JPH10303080A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a solid electrolytic capacitor superior to leak current characteristic under high temperature without losing high frequency characteristic. SOLUTION: In a method for manufacturing a solid electrolytic capacitor wherein a dielectric oxide film 2, a conductive polymer compound layer 3, a graphite layer 4 as a conductive layer and a silver paste layer 5 are successively formed on surface of a valve action metal 1 as an anode, and the dielectric layer is one electrode (cathode) 6 and the anode 1 is the other electrode (anode) 7, the dielectric oxide film is conversion-repaired after forming the graphite layer 4.

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 using a conductive polymer compound as a solid electrolyte.

[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, those using manganese dioxide as a part of the electrode have a large impedance in a high frequency range because their conductivity is not sufficiently low. 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 and electron-withdrawing compounds (dopants). Various solid electrolytic capacitors using a conductive polymer compound as a solid electrolyte have been proposed, and technical developments aimed at reducing the leakage current of these solid electrolytic capacitors have been made. For example, a solid electrolytic capacitor that reduces leakage current by forming manganese dioxide on an oxide film, forming a conductive polymer compound layer on the manganese dioxide layer, and then performing re-chemical formation is known (for example, Japanese Patent Application Laid-Open Publication No. H11-163873). See JP-A-2-219211). Further, a technique is known in which the formation of an oxide film is performed under a limited condition in a sulfuric acid solution to thereby improve the leakage current (for example, see Japanese Patent Application Laid-Open No. 3-285321).

[0004]

In a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte, various techniques have been developed to improve the leakage current of the capacitor. When placed underneath, or immediately after exposure to high temperatures, it is not perfect in terms of increased leakage current.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a method of manufacturing a solid electrolytic capacitor having excellent leakage current characteristics at high temperatures without deteriorating high frequency characteristics. To provide.

[0006]

Means for Solving the Problems In order to achieve this object, the present inventors have made intensive studies and as a result, formed a metal having a valve action as an anode body to form a dielectric oxide film on the surface, After forming a conductive polymer compound layer obtained by doping a conjugated polymer compound such as polypyrrole, polythiophene, or polyaniline with an electron-donating or electron-withdrawing compound on this oxide film, a graphite layer serving as a conductor layer serving as a cathode is formed. It has been found that the problem can be solved by forming and then repairing the dielectric oxide film by chemical conversion. The structural feature of the present invention is that a dielectric oxide film, a conductive polymer compound layer of a conjugated polymer compound, and a conductor layer are sequentially formed on the surface of a valve metal as an anode body, and the conductor layer is formed. In the method for manufacturing a solid electrolytic capacitor in which one electrode is used and the valve metal is used as the other electrode, after forming a graphite layer which is a part of the conductor layer, the dielectric oxide film may be subjected to a chemical conversion treatment. is there.

The metal having a valve action as the anode body in the present invention is selected from aluminum and tantalum, and is used by etching or sintering to increase the surface area. An oxide film is formed on the valve action metal. For this purpose, it can be formed by an ordinary method by electrochemical means using an aqueous solution of adipic acid or boric acid. After forming a conductive polymer compound layer of a conjugated polymer compound on the oxide film, a graphite layer and a silver paste layer as a conductor layer are sequentially formed.

The conductive polymer compound layer is formed by using a conductive polymer layer synthesized by a chemical polymerization method as a precoat layer,
It is formed by electrolytic polymerization on it. The conductive polymer formed by electrolytic polymerization is not particularly limited, but is preferably a compound having pyrrole, thiophene, aniline or a derivative thereof as a repeating unit because of the ease of the polymerization reaction. Oxidatively-polymerized polypyrrole, polyaniline, or polythiophene, or any of their derivatives is desirable, and further, any of polyaniline, polythiophene, and polypyrrole may be combined.

The above-mentioned chemical conversion repair treatment of the oxide film after the formation of the graphite layer is performed through a conductive polymer compound layer in a dilute solution of 1% or less of adipic acid, salicylic acid, phosphoric acid or the like.

[0010]

Embodiments of the present invention will be described. FIG. 1 is a schematic diagram of a cross-sectional structure of a solid electrolytic capacitor obtained by the method of the present invention. In FIG. 1, the surface of a metal 1 having a valve action as an anode body is greatly enlarged. Its surface area is increased. The metal oxide dielectric 2 is formed along the wall surfaces of the pores. Next, a conductive polymer compound layer 3 is formed on the surface of the dielectric oxide film 2. Next, after a graphite layer 4 as a conductor layer serving as a cathode is formed on the conductive polymer compound layer 3, a chemical conversion repair of the dielectric oxide film 2 is performed, and then a silver paste layer 5 is formed. And a cathode lead 6 from the conductive layer.
After the anode leads 7 are respectively pulled out from the valve metal 1, they are sealed with an exterior epoxy resin 8 to obtain a solid electrolytic capacitor. As a result, a solid electrolytic capacitor having excellent leakage current characteristics at high temperatures can be obtained without deteriorating high-frequency characteristics.

[0011]

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. The anode body 1 on which the tantalum oxide film 2 was formed was immersed in a pyrrole solution containing pyrrole and ethanol at a weight ratio of 30:70. Next, it is immersed in an oxidizing agent solution at a temperature of 15 ° C. containing dodecyl benzene sulfone ferric acid and ethanol at a weight ratio of 40:60. Was washed with water and dried in vacuo at 50 ° C. for 1 hour. This polymerization is
This was repeated twice to form a conductive polymer compound layer 3 having a predetermined thickness. Next, after a graphite layer 4 as a conductor layer was formed on the formed conductive polymer compound layer 3, a 35 V oxide film was repaired in a 0.3% aqueous solution of adipic acid by chemical conversion, washed with water, and dried. . Next, a silver paste layer 5 is formed, and a cathode lead 6 is drawn out from the conductor layer, and an anode lead 7 is drawn out from the anode body 1. Then, the entire peripheral surface of the anode body 1 is covered with an exterior epoxy resin material 8. The mold was sealed to complete a solid electrolytic capacitor.

Example 2 Etched surface (25 μF / cm ² ) Thickness 95 μm
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 on which the aluminum oxide film 2 was formed was immersed in a solution of 3,4-ethylenedioxy-thiophene. Next, iron (III) methanesulfonate 3
g was immersed in an oxidizing agent solution mixed with 15 g of water. After the reaction is completed, the unreacted oxidizing agent is washed with water, and
For 1 hour in vacuo. Until the specified thickness
This polymerization was repeated four times to form the conductive polymer compound layer 3. Next, after a graphite layer 4 as a conductor layer was formed on the formed conductive polymer compound layer 3, a 35 V oxide film was repaired in a 0.3% aqueous solution of adipic acid by chemical conversion, washed with water, and dried. . Next, a silver paste layer 5 is formed, and a cathode lead 6 is drawn out from the conductor layer, and an anode lead 7 is drawn out from the anode body 1. Then, the entire peripheral surface of the anode body 1 is covered with an exterior epoxy resin material 8. The mold was sealed to complete a solid electrolytic capacitor.

Example 3 Using the same anode body 1 as in Example 1, a dielectric 2 was formed in the same manner as in Example 1. Next, after the dielectric 2 is formed, it is immersed in an aniline solution containing aniline and ethanol at a weight ratio of 30:70, and then ammonium persulfate, toluenesulfonic acid and ethanol are added at a weight ratio of 2%.
The conductive polymer compound layer 3 was polymerized by immersion in an oxidizing agent at a temperature of 15 ° C. in a ratio of 0:20:60. After completion of the reaction, the polymer was washed and dried in the same manner as in Example 1, and this polymerization was repeated five times to form a conductive polymer compound layer 3 having a predetermined thickness. Next, after forming the graphite layer 4 in the same manner as in the first embodiment, the material was repaired by chemical conversion to complete a solid electrolytic capacitor in the same manner as in the first embodiment.

Example 4 Using the same anode body 1 as in Example 2, a dielectric 2 was formed in the same manner as in Example 2. Next, after forming the dielectric 2, it is immersed in a mixed solution of iron (III) dodecylbenzenesulfonate and pyrrole to form a precoat layer, and then has a pyrrole concentration of 0.05 mol / L and a supporting electrolyte. 0.1
In an acetonitrile solution containing mol / L of tetrabutylammonium perchlorate, a stainless wire as a working electrode is lightly contacted with the precoat layer, and a constant voltage of 3.5 V is applied using platinum as a counter electrode to carry out electrolytic polymerization for 30 minutes. ,
The conductive polymer compound layer 3 was polymerized. After the completion of the reaction, washing and drying were performed in the same manner as in Example 2, and the graphite layer 4
Was formed and repaired by chemical conversion to complete a solid electrolytic capacitor.

In each of Embodiments 1, 2, 3, and 4, except that the chemical conversion repair after the formation of the graphite layer 4 is not performed, completion is performed in the same procedure as in each embodiment. Of the solid electrolytic capacitors (Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4).

Examples 1 to 4 and Comparative Examples 1 to 4
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.

[0017]

[Table 1]

As is clear from Table 1, each of the examples of the present invention has excellent excellent equivalent series resistance characteristics in a high frequency range and good results in which the leakage current does not increase even in a high temperature life test. It turns out that it was obtained.

[0019]

As described above, according to the present invention, it is possible to manufacture a stable and high-quality solid electrolytic capacitor without increasing leakage current in a high-temperature life test without deteriorating excellent frequency characteristics.

[Brief description of the drawings]

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

[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 of a conjugated polymer compound, and a conductor layer are sequentially formed on the surface of a valve metal serving as an anode body, and the conductor layer is used as one electrode. A method for manufacturing a solid electrolytic capacitor using the valve metal as the other electrode, wherein after forming a graphite layer which is a part of the conductor layer, the dielectric oxide film is subjected to chemical conversion treatment. Manufacturing method of electrolytic capacitor.