Two step electrochemical etch process for high volt aluminum anode foil
AssigneeNorth American Philips Corporation
InventorMulk R. Arora
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Abstract
Aluminum electrolytic capacitor anode foil of a high cubic texture is etched using a two step process by treating the foil in an electrolyte bath containing 3% hydrochloric acid and 1% aluminum as aluminum chloride under the influence of a direct current of high current density and at a temperature of 75.degree. C., and in a second step treating said etched foil in a similar bath with a much lower current density and at a temperature of 80.degree. to 82.5.degree. C. The foil thus etched has a significantly higher capacitance resulting from a greater density of tunnels, and a fairly linear tunnel structure.
Claims12
A two step process for etching aluminum electrolytic capacitor anode foil wherein such foil has a high cubic texture, greater than 70% cubicity, comprising a first step of:
- treating said foil in an electrolyte bath containing between 1.5% and 7% hydrochloric acid and 0% to 2% aluminum as a chloride under the influence of direct current at a temperature between 70.degree. C. and 85.degree. C.;
- and
- passing a charge of 6 to 25 coulombs through said foil while said foil is immersed in said hydrochloric acid bath and having a current density between 0.25 and 0.60 amps/cm.sup.2 ;
- and
- in a second step, treating said foil emerging from said first bath in an electrolyte bath consisting of from 1.5 to 7% hydrochloric acid and between 0% to 2% aluminum as aluminum chloride, under the influence of direct current having a current density of 0.10 to 0.15 amps/cm.sup.2, with 40 to 50 etch coulombs at a temperature of 75.degree. to 90.degree. C.
Dependencies are inferred from the claim text.