The Effect on Switching Lifetime of Chromium Adhesion Layers in Gold-Coated Electrical Contacts under Cold and Hot Switching Conditions

Gold is commonly used for electrical contacts due to its many desirable electrical and mechanical properties. Throughout the switch lifetime, the contacts are required to survive a large number of opening and closing cycles and therefore it is important to understand the failure mechanisms. Adhesion layers (e.g. chromium or titanium) can be deposited to increase the adhesion of the gold layer to the contact surface. In this work, the inclusion of a chromium adhesion layer shows an improvement of the switching lifetime of gold-coated electrical contacts under cold and hot switching conditions. These testing conditions further the understanding of the failure mechanisms (e.g. fine transfer, etc.). The mechanism of failure when no chromium adhesion layer was used is attributed to delamination of the gold layer from one contact to the other. This failure mechanism is different in the cases where a chromium adhesion layer is included. We present a model which was developed in line with experimental results. These describe the effect of load current on material transfer between gold contacts and the contact failure.