Contact Area Analysis by FEM with Plating Layer for Electrical Contact

Abstract

Electrical contacts are the most important parts of electrical circuits, and many reliability problems of the circuits are related to contact failure. The contact resistance is one of the important factors for assessing connector reliability, and thus the prediction of contact resistance is essential to designing electrical terminals. In this study, embossments, each I mm to 3 mm in radius, were brought into contact with flat planes to simulate the point of contact on a terminal, and the contact resistance was measured using a four-probe method under a load up to 40 N. Copper alloy samples, each plated with tin or silver and having an embossment of 1 mm to 3 mm in radius, were used and the visually clear indentations resulting from the embossment to plane contact were measured to determine their areas. Since the contact resistance is dependent on the contact area, an FEM analysis must be carried out to determine the contact areas correctly. In this paper, an elasto-plastic FEM analysis was performed taking the plating layers into account, and a method was established to make precise determination of the contact areas for different shapes of contacts and loads. The resultant contact areas were used to calculate the contact resistance, which showed a good agreement with experimental results. It was established that the load-resistance curves can be predicted on the basis of the shapes of the contacts as well as plating.