Effect of silicone vapor and humidity on contact reliability of micro relay contacts

Contact resistance characteristics of a micro relay with Au(90 wt%)-Ag(10 wt%) cladded contacts were examined in air containing silicone vapor and in air mixed with the silicone vapor and high humidity. Electrical conditions for resistive loads of the contacts were covered with four regions such as bridge region, the first micro-arc region, the second micro-arc region, and arc region. Concentrations of the silicone vapor were selected: 1300 ppm which gives saturation of the vapor and 7 ppm which is the safety level for the contact reliability. Moreover, the effect of humidity on dynamic contact resistance characteristics in the silicone environment was also studied. As a result, a boundary of occurrence of contact failure in a relationship between voltage and current was found. This boundary was given by a certain electrical power. The number of operations to failure was found to be inversely proportional to electric power. Under condition of high humidity, low contact resistance maintained longer operation time than low humidity.