Design and Fabrication of Universal Inertial Switch Based on MEMS Technology

Aiming at such defects as the widely distributed threshold and poor universal performance in traditional inertial switch, a MEMS universal inertial switch was designed. The switch consisted of two annular lectrodes, each electrode was suspended by four serpentine flexures and could move freely. There was a gap between the two electrodes and the gap kept the swtich open during non-working state . When the absolute value of acceleration along a particular direction in the x-y plane exceeded a certain threshold value, one of the electrode (the sensing mass) contacted with the other electrode, the ON-state was held and the duration of the ON-state extended because of the flexible distortion of serpentine flexures . The finite element dynamic model was established and simulated in LS-DYNA and the simulation results showed that under the effect of 800g acceleration, the response time and the contact time of the switch were approximately 0.135ms and 20respectively. Compared with other inertial switch, the designed switch exhibited the higher trigger sensitivity and contact reliability. The micro inertial switch was fabricated using the MEMS bulk micromachining process, including the crucial technology of KOH etching, ICP etching spray coating method and so on. The testing system was designed and the shock testing was selected to test the performance of the switch. The test results showed that when the acceleration reached 800g, about 83% switches could work normally.