Evolution of contact bounces in MEMS switches under cycling

The reliability of Micro Electro Mechanical Switches (MEMS switches) still remains the main focus of attention, but only a few studies have dealt with their bouncing behavior. In this paper we investigate and compare contact bounces in three different types of electrostatic RF MEMS switches tested under similar hot switching conditions (5V/500μA). An instrumented test bench has been developed for monitoring and recording the contact closing voltage during several millions of cycles. The results point out that contact bounces are never observed during the early cycles with new components and may first appear after a few millions (or more) of cycles. They typically occur a few microseconds after contact closure and their duration is on the order of microseconds. Once a contact bounce appears, the number of contact bounces and their duration keep on increasing with the number of cycles. The origin of contact bounces is discussed in the paper and we show that this phenomenon is closely linked to the degradation of the electrical contacts that announces the failure of MEMS switches. Finally, the analysis of the experimental results reveals that contact bounces could be considered as a relevant indicator to predict the end of life of MEMS switches.