Abstract
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.
Highlights
The micro-electro-mechanical systems (MEMS) pressure sensor is the first industrial MEMS device in the world which was micromachined by Honeywell in 1962 [1]
Subbiah [17] characterized the influence of thermal stresses in the sensor and produced a final version of the sensor that is stable for operations at high temperature
The previous studies only focus on novel structures and different material parameters of adhesive but fail to reveal the influence of potting adhesive on the thermal-stress-induced output error of Wheatstone bridge in MEMS pressure sensors
Summary
The micro-electro-mechanical systems (MEMS) pressure sensor is the first industrial MEMS device in the world which was micromachined by Honeywell in 1962 [1]. Tran et al [8] designed a novel MEMS piezoresistive pressure sensor for low-pressure measurements which had four independent petal membranes This structure increased the sensitivity and decreased the nonlinearity of the sensor. These novel designs improved the performance of pressure sensor, but the scientists did not study the mechanism of output error. The previous studies only focus on novel structures and different material parameters of adhesive but fail to reveal the influence of potting adhesive on the thermal-stress-induced output error of Wheatstone bridge in MEMS pressure sensors. A full-scale geometric model was developed, and finite element simulations were performed, to optimize the potting process parameter by analyzing the output error of the sensor induced by different temperatures and thicknesses of potting adhesive
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