油封型高圧用半導体圧力センサ

抄録

This paper describes a structural analysis of the piezoresistive semicon ductor high pressure sensors for pressures from 0 to 35MPa range using the finite element method. The analysis reveals that a peak stress appeares in the thick wall part of the silicon diaphragm surface due to local flexibility. Here the local flexibility means elastic deformation of solid part of silicon diaphragm, which is considered to determine the best position of piezoresistive elements in order to produce the largest output voltage. The pressure sensor assembly has oil filled pressure reception part and includes a thin metal seal diaphragm to protect the piezoresistive elements from contamination due to the measuring fluid. A unique metal flow seal technique by using plastic flow characteristics of soft metal is developed to fasten the metal seal diaphragm airtightly to the case. By minimizing the error due to volume change of filled oil, an appropriate dimension of the metal seal diaphragm is designed and prototype sensors are fabricated according to this design. These sensors have the following characteristics: The nonlinearity is less than 0.2% of the full scale in the pressure range of 0 to 35MPa. Total errors, which include zero point change and span change, are less than ±1% in the temperature range of -40∼125°C. No change in these characteristics is observed even when a 150% load is applied repeatedly 10⁶ times to the sensors.