Research On High And Low Temperature Performance Stabilityof Large-capacitance Tantalum Chip Capacitor

with technology progressareas such asweaponry, aviation and space flight, electronic communication, thesequential requirementsto chip tantalum capacitor become severer,large-capacitance, high-voltage is the future of chip tantalum capacitor. In order to meet the different application environments and conditions, capacitor's electrical parameters should be stable and reliableat different temperatures. Main electrical parameters of chip tantalum capacitor are as follow: capacitance(C), leakage current(I), dissipation factor(tg?) and equivalent series resistance(ESR). For large-capacitance tantalum chip capacitor, because of the CV product requirements, tantalum powderwith high specific CV, big tantalum core size are needed. To ensure the stability of electrical parameters at different temperatures, higher requirements are proposed onto processes such as mixing, molding, sintering, formingand coating.This paper seek methods to improvehigh and low temperatureperformance stabilityof large-capacitance tantalum chip capacitor,through system researchof high and low temperature performanceof large-capacitance tantalum chip. The main research results are as follow:1.Variation of electrical parameters of large-capacitance chip tantalum capacitor at different temperatures is studied. Within-55?~125?working range, tantalum capacitor capacitance and leakage current value increase as the temperature rises, at a certain point, dissipation factor increases no matter temperature increases or decreases, the equivalent series resistance decreases with increasing temperature.2.A research of methods to reducing the rate of change in capacitance is conducted:The main method of reducing capacitance change rate is to increase cathode manganese dioxide layer's covering rate, the key lies in coating process, selecting the appropriate decomposition conditions(temperature, steam content), adjusting the gradient and dipping times of manganese nitrate impregnating solution, addition of surfactants to improve the surface activity of the impregnation solution, thereby increasing the coating rate of manganese dioxide coating layer.3.A research of methods to reducing the change of leakage current is conducted: Reduce the number of defects, improve the conditions of mixing powder, improve the tantalum powder flow ability, increase mold press density to get more complete tantalum molded blocks and reduce machining defects; increase the sintering temperature to remove tantalum powder impurities more thoroughly; improve forming liquid formulations of forming process, reduce formation current density to prevent heat-induced crystallization to reduce the generation of defects.4.The methods to reducing changes in dissipation factor and equivalent series resistance are studied: To reduce the ESR and dissipation factor value, require a uniform and dense manganese dioxide layer, and a cathode layer of ? type manganese dioxide, which have good conductivity. And need select appropriate decomposition conditions, add the corresponding decomposition catalyst in manganese nitrate impregnating solution in coating process, to get uniform and compact ?-type manganese dioxide layer which comes from decomposition.