JP2906473B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor using a solid electrolyte.

2. Description of the Related Art In recent years, with the digitization of circuits such as electric devices, it has been strongly required that capacitors used in the circuits have low impedance in a high frequency range, and have a small size and a large capacity.

Under such circumstances, development of large-capacity solid electrolytic capacitors using a conductive solid as an electrolyte has been actively conducted.

Conventionally, a solid electrolytic capacitor using manganese dioxide as a solid electrolyte is well known, but a sufficiently low impedance cannot be obtained in a high frequency region due to high resistance of manganese dioxide.

In addition, instead of the manganese dioxide layer, instead of a manganese dioxide layer, an organic semiconductor with high conductivity and excellent anodizing properties, 7,7,8,8-tetracyanoquinodimethane complex salt (TCNQ salt) is used. What is used for electrolytes
No. -10777) has been proposed.

Recently, a highly conductive polymer layer containing anion of the supporting electrolyte as a dopant is formed by using a solid electrolyte by electrolytic polymerization using a solution containing a heterocyclic compound monomer such as pyrrole or furan and a supporting electrolyte. (JP-A-60-37114) has been proposed. Further, a conductive polymer layer is formed by depositing a metal or a metal compound having conductivity (metal oxide) on a dielectric film, and then bringing an electrode for electrolytic polymerization reaction close to the metal or metal compound to form a conductive polymer layer. There has also been proposed a solid electrolytic capacitor which is formed by polymerization (Japanese Patent Application No. 63-142136).

Problems to be Solved by the Invention However, in the capacitor using the TCNQ salt as a solid electrolyte, there is a problem that a specific resistance rise occurs when the TCNQ salt is applied, adhesion to an anode metal foil is weak, and the practicality is low. .

On the other hand, in a capacitor using an electrolytically polymerized high conductive polymer layer as a solid electrolyte, there is technical difficulty in forming an electrolytically polymerized layer on a dielectric film itself. Normal anode (for example,
It is already known that a highly conductive electrolytic polymerized film can be formed on a platinum, carbon, etc.) solution using a solution of a heterocyclic compound such as pyrrole or thiophene or a derivative thereof and a suitable supporting electrolyte. This is because, in principle, it is difficult to form a conductive polymer layer on the dielectric film by electrolytic polymerization because the dielectric film, which is an object, does not pass a current.

It is also possible to first form an electropolymerized conductive polymer layer before forming a dielectric film (oxide film), and then form a dielectric film later by a chemical reaction, but in this case,
Since the deterioration and deterioration of the electrolytic polymer layer and the separation between the polymer layer and the metal body occur, a capacitor having sufficient characteristics cannot be obtained in practice, and the practicality is low.

Further, when an electropolymerized conductive polymer layer is formed on a conductive substance (conductive layer) formed on a dielectric film via a polymerization reaction electrode, formation of the polymer layer is easy, Such a capacitor has a problem that the leakage current is large and the withstand voltage characteristic is not good.

In view of the above circumstances, an object of the present invention is to provide a method for providing a solid electrolytic capacitor having an electrolytic polymerized polymer layer for a solid electrolyte, having a low leakage current, and having excellent withstand voltage characteristics. .

Means for Solving the Problems In order to solve the first problem, in the method for manufacturing a solid electrolytic capacitor according to claims 1 to 4, a dielectric film (oxide film) is formed on the surface by anodic oxidation or anodization. An electrode for polymerization reaction is brought into contact with the conductive layer of a metal body (valve metal) having a conductive layer laminated on the same film, and the metal body is kept at the same potential as the potential of the electrode. By conducting a polymerization reaction, a conductive polymer layer for a solid electrolyte is laminated on the conductive layer.

The metal of the metal body having a dielectric film (oxide film) formed on the surface by anodic oxidation, anodization or the like in the present invention includes, for example, at least one of aluminum and tantalum as in the invention according to claim 2. Is mentioned.
More specifically, the metal body is an aluminum foil, a tantalum foil, a titanium foil, an alloy foil of these metals, or the like.

As the conductive layer laminated on the dielectric film, for example, a conductive layer made of a manganese oxide such as manganese dioxide is preferable.

Examples of the heterocyclic compound monomer contained in the electrolytic solution for electrolytic polymerization of the present invention include at least one of pyrrole, thiophene, and a derivative thereof (for example, N-methylpyrrole). And the like, and examples of the supporting electrolyte include “sodium triisopropylnaphthalenesulfonate, n-butyl phosphate” and the like. For example, when pyrrole is used, the conductive polymer layer is polypyrrole, as in the fourth aspect of the present invention.

In addition, the monomer and the supporting electrolyte may not be used alone, and a plurality of the above-described monomers may be used in combination, such as a mixture of a plurality of supporting electrolytes or a mixture of pyrrole and thiophene with the respective derivatives. . In addition, an appropriate additive may be added to the electrolytic solution in order to composite the solid electrolyte.

The present invention is not limited to the above exemplified compounds and processing steps. It goes without saying that alternative compounds and processing steps other than those exemplified may be used.

In the production method of the present invention, the metal body is kept at the same potential as the electrode for the electrolytic polymerization reaction during the progress of the electrolytic oxidation polymerization, and the state where the metal body potential becomes negative does not occur.
It does not cause dissolution of the dielectric film. In the conventional case, the potential of the metal member separated by the dielectric film becomes negative, and the dielectric film is dissolved.

Furthermore, even when the dielectric film is damaged by the electrode for the electropolymerization reaction, since the positive potential is applied to the metal body, formation proceeds during the electropolymerization reaction, and the damaged portion is repaired.

As a result, the electrolytically polymerized high-conductivity polymer layer is formed without any damage to the dielectric film, so that a solid electrolytic capacitor having a small leakage current and excellent withstand voltage characteristics can be obtained.

Needless to say, the obtained capacitor is provided with a solid electrolyte composed of an electropolymerized conductive polymer layer of good film quality due to the function of the conductive layer, and thus has excellent frequency characteristics and loss characteristics.

EXAMPLES Hereinafter, specific examples of the method for manufacturing a solid electrolytic capacitor according to the present invention will be described.

Example 1 An aluminum etched foil having a length of 7 mm and a width of 10 mm, to which an anode lead was attached by caulking, was anodized at about 70 ° C. and an applied voltage of 70 V using a 3% ammonium adipate aqueous solution. A dielectric film was formed on the foil surface. Then, the film was immersed in a 30% aqueous solution of manganese nitrate and air-dried, and then heated at 250 ° C. for 30 minutes to perform a thermal decomposition treatment, manganese dioxide was adhered, and a conductive layer was formed on the dielectric film. Subsequently, the etched foil provided with the conductive layer is placed in an electrolytic solution consisting of pyrrole (0.5 M), sodium triisopropylnaphthalenesulfonate (0.1 M) and water, and the polymerization reaction electrode whose surface is covered with polypyrrole is used. Contact the conductive layer and apply 3V DC voltage to the electrode and anode lead simultaneously.
An electrolytic polymerization reaction was carried out by applying a voltage for 30 minutes, and an electropolymerized conductive polypyrrole layer for a solid electrolyte was laminated on the conductive layer.

After the formation of the solid electrolyte, it was washed with water and dried. Then, a carbon paste and a silver paste were sequentially applied on the electrolytic polymer layer, and the cathode lead was taken out to obtain a solid electrolytic capacitor. The production number is ten.

After aging the obtained solid electrolytic capacitor at 20 V for 1 hour, the initial capacity (120 Hz), the leakage current two minutes after the start of the application of the 16 V voltage, and the withstand voltage were measured.
The measurement results (average value of 10 samples) are as follows.

Initial capacity (120Hz) ... 5.3μF Leakage current ... 0.11μA Withstand voltage ... 40.5V For comparison, a solid electrolytic capacitor was obtained in the same manner as above except that no voltage was applied to the anode lead during electrolytic polymerization. Was.

 The measurement results of each characteristic are as follows.

Initial capacity (120 Hz)… 5.2 μF Leakage current… 2.3 μA Withstand voltage… 31.2 V By comparing both, it can be clearly understood that the solid electrolytic capacitor according to the present invention is far superior in leakage current in terms of withstand voltage. .

Example 2 A solid electrolytic capacitor was obtained in the same manner as in Example 1 except that n-butyl phosphate was used instead of sodium triisopropylnaphthalenesulfonate. As a result of measuring each characteristic, as in the case of Example 1, the solid electrolytic capacitor of the present invention, which applies a voltage to both the anode lead and the polymerization reaction electrode, is superior in terms of leakage current and withstand voltage. Was confirmed.

-Example 3-Instead of anodized aluminum etched foil,
A solid electrolytic capacitor was manufactured in the same manner as in Example 1 except that a 10% phosphoric acid aqueous solution was used after embossing, and a tantalum foil having a length of 8 mm and a width of 10 mm formed by anodizing at 90 ° C. to form a dielectric film on the surface was used. I got As a result of measuring each characteristic, Example 1 was obtained.
As in the case of, the solid electrolytic capacitor according to the present invention in which a voltage is applied to both the anode lead and the polymerization reaction electrode,
It was confirmed that it was excellent in terms of leakage current and withstand voltage.

Effect of the Invention As described above, in the production method according to any one of claims 1 to 4, during the electrolytic polymerization, the polymerization reaction electrode and the metal body are kept at the same potential, so that the leakage current is small and the withstand voltage characteristics are excellent. Solid electrolytic capacitors are obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshikuni Kojima 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd. (56) References JP-A-2-74020 (JP, A) Kaisho 64-32619 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01G 9/028

Claims (4)

(57) [Claims] An electrode for a polymerization reaction is brought into contact with the conductive layer of a metal body having a dielectric film formed on a surface thereof and a conductive layer laminated on the film, and the metal body has the same potential as the potential of the electrode. And a method for producing a solid electrolytic capacitor in which a conductive polymer layer for a solid electrolyte is formed on the conductive layer by performing an electrolytic polymerization reaction. 2. The method according to claim 1, wherein the metal of the metal body is at least one of aluminum and tantalum. 3. The method according to claim 1, wherein the conductive layer is made of manganese oxide.
Or a method for manufacturing a solid electrolytic capacitor according to item 2. 4. The method according to claim 1, wherein the conductive polymer layer is made of polypyrrole.