JPH10303075A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a fraction defective due to leakage current by, after a derivative of polythiophene expressed in a specific formula is formed on a dielectric oxide film in a chemical oxidative polymerization, performing a formation repair process for the dielectric oxide film. SOLUTION: A square-shaped anode material formed by sintering tantalum powder is anodized, and a tantalum oxide film is formed on the surface of a sintered body. On the tantalum oxide film, derivative of polythiophene expressed in a formula (in the formula, R1 and R2 are hydrogen or C1-C4- alkylene group while having no relation to each other, or, depending on the case, C1-C4-alkylene group substituted while making them cooperate with each other, preferably methylene substituted with alkyl group, or depending on the case, 1,2-ethylene group or 1,2-cyclohexylene group substituted with C1-C 12-alkyne or phenyl group) is formed in a chemical oxidative polymerization. Then formation repair process is performed for the tantalum oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 in which a conductive polymer compound is used as a solid electrolyte and leakage current stabilization treatment is performed. Things.

[0002]

2. Description of the Related Art In general, a solid electrolytic capacitor is formed by using a porous molded body of a valve metal such as tantalum or aluminum as an anode, an oxide film as a dielectric, and manganese dioxide, 7, 7, 8, 8-tetratetrafluoroethylene. Cyanoquinodimethane (T
It has a structure in which a solid electrolyte such as CNQ) complex salt is part of the cathode. In this case, the solid electrolyte has a function of electrically connecting the entire surface of the dielectric inside the porous molded body and the electrode leads, and furthermore, an electrical short circuit caused by an insulation defect of the dielectric oxide film is formed thereon. It is desirable to have a function to repair. Due to such demands, metals having high conductivity but no dielectric repair function are unsuitable as solid electrolytes.Conventionally, manganese dioxide or the like, which is transferred to an insulator by heat or the like due to short-circuit current, has been used as a solid electrolyte. Have been. However, when manganese dioxide is part of the electrode,
Since the conductivity is not sufficiently low, the impedance in a high frequency range is large. On the other hand, when the TCNQ complex salt is used as a part of the electrode, the TCNQ complex salt is easily decomposed by heat, so that the solid electrolytic capacitor using them has various problems such as poor heat resistance. In recent years, new solid electrolyte materials have been developed in the field of polymers, and as a result, conjugated polymer compounds such as polypyrrole, polythiophene, and polyaniline have been doped with electron-donating or electron-withdrawing compounds (dopants). Various solid electrolytic capacitors using a conductive polymer compound as a solid electrolyte have been proposed. More specifically, the basic structure of this type of solid electrolytic capacitor is, as schematically shown in FIG. 1, a dielectric oxide film 2 on a surface of an anode body 1 made of a metal having a valve action. A conductive polymer compound layer 3, a graphite layer 4 serving as a conductor layer serving as a cathode, and a silver paste layer 5 are sequentially formed, and a cathode lead 6 is formed from the conductor layer.
The anode lead 7 is pulled out from the anode body 1, and the entire peripheral surface of the anode body 1 is molded and sealed with an exterior resin material 8. In the solid electrolytic capacitor, a specific thiophene monomer is polymerized on a dielectric oxide film using an oxidizing agent to form a polythiophene derivative.

[0003]

However, as described above, a conventional solid electrolytic capacitor using a conductive polymer compound polymerized by using an oxidizing agent on a dielectric oxide film layer as a solid electrolyte has a high frequency characteristic. Although it is a solid electrolytic capacitor with excellent temperature characteristics, there is still room for study on its manufacturing method, and there is a problem in that as the number of polymerizations increases, the leakage current increases and the reproducibility is poor. Was.

The present invention has been made in view of such conventional problems, and has as its object to improve the high-frequency characteristics and the temperature characteristics, reduce the defective rate due to leakage current, and increase the production yield. It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor capable of improving the solid electrolytic capacitor.

[0005]

According to the present invention, a dielectric oxide film, a conductive polymer compound layer and a conductive layer are sequentially formed on the surface of a valve metal as an anode body. In the method for manufacturing a solid electrolytic capacitor in which the conductor layer is used as one electrode and the valve metal is used as the other electrode, a general formula is formed on the dielectric oxide film.

Embedded image Wherein R 1 and R 2 independently of one another are hydrogen or C
Represents a 1-C4-alkylene group or, jointly, an optionally substituted C1-C4-alkylene group, preferably a methylene group optionally substituted by an alkyl group, optionally a C1-C12 A 1,2-ethylene group or a 1,2-cyclohexylene group substituted by an alkyne or phenyl group] by chemical oxidative polymerization, and then repairing the dielectric oxide film by chemical conversion. It is characterized by processing.

In the present invention, the metal having a valve action as the anode body is selected from aluminum and tantalum, and is used by etching or sintering to increase the surface area. It is formed by an ordinary method by an electrochemical means using an aqueous solution of adipic acid or boric acid. The valve metal having an oxide film formed thereon is immersed in a mixed solution of a specific thiophene monomer, a specific oxidizing agent, and a solvent to deposit a conductive polymer compound layer on the oxide film. After completion of the reaction, the unreacted oxidizing agent and excess acid are washed with a solvent that is easy to dry, such as water or alcohol, and dried.
In addition, the metamorphosis repair treatment of the oxide film after the formation of the conductive polymer compound layer is performed through the conductive polymer compound layer in a dilute solution of 1% or less of adipic acid, salicylic acid, phosphoric acid or the like.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described.
In the solid electrolytic capacitor having the basic structure shown in FIG. 1, a metal having a valve action as an anode body is formed to form a dielectric oxide film on the surface, and a polythiophene derivative is formed on the dielectric oxide film. It is characterized in that the dielectric oxide film is subjected to a chemical conversion repair treatment after being repeatedly formed several times until a predetermined thickness is obtained by chemical oxidation polymerization.

[0008]

EXAMPLES Specific examples will be described below. Example 1 A square anode body (2.1 ×) formed by sintering tantalum powder
1.0 × 1.2 mm) 1 in an aqueous phosphoric acid solution
0V) to form a tantalum oxide film 2 on the surface of the sintered body. 4 g of the anode body 1 having the tantalum oxide film 2 formed thereon
Immersed in a solution of 1.5 g of iron (III) P-toluenesulfonate and 0.5 g of 3,4-ethylenedioxy-thiophene in isopropanol
Was polymerized. After the completion of the reaction, the unreacted oxidizing agent was washed with water and dried at 50 ° C. for 1 hour in vacuum. This polymerization was repeated twice until a predetermined thickness was obtained. next,
The oxide film was repaired at 35 V in a 0.5% aqueous solution of adipic acid, washed with water and dried. Next, a graphite layer 4 and a silver paste layer 5 as a conductor layer are sequentially formed, and a cathode lead 6 is pulled out from the conductor layer, and an anode lead 7 is pulled out from the anode body 1. The peripheral surface was molded and sealed with an exterior epoxy resin material 8 to complete a solid electrolytic capacitor.

Example 2 Etched surface (25 μF / cm ² ) Thickness 95 μm by etching
An aluminum foil (anode) 1 having a size of 5 × 3 mm and an area of 5 × 3 mm was anodized in ammonium borate at 50 V to form a dielectric oxide film 2. The anode body 1 having the aluminum oxide film formed thereon was mixed with a 1: 2 mixture 5 of acetone and isopropanol.
g of 1 g of iron (III) methanesulfonate and 0.5 g of a solution of 3,4-ethylenedioxy-thiophene to polymerize the conductive polymer compound 3. After the reaction,
The unreacted oxidant was washed by washing with water and dried at 50 ° C. for 1 hour in vacuo. This polymerization was repeated three times until a predetermined thickness was obtained. Next, the oxide film was repaired with a conversion at 35 V in a 0.5% aqueous solution of adipic acid, washed with water, and dried. Next, a graphite layer 4 and a silver paste layer 5 as a conductor layer are sequentially formed, and a cathode lead 6 is pulled out from the conductor layer, and an anode lead 7 is pulled out from the anode body 1. The peripheral surface was molded and sealed with an exterior epoxy resin material 8 to complete a solid electrolytic capacitor.

In each of the first and second embodiments, a solid electrolytic capacitor (completed in the same procedure as in each embodiment) except that the oxide film of a 0.5% aqueous solution of adipic acid was not chemically converted was repaired. Comparative Examples 1 and 2) were compared.

Examples 1 and 2 and Comparative Examples 1 and 2
Table 1 shows the initial values of the capacitance, the dielectric loss (tan δ), the equivalent series resistance, the leakage current, and the values after the high-temperature life test for each solid electrolytic capacitor.

[0012]

[Table 1]

As is apparent from Table 1, all of the solid electrolytic capacitors according to the embodiments of the present invention have excellent equivalent series resistance characteristics in a high frequency range and an increase in leakage current in a high temperature life test. It can be seen that no good results were obtained.

[0014]

According to the present invention, after a polythiophene derivative having a predetermined thickness is formed on an oxide film on a metal surface having a valve action as an anode body, a conversion repair treatment of the oxide film is performed. Therefore, it is possible to prevent a decrease in the defective rate due to leakage current without impairing excellent high-frequency characteristics, and to improve a manufacturing yield.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic structure of a solid electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve metal as an anode body 2 Dielectric oxide film 3 Conductive polymer compound layer 4 Graphite layer 5 Silver paste layer 6 Cathode lead 7 Anode lead 8 Exterior resin material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mika Ito 3-18-3 Shin-Yokohama, Kohoku-ku, Yokohama, Kanagawa Prefecture Inside Fujitsu Towa Electron Limited (72) Toshikatsu Terao 3-18 Shin-Yokohama, Kohoku-ku, Yokohama, Kanagawa No. 3 Inside Fujitsu Towa Electron Limited

Claims (1)

[Claims] 1. A dielectric oxide film, a conductive polymer compound layer, and a conductor layer are sequentially formed on the surface of a valve metal as an anode body, and the conductor layer is used as one electrode. In a method of manufacturing a solid electrolytic capacitor having the other electrode, a general formula is provided on the dielectric oxide film. Wherein R 1 and R 2 independently of one another are hydrogen or C
Represents a 1-C4-alkylene group or, jointly, an optionally substituted C1-C4-alkylene group, preferably a methylene group optionally substituted by an alkyl group, optionally a C1-C12 A 1,2-ethylene group or a 1,2-cyclohexylene group substituted by an alkyne or phenyl group] by chemical oxidative polymerization, and then repairing the dielectric oxide film by chemical conversion. A method for producing a solid electrolytic capacitor, characterized by performing a treatment.