JPH09246104A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid electrolytic capacitor which enable obtaining uniformity, compactness and excellent adhesion in the case where a conductive polyelectrolyte layer is formed on a dielectric oxide film. SOLUTION: A dielectric oxide film 12 is formed on the surface of an electrode body 11, and subsequently, the electrode body 11 is immersed into a metal oxide semiconductor forming solution having a density lower than 30wt.%, thereby forming a metal oxide semiconductor layer 13 as a conductive precoated layer on the dielectric oxide film. Such forming processing is performed twice or less at most. Then, a first conductive polyelectrolyte layer 14 is formed by chemical oxidation polymerization and a second conductive polyelectrolyte layer 15 is formed on the first conductive polyelectrolyte layer 14 by electrolytic oxidation polymerization.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a solid electrolytic capacitor having a conductive polymer electrolyte layer as a solid electrolyte.

[0002]

2. Description of the Related Art In recent years, with the increase in frequency of power supply circuits for electronic equipment, excellent electronic characteristics (impedance characteristics) are required for all electronic components. In order to achieve these, solid electrolytic capacitors are no exception, and in order to achieve these, improvements and studies from all angles, such as the surface condition of the anode, the method of forming the oxide film, the improvement of the electrolyte layer, the surface condition of the cathode, the structure of the capacitor element, etc. Has been done.

As shown in FIGS. 9 (a) and 9 (b), most solid electrolytic capacitors using aluminum or tantalum as an anode material and manganese dioxide or lead dioxide which is an inorganic solid electrolyte as an electrolyte are mostly used. The anode foil or the anode plate 4 having an internal terminal 1 and an anode body 2 or an internal terminal 3 formed by sintering fine powder, and having a substantial surface area increased by roughening due to restrictions in the manufacturing method. In addition, a structure is adopted in which the solid electrolyte 5 is baked and formed by utilizing a thermal decomposition reaction, and then the cathode layer 6 is sequentially formed by carbon, a conductive adhesive, or the like. Due to the characteristics of the electrolyte, these solid electrolytic capacitors have the advantages of less temperature dependence and lower resistance in the high-frequency region than aluminum electrolytic capacitors that use an electrolytic solution, but on the other hand, they have a high withstand voltage. Is low, and it is also disadvantageous in terms of productivity due to the limitations of the production method.

In order to further reduce the resistance of the solid electrolyte 5, a charge transfer complex, TCNQ
Organic semiconductor capacitors using salts and functional polymer capacitors using conductive polymers obtained by polymerizing heterocyclic compounds such as pyrrole, thiophene, and furan to make them conductive have been put to practical use.

Among these, the conductive polymer is a solid electrolyte which is effective for lowering the resistance of the capacitor because it has a characteristic that its specific resistance is remarkably low. However, the conductive polymer has an electrode body made of a porous valve metal. In order to coat and form a conductive polymer electrolyte layer that is uniform, dense, and has excellent adhesiveness on the surface of the dielectric oxide film, there are extremely large restrictions.

When the conductive polymer electrolyte layer is formed by coating on the dielectric oxide film formed on the surface of the electrode body made of a porous valve metal, it is generally formed by electrolytic oxidation polymerization. In the case of this electrolytic oxidative polymerization, it is possible to obtain an extremely dense and excellent conductive material under the selected conditions, but it is possible to obtain high conductivity even inside the pores that constitute the dielectric oxide film. It is extremely difficult to form a molecular electrolyte layer, and therefore, Japanese Patent Publication No.
Japanese Patent Publication No. 3 discloses a method in which a conductive polymer electrolyte layer is formed even inside pores by chemical oxidative polymerization and then electrolytic oxidative polymerization is performed using this as an anode.

[0007]

The chemical oxidative polymerization has the feature that it is advantageous for forming the conductive polymer electrolyte layer even inside the pores constituting the dielectric oxide film. In Japanese Patent Publication No. 4-74853,
The chemical oxidative polymerization is carried out prior to the electrolytic oxidative polymerization to make up for the drawbacks of the electrolytic oxidative polymerization. However, the surface of the dielectric oxide film consisting of pores is the surface tension of the liquid to be immersed and the dielectric oxide film. Since the wettability of the surface is greatly affected, it is extremely difficult to form a conductive polymer electrolyte layer that is uniform, dense, and has excellent adhesiveness even inside the pores. Therefore, the conductive polymer electrolyte layer obtained from the heterocyclic compound and its derivative is
Although there are some differences depending on the forming method, the adhesiveness is inherently poor and the density greatly depends on the forming conditions. Contrary to the low specific resistance of the electrolyte itself, this is the solid electrolytic capacitor actually obtained. Was one of the causes of lot variation in the electrical characteristics.

The present invention has been made in order to solve the above-mentioned conventional problems, and when forming a conductive polymer electrolyte layer on a dielectric oxide film, one which is uniform, dense and excellent in adhesion is desired. It is an object of the present invention to provide a method for manufacturing the obtained solid electrolytic capacitor.

[0009]

In order to achieve the above object, a method for producing a solid electrolytic capacitor of the present invention comprises forming a dielectric oxide film on the surface of an electrode body made of a porous valve metal,
Then, a forming treatment of forming a metal oxide semiconductor layer as a conductive precoat layer on the dielectric oxide film by immersing the electrode body in a solution for forming a metal oxide semiconductor layer having a concentration lower than 30% by weight. At most twice, and then immersing the electrode body in a solution containing a heterocyclic compound and its derivative, and an oxidizing agent and a dopant having an electrode potential higher than that of the heterocyclic compound and its derivative. The step of immersing the electrode body in a solution containing a is alternately repeated a plurality of times to form a first conductive polymer electrolyte layer by chemical oxidative polymerization, and further on the first conductive polymer electrolyte layer, The second conductive polymer electrolyte layer is formed by electrolytic oxidation polymerization. According to this manufacturing method, the conductive polymer electrolyte can be formed evenly on the dielectric oxide film. And in which is obtained has excellent dense and adhesion.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises forming a dielectric oxide film on the surface of an electrode body made of a porous valve metal, and then forming a metal oxide semiconductor at a concentration lower than 30% by weight. The formation treatment of forming the metal oxide semiconductor layer as the conductive precoat layer on the dielectric oxide film by immersing the electrode body in the layer forming solution is performed at most twice, and then the heterocyclic A plurality of steps of immersing the electrode body in a solution containing a compound and its derivative, and immersing the electrode body in a solution containing an oxidizing agent and a dopant having an electrode potential higher than the oxidation potential of the heterocyclic compound and its derivative The first conductive polymer electrolyte layer is formed by chemical oxidative polymerization by repeating alternately alternately, and the second conductive polymer is formed on the first conductive polymer electrolyte layer by electrolytic oxidative polymerization. The degrading layer is formed, and according to this manufacturing method, prior to forming the first conductive polymer electrolyte layer, which is a solid electrolyte, on the dielectric oxide film by chemical oxidative polymerization, A metal oxide semiconductor layer as a conductive precoat layer is formed on the dielectric oxide film by immersing the electrode body having the dielectric oxide film formed on the surface thereof in a solution for forming a metal oxide semiconductor having a concentration lower than 30% by weight. The metal oxide semiconductor layer as a conductive pre-coat layer is formed on the dielectric oxide film by performing the forming process of forming the metal oxide semiconductor layer at most twice. If you look at it, it is a collection of fine crystal particles, but macroscopically, for the dielectric oxide film formed on the surface of the electrode body made of porous valve metal,
In order to form a connection interface that is uniform, dense, and has excellent adhesiveness, the step of subsequently immersing the electrode body in a solution containing the heterocyclic compound and its derivative, and the heterocyclic compound and its derivative An oxidizer with a high electrode potential,
When the chemical oxidative polymerization was performed by alternately repeating the step of immersing the electrode body in the solution containing the dopant a plurality of times, the heterocyclic compound and its derivative were accumulated as fine crystal particles constituting the metal oxide semiconductor layer. The uneven portions prevent the heterocyclic compound and its derivative from moving very quickly to form the first conductive polymer electrolyte layer on the dielectric oxide film formed on the surface of the electrode body. It can be formed.

As described above, the metal oxide semiconductor layer as the conductive precoat layer has excellent adhesion to the first conductive polymer electrolyte layer due to the anchoring effect due to the irregularities in which the fine crystal particles are accumulated. Since the second conductive polymer electrolyte layer is formed on the first conductive polymer electrolyte layer by electrolytic oxidation polymerization, the second conductive polymer electrolyte layer is formed on the second conductive polymer electrolyte layer. It is possible to obtain a conductive polymer electrolyte layer that is extremely dense and has excellent electrical conductivity, and the resulting solid electrolytic capacitor will have extremely stable and excellent electrical characteristics and reliability.

The invention according to claim 2 provides a solution for forming a metal oxide semiconductor layer having a concentration of less than 30% by weight, which is 1% by weight.
The following nonionic surfactant is added, and according to this production method, 1% by weight or less of the nonionic surfactant is added to the solution for forming the metal oxide semiconductor layer. In addition to providing excellent stability, basic electric performance (capacitance, loss tangent, leakage current) can be further improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 are schematic cross-sectional views of the solid electrolytic capacitor of the present invention, in which 11 is an electrode body made of a porous valve metal serving as an anode.
A dielectric oxide film 12 is formed on the surface of the metal oxide film by means of anodic oxidation or the like, and a metal oxide in which fine crystal particles as an ultrathin conductive precoat layer are accumulated on the dielectric oxide film 12. After forming the semiconductor layer 13, the first conductive polymer electrolyte layer 14 is formed by chemical oxidative polymerization of the heterocyclic compound and its derivative, and further on the first conductive polymer electrolyte layer 14. The second conductive polymer electrolyte layer 15 is formed by electrolytic oxidation polymerization. Then, after this, colloidal graphite 16 and silver paint 17 are sequentially applied on the second conductive polymer electrolyte layer 15,
Then, a predetermined exterior 18 is applied to form a solid electrolytic capacitor.

Next, specific embodiments 1, 2 of the present invention will be described.
3 and Comparative Examples 1 and 2 will be described.

(Embodiment 1) As shown in FIG. 3, an anode is obtained by pressure molding and vacuum sintering tantalum powder having a thickness of 0.9 mm, a width of 2.0 mm and a length of 1.3 mm. Electrode body 21
A 30 V anodic oxidation is performed on the surface of the phosphor in an aqueous solution of phosphoric acid having a concentration of 5% by weight to form a dielectric oxide film 22.
The electrode body 21 was immersed in a 25 wt% manganese nitrate aqueous solution and thermally decomposed at 250 ° C. to form a metal oxide semiconductor layer 23 as a conductive precoat layer on the dielectric oxide film 22. In this case, 1 thermal decomposition work
Pre-coating product that has been subjected to repair formation after being subjected to heat treatment, heat-decomposition work has been performed twice, pre-coating product that has been subjected to repair formation, and heat-decomposition work has been performed three times and then pre-coating treatment to have been subjected to repair formation After the product and the thermal decomposition work were performed four times, four types of precoat-treated products were obtained, that is, a precoat-treated product subjected to restoration chemical conversion.

Then, a step of immersing the precoat-treated product in a solution containing 0.7 mol / l of a heterocyclic compound and a derivative thereof, a pyrrole monomer, and a surfactant,
The precoat treatment is performed on a solution containing 0.1 mol / l of ammonium peroxodisulfate, which is an oxidant having an electrode potential higher than that of a heterocyclic compound and its derivative, and 0.05 mol / l of naphthalenesulfonic acid, which is a dopant. The step of immersing the product is alternately repeated 10 times to form the first conductive polymer electrolyte layer 24 by chemical oxidative polymerization, and then 0.25 mol / l of a heterocyclic compound and its derivative, a pyrrole monomer, and a dopant. The second conductive polymer electrolyte layer 25 was formed by performing electrolytic oxidative polymerization in a solution containing 0.05 mol / l of naphthalenesulfonic acid. After that, colloidal graphite 26 and silver paint 27 are formed on the second conductive polymer electrolyte layer 25.
Was sequentially applied, and then a predetermined exterior was applied to form a solid electrolytic capacitor.

(Embodiment 2) As shown in FIG. 3, a tantalum powder having a thickness of 0.9 mm, a width of 2.0 mm and a length of 1.3 mm is pressure-molded and vacuum-sintered to obtain an anode. Electrode body 21
A 30 V anodic oxidation is performed on the surface of the phosphor in an aqueous solution of phosphoric acid having a concentration of 5% by weight to form a dielectric oxide film 22.
This electrode body 21 was prepared by using a manganese nitrate aqueous solution having a concentration of 20% by weight, a manganese nitrate aqueous solution having a concentration of 25% by weight, and a concentration of 3%.
The dielectric oxide film 22 is electrically conductive on the dielectric oxide film 22 by immersing it in a 0 wt% manganese nitrate aqueous solution and a 35 wt% manganese nitrate aqueous solution, thermally decomposing once at 250 ° C. As a result, four types of precoat-treated products having the metal oxide semiconductor layer 23 as a conductive precoat layer were obtained.

Thereafter, a step of immersing the precoat-treated product in a solution containing 0.7 mol / l of a pyrrole monomer which is a heterocyclic compound and its derivative and a surfactant,
The precoat treatment is performed on a solution containing 0.1 mol / l of ammonium peroxodisulfate, which is an oxidant having an electrode potential higher than that of a heterocyclic compound and its derivative, and 0.05 mol / l of naphthalenesulfonic acid, which is a dopant. The step of immersing the product is alternately repeated 10 times to form the first conductive polymer electrolyte layer 24 by chemical oxidative polymerization, and then 0.25 mol / l of a heterocyclic compound and its derivative, a pyrrole monomer, and a dopant. The second conductive polymer electrolyte layer 25 was formed by performing electrolytic oxidative polymerization in a solution containing 0.05 mol / l of naphthalenesulfonic acid. After that, colloidal graphite 26 and silver paint 27 are formed on the second conductive polymer electrolyte layer 25.
Was sequentially applied, and then a predetermined exterior was applied to form a solid electrolytic capacitor.

(Embodiment 3) As shown in FIG. 3, an anode is obtained by pressure molding and vacuum sintering tantalum powder having a thickness of 0.9 mm, a width of 2.0 mm and a length of 1.3 mm. Electrode body 21
A 30 V anodic oxidation is performed on the surface of the phosphor in an aqueous solution of phosphoric acid having a concentration of 5% by weight to form a dielectric oxide film 22.
Low-foaming polyoxyethylene alkyl ether-based nonionic surfactants of 0.01% by weight, 0.05% by weight,
After the electrode body 21 was immersed in each of the manganese nitrate aqueous solutions having a concentration of 0.1% by weight, 0.5% by weight and 1% by weight added thereto, the concentration was 25% by weight, and thermal decomposition was performed once at 250 ° C., respectively. A metal oxide semiconductor layer 23 as a conductive precoat layer is formed on the dielectric oxide film 22 by performing a repair formation.
Thus, 5 types of precoat-treated products were obtained.

Thereafter, a step of immersing the precoat-treated product in a solution containing 0.7 mol / l of a pyrrole monomer which is a heterocyclic compound and its derivative and a surfactant,
The precoat treatment is performed on a solution containing 0.1 mol / l of ammonium peroxodisulfate, which is an oxidant having an electrode potential higher than that of a heterocyclic compound and its derivative, and 0.05 mol / l of naphthalenesulfonic acid, which is a dopant. The step of immersing the product is alternately repeated 10 times to form the first conductive polymer electrolyte layer 24 by chemical oxidative polymerization, and then 0.25 mol / l of a heterocyclic compound and its derivative, a pyrrole monomer, and a dopant. The second conductive polymer electrolyte layer 25 was formed by performing electrolytic oxidative polymerization in a solution containing 0.05 mol / l of naphthalenesulfonic acid. After that, colloidal graphite 26 and silver paint 27 are formed on the second conductive polymer electrolyte layer 25.
Was sequentially applied, and then a predetermined exterior was applied to form a solid electrolytic capacitor.

Comparative Example 1 As shown in FIG.
On the surface of the electrode body 31 serving as an anode obtained by pressure-molding and vacuum-sintering tantalum powder having a width of 9 mm, a width of 2.0 mm, and a length of 1.3 mm, the concentration of 30 V in a phosphoric acid aqueous solution having a concentration of 5 wt% Anodization is performed to form the dielectric oxide film 32, and then the electrode body 31 is immersed in a manganese nitrate aqueous solution having a liquid temperature of 250 ° C. and a concentration of 25% by weight for four thermal decompositions. The body 31 has a liquid temperature of 250 ° C. and a concentration of 40
A metal oxide semiconductor layer 33 made of manganese dioxide is formed on the dielectric oxide film 32 by performing thermal decomposition four times by immersing in a weight% manganese nitrate aqueous solution, and thereafter, the metal oxide semiconductor layer 33 is formed. On 33, colloidal graphite 34 and silver paint 35 are sequentially applied, and then,
A solid electrolytic capacitor was formed by applying a predetermined exterior.

Comparative Example 2 As shown in FIG.
The surface of the electrode body 41 serving as an anode obtained by press-molding 9 mm, width 2.0 mm, and length 1.3 mm of tantalum powder, and vacuum-sintering the same was applied in a phosphoric acid aqueous solution having a concentration of 5% by weight at 30 V. A step of performing anodization to form a dielectric oxide film 42, and then immersing the electrode body 41 in a solution containing 0.7 mol / l of a pyrrole monomer which is a heterocyclic compound and its derivative and a surfactant; The step of immersing the electrode body 41 in a solution containing 0.1 mol / l of ammonium peroxodisulfate and 0.05 mol / l of a naphthalene sulfonic acid as a dopant is repeated 10 times to perform chemical oxidative polymerization to obtain the dielectric oxide film. A conductive polymer electrolyte layer 43 is formed on 42, and thereafter, colloidal graphite 44 and silver paint 45 are sequentially applied on the conductive polymer electrolyte layer 43, and thereafter, a predetermined amount is formed. To constitute a solid electrolytic capacitor subjected to instrumentation.

Table 1 shows the basic electrical performance (capacitance, loss tangent, leakage current) of each of the solid electrolytic capacitors obtained in Embodiment 1 of the present invention and Comparative Examples 1 and 2. The results of the measurement are shown in FIG.
Shows the frequency characteristics of those impedances.

[0024]

[Table 1]

As is clear from (Table 1), the first embodiment of the present invention is superior in basic electric performance to the first comparative example, and the concentration of the electrode body in the manganese nitrate aqueous solution is 25% by weight. It can be seen that the basic electrical performance is comparable to that of Comparative Example 2 when the treatment is carried out within 2 times as to the number of times of immersing in and thermally decomposing at 250 ° C.

Further, as is apparent from FIG. 6, the effects of the low inductance of the conductive polymer solid electrolyte in (1) and (2) in the first embodiment of the present invention are clear as compared with Comparative Examples 1 and 2. It is what

Table 2 shows the basic electric performance (capacitance, loss tangent, leakage current) of each of the solid electrolytic capacitors obtained in Embodiment 2 of the present invention and Comparative Examples 1 and 2. The measurement results are shown in FIG.
Shows the frequency characteristics of those impedances.

[0028]

[Table 2]

As is clear from (Table 2), Embodiment 2 of the present invention is superior to Comparative Example 1 in basic electric performance, and the electrode body is immersed in an aqueous manganese nitrate solution at 250 ° C. It can be seen that, when the concentration of the manganese nitrate aqueous solution in the case of carrying out the thermal decomposition once in 1. is less than 30% by weight, the basic electric performance is not inferior to that of Comparative Example 2.

Further, as is apparent from FIG. 7, (20), (25) and (30) in the second embodiment of the present invention have the effect of lower inductance of the conductive polymer solid electrolyte as compared with Comparative Examples 1 and 2. It is clear.

Table 3 shows the basic electric performance (capacitance, loss tangent, leakage current) of each of the solid electrolytic capacitors obtained in the third embodiment of the present invention and the comparative examples 1 and 2. The measurement results are shown in FIG.
Shows the frequency characteristics of those impedances.

[0032]

[Table 3]

As is clear from (Table 3), the third embodiment of the present invention is superior in basic electric performance to the first comparative example, and the manganese nitrate aqueous solution having a concentration of 25% by weight is used for the electrode body. Is added and the amount of the low-foaming polyoxyethylene alkyl ether-based nonionic surfactant added to the manganese nitrate aqueous solution when the thermal decomposition is performed once at 250 ° C. is 1% by weight or less. In comparison with Comparative Example 2, it can be seen that the basic electric performance is comparable to that of Comparative Example 2.

Further, as is clear from FIG. 8, (0.01) (0.05) (0 ..) in the third embodiment of the present invention.
1) (0.5) (1) clearly shows the effect of the low inductance of the conductive polymer solid electrolyte as compared with Comparative Examples 1 and 2.

Further, the metal oxide semiconductor layer as the conductive precoat layer can form a good connection interface with excellent adhesion to the conductive polymer electrolyte layer due to the anchor effect due to the uneven portion where the crystal particles are accumulated. , And the surface and the fracture surface of the sintered electrode body were observed by a scanning electron microscope (SEM).

Further, as confirmed in the third embodiment of the present invention, a low-foaming nonionic surfactant added to a low concentration solution for forming a metal oxide semiconductor layer (an aqueous solution of manganese nitrate). The effect is remarkable even with a very small amount, but when the concentration of the nonionic surfactant becomes high, the stability of the liquid and the effect of residual may be adversely affected. The amount of activator added should be kept to a very low level.

In the first embodiment of the present invention described above, the electrode body 21 used is one in which tantalum powder is pressure-molded and vacuum-sintered, but the invention is not limited to this, and the porous valve is used. Any material can be used as long as the electrode body is made of metal.

As the solution in which the electrode body 21 is dipped, in the first embodiment of the present invention, a heterocyclic compound and a derivative thereof, which is composed of a pyrrole monomer and a surfactant, is used. A single or mixed solution of a solvent that enhances the dissolution of the formula compound and its derivative, benzene, naphthalene and its derivative and the like may be used.

[0039]

As described above, according to the method for producing a solid electrolytic capacitor of the present invention, a dielectric oxide film is formed on the surface of an electrode body made of a porous valve metal, and then a metal oxide having a concentration lower than 30% by weight is formed. The metal oxide semiconductor layer as a conductive precoat layer is formed on the dielectric oxide film by immersing the electrode body in a solution for forming a semiconductor layer. A step of immersing the electrode body in a solution containing a formula compound and its derivative, and a step of immersing the electrode body in a solution containing an oxidizing agent and a dopant having an electrode potential higher than the oxidation potential of the heterocyclic compound and its derivative. By alternately repeating a plurality of times to form the first conductive polymer electrolyte layer by chemical oxidative polymerization,
Further, the second conductive polymer electrolyte layer is formed on the first conductive polymer electrolyte layer by electrolytic oxidation polymerization. According to this manufacturing method, the second conductive polymer electrolyte layer is formed on the dielectric oxide film. In order to form a first conductive polymer electrolyte layer, which is a solid electrolyte, by chemical oxidative polymerization, an electrode body having a dielectric oxide film formed on its surface is used for forming a metal oxide semiconductor at a concentration lower than 30% by weight. The formation treatment of forming a metal oxide semiconductor layer as a conductive precoat layer on the dielectric oxide film by immersing in a solution of
The metal oxide semiconductor layer as a conductive precoat layer is formed on the dielectric oxide film within the number of times, and the metal oxide semiconductor layer has fine crystal grains when viewed microscopically. Macroscopically, it is necessary to form a uniform, dense, and highly adhesive connection interface to the dielectric oxide film formed on the surface of the electrode body made of porous valve metal in macroscopic terms. Therefore, subsequently, the step of immersing the electrode body in a solution containing the heterocyclic compound and its derivative, and the step of immersing the electrode body in a solution containing an oxidant and a dopant having a higher electrode potential than the heterocyclic compound and its derivative When the chemical oxidative polymerization is repeated by repeating the process a plurality of times alternately, the heterocyclic compound and its derivative are prevented from moving due to the uneven portion where the fine crystal particles forming the metal oxide semiconductor layer are accumulated. As a result, the heterocyclic compound and its derivative can very rapidly form the first conductive polymer electrolyte layer on the dielectric oxide film formed on the surface of the electrode body. Is.

As described above, the metal oxide semiconductor layer as the conductive precoat layer is excellent in adhesiveness with the first conductive polymer electrolyte layer due to the anchor effect due to the concavo-convex portion where the fine crystal particles are accumulated. Since the second conductive polymer electrolyte layer is formed on the first conductive polymer electrolyte layer by electrolytic oxidation polymerization, the second conductive polymer electrolyte layer is formed on the second conductive polymer electrolyte layer. It is possible to obtain a conductive polymer electrolyte layer that is extremely dense and has excellent electrical conductivity, and the resulting solid electrolytic capacitor will have extremely stable and excellent electrical characteristics and reliability.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of part A in FIG.

FIG. 3 is a cutaway perspective view showing a solid electrolytic capacitor according to first, second and third embodiments of the present invention.

FIG. 4 is a cutaway perspective view showing a solid electrolytic capacitor in Comparative Example 1.

FIG. 5 is a cutaway perspective view showing a solid electrolytic capacitor in Comparative Example 2.

FIG. 6 is a characteristic diagram showing the relationship between the impedance and the measurement frequency of the solid electrolytic capacitors obtained in Embodiment 1 of the present invention and Comparative Examples 1 and 2.

FIG. 7 is a characteristic diagram showing the relationship between the impedance and the measurement frequency of the solid electrolytic capacitors obtained in the second embodiment of the present invention and Comparative Examples 1 and 2.

FIG. 8 is a characteristic diagram showing the relationship between the impedance and the measurement frequency of the solid electrolytic capacitors obtained in the third embodiment of the present invention and Comparative Examples 1 and 2.

9A is a cutaway perspective view of a capacitor element made of an anode body in a conventional solid electrolytic capacitor, and FIG. 9B is a cutaway perspective view of a capacitor element made of an anode foil or an anode plate in a conventional solid electrolytic capacitor.

[Explanation of symbols]

 11, 21 Electrode body 12, 22 Dielectric oxide film 13, 23 Metal oxide semiconductor layer 14, 24 First conductive polymer electrolyte layer 15, 25 Second conductive polymer electrolyte layer

Claims (2)

[Claims] 1. A dielectric oxide film is formed on the surface of an electrode body made of a porous valve metal, and then the electrode body is immersed in a solution for forming a metal oxide semiconductor layer having a concentration lower than 30% by weight. Forming treatment of forming a metal oxide semiconductor layer as a conductive precoat layer on the dielectric oxide film by at most twice, and then dipping the electrode body in a solution containing a heterocyclic compound and its derivative. And a step of immersing the electrode body in a solution containing an oxidant and a dopant having an electrode potential higher than the oxidation potential of the heterocyclic compound and its derivative, are alternately repeated a plurality of times to obtain the first conductivity by chemical oxidative polymerization. Forming a polyelectrolyte layer,
Furthermore, a method for producing a solid electrolytic capacitor, in which a second conductive polymer electrolyte layer is formed on the first conductive polymer electrolyte layer by electrolytic oxidation polymerization. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein 1% by weight or less of a nonionic surfactant is added to a solution for forming a metal oxide semiconductor layer having a concentration lower than 30% by weight.