JP2626845B2 - Hard aluminum foil for anode of electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum foil for an anode of an electrolytic capacitor, and more particularly to a low pressure hard aluminum foil having a low chemical solubility in a hydrochloric acid-based electrolyte and a high capacitance.

[0002]

2. Description of the Related Art Since the capacitance of an electrolytic capacitor is proportional to the surface area of an applicable electrode, an aluminum foil used for an anode is subjected to an etching process to increase the surface area.

[0003] Usually, the etching of the aluminum foil for the anode is performed chemically or electrochemically in a hydrochloric acid-based electrolytic solution. However, in the electrochemical treatment, direct current, alternating current or alternating current is used depending on the working voltage in the end use. The AC / DC superimposed current is properly used. For example, the working voltage of the aluminum foil for the anode is
For low-voltage foils of 150 V or less, AC etching that can obtain fine etching holes of about 0.2 μm is applied.

Generally, a foil for low pressure has a thickness of 65 to 100 μm.
Although hard or soft aluminum foil is used, AC etching has not been influenced much by the structure (crystal orientation) unlike DC etching. However,
Strictly speaking, the hard foil is affected by the melting loss and the capacitance by the rolling reduction. This is because the non-energized time is interposed in the line etching, which results in a different result from the beaker etching.

[0005] The loss of dissolution during AC etching of a hard aluminum foil is caused by two factors, namely, the loss of electrolytic etching caused by a reaction by an AC current and the loss of chemical dissolution due to a chemical reaction with a hydrochloric acid-based electrolyte. Among them, the former electrolytic etching weight loss shows a value according to the theoretical value proportional to the amount of electricity to be supplied, but the latter chemical melting weight loss has a strong relationship with the purity of the aluminum foil, and when the impurity component is large, the chemical melting weight decreases. It is known to increase. For this reason, it has conventionally been a necessary condition to use an aluminum foil of as high purity as possible, and a method of obtaining an aluminum foil by dissolving an impurity component by heat treatment during production has been proposed ( JP-A-62-63656).

[0006]

However, even in an aluminum foil manufactured by regulating the amount of impurity components and the manufacturing conditions, the amount of chemical dissolution during AC etching shows a fluctuation and an increasing tendency, and the variation and decrease of the capacitance. May cause phenomena.

The inventor of the present invention has conducted a multifaceted investigation into the above-mentioned variation factors of the amount of dissolution, and as a result, in addition to the purity of the aluminum foil, the existence ratio of the cubic orientation in the rolling texture is involved. )
When the ratio ((100) / (110)) of the (100) plane satisfies the requirement of a certain value or less, the fact that the dissolution loss was significantly reduced and the capacitance was increased was clarified.

The present invention has been developed on the basis of the above-mentioned findings, and is intended for low-pressure applications which can reduce the amount of chemical dissolution in hydrochloric acid electrolyte and the range of fluctuation during the etching process and can provide a stable and high capacitance. It is an object of the present invention to provide a hard aluminum foil for an electrolytic capacitor anode.

[0009]

In order to achieve the above object, a hard aluminum foil for an anode of an electrolytic capacitor according to the present invention has a content of 0.0020 to 0.0100% Si and 0.0015 to 0.0085 Fe.
%, Cu 0.0010-0.0080%, other unavoidable impurities 0.0
10% or less, the balance being composed of the Al component,
The ratio of (100) plane to (110) plane ((100) / (110)) is 0.05
It is characterized by having the following rolling texture.

In the above structure, the specification of the content ranges of Si, Fe, Cu and unavoidable impurities is a requirement of the composition of the present invention, and the first requirement is that the hard aluminum foil satisfies this purity level. Requirements. Si is a functional component that enhances the self-solubility of aluminum. If its content exceeds 0.0100%, the dissolution loss increases. F
e also promotes the self-solubility of aluminum, and since the solid solubility limit is small, if the upper limit is not suppressed to 0.0085%, the dissolution loss increases remarkably. The lower limits of the contents of these components do not need to be limited in the technical sense, but are set to 0.0020% for Si and 0.0015% for Fe in view of the difficulty of high purification and cost. Although the Cu component has a large solid solubility limit, it exhibits a behavior of increasing the self-solubility of aluminum by making the potential noble, so that the Cu component needs to be within the range of 0.0010 to 0.0080%. In addition, other unavoidable impurities exceeding 0.010% cause an increase in chemical dissolution loss.

A second requirement of the present invention is that the hard aluminum foil has a rolled texture in which the ratio of the (100) plane to the (110) plane [(100) / (110)] of the hard aluminum foil is 0.05 or less. That is. Since the aluminum foil manufactured for hard low-pressure applications has a rolled texture, the crystal morphology measured by X-ray diffraction occupies most of the (110) plane in the rolling direction and extremely small in the (100) plane in the cubic direction. Although there is only a small amount, in the present invention, in particular, by selecting the above-mentioned crystal plane ratio, it is possible to effectively reduce the amount of loss of dissolution in the hydrochloric acid-based electrolyte and the fluctuation range, and to increase the capacitance.

The aluminum foil for the anode of an electrolytic capacitor is
It is manufactured by a process of rolling an aluminum ingot having a selected purity, but the low-pressure hard foil having the above-mentioned compositional and crystallographic requirements is used for solid solution of impurity components. Performing a homogenization treatment at a temperature of 540 to 620 ° C. for at least 1 hour or more in the step;
Then, no impurities were precipitated, and the ratio of the (100) plane in the cubic orientation to the (110) plane in the rolling orientation [(100) / (11)
0)] is set to 0.05 or less, and hot rolling and cold rolling can be performed. As an example of the condition, for example, hot rolling is performed in a range of 400 to 45.
Performed at a low temperature such as 0 ° C., and finished the hot rolling with a thickness of 10 m.
m, the rolling speed and the rolling reduction are reduced so that the temperature of the aluminum foil does not exceed 120 ° C.

[0013]

According to the present invention, the first requirement for specifying the impurity content is to reduce the chemical solubility loss by reducing the solid solubility limit and reducing the components that enhance the self-solubility of aluminum. Is a prerequisite functional requirement. The second requirement is to specify the crystal plane properties by reducing the number of crystal planes (100) in the cubic orientation with high solubility and contributing to the reduction of dissolution and the fluctuation range and the improvement of the capacitance. Requirements.

The above-mentioned action based on the crystal plane properties is caused by the phenomenon that the solubility in the hydrochloric acid-based electrolyte varies depending on the crystal orientation, and the atom density is lower than those of the crystal planes (110) and (111). This is brought about by reducing the proportion of highly soluble (100) planes within certain limits. That is, the solubility of the crystal plane is in the relationship of (100)>(110)> (111),
If the ratio of the (100) plane to the (110) plane in the foil structure is suppressed to 0.05 or less, unnecessary dissolution (for example, dissolution of the etch pit cell wall) that does not contribute to the surface area is effectively prevented from progressing. In addition, a decrease in foil surface area is suppressed.

The function and function of these two requirements are synergistically combined to effectively reduce the chemical solubility during etching and improve the electrostatic capacity per amount of dissolution. Provision is possible.

[0016]

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

[0017] Ten kinds of aluminum ingots having different impurity components and crystal plane ratios (X-ray diffraction intensity ratios) shown in Table 1 were subjected to a soaking treatment in a temperature range of 540 to 620 ° C for 10 hours. Examples 1 to 4 and Comparative Examples 3 to 6 were heated to 400 to 450 ° C and hot-rolled to a thickness of 10 mm, and then cold-rolled so that the material temperature did not exceed 120 ° C. 5 for 1-2
Heated to 00 to 550 ° C and hot-rolled to a thickness of 3 mm,
Thereafter, cold rolling was performed by a usual method to produce an aluminum foil having a thickness of 0.1 mm. Then, each aluminum foil,
Immersed in an electrolyte consisting of 12.5% hydrochloric acid, 0.6% phosphoric acid and 0.5% nitric acid at a temperature of 45 ° C., and a current density of 30 A / d
The etching process was performed by applying an alternating current of m ² for 1 minute and 6 minutes.

[0018]

[Table 1]

The dissolution loss of each foil after the etching treatment was measured and is shown in Table 2 in comparison with the properties of the aluminum foil. Subsequently, each aluminum foil after the etching treatment was subjected to an addition treatment at 20 V in a 15% aqueous ammonium adipate solution, and the capacitance was measured with an LCR meter. The results are also shown in Table 2.

[0020]

[Table 2]

As is evident from the comparison between the examples in Table 2 and the comparative examples, Examples 1 to 4 satisfying the property requirements of the present invention have lower dissolution weight loss and fluctuation range than Comparative Examples 1 to 6 which do not satisfy the requirements. It can be seen that the capacitance has decreased and the capacitance has clearly improved.

[0022]

As described above, according to the hard aluminum foil for an anode of an electrolytic capacitor according to the present invention, the loss and dissolution of a hydrochloric acid-based electrolyte are reduced in the etching step, and a high level of capacitance is exhibited. In addition, since the etching efficiency is improved, the effect of relatively increasing the material strength of the aluminum foil of the core is also provided.

Claims (1)

(57) [Claims] (1) 0.0020-0.0100% of Si, 0.0015-0.
0085%, Cu 0.0010-0.0080%, other unavoidable impurities
0.010% or less, the balance being composed of Al, and the ratio of the (100) plane to the (110) plane of the crystal orientation [(100) / (110)]
A hard aluminum foil for an anode of an electrolytic capacitor, characterized by having a rolling texture of 0.05 or less.