Influence of topography on electrical contact resistance of copper-based materials

Abstract

The design of an electrical contact is crucial to ensure optimal performance, reliability, and efficiency of connectors. One key aspect is the surface quality of the contacting bodies—among other factors such as material selection, contact geometry, etc. In this work, we evaluated the influence on electrical contact resistance (ECR) of a smooth copper-based surface (brass, bronze, and tin-plated copper) when contacted against surfaces with different degrees of roughness. Furthermore, a carbon nanotube (CNT) coating was proposed with the goal of mitigating the topography-induced influence of the textured counter electrodes. The electrodes and counter electrodes were thoroughly characterized to understand the contacting mechanisms through numerical modeling,—namely, Greenwood-Williamson and Jackson-Green models—as well as using a practical-oriented slope analysis. Load-dependent ECR measurements were carried out to quantify the effect of roughness on contact resistance. When contacting against brass and bronze, a clear correlation between roughness and ECR can be established, with higher roughness equating to lower ECR In tin-plated copper, on the other hand, this hierarchy is not as well defined due to the ease with which the tin plating deforms, thus enabling the penetration of outstanding asperities and consequently establishing a better electrical contact. CNT-coated counter electrodes showed promising results, partially confirming the hypothesis proposed. However, unforeseen topography-related interactions with the CNT coating produced exceptions in the ECR measurements. Nonetheless, for most cases studied the coating did mitigate the influence of roughness.