Understanding of the static contact behaviors of rod and spring for microelectromechanical relay

The structure configuration of rod and spring contacts is widely used in the microelectromechanical relay. Low and stable electrical contact resistance is a fundamental requirement for reliability and electrical life of relays. In this paper, a theoretical model of rod and spring is presented to calculate the constriction resistance and compared with the classical Holm's models. Furthermore, the relationship between electrical contact resistance and contact force of rod and spring is investigated explicitly with our designed test rig. A power law for contact resistance versus contact force R_c=KF^- m is established. A schematic model of contact pair with a rough surface is introduced to explain the variation of contact resistance during the loading process. In particular, the transition phenomena from the initial single contact asperity to the whole rectangular contact area are analyzed. Finally, the effects of surface roughness of the Au coating and operating cycles on the static contact behavior are also discussed.