TEMPERATURE-DEPENDENCE OF THE ELECTRICAL-CONDUCTION IN RUO2-BASED THICK-FILM RESISTORS

In this paper, the temperature dependence of resistance of two generic RUO2-based resistors is investigated. The resistor compositions studied are 80 wt.% glass (63 wt.% PbO - 25 wt.% B2O3 - 12 wt.% SiO2, designated as G1) - 20 wt.% RuO2 and 80 wt.% glass (55.5 wt.% PbO - 22 wt.% B2O3 - 10.5 wt.% SiO2 - 12 wt.% Al2O3, designated as G2) - 20 wt.% RuO2. The sheet resistance of resistor 80 wt.% Gl - 20 wt.% RuO2 fired at 850-degrees-C decreases as the temperature is increased from 100 K to approximately 400 K, remains a minimum value at temperatures 400 K approximately 690 K, and then increases as the temperature is further raised. A negative temperature coefficient of resistance (TCR) of approximately -480 ppm/degrees-C is obtained from 100 K to 500 K. The TCR becomes less negative when temperature increases. Three models for conduction mechanism of thick film resistors are employed to explain the experimental results. A modified model, consisting of both tunneling and parallel conduction approaches, is proposed to elucidate the change in slope in the resistance-inverse temperature curve as well as the temperature dependence of the resistance. In addition, an equivalent circuit model is proposed to describe the electrical behavior of the thick film resistors.