JPH05226191A - Manufacture of solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent dielectric oxide films from being damaged by the contact of feeder electrodes during an electrolytic oxidation polymerization process and to prevent various characteristics from deteriorating. CONSTITUTION:A part of dielectric oxide film 3 in the vicinity of the drawing- out part of an anode wire 1 including the vicinity of the drawing-out part of the anode wire 1 is coated with a heat-resisting insulating substance 4, and a water absorptive resin substance 5 is formed on the surface of this heat resisting insulating substance 4. Subsequently, a chemical polymerization film 6 is formed on the surface of the remaining part of the dielectric oxide film including the surface of this water absorptive resin substance 5. Then a feeder electrode is brought into contact with a part of the chemical polymerization film 6 formed on the surface of the water absorptive resin substance 5, and an electrolytic polymerization film 7 is formed by electrolytic oxidation polymerization.

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 In recent years, various patents relating to a solid electrolytic capacitor using a conductive polymer film as a solid electrolyte have been proposed to meet the demand for miniaturization and high performance, and have been attracting attention.

In this solid electrolytic capacitor technology, a thin conductive polymer film is sequentially formed by chemical oxidative polymerization on the surface of an anode body obtained by forming an oxide film by forming a valve metal having a roughened surface. The thin conductive polymer film is used as an electrode to form an electrolytic oxidation polymerization means to form a thick conductive polymer film, on which a carbon layer and a conductive coating film are formed.

However, the solid electrolytic capacitor having such a structure is, in comparison with the conventional solid electrolytic capacitor,
It has characteristics such as good temperature characteristics and frequency characteristics, but since the feeding electrode in the electrolytic oxidation polymerization process is brought into contact with the thin conductive polymer film formed by chemical oxidation polymerization on the dielectric oxide film, As a result, the body oxide film is easily scratched, resulting in a factor of impairing the leakage current, and in an extreme case, it has a fatal defect that leads to a short circuit failure.

Therefore, a part of the anode wire drawn out from the sintered metal element is covered with a heat resistant insulator, and a conductive polymer film is formed on the dielectric oxide film including the surface of the heat resistant insulator by chemical oxidative polymerization. To form a conductive polymer film by electrolytic oxidation polymerization by contacting the feeding electrode on the conductive polymer film formed on the surface of the heat resistant insulator, thereby preventing damage to the dielectric oxide film. Preventive techniques are being tried.

However, since the surface of the heat-resistant insulator is smooth, the amount of the oxidant solution retained on the surface of the heat-resistant insulator in the chemical oxidative polymerization process is small, and as a result, the desired conductivity of the surface of the heat-resistant insulator is obtained. There was a problem that a polymer film was not formed, the capacity appearance rate and tan δ characteristics were both poor, and further, various characteristics over the life were deteriorated.

[0007]

As described above, a solid electrolytic capacitor using a conductive polymer film as a solid electrolyte is notable as one that meets the demand for miniaturization and high performance, but as an electrolytic oxidation polymerization means. However, in the structure that feeds electricity to the conductive polymer film formed by chemical oxidative polymerization formed on the oxide film, the dielectric oxide film is liable to be scratched and has a fatal drawback of inducing a short circuit defect. In the structure that feeds power to the conductive polymer film formed by chemical oxidative polymerization formed on the surface of the heat-resistant insulator coated on the part, the oxidant solution is not sufficiently retained on the surface of the heat-resistant insulator and It was difficult to form, and in any case there was a problem to be solved as this kind of solid electrolytic capacitor.

The present invention has been proposed in order to solve the problems of the prior art as described above, and an object thereof is to eliminate damage to a dielectric oxide film and to have a desired conductive polymer film structure. A method for manufacturing a solid electrolytic capacitor is provided.

[0009]

According to the method of manufacturing a solid electrolytic capacitor of the present invention, a dielectric oxide film is formed on the surface of an anode body made of a valve metal having an anode wire erected, and the anode wire lead-out portion is provided. Including a part of the dielectric oxide film located near the anode wire with a heat-resistant insulator, the surface of this heat-resistant insulator is covered with a water-absorbent resin body, and then a dielectric body containing this water-absorbent resin body surface. A conductive polymer film formed by chemical oxidative polymerization is formed on the oxide film, and then a part of the conductive polymer film formed by chemical oxidative polymerization formed on the surface of the water-absorbent resin body is brought into contact with a conductor as an anode. Electrolytically oxidatively polymerizes with the external cathode,
A conductive polymer film formed by electrolytic oxidation polymerization is formed on the conductive polymer film formed by the chemical oxidative polymerization.

Further, the water-absorbent resin is a polyacrylic acid salt, isobutylene maleic anhydride copolymer, starch acrylic acid graft copolymer, vinyl acrylate acrylate copolymer, polyacrylate acrylic fiber polymer,
It is characterized by being composed of polyvinyl alcohol, polyacrylic acid polyacrylic acid ester, and polyacrylamide polyethylene oxide.

[0011]

According to the method of manufacturing a solid electrolytic capacitor of the present invention having the above-described structure, the conductive polymer film formed by chemical oxidative polymerization, which is the contact point of the power feeding electrode in the electrolytic oxidative polymerization step, is heat resistant Since it is the surface portion of the water-absorbent resin body that covers the body surface, there is no damage to the dielectric oxide film, and the factor of characteristic deterioration due to damage to the dielectric oxide film is eliminated.

Further, since the water-absorbent resin body can absorb hundreds to thousands of times its own weight of water, it is possible to sufficiently hold the oxidant solution in the chemical oxidative polymerization and to obtain a desired thickness. The conductive polymer film can be uniformly formed by the chemical oxidative polymerization required for the formation of the conductive polymer film by the electrolytic oxidative polymerization, and has an excellent effect that can greatly contribute to the improvement of the life characteristics.

[0013]

EXAMPLES An example of the present invention will be described below.

That is, as shown in FIG. 1, the diameter is 0.3.
The tantalum powder in which the anode wire 1 made of a tantalum wire of mm is erected is molded into a size of 4.0 mm × 3.0 mm × 1.3 mm, and this is sintered at 1600 ° C. to form a sintered body 2. . Next, 70 V is applied to the sintered body 2 to perform a chemical conversion treatment to form a dielectric oxide film 3, and then the dielectric oxide film 3 located near the anode wire 1 lead-out portion including the anode wire 1 lead-out portion.
Is partially coated with a heat-resistant insulator 4 made of maleimide resin, and the surface of the heat-resistant insulator 4 is polyacrylate, isobutylene maleic anhydride copolymer, starch acrylic acid graft copolymer, vinyl acrylate acrylate. After being coated with a powder resin composed of a copolymer, a polyacrylic acid acrylic fiber polymer, polyvinyl alcohol, a polyacrylic acid polyacrylic acid ester, a polyacrylamide polyethylene oxide, etc., it is cured to form a water absorbent resin body 5. Then, the sintered body 2 on which the water-absorbent resin body 5 is formed is immersed in an aqueous solution of hydrogen peroxide 6M and sulfuric acid 3M for 10 minutes, and immediately immersed in a pyrrole solution for 20 minutes to perform chemical oxidative polymerization. Oxide film 3 and water absorbent resin body 5
A chemically polymerized film 6 made of polypyrrole, which is a conductive polymer film, is formed on top.

However, by immersion in an acetonitrile solution containing 1 mol / liter of a pyrrole monomer as an electrolytic solution and 1 mol / liter of sodium paratoluenesulfonate as a supporting electrolyte, a chemical oxidative polymerization formed on the surface of the water absorbent resin body 5 is performed. A platinum wire in contact with a part of the chemically polymerized film 6 made of polypyrrole, which is a conductive polymer film, is used as an anode, and constant current electrolytic oxidation polymerization (5
0 mA / cm ² , 1 h) to form an electropolymerized film 7 made of polypyrrole, which is a conductive polymer film, on the chemically polymerized film 6 and then immersed in colloidal carbon to form a carbon layer 8. A silver paste is applied on the carbon layer 8 to form a cathode conductor layer 9, and a capacitor element 10 is formed.
Make up.

Next, when a solid electrolytic capacitor having a chip structure is obtained by using this capacitor element 10, a cathode external terminal (not shown) is provided with a conductive silver adhesive on a part of the cathode conductor layer 9 of this capacitor element 10. And connecting an anode external terminal (not shown) to the anode lead wire 1 by welding, and then at least the cathode conductive layer 7 of the cathode external terminal.
A capacitor body (not shown) is formed by covering the entire capacitor element 10 including a connecting portion with and a connecting portion between the anode lead wire 1 and the anode external terminal with an exterior resin layer (not shown). The anode external terminal and the cathode external terminal led out from the side surface are bent so as to extend along the side surface of the capacitor body to the bottom surface of the capacitor body.

According to the method of manufacturing the solid electrolytic capacitor having the above-mentioned structure, the polypyrrole which is the conductive polymer film by the chemical oxidative polymerization which becomes the contact point of the platinum wire which is the power feeding electrode in the electrolytic oxidative polymerization step is formed. Chemically polymerized film 6
However, since it is the surface portion of the water-absorbent resin body 5 that covers the surface of the heat-resistant insulator 4, there is no damage to the dielectric oxide film 3, and the leakage current or tan resulting from the damage to the dielectric oxide film 3
There are no fatal defects such as δ characteristic deterioration and short circuit failure.

Further, since the water-absorbent resin body 5 can absorb several hundred to several thousand times its own weight of water, it is possible to sufficiently retain the oxidant solution in the chemical oxidative polymerization step, which is desirable. The chemically polymerized film 6 necessary for forming the electrolytic polymerized film 7 having a thickness can be uniformly formed, which greatly contributes to the improvement of tan δ and life characteristics.

Next, a characteristic comparison between the present invention and the conventional example will be described. That is, a solid electrolytic capacitor having a rated voltage of 10 V and a nominal capacitance of 33 μF (Example A) manufactured according to the above-described embodiment, and a solid electrolytic capacitor having a rated voltage of 10 V and a nominal capacitance of 33 μF manufactured by the following conventional example. When the initial characteristics of the capacitors (Conventional example B) and (Conventional example C) and the characteristics after the life test (85 ° C., 1000 h) were examined, the results shown in Tables 1 and 2 were obtained.

The number of samples in Table 1 and Table 2 is 100, respectively.
The numbers are average values, and the numbers in parentheses show variations. (Prior art example B) Except that the water absorbent resin was not formed, it was manufactured by the same means as in the above example. (Prior art example C) It was manufactured by the same means as the above-mentioned example except that the heat-resistant insulating coating and the water-absorbent resin body were not formed.

[0021]

[Table 1]

[0022]

[Table 2]

As is apparent from Tables 1 and 2, in the initial characteristics, the conventional example B has a poor capacity appearance rate and tan δ characteristic, and the conventional example C has an extremely poor leakage current characteristic and a short circuit failure. There are many occurrences and it is not practical. Further, in the conventional example B, the capacity appearance ratio and ta
The nδ characteristic is further deteriorated and unstable.

On the other hand, in the embodiment A of the present invention,
It was proved that the initial characteristics were stable in any of the characteristics, and that the stable characteristics were maintained even after the life test, and that it could contribute greatly to the improvement of the life characteristics.

The present invention is not limited to the above-mentioned embodiment. For example, as the sintered body, a metal having valve action such as aluminum or niobium other than tantalum, or a metal such as aluminum, tantalum, niobium or the like is used. Of course, it can be applied to the one using the metal foil having the valve action.

In the embodiments of the present invention, pyrrole was used as an example of the conductive polymer, but the same effect can be obtained by using thiophene, furan or aniline.

[0027]

As described above, according to the present invention, a solid electrolytic using a conductive polymer film having excellent initial characteristics and high practical value without deterioration of various characteristics at high temperature as a solid electrolyte. A method of manufacturing a capacitor can be obtained.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view showing a solid electrolytic capacitor in the process of manufacturing, which is obtained according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode wire 2 Sintered body 3 Dielectric oxide film 4 Heat resistant insulator 5 Water absorbent resin body 6 Chemically polymerized film 7 Electropolymerized film 8 Carbon layer 9 Cathode conductor layer 10 Capacitor element

Claims (2)

[Claims] 1. A step of forming a dielectric oxide film on a surface of an anode body made of valve metal having an anode wire planted thereon, and one of a dielectric oxide film located in the vicinity of the anode wire including the anode wire lead-out portion. Part with a heat-resistant insulator, the step of coating the surface of this heat-resistant insulator with a water-absorbent resin body, and the conductivity by chemical oxidative polymerization on the dielectric oxide film including this water-absorbent resin body surface. A step of forming a polymer film, and a conductive polymer film formed on the surface of the water-absorbent resin body by a chemical oxidation polymerization is brought into contact with a conductor as an anode to carry out electrolytic oxidation polymerization with an external cathode. And a step of forming a conductive polymer film by electrolytic oxidative polymerization on the conductive polymer film by chemical oxidative polymerization. 2. The water-absorbent resin material is polyacrylic acid salt, isobutylene maleic anhydride copolymer, starch acrylic acid graft copolymer, vinyl acrylate acrylate copolymer, polyacrylate acrylic fiber polymer, polyvinyl. The method for producing a solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is alcohol, polyacrylic acid polyacrylic acid ester, or polyacrylamide polyethylene oxide.