JP2001294961A - Aluminum alloy foil for electrode of electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aluminum alloy foil, by which the electrode foil of an electrolytic capacitor having high capacitance can be obtained. SOLUTION: This aluminum alloy foil has a composition containing, by weight, 0.002 to 0.07% Si, 0.005 to <0.05% Fe, <=0.02% Mg, <=0.02% Zn, <=0.005% Cu and 0.002 to 0.02% Ni, and the balance Al. In particular the contents of Mg and Zn are preferably controlled to 0.002 to 0.02%. The aluminum alloy foil has good etching characteristics, by which the cathode foil of an electrolytic capacitor having high capacitance can be obtained. Moreover, the aluminum alloy foil has high bending strength and, at the time of processing capacitor or the like, is less in trouble such as cutting, and has good workability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum alloy foil suitable for obtaining an electrolytic capacitor electrode foil (particularly a cathode foil) having a high capacitance and a high bending strength.

[0002]

2. Description of the Related Art Conventionally, an electrolytic capacitor electrode foil has been manufactured by etching an aluminum alloy foil. Etching is to form fine irregularities on the surface of the aluminum alloy foil, increase the surface area of the foil,
This is performed to increase the capacitance. Therefore, in order to obtain a high capacitance electrode foil for an electrolytic capacitor, it is necessary to use an aluminum alloy foil having good etching characteristics. Various etching methods are employed for the etching treatment so that etch pits suitable for the withstand voltage to be used can be obtained. For example, tunnel-like etch pits are preferably formed in the anode high-pressure foil, and sponge-like pits are preferably formed in the anode low-pressure foil or the cathode foil. The AC electrolytic etching method is widely adopted for the latter.

[0003] Japanese Patent Application Laid-Open No. 3-122239 discloses an aluminum alloy foil having good etching characteristics in an AC electrolytic etching method. This aluminum alloy foil has a Si content of 0.1% by weight or less and a Fe content of 0.05 to
0.2% by weight, Ni: 0.001 to 0.005% by weight,
Al: Consists of the remainder. This aluminum alloy foil is made of Ni
Is added in a predetermined amount, the etching characteristics are improved to some extent, but the degree is insufficient. The reason for this is not clear, but the content of Fe is too large, and the improvement of the etching characteristics by Ni is insufficient.
It is considered that no consideration has been given to these and other added elements.

[0004]

Therefore, the present inventors have developed an aluminum alloy foil which can sufficiently exhibit the action of Ni to obtain an electrode foil having a high capacitance.
During various studies, it has been found that good results can be obtained by lowering the Fe content and adding predetermined amounts of Mg and Zn. The present invention has been made based on such findings.

[0005]

[Means for Solving the Problems]

[0006] That is, the present invention relates to Si: 0.002-0.
07 wt%, Fe: 0.005 wt% or more and less than 0.05 wt%, Mg: 0.02 wt% or less, Zn: 0.02 wt% or less, Cu: 0.005 wt% or less, Ni: 0. 0
The present invention relates to an aluminum alloy foil for an electrode of an electrolytic capacitor, characterized in that the aluminum alloy foil comprises 02 to 0.02% by weight and Al: balance. In particular, Mg and Zn are 0.001 to
0.02% by weight is preferable, and 0.002 to 0.02% by weight is more preferable.

The constituent elements and their contents of the aluminum alloy foil for an electrolytic capacitor cathode according to the present invention are as follows. Si is 0.002 to 0.07% by weight. In order to make Si less than 0.002% by weight, a special aluminum refining step must be performed, which is not preferable because aluminum becomes expensive. In addition, Si is set to 0.0
If the content is less than 02% by weight, the etching characteristics also deteriorate.
If Si exceeds 0.07% by weight, excessive melting occurs at the time of etching, and fine irregularities once formed on the surface of the aluminum alloy foil are dropped off. As a result, it becomes difficult to increase the surface area of the foil, which is not preferable.

[0008] Fe is at least 0.005 wt% and less than 0.05 wt%. In order to make Fe less than 0.005% by weight, a special aluminum refining step must be performed, which is not preferable because aluminum becomes expensive. Fe
Is 0.05% by weight or more, the amount of Fe, which forms an intermetallic compound with Al together with Ni, greatly exceeds the amount, and the presence of a large amount of Fe precipitates cannot be avoided. Not preferred.

[0009] Mg is 0.02% by weight or less. That is, Mg is added in an amount of 0.02% by weight or less, preferably 0.001 to 0.02% by weight, and more preferably 0.002 to 0.02% by weight. Mg is 0.0
If the content exceeds 2% by weight, the amount of Mg segregated on the surface of the aluminum alloy foil increases due to thermal diffusion, and excessive melting occurs during etching, which is not preferable. Mg is Fe or Si
To form an intermetallic compound to lower the standard electrode potential of Fe, Si, etc., thereby preventing overdissolution during etching.
Therefore, if Mg is less than 0.002% by weight, the amount tends to be insufficient to produce an intermetallic compound with Fe or Si.

[0010] Zn is at most 0.02% by weight. That is, Zn is added in an amount of 0.02% by weight or less, preferably 0.001 to 0.02% by weight, and more preferably 0.002 to 0.02% by weight. Zn is 0.0
If the content exceeds 2% by weight, the standard electrode potential of Al in which Zn is dissolved is reduced, the difference between the standard electrode potentials of Al and Fe or the like is increased, and overdissolution is likely to occur during etching, which is not preferable. Zn dissolves well in Al,
The purpose is to improve the mechanical properties of the obtained aluminum alloy foil. Therefore, when Zn is less than 0.002% by weight, the degree of improvement in mechanical properties of the obtained aluminum alloy foil tends to decrease.

[0011] Cu is 0.005% by weight or less. C
If u exceeds 0.005% by weight, overdissolution tends to occur during etching, which is not preferable. Further, when the obtained electrode foil is incorporated in a capacitor, a trouble such as a short circuit may occur, which is not preferable.

Ni is 0.002 to 0.015% by weight.
is there. Ni combines with Al to form Al _ThreeNi compound or
Al_Three(Fe, Ni) compounds are formed. This compound
Is the starting point during AC etching and the surface of the foil
It contributes to product expansion. 0.002% by weight of Ni
If it is less than 1, the etching start point does not increase sufficiently,
The foil surface area cannot be sufficiently increased. In addition, Ni is 0.0
If it exceeds 15% by weight, the number of starting points for etching increases.
Over-dissolution during etching
No.

In the present invention, unavoidable impurities may be mixed in addition to the above-mentioned elements, and typically, Ti is used. This may be contained in bauxite, and may contain about 0.002% by weight or less of Ti. 0.002% by weight of unavoidable elements such as Ti
, The Al purity may decrease. In the present invention, the Al purity is 99.3% by weight.
It is preferable that this is the case. If the Al purity is less than 99.3% by weight, the amount of unavoidable impurities increases, and the etching characteristics often deteriorate.

The aluminum alloy foil for an electrolytic capacitor electrode according to the present invention can be rationally obtained, for example, by the following manufacturing method. That is, Si: 0.002
0.07% by weight, Fe: 0.005% by weight or more and 0.05
Wt%, Mg: 0.02 wt% or less, Zn: 0.0
2% by weight or less, Cu: 0.005% by weight or less, Ni:
The ingot consisting of 0.002 to 0.02% by weight, Al: balance, is homogenized at a temperature of 500 ° C. to 550 ° C. for a time of 20 hours or less, subjected to hot rough rolling and hot finishing rolling, Thereafter, by performing cold rolling, an aluminum alloy foil for an electrolytic capacitor electrode having a desired thickness can be manufactured. In addition, final annealing can be performed after cold rolling to obtain an aluminum alloy foil for an electrolytic capacitor electrode. By subjecting them to an appropriate etching treatment, an electrolytic capacitor cathode foil or an electrolytic capacitor anode low-pressure foil can be obtained.

[0015]

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to the examples. The present invention is based on the finding that an aluminum alloy foil having a specific elemental composition has good etching properties and also improves mechanical properties, so that a cathode foil or an anode low-pressure foil having high capacitance and easy to handle can be obtained. Should be interpreted as being based on

Examples 1 to 14 and Comparative Examples 1 to 8 Ingots (thickness: 500 mm) having the elemental compositions shown in Table 1 were prepared. Then, after performing a homogenization treatment at 520 ° C. for 1 hour, hot rolling was immediately performed to obtain an aluminum plate having a thickness of 3 mm. This aluminum plate was subjected to cold rolling to obtain an aluminum alloy foil for an electrolytic capacitor electrode having a thickness of 0.05 mm.

[0017]

[Table 1]

Aluminum foil for each of the obtained electrolytic capacitor electrodes
Etching and chemical treatment of the aluminum alloy foil under the following conditions
And the capacitance (μF / c) under the following conditions
m^Two) Was measured. [Etching treatment] 5 wt. % HCl + 6 wt. % Al
Cl_Three・ 6H_TwoO + 0.1 wt. % C_TwoH_TwoO _Four・ 2H_TwoO
Each electrolytic capacitor electrode in an aqueous solution (liquid temperature 30 ° C) containing
Immersion aluminum alloy foil for 0.4A / cm^TwoAt 5
0 Hz sine wave alternating current for 150 sec. Shed and etch
Was performed. [Chemical conversion treatment] Each foil after the etching treatment was subjected to the EIAJ method.
The test piece was cut into 13 wt. %Horse mackerel
Immersed in an aqueous solution of ammonium pinate (liquid temperature 85 ° C),
The counter electrode is SUS304 and 3V is based on EIAJ method.
Chemical conversion treatment was performed. [Capacitance] Two sheets of each foil after chemical conversion treatment face each other.
13 wt. % Ammonium adipate aqueous solution (liquid temperature
30 ° C.) and the counter electrode has a capacitance of 40,000.
120Hz as etched aluminum foil of μF or more
Is a series equivalent circuit of
(ΜF / cm^Two) Was measured. And according to Comparative Example 1
Capacitance of aluminum alloy foil for electrolytic capacitor electrode
As a reference (100%), each electrolytic capacitor
Table 2 shows the capacitance of aluminum alloy foil for sensor electrodes.
did.

Further, a bending test was performed on the aluminum alloy foil for each electrolytic capacitor electrode under the following conditions, and the bending strength (times / cm) was measured. [Bending Strength] Each of the foils having been subjected to the above etching treatment was subjected to a heat treatment at 400 ° C. for 5 minutes in the air. Each of the heat treated foils was subjected to JIS P 8115 “MI of paper and paperboard”.
The bending strength (times / cm) was measured with an MIT type bending tester in accordance with "Testing method for bending strength by T tester".
The results are shown in Table 2.

[0020]

[Table 2]

Examples 15 to 24 and Comparative Examples 9 to 15 Ingots (thickness: 500 mm) having the elemental compositions shown in Table 3 were prepared. And alkali washing after cold rolling (pH =
9.5 cleaning solution) and final annealing
An aluminum alloy foil for an electrolytic capacitor electrode having a thickness of 0.05 mm was obtained under the same conditions as in Example 1 except that the application was performed at 20 ° C. for 5 hours. Then, the capacitance (μF / cm ² ) was measured under the same conditions as in Example 1, and the capacitance of the aluminum alloy foil for an electrolytic capacitor electrode according to Comparative Example 9 was set as a reference (100%) and compared with that. Table 4 shows the capacitance of the aluminum alloy foil for each electrolytic capacitor electrode. Further, the bending strength (times / times) was obtained under the same conditions as in Example 1.
cm) was measured, and the results are shown in Table 4.

[0022]

[Table 3]

[0023]

[Table 4]

As is clear from the results in Tables 2 and 4,
In the case of the aluminum alloy foil for an electrolytic capacitor electrode according to the example, both the capacitance and the bending strength were superior to those according to the comparative example.

[0025]

As described above, the aluminum alloy foil for an electrolytic capacitor electrode according to the present invention has excellent etching characteristics, and an electrolytic capacitor electrode foil (particularly, a cathode foil or an anode) obtained by etching the aluminum alloy foil. The high-voltage foil) has an effect that the capacitance is large and a capacitor having a large capacity per unit area can be obtained. In addition, the aluminum alloy foil for an electrolytic capacitor electrode according to the present invention has an effect that bending strength is high, troubles such as cutting during capacitor processing (for example, winding) are reduced, and workability is improved.

Continued on the front page (72) Inventor Toshio Saito 61-8 Sasaya, Yamadera-cho, Kusatsu-shi, Shiga Japan Foil Co., Ltd. Shiga Plant (72) Inventor Akihiro Yamaguchi 61-8 Sasaya, Yamadera-cho, Kusatsu-shi, Shiga Foil made in Japan Inside Shiga Factory

Claims (2)

[Claims] 1. Si: 0.002 to 0.07% by weight, F
e: 0.005% by weight or more and less than 0.05% by weight, Mg:
0.02% by weight or less, Zn: 0.02% by weight or less, C
u: 0.005% by weight or less, Ni: 0.002 to 0.0
2% by weight, Al: aluminum alloy foil for an electrode of an electrolytic capacitor, characterized by comprising the balance. 2. Mg: 0.002 to 0.02% by weight, Z
The aluminum alloy foil for an electrolytic capacitor electrode according to claim 1, wherein n: 0.002 to 0.02% by weight.