JPS6135263B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy foil for electrolytic capacitor cathodes. In order to improve the performance of electrolytic capacitors,
It is necessary to increase not only the capacitance of the anode foil but also the capacitance of the cathode foil. To increase the capacitance of foil, it is effective to increase the surface area of the foil by etching it, but if there is a lot of corrosion loss during etching, the capacitance of the foil will decrease as a result. do. Therefore, the aluminum alloy foil for an electrolytic capacitor cathode must have a large capacitance and a small loss of corrosion during etching. An object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor cathode that can satisfy the above conditions. One of the aluminum alloy foils for electrolytic capacitor cathodes of this invention has a purity of 99.7% or more of aluminum used as a raw material, 0.03 to 0.5% of copper, and 0.03 to 0.5% of copper.
An aluminum alloy foil for an electrolytic capacitor cathode according to another invention of the present invention, which is characterized by containing 0.001 to 0.2% beryllium and having a total content of silicon and iron as impurities of 0.3% or less. The purity of the aluminum used as a raw material is 99.7% or more, and it contains 0.03-0.5% copper, 0.01-0.2% beryllium, 0.002-0.05% titanium, and the total content of silicon and iron as impurities. is 0.3% or less. In the above, the reason why the purity of aluminum used as a raw material is set to 99.7% or more is because if the purity is less than 99.7%, the effect of increasing the capacitance of the foil cannot be obtained. Copper has the property of increasing the capacitance of aluminum alloy foil when it is contained in aluminum. In other words, as is well known, the capacitance of foil is proportional to the surface area of the foil, and in order to increase the surface area of the foil, it is necessary to create recesses uniformly and densely on the surface of the foil by etching. . Iron is more noble than aluminum in terms of electrical potential, and has a higher potential than aluminum.
Because of its wide range of solid solution, when it is contained in aluminum, recesses are formed uniformly and densely on the surface of the foil during etching, compared to aluminum foil that does not contain it. However, if the copper content is less than 0.03%, it has no effect on increasing the capacitance of the foil, and if it exceeds 0.5%, etching becomes excessive and the number of depressions on the foil surface increases, while corrosion loss increases, resulting in Specifically, the capacitance decreases. Therefore, the copper content should be set to 0.03~
It should be selected within the range of 0.5%, but especially from 0.1 to
0.3% is preferred. Beryllium also has the property of increasing the capacitance of aluminum alloy foil when it is contained in aluminum.
In other words, since beryllium has a small solid solubility limit,
When it is included in aluminum, it is finely precipitated into the aluminum, so when this aluminum alloy foil is etched, more uniform and denser recesses are produced on the foil surface than with aluminum foil that does not contain beryllium. However, if the beryllium content is less than 0.001%, the effect of increasing the capacitance of the foil cannot be obtained, and if it exceeds 0.2%, the corrosion loss will increase. Therefore, the content of beryllium should be selected within the range of 0.001 to 0.2%, with 0.005 to 0.05% being particularly preferred. If the total content of silicon and iron as impurities exceeds 0.3%, even if the raw aluminum with a purity of 99.7% or more contains copper in the range of 0.03 to 0.5% and beryllium in the range of 0.001 to 0.2%, the foil The effect of increasing capacitance cannot be obtained. Therefore, the total content of silicon and iron as impurities should be below 0.3%. In the above, if the aluminum alloy foil contains 0.03% or more of copper in order to increase the capacitance, cracks may occur in the slab during the casting process of the alloy foil. The occurrence of this cracking poses a major problem in the production of foil. However, beryllium also has the property of preventing slab cracking, and can prevent this cracking to some extent. However, beryllium has the effect of preventing the cracking described above only when the beryllium content exceeds 0.02%.
Therefore, in order to completely prevent cracks from occurring in the slab during casting, the purity of the aluminum used as a raw material is 99.7% or more, and the purity of the copper is 0.03 to 0.5%.
%, beryllium by 0.001 to 0.2%, and the total content of silicon and iron as impurities is 0.3% or less. In the above, the titanium content was limited to less than 0.002% because it is not effective in preventing cracks from occurring in the slab when casting the slab during the foiling process of this aluminum alloy foil.
This is because if it exceeds 0.05%, the capacitance of the foil decreases. As mentioned above, the aluminum alloy foil for electrolytic capacitor cathodes of the present invention has a purity of 99.7% or more of aluminum used as a raw material, and contains copper to
Contains 0.03-0.5%, beryllium 0.001-0.2%,
The total content of silicon and iron as impurities is
Since it is 0.3%, the capacitance of this aluminum alloy foil is much greater than that of conventional foils, and the corrosion loss is small. Moreover, when the content of beryllium is 0.02 to 0.2%, cracks that occur in the slab during casting of the aluminum alloy foil can be prevented to some extent during the process of producing the aluminum alloy foil. In particular, in the second invention,
By containing titanium in the range of 0.002 to 0.05% in the aluminum alloy foil for an electrolytic capacitor cathode of the first invention, cracks that occur in the slab when the slab is cast during the foil manufacturing process of this alloy foil can be prevented. can be completely separated, making production easier and favorable in terms of production. Next, examples of the present invention will be shown together with comparative examples. The observation results of the presence or absence of cracks in the slabs during the foil-making process of the eight types of alloy foils shown in Table 1, as well as the observation results of the presence or absence of cracks in the slabs during the casting process of the eight types of alloy foils shown in Table 1. % hydrochloric acid and 0.5% oxalic acid aqueous solution, and etching was performed for 1 minute and 30 seconds through a photocurrent with a current density of 30 A/dm ³ . The results of capacitance measurements are shown in Table 2. 〓〓〓〓

【table】

[Table] As is clear from Table 2, the aluminum alloy foil for an electrolytic capacitor cathode of the present invention has a much greater capacitance than the control example. In particular, the aluminum alloy foil for an electrolytic capacitor cathode of the second invention can completely prevent cracks from occurring in the slab when the slab is cast during the foil manufacturing process. 〓〓〓〓〓

Claims (1)

[Claims] 1. The purity of aluminum used as a raw material is 99.7.
% or more, contains 0.03 to 0.5% of copper, 0.001 to 0.2% of beryllium, and has a total content of silicon and iron as impurities of 0.3% or less. 2 The purity of aluminum used as raw material is 99.7
% or more, containing 0.03 to 0.5% copper, 0.001 to 0.2% beryllium, and 0.002 to 0.05% titanium,
The total content of silicon and iron as impurities is
Aluminum alloy foil for electrolytic capacitor cathodes with a content of 0.3% or less.