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 mm
³
) 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.