JP5104007B2 - Electrode foil and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrode foil suitable for an anode foil of an electrolytic capacitor and a manufacturing method thereof.

  In general, an electrode foil for an aluminum electrolytic capacitor is manufactured using a rolled foil of 98% or more high-purity aluminum as a starting material. In acid or alkaline solution that dissolves aluminum, the known DC electrolytic etching method, AC electrolytic etching method, or both are alternately used to form innumerable pits on the surface of the aluminum foil, thereby increasing the substantial surface area. , The one with larger capacitance is used.

  By this etching method, the magnification per unit area is several hundred times, approximately 300 times to 400 times.

  Electrolytic capacitors are characterized in that since the dielectric layer is made of an extremely thin oxide film layer, the capacitance value per unit area of the electrode is high, and a small and large-capacity capacitor can be obtained. On the other hand, with the downsizing of electronic equipment, there is a demand for further downsizing and larger capacity of electrolytic capacitors.

    If an attempt is made to increase the capacity of the unit area by etching as described above, the entire aluminum foil is covered with etching pits, the electrode foil becomes brittle, and the electrode foil strength is reduced.

    In order to increase the surface area of the electrode foil while maintaining the foil strength, one method for this is to increase the capacity per unit area by etching a thick aluminum foil.

    In this method, the capacity of the unit area is large. However, when a general wound electrolytic capacitor is made using the above electrode foil, the thickness of the electrode foil is so large that the length of the usable electrode foil is reduced. Limitation occurs, and an element that cannot be stored in the case is formed.

  Furthermore, in the case of a multilayer solid electrolytic capacitor, there are restrictions on the height due to the nature of its shape, and the height cannot be increased unnecessarily. For foils with reduced strength, the welding conditions during lamination cannot be set easily, and the strength after welding also becomes problematic.

  For this reason, if the capacity is increased, the number of laminated layers must be increased or a thick electrode foil must be used, resulting in an increase in the height of the capacitor.

In addition to the above general prior art, in the case of a wound electrolytic capacitor, paying attention to the fact that the capacity is calculated by the combined capacity, as described in Patent Document 1, the deposition of metal nitride on the surface of the substrate is performed. A method of increasing the capacity by forming a film is known. Alternatively, as described in Patent Document 2, using a foil in which carbon is physically in contact with the cathode, the capacity on the cathode side is canceled, and only the capacity on the anode side is reflected in the composite capacity, thereby increasing the capacity. A method has been proposed.
Japanese Patent Laid-Open No. 2-117123 Patent 3,875,705

  However, even if these conventional methods are used, in order to further increase the capacity demanded from the market in the future, an anode material capable of realizing a large capacity while maintaining the same thickness, strength and pressure resistance as the current situation is available. Without this, it is not possible to obtain an electrolytic capacitor that can sufficiently cope.

  Accordingly, an object of the present invention is to provide a structure of an electrode foil suitable for an anode foil capable of dramatically increasing the surface area of the anode foil related to the capacitance of the capacitor while maintaining the same thickness, strength, and breakdown voltage as in the past, and its manufacture. It is to provide a method.

  To achieve the above object, an electrode foil according to the present invention has a structure in which metal particles and ceramic particles mainly composed of valve metal particles and / or ceramic particles having a dielectric constant are deposited on the surface of the metal foil. It is characterized by that.

  Further, the metal particles and / or ceramic particles are deposited using aerosol deposition.

  In order to achieve the above object, a method for producing an electrode foil according to the present invention comprises placing an aluminum foil in a film forming chamber of an aerosol chamber, aerosolizing the aluminum powder, and producing the aerosolized aluminum powder as the product. It sprays on the aluminum foil arrange | positioned in a film chamber, and aluminum particle | grains are deposited on the said aluminum foil, It is characterized by the above-mentioned.

  Preferably, ultrafine powder having a dielectric constant is uniformly diffused in a high-speed gas on the surface of the aluminum foil or the surface of the etching foil obtained by electrolytic etching of the surface of the aluminum foil in this way, The conventional aluminum single-piece etched foil is formed by injecting the gas of metal onto the surface of the target metal foil or etched foil to form an ultrafine powder molding film and then etching each fine powder. Compared with, the surface area of aluminum can be increased with the same thickness of foil.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view showing the structure of a wound electrolytic capacitor as an embodiment in which an electrode foil according to the present invention is applied as an anode foil.

  In FIG. 1, (a) is an external appearance, and (b) is a diagram in which the exterior (metal case) 10 is removed and the inside is observed in a perspective manner. An anode electrode lead 12 and a cathode electrode lead 13 are fixed to a sealing body (insulating resin) 11.

  The wound capacitor element 20 is fixed to the sealing body (insulating resin) 11 in the exterior (metal case) 10, and the anode electrode lead 12 and the cathode electrode lead 13 each use the electrode foil according to the present invention. The anode foil 21 and the cathode foil 22 are electrically connected.

  The anode foil 21 and the cathode foil 22 are wound into a cylindrical shape via an electrolytic paper 23 as a separator, and the terminal portion is fixed with a winding tape 24 to maintain the wound state.

  The electrolytic capacitor using the electrode foil of the present invention realizes a higher capacity than a conventional electrolytic capacitor using an etched electrode foil obtained by electrolytic etching of an aluminum foil serving as an anode foil.

  As a feature, the electrode foil according to the present invention is an ultrafine powder of metal having a particle diameter in the range of 100 nm to 100 μm on the surface of a conventional metal foil or an etched metal foil obtained by etching the metal foil. , Ultrafine powders of the above metals and / or ultrafine powders of oxides, nitrides and carbides having a high dielectric constant of 10 or more, or ultrafine powders obtained by oxidizing the surface of valve metals, 500 nm or less The ultrafine powder having a particle size of 1 is uniformly diffused in a high-speed gas, and the gas is sprayed onto the surface of the etched electrode foil, which is the object, to form a molded film of ultrafine powder.

  The valve metal particles include at least one of valve metal aluminum and its compound, titanium and its compound, tantalum and its compound, niobium and its compound.

  With the above structure, it is possible to obtain an electrode foil in which the surface area of the aluminum is expanded with the same thickness of the electrode foil as compared with the conventional etched electrode foil of a single aluminum foil. In addition, the ultrafine powder molded film formed on the etched electrode foil surface may be electrolytically etched.

  By these treatments, an electrode foil in which the surface area of aluminum is further expanded in the electrode foil having the same thickness can be obtained according to the present invention as compared with a conventional etched electrode foil of a single aluminum foil.

  With the characteristic configuration of the electrode foil according to the present invention, it is possible to provide a small-sized and large-capacity electrolytic capacitor when used as an anode foil.

  Hereinafter, the electrode foil configuration according to the present invention and the characteristics of the manufacturing method thereof will be described in detail based on examples.

[First embodiment]
(Example of depositing aluminum fine particles on a normal aluminum foil)
FIG. 2 is a flowchart showing the procedure of the method for manufacturing the electrode foil of the first embodiment according to the present invention. A state diagram corresponding to the processing steps is shown on the left side of the flow.

  An aluminum foil 21 having a purity of 99% by a rolling method having a thickness of 40 μm was prepared (Step S1: State I).

  Surface treatment was performed on the prepared aluminum foil 21 in an aerosol deposition chamber as follows. FIG. 3 is a diagram showing a schematic configuration example of the aerosol deposition chamber.

  The film forming chamber 303 has a stage 304 movable in the X and Y directions, and the rolled aluminum foil 21 prepared in step S1 is attached to the stage 304 (step S2).

  The inside of the film forming chamber 303 was evacuated by a vacuum pump 306 and depressurized to 10 Pa or less in advance (step S3).

  On the other hand, a raw material powder 300 mainly composed of Al powder, which is a valve metal having an average particle diameter of 8 μm, is placed in an aerosol generating container 301A, and ultrasonic waves are applied to the entire aerosol generating container 301A by a vibrator 301B and heated at about 150 degrees. Then, vacuum treatment was performed for 30 minutes, and a pretreatment was performed to remove moisture formed on the powder surface (step S4).

High-purity helium gas (gas pressure: 2 kg / cm ² , gas flow rate: 10 l / min.) 302 was introduced into the aerosol generator 301A, and the raw material powder 300 subjected to pretreatment was aerosolized (step S5).

  Next, this aerosol is fed into the film forming chamber 303 through a pipe by a nozzle 305. The nozzle 305 used was a spiral groove formed inside. Injection was performed for 3 minutes from the nozzle 305 having a spiral groove on the inner side toward the substrate aluminum foil 21 (step S6). The pressure in the chamber at this time was kept constant at 500 Pa.

  Thus, the Al film 201A formed on the upper surface of the substrate aluminum foil 21 by aerosol deposition with aluminum fine particles had a thickness of 20 μm (state II: aerosol deposition with aluminum fine particles).

  It is also possible to form an aluminum film on both surfaces of the substrate aluminum foil 21 in the manner described above.

Subsequently, a pre-sintering treatment for densifying the deposited aluminum metal particles was performed by annealing in an inert gas at 300 ° C. which is lower than (melting point + 100 ° C.) of the aluminum. This foil was subjected to an electrolytic treatment in hydrochloric acid, nitric acid, an AlCl ₃ aqueous solution at a current density of 0.2 A / m ² (50 Hz) for 8 minutes, and a roughening treatment (etching) was performed (step S7). By this etching process, a fine cavity layer 201B was formed (state III).

  Thereafter, chemical conversion treatment was performed in an aqueous solution of ammonium adipate (step S8).

  By this treatment, the surface area is enlarged by forming the fine cavity layer 201B, and the surface 201C of the fine cavity layer 201B is oxidized by the chemical conversion treatment in step S8, so that the dielectric oxide film layer 200 having a large dielectric constant becomes the substrate aluminum foil 21. (State IV).

  With respect to the dielectric oxide film layer 200 formed by the process flow of FIG. 3, the leakage current at 30 minutes after reaching the predetermined voltage of 20 V was measured. The tensile strength of the film was also measured.

  At this time, a test piece with a width of 1 cm and a length of 5 cm was cut out and pulled at 10 mm / min with a tensile tester, and the breaking strength was 1.5 kg / cm (not normalized with the thickness, but the two-dimensional shape of the test piece) If it is equal to or greater than the above), the measurement was accepted.

[Second Embodiment]
(Example of depositing aluminum fine particles on etched aluminum foil)
FIG. 4 is a flowchart showing the procedure of the method for manufacturing the electrode foil of the second embodiment according to the present invention. Here, in the first embodiment according to the flow of FIG. 2 described above, the example in which the substrate aluminum foil 21 having a thickness of 40% by 99% by the rolling method is used as the electrode foil has been described. Further, as the second embodiment, As shown in FIG. 5A, an etched aluminum foil having a rough surface (etched surface) 201 that was previously etched and was used in the prior art was used.

That is, pretreatment was performed by annealing a 99% aluminum foil of 40 μm thickness by rolling at 300 ° C. in an inert gas. The foil was subjected to an electrolytic treatment in an aqueous solution of hydrochloric acid, nitric acid, and AlCl ₃ at a current density of 0.2 A / m ² (50 Hz) for 8 minutes to roughen the surface. Thereby, the aluminum foil 21 having the etched surface 201 shown in the cross section of the aluminum foil in FIG. 5A was obtained (step S1).

  Then, the roughened aluminum foil was subjected to the processing from step S2 to step S8 in the same manner as the processing flow of FIG. 2 described for the first embodiment. However, the etching process in step S7 in FIG. 2 was omitted.

  It is also possible to form an aluminum film on both sides of the foil in the manner described above.

  FIG. 5B schematically shows a cross section of a layer 202 obtained by the above-described treatment, in which aluminum fine particles are deposited by aerosol deposition on a rough surface 201 that has been previously etched.

  As with the first embodiment, the leakage current at 30 minutes after reaching the predetermined voltage of 20 V was measured. Tensile strength is 1cm wide and 5cm long, cut out with a tensile tester at 10mm / min, breaking strength is 1.5kg / cm (not normalized by thickness, specified by two-dimensional shape of the specimen) If it is above, it is considered as a pass. In addition, the tensile strength of the membrane foil was measured.

[Third embodiment]
(Example of depositing ceramic fine particles on etched aluminum foil)
FIG. 6 is a flowchart showing the procedure of the method for manufacturing the electrode foil of the third embodiment according to the present invention. Similar to the second embodiment, 99% aluminum foil 40 μm thick by rolling was annealed at 300 ° C. in an inert gas and pretreated. The foil was subjected to an electrolytic treatment in an aqueous solution of hydrochloric acid, nitric acid, and AlCl ₃ at a current density of 0.2 A / m ² (50 Hz) for 8 minutes to roughen the surface. Thereby, etched aluminum foil 21 having rough surface (etched surface) 201 in FIG. 5A was obtained (step S1).

  Surface treatment was performed on the etched aluminum foil 21 (see FIG. 5A) in the aerosol deposition chamber shown in FIG. 2 according to the flow of FIG.

  The rolled aluminum foil 21 prepared in Step S1 is attached to the stage 304 that can move in the X and Y directions in the film forming chamber 303 (Step S2).

  The inside of the film forming chamber 303 was evacuated by a vacuum pump 306 and depressurized to 10 Pa or less in advance (step S3).

  On the other hand, an ultrafine ceramic made of barium titanate having an average particle diameter of 100 nm is placed as a raw powder 300 in an aerosol generating container 301A, and ultrasonic waves are applied to the entire aerosol generating container 301A by a vibrator 301B and heated at about 150 degrees, A pretreatment for removing moisture formed on the powder surface was performed by vacuum degassing for 30 minutes (step S4).

High-purity helium gas (gas pressure: 2 kg / cm ² , gas flow rate: 10 l / min.) 302 was introduced into the aerosol generator 301A, and the raw material powder 300 subjected to pretreatment was aerosolized (step S5).

  Next, this aerosol is fed into the film forming chamber 303 through a pipe by a nozzle 305. The nozzle 305 used was a spiral groove formed inside. Injection was performed for 3 minutes from the nozzle 305 having a spiral groove on the inner side toward the substrate aluminum foil 21 (step S6). The pressure in the chamber at this time was kept constant at 500 Pa.

  Thus, the ceramic (barium titanate) film formed on the upper surface of the substrate aluminum foil 21 by aerosol deposition with aluminum fine particles had a thickness of 2 μm.

  In addition, it is also possible to form a ceramic film on both surfaces of the substrate aluminum foil 21 in the above manner.

  Subsequently, a pre-sintering treatment for densifying the deposited aluminum metal particles was performed by annealing at 500 ° C., which is a temperature lower than (melting point + 100 ° C.) of the aluminum, in an inert gas.

  Next, chemical conversion treatment was performed in an aqueous solution of ammonium adipate (step S8).

  Also in the third embodiment, the etching process in step S7 in FIG. 2 was omitted.

  With respect to the dielectric oxide film layer 200 formed by the processing flow of FIG. 6, the leakage current at 30 minutes after reaching the predetermined voltage 20V was measured. The tensile strength of the film was also measured.

  At this time, a test piece with a width of 1 cm and a length of 5 cm was cut out and pulled at 10 mm / min with a tensile tester, and the breaking strength was 1.5 kg / cm (not normalized with the thickness, but the two-dimensional shape of the test piece) If it is equal to or greater than the above), the measurement was accepted.

[Fourth embodiment]
(Example in which a mixture of ceramic fine particles and aluminum fine particles is formed on an etched aluminum foil)
FIG. 7 is a flowchart showing the procedure of the electrode foil manufacturing method of the fourth embodiment according to the present invention. Similar to the second and third embodiments, a 99% aluminum foil having a thickness of 40 μm was annealed at 300 ° C. in an inert gas and subjected to pretreatment. The foil was subjected to an electrolytic treatment in an aqueous solution of hydrochloric acid, nitric acid, and AlCl ₃ at a current density of 0.2 A / m ² (50 Hz) for 8 minutes to roughen the surface. Thereby, the aluminum foil 21 having the rough surface 201 of FIG. 5A was obtained (step S1).

  Surface treatment was performed on the etched aluminum foil 21 (see FIG. 5A) in the aerosol deposition chamber shown in FIG. 2 according to the flow of FIG.

  The rolled aluminum foil 21 prepared in Step S1 is attached to the stage 304 that can move in the X and Y directions in the film forming chamber 303 (Step S2).

  The inside of the film forming chamber 303 was evacuated by a vacuum pump 306 and depressurized to 10 Pa or less in advance (step S3).

  On the other hand, a mixture of ultrafine ceramics composed of barium titanate with an average particle size of 100 nm and ultrafine aluminum particles with an average particle size of 8 μm is put as a raw material powder 300 in an aerosol generating container 301A and superposed on the entire aerosol generating container 301A by a vibrator 301B. A pretreatment was performed to remove moisture formed on the powder surface by vacuum degassing for 30 minutes while applying sonic waves and heating at about 150 degrees (step S4).

High-purity helium gas (gas pressure: 2 kg / cm ² , gas flow rate: 10 l / min.) 302 was introduced into the aerosol generator 301A, and the raw material powder 300 subjected to pretreatment was aerosolized (step S5).

  Next, this aerosol is fed into the film forming chamber 303 through a pipe by a nozzle 305. The nozzle 305 used was a spiral groove formed inside. Injection was performed for 3 minutes from the nozzle 305 having a spiral groove on the inner side toward the substrate aluminum foil 21 (step S6). The pressure in the chamber at this time was kept constant at 500 Pa.

  Thus, as shown in FIG. 8, the ceramic (barium titanate) -aluminum film 200 formed on the upper surface of the substrate aluminum foil 21 by the aerosol deposition by the ceramic fine particles 202a and the aluminum fine particles 202b has a thickness of 20 μm. It was.

  It is also possible to form a ceramic (barium titanate) ceramic-aluminum film on both surfaces of the substrate aluminum foil 21 in the manner described above.

  Next, chemical conversion treatment was performed in an aqueous solution of ammonium adipate (step S8).

  Also in the fourth embodiment, the etching process in step S7 in FIG. 2 was omitted.

  With respect to the dielectric oxide film layer 200 formed by the process flow of FIG. 7, the leakage current at 30 minutes after reaching the predetermined voltage of 20 V was measured. The tensile strength of the film was also measured.

  At this time, a test piece with a width of 1 cm and a length of 5 cm was cut out and pulled at 10 mm / min with a tensile tester, and the breaking strength was 1.5 kg / cm (not normalized with the thickness, but the two-dimensional shape of the test piece) If it is equal to or greater than the above), the measurement was accepted.

[Comparative example]
The comparative example compared with the said 1st-4th Example was implemented as follows.

A 99% aluminum foil having a thickness of 40 μm was annealed at 300 ° C. in an inert gas and pretreated. The foil was subjected to an electrolytic treatment in an aqueous solution of hydrochloric acid, nitric acid, and AlCl ₃ at a current density of 0.2 A / m ² (50 Hz) for 8 minutes to roughen the surface. Thereafter, chemical conversion treatment was performed in an aqueous solution of ammonium adipate.

  That is, the comparative example does not perform the roughening process by forming a film with the aluminum fine particles or ceramic fine particles in steps S2 to S7 in the process flow of the first embodiment.

  Then, the leakage current at 30 minutes after reaching the predetermined voltage of 20V was measured. The tensile strength of the film was also measured.

  At this time, a test piece with a width of 1 cm and a length of 5 cm was cut out and pulled at 10 mm / min with a tensile tester, and the breaking strength was 1.5 kg / cm (not normalized with the thickness, but the two-dimensional shape of the test piece) If it is equal to or greater than the above), the measurement was accepted. In addition, the tensile strength of the foil was measured.

  Table 1 below is a table comparing the first to fourth examples with comparative examples.

  In Table 1, the comparative example is compared with the 2nd-4th Example which is the foil which formed the deposit layer on the conventional etching aluminum foil by the aerosol deposition method of this invention.

  The tensile strength of the foils of the first to fourth examples is improved as compared with the comparative example. The electrostatic capacity per unit area is about 4 times as large as 40 μF in the comparative example and 150 to 180 μF in the second to fourth embodiments.

  Therefore, according to the present invention, it is possible to provide an electrolytic capacitor having a capacitance about four times that of the prior art.

  The aerosol deposition method is also advantageous in that it is possible to adjust the type and compounding ratio of valve metal particles to be stored in consideration of the relationship between the withstand voltage of the film and the capacity. Of course, only one type of valve metal is stored. You may let them.

（付記１）
金属箔表面上に誘電率を有する弁金属粒子及び／又はセラミック粒子を主成分とした金属粒子及びセラミック粒子が堆積された構造を有する電極箔。

(Appendix 1)
An electrode foil having a structure in which metal particles and ceramic particles mainly composed of valve metal particles and / or ceramic particles having a dielectric constant are deposited on the surface of the metal foil.

(Appendix 2)
In Appendix 1,
The electrode foil, wherein the metal particles and / or the ceramic particles are deposited using aerosol deposition.

(Appendix 3)
In Appendix 1,
The electrode foil, wherein the metal particles have a particle size in a range of 100 nm to 100 μm.

(Appendix 4)
In Appendix 1,
The ceramic particles are made of an oxide, nitride, or carbide having a dielectric constant of 10 or more.

(Appendix 5)
In Appendix 1,
The ceramic particles have a particle size of 500 nm or less.

(Appendix 6)
In Appendix 1,
The electrode metal foil includes at least one of valve metal aluminum and a compound thereof, titanium and a compound thereof, tantalum and a compound thereof, niobium and a compound thereof.

(Appendix 7)
An aluminum foil is placed in the deposition chamber of the aerosol chamber,
Aerosolize aluminum powder,
A method for producing an electrode film, wherein the aerosolized aluminum powder is sprayed onto an aluminum foil disposed in the film forming chamber, and aluminum particles are deposited on the aluminum foil.

(Appendix 8)
In Appendix 7,
The aluminum foil disposed in the film forming chamber has a surface roughened by electrolytic etching treatment.

(Appendix 9)
In Appendix 7 or 8,
An electrode foil, wherein the surface side of the aluminum foil on which the aluminum particles are deposited is etched.

(Appendix 10)
In Appendix 9,
A chemical conversion treatment is further performed on the surface on which the etched aluminum particles are deposited.

(Appendix 11)
An aluminum foil whose surface has been etched is placed in the deposition chamber of the aerosol chamber,
Aerosolize ceramic powder,
A method for producing an electrode film, the method comprising spraying the aerosolized ceramic powder onto an aluminum foil disposed in the film forming chamber and depositing ceramic particles on the aluminum foil.

(Appendix 12)
An aluminum foil whose surface has been etched is placed in the deposition chamber of the aerosol chamber,
Aerosolize a mixture of aluminum powder and ceramic powder;
A method for producing an electrode film, wherein the aerosolized mixture of aluminum powder and ceramic powder is sprayed onto an aluminum foil disposed in the film forming chamber, and aluminum particles and ceramic particles are deposited on the aluminum foil. .

It is the schematic which shows the structure of the winding type electrolytic capacitor as an Example which applies the electrode foil according to this invention as anode foil. It is a flowchart which shows the procedure of the manufacturing method of the electrode foil of 1st Example according to this invention. It is a figure which shows the schematic structural example of an aerosol deposition chamber. It is a flowchart which shows the procedure of the manufacturing method of the electrode foil of the 2nd Example according to this invention. It is a figure explaining the aluminum foil which has the rough surface (etched surface) etched beforehand. It is a flowchart which shows the procedure of the manufacturing method of the electrode foil of the 3rd Example according to this invention. It is a flowchart which shows the procedure of the manufacturing method of the electrode foil of the 4th Example according to this invention. It is a figure explaining the ceramic (barium titanate) -aluminum film | membrane formed in the board | substrate aluminum foil upper surface by the 4th Example.

Explanation of symbols

21 Anode foil, aluminum foil 22 Cathode foil 30 Electrolytic paper 31 Electrolyte 201A Al film 201B Fine cavity layer 201C Surface of the fine cavity layer (oxide layer)

Claims (2)

Having a structure in which valve metal particles having a dielectric constant and / or particles mainly composed of ceramic particles are deposited on the surface of the metal foil by aerosol deposition (excluding deposition in an atmosphere containing oxygen) ,
The electrode foil is characterized in that the structure has a fine cavity layer formed by an etching process. An aluminum foil is placed in the deposition chamber of the aerosol chamber,
Aerosolize aluminum powder,
Wherein the aerosolized aluminum powder was injected into the aluminum foil disposed in the film forming chamber, to the aluminum particles sedimentary onto the aluminum foil (excluding deposition in an atmosphere containing oxygen),
Etching treatment is performed on the surface side of the aluminum foil on which the aluminum particles are deposited.

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