Abstract: A method of producing electrodes for electrolytic capacitors by etching metal foil in a low pH etching electrolyte is disclosed. The low pH electrolyte is an aqueous solution, which comprises hydrochloric acid, glycerol, sodium perchlorate or perchloric acid, sodium persulfate and titanium (111) chloride. Anode foils etched according to the method of the invention maintain high capacitance gains, electrical porosity and strength. The electrical porosity of the etched foils is sufficiently high such that the overall Equivalent Series Resistance (ESR) is not increased in multilayer anodes configurations. Also described is a low pH electrolyte bath composition. Anode foils etched according to the present invention and electrolytic capacitors incorporating the etched anode foils are also disclosed.

Abstract: The present invention is directed to a method of etching anode foil in a non-uniform manner which increases the overall capacitance gain of the foil while retaining foil strength. In particular, by using a mask to protect a mesh grid of the foil from further etching, a previously etched foil can be further etched, prior to the widening step. Alternatively, the mask may be used in the initial etch, eliminating the need for the second process. In effect the foil may be etched to a higher degree in select regions, leaving a web of more lightly etched foil defined by the mask to retain strength. According to the present invention, the foil is placed between two masks with a grid of openings which expose the foil in these areas to the etching solution. The exposed area can be as little as 10% of the total foil to as much as 95% of the total foil, preferably 30% to 70% of the total foil area.

Abstract: The present invention is directed to a method of encasing electrolytic capacitor stacks or wound rolls to form an external package. First, a plastic sheet is heated to its soft transition temperature. Next, the plastic sheet is draped over a preassembled capacitor stack or wound roll. Then, a vacuum is applied to the capacitor stack or wound roll, such that the sheet is formed around the stack or wound roll. Finally, the plastic sheet is allowed to cool. This process results in a vacuum formed plastic capacitor case assembly which minimizes wasted volume in the capacitor package and minimizes capacitor assembly time.

Abstract: A surface active, viscosity modifying agent is used to promote additional tunnel initiation during the etching of high purity cubicity anode foil, preferably aluminum anode foil, to render it suitable for use in electrolytic capacitors. The anode foil is etched in the electrolyte bath composition by passing a charge rough the bath, resulting in an anode foil having a higher capacitance than foils etched using known methods or etching compositions. The etched anode foil is suitable for use in an electrolytic capacitor.

Abstract: This present invention is directed to a method of etching anodic foil for electrolytic capacitors and provides a method of electrolytically growing a porous oxide mask on a surface of a high purity etchable strip of anodic foil for forming etch tunnels at strategic locations on the foil. Unetched high purity aluminum foil is placed in a prepared electrolyte doped with chloride. By passing current through the foil, a porous oxide mask is formed on the surface of the anode foil, with an optimized pore spacing. This oxide mask is then partially removed with a stripping agent in order to expose the underlying anode foil at the bottom of the mask pores to the etch solution. The mask is not removed completely, and the anode foil is exposed only at the pore sites. The foil can then be etched using a conventional etch solution. Etch pits and tunnels form only at the pore sites.

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.

Abstract: An electrochemical cell for etching a metal workpiece such as an aluminum foil, a method for etching the foil using the electrochemical cell, and foil thus produced is provided. The cell includes an etch tank having an etch electrolyte disposed therein and containing at least a first and a second compartment each containing (i)an etch electrolyte, (ii) a cathode plate, and (iii) an ion exchange membrane separator portion having an ion exchange polymeric material effective to substantially retard or prevent reduction of the oxidizing agent or agents present in the etch electrolyte, the first and second compartments being arranged in the etch tank with the ion exchange membrane separator portions in facing relationship one to the other; and a metal workpiece such as an aluminum foil anode present in the etch tank and disposed between each said first and second compartments.

Abstract: An electrochemical cell for etching a metal workpiece such as an aluminum foil, a method for etching the foil using the electrochemical cell, and foil thus produced is provided. The cell includes an etch tank having an etch electrolyte disposed therein and containing at least a first and a second compartment each containing (i)an etch electrolyte, (ii) a cathode plate, and (iii) an ion exchange membrane separator portion comprising an ion exchange polymeric material effective to substantially retard or prevent reduction of the oxidizing agent or agents present in the etch electrolyte, the first and second compartments being arranged in the etch tank with the ion exchange membrane separator portions in facing relationship one to the other; and a metal workpiece such asan aluminum foil anode present in the etch tank and disposed between each said first and second compartments.