Process of preparing a solid electrolytic capacitor containing a conductive polymer counter electrode

The present invention relates to a method for making a solid electrolytic capacitor having a low equivalent series resistance by impregnating a porous capacitor pellet with conductive polymer. An oxidized pellet is dipped in a high concentration conductive polymer solution to deposit the polymer in doped (conductive) form. The solution also contains a crosslinking agent to prevent redissolution of the polymer when the pellet is re-dipped. After dipping, the solvent in the polymer solution is evaporated and a conductive film formed. In order to evaporate the solvent quickly, the solvent should have a boiling point of 80-220° C. and preferably a boiling point of 100-150° C. The conductive polymer film has a low resistivity (less than 1 ohm-cm, preferably less than 0.2 ohm-cm).