JP2012049574A - Manufacturing method for solid electrolytic capacitor and solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably manufacture a solid electrolytic capacitor with excellent leak current characteristic, when the solid electrolytic capacitor having a solid electrolyte layer containing an electrically conductive polymer layer formed by electrolytic oxidative polymerization is industrially manufactured.SOLUTION: A manufacturing method for a solid electrolytic capacitor having a solid electrolyte layer containing an electrically conductive polymer layer formed by electrolytic oxidative polymerization forms: a dielectric layer on a surface of an anode body made of a valve action metal; an electrically conductive precoat layer on the dielectric layer; and the electrically conductive polymer layer on the electrically conductive precoat layer, by performing electrolytic oxidative polymerization in an electrolytic polymerization solution containing a monomer, a dopant agent and a chelate agent.

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor including a solid electrolyte layer including a conductive polymer layer formed by electrolytic oxidation polymerization.

  In a solid electrolytic capacitor in which a solid electrolyte layer including a conductive polymer layer is formed on a valve action metal having a dielectric layer on the surface, a method for forming the conductive polymer layer includes a chemical oxidative polymerization method and an electrolytic oxidation method. Polymerization methods are known. The above-mentioned chemical oxidative polymerization method is a method of generating a conductive polymer by chemically oxidizing the monomer by causing an oxidant to act on the monomer. The electrolytic oxidative polymerization method is an electrolytic polymerization including the monomer. In this method, a conductive polymer is produced by energizing the liquid and subjecting the monomer to electrolytic oxidation polymerization. In general, the electrolytic oxidation polymerization method requires more complicated production equipment than the chemical oxidation polymerization method, but the polymerization conditions are easy to control, and a conductive polymer excellent in conductivity, mechanical strength, and homogeneity is required. Easy to obtain.

  When a conductive polymer layer for a solid electrolytic capacitor is formed by electrolytic oxidation polymerization, the dielectric layer formed on the surface of the valve metal serving as the anode body is an insulator, so that manganese nitrate is formed on the dielectric layer. First, a conductive precoat layer composed of a manganese dioxide layer by thermal decomposition, a conductive polymer layer by chemical oxidative polymerization, or the like is formed. Then, for example, the monomer is obtained by passing current between the anode and the cathode in an electrolytic polymerization solution containing the monomer and a dopant agent also serving as a supporting electrolyte, using the conductive precoat layer as an anode and a metal plate such as stainless steel as a cathode. Is electro-oxidatively polymerized to form a conductive polymer layer (for example, Patent Document 1).

Japanese Patent Publication No. 4-74853

  However, even if a solid electrolyte layer including a conductive polymer layer formed by electrolytic oxidation polymerization as described above is used, the leakage current characteristics of the obtained solid electrolytic capacitor are not improved as expected, and the above-mentioned When the electrolytic oxidation polymerization is industrially performed using such an electrolytic polymerization solution, there is a problem that the generation rate of a solid electrolytic capacitor having a large leakage current is high.

  The present invention has been made in order to solve the above problems, and in the case of industrially producing a solid electrolytic capacitor including a solid electrolyte layer including a conductive polymer layer formed by electrolytic oxidation polymerization, a leakage current is provided. The object is to stably produce a solid electrolytic capacitor having excellent characteristics.

The inventors of the present invention have led to the idea that the above-described leakage current characteristics are deteriorated, and many defective products with large leakage currents are caused by metal ions mixed in the electrolytic polymerization solution. The present inventors have found that a solid electrolytic capacitor having excellent leakage current characteristics can be stably manufactured by configuring as follows. That is, the present invention relates to a method for producing a solid electrolytic capacitor having a solid electrolyte layer including a conductive polymer layer formed by electrolytic oxidation polymerization, wherein a dielectric layer is provided on the surface of an anode body made of a valve metal. Forming a conductive precoat layer on the dielectric layer, and bringing the electrolytic polymerization solution containing a monomer and a dopant agent into contact with the first cation exchange resin, thereby subjecting the first electrolytic polymerization to an ion exchange treatment. This is a method for producing a solid electrolytic capacitor in which a liquid is prepared, and the conductive polymer layer is formed on the conductive precoat layer by electrolytic oxidation polymerization in the first electrolytic polymerization liquid.

  By bringing the electrolytic polymerization solution and the cation exchange resin into contact with each other in advance before electrolytic oxidation polymerization, the metal ions that inhibit electrolytic oxidation polymerization in the electrolytic polymerization solution can be exchanged with cations that do not inhibit electrolytic oxidation polymerization. . Thereby, the influence of the metal ion at the time of electrolytic oxidation polymerization can be reduced.

  In the manufacturing method, an ion exchange-treated second electrolytic polymerization solution is prepared by bringing the first electrolytic polymerization solution into contact with a second cation exchange resin during the electrolytic oxidation polymerization, The conductive polymer layer may be formed by further electrolytic oxidation polymerization in the electrolytic polymerization solution of No. 2.

  Since the electrolytic oxidation polymerization is performed by energizing between the metal members in an electrolytic polymerization liquid in which a metal member such as a metal plate or a metal anode pin is arranged, the electrolytic oxidation polymerization is performed from the metal member according to the electrolytic oxidation polymerization. Metal ions may be mixed in the electrolytic polymerization solution. Therefore, if the electrolytic polymerization solution is brought into contact with the cation exchange resin during the electrolytic oxidation polymerization, the influence of metal ions mixed in the electrolytic polymerization solution from the metal member can be reduced.

  The first and second cation exchange resins are preferably at least one selected from the group consisting of acid (H) cation exchange resins and metal salt cation exchange resins. If the electrolytic polymerization solution is brought into contact with these cation exchange resins, the metal ions mixed in the electrolytic polymerization solution are exchanged with cations such as hydrogen ions and alkali metal ions that do not inhibit electrolytic oxidation polymerization. Can do.

  And this invention is a solid electrolytic capacitor manufactured by the said manufacturing method. According to the above production method, the influence of metal ions mixed in the electrolytic polymerization solution can be suppressed, so that the electrolytic oxidation polymerization can be performed uniformly, and thereby the conductive property by electrolytic oxidation polymerization on the conductive precoat layer. A solid electrolytic capacitor having a solid electrolyte layer in which a polymer layer is densely formed is obtained.

  According to the present invention, when a solid electrolytic capacitor having a solid electrolyte layer including a conductive polymer layer formed by electrolytic oxidation polymerization is industrially produced, the metal ions mixed in the electrolytic polymerization solution are The influence can be reduced. Thereby, a solid electrolytic capacitor having excellent leakage current characteristics can be stably manufactured.

When a conductive polymer layer is formed by electrolytic oxidation polymerization, the leakage current characteristics deteriorate and the rate of occurrence of solid electrolytic capacitors with a large leakage current increases due to electrolysis in the electrolytic polymerization solution preparation process and electrolytic oxidation polymerization process. The influence of metal ions mixed in the polymerization solution is considered. That is, a metal supply pipe for supplying an electrolytic polymerization solution, a metal plate cathode such as stainless steel used in the electrolytic oxidation polymerization process, a metal plate anode, and a metal anode pin such as stainless steel used to make the conductive precoat layer an anode When metal members such as these come into contact with the electrolytic polymerization solution, metal ions such as Fe ²⁺ ions, Mn ²⁺ ions, and Cr ²⁺ ions are mixed into the electrolytic polymerization solution from these metal members. In particular, when a conductive polymer layer is formed by electrolytic oxidation polymerization, an acidic electrolytic polymerization solution is usually used. Therefore, when the metallic member as described above comes into contact with the acidic electrolytic polymerization solution, the metallic member is corroded. As a result, the amount of elution of metal ions such as Fe ²⁺ ions into the electrolytic polymerization solution increases. Moreover, although content of a metal ion is thought to be trace amount, metal ions may be contained in raw materials, such as a solvent used for preparation of an electrolytic polymerization liquid. When electrolytic oxidation polymerization is performed in an electrolytic polymerization solution in which such metal ions are mixed, metal ions such as Fe ²⁺ ions are energized on or near the conductive precoat layer, which is an anode, by Fe ³⁺ ions or the like. It is electrolytically oxidized to a high number of metal ions. For this reason, electrolytic oxidation polymerization of the monomer on the conductive precoat layer is hindered, and formation of a conductive polymer by electrolytic oxidation polymerization is hindered. Further, electrolytically oxidized metal ions such as an expensive number of Fe ³⁺ ions function as an oxidizing agent. For this reason, not only electrolytic oxidation polymerization but also chemical oxidation polymerization tends to occur as a side reaction. Furthermore, since the expensive metal ions functioning as an oxidant are reduced by chemical oxidative polymerization, they return to low-valent metal ions such as Fe ²⁺ ions that are electrolytically oxidized, and again electrolyze the low-valent metal ions. Oxidation is repeated. Furthermore, electrolytically oxidized metal ions such as expensive Fe ³⁺ ions are reduced at and near the cathode. For this reason, a chemical short circuit occurs, current loss occurs, and efficient electrolytic oxidation polymerization is prevented. As a result, it is difficult to sufficiently form a conductive polymer layer by electrolytic oxidation polymerization on the conductive precoat layer, and conductivity formed by chemical oxidation polymerization in the conductive polymer layer formed by electrolytic oxidation polymerization. It is considered that the polymer is mixed, the leakage current characteristics of the solid electrolytic capacitor are deteriorated, and the incidence of defective products having a large leakage current is increased.

  Based on the above findings, a method for reducing the influence of metal ions mixed in the electrolytic polymerization solution was studied. As a result, a method of performing electrolytic oxidation polymerization using an electrolytic polymerization solution containing a chelating agent, or an electrolytic polymerization solution was developed. Metal ion mixed in the electrolytic polymerization solution at the time of electrolytic oxidation polymerization can be obtained by using a method in which the electrolytic polymerization solution is subjected to the ion exchange treatment in advance with the cation exchange resin before the electrolytic oxidation polymerization. It has been found that the influence of the leakage current can be reduced, thereby improving the leakage current characteristics and reducing the incidence of defective products having a large leakage current. Hereinafter, the present invention will be described in detail by dividing it into the above-mentioned production methods.

(Embodiment 1)
The solid electrolytic capacitor of this embodiment is manufactured by sequentially forming a dielectric layer, a cathode layer made of a solid electrolyte layer, and a cathode lead layer on the peripheral surface of an anode body made of a valve metal having an anode lead. Is done. Examples of the valve metal include metals on which a dense and durable dielectric layer is formed. Specific examples thereof include tantalum, niobium, aluminum, and titanium. The dielectric layer on the surface of the valve metal can be formed by, for example, immersing an anode body made of a valve metal in an aqueous phosphoric acid solution and then electrolytically oxidizing it.

  Next, a solid electrolyte layer that is a cathode layer is formed on the dielectric layer. In forming the solid electrolyte layer, first, a conductive precoat layer is formed on the dielectric layer. Examples of the conductive precoat layer include an oxide conductor layer made of manganese dioxide or the like, an organic semiconductor layer made of TCNQ complex, or the like, and a conductive polymer layer formed by chemical oxidative polymerization of a monomer with an oxidizing agent. be able to. Among these, a conductive polymer layer formed by chemical oxidative polymerization is preferable.

  In order to form a conductive precoat layer by chemical oxidative polymerization, first, an anode body on which a dielectric layer is formed is immersed in a solution containing an oxidizing agent and a dopant agent that gives a dopant, or the solution is added to the anode. The oxidant and dopant agent are deposited on the dielectric layer by spraying or applying to the body. Next, the anode body is immersed in a chemical oxidative polymerization solution containing a monomer, dried, and the monomer is chemically oxidatively polymerized to form a conductive polymer layer on the dielectric layer. As the above monomer, pyrrole, thiophene, furan, aniline and the like are used. Further, as the oxidant, any generally known oxidant such as halogen and peroxide is used. As the dopant agent, a proton acid such as sulfuric acid or nitric acid, or a surfactant such as an alkyl sulfonate is used. In addition, what is necessary is just to include this compound in a solution if it is a compound (for example, halogens, a transition metal halide, a protonic acid, etc.) which can become any of an oxidizing agent and a dopant agent.

Next, a conductive polymer layer is formed on the conductive precoat layer by electrolytic oxidation polymerization. In this embodiment, electrolysis is performed using an electrolytic polymerization solution containing a chelating agent together with a monomer and a dopant agent. Oxidative polymerization is performed. That is, by adding a chelating agent to the electrolytic polymerization solution, the carboxylate ion of the chelating agent captures metal ions mixed in the electrolytic polymerization solution. As a result, electrolytic oxidation of metal ions such as Fe ²⁺ ions on the conductive precoat layer is suppressed, and electrolysis is performed in an electropolymerization solution having a small amount of metal ions such as Fe ³⁺ ions that are oxidized and function as an oxidizing agent. Oxidative polymerization can be performed. As a result, side-reaction chemical oxidative polymerization and chemical short-circuiting are suppressed, and electrolytic oxidative polymerization can be performed efficiently, and mixing of conductive polymers in the conductive polymer layer due to chemical oxidative polymerization is reduced. can do.

As the chelating agent, a chelating agent having a high chelate stability constant with respect to metal ions is preferable. Specific examples of such chelating agents include ethylenediaminetetraacetic acid, triethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylenediaminetriacetic acid, glycol etherdiaminetetraacetic acid, nitrilotriacetic acid, triethylenetetraminehexaacetic acid, hydroxy Examples include at least one aminocarboxylic acid type chelating agent selected from the group consisting of iminodiacetic acid, dihydroxyethylglycine, hydroxyiminodisuccinic acid, ethylenediamine disuccinic acid, and salts thereof. Among these, the chelating agent in which the carboxylate is substituted with at least one salt selected from the group consisting of sodium salt, potassium salt, and ammonium salt is excellent in solubility in the electrolytic polymerization solution, and in the electrolytic polymerization solution. This is preferable because the metal ions contained in the cation can be exchanged with cations that do not inhibit electrolytic oxidation polymerization such as Na ⁺ ions.

  The content of the chelating agent in the electrolytic polymerization solution can be appropriately selected according to the type of the chelating agent. The electrolytic polymerization solution can be prepared by stirring and mixing the chelating agent, monomer, and dopant agent as described above in a solvent. As the monomer, conventionally known pyrrole, thiophene, furan, aniline and the like are used. Moreover, as a dopant agent, the dopant agent which functions as a supporting electrolyte in order to make an electrolytic polymerization liquid into desired electric conductivity is preferable, for example, alkyl naphthalenesulfonic acid etc. are used. As the solvent, protic solvents such as water, ethanol and methanol, and aprotic solvents such as acetonitrile, propylene carbonate and N, N-dimethylformamide are used singly or in combination.

  As a method for forming the conductive polymer layer by electrolytic oxidation polymerization, a conventionally known method can be used. For example, the electrolytic polymerization solution is put into an electrolytic cell in which a metal anode pin made of stainless steel or the like and a metal plate made of stainless steel or the like are disposed, and a dielectric layer and a conductive precoat are formed on the valve action metal in the electrolytic polymerization solution. The element on which the layer is formed is immersed. Then, after the metal anode pin is brought into contact with the conductive precoat layer, the conductive polymer layer can be formed by energizing the anode and the cathode with the metal plate as the cathode and the conductive precoat layer as the anode. it can.

  In the present embodiment, after forming the conductive polymer layer (first solid electrolyte layer) by the electrolytic oxidation polymerization, a conductive polymer layer (second solid electrolyte layer) by chemical oxidation polymerization is further formed. May be. In the formation of the conductive polymer layer by the above chemical oxidative polymerization, the same monomers, dopant agents, and oxidizing agents as in the formation of the conductive precoat layer can be used.

After the solid electrolyte layer is formed as described above, a solid electrolytic capacitor element is manufactured by forming a cathode lead layer composed of a graphite layer, a silver paste layer, and the like on the solid electrolyte layer. Then, an anode lead and a cathode lead are respectively taken out from the solid electrolytic capacitor element, an outer shell is formed with an exterior resin such as an epoxy resin, and an aging treatment is performed, thereby producing a solid electrolytic capacitor.

(Embodiment 2)
In the present embodiment, a step of forming a dielectric layer on the surface of the valve metal that is an anode body, a step of forming a conductive precoat layer on the dielectric layer, and a solid electrolytic capacitor after forming the solid electrolyte layer The element manufacturing process and the solid electrolytic capacitor manufacturing process are the same as those in the first embodiment. However, the electrolytic polymerization liquid does not contain a chelating agent, and the electrolytic polymerization liquid is previously cationized before electrolytic oxidation polymerization. It differs from the process of Embodiment 1 in that electrolytic oxidation polymerization is performed using an electrolytic polymerization solution that has been subjected to ion exchange treatment in contact with an exchange resin.

That is, as described above, metal ions may be mixed in the electrolytic polymerization solution during the preparation thereof, so that it affects the electrolytic oxidation polymerization such as Fe ²⁺ ions in the electrolytic polymerization solution at the initial stage of electrolytic oxidation polymerization. When many metal ions are present, the formation of a conductive polymer by electrolytic oxidation polymerization tends to be hindered. For this reason, in this embodiment, before carrying out the electrolytic oxidation polymerization, the electrolytic polymerization liquid is brought into contact with the first cation exchange resin in advance, so that the metal ions mixed in the electrolytic polymerization liquid are electrolytically oxidized. A first electrolytic polymerization solution exchanged with a cation that does not inhibit the reaction is prepared, and electrolytic oxidation polymerization is performed using the first electrolytic polymerization solution subjected to the ion exchange treatment. As a result, electrolytic oxidation of metal ions such as Fe ²⁺ ions on the conductive precoat layer is suppressed, and electrolysis is performed in an electropolymerization solution having a small amount of metal ions such as Fe ³⁺ ions that are oxidized and function as an oxidizing agent. It can be oxidatively polymerized. As a result, side-reaction chemical oxidative polymerization and chemical short-circuiting are suppressed, and electrolytic oxidative polymerization can be performed efficiently, and mixing of conductive polymers in the conductive polymer layer due to chemical oxidative polymerization is reduced. can do. In particular, in the first embodiment, a chelating agent is added to the electrolytic polymerization solution in order to reduce the influence of metal ions. Therefore, the chelating agent captures metal ions that inhibit the polymerization reaction, and then enters the electrolytic polymerization solution. In the present embodiment, a substance that does not contribute to the polymerization reaction (unreacted) is present in the first electrolytic polymerization liquid after contacting the electrolytic polymerization liquid and the first cation exchange resin. Since a chelating agent and a chelating agent after capturing a metal ion that inhibits electrolytic oxidation polymerization) are not contained, the polymerization reaction can proceed well.

As said 1st cation exchange resin, if it is a cation exchange resin which can exchange the metal ion which inhibits the electropolymerization mixed in the electrolytic polymerization liquid into a cation, it can be used without a restriction | limiting in particular. . Especially, at least 1 sort (s) chosen from the group which consists of an acid (H) type cation exchange resin and a metal salt type cation exchange resin is preferable, from an acid (H) type cation exchange resin and an alkali metal salt type cation exchange resin More preferred is at least one selected from the group consisting of In the case of acid (H) type cation exchange resins, metal ions are exchanged for hydrogen ions, and in the case of alkali metal salt type cation exchange resins, metal ions are exchanged for cations such as Na ⁺ ions. Since the cation does not change to an expensive number of ions by electrolytic oxidation, even if it exists in the electrolytic polymerization solution, electrolytic oxidation polymerization is not inhibited. In particular, an acid (H) type cation exchange resin is preferable because it does not increase the metal ions in the electrolytic polymerization solution. Specific examples of cation exchange resins available on the market include acid (H) type cation such as Amberjet 1020H, Amberjet 1024H, Amberlite 1006FH, Amberlite FPC3500, and Amberlite IRC76 manufactured by Organo. Examples of ion exchange resins include alkali metal salt type cation exchange resins such as Amberlite IR120BNa, Amberlite IR124Na, Amberlite 200CTNa, Amberlite 252Na, Amberlite IRC748 and the like manufactured by Organo.

In the present embodiment, an electrolytic polymerization solution containing no chelating agent can be prepared in the same manner as in the first embodiment. The method for preparing the first electrolytic polymerization liquid that has been subjected to the ion exchange treatment by bringing the electrolytic polymerization liquid into contact with the first cation exchange resin is not particularly limited. A method of passing the liquid through a filling tank filled with the first cation exchange resin is preferable.

  In the present embodiment, a conductive polymer layer is formed on the conductive precoat layer by performing electrolytic oxidation polymerization in the same manner as in the first embodiment using the first electrolytic polymerization solution prepared as described above. Can be formed.

Further, in the present embodiment, the ion exchange treatment is performed by bringing the first electrolytic polymerization solution into contact with the second cation exchange resin during the electrolytic oxidation polymerization using the first electrolytic polymerization solution. A conductive polymer layer may be formed by preparing a second electrolytic polymerization solution and further performing electrolytic oxidation polymerization in the second electrolytic polymerization solution subjected to the ion exchange treatment. During the electrolytic oxidation polymerization, by bringing the electrolytic polymerization solution into further contact with the cation exchange resin, during the electrolytic oxidation polymerization, the metal ions such as Fe ²⁺ ions eluted from the disposed metal member are electrolytically oxidized. Can be exchanged with a cation that does not inhibit the cation. Thereby, the influence by a metal ion can further be reduced. As a contact method between the first electrolytic polymerization solution and the second cation exchange resin, a contact method similar to that of the prepared electrolytic polymerization solution and the first cation exchange resin can be used. In this case, the second cation exchange resin may be the same cation exchange resin as the first cation exchange resin, or may be a different cation exchange resin. In the contact, after the electrolytic oxidation polymerization is stopped, the first electrolytic polymerization solution may be passed through a filling tank filled with the second cation exchange resin, or the first reaction may proceed while the polymerization reaction proceeds. The electrolytic polymerization solution may be circulated between the electrolytic bath and the filling bath.

(Other forms)
In the second embodiment, when electrolytic oxidation polymerization is performed using the first electrolytic polymerization solution and the second electrolytic polymerization solution, the chelating agent in the first embodiment may be added to these electrolytic polymerization solutions. According to this method, the metal ions mixed in the electrolytic polymerization solution during the electrolytic oxidation polymerization can be captured by the chelating agent.

  Hereinafter, although an example is given and the present invention is explained still in detail, the present invention is not limited to these examples.

Example 1
First, the tantalum sintered body was immersed in a phosphoric acid aqueous solution, and a voltage was applied to perform electrolytic oxidation to form a dielectric layer on the surface of the tantalum sintered body. Next, an aqueous solution containing an oxidizing agent and a dopant agent was prepared. The tantalum sintered body on which the dielectric layer was formed was immersed in the aqueous solution and then subjected to chemical oxidative polymerization by exposure to pyrrole to form a conductive precoat layer made of polypyrrole on the dielectric layer.

Apart from the above, pyrrole (0.02 mol / l) as a monomer, alkylnaphthalenesulfonic acid (0.004 mol / l) as a dopant agent, and ethylenediaminetetraacetic acid-2Na salt (6.3 × 10 ⁻⁴ mol) as a chelating agent / L) was added to water and mixed with stirring to prepare an acidic electrolytic polymerization solution.

The electrolytic polymerization solution prepared as described above was put into an electrolytic cell equipped with a stainless steel anode pin and a cathode made of a stainless steel metal plate. Next, the tantalum sintered body on which the dielectric layer and the conductive precoat layer were formed was immersed in an electrolytic polymerization solution, and then a stainless steel anode pin was brought into contact with the conductive precoat layer. Then, the electrooxidation polymerization was conducted between the anode and the cathode for 6 hours to form a conductive polymer layer made of polypyrrole on the conductive precoat layer.

  Next, a graphite layer and a silver paste layer were sequentially formed on the conductive polymer layer to produce a capacitor element. Thereafter, a cathode lead frame was connected to the silver paste layer of the capacitor element, and an anode lead frame was connected to the anode lead. After each lead frame is connected, the capacitor element is covered with an exterior resin except for a part of the anode lead frame and the cathode lead frame, and each exposed lead frame is bent along the exterior to form a solid electrolytic capacitor. Produced.

(Example 2)
A solid electrolytic capacitor was prepared in the same manner as in Example 1 except that electrolytic oxidation polymerization was performed using an electrolytic polymerization solution containing 1.0 × 10 ⁻² mol / l of ethylenediaminetetraacetic acid-2Na salt. Produced.

(Example 3)
In the preparation of the electrolytic polymerization solution of Example 1, an electrolytic polymerization solution was prepared in the same manner as in Example 1 except that the chelating agent was not added. When the amount of Fe ions in this electrolytic polymerization solution was measured by the ICP method, the amount of Fe ions was 3.6 × 10 ⁻⁵ mol / l.

Next, the electrolytic polymerization solution was passed through a filling tank filled with an acid (H) type cation exchange resin (manufactured by Organo Corporation, Amberjet 1020H) to prepare a first electrolytic polymerization solution subjected to ion exchange treatment. . When the amount of Fe ions in the first electrolytic polymerization solution was measured by ICP method, the amount of Fe ions was 1.6 × 10 ⁻⁵ mol / l, and a decrease in the amount of Fe ions due to the ion exchange treatment was confirmed. .

A solid electrolytic capacitor was produced in the same manner as in Example 1, except that the first electrolytic polymerization solution subjected to the ion exchange treatment as described above was energized for 6 hours to perform electrolytic oxidation polymerization.

Example 4
In the electrolytic oxidation polymerization of Example 3, the electrolytic oxidation polymerization was performed by first energizing for 3 hours. Next, electricity supply was stopped and the electrolytic polymerization solution in the middle of the polymerization reaction was passed through a filling tank filled with the same acid (H) type cation exchange resin as in Example 3 to prepare a second electrolytic polymerization solution. . When the amount of Fe ions in the electrolytic polymerization solution before and after the ion exchange treatment was measured by the ICP method, the amount of Fe ions before the treatment was 2.1 × 10 ⁻⁵ mol / l, and the amount of Fe ions after the treatment was It was 1.2 × 10 ⁻⁵ mol / l, and a decrease in the amount of Fe ions due to the ion exchange treatment was confirmed. And using the 2nd electrolytic polymerization liquid ion-exchange-treated as mentioned above, it supplied with electricity further for 3 hours, and electrolytic oxidation polymerization was performed. A solid electrolytic capacitor was produced in the same manner as in Example 3 except that electrolytic oxidation polymerization was performed as described above.

(Comparative Example 1)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that electrolytic oxidation polymerization was performed using an electrolytic polymerization solution containing no ethylenediaminetetraacetic acid-2Na salt.

  For each of 500 solid electrolytic capacitors of Examples and Comparative Examples produced as described above, the leakage current was measured and the average value was obtained. Moreover, the number of solid electrolytic capacitors having a leakage current of 200 μA or more was evaluated as the number of defects in each of 500 solid electrolytic capacitors of Examples and Comparative Examples. Table 1 shows these results.

  As shown in Table 1, solid electrolysis of Examples 1 and 2 having a conductive polymer layer formed by electrolytic oxidation polymerization using an electrolytic polymerization solution containing ethylenediaminetetraacetic acid-2Na salt as a chelating agent It can be seen that the capacitor has a low leakage current and a low incidence of defective products with a large leakage current. This is considered because the influence of the metal ion which inhibits the electrolytic oxidation polymerization mixed in the electrolytic polymerization solution is reduced by adding ethylenediaminetetraacetic acid-2Na salt to the electrolytic polymerization solution.

  In addition, a conductive polymer formed by electrolytic oxidation polymerization using a first electrolytic polymerization liquid in which the amount of Fe ions is reduced by bringing the electrolytic polymerization liquid into contact with a cation exchange resin in advance before electrolytic oxidation polymerization. The solid electrolytic capacitor of Example 3 having a layer, or the second electrolytic polymerization in which the amount of Fe ions was reduced by further contacting the first electrolytic polymerization solution with the second cation exchange resin during the electrolytic oxidation polymerization. It can be seen that the solid electrolytic capacitor of Example 4 having a conductive polymer layer formed by electrolytic oxidation polymerization using a liquid has a very low leakage current and a low incidence of defective products with a large leakage current. . This is because the amount of Fe ions after contacting the electrolytic polymerization solution with the cation exchange resin was smaller than that before the contact, so that the metal ions mixed in the electrolytic polymerization solution were exchanged for cations. This is thought to be because the electrolytic oxidation polymerization was able to be performed in an electrolytic polymerization solution with few metal ions that inhibit the electrolytic oxidation polymerization.

Claims (4)

A method for producing a solid electrolytic capacitor comprising a solid electrolyte layer including a conductive polymer layer formed by electrolytic oxidation polymerization,
A dielectric layer is formed on the surface of the anode body made of a valve metal,
Forming a conductive precoat layer on the dielectric layer;
Preparing an ion exchange treated first electrolytic polymerization liquid by bringing an electrolytic polymerization liquid containing a monomer and a dopant agent into contact with the first cation exchange resin;
A method for producing a solid electrolytic capacitor, wherein the conductive polymer layer is formed on the conductive precoat layer by electrolytic oxidation polymerization in the first electrolytic polymerization solution. In the middle of the electrolytic oxidation polymerization, a second electrolytic polymerization solution subjected to an ion exchange treatment is prepared by bringing the first electrolytic polymerization solution into contact with a second cation exchange resin,
The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive polymer layer is formed by further performing electrolytic oxidation polymerization in the second electrolytic polymerization solution.   The solid according to claim 1 or 2, wherein the first and second cation exchange resins are at least one selected from the group consisting of an acid (H) type cation exchange resin and a metal salt type cation exchange resin. Manufacturing method of electrolytic capacitor.   The solid electrolytic capacitor manufactured by the manufacturing method of any one of Claims 1-3.