JP3337506B2 - Method for producing 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 a method for producing an aluminum material for an electrode of an electrolytic capacitor.

[0002]

2. Description of the Related Art An aluminum foil generally used as an electrode material for an aluminum electrolytic capacitor has an effective area which is increased to increase a capacitance per unit area.
Generally, an electrochemical or chemical etching process is performed. However, a sufficient capacitance could not be obtained simply by etching the foil.

Accordingly, the present applicant has proposed an aluminum material which is capable of forming a large number of etching pits with excellent etching suitability and thereby reliably and stably providing an electrolytic capacitor electrode material having a large surface area and a large capacitance. As the method, a method disclosed in JP-A-3-122260 was provided. This method comprises the steps of removing an aluminum foil surface layer, forming an oxide film having a thickness of 5 to 50 angstroms on the surface after the removal, and then applying a high temperature within a range not exceeding 70 angstroms in total thickness of the oxide film. The heating step is performed. According to this method, a non-uniform surface layer is removed by removing a surface layer of a foil, and an oxide film having a large number of etching nuclei consisting of film defects is formed in a subsequent oxide film forming step, and thus, the etching suitability is improved to improve the etching suitability. The purpose is to increase the capacitance.

[0004]

However, in the above-mentioned method, in the high-temperature heating step, the heating at the atmosphere, temperature, time, etc. is performed so that the thickness of the oxide film formed in the previous step does not exceed 70 angstroms. Conditions must be strictly controlled, which has been a problem for stable production of high quality products. This is because the thickness of the oxide film may be thicker or varied than expected due to slight differences in heating conditions, and if the thickness of the oxide film formed by the high-temperature heat treatment is too large,
This is because if the etching nuclei formed in the previous step are erased or the thickness becomes non-uniform, the etching suitability also varies. In particular, when an aluminum foil is subjected to an oxide film forming treatment in a coil state, there is a problem that a uniform oxide film cannot be obtained in the width direction and the length direction of the coil.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an oxide film having a uniform thickness in both the width and length directions of the aluminum foil and having an etching nucleus uniformly on the surface of the aluminum foil. Accordingly, it is an object of the present invention to provide a method for manufacturing an aluminum material for an electrolytic capacitor which is excellent in etching performance and can reliably obtain high capacitance.

[0006]

Means for Solving the Problems A method for producing an aluminum material for an electrolytic capacitor electrode according to the first invention of the present application is as follows.
In order to achieve the object, a heating step of heating the aluminum foil at a high temperature, a surface removing step of removing a surface layer of the aluminum foil that has been heat-treated by the heating step, and a surface layer removed by the surface removing step And an oxide film forming step of forming an oxide film on a new surface by continuously heating the aluminum foil in the longitudinal direction of the atmosphere.

Further, the method for producing an aluminum material for an electrolytic capacitor electrode according to the second invention of the present application is 10 ppm.
For the following aluminum foil containing Fe, a two-stage heating method is adopted in which the aluminum foil is heated at a low temperature and then further heated at a high temperature in the heating step.

It is desirable that the aluminum foil used in these inventions has a high purity of 99.9% or more.
The present invention is not limited to this, and any material having a purity within the range used for the electrolytic capacitor may be used.

The high-temperature heating commonly performed in the first heating step of these inventions is mainly intended to improve the etching characteristics by adjusting the orientation of the crystal structure of the aluminum foil to the (100) orientation. . The atmosphere for this high-temperature heating is not particularly limited, but in order to make the subsequent surface layer removal treatment as easy as possible, it is desirable to heat in an atmosphere from which moisture and oxygen have been removed as much as possible. Specifically, in an inert gas such as Ar gas or 1
It is preferable to heat in a vacuum of about 0 ⁻³ Torr or less.
The heating conditions vary depending on the composition of the aluminum foil, but the heating rate is 50 ° C./min or less, and the holding temperature is 460 to 460 ° C.
550 ° C., the holding time is preferably 10 minutes to 24 hours. The heating rate is usually set at a moderate rate of about 50 to 100 ° C./hour. In addition, Fe in the aluminum foil
When the content is 10 ppm or less, it is preferable to apply the method of the second invention in which heating is performed at a low temperature to remove the strain prior to the high-temperature heating, since distortion is likely to occur during foil rolling. The conditions for the low-temperature heat treatment are not particularly limited, but the heat treatment is preferably performed at 180 to 250 ° C. for about 1 to 10 hours.

[0010] In these inventions, the surface layer removing step performed after the heating step is performed for the purpose of removing a heterogeneous layer on the surface of the aluminum foil. That is, on the aluminum foil surface after the foil rolling, there is an oily component, a non-uniform oxide film formed by the rolling, or a contaminated layer such as a rolled altered layer or a roll coating during the rolling near the aluminum foil surface. They are present non-uniformly, and these cause non-uniformity of the oxide film. Therefore, the heterogeneous layer is removed in order to promote the formation of a uniform oxide film. However, it is not always necessary to remove the surface of the aluminum foil to a predetermined depth. The degreasing level, in other words, removing the oil to a level where the contact angle of pure water is about 30 ° or less (pure spray OK level). It may be. Of course, it is desirable to completely remove the non-uniform layer, but in this case, the removal thickness is preferably set to 5 angstrom or more, particularly preferably 50 angstrom or more. There is no upper limit, but 1
Since the effect of removing the surface layer saturates at about 000 angstroms, removal beyond that is useless.

The specific means of the surface layer removing treatment is not particularly limited. When removing over a predetermined depth,
A wet method such as alkali etching and acid etching may be used, or an excimer laser (KrF, ArF, XeC
l) etc., dry methods such as laser processing, electron beam processing, ion beam processing, reactive gas etching, plasma etching, etc. may be used. This is preferable because the time can be shortened. When the removal treatment of the surface layer is performed at a degreasing level, for example, an Nd: YAG laser, C
O ₂ laser, excimer laser (KrF, ArF, X
These laser beams may be irradiated using eCl) or the like.

In these inventions, the oxide film forming step after the surface layer removing step is performed continuously in an oxidizing atmosphere in order to form an oxide film having an etching nucleus uniformly on a new surface of the aluminum foil. Atmosphere heating is performed, that is, heating is performed by continuously contacting the atmosphere along the length direction while unwinding the coiled aluminum foil. The thickness of the oxide film formed in this step is 5 to 5 in order to exhibit optimum etching suitability.
The thickness is preferably 0 Å, more preferably 15 to 50 Å, and particularly preferably 30 to 50 Å. Heating conditions for this purpose are a dew point of + 60 ° C. as a guide and a temperature rising rate of 100 to 1000.
It is preferable that the temperature is rapidly raised to about 80 to 550 ° C. at about ° C./min, and that the temperature is further maintained for 10 seconds to 5 minutes.

The aluminum material produced as described above is
Then, after electrochemical or chemical etching treatment, it is used as an electrode material for an electrolytic capacitor.

For the purpose of further improving the etching suitability, before the high-temperature heating step in these inventions,
As in the conventional case, the surface layer removing treatment and the oxide film forming treatment may be arbitrarily performed.

[0015]

In the first and second aspects of the present invention, the removal of the surface layer of the aluminum foil and the formation of the oxide film are performed after a heating step including high-temperature heating, so that the oxide film once formed may be exposed to a high temperature again. Absent. Therefore, in an oxide film having a uniform etching nucleus formed on a new surface of the aluminum foil, the cause of deterioration in etching suitability such as an increase in thickness and elimination of the etching nucleus has been removed, and the aluminum for the manufactured electrolytic capacitor electrode has been removed. The material exhibits excellent etching suitability. In addition, since such an oxide film forming process is performed by continuously heating the atmosphere while unwinding the coil-shaped aluminum foil, the thickness of the oxide film is uniform in both the length and width directions of the coil. Become.

Further, when the aluminum foil contains 10 ppm or less of Fe, by heating at a low temperature prior to the high temperature heating in the heating step, the distortion generated at the time of foil rolling is eliminated, and the crystal orientation is controlled by the high temperature heating. And the etching characteristics are improved.

[0017]

Next, specific examples of the method for producing an aluminum material for an electrode of an electrolytic capacitor according to the present invention will be described.

In the following Examples 1 and 2 and Comparative Examples 1 and 2, a 100 μm thick aluminum foil having an Al purity of 99.99% and an Fe content of 30 ppm was used as a test material.
Further, in Example 3, an Al purity of 99.9 was used as a test material.
An aluminum foil having a thickness of 100 μm and a 9% Fe content of 8 ppm was used.

For Examples 1-3 and Comparative Examples 1-2,
The test material was subjected to a heating step, a surface removing step, and an oxide film forming step under the processing conditions shown in Table 1. In Example 3, the heating process was a two-stage heating in which high-temperature heating was performed after low-temperature heating. In Comparative Example 2, a high-temperature annealing step was performed after the oxide film forming step without performing the heating step.

The thickness of the oxide film at six locations was measured by the Hunter Hall method over the entire width and length directions of each test material subjected to the above-described series of treatments.
Table 2 shows the average thickness and variation of the oxide film of each test material.
Was as shown in FIG.

[0021]

[Table 1]

[Table 2] From the results in Table 2, it can be seen that the oxide film having a desired thickness and a uniform thickness in both the width and length directions of the aluminum foil is obtained by performing the surface removal treatment and the oxide film formation treatment by continuous treatment after heating at a high temperature. Was formed. Also, it is naturally expected that the formation of such a uniform oxide film stably provides a high capacitance.

[0022]

As described above, according to the present invention,
By performing the surface removal treatment and the oxide film formation treatment continuously in the length direction of the aluminum foil after heating at a high temperature, there is no danger that the etching nuclei once formed on the surface of the aluminum foil are erased by the high temperature treatment. It is possible to manufacture an aluminum material for an electrolytic capacitor electrode having an oxide film in a substantially uniform state as a whole without an increase or variation in thickness. Therefore,
An aluminum material for an electrolytic capacitor electrode having excellent etching performance, forming a large number of etching pits, improving the area coverage, and having a large capacitance can be provided reliably and stably.

Further, when the Fe content in the aluminum foil is 1
In the case of 0 ppm or less, by adopting a two-stage heating method in which heating is performed at a low temperature prior to the high-temperature heating in the heating step, distortion generated at the time of foil rolling is eliminated and crystal orientation control by high-temperature heating is facilitated. And the same etching characteristics as an aluminum foil having an Fe content exceeding 10 ppm can be obtained.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadao Fujihira 6,224, Kaiyamacho, Sakai-shi, Osaka Inside Showa Aluminum Co., Ltd. (72) Inventor Eizo Isoyama 6,224, Kaiyamacho, Sakai-shi, Osaka Showa (56) References JP-A-4-127412 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/04 H01G 9/055 C22F 1/04

Claims (2)

(57) [Claims] 1. A heating step of heating an aluminum foil at a high temperature, a surface removing step of removing a surface layer of the aluminum foil that has been heat-treated by the heating step, and a step of removing the aluminum foil from which the surface layer has been removed by the surface removing step. A process of forming an oxide film on a new surface by continuously heating the atmosphere in the length direction of the atmosphere, thereby performing an oxide film forming process. 2. A heating step of heating an aluminum foil containing 10 ppm or less of Fe at a low temperature and then further to a high temperature; a surface removing step of removing a surface layer of the aluminum foil heated by the heating step; An aluminum foil from which the surface layer has been removed by the removing step, and continuously heating the aluminum foil in the longitudinal direction of the aluminum foil to form an oxide film on a new surface thereof. A method for producing an aluminum material for an electrode.