JPH05148563A - Production of electrolytic capacitor electrode material - Google Patents

Abstract

PURPOSE:To obtain an anode material having high electrostatic capacity and CV product by incorporating and laminating an easily etchable alloy foil, produced by the single roll method, into a core material. CONSTITUTION:An Al alloy foil is made by quenching and solidificating a molten Al alloy by the single roll method. A solid solution phase is formed on the surface layer of the roll surface side of the Al foil and a dendrite type intermetallic compound is finely formed in the thickness direction. The casting raw material is dissolved again at a temp. range, at which the fine intermetallic compound is not dissolved and the Al mother phase and the solid solution phase are dissolved, and is solidified at a relatively low cooling speed. More than three Al alloy foils are piled on a surface of a conductive core material as a middle layer and etching is executed to the depth of the vicinity of the core material. Then, an insulating coated film is formed by chemically treating. In a result, the anode material for a large capacity electrolytic capacitor is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an Al alloy coagulated foil as an electrode material for an electrolytic capacitor which has a high capacitance by laminating a plurality of coagulated foils on a core material.

[0002]

2. Description of the Related Art Electrolytic capacitor electrode materials are made to have a roughened surface by electrolytic etching treatment, have a larger surface area, and have an insulating film formed by anodizing treatment to increase the electrostatic capacitance, thereby increasing the capacitance. I'm wearing. That is, in order to manufacture a large-capacity capacitor, it is necessary to increase the surface area of the electrode material and to form a thin film having a good insulating property on the surface.

Al foil, which is relatively easy to manufacture, has been used as a conventional electrode material. When this Al foil is subjected to an oxidation treatment, an Al ₂ O ₃ film is formed, but the dielectric constant of Al ₂ O ₃ is different from that of another metal such as an oxide film (Ta ₂
It is not so high compared to O ₅ and TiO ₂ ). Therefore, attempts have been made to increase the capacitance by increasing the surface area by mechanical means or an electrochemical etching method, while improving the anodizing method for forming an oxide film, etc. Even with these methods, sufficiently high characteristic improvement has not been achieved.

Recently, as an anode material, an Al alloy obtained by adding another alloy element (so-called valve metal) to pure Al is used, and this alloy is manufactured by a rapid solidification method to obtain a large capacity electrolytic capacitor. For example, Japanese Patent Laid-Open No. 1-1
It is disclosed in Japanese Patent No. 24212. This includes at least one valve metal such as Ti, Ta, Zr, Hf and Nb in Al.
An alloy foil electrode in which an intermetallic compound with Al is finely dispersed and crystallized is presented.

However, the intermetallic compound crystallized in such an alloy foil is hard and reduces the ductility of the alloy foil. In particular, if the amount of alloying element added is increased in order to secure the electrostatic capacity, this tendency increases, and there arises a problem that the bending strength, which is one of the important characteristics of the electrode material (foil) of the electrolytic capacitor, decreases.

In order to improve the bending strength, an electrode material for an electrolytic capacitor is disclosed in JP-A 1-2902, in which an Al foil is used as a core material and Al alloy foils produced by a rapid solidification method are laminated on both sides.
No. 17 publication.

According to the invention disclosed in the above-mentioned publication, some high characteristics are obtained, but the electrostatic capacity can be increased by further increasing the electrode surface area. For that purpose, the thickness of the electrode structure must be increased and the etching depth must be sufficient to increase the surface area. However, there is a limit to making the rapidly solidified foil produced by the single roll method into a fine solidified structure suitable for the electrode material, that is, to increase the thickness while keeping the cooling rate high, and therefore to increase the surface area. , There are restrictions naturally.

In view of the above situation, the inventors of the present invention have processed the rapidly solidified foil which is easily etched within a range in which the thickness of the rapidly solidified alloy foil obtained by the single roll method can be maximized. A plurality of sheets including the above are stacked, and the thickness of the electrode material is further increased to propose an anode material for an electrolytic capacitor having excellent characteristics such as capacitance and CV product. However, the rapidly solidified alloy foil produced by the single roll method, because the solid solution phase of the alloy element which is difficult to be etched is formed on the roll contact surface, even if a plurality of such foils are laminated,
The solid solution phase of the foil at the intermediate position serves as a barrier to prevent the progress of etching, and the thickness effect cannot be effectively obtained. Therefore, the purpose of the above proposal is to use a rapidly solidified foil from which the formed solid solution phase has been removed, as the intermediate layer.

[0009]

The thickness of the rapidly solidified alloy foil produced by the single roll method is 100 μm at the most,
It is technically necessary to remove the solid solution phase formed on the surface layer, and thus it takes a lot of trouble. The present invention eliminates the need for the complicated solid solution phase removing means as described above, and prevents the solid solution phase from being generated in the alloy foil itself produced by cooling and solidifying, which is used for the laminated intermediate layer. Accordingly, it is an object of the present invention to provide a method for producing a material for an electrolytic capacitor electrode which can obtain a high capacitance and a CV product.

[0010]

In order to achieve the above object, the present invention has the following structures. That is, a rapid solidification A in which a fine dendrite intermetallic compound is crystallized and a solid solution phase of an alloy element is present on the surface side in contact with a cooling roll.
l alloy foil, although the fine intermetallic compound is not dissolved,
Re-dissolve in a temperature range that dissolves the mother phase and the solid solution phase,
After that, the molten metal is ejected onto the surface of the rotating single roll and solidified at a relatively slow cooling rate without producing a solid solution phase, which is a method for producing a material for an electrolytic capacitor electrode.

[0011]

The present invention will be described in detail below. The solidified foil which is the object of the present invention is based on Al, on which Ti, Z
It is an alloy containing at least one of valve metals such as r, Hf and Ta and Nb, and intermetallic compounds of these valve metals and Al are finely crystallized.

The solidified foil produced by the single roll method is
The molten metal of the alloy contained in the container is ejected onto the surface of one rotating roll, and the foil is cooled by the roll. At this time, the cooling speed differs depending on the rotation speed of the roll, and when the roll is rotated at a high speed and rapidly cooled, a solid solution phase that is difficult to be etched is generated in the surface layer on the roll surface side of the foil that contacts the roll. On the other hand, the cooling rate of the free surface is slower than that of the roll surface, and a solidified structure in which fine intermetallic compounds are crystallized from the roll surface toward the free surface develops and forms. In order to obtain such a structure, it is necessary to increase the rotation speed of the roll (10 m / sec or more at the peripheral speed of the roll) and maintain a high cooling rate even on the free surface side, and therefore increase the foil thickness to that extent. I can't do it, at most 1
It is about 00 μm.

Here, the solid solution phase is a phase in which Al, which is a base metal, contains Ti, Zr, Hf and alloying elements such as Ta and Nb in a solid solution of, for example, 1 wt% or more. This solid solution phase is not formed by solidification at a normal cooling rate, but is formed when it can be rapidly solidified by a single roll method, for example, and when it is solidified at a very large cooling rate like a roll surface.

In order to increase the surface area, the rapidly solidified alloy foil is etched. At this time, the etching from the roll surface causes the solid solution phase to become a barrier for corrosion, and the Al base exposed between the solid solution phases is corroded by corrosion holes. Therefore, since the etching proceeds deeply and further along the finely crystallized solidified structure, the increase of the surface area becomes remarkable. Therefore, when a plurality of sheets are laminated to form an electrode material, they are arranged such that the outermost surface is in a solid solution phase. However, when a foil having a solid solution phase is used for the intermediate layer, etching does not proceed in this portion, and the purpose of stacking cannot be achieved.

The present invention produces a foil which does not have a solid solution phase and has fine intermetallic compounds crystallized in the Al matrix for use in such an intermediate layer. That is, the material of the present invention is Al
Is an Al alloy foil obtained by melting an alloy containing 3 at% or more of at least one kind of Ti, Zr, Hf, Ta, Nb, etc., and rapidly solidifying this by a single roll method. Although a solid solution phase is generated, dendrite-like intermetallic compounds are finely formed in the thickness direction. In order to eliminate the solid solution phase of this casting material and to use the formed fine intermetallic compound, the material is redissolved, but this remelting temperature is such that the fine intermetallic compound does not dissolve. , Al
The mother phase and the solid solution phase are melted in a temperature range, and the melt is solidified at a relatively low cooling rate. Since the melting temperature of Al is usually 660 ° C, the remelting temperature needs to be higher than this, and the melting temperature of the intermetallic compound varies depending on the type. For example, the melting temperature of Al ₃ Zr is 1582 ° C. However, it is preferable to set the temperature to 100 ° C. or lower than the melting point. The cooling rate for solidification is preferably 10 ² ° C / sec or less. As a result, the fine intermetallic compound is dispersed in the Al base without coarsening.

The present invention takes advantage of the characteristics of each surface of the rapidly solidified foil as described above, and if one sheet of rapidly solidified foil can only increase its surface area by at least one surface of the core material, By stacking three or more alloy foils and stacking the material of the present invention in the middle of the foils, etching proceeds deeply to the vicinity of the core material, and chemical conversion treatment is performed to form an insulating coating, which is extremely useful. It serves as an anode material for electrolytic capacitors of high capacity.

FIG. 1 is an example of a schematic cross-sectional view of an anode material for an electrolytic capacitor produced by using an alloy foil according to the present invention, in which 1 is a core material and 2 (2a, 2b, 2c, 2d,) are A rapidly solidified alloy foil having a solid solution phase on the roll surface R, 3 (3
a, 3b) represents an alloy foil produced by the method of the present invention without a solid solution phase. In the figure, F is a free surface. The core material 1 is preferably pure Al, which is excellent in conductivity and bending workability, and the rapidly solidified foil 2 is made of a valve metal having a high dielectric constant, such as T.
At least one kind of i, Zr, Hf, Ta, Nb and Al
Use alloy foil with. In the illustrated example, on each surface of the core material 1,
The rapidly solidified alloy foils 2a and 2b, and the alloy foil 3a of the present invention in the middle thereof, and the rapidly solidified alloy foils 2c and 2d and the alloy foil 3b of the present invention in the middle, each have three layers. The outermost surfaces of the foils 2a and 2d and the innermost foil 2
The innermost surface of b and 2c in contact with the core material is the roll surface R, and the intermediate foils 3a and 3b are laminated in seven layers in contact with the free surfaces F of the other foils 2a to 2d. ing. However, the present invention is not limited to this, and includes a case of laminating only one surface of the core material 1 and a case of laminating four or more sheets on one surface or both surfaces of the core material 1. The lamination method may be carried out by a known method such as thermocompression bonding or rolling of the core material 1 and the rapidly solidified alloy foil 2, and any method may be used as long as they are closely adhered so that they are not separated by etching or processing. May be adopted.

Although the above-mentioned laminated anode material is subjected to etching treatment, the solid solution phase on the outermost surface of the laminated rapidly solidified alloy foil is hard to be etched, so that the surface is maintained and the Al base exposed between the solid solution phases is removed. As a starting point, etching proceeds inside the foil along the solidified structure. Moreover, since the intermediate layer has no solid solution phase and is easily etched, the etching reaches deep inside through the surface layer, the intermediate layer and the inner layer.
At the boundaries between the core material 1 and the rapidly solidified alloy foils 2b and 2c, there are solid solution layers formed on the respective foils 2b and 2c. Since the present invention has such a multilayer structure that facilitates etching, the etching depth can be increased and the material surface area can be greatly expanded.

[0019]

EXAMPLES 1500: Al-Ti alloy containing Ti: 8 wt% and Al-Zr alloy containing Zr: 18 wt% 1500
It was heated and melted at 0 ° C., and the melt was jetted at a pressure of 0.8 kg / cm ² onto a single roll having a diameter of 300 mm rotating at 1600 rpm to be solidified to produce a rapidly solidified alloy foil (material). This material foil is further melted at 700 ° C, and this molten metal is melted to 100
A single roll coated with BN having a diameter of 300 mm rotating at 0 rpm is jetted at a pressure of 0.5 kg / cm ² and solidified to a width of 4
The alloy foil of the present invention having a thickness of 0 mm and a thickness of about 100 μm was manufactured.
When the cross-sectional structure of the obtained alloy foil was investigated, Ti and Zr solid solution phases were hardly observed on the roll surface side, and fine intermetallic compounds were dispersed.

A laminated material sample as shown in FIG. 1 was manufactured using two kinds of alloy systems of Al--Ti alloy and Al--Zr alloy, and after etching and chemical conversion treatment under the following conditions, The capacitance and withstand voltage were measured. The results are shown in Table 1.
Shown in. Samples A-1 and B-1 in the table are Al-8 wt% Ti
Alloys, Samples A-2 and B-2 are Al-18 wt% Zr alloys, Sample A does not use the alloy foil of the present invention as an intermediate layer, Sample B has the alloy foil of the present invention as an intermediate layer. This is the sample used. [Etching conditions] Etching solution: 6% hydrochloric acid solution, electricity: 300 C / cm ² [Chemical conversion conditions] Chemical conversion solution: boric acid solution, chemical conversion voltage: 20 V

[0021]

[Table 1]

As is clear from Table 1, all the samples B using the alloy foil manufactured according to the present invention as the intermediate layer show excellent CV products. Moreover, when a sample for an optical microscope was prepared from the clad foil after the measurement, and the surface was mirror-polished and then observed by an optical microscope, A-1 and 2 were regions where etching was stopped in the solid solution phase portion of the intermediate layer foil. In many cases, the peeling of the etching structure from the surface is remarkable. On the other hand, B-1,
In No. 2, etching progressed to the third layer, and peeling from the surface was extremely small.

[0023]

As described above, according to the method of the present invention, the rapidly solidified alloy foil produced by the single roll method is formed on one surface or both surfaces of the core material in three or more layers so as not to interfere with etching. By stacking the alloy foil produced by the method of the present invention on the intermediate layer and forming a clad foil by pressure bonding, the etching depth can be increased, and an anode material having an extremely large capacitance can be easily and easily formed. The electrolytic capacitor can be obtained with high productivity, and the electrolytic capacitor can have higher performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an anode material using an alloy foil obtained by the method of the present invention.

[Explanation of symbols]

 1: Core material 2: Rapidly solidified alloy foil 3: Alloy foil of the present invention

Claims (1)

[Claims] 1. A rapidly solidified Al alloy foil in which a fine dendrite-like intermetallic compound is crystallized and a solid solution phase of an alloy element is present on the surface side in contact with a cooling roll, although the fine intermetallic compound is not dissolved, A method for producing a material for an electrolytic capacitor electrode, characterized in that the mother phase and the solid solution phase are redissolved within a temperature range of melting, and then the molten metal is cooled by a single roll method to solidify without forming a solid solution phase. ..