Design, fabrication, and characterization of piezoresisitve strain gage-based pressure sensors for mechatronic systems

The pressure sensor is a key device in many mechatronic systems for automotive and industrial applications. We represent the piezoresitive pressure sensor based on the single crystal silicon strain gauges, which are glass-fused to the stainless steel diaphragm at high temperature. The silicon bulkmicromachined strain gauges have the through holes and the closed structure, unlike the current competitive devices with open structure. This unique design concept reduces shifting or rotation of gauge position during glass frit bonding and enables the automation of alignment and bonding processes, which improves the sensor performance and yield and hence reduces sensor cost. The prototype was characterized using specific long term tests such as PPTCB (pulsed pressure, temperature cycling, with bias). The pressure sensors tested under pressure ranging from 0 to 50 bar at different temperature have a linear output with a typical sensitivity of about 16mV/V/bar and an offset drift of -6 mV to 2 mV. The fatigue life tests run at a rate of 3 Hz up to 2 million pressure cycles from 0 to 50 bar showed no failures when the pressure cycle test was stopped.