Characterizing External Resistive, Inductive and Capacitive Loads for Micro-Switches

Abstract

Microelectromechanical systems (MEMS) switches offer much lower power consumption, much better isolation, and lower insertion loss compared to conventional field-effect transistors and PIN diodes however, the MEMS switch reliability is a major obstacle for large-volume commercial applications [1]. To enhance reliability, circuit designers need simple and accurate behavioral models of embedded switches in CAD tools to enable system-level simulations [2]. Where Macro-switch researchers assess electric contact performance based on the type of load that is being switched, in MEMS literature, micro-switch performance and reliability is characterized by testing the devices under “hot-switched” or “cold-switched” load conditions; simple models are developed from the “hot” and “cold” characterizations. By applying macro-switch performance characterization techniques, i.e. examining reliability based on the type of load that is being switched, clear characterizations of “hot” switching and “cold” switching external resistive, capacitive, and inductive loads are produced. External resistive loads were found to act as current limiters and should be suitable under certain criteria for reducing current density through the contact area and thus limiting device failure to mechanical failure modes. Alternatively, external capacitive loads increased current density under “hot” switching conditions at the moment the micro-switch closes; which increases the risk for material transfer and device failure. Under DC conditions, the inductive loads had little effect in either “hot” or “cold” switching environments.