Thick-film piezoresistors - benchmarking of LTCC substrates

The ceramic micro electro-mechanical systems (C-MEMS) are fabricated in most cases by low-temperature co-fired ceramics (LTCC). The sensors of mechanical quantities are fundamental parts of MEMS, and thick-film resistor can sense mechanical deformations in the C-MEMS structures. Relatively low elastic moduli of LTCC ceramics as compared to alumina ceramics imply an increased sensitivity of sensing elements. Selected thick film resistors (Du Pont 2041 and ESL 3414) were evaluated as piezo-resistors for force sensors. The 2041 resistor was chosen because of its low noise, whereas the 3414-B was developed specially for use in strain gauges Resistors were screen printed and fired on various LTCC tapes as well as on alumina substrates. Electrical characteristics, i.e., sheet resistivities, noise indices and gauge factors were measured. LTCC tapes were analysed by scanning electron microscopy, energy dispersive X-ray analysis and X-ray powder analysis. Crystalline phases in LTCC materials were determined.