JPH11233382A - Aluminum alloy foil for electrode of electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy foil for the electrode of an electrolytic capacitor which is soft and has superior etching property. SOLUTION: A soft foil alloy composition has a composition of 99.9% or more Al purity, 0.0010 to 0.0100 wt.% for Si, 0.0010 to 0.0100 wt.% for Fe, 0.0005 to 0.050 wt.% for Cu, 0.0050 or less wt.% for Ga, and unavoidable impurities. The alloy satisfies the expression 0.15-20X<=Y<=0.70-20X, where Y is the ratio of the total amount of deposition of Fe and Si as measured by a thermal phenol dissolution method with respect to the total content of Fe and Si, and X is the Ga content (wt.%).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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. It is conventionally known to control the amounts of Fe and Si deposited as an effective means for increasing the surface area ratio by etching. In order to further improve the etching characteristics, the amounts of Fe and Si deposited are controlled. In addition to these, various proposals have been made regarding the precipitation amount of other elements.

[0003] For example, Japanese Patent Publication No. 3-61333 discloses that the total amount of Fe and Si deposited is 10 to 10% of the content of these elements.
An aluminum alloy foil regulated to 70% is described, and Japanese Patent Application Laid-Open No. Hei 8-209275 discloses an aluminum foil in which the amounts of Fe, Si and Cu deposited are regulated to 10 to 70%.

[0004]

However, in the case of a soft foil such as an O foil, it is not sufficient to improve the etching characteristics simply by controlling the content and the precipitation amount of Fe and Si, or even Cu, so that a sufficient static property can be obtained. In some cases, the capacity could not be obtained.

The present invention has been made in view of such technical background,
An object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor electrode which is a soft foil and has excellent etching characteristics.

[0006]

Means for Solving the Problems As a result of earnest studies, the inventors have found that Ga is effective for improving the etching characteristics of a soft foil, and have completed the present invention. That is, 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 a foil alloy composition and Si:
0.0010 to 0.0100 wt%, Fe: 0.0010
０．０0.0100 wt%, Cu: 0.0005 to 0.050
wt.%, Ga: a soft foil containing 0.0050 wt.% or less and unavoidable impurities, wherein the total amount of Fe and Si measured by the hot phenol dissolution method is the total amount of Fe and Si Ratio (Y) and Ga content (wt
%) And (X) satisfy the relationship of 0.15-20X ≦ Y ≦ 0.70-20X.

The aluminum alloy foil targeted in the present invention is a soft foil subjected to a heat treatment after cold rolling,
A typical example is an O 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, while the aluminum purity is high purity of 99.9% or more, Fe, Si,
Regulate the content of Cu and Ga.

The reason why the purity of aluminum is set to 99.9% or more is that if the purity is less than 99.9%, the amount of impurities increases, and
This is because, even if the contents of e, Si, Cu, and Ga and the amounts of Fe and Si deposited are controlled, overdissolution is likely to occur during etching, and the etching characteristics deteriorate.

The reason why the content of Fe and the content of Si are set to 0.0010 to 0.0100%, respectively, is that if the content exceeds the upper limit, it becomes difficult to control the amount of precipitation to a predetermined value. This is because the cost of purification is high to remove. The preferred upper limit of the Fe content is 0.0080 wt%, and the preferred upper limit of the Si content is 0.0080 wt%.

Cu has the effect of uniformly distributing the etching pits and improving the etching characteristics. If the Cu content is less than 0.0005 wt%, the above effect is poor,
If it exceeds 0.0050 wt%, the foil surface will be over-dissolved, so it is necessary to make it 0.0005 to 0.050 wt%.
A preferred lower limit of the Cu content is 0.0008 wt%, and a preferred upper limit is 0.010 wt%.

Ga has the effect of promoting the growth of etching pits and increasing the area coverage. As the Ga content increases, the formation of etch pits increases in the direction in which the natural electrode potential becomes noble, but if it exceeds 0.0050 wt%, overdissolution occurs on the foil surface, so it is set to 0.0050 wt% or less. There is a need. The preferred upper limit of the Ga content is 0.0040 wt%.
And 0.0 in order to effectively improve the area coverage.
005 wt% or more is preferable. The content is 0.005
Since the content is 0 wt% or less, it is considered that Ga is dissolved in the Al matrix without being precipitated.

In the present invention, Fe, Si, Cu and Ga are defined within the above-mentioned ranges, and then Fe and Si are defined.
The amount of precipitation is also specified. In the aluminum alloy foil, some of Fe and Si precipitate as Al-Fe-based precipitates or Al-Fe-Si-based precipitates. These precipitates serve as a starting point of etching due to a potential difference from the aluminum matrix and play an important role in the formation of etch pits, and the amount of deposition affects the area coverage by etching. Therefore, in the present invention, the amounts of Fe and Si deposited are expressed as Fe, Si and G
The range of the following formula (I) is defined in relation to the content of a. In FIG. 1, the range indicated by the formula (I) is shown by oblique lines.

0.15-20X ≦ Y ≦ 0.70-20X (I) where X = Ga content (≦ 0.005 wt%) Y = Total amount of Fe and Si deposited / Fe and Si The total content is defined as follows. The reason why the ratio of the amount of precipitation is defined in the range of the formula (I) is that when the ratio of the amount of deposition increases and Y> 0.70-20X, the sponge layer of the etching is over-dissolved. This is because if the ratio decreases and Y <0.15-20X, the dissolution does not proceed, and an improvement in the surface area cannot be expected.

The amounts of Fe and Si deposited in the formula (I) are measured by a hot phenol dissolution method. The hot phenol dissolution method uses the property that heated phenol dissolves only components other than precipitates in the aluminum alloy, that is, the aluminum matrix and solid solution components, but does not dissolve the precipitates. This is a method in which the precipitate is separated and the elements in the precipitate are quantitatively analyzed. Also, the method of measuring the amount of precipitation using the hot phenol dissolution method is that Cu and Ga are used in addition to Fe and Si.
This is because even in an aluminum alloy foil containing unavoidable impurities, precipitated Fe and Si can be selectively quantified.

Fe and Si by hot phenol dissolution method
An example of a procedure for measuring the amount of the precipitation of is shown below.

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 test piece 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 the phenol. Next, the precipitate, which is an insoluble component, is separated from the phenol solution by filtration, and the precipitate is dissolved in an acid.
Then, the solution of the precipitate is subjected to quantitative analysis of Fe and Si by an atomic absorption method, an ICP emission analysis method, or the like,
The individual precipitation amounts of Fe and Si are obtained.

Further, Fe and Si obtained by the above method are used.
Using the amount of precipitation, the weight of the test piece and the known Fe and Si contents, the ratio (Y) of the total amount of precipitation of Fe and Si to the total of the contents of Fe and Si was calculated. , Based on the known Ga content (X),
It is determined whether equation (I) is satisfied.

The amount of precipitation of Fe and Si can be controlled by adjusting the temperature and time of the intermediate annealing performed during the cold rolling.

The aluminum alloy foil for an electrode of an electrolytic capacitor of the present invention has aluminum purity, Fe, Si, Cu and Ga contents which are defined, and furthermore, by precipitating Fe and Si at a predetermined ratio, the foil can be sufficiently etched. Dissolution is achieved and overdissolution is suppressed.

[0021]

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

First, after aluminum slabs having the alloy compositions of Examples 1 to 4 and Comparative Examples 5 and 6 shown in Table 1 were chamfered,
Homogenization treatment is performed, hot rolling is performed at a hot rolling start temperature of 530 ° C., and cold rolling is performed by a conventional method to obtain a thickness of 100 μ
m of foil. Furthermore, about Examples 1-4, 350
Annealing was performed at 5 ° C. × 5 hours, and in Comparative Example 6, annealing was performed at 220 ° C. × 5 hours. In Comparative Example 5, heat treatment after rolling was not performed.

Next, for each aluminum foil, the amount of each of Fe and Si deposited was measured by the hot phenol dissolution method, and the ratio of the total amount of Fe and Si deposited to the total content of Fe and Si (Y) Was calculated. Further, the relationship between the ratio (Y) of the precipitation amount and the Ga content (X) is shown in FIG.

Next, the respective aluminum alloy foils were subjected to etching and chemical conversion treatments. Etching conditions are
The aluminum alloy foil is 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 and a sine of 20 Hz. Wave alternating current was applied for 560 seconds. In addition, the chemical conversion conditions were such that treatment was performed at 22 V in a 15% aqueous ammonium adipate solution.

Next, the capacitance of each chemically treated aluminum alloy foil was measured by an LCR meter. The results are shown in Table 1 as a relative comparison when the capacitance of Comparative Example 6 is set to 100.

[0026]

[Table 1]

From the results shown in Table 1, Examples 1 to 3 in which the proportions of the amounts of Fe and Si precipitated were controlled within the scope of the present invention,
It was confirmed that good capacitance was good.

[0028]

As described above, according to the present invention, the aluminum alloy foil for an electrolytic capacitor electrode according to the present invention has
Aluminum purity is not less than 99.9% and S
i: 0.0010 to 0.0100 wt%, Fe: 0.00
10-0.0100 wt%, Cu: 0.0005-0.0
Soft foil containing 50 wt%, Ga: 0.0050 wt% or less and unavoidable impurities, wherein F is measured by a hot phenol dissolution method based on the total content of Fe and Si.
Since the ratio (Y) of the total amount of e and Si deposited and the Ga content (wt%) (X) satisfy the relationship of 0.15-20X ≦ Y ≦ 0.70-20X, the etching is performed. Thus, the foil is sufficiently dissolved and the overdissolution is suppressed, the 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 the precipitation amount of Fe and Si in an aluminum alloy foil for an electrolytic capacitor electrode of the present invention.

Claims (1)

[Claims] 1. A foil alloy composition having an aluminum purity of 99.9% or more and a Si content of 0.0010%.
-0.0100 wt%, Fe: 0.0010-0.010
0 wt%, Cu: 0.0005 to 0.050 wt%, Ga:
A soft foil containing 0.0050 wt% or less and unavoidable impurities, wherein the ratio (Y) 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, An aluminum alloy foil for an electrolytic capacitor electrode, wherein the Ga content (wt%) (X) satisfies the following relationship: 0.15-20X ≦ Y ≦ 0.70-20X.