JPH10223486A - Aluminum foil for electrolytic-capacitor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain crystal particles from becoming coarse and large after their heating by a method wherein three elements Cu, Sb and Ga in respectively specific contents coexist in an aluminum foil alloy of specific purity. SOLUTION: In an aluminum foil for an electrolytic-capacitor electrode, its aluminum purity is at 99.9% or higher, and 2 to 30ppm of Cu, 5 to 100ppm of Sb and 5 to 100ppm of Ga are contained. In addition to Cu, Sb and Ga in respective ranges which are used as fundamentally contained elements, 0.1 to 5ppm of Pb, or 1 to 50ppm of Zn, or 0.1 to 5ppm of Pb, or 0.1 to 5ppm of Pb and 1 to 50ppm of Zn are contained. Thereby, it is possible to prevent coarse and large crystals from growing after their heating treatment. As a result, it is possible to obtain the aluminum foil which obtains a large area expansion rate by an etching treatment, whose capacitance is large and which is excellent in an electric characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum foil for an electrode of an electrolytic capacitor.

[0002] In this specification, the unit of ppm indicates weight.

[0003]

2. Description of the Related Art An aluminum foil generally used as an electrode material for an aluminum electrolytic capacitor is usually subjected to an electrochemical or chemical etching treatment in order to increase its effective area and increase the capacitance per unit area. Will be applied.

[0004] In the anode foil of the type subjected to tunnel type etching called for high pressure, the effect is obtained by preferentially growing a cubic texture having a (100) crystal orientation perpendicular to the foil surface. It is already known that the capacitance can be increased in practice. Various proposals have been made on annealing conditions and foil surface roughness in order to increase the cubic orientation occupancy of the crystal (Japanese Patent Application Laid-Open Nos. 47-9953 and 62-228456).
No.). On the other hand, various proposals have been made to increase the cubic orientation occupancy by the alloy composition of the foil material, and the use of an aluminum alloy to which a small amount of Sb has been added as the foil material has been proposed. (Japanese Unexamined Patent Publication No. 50-104710,
No. 9-12736 and JP-A-7-150280).

[0005]

However, even when a foil material having the above-mentioned alloy composition is used, there is a problem that when the final annealing temperature is increased, the crystal grains become coarse and the capacitance is reduced.

Further, in the anode foil of the type subjected to sponge type etching called for low pressure, if the crystal grains grow coarse in the heat treatment in the final drying step, the strength of the etched foil is remarkably reduced and the foil is broken. There were also problems.

The present invention has been made in view of such technical background, and has been made in consideration of the above technical background, and is capable of suppressing the crystal grains from being coarsened by the heat treatment, thereby increasing the capacitance and maintaining the foil strength. The purpose is to provide aluminum foil for use.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies and found that Cu, Sb and Ga
It has been found that the coexistence of the three elements can suppress the coarsening of the crystal grains after heating.

[0009] The aluminum foil for an electrolytic capacitor electrode of the present invention has been made based on such knowledge.
In the foil alloy composition, aluminum purity is 99.9% or more, Cu: 2 to 30 ppm, Sb: 5-1.
The basic gist is that it contains 00 ppm and Ga: 5 to 100 ppm.

Further, the aluminum foil for an electrode of an electrolytic capacitor according to the present invention is characterized in that CuSb and Ga in the above-mentioned range are contained as basic elements, and in addition to these basic elements, Pb: 0.1 to 5 ppm is further contained. Containing Zn: 1 to 50 in addition to the basic element of Pb: 0.1 to 5 ppm of Pb and Zn: 1 to
It contains 50 ppm.

[0011] In the alloy composition of the aluminum foil for an electrolytic capacitor electrode according to the present invention, the aluminum purity is 9%.
The requirement of 9.9% or more is that at a purity of less than 99.9%, the growth of etching pits is hindered by the presence of many impurities at the time of etching, and even with the trace addition element of the present invention, a uniform deep tunnel is obtained. This is because it is not possible to form an etching pit in the shape of a circle, and thus it is impossible to obtain an aluminum foil having a high capacitance. Preferably, the aluminum purity is 99.95% or more.

In addition, Cu, Sb, and Ga, which are basic contained elements, independently improve the etching characteristics, and coexist with each other to suppress the growth rate of recrystallized grains after heating, thereby suppressing coarsening of crystal grains. It has an effect and contributes to increase in capacitance and maintenance of foil strength. That is, Cu
The solid solution in the matrix increases the solubility of the foil, promotes the growth of etching pits, and increases the capacitance. If the Cu content is less than 2 ppm, such effects are poor. If the Cu content is more than 30 ppm, local dissolution is strengthened, disturbing the uniform distribution of etching pits, and lowering the capacitance. The lower limit of the preferred Cu content is 5 ppm, and the upper limit is 20 pp.
m. Sb increases the capacitance by distributing the etching pits densely and uniformly. If the Sb content is less than 5 ppm, such an effect is poor, and
If it exceeds ppm, remarkable surface melting occurs, and a high capacitance foil cannot be obtained. Therefore, the Sb content is 5 to 10
The lower limit of the preferred Sb content is 5 ppm, and the upper limit is 50 ppm. Ga is A
l has the effect of promoting the growth of etching pits by increasing the solubility of the foil surface by forming a solid solution in the matrix.
If the Ga content is less than 5 ppm, the above effect is poor, and
Exceeding 0 ppm causes over-dissolution, so 5-100 ppm
Must be within the range. A particularly preferred lower limit of the Ga content is 5 ppm, and an upper limit is 20 ppm.

The effect of preventing the crystal grains from coarsening is as follows.
Even if it exceeds each upper limit of Cu, Sb, and Ga, it becomes larger, but on the other hand, the foil is excessively melted, and there is a decrease in etching characteristics exceeding the effect of suppressing the generation of coarse particles, and on the contrary, the capacitance decreases. . For this reason, in the present invention, the upper limit of the content of each of the above elements is set in the above-mentioned range.

Further, in the aluminum foil for an electrolytic capacitor electrode of the present invention, by adding Pb or Zn, or both elements in addition to the above basic contained elements in the foil alloy composition, the etching characteristics can be improved synergistically. Thus, the capacitance can be increased.

Pb has the effect of suppressing the local dissolution of etching pits at the beginning of etching by increasing the solubility of the foil surface, and can achieve a uniform distribution of etching pits. The content of such Pb is 0.1 pp
If it is less than m, the above effect is poor, and if it exceeds 5 ppm, excessive dissolution occurs, so it is necessary to be in the range of 0.1 to 5 ppm. A particularly preferred lower limit of the Pb content is 0.3 ppm, and an upper limit is 2 ppm.

Zn has an effect of promoting the growth of etching pits by increasing the solubility of the foil surface by forming a solid solution in the Al matrix. If the Zn content is less than 1 ppm, the above effect is poor, and if it exceeds 50 ppm, excessive dissolution occurs, so it is necessary to be in the range of 1 to 50 ppm. A particularly preferred lower limit of the Zn content is 5 ppm, and an upper limit is 20 ppm.

[0017]

Next, specific examples of the aluminum foil for an electrolytic capacitor electrode of the present invention will be described.

First, aluminum ingots of various compositions of Examples 1 to 11 and Comparative Examples 12 to 18 shown in Table 1 were face-cut, and then subjected to hot rolling and cold rolling (including intermediate annealing). The thickness was 100 μm. Intermediate annealing conditions are 250 ° C x
10 hours.

Each of the aluminum foils produced as described above was examined for the presence of coarse particles having a particle size of 1000 μm or more. Table 1 shows the results.

Next, each aluminum foil was etched under the following conditions, and then dried at 400 ° C. for 10 minutes.

[Etching Conditions] Pretreatment Liquid composition: 0.1% NaOH, liquid temperature: 30 ° C., time: 1 minute Electrolytic etching Liquid composition: 10% HCl + 0.1% H ₂ SO ₄ , liquid temperature: 40 ° C. Density: AC 60 Hz, 20 A / dm ² , Time: 8 minutes The bending strength of the dried foil was tested by the following method. Table 1 shows the results.

[Bending Test] Using an MIT type automatic bending tester based on JIS P8115, a test piece cut into a 10 mm × 150 mm strip was repeatedly bent at a curvature radius of 0.5 mm and a bending angle of 90 °. The number of times of bending was measured.

Further, the capacitance when the aluminum foil was converted to 20 V with ammonium phosphate (NH ₄ H ₂ PO ₄ ) 2 g / l, a liquid temperature of 90 ° C. and a current density of 10 mA / cm ² was measured. The result is shown as the capacitance of Comparative Example 12 being 1
Table 1 shows a relative comparison when the value is set to 00.

[0024]

[Table 1]

From the results in Table 1, it can be seen that Cu, Sb within the scope of the present invention.
In Examples where Ga and Ga coexisted, it was confirmed that there was no generation of coarse crystal grains after annealing and that the capacitance could be increased by etching, as compared with Comparative Examples deviating from the scope of the present invention.
It was also confirmed that by adding a predetermined range of Pb and Zn in addition to Cu, Sb and Ga, the capacitance could be further increased.

Further, it was also confirmed that the generation of coarse crystal grains was suppressed, so that the foil strength was not reduced even by drying after etching.

[0027]

The aluminum foil for an electrolytic capacitor electrode according to the present invention has an aluminum purity of 99.9% or more and a Cu content of 2 to 30 pp in the foil alloy composition.
m, Sb: 5 to 100 ppm and Ga: 5 to 100 ppm
, The growth of coarse crystals after the heat treatment is suppressed. Therefore, an extremely large surface area can be obtained by the etching process, and the aluminum foil for an electrolytic capacitor electrode having a large capacitance and excellent electrical characteristics can be obtained. Further, the foil strength is maintained by suppressing the growth of coarse crystals.

In the foil alloy composition, in addition to the basic elements of Cu, Sb and Ga, Pb: 0.1 to 5 ppm
Containing, Zn: 1 to 50 ppm,
Alternatively, Pb: 0.1 to 5 ppm and Zn: 1 to 50
In any case containing ppm, the solubility of the foil is further increased, and the aluminum foil for an electrode of an electrolytic capacitor having a larger capacitance can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadao Fujihira, 224 Kaiyamacho, Sakai City Showa Aluminum Co., Ltd.

Claims (4)

[Claims] 1. A foil alloy composition having an aluminum purity of 99.9% or more and Cu: 2 to 30 ppm.
, Sb: 5-100 ppm and Ga: 5-100 ppm
An aluminum foil for an electrode of an electrolytic capacitor, characterized by containing: 2. A foil alloy composition having an aluminum purity of 99.9% or more and Cu: 2 to 30 ppm.
, Sb: 5 to 100 ppm, Ga: 5 to 100 ppm, and Pb: 0.1 to 5 ppm. 3. The foil alloy composition has an aluminum purity of 99.9% or more and Cu: 2 to 30 ppm.
, Sb: 5 to 100 ppm, Ga: 5 to 100 ppm, and Zn: 1 to 50 ppm. 4. In the foil alloy composition, the aluminum purity is 99.9% or more and Cu: 2 to 30 ppm.
, Sb: 5-100 ppm, Ga: 5-100 ppm, P
b: An aluminum foil for an electrode of an electrolytic capacitor, characterized by containing 0.1 to 5 ppm and Zn: 1 to 50 ppm.