Mechanical Shock in MEMS

Abstract

This chapter addresses a reliability issue of MEMS that is crucial for their commercialization, which is their survivability under mechanical shocks. Unlike conventional electronics of passive elements, MEMS contain flexible components that are deliberately designed to undergo some kind of motion. Thus, a natural question comes of how these microstructures respond when they are subjected to dynamic shock loads? What about short circuit and stiction when they make contacts with the substrate or stationary electrodes due to shock loads? These are some of the issues that are treated in this chapter. In addition, the impact of electrostatic forces on the dynamic response is illustrated. The interaction of the motion of microstructures with the printed circuit boards where they are mounted on is also discussed. IntroductionWith the rapid growth and maturity of the MEMS technology, many device concepts are ready to make the transition from research labs to consumer products. One of the critical issues affecting the commercialization of MEMS devices is their reliability and survivability under mechanical shock and impact. Several MEMS components have already made it to the market and being increasingly integrated and embedded into handheld devices and consumer products, such as the interactive motion-sensitive video games and smart phones. In such environments, there is an obvious need to ensure the durability and reliability of MEMS to sustain the various dynamic loads while being used by consumers.MEMS generally can be exposed to shock during fabrication, deployment, shipping, and operation. Also, a crucial criterion for automotive and industrial applications is the survivability of portable devices containing MEMS when dropped on hard surfaces, which can induce significant shock loads. For some applications, MEMS are expected to survive sever dynamic loading, such as the harsh environments in military applications. In addition, aerospace applications rely on pyrotechnic devices, which generate dangerous shock waves of amplitude reaching hundreds of thousands of gs. MEMS sensors and devices in these applications are required to survive such severe environments.

Mechanical behavior simulation of MEMS-based cantilever beam using COMSOL multiphysics

“…Younis et al have developed analytical and computational techniques to investigate shock in MEMS. In [12][13][14][15][16][17] the response of microstructures under the combined effects of mechanical shock and electrostatic forces has been investigated theoretically and experimentally.…”