JP2006165356A - Manufacturing method of solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid electrolytic capacitor including a step of forming a chemical polymerization preliminary conductive precoat layer that uses less oxidizer-containing solution and is excellent in leak current characteristic. <P>SOLUTION: In the case of applying the oxidizer-containing solution, two coating rollers including the oxidizer-containing solution are located in contact with each other in parallel, valve action metallic foil passes through between the coating rollers to apply the oxidizer-containing solution on the surface of the valve action metallic foil, and vapor of a conductive high molecule monomer is in contact with the surface of the valve action metallic foil to form the preliminary conductive precoat layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer as a solid electrolyte.

  There has been proposed a solid electrolytic capacitor in which a dielectric oxide film is formed on a valve metal surface, and a conductive polymer film is formed on the dielectric oxide film to form a solid electrolyte.

  In Patent Document 1, a preliminary conductive precoat layer formed by a chemical polymerization method as a precoat layer is provided on the surface of the dielectric oxide film, and a conductive polymer layer is formed on the conductive precoat layer by an electrolytic polymerization method. Thus, a solid electrolytic capacitor having a structure in which this is used as a solid electrolyte is disclosed.

  The chemical polymerization method for forming the pre-conductive precoat layer is performed by, for example, applying an oxidant-containing solution to a valve metal surface on which a dielectric oxide film is formed, and attaching the oxidant and pyrrole, thiophene, aniline, and derivatives thereof. A conductive polymer layer can be formed by contacting and polymerizing a conductive polymer monomer typified by the above in a gas phase or a liquid phase.

  Patent Document 2 discloses a solid electrolytic capacitor in which a conductive polymer monomer is chemically polymerized in a gas phase to form a preliminary conductive precoat layer, and then an electrolytic polymerization conductive polymer layer is formed. . In this case, chemical polymerization by the vapor phase method is performed by immersing, applying or spraying an oxidant-containing solution on the valve action metal, and then bringing it into contact with the vapor of the conductive polymer monomer.

  When the oxidant-containing solution is attached to the valve metal for forming the preliminary conductive precoat layer, the method of dipping or spraying has a problem that the amount of the chemical solution used is large and the manufacturing cost increases. Further, since the oxidant-containing solution adheres to portions other than the cathode forming portion of the capacitor, the preliminary conductive precoat layer reaches the anode leading portion, and there is a problem that a leakage current failure of the obtained capacitor tends to occur.

  In addition, as a conventional coating method, a dispensing method or a brush coating method is known. However, in the case of a plate-shaped substrate, it is necessary to process each side one by one, and it takes a lot of time for the process. A coating method has been desired.

JP 63-173313 A Japanese Patent Laid-Open No. 3-6217

  In a method for producing a solid electrolytic capacitor including a step of forming a chemical polymerization pre-conductive precoat layer, the present invention provides a method for producing a solid electrolytic capacitor that uses a small amount of an oxidant-containing solution and has excellent leakage current characteristics. is there.

  The present invention includes a step of applying an oxidant-containing solution to a valve metal surface on which a dielectric oxide film is formed, and contacting a vapor of a conductive polymer monomer on the valve metal surface to which the oxidant solution is applied. In the method for producing a solid electrolytic capacitor, comprising a step of forming a preliminary conductive precoat layer by chemical polymerization, and a step of forming a conductive polymer layer by electrolytic polymerization on the preliminary conductive precoat layer, the oxidizing agent-containing solution When coating the surface of the valve action metal, two sponge-like application rollers holding the oxidant-containing solution are placed in parallel and the valve action metal is passed between the application rollers. A method for producing a solid electrolytic capacitor comprising: applying an oxidant-containing solution to the substrate, and contacting a vapor of a conductive polymer monomer to form a preliminary conductive precoat layer. That.

  Further, when applying the oxidant-containing solution, an external roller made of another material is pressed against the application roller holding the oxidant-containing solution to generate a liquid reservoir on the surface of the application roller, and then the application A method for producing a solid electrolytic capacitor, characterized in that an oxidizing agent-containing solution is applied by passing a valve metal between rollers for contact, and a conductive polymer monomer vapor is contacted to form a preliminary conductive precoat layer It is.

  In addition, the application roller is divided into an application part, a water repellent part, and a wiping part. After holding the oxidizing agent-containing solution in the application part, the valve metal is passed between the application rollers. A method for producing a solid electrolytic capacitor, characterized in that an oxidant-containing solution is applied to a desired position of the valve metal and a vapor of a conductive polymer monomer is contacted to form a preliminary conductive precoat layer. .

  The method for producing a solid electrolytic capacitor is characterized in that the preliminary conductive precoat layer formed using the coating method and the conductive polymer layer formed by electrolytic polymerization are made of polypyrrole.

  Moreover, when apply | coating an oxidizing agent containing solution using the said method, the solvent of the oxidizing agent containing solution to be used is a mixed solvent of water and alcohol, and the weight ratio is 9: 1 to 1: 9. This is a method for manufacturing a solid electrolytic capacitor.

  According to the present invention, the oxidizing agent-containing solution can be simply applied to the valve action metal foil, and the amount of the oxidizing agent-containing solution used can be reduced. Moreover, an oxidizing agent containing solution can be apply | coated only to the target part, ie, a cathode formation part, and the manufacturing method of the solid electrolytic capacitor excellent in the leakage current characteristic can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Examples of the valve metal used in the present invention include foil-like or plate-like aluminum, tantalum, and niobium.

  After the surface of the valve metal foil 1 is etched, anodization is performed in an aqueous solution such as ammonium adipate to form a dielectric oxide film, and then the valve metal foil is formed at regular intervals as shown in FIG. The through-hole 2 is formed in the substrate, the through-hole portion 2 is formed, the cathode forming portion 3 is left, and the insulating coating 4 is formed, and the conductive coating serving as a power supply electrode during electrolytic polymerization is formed on the insulating coating 4. A film 5 is formed. At this time, the conductive coating film 5 is formed so as not to be in direct contact with the dielectric oxide film.

  Next, a process of forming a preliminary conductive precoat layer on the valve metal surface on which the dielectric oxide film is formed will be described.

  As a method of applying the oxidizing agent-containing solution to the valve action metal surface, as shown in FIG. 2, two application rollers 6 are installed in parallel to each other, and the oxidizing agent-containing solution is composed of a dropping funnel, a dispenser or the like. The solution is dropped from the supply unit 7 onto the application roller 6 to sufficiently supply the oxidant-containing solution. Thereafter, the oxidant-containing solution is applied to the valve metal surface by pulling the valve metal from below the two application rollers 6 and passing between the rollers.

  According to the said method, it is possible to apply | coat an oxidizing agent containing solution simultaneously to the cathode formation part of both sides of valve action metal foil, and the time spent for an application | coating process can be shortened.

  In addition, after supplying the oxidizing agent-containing solution to the application roller 6, a liquid reservoir 9 is generated on the surfaces of the two application rollers 6 by placing the external roller 8 against the application roller 6. A desired amount of the oxidant-containing solution can be applied by passing the valve action metal foil between the rollers.

  According to the above method, the amount of the oxidant-containing solution applied to the valve metal surface can be reduced to the minimum necessary amount by appropriately selecting the pressing pressure of the external roller, the pulling speed of the valve metal, etc. The amount of drug used can be reduced.

  Moreover, if the roller 6 for application | coating uses what is divided into the application part 6a, the water repellent part 6b, and the wiping part 6c, it can apply | coat only to the cathode formation part 3 of a valve action metal. At this time, the width of the external roller 8 is set to be equal to or less than the total length of the cathode forming portion 3. The external roller 8 is pressed against the application part 6a of the application roller 6 to generate a liquid pool part 9, and water repellent parts 6b made of rubber packing or the like are installed at both ends of the application part 6a of the application roller 6, A wiping portion 6c is installed on the outer side of the water repellent portion 6b to wipe off the oxidant-containing solution overflowing from the liquid pool, preventing the generated liquid pool portion 9 from flowing out to other than the cathode forming portion 3. To do.

  According to the above method, since the oxidant-containing solution can be applied only to the cathode forming portion and the preconductive precoat layer can be formed thereon, there is little risk of contact between the anode lead portion and the cathode forming portion, and the leakage current characteristics are improved. An excellent solid electrolytic capacitor with a good yield can be obtained.

  Examples of the material of the application portion 6a of the application roller 6 include polyurethane, polyethylene, polyvinyl alcohol, natural rubber, polybutadiene rubber, styrene butadiene rubber, chloroprene rubber, ethylene propylene rubber, nitrile rubber, silicon rubber, fluoro rubber, melamine resin, and the like. And those formed into a sponge shape so as to maintain water absorption are preferable. In consideration of wear resistance, chemical resistance, flexibility, and retention of the oxidant-containing solution, polyurethane or polyethylene having a water absorption rate of 200 to 800% is more preferable. The thickness of the sponge is appropriately selected depending on the composition of the oxidizing agent-containing solution as 1.0 to 5.0 cm.

  The material of the water repellent portion 6b is not particularly limited, although a rubber-based material that does not absorb the oxidant-containing solution and has water repellency can be preferably used.

  The wiping portion 6c can be made of the same material as the coating portion 6a or a material having higher water absorption than the material of 6a. As shown in FIG. 1, the width of the wiping portion 6c is set so that the entire length of the coating portion 6a, the water repellent portion 6b, and the wiping portion 6c is larger than the width of the valve metal foil 1 to be coated. The thickness of 6c is preferably the same as that of the application part 6a.

  The material of the core rod 6d of the coating roller 6 is selected from metals such as stainless steel and plastics such as vinyl chloride, and may be either a round bar or a cored rod, and the diameter of the core rod 6d is appropriately selected.

  Examples of the material of the external roller 8 include metals, glass, and plastics, and metals that are durable against pressure applied to the coating roller 6 are preferable. Further, the width of the external roller 8 is applied to the application roller 6 so that the liquid pool 9 generated by pressing the external roller 8 against the application part 6 a of the application roller 6 does not overflow from the application roller 6. It is preferable to make it smaller than the width of the portion 6a.

  Next, the composition of the oxidizing agent-containing solution will be described.

  In the oxidizing agent-containing solution used in the present invention, the oxidizing agent can be alcohol, water, or a mixed solvent of water and alcohol.

  Examples of the oxidizing agent used in the present invention include iodine, bromine, bromine iodide, chlorine dioxide, iodic acid, periodic acid, chlorous acid and other halides, antimony pentafluoride, phosphorus pentachloride, phosphorus pentafluoride, Metal halides such as aluminum chloride and molybdenum chloride, permanganate, dichromate, chromic anhydride, ferric salt, cupric salt and other high-valent metal salts, sulfuric acid, nitric acid, trifluoromethane sulfuric acid, etc. Protonic acid, sulfur trioxide, nitrogen dioxide and other oxygen compounds, hydrogen peroxide, ammonium persulfate, peroxo acids such as sodium perborate or their salts, or heteropoly acids such as molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid An acid or its salt is mention | raise | lifted and at least 1 sort (s) is used. Peroxo acids or salts thereof, heteropoly acids or salts thereof are preferred from the viewpoint that chemical damage to the dielectric oxide film is small and the reaction is easy.

  Moreover, by adding a dopant to the oxidant-containing solution of the present invention, a desired dopant can be introduced into the conductive polymer, thereby further improving the heat resistance and conductivity of the conductive polymer film. be able to.

  As the dopant, a compound having the following anion component is used. Halogen anions such as iodine, bromine and chlorine, halide anions such as hexafluoroline, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron and perchloric acid, and alkyl group-substituted organic sulfonate anions such as methanesulfonic acid and dodecylsulfonic acid , Cyclic sulfonic acid anions such as camphorsulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, benzenedisulfonic acid and other alkyl group-substituted or unsubstituted benzene mono- or disulfonic acid anions, 2-naphthalenesulfonic acid , Alkyl group substituted or unsubstituted anion of naphthalene sulfonic acid substituted with 1 to 3 sulfonic acid groups such as 1,7-naphthalenedisulfonic acid, anthracene sulfonic acid, anthraquinone sulfonic acid, alkylbiphenyl sulfone Acids, alkyl group-substituted or unsubstituted biphenyl sulfonate ions such as biphenyl disulfonic acid, polymer sulfonate anions such as polystyrene sulfonate and naphthalene sulfonate formalin condensates, substituted or unsubstituted aromatic sulfonate anions, bissal Boron compound anions such as tylate boron and biscatecholate boron, and heteropolyacid anions such as molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid, and the like, selected from acids having these anion components, ammonium salts, etc. At least one compound is used.

  As the solvent used in the oxidant-containing solution of the present invention, an alcohol solvent such as methanol, ethanol, isopropyl alcohol, water, or a mixed solvent of water and alcohol can be used. It is necessary to sufficiently impregnate the oxidant-containing solution, and an alcohol solvent having a low surface tension or a mixed solvent of water and alcohol is preferable. Among them, a mixed solvent in which the weight ratio of water to alcohol is 9: 1 to 1: 9 is preferable because it has both the ability to dissolve the oxidizing agent and the permeability to the etched valve metal surface.

  Next, a process of forming a preliminary conductive precoat layer by bringing a conductive polymer monomer vapor into contact with the valve metal surface coated with the oxidant-containing solution will be described.

  The monomer is polymerized by bringing a conductive polymer monomer vapor typified by pyrrole, thiophene, aniline, and their derivatives into contact with the surface of the valve action metal coated with the oxidant-containing solution obtained in the above step. In addition, a preliminary conductive precoat layer can be formed on the valve action metal surface.

  In the gas phase polymerization method, a valve metal coated with an oxidizing agent-containing solution is held in an atmosphere containing a conductive polymer monomer vapor, or a gas containing the vapor is directly sprayed on the surface of the valve metal. It is suitable for forming the preliminary conductive polymer film of the present invention. Among conductive polymer monomers, pyrrole having relatively high volatility is a conductive polymer monomer suitable for gas phase polymerization.

  As a more specific method of the gas phase polymerization method, for example, a valve metal in which an oxidant-containing solution is applied is held in a reaction vessel in which a vapor of a conductive polymer monomer is introduced from the outside, or a reaction is performed. A conductive polymer monomer solution is sealed in a tank in advance, and the valve metal is held in a gas phase filled with the monomer vapor, or a conductive polymer monomer vapor in a carrier gas such as nitrogen or argon. Means such as directly spraying the mixed gas mixed with the gas onto the valve metal surface can be used.

  The gas phase polymerization temperature is not particularly limited, but considering safety, it is preferably below the flash point of the conductive polymer monomer. For example, when pyrrole is used, it is appropriately selected at 39 ° C. or below. The polymerization time is appropriately selected depending on the conditions such as the conductive polymer monomer used, the reaction vessel, or the gas phase polymerization temperature, but is about several minutes to 60 minutes.

  Next, the process of forming a conductive polymer layer by electrolytic polymerization on the preliminary conductive precoat layer and providing a solid electrolyte layer will be described.

  As the electrolytic polymerization solution used in the present invention, a conventionally known electrolytic polymerization solution is used, and a solution containing a conductive polymer monomer and a supporting electrolyte can be used. As the conductive polymer monomer, conventionally known monomers such as pyrroles, thiophenes, and anilines can be used. However, pyrrole is preferred from the viewpoint of electrical characteristics and thermal stability of the resulting polymer.

As the supporting electrolyte contained in the electrolytic polymerization solution, LiPF ₆ , LiAsF ₆ , LiBF ₄ , KI, NaPF ₆ , NaClO ₄ , sodium toluenesulfonate, tetrabutylammonium toluenesulfonate, sodium 1,7-naphthalenedisulfonate, The compound is selected from compounds such as tetraethylammonium alkylnaphthalene sulfonate and bis-sulcylate boron tetramethylammonium, and is not particularly limited. The solvent is selected from acetonitrile, alcohol, water and the like, and is not particularly limited.

  In the electrolytic polymerization solution, the valve action metal on which the preliminary conductive precoat layer is formed is immersed, and the conductive coating film formed on the valve action metal foil through an insulating coating film is used as an anode, and a stainless steel plate or the like. As a cathode, a voltage is applied to form an electropolymerized conductive polymer layer.

  Next, a carbon paste and a silver paste are sequentially applied on the electropolymerized conductive polymer layer to form a capacitor cathode.

  The obtained capacitors are individually separated, assembled by a conventionally known method, and the exterior is applied to complete the solid electrolytic capacitor of the present invention.

  EXAMPLES Hereinafter, although this invention is demonstrated more based on an Example, this invention is not limited by these.

Example 1
An aluminum foil with a surface etched (thickness 150 μm, length 80 mm, width 30 mm) was electrolytically oxidized in an aqueous solution of ammonium adipate at a voltage of 10 V to form a dielectric oxide film on the surface. Thereafter, 41 through-holes of 15 mm × 1.0 mm are punched at intervals of 1.0 mm in the length direction, and the punched end face of the through-hole 2 is formed, and the cathode forming portion 3 (15 mm × 1.0 mm: 40) In addition, an insulating coating film 4 was formed, and a conductive coating film 5 serving as a feeding electrode during electrolytic polymerization was formed on the insulating coating film 4.

  In the step of forming the preliminary conductive precoat layer on the surface of the valve action metal, an oxidant-containing solution is obtained by using the application roller 6 and the external roller 8 comprising the application part, the water repellent part, and the wiping part of the present invention. The dimensions and materials of each material are shown below.

<Coating roller for oxidizing agent-containing solution>
Application part 6a: width 15mm, thickness 10mm, polyurethane water-repellent part 6b: width 3mm, thickness 8mm, fluororubber wiping part 6c: width 15mm, thickness 10mm, polyurethane core 6d: diameter 10mm, length 60mm, Stainless steel core rod External roller 8: Diameter 5mm, length 15mm, stainless steel round bar

An oxidizing agent-containing solution was prepared to have the following composition.
<Oxidant-containing solution>
Oxidizing agent: ammonium persulfate 0.3 mol / L
Dopant: p-toluenesulfonic acid 0.3 mol / L
Solvent: Mixed solvent of ethanol and water (ethanol: water = 6: 4)

  After applying the oxidant-containing solution to the aluminum foil by the method described in the present invention using the application roller and the external roller, the solution is held in pyrrole vapor for 15 minutes, and this operation is repeated four times. Thus, a preliminary conductive precoat layer made of a gas phase polymerization polypyrrole film was formed on the dielectric oxide film. The preliminary conductive precoat layer can be formed only in the cathode forming portion, and the amount of the oxidant-containing solution used in the vapor phase polymerization four times was 20 mL. The time required for the step of applying the oxidizing agent-containing solution was 20 seconds.

Next, the end portion of the conductive coating film was used as a power feeding section, and the foil was immersed in an electrolytic polymerization solution containing 0.3 mol / L of pyrrole monomer and 0.2 mol / L of sodium 2-naphthalenesulfonate as a supporting electrolyte. An electropolymerized polypyrrole film was formed by applying a constant current (0.5 mA / cm ² , 60 minutes) between the conductive coating film as an anode and an external cathode.

  On the obtained electropolymerized polypyrrole film, a carbon paste and a silver paste are sequentially applied to form a cathode layer, a counter electrode is taken out from a part, molded with an epoxy resin, and a voltage of 8.2 V is applied. Aging was performed to complete a solid electrolytic capacitor with a rated voltage of 6.3V.

  For the 40 solid electrolytic capacitors obtained, the capacitance at a frequency of 120 Hz (hereinafter abbreviated as “C”), the dielectric loss at 120 Hz (hereinafter abbreviated as “tan δ”), and the equivalent series resistance at 100 kHz ( (Hereinafter abbreviated as “ESR”), the rated voltage of 6.3 V, and the leakage current at 40 seconds (hereinafter abbreviated as “LC”) were measured. Show.

Comparative Example 1
In the step of forming the preliminary conductive precoat layer on the valve metal surface, the solid electrolytic capacitor was formed in the same manner as in Example 1 except that the method of applying the oxidizing agent-containing solution to the valve metal was performed using a brush. Produced. The oxidant-containing solution was applied only to the cathode forming portion 3. The amount of the oxidant-containing solution used in the four gas phase polymerizations was 20 mL. The time required for the step of applying the oxidizing agent-containing solution was 60 seconds.

Comparative Example 2
In the step of forming the preliminary conductive precoat layer on the valve metal surface, a solid electrolytic capacitor was produced in the same manner as in Example 1 except that the method of applying the oxidizer-containing solution to the valve action metal was performed by immersion. . In addition, since the preliminary | backup conductive polymer film was formed in the whole surface of the aluminum foil 1, and it immersed in a 100 mL stainless steel container, the usage-amount of the oxidizing agent containing solution in the gas phase polymerization 4 times was 100 mL.

Comparative Example 3
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that in the step of forming the preliminary conductive precoat layer on the valve metal surface, the method of applying the oxidant-containing solution to the valve metal was performed by spraying. . The preliminary conductive precoat layer is formed on the entire surface of the aluminum foil 1 in the same manner as in Comparative Example 2, and the application of the oxidant-containing solution by spraying is performed with a commercially available sprayer, 20 times per gas phase polymerization. It sprayed from the front and back of the aluminum foil 1, and the usage-amount of the oxidizing agent containing solution of vapor phase polymerization 4 times was 80 mL.

  In this embodiment, a capacitor having excellent electrical characteristics can be obtained, and in particular, it has excellent leakage current characteristics. Further, the amount of the oxidizing agent-containing solution used and the time required for coating are the least. ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the solid electrolytic capacitor excellent in productivity can be provided.

Front view of application method of oxidant-containing solution Side view of coating method of oxidizing agent-containing solution

Explanation of symbols

1 Valve metal foil 2 Through hole 3 Cathode forming part
4 Insulating coating 5 Conductive coating 6 Application roller 6a Application unit 6b Water repellent unit 6c Wiping unit 6d Core rod 7 Supply unit 8 External roller 9 Liquid reservoir

Claims (5)

A step of applying an oxidant-containing solution to the valve metal surface on which the dielectric oxide film is formed, and chemical polymerization by bringing vapor of a conductive polymer monomer into contact with the valve metal surface to which the oxidant-containing solution is applied In the method for producing a solid electrolytic capacitor, including the step of forming a preliminary conductive precoat layer by the step of forming a conductive polymer layer by electrolytic polymerization on the preliminary conductive precoat layer, the oxidizing agent-containing solution is applied At this time, two application rollers holding the oxidant-containing solution are placed in contact with each other in parallel, and the oxidant-containing solution is applied to the surface of the valve metal by passing the valve metal between the application rollers. A method for producing a solid electrolytic capacitor, comprising applying a vapor of a conductive polymer monomer to form a preliminary conductive precoat layer. When applying the oxidant-containing solution, an external roller is pressed against the application roller holding the oxidant-containing solution to generate a liquid reservoir on the surface of the application roller, and the valve metal is applied between the application rollers. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the oxidizing agent-containing solution is applied by passing the solution. The application roller is divided into an application part, a water repellent part, and a wiping part, and after holding the oxidizing agent-containing solution in the application part, passing the valve metal between the application rollers, The method for producing a solid electrolytic capacitor according to claim 1, wherein the oxidizing agent-containing solution is applied to a desired position of the valve metal. The method for producing a solid electrolytic capacitor according to claim 1, wherein the preliminary conductive precoat layer and the conductive polymer layer are polypyrrole. 5. The method for producing a solid electrolytic capacitor according to claim 1, wherein the solvent of the oxidizing agent-containing solution is a mixed solvent of water and alcohol, and the weight ratio thereof is 9: 1 to 1: 9. .

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