JPH07150280A - Aluminum alloy foil for electrolytic capacitor electrode - Google Patents

Abstract

PURPOSE:To provide an aluminum alloy foil capable of stably giving an electrode foil with high electrostatic capacity. CONSTITUTION:This aluminum alloy foil essentially contains, as trace additive elements, Mg and respective elements of Pb, Bi, In, Sn, Sb, B, Ni, and Cr [group (y) elements]. An oxide film is formed on the surface. The content of Mg, respective contents of the group (y) elements, the thickness of the oxide film, and the hydration ratio in the oxide film satisfy the conditions in relations Y<=-X+6, 0.37t-7.16<=H<=1.67t-20.3, and 14.0X-12.0<=t<=10.5X+68.9. In the relations, X means Mg content (ppm) and is 0.1-5.0, Y means respective contents (ppm) of the group (y) elements and is 0.1-5.0, (t) means the thickness (Angstrom ) of the oxide film and is 30-90, and H means the hydration ratio (%) in the 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. Further, it was found that when the kinds of the trace addition elements were small, the characteristics were difficult to be leveled, and the electrode foil with high capacitance was or could not be obtained depending on the etching conditions.

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. Also,
By using a large number of elements as the kind of the trace addition element, it is intended to stably obtain an electrode foil having a high capacitance.

[0006]

Means for Solving the Problems That is, the present invention provides Mg0.1
.About.5.0 ppm, Pb, Bi, In, Sn, Sb, B, Ni, Cr (hereinafter, the aggregate of all of them is referred to as y group element) is contained as an essential element and the content of each element is 0.1. Aluminum alloy foil for an electrolytic capacitor electrode, which contains ˜5.0 ppm and unavoidable impurities and has an oxide film formed on the surface thereof, which contains Mg content, Pb, Bi, In, Sn, Sb, B, Ni, Cr
The respective contents of, the oxide film thickness and the hydration ratio in the oxide film are the conditions of the formulas (1), (2), (3) and / or (4) and / or (5) shown below. The present invention relates to an aluminum alloy foil for an electrolytic capacitor electrode, which satisfies: In the present invention, ppm is based on weight ratio. Note Y≤-X + 6 ... (1) 0.37t-7.16≤H≤1.67t-20.3 ... (2) 14.0X-12.0≤t≤10.5X + 68.9 ......... (3) 2.04X + 4.80≤ H ≦ −6.25X + 56.3 ……… (4) 6.25Y + 23.8 ≦ t ≦ 27.3Y + 57.3… (5) (However, the meaning and range of X, Y, t and H are as follows. That is, X represents the Mg content in ppm, and 0.1 ≦ X ≦ 5.0 Y is Pb, Bi, In, Sn, Sb,
The respective contents of B, Ni, and Cr are expressed in ppm, and 0.1 ≦ Y ≦ 5.0. t is the thickness of the oxide film expressed in angstroms, and 30 ≦ t ≦ 90.
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 Mg and a y-group element as trace additive elements. Mg changes the surface potential of the aluminum alloy foil and improves 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. The content of each y-group element is
It is 0.1 to 5.0 ppm. If the content of at least one of the y group elements is less than 0.1 ppm, the etching characteristics may be difficult to improve depending on the etching conditions even if the surface state of the aluminum alloy foil is optimized.
It is not preferable because an electrode foil having a high capacitance cannot be obtained. On the contrary, if the content of at least one of the y group elements exceeds 5.0 ppm, the aluminum alloy foil is likely to be overdissolved during etching, and an electrode foil having a high capacitance cannot be obtained, which is not preferable.

In the present invention, the content of Mg and the content of each of the y-group elements must satisfy the condition of the following formula (1). That is, the Mg content expressed in ppm is X, and the respective contents of the y group elements are
When Y is expressed in ppm, the formula Y ≦ −X + 6
It is necessary to satisfy (1). As is clear from the above, X is 0.1 to 5.0 and Y is 0.1
~ 5.0. Beyond this range, the content of Mg is high, or the content of at least one of the y group elements is high, or the content of Mg is low, or the content of at least one of the y group elements is If the amount is too small, the balance of minute additions of Mg and y group elements is poor,
This is not preferable because an electrode foil having a high capacitance cannot be obtained.

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 90 angstroms in the surface condition. 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 other hand, if the thickness of the oxide film exceeds 90 angstroms, the etching characteristics are deteriorated and it is not possible to obtain an electrode foil having a high capacitance, which is not preferable. Also, the hydration ratio in the oxide film is 10
Must be ~ 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 be deteriorated and it will not be possible to obtain a high capacitance electrode foil, which is 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 angstroms and H is the hydration rate in the oxide film, 0.37t-7.16≤H≤1.67t-
It is necessary to satisfy the equation (2) of 20.3. As is clear from the above, t is 30 to 90,
H is 10 to 50. Beyond this range, the thickness of the oxide film is too thick, or the hydration rate in the oxide film is too high,
Alternatively, if the oxide film is too thin or the hydration rate in the oxide film is too small, the oxide film is not in a state that improves etching characteristics, and a high capacitance electrode foil is obtained. It is not preferable because it cannot be done.

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, the Mg content and the thickness of the oxide film satisfy the condition of the following formula (3), or
The content and the hydration rate in the oxide film satisfy the condition as in the following formula (4), or the content of each y group element and the thickness of the oxide film satisfy the condition as in the following formula (5). It is necessary to be satisfied. That is, 14.0X-12.0≤t≤10.5X + 68.9
Satisfies (3) or 2.04X + 4.80 ≦ H ≦ −6.25X + 5
Satisfying formula (4) of 6.3 or 6.25Y + 2 3.8 ≦ t ≦ 2
It is necessary to satisfy the equation (5) of 7.3Y + 57.3. Thus, it is sufficient to satisfy any one of equation (3), equation (4) and equation (5), but satisfy equation (3) and equation (4) or equation (5). May be satisfied, or the expressions (4) and (5) may be satisfied. Furthermore,
All of the expressions (1) to (5) may be satisfied. Therefore, the formula (4) and the formula (5) are not satisfied, and beyond the range of the formula (3), the thickness of the oxide film is too thick or too thin, or the Mg content is too large or too small. If it is too much, the balance between the content of Mg and the thickness of the oxide film becomes poor, and an electrode foil having a high capacitance cannot be obtained, which is not preferable. Also, the formula
(3) and equation (5) are not satisfied, and beyond the range of equation (4),
If the hydration rate is too high or too low, or if the Mg content is too high or too low, the balance between the Mg content and the hydration rate in the oxide film becomes poor, resulting in a high capacitance. This is not preferable because the electrode foil of No. 1 cannot be obtained. Furthermore,
Not satisfying the formulas (3) and (4) and exceeding the range of the formula (5), the thickness of the oxide film is too thick or too thin, or the content of at least one of the y group elements is If the amount is too large or too small, the balance between the content of at least one of the y group elements and the thickness of the oxide film becomes poor, and an electrode foil with high capacitance cannot be obtained, which is not preferable.

For the aluminum alloy foil for electrolytic capacitor electrodes according to the present invention, an aluminum ingot containing a predetermined amount of Mg and a group y element is prepared, homogenized and hot rolled, and then cold rolled. It can be obtained by a method in which intermediate 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 12 Mg, Pb, Bi, In, Sn, Sb, B, Ni, and Cr, which are the trace amount additive elements (ppm) shown in Table 1 and Table 2, were added. An ingot of aluminum having a thickness of 400 mm was prepared. This aluminum ingot was homogenized at 530 ° C. for 3 hours, immediately followed by starting hot rolling and ending the hot rolling at 330 ° C. The plate after hot rolling is cooled, and cold rolling is repeatedly performed to form a thin plate with a thickness of 0.13 mm in an N ₂ gas atmosphere at 230 ° C.
The intermediate annealing was performed under the condition of 5 hr. After that, the rolling rate is 20%
Was finished and rolled into a foil having a thickness of 0.1 mm. Then
After degreasing and removing the oil components attached to the foil surface with acetone, the final annealing was performed at 530 ° C. for 10 hours at a vacuum degree of 10 ⁻³ Pa. As described above, an aluminum alloy foil for an electrolytic capacitor electrode was obtained.

[0015]

[Table 1]

[0016]

[Table 2]

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 3 and 4. It was shown to. Furthermore, the capacitance of this aluminum alloy foil was measured by the following method and shown in Tables 3 and 4. 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.

[0018]

[Table 3]

[0019]

[Table 4]

As is clear from the above Examples and Comparative Examples, the Mg content, the respective contents of the y group elements, the relationship between the Mg contents and the respective contents of the y group elements, the thickness of the oxide film, Relationship between hydration ratio in oxide film, relationship between Mg content and thickness of oxide film, relationship between Mg content and hydration ratio in oxide film, content of each y group element and oxide film It can be seen that the electrode foil having high capacitance can be obtained when the thickness of the electrode foil is within a predetermined range. On the other hand, it can be seen that the capacitance exceeding this predetermined range is low.

[0021]

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.
Mg 0.1 to 5.0 ppm and y-group element each containing 0.1 to 5.0 ppm, and the Mg content, the content of each y-group element, the oxide film thickness and the hydration ratio in the oxide film are as described above. Expression
Since the conditions of (1), (2), (3) and / or (4) and / or (5) are satisfied, a small amount of Mg and y group elements that improve etching characteristics are added in a well-balanced manner. The state of the oxide film becomes the optimum state according to the added amounts of Mg and y group element. 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. Further, since all the y-group elements of a large number of types are added, the characteristics thereof are leveled, and it is possible to prevent the etching characteristics from largely changing depending on the etching conditions. Therefore, it is possible to stably obtain an electrode foil having a high capacitance as long as the specific conditions described above are satisfied, so that the production efficiency is improved and a large amount of inexpensive electrode foil can be supplied. 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 (7)

[Claims] 1. Mg 0.1-5.0 ppm, Pb, Bi, In, Sn, Sb,
It is an aluminum alloy foil for electrolytic capacitor electrodes that contains B, Ni, and Cr as essential elements, contains 0.1 to 5.0 ppm of each element, and unavoidable impurities, and has an oxide film formed on the surface. , Mg content, Pb, B
The respective contents of i, In, Sn, Sb, B, Ni and Cr, the oxide film thickness and the hydration ratio in the oxide film are expressed by the following formula (1)
An aluminum alloy foil for electrolytic capacitor electrodes, which satisfies the conditions (3) to (3). Note Y≤-X + 6 ... (1) 0.37t-7.16≤H≤1.67t-20.3 ... (2) 14.0X-12.0≤t≤10.5X + 68.9 ... (3) (However, X, The meanings and ranges of Y, t and H are as follows: X is Mg content expressed in ppm and 0.1 ≦ X ≦ 5.0, and Y is Pb, Bi, In, Sn. , Sb,
The respective contents of B, Ni, and Cr are expressed in ppm, and 0.1 ≦ Y ≦ 5.0. t is the thickness of the oxide film expressed in angstroms, and 30 ≦ t ≦ 90.
H represents the hydration rate in the oxide film in%, and 10
≦ H ≦ 50. ) 2. Mg 0.1-5.0 ppm, Pb, Bi, In, Sn, Sb,
It is an aluminum alloy foil for electrolytic capacitor electrodes that contains B, Ni, and Cr as essential elements, contains 0.1 to 5.0 ppm of each element, and unavoidable impurities, and has an oxide film formed on the surface. , Mg content, Pb, B
The contents of i, In, Sn, Sb, B, Ni and Cr, the oxide film thickness, and the hydration ratio in the oxide film are expressed by the formulas shown below.
An aluminum alloy foil for an electrolytic capacitor electrode, which satisfies the conditions (1), (2) and (4). Note Y≤-X + 6 (1) 0.37t-7.16≤H≤1.67t-20.3 (2) 2.04X + 4.80≤H≤-6.25X + 56.3 ... (4) (However, X , Y, t and H have the following meanings and ranges: X is the Mg content expressed in ppm and 0.1 ≦ X ≦ 5.0, and Y is Pb, Bi, In, Sn, Sb,
The respective contents of B, Ni, and Cr are expressed in ppm, and 0.1 ≦ Y ≦ 5.0. t is the thickness of the oxide film expressed in angstroms, and 30 ≦ t ≦ 90.
H represents the hydration rate in the oxide film in%, and 10
≦ H ≦ 50. ) 3. Mg 0.1-5.0 ppm, Pb, Bi, In, Sn, Sb,
It is an aluminum alloy foil for electrolytic capacitor electrodes that contains B, Ni, and Cr as essential elements, contains 0.1 to 5.0 ppm of each element, and unavoidable impurities, and has an oxide film formed on the surface. , Mg content, Pb, B
The contents of i, In, Sn, Sb, B, Ni and Cr, the oxide film thickness, and the hydration ratio in the oxide film are expressed by the formulas shown below.
An aluminum alloy foil for an electrolytic capacitor electrode, which satisfies the conditions (1), (2) and (5). Note Y≤-X + 6 ... (1) 0.37t-7.16≤H≤1.67t-20.3 ... (2) 6.25Y + 23.8≤t≤27.3Y + 57.3 ... (5) (However, X, The meanings and ranges of Y, t and H are as follows: X is Mg content expressed in ppm and 0.1 ≦ X ≦ 5.0, and Y is Pb, Bi, In, Sn. , Sb,
The respective contents of B, Ni, and Cr are expressed in ppm, and 0.1 ≦ Y ≦ 5.0. t is the thickness of the oxide film expressed in angstroms, and 30 ≦ t ≦ 90.
H represents the hydration rate in the oxide film in%, and 10
≦ H ≦ 50. ) 4. The aluminum alloy foil for an electrolytic capacitor electrode according to claim 1, which satisfies the condition of the following formula (4). Note 2.04X + 4.80 ≦ H ≦ −6.25X + 56.3 (4) (However, the meanings and ranges of X and H are as described in claim 1.) 5. The aluminum alloy foil for an electrolytic capacitor electrode according to claim 1, which satisfies the condition of the following formula (5). Note 6.25 Y + 23.8 ≦ t ≦ 27.3Y + 57.3 (5) (However, the meaning and range of Y and t are as described in claim 1.) 6. The aluminum alloy foil for an electrolytic capacitor electrode according to claim 1, which satisfies the conditions of the following formulas (4) and (5). Note 2.04X + 4.80 ≦ H ≦ −6.25X + 56.3 ……… (4) 6.25Y + 23.8 ≦ t ≦ 27.3Y + 57.3 ……… (5) (However, the meaning and range of X, Y, t and H Claim 1
As described in. ) 7. The aluminum alloy foil for an electrolytic capacitor electrode according to claim 2, which satisfies the condition of the following formula (5). Note 6.25 Y + 23.8 ≦ t ≦ 27.3 Y + 57.3 (5) (However, the meaning and range of Y and t are as described in claim 2.)