JP2008108754A - Electrode material for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode material for electrolytic capacitor having a large capacitance and a low ESR. <P>SOLUTION: In the electrode material for electrolytic capacitor, a valve metal particle layer provided with an oxide film on the surface and having a porosity of 20-60% and a specific surface area of 30×10<SP>3</SP>cm<SP>2</SP>/cm<SP>3</SP>-400×10<SP>3</SP>cm<SP>2</SP>/cm<SP>3</SP>with the valve metal particles being mixed in a predetermined distribution of particle size in the range of 0.005-0.1 μm, or a valve metal particle layer having a porosity of 20-60% and a specific surface area of 20×10<SP>3</SP>cm<SP>2</SP>/cm<SP>3</SP>-70×10<SP>3</SP>cm<SP>2</SP>/cm<SP>3</SP>and containing valve metal particles having particle size of 0.2 μm or above is formed on the surface of a metal substrate different from the valve metal thus attaining a large capacitance and a low ESR. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrode material for an electrolytic capacitor, and more particularly to an electrode material for an electrolytic capacitor having unprecedented high capacitance characteristics.

  In recent years, with the miniaturization and high reliability of electronic devices, there has been a strong demand for miniaturization and high capacity of electrolytic capacitors.

  Electrolytic capacitors are generally strip-like high-purity aluminum foil that is chemically or electrochemically etched to enlarge the surface of the aluminum foil, and this aluminum foil is converted into a chemical conversion solution such as an aqueous ammonium adipate solution. Anode electrode foil formed by chemical conversion treatment inside to form an oxide film layer on the surface, and a cathode electrode foil made of high-purity aluminum foil subjected only to etching treatment are wound through a separator made of manila paper or the like. Turn to form a capacitor element. The capacitor element is impregnated with an electrolytic solution for driving an electrolytic capacitor, and then stored in a bottomed cylindrical outer case made of aluminum or the like. A sealing body made of elastic rubber is attached to the opening of the outer case, and the outer case is sealed by drawing.

    In such an aluminum electrolytic capacitor, in order to increase its capacitance, the effective surface area of the etching foil is increased to improve the capacitance per unit area, and the etching technology that increases the effective surface area of the etching foil. Development is underway. As such an etching technique, the composition of an etching solution and the development of a current waveform applied during etching have been performed.

  By the way, in recent years, with the progress of digitalization of electronic information equipment, electrolytic capacitors using such electrode foils are required to be small, have a large capacity and have a low impedance in a high frequency region. In particular, in communication devices such as personal computers and mobile phones, there is a strong demand for further increasing the capacitance of the capacitor as the calculation speed of the mounted CPU increases.

  Conventionally, multilayer ceramic capacitors and the like have been widely used as capacitors used in communication devices in order to meet the demand for miniaturization. However, these capacitors cannot meet the demand for larger capacity in recent years. Therefore, electrolytic capacitors have been used as capacitors having a low equivalent series resistance value (ESR value), a large capacitance, and a sufficiently small size.

And as an electrode foil for electrolytic capacitors, there is an attempt to further reduce ESR by thickening the unetched portion of the electrode foil, that is, the remaining core portion (Patent Documents 1 and 2), but the demand for large capacity is high. The conventional electrode foil cannot answer this requirement.
JP 2003-59768 A JP 2003-59776 A

Accordingly, an object of the present invention is to provide an electrode material for an electrolytic capacitor that has a large capacitance that cannot be achieved by a conventional etching foil and that has a low ESR.

The electrode material for a first electrolytic capacitor of the present invention comprises a valve metal particle layer having an oxide film on the surface, a porosity of 20 to 60%, a specific surface area of 30 × 10 ³ cm ² / cm ^{3 to} 400 × 10 ³ cm ² / and cm ^3, wherein the valve metal particles an electrode material formed on the surface of the aluminum hard material mixed with a predetermined distribution range of at least 0.005~0.1μm its particle size, several times a conventional electrode foil It has a capacitance.

    Further, in the electrode material, primary particles of the valve metal particles are mixed with a predetermined distribution in a particle diameter range of at least 0.005 to 0.1 μm. Capacitance is increased by particles having a small particle size, and voids can be secured by particles having a large particle size, so that clogging due to an oxide film generated by reaction with an electrolytic solution can be suppressed after an electrolytic capacitor is created. .

    Moreover, the electrode material for electrolytic capacitors of the present invention has a valve metal made of aluminum, and a valve metal particle layer having an oxide film on the surface has an Al / O composition ratio of 2.0 to 5.5. Furthermore, the bonding property between the valve metal particles is improved by the oxygen content of this composition ratio.

The electrode material for a second electrolytic capacitor of the present invention comprises a valve metal particle layer having an oxide film on the surface, a porosity of 20 to 60%, a specific surface area of 20 × 10 ³ × cm ² / cm ³ to 70 × 10 ³ cm ^2. / Cm ³ , an electrode material for an electrolytic capacitor formed on the surface of a hard aluminum material including the valve metal particles having a particle diameter of 0.2 μm or more, and having a capacitance that cannot be realized by a conventional electrode foil ing.

    Furthermore, since the electrode material includes valve metal particles having an oxide film on the surface having a particle diameter of 0.2 μm or more in the valve metal particle layer, a large gap can be provided between the valve metal particles. Therefore, when an anodic oxide film is formed by anodization, it is suppressed that the void is filled with the oxide film, and a high capacitance can be obtained.

    In the electrode material for electrolytic capacitors of the present invention, the valve metal is aluminum, and the Al / O composition ratio of the valve metal particle layer having an oxide film on the surface is 2.0 to 125. Furthermore, the bonding property between the valve metal particles is improved by the oxygen content of this composition ratio.

  The electrode material of the present invention has a capacitance characteristic that cannot be realized by an electrode foil obtained by etching technique.

The electrode material as described above can be obtained by a normal vapor deposition method. In such a vapor deposition method, a roll-shaped aluminum foil is sent out in a vapor deposition machine having a high degree of vacuum, and vapor deposition is performed in a flat state and wound up to produce an electrode material. However, at the time of feeding and winding, there is a problem that tension is applied to the aluminum foil and nonuniform stress is applied to the aluminum foil, so that vapor deposition cannot be performed well.
However, since the electrode material for an electrolytic capacitor of the present invention is made of a hard aluminum material, a favorable vapor deposition state can be obtained without applying non-uniform stress at the time of feeding and winding. A valve metal particle layer having an oxide film on the surface can be formed.

  As described above, the electrode material for an electrolytic capacitor of the present invention has a high capacitance, and the electrode material for an electrolytic capacitor is used as a cathode or the electrode material for an electrolytic capacitor is anodized and used as an anode. Thus, an electrolytic capacitor having a high capacitance that has not been conventionally available can be realized.

The electrode material for a first electrolytic capacitor of the present invention is an electrode material having a valve metal particle layer having an oxide film on the surface, and the porosity of the valve metal particle layer is 20 to 60%, preferably 25 to 55. %, More preferably 30 to 50%. The specific surface area is 30 × 10 ³ cm ² / cm ^{3 to} 400 × 10 ³ cm ² / cm ³ , preferably 70 × 10 ^{3 to} 400 × 10 ³ cm ² / cm ³ , more preferably 90 × 10 ^3. ˜400 × 10 ³ cm ² / cm ³ .

  The specific surface area is calculated from the capacitance and area of a plain foil on which a film having capacitance is formed on the electrode material of the present invention, and a similar film is formed. The porosity can be measured by a mercury intrusion method.

  In the electrode material, primary particles of the valve metal particles are mixed with a predetermined distribution within a particle diameter range of at least 0.005 to 0.1 μm. High capacitance can be obtained by such small particles, and voids can be secured by the large particles, so that clogging due to an oxide film generated by reaction with the electrolytic solution after the electrolytic capacitor is formed can be suppressed. Therefore, an electrode material having a large capacitance can be obtained by increasing the number of particles having a small particle diameter, and the stability of the capacitance can be increased by increasing the number of particles having a large particle diameter.

  In the electrode material, the valve metal is aluminum, and the Al / O composition ratio of the valve metal particle layer having an oxide film on the surface is 2.0 to 5.5. The Al / O composition ratio can be measured and calculated by GDS analysis.

  The electrode material is preferably used as a cathode, but may be subjected to cathodic conversion. Furthermore, it can also be used as an anode material for electrolytic capacitors by performing anodization at an extremely low pressure. As a chemical conversion method, a chemical conversion method similar to that of an aluminum foil for electrolytic capacitors can be used.

The electrode material for a second electrolytic capacitor of the present invention is an electrode material having a valve metal particle layer having an oxide film on the surface, and the porosity of the valve metal particle layer is 20 to 60%, preferably 22 to 58. %, More preferably 25-55%. The specific surface area is 20 × 10 ³ cm ² / cm ³ to 70 × 10 ³ cm ² / cm ³ , preferably 30 × 10 ^{3 to} 60 × 10 ³ cm ² / cm ³ , more preferably 35 × 10 ^3. ~ 55 × 10 ³ cm ² / cm ³ .

  Further, since the electrode material includes valve metal particles having an oxide film on the surface having a particle diameter of 0.2 μm or more in the valve metal particle layer, a large gap can be provided between the valve metal particles. Therefore, when an anodic oxide film is formed by anodization, it is suppressed that the void is filled with the oxide film, and a high capacitance can be obtained.

    In addition, the electrode material, the valve metal is aluminum, and the Al / O composition ratio of the valve metal particle layer having an oxide film on the surface is 2.0 to 125, so that the capacitance can be stable, Furthermore, the bondability between the valve metal particles is improved by the oxygen content of this composition ratio.

  The electrode material is preferably used as an anode material for electrolytic capacitors by anodizing. As a chemical conversion method, a chemical conversion method similar to that of an aluminum foil for electrolytic capacitors can be used.

  In the present invention, an aluminum hard material (H material) is used as a base material, and this aluminum hard material is a hard material for an electrode used for an electrolytic capacitor. This aluminum hard material is obtained by hot rolling, cold rolling, and foil rolling of an aluminum material that has been heated and homogenized.

  The electrode material as described above can be obtained by a normal vapor deposition method. In order to form a valve metal particle layer having an oxide film on the surface, vapor deposition is performed in an inert gas atmosphere containing oxygen. Argon, nitrogen, etc. can be used as the inert gas. The pressure of the inert gas is preferably 0.05 to 0.8 Pa, and the oxygen partial pressure is preferably 1/10 or less of the pressure of the inert gas.

The present invention will be described more specifically with reference to the following examples.
(Example 1) Nitrogen was deposited on a 99.8 wt% aluminum hard material of 25 μm in an oxygen atmosphere at a pressure of 1/10 or less of the pressure of nitrogen at a pressure of 0.1 Pa and the electrode of the present invention. Made the material.
(Comparative Example 1) Using a mixed solution of hydrochloric acid, sulfuric acid and nitric acid as an electrolyte, an alternating current having a frequency of 50 Hz or less and a current density of 1 A / cm ² or less was applied to a 99.9 wt% aluminum sheet, and the core thickness was 25 μm. Etching treatment was performed so as to obtain an etching foil.
Example 2 Electrode material of the present invention by depositing aluminum on 25 μm 99.9 wt% aluminum hard material in an oxygen atmosphere at a pressure of 1/10 or less of the nitrogen pressure and the pressure of 0.3 Pa It was created. Thereafter, anodization was performed by applying a voltage of 20 V in an aqueous solution of ammonium adipate.
(Comparative Example 2) Using a mixed solution of hydrochloric acid, sulfuric acid and nitric acid as an electrolyte, an alternating current having a frequency of 20 Hz or less and a current density of 1 A / cm ² or less was applied to an aluminum sheet having a core thickness of 25 μm. Etching treatment was performed to obtain an etching foil. Thereafter, anodization was performed in the same manner as in the example.

    As described above, the capacitances of Examples 1 and 2 which are the electrode material and the formed electrode material of the present invention are 2 to 7 times the conventional etching foil and Comparative Examples 1 and 2 which are the conversion foil. It can be seen that it has an electrostatic capacity and is an unprecedented electrode material for electrolytic capacitors.

Claims (4)

The valve metal particle layer having an oxide film on the surface has a porosity of 20 to 60% and a specific surface area of 30 × 10 ^{3 to} 400 × 10 ³ cm ² / cm ³ , and the valve metal particles have a particle size of at least 0.005 to 0.1 μm Electrode capacitor electrode material formed on the surface of a hard aluminum material mixed with a predetermined distribution in the range. The electrode material for an electrolytic capacitor according to claim 1, wherein the valve metal is aluminum, and the Al / O composition ratio of the valve metal particle layer having an oxide film on the surface is 2.0 to 5.5. A valve metal particle layer having an oxide film on the surface has a porosity of 20 to 60%, a specific surface area of 20 × 10 ³ to 70 × 10 ³ cm ² / cm ³ , and the valve metal particles include particles having a particle diameter of 0.2 μm or more. Electrolytic capacitor electrode material formed on the surface of a hard aluminum material. The electrode material for an electrolytic capacitor according to claim 3, wherein the valve metal is aluminum and the Al / O composition ratio of the valve metal particle layer having an oxide film on the surface thereof is 2.0 to 125.