JPH07150279A - Aluminum alloy foil for electrolytic capacitor electrode - Google Patents

Abstract

PURPOSE:To stably obtain an electrode foil with high electrostatic capacity by specifying Pb content, Mg content, oxide film thickness, and hydration ratio in oxide film, respectively, in an Al alloy foil for electrolytic capacitor, containing specific amounts of Pb and Mg and having oxide film on the surface. CONSTITUTION:In an Al alloy foil for electrolytic capacitor electrode, containing 0.1-5.0ppm Pb, 0.1-5.0ppm Mg, and inevitable impurities and having oxide film on the surface, Pb content, Mg content, oxide film thickness, and hydration ratio in oxide film are regulated so that they satisfy the conditions in relations 0.75X-1.75<=Y<=7.5X+1.25, 0 64t-14.1<=H<=0.95t-15.9, and 4.08X+9.59<=H<=5.17X+34.5 In the relations X means Pb content (ppm) and is 0.1-5.0, Y means Mg content (ppm) and is 0.1-5.0, (t) means the thickness (Angstrom ) of oxide film and is 30-100, and H means hydration ratio (%) in oxide film and is 10-50.

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 capable of obtaining an electrode foil for electrolytic capacitors (in particular, anode foil) having a high electrostatic capacity.

[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 to increase the surface area of the foil surface. Has been. This increase in surface area is to increase the electrostatic capacitance of the electrode foil for electrolytic capacitors. 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 regarding what kind of aluminum alloy foil has good etching characteristics, especially in terms of alloy composition. For example, Japanese Patent Publication Sho 59-1
No. 2736 discloses that Al having a purity of 99.99%, 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. In addition, JP-A-63-288
Japanese Unexamined Patent Publication No. 008 discloses an aluminum alloy foil containing Pb at a concentration of 10 to 100 ppm in the surface layer portion.

[0004]

However, according to the above-mentioned proposed technique, although an electrode foil having a high capacitance may be obtained in some cases, it has not been obtained. That is, there is a drawback that a stable electrode foil having a high capacitance cannot be obtained. Therefore, the present inventor has variously studied why an electrode foil having high capacitance cannot be stably obtained. As a result, even if a trace additive element such as Pb or Sb is included, the surface condition of the aluminum alloy foil (particularly the composition of the oxide film) is different, so the etching characteristics are also different, and an electrode foil with high capacitance can be obtained. It turned out that it was not stable.

Therefore, according to the present invention, the surface state of the aluminum alloy foil (thickness of oxide film and hydration ratio in oxide film) and trace additive elements are used as a tendency. It is intended to obtain an electrode foil with a high capacitance by increasing the sum ratio and making the oxide film thin and reducing the hydration ratio by decreasing the trace addition element. is there.

[0006]

[Means for Solving the Problems] That is, the present invention provides Pb0.1
~ 5.0ppm, Mg 0.1 ~ 5.0ppm, and unavoidable impurities, aluminum alloy foil for electrolytic capacitor electrodes, which has an oxide film formed on the surface, Pb content, Mg content, oxide film thickness And the hydration rate in the oxide film satisfy the conditions of the following formulas (1), (2), (3) and / or (4), and are aluminum alloy foils for electrolytic capacitor electrodes. 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 is Pb content in ppm. And 0.1 ≦ X ≦ 5.0, Y represents the Mg content in ppm, and 0.1 ≦ Y ≦ 5.0, and t represents the thickness of the oxide film in Angstrom. And 30 ≦ t
≦ 100. H represents the hydration rate in the oxide film in%, and 10 ≦ H ≦ 50. )

The aluminum alloy foil for electrolytic capacitor electrodes according to the present invention contains Pb and Mg as trace additive elements. The Pb content is 0.1 to 5.0 ppm. If the Pb content is less than 0.1 ppm, the etching characteristics are difficult to improve even if the surface condition of the aluminum alloy foil is optimized, and an electrode foil with high capacitance cannot be obtained, which is not preferable. On the contrary, if the Pb content exceeds 5.0 ppm,
At the time of etching, the aluminum alloy foil is excessively melted and an electrode foil having a high capacitance cannot be obtained, which is not preferable. Also, Mg changes the surface potential of the aluminum alloy foil,
It improves the etching characteristics. Therefore, if the content of Mg is less than 0.1 ppm, the etching characteristics cannot be improved, which is not preferable. On the other hand, if the content of Mg exceeds 5.0 ppm, the aluminum alloy foil is excessively dissolved during etching, and an electrode foil having a high capacitance cannot be obtained, which is not preferable.

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

The aluminum alloy foil for electrolytic capacitor electrodes according to the present invention is required to have an oxide film having a thickness of 30 to 100 angstroms in the surface state.
If the thickness of the oxide film is less than 30 Å, overdissolving is likely to occur during etching, and an electrode foil having a high capacitance cannot be obtained, which is not preferable. On the contrary, if the thickness of the oxide film exceeds 100 angstroms, the etching characteristics are deteriorated and the electrode foil having a high capacitance cannot be obtained, which is not preferable. Further, it is necessary that the hydration rate in the oxide film is 10 to 50%. If the hydration rate is less than 10%, overdissolving is likely to occur during etching, and an electrode foil having a high capacitance cannot be obtained, which is not preferable. On the other hand, if the hydration rate exceeds 50%, the etching characteristics will deteriorate and it will not be possible to obtain a high capacitance electrode foil.
Not preferable.

Further, in the present invention, it is necessary that the thickness of the oxide film and the hydration rate in the oxide film among the surface states of the aluminum alloy foil satisfy the condition represented by the following expression (2). . That is, where t is the thickness of the oxide film expressed in angstrom and H is the hydration rate in the oxide film, 0.64t-14.1≤H≤0.95t-
It is necessary to satisfy the formula (2) of 15.9. As is apparent from the above, t is 30 to 100 and H is 10 to 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. Then, the oxide film is not in a state of improving etching characteristics, and an electrode foil having a high capacitance cannot be obtained, which is not preferable.

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 The thickness of the oxide film (angstrom) was obtained by multiplying the ion sputtering time (min) that became equal by 50 angstrom. In addition, the hydration rate in the oxide film can be determined by using XPS [O
1s] spectrum is measured, and the spectrum is 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 area of the entire [O 1s] peak was determined, and this was multiplied by 100 to obtain the hydration rate (%).

Further, in the present invention, whether the Pb content and the hydration rate in the oxide film satisfy the condition of the following formula (3),
Alternatively, it is necessary that the Mg content and the hydration rate in the oxide film satisfy the condition represented by the following formula (4). That is, 4.08X + 9.59
≦ H ≦ 5.17X + 34.5 is satisfied (3) or 5.0Y
It is necessary to satisfy the equation (4) + 5.0 ≦ H ≦ 5.17Y + 34.5. As described above, it is sufficient to satisfy one of the equations (3) and (4), but it is more preferable to satisfy both of them. Therefore, if it does not satisfy the formula (4), and exceeds the range of the formula (3), the hydration rate is too high or too low, or the Pb content is too high or too low, a small amount is added. The balance between the amount of elements and the hydration rate in the oxide film becomes poor, and an electrode foil having a high capacitance cannot be obtained, which is not preferable. Further, if the formula (3) is not satisfied and the formula (4) is exceeded and the hydration rate is too high or too low, or the Mg content is too high or too low, a small amount is added. The balance between the amount of elements and the hydration rate in the oxide film becomes poor, and an electrode foil having a high capacitance cannot be obtained, which is not preferable.

An aluminum alloy foil for electrolytic capacitor electrodes according to the present invention is prepared by preparing an aluminum ingot containing a predetermined amount of Pb and Mg, subjecting it to homogenization treatment and hot rolling, followed by cold rolling and intermediate rolling. It can be obtained by a method in which annealing, finish rolling if desired, and final annealing are performed. In the present invention, in order to adjust the thickness of the oxide film and the hydration ratio in the oxide film, the atmosphere gas and atmosphere temperature of the intermediate annealing, the degreasing cleaning method after finish rolling, and the atmosphere gas and atmosphere temperature of the final annealing, etc. It 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 Table 1 and Table 2 was added to aluminum containing 0.001 wt% Si, 0.001 wt% Fe, and 0.045 wt% Cu. A 400 mm-thick high-purity aluminum ingot (Al 99.99% by weight) to which elements Pb and Mg were added was prepared. After subjecting this aluminum ingot to homogenization treatment at 530 ° C. for 3 hours, immediately start hot rolling,
The hot rolling was completed at 0 ° C. Cool the plate after hot rolling,
Repeated cold rolling to form a thin plate with a thickness of 0.13 mm, N ₂
Intermediate annealing was performed in a gas atmosphere at 230 ° C. for 5 hours.
After that, finish rolling was performed at a rolling rate of 20% to obtain a foil having a thickness of 0.1 mm. Next, after degreasing and removing the oil adhered on the foil surface with acetone, the final annealing was performed at 530 ° C for 10 hr.
It was conducted under the condition 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 and the hydration rate (%) in the oxide film of the aluminum alloy foil obtained as described above were measured by the methods described above, and the results are shown in Tables 1 and 2. It was shown to. Furthermore, the capacitance of this aluminum alloy foil was measured by the following method and shown in Tables 1 and 2. To measure the capacitance, use the obtained aluminum alloy foil for electrolytic capacitor electrodes at [5.1% HCl + 6.4
% AlCl ₃ 6H ₂ O + 6.8% H ₂ SO ₄ ] solution, DC 0.16A
Etching was carried out for 8 minutes at / cm ² . After that, the etched foil was immersed in a 5% H ₃ BO ₃ aqueous solution at 85 ° C. and 375 V.
Was subjected to chemical conversion treatment for 30 minutes. Then, the foil (size 1 cm x 2 cm) that had been subjected to chemical conversion treatment was placed in a 4.5% H ₃ BO ₃ aqueous solution for 2 sheets, 3 mm.
The electrodes were immersed in parallel with each other at intervals 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, the relationship between the thickness of the oxide film and the hydration rate in the oxide film. , Pb
If 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 the specified range, a high capacitance electrode foil may be obtained. I understand. It can be seen that the capacitance exceeding the predetermined range has a low capacitance.

[0018]

INDUSTRIAL APPLICABILITY As described above, the aluminum alloy foil for electrolytic capacitor electrodes according to the present invention is used as a trace additive element.
It contains Pb 0.1 to 5.0 ppm and Mg 0.1 to 5.0 ppm, and the Pb content, the Mg content, the oxide film thickness and the hydration ratio in the oxide film are expressed by the above formulas (1), (2 ), (3) and / or (4) are satisfied, Pb and Mg that improve the etching characteristics are added in a well-balanced amount and the state of the oxide film is Pb.
The optimum state is obtained depending on the addition amount of Mg and Mg. Therefore, when this aluminum alloy foil for electrolytic capacitor electrodes is used for etching, etching characteristics are improved, and an electrode foil having a high capacitance (in particular, an anode foil) can be obtained. Moreover, since it is possible to stably obtain an electrode foil having a high capacitance as long as the specific conditions described above are satisfied, it is possible to improve production efficiency and supply a large amount of inexpensive electrode foil. Also effective.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomokatsu Hata 61-8 Sasaya, Yamadera-cho, Kusatsu-shi, Shiga Nihon Foil Co., Ltd. Shiga factory

Claims (3)

[Claims] 1. An aluminum alloy foil for electrolytic capacitor electrodes, comprising Pb 0.1 to 5.0 ppm, Mg 0.1 to 5.0 ppm, and unavoidable impurities, 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 (3), an aluminum alloy foil for electrolytic capacitor electrodes. 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) (However, the meanings and ranges of X, Y, t, and H are as follows. That is, X represents the Pb content in ppm, and 0.1 ≦ X ≦ 5.0. Y is Y. The Mg content is expressed in ppm, 0.1 ≦ Y ≦ 5.0, t is the thickness of the oxide film in Angstrom, and 30 ≦ t
≦ 100. H represents the hydration rate in the oxide film in%, and 10 ≦ H ≦ 50. ) 2. An aluminum alloy foil for electrolytic capacitor electrodes, which contains Pb 0.1 to 5.0 ppm, Mg 0.1 to 5.0 ppm, and unavoidable impurities, and has 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), (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. That is, X represents the Pb content in ppm, and 0.1 ≦ X ≦ 5.0. Y represents Y. The Mg content is expressed in ppm, 0.1 ≦ Y ≦ 5.0, t is the thickness of the oxide film in Angstrom, and 30 ≦ t
≦ 100. H represents the hydration rate in the oxide film in%, and 10 ≦ H ≦ 50. ) 3. An aluminum alloy foil for electrolytic capacitor electrodes, which contains Pb 0.1 to 5.0 ppm, Mg 0.1 to 5.0 ppm, and unavoidable impurities, and has an oxide film formed on the surface thereof, wherein the Pb content is Pb content. , Mg content, oxide film thickness and hydration ratio in the oxide film satisfy the conditions of the following formulas (1) to (4), an aluminum alloy foil for electrolytic capacitor electrodes. 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 is Pb content in ppm. And 0.1 ≦ X ≦ 5.0, Y represents the Mg content in ppm, and 0.1 ≦ Y ≦ 5.0, and t represents the thickness of the oxide film in Angstrom. And 30 ≦ t
≦ 100. H represents the hydration rate in the oxide film in%, and 10 ≦ H ≦ 50. )