Zhang Yunfan, Li Bowen, Li Hui, Shen Shengnan, Li Feng, Ni Wentao, Cao Wan
The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China.
School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China.
Sensors (Basel). 2021 Mar 12;21(6):2011. doi: 10.3390/s21062011.
Thermal stress is one of the main sources of micro-electro-mechanical systems (MEMS) devices error. The Wheatstone bridge is the sensing structure of a typical piezoresistive MEMS pressure sensor. In this study, the thermal stress induced by potting adhesive in MEMS pressure sensor was investigated by experiments, calculated by analytics and analyzed by simulations. An experiment system was used to test the sensor at different air pressures and temperatures. The error becomes greater with the decrease in pressure. A set of novel formulas were proposed to calculate the stress-strain on Wheatstone bridge. The error increases with the temperature deviating from 25 °C. A full-scale geometric model was developed, and finite element simulations were performed, to analyze the effect of the stress on MEMS pressure sensor induced by different temperatures and thicknesses of potting adhesive. Simulation results agree well with the experiments, which indicated that there is a 3.48% to 6.50% output error in 0.35 mm potting adhesive at 150 °C. With the thickness of potting adhesive increasing, the variations of output error of the Wheatstone bridge present an N-shaped curve. The output error meets a maximum of 5.30% in the potting adhesive of 0.95 mm and can be reduced to 2.47%, by increasing the potting adhesive to 2.40 mm.
热应力是微机电系统（MEMS）器件误差的主要来源之一。惠斯通电桥是典型压阻式MEMS压力传感器的传感结构。在本研究中，通过实验研究了MEMS压力传感器中灌封胶引起的热应力，通过分析计算得出热应力，并通过模拟进行分析。使用实验系统在不同气压和温度下对传感器进行测试。误差随着压力的降低而增大。提出了一组新颖的公式来计算惠斯通电桥上的应力应变。误差随着温度偏离25℃而增大。建立了全尺寸几何模型，并进行了有限元模拟，以分析不同温度和灌封胶厚度对MEMS压力传感器应力的影响。模拟结果与实验结果吻合良好，这表明在150℃下，0.35mm灌封胶时存在3.48%至6.50%的输出误差。随着灌封胶厚度的增加，惠斯通电桥输出误差的变化呈现N形曲线。在0.95mm灌封胶时输出误差最大为5.30%，通过将灌封胶增加到2.40mm，输出误差可降低至2.47%。
