JPH06252003A - Capacitor manufacturing method - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain a small-sized, large-capacity nonpolar capacitor with excellent high-frequency characteristics. [Structure] A porous conductor surface is obtained by adding a poor solvent for polyamic acid to a solution containing a polyamic acid salt and using an electrodeposition liquid containing an additive made of a compound that acts as a smoothing agent during electrodeposition. Is subjected to electrodeposition to form a smooth thin film of polyamic acid along the shape of the surface of the conductor. Then, it is heated and dehydrated to obtain a polyimide film, and further,
A conductor layer serving as a counter electrode is formed on the surface of the polyimide coating by sequentially laminating a polypyrrole film formed by chemical oxidation polymerization and a polypyrrole film formed by electrolytic polymerization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a capacitor used in an electronic circuit mounted on an electric / electronic device.

[0002]

2. Description of the Related Art With the miniaturization and weight reduction of electric / electronic devices, there is an increasing demand for miniaturization and high performance of various electronic components mounted therein. Similarly, various attempts have been made to develop capacitors that are small and large in capacity and have excellent high frequency characteristics.

A film capacitor having excellent high-frequency characteristics is not suitable for practical use because its shape becomes large and its cost becomes high when a large capacity is obtained.

On the other hand, the aluminum electrolytic capacitor known as a large-capacity capacitor is inferior in high frequency characteristics. However, recently, an aluminum solid electrolytic capacitor using a conductive polymer as a solid electrolyte has emerged as a capacitor having excellent high frequency characteristics.

[0005]

An aluminum solid electrolytic capacitor using a conductive polymer as a solid electrolyte is said to be small in size and wound to obtain a large capacity, and the stress tends to cause cracks in the dielectric oxide film. There is a problem, and there is also a problem that the positive and negative directions must not be mistaken during mounting due to the polarity of the electrolytic capacitor.

The present invention solves the above-mentioned problems of the prior art, and is a method of manufacturing a small-sized, large-capacity, non-polarized capacitor excellent in high-frequency characteristics, which combines the characteristics of a film capacitor with the characteristics of an aluminum electrolytic capacitor. The purpose is to provide.

[0007]

In order to achieve this object, the method for producing a capacitor of the present invention comprises adding a poor solvent for polyamic acid to a solution containing a polyamic acid salt, and further acting as a smoothing agent during electrodeposition. By adding an additive consisting of a compound to form an electrodeposition liquid, and forming a thin film of polyamic acid by performing electrodeposition on the surface of the porous conductor, by heating and dehydrating the thin film of polyamic acid to imidize A polyimide film is formed, and then a conductor layer serving as a counter electrode is formed on the surface of the polyimide film.

[0008]

According to the above method, a smooth polyamic acid thin film is formed along the shape of the porous conductor surface. That is, the additive slightly added to the electrodeposition liquid becomes high in concentration at the convex portion of the porous surface of the conductor when electrodeposition starts, and part of the additive makes it difficult to pass current. .
On the other hand, the concentration of the additive in the recess is low, and a normal current flows.
Therefore, a thin polyamic acid thin film is formed in the convex portion and in the concave portion, and as a result, a smooth polyamic acid thin film can be formed along the shape of the porous conductor surface.

After that, the polyimide coating obtained by heating and dehydration is smooth along the shape of the porous conductor surface, so that the thickness of the dielectric formed on the conductor surface becomes uniform and the leakage occurs. It is possible to obtain a high withstand voltage dielectric with a small current.

Further, by forming a conductor layer as a counter electrode on the surface of this polyimide coating, a non-polar capacitor having a small size, a large capacity and excellent high frequency characteristics can be obtained.

Additives which act as a leveling agent in the present invention include polyethylene glycol, coumarin, 2-butyne-1,4-diol, 2-propyn-1-ol, 3-
Phenylpropionic acid, thiourea, 1-allyl-2-
Examples include thiourea and 1-phenyl-2-thiourea.

When no additive is added to the electrodeposition liquid, a thin film of polyamic acid is formed on the convex portion of the surface of the porous conductor and a thin polyamic acid film is formed in the concave portion. Therefore, polyimide obtained by heating and dehydrating it The coating is also a thick film with convex portions and thin with concave portions, and has a non-uniform thickness. Therefore, good characteristics cannot be obtained even if a capacitor is manufactured using this polyimide coating.

[0013]

EXAMPLE An example of the present invention will be described in detail below. Aluminum etching foil with surface roughened about 50 times 5mm ×
After cutting to 20 mm, an aluminum lead was joined by ultrasonic welding to obtain a metal electrode.

On the other hand, 3.3 parts by weight of p-phenylenediamine was dissolved in 90 parts by weight of N, N-dimethylformamide, 6.7 parts by weight of pyromellitic dianhydride was added, and the mixture was reacted at room temperature for 10 hours to obtain a polyamic acid solution. . To this polyamic acid solution, 1.8 parts by weight of triethylamine was added and reacted at room temperature for 1 hour to prepare a polyamic acid salt solution in which half of the carboxyl groups of polyamic acid were neutralized, and 1.2 parts by weight of polyethylene glycol was added. To 60 parts by weight of this solution, 40 parts by weight of methanol was added to prepare an electrodeposition liquid.

This electrodeposition solution was placed in a stainless steel container, and the roughened metal electrode was dipped into the anode, and the stainless steel container was used as the cathode. Electrodeposition was carried out by continuously applying the electrodeposition voltage of 50 V for 30 minutes to carry out the electrodeposition. A thin film of polyamic acid was formed on the surface. Subsequently, this was heated and dehydrated at 250 ° C. for 30 minutes to be imidized, and a polyimide coating was formed on the surface of the roughened metal electrode to obtain a device.

This device was dipped in a 2 mol / l pyrrole / ethanol solution for 5 minutes and then dipped in a 0.5 mol / l ammonium persulfate aqueous solution for 5 minutes to form a polypyrrole film by chemical oxidative polymerization. Then, the device was immersed in an acetonitrile solution containing 1 mol / l of pyrrole and 1 mol / l of tetraethylammonium p-toluenesulfonate as a supporting electrolyte, and the polypyrrole film formed by chemical oxidative polymerization was used as an anode for electrolytic polymerization with an external electrode. Was carried out for 30 minutes at a current density of 1 mA / cm ² to form a polypyrrole film by electrolytic polymerization.

By dipping this element in colloidal carbon,
A silver paste was applied to form a conductive coating film, a counter electrode was taken out from a part of the conductive coating film, and an exterior was coated with an epoxy resin to complete a capacitor.

(Comparative Example) In Example, except that addition of polyethylene glycol to the electrodeposition liquid was omitted.
A capacitor was completed according to the example.

The characteristics of the capacitors obtained in the above examples and comparative examples are shown in (Table 1).

[0020]

[Table 1]

As is clear from this (Table 1), the capacitors obtained in this example were superior in characteristics of leakage current and withstand voltage to the capacitors obtained in the comparative examples.

[0022]

As described above, according to the method of manufacturing a capacitor of the present invention, a poor solvent for polyamic acid is added to a solution containing a polyamic acid salt, and an additive is further added to form an electrodeposition liquid, which is made into a porous conductive material. By electrodeposition on the body surface,
A smooth thin film of polyamic acid can be formed along the shape of the surface of the porous conductor. The polyimide coating obtained by heating and dehydration thereafter is smooth along the shape of the porous conductor surface, and therefore the thickness of the dielectric formed on the conductor surface is uniform.

Further, a conductive layer serving as a counter electrode is formed on the surface of the polyimide coating by sequentially laminating a polypyrrole film formed by chemical oxidative polymerization and a polypyrrole film formed by electrolytic polymerization. It is possible to realize a non-polarized capacitor having excellent high frequency characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Takemoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hideo Yamamoto Inventor Hideo Yamada 2470 Handa Shibukawa City Gunma Central Research Institute, Japan Carlit Co., Ltd.

Claims (3)

[Claims] 1. A poor solution of polyamic acid is added to a solution containing a polyamic acid salt to prepare an electrodeposition solution, and the surface of a porous conductor is subjected to electrodeposition to form a thin film of polyamic acid, and then the polyamic acid is prepared. In the capacitor formed by forming a polyimide film by heating and dehydrating the thin film of to imidize, and further forming a counter electrode conductor layer on the surface of the polyimide film, in the electrodeposition liquid, as a smoothing agent at the time of electrodeposition A method of manufacturing a capacitor, which comprises adding an additive comprising a compound that acts. 2. The conductive layer serving as a counter electrode is formed by sequentially stacking a conductive polymer film formed by chemical oxidative polymerization and a conductive polymer film formed by electrolytic polymerization. Capacitor manufacturing method. 3. The method of manufacturing a capacitor according to claim 2, wherein the conductive polymer film is polypyrrole.