Effect of Mg doping on increase in the life with low contact resistance of Ag-Pd alloy switching contacts in silicone vapor environments

Abstract

When silicone vapor which adsorbed on contact surfaces is subjected to high temperature due to electric discharge in the atmosphere, SiO/sub 2/ is formed by chemical decomposition of the adsorbed silicone molecular. When SiO/sub 2/ is formed on contact surfaces and is caught in the interface of contacts, contact failure is caused by an insulation property of SiO/sub 2/. Newly developed contact material of Ag(40wt%)-Pd(60wt%) alloy with a small amount dopant of Mg was applied experimentally to a micro relay. This material shows remarkable improvement of contact resistance property for contaminant oxide film in comparison with usual Ag-Pd contacts. In this study, the contact resistance property for the number of make-break switching operations of the Ag-Pd-Mg alloy was examined by wide range electrical conditions under saturated (1300 ppm) silicone vapor. Obtained contact resistance properties were compared with the Ag-Pd alloy itself and Ag-Pd overlaid with Au(90wt%)-Ag(10wt%) which is used usually. As results, prolonged low contact resistance property of the Ag-Pd-Mg alloy for silicone environment was found. The mechanism of the low contact resistance property was clarified by cleaning effect based on removal of powder products formed from the contact traces.