Electrostatically actuated microswitches and relays have been developed at Northeastern University. These devices are approximately 100 x 100 microns in size and have been tested up to 10~9 cycles with a current of 2 mA per contact. In this paper we examine the thermal characteristics of a microswitch with Au-Au contacts. We describe a finite element model to study the temperature distribution in the microswitch. The modeling results show that the highest temperature is located in the thin film contact trace rather than at the contact interface. The hottest spot moves away from the contact if the contact radius increases. Measurements show a sharp decrease in the contact resistance at a switch voltage of about 0.08 V and a current of 0.15 A, which may be due to removal of surface contaminants or softening of the contact surfaces. The result is in rough agreement with the onset of softening predicted by the model. The contact trace melts at a switch current of 1 A. The melted region is 3.5-6 μm away from the center of the contact, slightly further than is predicted by the model.
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