Apparatus and methods for electrical contact resistance study of cleaned and corroded materials

Abstract

Contact resistance is the main reliability criterion for contact components such as relays, switches and connectors. In order to be free from the imposed mechanical and electrical parameters of these components, a complete apparatus has been adjusted in the authors' laboratory. It performs contact resistance measurements, mechanical and electrical evaluations of contact properties in a wide range of current and force levels (10 nA-10 A; 0.01 N-10 N). The mechanical part of this apparatus is an accurate cartesian table driven by stepping motors (0.1 mu m step) for contact displacement and progressive force application. The equipment is monitored by a computer which performs signal conditioning, data acquisition, control and graphic analysis. Some examples are reported. They concern: first the drawing of contact resistance maps (R) of freshly cleaned samples and their laws versus contact force (F), R=kF^-p; secondly, studies on corroded samples in controlled atmospheres, based on the analysis of current-voltage (I-V) characteristics, and finally contact resistance evolution during fretting corrosion. Some experimental results are available.