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

Patent metadata

Field	Value
Publication number	US-2018155849-A1
Application number	US-201715459808-A
Country	US
Kind code	A1
Filing date	Mar 15, 2017
Priority date	Dec 2, 2016
Publication date	Jun 7, 2018
Grant date	—

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.

21 . An etched anode foil, provided by a method comprising:
adding an etch resist onto the anode foil; passing a direct current (DC) charge through the anode foil while the foil is immersed in an aqueous electrolyte bath, such that the anode foil is etched; wherein the electrolyte aqueous bath composition comprises:
sulfuric acid at a level of about 0.6% by weight to about 1.0% by weight,
hydrochloric acid at a level of about 0.5% by weight to about 3.0% by weight,
sodium perchlorate at a level of about 2.0% by weight to about 6.0% by weight,
a surface active agent selected from the group consisting of a bis(perfluoroalkylsulfonyl)imide, a perfluoroalkylsulfonate, and a mixture thereof, at a level of about 10 parts per million (ppm) to about 40 ppm; and
a non-ionic surfactant, wherein the non-ionic surfactant is:
present in an amount ranging from about 0.1 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.

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