JPH0653087A - Manufacture of electrode material for capacitor - Google Patents

Abstract

PURPOSE:To obtain an electrode material for capacitor which is constituted by including Al and either one of valve metals Ti, Zr, Ta, Nb, Hf, V etc., or a plurality of them, dissolving Al which is a ground of an alloy with a dendritic structure of Al and an intermetallic compound in the Al ground, and allowing the intermetallic compound part to remain for increasing a surface area. CONSTITUTION:An electrode material for capacitor is obtained by positively utilizing that there are two structure, namely a structure which can be dissolved easily and a structure which cannot be dissolved easily of an intermetallic compound part and a ground part in an alloy containing Al and either one type or a plurality of types out of valve metals Ti, Zr, Ta, Nb, Hf, and V without controlling etching as conventionally done. A material consisting of two structures which are different in terms of metal is dissolved by a liquid solution containing Al which is the same constituent as the ground with a higher concentration than that of a normal etching liquid, thus allowing only the intermetallic compound which cannot be dissolved easily to remain and then enlarging the surface area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electrode material for capacitors, which is obtained by etching an Al alloy.

[0002]

2. Description of the Related Art In order to improve the electrostatic capacity of electrolytic capacitors, the usable surface area has been expanded by etching the Al foil as a raw material. The improvement of the surface area expansion rate is
This has been done by various etching process improvements and improvements by elements added to the Al foil. In the conventional etching foils, in order to increase the surface area, it was necessary to have a fine and uniform number of holes, an appropriate hole diameter, and evenness in the depth direction. Although the etching process and the development of Al foil have been improved to obtain a finer and more uniform number of holes and hole diameters, the generation and starting position of the etching pits cannot be completely controlled, and the etching Even if a large surface area is obtained in the initial stage, the etching pits are concentrated with the progress of etching for further expansion of the surface area, and the pits near the surface are removed, so that a large surface area cannot be finally obtained.

Conventionally, when an Al foil and an Al alloy foil are etched, a substantially uniform etching layer can be maintained by shallow etching, but when deep etching is performed to obtain a high capacitance, it does not contribute to the surface area, but rather remarkably. The etching pits to be reduced were concentrated near the surface, and when this progressed, the metal part was removed. In etching, the growth of etching pits differs depending on whether it is AC or DC, but it is difficult to obtain a larger surface area than the current one by any method.To solve this, it is necessary to evenly distribute the etching pits. is necessary.

Until now, by adding an element having a high dielectric constant,
Although the development of alloys that are thought to exhibit high electrostatic properties has been promoted, the conventional etching method causes concentration of etching pits, which causes the pits to fall off from the surface, and the surface area cannot be expanded easily. It did not reach the capacitance. The same applies to the Al alloy, and the etching treatment used for the conventional high-purity Al for capacitor electrodes has no effect of alloy addition, and the obtained capacitance remains low. Further, although the Al alloy was developed to utilize the dendritic structure for increasing the surface area, a sufficient etching method for making the dendritic structure stably contribute to the surface area expansion and obtaining the original capacitance has been found. There wasn't.

[0005]

In order to make the best use of the characteristics of the Al alloy, there is no etching method utilizing the metallographic difference between the dendritic structure and the surrounding Al base, and the etching progresses. The dendritic tissue was severely detached from the vicinity of the surface, and even when deeper etching was performed, the capacitance did not show a high value as expected.

[0006]

Means for Solving the Problems The present inventor has examined the above problems and conducted experiments and studies on various Al alloys capable of obtaining a high capacitance by carrying out various etchings. As a result, Al and other valve metals Ti, Zr, Ta, N
b, Hf, V, etc., including one or more kinds,
Al, which is the base material of the alloy having a dendritic structure of Al and intermetallic compound, is dissolved in the Al base material to leave the intermetallic compound portion, thereby making it possible to manufacture an electrode material for capacitors by expanding the surface area. did.

A portion (dendritic structure) to be left by etching by positively utilizing the fact that there is a structure that is easily dissolved and a structure that is not easily dissolved in a metal, rather than controlling etching as in the past. This is made possible by dividing the portion (Al base) to be melted with a metal structure. The etching conditions at this time are such that a large difference is found between the solubility of the base metal Al and the solubility of the intermetallic compound.

In order to realize this, it is necessary to contain a component such as sulfuric acid, phosphoric acid, boric acid, etc., which becomes a suppressing factor during etching, and to maintain the Al concentration at a high level.

[0009]

The present invention will be described in detail below.

Al and other valve metals Ti, Z in Al base
An alloy having an intermetallic compound of r, Ta, Nb, Hf, V, etc. as a fine structure is dissolved by etching to dissolve the Al base other than the intermetallic compound to increase the surface area. The etching conditions at this time are such that a large difference is found between the solubility of the base metal Al and the solubility of the intermetallic compound.

In order to realize this, it is necessary to maintain the Al concentration at a high level when the etching solution contains components such as sulfuric acid, phosphoric acid, boric acid, and the like that suppress the etching.
The conventional etching solution contains 1.0 to 2.0 wt% of Al, but the etching solution used in the present invention has a high concentration of 2.5 to 18 wt%, and etching with this solution has an etching behavior different from the conventional one. Show. With such an etching solution, the shape obtained is the same even when the etching current is DC, AC, or pulse, although the mechanism is slightly different. This is because the Al concentration in the vicinity of the progress of etching is not so different from the Al concentration of the entire bath, so that the etching proceeds to a portion where the dissolving power is weak and metallographically easy to dissolve.
In addition, at least 1 of the inhibitory factors sulfuric acid, phosphoric acid, and boric acid
By adding 0.05 to 70 wt% of the seed, a dendritic structure is left faithfully in the metallographic structure, and a high capacitance can be obtained because the joint portion of the dendritic is protected.

Originally, the intermetallic compound is chemically stable and difficult to be etched as compared with pure Al. By making the most of this difference, when both structures coexist, only Al is selectively dissolved so as to be dissolved. This is possible. As a result, unlike the etching of Al, an unnecessary portion is not dissolved with the progress of etching, and the portion does not drop off. Since the surface area is faithfully expanded to the metallographic structure and the material becomes a controlly advantageous material, the yield is significantly improved as compared with the conventional method.

The expanded surface area is determined by the shape of the intermetallic compound remaining after etching. The shape of the intermetallic compound is determined by casting, plastic working, and heat treatment of the metal, and the structure of the metal material determines most of the surface area.

The present invention is an electrode material for a capacitor obtained by excavating an intermetallic compound by etching from a material having two or more different metal textures of an intermetallic compound and a base metal. The method of leaving the intermetallic compound portion by increasing the concentration of the base metal to be made is based on the same idea as in the present invention. For example, a material having a structure in which a spherical intermetallic compound of Al and Ti and a structure in which a base Al is present are closely bonded and are bonded like a bead by etching with a liquid having a high Al concentration by adding an etching suppressing component. Can be obtained. Further, for controlling etching, Pb, Cu, S
The effects of the present invention can be expected sufficiently for etching a material composed of an intermetallic compound containing i, Fe, Bi, Mn, Ni, Cr and the like and a metal base.

[0015]

EXAMPLES Examples of capacitor electrode materials obtained by etching the Al alloy are shown below. Before etching, each electrode material shown in Table 1 was treated in a 10 wt% sodium hydroxide composition solution at 30 ° C. for 10 minutes and then treated with a 10% nitric acid composition solution for 10 minutes. Comparative Example No. In general etching of 1, 2, and 3, a liquid composition of 10 wt% hydrochloric acid and 0.9 wt% Al was applied at 70 ° C. and a current density of 0.02 A / cm ² for 5 minutes. Example No. 4 and 5 are 20 by etching according to the present invention
It was performed with a composition liquid of wt% sulfuric acid, 10 wt% hydrochloric acid, and 8 wt% Al.

The anodizing treatment was carried out at a liquid temperature of 60 ° C. and a voltage of 20 V using an aqueous solution of ammonium borate 80 g / l as the liquid. 30 after reaching 20V by anodizing
It was held for 10 minutes, then placed in an electric furnace at 400 ° C. for 10 minutes and anodized at 20V for 5 minutes. Table 1 shows the results of measuring the characteristics of each material subjected to these treatments. As is clear from the table, in the conventional Al etching, the electrostatic capacity of the Al alloys other than high-purity Al is small, and the Al alloys of the same composition are equal to or more than Al in the etching of the present invention. The characteristics of The etching of the present invention is optimal for using the Al alloy as an electrode material.

[0017]

[Table 1]

[0018]

As described above, Al and other valve metals Ti, Z
The capacitor material of the present invention which is compatible with alloys containing any one or more of r, Ta, Nb, Hf, V, etc.
It is possible to stably obtain a large capacitance as compared with the conventional etching of high-purity Al, which greatly contributes to the yield of the capacitor and has great industrial and practical utility value.

Claims (4)

[Claims] 1. Al and other valve metals Ti, Zr, Ta, N
b, Hf, V, etc., including one or more kinds,
In an alloy having a dendritic set of Al and an intermetallic compound in an Al base, the base Al is dissolved to leave a dendritic structure which is an intermetallic compound portion, thereby increasing the surface area. Method for manufacturing capacitor electrode material. 2. The etching of the Al alloy according to claim 1, wherein 0.05 to 70 wt% sulfuric acid and 0.05 to 30 wt% are used.
% Hydrochloric acid and a solution containing 2.5 to 18 wt% Al are used for etching, and a method for producing a capacitor electrode material. 3. The etching of the Al alloy according to claim 1, wherein 0.05 to 70 wt% phosphoric acid, 0.05 to 30 wt
% Hydrochloric acid and a solution containing 2.5 to 18 wt% Al are used for manufacturing a capacitor electrode material. 4. The etching of the Al alloy according to claim 1, wherein 0.05 to 70 wt% boric acid and 0.05 to 30 are used.
A method for producing a material for a capacitor electrode, which comprises treating with a liquid containing wt% hydrochloric acid and 2.5 to 18 wt% Al.