JPH05461B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an aluminum alloy for electrolytic capacitor cathode foil. Prior Art In order to increase the capacitance of an aluminum electrolytic capacitor and improve its performance, it is necessary to increase the capacitance of not only the anode aluminum foil but also the cathode foil. For this reason, the cathode foil is generally subjected to chemical or electrochemical etching treatment to expand the effective area and increase the capacitance per unit volume. Research has been conducted on the material composition of cathode foils. Aluminum alloy cathode foils containing approximately 0.1 to 0.5 wt% of Cu have been known as cathode foils with improved etching properties (e.g., JP-A-56-133444, JP-A-62-149858). issue). Problems to be Solved by the Invention However, when a cathode foil containing Cu is used in an electrolytic capacitor, the Cu in the foil may precipitate, increasing leakage current and even causing damage to the capacitor body. It was found that this occurs. The present invention has been made in view of the above circumstances, and provides an electrolytic capacitor that can be used as a cathode foil that does not cause damage due to increased leakage current when used in a capacitor, even though it has a high capacitance. The purpose is to provide an aluminum alloy for cathode foil. Means for Solving the Problems In order to achieve the above object, an aluminum alloy for cathode foil according to the present invention has a Ni content of 0.001 to 0.005wt.
%, Fe: 0.05 to 0.2wt%, Si: 0.1wt% or less, and Ti: 0.0015wt% or less as unavoidable impurities.
Cu, Mn, Mg, Cr, Zn, V, B: 0.005wt% each
The content thereof is regulated as follows, and the remainder consists of aluminum and other unavoidable impurities. In the above, Ni increases the etching starting point in the etching process for increasing the surface area, thereby contributing to an improvement in the area enlargement ratio and thus an increase in the capacitance. However, 0.001wt%
If the content is less than (10ppm), the effect will be poor,
On the other hand, if it exceeds 0.005 wt% (50 ppm), excessive surface dissolution prevents the improvement of the area expansion ratio, resulting in an inability to increase the capacitance, and increases corrosion loss, resulting in a decrease in mechanical strength. Like Ni, Fe also increases the etching starting point and contributes to increasing the capacitance. However, if the content is less than 0.05wt% (500ppm), the above effects will be poor;
If it exceeds this value, the formation of cube-oriented crystals in the crystal structure after annealing the aluminum foil is suppressed, the growth of etching pits is hindered, and the capacitance is reduced.
A particularly preferable content of Fe is 0.05 to 0.15 wt%. Si contributes to the uniformity and stability of etching, but if it exceeds 0.1 wt% (1000 ppm), it has no effect and the amount dissolved on the surface increases, resulting in a decrease in capacitance. Therefore, it must be contained in a range of 0.1 wt% or less, preferably 0.05 wt% or less. In addition to the above essential elements, Ga0.005~0.02wt% (50~
200ppm) may be included. Mn, Mg, Cr, Zn, V as inevitable impurities,
If a large amount of B is contained, the etching properties will deteriorate, resulting in excessive surface dissolution and a decrease in capacitance. Therefore, the content of each of Mn, Mg, Cr, Zn, V, and B must be regulated to 0.005 wt% (50 ppm) or less. Particularly preferably 0.003wt%
It is good to be regulated as follows. Similarly, Ti, which is an unavoidable impurity, also hinders the increase in capacitance, so it is desirable to reduce it as much as possible. but,
Ti content is allowed within a range of 0.0015 wt% or less because its harmful effects are small if it is within a range of 0.0015 wt% (15 ppm) or less. In addition, Cu is an unavoidable impurity, and if it is used in an electrolytic capacitor, if it is contained in a large amount, there is a danger that it will precipitate and increase leakage current or destroy the capacitor body. ) must be regulated below, preferably below 0.002wt%. The production of the aluminum alloy electrolytic capacitor cathode foil according to the present invention may be carried out according to a conventional method.
For example, after casting a slab from molten aluminum by a vertical or horizontal semi-continuous casting method, this slab may be hot-rolled, cold-rolled, and foil-rolled into a foil having a thickness of about 30 to 60 μm. The foil thus produced is generally softened by annealing and then electrochemically or chemically etched to enlarge the effective area of the foil surface, thereby forming an electrolytic capacitor cathode foil. Effects of the Invention According to the aluminum alloy for electrolytic capacitor cathode foil according to the present invention, as is clear from consideration of the examples described later, it has a large capacitance even though it does not substantially contain Cu. It becomes possible to provide a cathode foil having Moreover, since it does not substantially contain Cu, even when the cathode foil is used in an electrolytic capacitor, there is no increase in leakage current as in the conventional case.
The risk of damage to the capacitor can be avoided. Examples Next, examples of the present invention will be described. A slab is cast by a semi-continuous casting method from molten aluminum whose component amounts are adjusted to the content shown in Table 1 below, and then hot rolled, cold rolled, and then foil rolled by conventional methods to obtain a 50 μm thick foil. was produced. Next, this foil was annealed to soften it, and then immersed in a mixed aqueous solution of 7% hydrochloric acid, 0.2% phosphoric acid, and 0.2% nitric acid at a temperature of 55°C ± 1°C, with a current density of 60A/d. Etching was performed for 135 seconds using an alternating current of ² to form a cathode foil. Each of the cathode foils obtained above was immersed in a mixed aqueous solution of 5% boric acid and 5% citric acid (temperature: 30°C), and the capacitance was measured using an AC universal bridge. The results are also shown in Table 1.

[Table] As is clear from the results shown in Table 1, according to the alloy of the present invention, the capacitance of the cathode foil manufactured using the alloy can be extremely reduced while keeping the Cu content extremely low. I was able to confirm that it can be made even higher.

Claims (1)

[Claims] 1 Ni: 0.001-0.005wt%, Fe: 0.05-0.2wt%,
Si: Contains 0.1wt% or less, as an unavoidable impurity
Ti: 0.0015wt% or less, Cu, Mn, Mg, Cr, Zn,
V, B: An aluminum alloy for electrolytic capacitor cathode foil, characterized in that their contents are regulated to 0.005 wt% or less, and the remainder consists of aluminum and other unavoidable impurities.