Performance of Thick-Film Resistor Pastes

One of the main deficiencies of the conventional Pd-Ag system is its resistance and TCR sensitivity to firing atmospheres and temperatures. This occurs because Pd will oxidise from 300°C to 500°C in the presence of Ag and will be reduced above 600°C. It has been shown that the oxidation of the palladium and the decomposition of the palladium oxide are influenced catalytically by silver depressing the PdO decomposition temperature from 780°C to about 600°C. Therefore, this system when fired at peak temperatures in the 700–800°C range is prone to uncontrollable oxidation-reduction reactions, and that reduction to Pd from PdO is minimised at temperatures between 600°C and 900°C by increased glass concentration. This is attributed to the decomposition-retarding influence of the molten glass on PdO.