JP5020132B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly, to a solid electrolytic capacitor comprising a dielectric oxide film formed by anodic oxidation on the surface of an anode body, and an insulating layer on the dielectric oxide film. It relates to a manufacturing method.

Conventionally, an anode body is formed of a valve action metal such as tantalum, niobium, and aluminum, a dielectric oxide film is formed on the surface of the anode body by anodization, and a solid electrolyte is formed on the surface of the dielectric oxide film. In capacitors, manganese dioxide (MnO ₂ ) and 7,7 ′, 8,8′-tetracyanoquinodimethane (TCNQ) complex salts have been used as solid electrolytes.
However, since manganese dioxide has insufficient conductivity, the impedance of the solid electrolytic capacitor at a high frequency cannot be sufficiently reduced, and the TCNQ complex salt is easily thermally decomposed, and the heat resistance of the solid electrolytic capacitor is insufficient. Recently, solid electrolytic capacitors using a conductive polymer having higher conductivity than manganese dioxide and excellent heat resistance, such as polypyrrole or polyaniline, are being developed recently.

By the way, this type of solid electrolytic capacitor using a valve metal as an anode body, forming a sintered body by pressure molding and sintering, and using a dielectric oxide film obtained by anodizing the sintered body as a dielectric body However, the leakage current is large and adversely affects the characteristics of the solid electrolytic capacitor.
Therefore, in Patent Document 1, it is clarified that the direct contact of the conductive material with the surface of the dielectric oxide film formed by anodic oxidation using metal tantalum as the anode body is the cause of deterioration of the leakage current characteristics. An insulator is dissolved in a solvent and applied between the body oxide film and the solid electrolyte to form an insulating layer, and a solid electrolytic capacitor is formed, or the surface of the dielectric oxide film is made highly conductive by a chemical oxidative polymerization reaction. After forming the molecule, an insulating layer is formed by electrolytic polymerization, and a conductive polymer is formed thereon by a chemical oxidative polymerization reaction to form a solid electrolytic capacitor.
JP 2000-133556 A

However, as disclosed in Patent Document 1, when a substance intended to be an insulating layer is applied between a dielectric oxide film and a solid electrolyte in a solvent, uneven coating is likely to occur, and in order to eliminate uncoated portions. In the case of repeated coating, the thickness of the insulating layer increases and the resistance as a capacitor increases.
Further, as in Patent Document 1, after forming a conductive polymer by a chemical oxidative polymerization reaction on the surface of a dielectric oxide film, an insulating layer is formed by electrolytic polymerization, and a conductive polymer is formed thereon by a chemical oxidative polymerization reaction. In this case, the conductivity of the solid electrolyte is reduced because the conductive material is in direct contact with the surface of the dielectric oxide film and there is an insulating layer between the conductive polymer layer and the conductive polymer layer. Resulting in.
In addition, methods such as electrophoresis and electrolytic polymerization have a method of forming a thin insulating layer uniformly. However, in order to form a film by applying a voltage, it is generally necessary to form it on the surface of an electrical conductor. In the prior art, this method has been used to reduce the leakage current by intensively providing an insulator in a defective portion of the dielectric oxide film provided on the surface of the electrical conductor.
However, the direct contact of the conductive material with the surface of the dielectric oxide film, which is an electrically insulating surface, formed by anodizing with metal tantalum as the anode body, is the cause of the deterioration of leakage current characteristics. Even if an insulator is provided in the missing portion of the insulating film, which is an electrical conductor, it cannot be said that the problem of leakage current has been drastically solved.

The present invention has been made in order to solve the above-described problems. In order to form an insulating layer between a dielectric oxide film and a solid electrolyte, the tantalum anode body on which the dielectric oxide film is formed is provided on the negative side. By performing the electrolytic polymerization method with the counter electrode in the halogenated monomer-containing solution as the positive side, a thin insulating layer can be uniformly formed on the dielectric oxide film defects and the entire surface of the dielectric oxide film. An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor capable of drastically solving the problem of leakage current of a solid electrolytic capacitor.

  In order to solve the above problems, the present invention provides an anode body made of a valve metal, a dielectric oxide film formed on the surface of the anode body by anodization, and an insulating layer provided on the dielectric oxide film And a solid electrolyte capacitor of a conductive polymer provided on the insulating layer, wherein the anode body on which the dielectric oxide film is formed is a negative side, and a counter electrode in a solution containing a halogenated monomer Is provided on the positive side, and a method for producing a solid electrolytic capacitor is provided in which the insulating layer of an insulating polymer film is formed on the entire surface of the dielectric oxide film.

According to the present invention, in order to form the insulating layer between the dielectric oxide film and the solid electrolyte, the tantalum anode body in which the dielectric oxide film is formed without being dissolved and applied in a solvent is set to the negative side, By performing the electropolymerization method with the counter electrode in the solution containing the fluorinated monomer as the positive side, a thin insulating layer can be uniformly formed on the dielectric oxide film defects and the entire surface of the dielectric oxide film. It is possible to provide a method of manufacturing a solid electrolytic capacitor capable of drastically solving the problem of leakage current of the electrolytic capacitor.

  Anode bodies described in the present invention include those in which tantalum or niobium or the like is used as a porous sintered body to increase the surface area, and those in which aluminum foil or the like is etched to increase the surface area. In the case of a porous sintered body, one in which an anode lead is embedded at one end is used.

The solid electrolyte described in the present invention refers to a conductive polymer such as polypyrrole, polythiophene, or polyaniline.
To form a conductive polymer, thiophene, aniline, pyrrole or their derivatives are polymerized. The polymerization can be performed by chemical polymerization, electrolytic polymerization, or a combination thereof.

Halogenated monomers described in this invention refer to polymerizable monomers that are substituted with at least one halogen atom.
For example, tetrabromo-o-benzoquinone, 2,4,4,6-tetrabromo-2,5-cyclohexadienone, dichloroacetaldehyde diethyl acetal, tetrachlorocyclopropane, 1,3-dichloroacetone, 1,3-dibromopropane, 1,6-dibromohexane, 2-chloroacrylonitrile, ethyl trichloroacetate, 1,2,3-trichloropropane, 1,1,2-trichloroethane, butyl chloroformate, trichloroethylene, 2,3-dichloromaleic anhydride, 1,12-dibromododecane, hexachloro-1,3-butadiene, hexachlorocyclopentadiene, perchlorobutadiene, perchlorocyclopentadiene, 1,4-dichlorobut-2-ene, 1,3-dichlorobut-2-ene, 3, 4- Chlorobut-1-ene, dichloro-o-xylene, dibromo-m-xylene, dibromo-p-xylene, dibromo-2-methoxy-5-cyano-p-xylene, dibromo-2-methoxy-p-xylene, dibromo- 2-cyano-p-xylene, dibromo-tetrafluoro-p-xylene, 2,3,5,6-hexachloro-p-xylene, 2,5-dichlorothiophene, 2,5-dichloropyridine, dibromostyrene, Dichlorobenzene, hexabromobenzene, 1,4-bis (trichloromethyl) benzene, 2,5-dichloronitrobenzene, 2,5-dichlorobenzonitrile, 2,3-dichloro-5,6-dicyanobenzoquinone, 1-bromo- 2-chloroethane, 1-bromo-2-chloropropane, 2-bromoethyl, dibromo-N-hy B carboxymethyl phthalimide, 1,1-dibromo-2,2-bis (4-hydroxyphenyl) ethylene, dibromostyrene, etc. 1,9-dichloro-2,2-paracyclophane Fen can be used.

The insulating layer described in the present invention is a polymerized layer provided on the defect portion of the dielectric oxide film and the entire surface of the dielectric oxide film, and an anode body in which the dielectric oxide film is formed in the halogenated monomer-containing solution. Is the negative side, and the counter electrode in the halogenated monomer-containing solution is the positive side.
The thickness of the insulating layer on the surface of the dielectric oxide film is preferably about 0.1 nm to 100 nm.
In this electropolymerization, polymerization electrolysis is performed at a constant film formation rate at a constant current between 0.1 mA / g and 2.0 mA / g. When the anode body weight is less than 0.1 mA / g, the film formation rate is slow, and when it is more than 2.0 mA / g, the anode body tends to generate heat.
As the solvent, for example, tetrahydrofuran, acetonitrile, N, N-dimethylformamide, propylene carbonate, 1,2-dimethoxyethane, sulfolane, nitromethane, γ-butyrolactone and the like can be used without particular limitation.
Examples of the supporting electrolyte include tetrafluoroborate salts of quaternary salts such as triethylmethylammonium tetrafluoroborate and tetrabutylammonium tetrafluoroborate, perfluoromethanesulfonate, tetra-n-butylammonium perchlorate and the like. A perchlorate of a quaternary salt ammonium can be used without any particular limitation.

When polymerization electrolysis is performed with the negative electrode formed with the dielectric oxide film of the present invention on the negative side and the halogenated monomer-containing solution on the positive side, electrons are relatively easy to the dielectric oxide film formed by anodic oxidation. And flows over the entire surface of the dielectric oxide film, so that a polymer electrolyte membrane is formed on the entire surface. With this polymerized electrolytic film, the conductive material is not directly in contact with the surface of the dielectric oxide film, which is an electrically insulating surface, so that the problem of leakage current can be fundamentally solved. Further, since the resistance of the defective portion of the dielectric oxide film is lower than that of the good portion of the dielectric oxide film, the polymerization starts from the defective portion of the dielectric oxide film. Therefore, the defective portion of the oxide film is sufficiently covered with the insulator, so that the leakage current can be reduced. Further, since the applied voltage is such that the valve metal is less likely to become ions, the valve metal does not melt as ions and the interface between the valve metal and the polymerized film does not become unstable. Therefore, the insulating film can be satisfactorily covered with the defective portion of the dielectric oxide film.
On the other hand, when the electrolysis is carried out by applying a voltage with the anode body on which the dielectric oxide film is formed on the positive side and the halogenated monomer-containing solution on the negative side, the electrons are transferred to the dielectric oxide film formed by the anodic oxidation. Because it is difficult to move and flows concentrated on the defective portion of the dielectric oxide film, the polymer electrolyte membrane is formed only on that portion, and the conductive material is in direct contact with the surface of the dielectric oxide film. become. Therefore, the problem of leakage current cannot be fundamentally solved. In addition, since the defective portion of the dielectric oxide film is a portion where it is difficult to form an oxide film even when a voltage is applied in this direction, when the polymerization electrolysis is performed in this direction, the valve metal is formed at the defective portion of the dielectric oxide film. Since it is easy to melt as ions, the interface between the valve metal and the polymerized film is hardly a stable part.
In addition, when the polymerization electrolysis is performed with a constant current that does not cause the anode body to generate heat, a large current flows and the anode body does not generate heat and may not be destroyed.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 schematically shows a cross-sectional view of the solid electrolytic capacitor of the present invention.
Reference numeral 1 denotes an anode lead, which is made of a valve metal such as tantalum, niobium, or aluminum having a diameter of about 0.1 mm to 0.5 mm, or a strip-shaped plate having a thickness of about 0.1 mm to 0.5 mm. Become.
Reference numeral 2 denotes a capacitor element, in which one end of an anode lead 1 is embedded, and a powder obtained by mixing a valve metal such as tantalum, niobium, or aluminum with a fine powder having an average particle diameter of about 1 μm and a binder such as acrylic or camphor. A sponge-like anode body 3 formed by press-pressing and then sintered in a vacuum, and a dielectric oxide film 4 are provided on the anode body 3.
Reference numeral 5 denotes an insulating layer made of an insulating polymer film provided on the missing portion 14 of the dielectric oxide film 4 and the entire surface of the dielectric oxide film 4.
Reference numeral 6 denotes a solid electrolyte layer made of a conductive polymer provided on the surface of the insulating layer 5.
A current collector layer 7 is provided on the surface of the solid electrolyte layer 6 and includes a carbon layer and a silver layer sequentially provided.
A cathode terminal plate 8 is connected to the current collector layer 7 by a conductive adhesive 9 or the like.
Reference numeral 10 denotes an anode terminal plate, which is connected to the anode lead 1 by welding such as resistance welding or laser welding or a conductive adhesive.
Reference numeral 11 denotes an exterior that seals the capacitor element and the like with a sealing resin such as an epoxy resin. The lead-out portions of the cathode terminal plate 8 and the anode terminal plate 10 are folded in the direction of the capacitor body in FIG. 1, but conversely, they may extend from the lower side to the outside. There is no particular limitation on the external lead-out method of the cathode terminal plate 8 and the anode terminal plate 10.

FIG. 2 schematically shows a method for forming an insulating layer made of an insulating polymer film according to the present invention.
The insulating layer 5 is formed by immersing the capacitor element 2 in the halogenated monomer-containing solution 12 so that the anode lead 1 led out from the capacitor element 2 is on the negative side, and the counter electrode 13 in the halogenated monomer-containing solution 12 is formed. Perform electropolymerization as the positive side.

[Example 1]
First, in a fine powder of metal tantalum, one end of the anode lead is inserted and pressure-molded, and the resulting molded body is sintered at a high temperature in a vacuum, 0.5 mm × 0.5 mm An anode body made of a sintered body of × 1.0 mm is formed. Next, the obtained anode body was immersed in a dilute nitric acid aqueous solution, and then a chemical conversion treatment was performed to form a 25 V dielectric oxide film on the surface of the anode body to obtain a 10 μF capacitor.
Next, the anode body was immersed in an electrolytic solution in which 0.1 M dibromo-p-xylene as a monomer for electrolytic polymerization and 0.1 M tetra-n-butylammonium perchlorate as a supporting electrolyte were dissolved in acetonitrile, Was subjected to polymerization electrolysis at a constant current of 0.5 mA / g to form an insulating layer having an average thickness of 5 nm.
Subsequently, a 0.5 M ammonium peroxodisulfate aqueous solution was prepared, and the anode body on which the insulating layer was formed was immersed in a 0.5 M ammonium peroxodisulfate aqueous solution for 10 seconds. Next, an aniline solution having a concentration of 0.5 M was prepared with an equal amount of an aniline and p-phenolsulfonic acid aqueous solution. Then, 30 minutes after the immersion in the 0.5 M aqueous ammonium peroxodisulfate solution, the anode body was immersed in the aniline solution for 10 seconds. Next, after immersing the aniline solution, the anode body was held at 50 ° C. for 30 minutes to cause a chemical oxidative polymerization reaction on the anode body. Further, the anode body is alternately immersed in the ammonium peroxodisulfate aqueous solution and the aniline solution 20 times alternately, and the surface of the anode body is a conductive polymer solid obtained by a chemical oxidative polymerization reaction. An electrolyte layer was formed.
Then, the carbon paste and the silver paste were apply | coated to the predetermined location of the anode body, and the electrical power collector layer was formed.
Next, an anode terminal was conductively connected to the other end of the anode lead by welding, and a cathode terminal was connected to the current collector layer via a conductive adhesive.
Subsequently, the resin was applied to the whole by a molding method except for the lead-out end portions of the anode terminal and the cathode terminal, and a solid electrolytic capacitor (tantalum capacitor) covered with an exterior was produced.

[Example 2-4]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that dibromo-p-xylene was changed to dichloro-p-xylene, dibromostyrene, or hexachloro-1,3-butadiene. Further, except that this insulating layer was omitted, the leakage current was compared as shown in Table 1 as a comparative example 1 in which a solid electrolytic capacitor was produced in the same manner as in Example 1. In addition, the leakage current of Table 1 shows the leakage current 1 minute after applying 7V.

In Table 1, the leakage current of the solid electrolytic capacitor of this example in which the insulating layer is formed is in the range of 0.16 to 0.23 μA, and the leakage current of Comparative Example 1 is 2.5 μA. Thus, the leakage current of the solid electrolytic capacitor of this embodiment is greatly reduced.
As described above, according to the present invention, the dielectric oxide film and the conductive polymer layer (solid electrolyte) and the dielectric oxide film and the conductive polymer layer (solid electrolyte) Since an insulating layer is provided between the conductive material and the conductive layer, the insulating layer does not directly contact the surface of the dielectric oxide film formed by anodic oxidation. Can be reduced.

1 schematically shows a cross-sectional view of a solid electrolytic capacitor of the present invention. The formation method of the insulating layer of the insulating polymer film of this invention is typically shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lead for anode 2 ... Capacitor element 3 ... Anode body 4 ... Dielectric oxide film 5 ... Insulating layer 6 ... Solid electrolyte layer 7 ... Current collector layer 8 ... Cathode terminal board 9 ... Conductive adhesive 10 ... Anode terminal board 11 ... Exterior 12 ... Solution 13 ... Counter electrode 14 ... Missing part.

Claims (1)

  An anode body made of a valve metal, a dielectric oxide film formed by anodic oxidation on the surface of the anode body, an insulating layer provided on the dielectric oxide film, and an electrically conductive high electrode provided on the insulating layer In a solid electrolytic capacitor having a molecular solid electrolyte, electrolytic polymerization is carried out with the anode body on which the dielectric oxide film is formed as the negative side and the counter electrode in the halogenated monomer-containing solution as the positive side. A method for manufacturing a solid electrolytic capacitor, wherein the insulating layer of an insulating polymer film is formed on the entire oxide film surface.

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