JP4033539B2 - Aluminum alloy foil for electrolytic capacitor electrode - Google Patents

Description

【００２７】
表１の結果から、ＦｅおよびＳｉの析出量の割合をこの発明の範囲内に規制した実施例１〜３は、良好な静電容量が良好であることを確認できた。
【００２８】
【発明の効果】
以上の次第で、この発明の電解コンデンサ電極用アルミニウム合金箔は、箔合金組成において、アルミニウム純度が９９．９％以上であるとともに、Ｓｉ：０．００１０〜０．０１００wt％、Ｆｅ：０．００１０〜０．０１００wt％、Ｃｕ：０．０００５〜０．０５０wt％、Ｇａ：０．００５０wt％以下および不可避不純物を含有する硬箔であって、ＦｅおよびＳｉの含有量の合計に対し、熱フェノール溶解法により測定されるＦｅおよびＳｉの析出量の合計の割合（Ｙ）とＧａ含有量（wt％）（Ｘ）とが，
０．０２−４Ｘ≦Ｙ≦０．１５−２０Ｘ
の関係を満たすものであるから、エッチングによる箔の十分な溶解がなされかつ過溶解が抑制され、エッチピットの形成が適正に行われ、静電容量の増大を図ることができる。
【図面の簡単な説明】
【図１】この発明の電解コンデンサ電極用アルミニウム合金箔において、ＦｅおよびＳｉの析出量の割合を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum alloy foil for electrolytic capacitor electrodes.
[0002]
[Prior 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 the capacitance per unit area by expanding the effective area. In addition, as an effective means for increasing the surface expansion ratio by etching, it has been conventionally known to control the precipitation amount of Fe and Si, and in order to further improve the etching characteristics, the precipitation amount of Fe and Si. In addition to the above, various precipitation amounts of other elements have been proposed.
[0003]
For example, Japanese Patent Publication No. 3-61333 describes an aluminum alloy foil in which the total precipitation amount of Fe and Si is regulated to 10 to 70% of the content of these elements, and Japanese Patent Application Laid-Open No. 8-209275 discloses Fe, Si. An aluminum foil in which the amount of deposited Cu is regulated to 10 to 70% is disclosed.
[0004]
[Problems to be solved by the invention]
However, for hard foils such as H18 foil, if the precipitation amount of Fe and Si or Cu is further in the above range, over-dissolution often occurs during etching, and the total precipitation amount of Fe and Si is particularly 20 If it exceeds%, there is a problem that the loss of dissolution increases and the capacitance decreases.
[0005]
In view of such a technical background, an object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor electrode that is a hard foil and excellent in etching characteristics.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the aluminum alloy foil for an electrolytic capacitor electrode of the present invention has an aluminum purity of 99.9% or more in the foil alloy composition, Si: 0.0010 to 0.0100 wt%, Fe: 0.0010 to 0.0100 wt%, Cu: 0.0005 to 0.050 wt%, Ga: 0.0050 wt% or less and a hard foil containing inevitable impurities, with respect to the total content of Fe and Si, The total ratio (Y) of the precipitation amount of Fe and Si measured by the hot phenol dissolution method and the Ga content (wt%) (X) are:
0.02-4X ≦ Y ≦ 0.15-20X
The main point is to satisfy this relationship.
[0007]
The aluminum alloy foil targeted in this invention is a hard foil that is not annealed or stabilized after cold rolling, and a typical one is H18 foil. Further, it can be suitably used as a low pressure foil for forming a sponge-like etch pitch by AC etching.
[0008]
In the foil alloy composition, the aluminum purity is set to a high purity of 99.9% or more, and the contents of Fe, Si, Cu and Ga are regulated.
[0009]
The aluminum purity is set to 99.9% or more when the amount of impurities increases when it is less than 99.9%, and even when the Fe, Si, Cu and Ga contents and the precipitation amount of Fe and Si are controlled, This is because over-dissolution tends to occur and the etching characteristics deteriorate.
[0010]
The reason why the Fe content and the Si content are 0.0010 to 0.0100%, respectively, is that when the upper limit is exceeded, it becomes difficult to control the amount of precipitation, and Fe and Si are removed below the lower limit. This is because of the purification cost. A preferable upper limit of the Fe content is 0.0080 wt%, and a preferable upper limit of the Si content is 0.0080 wt%.
[0011]
Cu has an effect of improving etching characteristics by uniformly distributing etching pits. If the Cu content is less than 0.0005 wt%, the above effect is poor, and if it exceeds 0.0050 wt%, overmelting occurs on the foil surface, so it is necessary to be 0.0005 to 0.050 wt%. A preferable lower limit of the Cu content is 0.0008 wt%, and a preferable upper limit is 0.010 wt%.
[0012]
Ga has the effect of promoting the growth of etching pits and increasing the surface expansion ratio. As the Ga content increases, the natural electrode potential increases in a noble direction and the formation of etch pits increases. However, if it exceeds 0.0050 wt%, overmelting occurs on the foil surface, so the content is set to 0.0050 wt% or less. There is a need. A preferable upper limit of the Ga content is 0.0040 wt%, and 0.0005 wt% or more is preferable in order to effectively improve the surface expansion ratio. In addition, since content is 0.0050 wt% or less, it is thought that Ga does not precipitate but is dissolved in the Al matrix.
[0013]
In the present invention, Fe, Si, Cu, and Ga are defined in the above range, and the precipitation amount of Fe and Si is also defined. In the aluminum alloy foil, part of Fe and Si is deposited as an Al—Fe based precipitate or an Al—Fe—Si based precipitate. These precipitates serve as etching starting points due to a potential difference with the aluminum matrix and play an important role in the formation of etch pits, and the area expansion ratio due to etching depends on the amount of precipitation. Therefore, in the present invention, the range of the following formula (I) is defined in relation to the amounts of Fe and Si precipitated and the contents of Fe, Si and Ga. Further, the range indicated by the formula (I) in FIG.
[0014]
0.02-4X ≦ Y ≦ 0.15-20X (I)
However,
X = Ga content (≦ 0.005 wt%)
The ratio of the total precipitation amount of Y = Fe and Si / the total precipitation amount of Fe and Si is defined in the range of the formula (I) because the ratio of the precipitation amount increases and Y> 0.15-20X This is because the etching sponge layer is over-dissolved, and on the other hand, when the ratio of the amount of precipitation decreases and Y <0.02-4X, dissolution does not proceed and improvement of the surface expansion ratio cannot be expected.
[0015]
The precipitation amount of Fe and Si in the formula (I) is measured by a hot phenol dissolution method. With the hot phenol dissolution method, heated phenol dissolves components other than precipitates in the aluminum alloy, that is, only the aluminum matrix and solid solution components, but does not dissolve the precipitates. This is a method of quantitatively analyzing elements in the precipitate after separating the precipitate. In addition, the hot phenol dissolution method is adopted as a method for measuring the precipitation amount. In addition to Fe and Si, Cu and Ga are contained, and even in an aluminum alloy foil containing inevitable impurities, the precipitated Fe and Si are selected. This is because it can be quantitatively determined.
[0016]
An example of the procedure for measuring the amount of Fe and Si deposited by the hot phenol dissolution method is shown below.
[0017]
First, as a test piece, an aluminum alloy foil is appropriately cut, and dirt adhering to the surface is removed by washing and weighed. Next, the specimen is put into phenol heated to 170 to 180 ° C., and components other than the precipitate are dissolved while heating. Heating is performed while refluxing to prevent evaporation of phenol. Next, the precipitate which is an insoluble component is filtered off from the phenol solution, and the precipitate is dissolved in an acid. The precipitate solution is subjected to quantitative analysis of Fe and Si by an atomic absorption method, an ICP emission analysis method, or the like to obtain individual precipitation amounts of Fe and Si.
[0018]
Furthermore, using the Fe and Si precipitation amounts obtained by the above method, the weight of the specimen and the known Fe content and Si content, the total precipitation amount of Fe and Si with respect to the total Fe and Si content The ratio (Y) is calculated, and it is further determined whether or not the formula (I) is satisfied based on the known Ga content (X).
[0019]
In addition, the precipitation amount of Fe and Si can be controlled by adjusting the temperature and time of intermediate annealing performed in the middle of cold rolling.
[0020]
The aluminum alloy foil for electrolytic capacitor electrodes according to the present invention has a specified aluminum purity, Fe, Si, Cu and Ga contents, and further precipitates Fe and Si at a predetermined ratio, so that the foil can be sufficiently dissolved by etching. And over-dissolution is suppressed.
[0021]
【Example】
Next, specific examples of the aluminum alloy foil for electrolytic capacitor electrodes according to the present invention will be described.
[0022]
First, the aluminum slabs having the alloy compositions of Examples 1 to 3 and Comparative Examples 4 to 6 shown in Table 1 were subjected to homogenization treatment and then hot rolled at a hot rolling start temperature of 530 ° C. Cold rolling was performed by a conventional method to obtain a foil having a thickness of 100 μm. In Comparative Example 4, when the thickness was 0.6 mm during the cold rolling, intermediate annealing was performed at 240 ° C. for 6 hours to promote precipitation of Fe and Si.
[0023]
Next, for each aluminum foil, the individual precipitation amounts of Fe and Si are measured by a hot phenol dissolution method, and the ratio (Y) of the total precipitation amount of Fe and Si to the total content of Fe and Si is calculated. Asked. Furthermore, the relationship between the ratio (Y) of this precipitation amount and Ga content (X) is shown on FIG.
[0024]
Next, each aluminum alloy foil was subjected to etching and chemical conversion treatment. Etching conditions were as follows: an aluminum alloy foil was immersed in a solution of 17% hydrochloric acid + 0.04% sulfuric acid + 0.3% phosphoric acid + 0.6% nitric acid + 3% aluminum chloride at 35 ° C., and a current density of 0.3% A / cm ^2. A 20 Hz sine wave alternating current was applied for 560 seconds. Further, the chemical conversion conditions were such that the treatment was performed at 22 V in a 15% ammonium adipate aqueous solution.
[0025]
Next, the electrostatic capacity of each aluminum alloy foil subjected to chemical conversion treatment was measured with an LCR meter. The results are shown in Table 1 as a relative comparison when the capacitance of Comparative Example 6 is 100.
[0026]
[Table 1]

[0027]
From the results of Table 1, it was confirmed that Examples 1 to 3 in which the ratio of the precipitation amount of Fe and Si was regulated within the scope of the present invention had good electrostatic capacity.
[0028]
【The invention's effect】
As described above, the aluminum alloy foil for an electrolytic capacitor electrode according to the present invention has an aluminum purity of 99.9% or more, Si: 0.0010 to 0.0100 wt%, Fe: 0.0010 in the foil alloy composition. ~ 0.0100wt%, Cu: 0.0005 ~ 0.050wt%, Ga: 0.0050wt% or less and hard foil containing inevitable impurities, dissolved in hot phenol with respect to the total content of Fe and Si The total proportion (Y) of Fe and Si precipitation measured by the method and Ga content (wt%) (X)
0.02-4X ≦ Y ≦ 0.15-20X
Therefore, the foil is sufficiently dissolved by etching and over-dissolution is suppressed, etch pits are properly formed, and the capacitance can be increased.
[Brief description of the drawings]
FIG. 1 is a graph showing the ratio of Fe and Si precipitation in an aluminum alloy foil for electrolytic capacitor electrodes according to the present invention.

Claims (3)

In the foil alloy composition, the aluminum purity is 99.9% or more, Si: 0.0010 to 0.0100 wt%, Fe: 0.0010 to 0.0100 wt%, Cu: 0.0005 to 0.050 wt%, Ga: Hard foil containing 0.0050 wt% or less and unavoidable impurities, and the ratio of the total amount of precipitation of Fe and Si measured by the hot phenol dissolution method to the total content of Fe and Si (Y ) And Ga content (wt%) (X)
0.02-4X ≦ Y ≦ 0.15-20X
An aluminum alloy foil for electrolytic capacitor electrodes, characterized by satisfying the relationship: An aluminum alloy etching foil obtained by electrochemically or chemically etching the aluminum alloy foil according to claim 1. An aluminum alloy foil for an electrolytic capacitor electrode for low pressure obtained by AC etching the aluminum alloy foil according to claim 1.

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