Patent ID: 7605048

Claim:
A method of forming a capacitor having a bimetal copper and aluminum structure, comprising: providing first and second bimetal foils, each comprising an aluminum layer attached to a copper layer; temporarily attaching the first bimetal foil copper layer to the second bimetal foil copper layer to form a sandwich, such that the aluminum layers of the sandwich are exposed, sufficient to protect the copper layers from attack in a subsequent treatment; treating the exposed aluminum layers of the sandwich in a manner sufficient to increase the surface area of each of the aluminum layers by at least one order of magnitude, and not reveal any of the underlying copper layers; separating, after treating, the first bimetal foil from the second bimetal foil; and forming the capacitor from one of the separated bimetal foils, wherein the copper layer is one electrode of the capacitor and the treated aluminum layer is in intimate contact with a dielectric layer of the capacitor.