JPH1070043A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid electrolytic capacitor capable of obtaining a uniform, dense and excellent adhesion when a solid electrolyte layer made of a conductive polymer is formed on a dielectric oxide film. The purpose is to do. SOLUTION: A dielectric oxide film 12 is formed on the surface of an anode body 11 made of a porous valve metal, and two kinds of different liquid phase chemical oxidation polymerization and gas phase chemical oxidation polymerization are formed on the dielectric oxide film 12. Used solid electrolyte layer 1 made of conductive polymer
No. 3 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid electrolytic capacitor having a solid electrolyte layer made of a conductive polymer formed by chemically oxidatively polymerizing a heterocyclic compound and a derivative thereof.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become more sophisticated, electronic components having functions superior to conventional products have been demanded. Numerous functional materials have been developed and supplied to meet this demand, and one of them is a solid electrolyte layer made of a conductive polymer formed by chemically oxidizing and polymerizing a heterocyclic compound and its derivative. Some have been used.

As shown in FIGS. 5A and 5B, most of the solid electrolytic capacitors using aluminum or tantalum as an anode material and using manganese dioxide or lead dioxide as an inorganic solid electrolyte as an electrolyte. The anode foil 2 provided with the internal terminal portion 1 and sintering fine powder, or the anode foil provided with the internal terminal portion 3 and having a substantial surface area increased by roughening, A structure is employed in which the solid electrolyte 5 is baked on the anode plate 4 using a thermal decomposition reaction, and then the cathode layer 6 is sequentially formed with carbon, a conductive adhesive or the like. These solid electrolytic capacitors have the advantage that they are less temperature-dependent and have lower resistance in the high-frequency region than aluminum electrolytic capacitors that use an electrolytic solution, due to the characteristics of their electrolytes. It is also low and has a disadvantage in productivity due to restrictions on production methods.

In order to further reduce the resistance of the solid electrolyte 5, a charge transfer complex, TCNQ
An organic semiconductor capacitor using a salt, a solid electrolytic capacitor using a conductive polymer obtained by polymerizing a heterocyclic compound such as pyrrole, thiophene, or furan to make it conductive have been put into practical use.

[0005] Among them, conductive polymers have the characteristic that their specific resistance is remarkably low. Therefore, they are effective solid electrolytes for low resistance of capacitors, but the dielectric of the surface of the anode body made of porous valve metal is important. There is an extremely large restriction in forming a solid electrolyte layer made of a conductive polymer that is uniform, dense, and excellent in adhesion to a body oxide film.

[0006]

SUMMARY OF THE INVENTION Since conductive polymers have the characteristic that their specific resistance is extremely low, various kinds of solid electrolytes have been proposed and improved with respect to their production methods in recent years. When a solid electrolyte layer made of a conductive polymer is coated on a dielectric oxide film formed on the surface of an anode body made of a valve metal, the surface of the dielectric oxide film consisting of pores has a surface tension of the liquid to be immersed. Since it is greatly affected by the wettability of the dielectric oxide film surface and the surface of the dielectric oxide film, it is extremely difficult to form a solid electrolyte layer made of a conductive polymer that is uniform, dense and has excellent adhesion to the inside of the pores. is there.

In order to form a solid electrolyte layer made of a conductive polymer having uniform, dense and excellent adhesion to the inside of the pores, a heterocyclic compound and a derivative thereof are prepared by a liquid phase chemical method. There is a method of forming a fixed electrolyte layer made of a conductive polymer by oxidative polymerization. In this method, in order to carry out the oxidative polymerization of the heterocyclic compound and its derivative, it is general to treat with an oxidizing solution containing an oxidizing agent and / or an oxidation catalyst for promoting the oxidation. However, although this method can achieve its purpose, the coating efficiency on the outer layer is extremely poor, and there are large problems such as a rise in production cost and a problem in productivity associated with treatment of a large amount of waste liquid.

Further, in the liquid phase chemical oxidation polymerization, the balance between the reaction rate and the diffusion rate of the reacting polymerization liquid and the oxidizing liquid depends on the coating state of the solid electrolyte layer made of a conductive polymer formed on the dielectric oxide film. Therefore, it is very difficult to form a solid electrolyte layer made of a conductive polymer having a uniform, dense and excellent adhesion on the dielectric oxide film with a constant thickness.

The present invention has been made to solve the above-mentioned conventional problems. When a solid electrolyte layer made of a conductive polymer is formed on a dielectric oxide film, it is uniform, dense, and excellent in adhesion. It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor that can obtain the same.

[0010]

In order to achieve the above object, a method for manufacturing a solid electrolytic capacitor according to the present invention comprises forming a dielectric oxide film on a surface of an anode body made of a porous valve metal,
Further, a solid electrolyte layer made of a conductive polymer is formed on the dielectric oxide film by using two kinds of liquid phase chemical oxidation polymerization and gas phase chemical oxidation polymerization. In addition, a solid electrolyte layer made of a conductive polymer having uniform, dense, and excellent adhesion can be formed on the dielectric oxide film.

[0011]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, a dielectric oxide film is formed on the surface of an anode body made of a porous valve metal, and two different types of different oxide films are formed on the dielectric oxide film. A solid electrolyte layer made of a conductive polymer is formed by using liquid phase chemical oxidation polymerization and gas phase chemical oxidation polymerization. According to this production method, two different liquid phase chemical oxidation polymerizations and gas By the combination of phase chemical oxidation polymerization, it is possible to form a solid electrolyte layer made of a conductive polymer with uniform, dense and excellent adhesion from the inside of the pores of the anode body made of a porous valve metal to the outer layer. Therefore, the present invention can be applied to a product requiring low impedance in a high frequency region.

According to a second aspect of the present invention, a liquid-phase chemical oxidation polymerization and a gas-phase chemical oxidation polymerization are alternately applied. When the solid electrolyte layer is formed by chemical oxidation polymerization, a solid electrolyte layer made of a conductive polymer having uniform, dense, and excellent adhesion from the inside of the pores of the anode body made of a porous valve metal to the outer layer is formed. It can be formed efficiently.

According to a third aspect of the present invention, the liquid-phase chemical oxidation polymerization and the gas-phase chemical oxidation polymerization are alternately applied a plurality of times, respectively. When the solid electrolyte layer is formed by chemical oxidation polymerization, a uniform, dense, and highly adherent conductive polymer film is formed from the inside of the pores of the anode body made of porous valve metal to the outer layer with high productivity. It can be formed.

According to a fourth aspect of the present invention, the removal of the oxidizing agent residue and the repair of the anodic oxide film are performed for each of the repeating units of the liquid-phase chemical oxidation polymerization and the gas-phase chemical oxidation polymerization which are applied alternately several times. According to this manufacturing method, since the oxidizing agent residue is removed and the anodic oxide film is repaired for each repeating unit of chemical oxidation polymerization, it is possible to obtain an excellent leakage current characteristic. You can do it.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to the present invention. Reference numeral 11 denotes an anode body made of a porous valve metal, and the surface of the anode body 11 has a dielectric oxide film 12 formed by means such as anodic oxidation. Is formed, and a solid electrolyte layer 13 made of a conductive polymer is formed on the dielectric oxide film 12 by alternately applying liquid phase chemical oxidation polymerization and gas phase chemical oxidation polymerization once or a plurality of times. Thereafter, the solid electrolyte layer 13 made of a conductive polymer is formed.
, A colloidal graphite 14 and a silver coating 15 are sequentially applied, and thereafter, a predetermined exterior 16 is applied to form a solid electrolytic capacitor.

Next, specific embodiments 1, 2, 2
3 and a comparative example will be described. (Embodiment 1) As shown in FIG. 2, a tantalum powder as a porous valve metal having a thickness of 0.9 mm, a width of 2.0 mm and a length of 1.3 mm was obtained by pressure molding and vacuum sintering. Anodizing was performed on the surface of anode body 21 at 30 V in a phosphoric acid aqueous solution having a concentration of 5% by weight to form dielectric oxide film 22. Next, this anode body 21 was prepared by mixing 0.7 mol / l of a pyrrole monomer which is a heterocyclic compound and its derivative, and 0.05 mol / l of naphthalenesulfonic acid which was a surfactant and a dopant.
After immersion in an aqueous solution containing
Liquid phase chemical oxidation polymerization is performed by immersing in an oxidizing solution containing 0.05 mol / l of an iron salt of naphthalene sulfonic acid, and then gas phase chemical oxidation polymerization is performed by directly exposing to a pyrrole monomer vapor at 0 ° C. for 30 minutes. Thereafter, the oxidizing agent residue was removed by washing in running water of ion-exchanged water for 10 minutes.
The unit chemical oxidative polymerization of drying for 10 minutes was repeated 15 times to form a solid electrolyte layer 23 made of a conductive polymer. Thereafter, colloidal graphite 24 and silver paint 25 were applied on solid electrolyte layer 23 made of a conductive polymer, and thereafter, a predetermined exterior was provided to form a solid electrolytic capacitor.

(Embodiment 2) As shown in FIG. 2, tantalum powder, which is a porous valve metal having a thickness of 0.9 mm, a width of 2.0 mm and a length of 1.3 mm, is subjected to pressure molding and vacuum sintering. A phosphoric acid solution having a concentration of 5% by weight
The dielectric oxide film 22 was formed by anodic oxidation of 0V. Next, the anode body 21 is immersed in an aqueous solution containing 0.7 mol / l of a pyrrole monomer which is a heterocyclic compound and a derivative thereof, and 0.05 mol / l of naphthalenesulfonic acid which is a surfactant and a dopant, and subsequently Liquid phase chemical oxidative polymerization is carried out by immersion in an oxidizing solution containing a surfactant and 0.05 mol / l of an iron salt of naphthalenesulfonic acid.
After performing gas phase chemical oxidation polymerization by exposing for 0 minute, and then immersing again in the oxidizing solution to perform liquid phase chemical oxidation polymerization, repeating gas phase chemical oxidation polymerization by exposing to pyrrole monomer vapor at 0 ° C. for 30 minutes. After that, a solid electrolyte composed of a conductive polymer is obtained by repeating unit chemical oxidation polymerization eight times, in which the oxidizing agent residue is removed by washing in running water of ion-exchanged water for 10 minutes and then drying at 105 ° C. for 10 minutes. Layer 23 was formed. Thereafter, the electrolyte layer 2 made of a conductive polymer is used.
3 was coated with colloidal graphite 24 and silver paint 25 in that order, and then provided with a predetermined exterior to form a solid electrolytic capacitor.

(Embodiment 3) Oxidative polymerization is carried out in the same manner as in Embodiment 2, and the oxidizing agent residue is washed and removed. Then, the anodic oxide film is repaired for 10 minutes in an electrolytic solution having a conductivity of 100 mS / cm. After that, the unit chemical oxidation polymerization of drying at 105 ° C. for 10 minutes was repeated eight times to form a solid electrolyte layer 23 made of a conductive polymer. Thereafter, a colloidal graphite 24 and a silver paint 25 were sequentially applied on a solid electrolyte layer 23 made of a conductive polymer, and thereafter, a predetermined exterior was provided to form a solid electrolytic capacitor.

Comparative Example As shown in FIG.
Anode body 3 obtained by pressing and vacuum sintering tantalum powder, which is a porous valve metal having a diameter of 2.0 mm, a width of 2.0 mm and a length of 1.3 mm.
A dielectric oxide film 32 was formed on the surface of No. 1 by performing anodization at 30 V in a phosphoric acid aqueous solution having a concentration of 5% by weight. Next, the anode body 31 is immersed in an aqueous solution of manganese nitrate having a concentration of 15% by weight, and then thermally decomposed in a pyrolysis furnace at 250 ° C. for 10 minutes, and then washed in running water of ion-exchanged water for 10 minutes. Is performed, the unit thermal decomposition of repairing the anodic oxide film in an electrolytic solution having a conductivity of 100 mS / cm for 10 minutes is repeated six times, and then the unit is thermally immersed in a 30% by weight manganese nitrate aqueous solution. Is repeated four times to form a solid electrolyte layer 33 made of manganese dioxide on the dielectric oxide film 32. Thereafter, a colloidal graphite 34 and a silver paint 35 were sequentially applied onto the solid electrolyte layer 33, and then a predetermined exterior was provided to form a solid electrolytic capacitor.

Table 1 shows Embodiments 1, 2, and 3 of the present invention.
FIG. 9 shows the results of measurement of basic electrical properties (capacitance, loss angle tangent, and leakage current) of each of the tantalum solid electrolytic capacitors obtained by Comparative Examples and Comparative Examples.
FIG. 4 shows the frequency characteristics of these impedances.

[0021]

[Table 1]

As apparent from Table 1, the first, second, and third embodiments of the present invention are superior in the basic electric performance as compared with the comparative example, and as is clear from FIG. Regarding the frequency characteristics, the effects of the low resistance of the solid electrolyte layer made of the conductive polymer are clear in the first, second, and third embodiments of the present invention as compared with the comparative example.

In Embodiments 1 and 2 of the present invention, both retain the advantages of basic liquid phase chemical oxidative polymerization as they are, but in Embodiment 2 of the present invention, the coating efficiency is further improved. It is excellent.

In Embodiments 2 and 3 of the present invention, the anodic oxide film is not thermally degraded as in the case of manganese dioxide utilizing thermal decomposition shown in the comparative example. By repairing the anodic oxide film for each unit of chemical oxidation polymerization as in Embodiment 3, a material having excellent leakage current characteristics can be obtained.

The first, second, and third embodiments of the present invention are described.
, Pressure molding of tantalum powder as the anode body 21,
Vacuum sintered was used, but the material is not limited to this, and any material can be used as long as the anode body is made of a porous valve metal. An aqueous solution is generally used as a solution for liquid phase chemical oxidation polymerization, but a single or mixed solution of a solvent that enhances the dissolution of a heterocyclic compound and its derivative, benzene, naphthalene and its derivative, and the like is used. It may be.

[0026]

As described above, according to the method for manufacturing a fixed electrolytic capacitor of the present invention, a dielectric oxide film is formed on the surface of an anode body made of a porous valve metal, and two types of dielectric oxide films are formed on the dielectric oxide film. A solid electrolyte layer made of a conductive polymer is formed by using different liquid phase chemical oxidation polymerization and gas phase chemical oxidation polymerization. When formed on a dielectric oxide film by chemical oxidative polymerization, the liquid phase chemical oxidative polymerization introduces a uniform, dense and highly adherent conductive polymer inside the pores of the anode body. The solid electrolyte layer can be formed by coating, and a solid electrolyte layer made of a uniform conductive polymer can be formed by coating on the outer part of the anode body by introducing gas phase chemical oxidation polymerization. Oxidative polymerization is mono What can be effectively used over, because of the advantages such that no waste, in view of resource saving,
It is also desirable from the viewpoint of environmental protection. Also, since there is no loss due to diffusion of the oxidizing solution held on the surface of the dielectric oxide film, and gas phase chemical oxidation polymerization proceeds from the surface layer, the outer layer portion of the dielectric oxide film is particularly preferable. It has the characteristic that a solid electrolyte layer made of a uniform conductive polymer can be formed to a certain thickness in a small number of times, and the electrical characteristics of the resulting solid electrolytic capacitor are stable and excellent. Is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a solid electrolytic capacitor of the present invention.

FIG. 2 is a cutaway perspective view showing a solid electrolytic capacitor according to Embodiments 1, 2, and 3 of the present invention.

FIG. 3 is a cutaway perspective view showing a solid electrolytic condenser in a comparative example.

FIG. 4 is a characteristic diagram showing the relationship between the impedance and the measurement frequency of the solid electrolytic capacitors obtained by the first, second, and third embodiments of the present invention and the comparative example.

5A is a cutaway perspective view of a capacitor element formed of an anode body in a conventional solid electrolytic capacitor, and FIG. 5B is a cutaway perspective view of a capacitor element formed of an anode foil or an anode plate in a conventional solid electrolytic capacitor.

[Explanation of symbols]

 11, 21 Anode body 12, 22 Dielectric oxide film 13, 33 Solid electrolyte layer made of conductive polymer

Claims (4)

[Claims] 1. A dielectric oxide film is formed on the surface of an anode body made of a porous valve metal, and two different liquid-phase chemical oxidation polymerizations and gas-phase chemical oxidation polymerizations are formed on the dielectric oxide film. A method for manufacturing a solid electrolytic capacitor that forms a solid electrolyte layer made of a conductive polymer. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein liquid phase chemical oxidation polymerization and gas phase chemical oxidation polymerization are alternately applied. 3. The method according to claim 1, wherein the liquid-phase chemical oxidation polymerization and the gas-phase chemical oxidation polymerization are alternately applied a plurality of times.
The manufacturing method of the solid electrolytic capacitor described in the above. 4. The method according to claim 3, wherein the oxidizing agent residue is removed and the anodic oxide film is repaired for each repeating unit of the liquid phase chemical oxidation polymerization and the gas phase chemical oxidation polymerization, which are applied alternately a plurality of times. The manufacturing method of the solid electrolytic capacitor described in the above.