The Impact of Plating on Equipotential Surfaces and Contact Resistance

Abstract

It was found that equipotential surfaces, in layered contact systems of differing conductivities, can significantly change in shape as they pass across the layer boundary. Specifically, at the boundary a discontinuity in the equipotential surfaces was found using an image charge analysis from the electrostatic equivalent of a steady state current situation. These results provided a method to determine the shape in the layer as a function d/a and $\sigma$, the layer thickness and conductivity respectively. It was found that the shape in the layer significantly changed when the ratio of plating to base metal conductivity increased above 1 $(\sigma_{0}/\sigma > 1)$. In this case, it is shown how the constriction resistance increases as the layer thickness increases. These results show a difference when compared to earlier work [1]. In addition, it is found that when the conductivity ratio falls below 1 $(\sigma_{0}/\sigma$ < 1), the change in shape is very small but still produces different results from the present authors previous work [1]. It is believed these results provide reasonable estimates for layered (plated) contact systems and that these results represent an improvement over earlier work.