JPH0344411B2 - - 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 fine recesses on the surface at a high density, but if the etching becomes excessive, corrosion may occur. The weight loss is also excessive, resulting in a decrease in the capacitance of the foil, and
Mechanical strength also decreases. Therefore, the aluminum alloy foil for the cathode of an electrolytic capacitor must have a large capacitance and an appropriate amount of corrosion loss during etching without becoming excessive. An object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor cathode that can satisfy 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, at least one of the following: 0.1 to 1.0% copper, and 0.003 to 0.3% vanadium. It is characterized by containing seeds, and further containing 0.5% or less of iron as an impurity, with the remainder consisting of aluminum and unavoidable impurities. Silicon has the property of increasing the capacitance of aluminum alloy foil when it is included in aluminum, but silicon has the property of increasing the capacitance of aluminum alloy foil when its content is 0.5%.
If it is less than 1.0%, the above effect will be small, and if it exceeds 1.0%, it will not be possible to obtain a fine etched structure, resulting in small capacitance and excessive corrosion loss. Therefore, the silicon content should be selected within a range of more than 0.5% and less than 1.0%. The reason why silicon increases the capacitance of aluminum alloy foil is as follows. As is well known, the capacitance of foil is proportional to the surface area of the foil, but in order to increase the surface area of the foil, it is necessary to uniformly and densely create minute depressions on the surface of the foil by etching. It is. When silicon is contained in aluminum in an amount exceeding 0.5%, a structure in which silicon is finely and uniformly precipitated in an aluminum matrix can be obtained. Since this precipitated silicon is electrically much nobler than aluminum, it creates a large electrode potential difference with the aluminum matrix, and when it is etched, it preferentially corrodes the aluminum matrix, uniformly and uniformly covering the surface of the foil. Concavities are formed at high density.
However, if the silicon content exceeds 1.0%, the corrosion loss becomes excessive, making it impossible to obtain a fine etched structure, and the capacitance also decreases. By incorporating at least one of these into an aluminum alloy containing silicon, copper and vanadium lower the solid solubility limit of silicon, and also dissolve themselves in solid solution in an aluminum matrix, thereby preventing etching of the matrix. It has the property of increasing the properties of silicon and increasing the effects of silicon as described above. However, if each content is less than the above lower limit, the effect of improving etching properties is small, and if it exceeds the upper limit, etching becomes excessive and the capacitance decreases. Therefore, each content should be selected within the above range. The above aluminum alloy foil contains unavoidable impurities such as iron, but especially in the case of iron, if the content exceeds 0.5%, coarse Al-Si-
Because it crystallizes Fe compounds and inhibits the effect obtained by adding silicon as described above,
The content of iron among impurities should be less than 0.5%. Examples Next, examples of the present invention will be shown together with comparative examples. Seven types of alloys were made into foils using the usual foil-making method, then immersed in a 3% hydrochloric acid and 0.5% oxalic acid aqueous solution at a temperature of 60°C, and then passed through an alternating current at a current density of 30 A/dm ² for 1 minute. The capacitance was measured after etching for 30 seconds. The results were as shown in the table below.

[Table] As is clear from the table above, a certain amount of silicon,
Aluminum alloy foils containing copper, vanadium, and iron have much greater capacitance than those that do not. Effects of the Invention According to the aluminum alloy foil of the present invention, the capacitance increases and the corrosion loss does not become excessive and the strength does not decrease.

Claims (1)

[Scope of Claims] 1 Contains silicon in excess of 0.5% and 1.0% or less, contains at least one of 0.1 to 1.0% copper and 0.003 to 0.3% vanadium, and further contains 0.5% or less iron as an impurity. An aluminum alloy foil for an electrolytic capacitor cathode, the foil comprising: , and the remainder consisting of aluminum and inevitable impurities.