Study Of Complex Working Electoryte Of Low Voltage Large Capacitance Wet Tantalum Capacitors

Working electrolyte of the large capacitance, low voltage (40V/350μF) wet tantalum electrolytic capacitor is studied in the paper.The ion distribution at the surface that the working electrolyte contacts with the cathode metal and the factors that affect the conductivity of the working electrolyte were studied.The conductivity of the working electrolyte is a very important factor that affects the performance of tantalum capacitor. According to the conductance theory, complex acid system of sulfuric acid and X-acid, which can complement each other, is used to reduce the viscosity of the working electrolyte and increase the mobility of the ion conductivity. It also can improve the conductivity of the working electrolyte and the ESR of the tantalum capacitor.According to the cathode capacitance theory and depolarizing theory, adding some depolarizer that is optimized for the type and the best content, can decrease the distance of the double electronic layer and enhance cathode capacity of the capacitor. Meanwhile, it can reduce the loss of capacitance in the high frequency circuit.Depending on the conductance theory, the cathode capacitance theory and depolarizing theory, orthogonal tests were performed to determine the formula of electrolyte. Then, 40V/350μF tantalum capacitors were assembled with it. Their performance was measured at room, high and low temperature. 1000h high temperature burden test was carried out. The performance turned out to be very good, and satisfied the requirement of the project.