Measurement of package-induced stress and thermal zero shift in transfer molded silicon piezoresistive pressure sensors

Abstract

The package-induced stress in a transfer molded piezoresistive pressure sensor has been measured by monitoring the individual piezoresistors in the measuring bridge. Based on measurements on six different samples, the induced difference between longitudinal and transversal stress in the sensor diaphragm has been measured as MPa at room temperature. The induced stress creates thermal zero shift and long term drift of the sensor signal. By covering the sensor chip with a low modulus glob top before molding, the stress and thermal zero shift may be considerably reduced.