Multi-Walled CNT (MWCNT) are synthesized on a silicon wafer and sputter coated with a gold film. The planar surfaces are mounted on the tip of a piezo-electric actuator and mated with a gold coated hemispherical surface to form an electrical contact. These switching contacts are tested under conditions typical of MEMS relay applications; 4 V, with a static contact force of 1 mN, at a low current between 20 -50 mA. The evolution of contact resistance is considered in a newly developed test procedure. The contact resistance performance is then linked to a study of the contact changes in the surface. The contact surfaces have been shown to exhibit a transfer process over a large number of switching cycles. The continuous monitoring of contact resistance can be used for the identification of surface failure. The results show that for the surfaces presented the contact resistance remains stable for between 80 and 120 million switching cycles. Interestingly the number of bounces is related to the fine transfer failure mechanism.

Material transfer in switching contacts is considered at very low currents, (below 20mA). The transfer process is critical to a wide range of electronic switching technologies and is a limiting factor for MEMs relays. A test system is described and characterized for bench-marking surfaces. This is followed by a study of Multi-walled CNT's (MWCNT's), synthesized on a silicon planar and sputter coated with a gold film. The planar surfaces are mounted on the tip of a piezo-electric actuator and mated with a Au coated hemispherical surface. The switching contacts are tested under conditions typical of MEMS relay applications; 4V, 1mA; with a static contact force of 1mN, results are presented on the bounce process and on the opening characteristic with respect to the melting and boiling voltages for the materials tested.

Wear processes of the switching contact pair consisting of a gold layer on multiwall carbon nanotubes (Au/MWCNT) and a chromium and gold coated hemispherical ball (Au/Cr) are evaluated over a range of current conditions. The switching experiments were conducted using typical conditions for a MEMS relay application, i.e. 4 V, with static contact force 1 mN with currents level of 20 -200mA. The Au coated MWCNT substrate exhibited a transfer process over a large number of switching cycles. On the assumption that the transfer process was a combination of a fine transfer and delamination processes; a previous experimental investigation was considered by dividing the wear processes into four stages of a failure behavior. It is observed that the fine transfer process dominates in the unstable and stable contact resistance stage and then the delamination dominates in the rising stage and a failure process. The increase of contact resistance was used to identify contact failure.

To improve the switching performance of MEMS relays, carbon nanotubes (CNTs) have been used to provide a compliant layer on switching contacts. In this study a Gold coated CNT composite surface synthesized on a silicon wafer, was mounted on the tip of a piezo-electric actuator and mated with a Au coated hemispherical surface. The switching contacts were tested under conditions typical of MEMS relay applications; 4V, 1-20mA; with a static contact force 1mN. The switching characteristics of the surfaces are investigated, with particular focus given to the opening and closing voltage transients. At opening, to evaluate the thermodynamic process associated with the contact interface known as molten metal transfer; and at closing to evaluate the bounce characteristics.

-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.