Manganese nitrate impregnation cycles optimization by addition of surfactants on Ta capacitors with high charge powders (>80000μC/G) manufacturing

The request for systems miniaturization increases the demands on using high CV tantalum powders in solid tantalum capacitors (STCs), in order to increase the volumetric efficiency together with the expected capacitance stability. To achieve this purpose, the Mn(NO₃)₂ impregnation process and the use of new materials has been researched. Surfactants are widely used in different applications because of their remarkable ability to influence the properties of surface and interfaces. It reduces the surface tension between a liquid and a surface which allow improving the coverage of capacitor.With these work we will present new results in how is possible to increase the impregnation efficiency on high CV tantalum capacitors. By addition of a surfactant to manganese nitrate,we were able to reduce the number of manganese nitrate dips necessary to obtain a acceptable coverage in capacitors manufactured with medium and high CV powders, achieving a good operational performance and long term life tests stability. Intermediate measurements allow a sequence control during impregnation development being used in our assessments. Traditional coverage measurements, contact angle measurements and Thermal Gravimetric Analysis (TGA) are used to quantify the influence of this technique in the converted manganese dioxide semiconductor. Additionally, physical features of the MnO2 inner coat are compared. The electrical parameters as DF, LC and ESR (Dissipation Factor, Leakage current and Equivalent Series Resistance) are measured to verify the experimental samples reliability.