JPS6035511A - 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 provides aluminum foil for electrolytic capacitors! This relates to a JLL construction method.

Conventionally, aluminum electrode foils used in aluminum electrolytic capacitors are etched or left in plain form and then immersed in pure water and boiled to generate hydrated oxides on the surface. Then, this aluminum foil is immersed in a solution such as boric acid or oxalic acid, and a certain voltage is applied to form an oxide film of the desired thickness.Then, it is heated at a high temperature of several 100 degrees Celsius in an atmosphere to create a rough texture. It is re-formed into.

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 treatment is performed to remove the hydrated oxide present on the surface of the oxide film, but the annealing treatment requires high humidity and increases manufacturing cost. 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 treatment, the aluminum foil has a concentration of 4
The present invention provides a method for manufacturing an aluminum foil for an electrolytic capacitor, characterized in that a second treatment of immersing the aluminum foil in a weak acid solution below a specified value is performed.

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

First, a first treatment is performed in which an etched or blank aluminum foil is immersed in pure water and boiled to form a hydrated oxide on the surface of the aluminum foil.

Next, the boiled aluminum board 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, or maleic acid for a predetermined period of time to dissolve and remove the feather-like film on the surface. At this time, a weak acid solution of 4N or less is particularly used. Even if the concentration of the weak acid solution is higher than this, the effect on capacity increase etc. will hardly change, and the normal oxide film will be more likely to be damaged, and the treatment time will have to be extremely shortened, making production difficult.

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

That is, by immersing aluminum foil with hydrated oxide on its surface in a weak mWa solution, it is possible to remove the feather-like film that has been an obstacle to reducing loss and increasing capacity. By setting the degree to 4 or less, manufacturing is facilitated. In addition, the cost is much lower than that of annealing treatment, and manufacturing costs are reduced because annealing treatment is not required or the additional treatment time and number of treatments can be significantly reduced.

In addition, especially using phosphoric acid as the weak acid, the concentration is A...1
M constant, B...2NA constant, C...4JJl constant, and D
The figure shows a graph of changes in capacity versus treatment time when aluminum foil was immersed in four types of 8-standard solutions. Etching foil was used for aluminum heat, boiled in pure water at 95°C or higher, and then heated at 150V, 30'OV, 450V and 500V in 1131F111 ammonium solution.
Apply the voltage (2) sequentially to form a chemically formed oxide film until the leakage current is 0.111A/ or less, then immerse it in a phosphoric acid solution at a temperature of 60°C, and roughly apply the same liquid as chemically Inside, a voltage of 500 V is applied to perform re-formation. As is clear from the figure, the aluminum plate treated in this manner shows almost no change in capacity when the phosphoric acid solution concentration becomes higher than 41 constant. Also, the processing time is 18
When 0 seconds or more elapse, the capacity becomes saturated.

Weak ill! 8! When the rinsing treatment is performed, a 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 deterioration due to storage. Also,
Weak acids such as acetic acid, citric acid, and succinic acid are used in larger amounts 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. A method for manufacturing aluminum foil for capacitors is obtained.

[Brief explanation of the drawing]

The figure shows a graph of the change in capacity versus immersion time in a phosphoric acid solution. Patent applicant: Hitachi Capacitor Co., Ltd. Procedural amendment (voluntary) 1. Display of the case Manufacturing method of aluminum foil for electrolytic capacitors 3, Person making the amendment 4, Detailed description of the invention in the specification subject to amendment 5, Contents of the amendment (1) Page 2, line 5 of the specification Correct "oxalic acid" to "adipic acid".

Claims (3)

[Claims] (1) A method for manufacturing aluminum foil for electrolytic capacitors in which aluminum foil is subjected to chemical conversion treatment to form an oxide film, including a first treatment in which the aluminum foil is boiled in pure water, and after the first treatment, the aluminum foil is boiled at 81 degrees Immersion in a weak acid solution below the specified level! t
! 1. A method for manufacturing aluminum for electrolytic capacitors, characterized in that a second treatment is performed. (2) The method for producing aluminum foil for an electrolytic capacitor according to claim 1, wherein the weak acid is phosphoric acid. (3) 11. The method for manufacturing aluminum foil for electrolytic capacitors according to claim 1, wherein the weak acid is acetic acid, succinic acid, or maleic acid.