Investigation of the Static Electrical Contact Behaviors of Rod and Spring for Micro-electromechanical-relay

The structure configuration of rod and spring contacts is widely used in the micro electromechanical relay. Low and stable electrical contact resistance is a fundamental requirement for reliability and electrical life of relays. In this paper, the relationship between electrical contact resistance and contact force of rod and spring contacts is investigated explicitly with our designed test rig. In order to interpret the variations of contact resistance, the apparent contact area is estimated with the help of imaging system. In addition, the shift from the unstable contact regime to the stable one is determined with the use of contact resistance absolute value and fluctuation range. Moreover, a power law for contact resistance versus contact force R_c = KF_c^-n is established with experimental measurements and -n theoretical calculations. The effects of surface roughness and Au coating thickness of samples on the static electrical contact resistance are discussed.