Glass-frit bonding of silicon strain gages on large thermal-expansion-mismatched metallic substrates

Bonding of silicon strain gages on stainless-steel substrates is a critical issue in diaphragm-type pressure sensors because of the large mismatch in coefficients of thermal expansion between silicon and metal resulting in serious reliability problems. A new method to significantly improve the glass-frit bonding of silicon gages on metal diaphragms is reported based on an intermediate thin glass plate onto which silicon strain gages are fabricated. The glass interlayer enables very reliable bonds without post-bond misalignment, debonding, or cracking through the selection of glasses that very closely match silicon and the compressive surface strengthening of glasses. Furthermore, the proposed gage structure provides great improvement in the electrical performance, especially the thermal drifts of offset (zero) and span of Si strain-gage-based bridge transducers.