JP3248251B2 - Method for producing electrode foil for aluminum electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an electrode foil for an aluminum electrolytic capacitor.

[0002]

2. Description of the Related Art Generally, a capacitor element in an aluminum electrolytic capacitor is formed by winding a pair of aluminum foils together with insulating paper and impregnating a driving electrolyte. The electrode foil for aluminum electrolytic capacitors is roughened by subjecting its surface to electrochemical or chemical etching in a solution containing chlorine ions to increase the capacitance per unit area. The size and weight of electrolytic capacitors have been reduced. In particular, in the etching of the low-voltage electrode foil, an etching process using an alternating current is performed, and a high magnification ratio is obtained.

[0003] Here, the surface condition of the aluminum foil before the start of etching has a large effect on the surface roughening by AC etching, and may affect the capacitance of the aluminum foil after etching.

[0004] In actual etching treatment, in many cases, the purpose is to remove dirt such as lubricating oil during foil rolling and a natural oxide film remaining on the surface of the original aluminum foil, or to generate a starting point of etching corrosion. For example, immersion treatment in, for example, phosphoric acid or an alkaline aqueous solution is performed as pre-etching treatment.

[0005]

However, in the method using the immersion treatment, unevenness in the treatment occurs due to the surface condition of the aluminum foil, that is, contamination or a natural oxide film, or the effect is insufficient. In addition, there was a problem that a sufficient capacitance was not obtained.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a method of manufacturing an electrode foil for an aluminum electrolytic capacitor capable of obtaining a stable and high capacitance as compared with the conventional method. is there.

[0007]

In order to achieve the above-mentioned object, a method of manufacturing an electrode foil for an aluminum electrolytic capacitor according to the present invention comprises the steps of: Sulfuric acid concentration 3 ~
In an aqueous solution containing 25 wt% as an essential component, 0.05 to 0.1% is used.
An etching process using a direct current is performed by applying a current density of 3 A / cm ² .

[0008]

According to the above-mentioned manufacturing method, before the etching treatment of the aluminum foil by the alternating current, the hydrochloric acid concentration is 3 to 1%.
Water with essential components of 0 wt% and sulfuric acid concentration of 3-25 wt%
Apply current density of 0.05-0.3 A / cm ^{2 in} solution
And because it to perform etching treatment by direct current, it is possible to dirt and spontaneous oxide film on the surface of the aluminum raw foil uniformly and sufficiently removed, as a result,
A uniform protective film can be formed on the surface of the minium foil. This protective coating is porous, and the portion other than the pores is inactive because it is covered with the coating, but the portion of the pores is eroded by chlorine ions and becomes active. Therefore, if an etching process using an alternating current is performed thereafter,
Corrosion from the active portion on the surface of the aluminum foil, that is, the hole portion occurs uniformly and at high density, and corrosion from the inactive portion does not occur, so that a high capacitance can be stably obtained.

[0009]

Embodiments of the present invention will be described below.

In an embodiment of the present invention, 7 wt% HCl, 15 wt% H ₂ SO ₄ , 10 wt% are applied to the etching process using a DC current before the etching process using an AC current.
Using an aqueous solution of AlCl ₃ , a direct current having a current density of 0.3 A / cm ² was applied to the aluminum foil for 10 seconds in an aqueous solution at a liquid temperature of 80 ° C. Thereafter, an etching process using an alternating current is performed with 8 wt% HCl, 2 wt% AlC
l ₃ , in an aqueous solution at a liquid temperature of 35 ° C, a current density of 0.3 A / c
The test was performed for 420 seconds with an alternating current of m ² and a frequency of 60 Hz.

As a comparative example, 3 wt% N was added to an aluminum foil before etching by an alternating current.
NaOH, in an aqueous solution of a liquid temperature of 50 ° C., subjected to immersion treatment by immersing for 180 seconds, thereafter, 8 wt% HCl etching treatment with alternating current, 2 wt% AlCl _3, the liquid temperature 3
In an aqueous solution at 5 ° C., current density 0.3 A / cm ² , frequency 6
The test was performed for 420 seconds with an alternating current of 0 Hz.

For each of the aluminum foils etched in the above-described Examples and Comparative Examples, 7
Comparing both the electrostatic capacity when carrying out the chemical conversion treatment at 0V, in the comparative example while a 16.3μF / cm ^2, in the embodiment of the present invention was 17.9μF / cm ^2.

As described above, the electrode foil for an aluminum electrolytic capacitor in the embodiment of the present invention is 10
% Can be obtained. This is because the etching process using the DC current of the embodiment of the present invention, which is performed before the etching process using the AC current, is less affected by the surface state of the aluminum foil as compared with the dipping process of the comparative example. By controlling, uniform and sufficient removal of surface dirt and natural oxide film can be performed electrochemically, and uniform and high-density corrosion is achieved by sulfuric acid which has a film-forming action contained in the processing solution. This is because a protective film that can generate a starting point is formed.

The concentration of hydrochloric acid in the etching solution by a direct current used in the embodiment of the present invention is preferably 3 to 10% by weight, and the concentration of sulfuric acid is preferably 3 to 25% by weight. The conditions for the DC etching treatment are 0.05 to 0.3 A.
/ Cm ² for 10 to 90 seconds. Further, the temperature of the treatment liquid is preferably from 20 to 90C, and more preferably from 60 to 90C.

[0015]

[0016]

As described above, according to the method for manufacturing an electrode foil for an aluminum electrolytic capacitor of the present invention, before the aluminum foil is subjected to the etching treatment with the alternating current, the hydrochloric acid is concentrated.
Indispensable components with 3-10 wt% degree and sulfuric acid concentration of 3-25 wt%
Current density of 0.05-0.3 A / cm ² in the prepared aqueous solution
Since the etching process is performed by applying a DC current by applying a temperature, an electrode foil for an aluminum electrolytic capacitor having a high capacitance can be obtained.

Continuation of the front page (56) References JP-A-52-133043 (JP, A) JP-A-2-84711 (JP, A) JP-A-57-66615 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) H01G 9/04 304

Claims (1)

(57) [Claims] 1. An etching method for an aluminum foil using an alternating current, wherein a hydrochloric acid concentration is 3 to 10 wt% and a sulfuric acid concentration is
In an aqueous solution containing 3 to 25 wt% as an essential component.
A method for producing an electrode foil for an aluminum electrolytic capacitor, wherein a current density of about 0.3 A / cm ² is applied to perform an etching treatment with a direct current.