Thick-film Temperature Sensors and LTCC Substrates - Evaluation and Characterization

The electrical and microstructural characteristics of 1 kohm/sq. thick-film thermistors with high positive (PTC) and negative (NTC) temperature coefficients of resistivity (TCR) fired on "green" LTCC (Low-Temperature Cofired Ceramics) substrates were evaluated. Electrical characteristics, i.e., sheet resistivities, TCRs and noise indices were measured. Microstructures of thick films were investigated by scanning electron microscopy (SEM) and analysed by energy dispersive X-ray analysis (EDS). Functional phases in thermistors were determined by X-ray powder diffraction analysis. Obtained results were compared with characteristics of thick film thermistors fired on relatively inert alumina substrates which were used as a reference.