Intermittency phenomena in electrical connectors

Fretting is known to be a major cause of contact deterioration and failure, particularly in tin-plated contacts. During fretting the contact resistanc e generally increases slowly with time. Superimposed on this slow increase in contact resistance are rapid changes in contact resistance within fracti ons of a second, called intermittences or short duration discontinuities. A lthough intermittences have been reported by several authors, they are freq uently overlooked in traditional fretting experiments and not much is known about their origin. The present study aims at filling this gap. A test apparatus has been built to measure the contact voltage-drop profile during an intermittence and fretting experiments on tin-plated copper cont acts have been carried out. The results lead to a set of requirements for a model to explain intermittency phenomena.