环形无源万向微机电惯性开关

Annular passive universal MEMS inertial switch

针对传统惯性开关阈值散布大、万向性差等缺点,设计了一种环形无源万向微机电惯性开关。环形的可动质量框作为可动电极,由内部的四根折叠悬臂梁支撑,和外部的环状固定电极有一定间隙,构成xy平面内的万向开关。对设计开关进行有限元动态接触仿真,结果表明开关在1000g加速度作用下的响应时间和接触时间分别约为0.142 ms和5 s,表现出较高的触发灵敏度和良好的接触效果。研究悬臂梁线宽与开关阈值加速度的关系,结果表示悬臂梁线宽的微小变化会引起阈值加速度的较大变化。利用冲击台试验对封装后的开关进行阈值试验,试验结果表明实际阈值分布在900g^1300g范围内,80%的开关阈值比设计值大。用微电镜对悬臂梁线宽进行静态测量,悬臂梁线宽加工误差大多分布于0^+2 m,加工误差直接导致开关的阈值加速度增加,设计阶段应充分考虑加工误差对阈值加速度的影响。

To overcome traditional inertial switch＇s defects such as board distributed threshold and poor universality, a MEMS annular passive universal inertial switch was designed. The movable annular mass frame was used as the movable electrode which was supported by internal four snake-like cantilever beams and had a certain clearance with external annular fixed electrodes. The finite element dynamic contact simulation for the designed switch indicate that, under the effect of 1000g acceleration, the switch＇s response time and contact time were approximately 0.142 ms and 5 kts, respectively, showing that the switch has high trigger sensitivity and good contact effect. The study on the relationship between the device threshold acceleration and the width of the cantilever beam shows that even a small change of the cantilever beam width could induce a large increase of the switch＇s threshold. After fabrication and packaging, the threshold accelerations of the MEMS switches were tested on shocking platform, and the results show that the threshold accelerations are distributed between 900 g and 1300 g, and most of them are bigger than the expected 1000 g. The static measurements on the width of cantilever beam were made by using SEM, which show that most of the cantilever beam＇s processing errors are distributed in 0-＋2 μm. Since the processing errors could induce the threshold acceleration errors, they should be considered during the design stage.