JPH06264201A - Production of electrode material for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a production method of an electrode material for an electrolytic capacitor using pure aluminum foil as the anode element an a rapidly solidified alloy foil as an insulating film. CONSTITUTION:A rapidly solidified alloy foil consisting of 1-25 atomic % Zr and the balance Al is joined to clad both surfaces of a pure Al foil by hot rolling. In this process, hot rolling is carried out under conditions of 250-400 deg.C heating temp. and 3-90% reduction rate by one-pass or multipass system. Then the material is again heat-treated at 250-400 deg.C. By this method, an electrode material having high CV product as >=3000muFV/cm<2> can be stably produced.

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 electrode material for an electrolytic capacitor, which is obtained by clad-bonding a pure Al foil and an Al alloy rapidly solidified foil containing a valve metal and having excellent CV product characteristics.

[0002]

2. Description of the Related Art Conventionally, pure Al foil has been used as an electrode material for electrolytic capacitors. However, in order to further increase the electrostatic capacity, Ti, Ta, Zr, Hf, which increase the relative dielectric constant,
A technique for producing an Al alloy foil containing at least one kind of valve metal such as Nb by a rapid solidification method has been developed. Since a foil containing such an alloy element has a low ductility and has a problem in forming an electrode, a three-layer clad foil in which a pure Al foil is used as a core material and the Al alloy foil containing the valve metal is laminated on both surfaces thereof Is used as an electrode material.
It is proposed in Japanese Patent No. 0217. According to the electrode material described in the publication, a CV product of 2000 μFV / cm ² or more can be achieved, and a high CV product exceeding 3000 μFV / cm ² or more can be achieved.

[0003]

Although such a CV product value is very high for an Al electrolytic capacitor,
It is not always easy to stably produce such an electrode material having a high characteristic value, and there is a large variation, which causes a problem that the capacitance of the electrolytic capacitor as a final product also varies. On the other hand, there is a demand for further miniaturization and higher performance of solid electrolytic capacitors at present, and an electrode material for a solid electrolytic capacitor having a higher CV product is required.

Under these circumstances, the present invention makes use of the high electrostatic characteristics of the rapidly solidified alloy, thereby making it possible to stably produce an electrode material having a higher CV product. It is intended to provide a manufacturing method.

[0005]

In order to achieve the above object, the present invention has the following structures. That is, Z
In the method for producing an electrode material for an electrolytic capacitor, wherein: a rapidly solidified alloy foil containing r: 1 to 25 atomic% and the balance substantially consisting of Al is laminated on both surfaces of a pure Al foil, and the mixture is warm-rolled and clad-joined. It is characterized in that the bonding is heated to a temperature range of 250 to 400 ° C., then is subjected to one-pass or multi-pass rolling having a reduction rate of 3 to 90%, and then heat-treated at a temperature of 250 to 400 ° C. Is a method of manufacturing an electrode material for an electrolytic capacitor. Further, the heat treatment performed after the rolling is more preferably performed at a temperature higher than the temperature heated before the rolling by 75 ° C. as an upper limit and at a temperature not higher than that temperature and in the range of 250 to 400 ° C. In the rapidly solidified alloy foil, at least one of Ti, Nb, Ta and Hf may be replaced with all or part of Zr.

The present invention will be described in detail below. In the present invention, first, an Al alloy foil is manufactured. That is, an Al-based molten alloy in which components are adjusted and melted so that Zr is 1 to 25% in atomic ratio is rapidly solidified by a single roll method,
The alloy foil has a thickness of 100 μm or less. The addition of Zr is to increase the capacitance as is already known in itself, and for this purpose, 1 atomic% or more is required. Further, if the content exceeds 25 atom%, the workability of the material is significantly deteriorated and the rapidly solidified foil cannot be formed.

In the present invention, it is possible to properly add at least one valve metal of Ti, Nb, Ta, and Ha to part or all of Zr. These elements produce a dense dielectric oxide film similar to Al and Zr, and do not reduce the capacity of the capacitor. Further, in the case of adding a trace amount, it becomes a shell for precipitation of rapid solidification, or it slows the solidification rate, so replacement or addition of some elements is effective. However, since these compounds do not form a finer dendrite structure than Zr with Al,
When all of Zr is replaced and added alone, the capacity cannot be increased as much as Zr.

The alloy foil produced in this manner is laminated on both sides of a pure Al foil as a core material to form a three-layer structure.
It is heated to a temperature range of 0 to 400 ° C. and then warm-rolled.
Rolling is carried out in at least one pass so that the total rolling reduction is 3 to 90%, and a clad foil in which metal foils are bonded to both surfaces of a core material is manufactured. If the heating temperature is lower than 200 ° C., the joining of both foils cannot be sufficiently obtained, while if it exceeds 400 ° C., the crystals (dendrites) become coarse and the etching area is reduced, which is not preferable. This tendency becomes larger as the heating temperature becomes higher. Therefore, it is preferable to set the temperature as low as possible to enable the bonding. The heating method is not particularly limited, and a normal method may be adopted.

The clad foil formed after the rolling is 250 to
Heat treatment is performed in the range of 400 ° C. The present invention can remarkably improve the CV product by performing this heat treatment. The present inventors presume the cause of the effect of heat treatment on the CV product as follows. That is, the rapidly solidified alloy foil receives a strong shearing force in the interface direction during clad rolling. As a result, the dendrite structure of the rapidly solidified alloy foil is deformed, or strain energy is accumulated in the dendrite, and the heat is removed from the roll to fix the structure.
It is considered that the deformation of the structure and the accumulation of strain energy cause abnormal peeling starting from it in the later etching process and cause peeling, which affects the variation of the characteristic values of the product. .

The heat treatment after rolling restores such deformed structure and releases strain energy. Therefore, the higher the temperature or the longer the heat treatment is, the more effective it is to repair the deformed structure and release the strain energy, but on the other hand, the coarsening of the crystal occurs and the surface area in the subsequent etching step is increased. The magnifying effect is impaired. Therefore, in the present invention, the temperature is specified to be 400 ° C or lower. Further, if it is lower than 250 ° C, the strain cannot be sufficiently removed.

Further, the heat treatment temperature after rolling needs to be regulated by the heating temperature before rolling. That is, within the above-mentioned range of 250 to 400 ° C., the heat treatment temperature after rolling is 75% higher than the heating temperature before rolling.
It is preferable that the temperature does not rise above 0 ° C. The reason why the difference between the heating temperature before and after rolling and the heat treatment temperature is 75 ° C. or less is that if this difference exceeds 75 ° C., the gas adsorbed before rolling is released by the heat treatment, causing peeling of the foil. .

On the other hand, the heat treatment time is determined by the correlation with temperature,
A low temperature requires a long time and a high temperature requires a short time. In this case, it is necessary to comprehensively consider the heating time during rolling and the heat treatment time after rolling. That is, it is preferable that the total of the heating time and the heat treatment time is at least 10 minutes (treatment on the high temperature side), and that the treatment on the low temperature side is within 4 hours. The heat treatment time after rolling is preferably about 10 minutes to 4 hours.

The clad foil thus heat-treated is subjected to a step of etching with a 6% hydrochloric acid solution at a DC current of 100 coulomb / cm ² , and the etched rapidly solidified alloy foil is treated with, for example, 20 V of ammonium phosphate solution as described above. Chemical conversion treatment to form an Al ₂ O ₃ + ZrO ₂ oxide film, cutting this into a specified chip size, and then joining it to the anode lead of the lead frame, and impregnation into the cathode material solution and rapid solidification It comprises a step of forming a cathode layer on the alloy foil and joining it to the cathode lead of the lead frame, and a step of molding the whole with resin, whereby an electrolytic capacitor as a product can be manufactured.

Although the three-layer clad material has been mainly described above, the present invention is not limited to this, and pure A
The electrode material may be a clad material obtained by laminating and rolling three layers of 1-foil and alloy foil, or multilayer alloy foils on both sides or one side.

[0015]

EXAMPLES Examples of the present invention will be described below. First, with a single roll casting machine, Al content of 95 atomic% or more, Z
Molten metal consisting of 4 atomic% of r and the balance unavoidable impurities was ejected from a nozzle, and the width was 40 mm and the thickness was 100 to 120 μm.
A rapidly solidified alloy foil of m was prepared. Using this as a core material of 99.9% or more high-purity aluminum foil (thickness 0.3 mm),
Various temperature conditions shown in Table 1 (heating time 15
After clad rolling (15% reduction) by heat treatment, heat treatment was performed for 1 hour under various temperature conditions shown in Table 1. The clad material thus obtained was etched with a 6% hydrochloric acid solution at a direct current of 100 coulomb / cm ² , and then thoroughly washed, and then 20 V chemical conversion was performed with an ammonium phosphate solution.
Each characteristic was investigated. The results are shown in Table 1 together with examples outside the scope of the present invention and conventional examples.

[0016]

[Table 1]

As is clear from the results shown in Table 1,
According to the present invention, the heating during rolling or the heat treatment after rolling is performed according to the present invention.
3000 at a temperature in the range of 50 to 400 ° C
A product with a CV product of μFV / cm ² or more can be stably obtained, but if the heating temperature during rolling or the heat treatment temperature after rolling exceeds 400 ° C, or if no heat treatment is performed after rolling, the CV product can be obtained. Is not so high, and CV
The product variation is also large.

[0018]

As described in detail above, according to the present invention,
An electrode material having a high CV product of 3000 μFV / cm ² or more can be stably produced, and a small-sized, large-capacity stable electrolytic capacitor can be obtained.

Claims (3)

[Claims] 1. A method of producing an electrode material for an electrolytic capacitor, comprising laminating a rapidly solidified alloy foil containing Zr: 1 to 25 atomic% and the balance substantially consisting of Al on both sides of a pure Al foil, followed by warm rolling and clad bonding. In the method, the clad junction is 250 to 40
After heating to a temperature range of 0 ° C., rolling is performed in one pass or multiple passes with a rolling reduction of 3 to 90%, and then 250
A method for producing an electrode material for an electrolytic capacitor, which comprises performing heat treatment at a temperature in the range of to 400 ° C. 2. The electrode material for an electrolytic capacitor according to claim 1, wherein the heat treatment performed after rolling is performed at a temperature not higher than 75 ° C. higher than the heating temperature before rolling and at a temperature in the range of 250 to 400 ° C. Manufacturing method. 3. All or part of Zr is Ti, Ta, H
The method for producing an electrode material for an electrolytic capacitor according to claim 1 or 2, wherein at least one of f and Nb is substituted.