JPS60175409A - Method of producing aluminum alloy foil for electrolytic condenser cathode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for manufacturing an aluminum alloy foil used as an electrolytic capacitor cathode, and in particular an etching method for improving the electrostatic capacity and high mechanical strength of the alloy foil. Regarding improvement.

In addition, in this specification, all "%" indicates [weight %J].

(Prior art) Generally, as an electrode for an aluminum electrolytic capacitor,
Aluminum foil with a purity of 99.9.9% or more is used for the anode, and aluminum foil with a purity of 99.0% or more is used for the cathode, especially 99.2~
Approximately 99.8% of these are used. In the past, in order to improve the performance of electrolytic capacitors, a lot of research has been carried out on trace additive elements and manufacturing processes, especially for anode foils, but recently, with the increase in demand for medium-voltage and low-voltage capacitors, Increasing the capacitance of cathode foils has become an increasingly important issue, and various studies have been conducted. There are some cases in which the effectiveness of nurturing has been reported (e.g., 4.4-2
No. 5016), but the current situation is that fully satisfactory results have not yet been obtained.

Incidentally, similarly to the anode foil, the cathode foil for an electrolytic capacitor is generally subjected to electrochemical or chemical etching in order to expand its effective surface area and increase the capacitance per unit volume. Such etching can be carried out using an aqueous solution of hydrochloric acid, common salt, or other chloride, and among these, an aqueous solution of hydrochloric acid is generally used. However, when a single bath of hydrochloric acid aqueous solution is used, a large surface area expansion rate cannot be expected, and a capacitance at Ov of only about 100 to 200 μF/ad can be obtained. Therefore, as an improvement measure, we added 0.01 to 10% nitric acid as an additive to the hydrochloric acid aqueous solution.
Phosphorus Al10.01-10%, Sulfuric acid 0.001-5゜0
%, by adding other inorganic acids and organic acids,
It has been known in the past that the area expansion ratio can be further improved. However, it is undeniable that the addition of these acids also tends to increase the amount of addition in order to obtain a large area expansion ratio, the melting loss of aluminum tends to increase slightly.
As a result, the surface magnification ratio is reduced and the mechanical strength of the foil is significantly reduced. Therefore, the amount added is limited to the relatively low concentration range mentioned above, and it is not always possible to obtain great satisfaction. However, there were problems in that it was difficult to achieve the effect of improving the area expansion ratio.

(Objective of the Invention) The present invention improves the problems of the prior art as described above, and makes it possible to provide an aluminum foil for an electrolytic condenser cathode with superior capacitance by significantly increasing the area expansion ratio. It is an object of the present invention to provide a method for producing the same, which can reduce the loss in dissolution and maintain high mechanical strength.

(Structure) For the above purpose, as a result of various experiments and researches, the present invention has found that, among the various additives mentioned above,
Even if the amount of acid added increases, the amount of dissolution loss of the foil increases little. Even if a hydrochloric acid aqueous solution with a high sulfuric acid content, which was considered impossible in the past, is used as an etching solution, by using a solution containing a certain amount of copper in the original language, extremely large surface enlargement can be achieved while suppressing dissolution loss. This was completed by discovering that it was effective.

Therefore, the present invention uses an aluminum alloy foil having an aluminum purity of 11% to 99.0% or more containing 2 to 0.6% of CUo, and using the aluminum alloy foil as an additive containing 3 to 20% of aluminum containing 5 to 20% of sulfuric acid. We have proposed a method for producing aluminum alloy foil for electrolytic condensation cathodes, which is characterized by electrolytic etching in a 13% hydrochloric acid aqueous solution. ' It is well known that the aluminum alloy foil used as the raw foil is required to have an aluminum purity of 99.0% or higher, and for practical purposes, it is recommended to use one with a purity of 99.2% or higher. desirable.

If the content of copper that should be contained in this aluminum alloy foil is less than 0.2%, it will have a poor effect in increasing the capacitance, and if the content exceeds 0.6%, the amount of melted copper will increase, resulting in an increase in electrostatic capacity. This results in a decrease in capacity and mechanical strength.

The most desirable copper content is approximately 0.3 to 0.5%.

The concentration of hydrochloric acid in the etching solution may be in the conventionally commonly used range, that is, in the range of 3 to 20%, and generally 7 to 15%. i! It becomes Maro's property. on the other hand,
The reason why the additive added to this hydrochloric acid aqueous solution is specifically limited to sulfuric acid is that, compared to the case of using other additives, even if the amount added is increased, the amount of dissolution loss of the aluminum alloy foil increases less. This is due to the scales, which maintain the mechanical strength of the foil well. However, adding it at a high concentration exceeding 20% is harmful because surface dissolution of the foil progresses, and the effect of increasing capacitance cannot be obtained. On the other hand, when the content is less than 5.0%, the effect of the additive is not sufficiently exhibited, and the desired effect of increasing the area expansion ratio cannot be achieved. The most preferable range of the amount of sulfuric acid added is:
It is about 10-15% coarse.

(Effects) According to the present invention, compared to aluminum alloy foils obtained by conventional methods, it has a significantly higher area expansion ratio and therefore has a higher capacitance, while at the same time having a smaller melt loss, It is possible to obtain an aluminum alloy foil for electrolytic capacitor cathodes that has high mechanical strength, and can improve the performance, miniaturize, and improve the performance of aluminum electrolytic capacitors.
It has the effect of contributing to weight reduction.

Example 1 Raw S: CU content 0.3%, Aj2 purity 99°5
%, thickness 0.1#Ill+ annealed aluminum alloy persimmon Etching solution composition: Aqueous solution of 10% hydrochloric acid and 5 to 30% sulfuric acid added Etching solution temperature: 260°C Current density: 2OA/dm Electricity = 700 Coulomb/dm Etching time = 70 seconds The capacitance at OV, dissolution loss, and tensile strength of each of the etched foils obtained above were measured, and the results were as shown in Table 1.

Table 1 (Effect of 11% additive) As can be seen from the results in Table 1, when sulfuric acid is added to the etching solution as an additive in the range of 5 to 20%, the capacitance increases significantly due to the increase in area expansion ratio. It is possible to increase the etching foil's mechanical strength by suppressing the dissolution loss to a low level.

Example 2 The amount of additive (sulfuric acid) added in the etching solution was 15%.
%, and the etching process was performed under the same conditions as in Example 1, except that the Cu content in the original language was varied in the range of 0.1 to 0.7%. Table 2 shows the results of measuring the capacitance of the various etched foils thus obtained.

Table 2 (Influence of GO content) ■Tubung solution: Hydrochloric acid 10% @ acid 15% From the results in Table 2, it is clear that copper is added to aluminum alloy foil by 0.2~
It can be seen that by using aluminum alloy foil with a content in the range of 0.6%, a relatively superior capacitance can be obtained compared to using an aluminum alloy foil that deviates from this range.

Therefore, by using an aluminum alloy foil containing copper in the above range and electrolytically coating it in an aqueous hydrochloric acid solution containing 5 to 20% sulfuric acid as described above,
By combining these, it is possible to obtain the desired excellent effect, that is, an aluminum alloy foil for an electrolytic capacitor cathode that has both high capacitance and high mechanical strength and has excellent performance.

that's all

Claims (1)

[Claims] Pure aluminum containing CI 0.2-0.6% [9
An aluminum alloy foil for an electrolytic capacitor cathode characterized by using an aluminum alloy foil of 9.0% or more and electrolytically etching it in a 3-20% aqueous solution of hydrochloric acid containing 5-20% @acid as an additive. Production method.