Assembly of α-quartz for surface acoustic wave (SAW) strain gauges application

In this paper a finite element (FE) model has been developed for the simulation of thermo-mechanical stress in the sensor substrate. The bond topology has been optimized with respect to bond material properties. Based on the simulations, experiments with two bond technologies and three bond materials were carried out. The effect of thermo-mechanical stress on an α-quartz sample, attached to a heat-treatable steel carrier has been measured and evaluated with white-light interferometry. The bond quality has been evaluated with shear tests, thermal load cycle tests and micro-sections. The corresponding offset due to the remaining thermo-mechanical stress in the sensor substrate was measured and analyzed with a network analyzer. The investigated bond materials and technologies are providing low offset of the sensor signal and a high coupling of the measuring quantity into the SAW sensor.