The influence of firing procedures on strain sensitivity of thick-film resistors

Thick-film resistors are electrical composites containing particles of ruthenate/ruthenium oxide conductor distributed in a highly modified silicate glass. Thick-film technology is widely used for the fabrication of force and pressure sensors for its virtues of good piezoresistivity and reliability. This paper reports a systematic study on the influence of firing conditions on the gauge factor (GF) of thick-film resistors. The relationship between sheet resistivity and GF of thick-film resistors with various concentrations of the conductive phase (10-30 wt% RuO2) fired through different firing procedures was studied. The results show that the GF and the sheet resistivity of the thick-film resistor will decrease with the increase of conductive phase concentration, peak firing temperature and dwell time. When resistors of the same sheet resistivity are considered, the increase of the firing temperature will lead to a decrease of GF. The sheet resistivity and GF decrease simultaneously with the increase of dwell time and move along the straight line. The results indicate that the influence of firing conditions on the microstructure of thick-film resistors comprises two aspects. The first one is the increase in the number of conductive chains, and the second is the changes in the distribution of conductive chain particles.