JPH1187178A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid electrolytic capacitor having superior electrical characteristics and a large capacitance with superior productivity by generating a solid electrolyte layer made of dense and uniform conductive polymer in a wound capacitor element. SOLUTION: After a capacitor element 10 obtained by winding an anode foil 1 and cathode foil 2 via a separator 3 has been impregnated with a monomer solution obtained by mixing 3,4-ethylenedihydroxythiophene with a volatile solvent at a volumetric ratio of 1:1 to 1:3, the capacitor 10 is heat treated. Thereafter, the element 10 is impregnated with an oxidizer solution, and a solid electrolyte formed of polyethylenedihydroxythiophene by chemical polymerization reaction with the monomer solution impregnated in the separator 3 is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly, to a solid electrolytic capacitor using a conductive polymer as an electrolyte.

[0002]

2. Description of the Related Art An electrolytic capacitor is made of a valve metal such as tantalum and aluminum, and has an oxide film layer serving as a dielectric formed on the surface of an anode electrode having fine holes and etching pits. It is configured by extracting electrodes.

[0003] The extraction of the electrode from the oxide film layer is performed by a conductive electrolyte layer. Therefore, in the electrolytic capacitor, the electrolyte layer serves as a true cathode. For example, in an aluminum electrolytic capacitor, a liquid electrolyte is used as a true electrode, and a cathode electrode only serves to electrically connect the liquid electrolyte to an external terminal.

[0004] The electrolyte layer functioning as a true cathode is required to have adhesion, denseness, uniformity, etc. with the oxide film layer.
In particular, the adhesion in the fine holes of the anode electrode and the inside of the etching pits has a great effect on the electrical characteristics, and a number of electrolyte layers have been proposed.

The solid electrolytic capacitor uses a solid electrolyte having conductivity instead of a liquid electrolyte which lacks impedance characteristics in a high frequency range because of ionic conduction. Among them, manganese dioxide, 7, 7, and 8 are used. , 8-
Tetracyanoquinodimethane (TCNQ) complexes are known.

[0006] Among them, the solid electrolyte layer composed of manganese dioxide is formed by immersing an anode element composed of a sintered body of tantalum in an aqueous solution of manganese nitrate and thermally decomposing it at a temperature of about 300 to 400 ° C. . In a capacitor using such a solid electrolyte layer, the oxide film layer is easily damaged during the thermal decomposition of manganese nitrate, which tends to increase the leakage current, and the specific resistance of manganese dioxide itself is high. It has been difficult to obtain sufficiently satisfactory impedance characteristics. In addition, the lead wire was damaged by the heat treatment, and it was necessary to separately provide an external terminal for connection as a later process.

On the other hand, as a solid electrolytic capacitor using a TCNQ complex, one described in Japanese Patent Application Laid-Open No. 58-191414 is known. The TCNQ complex is melted by heat, dipped and coated on an anode electrode. To form a solid electrolyte layer. This TCNQ complex has high conductivity and can obtain good results in frequency characteristics and temperature characteristics.

However, the TCNQ complex has a melting point and a decomposition point close to each other and, depending on temperature control, has a property of melting and then transferring to an insulator in a short time. Therefore, it is difficult to control the temperature in the manufacturing process of the capacitor. Since the complex itself lacks heat resistance, a remarkable characteristic change is observed due to the heat of the solder when mounted on a printed circuit board.

Further, manganese dioxide and T
In order to solve the inconvenience of the CNQ complex, use of a conductive polymer such as polypyrrole as a solid electrolyte layer has recently been attempted.

[0010] The conductive polymer represented by polypyrrole is mainly produced by a chemical oxidation polymerization method (chemical polymerization) or an electrolytic oxidation polymerization method (electrolysis polymerization). Was difficult to produce. On the other hand, in the case of electrolytic polymerization, it is necessary to apply a voltage to an object on which a film is to be formed, and therefore, it is difficult to apply the method to an anode electrode for an electrolytic capacitor having an oxide film layer as an insulator formed on the surface. On the surface of the coating layer, there is a method in which a conductive precoat layer, for example, a conductive polymer film chemically polymerized using an oxidizing agent is used as a precoat layer, and then the electrolyte layer is formed by electrolytic polymerization using the precoat layer as an electrode. It has been proposed (JP-A-63-173313,
JP-A-63-158829: Manganese dioxide is used as a precoat layer).

However, the manufacturing process becomes complicated because the pre-coat layer is formed in advance, and in the electrolytic polymerization, a solid electrolyte layer is generated from the vicinity of the external electrode for polymerization arranged on the surface of the anode electrode to be coated. It has been very difficult to continuously produce a conductive polymer film having a uniform thickness over a wide range.

Therefore, a foil-like anode electrode and a cathode electrode are
By winding through a separator, a so-called wound capacitor element is formed, and a monomer such as pyrrole and an oxidizing agent are immersed in the capacitor element to form an electrolyte layer composed of a conductive polymer film formed only by chemical polymerization. Attempted to form.

[0013] Such a wound type capacitor element is well known for an aluminum electrolytic capacitor, but by holding a conductive polymer layer with a separator, it is possible to avoid the complication of electrolytic polymerization and also to increase the surface area. It was expected that the capacity would be expanded by the foil-like electrode.

Further, it was expected that the use of a wound-type capacitor element would maintain the electrodes and separators of both electrodes with a constant tightening force, and would contribute to the adhesion between the electrodes of both electrodes and the electrolyte layer.

However, when a capacitor element is impregnated with a mixed solution of a monomer and an oxidizing agent, a polymerization reaction of the monomer and the oxidizing agent proceeds rapidly, so that a solid electrolyte layer is formed even inside the capacitor element. It has been found that the expected electrical characteristics cannot be obtained.

Attempts have been made to lower the polymerization temperature of the solution during the reaction, and although some good electrical characteristics have been obtained, there has been the problem that only the withstand voltage characteristics are insufficient. In addition, when chemical polymerization is carried out at a low temperature, strict temperature control is required, and the production apparatus becomes complicated, resulting in an increase in product cost.

On the other hand, various conductive polymers have been studied, and attention has been paid to polyethylenedioxythiophene (PEDT), which has a slow reaction rate and excellent adhesion to the oxide film layer of the anode electrode. Technology (Japanese Unexamined Patent Publication No.
No. 15611).

The present applicant has noticed that the polymerization reaction rate of polyethylene dioxythiophene is slow, and added a monomer and an oxidizing agent to a capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator. The invention is characterized in that polyethylene dioxythiophene, which is a solid electrolyte, is produced inside a capacitor element by a chemical polymerization reaction between a monomer and an oxidizing agent, which occurs slowly after that, by impregnating a mixed solution obtained by mixing the mixed solution with a solution. 8-131374).

[0019]

However, as described above, when a capacitor element is impregnated with a mixed solution obtained by mixing a monomer and an oxidizing agent solution in order to form a solid electrolyte layer made of polyethylenedioxythiophene. Since the polymerization reaction of this mixed solution proceeds with time, the mixed solution is impregnated into the capacitor element in parallel with the polymerization reaction. Therefore, the solid electrolyte layer to be formed is likely to be non-uniform, for example, because the mixed solution does not penetrate into the capacitor element but solidifies on the way. In addition, in order to allow the mixed solution to further penetrate into the interior in anticipation of the case where the mixed solution solidifies in the middle, the mixed solution is continuously impregnated. Such impregnation wastes a lot of material and time, and lowers productivity.

The present invention has been proposed to solve such problems of the prior art, and an object of the present invention is to form a dense and uniform conductive polymer inside a wound capacitor element. An object of the present invention is to provide a production method which is capable of producing a solid electrolyte layer, has excellent electric characteristics and is capable of producing a large-capacity solid electrolytic capacitor, and has excellent productivity.

[0021]

In order to solve the above-mentioned problems, a method for manufacturing a solid electrolytic capacitor according to the present invention comprises the steps of: forming a capacitor element having an anode electrode foil and a cathode electrode foil wound through a separator; In a method of manufacturing a solid electrolytic capacitor for producing polyethylene dioxythiophene by a chemical polymerization reaction by impregnating 4-ethylenedioxythiophene and an oxidizing agent, a capacitor element is impregnated with a monomer composed of 3,4-ethylenedioxythiophene After that, an oxidizing agent is impregnated.

First, in the manufacturing method according to the present invention, the capacitor element is impregnated with a monomer composed of 3,4-ethylenedioxythiophene, and after the step of impregnating the monomer, the oxidizing agent is added to the capacitor element. Characterized by having a step of impregnating with.

In the manufacturing method according to the first aspect having the above structure, the formation of the solid electrolyte layer by the chemical polymerization can be
It is intended to improve the monomer distribution based on the knowledge that the distribution is determined by the monomer distribution in the capacitor element. That is, in the manufacturing method according to claim 1, by separately impregnating the monomer and the oxidizing agent in this order, the monomer that has been impregnated and distributed inside the capacitor element and the oxidizing agent that has been impregnated later are separately charged in the capacitor. Since chemical polymerization is performed inside the element, a dense and uniform solid electrolyte layer made of polyethylenedioxythiophene can be formed inside the wound capacitor element.

According to a second aspect of the present invention, the capacitor element is impregnated with a monomer solution obtained by mixing 3,4-ethylenedioxythiophene and a volatile solvent, and after this step, the capacitor element is heat-treated. And a step of impregnating the capacitor element with an oxidizing agent solution after this step.

According to the manufacturing method of the first aspect having the above structure, not only the monomer and the oxidizing agent solution are individually impregnated but also the monomer is diluted with a volatile solvent and impregnated. Since the oxidizing agent solution is impregnated after the heat treatment, the following effects can be obtained.

That is, when the monomer and the oxidizing agent are simply impregnated individually based on the production method according to the first aspect, the monomer amount is overwhelmingly about 1: 3 to 1: 6 by volume ratio. Since the amount is small, the amount of the monomer is biased in the capacitor element, and the characteristics of the obtained capacitor may be insufficient. In this case, heat treatment may be performed to improve the characteristics of the capacitor.However, in order to improve the characteristics of the capacitor to a satisfactory level, at least after the monomer is impregnated at a constant temperature for a long time. It is necessary to leave it, and it is difficult to improve productivity.

On the other hand, in the production method according to the second aspect, the monomer is uniformly impregnated into the capacitor element by diluting 3,4-ethylenedioxythiophene, which is a monomer, with a volatile solvent. And the volatile solvent can be volatilized by the subsequent heat treatment. Therefore, by the subsequent impregnation of the oxidizing agent solution, the oxidizing agent solution and the monomer uniformly impregnated in the capacitor element are subjected to a chemical polymerization reaction. A higher quality solid electrolyte layer made of polyethylene dioxythiophene can be produced. Further, since the heat treatment time is short, the productivity is excellent.

According to the third and fourth aspects of the present invention, the material of the volatile solvent is further limited in the first aspect of the present invention. First, the production method according to claim 3 is the production method according to claim 2, wherein the volatile solvent is selected from hydrocarbons, ethers, esters, ketones, alcohols, and nitrogen compounds. It is characterized by using a material that has been prepared. Also,
According to a fourth aspect of the present invention, in the manufacturing method of the third aspect, a material selected from methanol, ethanol, and acetone is used as the volatile solvent.

According to the manufacturing method of the third and fourth aspects having the above configuration, the following operations can be obtained.
First, in the production method according to claim 2, as the volatile solvent to be used, the volatile solvent is reciprocally dissolved with 3,4-ethylenedioxythiophene and has high volatility, and does not act on the electrode foil made of aluminum or the like. Anything can be used. However, in particular, as described in claim 3, hydrocarbons, ethers, esters, ketones,
By using alcohols, nitrogen compounds, and the like, the conditions required for the volatile solvent as described above can be satisfied. That is, by using these materials as volatile solvents, uniform impregnation of the monomer can be promoted, and no adverse effect on the electrode foil occurs.

Among the volatile materials described above, it is particularly desirable to use methanol, ethanol, acetone or the like as described in claim 4 at present. That is, since methanol, ethanol, and acetone are particularly inexpensive and relatively easy to handle among the materials listed above, any of these materials is used as the volatile solvent according to the present invention. Thereby, productivity can be further improved.

According to a fifth aspect of the present invention, in the method of the second aspect, in the step of impregnating the monomer solution, 3,4-ethylenedioxythiophene and a volatile solvent are separately impregnated. It is characterized by:

According to the manufacturing method of the fifth aspect having the above configuration, the following operation can be obtained. First, in the manufacturing method according to claim 2, in the step of impregnating the monomer solution, the capacitor element can be directly impregnated with a monomer solution obtained by mixing a monomer and a volatile solvent. However, in this case, since the volatile solvent may evaporate after mixing and the composition may change with time, the monomer and the volatile solvent are separately separated as described in claim 5. The impregnation allows the capacitor element to be impregnated with a monomer solution having a small composition change.

According to a sixth aspect of the present invention, in the method of the second aspect, in the step of impregnating the monomer solution, 3,4-ethylenedioxythiophene and a volatile solvent are mixed in a ratio of 1: 1. It is characterized by impregnating with a monomer solution mixed in a volume ratio of １ ： 1: 3.

According to the manufacturing method of the sixth aspect having the above configuration, the following operation can be obtained. First, in the production method according to claim 2, the volume ratio of the monomer and the volatile solvent can be appropriately selected, but if the proportion of the volatile solvent is too small, the uniform distribution action of the monomer due to the use of the volatile solvent. Is not sufficiently obtained, and when the proportion of the volatile solvent is too large, a large amount of the volatile solvent is simply wasted. Therefore, specifically, as described in claim 6, the monomer and the volatile solvent are mixed in a ratio of 1: 1 to 1: 3.
By impregnating the monomer solution mixed at a volume ratio of, the capacitor element can be uniformly impregnated with the monomer, and a high-quality solid electrolyte layer can be formed inside the capacitor. Further, since only the minimum necessary amount of volatile solvent is used, the productivity does not decrease.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a solid electrolytic capacitor according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows a solid electrolytic capacitor manufactured by the manufacturing method of the present invention.
It is manufactured by the following procedure. First, an anode electrode foil (anode foil) 1 made of a valve metal such as aluminum and having an oxide film layer formed on its surface, and a cathode electrode foil (cathode foil) 2 are wound through a separator 3 to form a capacitor element. Form 10.

Next, 3, 4
1: 1 ethylenedioxythiophene and volatile solvent
Impregnate the mixed monomer solution in a volume ratio of １ ： 1: 3.
Specifically, the capacitor element 10 is impregnated with 3,4-ethylenedioxythiophene and a volatile solvent. And
The capacitor element 1 thus impregnated with the monomer solution
The volatile solvent is volatilized by heat-treating 0.

Thereafter, the capacitor element 10 is impregnated with the oxidizing agent solution, and the solid electrolyte layer 5 made of polyethylenedioxythiophene is generated by a chemical polymerization reaction with the monomer solution permeated into the separator 3. This solid electrolyte layer 5 is held by the separator 3.

As described above, the capacitor element 10
As a method of impregnating a monomer solution in which 3,4-ethylenedioxythiophene and a volatile solvent are mixed, or a method of impregnating an oxidizing agent solution after heat treatment, known methods, for example, a vacuum impregnation method, pressure impregnation, Method or the like can be used.
Here, 3,4-ethylenedioxythiophene can be obtained by a known production method disclosed in JP-A-2-15611 and the like.

As the volatile solvent, a material selected from hydrocarbons, ethers, esters, ketones, alcohols, and nitrogen compounds is used. More specifically, pentane, hexane and the like can be used as hydrocarbons, and tetrahydrofuran, dipropyl ether and the like can be used as ethers. Further, as esters, ethyl formate, ethyl acetate and the like can be used, and as ketones, acetone, methyl ethyl ketone and the like can be used. Furthermore, methanol, ethanol, propanol and the like can be used as alcohols, and acetonitrile and the like can be used as nitrogen compounds.

Among the above volatile materials, in particular,
As described above, it is desirable to use methanol, ethanol, acetone, or the like. Since water hardly dissolves in 3,4-ethylenedioxythiophene, it is not preferable to use water as a volatile solvent.

Further, the oxidizing agent is p dissolved in butanol.
Using ferric toluenesulfonate; in this case,
The ratio between butanol and ferric p-toluenesulfonate may be arbitrary, but in the present invention, a 40 to 60% solution is used as an example. The mixing ratio of 3,4-ethylenedioxythiophene to the oxidizing agent is preferably in the range of 1: 3 to 1: 6.

On the other hand, the anode foil 1 is made of a valve metal such as aluminum, and as shown in FIG. 2, its surface is roughened by electrochemical etching in a chloride aqueous solution to form a large number of etchings. Pits 8 are formed. Further, on the surface of the anode foil 1, an oxide film layer 4 serving as a dielectric is formed by applying a voltage in an aqueous solution of ammonium borate or the like. The cathode foil 2 is made of aluminum or the like, similarly to the anode foil 1, and has a surface subjected to only an etching process.

Lead wires 6 and 7 for connecting respective electrodes to the outside are connected to the anode foil 1 and the cathode foil 2 by known means such as stitching and ultrasonic welding.
The lead wires 6 and 7 are made of aluminum or the like, and constitute an external connection portion for electrically connecting a connection portion with the anode foil 1 and the cathode foil 2 to the outside. Derived from the end face.

The separator 3 includes a separator such as ordinary manila paper, glass paper or glass paper,
Separators (Japanese Patent Application No. 8-131374) in which paper such as manila paper and kraft paper are mixed may be used, but nonwoven fabrics mainly containing vinylon fibers, vinylon fibers, glass fibers, polyester fibers, and nylon fibers It is preferable to use a nonwoven fabric (Japanese Patent Application No. Hei 9-165230) in which a nonwoven fabric is mixed with paper fibers such as rayon fiber and manila paper.

The capacitor element 10 is formed by winding the anode foil 1 and the cathode foil 2 with the separator 3 interposed therebetween. The dimensions of the two electrode foils 1 and 2 are arbitrary according to the specifications of the solid electrolytic capacitor to be manufactured, and the separator 3 may have a slightly larger width depending on the dimensions of the two electrode foils 1 and 2. .

The operation of the present embodiment having the above configuration is as follows. That is, the monomer 3,
Since the amount of 4-ethylenedioxythiophene is overwhelmingly smaller than that of the oxidizing agent, when this monomer alone is impregnated into the capacitor element 10, the monomer amount tends to be uneven in the capacitor element 10, but this embodiment By diluting the monomer with a volatile solvent such as methanol, ethanol, acetone or the like, it is possible to uniformly impregnate the monomer into the capacitor element 10. In this case, the monomer solution in which the monomer and the volatile solvent are mixed can be directly impregnated into the capacitor element 10, but in the present embodiment, particularly, the monomer and the volatile solvent are separately impregnated. Thereby, the capacitor element can be impregnated with a monomer solution having little change over time.

By subjecting the capacitor element 10 impregnated with the monomer and the volatile solvent to a heat treatment, the volatile solvent can be volatilized.

Therefore, the oxidizing agent solution is impregnated with the monomer uniformly impregnated in the capacitor element 10 to cause a chemical polymerization reaction between the oxidizing agent solution and the monomer uniformly impregnated in the capacitor element 10, thereby forming a dense and uniform inside of the wound-type capacitor element 10. The solid electrolyte layer 5 made of a suitable polyethylene dioxythiophene can be produced.

Further, since the heat treatment time is short, the productivity is excellent. Further, by using methanol, ethanol, acetone, or the like which is inexpensive and relatively easy to handle as a volatile solvent, productivity can be further improved.

[0051]

Next, a method for manufacturing a solid electrolytic capacitor according to the present invention and an example of a solid electrolytic capacitor obtained by the method will be specifically described in comparison with comparative examples. First, the following Table 1 comparatively shows procedures for forming a solid electrolyte layer in typical Examples 1 to 5 to which the present invention is applied and Comparative Examples 1 to 3.

[0052]

[Table 1]

Each example shown in Table 1 will be described.
Example 1 according to the present invention performs a monomer impregnation treatment,
In this example, an oxidizing agent is impregnated after heat treatment for about several minutes. Examples 2 to 5 are examples in which a monomer is impregnated using a volatile solvent such as acetone or methanol, and an oxidizing agent is impregnated after a heat treatment for about several minutes. It differs in the type of the ionic solvent and the volume ratio of the monomer to the ionic solvent. Further, Comparative Examples 2 and 3 are examples in which a volatile solvent was not used and the mixture was left at room temperature, and the time from the monomer impregnation to the oxidant impregnation was different. Further, Comparative Example 1
This is an example in which a technique of impregnating a mixed solution of a monomer and an oxidizing agent according to a conventional technique is applied. When the initial characteristics of each of Examples 1 to 5 and Comparative Examples 1 to 3 were measured, the results shown in Table 2 below were obtained.

[0054]

[Table 2]

As is clear from these results, Examples 1 to 5 according to the present invention show comparative examples 1 to 5 with respect to any of the characteristics of capacitance, tan δ, and equivalent series resistance (ESR).
It shows a better value than 3. Comparative Examples 2 and 3
Shows a better value than that of Comparative Example 1. In Comparative Example 3, however, it takes a long time from the monomer impregnation to the oxidizing agent impregnation, and the heat treatment is performed for a short time of about several minutes. The productivity is lower than in Examples 1 to 5.

The present invention is not limited to the above-described embodiment and Examples 1 to 5. The type of the volatile solvent can be appropriately selected, and the volume ratio between the monomer and the volatile solvent is not limited. It can be appropriately selected within the range of 1: 1 to 1: 3. Further, in the above embodiment, the capacitor element was impregnated with a monomer solution obtained by mixing a monomer and a volatile solvent.
It is also possible to separately impregnate the monomer and the volatile solvent, and in this case, it is possible to impregnate the capacitor element with a monomer solution having a small composition change. Further, the type of the oxidizing agent and its solvent, the ratio thereof, and the like can be appropriately selected.

[0057]

As described above, according to the method for manufacturing a solid electrolytic capacitor of the present invention, when a solid electrolyte layer made of polyethylene dioxythiophene is produced,
By impregnating the capacitor element with the oxidizing agent after impregnating the monomer, a solid electrolyte layer made of a uniform conductive polymer is generated inside the wound capacitor element, which has excellent electrical characteristics and large capacity. Solid electrolytic capacitors can be manufactured.

In particular, in a typical manufacturing method according to the present invention, a capacitor element is impregnated with a monomer solution in which a monomer and a volatile solvent are mixed, the capacitor element is heat-treated, and then the capacitor element is impregnated with an oxidizing agent solution. By doing so, a higher quality solid electrolyte layer can be generated inside the wound capacitor element, so that a solid electrolytic capacitor having higher electrical characteristics can be manufactured.
This manufacturing method is particularly practical because it requires only a few minutes of heat treatment and can use a volatile solvent that is inexpensive and easy to handle.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an example of a capacitor element targeted by the present invention.

FIG. 2 is an enlarged sectional view showing an anode foil having a solid electrolyte layer produced according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode foil 2 ... Cathode foil 3 ... Separator 4 ... Oxide film layer 5 ... Solid electrolyte layer 6, 7 ... Lead wire 8 ... Etching pit 10 ... Capacitor element

Claims (6)

[Claims] A capacitor element in which an anode electrode foil and a cathode electrode foil are wound with a separator interposed therebetween is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent to obtain polyethylenedioxythiophene by a chemical polymerization reaction. In the method for producing a solid electrolytic capacitor to be produced, a step of impregnating the capacitor element with a monomer composed of 3,4-ethylenedioxythiophene; and a step of impregnating the capacitor element with an oxidizing agent after the step of impregnating the monomer. A method for manufacturing a solid electrolytic capacitor, comprising: 2. A capacitor element in which an anode electrode foil and a cathode electrode foil are wound with a separator interposed therebetween is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent, and is made of polyethylenedioxythiophene by a chemical polymerization reaction. In the method for producing a solid electrolytic capacitor to be produced, a step of impregnating the capacitor element with a monomer solution obtained by mixing 3,4-ethylenedioxythiophene and a volatile solvent; and a step of impregnating the monomer solution with the capacitor element And a step of impregnating the capacitor element with an oxidizing agent solution after the step of heat treating. 3. The solid according to claim 2, wherein a material selected from hydrocarbons, ethers, esters, ketones, alcohols, and nitrogen compounds is used as the volatile solvent. Manufacturing method of electrolytic capacitor. 4. The method according to claim 3, wherein a material selected from methanol, ethanol and acetone is used as said volatile solvent. 5. In the step of impregnating the monomer solution,
3. The method for producing a solid electrolytic capacitor according to claim 2, wherein 3,4-ethylenedioxythiophene and a volatile solvent are separately impregnated. 6. In the step of impregnating the monomer solution,
3. The method for producing a solid electrolytic capacitor according to claim 2, wherein a monomer solution in which 3,4-ethylenedioxythiophene and a volatile solvent are mixed at a volume ratio of 1: 1 to 1: 3 is impregnated.