Protective coating for electrolytic capacitors

• US 6,864,147 B1
• Filed: 08/22/2003
• Issued: 03/08/2005
• Est. Priority Date: 06/11/2002
• Status: Expired due to Term

• Current Assignee: Kyocera AVX Components Corporation (Kyocera Corporation)
• Original Assignee: AVX Corporation (Kyocera Corporation)
• Inventors: Sebald, Zebbie L., Fife, James A.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Nguyen, Thinh T
• Application Number:
  US10/646,219
• Time in Patent Office: 564 Days
• Field of Search: 438/399, 438/171, 438/393, 438/387, 438/425, 438/768, 438/763, 438/754
• US Class Current: 438/399
• CPC Class Codes: H01G 9/0032 formation of the dielectric layer
• CPC Class Codes: H01G 9/0036 Formation of the solid electrolyte layer
• CPC Class Codes: H01G 9/07 Dielectric layers
• CPC Class Codes: H01G 9/15 Solid electrolytic capacitors H01G11/00 takes precedence

Abstract

A solid electrolytic capacitor that comprises an anode that contains a valve-action metal (e.g., tantalum, niobium, and the like) and a dielectric film overlying the anode is provided. The capacitor also comprises a protective coating overlying the dielectric film, wherein the protective coating contains a relatively insulative, resinous material. For example, in one embodiment, the resinous material can be a drying oil, such as olive oil, linseed oil, tung oil, castor oil, soybean oil, shellac, and derivatives thereof. The capacitor also comprises a conductive polymer coating overlying the protective coating. As a result of the present invention, it has been discovered that a capacitor can be formed that can have a relatively low leakage current, dissipation factor, and equivalents series resistance.

Claims

1. A method for forming a solid electrolytic capacitor, said method comprising:

forming an anode that contains a valve-action metal;

anodizing a surface of said anode to form a dielectric film;

forming a protective coating on said dielectric film, said protective coating containing a relatively insulative, resinous material; and

forming a conductive polymer coating.

2. A method as defined in claim 1, wherein said resinous material contains esters of unsaturated or saturated fatty acids.

3. A method as defined in claim 1, wherein said resinous material contains at least one drying oil or derivatives thereof.

4. A method as defined in claim 3, wherein said drying oil is selected from the group consisting of olive oil, linseed oil, tung oil, castor oil, soybean oil, shellac, and derivatives thereof.

5. A method as defined in claim 1, wherein said protective coating contains shellac or derivatives thereof.

6. A method as defined in claim 1, wherein said protective coating is formed by from a solution containing said relatively insulative, resinous material.

7. A method as defined in claim 6, wherein said solution further contains a non-aqueous solvent having a boiling point greater than about 80°

C.

8. A method as defined in claim 6, wherein said solution further contains a non-aqueous solvent having a boiling point greater than about 120°

C.

9. A method as defined in claim 6, wherein said solution further contains a non-aqueous solvent having a boiling point greater than about 150°

C.

10. A method as defined in claim 6, wherein said protective coating is formed by dipping said anode into said solution.

11. A method as defined in claim 1, further comprising applying a curing agent to the protective coating before forming said conductive polymer coating.

12. A method as defined in claim 10, wherein said curing agent contains sulfuric acid.

13. A method as defined in claim 1, wherein said protective coating includes multiple layers.

14. A method as defined in claim 13, wherein each protective coating layer is dried at a temperature ranging from about 30°

C. to about 300°

C.

15. A method as defined in claim 13, wherein each protective coating layer is dried at a temperature ranging from about 50°

C. to about 150°

C.

16. A method for forming a solid electrolytic capacitor, said method comprising:

forming an anode that contains a valve-action metal;

anodizing a surface of said anode to form a dielectric film;

applying a solution to said anodized anode that contains a conductive polymer catalyst and a relatively insulative, resinous material; and

thereafter, applying a conductive monomer to said anodized anode, wherein said conductive monomer polymerizes to form a conductive polymer coating.

17. A method for forming a solid electrolytic capacitor, said method comprising:

forming an anode that contains a valve-action metal;

anodizing a surface of said anode to form a dielectric film;

applying a solution to said anodized anode that contains a conductive monomer and a relatively insulative, resinous material; and

thereafter, applying a conductive monomer catalyst to said anodized anode, wherein said conductive monomer polymerizes to form a conductive polymer coating.

18. A method for forming a solid electrolytic capacitor, said method comprising:

forming an anode that contains a valve-action metal;

anodizing a surface of said anode to form a dielectric film;

applying a solution to said anodized anode that contains a conductive monomer, a catalyst for said conductive monomer, and a relatively insulative, resinous material, wherein said conductive monomer polymerizes to form a conductive polymer coating.