Strength of ceramic substrates for piezoresistive thick-film sensor applications

Abstract: Force and pressure sensors based on the piezoresistive properties of thick-film resistors are widely used due to their reliability, simplicity and low cost. Recently, the introduction of low-temperature co-fired ceramic (LTCC) substrates has allowed further increases in miniaturisation and integration, while new high-strength ceramic substrates such as zirconia-toughened alumina (ZTA) has enabled better sensor response. However, the materials ' properties are still insufficiently characterised for sensor applications. Properties such as long-term strength, and especially the effect on the strength and reliability of thick-film processing, have received insufficient attention so far. In this work, the short and long-term strength of these substrates is compared with that of standard 96 % alumina, and the effect of various thick-films (resistors, dielectrics, conductors) on the mechanical behaviour is studied. It is shown that thick-film compositions can have a dramatic effect on the strength of the substrates