Environment friendly perovskite ruthenate based thick film resistors

It is well known that the dielectric matrix of air-fireable thick film resistors (TFRs) presently used in hybrid microelectronics and passive components invariably consists of a high-lead silicate glass. However, the current trend in the electronic industry is to restrict and eliminate the hazardous elements viz. lead, cadmium etc. from electronic components. An attempt to develop suitable RuO2-based or pyrochlore ruthenate based Pb–Cd free TFRs has been only partially successful till now. We report here the preliminary results of a study aimed to investigate the feasibility of CaRuO3 perovskite-based lead-free TFRs. Our results showed that sheet resistances higher than 1 kΩ/sq. can be easily achieved in a controlled way, with hot and cold temperature coefficients of resistance (TCR) in the range of 325–580 ppm/°C and 180–500 ppm/°C, respectively. Similarly, the compositions also exhibit negligible piezoresistive effects with gauge factor, GF < 1. Additionally, the resistors do not exhibit negative structural features, like bleeding or devitrification of glass, observed in previous attempts to develop reliable lead-free TFRs.