Process additives to reduce etch resist undercutting in the manufacture of anode foils

Patent metadata

Field	Value
Publication number	US-10309033-B2
Application number	US-201715459808-A
Country	US
Kind code	B2
Filing date	Mar 15, 2017
Priority date	Dec 2, 2016
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

Anode foil, preferably aluminum anode foil, is etched using a process of adding an etch resist to the anode foil and treating the foil in an electrolyte bath composition comprising a sulfate, a halide, an oxidizing agent, a surface active agent, and a non-ionic surfactant. The anode foil is etched in the electrolyte bath composition by passing a 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;
a surface active agent selected from the group consisting of a bis(perfluoroalkylsulfonyl)imide, a perfluoroalkylsulfonate, and a mixture thereof; and
a non-ionic surfactant, wherein the non-ionic surfactant is:
present in an amount ranging from about 0.01 parts per million (ppm) to about 4 ppm,
surface active at a pH level from about 1 to about 7,
surface active at temperatures from about 0° C. to about 100° C., and
water-soluble.

2. The composition of claim 1 , wherein the surface active agent is a bis(perfluoroalkylsulfonyl)imide.

3. The composition of claim 2 , wherein the bis(perfluoroalkylsulfonyl)imide is provided as an alkali metal salt or an ammonium salt.

4. The composition of claim 2 , wherein the alkyl group of the bis(perfluoroalkylsulfonyl)imide is a C 1 -C 4 alkyl group.

5. The composition of claim 2 , wherein the bis(perfluoroalkylsulfonyl)imide is a bis(perfluoroethylsulfonyl)imide.

6. The composition of claim 2 , wherein the bis(perfluoroalkylsulfonyl)imide is present in an amount ranging from about 10 to about 150 ppm.

7. The composition of claim 1 , wherein the surface active agent is a perfluoroalkylsulfonate.

8. The composition of claim 7 , wherein the perfluoroalkylsulfonate is provided as a perfluoroalkylsulfonic acid, or a salt thereof.

9. The composition of claim 7 , wherein the perfluoroalkylsulfonate is nonafluorobutanesulfonate.

10. The composition of claim 1 , wherein the non-ionic surfactant is surface active at a pH level from about 1 to about 4 and at temperatures from about 70° C. to about 90° C.

11. The composition of claim 1 , wherein the non-ionic surfactant has the Formula I:
R 1 -Cy-(EO) x —OR 2   (Formula I),

wherein EO is a -OCH 2 CH 2 — group;
x is 1 to 20;
R 1 is H or a C 1 -C 20 alkyl group;
R 2 is H or an alkyl group; and
Cy is saturated, partially saturated, unsaturated, or aromatic carbocyclic group comprising 3 to 10 carbon atoms, or Cy is a saturated, partially saturated, unsaturated, or aromatic heterocyclic group comprising 1 to 3 heteroatoms.

12. The composition of claim 1 , wherein the non-ionic surfactant has the Formula II:

wherein x is 1 to 20.

13. The composition of claim 12 , wherein x is 9 to 10.

14. The composition of claim 1 , wherein the non-ionic surfactant is present in an amount ranging from about 0.1 ppm to about 2 ppm.

15. The composition of claim 1 , wherein the sulfate is sulfuric acid, and wherein said electrolyte bath composition comprises about 0.6% by weight to about 1.0% by weight sulfuric acid.

16. The composition of claim 1 , wherein the halide is hydrochloric acid, and wherein said electrolyte bath composition comprises about 0.5% by weight to about 3.0% by weight hydrochloric acid.

17. The composition of claim 1 , wherein the oxidizing agent is sodium perchlorate, and wherein said electrolyte bath composition comprises about 2.0% by weight to about 6.0% by weight sodium perchlorate.

18. A method of etching an anode foil, comprising:
adding an etch resist onto an anode foil;
passing a direct current (DC) charge through the anode foil while the foil is immersed in an aqueous electrolyte bath, wherein said aqueous electrolyte bath composition comprises:
a sulfate;
a halide;
an oxidizing agent;
a surface active agent selected from the group consisting of a bis(perfluoroalkylsulfonyl)imide, a perfluoroalkylsulfonate, and a mixture thereof; and
a non-ionic surfactant, wherein the non-ionic surfactant is:
present in an amount ranging from about 0.01 parts per million (ppm) to about 4 ppm,
surface active at a pH level from about 1 to about 7,
surface active at temperatures from about 0° C. to about 100° C., and
water-soluble.

19. The method of claim 18 , wherein the non-ionic surfactant has the Formula II:

wherein x is 1 to 20.

20. The method of claim 19 , wherein foam does not form in the electrolyte bath.

Assignees

• Pacesetter Inc

Inventors

• Hemphill Ralph Jason
• Marshall Timothy R
• Strange Thomas F

Classifications

• C25F3/04 Primary

  of light metals · CPC title

• C25F3/14

  locally · CPC title