Microstructural, XRD and electrical characterization of some thick film resistors

The microstructural and electrical characteristics (sheet resistivities, TCRs, and noise indices) of some 1 k Ohm/sq. and 10 k Ohm/sq. thick films were evaluated. The conductive phase was determined by X-ray diffraction (XRD) analysis. The microstructures of fired resistors were investigated by scanning electron microscopy (SEM) and analyzed by energy dispersive spectrometry (EDS). Some resistors were fired for a relatively long time at the highest temperature, i.e., 6 h at 850 degrees C, to allow the reactions in the material to reach equilibria. Sheet resistivities, temperature coefficients of resistivity, and noise indices of these resistors were compared with "normally" (10 min at 850 degrees C) fired resistors. After 6 h firing absolute temperature coefficient of resistivity (TCR) values of most resistors increased significantly, while sheet resistivities decreased. Complex impedance analysis showed that in most cases resistors with low noise indices showed nearly ideal resistor response while those with higher noise had a larger imaginary part.