A MEMS Inertia Switch With Bridge-Type Elastic Fixed Electrode for Long Duration Contact

A multilayer structural inertia microswitch with a bridge-type elastic fixed electrode for long duration contact has been designed and fabricated based on surface micromachining technology. The microswitch mainly consists of a suspended thick proof mass as a movable electrode and two parallel elastic beams with holes as a fixed electrode. The proof mass is designed to be much thicker than attached snake spring section. As a new type of fixed electrode, the bridge-type elastic beams can effectively improve the contact of the microswitch. The packaged microswitch (3.2 times 2.1 times1.3 mm3) has been tested and characterized by a dropping hammer system. The response time and the contact time of the microswitch are about 0.25 ms and 12 mus, respectively, when 100 g acceleration is applied, which indicates a better contact effect than current reported switches. Dependence of the contact time on the thickness of the parallel beam under applied acceleration of 100 g has been discussed. The contact time increases as the thickness of the parallel elastic beam decreases. The test data have an agreement with dynamic finite element simulation results.

[1]  Y. Loke,et al.  Fabrication and characterization of silicon micromachined threshold accelerometers , 1991 .

[2]  P. Zavracky,et al.  Micromechanical switches fabricated using nickel surface micromachining , 1997 .

[3]  T. R. Hsu,et al.  MEMS and Microsystems: Design and Manufacture , 2001 .

[4]  Masayoshi Esashi,et al.  Acceleration switch with extended holding time using squeeze film effect for side airbag systems , 2002 .

[5]  Gang Li,et al.  Fabrication and packaging of inertia micro-switch using low-temperature photo-resist molded metal-electroplating technology , 2004 .

[6]  L. Zimmermann,et al.  Airbag application: a microsystem including a silicon capacitive accelerometer, CMOS switched capacitor electronics and true self-test capability , 1995 .

[7]  R. G. Hamel,et al.  Microminiature ganged threshold accelerometers compatible with integrated circuit technology , 1972 .

[8]  T Tønnesen,et al.  Simulation, design and fabrication of electroplated acceleration switches , 1997 .

[9]  Wei Ma,et al.  Design and characterization of inertia-activated electrical micro-switches fabricated and packaged using low-temperature photoresist molded metal-electroplating technology , 2003 .

[10]  Josef Binder,et al.  Additive electroplating technology as a post-CMOS process for the production of MEMS acceleration-threshold switches for transportation applications , 2000 .

[11]  G. Kovacs.  Micromachined Transducers Sourcebook , 1998 .

[12]  Rod Black.  Design and Manufacture , 1996 .

[13]  Byung Man Kwak,et al.  Snapping microswitches with adjustable acceleration threshold , 1996 .

[14]  Yuelin Wang,et al.  Micro-cantilever shocking-acceleration switches with threshold adjusting and 'on'-state latching functions , 2007 .

[15]  T Tønnesen,et al.  Low-cost post-CMOS integration of electroplated microstructures for inertial sensing , 2000 .