# US 10,309,033 B2 · Process additives to reduce etch resist undercutting in the manufacture of anode foils > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,309,033 B2 - Document ID: US10309033B2 - Status: Granted - Kind: B2 - Application number: 15/459,808 - Filed: 2017-03-15 - Published: 2018-06-07 - Granted: 2019-06-04 - Earliest claimed: 2016-12-02 - Assignees: Pacesetter, Inc. - Applicants: Pacesetter, Inc. - Inventors: Ralph Jason Hemphill; Timothy R. Marshall; Thomas F. Strange - Web page: https://patentgrep.com/patent/US10309033B2 ## CPC - C25F 3/04: of light metals - C25F 3/14: locally - C25F: PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR ## 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) The composition of claim 1, wherein the surface active agent is a bis(perfluoroalkylsulfonyl)imide. ### Claim 3 (depends on 2) The composition of claim 2, wherein the bis(perfluoroalkylsulfonyl)imide is provided as an alkali metal salt or an ammonium salt. ### Claim 4 (depends on 2) The composition of claim 2, wherein the alkyl group of the bis(perfluoroalkylsulfonyl)imide is a C1-C4 alkyl group. ### Claim 5 (depends on 2) The composition of claim 2, wherein the bis(perfluoroalkylsulfonyl)imide is a bis(perfluoroethylsulfonyl)imide. ### Claim 6 (depends on 2) The composition of claim 2, wherein the bis(perfluoroalkylsulfonyl)imide is present in an amount ranging from about 10 to about 150 ppm. ### Claim 7 (depends on 1) The composition of claim 1, wherein the surface active agent is a perfluoroalkylsulfonate. ### Claim 8 (depends on 7) The composition of claim 7, wherein the perfluoroalkylsulfonate is provided as a perfluoroalkylsulfonic acid, or a salt thereof. ### Claim 9 (depends on 7) The composition of claim 7, wherein the perfluoroalkylsulfonate is nonafluorobutanesulfonate. ### Claim 10 (depends on 1) 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. ### Claim 11 (depends on 1) The composition of claim 1, wherein the non-ionic surfactant has the Formula I: R1-Cy-(EO)x—OR2 (Formula I), wherein EO is a -OCH2CH2— group; x is 1 to 20; R1 is H or a C1-C20 alkyl group; R2 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. ### Claim 12 (depends on 1) The composition of claim 1, wherein the non-ionic surfactant has the Formula II: wherein x is 1 to 20. ### Claim 13 (depends on 12) The composition of claim 12, wherein x is 9 to 10. ### Claim 14 (depends on 1) 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. ### Claim 15 (depends on 1) 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. ### Claim 16 (depends on 1) 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. ### Claim 17 (depends on 1) 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. ### Claim 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. ### Claim 19 (depends on 18) The method of claim 18, wherein the non-ionic surfactant has the Formula II: wherein x is 1 to 20. ### Claim 20 (depends on 19) The method of claim 19, wherein foam does not form in the electrolyte bath.