Giuseppe Noviello

Micromachined passive magnetostatic relays for portable applications

A passive MEMS magnetostatic relay using only one electroplated magnetic layer was presented. The relay consists of an electroplated Ni80Fe20 plate supported by a pair of torsion bars from two sides. The relay is actuated by approaching an external magnet to the relay. The switching-on magnetic field is about 4.8 mT and the contact resistance is about 3 Ohms with gold contact. The lifetime testing shows more than 7.5 million hot switching cycles with 1–2 mA current. This passive magnetic relay could find applications in portable electronics, such as cellular phones, personal data assistant (PDA), pace makers, hearing aids, etc.

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.

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.