Effect of high-temperature glass frit bonding process on performance of polysilicon strain gauges

This Letter presents the effect of high-temperature glass frit bonding conditions on the resistivity coefficient of gauge factor (RCGF), resistivity and gauge factor of polysilicon strain gauges. In previous works, the authors proposed the use of thin polysilicon strain gauges that were bonded onto metal structures with an inorganic glass frit adhesive. However, this glass frit bonding process was carried out at a high temperature, which could cause performance changes of the polysilicon strain gauges in terms of their RCGF, resistivity and gauge factor. To investigate the effect of the glass frit bonding process, the RCGF, resistivity and gauge factor of the polysilicon strain gauge before and after heat treatment by the conventional Al annealing condition and the glass frit bonding condition were compared and evaluated. In the results, large resistivity and gauge factor deviations in the polysilicon strain gauges that were not heat treated were observed. In spite of these large deviations, a linear relationship between the resistivity and the gauge factor was observed. After the polysilicon strain gauges were heat treated by the conventional Al annealing condition and the glass frit bonding condition, the deviations in the values of the resistivity and gauge factor became more uniform than those seen in the strain gauges that were not heat treated. The RCGFs of the polysilicon strain gauges heat treated with the Al annealing condition and the glass frit bonding condition coincided with that of the gauge that was not heat treated.