JPH01105523A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a solid electrolytic capacitor where the leakage of a current is limited, by forming an insulating polymer film at a specified part on the oxide film of dielectrics and making the surface of a protecting layer conductible, thereby performing electrolytic polymerization from the protecting layer which becomes conductive. CONSTITUTION:An anode lead 7 is installed at a film formation metal 1 consisting of aluminum foil through a lead boss 8 made of aluminum. An oxide film of dielectrics 2 is formed at a part of the boss 8 and at the whole surface of the metal 1 and further, the boss 8 and a part of the lead 7 are coated with an insulating polymer film 3. A chemically and oxidatively polymerized conductive polymer film 4 is formed on a part of the polymer 3 and the film 2. On the polymer film 4 an electrolytically and oxidatively polymerized conductive polymer film 5 is formed. The polymer film 4 is obtained by polymerizing pyrrole, thiophene, aniline or furan by an oxidizer, while the polymer film 5 is obtained by electrochemically oxidative polymerization of pyrrole, thiophene, aniline or furan. Thus a solid electrolytic capacitor where the leakage of a current is limited can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a capacitor using a conductive polymer as a solid electrolyte. .

(Prior Art) First, the present inventors formed a dielectric oxide film on a film-forming metal, formed a chemical oxidation polymerized conductive polymer film on the dielectric oxide film, and further coated a conductive polymer film on this dielectric oxide film. We proposed a solid electrolytic capacitor with a structure in which a molecular electrolytic polymer film was formed (4
8 Gansho 62-4053).

Furthermore, in order to improve the efficiency of electrolytic polymerization in the production of the solid electrolytic capacitor described above, we proposed a method in which electrolytic polymerization is carried out by placing a conductor in contact with or within a distance of 11 from a chemically oxidized conductive polymer film. (Special application 1986-1)
87739). Although the above-mentioned capacitor is a solid electrolytic capacitor with a large capacitance and excellent electrical characteristics and temperature characteristics, there is still room for improvement in its structure.

(Problems to be Solved by the Invention) In other words, when electrolytic polymerization is performed by bringing conductors into contact as described above, if the dielectric oxide film is thin or mechanically brittle, the conductor may become dielectric. In some cases, the oxidation film of the capacitor was damaged and the capacitor characteristics deteriorated.

(Means for Solving the Problems) As a result of various studies in order to solve the above-mentioned problems, the present inventors have found that, in a solid electrolytic capacitor, a film-forming metal is attached with an anode lead that is partially or entirely made of a film-forming metal. a dielectric oxide film formed on a part of the anode lead; an insulating polymer film covering a part of the dielectric oxide film formed on the anode lead; A chemically oxidatively polymerized conductive polymer film of pyrrole, thiophene, aniline or furan formed on a dielectric oxide film of a partial surface and film-forming metal, and a conductive polymer film formed on the chemically oxidatively polymerized conductive polymer film. It has been found that the above problems can be solved by creating a structure consisting of an electrolytically oxidized conductive polymer film of pyrrole, thiophene, aniline, or furan.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a capacitor in which tantalum is used as the film-forming metal, fine powder is sintered, and an anode lead is taken out from the center using a tantalum wire. A dielectric oxide film (2) is formed by anodic oxidation on a part of the film-forming metal (1) made of tantalum and the anode lead (7) made of tantalum wire.
) is formed. Next, the anode lead (7) is coated with an insulating polymer 111 (3) by a method such as coating an insulating polymer. The area to be coated is the zero-order insulating polymer film (3) and the dielectric oxide film ( 2) is immersed in an oxidizing agent or a solution containing an oxidizing agent, and further immersed in a conductive polymer monomer or a solution containing the monomer to form the surface of the insulating polymer film (3) and the dielectric oxide film ( 2) A chemically oxidized and polymerized conductive polymer film (4) is formed thereon. The area in which the chemical oxidation polymerized conductive polymer film (4) is formed is below the insulating polymer film (3). Next, the conductor (6) is brought into contact with the chemically oxidized conductive polymer film (4) formed on the insulating polymer 11 (3), and immersed in an electrolytic solution containing a supporting electrolyte and a conductive polymer monomer. Then, electrolytic oxidative polymerization is performed using the conductor (6) as an anode to form an electrolytic oxidatively polymerized conductive polymer film (5). In this electrolytic oxidation polymerization, if the insulating polymer film (3) is not present, the dielectric oxide film (2) may be damaged by the conductor (6), and the leakage current of the resulting capacitor may increase.

FIG. 2 is a schematic cross-sectional view of the vicinity of the lead attachment portion of a wound type capacitor. An anode lead is attached to a film-forming metal (1) made of an aluminum whistle via an aluminum lead boss (8).

A dielectric oxide film (2)-ht shadow is formed on a part of the lead boss (8) and the entire surface of the film-forming metal (1), and a part of the lead boss and anode lead (7) is covered with an insulating polymer film (3). Covered. Furthermore, a chemically oxidatively polymerized conductive polymer film (4) is formed on a part of the insulating polymeric film (3) and the dielectric oxidation degree II (2), and an electrolytically oxidatively polymerized conductive polymer film (4) is further formed on the dielectric oxidation degree II (2). A membrane (5) is formed.

Insulating polymers used in the present invention include vinyl chloride, polyethylene terephthalate, silicone resin, epoxy resin,
Various materials such as vinylidene tsunide, polyimide, polyetherimide, polyamideimide, polyethylene, and polypropylene can be used, and these polymers can be dissolved in an appropriate solvent and applied, then dried and cured, or heated and melted. It is used by methods such as applying the compound and cooling it to harden it, or mixing it with a hardening agent and applying it.

The film-forming metal used in the present invention is N or a sintered body such as full minute or tantalum. For example, when a foil is used, it can be in a rolled shape or a flat plate shape. Further, in the case of a wound type, an anode and/or a separator paper are not necessarily required.

The chemically oxidized conductive polymer film of the present invention is obtained by polymerizing pyrrole, thiophene, aniline, or furan with an oxidizing agent, and preferably uses a pyrrole polymer. Examples of the oxidizing agent include halogens such as iodine and bromine, metal halides such as arsenic pentafluoride and phosphorous pentafluoride, protonic acids such as sulfuric acid and nitric acid, sodium persulfate, potassium persulfate, ammonium persulfate, etc. Peroxides such as persulfate, hydrogen peroxide, and peracetic acid are used.

The order of treatment with an oxidizing agent and treatment with a polymer monomer during chemical oxidative polymerization does not matter.

The electrolytically oxidatively polymerized conductive polymer membrane of the present invention is obtained by electrochemically oxidatively polymerizing pyrrole, thiophene, aniline, or furan, and preferably uses a pyrrole polymer. In electrolytic oxidative polymerization, as a supporting electrolyte, the anion is a sulfonic acid 7 anion such as alkylbenzenesulfonic acid, benzenesulfonic acid, diF lobenzenesulfonic acid, a perchlorate anion, a halogen such as tetra-70 loboron, hexafluoroline, etc. A compound 7 anion is used, and water or an organic solvent is used as a solvent.

The capacitor structure of the present invention is particularly effective for capacitors with thin or brittle dielectric oxide films, but is also effective for capacitors with thick dielectric oxide films.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 The anode lead was taken out from the tank 4 using a tantalum wire (length 10 m+), and the sintered body was anodized at a voltage of 1 sov, and the anode lead from the sintered body and the connecting part of the sintered body to the point 5I@I11 was removed. A dielectric oxide film was formed on the portion (liquid capacitance: 3 μF). Vinyl chloride resin (solvent consisting of 80% methyl ethyl ketone and 20% acetone) was applied to the anode lead portion from the sintered body connecting portion to 2IllIO, and then dried at 80° C. for 30 minutes.

Next, from the sintered body and the sintered body connection part, 1.511II1
The anode lead part up to point 1 was immersed in an aqueous ammonium persulfate solution (3 mol/l) for 10 minutes.
) for 10 minutes.
．． A chemically oxidized conductive polymer film of pyrrole was formed on the anode lead portion up to 5 mm.

Tetraethylammonium paratoluenesulfonic acid 0.
The sintered body subjected to the above treatment and the anode lead portion up to 1.5 mm from the sintered body connection portion were immersed in an aqueous solution containing 7 mol/l and pyrrole 0.2 mol/l. Next, the platinum wire was brought into contact with the chemically oxidized conductive polymer film of pyrrole formed on the anode lead, and the platinum wire was used as the anode and the stainless steel plate was used as the cathode at 0.511 IA/c.
Electrolytic polymerization was carried out at a constant current of II12. As a result, a dark green conductive polymer film of pyrrole was formed by electrolytic oxidation on the chemically oxidized conductive polymer film.

After washing with water and acetone and drying, a silver paste was applied to the surface of the electrolytically oxidized conductive polymer membrane, a cathode lead was attached, and a capacitor was completed by molding with epoxy resin.

1208 of this capacitor. The capacitance at z, tangent of loss angle (tan δ), equal series resistance at 100 KHz and leakage current at 35V are shown in Table 1.

Example 2 Roughened aluminum M (medium 511II11, length 6
An aluminum lead boss was attached to the end of the aluminum plate by caulking, and an anode lead was attached to the lead boss portion using a CP (katsuno kuichi ply) wire. An aluminum foil was wound to a diameter of 4III11, and a voltage of 20 V was applied together with the lead boss in a chemical solution to form a dielectric oxide film by anodic oxidation (capacity in the solution: 120 μF). Epoxy resin was applied to the part of the lead boss that protruded from the aluminum foil (length 2 mm) and the anode lead over a length of 2 mm, and was cured at 100°C for 1 hour. The part where the aluminum foil is wound and the part where the aluminum foil is wound (hereinafter referred to as the capacitor element part) were placed in an ethanol/water mixed solution with a pyrrole concentration of 2 mol/I (water/ethanol ratio of 1:1 by weight). After 5 minutes of immersion, the capacitor element part was immersed in an ammonium persulfate 3a+ol/l aqueous solution,
A chemically oxidized and polymerized conductive polymer film was formed on the capacitor element.

Tetrabutylammonium paratoluenesulfonic acid 0
．． The capacitor element part is immersed in an aqueous solution containing 8+*ol/l and 0.2 m of pyrrole, a stainless steel wire is brought into contact with the chemical oxidation polymerized conductive polymer film on the upper part of the capacitor element part, and the stainless steel wire is used as an anode to connect the stainless steel plate. Electrolytic loading was carried out with a constant current of 0.5 mA using as a cathode. As a result, a dark green conductive polymer film of pyrrole was formed on the capacitor element by electrolytic oxidation polymerization.

After washing with water and acetone, a silver paste was applied to the surface of the electrolytically oxidized conductive polymer membrane, a cathode lead was attached, and the membrane was placed in an aluminum case and sealed with epoxy resin.

Table 1 shows the capacitance of this capacitor at 120 Hz, the tangent of the loss angle (tan δ), the equivalent series resistance at 100 KHz, and the leakage current at IOV.

Comparative Example 1 A capacitor was completed in the same manner as in Example 1 except that the application of vinyl chloride resin to the anode lead portion was omitted. Table 1 shows the capacitance of this capacitor at 120 Hz, the tangent of the loss angle (tan δ), the equivalent series resistance at 100 KHz, and the leakage current at 3SV.

Comparative Example 2 A capacitor was completed in the same manner as in Example 2, except that the application of epoxy resin to the lead boss portion and the anode lead portion was omitted. The capacitance of this capacitor at 120 Hz, the tangent of the loss angle (tan δ), the equivalent series resistance at 100 KHz, and the leakage current at 10 V are expressed as the first
Shown in the table.

(Effects of the invention) An insulating polymer film is formed on a certain part of the dielectric oxide film as a protective layer, the surface of this protective layer is made conductive, and electrolytic polymerization is performed from the conductive protective layer. A solid electrolytic capacitor with low leakage current could be obtained without damaging the film.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a capacitor in which tantalum is used as a film-forming metal and fine powder is sintered, and an anode lead is taken out from the center. FIG. 2 is a schematic cross-sectional view of the vicinity of the lead attachment portion of the desired capacitor. 1. Film-forming metal 2. Dielectric oxide film 3. Insulating polymer film 4. Chemical oxidation polymerized conductive polymer II
5. Electrolytic oxidation polymerized conductive polymer membrane
6. Conductor 7. Anode lead patent applicant Nippon Carlit Co., Ltd.

Claims (1)

[Claims] A film-forming metal to which an anode lead partially or entirely made of a film-forming metal is attached, a dielectric oxide film formed on a part of the anode lead, and one part of the dielectric oxide film formed on the anode lead. an insulating polymer film covering the
A chemical oxidation polymerized conductive polymer film of pyrrole, thiophene, aniline, or furan formed on a part of the surface of the insulating polymer film and the dielectric oxide film of the film-forming metal, and the chemical oxidation polymerized conductive polymer. Pyrrole formed on the membrane,
A solid electrolytic capacitor consisting of an electrolytically oxidized and polymerized conductive polymer film of thiophene, aniline, or furan.