Impact of Ruthenium Diffusion on the Electrical Properties of Thick Film Resistors

The diffusion profile of the RuO2 into silicate glass and the electrical resistance distribution across diffusion layer have been studied by beveled sample method and energy dispersion spectroscopy. The distribution of content of Ru atoms in the diffusion layer is described by the erfc(x) what means that the diffusion coefficient is independent of the content of Ru atoms. The correlation of the distribution of Ru atom content and the resistance distribution in the diffusion layer showed that it is the diffusion doping of glass that is responsible for the conductivity of thick-film resistors. Thickness of the diffusion layer is more than 100 μm while average distance between RuO2 particles is about 0.5-2 μm. It means that all volume of the thick-film resistor comes conductive in firing process at 850°C in 10 minutes.