JPH11121280A - Solid electrolytic capacitor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply electricity to a precoated film, without impairing the quality of a capacitor and manufacturing workability in a process for forming a conductive macromolecular layer by electrolytic oxidation polymerization. SOLUTION: In a method of manufacturing an organic solid electrolytic capacitor, which includes a process for fixing an anode lead wire 10 to an anode 1 formed of a valve action metal such as Al, Ta, a process for forming a dielectric oxide film 2 on the surface of the anode 1, a process for forming a precoated film 3 made of a solid conductive material, such as MnO2 and conductive organic material on the dielectric oxide film 2, and a process for forming a conductive macromolecular layer 4 on the precoated film 3 through electrolytic oxidation polymerization, the process for forming the precoated film 3 forms the precoated film 3 made of a conductive organic material such as conductive macromolecule, organic semiconductor or the dielectric oxide film 2 and a part of the anodic lead wire 10, and a process for forming the conductive macromolecular layer 4 which conducts electrolytic oxidation polymerization by supplying electricity to the anodic lead wire 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same. In particular, the present invention relates to a high performance solid electrolytic capacitor having excellent high frequency characteristics and a method for manufacturing the same.

[0002]

2. Description of the Related Art An electrolytic capacitor is formed by forming a dielectric oxide film on the surface of an anode body made of a valve metal such as Al (aluminum) or Ta (tantalum) by electrolytic oxidation. A cathode layer is formed by adhering a conductive material such as an electrolytic solution, MnO ₂ (manganese dioxide), or a conductive organic material on the oxide film. Here, the valve metal is a metal that forms a very dense and durable dielectric oxide film by the electrolytic oxidation treatment. In addition to Al and Ta, Ti (titanium), Nb (niobium), etc. Is applicable.
Since the thickness of the dielectric oxide film is extremely small, the electrolytic capacitor can produce a small-sized and large-capacity capacitor as compared with other paper capacitors, film capacitors, and the like. The electrolytic capacitor uses a solid conductive material such as MnO _{2 or} a conductive organic material as a cathode layer as a solid electrolytic capacitor, and further uses a solid conductive organic material as an organic solid electrolytic capacitor. It is called a capacitor.

With the recent development of electronic equipment, there is a need for a small and large-capacity capacitor having a low internal impedance and excellent high-frequency characteristics in a high-frequency region. The internal impedance of the capacitor
ESR (equivalent serie) mainly caused by the material of the cathode layer
s resistance (equivalent series resistance) and self-inductance mainly caused by the lead wire. Among the conductive materials used for the cathode layer of the electrolytic capacitor, TCNQ
(7,7,8,8-tetracyanoquinodimethane) complex salt,
A conductive organic material such as polypyrrole has a higher electric conductivity than an electrolytic solution or MnO ₂ . Therefore, an organic solid electrolytic capacitor using a conductive organic material is used in various electronic devices as a small and large-capacity capacitor excellent in high-frequency characteristics because of its low ESR. Further, among conductive organic materials, a conductive polymer material such as polypyrrole has higher electric conductivity than an organic semiconductor such as a TCNQ complex salt. Therefore, an organic solid electrolytic capacitor using a conductive polymer material such as polypyrrole has a smaller ESR and is a small and large-capacity capacitor having extremely excellent high frequency characteristics.

In order to increase the capacity of a capacitor,
It is desirable to increase the area of the electrode. Therefore, in the electrolytic capacitor, a foil or a sintered body is used for the anode body. In the case of foil, the area of the electrode is increased by winding or laminating it on a core. To further increase the electrode area,
The foil is formed on a rough surface by etching. The sintered body is made by sintering particulate metal and is porous,
Large electrode area. At this time, unless the dielectric oxide film and the cathode layer are formed in close contact with the surface of the anode body,
This does not mean that the electrode area is increased. The dielectric oxide film is formed along the surface of the anode body because it is formed by immersing the anode body in an electrolytic solution and performing electrolytic oxidation. Similarly, when an electrolytic solution is used for the cathode layer, the electrolytic solution can easily adhere to the surface of the dielectric oxide film covering the surface of the anode body. However, in the case of a solid electrolytic capacitor using a solid conductive material for the cathode layer, it is not easy to bring the cathode layer into close contact with the surface of the dielectric oxide film, and therefore various methods have been proposed and implemented. ing.

In the case of forming the cathode layer using a conductive polymer material such as polypyrrole, chemical oxidation polymerization or electrolytic oxidation polymerization has been conventionally used.
5009, Japanese Patent Publication 4-23410, Japanese Patent Publication 4-6776
7, Japanese Patent Publication No. 4-74853 and the like. Chemical oxidation polymerization is a method in which monomers are oxidized and polymerized by an oxidizing agent.In electrolytic oxidation polymerization, monomers are oxidized and polymerized by an oxidation reaction generated at an anode in electrolysis, and a polymer layer is formed on the anode. It is a method of forming. In the method utilizing chemical oxidative polymerization, an oxidizing agent is deposited on a dielectric oxide film, and then a monomer solution or gas that can be a conductive polymer is brought into contact with the oxidizing polymer to oxidize and polymerize the monomer. Thus, a conductive polymer layer is formed on the dielectric oxide film. However, the conductive polymer layer formed by this method has disadvantages such as low strength, easy occurrence of unevenness, and lower electric conductivity than the conductive polymer layer formed by electrolytic oxidation polymerization. Having. Therefore, in this method,
A cathode layer that is sufficiently satisfactory as a high-performance solid electrolytic capacitor is not formed. On the other hand, when using electrolytic oxidation polymerization,
In general, the strength is high, the electrical conductivity is high, and uniform,
A good quality conductive polymer layer is formed. However, it is impossible or very difficult to form a conductive polymer layer directly on a dielectric oxide film using electrolytic oxidation polymerization because the dielectric oxide film is an insulator. Therefore,
A conductive film (hereinafter, referred to as a “precoat film”) is previously coated on the dielectric oxide film, and electrolytic oxidation polymerization is performed using the precoat film as an anode, so that a conductive polymer layer is formed on the precoat film. Has been proposed and is described in the above-mentioned publication.

[0006]

Generally, in the above-described method of forming a conductive polymer layer on a precoat film by electrolytic oxidation polymerization, power is supplied to the precoat film as shown in FIGS. 4 and 5 (a). , The external electrode (5
0) is contacted to supply power from the external electrode (50). However, in this case, the external electrode (50) and the precoat film (3)
The current density is not constant due to the degree of contact with the conductive polymer layer, so that it is difficult to form the conductive polymer layer (4) uniformly. When the external electrode (50) is removed after the formation of the conductive polymer layer (4), a part (40) of the conductive polymer layer (4) is lost, and at the same time, the dielectric oxide film (2) is removed. ) Is damaged, causing various problems such as an increase in leakage current of the capacitor. On the other hand, FIG.
After the formation of the precoat film (3), one end of the anode body (1) is cut to provide a metal exposed portion (11), and power is supplied to the anode lead wire (10) in electrolytic oxidation polymerization. Thus, a conductive polymer layer (4) is formed on the exposed metal part (11), and the formed conductive polymer layer (4) grows and comes into contact with the pre-coat film (3), thereby pre-coating. There is a method of supplying power to the membrane (3), which is described in Japanese Patent Publication No. 3-65009. According to this method, the above-mentioned problem caused by using the external electrode (50) can be solved. However, the region where the conductive polymer layer (4) and the precoat film (3) come into contact first comes into contact later. Thicker than the region, resulting in non-uniform layer growth. In this method, as shown in FIG. 6B, after the conductive polymer layer (4) is formed, the anode body is formed on the conductive polymer layer (4).
It is necessary to insulate the region (41) in contact with (1) using an oxidizing agent or a reducing agent, but this operation is very difficult because the capacitor is very small.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new method for supplying power to a pre-coated film in electrolytic oxidation polymerization without impairing the characteristics and manufacturing workability of a capacitor.

[0008]

According to a method of manufacturing a solid electrolytic capacitor of the present invention, in a step of forming a precoat film, a precoat film made of a conductive organic material such as a conductive polymer or an organic semiconductor is formed by dielectric oxidation. In the step of forming a conductive polymer layer by electrolytic oxidation polymerization formed on the surface of the coating and a part of the anode lead wire, power is supplied to the anode lead wire. In the above method, in the step of attaching the metal terminal plate to the anode lead, it is desirable that the metal terminal plate be welded at a position near the anode body in the anode lead.

[0009]

In the present invention, the precoat film is connected to the anode lead wire in the precoat film formation step. Therefore, in the conductive polymer layer forming step, when power is supplied to the anode lead wire, power is also supplied to the precoat film, and the conductive polymer layer can be formed on the precoat film. As a result, external electrodes are not required, and deterioration of capacitor characteristics such as leakage current due to the use of external electrodes can be prevented.
Further, since organic conductive materials such as conductive polymers and organic semiconductors become insulated when high heat is applied, the metal terminal plate is welded at a position close to the anode body in the anode lead wire in the metal terminal plate mounting step. Then, the precoat film formed on the anode lead wire is insulated by heat during welding. Therefore, insulation between the anode lead wire and the precoat film can be easily performed without increasing the number of working steps.

[0010]

Embodiments of the present invention will be described below. The solid electrolytic capacitor element (100), which is a main part of the solid electrolytic capacitor of the present embodiment, is, as shown in FIG.
Anode lead wire to anode body (1) made of valve metal such as Al, Ta, etc.
(10), a dielectric oxide film (2) is formed on the surface of the anode body (1) and a part of the anode lead wire (10) by electrolytic oxidation treatment, and the dielectric oxide film (2) is formed. ) And a part of the anode lead wire (10), a precoat film (3) is formed, and a conductive polymer layer (4) is formed on the precoat film (3) by electrolytic oxidation polymerization. Precoat film (3) and conductive polymer layer (4)
As a cathode layer. In the solid electrolytic capacitor element (100) thus formed, a carbon and silver paste layer is formed on the cathode layer, and a metal terminal plate is attached to the anode lead wire (10) and the carbon and silver paste layer, respectively. An outer shell is formed of an epoxy resin or the like, and an aging process is performed to complete the solid electrolytic capacitor of the present embodiment. A foil, a sintered body, or the like is used for the anode body (1). In the following examples and comparative examples, Ta is used as a valve metal.
A Ta sintered body (1a) is used. In addition, a conductive organic material such as a conductive polymer and an organic semiconductor is used for the precoat film (3). In the following Examples and Comparative Examples, polypyrrole, which is a conductive polymer, is used. For the conductive polymer layer (4), polypyrrole, polyaniline, polythiophene, derivatives thereof, and the like are used. In the following examples, polypyrrole is used.

[0011]

EXAMPLES Examples of the present invention and comparative examples will be described below.

(Example) A Ta sintered body (1a) to which an anode lead wire (10) was attached was immersed in a phosphoric acid aqueous solution (0.02% by weight), and a voltage was applied to perform electrolytic oxidation to perform Ta sintering. Body (1a)
And a part of the anode lead wire (10)
(2) was formed. Next, the Ta sintered body subjected to the above-described treatment
(1a) was converted to hydrogen peroxide (concentration 1 mol / l) and sulfuric acid (concentration 0.2 mol / l).
l / l) for 10 minutes and then exposed to a pyrrole monomer for 30 minutes to carry out chemical oxidative polymerization, and a part of the dielectric oxide film (2) and the anode lead (10) A chemically polymerized polypyrrole film (3a) was formed on the surface. At this time, in order to form a chemically polymerized polypyrrole film (3a) on a part of the surface of the anode lead (10), an aqueous solution of hydrogen peroxide and sulfuric acid was also applied to the surface where the anode lead (10) was exposed. And the pyrrole monomer was contacted. Next, as shown in FIG. 3, the Ta sintered body (1a) subjected to the above-mentioned treatment was mixed with tetraethylammonium / paratoluenesulfonic acid (concentration 0.05 mol / mol).
l) and an acetonitrile solution (6) containing a pyrrole monomer (concentration: 0.1 mol / l), the positive electrode of the power supply (7) is connected to the anode lead wire (10), and the negative electrode is the cathode electrode (51). And apply a voltage. Then, since the anode lead wire (10) is connected to the chemically polymerized polypyrrole film (3a), power is supplied from the anode lead wire (10) to the chemically polymerized polypyrrole film (3a), and the anode is connected to the chemically polymerized polypyrrole film (3a). Then, an electropolymerized polypyrrole layer (4a) was formed. Thereafter, the substrate was washed and dried to complete a solid electrolytic capacitor element (100).

Next, the solid electrolytic capacitor element (100)
In FIG. 2, as shown in FIG.
(4a) A carbon and silver paint layer (9) is formed, and metal terminal plates (80) and (81) are attached to the anode lead wire (10) and the carbon and silver paint layer (9), respectively. At this time, the chemically polymerized polypyrrole film (3) formed on the anode lead wire (10)
At a position close to a), the anode lead wire (10) and the metal terminal plate (80) are welded. Then, the chemically polymerized polypyrrole film (3a) formed on the anode lead wire (10) is insulated by the heat at the time of welding (30), and is formed between the anode lead wire (10) and the chemically polymerized polypyrrole film (3a). Is insulated. On the other hand, the carbon and silver paint layer (9) and the metal terminal plate (81) are bonded with a silver adhesive. Then, after the outer shell was formed with an epoxy resin or the like on the solid electrolytic capacitor element (100) to which the metal terminal plates (80) and (81) were attached, aging treatment was performed at 25 V to complete the solid electrolytic capacitor.

(Comparative Example) A Ta sintered body (1a) on which a dielectric oxide film (2) was formed in the same manner as in the example was immersed in an aqueous hydrogen peroxide solution (concentration: 1 mol / l) for 10 minutes. Chemical oxidation polymerization is carried out by exposing to a pyrrole monomer for 30 minutes, and a chemically polymerized polypyrrole film (3
a) was formed. That is, in the comparative example, unlike the example, the chemically polymerized polypyrrole film (3a) is provided on the anode lead wire (10).
Did not form. Next, as shown in FIG. 4, the Ta sintered body (1a) subjected to the above-mentioned treatment was acetonitrile containing paratoluenesulfonic acid (concentration 0.05 mol / l) and pyrrole monomer (concentration 0.1 mol / l). Immerse in the solution (6) and use a platinum external electrode
(50) is brought into contact with the chemically polymerized polypyrrole film (3a),
The positive electrode of the power supply (7) is connected to the external electrode (50), and the negative electrode is connected to the cathode electrode (51) to apply a voltage. Then, power was supplied from the external electrode (50) to the chemically polymerized polypyrrole film (3a), and an electrolytically polymerized polypyrrole layer (4a) was formed on the chemically polymerized polypyrrole film (3a). Thereafter, the external electrode (50) was removed, washed, and dried to complete a solid electrolytic capacitor element. Then, in the solid electrolytic capacitor element, a carbon and silver paint layer (9) is formed on the electropolymerized polypyrrole layer (4a), and a metal terminal plate is provided on the anode lead wire (10) and the carbon and silver paint layer (9). After attaching (80) and (81), and forming the outer shell with epoxy resin etc.,
Aging treatment was performed at 25 V to complete a solid electrolytic capacitor. Table 1 shows the capacitor characteristics in the above Examples and Comparative Examples.

[0015]

[Table 1]

In Table 1, δ is a loss angle,
The leakage current is a value after applying a voltage of 25 V for 60 seconds. Comparing the manufacturing process of the example and the comparative example with the capacitor characteristics (Table 1), the present example is considered to have the following effects. In this embodiment, since the external electrode (50) is unnecessary in the electrolytic oxidation polymerization, there is no damage to the dielectric oxide film that occurs when the external electrode is removed, and therefore, the leakage current can be reduced. Further, in this embodiment, since power is also supplied from the anode lead wire (10) to the Ta sintered body (1a) in the electrolytic oxidation polymerization, the dielectric oxide film is repaired or reformed, and therefore, the leakage current is reduced. It can be even smaller. In addition, this example uses an anode lead wire by chemical oxidation polymerization.
Since (10) and the chemically polymerized polypyrrole film (3a) are short-circuited in advance, the chemically polymerized polypyrrole film (3
a) An electrolytically polymerized polypyrrole layer (4a) can be uniformly formed on the
Therefore, capacitor characteristics (capacitance and ESR) can be improved. Furthermore, in this example, since the external electrode (50) is unnecessary in the electrolytic oxidation polymerization, there is no need to carefully contact the external electrode (50) with the chemically polymerized polypyrrole film (3a),
The operation is simplified, and the electropolymerized polypyrrole layer (4a) is not formed on the external electrode (50), and no waste of material occurs. Further, in this embodiment, the short circuit between the anode lead wire (10) and the chemically polymerized polypyrrole film (3a) is performed by chemical oxidation polymerization, and the short circuit between the anode lead wire (10) and the chemically polymerized polypyrrole film (3a) is performed. Insulation is made with anode lead wire (10) and metal terminal board
Since it is performed in welding with (80), there is no need to add a new process. Therefore, this embodiment is suitable for mass production of solid electrolytic capacitors.

The description of the above embodiments is for describing the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof.
Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an organic solid electrolytic capacitor element of the present embodiment.

FIG. 2 is a sectional view showing a state in which a metal terminal plate is attached to the organic solid electrolytic capacitor element of FIG.

FIG. 3 is a schematic view showing a step of performing electrolytic oxidation polymerization using an anode lead wire as an anode electrode.

FIG. 4 is a schematic view showing a step of performing electrolytic oxidation polymerization by connecting an external electrode to a precoat film.

FIG. 5 is a cross-sectional view showing a conventional organic solid electrolytic capacitor element having a conductive polymer layer formed using external electrodes, wherein (a) shows a state immediately after the conductive polymer layer is formed; (B) shows a state in which the external electrode has been removed.

FIG. 6 is a cross-sectional view showing a conventional organic solid electrolytic capacitor element in which a conductive polymer layer is formed by exposing one end of an anode body, wherein (a) is a state immediately after forming a conductive polymer layer. (B) shows a state in which a region of the conductive polymer layer that contacts the anode body is insulated.

[Explanation of symbols]

 (1) Anode body (2) Dielectric oxide film (3) Precoat film (4) Conductive polymer layer (10) Anode lead wire (30) Insulated part of precoat film (80) Metal terminal plate for anode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takefumi Takamatsu 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A step of attaching an anode lead wire (10) to an anode body (1) formed of a valve metal such as Al, Ta, etc., and forming a dielectric oxide film (2) on the surface of the anode body (1). Forming a pre-coat film (3) made of a solid conductive material such as MnO _{2 or} a conductive organic material on the dielectric oxide film (2); and forming the pre-coat film by electrolytic oxidation polymerization. film
(3) a step of forming a conductive polymer layer (4) on the anode body;
In the method for manufacturing a solid electrolytic capacitor including the step (1) of attaching a metal terminal plate (80) to the anode lead wire (10), the step of forming the pre-coat film (3) comprises the steps of: Precoat film made of conductive organic materials such as semiconductors (3)
Is formed on the surface of the dielectric oxide film (2) and a part of the anode lead wire (10), and the step of forming the conductive polymer layer (4) comprises the steps of:
0) A method for producing a solid electrolytic capacitor, characterized in that electrolytic oxidation polymerization is performed by supplying power to (0). 2. The step of attaching the metal terminal plate (80) to the anode lead (10) includes the step of attaching the anode body (1) to the anode lead (10).
The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the metal terminal plate (80) is welded at a position close to the terminal. 3. An anode body (1) formed of a valve metal such as Al or Ta, and an anode lead wire attached to the anode body (1).
(10) and a dielectric oxide film formed on the surface of the anode body (1)
(2), a precoat film (3) formed of a solid conductive material such as MnO _{2 or} a conductive organic material on the dielectric oxide film (2), and electrolytic oxidation on the precoat film (3). In a solid electrolytic capacitor comprising a conductive polymer layer (4) formed by polymerization and a metal terminal plate (80) attached to an anode lead (10), the pre-coated film (3) has a conductive property. The metal terminal plate (80) is formed of a conductive organic material such as a polymer or an organic semiconductor on the surface of the dielectric oxide film (2) and a part of the anode lead wire (10). A region (30) of the precoat film (3) formed on the anode lead wire (10) is welded at a position near the anode body (1) in the wire (10), and is insulated by the welding. A solid electrolytic capacitor.