Effect of oxide films and arc duration characteristics on Ag contact resistance behavior

In order to confirm that oxide films are the predominant reason for contact resistance degradation of Ag contacts operating in normal air conditions, experiments were performed in mixed nitrogen-oxygen gas with switching inductive load and in normal air condition without switching load. Even-though the failure rate of contact resistance in nonload conditions is quite low, the strong carbon peak exists in the AES spectra. While in load condition, the oxygen peak usually occurs in the AES spectra and the carbon-peak is not found in mixed oxygen-nitrogen gas, although, sometimes in normal air. It is very interesting to note that contact resistance degradation is not only dependent on oxygen density, but also on the difference of arc duration in both the metallic and gaseous phases. The tested results help verify that oxide films dominate the contact resistance behavior of Ag contacts in mixed oxygen-nitrogen gas, as well as in normal air condition