Simulation, fabrication and characterization of an all-metal contact-enhanced triaxial inertial microswitch with low axial disturbance

An all-metal inertial microswitch that is sensitive to three axial accelerations (+x, +y and +z) is fabricated by low-temperature photoresist modeled metal-electroplating technology. The inertial switch consists of four main parts: a quartz wafer with anti-stiction strips as the substrate; a proof mass suspended by conjoined serpentine springs as the movable electrode; two L-shaped flexible cantilevers and a multi-hole crossbeam as horizontal and vertical fixed electrodes, respectively; two anchors located in the middle of proof mass as limit blocks. ANSYS software is used to simulate the dynamic contact process in the microswitch, and the simulation results reveal that the flexible fixed electrode can prolong the contact time and eliminate the rebound during the contact process. The axial disturbance among different sensitive directions has been discussed by dynamic simulation. The modal analysis, crosstalk between horizontal and vertical directions, cross-axis sensitivity, and the disturbance under overload shock along the reverse sensitive direction are also simulated and discussed. The suspension and gap in the device structure can be precisely controlled utilizing the photoresist modeled metal-electroplating technology to reduce the axial disturbance effectively. Finally, the prototype is fabricated successfully and tested by dropping hammer system. It is shown that the test threshold acceleration is 255-260 g in horizontal directions (+x and +y), ∼75 g in vertical direction. The contact time of the switch with elastic contact point is ∼60 μs in horizontal direction and ∼80 μs in vertical direction. The crosstalk between horizontal and vertical direction, cross-axis and overload disturbance have been also demonstrated by test results, which indicate the axial disturbance is low in the present inertial switch.