Field Failures of Relays With Au10Ag Contacts.

High contact resistance has been observed with relays containing Au10Ag (10 weight percent Ag) contacts after approximately one year in the field. This alloy has been used successfully in a variety of relays for many years. Contact force measurements show that the high contact resistance was not a result of low contact force in most cases. Crazing of the polycarbonate relay covers suggested that a Freon TMC rinse of the circuit board caused material to be leached from the plastic and then to condense in the contact region. However, gas chromatography/mass selective detection of solvent extracts of the metal parts from the relay and the cleaning bath showed that negligible amounts of organic material were deposited on the relay elements or even extracted from the plastic case.