Compatibility of Gold Deposits for Connector Contacts

A forty way, two part, printed circuit board connector has been the test vehicle for the evaluation of wear of a number of gold deposits in similar and dissimilar combinations. The proprietary electrolytes, from four suppliers, consisted of four acid cyanide types (cobalt or nickel hardened) two noncyanide (sulphite) and two neutral cyanide organically hardened golds. Assessment of wear was made by scanning electron microscope examination of wear tracks and by changes in contact resistance when the connectors were subsequently exposed to a corrosive environment. The acid Cyanide deposits exhibited least wear, the sulphite types wore excessively by cold pressure welding to produce platelets of debris, and the neutral cyanide golds were of mixed extent of wear. A hypothesis involving a polymer lubrication mechanism is proposed to explain the Iow wear of the acid golds. Scanning electron micrographs support this pro- posal.