JP3340476B2 - Aluminum material for electrolytic capacitor electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum material for an electrode of an electrolytic capacitor, and more particularly to an aluminum material suitable for an anode.

[0002]

2. Description of the Related Art Generally, an aluminum foil or an aluminum plate used as an aluminum material for an electrode of an electrolytic capacitor is subjected to etching for the purpose of increasing the capacitance by increasing the surface area.

[0003] As an aluminum material for an electrode of an electrolytic capacitor, especially for an anode, the purity is 99.9%.
Although the high-purity materials described above are used, the etching suitability of the material is strongly affected by the trace elements contained in the material. For this reason, as disclosed in JP-A-57-194516, Pb, In, and Bi are concentrated and concentrated only in the surface layer within 0.1 μm from the surface.
As described in Japanese Patent No. 718, an attempt has been made to improve the etching suitability by focusing on an extremely thin oxide film to improve the capacity.

[0004]

However, in the above-mentioned conventional proposals, it has been found that there is no effect of improving the etching suitability with respect to the aluminum material used recently, and there is a limit in increasing the capacity.

In other words, recently, due to demands for cost reduction, etc.,
There is an increasing tendency to use Al raw metal that contains trace impurities, but when Zn is particularly included as an impurity,
Etching pits were difficult to grow, the surface was easily melted, and sufficient surface effects by etching could not be obtained, and the capacitance could not be increased.

The present invention has been made in view of such technical background, and has been made in view of the above technical background, and is capable of providing an electrolytic capacitor electrode which is excellent in etching suitability and can obtain a high capacitance even when a trace amount of impurities, particularly Zn, is contained. The purpose is to provide aluminum materials for use.

[0007]

In order to achieve the above object, an aluminum material for an electrode of an electrolytic capacitor according to the present invention, as shown with reference to FIG.
In an aluminum material (1) for an electrolytic capacitor electrode having a purity of 99.9% or more containing 5 to 50 ppm of n,
One, two or more of b, In, and Sn are added to the surface layer (2) from the surface to a depth of 0.1 μm in a total of 100 to 500.
It is characterized by being present at 0 ppm and being contained in a total of 1 to 5 ppm in the inside (3) excluding the surface layer portion (2).

[0008] The aluminum material (1) may be an aluminum foil, an aluminum thin plate or the like, and the form thereof is not particularly limited.

The aluminum material (1) according to the present invention comprises:
Al purity of 99.9% or more (Fe + Si + Cu is 0.1
%), But as trace impurities, Zn5 to 50p
pm is acceptable. When Zn is less than 5 ppm, the etching pits can be sufficiently grown to the inside by the above-described conventional technique, and thus there is no application significance of the present invention. On the other hand, if it exceeds 50 ppm, the growth of the etching pit cannot be promoted by the present invention, and the effect of increasing the capacitance cannot be expected.

In the surface layer (2) from the surface of the aluminum material (1) to a depth d: 0.1 μm, Pb
(Lead), In (indium), and Sn (tin) serve as starting points of etching pits. Pb, In, and Sn should be evaluated as equivalents from each other in terms of such effects, and it is sufficient if at least one of them is present. However, if the total amount of one or more of Pb, In, and Sn in the surface layer (2) is less than 100 ppm, the number of etching start points is too small, so that a large number of etching pits cannot be formed. The effect of increasing the capacitance cannot be obtained. On the other hand, if the total amount exceeds 5000 ppm, the etching start point becomes too large, leading to the entire surface dissolution, and as a result, a large surface area cannot be obtained. Therefore, it is necessary that one or more of Pb, In, and Sn be present in the surface layer portion (2) in a total amount of 100 to 5000 ppm.
Preferably, 150 to 2000 ppm is present.

On the other hand, in the inside (3) of the aluminum material (1) except for the surface layer (2), Pb, In, Sn
Plays a role in promoting the growth of etching pits.
However, if the amount of one or more of Pb, In, and Sn in the inside (3) is less than 1 ppm, the etching pits may be formed inside by the action of Zn even if the etching start point of the surface layer portion exists appropriately. It does not grow to the point where the capacitance is poor. On the other hand, when the content exceeds 5 ppm, the inside (3) is easily melted, etching pits do not grow on the contrary, and the surface area ratio is reduced. Therefore, it is necessary to include one or more of Pb, In, and Sn in the interior (3) in a total of 1 to 5 ppm. The preferred content is 1.5 to 3.5 ppm.

A method for causing one or more of Pb, In, and Sn to be present at the above-mentioned concentration is not particularly limited, but the following method may be mentioned as an example.

That is, first, the concentration of the inside (3) of the aluminum material (1) may be adjusted by adjusting the contents of Pb, In, and Sn during melting and casting. The concentration of the surface layer (2) is adjusted by Al-Pb, Al-In, or Al-Pb.
What is necessary is just to carry out by sputtering a Sn alloy on the surface of an aluminum material. Desirably, heating is performed after sputtering. When the heating is performed, the sputtered layer diffuses into the aluminum material, and the concentration distribution of Pb, In, and Sn becomes continuous, so that a more preferable state is obtained. However, it is not limited to these methods.

The Pb, In, and Pb in the surface layer (2)
The measurement of the amount of Sn may be performed, for example, by dissolving the aluminum material with a Na0H solution, removing the smut adhered to the surface with an HNO ₃ solution, and analyzing the amount in the solution.

The aluminum material for an electrolytic capacitor according to the present invention may be used for any of an anode and a cathode. However, since the aluminum purity is 99.9% or more, it is generally used for an anode requiring high purity. It is preferred to use.

[0016]

One or more of Pb, In and Sn are added to the surface layer (2) of the aluminum material (1) in a total amount of 100 to 100%.
By the presence of 5000 ppm, an appropriate amount of the etching start point is present, and there is no occurrence of excessive dissolution of the surface or shortage of the etching start point during etching. Further, 1 of Pb, In, Sn in the inside (3)
When the content of the species or two or more species is 1 to 5 ppm, even if the content of Zn is 5 to 50 ppm,
The growth of the etching pits is promoted, a large number of etching pits are formed uniformly, and the surface area is increased.

[0017]

Next, an embodiment of the present invention will be described.

Fe: 30 ppm, Si: 40 ppm, C
u: 20 ppm, Ga: 15 ppm, B: 5 ppm, and an aluminum foil having a purity of 99.9% or more (thickness: 100 μm) containing Zn in an amount shown in Table 1 and having a surface of Al-Pb, Al One or more of -In and Al-Sn alloys were sputtered. Then, by changing the material to be sputtered and the deposition thickness, the concentration of the surface layer from the surface to a depth of 0.1 μm is adjusted as shown in Table 1.
Was adjusted as follows.

The content of one or more of Pb, In, and Sn in each material excluding the surface layer is as shown in Table 1.
It was as follows. The internal content was adjusted by adding Pb or the like during casting.

Next, each aluminum material was etched. The etching was performed by two-stage etching under the following conditions.

<First Stage> Etching solution: mixed solution of 3 wt% hydrochloric acid + 40 wt% sulfuric acid, liquid temperature: 70 ° C., current density: 0.2 A / cm ² , time: 10
0 sec <Second stage> Etching solution: mixed solution of 5 wt% hydrochloric acid + 0.1 wt% oxalic acid, liquid temperature: 85 ° C., current density: 0.05 A / cm ² , time: 10 minutes After the above etching, in a boric acid solution After the formation at 380 V, the capacitance was measured. The results are shown by relative comparison when the capacitance of Comparative Example No. 9 is set to 100%.

[0022]

[Table 1] As can be seen from the results in Table 1, it was confirmed that according to the present invention, the capacitance of an aluminum material containing 5 to 50 ppm of Zn could be increased.

[0023]

Since the present invention is dependent on the above, Zn
, The etching can proceed to the inside of the aluminum material while suppressing the surface dissolution, and a large number of etching pits can be effectively formed. As a result, while using a relatively inexpensive aluminum material with a large amount of Zn, it is possible to increase the surface area ratio and consequently to increase the capacitance.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of an aluminum material according to the present invention.

[Explanation of symbols]

 1: Aluminum material 2: Surface layer 3: Internal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadao Fujihira 6, 224 Kaiyama-cho, Sakai City, Osaka Prefecture Showa Aluminum Co., Ltd. (56) References JP-A-57-194516 (JP, A) JP-A-2 JP-A-8029 (JP, A) JP-A-4-62818 (JP, A) JP-A-58-42747 (JP, A) JP-A-4-120234 (JP, A) JP-A-5-315199 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/055

Claims (1)

(57) [Claims] 1. In an aluminum material (1) for electrolytic capacitor electrodes containing 5 to 50 ppm of Zn as an impurity and having a purity of 99.9% or more, one or more of Pb, In and Sn have a depth from the surface. A total of 100 to 5000 ppm is present in the surface layer (2) up to 0.1 μm, and a total of 1 to 5 in the inside (3) excluding the surface layer (2).
An aluminum material for an electrode of an electrolytic capacitor, characterized by being contained in ppm.