric contacts has been determined in the interests of improving the reliability of electrical connections in the marine environment and of conserving precious metals. In cooperation with the Electronics Industry Association P-5.1 Committee on Electrical Contacts, this Center investigated the effects of marine and laboratory salt spray atmospheres on various contact platings in order to determine optimum platings; the emphasis was on platings with silver underplating. The work described includes establishment of experimental techniques, equipment development, a discussion of the marine exposure site at Ft. Tilden, New York, and the laboratory salt spray environment and procedures. The results with various platings show that the use of nickel as an underplating is very undesirable, but 30 millionths of an inch of gold over 100 millionths of an inch of silver is superior, and 30 millionths of an inch of gold over 100 millionths of an inch of copper is adequate in the marine environment. An examination of 4000 hours of laboratory salt spray exposure and 108,000 hours (11-1/2 years) of marine exposure indicates a corrosion acceleration factor ranging from 18 to 25 for gold-over-nickel plating systems.