Study Of Working Electrolyte Of High Voltage Large Capacitance Low ESR Wet Tantalum Capacitors

The main content of this project is to prepare working electrolyte for highvoltage, large capacitance, low ESR wet tantalum capacitors.We analyzed the ion distribution at the surface that the electrolyte contact withthe anode dielectric oxide film and at the surface that the electrolyte contact with thecathode metal, and studied the factors that affect the broken voltage of electrolyte.Cathode capacitance theory, depolarizing theory, and conductance theory of theelectrolyte were used during the study.Broken voltage of working electrolyte is a very important factor that affects theperformance of capacitor. It should be higher than 1.2 times of the rating voltage ofcapacitor. On this premise, efforts were made to increase its specific conductance,improve its mending ability for the dielectric film, and increase its boiling point,decrease its saturation steam pressure, in order to improve the electrical performanceof the electrolyte solution and that of the capacitor roundly.Adding big molecule organic substance into electrolyte will prevent the invasionof baneful substances into the dielectric film and restrain the discharge of oxygen ionsby decreasing the anion consistence at the cathode surface, and accordingly increasethe broken voltage of the electrolyte. Increasing the specific conductance of theelectrolyte can help to decrease ESR and tgδ of capacitor. Reducing the organiccontent in the gel electrolyte will decrease the ESR and tgδ. Selecting electrolyte withlower saturation steam pressure may make the capacitor have higher reliability andlonger life.Depending on above theory, experiments were performed to select elementaryformula, than 160V/47μF tantalum capacitors were assembled with it. Theirperformances were measured at room temperature, high and low temperature and highfrequency after aging, and than 2000h high temperature burden examination and otherentirely duty exams were carried out. The performances turned out to be very good,and satisfied the requirement of the project.