JPH10223485A - 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 Cu and Sb in a definite ratio coexist in an aluminum foil alloy of specific purity. SOLUTION: Regarding a foil alloy composition, the purity of aluminum is at 99.9% or higher, 30 to 100ppm of Cu and 5 to 100ppm of Sb are contained, and a Cu content Ccu (in ppm) and an Sb content Csb (in ppm) satisfy a relationship of 10 Ccu+7Csb<=1350. In addition to Cu and Sb in the ranges which are used as fundamentally contained elements, one kind or two kinds out of 0.1 to 5ppm or Pb, 1 to 50ppm of Ga and 1 to 50ppm of Zn are contained, or one kind or two kinds out of 0.1 to 50ppm of Pb, 1 to 50ppm of Ga and 1 to 50ppm of Zn are contained. Thereby, it is possible to restrain coarse and large crystals from growing after their heating treatment.

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.

In an 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 conducted intensive studies and as a result, have found that Cu and S
It has been found that the coexistence of b can suppress the coarsening of the crystal grains after heating.

The aluminum foil for an electrode of an electrolytic capacitor of the present invention has been made based on such knowledge, and has an aluminum purity of 99.9 in the foil alloy composition.
% Or more and Cu: more than 30 ppm and 100 pp
m or less and Sb: 5 to 100 ppm, and Cu
Content C _Cu (ppm) and Sb content C _Sb (ppm) are 10C
_The basic point is that the relationship of _Cu + 7C _Sb ≦ 1350 is satisfied.

Further, the aluminum foil for an electrode of an electrolytic capacitor according to the present invention is characterized in that Cu and Sb in the above-mentioned range are used as basic elements, and P
b: containing 0.1 to 5 ppm, and in addition to these basic elements, Ga: 1 to 50 ppm or Zn: 1 to 50 ppm
Containing one or two of the above, Pb: 0.1 to 5 ppm, and Ga: 1 to 50
ppm or Zn: one or two of 1 to 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 therefore it is not possible to obtain an aluminum foil having a high capacitance. Preferably, the aluminum purity is 99.95% or more.

Further, the basic elements Cu and Sb
Has the effect of suppressing the growth of recrystallized grains after heating and the coarsening of crystal grains by coexistence, in addition to improving the etching characteristics independently, increasing the capacitance and maintaining the foil strength. Contribute. That is, Cu dissolves in the Al matrix to increase the solubility of the foil, promote the growth of etching pits, and increase the capacitance. When the Cu content C _Cu is 30 ppm or less, such an effect is poor. When the Cu content exceeds 100 ppm, local dissolution increases,
The uniform distribution of the etching pits is prevented, and the capacitance is reduced. Further, Sb increases the capacitance by distributing the etching pits densely and uniformly. When the Sb content C _Sb is less than 5 ppm, such effects are poor. When the Sb content exceeds 100 ppm, remarkable surface melting occurs, and a high capacitance foil cannot be obtained. Further, Cu
Due to the coexistence of Sb and Sb, in addition to the above effects, the coarsening of the crystal grains after annealing is suppressed, and the capacitance can be increased. However, when the Cu content C _Cu (ppm) and the Sb content C _Sb (ppm) both increase, the effect of preventing the coarsening of the crystal grains increases, but on the other hand, the foil is excessively dissolved, The etching characteristics are reduced more than the effect of suppressing the generation of coarse particles, and the capacitance is reduced. Therefore, in the present invention, the case where both Cu and Sb are contained in large amounts is excluded, and the Cu content C _Cu (ppm) and S
It is necessary that the b content C _Sb (ppm) is within the above range, and that the relationship of 10C _Cu + 7C _Sb ≦ 1350 is satisfied.

Accordingly, the Cu content C _Cu (p
pm) and the Sb content C _Sb (ppm) fall within the ranges shown in FIG. The lower limit of the particularly preferred Cu content C _Cu is 35 ppm, and the upper limit is 70 ppm. Particularly preferred Sb
The lower limit of the content C _Sb is 5 ppm, and the upper limit is 70 ppm.

Further, in the aluminum foil for an electrode of an electrolytic capacitor of the present invention, by adding Pb, Ga, and Zn to the foil alloy composition in addition to the above-mentioned basic contained elements, the etching characteristics are further improved so that the capacitance is improved. 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.

Both Ga and Zn have the effect of promoting the growth of etching pits by forming a solid solution in the Al matrix to increase the solubility of the foil surface. In such an effect, Ga and Zn are equivalent and may contain at least one kind. If the content of Ga and the content of Zn are less than 1 ppm, the above effects are poor.
If it exceeds 50ppm, it will cause over-dissolution, so 1-50ppm
Must be within the range. Particularly preferred Ga content, Z
The lower limit of the n content is 5 ppm and the 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, after the aluminum ingots of various compositions of Examples 1 to 13 and Comparative Examples 14 to 17 shown in Table 1 were face-cut, they were subjected to hot rolling and cold rolling (including intermediate annealing) to obtain a thickness. A 100 μm thick foil was further annealed. The intermediate annealing condition is 250 ° C. × 10 hours, and the final annealing condition is 50
0 ° C. × 5 hours.

With respect to each of the aluminum foils prepared as described above, the occupancy of the cube (100) orientation and the presence or absence of coarse particles having a particle diameter of 1000 μm or more were examined. Table 1 shows the results.

Next, each aluminum foil was etched under the following conditions, and then the capacitance when the obtained aluminum foil was formed under the following conditions was measured. The results are also shown in Table 1 by a relative comparison when the capacitance of Comparative Example 14 is set to 100.

[Chemical formation conditions] Liquid composition: boric acid 100 g / l, ammonium borate 0.9 g / l liquid temperature: 90 ° C., current density: 50 mA / cm ² , 250 V [etching conditions] pretreatment: none primary etching liquid Composition: 5% HCl + 10% H ₂ SO ₄ , liquid temperature: 80 ° C. Current density: DC 20 A / dm ² , time: 90 seconds Secondary etching Liquid composition: 5% HCl, liquid temperature: 85 ° C. Current density: DC 5 A / dm ² , time: 10 minutes

[Table 1]

From the results shown in Table 1, it can be seen that the examples in which Cu and Sb coexist in the range of the present invention have a higher cubic (100) orientation occupancy than the comparative examples that deviate from the range of the present invention, and that the coarse particles after annealing have a larger size. It was confirmed that there was no occurrence and that the capacitance could be increased by etching. In addition, Cu and Sb
In addition, it was confirmed that by adding Pb, Ga, and Zn in a predetermined range, the capacitance could be further increased.

[0023]

The aluminum foil for an electrolytic capacitor electrode according to the present invention has, in the foil alloy composition, an aluminum purity of 99.9% or more, Cu: more than 30 ppm and 100 ppm or less, and Sb: 5 to 100 ppm. , And Cu content C _Cu (ppm) and Sb content C _Sb (pp
m) satisfies the relationship of 10C _Cu + 7C _Sb ≦ 1350, so that the growth of coarse crystals after the heat treatment is suppressed, and the occupancy of the cubic (100) orientation is also increased. for that reason,
An extremely large surface area can be obtained by the etching treatment, and the aluminum foil for an electrolytic capacitor electrode having a large capacitance and excellent electric characteristics can be obtained. Further, the growth of coarse crystals is suppressed, so that the foil strength is also maintained.

In the foil alloy composition, Cu and S
In addition to the basic element b, Pb: 0.1 to 5 ppm, Ga: 1 to 50 ppm or Zn: 1 to 50 pp
m containing one or two of m, or
Pb: 0.1 to 5 ppm, Ga: 1 to 50 ppm or Z
In any case containing one or two of n: 1 to 50 ppm, the solubility of the foil is further increased, and an aluminum foil for an electrolytic capacitor electrode having a larger capacitance can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the content ranges of Cu and Sb in a foil alloy composition of an aluminum foil for an electrolytic capacitor electrode of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadao Fujihira 6224, Kaiyama-cho, Sakai City Showa Aluminum Co., Ltd.

Claims (4)

[Claims] In a foil alloy composition, aluminum purity is not less than 99.9%, Cu is more than 30 ppm and not more than 100 ppm and Sb is 5 to 100 ppm, and Cu content is C _Cu (ppm) and Sb. Content C _Sb (p
pm) satisfying the relationship of 10C _Cu + 7C _Sb ≦ 1350. 2. A foil alloy composition, which has an aluminum purity of 99.9% or more, Cu of more than 30 ppm and 100 ppm or less and Sb of 5 to 100 ppm, and a Cu content of C _Cu (ppm) and Sb. Content C _Sb (p
pm) satisfies the relationship of 10C _Cu + 7C _Sb ≦ 1350,
An aluminum foil for an electrolytic capacitor electrode, further comprising Pb: 0.1 to 5 ppm. 3. The foil alloy composition has an aluminum purity of 99.9% or more, Cu of more than 30 ppm and 100 ppm or less and Sb of 5 to 100 ppm, and Cu content C _Cu (ppm) and Sb content. Quantity C _Sb (ppm)
Satisfies the relationship of 10C _Cu + 7C _Sb ≦ 1350, and further contains one or two of Ga: 1 to 50 ppm or Zn: 1 to 50 ppm. 4. A foil alloy composition having an aluminum purity of not less than 99.9%, a Cu content of more than 30 ppm and 100 ppm or less and a Sb content of 5 to 100 ppm, and a Cu content of C _Cu (ppm) and Sb. Content C _Sb (p
pm) satisfies the relationship of 10C _Cu + 7C _Sb ≦ 1350,
Further, Pb: 0.1 to 5 ppm, and Ga: 1 to 50
ppm or Zn: an aluminum foil for an electrode of an electrolytic capacitor, characterized by containing one or two of 1 to 50 ppm.