JP2000091164A - Aluminum-clad material and aluminum foil for electrolytic capacitor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase capacitance and improve break resistance by cladding an Al reinforced layer that has an Al layer with a specific purity or higher, at the same time contains a specific amount of Sc, and has a remaining part being made of an unavoidable impurity onto at least one layer. SOLUTION: In Al foil for electrolytic capacitor electrode, an Al-clad material is subjected to foil rolling, Al purity is set to 99.8 wt.% or higher, at the same time Sc that is 5 ppm or higher and less than 2,000 ppm is contained, and a high-purity Al with an Al purity of 99.8 wt.% is clad on at least one surface of a reinforced surface where a remaining part is made of an unavoidable impurity. Or, an Al concentration is set to 99.8% or higher. At the same time, Sc that is 5 ppm or higher and less than 2,000 ppm, Fe that is 5-60 ppm, Si that is 5-80 ppm, and Cu that is 5-150 ppm are contained, and an etching layer made of high-purity Al with an Al purity of 99.8% or higher is clad onto at least one surface of the reinforced layer where a remaining part is made of an unavoidable impurity, thus improving a surface-spread rate and achieving both improved capacitance and strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002] In this specification, the term "aluminum" is used to include both aluminum and its alloys.

[0003]

2. Description of the Related Art An aluminum foil used as an electrode material of an aluminum electrolytic capacitor is required to be subjected to an electrochemical or chemical etching process in order to increase its effective area and increase the capacitance per unit area. Will be applied. In particular, there is a growing need for higher capacitance due to the demand for downsizing of components due to downsizing of products.

However, simply etching the foil cannot provide a sufficient capacitance. In order to improve the etching characteristics, a variety of alloy compositions such as adding a small amount of Pb or Cu, heat treatment methods, crystal structures, etc. Improvements have been made from the point of view.

[0005] On the other hand, the etching layer tends to be thicker with an increase in the surface area for higher capacitance, and it is difficult to secure the bending strength of the aluminum foil.

The present invention has been made in view of such technical background,
An object of the present invention is to provide an aluminum foil for an electrolytic capacitor electrode, which is excellent in etching characteristics and can realize high capacitance and has excellent bending strength, and an aluminum clad material as a material of the foil.

[0007]

In order to achieve the above object, the aluminum clad material of the present invention has at least one layer having an Al purity of at least 99.8 wt%,
A reinforcing layer containing 5 ppm or more and less than 2000 ppm of Sc and the balance of unavoidable impurities is clad, or at least one layer has an Al purity of 99.8 wt.
% And at least 5 ppm and less than 2000 ppm of Sc, 5 to 60 ppm of Fe, and 5 to 80 ppm of S
It is characterized in that a reinforcing layer containing i and 5 to 150 ppm of Cu, the remainder being inevitable impurities, is clad.

The aluminum foil for an electrolytic capacitor electrode according to the present invention is obtained by foil rolling the above-mentioned aluminum clad material and has an Al purity of not less than 99.8 wt% and contains Sc of not less than 5 ppm and less than 2,000 ppm. An etching layer made of high-purity aluminum having an Al purity of 99.8% or more is clad on at least one surface of the reinforcing layer whose remainder is made of unavoidable impurities;
Alternatively, while making the Al purity 99.8 wt% or more,
Sc of 5 ppm or more and less than 2000 ppm, 5 to 60 pp
m Fe, 5-80 ppm Si and 5-150 pp
An etching layer made of high-purity aluminum having an Al purity of 99.8% or more is clad on at least one surface of a reinforcing layer containing m of Cu and the remainder made of unavoidable impurities. Further, in the etching layer, it is preferable that 80% or more of crystal grains having a deviation angle of 10 ° or less from the cubic orientation {001} <100> on the foil surface.

In the aluminum clad material and the aluminum foil for an electrolytic capacitor electrode of the present invention, the reinforcing layer secures strength and elongation by adding a small amount of Sc. Generally, a high-purity aluminum foil for an electrode is exposed to a high-temperature atmosphere of 300 ° C. or more in a drying step or a chemical conversion step after etching. At this time, even if the hard foil is used, softening or recrystallization occurs, and the strength is reduced. In the case of soft foil,
Since the Al purity is high, the crystal grain size increases, the number of crystal grains in the thickness direction decreases, and elongation and bending strength decrease. In response to such a phenomenon, by adding a small amount of Sc to Al, recrystallization after final annealing can be delayed and recrystallized into fine grains, so that strength and elongation can be maintained even after recrystallization. . Then, by cladding the Sc-added reinforcing layer on the etching layer made of high-purity Al, an aluminum foil having excellent strength and elongation can be obtained without impairing the etching characteristics.

[0010] In the chemical composition of the reinforcing layer, the Al purity needs to be 99.8% or more in order to restrict the amount of impurities and prevent the etching characteristics from being deteriorated due to overdissolution.
If the Sc content is less than 5 ppm, the above effect is poor, and if it is 2,000 ppm or more, the effect is saturated and a large amount is wasted and the cost is increased.
It must be less than 00 ppm. A preferred lower limit of the Sc content is 50 ppm, and a particularly preferred lower limit is 2 ppm.
It is 00 ppm and the upper limit is 1000 ppm.

Further, in addition to Sc, a small amount of Fe, S
It is preferable to add i and Cu. The reason why Fe is added is that the effect of improving the bending strength by preventing the crystal grains from becoming coarse is recognized. When the Fe content is less than 5 ppm, the effect is not obtained. When the Fe content is more than 60 ppm, the recrystallization delay effect by Sc is reduced and the strengthening effect is reduced.
It is necessary to be 60 ppm. A preferred lower limit of the Fe content is 8 ppm, and a preferred upper limit is 50 ppm. The reason for adding Si is to suppress the coarsening of crystal grains. When the Si content is less than 5 ppm, coarse crystal grains are generated during recrystallization, and when the Si content exceeds 80 ppm, S
In order to reduce the recrystallization delay effect by c and reduce the strengthening effect, the content needs to be 5 to 80 ppm. A preferred lower limit of the Si content is 8 ppm, and a preferred upper limit is 50 ppm.
ppm. The reason for adding Cu is to suppress the coarsening of crystal grains. If the Cu content is less than 5 ppm, coarse grains are generated, and if it exceeds 150 ppm, the recrystallization retarding effect by Sc is reduced and the strengthening effect is reduced similarly to Fe and Si. Therefore, the Cu content needs to be 5 to 150 ppm. A preferred lower limit of the Cu content is 25 ppm, and a preferred upper limit is 80 ppm.

The aluminum clad material according to the first and second aspects has the reinforcing layer in at least one layer, and the composition of the other layers is not limited.

The aluminum foil for an electrolytic capacitor electrode according to any one of claims 3 to 5 is a foil in which an etching layer made of high-purity aluminum is clad on one or both sides of the reinforcing layer as a core material. These aluminum foils are the aluminum clad material according to claim 1 or 2, wherein one layer is composed of the reinforcing layer, and the high-purity aluminum layer clad on one or both sides of the reinforcing layer is reduced to a required thickness. It is manufactured by foil rolling. For the etching layer, high-purity aluminum having excellent etching characteristics of 99.8% or more, preferably 99.9% or more is used. Since the strength of the foil is ensured by the presence of the reinforcing layer, it is possible to increase the surface area of the etching layer and to increase the capacitance.

In order to secure the strength of the foil, it is preferable that the etching layer has a crystal structure having a high cubic orientation occupancy on the foil surface. This is because if the difference in cubic orientation of the etched surface is large, the amount of dissolution of the foil surface at the time of etching increases, the foil thickness becomes partially thin, and local strength is reduced. Further, by maintaining the foil strength, the area expansion ratio can be increased, and the capacitance can be increased. Since such an overdissolution phenomenon occurs in units of crystal grains, it is desirable that the number of crystal grains having a large deviation from the cubic orientation be as small as possible. Specifically, on the foil surface,
Angle of deviation from cubic orientation {001} <100> is 10 °
It is necessary that the following crystal grains occupy 80% or more,
In particular, a remarkable effect is obtained when occupying 95% or more. Such a crystal structure, the combination of intermediate annealing and light reduction rolling,
It is obtained by low-temperature (400 to 500 ° C) soaking heat treatment of the ingot and high-temperature heating (500 to 580 ° C) during final annealing.

The aluminum foil for an electrolytic capacitor electrode of the present invention does not limit the thickness of the foil or the ratio of the thickness of the reinforcing layer (core material) to the thickness of the etching layer. As a range in which an improvement in bending strength is recognized and a high capacitance can be ensured, a core material ratio of 10 to 60% for single-sided cladding and 5 to 40% for double-sided cladding can be recommended.

[0016]

Next, specific examples of the aluminum clad material and the aluminum foil for an electrode of an electrolytic capacitor of the present invention will be described in detail.

First, aluminum ingots having five compositions of b to f shown in Table 1 were sequentially subjected to face milling, hot rolling and cold rolling to produce a flat plate having a thickness of 5 mm. On the other hand, for the aluminum ingot of the composition a,
A 2.5 mm flat plate was prepared. And b to f are core materials,
Using the material a as an etching layer, an etching layer is clad on one or both sides of the core material in a combination and a core material ratio shown in Table 2 and subjected to hot rolling, cold rolling, and foil rolling, each having a thickness of 0.1 mm. Aluminum foil was manufactured. Further, these aluminum foils were placed at 550 ° C. × 10 in an Ar atmosphere.
The final annealing was performed under the conditions of a time and a heating rate of 50 ° C./hour.

With respect to the annealed foil, the cubic orientation of the crystal structure was examined, and the occupation ratio of crystal grains having a deviation angle of 10 ° or less from {001} <100> was examined. Table 2 shows the results.

Next, each of the manufactured aluminum foils was etched under the following conditions without any pretreatment.

Primary etching: liquid composition 5% HCl + 10% H ₂ S
O ₄ , liquid temperature 75 ° C, current density C. 20A / dm ² ,
Time 100 sec Secondary etching: liquid composition 5% HCl, liquid temperature 80 ° C., current density C. 5A / dm ² For 8 minutes, the bending strength of the etched foil was measured, and the bending strength of Comparative Example 1 consisting of only the etching layer was relatively evaluated as 100%. Further, after the chemical conversion treatment, the capacitance was measured, and Comparative Example 1 was relatively evaluated as 100%. Table 2 shows the results.

[0021]

[Table 1]

[0022]

[Table 2]

From the results shown in Table 2, it was found that the aluminum foil of the present invention has both excellent capacitance and bending strength. On the other hand, Comparative Example 1 consisting of only an etching layer
Has low bending strength, and 2,000 ppm of S
Comparative Examples 6 and 11 containing c have excellent bending strength, but are not disadvantageous in terms of cost because no further improvement in capacitance is observed.

[0024]

As described above, the aluminum clad material of the present invention has an Al purity of at least 99.8% by weight and a content of at least 5 ppm of 200 ppm.
A reinforcing layer containing less than 0 ppm of Sc and the balance being unavoidable impurities, or having an Al purity of at least 99.8 wt% and an S content of at least 5 ppm and less than 2,000 ppm.
The strength of the clad material is high because the reinforcing layer containing c, 5 to 60 ppm of Fe, 5 to 80 ppm of Si, and 5 to 150 ppm of Cu and the remainder is made of unavoidable impurities is clad.

Further, the aluminum foil for an electrolytic capacitor electrode of the present invention is characterized in that at least one surface of the reinforcing layer has an aluminum foil.
Since the etching layer made of high-purity aluminum having a purity of 99.8% or more is clad, the foil strength is improved, and the enhancement of the foil strength enables an increase in the area coverage, thereby increasing the capacitance. It becomes possible. Therefore, the etching characteristics are secured by the etching layer, and the bending strength and elongation as a foil are secured by the reinforcing layer to which a small amount of Sc is added. It has both capacity and strength.

Further, when the etching layer occupies 80% or more of crystal grains having a deviation angle of 10 ° or less from the cubic orientation {001} <100> on the foil surface, overdissolution due to etching is prevented. A decrease in foil strength is suppressed, and the area enlargement ratio can be further increased, so that a higher capacitance can be achieved.

Claims (5)

[Claims] (1) at least one layer having an Al purity of 99.8;
not less than wt% and 5 ppm or more and 2000 ppm
An aluminum clad material comprising: a clad reinforcing layer containing less than Sc and a balance of inevitable impurities. 2. At least one layer having an Al purity of 99.8.
not less than wt% and 5 ppm or more and 2000 ppm
An aluminum clad material comprising less than Sc, 5 to 60 ppm of Fe, 5 to 80 ppm of Si and 5 to 150 ppm of Cu, the remainder being clad with a reinforcing layer composed of unavoidable impurities. 3. An Al purity of at least 99.8% by weight, containing at least 5 ppm to less than 2,000 ppm of Sc, and a balance of at least one surface of a reinforcing layer composed of unavoidable impurities having an Al purity of at least 99.8%. An aluminum foil for an electrode of an electrolytic capacitor, characterized in that an etching layer made of pure aluminum is clad. 4. An aluminum alloy having an Al purity of at least 99.8 wt% and a Sc, 5 to 6 ppm of 5 ppm to less than 2000 ppm.
0 ppm Fe, 5-80 ppm Si and 5-15
An electrolytic capacitor electrode characterized in that an etching layer made of high-purity aluminum having an Al purity of 99.8% or more is clad on at least one surface of a reinforcing layer containing 0 ppm of Cu and the remainder made of unavoidable impurities. Aluminum foil. 5. The etching layer according to claim 1, wherein the etching layer comprises:
Angle of deviation from cubic orientation {001} <100> is 10 °
The aluminum foil for an electrolytic capacitor electrode according to claim 4 or 5, wherein the following crystal grains occupy 80% or more.