JP3568382B2 - Organic solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic solid electrolytic capacitor using a conductive polymer for a cathode layer and a method for manufacturing the same. In particular, the present invention relates to an improvement in a method for forming a cathode layer made of a conductive polymer.
[0002]
[Prior art]
The electrolytic capacitor forms a dielectric oxide film by electrolytic oxidation on the surface of an anode body made of a valve metal such as Al (aluminum) or Ta (tantalum). A cathode layer is formed by closely attaching a conductive substance such as an electrolytic solution, MnO ₂ (manganese dioxide), or a conductive organic compound. Here, the valve metal refers to a metal that forms a very dense and durable dielectric oxide film by electrolytic oxidation treatment. In addition to Al and Ta, Ti (titanium), Nb (niobium), and the like are used. Applicable. Since an electrolytic capacitor has a very thin dielectric oxide film, a capacitor having a small size and a large capacity can be produced as compared with other paper capacitors and film capacitors.
[0003]
The electrolytic capacitor uses a solid conductive material such as MnO ₂ as a cathode layer as a solid electrolytic capacitor. Among them, an organic solid electrolytic capacitor using a solid conductive organic material is used. It is called. Examples of the conductive organic material include conductive polymers such as polypyrrole and polyaniline, and TCNQ (7,7,8,8-tetracyanoquinodimethane) complex salt.
The solid conductive organic material has higher conductivity than the electrolytic solution and MnO _2. Therefore, the organic solid electrolytic capacitor using the solid conductive organic material for the cathode layer uses the electrolytic solution and MnO ₂ for the cathode layer. Compared to the case, it has a low ESR (equivalent series resistance) and excellent high frequency characteristics, and is currently used in various electronic devices.
[0004]
As a method for forming a cathode layer made of a conductive polymer among solid conductive organic materials, a method utilizing chemical oxidation polymerization or electrolytic oxidation polymerization is known. Chemical oxidative polymerization is a method of generating a polymer by oxidatively polymerizing a monomer using an oxidizing agent. In this method, a polymer is produced on an anode by oxidative polymerization of a monomer.
In general, a conductive polymer layer formed by electrolytic oxidative polymerization is a uniform, high-quality conductive polymer layer having higher strength, higher conductivity, and uniformity than in the case of chemical oxidative polymerization. However, it is impossible or very difficult to directly form a conductive polymer layer on a dielectric oxide film by electrolytic oxidation polymerization because the dielectric oxide film is an insulator.
Therefore, first, a first conductive polymer layer is formed on the dielectric oxide film by chemical oxidation polymerization, and then a second conductive polymer layer is formed on the first conductive polymer layer by electrolytic oxidation polymerization. Methods for forming a conductive polymer layer have been proposed, and are described in, for example, Japanese Patent Publication No. 4-74853 (H01G 9/02) and Japanese Patent Publication No. 5-83167 (H01G 9/02).
[0005]
[Problems to be solved by the invention]
In Japanese Patent Publication No. 4-74853, a solution containing an oxidizing agent is applied or sprayed to an anode body on which a dielectric oxide film is formed, and then a solution containing a monomer of a conductive polymer or a solution containing only the monomer. To form a first conductive polymer layer by chemical oxidation polymerization. Hereinafter, this method is referred to as liquid phase oxidative polymerization.
On the other hand, Japanese Patent Publication No. 5-83167 discloses that an anode body having a dielectric oxide film formed thereon is immersed in a solution containing an oxidizing agent, or after spraying or applying the solution, a conductive polymer monomer is formed. The first conductive polymer layer is formed by chemical oxidative polymerization by introducing the solution into the anode body accompanied by an inert gas, or by introducing the vapor of the monomer solution into the anode body. I have. Hereinafter, this method is referred to as gas phase oxidation polymerization.
However, using either of the above methods, the completed capacitor is lower than the theoretically expected value of the capacitor capacity, and therefore, there is still room for improvement in the method of manufacturing the capacitor.
[0006]
[Object of the invention]
The inventor of the present application examined capacitors formed using the above-described respective methods, and found that in the former liquid phase oxidative polymerization, there was a portion where the conductive polymer was not formed on the inner surface of the anode body. Was. Thus, in liquid phase oxidative polymerization, it is considered that the monomer is polymerized quickly on the outer surface of the anode body, the polymer covers the outer surface, and the monomer permeates into the anode body. It is considered to be preventing.
On the other hand, in the latter gas phase oxidation polymerization, a conductive polymer was formed on substantially the entire inner surface of the anode body. However, in the case of gas phase oxidation polymerization, the formation amount per unit time is smaller than in the case of liquid phase oxidation polymerization due to the property of using gas, and the step of forming the conductive polymer needs to be performed for a long time or repeated. There is.
The inventor of the present application considered that the capacitor capacity could be improved by combining the above methods from the above considerations, and conducted an experiment. As a result, good results were obtained.
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an organic solid electrolytic capacitor having a capacitor capacity improved compared to the conventional one without reducing production efficiency.
[0007]
[Means for Solving the Problems]
In the method for manufacturing an organic solid electrolytic capacitor of the present invention, the step of forming the first conductive polymer layer includes a step of forming a conductive polymer by vapor phase oxidation polymerization, and a step of forming the conductive polymer by liquid phase oxidation polymerization. Forming step.
[0008]
[Action and effect]
In the present invention, in the chemical oxidation polymerization, since the liquid phase oxidation polymerization is performed after the gas phase oxidation polymerization is performed, the conductive polymer can be formed also on the inner surface of the anode body by the gas phase oxidation polymerization, The first conductive polymer layer can be quickly formed by the polymerization.
Therefore, a capacitor having a higher capacitor capacity than before can be produced without reducing production efficiency.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
The capacitor element, which is a main part of the organic solid electrolytic capacitor of the present embodiment, has an anode lead wire attached to an anode body made of a valve metal such as Al or Ta. A dielectric oxide film is formed by electrolytic oxidation treatment, a first conductive polymer layer is formed on the dielectric oxide film by chemical oxidation polymerization, and electrolytic oxidation polymerization is formed on the first conductive polymer layer. To form a second conductive polymer layer, and use the first and second conductive polymer layers as cathode layers. In the capacitor element thus formed, a carbon and silver paste layer is formed on the cathode layer, a metal terminal plate is attached to each of the anode lead wire and the carbon and silver paste layers, and an outer shell is formed with epoxy resin or the like. By doing so, the organic solid electrolytic capacitor of the present embodiment is completed.
Although a foil, a sintered body, or the like can be used for the anode body, a sintered body is used in the present embodiment. In addition, as the conductive polymer, polypyrrole, polythiophene, polyfuran, polyaniline, derivatives thereof, and the like are used.
[0010]
In the manufacturing process of the capacitor element, a process of forming the first conductive polymer layer by gas phase oxidation polymerization and liquid phase oxidation polymerization which is a feature of the present invention will be described.
First, as shown in FIG. 1, the anode body (1) on which the dielectric oxide film is formed is immersed in a solution (2) containing the oxidant, so that the oxidant is deposited on the dielectric oxide film of the anode body. Attach. Here, as the oxidizing agent, any generally known oxidizing agent such as halogen and peroxide can be used.
Then, in order to open the holes closed by the solution (2) inside the anode body (1) which is a sintered body, a step of drying the anode body (1) to which the oxidizing agent is attached is added. Is also good.
[0011]
Next, as shown in FIG. 2A, the anode body (3) to which the oxidizing agent is attached is disposed above a solution (4) containing a monomer that can be a conductive polymer, and the solution ( The monomer evaporated from 4) is brought into contact with the anode body (3) for a predetermined time. Then, the evaporated monomer is oxidized and polymerized by the oxidizing agent attached to the anode body (3), and a conductive polymer is formed on the inner surface and the outer surface of the anode body (3) which is a sintered body. Is done. At this time, it is desirable that the anode body (3) is arranged near the liquid surface of the solution (4).
[0012]
Next, as shown in FIG. 2B, the anode body (3) is immersed in the solution (4). Then, the monomers in the solution (4) are oxidized and polymerized by the oxidizing agent attached to the anode body (3), and a conductive polymer is formed on the surface of the anode body (3). At this time, when the anode body (3) is immersed in the solution (4), the upper surface of the anode body (3) is at the same level as or slightly above the liquid level of the solution (4). It is desirable to arrange.
Through the above steps, the first conductive polymer layer is formed on the dielectric oxide film.
[0013]
When an appropriate substance is doped into the inside of the conductive polymer, the conductive polymer exhibits metallic properties and the conductivity is significantly increased. The substance to be doped is called a dopant.
Therefore, in the case of an electrolytic capacitor using a conductive polymer as the cathode layer, generally, in the step of forming the conductive polymer layer, by adding a dopant agent that gives a dopant, an appropriate substance is contained in the conductive polymer. Is doped.
As the dopant agent, a protic acid such as sulfuric acid or nitric acid, or a surfactant such as an alkyl sulfonate can be used. Examples of other compounds that can be used as the dopant agent are described in detail in Japanese Patent Publication No. 5-83167 and other books (eg, Katsumi Yoshino, Mitsunori Onoda: "Polymer Electronics", Corona Co., Ltd. (1996)). In the present application, the details are omitted.
[0014]
In the step of forming the first conductive polymer layer by the gas phase oxidation polymerization and the liquid phase oxidation polymerization, a dopant agent is added to the solution (2) containing the oxidizing agent or the solution (4) containing the monomer. .
In addition, when the dopant agent is added to the solution (2) containing the oxidant, if the compound (for example, a halogen, a transition metal halide, a protonic acid, or the like) can be used as both the oxidant and the dopant agent, the compound is added. Need only be included in the solution, and it is not necessary to include the two compounds of the oxidizing agent and the dopant agent in the solution.
[0015]
【Example】
Hereinafter, examples of the present invention and comparative examples will be described. In the following examples and comparative examples, a sintered body made of Ta was used as the anode body.
Example A Ta sintered body having a dielectric oxide film formed thereon was treated with hydrogen peroxide (concentration: 1 mol / L (mol / liter)) as an oxidizing agent and sulfuric acid (concentration: 0.2 mol / L) as a dopant agent. L) and immersed in an aqueous solution containing the solution for 10 minutes, and then taken out of the solution and dried.
Next, the Ta sintered body subjected to the above treatment is placed near the upper liquid surface of the solvent-free solution made of a pyrrole monomer for 20 minutes, and then the Ta sintered body is immersed in the solution for 10 minutes. Thereby, a first polypyrrole layer was formed on the dielectric oxide film by gas phase oxidation polymerization and liquid phase oxidation polymerization.
Next, the Ta sintered body that has been subjected to the above treatment is mixed with sodium alkylnaphthalenesulfonate (concentration: 0.05 mol / L, the average number of carbon atoms of the alkyl group is about 18) as a dopant agent, and pyrrole alone. A second polypyrrole layer by electrolytic oxidation polymerization on the first polypyrrole layer by immersing in an aqueous solution containing a monomer (concentration: 0.1 mol / L) and passing the aqueous solution with the first polypyrrole layer as a positive electrode did. Thereafter, the substrate was washed and dried to complete a capacitor element.
[0016]
Next, in the capacitor element, as described above, a carbon and silver paste layer is formed on the second polypyrrole layer, and a metal terminal plate is attached to each of the anode lead wires and the carbon and silver paint layers, and the epoxy resin or the like is used. After forming the outer shell, aging treatment was performed at 25 V to complete an organic solid electrolytic capacitor.
[0017]
Comparative Example 1
Comparative Example 1 was different from the above-described example in that the first polypyrrole layer was formed only by liquid phase oxidative polymerization. That is, in Comparative Example 1, a Ta sintered body having a dielectric oxide film formed thereon was treated with hydrogen peroxide (concentration 1 mol / L) as an oxidizing agent and sulfuric acid (concentration 0.2 mol / L) as a dopant agent. After being immersed in an aqueous solution for 10 minutes, taken out of the solution and dried, and then immersed in a solvent-free solution composed of a pyrrole monomer for 30 minutes, the dielectric oxide film is coated on the dielectric oxide film by liquid phase oxidative polymerization. One polypyrrole layer was formed.
[0018]
Comparative Example 2
Comparative Example 2 was different from the above example in that the first polypyrrole layer was formed only by gas phase oxidation polymerization, and the other steps were completed in the same manner as in the above example to complete an organic solid electrolytic capacitor. That is, in Comparative Example 2, the Ta sintered body on which the dielectric oxide film was formed was mixed with hydrogen peroxide (concentration 1 mol / L) as an oxidizing agent and sulfuric acid (concentration 0.2 mol / L) as a dopant agent. After being immersed in an aqueous solution for 10 minutes, taken out of the solution and dried, and then placed for 30 minutes near the upper liquid surface of a non-solvent solution composed of a pyrrole monomer, the solution is placed on the dielectric oxide film. Then, a first polypyrrole layer was formed by gas phase oxidation polymerization.
[0019]
When the capacitance at 120 Hz was measured for each of the capacitors manufactured as described above, it was 13.8 μF in the example, 12.0 μF in comparative example 1, and 9.6 μF in comparative example 2. Was. Therefore, it is understood that a capacitor having a higher capacitance than the conventional one can be manufactured by the present invention.
It is considered that the reason why the capacitance of Comparative Example 1 is lower than that of the Example is that the formation of the conductive polymer layer inside the Ta sintered body is insufficient. It is considered that the reason for the extremely low level is that the amount of the conductive polymer formed is insufficient.
[0020]
In the present invention, chemical oxidative polymerization is carried out by two steps of gas phase oxidative polymerization and liquid phase oxidative polymerization. More steps than polymerization.
However, as in the present embodiment shown in FIGS. 2A and 2B, gas phase oxidation polymerization and liquid phase oxidation polymerization can be performed by the same apparatus, and gas phase oxidation polymerization and liquid phase oxidation can be performed. Since the polymerization can be carried out continuously, a decrease in production efficiency due to an increase in the number of steps is small. Further, in the example, the comparative example 1 and the comparative example 2, since the time for forming the first conductive polymer layer is the same, the production efficiency does not decrease.
[0021]
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. In addition, the configuration of each part of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a step of attaching an oxidizing agent to an anode body having a dielectric oxide film formed thereon.
FIG. 2 (a) is a schematic diagram illustrating a process of gas phase oxidation polymerization in the present embodiment, and FIG. 2 (b) is a schematic diagram illustrating a process of liquid phase oxidation polymerization in the present embodiment.
[Explanation of symbols]
(1) Anode body on which dielectric oxide film is formed (2) Solution containing oxidant (3) Anode body with oxidant attached (4) Solution containing monomer that can be conductive polymer

Claims (5)

An anode body formed of a valve metal such as Al or Ta, a dielectric oxide film formed on the surface of the anode body, and a cathode layer formed of a conductive polymer on the dielectric oxide film. The cathode layer includes a first conductive polymer layer formed on the dielectric oxide film by chemical oxidative polymerization, and a second conductive polymer layer formed on the first conductive polymer layer by electrolytic oxidative polymerization. In an organic solid electrolytic capacitor comprising a conductive polymer layer,
An organic solid electrolytic capacitor, wherein the first conductive polymer layer is formed by performing gas-phase oxidation polymerization and liquid-phase oxidation polymerization in this order. The solid electrolytic capacitor according to claim 1, wherein the conductive polymer is polypyrrole, polyaniline, polythiophene, or a derivative thereof. A step of forming a dielectric oxide film on the surface of the anode body formed of a valve metal such as Al or Ta, and a step of forming a cathode layer on the dielectric oxide film using a solid conductive organic material. Including
The step of forming the cathode layer includes forming a first conductive polymer layer on the dielectric oxide film by chemical oxidative polymerization, and forming a second conductive polymer layer on the first conductive polymer layer by electrolytic oxidative polymerization. And forming a conductive polymer layer, the method for producing an organic solid electrolytic capacitor,
The step of forming the first conductive polymer layer is characterized in that a step of forming a conductive polymer by vapor phase oxidation polymerization and a step of forming a conductive polymer by liquid phase oxidation polymerization are performed in this order. To manufacture an organic solid electrolytic capacitor. The step of forming the first conductive polymer layer includes, first, a step of attaching an oxidizing agent to the anode body on which the dielectric oxide film has been formed,
The step of forming a conductive polymer by vapor phase oxidation polymerization is a step of introducing a gas containing a monomer of the conductive polymer to the anode body to which the oxidizing agent is attached,
The step of forming a conductive polymer by liquid-phase oxidation polymerization is a step of immersing the anode body on which the conductive polymer is formed by gas-phase oxidation polymerization, in a solution containing a monomer of the conductive polymer, A method for manufacturing an organic solid electrolytic capacitor according to claim 3. The method for manufacturing a solid electrolytic capacitor according to claim 3, wherein polypyrrole, polyaniline, polythiophene, or a derivative thereof is used as the conductive polymer.

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