Low temperature cofired ceramics (LTCC)-based miniaturized load cells

This work presents miniaturized piezoresistive load cells in LTCC for low force ranges. Compared to former investigations on this area we designed the load cells according to commercial products. We used a freestanding cartwheel structure with co-fired piezoresistive resistors as deformable bodies which combines both: high sensitivity and a high robustness against shear forces. The designed packaging allows the sensing of compressive and tensile forces for different ranges (2 N, 5 N and 10 N) and is characterized by a high miniaturization. We developed an analytical model to design the cartwheel structures and to predict the expected characteristics. To increase the repeatability and the reliability we studied different fabrication techniques to reduce cracks, delaminations and sagging. The sensor elements were fabricated in the standard LTCC-technology on GT 951. The fabricated load cells were characterized between 25 °C and 80 °C regarding relevant parameters. The results show a good match to the theoretically calculated values.