JP2001358039A - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A low ES with a small pressurization at the time of anode and cathode bonding of a solid electrolytic capacitor using a conductive polymer as a solid electrolyte.
R is obtained and the peeling of the conductive polymer layer is eliminated. The solid electrolytic capacitor has a conductive polymer layer disposed between an anode body and a cathode body made of a valve metal having a dielectric oxide film layer formed on the surface thereof. By mixing a softening agent for softening the conductive polymer layer in the molecular layer, variation in characteristics is small and low.
Provide a solid electrolytic capacitor with excellent ESR (Equivalent Series Resistance) and high frequency characteristics. Also, the anode of a solid electrolytic capacitor using a conductive polymer for the solid electrolyte,
A lower ESR can be obtained with a smaller pressure at the time of cathode bonding, and peeling of the conductive polymer layer can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor using a valve metal such as aluminum or tantalum as an anode and a conductive polymer as a solid electrolyte, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, solid electrolytic capacitors have been widely used in computers, mobile phones and the like.

FIG. 5 shows a structure of a conventional solid electrolytic capacitor using a valve metal as an anode. In FIG. 5, 5 is a valve metal porous body, 6 is a dielectric oxide film, 7 is a solid electrolyte layer, 8 is a carbon layer, 9 is an Ag paste layer, 10 is an anode lead terminal, and 11 is a cathode lead terminal. First, a dielectric oxide film 6 is formed on the surface of a valve metal porous body 5 such as aluminum whose surface is roughened or powdered tantalum, and then a solid electrolyte layer 7 is formed on the dielectric oxide film surface 6.
As a conductive polymer such as polypyrrole or manganese dioxide. Subsequently, a cathode layer including a carbon layer 8 and a silver paste layer 9 is formed on the solid electrolyte layer to manufacture a capacitor element. Thereafter, the anode lead-out terminal 10 is attached to the anode lead portion by welding or the like, and the cathode lead-out terminal 11 is attached to the cathode layer with a conductive adhesive. Finally, an exterior covering the entire capacitor element except for the anode lead-out terminal and a part of the cathode lead-out terminal (Not shown) to obtain a solid electrolytic capacitor. The exterior has a role of maintaining airtightness with the outside, and is molded using an epoxy-based thermosetting resin or the like containing a silicon oxide filler.
(Chip type) or dip molding (lead wire type) is common. In this configuration, low ESR (E
In order to achieve equivalent series resistance, it is necessary to increase the conductivity of the solid electrolyte layer and to devise material characteristics and a method of forming the carbon layer and the silver paste layer. Further, in order to improve the capacity of the product and to reduce the ESR, a structure in which an anode body and a cathode body are stacked (Japanese Patent Laid-Open No.
99) -219861), and in this case, there has been proposed a method of directly connecting a solid electrolyte layer to a cathode extraction electrode. In conventional solid electrolytic capacitors using a conductive polymer for these solid electrolytes, as proposed in Patent No. 1949637 (1995), a conductive polymer is used by using an electrolytic solution (polymer monomer solution). Is formed by electrolytic polymerization, to increase the reaction resistance of the polymerization reaction, to uniformly form the conductive polymer in the pores, and to increase the adhesive force between the conductive polymer layer and the polymer. The electrolyte solution (polymer monomer solution) usually contains a binder resin. This binder resin is usually contained in the conductive polymer layer.

[0004]

However, since the conductive polymer layer of the conventional solid electrolytic capacitor contains a binder resin, there is a problem that the resistance of the conductive polymer increases. On the other hand, if the binder resin is removed to reduce the resistance, the conductive polymer layer will be easily peeled off. Further, even when a binder resin is contained, the conductive polymer may be partially peeled from the polymer during the drying step.

[0005] When a solid electrolytic capacitor is formed by directly connecting an anode body and a cathode body through a conductive polymer formed on the anode body using a metal foil for the cathode body, the conductive polymer is used. In order to firmly adhere and increase the connection area, it is necessary to apply considerable pressure, but even if 100 kgf / cm ² is applied, an ESR of 10 mΩ or less cannot be obtained (effective element area 3 ×
5mm ^2). If the pressure applied at this time is small, the contact area between the metal foil as the cathode body and the conductive polymer also decreases, and the contact resistance tends to increase.

Therefore, in order to reduce the ESR by increasing the contact area, it is necessary to form an exterior so that a large pressure is applied to the contact interface. However, it is difficult to form such an exterior, and The dielectric oxide film may be broken by pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid electrolytic capacitor having a small characteristic variation, a low ESR and an excellent high-frequency characteristic, and a method of manufacturing the same in order to solve the above-mentioned conventional problems.

[0008]

In order to achieve the above object, the solid electrolytic capacitor of the present invention comprises a conductive material between an anode body and a cathode body made of a valve metal having a dielectric oxide film layer formed on the surface. A solid electrolytic capacitor having a conductive polymer layer disposed thereon, wherein a softener for softening the conductive polymer layer is present in the conductive polymer layer.

Next, according to the method for manufacturing a solid electrolytic capacitor of the present invention, a conductive polymer layer is disposed between an anode body and a cathode body made of a valve metal having a dielectric oxide film layer formed on the surface. A method for manufacturing a solid electrolytic capacitor, comprising forming a conductive polymer layer on at least one electrode body selected from the anode body and the cathode body, and then diluting the conductive polymer layer with a low boiling point solvent. The conductive polymer layer is softened by impregnating the conductive polymer layer with a softening agent to be softened, and then the low boiling point solvent is evaporated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The solid electrolytic capacitor of the present invention
By softening the conductive polymer layers formed on both sides or one side of the anode body and the cathode body by impregnating with a softener, the conductive polymer becomes soft, and the anode body and the cathode body are brought into contact with the conductive body. When the connection is made via a molecule, the connection resistance can be reduced. The reason for this is that the conductive polymer and the anode body or the cathode body are easily brought into surface contact due to softening of the conductive polymer. At the same time, peeling of the conductive polymer can be eliminated.

In the present invention, the softening agent has a melting point of 30.
° C or lower, and the boiling point is 200 ° C or higher at normal pressure, and 2
The temperature is preferably 40 ° C. or higher. Examples of the softener include at least one selected from polyhydric alcohols, aliphatic alcohols, aromatic alcohols, and ethers. More specifically, glycerin (bp 290.5
° C), diethylene glycol (bp 245.8 ° C), 2-anilinoethanol, m-methoxyphenol and ethylene glycol monobenzyl ether are preferred.

The amount of the softener is preferably 5.0% by weight or less based on the conductive polymer layer.

In the present invention, it is preferable that the conductive polymer layer does not contain a binder resin.

Next, in the method of the present invention, the boiling point of the low-boiling solvent is preferably 150 ° C. or less at normal pressure. The low boiling point solvent is preferably at least one selected from methanol, ethanol, isopropyl alcohol, acetone, toluene and xylene. Further, the drying temperature of the low boiling point solvent is preferably 150 ° C. or less at normal pressure. Preferably, the softening agent has a boiling point of 200 ° C. or higher at normal pressure. The softening agent has a boiling point of 240 ° C. at normal pressure.
It is preferable that it is above. Further, the softener is preferably at least one selected from polyhydric alcohols, aliphatic alcohols, aromatic alcohols, phenols and ethers. Further, it is preferable that the softening agent is at least one selected from glycerin, diethylene glycol, 2-anilinoethanol, m-methoxyphenol and ethylene glycol monobenzyl ether. Of course, they can be used in combination. Further, it is preferable that the blending amount of the softener is 5.0% by weight or less based on the conductive polymer layer.

In the method of the present invention, an electrolyte solution containing no binder resin (a monomer solution for forming a polymer)
When the conductive polymer layer is formed by the method described above, it is highly possible that peeling occurs in a drying step after the formation, so that the step of impregnating the conductive polymer layer with the softening agent is preferably performed before the drying step.

In the solid electrolytic capacitor of the present invention, the softening agent may be any substance that softens the polymer layer by impregnating the polymer layer, but is typically glycerin. preferable.

Further, the solid electrolytic capacitor of the present invention preferably does not contain a binder resin in the conductive polymer, so that the resistance and interface resistance of the conductive polymer itself are reduced, and the ESR of the capacitor is reduced. .

In the solid electrolytic capacitor of the present invention,
The cathode body may be composed of a carbon layer and a silver paste layer, or may be a metal foil.

According to the solid electrolytic capacitor and the method for manufacturing the solid electrolytic capacitor of the present invention, a solid electrolytic capacitor having low ESR and excellent high-frequency characteristics can be realized.

Hereinafter, embodiments of the present invention will be described in detail.

In the solid electrolytic capacitor of the present invention,
The anode is made of a valve metal, and aluminum, tantalum, or niobium is preferably used as the valve metal.

The valve metal is a porous body having a large number of fine holes or pores communicating with the outer surface.

As an example of the anode, in the case of aluminum,
A porous body in which a number of small holes are formed by subjecting an aluminum foil to a surface roughening treatment such as electrolytic etching. In the case of tantalum, the porous body is formed by pressing and sintering the tantalum powder to form a porous body, or by applying the tantalum powder to a tantalum sheet and then sintering.

The dielectric oxide film layer is formed as an oxide film by anodic oxidation on the surface of the valve metal porous body as the anode to obtain an anode body. This dielectric oxide film layer is also formed on the surface of many fine pores of the porous anode material.

In the present invention, a conductive polymer material such as polypyrrole, polythiophene and polyaniline is used as the solid electrolyte. This solid electrolyte layer is formed on the anode body, and is also formed in fine pores of the porous body. The conductive polymer is not particularly limited in the present invention, and may be any one which is generally used for a solid electrolytic capacitor.

In the solid electrolytic capacitor of the present invention,
The cathode body is for collecting electric charges drawn by the solid electrolyte layer. As an example of the cathode body, when using a metal foil, use a Ni foil or an aluminum foil with carbon embedded in the surface, and form a conductive polymer on the surface by electrolytic polymerization or use it as it is .

Forming a conductive polymer layer on the anode body;
Connected to the anode body and the cathode body through the conductive polymer layer,
Construct an evaluation capacitor element. In this state, the characteristics as a capacitor can be evaluated using an impedance analyzer.

Using a metal foil for the cathode body, an anode body having an arbitrary number of conductive polymers formed thereon and a cathode body are alternately pressed and laminated to be connected to each other to form a conductive polymer layer of the anode body. Parts that are not in contact with the anode body of the cathode body are joined by welding, etc., and the outer body is formed of epoxy or the like except for a part of the anode body and the cathode body. Molding is performed using a thermosetting resin to obtain a solid electrolytic capacitor.

In the present invention, the conductive polymer layer disposed between the anode body and the cathode body in the solid electrolytic capacitor is impregnated with a softening agent to soften the conductive polymer. The conductive polymer layer at the connection part of the body becomes soft, the contact area can be increased with a small pressure at the time of connection, and the contact resistance can be reduced.

The solid electrolytic capacitor of the present invention is formed by electrolytic polymerization using an electrolyte solution (polymer monomer solution) containing no binder resin when forming the conductive polymer layer. The polymer layer does not contain a binder resin. As a result, the resistance and connection resistance of the conductive polymer itself are reduced, and a solid electrolytic capacitor with low ESR can be obtained. In addition, since the conductive polymer is moistened by the softening agent, peeling does not occur, and an effect of preventing peeling is obtained in addition to softening.

The softening agent used for softening the conductive polymer preferably has a boiling point of 200 ° C. or higher. For example, if transfer molding or dip molding of resin is used to form the exterior,
It goes through a superheating process from ℃ to 200 ℃. Since it is necessary not to boil during these steps, it is desirable to have a boiling point of 200 ° C. or more when going through such a process.

Further, when the solid electrolytic capacitor is mounted on a substrate using solder or the like, the solid electrolytic capacitor is subjected to a heat treatment at about 240 ° C. to 260 ° C. Addition and inclusion of a material that rapidly gasifies in such a process raises the internal pressure of the capacitor, especially when resin transfer molding or dip molding is used to form the exterior.
In some cases, cracks may be generated on the exterior to release the gas pressure. Therefore, it is desirable that the softener contained has a boiling point of 260 ° C. or higher.

FIG. 1 shows an embodiment of a method for manufacturing the above-described solid electrolytic capacitor of the present invention.

First, as the above-mentioned anode body forming step, an Al foil is electrolytically etched in an acidic solution or a powder sintered body is formed with Ta powder. Next, a step of forming a dielectric oxide film by anodic oxidation is performed, and thereafter, a conductive polymer is formed on the anode body and the cathode body, or only on the anode body. Thereafter, after a washing step with pure water, the conductive polymer was softened with a softener (softening step), and then, through a drying step, an anode body and a cathode body were alternately pressed and laminated to form a capacitor portion. Thereafter, the anode lead and the cathode lead may be joined in some cases. Finally, the capacitor portion is sealed to form a solid electrolytic capacitor. At this time, the number of alternately stacked anodes and cathodes is changed as necessary.

In the process of softening the conductive polymer, the softening agent is diluted with a low-boiling solvent, the diluted solvent is impregnated into the conductive polymer layer, and the softening step is softened. And a drying step of evaporating. In addition, the softening step needs to be performed immediately after the conductive polymer is dried (before the drying step) after forming the conductive polymer and performing the washing step with pure water to eliminate the peeling. This allows
The softener can be efficiently penetrated into the conductive polymer layer and softened, and the contact area can be increased with a small pressure when joining the anode body and the cathode body via the conductive polymer layer. The formation process becomes easy. Further, since the peeling of the conductive polymer layer can be eliminated, it is possible to eliminate the variation in the characteristics of the solid electrolytic capacitor due to the peeling.
In addition, as a method of softening the conductive polymer with a softener, there are other methods such as generating vapor of the softener, exposing the conductive polymer portion to the vapor atmosphere, and using a solution for forming the conductive polymer with the softener. There is a method of dissolving it inside.

In the conductive polymer forming step, the conductive polymer is formed by electrolytic polymerization using an electrolytic solution (polymer monomer solution) which does not contain a binder resin usually contained in the electrolytic solution.

According to the present invention, the conductive polymer formed between the anode body and the cathode body is formed by electrolytic polymerization using an electrolyte solution without a binder resin, thereby making it possible to compare with a conventional solid electrolytic capacitor. ESR can be reduced. Further, the solid electrolyte layer made of the conductive polymer is softened with a higher alcohol or a softener, whereby the separation of the conductive polymer from the electrode foil can be eliminated. Further, according to the present invention, it is possible to manufacture a solid electrolytic capacitor having small variations in characteristics, low ESR and excellent high-frequency characteristics.

[0038]

EXAMPLES Hereinafter, specific examples will be described, but embodiments of the present invention are not limited to the following examples.

(Example 1) In this example, aluminum was used as the valve metal of the anode, aluminum foil with carbon embedded in the surface was used as the cathode metal foil, and polythiophene was used as the conductive polymer.

Except for the lead portion of the aluminum foil whose surface is roughened, anodizing treatment is performed on both surfaces of a part of the surface (3 mm in length and 3.5 mm in width) at a formation voltage of 8 V to form a dielectric oxide film layer. did. After that, the entire surface of the dielectric oxide film layer including the inside of the pores is impregnated into a solution containing a thiophene monomer and a dopant, and is impregnated into an oxidizing agent solution. An electrolyte precoat layer was formed, and polythiophene was formed on the precoat layer by electrolytic polymerization to obtain a solid electrolyte layer. Then 3 × 1
Part of aluminum foil with carbon embedded on the surface of 0 mm ² (3 ×
5 mm ² ) was used as a lead portion, and a conductive polymer polythiophene was formed on the surface of the aluminum foil other than the lead portion (3 × 5 mm ² ) by electrolytic polymerization to obtain a cathode. At this time, an electrolyte containing a binder resin was used.

The polythiophene formed on the dielectric oxide film layer and on the surface of the aluminum foil having carbon embedded in the surface was softened with a softener to obtain a capacitor element for evaluation. Glycerin having a melting point of 17 ° C and a boiling point of 290 ° C was used as a softening agent. As an impregnation method, glycerin was added to ethanol at 10 wt.
The anode foil and the cathode foil on which the above-mentioned polythiophene was formed were immersed in the solution in which the polythiophene was dissolved for 20 minutes, and then the anode foil and the cathode foil were pulled up and heated to 60 ° C. to evaporate ethanol for 20 minutes.

Thereafter, an evaluation capacitor element is assembled.
Was. FIG. 2 shows an outline of the evaluation capacitor element. Figure 2
1 is an aluminum anode foil, which is the anode body, and 2 is a dielectric oxide skin.
The film, 3 is a conductive polymer, and 4 is a cathode metal foil. At this time
Terminal part of two cathode metal foils that play the role of cathode drawer
Was resistance welded. The contact area between anode and cathode is 21mm ^Two
It is.

The evaluation results will be described later.

Example 2 This example is an example in which a binder is not used and a softener glycerin is not used.

Polythiophene was formed by electrolytic polymerization on the dielectric oxide film layer and on the surface of the aluminum foil having carbon embedded in the surface. At this time, an electrolytic solution having no binder resin was used during the electrolytic polymerization, and the conductive polymer was not softened with glycerin. The evaluation results will be described later.

(Example 3) Polythiophene formed by electrolytic polymerization on the dielectric oxide film layer and on the surface of an aluminum foil having carbon embedded in the surface was formed using an electrolytic solution without a binder resin during electrolytic polymerization. An evaluation capacitor element was obtained in the same manner as in Example 1 except that the formed polythiophene was softened with glycerin. The impregnation was performed in the same manner as in Example 1. The evaluation results will be described later.

(Comparative Example 1) In Example 1, a conventional capacitor element without using the softener glycerin was obtained. The evaluation results will be described later.

(Evaluation Results) The ESR of the evaluation capacitor elements of Comparative Example 1 and Examples 1 to 3 was measured using a measuring instrument IMPEDANCE / GAIN-PHASE ANALYZER while pressurizing the respective connection parts.
(4194A, Yokogawa Hewlett-Packard Co., Ltd.).

FIG. 3 shows the measurement results. In Figure 3, ESR
Are values at 400 kHz. Compared to the evaluation capacitor element of Comparative Example 1, the ESR of the evaluation capacitor element of Example 1 in which the conductive polymer layer was softened with glycerin was reduced, and this tendency was particularly noticeable in a low pressure region. ing.
Furthermore, the evaluation capacitor elements of Examples 2 and 3 in which polythiophene was formed by electrolytic polymerization using an electrolyte solution without a binder resin had a large ESR reduction as compared with the evaluation capacitor elements of Comparative Example 1 and Example 1. I have.

That is, Example 1 is different from Comparative Example 1 in that
It shows the effect of lowering ESR by adding glycerin,
Examples 2 and 3 show the effect of lowering the ESR by using the electrolyte solution from which the binder resin was further removed as compared with Comparative Example 1.

Further, in the evaluation capacitor elements of the comparative example and the example 2, some of the polythiophene peeling was observed, but the solid electrolytic capacitors of the examples 1 and 3 in which the polythiophene was softened with glycerin were used. No peeling was observed. FIGS. 4A and 4B show frequency characteristics of impedance and capacitance of the capacitor element for evaluation of Example 3 at the time of pressurization of about 100 kgf / cm ² with the lowest ESR. 4A and 4B that the capacitor element of Example 3 has very low impedance and excellent high-frequency characteristics.

As is clear from the above experimental results, the combination of the features of Examples 1 and 2 as in Example 3, ie, the combination of softening with glycerin and using an electrolyte solution without a binder resin makes it possible to reduce the ESR. Was very low and showed excellent high-frequency characteristics, and it was confirmed that a solid electrolytic capacitor in which the conductive polymer was not peeled off from the electrode foil was obtained.

As described above, according to the present invention, very high ESR
Therefore, it is possible to provide a good solid electrolytic capacitor having low ESR and a very small variation in ESR between samples. According to the present invention, it is possible to reduce the pressure applied to the connection portion when forming the exterior. In this embodiment, an aluminum solid electrolytic capacitor is described, but the present invention can be similarly applied to a tantalum solid electrolytic capacitor.

Further, in this embodiment, an example in which polythiophene is used as the solid electrolyte has been described, but the effect can be obtained with other conductive polymers.

In this embodiment, an aluminum foil in which carbon is embedded in the surface of the cathode metal foil is used. However, similar effects can be obtained by using other metal foils.

[0056]

As described above, the present invention provides a conventional solid electrolyte by forming a conductive polymer formed between an anode body and a cathode body by electrolytic polymerization using an electrolyte solution having no binder resin. ESR can be reduced compared to a capacitor. Further, the solid electrolyte layer made of the conductive polymer is softened with a softener, whereby the peeling of the conductive polymer from the electrode foil can be eliminated. Further, according to the present invention, it is possible to manufacture a solid electrolytic capacitor having small variations in characteristics, low ESR and excellent high-frequency characteristics.

[Brief description of the drawings]

FIG. 1 is a process diagram showing an outline of a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a configuration of a capacitor element portion of the solid electrolytic capacitor according to one embodiment of the present invention.

FIG. 3 shows a relationship between a pressing force applied to an anode-cathode connection of an evaluation capacitor element and an ESR (Equivalent Series) in one embodiment of the present invention.
FIG. 4 is a diagram showing a relationship with the s resistance.

FIG. 4A is a characteristic diagram illustrating an example of the frequency characteristic of the impedance of the solid electrolytic capacitor according to the third embodiment of the present invention, and FIG. 4B is a characteristic diagram illustrating an example of the frequency characteristic of the capacitance;

FIG. 5 is a cross-sectional view showing an example of a configuration of a conventional solid electrolytic capacitor using a valve metal for an anode.

[Explanation of symbols]

 1 Aluminum anode foil as anode body 2, 6 Dielectric oxide film 3 Conductive polymer 4 Cathode body 5 Valve action metal porous body 7 Solid electrolyte layer 8 Carbon paste 9 Ag paste 10 Anode lead-out terminal 11 Cathode lead-out terminal

Continued on the front page (72) Inventor Emiko Igaki 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masakazu Tanahashi 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Invention Mikiya Shimada 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (17)

[Claims] 1. A solid electrolytic capacitor in which a conductive polymer layer is disposed between an anode body and a cathode body made of a valve metal having a dielectric oxide film layer formed on a surface thereof, A solid electrolytic capacitor, wherein a softener for softening the conductive polymer layer is present in the polymer layer. 2. The solid electrolytic capacitor according to claim 1, wherein the softening agent has a melting point of 30 ° C. or lower at normal pressure and a boiling point of 200 ° C. or higher at normal pressure. 3. The solid electrolytic capacitor according to claim 2, wherein the softening agent has a boiling point of 260 ° C. or higher at normal pressure. 4. The softener according to claim 1, wherein the softener is at least one selected from polyhydric alcohols, aliphatic alcohols, aromatic alcohols, phenols and ethers.
3. The solid electrolytic capacitor according to item 1. 5. The solid electrolytic capacitor according to claim 4, wherein said softener is at least one selected from glycerin, diethylene glycol, 2-anilinoethanol, m-methoxyphenol and ethylene glycol-monobenzyl ether. 6. The solid electrolytic capacitor according to claim 1, wherein the amount of the softening agent is 5.0% by weight or less based on the conductive polymer layer. 7. The solid electrolytic capacitor according to claim 1, wherein said conductive polymer layer does not contain a binder resin. 8. A method for manufacturing a solid electrolytic capacitor comprising a conductive polymer layer disposed between an anode body and a cathode body made of a valve metal having a dielectric oxide film layer formed on a surface thereof, After forming a conductive polymer layer on at least one electrode body selected from the anode body and the cathode body, a softener for softening the conductive polymer layer diluted with a low-boiling solvent is used as the conductive polymer layer. A method for producing a solid electrolytic capacitor, wherein the conductive polymer layer is softened by impregnating the conductive polymer layer therein, and then the low boiling point solvent is evaporated. 9. The method for producing a solid electrolytic capacitor according to claim 8, wherein the boiling point of the low boiling point solvent is 150 ° C. or less at normal pressure. 10. The method for producing a solid electrolytic capacitor according to claim 8, wherein the low boiling point solvent is at least one selected from methanol, ethanol, isopropyl alcohol, acetone, toluene and xylene. 11. The drying temperature of the low boiling point solvent is 15 at normal pressure.
The method for producing a solid electrolytic capacitor according to claim 8, wherein the temperature is 0 ° C. or less. 12. The method according to claim 8, wherein the softening agent has a boiling point of 200 ° C. or more at normal pressure. 13. The method according to claim 12, wherein the softening agent has a boiling point of 240 ° C. or higher at normal pressure. 14. The method according to claim 8, wherein the softening agent is at least one selected from polyhydric alcohols, aliphatic alcohols, aromatic alcohols, phenols and ethers. . 15. The production of a solid electrolytic capacitor according to claim 14, wherein the softener is at least one selected from glycerin, diethylene glycol, 2-anilinoethanol, m-methoxyphenol and ethylene glycol-monobenzyl ether. Method. 16. The method for manufacturing a solid electrolytic capacitor according to claim 8, wherein the amount of the softening agent is 5.0% by weight or less based on the conductive polymer layer. 17. The method according to claim 8, wherein the conductive polymer layer does not contain a binder resin.