CAPACITOR FOIL WITH ENHANCED SURFACE AREA

摘要

An improved electrolytic capacitor is provided by producing an anode foil which has areas which are not subject to stress during manufacturing being highly etched and those areas which are subject to stress during manufacturing being lightly etched or not etched at all. The process of the invention provides an etch mask to cover during the etch process those portions of the anode foil which will be subjected to stress during construction of the capacitor. The highly etched areas, which are very brittle, provide increased capacitance and thus improved energy density. For layered or stacked capacitors, a weld tab is covered with the etch mask to allow connection of the anode layers. Additionally, strong edges may be maintained thereby reducing the possibility of cracking that would normally occur during the stamping and assembly operations. For flat or oval capacitors made by rolling or winding the capacitor element on a large arbor, and then flattening the element by compressing it in a press, high stress occurs at the sharp bends resulting in cracking or breaking if the foil is not flexible. The method of the invention allows high gain foil to be used in the flat areas, while masking strengthens the locations where the sharp bends occur, thereby improving the capacitance.