Tantalum electrolytic capacitor employing polypyrrole as solid electrolyte

Abstract

AbstractThe conventional tantalum electrolytic capacitor is made by anodically oxidizing sintered porous tantalum metal powder to form tantalum oxide film, followed by precipitating manganese dioxide by thermal decomposition of the tantalum oxide film soaked in manganese nitrate solution. The electrical conductivity of manganese dioxide is as low as 10−2 to 10−1 S/cm, and manganese dioxide is poor in its electrical property, in particular, the high‐frequency characteristic.In this paper, a precoating layer with a slightly higher resistance is used. The polypyrrole film is deposited by electrolytic polymerization using the precoating layer as the anode. It is found that the capacitor with polypyrrole formed by chemical oxidative polymerization has superior electrical properties compared to the capacitor formed by using manganese dioxide instead of a precoated layer. Using hydrogen peroxide as the oxidizer for chemical oxidative polymerization, polymerization of pyrrole can be achieved even inside the sintered body and the electrical conductivity and thermal stability of the polymer were excellent. The resultant capacitor has excellent electrical and temperature characteristics, its lifetime is long, and it can be surface‐mounted.