JP3216433B2 - Manufacturing method of electrode foil for aluminum electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode foil for a low-pressure aluminum electrolytic capacitor.

[0002]

2. Description of the Related Art Generally, an aluminum electrolytic capacitor is constructed by winding an electrode foil for an aluminum electrolytic capacitor and insulating paper to form a capacitor element, impregnating the capacitor element with a driving electrolyte, and placing the capacitor element in a case. It is constituted by enclosing.

The electrode foil for an aluminum electrolytic capacitor has an etching step of etching the surface of the aluminum foil to form irregularities to increase its surface area, and forming an oxide film on the surface of the etching foil obtained by the etching step. In the above-mentioned etching step, the surface of the aluminum foil is electrochemically dissolved in an aqueous solution containing chlorides to roughen the surface, and then the aluminum foil is removed with nitric acid, sulfuric acid, or the like. Chlorinated. Thereafter, the etched aluminum foil is dried and wound up, and then transferred to the next chemical conversion step.

In order to obtain an electrode foil having a larger capacitance, the etching foil is boiled in an aqueous solution containing an amine as a post-etching treatment, as disclosed in Japanese Patent Application Laid-Open No. Hei 2-216810. There has been proposed a method of performing a treatment, or a method of performing a heat treatment in an atmosphere of an inert gas such as argon or nitrogen after etching an aluminum foil disclosed in Japanese Patent Application Laid-Open No. 53-26960.

[0005]

However, in the method of roughening the surface of the aluminum foil and boil-treating the dechlorinated etching foil in an aqueous solution containing an amine as in the above-described prior art, , Temperature 9
Since the temperature is as high as 0 ° C. or more, the thickness of the hydrated film on the surface of the aluminum foil becomes too large, and there is a problem that the leakage current after chemical formation increases.

[0006] The temperature for the boil treatment is set to 90 ° C or less.
When the treatment is full, the hydrated film becomes thin and the leakage current after chemical conversion is reduced.
Although it can be reduced somewhat, no significant effect can be expected
It was a terrible thing.

In addition, in the electrode foil for an aluminum electrolytic capacitor, which is subjected to a heat treatment in an inert gas atmosphere such as argon or nitrogen after etching the aluminum foil and then performing a chemical conversion treatment, the capacitance per unit area is increased. Is insufficient.

The present invention solves the above-mentioned conventional problems and provides a method of manufacturing an electrode foil for an aluminum electrolytic capacitor capable of increasing the capacitance per unit area and reducing the leakage current. It is intended to provide.

[0009]

Means for Solving the Problems The method for aluminum electrolytic capacitors electrode foil of the present invention in order to achieve the above object, the surface of the aluminum foil is roughened, 50 ° C. The etching foil was dechlorination Immersion in pure water of 0.01
~ 1 mg / cm ² of hydrated film is formed ,
After a drying treatment in an atmosphere of 400 ° C. for one minute , a heating treatment is performed in an inert gas atmosphere or vacuum, and then a chemical conversion treatment for forming an oxide film on the surface of the etching foil is performed.

[0010]

According to the above-mentioned manufacturing method, 50 parts of the hydrated film having an amount of the hydrated film in the range of 0.01 to 1 mg / cm ² are applied to the etched foil which has been roughened and dechlorinated. It is produced by immersion in pure water at a temperature of ℃ C. By this hydration treatment, dense and thin hydrated alumina ( Al (OH) ₃ and
Al ₂ O ₃ .3H ₂ O ) is formed, and the hydrated alumina ( Al (OH) ₃ and
And Al ₂ O ₃ .3H ₂ O ) in air at 400 ° C. for 1 minute.
Monohydrate of aluminum oxide by drying
In the _{(Al 2 O 3 · H 2} O), after this, because you have to heat treatment at or in a vacuum in an inert gas atmosphere, 1 hydrate of the aluminum oxide by the heat treatment
The material is easily crystallized by a dehydration reaction, and a crystalline thermal oxide film is formed. Then, by the subsequent chemical conversion treatment, a thin composite oxide film having a withstand voltage is formed on the surface of the etching foil,
This electrode foil can increase the capacitance per unit area and reduce the leakage current.

[0011]

EXAMPLES Hereinafter, Example 1 of the present invention and Comparative Examples 1 and 2 for comparison with Example 1 will be described.

(Example 1) (A) Etching step: purity 99.98%, thickness 100
5% hydrochloric acid aluminum raw foil [mu] m, were immersed in the etching solution temperature 30 ° C. of an aqueous solution of aluminum chloride 2%, a current density of 0.2 A / cm ² in sinusoidal alternating current electrical quantity 120 C / cm ² was etched. (B) Dechlorination treatment: The substrate was immersed in a 10% aqueous nitric acid solution (solution temperature 60 ° C.) for 1 minute to perform a dechlorination treatment. (C) Hydration treatment: immersion in pure water (liquid temperature 50 ° C.) for 3 minutes to perform hydration treatment to obtain a hydrated film amount of 0.2 mg / cm ² . (D) Drying treatment: Drying treatment was performed in the air at 400 ° C. for 1 minute. (E) Heat treatment: Heat treatment was performed at 400 ° C. in a vacuum for 1 hour.

Comparative Example 1 (A) Etching Step: Same as in Example 1. (B) Dechlorination treatment: Same as in Example 1. (C) Hydration treatment: A hydration treatment was carried out by immersion in an ethylamine aqueous solution (liquid temperature: 98 ° C.) having a concentration of 0.01 mol / l for 1 minute. (D) Drying treatment: Same as in Example 1.

Comparative Example 2 (A) Etching Step: Same as in Example 1. (B) Dechlorination treatment: Same as in Example 1. (C) Drying treatment: Same as in Example 1. (D) Heat treatment: Same as in Example 1.

The results of measuring the capacitance per unit area and the leakage current of the electrode foil obtained by forming each of the etching foils obtained in Example 1 and Comparative Examples 1 and 2 at 35 V are shown in Table 1. Shown in

[0016]

[Table 1]

As is clear from Table 1, the electrode foil obtained according to the first embodiment of the present invention is obtained by roughening the surface of an aluminum foil, dechlorinating an etched foil, hydrating and drying the foil. Comparative Example 1 and Comparative Example 1
2, the capacitance per unit area can be increased and the leakage current can be reduced as compared with the electrode foil obtained in Step 2.

In the first embodiment of the present invention, when the hydration treatment is performed, the amount of the hydrated film is set to 0.2 mg / cm ² , but the hydration treatment forms the surface of the etching foil. In order to obtain an appropriate hydrated film thickness of hydrated alumina (aluminum hydroxide), the amount of the hydrated film is preferably in the range of 0.01 to 1 mg / cm ² .

In the first embodiment of the present invention,
In the case where the heat treatment is performed, the case where the heat treatment is performed for 1 hour in a vacuum at a temperature of 400 ° C. has been described. However, the heat treatment may be performed in an inert gas atmosphere such as argon and nitrogen other than the vacuum. Heat treatment temperature is 250 ℃ ～ 5
The temperature is preferably in the range of 50 ° C., and the treatment time is 0.1 to
A range of 5 hours is preferred.

That is, the heat treatment temperature is 250 ° C. or less,
Alternatively, when the treatment time is 0.1 hour or less, a sufficient effect of the heat treatment cannot be obtained, and the temperature of the heat treatment is 55
If the temperature is 0 ° C or more, or the processing time is 5 hours or more,
Since the crystallization of the hydrated film formed by the hydration treatment is excessively promoted and the leakage current of the chemical conversion film generated later increases, the heat treatment temperature is preferably in the range of 250 to 550 ° C. The treatment time is preferably in the range of 0.1 to 5 hours.

[0021]

As described above, according to the method for producing an electrode foil for an aluminum electrolytic capacitor of the present invention, the surface of the aluminum foil is roughened, and the etching foil which has been subjected to the dechlorination treatment is used.
A hydrated film of 0.01 to 1 mg / cm ² is formed by immersion in pure water at ℃ C. By this hydration treatment, dense and thin hydrated alumina ( Al (OH) ₃ and Al ₂ O ₃ .3H ₂ O ) are formed,
Subsequently, this is dried for 1 minute in the air at 400 ° C.
The hydrated alumina was converted to aluminum oxide monohydrate (Al ₂
In the O ₃ · H ₂ O), since this then has to be heat treated in an inert gas atmosphere or in a vacuum, the 40
Formed on the surface of etching foil by drying at 0 ° C
By this heat treatment, monohydrate of aluminum oxide is
It is crystallized to form a crystalline thermal oxide film. Then, by the subsequent chemical conversion treatment, a thin composite oxide film having a withstand voltage is formed on the surface of the etching foil, so that this electrode foil can increase the capacitance per unit area. At the same time, the leakage current can be reduced.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/04 301 H01G 9/055

Claims (2)

(57) [Claims] 1. An aluminum foil having a roughened surface and a dechlorinated etching foil is immersed in pure water at 50 ° C.
To produce a hydrated film of 0.01 to 1 mg / cm ² Te, continued
After drying this in the air at 400 ° C. for 1 minute ,
After heat treatment in an inert gas atmosphere or vacuum,
A method of manufacturing an electrode foil for an aluminum electrolytic capacitor, wherein a chemical conversion treatment for forming an oxide film on the surface of the etching foil is performed. 2. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the temperature of the heat treatment is in the range of 250 to 550 ° C., and the treatment time is in the range of 0.1 to 5 hours.