The influence of electrowetting and surfactants on MnO2 coverage and in electrical properties of Ta capacitors with high CV powders

The current 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 liquid/surface tension. On the other hand, electrowetting is a useful technique, which allows a decrease on the contact angle between a conductive droplet and a substrate when an electric field is applied. With this work we will present results that show that the use of surfactants and its combination with electrowetting can improve the coverage on high CV powders used in Ta capacitors. Intermediate measurements allow a sequence control during impregnation development being used in our assessments. Traditional coverage measurements and high resolution Scanning Electron Microscope (HR-SEM) analysis are used to quantify the converted MnO2. 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.