JPS6350849B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an aluminum alloy foil for an electrolytic capacitor cathode. In this specification, "%" refers to "% by weight". Conventional technology and its problems 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. In order to increase the capacitance of foil, it is effective to increase the surface area by etching the foil and forming minute depressions on the surface of the foil at a high density. In this case, the corrosion loss becomes excessive, and as a result, the capacitance of the foil decreases, and the mechanical strength also decreases. Additionally, in order to make capacitors smaller and lighter, it is necessary to reduce the thickness of the foil.
To achieve this, the strength of the foil must be increased. Therefore, the conditions that an aluminum alloy foil for an electrolytic capacitor cathode must meet are that it has a large capacitance, that the amount of corrosion loss during etching is not excessive but is an appropriate amount, and that it has a high mechanical strength. . Although various aluminum alloy foils for electrolytic capacitor cathodes have conventionally existed, the reality is that there has been no foil that satisfies all of the above three conditions. An object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor cathode that can satisfy all of the above conditions. Means for Solving the Problems The aluminum alloy foil for an electrolytic capacitor cathode according to the present invention contains more than 0.5% and less than 1.0% silicon, 0.2 to 2.0% manganese, and less than 0.5% iron as an impurity, It is characterized in that the remainder consists of aluminum and unavoidable impurities. Silicon and manganese have the property of increasing the capacitance of aluminum alloy foil when they are both contained in aluminum, but if the silicon content is less than 0.5% and the manganese content is less than 0.2%, the above-mentioned No effect was obtained, and the silicon content exceeded 1.0% and the manganese content
If it exceeds 2.0%, a fine etched structure cannot be obtained, so the capacitance of the foil becomes small and the weight loss due to corrosion becomes excessive. Therefore, the silicon content should be reduced to 0.5
% and 1.0% or less, manganese content 0.2%
Should be ~2.0%. The reason why the capacitance of aluminum alloy foil increases by containing both silicon and manganese is as follows. In other words, as is well known, the capacitance of aluminum alloy foil is proportional to the surface area of the foil, and in order to increase the surface area of the foil, fine recesses are uniformly and densely created on the surface of the foil by etching. There is a need. When aluminum contains more than 0.5% silicon and 0.2% or more manganese, it is possible to obtain a structure in which a large number of fine Al--Si--Mn compounds are dispersed in the aluminum matrix.
Since the Al--Si--Mn compound is potentially noble and has a large electrode potential difference with the aluminum matrix, the aluminum matrix is preferentially corroded during etching, resulting in uniform fine depressions on the surface of the foil. Moreover, it is formed with high density and its surface area increases. However, the silicon content
If the manganese content exceeds 1.0% and the manganese content exceeds 2.0%, the Al-Si-Mn compound becomes coarse and not uniformly dispersed in the alloy foil, making it impossible to obtain a fine etched structure and reducing the capacitance. decreases. The aluminum alloy foil according to the present invention contains impurities such as iron that are unavoidable during manufacturing.
If it exceeds 0.5%, coarse Al―Si―Mn― will form during casting.
The content of iron among impurities should be 0.5% or less, since it crystallizes Fe compounds and inhibits the effects obtained by adding silicon and manganese as described above. Examples Examples of the present invention will be described below along with comparative examples. After manufacturing foils from 16 types of aluminum alloys having the compositions shown in the table below using a normal foil manufacturing method, these alloy foils were immersed in an aqueous solution of 3% hydrochloric acid and 0.5% oxalic acid at a temperature of 60°C. Etching was performed for 1 minute and 30 seconds using an alternating current with a current density of 30 A/dm ² to measure the capacitance. The results were as shown in the table below.

[Table] As is clear from the above table, alloys L to P have a larger capacitance than alloys A to K. Effects of the Invention The aluminum alloy foil for an electrolytic capacitor cathode of the present invention contains more than 0.5% silicon and less than 1.0% silicon, and 0.2 to 2.0% manganese, so that fine Al--Si--Mn compounds form an aluminum matrix. It is possible to obtain a large number of tissues dispersed inside. Since the Al--Si--Mn compound is potentially noble and has a large electrode potential difference with the aluminum matrix, the aluminum matrix is preferentially corroded during etching, resulting in minute depressions on the surface of the foil. It is formed uniformly and densely, increasing its surface area and, as a result, significantly increasing its capacitance. Moreover, the corrosion loss does not become excessive. In addition, since it contains less than 0.5% iron as an impurity, coarse Al
-Si--Mn--Fe compounds can be prevented from crystallizing, and the effects obtained by adding silicon and manganese as described above are not inhibited.

Claims (1)

[Claims] 1 Silicon more than 0.5% and less than 1.0%, manganese 0.2-2.0%, and impurity iron 0.5%
An aluminum alloy foil for an electrolytic capacitor cathode containing the following, with the balance being aluminum and unavoidable impurities.