Study On Series Of The Thick-Film PTC Thermal Paste

With the spreading of thermistor's application, the accurate measure, transmission and control of temperature is on demand. On the base of the development of domestic and foreign thermistor material, the study on series of the thick film PTC thermistor, was selected as aim as to improve TCR.By contrast with performance of the thick film PTC thermistor, RuO2-CuO, as the conducting phase of thick film resistors, was made by new and old technics. The new technics, ruthenate and copper hydrate taken as material, had a better ratio of performance and price. Furthermore, thermal sensitive performance of the conducting phase was analyzed by the semiconductor doped theory.The technics of the conducting phase was optimized, the equation of reaction kinetics was made, and that reaction mechanism and effect factor were analyzed. It is showed that the conducting phase made at 1100℃for 6h has the best thermal sensitive performace because of the creating of minim Cu2O. In order to study further as contrasted, Nb2O5, Cu2O and Bi2O3 were filtered as additives and their effect to performance of the thick film PTC thermistor was studied. It is showed that Nb2O5 can improve sheet resistivity of the thick film resistor and reduce TCR. Cu2O can improve sheet resistivity and little Cu2O can improve TCR. Cu2O improves sheet resistivity but can't adjust TCR for the range of the quality fraction of Cu2O is more than 8. Bi2O3 not only reduces the sheet resistivity and improves TCR.How the sintering technics affected performance of the thick film PTC thermistor was studied. It is found that sheet resistance descends and TCR increases with the increasing of sintering peak temperature. Performance of the first refiring is less than 10% for the range of 850℃to 865℃, and the structure of film is compact, when the thickness of sintering thick film is 18μm.It is found that the glass content is the furthest factor of which affects performance of the thick film PTC thermistor. Sheet resistivity increases and TCR reduces with the increasing of the glass content. Granularity of the conducting phase further affects sheet resistivity, sheet resistivity reduces and TCR improves with decrease of granularity of the conducting phase. Low sheet resistivity (sheet resistivity is less than 10?·sq.-1) of the thick film PTC thermistor is made, granularity of the conducting phase should be less than 1μm. The effect of granularity of the glass is slim to sheet resistivity and TCR of the thick film resistor.Series of the thick film PTC thermistor is made by selecting reasonable prescription and technical parameters based on studing the factors of its performance.Conductive mechanism of the thick film PTC thermistor is explained by charge mechanism and metal contact mechanism respectively.