JPS6035513A - Method of producing aluminum foil for electrolytic condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing aluminum foil for electrolytic capacitors.

Conventionally, aluminum electrode foil used in aluminum electrolytic capacitor V is etched or left as is, then immersed in pure water and boiled to generate hydrated oxides on the surface. Then, this aluminum foil is immersed in a solution of boric acid, oxalic acid, etc., and a certain voltage is applied to form an oxide film of the desired thickness.

It is heated at a high temperature of several 100 degrees Celsius and further re-formed.

By the way, the hydrated oxide produced on the surface of aluminum foil by pure water boiling is a feather-like film with a porous surface, and even if a chemical conversion treatment is performed afterwards, this feather-like film will not turn into an oxide film. It remains on the surface of the oxide film. As an electrolytic capacitor, electrolysis occurs, which hinders loss improvement and capacity increase.

In order to improve this drawback, conventionally annealing is performed to remove the feather-like film that exists on the surface of the oxide film, but annealing requires high temperatures and increases manufacturing costs. There are drawbacks, such as damage to the normal film.

The object of the present invention is to improve the above-mentioned drawbacks, improve loss and capacity characteristics, and provide an inexpensive method for manufacturing aluminum foil for electrolytic capacitors.

In order to achieve the above object, the present invention provides a method for manufacturing aluminum foil for electrolytic capacitors in which aluminum foil is subjected to a chemical conversion treatment to form an oxide film, including a first treatment of boiling the aluminum foil in pure water; After the treatment, the aluminum foil is coated with an aluminum concentration of 2.0 after chemical conversion treatment or without chemical conversion treatment. The present invention provides a method for manufacturing an aluminum foil for an electrolytic capacitor, which comprises performing a second treatment of immersing the aluminum foil in a weak acid solution maintained at Oa/1 or less.

Hereinafter, the present invention will be explained based on examples.

First, a hydrated oxide is formed on the surface of the aluminum foil without performing a first treatment in which etched or plain aluminum foil is immersed in pure water and boiled.

Next, the boiled aluminum foil is immersed in a boric acid solution or an oxalic acid solution, and a voltage is applied to perform a chemical conversion treatment to form an oxide film of a predetermined thickness.

After chemical formation, a second treatment is performed in which the aluminum foil is immersed in a weak acid solution such as phosphoric acid, acetic acid, succinic acid, maleic acid, etc. for a predetermined period of time to remove the feather-like film on the surface.

At this time, the weak acid solution should have an aluminum concentration of 2.0 in particular.
g/λ or less, and if the aluminum foil surface exceeds this value, the reaction to dissolve the feather-like film decreases, and the improvement in loss characteristics and capacity characteristics decreases.

After the aluminum foil is treated with a weak acid solution, it is again immersed in a solution such as boric acid to perform a chemical conversion treatment, and the film damaged by the second treatment is repaired.

However, by immersing aluminum foil with hydrated oxide on its surface in a weak acid solution, it is possible to remove the feather-like film that hinders loss reduction and capacity increase. By setting the concentration to 2.0 g/λ or less, loss characteristics and capacity characteristics can be significantly improved. Furthermore, the cost is much lower than that of annealing treatment, and since annealing treatment is not required or the treatment time and number of times can be significantly reduced, manufacturing costs are reduced.

For example, etched aluminum foil is boiled in pure water at a temperature of 95°C or higher, and then heated in an ammonium borate solution with rl 5
Voltages of 0 V, 300 V, 450 V and 500 V are sequentially applied to form an oxide film by chemical conversion until the leakage current becomes 0.1 taA/at or less. After chemical formation, aluminum foil is
Immerse in phosphoric acid solution at aeo°C for 5 minutes. The concentration of the phosphoric acid solution is A...0.5 normal, B...0.6 normal,
C...1.0 regulation, and D...2.0) 14 constant 4
Name the type. 8 in phosphoric acid solution! ! After drinking, reconstitute with a voltage of 500V to reduce the leakage current to 0.111A1011 or less. Regarding the aluminum foil thus produced, the equivalent series resistance reduction rate and capacity increase rate with respect to the aluminum concentration in the phosphoric acid solution were measured, and the results shown in FIGS. 1 and 2 were obtained. As is clear from these figures, phosphorus m
When the m degree of aluminum in the solution exceeds 2.0a/1, the capacity increase rate and equivalent series resistance decrease rate decrease significantly, and the aluminum concentration of 2.0a11 or less is a necessary condition for improving each characteristic. It is clear that

Note that when the weak acid immersion treatment is performed, the weak acid remains in the oxide film, but phosphoric acid in particular has the effect of improving the water resistance of the oxide film, improving characteristics such as several times deterioration. Furthermore, weak acids such as acetic acid, citric acid, and succinic acid increase the capacity more than phosphoric acid.

As described above, according to the present invention, since the feather-like film on the surface of the oxide film can be effectively removed, loss can be reduced and capacity can be increased, and the manufacturing cost can be reduced and aluminum foil for hanging electrolytic capacitors A manufacturing method is obtained.

[Brief explanation of the drawing]

Figure 1 is Rinltl! FIG. 2 shows a graph of the rate of reduction in equivalent series resistance when the concentration of aluminum in the solution is changed, and FIG. 2 is a graph of the rate of increase in capacity when the concentration of aluminum in the phosphorus solution is changed. Patent applicant: Hitachi Capacitor Co., Ltd. Procedural amendment (voluntary) 1. Display of the case Manufacturing method of aluminum foil for electrolytic condenser 3, Person making the amendment 4, Detailed explanation column 5 of the invention subject to amendment S*, Contents of the amendment (1) Page 2, line 5 of the specification Correct "Oxalic acid" to "Adipic acid".

Claims (3)

[Claims] (1) How to make aluminum foil for electrolytic capacitors, which involves chemical conversion treatment to form an oxide film.
An electrolytic capacitor characterized by performing a first process of boiling the aluminum foil in pure water, and a second process of immersing the aluminum foil in a weak acid solution maintained at an aluminum temperature of 11 degrees 20 g or less after the first process. Method of manufacturing aluminum foil for use in aluminum foil. (2) - The method for producing an aluminum strip for electrolytic capacitors according to claim 1, wherein the weak acid is phosphoric acid. (3) The method for producing aluminum foil for an electrolytic capacitor according to claim 1, wherein the weak acid is acetic acid, succinic acid, or maleic acid.