Particle size effects on electrical properties of thick film resistors

Resistors were made with varying combinations of glass and RuO2 particle sizes at varying weight percents of RuO2. Spherical glass particles were used in order to eliminate any possible particle shape defect. The sizes of glass and RuO2 powders were determined with the scanning electron microscope and nitrogen adsorption surface area measurement. In making resistors, special care was taken to throughly blend the resistor pastes so that the blending factor was removed or reduced to a minimum. Different firing temperatures and times were used to fire resistors in an attempt to find a single firing condition that would make all resistors in their optimum sintered regions where optimum conducting chains were formed. The optimum single firing condition could not be found, and compromise conditions were chosen. Resistivities and temperature coefficients of resistance were measured, blending curves were plotted, and the critical conductive volume percents V sub mc's were obtained for plots of log G vs. log (V sub m-V sub mc)(G and V sub m being the conductivity and conductive volume percent respectively).