JP2006274375A - Aluminum foil to be etched and aluminum electrode foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum foil to be etched which provides an electrode foil having both adequate capacitance and excellent formability. <P>SOLUTION: The aluminum foil to be etched has a particular region in one part of the aluminum foil. The particular region has an oxide film having twice the thickness of that in its perimeter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aluminum foil for etching used for manufacturing an electrolytic capacitor. Furthermore, the present invention relates to an aluminum foil for electrolytic capacitors that can achieve high capacitance and easy processability after etching and anodizing treatment.

  The aluminum foil can be increased in surface area by etching and forming etching pits. And the surface is anodized to form an oxide film, which functions as a dielectric. For this reason, various capacitors suitable for the application can be manufactured by etching the aluminum foil and forming an anodized film on the surface at various voltages according to the operating voltage.

  The etching pit formed by the etching process is processed into a shape corresponding to the anodic oxidation voltage.

  Specifically, it is necessary to form a thick oxide film for a medium-high voltage capacitor application. For this reason, in order to prevent the etching pits from being filled with such a thick oxide film, the aluminum pits for medium- and high-pressure anodes are mainly formed by direct-current etching so that the etching pit shape is a tunnel type and processed to a thickness corresponding to the voltage. Is done.

  On the other hand, for low-voltage capacitor applications, fine etching pits are required, and spongy etching pits are formed mainly by AC etching.

In order to improve the capacity of the capacitor, it is effective to increase the surface area per unit area, and various etching treatments and various aluminum foils for etching treatment are manufactured.
However, the electrode foil with an increased surface area per unit area and an anodized film formed as described above becomes very brittle. When the lead terminal is fixed to the electrode, bonding failure occurs, or when it is wound into a small shape. May break.

  As a method for solving these problems, a method has been proposed in which a pattern is formed on the surface of an aluminum foil and an unetched portion is generated to ensure strength.

  For example, in Patent Document 1, a multiline pattern having a line width of 0.1 to 5 mm and a line interval of 0.5 to 10 mm is formed on one side or both sides of an aluminum foil having a purity of 99.9% by mass or more with an alkali-removable resist ink. An aluminum foil for electrolytic capacitor electrodes, characterized by being applied and formed at an area ratio of 3 to 20%, is disclosed. However, this method requires a step of removing the resist ink portion after etching, and the operation becomes complicated accordingly.

Patent Document 2 discloses an aluminum foil for electrolytic capacitor electrodes, in which an oxide film having a withstand voltage of 2 to 20 V is formed in stripes on both surfaces of an aluminum foil having a purity of 99.9% by mass or more. However, the means listed as a method for obtaining the above foil is irradiation of laser light having an appropriate energy and wavelength on the surface of the aluminum foil. In this method, the obtained oxide film tends to be non-uniform, There is a problem that a sufficient unetched portion cannot be formed.
JP-A-60-31217 JP-A 62-198112

  In this way, any of the above aluminum foils for electrolytic capacitors can be used as electrode foils while maintaining their capacitance, and inadequate bonding when fixing lead terminals or defective damage when winding into small shapes. It is not sufficient in terms of reducing the amount of material, and there is room for further improvement including ease of processing.

  Accordingly, a main object of the present invention is to provide an aluminum foil for etching that provides an electrode foil having both a good electrostatic capacity and excellent workability.

  As a result of intensive studies to solve the problems of the prior art, the present inventor has found that the above object can be achieved by producing an aluminum foil under specific conditions, and has completed the present invention.

That is, the present invention relates to the following aluminum foil for etching and aluminum electrode foil for electrolytic capacitors.
1. An aluminum foil to be used for etching, having a specific region in a part of the aluminum foil, wherein the specific region has an oxide film thickness that is twice or more the thickness of the surrounding oxide film. Aluminum foil for etching.
2. Item 2. The aluminum foil for etching according to Item 1, wherein the oxide film thickness in the specific region is 50 mm or more.
3. Item 3. The aluminum foil for etching according to Item 1 or 2, wherein the total area of the specific region is 10% or less of the aluminum foil.
4). Item 4. The aluminum foil for etching according to any one of Items 1 to 3, wherein the specific region is formed by anodizing.
5. Item 5. The aluminum foil for etching according to Item 4, wherein the anodizing treatment is performed by energizing the flexible porous body impregnated with the electrolytic solution while contacting a part of the aluminum foil.
6). Item 2. The method for producing an etching aluminum foil according to Item 1, comprising a step of anodizing the contact portion by energizing a flexible porous body impregnated with an electrolytic solution while being in contact with a portion of the aluminum foil. .
7). In item 6, the flexible porous body impregnated with the electrolytic solution is brought into contact with a part of the aluminum foil by passing the aluminum foil while rotating a roller having a flexible porous body impregnated with the electrolytic solution on the surface. The method described.
8). The aluminum electrode foil for electrolytic capacitors obtained by etching the aluminum foil for etching according to any one of Items 1 to 6 and then anodizing the aluminum foil.
9. Item 9. The aluminum electrode foil for electrolytic capacitors according to Item 8, which is wound in a roll shape with the specific region as a core.
10. Item 10. The aluminum electrode foil for electrolytic capacitors according to Item 8 or 9, wherein a lead terminal is fixed to the specific region.

  According to the aluminum foil for etching of the present invention, since the oxide film has a specific region thicker than other portions, it has excellent workability while maintaining the same capacitance as the electrode foil obtained by the conventional method. An electrode foil can be provided.

  Moreover, in the manufacturing method of this invention, since a partial anodizing process can be performed by a comparatively simple method, the aluminum foil for etching of this invention can be produced efficiently.

The aluminum foil for etching of the present invention (hereinafter also referred to as “Al foil for etching”) is an aluminum foil subjected to etching, and has a specific region in a part of the aluminum foil, The oxide film thickness is more than twice the thickness of the surrounding oxide film.
(1) Specific area | region in Al foil for etching What is necessary is just to form a specific area | region in the desired position of aluminum foil. The specific region may be formed on at least one surface on the aluminum foil.

  The shape (planar shape) of the specific region is not limited, and may be any shape such as a polygon, a rectangle, a circle, an ellipse, and an indefinite shape. Further, the specific region can be formed in a stripe shape or a mesh shape. In this case, the strength of the etching Al foil as a whole can be increased.

  In general, the total area of the specific region is desirably 10% or less, particularly 5% or less of the aluminum foil. When the total area exceeds 10% of the aluminum foil, there is a possibility that the capacitance of the obtained etching foil is lowered. The lower limit value of the total area is not limited, but is usually 0.01% or more.

Further, the lower limit value of the area of each specific region is not particularly limited as long as it can be formed, but it may be generally 5 mm ² or more. Moreover, what is necessary is just to let an upper limit be 100 mm < ² > or less.

  Such an Al foil for etching has a high capacitance, a low density of etching pits in a specific region, and a slow growth rate. Therefore, the strength of the specific region is increased when anodization is performed after etching to form an electrode foil. Can be higher than that of surrounding tissue.

(2) Composition of Al foil for etching, etc. The composition of the Al foil for etching is not limited, but in particular, the aluminum purity is 99% by mass or more as measured by the method described in “JIS H 2111”. Those are preferred. As such an aluminum foil, at least one significant or unavoidable impurity element of Pb, Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, V, Ga, Ni and B is blended within a necessary range. Or regulated aluminum foil is also included.

  As a specific composition of the Al foil for etching, for example, an aluminum foil containing Si: 5 to 150 ppm, Fe: 5 to 150 ppm and Cu: 20 to 200 ppm can be preferably used.

The thickness of the etching Al foil is not limited, but is usually 20 to 200 μm, and preferably 50 to 150 μm.
(3) Preparation of Al foil for etching After preparing a molten aluminum having a predetermined composition and homogenizing an ingot obtained by casting the aluminum ingot at 450 to 660 ° C., hot rolling and cold rolling are performed. By applying, a rolled foil can be obtained. It is also possible to prepare a molten aluminum having a predetermined composition, directly cast and roll it, and then cold rolled to obtain a rolled foil. The thickness of the rolled foil in these cases is not limited, but is generally preferably 20 to 200 μm.

  The rolled foil may be appropriately annealed during the process, or the rolled foil may be annealed to form a soft foil. When annealing at 300 ° C. or higher, the annealing atmosphere is preferably a vacuum or an inert gas.

  Regardless of whether the Al foil for etching is a hard foil or a soft foil, the production method is not particularly limited as long as the predetermined specific region can be formed. For example, when a predetermined aluminum foil is manufactured from an aluminum raw material through a rolled foil, a process for forming the specific region may be performed in any process after the hot rolling process.

  As a method of forming the specific region, a predetermined oxide film may be applied by performing thermal, mechanical, or chemical treatment on a part of the aluminum foil in any step after the hot rolling step. . In particular, in the present invention, a method of forming a specific region by anodizing treatment is preferable.

  The method of the anodizing treatment is not particularly limited, and is not particularly limited as long as it can be processed with a desired dimensional accuracy such as a wet or dry etching treatment using a printing method or a corrosion treatment using a stamp method.

  More specifically, a method of performing anodization by using an Al foil for etching as an anode and bringing an electrolytic solution into contact with a specific region is preferable. The electrolytic solution is not particularly limited as long as an anodic oxide film can be formed, and phosphoric acid, sulfuric acid, boric acid, oxalic acid solution and the like are preferably used.

  In the present invention, a method of energizing a flexible porous body impregnated with an electrolytic solution (for example, a porous resin, a foam, a sponge, etc.) while being in contact with a part of the aluminum foil can be suitably employed. In this method, by designing the flexible porous body to have a desired shape and size, a specific region having a shape and size corresponding to it can be formed relatively easily and reliably. As a result, processing such as masking required in the prior art can be omitted.

  Furthermore, in the present invention, the flexible porous body impregnated with the electrolytic solution is brought into contact with a part of the aluminum foil by passing the aluminum foil while rotating the roller having the flexible porous body impregnated with the electrolytic solution on the surface. By doing so, the specific region can be formed continuously. As an energization method (voltage application method) at this time, for example, a conductive roller (shaft) may be connected to a power source (− pole), and a shaft for winding an aluminum foil may be connected to a power source (+ pole). The method including these steps is included in the method for producing an Al foil for etching according to the present invention.

  The average value of the oxide film thickness in the Al foil for etching is 100 mm or less, preferably 50 mm or less, and more preferably 20 mm or less. If the thickness of the oxide film exceeds 100 mm, the capacitance may be reduced. The lower limit is not particularly limited, but is usually 5 mm.

  The oxide film thickness (average value) in the specific region of the Al foil for etching is at least twice the average value of the thickness of the surrounding oxide film, preferably at least five times. If the average value of the oxide film thickness in the specific region of the Al foil for etching is smaller than twice the average value of the thickness of the surrounding oxide film, the specific region may not have sufficient strength.

  It is desirable to use the specific region as a portion where strength is required when an etching process and an anodizing process are performed to form an electrode foil. Examples of the portion that requires strength when the electrode foil is used include a portion that becomes a winding core portion, a lead terminal fixing portion, and the like.

  If the Al foil for etching of the present invention is subjected to known treatments such as degreasing and surface adjustment as necessary, then the etching treatment and anodizing treatment are carried out according to a conventional method, and then the aluminum electrode for electrolytic capacitors of the present invention A foil can be obtained. That is, the aluminum foil obtained by performing the above-described treatment on the etching Al foil of the present invention can be suitably used as an aluminum electrode foil for electrolytic capacitors.

  Examples and conventional examples are shown below to further clarify the features of the present invention. However, the scope of the present invention is not limited to these examples.

  Aluminum foil for electrolytic capacitors was produced according to the following examples and conventional examples. In addition, Comparative Example 1 was prepared for comparison with Examples.

1) In each example, an aluminum foil for etching is first prepared, and the obtained aluminum foil is etched under the following conditions, and then an anodizing treatment of 200 V is performed in an aqueous boric acid solution (65 g / L). To give an electrode foil.
<Etching treatment conditions>
Primary etching Etching solution: Mixed solution of hydrochloric acid and sulfuric acid (hydrochloric acid concentration: 1 mol / L, sulfuric acid concentration: 3 mol / L, 80 ° C.)
Electrolysis: DC 200 mA / cm ² × 2 minutes ・ Secondary etching Etching solution: Mixed solution of hydrochloric acid and oxalic acid (hydrochloric acid concentration: 2 mol / L, oxalic acid concentration: 0.01 mol / L, 80 ° C.)
Electrolysis: DC 50 mA / cm ² × 9 min 2) About the obtained aluminum foil, with a 13% by mass ammonium adipate aqueous solution (liquid temperature 25 ° C.), with the counter electrode as the same purity aluminum foil, a constant current of DC 0.4 mA in the measurement region The voltage (V) at the inflection point of the voltage-time curve was measured, and the oxide film thickness was determined according to the following formula.

<Oxide film thickness>
Oxide film thickness (Å) = 13 (Å / V) × bending point voltage (V) (formula)
3) About the obtained electrode foil, the electrostatic capacitance and intensity | strength were measured as follows.

<Capacitance>
It measured with the ammonium borate aqueous solution (8g / L) using the LCR meter. In addition, each measurement area was 30 mm × 30 mm, and an average value of 20 sheets or more was obtained so that the ratio of the specific area in the measurement area was substantially equal to the ratio of the specific area in the total area of the aluminum foil, and the conventional example was set to 100. It was shown as a relative value.

<Strength>
-Bending strength The specific region having an oxide film thickness of twice or more of the surrounding area was a bent portion, and was measured with an MIT type automatic bending tester in accordance with JIS P8115. The number of times until cutting was performed with a 90 ° bend as one time was measured under the conditions of a curvature radius of 1 mm, a load of 250 g, and a bending angle of 90 ° to the left and right. When there was no site having a texture different from the surrounding, an arbitrary site was measured.
・ Lead terminal fixation strength A specific area with an oxide film thickness more than twice the surrounding area becomes the fixed part, and the electrode foil of 25 mm x 50 mm is 150 μm thick, 2 mm wide, 7 mm long, and 20 mm long. Spot welding was performed at two locations using pure aluminum wires as lead terminals. Ten samples were prepared, the lead terminal fixing state was observed visually, and evaluated by the following AC. When there was no site having an oxide film thickness more than twice that of the surrounding area, an arbitrary site was used as a part to be tested.

A: All lead terminals are crimped and the electrode foil is not damaged B: All lead terminals are crimped, but the electrode foil is cracked C: The lead terminal or electrode foil has a drop-off portion (conventional example)
Molten aluminum (Si: 20 ppm, Fe: 10 ppm, Cu: 50 ppm, balance: Al and inevitable impurities) was semi-continuously cast to obtain an ingot having a thickness of 500 mm. The ingot was homogenized at 550 ° C., then hot rolled to 5 mm, and then cold rolled to 100 μm to obtain an etching aluminum foil. Moreover, the electrode foil was obtained by processing this aluminum foil by the said method. Table 1 shows the evaluation results of these aluminum foils and electrode foils.

Example 1
A porous resin impregnated with a 1% by volume boric acid aqueous solution was pressed against one side of the part that would be the desired position and shape when used as an electrode foil against the 100 μm cold rolled foil obtained in the conventional example. A voltage was applied for 10 seconds, followed by washing with hot water and drying to obtain an aluminum foil for etching. Moreover, the electrode foil was obtained by processing this aluminum foil by the said method. Table 1 shows the evaluation results of these aluminum foils and electrode foils.

  The schematic diagram of the electrode foil obtained in FIG. 1 is shown. From a rolled electrode foil having a width of 500 mm and a length of 300 m, a width of 20 mm and a length of 600 mm are cut out to form an electrode foil product unit. In the electrode foil product unit, the upper left part 5 mm × 5 mm corresponding to the lead wire attachment portion was defined as a specific region.

(Example 2)
Aluminum foil and electrode foil were obtained in the same manner as in Example 1 except that a voltage of DC 10 V was applied for 10 seconds. The evaluation results are shown in Table 1.

(Example 3)
An aluminum foil and an electrode foil were obtained in the same manner as in Example 1 except that a voltage of DC 20 V was applied for 10 seconds. The evaluation results are shown in Table 1.

(Comparative Example 1)
An aluminum foil and an electrode foil were obtained in the same manner as in Example 1 except that a voltage of DC 2 V was applied for 1 second. The evaluation results are shown in Table 1.

The schematic diagram (plan view) of the electrode foil obtained in Example 1 is shown.

Explanation of symbols

(1) Electrode foil (2) Part with oxide film thickness different from the surroundings (3) Part to be the final product unit

Claims (10)

An aluminum foil to be used for etching, having a specific region in a part of the aluminum foil, wherein the specific region has an oxide film thickness that is twice or more the thickness of the surrounding oxide film. Aluminum foil for etching. The aluminum foil for etching according to claim 1, wherein the oxide film thickness in the specific region is 50 mm or more. The aluminum foil for etching according to claim 1 or 2 whose total area of said specific field is 10% or less of aluminum foil. The aluminum foil for etching according to any one of claims 1 to 3, wherein the specific region is formed by anodizing. The aluminum foil for etching according to claim 4, wherein the anodizing treatment is performed by energizing the flexible porous body impregnated with the electrolytic solution while contacting a part of the aluminum foil. The method for producing an aluminum foil for etching according to claim 1, comprising a step of anodizing the contact portion by energizing the flexible porous body impregnated with the electrolytic solution while being in contact with a portion of the aluminum foil. . The flexible porous body impregnated with the electrolytic solution is brought into contact with a part of the aluminum foil by passing the aluminum foil while rotating a roller having a flexible porous body impregnated with the electrolytic solution on the surface thereof. The method described. An aluminum electrode foil for electrolytic capacitors obtained by etching the aluminum foil for etching according to any one of claims 1 to 6 and then anodizing it. The aluminum electrode foil for electrolytic capacitors according to claim 8, which is wound in a roll shape with the specific region as a core portion. The aluminum electrode foil for electrolytic capacitors according to claim 8 or 9, wherein a lead terminal is fixed to the specific region.

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