For High Voltage Electrolytic Capacitor Tantalum Powder Preparation

Tantalum capacitors have the characteristics of small size, high capacity, low leakage current, instable properties and high reliability, so they can be usd extensively for military, aerospace and electrics. The current method of producing high-voltage tantalum powders existing some disadvantages, such as a complex process and many harmful effects, caused the electrical properties of tantalum capacitors instability. In this dissertation, the effects of producing and post-processing conditions of tantalum powders on the electrical properties of tantalum capacitors were investigated. On the basis of the optimal post-processing conditions, multiple regression equations for relationship of the post-processing conditions and the electrical properties were established. The equations were proved by the commercial production.Tantalum powders were produced by vaccum carbon reduction method using tantalum oxide as crude material and carbon powders as reducer. The high-purity tantalum ingot was made from tantalum powders through vaccum sinter and electron bombardment. After hydrogenating, crashing, washing, heat treatment and magnesium treatment, the tantalum ingot was changed into high-voltage tantalum powders. A Li6(five factors in four levels) standard orthogonal array was employed to evaluate the effects of amount of absorbed hydrogen, crashing time, heat-treatment temperature and amount of magnesium on the CV and breakdown voltage of tantalum powders. The optimal conditions were chose as:amount of absorbed hydrogen0.30%, crashing time5h, heat-treatment temperature1450℃and amount of magnesium0.8%. The tantalum powers were produced under the optimal conditions, their purity and electrical properties obtained the foreign quality standard.The effects of initial particle size, first heat treatment temperature and second heat treatment temperature on the CV and breakout voltage of tantalum powders were investigated. The multiple regression equations demonstrated that the increasing of initial particle size, first heat treatment temperature and second heat treatment temperature caused the electric capacity decreased. The leakage current decrased with the increasing of initial particle size and second heat treatment temperature, and increased with the increasing of first heat treatment temperature. The equations can be used to control production quality and improve production stability.