# US 8,784,637 B2 · Method for manufacturing anode foil of aluminium electrolytic capacitor

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- Number: US 8,784,637 B2
- Document ID: US8784637B2
- Status: Granted
- Kind: B2
- Application number: 12/794,895
- Filed: 2010-06-07
- Published: 2010-12-30
- Granted: 2014-07-22
- Earliest claimed: 2009-06-18
- Assignees: Panasonic Corporation
- Applicants: Naomi Kurihara; Katsunori Matsuda; Fumiaki Kawaguchi; Takahiro Suzuki
- Inventors: Naomi Kurihara; Katsunori Matsuda; Fumiaki Kawaguchi; Takahiro Suzuki
- Web page: https://patentgrep.com/patent/US8784637B2

## CPC

- H01G 9/045: based on aluminium
- C23C 22/83: Chemical after-treatment
- C25D 11/024: {Anodisation under pulsed or modulated current or potential}
- C25D 11/04: of aluminium or alloys based thereon
- C25D 11/12: Anodising more than once, e.g. in different baths
- C25D 11/36: Phosphatising
- H01G 9/0029: {Processes of manufacture}
- H01G 9/0032: {formation of the dielectric layer}
- H01G 9/055: Etched foil electrodes
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR

## Abstract

The present invention provides a method of manufacturing anode foil for aluminum electrolytic capacitors with high capacitance and decreased leakage current. The method has the following steps: dipping etched aluminum foil into pure water having a temperature of 90° C. or higher so as to form a hydrated film on the foil; attaching organic acid to the surface of the hydrated film; performing main chemical conversion on the aluminum foil with application of formation voltage after the attaching step; performing depolarization on the aluminum foil after the main chemical conversion step; and performing follow-up chemical conversion on the aluminum foil after the main chemical conversion step. The main chemical conversion treatment has two-or-more stages. In the first stage of the treatment, the foil is dipped into a phosphate aqueous solution, and in the last stage, it is dipped into an aqueous solution different from the phosphate aqueous solution.

## Claims

### Claim 1

A method of manufacturing anode foil for aluminum electrolytic capacitors, said method comprising:
dipping etched aluminum foil into pure water having a temperature of 90° C. or higher so as to form a hydrated film on the foil;
attaching organic acid to a surface of the hydrated film;
performing a main chemical conversion treatment on the aluminum foil with application of a formation voltage after said attaching of organic acid;
performing a depolarization treatment on the aluminum foil after said performing of the main chemical conversion treatment; and
performing a follow-up chemical conversion treatment on the aluminum foil after said performing of the depolarization treatment;
wherein the main chemical conversion treatment includes a plurality of first stages and a second stage after the plurality of first stages, wherein in each stage of the plurality of first stages, the aluminum foil undergoes chemical conversion while being dipped into an aqueous solution of phosphate, and in the second stage, the aluminum foil undergoes chemical conversion while being dipped into an aqueous solution having a solute different from the solution of phosphate,
wherein a formation voltage in a last stage of the plurality of first stages is 80% or greater of a formation voltage in the second stage.

### Claim 2 (depends on 1)

The method of manufacturing anode foil for aluminum electrolytic capacitors of claim 1, wherein the aqueous solution in the second stage of the main chemical conversion treatment is an aqueous solution of boric acid.

### Claim 3 (depends on 1)

The method of manufacturing anode foil for aluminum electrolytic capacitors of claim 1, wherein the aluminum foil undergoes the depolarization treatment while being dipped into an aqueous solution of phosphoric acid or an aqueous solution of oxalic acid.

### Claim 4 (depends on 2)

The method of manufacturing anode foil for aluminum electrolytic capacitors of claim 2, wherein the second stage of the main chemical conversion treatment is the last stage of the main chemical conversion treatment.