Temperature as an accelerating factor for lifetime estimation of RF-MEMS switches

In satellite applications the devices have to retain their functionality for years and this requirement necessitate of reliable methodologies to predict the switch lifetime. At present, a consolidated accelerating test to predict lifetime is still lacking for RF-MEMS devices. The most natural choice of an accelerating factor is temperature. However, MEMS are subjected to both electrical and mechanical degradation mechanisms and temperature has important effects on both. Due to design improvements it is now possible to realize switches where dielectric charging is extremely low and mechanical issues are the dominant mechanisms in the determination of the switch lifetime in long-term actuation experiments. In this paper temperature is used as accelerating factor for the estimation of switch lifetime. The most relevant parameter for failure prediction is the variation of spring constant, which is simply related to the square of the actuation voltage. Based on prolonged actuation measurements at different temperatures on a clamped clamped ohmic switch, a method to extract lifetime is presented, living in this specific case a failure time of 10 years at 25 °C. Limits and possibilities of this approach are also carefully analyzed.