KR101729382B1

KR101729382B1 - Method of manufacturing aluminium foil, aluminium foil having high dielectric constant, electrolytic capacitor having the aluminium foil and apparatus for manufacturing aluminium foil

Info

Publication number: KR101729382B1
Application number: KR1020150026906A
Authority: KR
Inventors: 박상식
Original assignee: 경북대학교 산학협력단
Priority date: 2015-02-26
Filing date: 2015-02-26
Publication date: 2017-05-02
Also published as: WO2016137057A1; KR20160104211A

Abstract

In a method for producing an aluminum foil for an electrolytic capacitor, an aluminum foil having a high dielectric constant, and an apparatus for manufacturing the same, a manufacturing method includes the steps of: impregnating a porous aluminum foil containing a plurality of etching- A drying step of drying the aluminum foil coated with the metal oxide sol in a non-vacuum state, a sintering step of sintering the dried coating film, an aluminum foil having a sintered coating film formed thereon, To form a composite oxide layer including an aluminum oxide layer and a metal oxide layer stacked on the inner wall surface inside the etching-pores.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an aluminum foil for an electrolytic capacitor, an aluminum foil having a high dielectric constant, an electrolytic capacitor including the same, and an apparatus for manufacturing an aluminum foil. FOR MANUFACTURING ALUMINUM FOIL}

The present invention relates to a method for producing an aluminum foil for an electrolytic capacitor, an aluminum foil having a high dielectric constant, an electrolytic capacitor including the same, and an apparatus for producing the aluminum foil. More particularly, An electrolytic capacitor including the aluminum foil, and an apparatus for manufacturing the aluminum foil.

BACKGROUND ART [0002] Electrolytic capacitors having a small size and large capacitance have been used in many electronic devices. In an aluminum electrolytic capacitor using an alumina layer (Al ₂ O ₃ ) formed by anodic oxidation of 99.99% or more of a high purity aluminum foil as a dielectric, theoretically, the effective surface area of the electrode is increased or the thickness of the dielectric layer is reduced Or by increasing the dielectric constant of the dielectric layer, the capacitance of the electrolytic capacitor can be increased.

However, there is a limitation in minimizing the thickness of the dielectric layer due to deterioration of the withstand voltage characteristic. Techniques for increasing the effective surface area of the electrodes have been continuously developed. However, there is a limitation in achieving the miniaturization of capacitors and improving the withstand voltage characteristics.

To solve this problem, research has been conducted on the development of a dielectric layer having a dielectric constant higher than that of alumina having a dielectric constant of about 8 to 9, which is conventionally used. An oxide layer such as zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ) or the like is coated by a sol-gel method and used as a dielectric layer. Since the oxide layer has a high dielectric constant of 20 or more, it can contribute to the miniaturization of the capacitor compared to the alumina layer of the same thickness. The oxide films as described above may be used alone or in the form of a separately formed alumina layer.

At this time, the oxide films are easily coated on the flat thin film, but it is not easy to coat the thin film on the surface through the sol-gel method. That is, in an aluminum electrolytic capacitor, a plurality of pores or pits are formed through etching on the surface of a flat aluminum foil to increase the effective surface area. In this case, the inside diameter of the pores is generally 1 to 2 μm And has a length of 10 to 50 mu m, it is difficult to uniformly coat the oxide film on the inner wall of the pores by the sol-gel method. Accordingly, there is a limit in improving the capacitance of the capacitor and it is difficult to maintain the withstand voltage.

It is an object of the present invention to provide a method of manufacturing an aluminum foil in which a metal oxide layer is uniformly coated on the inner wall of a pore of an aluminum foil.

Another object of the present invention is to provide an aluminum foil having a high dielectric constant and a high dielectric constant by uniformly coating a metal oxide layer on the inner wall of a pore of an aluminum foil.

It is still another object of the present invention to provide an electrolytic capacitor comprising the aluminum foil.

It is still another object of the present invention to provide an apparatus for producing the aluminum foil.

A method of manufacturing an aluminum foil according to an embodiment of the present invention is provided. The method includes the steps of impregnating a porous aluminum foil containing a plurality of etch-pores in a vacuum state with a metal oxide sol contained in a chamber, a step of recovering a metal oxide sol remaining in the chamber, A drying step of drying the coated aluminum foil, a sintering step of sintering the dried coating film, and an anodic oxidation of the aluminum foil on which the sintered coating film is formed to form an aluminum oxide layer and a metal oxide layer stacked on the inner wall surface of the etching- To form a composite oxide layer.

In the above manufacturing method, the cycle including the impregnation step, the recovery step and the drying step may be repeatedly performed before the sintering step is performed or before the sintered aluminum foil is anodized.

In one embodiment, the method may further comprise a pressurizing step in which the aluminum foil is impregnated with the metal oxide sol before the recovery step is performed. At this time, the cycle including the impregnation step, the pressurization step, the recovery step and the drying step may be repeatedly performed before the sintering step or before the anodizing of the sintered aluminum foil.

In one embodiment, the step of impregnating the metal oxide sol comprises the steps of disposing an aluminum foil in a chamber in a non-vacuum state, making the chamber in a vacuum state with the aluminum foil placed, . &Lt; / RTI >

In one embodiment, the metal oxide sol of the coating material supply portion can be supplied to the chamber by a pressure difference between the coating material supply portion that receives the metal oxide sol and the vacuum chamber.

In one embodiment, the recovering step may adjust the discharge rate of the metal oxide sol from 0.2 mm / s to 10 mm / s based on the height of the metal oxide sol accommodated in the chamber.

In one embodiment, the sintering step may be performed at 350 ° C to 600 ° C.

In one embodiment, the anodization can be performed by applying a current of 20 mA / cm ² to 50 mA / cm ² up to a voltage of 100 V to 1000 V.

The aluminum foil having a high dielectric constant according to an embodiment of the present invention is characterized in that in a porous aluminum foil including a plurality of etching pores, a metal foil formed on an alumina layer formed on the inner wall surface of the etching- And an oxide layer.

In one embodiment, the thickness variation of the metal oxide layer may be within 10%.

An electrolytic capacitor including an aluminum foil having a high dielectric constant according to an embodiment of the present invention includes a first electrode structure, a second electrode structure facing the first electrode structure, Wherein at least one of the first electrode structure and the second electrode structure comprises an etch-pores, wherein the porous aluminum foil comprises an electrolyte disposed between the first electrode structure and the second electrode structure, wherein the alumina And a metal oxide layer formed on the layer at a uniform thickness.

An apparatus for producing an aluminum foil having a high dielectric constant according to an embodiment of the present invention includes a chamber in which a porous aluminum foil including a plurality of etching pores is disposed, a coating material supply unit for providing the metal oxide sol as the chamber, Includes a vacuum pump.

In one embodiment, the manufacturing apparatus may further include a gas supply unit connected to the chamber and supplying gas to the chamber so that the aluminum foil is impregnated with the metal oxide sol.

According to the method for producing an aluminum foil for an electrolytic capacitor of the present invention, an aluminum foil having a high dielectric constant and an apparatus for producing the same, a metal oxide layer having a high dielectric constant is uniformly formed in a porous aluminum foil containing a plurality of etching- . It is possible to manufacture an aluminum foil in which a complex oxide layer including both aluminum oxide and a metal oxide layer is formed while increasing the effective surface area of the electrode through the etching-pores, so that the capacitance can be improved in the same volume. As a result, the size of the aluminum electrolytic capacitor can be reduced, and the market competitiveness of the product can be improved.

1 is a flowchart illustrating a method of manufacturing an aluminum foil according to an embodiment of the present invention.
2 is a conceptual diagram for explaining an apparatus for manufacturing an aluminum foil for performing the manufacturing method of FIG.
3 is an electron micrograph of Sample 1 and Comparative Sample 1 according to the present invention.
4 is a graph showing capacitance measurement results of Samples 1 to 3 and Comparative Sample 2 according to the present invention.
5 is a graph showing the results of measurement of breakdown voltage of Samples 1 to 3 and Comparative Sample 2 according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having ", etc. is intended to specify that there is a feature, step, operation, element, part or combination thereof described in the specification, , &Quot; an ", " an ", " an "

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

FIG. 1 is a flow chart for explaining a method of manufacturing an aluminum foil according to an embodiment of the present invention, and FIG. 2 is a conceptual diagram for explaining an apparatus for manufacturing an aluminum foil for performing the manufacturing method of FIG.

Referring to FIGS. 1 and 2, an aluminum foil TG is immersed in a metal oxide sol 212 in a vacuum chamber 210 in an aluminum foil manufacturing apparatus 200 (step S110).

At this time, the aluminum foil (TG) is immersed in the metal oxide sol 212 in a state including a plurality of etch-pores formed on the surface.

Specifically, an aluminum foil (TG) is disposed in the empty non-vacuum chamber 210, and the inside of the chamber 210 is evacuated. Air in the etching-pores of the aluminum foil (TG) can be discharged to the outside while being made into a vacuum state. At this time, the chamber 210 may be evacuated using the pump 240 of the manufacturing apparatus 200, and a valve may be installed in the tube connecting the pump 240 and the chamber 210. The vacuum state pressure may be between about 759 torr and 1 millitorr. The air inside the aluminum foil pore is discharged. In the vacuum state, the aluminum foil TG is immersed in the metal oxide sol 212. Since the air inside the etching pores of the aluminum foil TG is in a vacuum state while the vacuum state is being formed, the metal oxide sol 212 is sucked into the etching pores in the soaking process, The wall surface can be uniformly coated with the metal oxide sol 212.

The metal oxide sol 212 is a coating material in the form of a sol consisting of a metal oxide such as zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), niobium oxide (Nb ₂ O ₅ ) (Ta ₂ O ₅ ), barium titanate (BaTiO ₃ ), and the like. These may be used alone or in combination of two or more. The metal oxide sol 212 may be prepared using a precursor of a metal oxide. Depending on the type of the metal oxide sol 212, the kind and concentration of the precursor and the solvent, the kind of the additive, and the compounding ratio may vary.

The aluminum foil TG may be attached to the support 214 of the chamber 210 and may be immersed in the metal oxide sol 212. The front surface of the chamber 210 includes a transparent window for confirming the coating state of the chamber 210 and a pressure gauge 250 for confirming the pressure inside the chamber 210 may be installed in the chamber 210.

The metal oxide sol 212 is stored in the coating material supply unit 220 and then supplied to the chamber 210 through the supply channel after the chamber 210 is evacuated to be accommodated in the inner space of the chamber 210, TG) can be immersed. At this time, a valve is provided in the supply passage to open / close the flow of the metal oxide sol 212. That is, the valve provided in the tube connecting the pump 240 and the chamber 210 is closed, and the valve connected to the supply channel is gradually opened, so that the metal oxide sol 212 is supplied into the chamber 210 And the amount of liquid of the metal oxide sol 212 in the chamber 210 can be adjusted through the opening amount of the valve connected to the supply flow path.

After the aluminum foil TG is immersed in the metal oxide sol 212 for a predetermined period of time, the remaining metal oxide sol 212 is recovered (Step S120), and the metal oxide sol (Step S130).

The valve connected to the supply flow path is closed to stop the supply of the metal oxide sol 212 and the valve connected to the discharge flow path connected between the chamber 210 and the supply material supply unit 220 is opened, The oxide sol 212 is recovered to the coating material supply unit 220 again.

If the rate at which the metal oxide sol 212 is discharged through the discharge channel, that is, the height of the metal oxide sol 212 remaining in the chamber 210 is set to more than 10 mm / s, the dip- coating layer may increase the pulling speed of the aluminum foil TG and increase the amount of the metal oxide sol 212 coated on the surface of the aluminum foil TG so that a thick coating layer may be formed. There is a disadvantage in that the thickness is uneven and cracks can easily occur. Therefore, the rate at which the metal oxide sol 212 is discharged is preferably 10 mm / s or less, and may be about 0.2 mm / s to about 10 mm / s.

At this time, before the remaining metal oxide sol 212 is recovered, a step of applying pressure while immersing the aluminum foil TG in the metal oxide sol 212 may be further performed. This process can be performed additionally in order to more uniformly and easily proceed the coating of the metal oxide sol 212, and a pressure of about 1 to 5 atm may be applied. A pressurization process may be performed for about 10 minutes to 1 hour. If the coating is not easy due to the depth and / or shape of the etching-pores, the metal oxide sol 212 can be uniformly coated on the inner wall of the etching-pores by applying the pressure as described above. When the depth of the etching-pores is more than 10 mu m, it is preferable to perform the pressing process. As the inert gas, argon (Ar), helium (He) or the like can be used as the gas used in the pressurizing step. After applying pressure, keep the coating for a certain time (10 ~ 30 minutes). The inert gas may be supplied through the gas supply unit 230 connected to the chamber 210.

As described above, the remaining metal oxide sol 212 is recovered and dried. The drying process may be performed at about 100 ° C to 200 ° C, and may be performed for about 30 to 60 minutes. Accordingly, the metal oxide sol 212 is uniformly coated on the surface of the aluminum foil (TG), particularly the inner wall surface of the etch-pores, to form a coating film. The thickness of the coating film can be determined by adjusting the number of cycles including the immersion step (S110), the recovery step (S120), and the drying step (130). That is, the coating thickness can be determined depending on whether the immersion step (S110), the collection step (S120), and the drying step (130) are performed in one cycle and the cycle is repeated several times. At this time, a pressurizing process may be further added to the cycle.

Subsequently, a sintering process is performed on the aluminum foil (TG) on which the coating film is formed (step S140), and an anodizing process is performed on the sintered aluminum foil (TG) (step S150) do.

Specifically, the sintering process is a process of crystallizing the coating film, and can be performed at about 350 ° C to about 600 ° C. At this time, the sintering process can be performed for about 10 minutes to about 60 minutes. The sintering process may be performed at atmospheric pressure or under an oxygen atmosphere.

In one example, the sintering process may be performed subsequently after at least one cycle including the above-described immersion process (S110), recovery process (S120), and drying process (130) is performed. Alternatively, the sintering process may be performed subsequent to the immersion step (S110), the collecting step (S120), and the drying step (130) each time the cycle is included in the cycle.

After the sintering process is performed as described above, an anodizing process is performed on the sintered aluminum foil (TG), wherein the anodizing process is performed at a voltage of about 100 V to 1000 V at a rate of 20 mA / cm ² to 50 mA / cm ² The aluminum foil TG can be anodized. Particularly, the inner wall surface of the etching pores of the aluminum foil (TG) is oxidized to a predetermined thickness to be converted into aluminum oxide, and a coating film is formed on the metal oxide layer. Since the coating film has a uniform thickness and is formed on the inner wall surface of the etching pores of the aluminum foil TG, ultimately a metal oxide layer having a uniform thickness is formed on the inner wall surface, An aluminum foil including a composite oxide layer which is a mixed layer of a metal oxide layer having a high dielectric constant is formed. Such an aluminum foil can be applied to electrolytic capacitors for high voltage.

According to the above description, a metal oxide layer having a high dielectric constant can be uniformly formed on a porous aluminum foil (TG) including a plurality of etching-pores. It is possible to manufacture an aluminum foil in which a composite oxide layer including both aluminum oxide and a metal oxide layer is formed while increasing the effective surface area of the electrode through the etching-pores. Such an aluminum foil can improve the electrostatic capacitance in the same volume by constructing an electrolytic capacitor together with an electrolyte as an electrode structure. As a result, the size of the aluminum electrolytic capacitor can be reduced, and the market competitiveness of the product can be improved. That is, in an electrolytic capacitor including two electrode structures and an electrolyte interposed therebetween, at least one electrode structure may be composed of the aluminum foil according to the present invention.

Hereinafter, the present invention will be described more specifically with reference to specific examples and comparative examples.

Example 1: Preparation of Sample 1

A zirconia sol solution having a concentration of 0.4 mol / l was prepared by using zirconium n-butoxide (Zr [O (CH ₂ ) ₃ CH ₃ ] ₄ ] as a precursor of zirconium oxide. The solvent of the zirconia sol solution was 2-methoxyethanol, [CH ₃ OCH ₂ CH ₂ OH], and acetic acid [CH ₃ COOH] was used as an additive. In the preparation of the zirconia sol solution, the molar ratio of zirconium to acetic acid was 1: 6, and after stirring at room temperature for 60 minutes, nitric acid (HNO ₃ ) was added to prevent precipitation of zirconium oxide.

(50 mTorr) in a state where the aluminum foil having the etch-pores formed therein was placed in the chamber, and the air inside the etching-pores was discharged for about 30 minutes, and then the zirconia sol solution prepared as described above was supplied to the chamber Respectively.

The aluminum foil was immersed in the zirconia sol solution for 15 minutes, and then the pressure of 3 atm was applied with argon gas for 10 minutes, and the residual zirconia sol solution was regulated to fall to 0.5 mm / s. Subsequently, after the chamber was opened, the aluminum foil having the coating film formed thereon was dried at 100 DEG C for 1 hour. The immersion, pressurization and drying processes were performed four times.

The aluminum foil was anodized with an anodic oxidizing solution of pH 3.2 prepared by mixing 100 g of boric acid (H ₃ BO ₃ ) with 1 L of distilled water by performing a sintering process at 500 ° C. for 30 minutes to carry out the present invention Sample 1 according to Example 1 was prepared. At this time, in the anodic oxidation, an anodic oxidation treatment was performed up to 100 V by applying a constant current of 50 mA / cm ² .

Comparative Example 1: Preparation of Comparative Sample 1

The aluminum foil on which the etching pores were formed was immersed in the metal oxide sol solution in Example 1, dried and anodized to prepare Comparative Sample 1 according to the comparative example.

Experiment and Evaluation 1: Check coating uniformity

For each of Sample 1 and Comparative Sample 1, the surface layer was polished and photographed by an electron microscope. The results are shown in Fig.

3 is an electron micrograph of Sample 1 and Comparative Sample 1 according to the present invention.

In FIG. 3, (a) and (c) are electron micrographs of Comparative Sample 1, and (b) and (d) are electron micrographs of Sample 1. At this time, the scale of (a) and (b) is 1 占 퐉, and the scale of (c) and (d) is 100 nm.

Referring to FIG. 3, it can be seen that, in the case of the comparative sample 1 prepared simply by dip coating, the zirconia layer is formed unevenly on the inner wall surface of the etch-pores. (a), etch-pores in which a zirconia layer is not formed are also confirmed, and referring to (c), it can be confirmed that the thickness is uneven.

On the other hand, when the vacuum chamber is subjected to a pressurizing process, it can be seen that a zirconia layer is formed on the inner wall surface of almost all of the etch-pores as shown in (b). Further, referring to (d), it can be seen that the zirconia layer is formed on the inner wall surface of the etch-pore with a uniform thickness.

Examples 2 and 3: Preparation of Samples 2 and 3

The cycle including the immersion process, the pressurization process, the recovery process, and the drying process is substantially the same as the process for producing Sample 1, and the cycle is once performed, and then sintered and anodized to prepare Sample 2 according to Embodiment 2 of the present invention Respectively.

Also, Sample 3 according to Example 3 of the present invention was produced by substantially the same process as that of Sample 1, which was performed twice and then sintered and anodized.

Comparative Example 2: Preparation of Comparative Sample 2

The aluminum foil on which the etching-pores were formed was anodized at 100 V as a comparative sample 2.

Experiment and evaluation 2: Measurement of capacitance

The capacitance of each of the samples 1 to 3 and the comparative sample 2 according to the present invention was measured, and the results are shown in FIG. 4, "0L" is for comparison sample 2, and "4L "," 1L ", and "2L" are for samples 1, 2 and 3, respectively.

4 is a graph showing capacitance measurement results of Samples 1 to 3 and Comparative Sample 2 according to the present invention.

Referring to FIG. 4, it can be seen that the more the zirconia layer becomes thicker as the sample 2 (1L), the sample 3 (2L), and the sample 1 (4L), as compared with the comparative sample 2 (0L), the more the cost increases. In particular, in the case of Sample 1 (4L), it was confirmed that the capacity increase was about 42% at a frequency of 1 kHz as compared with Comparative Sample 2 (0L). This is because the use of about 40% of aluminum foil can be reduced when a capacitor of the same capacity is manufactured, which is a result that the capacitor product can be miniaturized.

Experiment and evaluation 3: Measurement of withstand voltage

The withstand voltage of each of the samples 1 to 3 and the comparative sample 2 according to the present invention was measured, and the results are shown in Fig. 5, "0L" is for comparison sample 2, and "4L "," 1L ", and "2L" are for samples 1, 2 and 3, respectively.

5 is a graph showing the withstand voltage measurement results of Samples 1 to 3 and Comparative Sample 2 according to the present invention.

Referring to FIG. 5, it can be seen that a withstand voltage of 100 V or more is exhibited in all the samples anodized at 100 V, that is, in all of the samples 1 to 3 and the comparative sample 2. That is, it can be seen that there is no problem in applying to all capacitors regardless of zirconia.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

200: manufacturing apparatus 210: chamber
212: metal oxide sol 214: support
220: coating material supply unit 230: gas supply unit
240: Pump 250: Pressure gauge

Claims

A method of manufacturing an electrode structure for an electrolytic capacitor,
Disposing an aluminum foil having a plurality of etch-pores on its surface with a diameter of 1 to 2 占 퐉 and a depth of 10 to 50 占 퐉 in a chamber in a non-vacuum state;
Lowering the internal pressure of the chamber in which the aluminum foil is disposed to a vacuum of 759 Torr to 1 milliTorr;
Impregnating the aluminum foil with the metal oxide sol by providing a metal oxide sol into the chamber in a vacuum state;
A pressurizing step of supplying an inert gas into the chamber while the aluminum foil is impregnated in the metal oxide sol to raise the pressure inside the chamber to 1 atm to 5 atm;
A discharging step of discharging the metal oxide sol from the chamber to form a coating film of the metal oxide sol on the inner wall surface of the etching pores;
A drying step of drying the coating film of the metal oxide sol;
A sintering step of sintering the coating film of the dried metal oxide sol; And
And anodic oxidation of the aluminum foil to form a composite oxide layer comprising an aluminum oxide layer and a metal oxide layer stacked on a wall surface of the etch-
And the pores corresponding to the etch-pores are formed on the surface of the electrode structure on which the complex oxide layer is formed.
A method for manufacturing an electrode structure for an electrolytic capacitor.

The method according to claim 1,
Characterized in that the cycle including the impregnation step, the pressurization step, the discharge step and the drying step is repeatedly carried out before carrying out the sintering step or before anodizing the sintered aluminum foil,
A method for manufacturing an electrode structure for an electrolytic capacitor.

The method according to claim 1,
Characterized in that the metal oxide sol of the coating material supply portion is supplied to the chamber by a pressure difference between a coating material supply portion for accommodating the metal oxide sol and a vacuum chamber.
A method for manufacturing an electrode structure for an electrolytic capacitor.

The method according to claim 1,
The draining step
Wherein the rate of discharge of the metal oxide sol is adjusted to 0.2 mm / s to 10 mm / s based on the height of the metal oxide sol accommodated in the chamber.
A method for manufacturing an electrode structure for an electrolytic capacitor.

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The method according to claim 1,
Characterized in that the sintering step is carried out at 350 ° C to 600 ° C.
A method for manufacturing an electrode structure for an electrolytic capacitor.

The method according to claim 1,
Wherein the anodic oxidation is carried out by applying a current of 20 mA / cm ² to 50 mA / cm ² up to a voltage of 100 V to 1000 V,
A method for manufacturing an electrode structure for an electrolytic capacitor.

delete