A MEMS Microreed Switch With One Reed Embedded in the Silicon Substrate

This paper presents design, fabrication, and characterization of a novel microelectromechanical microreed switch, which consists of two Ni₈₀Fe₂₀ magnetic plates as microreeds. One is embedded in a silicon trench. The other is suspended above the substrate and supported by a pair of crab-leg flexures from the two sides. Both Ni₈₀Fe₂₀ plates are split into two long, narrow strips to improve the sensitivity. The switch is actuated by bringing an external magnet closer to the switch. The magnetic field required to turn on the switch can be as low as 0.5 mT and the initial contact resistance is <; 10 Ω with gold contacts. The switch has been tested to pass more than 40 million hot switching cycles at 2 mA current at room temperature when packaged at wafer level with SU-8 sealing. The die size is 1.7 × 1.8 × 1.1 mm³. The proposed microreed switch can be used as the proximity sensor to sense the magnetic field. It also has the potential to replace the conventional reed switch in portable electronics, such as cellular phones, hearing aids, and laptops, where conserving battery power and device size is critical.