JP3083587B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer film as a solid electrolyte.

[0002]

2. Description of the Related Art A conductive polymer film such as polypyrrol, polythiophene, polyaniline or polyfuran is used as a solid electrolyte for an anode body made of a film-forming metal such as aluminum or tantalum having a dielectric oxide film formed on the surface. Known solid electrolytic capacitors are known.

A solid electrolytic capacitor using such a conductive polymer film as a solid electrolyte is one using a generally used driving electrolyte, or one using an organic semiconductor, which has recently attracted attention, as a solid electrolyte. It has better temperature characteristics, frequency and high-temperature load characteristics (lifetime) than electrolytic capacitors, but when forming a conductive polymer film by chemical oxidation polymerization reaction, the complex five-membered ring compound of the chemical oxidation polymerization solution is simply Since it consists only of a monomer and has no reaction nuclei, the efficiency of forming a conductive polymer film as a solid electrolyte on the fine pores and the inner surface of the voids in the anode body is poor, and the capacitance decreases, the withstand voltage decreases,
As a result, there is a problem that tan δ is likely to occur.

[0004]

As described above, in the conductive polymer film forming technology as a solid electrolyte disclosed in the prior art, the conductive polymer as a solid electrolyte is applied to the fine pores and the inner surfaces of the voids in the anode body. The formation efficiency of the film was poor, causing a decrease in various characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and efficiently forms a conductive polymer film as a solid electrolyte on the inner surfaces of micropores and voids of an anode body having a dielectric oxide film formed thereon. The present invention provides a method for manufacturing a solid electrolytic capacitor capable of improving a decrease in capacitance, a decrease in withstand voltage, a large tan δ, and the like caused by a shortage of a solid electrolyte formed on a surface of a dielectric oxide film formed on an anode body. It is intended for.

[0006]

According to a method of manufacturing a solid electrolytic capacitor according to the present invention, as a means for forming a chemically polymerized film on an anode body on which a dielectric oxide film has been formed, an anode body on which a dielectric oxide film has been formed is polymerized. Is immersed in a heteropentacyclic compound solution containing 3 to 10 heteropentacyclic polymer,
It is characterized in that chemical oxidative polymerization is immediately performed in an oxidizing agent solution.

[0007]

According to the method of manufacturing a solid electrolytic capacitor having the above-described structure, a heteropentacyclic compound compound having a degree of polymerization of 3 to 10 contained in a heteropentacyclic compound solution acts as a reaction nucleus and has a high conductivity. Since the formation reaction of the molecular film is remarkably promoted, the conductive polymer film is efficiently formed up to the fine pores and the inner surfaces of the voids of the anode body, which greatly contributes to the improvement of various characteristics.

[0008]

An embodiment of the present invention will be described below.

That is, after the surface is roughened, an anode foil made of a high-purity aluminum foil having a dielectric oxide film formed by applying a voltage of 50 V in an aqueous solution of ammonium adipate, for example, is reformed. Was immersed in a 2 mol / l pyrrol / ethanol solution containing 0.01 mol / l, and immediately immersed in an oxidizing agent solution composed of an aqueous solution of 5 mol / l ammonium persulfate to carry out chemical oxidative polymerization. A chemically polymerized polypyrrole film is formed on the surface of the formed dielectric oxide film.

Next, a capacitor element is manufactured by winding the anode foil having the above-described structure, and then the dielectric oxide film is repaired by re-chemical formation.
A chemically polymerized polypyrrole film formed by chemical oxidative polymerization by immersion in an acetonitrile solution containing 1 mol / l of lumonomer and 1 mol / l of sodium paratoluenesulfonate as a supporting electrolyte is used as an anode, and a direct current is measured between the film and an external cathode. An electric current is applied, and an electrolytically polymerized polypyrrole film is formed inside and outside the element including the surface of the anode foil by electrolytic oxidation polymerization.

Next, a colloidal carbon is applied to the surface of the electrolytically polymerized polypyrrole film formed on the surface of the capacitor element and dried to form a colloidal carbon layer, and then a silver paste is applied to form a cathode layer. Finally, a resin sheath is applied to obtain a solid electrolytic capacitor.

FIG. 1 is a cross-sectional view for explaining a capacitor element structure obtained by the above configuration, wherein 1 is an anode foil,
2 is a dielectric oxide film, 3 is a chemically polymerized polypyrrole film, 4
Denotes an electrolytic polymerized polypyrrole film, 5 denotes a colloidal carbon layer, and 6 denotes a cathode layer.

According to the method of manufacturing a solid electrolytic capacitor having the above-described structure, the pyrrole hexamer contained in the pyrrole / ethanol solution as a heteropentacyclic compound acts as a reaction nucleus, and Since the formation reaction of the chemically polymerized polypyrrole film as the film is remarkably accelerated, the chemically polymerized polypyrrole film as the conductive polymer film is efficiently formed up to the fine pores and the inner surfaces of the voids of the anode body, thereby improving the capacitance appearance rate. At the beginning, it greatly contributes to the improvement of the reduction of tan δ and leakage current.

Next, comparison of characteristics between the present invention and the conventional example will be described based on experimental results. That is, the characteristics of the present invention (A) manufactured by the above embodiment and the conventional example (B) manufactured by the same means as the above embodiment except that the hexamer of pyrrole is not included as the chemical oxidation polymerization means are compared. The results were as shown in the table below.

The samples were rated at 16 V for both (A) and (B).
The values are -10 μF, and each of them is 50, and the values in the table are average values.

[0016]

【table】

As is clear from the above table, the device according to the present invention demonstrated superior effects in the capacitance, tan δ and leakage current characteristics as compared with the conventional example.

In the above example, the degree of polymerization of the heteropentacyclic compound compound contained in the heteropentacyclic compound solution was 6
However, from the experimental results of the present inventors, it was confirmed that the degree of polymerization of these polymers is preferably 3 to 10, and preferably 5 to 7 is more effective.

The reason for this is that if the degree of polymerization is less than 3, no reaction accelerating effect can be obtained, and if the degree of polymerization exceeds 10, the chemically polymerized polypyrrole film as the conductive polymer film formed will be inferior. In addition, the deposition rate on the dielectric oxide film decreases, and at the same time, the resistance value of the chemically polymerized polypyrrole film as a whole increases, conversely, the capacitance decreases, the withstand voltage decreases, and the tan δ increases. This is based on the experimental results of the present inventor who bring about such effects.

In the above embodiment, the means for forming a conductive polymer film as a solid electrolyte has been described by exemplifying a means for forming an electrolytically polymerized polypyrrole film on a chemically polymerized polypyrrole film by electrolytic oxidation polymerization. However, the anode body on which the first chemically polymerized polypyrrole film is formed by the means described in the above embodiment is immersed in an unreacted mixed solution of a heteropentacyclic compound and an oxidizing agent, and the mixed solution is reacted. The second chemical oxidation polymerization is performed a plurality of times to form a second-layer chemically polymerized polypyrrole film, or the chemical oxidation polymerization means described in the above embodiment is repeated to perform electrolytic oxidation polymerization. Even if a conductive polymer film is formed without performing this, the same effect can be achieved in achieving the object of the present invention.

Further, in the above-described embodiment, a foil wound type is described as an example of a capacitor element configuration, but a capacitor element formed by molding and sintering a valve action metal powder or a foil laminated type element including a single foil type It is needless to say that the present invention can be applied to those having a configuration.

[0022]

According to the present invention, it is possible to efficiently form a conductive polymer film as a solid electrolyte evenly from the surface of the anode foil on which the dielectric oxide film has been formed to the inner surface of the fine pores and voids of the anode foil. And thus the capacitance, t
An δ and a method of manufacturing a solid electrolytic capacitor having a high practical value and capable of significantly improving the leakage current characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an element structure of a solid electrolytic capacitor obtained according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 anode foil 2 dielectric oxide film 3 chemically polymerized polypyrrole film 4 electrolytically polymerized polypyrrole film

Claims (1)

(57) [Claims] 1. A method for manufacturing a solid electrolytic capacitor, comprising sequentially forming at least a chemically polymerized film, a carbon layer and a conductive coating film on an anode body made of a film-forming metal having a dielectric oxide film formed thereon. As means, the anode body is immersed in a heteropentacyclic compound solution containing a heteropentacyclic polymer having a degree of polymerization of 3 to 10, and then chemically oxidized and polymerized immediately in an oxidizing agent solution. To manufacture solid electrolytic capacitors.