Two step electro chemical and chemical 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 etched in 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 and at a temperature of 75.degree. C., and in a second step treating said etched foil in an aqueous bath of 8% nitric acid and 2.6% aluminum as a nitrate at a temperature of 85.degree. C. for 5 to 7 minutes. The foil thus etched has a significantly higher capacitance resulting from a greater density of tunnels, an elongation of the tunnels, and a fairly linear tunnel structure.
Claims11
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 0.6 amperes/cm.sup.2 ;
- and
- in a second step, treating said foil emerging from said first bath in an aqueous bath consisting of from 2 to 11% nitric acid and between 0% to 3.5% aluminum as aluminum nitrate for a period of 3 to 12 minutes at a bath temperature of 80.degree. to 95.degree. C.
Dependencies are inferred from the claim text.