Peculiar patterns of SiO2 contamination on the contact surface of a micro relay operated in a silicone vapor environment

Peculiar patterns of SiO2 contamination around the periphery of the contact trace caused by silicone vapor under switching at the boundary of 1.6 W we re confirmed. For micro relays, the electrical power conditions are restric ted to lower level. Therefore, it is important to ascertain the upper limit of the electrical power conditions for normal operation. The peculiar patt ern is important as it is recognized as the first stage of the origination of contact failure. Causes of this pattern were discussed from the viewpoin ts of temperature distribution in the contact trace, molten metallic bridge , micro are discharge, and supply of silicone vapor with oxygen. It is prop osed that during the closing contacts, as maximum Joule heating occurs at t he periphery of the true contact area and silicone vapor with oxygen is eas ily supplied at the periphery, SiO2 grows around the contact trace. For the opening contacts, as the bridge or micro are appears, silicone vapor with oxygen is supplied only outside of the contacts. Thus SiO2 is formed mainly around the periphery of the trace. Moreover, SiO2 was scattered radially d epending on the sputtering of molten metal under rupture of the bridge. The refore, the peculiar pattern forms as a result.