JP2833686B2 - Aluminum alloy foil for electrolytic capacitor electrodes - 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 alloy foil from which an electrode foil (particularly an anode foil) for an electrolytic capacitor having a high capacitance can be obtained.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture an electrode foil for an electrolytic capacitor, an aluminum alloy foil is subjected to an etching treatment to form a large number of fine holes on the foil surface, thereby increasing the surface area of the foil surface. Have been. This increase in the surface area is to increase the capacitance of the electrode foil for the electrolytic capacitor. Therefore, in order to obtain an electrode foil for an electrolytic capacitor having a high capacitance, it is necessary to use an aluminum alloy foil having good etching characteristics.

Various proposals have been made as to which aluminum alloy foil has good etching characteristics, particularly from the viewpoint of alloy composition. For example,
No. 2736 discloses that 99.99% pure Al, Sb 20 to 50 ppm, Pb
Alternatively, an aluminum alloy foil containing 0.5 ppm or less of Bi and 2 ppm or less of Ca or Cr is disclosed. Also, JP-A-63-288
No. 008 discloses an aluminum alloy foil in which Pb is contained in the surface layer at a concentration of 10 to 100 ppm.

[0004]

However, according to the above-mentioned proposed technique, an electrode foil having a high capacitance may be obtained in some cases, but not in other cases. That is, there is a disadvantage that an electrode foil having a high capacitance cannot be stably obtained. For this reason, the present inventor has studied variously why an electrode foil having a high capacitance cannot be stably obtained. As a result, even if a small amount of additional element such as Pb or Sb is contained, the etching properties are different because the surface state of the aluminum alloy foil (especially, the configuration of the oxide film) is different, and the electrode foil having a high capacitance is required. It turned out that it could not be obtained stably.

Therefore, the present invention tends to change the surface state (the thickness of the oxide film and the hydration rate in the oxide film) of the aluminum alloy foil and the trace additive element, and if the trace additive element is increased, the oxide film becomes thicker and more watery. By increasing the summation rate and decreasing the amount of trace elements, the oxide film becomes thinner and has a specific correlation that reduces the hydration rate, so that an electrode foil with high capacitance can be obtained. is there.

[0006]

Means for Solving the Problems That is, the present invention provides Pb0.1
An aluminum alloy foil for an electrolytic capacitor electrode, which contains -5.0 ppm, Mg 0.1-5.0 ppm, and unavoidable impurities, and has an oxide film formed on its surface, and contains Pb content, Mg content, and oxide film thickness. Aluminum alloy foil for an electrode of an electrolytic capacitor, characterized by satisfying the conditions of the following formulas (1), (2), (3) and / or (4). It is about. In the present invention, ppm is based on weight ratio. Note 0.75X-1.75≤Y≤7.5X + 1.25 ... (1) 0.64t-14.1≤H≤0.95t-15.9 ... (2) 4.08X + 9.59≤H≤5.17X + 34.5 ... ( 3) 5.0Y + 5.0 ≦ H ≦ 5.17Y + 34.5 (4) (However, the meanings and ranges of X, Y, t and H are as follows. That is, X represents the Pb content in ppm. Where X is 0.1 ≦ X ≦ 5.0 Y is the Mg content in ppm and 0.1 ≦ Y ≦ 5.0 t is the thickness of the oxide film in Angstroms And 30 ≦ t
≦ 100. H is the percentage of hydration in the oxide film expressed in%, and 10 ≦ H ≦ 50. )

The aluminum alloy foil for an electrolytic capacitor electrode according to the present invention contains Pb and Mg as trace addition elements. The content of Pb is 0.1 to 5.0 ppm. If the content of Pb is less than 0.1 ppm, even if the surface state of the aluminum alloy foil becomes optimal, the etching characteristics are hardly improved, and an electrode foil with high capacitance cannot be obtained. Conversely, if the Pb content exceeds 5.0 ppm,
At the time of etching, the aluminum alloy foil is excessively melted, so that an electrode foil having a high capacitance cannot be obtained. Also, Mg changes the surface potential of the aluminum alloy foil,
This is for improving the etching characteristics. Therefore, if the content of Mg is less than 0.1 ppm, it is not preferable because the etching characteristics cannot be improved. Conversely, if the Mg content exceeds 5.0 ppm, the aluminum alloy foil is excessively dissolved at the time of etching, and an electrode foil with high capacitance cannot be obtained, which is not preferable.

In the present invention, the content of Pb and
The content of Mg needs to satisfy the following condition (1). That is, the Pb content expressed in ppm is expressed as X
When the Mg content in ppm is represented by Y,
It is necessary to satisfy the expression (1) of 0.75X-1.75 ≦ Y ≦ 7.5X + 1.25. In addition, as is clear from the above, X is 0.1 to 5.0 and Y is 0.1 to 5.0. Beyond this range, the content of Pb or Mg is high, or
When the content of Mg or Mg is small, the balance of the trace added elements is poor, and an electrode foil with high capacitance cannot be obtained.
Not preferred.

The aluminum alloy foil for an electrolytic capacitor electrode according to the present invention is required to have an oxide film having a thickness of 30 to 100 angstroms in the surface condition.
If the thickness of the oxide film is less than 30 angstroms, overdissolution is likely to occur during etching and an electrode foil having a high capacitance cannot be obtained, which is not preferable. Conversely, if the thickness of the oxide film exceeds 100 angstroms, the etching characteristics deteriorate, and an electrode foil having a high capacitance cannot be obtained. It is necessary that the hydration rate in the oxide film is 10 to 50%. If the hydration rate is less than 10%, overdissolution is likely to occur during etching, and an electrode foil having a high capacitance cannot be obtained. Conversely, if the hydration rate exceeds 50%, the etching characteristics deteriorate, and it becomes impossible to obtain a high capacitance electrode foil.
Not preferred.

In the present invention, among the surface conditions of the aluminum alloy foil, the thickness of the oxide film and the hydration rate in the oxide film must satisfy the following condition (2). . That is, assuming that the thickness of the oxide film is expressed in Angstroms as t and the hydration rate in the oxide film as% is H, 0.64t-14.1 ≦ H ≦ 0.95t−
It is necessary to satisfy the expression (2) of 15.9. In addition, as is clear from the above, t is 30-100, and H is 10-50. Beyond this range, the oxide film is too thick, or the hydration rate in the oxide film is too high, or the oxide film is too thin or the hydration rate in the oxide film is too low This is not preferable because the oxide film is not in a state of improving the etching characteristics and an electrode foil having a high capacitance cannot be obtained.

In the present invention, the thickness of the oxide film and the hydration rate in the oxide film are measured by the following methods. That is, the peak intensity of the [Al 2p] spectrum in the depth direction (thickness direction) of the aluminum alloy foil is measured using XPS, and the peak area due to the Al—O bond and the peak area due to the Al—Al bond are determined. The value obtained by multiplying the equalized ion sputtering time (min) by 50 Å was defined as the thickness of the oxide film (Å). The hydration rate in the oxide film was determined by XPS using [O
1s] Spectrum was measured, and the spectrum was separated into a peak due to Al-O bond and a peak due to Al-OH bond,
The ratio of the area of the peak due to the Al-OH bond to the total area of the [O 1s] peak was determined and multiplied by 100 to obtain the hydration rate (%).

Further, in the present invention, it is determined whether the Pb content and the hydration ratio in the oxide film satisfy the following condition (3):
Alternatively, it is necessary that the Mg content and the hydration ratio in the oxide film satisfy the following condition (4). That is, 4.08X + 9.59
Satisfies the formula (3) of ≦ H ≦ 5.17X + 34.5 or 5.0Y
+ 5.0 ≦ H ≦ 5.17Y + 34.5 It is necessary to satisfy Expression (4). Thus, it suffices to satisfy either one of Equations (3) and (4), but it goes without saying that it is more preferable to satisfy both. Therefore, if formula (4) is not satisfied and exceeds the range of formula (3), if the hydration rate is too high or too low, or if the Pb content is too high or too low, a small amount is added. Since the balance between the amount of the element and the hydration ratio in the oxide film is deteriorated, an electrode foil having a high capacitance cannot be obtained, which is not preferable. In addition, if the hydration rate is too high or too low, or the Mg content is too high or too low, which does not satisfy the formula (3) and exceeds the range of the formula (4), a small amount is added. Since the balance between the amount of the element and the hydration ratio in the oxide film is deteriorated, an electrode foil having a high capacitance cannot be obtained, which is not preferable.

The aluminum alloy foil for an electrode of an electrolytic capacitor according to the present invention is prepared by preparing an aluminum ingot to which a predetermined amount of Pb and Mg is added, subjecting the aluminum ingot to homogenization treatment and hot rolling, followed by cold rolling and intermediate rolling. It can be obtained by a method of performing annealing, finish rolling if desired, and performing final annealing. In the present invention, the thickness of the oxide film and the hydration ratio in the oxide film are adjusted by adjusting the atmosphere gas and the atmosphere temperature of the intermediate annealing, the degreasing method after finish rolling, and the atmosphere gas and the atmosphere temperature of the final annealing. This can be performed by selecting various conditions.

[0014]

【Example】

Examples 1 to 18 and Comparative Examples 1 to 14 A small amount of the weight ratio (ppm) shown in Tables 1 and 2 was added to aluminum containing 0.001% by weight of Si, 0.001% by weight of Fe, and 0.045% by weight of Cu. A high-purity aluminum ingot (Al99.99% by weight) with a thickness of 400 mm to which elements Pb and Mg were added was prepared. This aluminum ingot was subjected to homogenization at 530 ° C for 3 hours.
Hot rolling was completed at 0 ° C. Cool the hot-rolled plate,
Subjected repeatedly to cold rolling to a thin plate having a thickness of 0.13 mm, N ₂
Intermediate annealing was performed at 230 ° C. for 5 hours in a gas atmosphere.
Thereafter, finish rolling was performed at a rolling ratio of 20% to obtain a foil having a thickness of 0.1 mm. Next, after the oil adhering to the foil surface is degreased and removed with acetone, final annealing is performed at 530 ° C. for 10 hours.
The test was performed under the conditions of 10 ⁻³ Pa. As described above, an aluminum alloy foil for an electrolytic capacitor electrode was obtained.

The thickness (angstrom) of the oxide film of the aluminum alloy foil obtained as described above and the hydration rate (%) in the oxide film were measured by the above-mentioned method, and the results were shown in Tables 1 and 2. It was shown to. Further, the capacitance of this aluminum alloy foil was measured by the following method, and is shown in Tables 1 and 2. The method of measuring the capacitance is as follows. The obtained aluminum alloy foil for the electrolytic capacitor electrode is placed at 75 ° C. [5.1% HCl + 6.4%].
% AlCl ₃ 6H ₂ O + 6.8% H ₂ SO ₄ ] solution, and DC 0.16 A
The etching was performed at 8 cm / cm ² for 8 minutes. Thereafter, the etched foil was immersed in a 5% H ₃ BO ₃ aqueous solution at 85 ° C.
For 30 minutes. Then, two sheets of chemically converted foil (size 1 cm × 2 cm) were placed in a 4.5% H ₃ BO ₃ aqueous solution, 3 mm
And immersed in parallel with each other at an interval of, and the capacitance (nF / cm ² ) was measured using an LCR meter in a 120 Hz series equivalent circuit.

[0016]

[Table 1]

[Table 2]

As is clear from the above Examples and Comparative Examples, the relationship between the Pb content, the Mg content, the Pb content and the Mg content, and the relationship between the thickness of the oxide film and the hydration rate in the oxide film. , Pb
When the relationship between the content and the hydration rate in the oxide film and the relationship between the Mg content and the hydration rate in the oxide film are within a predetermined range, an electrode foil with high capacitance can be obtained. I understand. It can be seen that the capacitance outside this predetermined range is low.

[0018]

As described above, the aluminum alloy foil for an electrolytic capacitor electrode according to the present invention can be used as a trace additive element.
It contains Pb 0.1-5.0 ppm and Mg 0.1-5.0 ppm, and the Pb content, Mg content, oxide film thickness and hydration rate in the oxide film are expressed by the above formulas (1), (2) ), (3) and / or (4) are satisfied, so that a small amount of Pb and Mg for improving the etching characteristics is added in a well-balanced manner, and the state of the oxide film is Pb.
And an optimum state according to the amount of Mg added. Therefore, when etching is performed using the aluminum alloy foil for an electrolytic capacitor electrode, the etching characteristics are improved, and an effect is obtained that an electrode foil (particularly, an anode foil) having a high capacitance can be obtained. In addition, as long as the specific conditions described above are satisfied, an electrode foil having a high capacitance can be obtained stably, so that production efficiency can be improved and a large amount of inexpensive electrode foil can be supplied. It also has an effect.

────────────────────────────────────────────────── ─── Continued on the front page (72) Tomokatsu Hata Inventor 61-8 Sasaya, Yamadera-cho, Kusatsu-shi, Shiga Japan Foil Co., Ltd. Shiga Plant (58) Field surveyed (Int. Cl. ⁶ , DB name) C22C 21/00 H01G 9/055

Claims (3)

(57) [Claims] 1. An aluminum alloy foil for an electrolytic capacitor electrode comprising 0.1 to 5.0 ppm of Pb, 0.1 to 5.0 ppm of Mg, and an unavoidable impurity, and having an oxide film formed on the surface thereof. , Mg content, oxide film thickness and hydration rate in the oxide film satisfy the conditions of the following formulas (1) to (3). 0.75X-1.75≤Y≤7.5X + 1.25 ... (1) 0.64t-14.1≤H≤0.95t-15.9 ... (2) 4.08X + 9.59≤H≤5.17X + 34.5 ... ( 3) (However, the meanings and ranges of X, Y, t, and H are as follows: X is the Pb content in ppm, and 0.1 ≦ X ≦ 5.0. Y is The Mg content is expressed in ppm, and 0.1 ≦ Y ≦ 5.0, and t is the thickness of the oxide film expressed in angstrom, and 30 ≦ t
≦ 100. H is the percentage of hydration in the oxide film expressed in%, and 10 ≦ H ≦ 50. ) 2. An aluminum alloy foil for an electrode of an electrolytic capacitor comprising 0.1 to 5.0 ppm of Pb, 0.1 to 5.0 ppm of Mg, and an unavoidable impurity, and having an oxide film formed on its surface, wherein the Pb content is , Mg content, oxide film thickness and hydration rate in the oxide film, satisfying the following formulas (1), (2) and (4): Alloy foil. Note 0.75X-1.75≤Y≤7.5X + 1.25 ... (1) 0.64t-14.1≤H≤0.95t-15.9 ... (2) 5.0Y + 5.0≤H≤5.17Y + 34.5 ... ( 4) (However, the meanings and ranges of X, Y, t, and H are as follows: X is the Pb content in ppm, and 0.1 ≦ X ≦ 5.0. Y is The Mg content is expressed in ppm, and 0.1 ≦ Y ≦ 5.0, and t is the thickness of the oxide film expressed in angstrom, and 30 ≦ t
≦ 100. H is the percentage of hydration in the oxide film expressed in%, and 10 ≦ H ≦ 50. ) 3. An aluminum alloy foil for an electrolytic capacitor electrode comprising 0.1 to 5.0 ppm of Pb, 0.1 to 5.0 ppm of Mg, and an unavoidable impurity, and having an oxide film formed on the surface thereof, wherein the Pb content is , Mg content, oxide film thickness, and hydration ratio in the oxide film satisfy the conditions of the following formulas (1) to (4). 0.75X-1.75≤Y≤7.5X + 1.25 ... (1) 0.64t-14.1≤H≤0.95t-15.9 ... (2) 4.08X + 9.59≤H≤5.17X + 34.5 ... ( 3) 5.0Y + 5.0 ≦ H ≦ 5.17Y + 34.5 (4) (However, the meanings and ranges of X, Y, t and H are as follows. That is, X represents the Pb content in ppm. Where 0.1 ≦ X ≦ 5.0 Y is the Mg content in ppm and 0.1 ≦ Y ≦ 5.0 t is the thickness of the oxide film in Angstroms And 30 ≦ t
≦ 100. H is the percentage of hydration in the oxide film expressed in%, and 10 ≦ H ≦ 50. )