JP3218176B2 - Aluminum foil for electrolytic capacitor electrodes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Al foils generally used as electrode materials for aluminum electrolytic capacitors generally have an effective area which is increased to increase the capacitance per unit area.
An electrochemical or chemical etching process is performed.

[0003] However, a sufficient capacitance cannot be obtained simply by etching the foil. For this reason, generally, in the final annealing step after the foil rolling, a high-temperature heat treatment of about 450 ° C. or more is performed to improve the etching characteristics of the foil by forming a texture having many cubic orientations, or furthermore, an etch pit is used. In order to uniformly and densely distribute the alloy, addition of various trace elements has also been proposed from the viewpoint of the alloy composition of the foil.

[0004] An example of the latter aluminum foil to which a trace element is added is described in Japanese Patent Application Laid-Open No. 7-150279. This aluminum foil has a Pb: 0.1 to
By adding 5 ppm and Mg: 0.1 to 5 ppm, the etching characteristics are to be improved.

[0005]

However, the aluminum foil which has been subjected to the above-mentioned high-temperature heat treatment or the aluminum foil to which a trace element has been added can sufficiently satisfy the recent demand for higher capacitance of electrolytic capacitors. Did not get. In particular, there is room for improvement in the latter trace element addition amount.

The present invention has been made in view of such a technical background, and an object of the present invention is to provide an aluminum foil for an electrode of an electrolytic capacitor which can increase the capacitance.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have made intensive studies and found that the content of Mg in an aluminum foil composition was greatly increased by increasing the Mg content from that described in JP-A-7-150279. It has been found that the aluminum foil having a high capacitance can be obtained synergistically by adding various trace elements.

[0008] The present invention has been made based on this finding, and the first aluminum foil for an electrolytic capacitor electrode has an aluminum purity of 99.9% or more and Mg:
It is characterized by containing 20 to 50 ppm and Pb: 0.1 to 5 ppm. The aluminum foil for the second electrolytic capacitor electrode has an aluminum purity of 99.9%.
As described above, Mg: 20 to 50 ppm and Pb: 0.1 to
5 ppm, Zn: 1-50 ppm, G
a: 1 to 50 ppm, Fe: 5 to 60 ppm, Si: 5
To 80 ppm, Cu: 5 to 80 ppm.

In the two kinds of aluminum foils for electrolytic capacitor electrodes 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 etch pits during etching is inhibited by the presence of many impurities, and the presence of Mg and other trace elements within the scope of the present invention. This is because a uniform deep tunnel-like etch pit cannot be formed, and an aluminum foil having a high capacitance cannot be obtained. Preferably, the aluminum purity is 99.98% or more.

[0010] Mg in the aluminum foil is an element necessary for distributing pits with high density and uniformity during etching. That is, in general, in the initial stage of etching, unevenness of the surface existing on the foil surface, oils, deposits such as roll coating, or non-uniform local dissolving pits generated due to the deterioration thereof are generated, and the unevenness of the etch pit density is uneven. Property (sparse / dense), and in a significant case, the surface dissolves like a crater. This non-uniformity remains even after the end of the etching, causing a decrease in capacitance. In order to prevent such disadvantages, attempts have been made to control the causes of non-uniformity of the etch pits existing on these surfaces.
It has been found that g has the effect of eliminating the locality of the etch pits and having a high density. If the Mg content is less than 10 ppm as in the above-mentioned JP-A-7-150279, such an effect is poor. On the other hand, if it exceeds 100 ppm, the occupancy of the (100) crystal plane after the final annealing decreases, so that a high capacitance foil cannot be obtained. In addition,
When the occupation ratio of the (100) crystal plane is 95% or more, the capacitance can be increased. However, if the Mg content is within the above range, 95% or more can be achieved. Therefore, the Mg content needs to be 10 to 100 ppm , especially M
The lower limit of the g content is 20 ppm, and the upper limit is 50 ppm.
There is a need to.

Pb suppresses local solubility at the beginning of etching and contributes to uniform distribution of etch pits. Pb
When the content is 0.1 ppm, the above effect is poor, and the content is 5 ppm.
If it exceeds, the surface may be dissolved. for that reason,
The Pb content needs to be 0.1 to 5 ppm, the preferred lower limit is 0.3 ppm, and the preferred upper limit is 2.5 p.
pm. Further, since it is an element that exerts an effect in the initial stage of etching, it is preferable that it is present at a high concentration in the surface layer of the foil.

Furthermore, the trace element Z contained in the foil composition
As described in detail below, n, Ga, Fe, Si, and Cu each contribute to improving the etching characteristics of the foil, and the presence of at least one of them contributes to the above-described Mg and Pb.
In addition, the capacitance can be increased synergistically.
Each of these trace elements may be added alone, or two or more of them may be added, and a synergistic effect corresponding to each action is obtained.

Zn dissolves in the Al matrix to increase the solubility of the foil, promote the growth of etch pits, and increase the capacitance. If the Zn content is less than 1 ppm, the above effect is poor, and if it exceeds 50 ppm, the local solubility is enhanced and the uniform distribution of etch pits is hindered.
Therefore, the Zn content needs to be 1 to 50 ppm, a preferable lower limit is 8 ppm, and a preferable upper limit is 20 ppm.
ppm.

Ga is an element that easily segregates at a crystal grain boundary or a sub-grain boundary, and alone causes an uneven distribution of etch pits.
In the presence of g, there is an effect of improving the uniform dispersibility of the etch pit. If the Ga content is less than 1 ppm, the above effect is poor, and if it exceeds 50 ppm, the local solubility is enhanced and the uniform distribution of etch pits is hindered. Therefore, the Ga content is 1
Ｐｐｍ50 ppm, and a preferred lower limit is 8 p
pm, and a preferred upper limit is 20 ppm.

Fe and Si easily form a compound with Al in the matrix, and by controlling the dispersion state of these elements, the Mg concentration distribution can be made uniform and, consequently, the etch pit distribution can be made uniform. Can be In such an effect, Fe and Si are equivalent, and at least one of them may be contained. However, if the content is too large, it causes overdissolution during etching, and the capacitance is reduced. Therefore, the Fe content is 5 to 60 pp
m, with a preferred lower limit of 10 ppm and a preferred upper limit of 30 ppm. Further, the Si content needs to be 5 to 80 ppm, and a preferable lower limit is 1 ppm.
5 ppm, a preferred upper limit is 40 ppm.

By dissolving Cu in the Al matrix, Cu increases the solubility of the foil, promotes the growth of the etch pits, forms deep etch pits, and increases the capacitance. If the Cu content is less than 5 ppm, the above effect is poor, and if it exceeds 80 ppm, the local solubility is enhanced and the uniform distribution of etch pits is hindered. Therefore, the Cu content needs to be 5 to 80 ppm, and a preferable lower limit is 15 ppm and a preferable upper limit is 60 ppm.

[0017]

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

First, aluminum ingots having various compositions shown in Table 1 were chamfered, then hot-rolled and cold-rolled (including intermediate annealing), and further subjected to final annealing to finally have a thickness of 1 mm.
A 00 μm aluminum foil was produced.

Next, each aluminum foil was etched under the following conditions, and then the capacitance when the obtained aluminum foil was converted to 250 V in a 5% boric acid solution was measured. The results are shown in Table 1 as a relative comparison when the capacitance of Comparative Example 19 was set to 100%. [Etching conditions] No pretreatment No primary etching liquid composition: 5% HCl + 10% H2 SO4, liquid temperature: 75 DEG C. Current density: DC 20 A / dm2, time: 80 seconds Secondary etching liquid composition: 5% HCl, liquid temperature: 75 ° C, current density: DC 5A / dm2, time: 10 minutes

[0020]

[Table 1]

From the results shown in Table 1, it was confirmed that the product of the present invention containing Mg and Pb in the range of the present invention can increase the capacitance as compared with the comparative product outside the range of the present invention. Furthermore, it was confirmed that those containing one or more trace elements in addition to Mg and Pb synergistically improve the etching characteristics and can further increase the capacitance.

[0022]

The first aluminum foil for an electrolytic capacitor electrode according to the present invention has an aluminum purity of 99.9%.
As described above, Mg: 20 to 50 ppm and Pb: 0.1 to
Since it contains 5 ppm, it is possible to increase the density of the etch pits, increase the depth and uniformly disperse them, and obtain an extremely large surface area by etching. Therefore, it is possible to provide an aluminum foil for an electrolytic capacitor electrode having a large capacitance and excellent electrical characteristics.

The second aluminum foil for an electrolytic capacitor electrode has an aluminum purity of 99.9% or more,
g: 20 to 50 ppm and Pb: 0.1 to 5 ppm, Zn: 1 to 50 ppm, Ga: 1 to 50
ppm, Fe: 5 to 60 ppm, Si: 5 to 80 pp
m, Cu: contains at least one of 5 to 80 ppm, so that the etching characteristics are synergistically improved, and the electrical characteristics having a larger capacitance than the first aluminum foil are more excellent. An aluminum foil for an electrolytic capacitor electrode can be formed.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tomoaki Yamanoi 6,224 Kaiyamacho, Sakai City Showa Aluminum Co., Ltd. (72) Inventor Yutaka Kato 6,224 Kaiyamacho Sakai City, Showa Aluminum Co., Ltd. ( 72) Inventor Kenji Gosho 6, 224 Kaiyama-cho, Sakai City, Showa Aluminum Co., Ltd. (72) Inventor Shigeru Endo 6, 224 Kaiyama-cho, Sakai City, Showa Aluminum Co., Ltd. (56) References 5-5145 (JP, A) JP-A-7-235457 (JP, A) JP-A-7-150279 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/042 H01G 9/055

Claims (2)

(57) [Claims] (1) an aluminum purity of 99.9% or more;
Mg: 20 to 50 ppm and Pb: 0.1 to 5 ppm
An aluminum foil for an electrode of an electrolytic capacitor, comprising: 2. The method according to claim 1, wherein the aluminum purity is 99.9% or more.
Mg: 20 to 50 ppm and Pb: 0.1 to 5 ppm
And Zn: 1 to 50 ppm, Ga: 1 to 5
0 ppm, Fe: 5 to 60 ppm, Si: 5 to 80 pp
m, Cu: An aluminum foil for an electrolytic capacitor electrode containing at least one of 5-80 ppm.