Roughened aluminum foil, method for producing same, and laminate

Abstract

Provided are: a roughened aluminum foil that is capable of suppressing any disconnection of a circuit and exhibiting exceptional adhesion to a metal plating layer, and that is exceptional in terms of handling properties in etching; and a method for producing the roughened aluminum foil.　The present invention provides a roughened aluminum foil having, on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate, a powder sintered layer of at least one powder selected from the group consisting of aluminum powder and aluminum alloy powders, the roughened aluminum foil being characterized in that the thickness of the powder sintered layer is 0.4-4.0 μm, the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4-4.0 μm, and the proof stress of the roughened aluminum foil is 40 N / mm 2 or greater.

Description

Roughened aluminum foil, its manufacturing method, and laminate

[0001] The present invention relates to a roughened aluminum foil, a method for producing the same, and a laminate.

[0002] 2. Description of the Related Art Conventionally, metal circuits have been formed on electronic components such as printed wiring boards, and copper has been mainly used as a metal for forming such metal circuits.

[0003] In recent years, the use of aluminum as a metal for forming metal circuits has been considered with the aim of reducing costs, weight, etc. Although aluminum is a lighter and cheaper metal than copper, the oxide film present on the surface prevents bonding with solder, so there is a problem in that the bond strength is insufficient even when soldering is performed directly on the aluminum surface.

[0004] When joining an aluminum surface with solder, a method for improving the joining strength has been proposed (see, for example, Patent Document 1).

[0005] Patent Document 1 discloses a method of forming a zinc layer by zinc displacement plating and then forming a nickel plating layer thereon. It is proposed that forming the zinc layer by zinc displacement plating ensures adhesion between the aluminum substrate and the nickel plating layer.

[0006] Furthermore, the present inventors have discovered that roughening the surface of an aluminum substrate into a specific shape improves adhesion to a metal plating layer such as a nickel plating layer without forming a zinc displacement plating. This method makes it possible to reduce plating costs and environmental impact.

[0007] In fields requiring solder bonding, such as component mounting on printed wiring boards, simplifying the plating process on aluminum is important for replacing copper with aluminum. While the above method allows for the elimination of zinc substitution plating, its application to printed wiring boards remains to be explored. The above method improves adhesion by providing anchor-like portions that protrude in the thickness direction at the interface between the nickel plating layer and the aluminum substrate. When using a laminate of this nickel plating and aluminum substrate in a printed wiring board, etching the circuit after fabrication of the laminate results in the nickel / aluminum interface being exposed to the outside at the etched edge. Exposing the contact point between dissimilar metals to the outside increases the risk of galvanic corrosion, adversely affecting the reliability of the circuit.

[0008] The inventors also discovered that a laminate can be formed by etching an aluminum substrate, roughening the aluminum surface to form anchor-shaped portions, and then plating the aluminum with nickel, thereby suppressing corrosion because the etched edges of the circuit are also covered with nickel plating. However, roughening the aluminum by chemical etching after circuit etching poses the problem of disconnection of the fine wiring. While the method of roughening the surface of an aluminum substrate, etching the circuit, and then plating the aluminum with nickel can also suppress corrosion and disconnection, there is still room for improvement.

[0009] In circuit etching, a resist film is first formed on an aluminum substrate to form the desired wiring shape. Next, the aluminum in the areas where the resist film is not formed is dissolved using an acid or alkaline solution, and finally, the resist film is peeled off to form the desired aluminum wiring. If a resist film is formed on the surface of an aluminum substrate after roughening it, gaps will form between the roughened areas of the aluminum substrate surface and the resist film. When dissolving aluminum with an acid or alkaline solution, the acid or alkaline solution can penetrate through the gaps, causing excessive dissolution of the aluminum wiring and resulting in disconnections.

[0010] It is believed that the risk of wire breakage can be reduced by minimizing the depth of the roughened portion of the aluminum substrate surface. However, it is difficult to roughen the surface uniformly and shallowly using chemical etching. Attempting to reduce the depth of the roughened portion by etching results in an uneven surface with a mixture of etched and unetched areas. When metal plating is applied to such a surface, the surface of the metal plating layer also becomes uneven.

[0011] Furthermore, as a roughening method for roughening an aluminum substrate by a method other than etching, a method of welding aluminum-based particles to the surface of an aluminum-based substrate has been proposed (see, for example, Patent Document 2).

[0012] However, the aluminum powder particle size to be welded disclosed in the examples of Patent Document 2 is 3 μm, and the thickness of the welded layer is 5 μm, which are the smallest values. When both the powder particle size and the thickness of the welded layer are small, there is a problem that the adhesive strength is insufficient. Furthermore, Patent Document 2 requires heat treatment at approximately 600 ° C, which results in an extremely low strength of the aluminum substrate, making it difficult to handle in thin foil form. If the strength is low immediately after high-temperature heat treatment, there is a problem that handling is difficult even in the circuit etching process, and wrinkles are easily generated in the aluminum foil substrate.

[0013] Therefore, there is a need for the development of a roughened aluminum foil that has a small depth of the roughened surface, which can suppress circuit breaks, exhibits excellent adhesion to a metal plating layer such as a nickel plating layer, and is easy to handle.

[0014] JP 2005-060809 A JP 2017-100324 A

[0015] An object of the present invention is to provide an aluminum roughened foil that can suppress circuit breakage, exhibits excellent adhesion to a metal plating layer, and has excellent handleability during etching, and a method for producing the same.

[0016] As a result of extensive research, the present inventors have discovered that in an aluminum roughened foil having a powder sintered layer of at least one type of powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one side of an aluminum foil substrate or an aluminum alloy foil substrate, the above-mentioned object can be achieved by setting the thickness of the powder sintered layer, the ten-point average roughness Rz of the surface of the powder sintered layer, and the yield strength of the aluminum roughened foil within specific ranges, and have thus completed the present invention.

[0017] That is, the present invention relates to the following roughened aluminum foil, its manufacturing method, and laminate: 1. A roughened aluminum foil having a powder sintered layer of at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate, wherein the thickness of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, and the yield strength of the roughened aluminum foil is 40 N / mm ２or more. 2. The roughened aluminum foil according to item 1, wherein the arithmetic mean roughness Ra of the surface of the powder sintered layer is 0.06 μm or more and 0.5 μm or less. 3. The roughened aluminum foil according to item 1, wherein the arithmetic mean roughness Ra of the surface of the powder sintered layer is 0.06 μm or more and 0.3 μm or less. 4. The roughened aluminum foil according to any one of items 1 to 3, wherein the ten-point mean roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 2.0 μm or less. 5. The roughened aluminum foil according to any one of items 1 to 4, wherein the thickness of the powder sintered layer is 0.4 μm or more and 2.0 μm or less. 6. The roughened aluminum foil according to any one of items 1 to 5, wherein the thickness of the aluminum foil substrate or the aluminum alloy foil substrate is 9 μm or more and 50 μm or less. 7. The roughened aluminum foil according to any one of items 1 to 6, which is used for producing a printed wiring board including a metal plating step. 8. Item 8. A laminate further comprising a surface layer on the surface of the powder sintered layer of the roughened aluminum foil according to any one of Items 1 to 7. 9. The laminate according to Item 8, wherein the surface layer is a metal plating layer or a resin layer. 10. A method for producing a roughened aluminum foil, comprising: (1) a first step of forming a film of a paste composition containing at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate; (2) a second step of sintering the film at a temperature of 560°C or higher and 660°C or lower to produce a sintered material; and (3) a third step of subjecting the sintered material to roll pressing. 11. The roughened aluminum foil has a powder sintered layer of at least one powder selected from the group consisting of the aluminum powder and the aluminum alloy powder on at least one surface of the aluminum foil substrate or the aluminum alloy foil substrate, the powder sintered layer has a thickness of 0.4 μm or more and 4.0 μm or less, the ten-point mean roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, and the yield strength of the roughened aluminum foil is 40 N / mm ２ Item 11. The manufacturing method according to Item 10.

[0018] According to the roughened aluminum foil of the present invention, it is possible to suppress circuit breakage, to exhibit excellent adhesion to a metal plating layer, and to exhibit excellent handleability during etching. Furthermore, according to the manufacturing method of the present invention, the above-mentioned roughened aluminum foil of the present invention can be easily manufactured.

[0019] 1 is a SEM photograph of a cross section of an example of a roughened aluminum foil of the present invention, FIG. 2 is a SEM photograph of a cross section of an example of a roughened aluminum foil of the present invention in a state where nickel plating has been applied to the roughened aluminum foil, and FIG. 3 is a schematic diagram showing the wiring shape in a circuit (wiring) etching test.

[0020] 1. Roughened Aluminum Foil The roughened aluminum foil of the present invention is an aluminum foil having a powder sintered layer of at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate, wherein the thickness of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, and the yield strength of the roughened aluminum foil is 40 N / mm ２ The roughened aluminum foil is as described above.

[0021] Generally, chemical etching of aluminum tends to cause uneven dissolution in the surface and thickness directions. If etching is performed until the entire surface is roughened, the degree of dissolution in the thickness direction varies greatly depending on the location, resulting in many areas that are dissolved unnecessarily deeply. This causes breaks in the wiring formed in the thin wire. The roughened aluminum foil of the present invention has a small depth of the surface roughening, so it has excellent circuit etching properties and can exhibit excellent adhesion to the metal plating layer.

[0022] The operation of the present invention is described below. That is, by coating and sintering aluminum powder on the surface of an aluminum substrate, a roughened surface can be formed according to the particle size of the aluminum powder. Aluminum powder can be uniformly coated on the surface using various coating methods, and macroscopic variations such as those caused by chemical etching can be suppressed. However, even if the aluminum powder is coated as thinly as possible, a roughened surface larger than the average particle size will result. In the present invention, further roll pressing can be performed to obtain a finer roughened surface, resulting in an aluminum foil that combines both circuit etching properties and adhesion to a metal plating layer. Furthermore, compression by roll pressing improves the yield strength of the roughened aluminum foil, allowing it to withstand the actual etching process and therefore exhibiting excellent handleability during etching.

[0023] FIG. 1 shows an SEM photograph of a cross section of an example of a roughened aluminum foil of the present invention. FIG. 2 shows an SEM photograph of a cross section of the roughened aluminum foil of the present invention after nickel plating. From FIG. 2, it can be seen that the nickel plating has penetrated into the gaps between the sintered powder particles. This allows for even fine irregularities to exhibit even better adhesion with the nickel plating. As shown in FIG. 2, bonding via irregularities that maintain the shape of the powder particles can improve physical adhesion, and can exhibit excellent adhesion not only with metals but also with different materials.

[0024] The roughened aluminum foil of the present invention will be described in detail below.

[0025] The yield strength of the roughened aluminum foil of the present invention is 40 N / mm ２ The yield strength is 40N / mm ２ If the yield strength is less than 45 N / mm, it is not possible to prevent the circuit from breaking, and the handling property during etching is poor. ２ The upper limit of the yield strength is not particularly limited, and is 80 N / mm ２ Preferably less than 60 N / mm ２ The following is more preferred:

[0026] In this specification, the proof stress of the roughened aluminum foil is measured by the method described in the examples below.

[0027] (Sintered Powder Layer) The roughened aluminum foil of the present invention has a sintered powder layer of at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or aluminum alloy foil substrate.

[0028] The powder sintered layer may be formed on at least one surface of the aluminum foil substrate or aluminum alloy foil substrate, or may be formed on both surfaces.

[0029] The powder sintered layer is preferably a porous sintered layer having a three-dimensional network structure formed by sintering and bonding powder particles together while maintaining voids between them. This structure increases the surface area of ​​the powder sintered layer, further improving the adhesion between the roughened aluminum foil of the present invention and the metal plating layer.

[0030] As the aluminum powder, either aluminum powder made of pure aluminum or aluminum alloy powder can be used, but it is preferable to use aluminum alloy powder.

[0031] The aluminum content of the aluminum alloy powder is preferably 95.0% by mass or more, more preferably 99.0% by mass or more, and even more preferably 99.5% by mass or more.

[0032] The aluminum alloy powder may contain one or more elements selected from silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), boron (B), zirconium (Zr), etc. The total content of these elements in the aluminum alloy is preferably 5% by mass or less, more preferably 1% by mass or less.

[0033] The aluminum content of the aluminum powder made of pure aluminum is preferably 99.80% by mass or more, more preferably 99.85% by mass or more, and even more preferably 99.99% by mass or more.

[0034] The above powders may be used alone or in combination of two or more.

[0035] The 50% particle diameter D in the volume-based particle size distribution of the powder ５０ (hereinafter referred to as "volume-based particle diameter D ５０ "," "D ５０ ") is preferably 0.5 μm or more, more preferably 0.7 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. ５０ is preferably 4.5 μm or less, more preferably 4.2 μm or less, even more preferably 4.0 μm or less, particularly preferably 3.5 μm or less, and most preferably 3.0 μm or less. ５０ When the lower limit of is within the above range, the adhesion between the roughened aluminum foil of the present invention and the metal plating layer is further improved. ５０ When the upper limit of is within the above range, the thickness of the powder sintered layer can be controlled to be thinner, and the circuit etching properties are further improved.

[0036] In this specification, the 50% particle diameter D in the particle size distribution based on the volume of the powder ５０ The measurement method is the same as that described in the Examples below.

[0037] The roughened aluminum foil of the present invention has a powder sintered layer thickness of 0.4 μm or more and 4.0 μm or less. If the thickness of the powder sintered layer is less than 0.4 μm, the adhesion between the roughened aluminum foil of the present invention and the metal plating layer decreases. If the thickness of the powder sintered layer exceeds 4.0 μm, circuit breakage cannot be suppressed. The thickness of the powder sintered layer is preferably 0.7 μm or more, more preferably 1.0 μm or more. Furthermore, the thickness of the powder sintered layer is preferably 3.5 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less.

[0038] In this specification, the thickness of the powder sintered layer is measured by the method described in the examples below.

[0039] The roughened aluminum foil of the present invention has a ten-point average roughness Rz of the surface of the powder sintered layer of 0.4 μm or more and 4.0 μm or less. If Rz is less than 0.4 μm, the adhesion between the roughened aluminum foil of the present invention and the metal plating layer decreases. If Rz exceeds 4.0 μm, circuit breakage cannot be suppressed. Rz is preferably 0.7 μm or more, more preferably 1.0 μm or more. Furthermore, Rz is preferably 3.5 μm or less, more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and particularly preferably 2.0 μm or less.

[0040] In this specification, the ten-point average roughness Rz of the surface of the powder sintered layer is measured by the method described later in the Examples.

[0041] In the roughened aluminum foil of the present invention, the arithmetic mean roughness Ra of the surface of the powder sintered layer is preferably 0.06 μm or more and 0.5 μm or less. When Ra is 0.06 μm or more, the adhesion between the roughened aluminum foil of the present invention and the metal plating layer is further improved. When Ra is 0.5 μm or less, circuit breakage is further suppressed. Ra is more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. Furthermore, Ra is more preferably 0.45 μm or less, even more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less.

[0042] In this specification, the arithmetic mean roughness Ra of the surface of the powder sintered layer is measured by the method described in the examples below.

[0043] (Aluminum Foil Substrate, Aluminum Alloy Foil Substrate) The roughened aluminum foil of the present invention has an aluminum foil substrate or an aluminum alloy foil substrate (hereinafter, also referred to as "substrate").

[0044] As the aluminum foil forming the aluminum foil substrate, it is preferable to use an aluminum alloy foil.

[0045] The aluminum content of the aluminum alloy foil is preferably 95.0% by mass or more, more preferably 99.0% by mass or more, and even more preferably 99.5% by mass or more.

[0046] The aluminum alloy used for the aluminum alloy foil forming the aluminum alloy foil substrate may be an aluminum alloy in which at least one metal element selected from the group consisting of silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), and boron (B) is added to aluminum within a required range, or an aluminum alloy containing the above element as an unavoidable impurity. The total content of these elements in the aluminum alloy is preferably 5% by mass or less, more preferably 1% by mass or less.

[0047] It is also preferable to use an aluminum foil made of pure aluminum as the aluminum foil forming the aluminum foil substrate.

[0048] The aluminum content of the aluminum foil made of pure aluminum is preferably 99.80% by mass or more, more preferably 99.85% by mass or more, and even more preferably 99.99% by mass or more.

[0049] The aluminum foil substrate made of pure aluminum may be aluminum containing at least one metal element selected from the group consisting of silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), and boron (B) as an unavoidable impurity. The content of these elements in aluminum is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less.

[0050] As the substrate, aluminum alloy foil such as 1N30, 8079, or 8021 as specified in general JIS H4160 is preferred from the viewpoint of excellent rolling properties.

[0051] The thickness of the substrate is preferably 9 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, from the viewpoints of facilitating thinning of the wiring portion, shortening the aluminum dissolution time, and further improving the strength of the roughened aluminum foil. The thickness of the substrate is preferably 70 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less.

[0052] The roughened aluminum foil of the present invention may further have a metal plating layer on the surface of the powder sintered layer. The roughened aluminum foil of the present invention having a metal plating layer on the surface of the powder sintered layer is useful as a circuit with excellent adhesion between the powder sintered layer and the metal plating layer. That is, the roughened aluminum foil of the present invention is preferably used for producing a printed wiring board including a metal plating step.

[0053] 2. Laminate The laminate of the present invention is a laminate that further has a surface layer on the surface of the powder sintered layer of the roughened aluminum foil of the present invention. The laminate of the present invention can exhibit high adhesion between the powder sintered layer and the surface layer by filling the voids in the powder sintered layer of the roughened aluminum foil with the same substance that forms the surface layer.

[0054] When the surface layer is a metal plating layer, the laminate of the present invention is useful as a circuit having excellent adhesion between the powder sintered layer and the metal plating layer.

[0055] The metal plating layer can be made of a wide range of metals used in forming circuits, including nickel, zinc, copper, gold, and tin.

[0056] The thickness of the metal plating layer is appropriately set depending on the application, but is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 5 μm or less.

[0057] When the surface layer is a resin layer, the resin forming the resin layer is not particularly limited, and examples thereof include polyethylene resin, polyimide resin, fluororesin, and liquid crystal polymer.

[0058] The thickness of the resin layer is appropriately set depending on the application, but is preferably 5 μm or more and 1000 μm or less, and more preferably 20 μm or more and 300 μm or less.

[0059] 3. Manufacturing Method of Roughened Aluminum Foil The manufacturing method of the roughened aluminum foil of the present invention is a manufacturing method including: (1) a first step of forming a coating of a paste composition containing at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate, (2) a second step of sintering the coating at a temperature of 560°C or higher and 660°C or lower to produce a sintered material, and (3) a third step of roll pressing the sintered material. This will be described in detail below.

[0060] (First Step) The first step is (1) forming a coating of a paste composition containing at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate (hereinafter, also referred to as "substrate").

[0061] As the raw aluminum powder, for example, an aluminum alloy powder having an aluminum purity of 95.0% by mass or more is preferred, an aluminum alloy powder having an aluminum purity of 99.0% by mass or more is more preferred, and an aluminum alloy powder having an aluminum purity of 99.5% by mass or more is even more preferred. Furthermore, as the raw aluminum alloy powder, an alloy containing one or more of elements such as silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), boron (B), and zirconium (Zr) is preferred. The total content of these elements in the aluminum alloy is preferably 5% by mass or less, particularly 1% by mass or less.

[0062] The above powders may be used alone or in combination of two or more.

[0063] The 50% particle diameter D in the volume-based particle size distribution of the powder ５０ (hereinafter referred to as "volume-based particle diameter D ５０"," "D ５０ ") is preferably 0.5 μm or more, more preferably 0.7 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. ５０ is preferably 4.5 μm or less, more preferably 4.2 μm or less, even more preferably 4.0 μm or less, particularly preferably 3.5 μm or less, and most preferably 3.0 μm or less. ５０ When the lower limit of D is within the above range, the adhesion between the roughened aluminum foil produced by the production method of the present invention and the metal plating layer is further improved. ５０ When the upper limit of is within the above range, the thickness of the powder sintered layer can be controlled to be thinner, and the circuit etching properties are further improved.

[0064] The shape of the aluminum powder and aluminum alloy powder is not particularly limited, and any shape such as spherical, irregular, scaly, or fibrous can be suitably used, but for industrial production, powders consisting of spherical particles are particularly preferred.

[0065] The paste composition may contain a resin binder. A wide variety of known resin binders can be used, including, for example, synthetic resins such as ethyl cellulose-based binder resins, carboxy-modified polyolefin resins, vinyl acetate resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymer resins, vinyl alcohol resins, butyral resins, vinyl fluoride resins, acrylic resins, polyester resins, urethane resins, epoxy resins, urea resins, phenolic resins, acrylonitrile resins, cellulose resins, paraffin wax, and polyethylene wax, as well as natural resins or waxes such as wax, tar, glue, urushi, pine resin, and beeswax. Depending on the molecular weight, type, and other factors, these binder resins may volatilize upon heating or may remain as residues together with the aluminum powder upon thermal decomposition, but the binder resin is not particularly limited.

[0066] The content of the binder resin in the paste composition is preferably 0.5 to 10% by mass, and more preferably 0.75 to 7% by mass, based on 100% by mass of the paste composition. By having the resin binder content in the paste composition be 0.5% by mass or more, the adhesive strength between the substrate and the paste composition coating can be improved. On the other hand, by having the resin binder content be 10% by mass or less, degreasing is facilitated in the sintering step and degreasing step, and problems caused by residual binder resin can be suppressed.

[0067] In addition, the paste composition may contain a solvent, a sintering aid, a surfactant, etc. as needed. These may all be publicly known or commercially available products. This allows for efficient formation of a coating.

[0068] As the solvent, a wide variety of known solvents can be used, including, for example, water, toluene, alcohols, ketones, esters, and other organic solvents, and propylene glycol monomethyl ether is preferred.

[0069] As the sintering aid, a wide variety of known sintering aids can be used, such as aluminum fluoride and potassium fluoride.

[0070] As the surfactant, a wide variety of known surfactants can be used, such as betaine-based, sulfobetaine-based, and alkylbetaine-based surfactants.

[0071] When the paste composition is applied to one or both surfaces of a substrate to form a film of the paste composition, the thickness of the film per surface is preferably 0.8 μm or more and 6 μm or less, and more preferably 1 μm or more and 3 μm or less.

[0072] The method for forming a coating on a substrate is not particularly limited, and the coating can be formed by applying the paste composition using a coating method such as die coating, gravure coating, direct coating, roller coating, brush coating, spraying, or dipping, or by a known printing method such as silk screen printing.

[0073] If necessary, it is also preferable to dry the film adhered to the substrate together with the substrate at a temperature in the range of 20 to 300° C. for 1 to 30 minutes.

[0074] (Second Step) The second step is (2) sintering the coating at a temperature of 560°C or higher and 660°C or lower.

[0075] The second step sinters the powder in the coating, forming a sintered material on the substrate. The sintering temperature is 560°C or higher and 660°C or lower. If the sintering temperature is lower than 560°C, sintering does not proceed and a powder sintered layer cannot be obtained. If the sintering temperature exceeds 660°C, the powder melts and the desired surface shape of the powder sintered layer cannot be obtained. The sintering temperature is preferably 570°C or higher and lower than 650°C, and more preferably 580°C or higher and lower than 620°C.

[0076] The sintering time is affected by the sintering temperature, etc., but can usually be set appropriately within a range of about 5 to 24 hours. The sintering atmosphere is not particularly limited and may be, for example, a vacuum atmosphere, an inert gas atmosphere, an oxidizing gas atmosphere (air), a reducing atmosphere, etc., but a vacuum atmosphere or a reducing atmosphere is particularly preferred. The pressure condition may also be normal pressure, reduced pressure, or increased pressure.

[0077] (Degreasing Step) In the manufacturing method of the present invention, a degreasing step is preferably carried out prior to the second step in order to vaporize the binder resin in the coating. Examples of the degreasing step include heating in an oxidizing gas atmosphere (air) at 200 to 500°C for 1 to 20 hours. By setting the lower limit of the heating temperature or the lower limit of the heating time within the above range, the binder resin in the coating is more easily vaporized, making it possible to suppress the binder resin from remaining in the coating. Furthermore, by setting the upper limit of the heating temperature or the upper limit of the heating time within the above range, it is possible to suppress excessive sintering of the aluminum powder in the coating.

[0078] (Third Step) The third step is (3) a step of applying roll pressing to the sintered material. By applying roll pressing to the sintered material produced in the second step, the above-mentioned roughened aluminum foil of the present invention can be obtained. That is, according to the manufacturing method of the present invention, at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate has a powder sintered layer of at least one powder selected from the group consisting of aluminum powder and aluminum alloy powder, the thickness of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, and the yield strength of the roughened aluminum foil is 40 N / mm ２ A roughened aluminum foil having the above properties can be produced.

[0079] The method of roll pressing is not particularly limited, and roll pressing can be performed by a conventionally known method, such as a method of performing roll pressing using a two-roll vertically arranged roll press device.

[0080] The load of the roll press may be adjusted appropriately depending on the thickness of the sintered material obtained in the second step and the desired thickness of the roughened aluminum foil after roll pressing, and is, for example, about 1 to 500 kN.

[0081] The roll press speed is not particularly limited as long as it can stably produce a roughened aluminum foil, but is generally about 1 to 50 m / min.

[0082] The above-described manufacturing method can produce the roughened aluminum foil of the present invention.

[0083] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0084] (Example 1) (First step) 50% particle diameter D in volume-based particle size distribution ５０A paste composition (slurry) was prepared by dispersing aluminum powder having a particle size of 1.92 μm in a binder resin solution. The weight ratio of the aluminum powder to the binder resin solution was 1:1. The binder resin solution was prepared by dissolving 5% by weight of an ethyl cellulose-based binder resin in propylene glycol monomethyl ether as an organic solvent.

[0085] Using aluminum foil (JIS-A8021 material, hard, 30 μm thick, one-sided gloss) as the aluminum foil substrate, the slurry was gravure coated onto the glossy side and dried to form a coating of the paste composition containing the powder. The thickness of the coating (coating thickness) was adjusted to be as thin as possible, and was 2.51 μm.

[0086] (Second step) The aluminum foil substrate on which the paste composition coating was formed was subjected to a degreasing heat treatment at 400°C in air (to decompose the binder), and then to a sintering heat treatment at 610°C in argon gas (to sinter the powders together and the powder and the substrate), thereby producing a sintered material in which a powder sintered layer was formed on the aluminum foil substrate.

[0087] (Step 3) The obtained sintered material was subjected to pressure treatment by roll pressing using a roll press device (two rolls arranged vertically: manufactured by Yuri Roll Co., Ltd., maximum load 100 kN) and controlled to a predetermined surface roughness to produce a roughened aluminum foil. The thickness of the powder sintered layer after roll pressing was controlled to 1.47 μm.

[0088] (Example 2) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 4.05 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 5.17 μm. After a sintering process, roll pressing was performed, and the thickness of the powder sintered layer after roll pressing was adjusted to 3.45 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0089] (Example 3) 50% particle diameter D in volume-based particle size distribution ５０Aluminum powder having a surface roughness of 0.81 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 0.84 μm. After a sintering process, roll pressing was performed, and the thickness of the powder sintered layer after roll pressing was adjusted to 0.46 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0090] (Example 4) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 1.54 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 2.14 μm. After a sintering process, roll pressing was performed, and the thickness of the powder sintered layer after roll pressing was adjusted to 1.74 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0091] (Example 5) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 1.92 μm was uniformly coated on the surface of an aluminum foil substrate. The aluminum powder was piled up to adjust the coating thickness to 4.05 μm. After a sintering process, roll pressing was performed, and the thickness of the powder sintered layer after roll pressing was adjusted to 3.33 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0092] (Comparative Example 1) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 1.92 μm was uniformly coated on the surface of an aluminum foil substrate. The aluminum powder was piled up to adjust the coating thickness to 4.95 μm. After a sintering process, roll pressing was performed to adjust the thickness of the powder sintered layer after roll pressing to 4.06 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0093] (Comparative Example 2) 50% particle diameter D in volume-based particle size distribution ５０An aluminum powder having a surface roughness of 4.05 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 5.17 μm. After the sintering process, the aluminum foil was directly roughened without being subjected to roll pressing. Otherwise, the same procedure as in Example 1 was used to produce a roughened aluminum foil.

[0094] (Comparative Example 3) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 0.81 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 0.84 μm. After a sintering process, roll pressing was performed, and the thickness of the powder sintered layer after roll pressing was adjusted to 0.34 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0095] (Comparative Example 4) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 1.92 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 2.51 μm. After the sintering process, the aluminum foil was directly roughened without being subjected to roll pressing. Otherwise, the same procedure as in Example 1 was used to produce a roughened aluminum foil.

[0096] (Comparative Example 5) 50% particle diameter D in volume-based particle size distribution ５０ Aluminum powder having a surface roughness of 1.92 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 2.51 μm. After a sintering process, roll pressing was performed, and the thickness of the powder sintered layer after roll pressing was adjusted to 2.24 μm. Otherwise, a roughened aluminum foil was produced in the same manner as in Example 1.

[0097] (Comparative Example 6) 50% particle diameter D in volume-based particle size distribution ５０Aluminum powder having a surface roughness of 0.81 μm was uniformly coated on the surface of an aluminum foil substrate. The coating thickness was adjusted to be as thin as possible, resulting in a thickness of 0.84 μm. After the sintering process, the aluminum foil was directly roughened without being subjected to roll pressing. Otherwise, the same procedure as in Example 1 was used to produce a roughened aluminum foil.

[0098] Reference Example 1 Aluminum foil (JIS-A8021 material, soft, heat-treated in air at 250° C., thickness 30 μm, glossy on one side) was used as it was in Reference Example 1. The evaluation test of the properties was carried out on the glossy side.

[0099] (Reference Example 2) Aluminum foil (JIS-A8021 material, soft, heat-treated in air at 250°C, thickness 30 µm, one-sided gloss) was used as it was in Reference Example 2. The properties were evaluated on the matte side (the side opposite to the gloss side).

[0100] (Reference Example 3) Aluminum foil (JIS-A8079 material, soft, heat-treated in air at 250°C, thickness 30 µm, glossy on one side) was used as it was in Reference Example 3. The evaluation test of the properties was carried out on the glossy side.

[0101] (Evaluation Method) The characteristics of the examples and comparative examples were evaluated by the following methods.

[0102] Aluminum powder D ５０ Measurement: Using a Microtrac MT3300EXII (manufactured by Nikkiso Co., Ltd.), the particle size distribution was measured on a volume basis by the laser diffraction / scattering method (wet method). ５０ The value was calculated.

[0103] Measurement of coating thickness after coating (thickness of coating of paste composition) The slurry (paste composition) was coated, and the ND-TD cross section of the dried coating material was polished and observed using a field emission scanning electron microscope (JSM-7200F, manufactured by JEOL Ltd.). ND is the thickness direction of the aluminum foil, and TD is the direction parallel to the aluminum foil substrate surface and perpendicular to the rolling direction. The field of view in which the coating thickness could be measured was observed at a magnification of 5000 times (observation range 18 μm × 24 μm), and the distance from the aluminum foil substrate surface to the highest point of the coating thickness was taken as the coating thickness. Five fields of view were observed at random, and the average value was calculated to obtain the measured value.

[0104] Measurement of the thickness of the powder sintered layer The ND-TD cross section of the roughened aluminum foil was polished and observed using a field emission scanning electron microscope (JSM-7200F, manufactured by JEOL Ltd.). ND is the thickness direction of the roughened aluminum foil, and TD is the direction parallel to the surface of the roughened aluminum foil and perpendicular to the rolling direction. A field of view in which the thickness of the powder sintered layer could be measured was observed at 5000x magnification (observation area 18 μm × 24 μm), and the distance from the surface of the aluminum foil substrate to the highest point of the thickness of the powder sintered layer was taken as the thickness of the powder sintered layer. Five fields of view were observed at random, and the average value was calculated to obtain the measured value.

[0105] Surface roughness measurement of powder sintered layer The ten-point average roughness Rz and arithmetic average roughness Ra were measured using a stylus roughness meter (SURFCOM1400D, manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B0601:1994. The measurement direction was the RD (rolling direction of the aluminum foil). The average value of N = 3 was taken as the measured value.

[0106] Yield strength measurement A tensile test was performed on the roughened aluminum foil. Specifically, a strip-shaped test piece 15 mm wide x 200 mm long was cut out so that the tensile direction was parallel to the rolling direction. The tensile tester was a Strograph VES5D manufactured by Toyo Seiki Seisakusho Co., Ltd., and the test was performed at a tensile speed of 10 mm / min with a chuck distance of 100 mm as the gauge length. The test was performed three times, and the average value of the measured 0.2% yield strength was calculated and used as the measured value. The thickness of the roughened aluminum foil required for yield strength measurement was measured using a micrometer.

[0107] Circuit (Wiring) Etching Test: A 25 μm dry film resist was bonded to the powder sintered layer side of the roughened aluminum foil. A 25 μm polyimide film was bonded to the opposite side. The dry film resist was then exposed to UV light through a photomask. The dry film resist was cured only in designated areas through the photomask. The uncured areas of the resist were then removed, forming a resist film in the desired wiring shape. The roughened aluminum foil in areas where the resist film was not formed was etched and dissolved with an aqueous solution of ferric chloride, and finally the resist film was peeled off with caustic soda, thereby performing wiring etching. As shown in Figure 3, the wiring shape consisted of repeated arrangements of wiring (aluminum portions) and spaces (dissolved portions), with two widths: 150 μm and 200 μm. The length of the wiring was 50 mm, and there were 10 of them. Observation was performed using an optical microscope to confirm whether wiring etching was possible without disconnection, and evaluation was performed according to the following evaluation criteria. A rating of ○ or higher was considered acceptable for practical use. ⊚: Etching was possible up to a line width of 150 μm. ◯: Wire breakage occurred at a line width of 150 μm, but etching was possible at a line width of 200 μm. ×: Wire breakage occurred even at a line width of 200 μm.

[0108] Nickel plating adhesion evaluation: The roughened aluminum foil was immersed in an electroless nickel plating solution (Top Nicoron MP-GE heavy metal-free, medium phosphorus type, manufactured by Okuno Chemical Industries Co., Ltd.) to perform nickel plating. The solution temperature was set to 90°C, and the foil was immersed for 15 minutes to form a nickel plating layer, followed by rinsing with water and drying. After nickel plating, solder paste (product name "SN97C P506 D4", manufactured by Nippon Superior Co., Ltd., containing Sn, Ag, and Cu) was applied to the powder sintered layer side of the roughened aluminum foil, with a center-to-center distance of 3.35 mm, each measuring 1.25 mm x 1.60 mm, and a thickness of 80 μm. A 3216-type chip resistor was placed so that it evenly spanned the two points. After applying the solder paste and placing the chip, the roughened aluminum foil was placed in a tabletop vacuum solder reflow device (manufactured by Unitemp Japan Co., Ltd.; model number RSS-450-210). After evacuation, the device was heated to 250°C in a nitrogen atmosphere with a flow rate of 1 L / min and held for 30 seconds. After reflow was completed, the shear strength of the soldered chip resistor was measured using a bond tester (Nordson Dage Series 4000, manufactured by Day Japan Co., Ltd.). The tool movement speed was 0.3 mm / sec. Ten measurements were taken, and the average value was used as the bond strength. Evaluation was performed according to the following evaluation criteria. Note that a rating of ○ indicates that sufficient adhesion between the nickel plating layer and the roughened aluminum foil was ensured, and is therefore considered to be acceptable for practical use. ○: Bond strength was 50 N or greater. ×: Bond strength was less than 50 N.

[0109] The results are shown in Table 1.

[0110]

[0111] The results in Table 1 show that Examples 1 to 5, in which the thickness of the powder sintered layer was 0.4 μm or more and 4.0 μm or less, exhibited both good etching properties and nickel plating adhesion, demonstrating that these properties were combined. In particular, Examples 1, 3, and 4, in which the thickness of the powder sintered layer was 2.0 μm or less, exhibited particularly excellent etching properties. Furthermore, in terms of strength, the thickness of the powder sintered layer was 40 N / mm ２ The above yield strength was found to be equal to or greater than that of the 8079 material of Reference Example 3, which is a normal soft material.

[0112] In Comparative Examples 1 and 2, the thickness of the powder sintered layer exceeded 4.0 μm, and the wiring etching evaluation was ×. In Comparative Example 3, the thickness and surface roughness of the powder sintered layer were small, and sufficient adhesion to the nickel plating was not ensured. In Comparative Examples 4 and 6, roll pressing was not performed, and the strength of the roughened aluminum foil was low, indicating poor handleability during etching. In Comparative Example 5, roll pressing was performed, but the amount of pressing was small, and strength was not sufficiently improved.

[0113] No roughening treatment was performed in Reference Examples 1 to 3, and the results are shown for plain foils. In Reference Example 2, the ten-point average roughness Rz of the surface was 0.4 μm to 4.0 μm, but the nickel plating adhesion was poor, indicating that the presence of a powder sintered layer improves the adhesion between the roughened aluminum foil and the plating film.

Claims

1. A roughened aluminum foil having a powder sintered layer of at least one type of powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one side of an aluminum foil substrate or an aluminum alloy foil substrate, wherein the thickness of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 4.0 μm or less, and the yield strength of the roughened aluminum foil is 40 N / mm ２ The above-mentioned roughened aluminum foil.

2. The roughened aluminum foil according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the powder sintered layer is 0.06 μm or more and 0.5 μm or less.

3. The roughened aluminum foil according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the powder sintered layer is 0.06 μm or more and 0.3 μm or less.

4. The roughened aluminum foil according to claim 1, wherein the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4 μm or more and 2.0 μm or less.

5. The roughened aluminum foil according to claim 1, wherein the powder sintered layer has a thickness of 0.4 μm or more and 2.0 μm or less.

6. The roughened aluminum foil according to claim 1, wherein the aluminum foil substrate or the aluminum alloy foil substrate has a thickness of 9 μm or more and 50 μm or less.

7. The roughened aluminum foil according to claim 1, which is used for producing a printed wiring board including a metal plating process.

8. A laminate comprising the roughened aluminum foil according to claim 1 and a surface layer on the surface of the powder sintered layer.

9. The laminate according to claim 8, wherein the surface layer is a metal plating layer or a resin layer.

10. A method for producing a roughened aluminum foil, comprising: (1) a first step of forming a coating of a paste composition containing at least one type of powder selected from the group consisting of aluminum powder and aluminum alloy powder on at least one surface of an aluminum foil substrate or an aluminum alloy foil substrate; (2) a second step of sintering the coating at a temperature of 560°C or higher and 660°C or lower to produce a sintered material; and (3) a third step of subjecting the sintered material to roll pressing.

11. The aluminum roughened foil has a powder sintered layer of at least one type of powder selected from the group consisting of the aluminum powder and the aluminum alloy powder on at least one side of the aluminum foil base material or the aluminum alloy foil base material, the powder sintered layer has a thickness of 0.4 μm to 4.0 μm, the ten-point average roughness Rz of the surface of the powder sintered layer is 0.4 μm to 4.0 μm, and the yield strength of the aluminum roughened foil is 40 N / mm ２ The manufacturing method according to claim 10 .

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