A steel pressure sensor based on micro-fused glass frit technology

In this paper, we propose a pressure sensor using strain gages bonded on 17-4PH stainless steel (SS) diaphragm based on micro-fused glass frit technology. The strain gages with uniform resistance are obtained by growing an epi-silicon layer on a single crystal silicon wafer using epitaxial deposition technique rather than conventional photolithography and etching techniques. The inorganic micro-fused glass frits are used as the bonding material between the strain gages and the 17-4PH SS diaphragm. Compared to organic adhesives, the glass frits bonding material can minimize the hysteresis error in the high temperature applications and improve the mechanical properties of semiconductor strain gage based pressure transducers. After wire bonds being made between the two half bridge strain gages and an interface printed circuit board (PCB), the output characteristics of sensors are evaluated. Results show that the sensors exhibit a stable output with 0.045% full-scale (FS) hysteresis error, and linearity and repeatability are less than 0.04% FS 0.12% FS at the room temperature. Furthermore, the output performance of sensors in the high temperature of 125 °C almost equals that of the room temperature, which indicates that the glass frit bonding is a good method which would lead to a significant advance in the high temperature applicability of silicon strain gage transducers.