A Magnetostatic MEMS Switch Designed for Portable Applications

A passive magnetostatic microelectromechanical systems (MEMS) switch using only one electroplated soft magnetic layer of nickel-iron (Ni₈₀Fe₂₀) alloy was designed, fabricated, and characterized. The switch is composed of an electroplated Ni₈₀Fe₂₀ plate supported by a pair of torsion bars from two sides. The Ni₈₀Fe₂₀ plate is patterned into long and narrow strips to improve the sensitivity. The switch is actuated by bringing an external magnet closer to the switch. Therefore, no internal electrical power is consumed by the device for actuation. The magnetic field required to turn on the switch is 4.8 mT, and the initial contact resistance is 0.5 Ω with gold contacts. The switch has been tested to pass more than 34 million hot-switching cycles at 2-mA current at room temperature when packaged at the wafer level with SU-8 sealing. The die size is 2.1 × 1.94 × 1.1 mm³. The magnetic switch of this paper has the potential to replace the conventional reed switch in portable electronics such as laptops, cellular phones, personal data assistants, pacemakers, and hearing aids.