Abstract: An oxide dissolving acid dip is integrated into an anodic foil formation process. After a foil, either etched or un-etched, is hydrated in a bath of deionized water at an elevated temperature, the foil is then dipped in an organic acid mixture. Next, an oxide layer formation step is utilized to form a barrier oxide layer on a surface of the foil. Next, an oxide dissolving acid dip is utilized to selectively remove a diffuse hydrate layer formed in the formation process. The diffuse hydrate layer is responsible for the reduction of capacitance of the anodic foil. By the use of this oxide dissolving acid dip in conjunction with an organic acid dip, the foil exhibits reduced leakage current properties, while maintaining its capacitance. The treated foil can then be incorporated into a high voltage electrolytic capacitor suitable for use in an implantable cardioverter defibrillator.

Abstract: Aluminum anode foil is etched using a process of treating the foil in an electrolyte bath composition comprising aluminum chloride hexahydrate, hydrochloric acid, sulfuric acid and perchloric acid or perchlorate. The anode foil is etched in the electrolyte bath composition by passing a direct current (DC) through the bath, resulting in an aluminum anode foil having a higher capacitance and/or metal strength than using known methods or etching compositions. The etched anode foil is suitable for use in an electrolytic capacitor.