Simulation and characterization of dynamic contact in a MEMS passive vibration threshold sensor

A micro-machined passive vibration threshold sensor with a compliant stationary electrode has been designed, simulated and characterized. Bridge-type elastic beams as the compliant stationary electrode is adopted to improve the contact effect of the vibration threshold sensor and prolong its contact time. The dynamic contact between the two electrodes of the micro-machined vibration threshold sensor is simulated and analyzed by finite-element method (FEM). It’s indicated that a ‘skip contact’ phenomenon occurred during the switching on, which has been described and successfully explained in this paper. Deformations and stress distributions of the compliant electrode during contact under 55 g half-sine applied shock acceleration is also simulated. An all-metal cap that can undergo 6.08 × 105 Pa has been designed and fabricated by UV-LIGA process for package of the vibration threshold sensor. A drop hammer test of the fabricated vibration threshold sensor has been done, which is in accordance with the FEM simulation of dynamic contact process. The measured response time of the threshold sensor is about 0.3 ms under 55 g applied acceleration and two contact times in the skip contact are 16 and 4 µs, respectively, which are in agreement with simulated results. The obtained natural frequency of the vibration threshold sensor by a vibration test is about 810 Hz in the first model, which also agrees with the model.

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

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

[3]  Keekeun Lee,et al.  MEMS spring probe for non-destructive wafer level chip test , 2005 .

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

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

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

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

[8]  George G. Adams,et al.  A dynamic model, including contact bounce, of an electrostatically actuated microswitch , 2002 .

[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]  Hsu Tai-Ran.  MEMS & microsystems: design and manufacture / Tai-Ran Hsu , 2002 .

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

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

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