JPH07169657A - Aluminum alloy foil for electrolytic capacitor anode - Google Patents

Abstract

(57) [Summary] [Structure] Aluminum purity of 99.97% or more, S
i: 5-60 ppm, Fe: 5-60 ppm, Cu: 1
Including 0 to 60 ppm, Ti: 0.1 to 1 pp
m, V: 0.1 to 1 ppm and Zr: 0.1 to 1 pp
It contains one or more of m. [Effect] The amount of defects in an etch film formed by AC electrolytic etching mainly containing hydrochloric acid is controlled, and an aluminum alloy foil for electrolytic capacitor anode having a high capacitance per dissolved amount can be obtained. Suitable for low pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy foil for electrolytic capacitor anodes, and more particularly to an aluminum alloy foil for electrolytic capacitor anodes suitable as a low voltage anode foil used at low voltage.

[0002]

2. Description of the Related Art Since the capacitance of the anode foil of an aluminum electrolytic capacitor is proportional to the surface area, it is etched. The etching treatment is performed on the anode foil for medium and high pressure by constant current direct current electrolysis in a mixed acid such as hydrochloric acid and sulfuric acid to form tunnel-shaped etching holes. Further, the anode foil for low voltage is subjected to constant current AC electrolysis in a hydrochloric acid solution to form a fine rectangular parallelepiped etch pit cell in the shape of a sponge. Therefore, in order to prevent the etch pit cells produced by electrolysis from being chemically dissolved, high-purity aluminum with little chemical dissolution is used for the aluminum foil for the anode. Further, in order to form a solid solution of the impurity component in the matrix, the ingot is subjected to solution treatment, and steps such as taking steps for minimizing precipitation in hot rolling are taken into consideration. There is. (JP-A-58-22126
(Gazette No. 5)

On the other hand, there is also a method of adding or controlling a specific metal component in order to enhance the etching property of the aluminum foil for an anode, for example, a method of controlling Cu (Japanese Patent Publication No. 51-44306), Zr. Of adding (JP-A-57-6)
No. 6618), or a method for adjusting Ti, V, and Zr (Japanese Patent Laid-Open No. 4-62822). However, in the case of a low-voltage anode foil for AC electrolytic etching in a hydrochloric acid solution, the reduction in chemical dissolution was insufficient with the above-mentioned conventional method, so the cell wall of the fine etch pits formed by electrolysis is chemically When dissolved, the actual amount of dissolution became larger than the theoretical amount of dissolution, impeding the effect of increasing the surface area.

[0004]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned conventional problems in the aluminum foil for aluminum electrolytic capacitor anodes, the present invention provides an electrolyte solution containing a trace amount of components in a high-purity aluminum alloy and hydrochloric acid as a main component. It was made as a result of detailed investigations on the correlation with the dissolution of the etch pit wall caused by AC electrolytic etching at
The purpose is to control the amount of defects in the etch film formed by AC electrolytic etching by adjusting the specific metal element in high-purity aluminum, and to increase the capacitance per amount of aluminum alloy for electrolytic capacitor anodes. To provide foil.

[0005]

An aluminum alloy foil for an electrolytic capacitor anode according to the present invention for achieving the above object has an aluminum purity of 99.97% or more and S
i: 5-60 ppm, Fe: 5-60 ppm and C
u: 10 to 60 ppm, further Ti: 0.1 to 1
ppm, V: 0.1 to 1 ppm and Zr: 0.1 to 1
It is a structural feature that one or more of ppm is contained.

The aluminum alloy foil for an anode of the present invention has an aluminum purity of 99.97% or more and contains Si, Fe and Cu as essential components. Limiting the components of Si and Fe is necessary to control the chemical solubility in hydrochloric acid, which is the main component of the etching solution, and maintain the distribution of fine etch pits formed by electrolysis. The preferable content range of Si is 5 to 60 ppm, and if it exceeds 60 ppm, the chemical dissolution in hydrochloric acid becomes large and the walls of the etch pits are dissolved, resulting in a decrease in capacitance. The preferable content of Fe is 5 to 60 ppm, and when the content exceeds 60 ppm, the chemical solubility of the material in hydrochloric acid increases as in the case of Si. Si and Fe contents are 5 p each
When it is less than pm, the aluminum purity is 99.99% or more and the material cost is high, which is not preferable in practical use.
There are also problems such as softening during rolling.

The addition of Cu is necessary for improving the etching property of the material. The preferred content is 10 to 60
It is in the ppm range. If it is less than 10 ppm, the effect of improving the etching property is not sufficient, and if it exceeds 60 ppm, etching becomes excessive and excessive dissolution may occur.

The aluminum alloy foil of the present invention is further added with one or more of Ti, V and Zr. These components are related to the generation amount of the defective portion of the etch film at the time of AC electrolytic etching and have the effect of improving the etching property similarly to Cu, but are strictly controlled because they act effectively even in a very small amount. It is necessary. The preferred content of each component is in the range of 0.1 to 1 ppm, and when the content of each component exceeds 1 ppm, the number of defects in the etch film becomes excessive and the amount of dissolved etching increases. If the content of each component is less than 0.1 ppm, the amount of defects in the etch film is too small to allow the etching to proceed sufficiently.

[0009]

In the present invention, in an aluminum alloy foil for electrolytic capacitor anodes, which is subjected to AC electrolytic etching in an electrolytic solution containing hydrochloric acid as a main component, the Cu content and chemical dissolution of the etch pit wall that give excellent etching properties to the material. The contents of Si and Fe that influence the heat treatment are regulated, and the contents of Ti, V and Zr, which are involved in the generation of the defective portion of the etch film, are limited to control the etch pit formation. It is possible to give an optimum distribution form of the etch pits.

[0010]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Example 1 An aluminum alloy ingot having the composition shown in Table 1 was homogenized, and then hot-rolled and cold-rolled by an ordinary method to produce an aluminum alloy foil having a thickness of 0.1 mm. These aluminum alloy foils were subjected to 25 H at a current density of 0.2 A / cm ² in an electrolyte solution containing 12.5% by volume hydrochloric acid, 0.5% by volume nitric acid and 0.6% by volume phosphoric acid at 32 ° C.
The alternating current electrolysis of z was carried out for 450 s for etching. Then, in a 3% ammonium adipate solution at 60 ° C., 20
After chemical conversion treatment to V, the capacitance was measured with an LCR meter. The amount of dissolution was determined by measuring the weight change before and after the etching treatment. Table 1 shows the measurement results of the capacitance per dissolved amount.

[0011]

[Table 1]

Comparative Example 1 Ingots of aluminum alloy having the composition shown in Table 2 were used in Example 1
Under the same conditions as above, homogenization treatment, hot rolling and cold rolling were performed to produce an aluminum alloy foil having a thickness of 0.1 mm.
These aluminum alloy foils were subjected to etching treatment and chemical conversion treatment under the same conditions as in Example 1, the electrostatic capacity was measured by LCR, and the electrostatic capacity per dissolved amount was determined. The results are shown in Table 2. In Table 2, the items that do not satisfy the conditions of the present invention are underlined. Comparing the capacitances shown in Table 1 and Table 2, it can be seen that the capacitance per amount of aluminum alloy foil according to the present invention is clearly improved.

[0013]

[Table 2]

[0014]

As described above, according to the present invention, the amount of defects in the etch film formed by AC electrolytic etching is controlled, and an aluminum alloy foil for electrolytic capacitor anode having a high capacitance per dissolved amount can be obtained. . It is suitable as a low voltage anode foil.

Claims (1)

[Claims] 1. Aluminum purity is 99.97% or more, Si: 5 to 60 ppm, Fe: 5 to 60 ppm and Cu: 10 to 60 ppm, and Ti: 0.1.
~ 1 ppm, V: 0.1-1 ppm and Zr: 0.1
Aluminum alloy foil for electrolytic capacitor anodes, which contains one or more of 1 to 1 ppm.