Package-induced temperature dependence of MEMS capacitive strain sensor and system design considerations

MEMS capacitive strain sensors are attractive for a wide range of industrial sensing applications due to their high sensitivity, large dynamic range and low temperature dependence. However, after sensors packaging and attachment to a targeted metallic surface, the overall sensing system can exhibit a substantial package-induced temperature dependence caused by different thermal expansion coefficients of silicon, metallic surface and bonding adhesives, thus degrading overall performance. Temperature characterization from -20°C to 150°C of prototype strain sensing modules attached on a stainless steel surface reveals a temperature dependence of -6.2 με/°C. As a results, an increased dynamic range of the sensing electronics are required at the expense of an increased system supply voltage as well as power dissipation. A careful system characterization over the operating temperature range and optimized system design considerations are, therefore, critical for achieving stringent performance requirements.