JPH10247612A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having no increase in leakage current due to thermal stress generated when mounting in the state wherein excellent high frequency characteristics, which are the special character of a conductive high molecular compound, are being maintained. SOLUTION: A conductive high molecular compound layer 4, a graphite layer 5 which is a conductive layer and a silver paste layer 4 are successively formed on an anode member, where a dielectric oxide film layer 2 is formed, in this electrolytic capacitor. The conductive layer is used as an electrode (cathode) 7 on one side, and an anode member 1 is used as the other electrode (anode) 8. In this case, an insulative thin film layer (polyimide thin film layer) 3 is selectively formed on the insulating defective part of the dielectric oxide film layer by an electrodeposition method, the insulating defective part of the dielectric oxide film layer 2 is repaired by the insulative thin film layer (polyimide thin film layer) 3, and the increase of a leakage current caused by the thermal stress at the time of mounting can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a solid electrolytic capacitor using a conductive polymer compound of a conjugated polymer compound as a solid electrolyte, and more specifically, means for preventing an increase in leakage current due to thermal stress during mounting. The present invention relates to a solid electrolytic capacitor provided with.

[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). A solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte has been proposed. More specifically, as shown in FIG. 2, the solid electrolytic capacitor has a conjugated system on an anode body 1 having a dielectric oxide film layer 2 formed on the surface of a sintered body of tantalum powder. A conductive polymer compound layer 4 of a polymer compound, a graphite layer 5 as a conductor layer serving as a cathode, and a silver paste layer 6 are sequentially laminated, and a cathode lead wire 7 extends from the conductor layer to the anode body 1. The anode lead wires 8 are respectively drawn out, and the entire peripheral surface of the anode body 1 is molded with an exterior resin material 9 so as to be molded. In the solid electrolytic capacitor, the conductive polymer compound layer 4 is formed, for example, by adding an aniline monomer to the dielectric oxide film layer 2.
Above, polymerization was carried out using an oxidizing agent to form polyaniline as a conductive polymer compound layer.

[0003]

However, as described above, a conventional solid electrolytic capacitor using a conductive polymer compound polymerized with an oxidizing agent on a dielectric oxide film layer as a solid electrolyte is a solid electrolytic capacitor. Since the polyaniline film, which is only a thin layer, is formed only thinly, the polyaniline film and the dielectric oxide film may peel off due to thermal stress or the like applied during mounting, causing damage to the dielectric oxide film layer and causing leakage of the capacitor. There is a problem that the current increases.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and an object of the present invention is to maintain the high frequency characteristics characteristic of a conductive polymer compound while maintaining the high frequency characteristics during mounting. An object of the present invention is to provide a solid electrolytic capacitor using a conjugated polymer compound as a solid electrolyte without increasing leakage current due to stress.

[0005]

In order to achieve this object, the present invention provides a conductive polymer compound layer of a conjugated polymer compound on an anode body having a dielectric oxide film layer formed on a surface thereof.
In a solid electrolytic capacitor in which a conductor layer is sequentially formed and the conductor layer is used as one electrode and the anode body is used as the other electrode, an insulating thin film is formed on an insulation defect portion of the dielectric oxide film layer. A layer formed by an electrodeposition method, wherein the insulating thin film layer repairs an insulation defect portion of the dielectric oxide film layer, thereby preventing an increase in leakage current due to thermal stress during mounting. is there.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1 in which parts corresponding to those in FIG. 2 are assigned the same reference numerals. The solid electrolytic capacitor according to the present invention is shown in FIG. As shown in FIG. 2, in the solid electrolytic capacitor having the conventional structure shown in FIG.
The insulating thin-film layer (polyimide thin-film layer) 3 is selectively formed in the insulation defect part of (1). More specifically, a sintered body of a metal powder capable of forming a dielectric oxide film such as titanium, tantalum, and aluminum is formed, and a dielectric material is formed along a U-shape on a pore wall surface of the sintered body having a large surface area. An anode body 1 serving as an anode on which the oxide film layer 2 is formed is formed, and an insulating defect portion of the anode body 1 requiring repair of the surface of the dielectric oxide film layer 2 is formed by an electrodeposition method using an insulating thin film. A layer (polyimide thin film layer) 3 is selectively formed, and then a conductive polymer compound layer 4 of a conjugated polymer compound and a graphite layer as a conductive layer are formed on the insulating thin film layer (polyimide thin layer) 3. 5 and a silver paste layer 6 are sequentially laminated, and a cathode lead wire 7 is drawn out from the conductor layer, and an anode lead wire 8 is drawn out from the anode body 1. Molded exterior It become one.

As a method of forming a polyimide thin film as the insulating thin film layer 3, a spin coating method, a vacuum deposition polymerization method, an electrodeposition method and the like are known. Because it is difficult to form a thin film inside the pores that have been made porous, in this solid electrolytic capacitor, a solution containing a polyamic acid salt is used as an electrodeposition solution, and a polyamic acid is electrodeposited, and then heated and imidized to form a polyimide thin film. The electrodeposition method of forming was adopted. The conductive polymer compound layer 4 is formed by using a conductive polymer layer synthesized by a chemical polymerization method as a precoat layer, and performing electrolytic polymerization on the precoat layer. 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 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.

In the solid electrolytic capacitor manufactured and manufactured as described above, the insulation defect of the dielectric oxide film layer 2 is repaired by the polyimide thin film layer 3 which is an insulating thin film layer. Is a solid electrolytic capacitor in which the leakage current does not increase due to the thermal stress.

[0009]

EXAMPLES Specific examples will be described below. Example 1 A square sintered body of tantalum powder (2.1 × 1.0 × 1.2 m
m) is anodized (50 V) in a phosphoric acid aqueous solution, and a tantalum oxide film layer 2 as a dielectric oxide film layer is formed on the surface of the sintered body.
To form an anode body 1. The anode body 1 is immersed in a solution containing a polyamic acid salt, electrodeposited at 40 V for 1 hour, washed with methanol and heated at 250 ° C. for 1 hour to form a tantalum oxide film layer 2 An imidized polyimide thin film layer 3 as an insulating thin film layer was formed thereon. The electrodeposition solution was prepared by adding 1.2 g of biphenyltetracarboxylic dianhydride and 0.44 g of P-phenylenediamine to N-methylpyrrolidone 2
The reaction was carried out in 1.8 g to prepare a polyamic acid solution.
After diluting 2.1 g of this polyamic acid solution with 33.5 g of N, N-dimethylformamide, 0.034 g of triethylamine was added with good stirring to form a polyamic acid salt solution. Of polyamic acid salt.
A 145% electrodeposition solution was obtained. After forming the polyimide thin film layer 3, it was immersed in a pyrrole solution containing pyrrole and ethanol at a weight ratio of 30:70. Next, ferric dodecyl benzene sulfone and ethanol were added in a weight ratio of 4%.
The conductive polymer compound layer 4 was polymerized by immersion in an oxidizing solution at a temperature of 15 ° C. containing 0:60. After completion of the reaction, the unreacted oxidizing agent and excess acid were washed with water and dried at 50 ° C. for 1 hour in vacuum. Next, a graphite layer 5 and a silver paste layer 6 as conductor layers are sequentially formed on the formed conductive polymer compound layer 4, and a cathode lead wire 7 is provided from the silver paste layer 6, and an anode lead is provided from the anode body 1. After each lead wire 8 was drawn out, the entire peripheral surface of the anode body 1 was molded and packaged with a packaged epoxy resin material 9 to complete a solid electrolytic capacitor.

Example 2 A polyimide thin film layer 3 was formed on the dielectric oxide film layer 2 of the same anode body 1 as in Example 1 by the same method as in Example 1. After forming the polyimide thin film layer 3, 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 at a weight ratio of 20:20:60. The conductive polymer compound layer 4 was immersed in an oxidant solution having a temperature of 15 ° C. and polymerized. After the completion of the reaction, the solid electrolytic capacitor was completed by washing and drying in the same manner as in Example 1.

Example 3 A polyimide thin film layer 3 was formed on the dielectric oxide film layer 2 of the same anode body 1 as in Example 1 by the same method as in Example 1. After forming the polyimide thin film layer 3, 1.5 g of iron P-toluenesulfonate (II) in 4 g of isopropanol
I) was immersed in a solution of 0.5 g of 3,4-ethylenedioxy-thiophene to polymerize the conductive polymer compound layer 4. After the completion of the reaction, the solid electrolytic capacitor was completed by washing and drying in the same manner as in Example 1.

Example 4 A polyimide thin film layer 3 was formed on the dielectric oxide film layer 2 of the same anode body 1 as in Example 1 by the same method as in Example 1. After forming the polyimide thin film layer 3, 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.
In an acetonitrile solution containing 0.05 mol / L of tetrabutylammonium perchlorate as a supporting electrolyte and 0.1 mol / L as a supporting electrolyte, a stainless steel wire serving as a working electrode is lightly contacted with the precoat layer, and platinum is used as a counter electrode to give a constant voltage of 3. 5
Electrolytic polymerization was performed by applying V for 30 minutes to polymerize the conductive polymer compound layer 4. After the completion of the reaction, the solid electrolytic capacitor was completed by washing and drying in the same manner as in Example 1.

Example 5 Film thickness 9 (25 μF / cm ² ) expanded by etching
An aluminum foil (anode) having a size of 5 μm and an area of 5 × 3 mm was anodized in ammonium borate at 50 V to form a dielectric oxide film layer 2, and then a polyimide thin film layer 3 was formed in the same manner as in Example 1. . After forming the polyimide thin film layer 3,
1 in 5 g of a 1: 2 mixture of acetone and isopropanol
g of iron (III) metasulfonate and 0.5 g of 3,4-ethylenedioxy-thiophene, and the conductive polymer layer 4 was polymerized. After completion of the reaction, Example 1
The solid electrolytic capacitor was completed by washing and drying in the same manner as described above.

In each of Examples 1, 2, 3, 4, and 5, except that the polyimide thin film layer 3 was not formed, the procedure was completed in the same procedure as in each example. It was compared with solid electrolytic capacitors (Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Comparative Example 5).

Examples 1 to 5 and Comparative Examples 1 to 5
For each solid electrolytic capacitor of
Table 1 shows the impedance at 0 KHz and the leakage current before and after the solder heat resistance test (immersion at 270 ° C. for 10 seconds).

[0016]

[Table 1]

As is clear from Table 1, each of the solid electrolytic capacitors of the embodiments according to the present invention has excellent impedance characteristics in a high frequency range and an increase in leakage current due to thermal stress during mounting. It turns out that there is no.

[0018]

According to the present invention, a polyimide thin film layer, which is an insulating thin film layer, is selectively formed on an insulating defect portion of a dielectric oxide film layer by an electrodeposition method. The insulation defect portion of the oxide film layer is repaired by this insulating thin film layer (polyimide thin film layer), so that it is possible to provide a solid electrolytic capacitor in which leakage current does not increase due to thermal stress during mounting. is there.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode body 2 Dielectric oxide film layer 3 Insulating thin film layer (polyimide thin film layer) 4 Conductive polymer compound layer 5 Graphite layer 6 Silver paste layer 7 Cathode lead wire 8 Anode lead wire 9 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] A conductive polymer compound layer of a conjugated polymer compound on an anode body having a dielectric oxide film layer formed on a surface thereof;
In a solid electrolytic capacitor in which a conductor layer is sequentially formed and the conductor layer is used as one electrode and the anode body is used as the other electrode, an insulating thin film is formed on an insulating defect portion of the dielectric oxide film layer. A layer formed by an electrodeposition method, wherein the insulating thin film layer repairs an insulating defect portion of the dielectric oxide film layer to prevent an increase in leakage current due to thermal stress during mounting. Capacitors.