Prediction of Electrical Contact Resistance of Tin-Plated and Silver-Plated Terminals

Abstract

For virtual connector designing, it is important to predict contact resistance at a mating point. This study investigated the relationship between contact load and contact resistance in terms of contact shape, plating material and plating thickness. Tin plated and silver plated copper alloy samples were used. The contact resistance between an embossment pattern and a flat plate was measured by the four-probe method, and the indentation contact area was examined using an optical microscope. This study consisted of two phases: the analysis of load-contact area relationship by FEM (Finite Element Method), and that of contact area-resistance relationship based on the constriction resistance theory with plated layers. For a silver plated sample, which has no oxide films, the experimental results agreed with the theoretical prediction. Meanwhile, the results of a tin plated sample, which has oxide films, corresponded to the theoretical prediction at a high load region, in which terminal connectors are practically used. Thus it has become possible to predict a load-contact resistance curve.