JPH0690995B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer film as a solid electrolyte.

2. Description of the Related Art Recently, with the digitization of electric equipment circuits, there is an increasing demand for capacitors used therein to have a low impedance in a high frequency region and a small size and a large capacity.

Conventionally, a plastic film capacitor, a mica capacitor, a monolithic ceramic capacitor and the like are generally known as high frequency capacitors. However, the former two types of plastic film capacitors and mica capacitors are too large in shape, so it is difficult to increase the capacity, and the third type of monolithic ceramic capacitors was born from the demand for large capacity and miniaturization. However, it is very expensive and has insufficient temperature characteristics.

In addition to the above capacitors, there are aluminum dry electrolytic capacitors, aluminum solid electrolytic capacitors, and tantalum solid electrolytic capacitors.

In the aluminum dry electrolytic capacitor, the etched positive and negative aluminum foils are wound around a paper separator to use a liquid electrolyte. However, in the case of this electrolytic capacitor, leakage of electrolyte solution,
There are drawbacks such as a decrease in capacitance and an increase in loss that occur over time due to ionic conductivity and the like, and a large loss in a high frequency region and a low temperature region.

Aluminum solid electrolytic capacitors and tantalum solid electrolytic capacitors are intended to be solidified in order to improve the above problems due to liquid electrolytes. In providing the solid electrolyte, the valve metal on which the dielectric film is formed is immersed in a manganese nitrate solution and pyrolyzed in a high temperature furnace at about 350 ° C. to form a manganese dioxide layer. Since this capacitor is a solid electrolyte, it has no drawbacks such as volatilization of the electrolytic solution at high temperatures and functional deterioration due to solidification in low temperature regions, and frequency characteristics and temperature characteristics are improved. Also,
Since the dielectric film on the valve metal surface can be made extremely thin, a large capacity can be achieved.

Recently, 7,7,8,8-tetracyanoquinodimethane (TCN
Q) A solid electrolytic capacitor using an organic semiconductor such as a salt as a solid electrolyte (Japanese Patent Application No. 58-17609), or a conductive polymer obtained by electrolytically polymerizing a polymerizable monomer such as pyrrole or France as a solid electrolyte. There is a solid electrolytic capacitor used in (Japanese Patent Application No. 60-244017).

However, when the solid electrolyte is manganese dioxide, the loss in the high frequency region is not small because of the damage of the oxide film due to several high temperature pyrolysis and the high specific resistance of manganese dioxide. When the solid electrolyte is an organic semiconductor such as TCNQ salt, it shows superior high frequency characteristics compared to a capacitor using manganese dioxide, but there is an increase in the resistivity when applying the organic semiconductor and insufficient adhesion to the valve metal foil. There isn't enough.

On the other hand, when the solid electrolyte is a conductive polymer obtained by electrolytic polymerization, it has excellent frequency characteristics, temperature characteristics, and life characteristics, and can be said to be an expected solid electrolytic capacitor.

Problems to be Solved by the Invention However, a solid electrolytic capacitor in which the solid electrolyte is a conductive polymer obtained by electrolytic polymerization has a problem of large leakage current.

When a conductive polymer film is formed on the dielectric film, an electrode for initiating polymerization (for example, a needle-shaped metal electrode) is applied from outside to bring it into contact with the dielectric film. This is because it will be damaged. In addition, when the electrode for initiating the polymerization is externally applied and brought into contact, there is a problem in that the whole manufacturing apparatus becomes large and it is not easy to carry out.

In order to prevent damage to the dielectric film, the following methods have been proposed.

That is, after forming a conductive polymer thin film on a valve metal foil having a dielectric film formed on its surface by electrolytic polymerization, the metal surface of the valve metal foil is partially exposed by partially cutting it. This is a method of using the electrolytic polymerization initiation part (anode). However, in this case, since the exposed metal surface is anodized by the electrolytic polymerization solution and the electrical insulation is cut off, the current stops flowing during the formation of the polymer film, and the progress of the polymer film formation is extremely delayed. In a remarkable case, there is a problem that the polymerization reaction is stopped.

In view of the above circumstances, the present invention provides a method capable of promptly forming a dielectric polymer film for a solid electrolyte without damaging the dielectric film and obtaining a solid electrolytic capacitor with a small leakage current. The purpose is to

Means for Solving the Problems In order to achieve the above object, in the method for producing a solid electrolytic capacitor of the present invention, a valve metal having a surface covered with a dielectric film and a manganese oxide film laminated on the dielectric film. The metal surface of the foil is partially exposed, and a conductive part for the electrolytic polymerization solution is provided on the exposed part with a material that is not anodized, and this conductive part is used to conduct high conductivity for solid electrolyte by electrolytic polymerization. A molecular film is laminated on the manganese oxide film, a conductive paint film is further laminated thereon, and then the conductive portion is removed.

Hereinafter, the present invention will be described in more detail.

The dielectric film on the surface of the valve metal is formed by anodic oxidation or anodization.

Specifically, the conductive portion that becomes the electrolytic polymerization initiation portion is provided as follows.

When the conductive part is made of a metal material, the metal valve that is not anodized is welded to the exposed metal surface as in claim 2, but the metal piece that is not anodized is exposed as in claim 3. Be caulked on a metal surface.

When the conductive portion is composed of conductive paint, Ag paint is applied to the exposed metal surface as in claim 4, or carbon paint is applied to the exposed metal surface as in claim 5. To do so.

When the conductive portion is made of a conductive polymer, the conductive polymer layer is formed by chemical polymerization on the exposed metal surface as in the sixth aspect.

The conductive portion may be provided not only at one location but also at a plurality of locations.

The manganese oxide film has conductivity and functions to facilitate the formation of a conductive polymer film for solid electrolyte by electrolytic polymerization.

When forming a conductive polymer film for a solid electrolyte, for example, as in claim 7, an electrolytic polymerization solution containing at least one of pyrrole, thiophene or a derivative thereof and a supporting electrolyte is used, and a valve metal is added to the solution. Soak the foil to form an electropolymerized film.

As the valve metal, specifically, one of aluminum and tantalum is exemplified as in claim 8.

Examples of the structure of the dielectric paint film formed on the conductive polymer film include a two-layer structure composed of a carbon paint layer and an Ag paint layer formed on the carbon paint layer.

Action In the case of the method for manufacturing a solid electrolytic capacitor of the present invention, the conductive portion for the electrolytic polymerization initiation portion is formed of a material that does not anodize, while forming the conductive polymer film for the solid electrolyte,
Since anodic oxidation does not occur in the conductive portion and a normal energized state is maintained during the reaction, electrolytic polymerization formation of the conductive polymer film proceeds rapidly.

In the case of the present invention, since it is not necessary to contact the electrode by contacting the electrode from the outside in order to start the electrolytic polymerization from above the derivative film, the dielectric film is not damaged by the electrode contact, and as a result, the leakage current of the obtained capacitor is reduced. And the entire device is small, which is easy to implement.

If the conductive part for the electrolytic polymerization initiation part is left as it is, a short circuit occurs between the valve metal foil and the conductive polymer film and the capacitor function is impaired, but in the present invention, the conductive part is usually formed on the conductive part. Since it is removed together with the conductive polymer film and the conductive paint film, the capacitor function is not impaired.

Examples Examples of the present invention will be described below. The present invention is not limited to the embodiments described below.

Example 1 A method of manufacturing a solid electrolytic capacitor according to Example 1 of the present invention will be described with reference to FIGS. 1 to 10. In each figure, (b) shows a front view and (a) shows a side view or a partially crushed side view.

The valve action metal foil 2 (aluminum etched foil) shown in FIGS. 1 (a) and (b) was anodized using a 7% ammonium adipate aqueous solution at about 70 ° C. for 40 minutes under an applied voltage of 42 V, A dielectric film 3 was formed as shown in FIGS. 2 (a) and 2 (b). An aqueous solution of manganese nitrate was applied and thermally decomposed at 300 ° C. for 20 minutes to form a dielectric layer composed of the manganese oxide film 4 as shown in FIGS. 3 (a) and 3 (b). Then, as shown in FIGS. 4 (a) and 4 (b), a polymerization initiating dielectric portion 10 (a nickel foil piece, a diameter of 1 mm, and a thickness of 50 μm in the embodiment) was placed on the manganese oxide film 4 by welding. . The polymerization initiation conductive portion 10 penetrates the dielectric film 3 and the manganese oxide film 4 and is in contact with the valve action metal foil 2, as shown in the AA 'sectional view of FIG. 4 (b).

Dip the valve metal foil in an electrolytic polymerization solution consisting of pyrrole (0.25M), triisopropylnaphthalene sulfonate (0.1M), and water, and apply a constant voltage of 2.5V for 30 minutes with the nickel foil piece as the electrolytic polymerization start part. As shown in FIGS. 6 (a) and 6 (b), the dielectric polymer film 5 for solid electrolyte is formed on the manganese oxide.
(Polypyrrole film) was formed. Thereafter, as shown in FIGS. 7A, 7B, 8A, and 8B, a carbon paint film 6 and then a silver paint film 7 were formed. Subsequently, as shown in FIGS. 9A and 9B, the nickel foil piece 10 is provided with the valve metal foil 2, the dielectric film 3, the manganese oxide film 4, the conductive polymer film 5 above and below the nickel foil piece 10. The carbon paint film 6 and the silver paint film 7 were bent and removed. Finally, as shown in FIG. 10, the anode lead 1 is attached to the valve action metal foil 2 by welding and the cathode lead 8 is attached to the silver paint film 7.
Was connected to the above and was packaged with a resin to obtain a solid electrolytic capacitor.

Example 2 A method for manufacturing a solid electrolytic capacitor according to Example 2 of the present invention will be described with reference to FIGS. 11 to 21. In each figure, (b) is a front view and (a) is a side view or a partially crushed side view.

The valve action metal foil 2 (aluminum etched foil) shown in FIGS. 11 (a) and 11 (b) was anodized using a 7% ammonium adipate aqueous solution at about 70 ° C. for 40 minutes under an applied voltage of 42 V. A dielectric film 3 was formed as shown in FIGS. 12 (a) and 12 (b). Next, apply a manganese nitrate aqueous solution at 300 ° C for 20
Thermal decomposition was carried out under the conditions of minutes to form a conductive layer composed of the manganese oxide film 4 as shown in FIGS. 13 (a), 13 (b) and 13 (c). Then, the element is cut along the line AA ′ shown in FIG.
As shown in FIGS. 15A and 15B, the valve action metal foil 2 covered with the dielectric film 3 and the manganese oxide film 4 is exposed. Then, a paste-like silver paint was applied to the cut surface and heated and cured at 120 ° C. for 10 minutes to provide a conductive portion 10 for an electrolytic polymerization initiation portion. (See FIGS. 16 (a) and 16 (b)). Pyrrole (0.25M), triisopropyl naphthalene sulphonate (0.1M), dip the valve metal foil in an electropolymerization solution consisting of water, using the conductive part 10 made of silver paint as the electropolymerization initiation part, and a constant voltage of 2.5V. Was applied for 40 minutes to form a conductive polymer film 5 (polypyrrole film) for solid electrolyte on the manganese oxide as shown in FIGS. 17 (a) and 17 (b). After this, FIG. 18 (a), (b) FIG. 19 (a),
As shown in (b), a carbon paint film 6 and then a silver paint film 7 were formed. Then, FIG. 20 (a),
As shown in (b), the conductive portion 10 made of silver paint is provided on the upper and lower sides of the valve action metal foil 2, the dielectric film 3, the manganese oxide film 4, the conductive polymer film 5, the carbon paint film 6, and the silver paint. It was bent and removed together with the membrane 7. Finally, as shown in FIG. 21, the anode lead 1 is attached to the valve action metal foil 2 by welding, and the cathode lead 8 is connected on the silver paint film 7.
It was packaged with a resin to obtain a solid electrolytic capacitor.

Comparative Example 1 Instead of the silver pace, the exposed valve metal foil itself was immersed in an electrolytic solution containing pyrrole (0.25M), triisopropylnaphthalene sulfonate (0.1M) and water as the electroconductive polymerization initiation part conductive part 10. When electrolysis was carried out by applying a constant voltage of 2.5 V, the valve metal foil caused a chemical conversion reaction in the electrolytic solution to increase the resistance and interfered with the electropolymerization reaction.
It was a minute. A solid electrolytic capacitor was obtained in the same manner as in Example 2 except for the above.

Comparative Example 2 The nickel foil piece 10 and the valve metal foil 2 above and below it, the dielectric film 3, the manganese oxide film 4, the conductive polymer film 5, the carbon paint film 6, and the silver paint film 7 were not removed, 8th
A solid electrolytic capacitor was obtained in the same manner as in Example 1 except that the lead 8 was connected to the silver paint film 7 in the states shown in FIGS.

Example 3 Carbon paint was used instead of Ag paint, and 120
A solid electrolytic capacitor was obtained in the same manner as in Example 2 except that the conductive portion was provided by curing by heat treatment at 5 ° C. for 5 minutes, and the electrolytic polymerization time was 60 minutes.

Example 4 Instead of Ag paint, an aqueous solution of ammonium persulfate (0.0
1 mol / l) and after drying, the coated surface was immersed in a pyrrole monomer solution for 5 minutes to form a chemically polymerized conductive polymer layer, which was used as a conductive part for electrolytic polymerization opening, A solid electrolytic capacitor was obtained in the same manner as in Example 2.

Example 5 A tantalum valve metal having a liquid content of 1.1 μF / cm ² and having a dielectric film formed on its surface by anodizing using a 1% phosphoric acid aqueous solution at a voltage of 30 V for 60 minutes at about 90 ° C. Body (tantalum sintered body) coated with manganese nitrate aqueous solution, 300 ℃, 2
It was thermally decomposed under the condition of 0 minutes to form a conductive layer made of a manganese oxide film. Then, cut the lower end of the valve metal foil by 1 mm to expose the metal surface of the valve metal foil, apply Ag paste to the same metal surface, heat at 120 ° C. for 10 minutes to cure, and set the conductive part for the electrolytic polymerization initiation part. Provided.

Then, dip the valve metal foil in an electropolymerization solution consisting of pyrrole (0.25 mol), n-butyl phosphate (0.1 mol), and water, and use the Ag paint conductive part as the electropolymerization start part and apply a constant voltage of 2.5 V to 20%. Was applied to form a conductive polymer film for a solid electrolyte on the manganese oxide film.

After this, a carbon paint film and then an Ag paint film are formed on the conductive polymer film, and then Ag paint for the electrolytic polymerization initiation portion is formed on the conductive polymer film and the carbon paint film. And removed with Ag paint film.

Finally, the lead was connected to the top of the Ag paint film and covered with resin to obtain a solid electrolytic capacitor.

The initial characteristics of the capacitors of Examples and Comparative Examples were measured. The measurement results are shown in Table 1. In Table 1, the capacity and loss were measured at 120 Hz and the impedance was 1 MHz, and the leakage current was measured 2 minutes after the rated voltage was applied.

As shown in Table 1, each capacitor of the embodiment has a capacitance
The impedance and leakage current are sufficient, and the solid electrolyte can be formed quickly. In the case of the capacitor of Comparative Example 1, the loss is large and the time required to form the solid electrolyte is long. Also, in the case of the capacitor of Comparative Example 2, the leakage current is too large to fulfill the capacitor function.

EFFECTS OF THE INVENTION In the case of the method for producing a solid electrolytic capacitor of the present invention, since the conductive portion with respect to the electrolytic polymerization solution is not anodized, the conductive polymer film for the solid electrolyte can be quickly formed, and the electrolysis is performed on the dielectric film. Since it is not necessary to contact the polymerization initiating electrode to bring it into contact with each other, the dielectric film is not damaged by the contact of the electrodes, the leakage current is small, and the entire apparatus is small and easy to carry out.

[Brief description of drawings]

1 to 10 are process drawings showing a method of manufacturing a solid electrolytic capacitor according to a first embodiment of the present invention, and FIG.
FIG. 21 to FIG. 21 are process drawings showing a method for manufacturing a solid electrolytic capacitor according to the second embodiment of the present invention. 1 ... Anode lead, 2 ... Valve metal foil, 3 ... Dielectric film, 4 ... Manganese oxide film, 5 ... Conductive polymer film, 6 ... Carbon paint film, 7 ... Ag paint film,
8: cathode lead, 10: conductive part.

Claims (8)

[Claims] 1. A metal surface of a valve metal body, the surface of which is covered with a dielectric film and a manganese oxide film is laminated on the dielectric film, is partially exposed, and the exposed portion is subjected to an electrolytic polymerization solution. After providing a conductive portion for a material not to be anodized, a conductive polymer film for solid electrolyte by electrolytic polymerization is laminated and formed on the manganese oxide film, and a conductive paint film is further laminated thereon. A method for manufacturing a solid electrolytic capacitor, wherein the conductive portion is removed. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive portion is provided by welding and joining a metal piece to the exposed metal surface. 3. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive portion is provided by caulking a metal piece to the exposed metal surface. 4. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive portion is provided by applying Ag paint on the exposed metal surface. 5. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive portion is provided by applying carbon paint on the exposed metal surface. 6. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive portion is provided by forming a conductive polymer layer on the exposed metal surface by chemical polymerization. 7. The conductive polymer membrane for a solid electrolyte is formed by using an electrolytic polymerization solution containing at least one of pyrrole, thiophene or a derivative thereof and a supporting electrolyte. Manufacturing method of solid electrolytic capacitor. 8. The method for producing a solid electrolytic capacitor according to claim 1, wherein the valve metal is one of aluminum and tantalum.