Use of nonafluorobutanesulfonic acid in a low PH etch solution to increase aluminum foil capacitance

Patent metadata

Field	Value
Publication number	US-11230794-B2
Application number	US-201916276319-A
Country	US
Kind code	B2
Filing date	Feb 14, 2019
Priority date	Dec 2, 2016
Publication date	Jan 25, 2022
Grant date	Jan 25, 2022

Abstract

Anode foil, preferably aluminum anode foil, is etched using a process of treating the foil in an electrolyte bath composition comprising a perfluoroalkylsulfonate, a sulfate, a halide, and an oxidizing agent. The anode foil is etched in the electrolyte bath composition by passing a direct current charge through the bath. The etched anode foil is suitable for use in an electrolytic capacitor.

First claim

What is claimed is:

1. An aqueous electrolyte bath composition for etching anode foil, comprising:
a sulfate;
a halide;
an oxidizing agent; and
a C 1 -C 8 perfluoroalkylsulfonate in an amount ranging from about 10 to 90 parts per million (ppm).

2. The composition of claim 1 , wherein said C 1 -C 8 perfluoroalkylsulfonate is present in the electrolyte bath composition in an amount ranging from about 20 to about 70 ppm.

3. The composition of claim 1 , wherein the C 1 -C 8 perfluoroalkylsulfonate comprises nonafluorobutanesulfonic acid (FBSA) and/or a salt thereof.

4. The composition of claim 1 , wherein the C 1 -C 8 perfluoroalkylsulfonate is an alkali metal nonafluorobutanesulfonate.

5. The composition of claim 4 , wherein the alkali metal is potassium.

6. The composition of claim 1 wherein:
the C 1 -C 8 perfluoroalkylsulfonate is selected from the group consisting of nonafluorobutanesulfonic acid (FBSA), potassium perfluoroalkylsulfonate (KFBS), and mixtures thereof,
the sulfate is sulfuric acid and said electrolyte bath composition comprises about 0.8% by weight to about 1.0% by weight sulfuric acid,
the halide is hydrochloric acid and said electrolyte bath composition comprises about 0.5% by weight to about 3% by weight hydrochloric acid, and
the oxidizing agent is sodium perchlorate and said electrolyte bath composition comprises about 2% by weight to about 6% by weight sodium perchlorate.

7. The composition of claim 6 , wherein said electrolyte bath composition comprises:
about 0.92% by weight sulfuric acid;
about 0.62% by weight hydrochloric acid; and
about 3.5% by weight sodium perchlorate.

8. The composition of claim 7 , wherein the C 1 -C 8 perfluoroalkylsulfonate is FBSA and/or KFBS.

9. The composition of claim 8 , further comprising diethanolamine (DEA).

10. A method of etching an anode foil, comprising:
passing a direct current (DC) charge through an anode foil while the anode foil is immersed in an aqueous electrolyte bath, wherein said aqueous electrolyte bath comprises:
a sulfate;
a halide;
an oxidizing agent; and
a C 1 -C 8 perfluoroalkylsulfonate in an amount ranging from about 10 to 90 parts per million (ppm); such that the anode foil is etched.

11. The method of claim 10 , wherein the C 1 -C 8 perfluoroalkylsulfonate is provided as an aqueous solution of C 1 -C 8 perfluoroalkylsulfonic acid and/or a salt thereof.

12. The method of claim 11 , wherein the C 1 -C 8 perfluoroalkylsulfonic acid or salt thereof is nonafluorobutanesulfonic acid (FBSA) and/or potassium nonafluorobutanesulfonate (KFBS).

13. The method of claim 10 , wherein the anode foil is etched so as to form branched tunnels in the anode foil.

14. The method of claim 10 , wherein the anode foil is etched so as to form tunnels in the anode foil, and further comprising:
widening the tunnels after etching the anode foil.

15. The method of claim 10 , further comprising:
making a capacitor that includes the etched anode foil as an anode.

16. The composition of claim 1 , wherein the foil is immersed in the bath.

17. The composition of claim 16 , wherein the bath etches tunnels in the foil.

18. The composition of claim 1 , wherein the bath further comprises: an amine base.

19. The composition of claim 18 , wherein the amine base is selected from a group consisting of: ethanolamine, diethanolamine, triethanolamine, ethylamine, diethylamine, triethyamine, methylamine, dimethylamine, trimethylamine, and ammonia.

20. The composition of claim 1 , wherein the bath has a composition of 4 to 9.

Assignees

• Pacesetter Inc

Inventors

• Hemphill Ralph Jason
• Marshall Timothy R

Classifications

• H01G9/055

  Etched foil electrodes · CPC title

• C25F3/20

  of aluminium · CPC title

• C25F3/02

  Etching · CPC title

• C25F3/04 Primary

  of light metals · CPC title

• H01G9/0032

  formation of the dielectric layer · CPC title