Evaluation of Degradation Degree of Plated Base Metal Contacts by Impedance Measurement

Oxidation and wear affect the degradation of connectors with plated base metal contacts. Since these phenomena process gradually and they are accelerated by fretting motion caused by thermal cycle or mechanical vibration, it is important to evaluate such degradation degree of connectors especially of wire-harnesses for automobiles. The change in DC resistance of plated base metal contacts is well-known to behave characteristically as degradation process progresses. Since the change reflects both degradations of plating material and base material, in most cases, it is too complicated to evaluate the degradation degree by DC resistance measurement. Therefore, we introduce nondestructive impedance measurement as a degradation diagnosis method for contacts. It has been found that the changes in reactance at a certain frequency behave characteristically and independently of the DC resistance changes during fretting test. It is considered that the change reflects the micro-structural changes near contacts. The relationship between the degradation degree of contacts and the change in impedance has been observed.