Ru and RuO2 as Electrical Contact Materials: Preparation and Environmental Interactions

Abstract

Ruthen ium and ruthenium dioxide, an electronic conductor, have been evaluated as electrical contact materials for low voltage, low force contacts, and separable connectors. The contact resistance (CR) of bulk RuO2 is 1 rn~, only slightly higher than that of gold or ruthenium. A technologically more feasible contact, titanium coated with RuO2, has been developed and has a CR of less than 15 nan. Environmental studies show that both Ru and RuO2 are reasonably stable at temperatures at least as high as 90 ~ and at all rela-tive humidities, even in the presence of 1 ppm HaS or flowers of sulfur vapor. Unlike other contact materials, sulfidation appears to be retarded by the pres-ence of a high relative humidity. The contact resistance (CR) of separable contacts increases with the formation of tarnish films on them. For low force, low voltage contacts, films as thin as 100-200A can have sufficient resistance to give an