JP2014065940A - Porous aluminum body, aluminum electrolytic capacitor, and method of manufacturing porous aluminum body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous aluminum body capable of forming a good anodic oxidation coating film having efficient bending strength and showing low leakage current value, an aluminum electrolytic capacitor using the porous aluminum body, and a manufacturing method of the porous aluminum body.SOLUTION: A porous aluminum body 10 contains an aluminum foil 20 and an aluminum porous layer 30 laminated on at least one surface side of the aluminum foil 20. The aluminum foil 20 has a thickness of 10 to 50 μm, an iron content of less than 1000 wt.ppm, and a silicon content of 500 to 5000 wt.ppm. The aluminum porous layer 30 is a layer manufactured by sintering an aluminum powder having the iron content of less than 1000 wt.ppm and the silicon content of 50 to 3000 wt.ppm.

Description

  The present invention relates to a porous aluminum body provided with an aluminum porous layer on at least one surface of an aluminum foil, an aluminum electrolytic capacitor using the porous aluminum body, and a method for producing the porous aluminum body.

  As for the aluminum foil, there have been proposed uses such as an electrode for an aluminum electrolytic capacitor and a carrier for a catalyst for purifying contaminated air. For example, such an aluminum foil has an oxide film formed on the surface thereof by anodic oxidation after the surface area is enlarged by etching in an etching solution such as hydrochloric acid.

  On the other hand, a porous aluminum body in which aluminum powder is sintered and an aluminum porous layer is laminated on an aluminum foil has been proposed. According to such a porous aluminum body, it is necessary to perform etching using hydrochloric acid or the like. There is an advantage of not (see Patent Document 1).

  Moreover, when forming a porous aluminum body, the technique which improves the bending strength of a porous aluminum body is proposed by using the aluminum powder whose silicon content is 100-3000 weight ppm as aluminum powder. (See Patent Document 2).

JP-A-2-267916 JP 2011-52291 A

  However, when manufacturing an aluminum electrolytic capacitor having a porous aluminum body, there are steps such as winding porous aluminum, and a bending strength of a predetermined level or more is required for the porous aluminum body. There is a problem that sufficient bending strength cannot be obtained only by the configuration described in Patent Document 2. Moreover, the leak current value of the porous aluminum body may be large only with the configurations described in Patent Documents 1 and 2 above.

  In view of the above problems, an object of the present invention is to provide a porous aluminum body that has a sufficient bending strength and can form a high-quality anodized film exhibiting a low leakage current value, and the porous aluminum body It is providing the manufacturing method of the aluminum electrolytic capacitor using this, and the said porous aluminum body.

  In order to solve the above problems, the present invention provides a porous aluminum body having an aluminum foil and an aluminum porous layer laminated on at least one side of the aluminum foil, wherein the aluminum foil has a thickness of 10-50 μm, the iron content is less than 1000 ppm by weight, the silicon content is 500-5000 ppm by weight, and the aluminum porous layer has an iron content of less than 1000 ppm by weight and a silicon content of It is a layer formed by sintering 50 to 3000 ppm by weight of aluminum powder.

  In addition, the method for producing a porous aluminum body of the present invention is provided on at least one surface of an aluminum foil having a thickness of 10 to 50 μm, an iron content of less than 1000 ppm by weight, and a silicon content of 500 to 5000 ppm by weight. A first step of forming a film comprising an aluminum powder having an iron content of less than 1000 ppm by weight and a silicon content of 50 to 3000 ppm by weight; And a second step of sintering at a temperature.

  In the present invention, by using an aluminum foil and aluminum powder having a specific composition, a low leakage current value is exhibited, the sinterability between the aluminum foil and the aluminum powder is improved, and the bending strength is increased. is there. More specifically, the silicon content of the aluminum foil is 500 to 5000 ppm by weight, and the silicon content of the aluminum powder used for the aluminum porous layer is 50 to 3000 ppm by weight. When aluminum foil and aluminum powder having a silicon content in the above range are sintered, a high bonding strength (sintering strength) between the aluminum foil and the aluminum porous layer (aluminum powder) is obtained. The aluminum body has a high bending strength. In addition, when the anodization is performed on the aluminum porous layer due to the iron content of the aluminum foil and the iron content of the aluminum powder used in the aluminum porous layer being less than 1000 ppm by weight, a low leakage current value is obtained. It is possible to form a high-quality anodic oxide film exhibiting Moreover, since aluminum foil is 10-50 micrometers in thickness, appropriate intensity | strength can be acquired. More specifically, even if the thickness of the aluminum foil exceeds 50 μm, the surface area and strength are not improved, and the thickness is increased unnecessarily. On the other hand, if the thickness of the aluminum foil is less than 10 μm, the porous aluminum The strength of the body is low.

  In the present invention, the average particle size of the aluminum powder is preferably 1 to 10 μm. According to this configuration, the surface area of the porous aluminum body can be effectively expanded. More specifically, if the average particle size of the aluminum powder is less than 1 μm, the gap between the aluminum powders is too narrow and the ineffective portion that does not function as an electrode increases, while the average particle size of the aluminum powder is 10 μm. If it exceeds, the gap between the aluminum powders is too wide, and the expansion of the surface area is insufficient.

  In this invention, the structure which has the said aluminum porous layer on both surfaces of the said aluminum foil is employable.

  In the present invention, a configuration in which an anodized film is formed on the aluminum porous layer can be adopted. Such a porous aluminum body is used as an anode or the like of an aluminum electrolytic capacitor. In this case, a third step of anodizing the porous aluminum body is performed after the first step and the second step.

  The porous aluminum body of the present invention comprises an aluminum foil having an iron content of less than 1000 ppm by weight and a silicon content of 500 to 5000 ppm by weight, an iron content of less than 1000 ppm by weight, and a silicon content of 50 By providing an aluminum porous layer of ˜3000 ppm by weight, a high bending strength can be obtained, and a good anodic oxidation exhibiting a low leakage current value can be formed. Moreover, an aluminum foil can obtain suitable intensity | strength because thickness is 10-50 micrometers.

It is explanatory drawing which shows the cross-section of the porous aluminum body to which this invention is applied. It is explanatory drawing which shows the surface structure of the porous aluminum body to which this invention is applied.

(Configuration of porous aluminum body)
FIG. 1 is an explanatory view showing a cross-sectional structure of a porous aluminum body to which the present invention is applied, and is a photograph taken by enlarging the cross section of the porous aluminum body 600 times with an electron microscope. FIG. 2 is an explanatory view showing the surface structure of a porous aluminum body to which the present invention is applied, and is a photograph of the surface of the porous aluminum body taken with an electron microscope. FIG. 2 shows a photograph in which the surface of the porous aluminum body is magnified 1000 times and a photograph in which the surface is magnified 3000 times.

  A porous aluminum body 10 shown in FIGS. 1 and 2 has an aluminum foil 20 and an aluminum porous layer 30 laminated on at least one surface side of the aluminum foil 20. The body 10 has an aluminum porous layer 30 on both surfaces of the aluminum foil 20.

  In this embodiment, the aluminum foil 20 has a thickness of 10 to 50 μm. FIG. 1 shows a porous aluminum body 10 using an aluminum foil 20 having a thickness of about 30 μm. FIG. 1 shows a porous aluminum body 10 in which an aluminum porous layer 30 having a thickness of about 50 μm is formed.

  Here, the aluminum foil 20 has an iron content of less than 1000 ppm by weight and a silicon content of 500 to 5000 ppm by weight. This is because if the silicon content of the aluminum foil 20 is less than 500 ppm by weight, the bending strength decreases, and if it exceeds 5000 ppm by weight, the leakage current value increases. More preferably, the aluminum content of the aluminum foil 20 is 500 to 3000 ppm by weight because a high capacitance can be obtained. The aluminum porous layer 30 is a layer formed by sintering aluminum powder having an iron content of less than 1000 ppm by weight and a silicon content of 50 to 3000 ppm by weight. It is sintered while maintaining. This is because if the silicon content of the aluminum porous layer 30 is less than 50 ppm by weight, the bending strength decreases, and if it exceeds 3000 ppm by weight, the leakage current value increases. More preferably, the silicon content of the aluminum porous layer 30 is 50 to 1000 ppm by weight because a high capacitance can be obtained. In this embodiment, the shape of the aluminum powder is not particularly limited, and any of a substantially spherical shape, an indefinite shape, a scale shape, a fiber shape, and the like can be suitably used. In particular, a powder composed of substantially spherical particles is preferable in order to maintain a gap between aluminum powders. The average particle size of the aluminum powder in this embodiment is preferably 1 to 10 μm. Such a porous aluminum body 10 can obtain a capacitance equal to or higher than that of a conventional etching foil. In particular, the porous aluminum body 10 of this embodiment is used as a substitute for an etching foil having thick etching pits for use in capacitors for medium and high pressure.

  In this embodiment, when the porous aluminum body 10 is used as an anode of an aluminum electrolytic capacitor, an anodic oxide film is formed on the aluminum porous layer 30. At that time, when there is a portion exposed from the aluminum porous layer 30 in the aluminum foil 20, an anodized film is also formed on the aluminum foil 20.

(Production method)
The manufacturing method of the porous aluminum body 10 to which the present invention is applied is as follows. First, in the first step, the thickness is 10 to 50 μm, the iron content is less than 1000 ppm by weight, and the silicon content is 500 to 5000 ppm by weight. A film made of a composition containing aluminum powder having an iron content of less than 1000 ppm by weight and a silicon content of 50 to 3000 ppm by weight is formed on at least one surface of the aluminum foil 20. The average particle size of the aluminum powder is preferably 1 to 10 μm. Here, the aluminum foil 20 and the aluminum powder are copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga). ), Nickel (Ni), boron (B), zirconium (Zr), or other elements. In this case, however, the content of these elements is preferably 100 ppm by weight or less, particularly 50 ppm by weight or less.

  The aluminum powder is manufactured by an atomizing method, a melt spinning method, a rotating disk method, a rotating electrode method, other rapid solidification methods, or the like. Among these methods, the atomizing method, particularly the gas atomizing method is preferable for industrial production. In the atomizing method, powder is obtained by atomizing the molten metal.

  The composition may contain a resin binder, a solvent, a sintering aid, a surfactant and the like as necessary. Any of these may be known or commercially available. In this embodiment, it is preferable to use at least one of a resin binder and a solvent as a paste composition. Thereby, a film can be formed efficiently. Examples of the resin binder include carboxy-modified polyolefin resin, vinyl acetate resin, vinyl chloride resin, vinyl chloride copolymer resin, vinyl alcohol resin, butyral resin, vinyl fluoride resin, acrylic resin, polyester resin, urethane resin, epoxy resin, A synthetic resin such as urea resin, phenol resin, acrylonitrile resin, nitrocellulose resin, paraffin wax, polyethylene wax or the like, natural resin such as wax, tar, glue, urushi, pine resin, beeswax, or wax can be suitably used. These binders are classified into those that volatilize when heated, depending on the molecular weight, the type of resin, etc., and those that remain together with the aluminum powder due to thermal decomposition. it can.

  When preparing the composition, a solvent may be added. As such a solvent, water, ethanol, toluene, ketones, esters and the like can be used alone or in combination.

  The formation of the film can be appropriately selected from known methods depending on the properties of the composition. For example, when the composition is a powder (solid), the green compact may be formed on a substrate (or thermocompression bonding). In this case, the green powder can be solidified by sintering and the aluminum powder can be fixed on the aluminum foil 20. Moreover, when it is liquid (paste-like), it can be formed by a known printing method in addition to a coating method such as roller, brush, spray, dipping and the like. The film may be dried at a temperature in the range of 20 ° C. to 300 ° C. as necessary.

  The thickness of the film is not particularly limited, but generally it is preferably 20 μm or more and 1000 μm or less, particularly preferably 20 μm or more and 200 μm or less. When the thickness is less than 20 μm, a desired capacitance may not be obtained. On the other hand, when the thickness is larger than 1000 μm, adhesion failure with the foil may occur or cracks may occur in the subsequent process.

  In addition, about the aluminum foil 20, you may perform the process of roughening the surface of the aluminum foil 20 before formation of a membrane | film | coat. As the roughening method, for example, a known technique such as cleaning, etching, blasting or the like can be used.

  Next, in the second step, the coating is sintered at a temperature of 560 ° C. or higher and 660 ° C. or lower. The sintering time varies depending on the sintering temperature and the like, but can usually be appropriately determined within a range of about 5 to 24 hours. The sintering atmosphere is not particularly limited, and may be any of, for example, a vacuum atmosphere, an inert gas atmosphere, an oxidizing gas atmosphere (air), a reducing atmosphere, etc. In particular, a vacuum atmosphere or a reducing atmosphere is used. It is preferable. The pressure condition may be normal pressure, reduced pressure or increased pressure. If the composition (in the film) contains an organic component such as a resin binder, after the first step, prior to the second step, the holding time is in the range of 100 ° C. to 600 ° C. in advance. It is preferable to perform a heat treatment (degreasing treatment) for 5 hours or more. The heat treatment atmosphere at that time is not particularly limited, and may be, for example, a vacuum atmosphere, an inert gas atmosphere, or an oxidizing gas atmosphere. The pressure condition may be normal pressure, reduced pressure or increased pressure.

  When the porous aluminum body 10 is used as an anode of an aluminum electrolytic capacitor, an anodized film is formed on the aluminum porous layer 30 in the third step after the first step and the second step. At that time, in the aluminum foil 20, an anodized film is also formed on a portion exposed from the aluminum porous layer 30.

  In order to manufacture an aluminum electrolytic capacitor using such anodized porous aluminum body 10, first, an anode foil made of anodized porous aluminum body 10 and a cathode foil are wound with a separator interposed therebetween. To form a capacitor element. Next, the capacitor element is impregnated with an electrolytic solution. After that, the capacitor element containing the electrolytic solution is housed in an outer case, and the case is sealed with a sealing body.

(Main effects of this form)
As described above, in this embodiment, the silicon content of the aluminum foil 20 is 500 to 5000 ppm by weight, and the silicon content of the aluminum powder used for the aluminum porous layer 30 is 50 to 3000 ppm by weight. . For this reason, when sintered, a high bonding strength (sintering strength) between the aluminum foil 20 and the aluminum porous layer 30 (aluminum powder) is obtained, and the porous aluminum body 10 has a high bending strength. Therefore, when the porous aluminum body 10 is manufactured, when anodizing the porous aluminum body 10 and when manufacturing an aluminum electrolytic capacitor using the anodized porous aluminum body 10, the porous aluminum body 10 is porous. Generation | occurrence | production of malfunctions, such as the aluminum body 10 breaking, can be suppressed.

  Moreover, since the iron content of the aluminum foil 20 and the iron content of the aluminum powder used for the aluminum porous layer 30 are less than 1000 ppm by weight, when the aluminum porous layer 30 is anodized, a good quality is obtained. An anodized film can be formed. That is, if the iron content is 1000 ppm by weight or more, the leakage current value becomes large starting from the coarse Al-Fe intermetallic compound remaining in the anodized film, but the iron content is 1000 wt. If it is less than ppm, the increase of the leakage current value does not occur.

  Moreover, since the aluminum foil 20 is 10-50 micrometers in thickness, it can acquire appropriate intensity | strength. More specifically, even if the thickness of the aluminum foil 20 exceeds 50 μm, the surface area and the strength are not improved, so that the aluminum foil 20 becomes unnecessarily thick. Moreover, if the thickness of the aluminum foil 20 is less than 10 μm, the strength of the porous aluminum body 10 is low.

  Moreover, since the average particle diameter of aluminum powder is 1-10 micrometers, a surface area can be expanded effectively. More specifically, if the average particle size of the aluminum powder is less than 1 μm, the gap between the aluminum powders is too narrow and the ineffective portion that does not function as an electrode increases, while the average particle size of the aluminum powder is 10 μm. If it exceeds, the gap between the aluminum powders is too wide, and the expansion of the surface area is insufficient. That is, when an anodized film having a withstand voltage of 200 V or more is formed by anodization, the voids are buried and the capacitance is lowered. On the other hand, if the average particle size exceeds 10 μm, the void portion becomes too large, the surface area is reduced, and a desired capacitance cannot be obtained. The average particle diameter of the aluminum powder can be measured with a laser diffraction particle size distribution meter.

(Example)
Next, examples of the present invention will be described. First, a porous aluminum body is formed by forming an aluminum porous layer in which aluminum powders having different average particle diameters and the like are sintered on both sides of an aluminum foil having a thickness of 30 μm and a width of 500 mm, each having a thickness of 40 μm while maintaining voids. Was made. More specifically, 60 parts by weight of aluminum powder is mixed with 40 parts by weight of a cellulosic binder (solvent: toluene, 7% by weight of the resin component) to obtain a composition having a solid content of 60% by weight, and then the composition. The product was coated on both sides of an aluminum foil (JIS 1N30-H18) using a comma coater to form a film (first step). Next, after drying the film, the aluminum foil was sintered in an argon gas atmosphere at a temperature of 635 ° C. for 7 hours to produce a porous aluminum body (second step). The thickness of the sintered porous aluminum body was about 130 μm (aluminum foil: 30 μm + aluminum porous layer 30: 50 μm on each side).

  Next, the porous aluminum body was anodized in a boric acid-based chemical liquid (third step).

  An appropriate amount of a sample for characteristic measurement was punched out from the porous aluminum body before anodic oxidation, and the bending strength was measured. The bending strength was measured according to the MIT type automatic bending test method (EIAJ RC-2364A) stipulated by the Japan Electronic Machinery Manufacturers Association. The MIT type automatic bending test apparatus uses an apparatus defined in JIS P8115, and the number of bendings is the number of bendings at which each electrode material breaks. ° Bented 3 times, put back and counted 4 times. When the bending strength measurement result is less than the predetermined number of times, the bending strength is “impossible” and excluded from the object of anodization. When the bending strength measurement result is the predetermined number of times or more, the bending strength is “good”. Targeted for oxidation. The porous aluminum body after anodization was measured for capacitance and film withstand voltage according to JEITA standards. The film withstand voltage of the samples is around 410V. In addition, a voltage 0.9 times the film withstand voltage was applied in a boric acid solution under the same conditions as the chemical conversion solution, and the current value after 10 minutes was measured to obtain a leakage current value. The results are shown in Table 1. In Table 1, “Al powder” means aluminum powder, and “particle size” means average particle size. “Fe amount” means iron content (weight ppm), and “Si amount” means silicon content (weight ppm).

  As can be seen from Table 1, Comparative Example 1 in which the silicon content of the aluminum foil is less than 500 ppm by weight and Comparative Example 5 in which the silicon content of the aluminum powder is less than 50 ppm by weight have low bending strength. Comparative Example 2 in which the silicon content of the aluminum foil exceeds 5000 ppm by weight, Comparative Example 3 in which the iron content of the aluminum powder exceeds 1000 ppm by weight, and Comparative Example in which the iron content of the aluminum foil exceeds 1000 ppm by weight No. 4 has a remarkably high leakage current value.

  In contrast, an aluminum foil with an iron content of less than 1000 ppm by weight, a silicon content of 500 to 5000 ppm by weight, and an iron content of less than 1000 ppm by weight and a silicon content of 50 to 3000 ppm by weight In each of Examples 1 to 7 using aluminum powder, the bending strength is high and the leakage current value is low.

  In Examples 1 to 7, Example 5 in which the average particle diameter of the aluminum powder is less than 1 μm and Example 6 in which the average particle diameter of the aluminum powder exceeds 10 μm are compared with Examples 1 to 4. In view of the low capacitance, the average particle size of the aluminum powder is preferably 1 to 10 μm.

  In addition, among Examples 1 to 7, Example 7 in which the silicon content of the aluminum powder is 1500 ppm by weight and the silicon content of the aluminum foil is 3500 ppm by weight is electrostatic compared to Examples 1 to 4. Since the capacity is low, the silicon content of the aluminum powder is preferably 50 to 1000 ppm by weight, and the silicon content of the aluminum foil is preferably 500 to 3000 ppm by weight.

(Other embodiments)
In the above-described embodiment, the description has focused on the use of a porous aluminum body as an anode of an aluminum electrolytic capacitor. However, a porous aluminum body or a porous aluminum body on which an anodized film is formed is used as a catalyst carrier. be able to. For example, when applied to deodorization or decomposition treatment of volatile organic compounds, automobile exhaust gases, etc., the porous aluminum body is a supported catalyst, such as palladium, platinum, ruthenium, rhodium, iridium, nickel, cobalt, iron, copper, zinc. , Gold, silver, rhenium, manganese, tin, alloys or mixtures thereof.

10 .. Porous aluminum body 20 .. Aluminum foil 30 .. Aluminum porous layer

Claims (8)

In a porous aluminum body having an aluminum foil and an aluminum porous layer laminated on at least one surface side of the aluminum foil,
The aluminum foil has a thickness of 10 to 50 μm, an iron content of less than 1000 ppm by weight, and a silicon content of 500 to 5000 ppm by weight,
The porous aluminum body is a layer obtained by sintering an aluminum powder having an iron content of less than 1000 ppm by weight and a silicon content of 50 to 3000 ppm by weight.   The porous aluminum body according to claim 1, wherein the average particle size of the aluminum powder is 1 to 10 µm.   The porous aluminum body according to claim 1, wherein the aluminum porous layer is provided on both surfaces of the aluminum foil.   The porous aluminum body according to any one of claims 1 to 3, wherein an anodic oxide film is formed on the aluminum porous layer.   An aluminum electrolytic capacitor comprising the porous aluminum body according to any one of claims 1 to 4 as an anode. At least one surface of an aluminum foil having a thickness of 10 to 50 μm, an iron content of less than 1000 ppm by weight, and a silicon content of 500 to 5000 ppm by weight, and an iron content of less than 1000 ppm by weight and containing silicon A first step of forming a film comprising a composition containing aluminum powder in an amount of 50 to 3000 ppm by weight;
A second step of sintering the film at a temperature of 560 ° C. or higher and 660 ° C. or lower;
The manufacturing method of the porous aluminum body characterized by including.   The method for producing a porous aluminum body according to claim 6, wherein the average particle size of the aluminum powder is 1 to 10 µm.   The method for producing a porous aluminum body according to claim 6 or 7, further comprising a third step of anodizing the porous aluminum body after the first step and the second step. .