JPS6379311A - Electrode foil for electrolytic capacitor and manufacture of the same - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrode foil for electrolytic capacitors and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Conventional techniques have conventionally been used to increase the surface area of electrode foils for electrolytic capacitors by etching their surfaces as skillfully as possible, with the aim of making capacitors smaller and larger in capacity. For example, Japanese Patent Publication No. 57-17080 discloses a method in which electrode foil is anodized and then etched, and Japanese Patent Publication No. 60-38861 discloses a method for enlarging the surface of electrode foil using a multi-step etching method. Furthermore, a method of etching in tripolyphosphate is known from JP-A-55-11364. Furthermore, the JP-A-6
Publication No. 1-5187 and also JP-A-61-5188
Lord! [This is an electrolytic capacitor in which a resistant film that is resistant to electrolytic etching liquid and has a large number of micropores that form etching nuclei is integrally adhered to the surface of an aluminum foil.] When forming aluminum electrode materials and micropores, on the surface of aluminum foil,
It is disclosed that a durable coating having a large number of micropores can be formed by applying a coating material containing fine particles of metal or non-metal and then removing the fine particles.

Problems to be Solved by the Invention Among the conventional techniques, in the structure disclosed in the first three inventions, the surface of the electrode foil is always in uniform contact with the etching solution during etching. As a result, excessive etching 6 as shown in FIG. 2 cannot be substantially prevented, and the degree of surface roughening becomes poor. In addition, in the configurations according to the latter two inventions, when a film such as photoresist that is insoluble in ethostyrene and corrosion resistant is deposited on aluminum as a capacitor electrode material, a step of removing the resist film after etching is required. At that time, when immersed in the removal solution, resist components enter the inside of the aluminum electrode material that has already been finely etched, so it takes time and effort to remove it, and furthermore, it is difficult to remove it thoroughly. This is extremely difficult and may result in deterioration of capacitor characteristics.

In view of the above-mentioned problems, the present invention provides an electrode foil for electrolytic capacitors that can prevent excessive etching of the electrode foil and form etch pitches evenly and uniformly on the valve metal that is the capacitor material. A method of manufacturing the same is provided.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention forms micro bumps on the surface of a metal foil having a valve action, and uses a suspension containing micro resin particles. The valve metal is immersed in the liquid, dried, and heated to form minute bumps on the metal surface.

Effect of the present invention With the above configuration, by forming bumps on the surface of the valve metal, when the bumps are removed after oxidation treatment, the metal in the area where the bumps were present is exposed. Therefore, during etching for producing an electrolytic capacitor, etching occurs only on this metal part, resulting in good etching with a large surface area and no excessive etching.

EXAMPLES Below, the configuration of the present invention will be explained in an easy-to-understand manner based on FIG. As the metal having a valve action, metals well known for use in electrolytic capacitors such as aluminum, tantalum, and titanium are used. Bumps 2 are formed on these valve metal foils 1. The bump 2 is most suitable for being made of resin, specifically styrene, acrylic,
The valve metal 1 is immersed in a suspension containing particles of a thermoplastic resin such as vinyl chloride, cellulose acetate, polycarbonate, polyethylene, etc., and heated after drying to soften the particles. Attach to. Another method for forming resin bumps on metal foil is by electrodeposition coating or by introducing a heated valve metal foil into an atmosphere in which resin particles are suspended.

The particle size of the resin particles should be adjusted according to the etching bit diameter.
You can choose the desired size, but given that the formation of etch bits for electrolytic capacitors
It is not a good idea to use too large particles (0.1 to 10 microns, which is about the same particle size as the etch bit, is suitable.
The number of bits can be easily adjusted, for example, by controlling the number of particles in the suspension and the coating thickness.

Such resin particles having a relatively small particle size may be synthesized by emulsion or suspension polymerization, or may be obtained by mechanically crushing large particles into fine particles. The valve metal foil 1 on which the bumps 2 have been formed is then anodized or by using various oxidizing agents to oxidize the exposed metal surface with no bumps formed thereon to form an oxide film 3. form. Electrolytic oxidation can be carried out by a conventional anodic oxidation method using a relatively conductive solution such as an organic acid such as carboxylic acid, halonic acid or phosphoric acid, or a salt thereof. In the case of chemical oxidation, an oxidizing agent such as nitric acid, nitrate, hydrogen peroxide, etc. may be used, or simply immersion in a hot solution may be used.

The valve metal Pi 1 with the resin bumps 2 and the oxide film 3 attached to its surface is immersed in a solvent to remove the bumps 2.

The state when the bump 2 is removed is shown at 4 in FIG.

When the metal in the portion covered with the bumps 2 is exposed through the above procedure, a metal foil for an electrolytic capacitor electrode is obtained in which a valve metal oxide having selectively minute pores is formed on the surface. Thereafter, this is immersed in an etching solution to form a desired etching 5 on the metal part. Etching can be carried out using any known method, but a typical one is a method in which the metal foil is immersed in an aqueous solution containing chlorine ions and electrical current is applied.

Next, Examples 1 and 2 show the electrode foil of the present invention and the characteristics of a capacitor made using the electrode foil.

Example 1 An aluminum foil with a thickness of 100 microns and a purity of 99.99% was immersed in an aqueous solution containing 0.8% by weight of PMMA particles with an average particle size of 0.2 microns, and the aluminum foil was uniformly coated with a thickness of 5 microns. Apply to. PMMA bumps are evenly formed on the aluminum electrode foil by heating and drying at 60° C. for 15 minutes and heating at 140 to 170° C. for 5 minutes. Next, the exposed aluminum part is
A 7% oxide film is formed by chemical conversion at 55V in an aqueous solution of oxalic acid. This is thoroughly washed with water, dried, and then immersed in methyl ethyl ketone to dissolve and remove the PMMA bump. Next, it was immersed in an aqueous solution consisting of 5% hydrochloric acid and 0.03% oxalic acid, and was heated for 2 hours at a liquid temperature of 80°C and a current density of 3.5 mA/cut.
Etched for a minute. Thereafter, this aluminum foil was chemically converted in a 10% aqueous oxalic acid solution at 380 μm, and the capacitance of the obtained electrode foil was 0.88 μF/cot. For comparison, the capacitance of aluminum electrode foil without resin bumps is 0.73μF/c++t
Therefore, an increase in capacity of about 20% was achieved with the aluminum electrode foil of the present invention.

Example 2 An aqueous solution containing turbid polystyrene particles with an average particle size of 0.45 microns and a concentration of 5% was prepared, and an aluminum foil with a thickness of 104 microns and a purity of 99.99% was immersed in this solution. The suspension was then uniformly applied to an aluminum foil with a diameter of about 10 microns. After drying at 70°C for 10 minutes, heat treatment is performed at 120-150°C for 7 minutes to fuse the polystyrene particles onto the aluminum, thereby forming resin bumps evenly on the aluminum. This is chemically converted with a 5% phosphoric acid aqueous solution at 75V to form an oxide film on the exposed parts of the metal aluminum where bumps are not formed, washed with water, dried, and then treated with a toluene solution to remove polystyrene bumps. Remove.

Next, etching was carried out for 2 minutes in a 5% hydrochloric acid and 0.03% oxalic acid aqueous solution at a liquid temperature of 85° C. and a current density of 3.0 mA/cnl. Thereafter, the aluminum electrode foil was immersed in a 10% aqueous oxalic acid solution and chemically converted at 380 μm, and the capacitance was measured, and a value of 0.82 μF/cJ was obtained.

As a comparative example, the electrostatic capacitance of an electrode foil obtained by processing a polystine resin hump without forming it on aluminum and then chemically treating it was 0.96μ.
It was F/CII+. As is clear from the above results, a 17% increase in capacity was observed by using the resin bump formed electrode of the present invention.

Effects of the Invention As described above, the present invention forms a large number of microbumps on the surface of a valve metal, then oxidizes the surface,
An oxide film of the valve metal is formed on the exposed surface of the valve metal, and then the bumps are removed and an etching process is performed to prevent excessive etching and ensure uniform etching. It is possible to perform etching, and as a result, the surface roughness of the electrode foil becomes much larger than before, making it possible to greatly contribute to the miniaturization and increase in capacity of electrolytic capacitors.

Further, it is possible to control the bit diameter and the focusing force to some extent by selecting the particle size of the resin bump, which is convenient for stabilizing the quality. Furthermore, since the present invention does not use an insoluble, corrosion-resistant resist material in the etching solution, it is not necessary to remove it, and the capacitor characteristics will not be deteriorated due to this component remaining in the electrode material. Furthermore, the present invention can also be applied to the etching of fine grooves on general metals other than valve metals for electrolytic capacitors.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an electrode foil for an electrolytic capacitor according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional electrode foil for an electrolytic capacitor. ■・・・Valve metal foil, 2・・・Banbu,
3...Oxide film, 5...Etched bit, 6...Excessive etching. Agent's name: Patent attorney Toshio Nakao One idiot

Claims (2)

[Claims] (1) Electrode foil for electrolytic capacitors formed by forming a large number of micro bumps on the surface of a valve metal. (2) A method for manufacturing an electrode foil for an electrolytic capacitor, which comprises immersing a valve metal in a suspension containing fine resin particles, drying and heating the metal, and then forming bumps of the fine resin particles on the valve metal.