Optimized assembly of a CMOS-integrated strain sensor for high-precision deformation measurements

Abstract:
This paper investigates the use of CMOS-integrated strain sensors for high-precision deformation measurements and, in particular, for detecting extremely small relative strain changes in the range of 10^-6 (microstrain). For this purpose, the sensor chips were mounted on stainless steel substrates using two different bonding methods: In addition to a commercially available epoxy resin adhesive, a foil based on the reactive multilayer system (RMS) of nickel and aluminum with 10 µm tin on both sides was used. Tensile tests and 4-point bending tests were performed as test methods. The load on the substrate was changed and the sensor signal was read out to determine the sensor characteristics. In addition to previous studies, strain changes down to below 10(exp-6) were performed. Additional temperature measurements were performed to determine the change in sensor offset as a function of ambient temperature. The results show that both bonding methods enable similar sensor properties and the detection of deformation changes below the microstrain range.