JPH09320897A - Manufacture of solid-electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily manufacturing a solid-electrolytic capacitor, wherein characteristics thereof such as electrostatic capacity, tan δ, impedance, and leakage current, etc., are improved. SOLUTION: In a manufacturing method for a solid-electrolytic capacitor wherein an electrically conductive polymer film is stacked on an element 1 consisting of a valve action metal member formed with an oxide film 3 thereon, the film of the electrically conductive polymer 6 is formed by carrying out a process of spreading a solution of the electrically conductive polymer 6 on the element 1, and after this process, carrying out a process of spreading a dedoped polymer solution and then bringing a doping solution in contact with it.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A solid electrolytic capacitor is formed by anodizing a foil or sintered body of a valve metal such as aluminum or tantalum to form an oxide film, and then forming a conductive polymer on the surface of the oxide film. Is formed, and further, a carbon layer or a silver layer is laminated on the surface of this film to form a cathode layer to manufacture. Then, the film made of a conductive polymer is 1) coated with a solution of a polymer that has been previously doped to make it conductive, or 2) coated with a solution of a polymer that has been undoped, and then brought into contact with a doping solution to make it conductive. Is formed by

[0003]

However, since the dopant is difficult to dissolve in the solution of the conductive polymer, only a low-concentration solution can be obtained. For this reason, in order to obtain a conductive polymer film having a predetermined thickness, it is necessary to increase the number of times the solution is applied, resulting in a long manufacturing time and a possibility of causing defects.

Further, when a solution of the dedoped polymer is used, a solution having a high concentration can be obtained, and the number of times of coating for obtaining a conductive polymer film having a predetermined thickness can be reduced. However, since the solution is in contact with the doping solution after being applied, the portion near the outer surface is doped, but the inner portion is less likely to be doped. Therefore, it is difficult to improve characteristics such as capacitance, tan δ, impedance, and leakage current.

It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor, which is capable of improving the above-mentioned drawbacks, can be easily manufactured, and can improve the characteristics such as capacitance, tan δ, impedance and leakage current. Is.

[0006]

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a solid electrolytic capacitor in which a conductive polymer film is laminated on a device having an oxide film formed on a valve metal. Solid electrolyte characterized by forming a conductive polymer film by performing a step of applying a solution of a conductive polymer on the substrate, a step of applying a solution of a dedoped polymer after this step, and then a step of contacting with a doping solution. A method for manufacturing a capacitor is provided.

Since the present invention forms a film of a conductive polymer having a predetermined thickness using a solution of a conductive polymer and a solution of a dedoped polymer, it is manufactured using only the solution of a conductive polymer. It is easy to shorten the manufacturing time as compared with the case of performing. Further, the present invention is formed by applying a solution of a conductive polymer to the inside of a film of a conductive polymer which is difficult to be doped when only a solution of the dedoped polymer is used, and thereby the The portion of the film formed by using the solution can be thinned. Therefore, the conductive polymer film can be sufficiently doped from the inside to the outside surface, and characteristics such as capacitance and tan δ can be improved.

[0008]

Embodiments of the present invention will be described below. First, tantalum, aluminum, titanium or the like is used as the valve metal. Then, as shown in FIG. 1, a fine powder of the valve action metal is used to form a sintered body such as a cylindrical shape or a rectangular parallelepiped shape, or a valve action metal foil is laminated or wound to form the element 1. For example, when tantalum powder is used, the powder is formed into a predetermined shape and then sintered at a temperature of 1450 to 1550 ° C. in vacuum to form the element 1.
An anode lead wire 2 made of tantalum or the like is drawn from the element 1.

Next, the element 1 is anodized using an aqueous solution of nitric acid, phosphoric acid or the like to form an oxide film 3.

After forming the oxide film 3, the element 1 is dipped in a solution of a conductive polymer or sprayed with this solution to apply the solution of the conductive polymer to the surface of the oxide film 3. After coating, it is dried and the solvent is evaporated. Then, if necessary, the steps from coating to drying are repeated. An inner conductive polymer film 4 having a predetermined thickness is formed.

The conductive polymer solution is prepared, for example, by mixing the dedoped polymer with a dopant and dissolving it in an organic solvent. As the polymer, polyaniline, polypyrrole, polythiophene, polyparaphenylene,
A simple substance such as polyacetylene or a mixture of these with a polymer such as polystyrene, polyethylene, polymethylmethacrylate, or polyacrylonitrile butanediene-styrene is used. Among them, polyaniline has a high solubility in a solvent, and a relatively high concentration solution can be prepared. When polyaniline is used as the polymer, dedoped polyaniline is produced by, for example, dedoping polyaniline produced by chemical oxidative polymerization of aniline with an alkali and dissolving this in a solvent. In order to chemically oxidatively polymerize aniline, an aniline salt is oxidatively polymerized in a hydrogen solution containing a dopant and an oxidizing agent. As the aniline salt, salts of aniline such as hydrochloric acid, sulfuric acid, and borofluoric acid are used. Further, hydrochloric acid, sulfuric acid, borofluoric acid, or the like is used as the dopant. Further, as the oxidizing agent, a persulfate such as ammonium persulfate and potassium persulfate, a high valence compound such as hydrogen peroxide, potassium permanganate and ferric chloride, which can oxidize aniline, is used. When the aniline is chemically oxidatively polymerized, the temperature rises due to the heat of reaction, so the temperature is cooled to control the reaction temperature to 0 to 10 ° C., and the aqueous solution of the oxidant is reacted for a sufficient time. Further, the produced polymer is repeatedly washed and then dried. Then, the produced polyaniline powder is filtered with ammonia water, stirred, and separated by filtration to obtain dedoped polyaniline.

As the dopant, for example, camphorsulfonic acid, dodecylbenzenesulfonic acid, P-toluenesulfonic acid, naphthalenesulfonic acid, styrenesulfonic acid and organic sulfonic acids such as polymers thereof, phthalic acid, oxalic acid and maleic acid. , Aliphatic or aromatic carboxylic acids such as citric acid, chloroacetic acid, dichloroacetic acid, benzoic acid, salicylic acid, hydrochloric acid, sulfuric acid, borofluoric acid and the like are used.

As the organic solvent, N-methyl-2 is used.
-Pyrrolidone and N, N'-dimethylpropylene urea,
Chloroform, m-cresol, trichlorobenzene,
Xylene, decalin, etc. are used.

In the case of a polyaniline solution doped with a conductive polymer, the concentration of polyaniline is 0.1-0.1%.
A range of 2 wt% and a dopant concentration of 0.1 to 2 wt% is preferable.

Next, after forming a film of the conductive polymer using the conductive polymer solution, it is washed with an organic solvent such as alcohol and dried.

After drying, the device 1 is dipped in a solution of the dedoped polymer or sprayed with this solution to apply the polymer solution to the surface of the conductive polymer film.
After coating, it is dried and the solvent is evaporated. Then, the steps from coating to drying are repeated as necessary to form a dedoped polymer film.

When polyaniline is used as the dedoped polymer, the dedoped polyaniline is dissolved in N-methyl-2-pyrrolidone or a mixed solvent of N-methyl-2-pyrrolidone and another solvent to remove the polyaniline. A doped polyaniline solution is prepared. At this time, the solubility can be increased by adding a reducing agent to the dedoped polyaniline to form the reduced dedoped polyaniline. In order to obtain the reduced form, a reducing agent is added to the dedoped polyaniline solution or is separated by filtration, and the dedoped polyaniline is dispersed in a non-solvent and the reducing agent is added. As the reducing agent, hydrazine compounds such as phenylhydrazine, hydrazine, hydrazine hydrate, and hydrazine sulfate, and hydrogenated metal compounds are used. At this time, the concentration of polyaniline is preferably in the range of 5 to 10%.

After applying the dedoped polyaniline solution, the element 1 is immersed in the doping solution for several tens of minutes to several hours to be contacted, and the dedoped polymer film is doped,
An outer conductive polymer film 5 is formed. The conductive polymer film 4 on the inner side and the conductive polymer film 5 on the outer side form a conductive polymer film 6.

The doping solution has a composition in which, for example, a dopant or a dopant and an oxidizing agent are dissolved in an organic solvent. The dopant and the oxidant are selected from the substances used when producing the conductive polymer solution, for example. The concentration of these substances is preferably in the range of 0.01 to 1 mol / l. Further, as the organic solvent, for example, ketones, esters, alcohols, aromatic hydrocarbons, nitriles, cellosolves, nitrogen-containing compounds and the like are used.

After forming the conductive polymer film 6, the film 6 is formed.
A carbon paste is applied to the surface of to form a carbon layer 7, and a silver paste is applied to the surface of the carbon layer 7 to form a silver layer 8. After forming the silver layer 8, the cathode terminal 10 is connected to the silver layer 8 by the silver conductive paste 9 and the anode terminal 11 is connected to the anode lead wire 2. The resin exterior 12 is formed by a resin molding method, a resin dipping method, or the like.

[0021]

Next, an embodiment of the present invention will be described. Example 1 A method for manufacturing a tantalum solid electrolytic capacitor having a rating of 4 V and 10 μF will be described. Tantalum powder is used as the valve metal. Then, first, this tantalum powder is molded into a rectangular parallelepiped shape of 1.0 × 1.7 × 1.4 mm square, and the tantalum anode lead wire is drawn out. Next, this compact is sintered at a temperature of 1450 ° C. 0.1% after forming a sintered body
This sintered body is dipped in the nitric acid aqueous solution of, and anodized at a voltage of 24 V to form an oxide film. 50 ml of distilled aniline in an Erlenmeyer flask of 1 <<
Prepare 50 ml of 35% hydrochloric acid and 400 ml of pure water,
An aniline solution is prepared. Thereafter, the flask is kept in a cooling bath at a temperature of 0 ° C. Then, a solution prepared by dissolving 46 g of ammonium persulfate in 100 ml of pure water is added dropwise to the above aniline solution over about 2 hours, and stirring is continued for 3 hours to chemically oxidize and polymerize aniline. Then, the precipitate is filtered, washed with pure water, and repeatedly decanted until the pH of the washing liquid becomes 6 to 7. Further, in order to remove water, the substrate is washed with ethanol and methanol, and then dried under reduced pressure at room temperature for 48 hours. Powder 10 produced after drying
g is dispersed in 3% ammonia 1 <<, stirred for 2 hours to dedope, and separated by filtration. After filtration, wash with pure water,
Then wash with methanol. After washing, it is dried under reduced pressure for 48 hours to produce undoped polyaniline powder.
Next, 0.1 g of this dedoped polyaniline powder was added to P
Mix with 0.1 g of dodecylbenzene sulfonic acid.
After mixing, dissolve the mixture in 20 g of xylene,
Treat in an ultrasonic bath for 2 hours. After ultrasonic treatment, undissolved substances are decanted and removed to produce a polyaniline solution in which P-dodecylbenzenesulfonic acid is dissolved. Separately, 1 g of the dedoped polyaniline powder was added to
Dissolve in 10 g of methyl-2-pyrrolidone and treat for 2 hours in an ultrasonic bath. After ultrasonic treatment, the main lysate is decanted and removed to produce a dedoped polyaniline solution. Further, 0.5 g of naphthalene sulfonic acid and 0.2 g of ammonium persulfate are dissolved in 20 g of butanol to prepare a doping solution. Then, first, the element having the oxide film formed thereon is immersed in a polyaniline solution in which P-dodecylbenzenesulfonic acid is dissolved for 5 minutes. After the immersion, it is dried in air at 150 ° C. for 30 minutes to evaporate the solvent. Then, the steps from dipping to drying are repeated twice to form a polyaniline film having P-dodecylbenzenesulfonic acid as a dopant on the surface of the oxide film. Next, the element having the polyaniline film formed thereon is immersed in the above-mentioned undoped polyaniline solution for 2 minutes. After the immersion, it is dried in air at a temperature of 150 ° C. for 30 minutes. After drying, the device is immersed in the doping solution for 3 hours to make contact. After immersion, it is repeatedly washed with ethanol. After washing, it is dried in air at a temperature of 120 ° C., the solvent is evaporated, and a polyaniline film having naphthalenesulfonic acid as a dopant is laminated on the surface of the polyaniline film having P-dodecylbenzenesulfonic acid as a dopant. Then, after forming a conductive polyaniline film composed of this polyaniline film having P-dodecylbenzenesulfonic acid as a dopant and the polyaniline film having naphthalenesulfonic acid as a dopant, the device is immersed in a colloidal carbon dispersion liquid. After immersion, in a nitrogen atmosphere, a temperature of 150
Dry at 30 ° C. for 30 minutes to form a carbon layer. After forming the carbon layer, a silver paste is applied to the surface of the carbon layer and dried in a nitrogen atmosphere at a temperature of 150 ° C. for 30 minutes to form a silver layer. After forming the silver layer, the anode terminal and the cathode terminal are connected to each other, and further a molding process is performed with an epoxy resin to form a resin exterior.

Example 2: The same conditions as in Example 1 are used except for the conductive polymer film laminated on the surface of the oxide film. That is, 0.1 g of dedoped polyaniline powder manufactured by the same method as in Example 1 was used, and this powder and 0.1 g of camphorsulfonic acid were added to 20 g of m-cresol,
Stir for 2 hours in an ultrasonic bath to dissolve. After ultrasonic treatment, the undissolved material is decanted and removed to produce a polyaniline solution containing camphorsulfonic acid as a dopant. Further, the above-mentioned dedoped polyaniline powder is used, and this is dissolved in N-methyl-2-pyrrolidone to prepare a dedoped polyaniline solution having a concentration of 10%. Further, 0.35 g of P-toluenesulfonic acid and 0.2 g of ammonium persulfate are dissolved in butanol to prepare a doping solution. Then, first, the element having the oxide film formed thereon is immersed in the above-mentioned doped polyaniline solution for 5 minutes. After the immersion, it is dried in air at a temperature of 150 ° C. for 30 minutes. This process from dipping to drying is repeated twice to form a polyaniline film having camphorsulfonic acid as a dopant. Next, the device is immersed in the dedoped polyaniline solution for 2 minutes. After the immersion, it is dried in air at a temperature of 150 ° C. for 30 minutes. After drying, the device is immersed in the doping solution for 3 hours. After the immersion, the element is pulled up and washed repeatedly with ethanol. After washing, it is dried in air at a temperature of 120 ° C. to form a polyaniline film having P-toluenesulfonic acid as a dopant.

Example 3: The conditions are the same as in Example 1 except for the conductive polymer film laminated on the surface of the oxide film. That is, 0.1 g of the dedoped polyaniline powder produced by the same method as in Example 1 was used, and this powder and 0.1 g of P-octylbenzene were added to m-cresol, and the same method as in Example 1 was performed. By processing, a polyaniline solution containing P-octylbenzene as a dopant is manufactured. Further, using the above-mentioned dedoped polyaniline powder, N-
Dissolve in methyl-2-pyrrolidone to prepare a 10% concentration dedoped polyaniline solution. Then, first, the element having the oxide film formed thereon is immersed in the above-mentioned doped polyaniline solution for 5 minutes. After the immersion, it is dried in air at a temperature of 150 ° C. for 30 minutes. After drying, it is dried in air at a temperature of 150 ° C. for 30 minutes. This dipping to drying is repeated twice to form a polyaniline film having P-octylbenzene as a dopant. Next, concentration 10%
Immerse the device in the dedoped polyaniline solution of 1. for 2 minutes. After the immersion, it is dried in air at a temperature of 150 ° C. for 30 minutes. After drying, the device is immersed in the same doping solution as in Example 1 for 3 hours. After the immersion, the element is pulled up and washed repeatedly with ethanol. After washing, it is dried in air at a temperature of 120 ° C. to form a polyaniline film having naphthalenesulfonic acid as a dopant.

Next, with respect to the tantalum solid electrolytic capacitors of Examples 1 to 3, the initial characteristics and the respective characteristics after the high temperature no-load leaving test of leaving them in the high temperature atmosphere of 150 ° C. for 10 hours were measured together with the comparative example. The results are shown in Table 1. The measurement is performed by applying a capacitance and tan δ of 120 Hz, an impedance of 100 KHz and a leakage current of 4V. The manufacturing method of the comparative example is as follows.

Comparative Example 1: The same conditions as in Example 1 were used except that the conductive polymer film was laminated on the surface of the oxide film. That is, 0.1 g of dedoped polyaniline powder produced by the same method as in Example 1 was used, and N-
Dissolve in 10 g of methyl-2-pyrrolidone to prepare a 10% concentration dedoped polyaniline solution. Further, 2.5 g of naphthalene sulfonic acid is dissolved in 20 g of pure water to produce a doping solution. Then, the element having the oxide film formed thereon is immersed in the above-mentioned dedoped polyaniline solution for 5 minutes. After the immersion, it is dried in air at a temperature of 100 ° C. for 30 minutes. This process from immersion to drying is repeated twice. After this, the device is immersed in a doping solution at 50 ° C. for 3 hours. After the immersion, the element is pulled up and washed repeatedly with ethanol. After washing, the temperature in air is 70 ℃
For 30 minutes and then at 120 ° C. for 30 minutes to form a conductive polyaniline film.

Comparative Example 2: The same conditions as in Example 1 were used except for the conductive polymer film laminated on the surface of the oxide film. That is, 0.1 g of dedoped polyaniline powder produced by the same method as in Example 1 was used, and this powder and 0.1 g of P-dodecylbenzenesulfonic acid were mixed with 20 g of xylene solvent.
In addition to g, treat in an ultrasonic bath for 2 hours. After the ultrasonic treatment, insoluble matters in the solution are removed by filtration to produce a polyaniline solution having P-dodecylbersensulfonic acid as a dopant. Then, the element having the oxide film formed thereon is immersed in this doped polyaniline solution for 5 minutes. After the immersion, it is dried in air at a temperature of 100 ° C. for 30 minutes. This process from dipping to drying is repeated 6 times to form a conductive polyaniline film.

[0027]

[Table 1]

As is apparent from Table 1, the rate of change of the capacitance after the test with respect to the initial capacitance is about 1.5 to 2.5% in Examples 1 to 3. Comparative Example 1 and Comparative Example 2 are about 3.0 to 13.6%, and the former is lower. Further, after the test, in Examples 1 to 3, tan δ was about 73.2 to 86.8% and impedance was about 68.2 as compared with Comparative Example 1 and Comparative Example 2.
2 to 73.8% and the leakage current is 10 to about 66.7%
Has fallen to.

[0029]

As described above, according to the present invention, a solution of a conductive polymer is applied to an element to form an inner conductive polymer film, and then a dedoped polymer solution is applied, and then doping is performed. Since the film of the conductive polymer on the outside is formed by contacting the solution, the manufacturing time can be shortened and the manufacturing is facilitated, and the characteristics such as capacitance, tan δ, impedance and leakage current can be stabilized and improved. A method for manufacturing a solid electrolytic capacitor is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a solid electrolytic capacitor manufactured according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Element, 3 ... Oxide film, 6 ... Conductive polymer film.

Claims (1)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor, comprising laminating a conductive polymer film on an element having an oxide film formed on a valve metal, the step of applying a solution of the conductive polymer to the element, and dedoping after this step. A method for manufacturing a solid electrolytic capacitor, comprising the steps of applying a solution of the polymer described above, and then contacting the solution with a doping solution to form a film of a conductive polymer.