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

When silicone vapor which adsorbed on contact surfaces is subjected to high temperature due to electric discharge in the atmosphere, SiO2 is formed by chemical decomposition of the adsorbed silicone molecular. When SiO2 is fo rmed on contact surfaces and is caught in the interface of contacts, contac t failure is caused by an insulation property of SiO2, Newly developed cont act material of Ag(40wt%)-Pd(60wt%) alloy with a small amount dopant of Mg was applied experimentally to a micro relay [1], [2], This material shows r emarkable 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 elec trical conditions under saturated (1300 ppm) silicone vapor. Obtained conta ct resistance properties were compared with the Ag-Pd alloy itself and Ag-P d overlaid with Au(90wt%)-Ag(10wt%) which is used usually. As results, prol onged low contact resistance property of the Ag-Pd-Mg alloy for silicone en vironment was found. The mechanism of the low contact resistance property w as clarified by cleaning effect based on removal of powder products formed from the contact traces. Moreover, activation of contact surfaces due to fo rmation of MgO (magnesium oxide) on the Surface of the Ag-Pd-Mg alloy was n ot observed by examination of are duration, The are duration of the Ag-Pd-M g alloy was not so long as usual Ag-Pd alloy contact.