# Failure Analysis and Optimized Simulation Design of Silicon Micromechanical Resonant Accelerometers

## TL;DR

This paper investigates why silicon micromechanical accelerometers fail under temperature and vibration stress and proposes design improvements to enhance their stability and performance.

## Contribution

A novel isolation frame design is proposed to reduce frequency instability and structural stress in resonant accelerometers.

## Key findings

- Silicon's Young’s modulus variation causes a resonance frequency shift of −1.364 Hz/°C.
- Residual stress from temperature changes affects resonance frequency by ±5 Hz/MPa.
- The isolation frame reduces stress effects by up to 71.3% under vibrational stresses.

## Abstract

To develop solutions to the frequency instability and failure of silicon micromechanical resonant accelerometers, the state characteristics of micromechanical resonant accelerometers are investigated under temperature and vibration stresses. Through theoretical analysis and finite element simulation, the following is found: the Young’s modulus of silicon varies with temperature, causing a resonance frequency shift of −1.364 Hz/°C; the residual stress of temperature change affects the resonance frequency shift of the microstructure, causing it to be 5.43 Hz/MPa (tensile stress) and −5.25 Hz/MPa (compressive stress); thermal expansion triggers the failure of the bonding wire, and, in the range of 10 °C to 150 °C, the peak stress of the electrode/lead bond area increases from 83.2/85.6 MPa to 1.08/1.28 GPa. The failure mode under vibration stress is resonance structure fracture and interlayer peeling. An isolation frame design is proposed for the sensitive part of the microstructure, which reduces the frequency effects by 34% (tensile stress) and 15% (compressive stress) under temperature-variable residual stresses and the maximum value of the structural root mean square stresses by 69.7% (X-direction), 63.6% (Y-direction), and 71.3% (Z-direction) under vibrational stresses.