JP2602013B2 - Aluminum foil for electrolytic capacitors for etching - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aluminum foil for an electrolytic capacitor for an etching process.

2. Description of the Related Art Conventional technology and its problems In general, an aluminum foil for an electrolytic capacitor (hereinafter simply referred to as an aluminum foil) has a surface area enlarged by roughening by etching, thereby improving the capacitance. Conventionally, etching properties have been improved mainly by adding a small amount of alloying elements to Al foil.However, even when aluminum foil of the same component is used, the capacitance is increased due to differences in the foil making process. It is known to fluctuate.

Means for Solving the Problems The present inventor has conducted studies on various factors during the foil making process affecting the etching properties of the Al foil, and as a result, the inventors have specified that the content of impurities such as Fe is less than a certain limit. It has been found that when an oxide film having a withstand voltage is formed, the etching property can be improved and the capacitance can be increased accordingly. That is, the present invention is directed to an etching treatment in which an oxide film having a withstand voltage of 0.5 to 1.0 V is formed on an aluminum foil surface having a purity of 99.7% or more, Fe 0.17% or less, Si 0.07% or less, and Cu 0.005% or less. And aluminum foil for electrolytic capacitors.

The Al foil used in the present invention has a purity of 99.7% or more and a Fe 0.1%.
It must be 7% or less, Si 0.07% or less and Cu 0.005% or less. If the content of any one of Fe, Si and Cu exceeds these upper limits, the surface roughening efficiency at the time of etching is reduced and the stability of the electrolytic capacitor is hindered. There is a problem that it is not practical.

The withstand voltage of the oxide film formed on the Al foil surface is 0.
Must be 5 to 1.0 volts. If the withstand voltage is less than 0.5 volts, corrosion of the Al foil proceeds excessively during the etching operation, so that an increase in capacitance due to roughening cannot be expected. On the other hand, if the withstand voltage exceeds 1.0 volt, the precipitation of impurities, particularly Fe, is promoted to increase the chemical solubility of the Al foil, so that the capacitance is reduced.

As a method of forming an oxide film in the present invention, a method of holding an Al foil at about 100 to 200 ° C. in air for about 0.5 to 24 hours, Al
Examples include a method of anodizing the foil.

The Al foil of the present invention exhibits a high capacitance by being subjected to an etching treatment according to a conventional method. When the aluminum foil of the present invention is used as an anode foil or a cathode foil of an electrolytic capacitor, it can be used in the same manner as an existing aluminum foil.

Effect of the Invention According to the present invention, a purity of 99.9%
Capacitance of a wide range of Al foils for capacitors up to 9% medium and low pressure anode foils can be significantly improved.

Examples Hereinafter, examples will be shown to further clarify features of the present invention.

Example 1 99.98% purity, 0.006% Fe, 0.005% Si, 0.005% Cu
Rolled aluminum foil (thickness 0.1mm) at various temperatures in air
Heat treatment was performed for a time to form an oxide film.

The heat-treated Al foil is treated with HCl 10%, AlCl ₃
・ 6H ₂ O 5% and H ₃ PO ₄ 1% bath temperature 50 ℃, current density 5
AC etching treatment was performed at 0 A / dm ² for 3 minutes.

Next, the etching-treated Al foil was subjected to a chemical conversion treatment in an 8% ammonium borate solution by applying a direct current of 50 V at 30 ° C. for 20 minutes. Table 1 shows the relationship between the coating withstand voltage of the Al foil after the heat treatment and the capacitance of the resulting chemical conversion treated foil.

Example 2 99.98% purity, 0.006% Fe, 0.005% Si, 0.005% Cu
Was heat-treated at various temperatures in the air to form an oxide film.

Treated Al foil in a 20% NaCl bath at a temperature of 95 ° C and current density
DC etching treatment was performed at 50 A / dm ² for 2 minutes. Next, a chemical conversion treatment was performed under the same conditions as in Example 1. The capacitance of the resulting chemical conversion treated foil was measured, and the results are shown in Table 2.

Example 3 Rolled Al foil (thickness 0.05 mm) having a purity of 99.75%, Fe 0.16%, Si 0.06%, and Cu 0.00% was subjected to heat treatment at various temperatures.
An oxide film was formed.

The heat-treated Al foil is treated with HCl 10%, AlCl ₃
・ 6H ₂ O 5% and H ₃ PO ₄ 1% bath temperature 50 ℃, current density 5
AC etching treatment was performed at 0 A / dm ² for 2 minutes.

Table 3 shows the relationship between the coating withstand voltage of the Al foil after the heat treatment and the non-chemical capacitance of the obtained etch foil.

Example 4 Anodized aluminum foil having a purity of 99.98% was rolled and anodized in a 5% boric acid bath to give a film of 0.5 to 5V. Etching and chemical conversion treatment were performed in the same manner as in Example 1.
Table 4 shows the results.

As shown in Examples 1 to 4, the film withstand voltage was 0.5 to 1.0 Vo
Al foil with an oxide film within the range of lt (purity 99.7% or more)
Is excellent in the surface roughening efficiency at the time of electrolytic etching and clearly shows a high capacitance.

Claims (1)

(57) [Claims] (1) Purity is 99.7% or more, Fe is 0.17% or less, Si is 0.1% or less.
Aluminum foil for an electrolytic capacitor for etching processing, in which an oxide film with a film withstand voltage of 0.5 to 1.0 V is formed on the surface of an aluminum foil of 07% or less and Cu of 0.005% or less.