JPH05315198A - Method of manufacturing aluminum electrolytic capacitor - Google Patents

Abstract

PURPOSE:To reduce a leak current and prevent deterioration of, of course, the initial characteristics and the characteristic after tests under non-load at a high temperature and under a load at a high temperature by a method wherein a dense and thin dielectric oxide film is produced which does not have any detective parts such as voids, cracks, or the like and which has a high insulation. CONSTITUTION:An unformed anode foil and a cathode are wound through a spacer to form a capacitor element, which is impregnated with electrolytic liquid for driving which does not produce water by an esterifying reaction with a contained moisture 500ppm or less, and thereafter a voltage application treatment is performed to produce an amorphous dielectric oxide film on the unformed anode foil constituting a capacitor element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum electrolytic capacitor which can improve the means for producing an anodized film and contribute to the reduction of the number of steps.

[0002]

2. Description of the Related Art Generally, as a method for manufacturing an aluminum electrolytic capacitor, for example, a wide aluminum plain foil having a width of, for example, 500 mm is electrochemically etched using an aqueous solution of an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid. The surface of the roughened aluminum foil is subjected to electrolytic oxidation (hereinafter referred to as chemical conversion) in an aqueous solution of ammonium adipate or an aqueous solution of ammonium borate to form a dielectric oxide film, and then according to the rating and dimensions of the capacitor to be manufactured. The anode foil formed by cutting and the cathode foil formed by cutting in accordance with the rating and dimensions of the capacitor to be manufactured in the same way as the anode foil are wound with a spacer between them by expanding the surface area through the etching process as described above. After forming a capacitor element, impregnating this capacitor element with a driving electrolyte, and then storing it in an outer case, seal the outer case opening. Seal the body, and then cut the anode foil, which will become the exposed part of the aluminum foil, to create a dielectric oxide film on the cut and repair the cracked part of the dielectric oxide film caused during the winding process of the capacitor element. For the purpose of, the voltage treatment (hereinafter referred to as aging) is performed.

However, according to the method of manufacturing an aluminum electrolytic capacitor having such a structure, since the chemical conversion liquid is an aqueous solution, H ₂ O is taken into the formed film, which becomes a defective portion of the film. At the same time, the oxo bridge (-Al-O-Al-) of this film is divided at various places and Al-OH
The non-cross-linking oxygen portion like that increases, which is the main cause of further decrease in withstand voltage and increase in LC, and there is a limit to thinning the dielectric oxide film, which meets the recent demand for miniaturization of aluminum electrolytic capacitors. It was one of the hindrance factors for this.

Further, since the dielectric oxide film repaired by aging is incomplete, there is a problem that the high temperature no-load characteristic is poor.

Therefore, as disclosed in JP-A-53-138045, a capacitor element formed by winding an unformed anode foil and a cathode foil with electrolytic paper in between is formed by using ethylene glycol as a main solvent. There is a technique of forming a dielectric oxide film on an anode foil which constitutes the capacitor element, by performing chemical conversion with a chemical conversion liquid containing a driving non-aqueous electrolytic solution containing an organic carboxylic acid added thereto.

With this technique, however, a dielectric oxide film is formed on the cut portion of the anode foil which becomes the exposed portion of the aluminum foil metal and a crack portion of the dielectric oxide film is generated during the winding process of the capacitor element. It has an advantage that it is not necessary to perform an aging process for the purpose of repair.

However, since the chemical conversion liquid uses ethylene glycol as a main solvent and an organic carboxylic acid is added to this, water is produced by esterification even in a non-aqueous electrolytic solution at the beginning, and this water is generated during electrolysis. Water will be taken into the generated film, and the dielectric oxide film obtained by this technology is a crystalline oxide film containing voids, similar to the conventional technology that uses an aqueous solution as a chemical conversion liquid, so an effective countermeasure is In addition, the generation of water by esterification during electrolysis is more remarkable in high-temperature chemical conversion, and in that sense, the above-mentioned disclosed technique cannot be said to be a measure for completely solving the problems of the conventional technique.

It is also conceivable to use a completely non-aqueous electrolyte solution, that is, an electrolyte solution having a water content of 0%, but in this case, sufficient oxygen is not supplied when the dielectric oxide film is formed, and a high-quality dielectric material is used. No oxide film was formed.

[0009]

As described above, since the conventional technique is to form an anodized film in an aqueous solution or a chemical conversion liquid in which reaction product water generated by esterification produces, voids, cracks, etc. in the dielectric oxide film. Of high quality dielectric oxide film and the aluminum foil exposed part, the dielectric oxide film generated at the cut part by cutting the anode foil that becomes the exposed part of the aluminum foil and the dielectric oxide film caused during the winding process of the capacitor element The cracked part of the was not completely repaired.

The present invention has been proposed in order to solve the problems of the prior art as described above, and an object thereof is to have a dense, thin and high insulating property without a defect such as a void or a crack. It is an object of the present invention to provide a method of manufacturing an aluminum electrolytic capacitor, which can obtain good effects of leakage current, high temperature no-load and load life characteristics by forming a dielectric oxide film.

[0011]

According to the method for producing an aluminum electrolytic capacitor of the present invention, a capacitor element formed by winding an unformed anode foil and a cathode foil via a spacer has a water content of 500 ppm or less and a water content due to an esterification reaction. It is characterized in that it is impregnated with a driving electrolytic solution which does not occur, and is then subjected to a voltage treatment to form an amorphous dielectric oxide film on the unformed anode foil constituting the capacitor element.

[0012]

[Advantage] According to the above constitution, since the water content is controlled to be very small, aluminum hydroxide is not formed on the anode, or even if it is formed, it is immediately converted into an oxide and crystallized. Since it does not occur and becomes an amorphous dielectric oxide film, a dense and highly insulating dielectric oxide film without voids and crystal grain boundaries like a crystalline film can be obtained.

When the water content of the non-aqueous chemical conversion liquid exceeds 1%, the crystalline portion increases and grain boundaries occur in the crystal portion in the film, which becomes a weak point and deteriorates the characteristics, so that the water content is kept below this. The water content is preferably 500 ppm or less in order to obtain the desired amorphous dielectric oxide film. Further, as the non-aqueous chemical conversion liquid, since it is necessary to control the water content, water is generated by the reaction, for example, alcohol / carboxylic acid, or boric acid in which water molecules are coordinated with itself. Is inappropriate.

[0014]

EXAMPLES An example of the present invention will be specifically described below. That is, after undergoing an etching process that matches the conditions as the anode foil, an unformed anode foil obtained by cutting into a desired size and attaching an anode wire, and after undergoing an etching process, cutting into a desired size A capacitor is formed by interposing a spacer between a cathode foil formed by attaching a cathode wire and the cathode foil, and then the anode wire and the cathode wire are respectively connected to an anode terminal and a cathode terminal fixed to a sealing body to form the capacitor. The element is housed in a bottomed cylindrical aluminum case, the aluminum case is filled with a non-esterified driving electrolyte solution, and the case opening is sealed with the sealing body.
After that, a voltage treatment is performed to form an amorphous dielectric oxide film on the unformed anode foil forming the capacitor element.

The driving electrolyte is used as a solvent in N-methylformamide, N-ethylformamide, N, N-
Dimethylformamide, N-methylacetamide, N,
Amides such as N-dimethylacetamide, lactones such as γ-butyrolactone and γ-valerolactone, carbonates such as ethylene carbonate and propylene carbonate, nitriles such as acetonitrile and 3-methoxypropionitrile, trimethyl phosphate, triethyl phosphate. Phosphoric acid esters such as N-methyl-2-
Pyrrolidone, pyrrolidones such as 2-pyrrolidone, ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, and other organic solvents having no -OH group such as dimethylsulfoxide and tetrahydrofuran, as a solute, in combination with the above solvent Then, 1,2 of normal organic carboxylic acids that do not have water of crystallization
It is composed of a mixture of at least one of the above-mentioned solvent and solute using a tertiary and quaternary ammonium salt or the like. However, in terms of stability and safety, γ-butyrolactone is used as a solvent, and the organic carboxylic acid It is desirable to use a driving electrolytic solution containing a solute of a quaternary or quaternary ammonium salt.

The water content in the driving electrolyte is adjusted by adding a molecular sieve and stirring for 10 hours. However, if the water content exceeds 1%, the crystalline portion will increase, and the crystalline portion particles in the film will increase. A field is generated, which becomes a weak point and deteriorates the characteristics. Therefore, it is necessary to suppress the water content to less than this, and in order to obtain a desired amorphous dielectric oxide film, the water content is 500 pp.
It is important to make it m or less.

According to the method for manufacturing an aluminum electrolytic capacitor having the above-described structure, the amount of water in the chemical conversion solution in the chemical conversion step is controlled to be very small, and aluminum hydroxide is not formed on the anode. Since it is immediately added to the oxide, crystallization does not occur, and a dense, thin, highly insulating amorphous dielectric oxide film with no voids or grain boundaries is obtained, and aluminum electrolytic with good leakage current characteristics is obtained. Capacitor can be obtained.

Next, a characteristic comparison between the aluminum electrolytic capacitor according to the present invention and the conventional aluminum electrolytic capacitor will be described.

Initial characteristics and no-load test (105 ° C., 1000) in Example 1, Example 2, Example 3, Example 4, Conventional Example 1, Conventional Example 2, and Conventional Example 3 shown below.
Time) and load test (105 ° C.-10 V applied, 200
When the characteristics were compared after 0 hour), the results are shown in Table 1.

All samples are rated 10V-470.
There are 100 pieces of 0 μF.

Example 1, Example 2, Example 3, Example 4
Is the means described in the above embodiment, that is, the capacitor element formed by winding in the unformed anode foil state is housed in a case, and after the case is filled with a non-esterified driving electrolyte solution, the case opening A means for sealing the parts with a sealing body and then applying a voltage treatment is provided. The difference between the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment is that the drive for filling the case is performed. This is an electrolytic solution for use, and its specific example is shown below. [Example 1] Solvent-80 wt% γ-butyrolactone solute-20 wt% tetramethylammonium phthalate [Example 2] Solvent-75 wt% γ-butyrolactone solute-25 wt% tetraethylammonium maleate [Example 3] Solvent-60 wt% N, N-Dimethylformamide Solute-40 wt% Triethylamine Maleate [Example 4] Solvent-40 wt% γ-butyrolactone 40 wt% N, N-Dimethylformamide Solute-20 wt% Tetramethylammonium Phthalate Also, Conventional Example 1 and Conventional Example 2 is for driving a capacitor element that is formed by winding an anode foil and a cathode foil, which are cut into a predetermined size, after forming a dielectric oxide film by chemical conversion treatment on the surface of an aluminum foil that has been etched and roughened. After impregnating with electrolyte and housing in a case, aging treatment Which was taken means for performing, the conventional example 1, the conventional example 2, respectively differences,
A chemical conversion solution and a driving electrolytic solution, specific examples of which are shown below. [Conventional example 1] Composition liquid-5 wt% ammonia borate aqueous solution Driving electrolyte-Solvent-90 wt% ethylene glycol solute-10 wt% ammonium adipate [Conventional example 2] Composition liquid-3 wt% ammonia adipate aqueous solution Electrolyte-Solvent-80 wt% γ-butyrolactone Solute-20 wt% Tetramethylammonium phthalate Furthermore, Conventional Example 3 takes the same means as this Example, and the difference from this Example lies in the case. A specific example of the driving electrolytic solution to be filled is shown below. [Conventional Example 3] Solvent-90 wt% ethylene glycol Solute-10 wt% ammonium adipate

[0022]

[Table 1]

As is apparent from Table 1, the initial leakage current characteristics of Examples 1 to 4 are 1/2 or more smaller than those of Conventional Examples 1 to 3, and no In the load test, the leakage current does not change so much in each of the examples and each of the conventional examples, but the tan δ characteristic is largely changed in each of the conventional examples, whereas each of the examples is stable, and the tan δ characteristic is further in the load test. Although there is not much change in each of the examples and each of the conventional examples, the leakage current greatly changes in each of the conventional examples, whereas each of the examples only slightly increases, demonstrating the excellent effect of the present invention. This is because the conventional example is due to the fact that the generation and repair of the dielectric oxide film by the aging treatment are incomplete, and the influence of water generated by the esterification reaction of the driving electrolyte solution.

In the above embodiment, the method for forming the dielectric oxide film on the unformed anode foil forming the capacitor element is described with the capacitor element housed in the case, but it is housed in the case. Before, the capacitor element was impregnated with the above-mentioned water-containing drive electrolyte solution containing 500 ppm or less of moisture, which did not generate water due to the esterification reaction, was subjected to a predetermined voltage treatment, and was then housed in the case to seal the case opening. The same effect can be obtained by taking measures.

[0025]

According to the present invention, since no moisture is generated by the esterification reaction, a high-quality amorphous dielectric oxide film can be obtained, the leakage current is small, and the no-load and high-temperature load life characteristics are extremely stable. It is possible to obtain a method of manufacturing an aluminum electrolytic capacitor having an effect.

Claims (1)

[Claims] 1. A capacitor element formed by winding an unformed anode foil and a cathode foil with a spacer interposed between them and having a water content of 500 p.
characterized in that it is impregnated with a driving electrolyte solution which does not generate water due to an esterification reaction at pm or less and is then subjected to a voltage treatment to form an amorphous dielectric oxide film on an unformed anode foil constituting the capacitor element. Aluminum electrolytic capacitor manufacturing method.