Study of contacts in an electrostatically actuated microswitch

Surface micromachined, electrostatically actuated microswitches have been developed at Northeastern University. Microswitches have an initial contact resistance of 0.5-1 /spl Omega/, and current handling capability of about 20 mA. Typically, contact resistance degrades progressively when the switches are cycled beyond approximately 10/sup 6/ cycles. In this work, the microswitch contact resistance is studied on the basis of a simple, clean metal contact resistance model. Comparison of measured contact resistance (measured as a function of contact force) with the characteristics predicted by the model shows the measured resistance to be higher than the prediction, approximately by an order of magnitude, suggesting that insulating films at the contact interface need to be taken into account. Microswitches with a large number of parallel contacts have also been developed, and measurement data is presented showing that these devices have a current handling capability greater than 150 mA.