CONTACT RESISTANCE CHARACTERISTICS OF NOBLE-METAL ALLOYS FOR CONNECTOR CONTACTS

Contact resistance characteristics, corrosion characteristics, and the degradation mechanism for several binary and ternary alloys are investigated to evaluate the applicability of lower cost noble metal alloys to connector contacts. These alloys include Pd, Ag, low content Au, and Ni. The test connector contacts are clad inlays mated with each other, clad inlays mated with hard gold plating, and clad inlays with hard gold flash mated with inlays of the same material. The atmospheric conditions are air mixed with one or more of the following gases: SO2, NO2, Cl2, or H2S. The following alloys, used in inlays of the same alloy that are mated with each other, are listed in order of increasing contact resistance: Au-Ag, Ag-Pd, Au-Ag-Pd, Au-Pd, and Pd-Ni. The contact resistance characteristics of inlays mated with hard gold plating and those of inlays with hard gold flash mated with inlays of the same material are as stable as those of hard gold plating mated with hard gold plating. The dominant degradation mechanism affecting the inlay contacts of these alloys is the formation of a corrosion product on the surface area of the contact material. The dominant corrosion products causing an increase in contact resistance are the chlorides in Pd alloys. In addition, more chloride builds up on Au-Pd than on Ag-Pd, even though Au is more corrosion resistant than Ag. This is because the formation of Ag corrosion products suppresses the formation of Pd chloride on Ag-Pd.