A model for sheet resistivity of RuO2 thick film resistors

Considerations of microstructure composition relationships led to the conclusion that RuO₂-based thick-film resistors can have five different types of microstructure for different ranges of the volume fraction of RuO₂(V_c). A theoretical value consistent with the microstructure was developed to predict the sheet resistivity as a function of V_c and particle sizes of RuO₂ and glass for the range 0.032< V_c<0.24. Experimental data are presented for two resistor systems containing the same RuO₂ but different glass compositions. The sheet resistivities for the two resistor systems were similar at high values of V_c but differed by three orders of magnitude at low values of V_c. The two glasses had the same viscosity at the firing temperature, but the solubility of RuO₂ was significantly different in the two glasses. The theoretical loading curve model was in excellent agreement with experimental results from the system using the glass with high RuO ₂ solubility, but has not as yet been extended to the other system