JP2002080928A - Aluminum alloy foil for electrolytic capacitor cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aluminum alloy foil and the cathode foil of electrolytic a capacitor having a high capacitance foil using the aluminum alloy. SOLUTION: This aluminum alloy foil contains 0.2 to 1.0% Cu, 0.01 to 0.1% Si, 0.02 to 0.2% Fe, 0.002 to 0.2% Mg, 0.0005 to 0.05% Ti, 0.0001 to 0.01% V and 0.0001 to 0.01% B, and the balance Al with inevitable impurities of <=0.05%. Thus, the aluminum alloy foil has good etching characteristics, by which electrolytic capacitance cathode foil with high capacitance can be obtained. Further, the cathode foil obtained by using the same aluminum alloy foil has high bending strength and is almost free from troubles such as cutting in capacitor working or the like.

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 suitable for obtaining an electrolytic capacitor cathode foil having a high capacitance and a high bending strength.

[0002]

2. Description of the Related Art Electrode capacitor electrode foils are manufactured by etching an aluminum alloy foil. The etching is performed to form fine irregularities on the surface of the aluminum alloy foil, increase the surface area of the foil, and 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 on the anode high-pressure foil, and sponge-like pits are preferably formed on the anode low-pressure foil or the cathode foil. The AC electrolytic etching method is widely adopted for the latter.

Various aluminum alloy foils having good AC etching characteristics have been proposed. For example, a predetermined amount of Mg, Z
It has been proposed to improve the etching characteristics by adding n, Ti, Ni or the like (Japanese Patent Application Laid-Open Nos. 2-51210, 3-130340, 5-823).
No. 97). This proposed aluminum alloy foil is
A cathode foil having excellent AC etching property and high capacitance is obtained, which is preferable.

On the other hand, the following aluminum alloy foils have been proposed as aluminum alloy foils which focus on improving the bending resistance of the obtained electrode foil rather than improving the capacitance. That is, JP-A-10-28794
No. 4 discloses that Ti is less than 0.0002% and V is 0.0
An aluminum alloy foil for an electrolytic capacitor anode low pressure containing less than 002% and 0.0002 to 0.001% of B has been proposed. JP-A-6-220561 discloses that 0.00001 to 0.0001% of Ti, 0.00005 to 0.0005% of V, and 0.00005 of B
There has been proposed an aluminum alloy foil for electrolytic capacitor anode low pressure containing about 0.0025%. Certainly, when these aluminum alloy foils are subjected to an AC etching treatment, an anode low-pressure foil having excellent bending strength and a certain capacitance can be obtained.

[0005]

However, when the aluminum alloy foil for the anode low voltage of the electrolytic capacitor is directly used as the aluminum alloy foil for the cathode, the capacitance of the cathode foil obtained by AC etching is insufficient. There was found. Therefore, the present inventors have adjusted the content of Si and Fe in the aluminum alloy foil, and further increased the content of B to obtain a cathode foil having high capacitance and excellent bending strength. An aluminum alloy foil that can be obtained has been proposed (Japanese Patent Application No. 2000-150439).

According to the invention, Al purity is not less than 99.8%, Si: 0.02 to 0.08%, Fe: 0.02 to
0.08%, Ti: 0.00005 to 0.0005%,
V: 0.00005 to 0.0005%, B: 0.002
An aluminum alloy foil for a cathode of an electrolytic capacitor, characterized by containing 5 to 0.01%, Cu: 0.003% or less, and other unavoidable impurities.

[0007] The present inventors have further studied and found that, in the above invention, while adding a predetermined amount of Mg,
It has been found that when the content of Cu is increased, an aluminum alloy foil capable of obtaining a cathode foil having high capacitance and excellent bending strength can be obtained. The present invention has been made based on such findings.

[0008]

That is, the present invention provides Cu:
0.2-1.0%, Si: 0.01-0.1%, Fe:
0.02-0.2%, Mg: 0.002-0.2%, T
i: 0.0005 to 0.05%, V: 0.0001 to
The present invention relates to an aluminum alloy foil for a cathode of an electrolytic capacitor, comprising 0.01%, B: 0.0001 to 0.01%, other unavoidable impurities: 0.05% or less, and Al: balance. In this specification, “%” indicating the alloy composition means “% by mass”.

The constituent elements and their contents of the aluminum alloy foil for a cathode of an electrolytic capacitor according to the present invention are as follows. Cu is 0.2 to 1.0%. If Cu is less than 0.1%, the etching characteristics deteriorate and the surface area cannot be increased, which is not preferable. On the other hand, if Cu exceeds 2.0%, overdissolution tends to occur during etching, which is not preferable.

[0010] Si is 0.01 to 0.1%. Si
Is less than 0.01%, the number of Si precipitates decreases, the starting point of etching decreases, the etching property becomes poor, and it becomes difficult to obtain a cathode foil with high capacitance, which is not preferable. If the Si content exceeds 0.1%, the number of starting points for etching becomes too large, excessive melting occurs during etching, and fine irregularities on the surface of the once formed aluminum alloy foil fall off, resulting in an increase in the surface area of the foil. It is not preferable because it becomes difficult.

[0011] Fe is 0.02 to 0.2%. Fe
Is less than 0.02%, the number of Fe precipitates decreases, the etching property becomes poor, and it becomes difficult to obtain a cathode foil having high capacitance, which is not preferable. 0.2% Fe
Exceeding the maximum value is not preferable because it is impossible to avoid the presence of a large amount of Fe precipitates and cause excessive dissolution during etching.

Mg is 0.002 to 0.2%. M
When g is less than 0.002%, the amount of Mg bonded to Si decreases, and the precipitation of elemental Si or Al—Fe—Si compound increases. For this reason, a plurality of potential differences are generated between the matrix and each compound as compared with an aluminum alloy foil in which only an Al-Fe compound is present. When Mg exceeds 0.2%, due to thermal diffusion,
The segregation amount of Mg on the aluminum alloy foil surface increases,
This is not preferable because overdissolution occurs during etching.

[0013] Ti is 0.0005 to 0.05%. If the content of Ti is less than 0.0005%, uniform etching becomes difficult to be performed as a whole, and the bending strength decreases, which is not preferable. If the Ti content exceeds 0.05%, etching in the thickness direction of the aluminum alloy foil becomes poor, the effect of increasing the surface area is reduced, and it becomes difficult to obtain a cathode foil having a high capacitance.

V is 0.0001 to 0.01%.
If V is less than 0.0001%, uniform etching becomes difficult to be performed as a whole, and the bending strength decreases, which is not preferable. If V exceeds 0.01%, etching in the thickness direction of the aluminum alloy foil becomes poor, which is not preferable.

B is 0.0001 to 0.01%.
If B is less than 0.0001%, uniform etching becomes difficult to be performed as a whole, and the bending strength decreases, which is not preferable. If B exceeds 0.01%, overdissolution occurs during etching, which is not preferable.

The aluminum alloy foil for a cathode of an electrolytic capacitor according to the present invention may contain several kinds of elements as unavoidable impurities in addition to the above-mentioned elements. Even in such a case, the total content of inevitable impurities must be 0.05% or less. If the total content of unavoidable impurities exceeds 0.05%, a local battery is formed with Al, and overdissolution may occur during etching, which is not preferable.

The aluminum alloy foil for an electrolytic capacitor cathode according to the present invention can be rationally obtained, for example, by the following production method. That is, Cu: 0.2 to 1.0
%, Si: 0.01 to 0.1%, Fe: 0.02 to 0.
2%, Mg: 0.002 to 0.2%, Ti: 0.000
5 to 0.05%, V: 0.0001 to 0.01%, B:
0.0001 to 0.01%, other unavoidable impurities: 0.
05% or less, ingot of Al: balance
~ 620 ° C, homogenization treatment under the condition of time 20 hours or less,
Hot rough rolling and hot finishing rolling are performed, and then cold rolling is performed.
Intermediate annealing is performed under the condition of 480 ° C. and time of 20 hours or less,
Thereafter, finish cold rolling is performed to produce an aluminum alloy foil for a cathode of an electrolytic capacitor having a desired thickness. By subjecting the aluminum alloy foil to an appropriate etching treatment, an electrolytic capacitor cathode foil can be obtained.

[0018]

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to the examples. According to the present invention, the aluminum alloy foil having a specific elemental composition has good etching characteristics (because both uniform etching and etching imparting to increase the surface area are good), and thus has a high capacitance and a high folding endurance. It should be interpreted as being based on the finding that a strong cathode foil is obtained.

Examples 1 to 3 and Comparative Examples 1 to 6 Ingots (thickness: 500 mm) having the elemental compositions shown in Table 1 were prepared. Then, after performing a homogenization treatment at 580 ° 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 thin plate having a thickness of 0.4 mm.
Thereafter, the aluminum sheet was subjected to intermediate annealing at a temperature of 450 ° C. for 10 hours, and then to finish cold rolling to obtain a 0.05 mm thick aluminum alloy foil for a cathode of an electrolytic capacitor.

[0020]

[Table 1]

The obtained aluminum alloy foil for a cathode of an electrolytic capacitor is subjected to an etching treatment under the following conditions.
The capacitance (μF / cm ² ) was measured under the following conditions without chemical conversion. [Etching treatment] 6 wt. % Hydrochloric acid + 0.5 wt. % Phosphoric acid + 0.5 wt. % Aqueous solution containing oxalic acid (liquid temperature 50 ℃ ± 1
C), the aluminum alloy foil for the cathode of each electrolytic capacitor was immersed, and subjected to AC electrolytic etching for 200 seconds at an apparent current density of 0.25 A / cm ² by a sine wave AC of 30 Hz. [Capacitance] Two sheets of each unformed foil after the etching process were opposed to each other, and 13 wt. % Ammonium adipate aqueous solution (liquid temperature 30 ℃ ± 1 ℃), 120Hz
, The capacitance (μF / cm ² ) was measured using an LCR meter. The capacitance of the aluminum alloy foil for an electrolytic capacitor cathode according to Example 3 was set as a reference (100%).

Further, a bending test was performed on the aluminum alloy foil for each electrolytic capacitor cathode under the following conditions, and the bending strength (times / cm) was measured. [Bending Strength] Each of the foils having been subjected to the above-described etching treatment was subjected to a heat treatment at 400 ° C. for 5 minutes in the air.
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.

[0023]

[Table 2]

As is clear from the results in Table 2, in the case of the aluminum alloy foil for a cathode of an electrolytic capacitor according to the embodiment,
It can be seen that both the capacitance and the bending strength are improved in a better balance than in the comparative example.

[0025]

As described above, the aluminum alloy foil for a cathode of an electrolytic capacitor according to the present invention has a sufficiently increased surface area and is uniformly etched by an AC etching process. Therefore, the obtained electrolytic capacitor cathode foil has a large capacitance and a large capacitance per unit area can be obtained. In addition, the bending strength is high, and the capacitor is processed at the time of processing (for example, winding). Thus, there is an effect that troubles such as cutting are reduced and workability is improved.

Claims (1)

[Claims] 1. Cu: 0.2-1.0%, Si: 0.0
1 to 0.1%, Fe: 0.02 to 0.2%, Mg: 0.1%
002-0.2%, Ti: 0.0005-0.05%,
V: 0.0001-0.01%, B: 0.0001-
0.01%, other unavoidable impurities: 0.05% or less, A
l: an aluminum alloy foil for a cathode of an electrolytic capacitor, comprising the remainder.