Friction and Wear of Electrodeposited Palladium Contacts: Thin Film Lubrication with Fluids and with Gold

Palladium deposits with a thin gold overcoat are less expensive than an equivalent thickness of gold plate. They have, therefore, become an important contact material for high reliability separable electronic connectors. The purpose of the gold overcoat in wiping contacts is to provide a low shear strength interfacial layer, or solid lubricant, thereby lowering the adhesive wear rate of the system. In the present study, the friction and wear of various thicknesses and compositions of gold plate on the palladium were determined in sliding against diffused gold 60Pd40Ag (DG R-156) and a cobalt-hardened gold plate. In some cases, a supplementary coating of a polyphenylether fluid was applied to the contacts. It was found that cobalt-gold electroplate on the palladium was superior to pure soft gold despite its much greater hardness. Furthermore, the polyphenylether markedly improved sliding performance in all cases. These results are discussed in the light of friction and wear theory.