JP3293241B2 - Aluminum foil material for electrodes of electrolytic capacitors with excellent surface area expansion effect - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to an etching process,
The present invention relates to an aluminum foil material for an electrode of an electrolytic capacitor capable of forming a larger surface area.

[0002]

2. Description of the Related Art Conventionally, an aluminum foil material made of Al having a purity of 99.9% by weight or more is generally used as an electrode of an electrolytic capacitor, and a higher capacitance is obtained as the surface area of the electrode is larger. That is, since the surface area is proportional to the capacitance, for the purpose of obtaining a higher surface area during the etching process, for example, Japanese Patent Publication No. Sho 62-42
As described in JP-A-370 and JP-A-1-128419, one or two or more of Pb, Bi, In, Sn, and the like having a surface area increasing action are provided on the surface of the foil material. , 0.001-0.2% by weight (10-2
An aluminum foil material having a surface diffusion layer containing 2,000 ppm) is also proposed.

[0003]

On the other hand, in recent years, there has been a strong demand for downsizing and high performance of electrolytic capacitors, and accordingly, it has been desired to further increase the surface area of the electrodes. In an aluminum foil material, a sufficient surface area that satisfies the above-mentioned requirements cannot be formed by etching, and on the other hand, the content of the above-mentioned surface area increasing action component in the foil material surface portion is increased, so that Attempts have been made to further increase the surface area, but when these components are increased, the etching proceeds excessively and the entire surface becomes corrosive, and the desired surface area cannot be increased at present.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of conducting research to develop an aluminum foil material for an electrode of an electrolytic capacitor capable of further increasing the surface area by etching, the center of the foil material was substantially 99.9% by weight or more. Pb, Bi, In, and Sn are formed on the surface of the foil material while the strength and electrical characteristics required for the electrode are ensured.
And one or more of these (hereinafter, collectively referred to as a first diffusion component), Fe, Ni, Co, Cr, M
One or more of n and Zr (hereinafter, these are collectively referred to as a second diffusion component) have a content in the outermost surface of the foil material of the first diffusion component of 0.25, respectively.
To 3% by weight and 0.001 to 1% by weight of the second diffusion component, and the content of these components decreases from the surface to a predetermined depth within a range of 0.5 to 20 μm. When an aluminum foil material having a concentration gradient layer formed thereon is subjected to an etching treatment, a relatively high content of the first diffusion component and the second diffusion component having a relatively high content at the outermost surface of the foil material, According to the research results, the concentration gradient of the portion allows the deep and fine pits to be uniformly formed at a high density on the foil material surface, resulting in a remarkable increase in the surface area.

The present invention has been made based on the above research results, wherein the content of the first diffusing component in the outermost surface of the foil material is 0.25 to 3% by weight, and the content of the second diffusing component is the same. The amount is set to 0.001 to 1% by weight, and at the surface of the foil material, the first and second diffusion components in the outermost surface are located at a predetermined depth within a range of 0.5 to 20 μm from the surface. Aluminum foil material for electrodes of electrolytic capacitors that has a concentration gradient that decreases to a minimum and that the center of the foil material is substantially composed of Al having a purity of 99.9% by weight or more, and exhibits an excellent surface area expansion effect by etching. It is characterized by the following.

The aluminum foil material of the present invention contains the first diffusion component: 1.5 to 20 ppm, and the balance is A
1 and an unavoidable impurity, an Al alloy foil material is prepared, and a thin film of the second diffusion component is formed on the surface of the Al alloy foil material by an ion plating method or the like to a predetermined thickness. One of the diffusion components acetylacetone, stearic acid, naphthenate, etc.
An IPA solution or a mineral spirit solution generally containing about 0.1 to 0.5% by weight of a seed or two or more kinds is applied to a predetermined thickness, and the Al alloy foil material in this state is placed in a non-oxidizing atmosphere in a non-oxidizing atmosphere. It is desirable to manufacture by performing a heat treatment under the condition of heating and holding at a temperature of up to 600 ° C., and the first diffusion component uniformly contained in the Al alloy foil material is diffused to the surface of the foil material by the heat treatment. By moving, the central portion of the foil material becomes Al having a purity of 99.9% by weight or more, while a concentration gradient layer in which the content of the first diffusion component is higher at the outermost surface portion is formed on the surface portion of the foil material. Further, the second diffusion component existing on the surface of the Al alloy foil material also diffuses from the surface into the inside of the material, so that a concentration gradient layer in which the content of the second diffusion component becomes higher toward the outermost surface is formed. And the top of the foil material Content of the first and second diffuse component in section, and the depth of the concentration gradient layer is mainly Al
It can be controlled by appropriately adjusting the content of the first diffusion component in the alloy foil material, the heating temperature, and the heating time.

In the aluminum foil material of the present invention, the contents of the first and second diffusion components at the outermost surface of the foil material, the depth of the concentration gradient layer at the surface portion, and the Al purity at the center of the foil material are as described above. The reason for the limitation will be described below. That is, the content of these first and second diffusion components, the depth of the concentration gradient layer, and the Al purity are as described above.
It is controlled to a predetermined value by the content of the first diffusion component in the alloy foil material and the heat treatment conditions, but the content of the first diffusion component at the outermost surface of the foil material is less than 0.25% by weight. In this case, it is difficult to make the depth of the concentration gradient layer formed on the surface of the foil material 0.5 μm or more. In this case, the content of the second diffusion component is also less than 0.001% by weight. In this case, it is difficult to form fine and deep pits at a high density so that a remarkable surface area enlargement effect can be obtained by the etching process, while the content of the first and second diffusion components in the outermost surface of the foil material is 3% respectively. If it exceeds 1% by weight, the weight loss due to corrosion becomes too large, and the strength of the foil material decreases. Therefore, the contents of the first and second diffusion components are 0.25 to 3% by weight and 0. 001 to 1% by weight.

The concentration gradient layer is indispensable for forming deep and fine pits at high density in combination with the high content of the first and second diffusion components in the outermost surface portion. If the thickness is less than 5 μm, the corrosion becomes a general corrosion type, and the desired excellent surface area enlarging effect cannot be obtained. On the other hand, if the depth exceeds 20 μm, the strength of the foil material is reduced. 0.5 to 20 layer depth
μm. Furthermore, the purity of Al at the center of the foil material is 99.
If the content is less than 9% by weight, the strength and electrical characteristics required for the electrodes of the electrolytic capacitor cannot be maintained, so the purity is determined to be 99.9% by weight or more.

[0009]

EXAMPLES Next, the aluminum foil material of the present invention will be specifically described with reference to examples. Purity used as a raw material in a normal low-frequency induction melting furnace: purity 99.99% by weight pure A
l: 5 kg each was dissolved, and the first diffusion component in the amount shown in Table 1 was added thereto.
40mm x 180mm, length: 250mm ingot, with both sides of this ingot having a 0.5mm thick face cut,
Hot rolling is performed at a hot rolling start temperature of 520 ° C. to form a hot-rolled sheet having a thickness of 6 mm, which is subjected to cold rolling under ordinary conditions while adding intermediate annealing as necessary. Table 1
To form the Al alloy foil materials A to O having the thickness shown in FIG.
A second diffusion component thin film is formed on each surface of the Al alloy foil material of J in accordance with the combination shown in Table 2 by ion plating under normal conditions, and then the second diffusion component thin film is formed on the resulting surface. Al alloy foil material A with component thin film
J and the Al alloy foil materials KO having no second diffusion component thin film formed thereon are subjected to a heat treatment under the same conditions as shown in Table 2 to obtain the foil materials 1 to 10 of the present invention and the conventional foil material 1. To 5 were each manufactured.

Regarding the foil materials 1 to 10 of the present invention and the conventional foil materials 1 to 5 obtained as a result, the content and the center of the first diffusion component at the outermost surface, that is, at a depth of 0.05 μm from the surface. Was measured, and the foil materials 1 to 5 of the present invention were further measured.
For 10, the content of the second diffusion component in the outermost surface was measured, and the content of the first and second diffusion components decreased from the outermost surface, respectively. Part, and the depth position from the surface at which the second diffusion component is not substantially contained, that is, the average thickness of the surface concentration gradient layer, and the middle position of the surface concentration gradient layer. The contents of the first and second diffusion components were measured, and the measurement results are shown in Tables 3 and 4.
Tables 3 and 4 show that the sample was immersed in a mixed acid aqueous solution at 80 ° C. added at a ratio of 1 mol of hydrochloric acid and 3 mol of sulfuric acid to 1 liter of water, current density: 0.6 A / cm ² , time: The results obtained by performing the etching treatment under the condition of 40 seconds and measuring the capacitance at a formation voltage of 250 V are also shown.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

[0014]

[Table 4]

[0015]

From the results shown in Tables 1 to 4, all of the foil materials 1 to 10 of the present invention have a high content of the first diffusion component and a coexistence content of the second diffusion component in the outermost surface, and Due to the formed concentration gradient layers of the first and second diffusion components, a large capacitance is shown as compared with the conventional foil materials 1 to 5,
It is clear that the surface area expansion rate by the etching process is extremely high. As described above, since the aluminum foil material of the present invention shows a high surface area expansion rate by etching, when this is used as an electrode of an electrolytic capacitor,
This greatly contributes to downsizing and high performance.

Continuation of the front page (56) References JP-A-3-257913 (JP, A) JP-A-56-142623 (JP, A) JP-A-4-213810 (JP, A) JP-A-4-120234 (JP) JP-A-60-101917 (JP, A) JP-B-54-2376 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/00-9/28 C22C 21/00

Claims (1)

(57) [Claims] 1. Pb, Bi, I at the outermost surface of a foil material
n, and the content of the first diffusion component composed of one or more of Sn is 0.25 to 3% by weight.
e, Ni, Co, Cr, Mn, and Zr, when the content of the second diffusion component composed of one or more of them is 0.0
On the other hand, the content of the first and second diffusion components in the outermost surface portion is reduced to a predetermined depth position within a range of 0.5 to 20 μm from the surface at the surface portion of the foil material. Having a concentration gradient layer and a substantially central purity of the foil material:
An aluminum foil material for an electrode of an electrolytic capacitor having an excellent surface area increasing effect, comprising at least 99.9% by weight of Al.