Investigation of package effect of Si-based piezo-resistive micro pressure sensor

• Main Authors: Chen-Hing Chu, 朱振宏
• Other Authors: Kuo-Ning Chiang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/09882182418424041556

碩士 === 國立清華大學 === 動力機械工程學系 === 94 === Since the piezoresistive effect was discovered, the applications of piezoresistive sensors have been widely employed in mechanical signal sensing. The silicon-based pressure sensor is one of the major applications of the MEMS device. Nowadays, the silicon piezoresistive pressure sensor is a mature technology in industry and its measurement accuracy is more rigorous in many advanced applications. For the purpose of operating the piezoresistive pressure sensor in harsh environment, the silicone gel is usually adopted to protect the die surface and wire bond while allowing the pressure signal to be transmitted to the silicon diaphragm. In addition, because the major factor that affects the high performance applications of the piezoresistive pressure sensor is the temperature dependence of its pressure characteristics, therefore both the thermal and packaging effects should be taken into account to obtain better sensor accuracy. To achieve this object, a finite element method (FEM) is adopted for the sensor performance evaluation. Moreover, the thermal and pressure loadings are applied on the sensor to study the sensitivity of output signals, the packaging-induced signal variation, reduction of thermal/packaging effects, and the output signal prediction for the pressure sensors. In this study, two types of FEM models are included. In model 1, the surface of the silicone gel is convex. By comparison, the surface of silicone gel is concave in model 2. Besides FEM analysis, this study use experiment to validate FEM simulation results rationality. Furthermore, in order to obtain a better sensor performance, the FEM parametric and factorial design analysis are performed. The design parameters include the length and thickness of silicon chip, the membrane length, the thickness and material of silicone gel, and so on. In model 1, the findings show that a reduction in the packaging-induced thermal effect can be acquired when a shorter length and thicker thickness that the silicon chip has. In model 2, a constrained condition is applied in the silicone gel peripheral. The foregoing situation makes the silicone gel become the most significant factor. The analytic result shows that a proper selection in the silicone gel’s material and thickness can greatly reduce the packaging-induced thermal effect.