Process for using persulfate in a low pH etch solution to increase aluminum foil capacitance
AssigneePacesetter, Inc.
InventorsRalph Jason Hemphill, David R. Bowen, James Brian Smith, Timothy R. Marshall
Life of this patent
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Abstract
Anode foil, preferably aluminum anode foil, is etched using a process of treating the foil in an electrolyte bath composition comprising a persulfate, a halide, an oxidizing agent, and a sulfate. An etch resist can be added to the anode foil prior to etching. The anode foil and the attached etch resist can be heated prior to immersing both in an electrolyte bath composition. The anode foil is etched in the electrolyte bath composition by passing a charge through the bath, while maintaining a constant level of persulfate. The etched anode foil is suitable for use in an electrolytic capacitor.
Claims16
A method comprising:
- etching an anode foil by passing a direct charge (DC) current through the anode foil while the foil is immersed in an aqueous electrolyte bath, wherein said aqueous electrolyte bath composition comprises:
- a persulfate,
- a halide,
- an oxidizing agent, and
- a sulfate;
- and
- maintaining the persulfate concentration at a level from at least about 100 ppm to about 10,000 ppm during the course of etching the anode foil, wherein:
- the sulfate is sulfuric acid, wherein said electrolyte bath composition comprises about 0.8% by weight to about 1.0% by weight sulfuric acid,
- the halide is hydrochloric acid added, wherein said electrolyte bath composition comprises about 0.5% by weight to about 3% by weight hydrochloric acid, and
- the oxidizing agent is sodium perchlorate, wherein said electrolyte bath composition comprises about 2% by weight to about 6% by weight sodium perchlorate, and
- said aqueous electrolyte bath composition further comprises a surface active agent selected from the group consisting of a bis(perfluoroalkylsulfonyl)imide, a perfluoroalkylsulfonate, and a mixture thereof, present in an amount ranging from about 10 ppm to about 150 ppm.
A method comprising:
- etching an anode foil by passing a direct charge (DC) current through the anode foil while the foil is immersed in an aqueous electrolyte bath, wherein said aqueous electrolyte bath composition comprises:
- a persulfate,
- a halide,
- an oxidizing agent, and
- a sulfate;
- maintaining the persulfate concentration at a level from at least about 100 ppm to about 10,000 ppm during the course of etching the anode foil;
- adding an etch resist onto an anode foil;
- and
- heating the anode foil with the etch resist at a temperature from about 40° C. to about 400° C. for about 0.1 minutes to about 40 hours.
Dependencies are inferred from the claim text.