The FE model assumes that the packageintroduced
stress is mostly from the CTE mismatch of packaging components. The discrepancy could
have resulted from the non-symmetrical placement of the pressure sensor in the packaging process,
since the different stress distributions on the silicon membrane of the pressure sensor change the final
output voltage of the pressure sensor. The final material properties of the EMC are strongly dominated
by the final curing situation. In addition, a simplified linear model could also contribute to the
discrepancy [25,26]. However, the signal outputs of the packaged pressure sensor obtained from the
FE model and the experiment have similar trend. In addition, the thickness variation of the silicon
membrane is ±10% for a commercial specification of the piezoresistive pressure sensors. This induces
a shift on zero-offset output for pressure sensors. Therefore, the zero offset voltage (ΔV) of each
pressure sensor is a non-zero value and varies from sensor to sensor. To set the signal output of a
pressure sensor always on a positive voltage output at all pressure and temperature range, a series
resistor is added on the sensing circuit to shift the zero-offset output of the pressure sensor to a
specified positive zero-offset value. In contrast, the output voltage of the pressure sensor is caught
directly from the output of the Wheatstone bridge (without adding the series resistor). This explains
why the signal output of the pressure sensor may cover a range of positive and negative voltages.