Electrostatically actuated MEMS relay arrays for high-power applications

Micro-electromechanical systems (MEMS) relays should have high current-carrying capability and high device reliability for high-power applications. The current-carrying capability of MEMS relays is mainly limited by the thickness of metal contacts fabricated by micromachining process. Another significant limiting factor is the high contact resistance resulted from the low driving force, which is provided by microactuators. This paper presents a matrix configuration of electrostatically actuated microcantilever relay arrays that are connected in parallel to shunt high currents to individual relay elements. This method allows the matrix to be configured for different power requirements. The proposed novel hollow suspended spring lowers the driving voltage and enhances the device stability considerably because of its low longitudinal stiffness while high lateral stiffness. The average of pull-in voltages is approximately 39.4 V and the overdamped switching-on time is approximately 180 μs when 42 V of driving voltage is applied. Contact resistance of each relay is less than 1 Ω, and the equivalent contact resistance of the 2 × 2 relay arrays is lower than 250 mΩ. Each relay can operate in over 6.5 × 103 hot-switching cycles without failing at a current of 20 mA with 0.3 μm thick Au contacts, thus the 2 × 2 relay arrays can carry four times currents more than one single relay. Therefore, the proposed MEMS relay arrays are suitable for applications in high-power switching systems that require high reliability and stability, such as space applications.

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