三轴压阻微加速度计的结构力学分析

Structure mechanics analysis on three-axis piezoresistive micro accelerometer

为了提高三轴加速度计机械精度和加工过程中硅片的一致性,设计了基于SOI的单质量块四边八梁结构的三轴加速度计。通过连接扩散在梁上的压敏电阻构成得惠斯通电桥检测三个方向的加速度信号。电桥设计为开环形式,并给出三个方向的电桥输出。结合材料力学和振动力学中的相关理论,建立了结构的数学模型,并对其进行了系统的力学分析,从而得出结构参数对加速度计的一阶固有频率、灵敏度等性能的影响。利用有限元ANSYS仿真软件对结构模型进行了静态和模态分析,验证了力学分析的正确性。最后设计了八张版图及一套可行的工艺流程并加工出加速度计裸片。该微加速度计可同时检测三维加速度矢量,且电桥和结构的设计均较好的抑制了横向效应。

A three-axis piezoresistive accelerometer based on SOI with single mass and four side-eight beam structure was designed to improve the mechanical precision and the consistency of silicon process. The accelerometer detected three-axis acceleration signals by connecting the resistances on the beams to form three Wheatstone bridges. The mathematics model was established by using the theory of Mechanics of Material and Mechanics of Vibration, and the systemic mechanics analysis of the structure was made. The results indicate the influence of the structure parameters on the performance such as intrinsic frequency and sensitivity of three directions. The static and modal simulations were carded out by ANSYS sottware, which proved the correctness of the mechanics analysis. Finally, the processing flows were designed, and the unpacked aceelerometer was showed. The micro-accelerometer can test three-dimensional vector simultaneously, and the design of Wheatstone bridge and structure restrain the transverse effect effectively.