Aluminum foil

Abstract

The present invention is an aluminum foil having an uneven structure provided on at least one surface, the aluminum foil having a surface roughness (Sa) of 15-50 nm (inclusive), a surface roughness (SzJIS) of 150-400 nm (inclusive), and a surface roughness (SzJIS) of 25-50 nm (inclusive) in a first rectangular field of view having a size of 5 [mu] m * 5 [mu] m and a resolution of 256 * 256 pixels when the surface is viewed with an atomic force microscope. The number of peaks counted at a length of 5 [mu] m is 25 or more; when the surface is observed with a laser microscope, the surface roughness Sa is 30 nm or less and the surface roughness Sz is 600 nm or less in a second rectangular field of view having a size of 95 [mu] m * 71 [mu] m and a resolution of 1024 * 768 pixels.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an aluminum foil, a manufacturing method of the aluminum foil, a manufacturing method of a laminate of the aluminum foil and a resin substrate, and a manufacturing method of the resin substrate. BACKGROUND

[0002] In the field of electric and electronic, resin substrates are widely used as a base material of semiconductor package substrates and printed circuit boards. It is known that a resin substrate is provided with a concavo-convex structure on a surface thereof in order to obtain sufficient adhesion between the resin substrate and other metal or other resin laminated on the surface of the resin substrate. In recent years, along with high integration, three kinds of circuit formation methods, for example, have attracted attention as a circuit formation method of semiconductor package substrates and printed circuit boards. That is, (1) a circuit formation method in which an extremely thin copper foil is used as a power supply layer, pattern plating is performed, and finally, an extremely thin copper layer is removed by flash etching to form a wiring; (2) a circuit formation method in which a pre-impregnated material (Pregreg) or a build-up film is cured by vacuum pressurization or the like, the surface thereof is roughened to form an appropriate concavo-convex on the surface of the substrate, and thereby a fine wiring having reliability is formed; and (3) a circuit formation method in which an appropriate concavo-convex is formed on the surface of the substrate by transferring the profile of the surface of a copper foil to the surface of the substrate, and thereby a fine wiring having reliability is formed. These methods are generally referred to as SAP (Semi-Additive Process) methods.

[0003] For example, Patent Literature 1 discloses one example of the SAP method using the profile of the surface of the copper foil described in (3) above. It is a surface-treated copper foil in which the surface roughness Sz of the surface layer surface is controlled within a prescribed range, and after the surface-treated copper foil is attached to a substrate on which a circuit is formed, it is removed, and thereby the profile shape of the substrate surface after the copper foil is removed can be imparted, and the substrate surface after the copper foil is removed maintains fine wiring formability and realizes good adhesion of a chemical copper plating film.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent No. 5963824 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in recent years, along with further high integration, a demand for further fine wiring of semiconductor package substrates and printed circuit boards has been made, for example, a wiring having a width of 2 μm or the like.

[0009] In addition, from the viewpoint of communication traffic and communication speed, the use of higher frequency band electromagnetic waves is increasingly being promoted. The use of high frequency band electromagnetic waves is accompanied by a skin effect, that is, the electric signal passing through the circuit is more concentrated near the surface. For example, in the case of a frequency band of 5 GHz, in a copper conductor, the current flows in a concentrated manner in a depth region of about 0.9 μm from the surface layer of the conductor. On the other hand, in the case of a frequency band of 20 GHz, the current flows in a concentrated manner in a depth region of about 0.5 μm from the surface layer of the conductor. Therefore, it is necessary to impart a concave-convex structure to the surface of the resin base material for forming the circuit, the concave-convex structure ensuring sufficient adhesion with the circuit, the height of the concave-convex structure being smaller than the depth at which the above-described skin effect is obtained.

[0010] Thus, the present disclosure provides an aluminum foil capable of imparting a concave-convex structure having a height smaller than a depth at which a skin effect is obtained to the surface of a resin base material, a method for manufacturing the aluminum foil, a method for manufacturing a laminate of the aluminum foil and a resin base material, and a method for manufacturing a resin base material.

[0011] Technical Solution to Solve the Technical Problem

[0012] The present inventors, in order to solve the above-described problems, have made earnest investigations, and as a result, have completed an aluminum foil capable of imparting a concave-convex structure to various resin base materials laminated on the surface, the concave-convex structure having sufficient smoothness on a macroscopic scale and being capable of ensuring sufficient adhesion between the resin base material and a material laminated on the resin base material on a microscopic scale.

[0013] That is, one aspect of the aluminum foil disclosed herein is an aluminum foil characterized by comprising:

[0014] The aluminum foil has a concave-convex structure provided on at least one surface,

[0015] When the surface is observed with an atomic force microscope, in a first rectangular field of view having a size of 5 μm x 5 μm and a resolution of 256 x 256 pixels,

[0016] The surface roughness Sa is 15 nm or more and 50 nm or less,

[0017] The surface roughness SzJIS is 150 nm or more and 400 nm or less,

[0018] The number of peaks counted in 5 μm length is 25 or more,

[0019] When the surface is observed with a laser microscope, in a second rectangular field of view having a size of 95 μm x 71 μm and a resolution of 1024 x 768 pixels,

[0020] The surface roughness Sa is 30 nm or less,

[0021] The surface roughness Sz is 600 nm or less.

[0022] In the present configuration, the concavo-convex structure is provided on at least one surface of the aluminum foil, and thus the resin substrate whose surface has been transferred with the concavo-convex structure can obtain sufficient physical adhesion between it and other material laminated on the surface, and thus can have high peeling strength. In particular, the concavo-convex structure of the aluminum foil in the present configuration has the surface roughness Sa, Sz JIS in the above range in the first rectangular field, and thus has a concavo-convex structure whose shape can sufficiently ensure the above adhesion in a microscopic manner. On the other hand, the surface of the aluminum foil in the present configuration has the surface roughness Sa, Sz in the above range in the second rectangular field, and thus has sufficient smoothness in a macroscopic manner. That is, according to the aluminum foil in the present configuration, it is possible to impart a concavo-convex structure having a height smaller than a depth at which skin effect can be obtained to the surface of the resin substrate, and thus it is possible to both ensure sufficient adhesion between the resin substrate and other material and sufficiently suppress transmission loss due to skin effect.

[0023] Note that, in the present specification, the surface roughness Sa is one of parameters indicating the height of the surface roughness of ISO 25178, and is the arithmetic average height of the surface (obtained by extending the arithmetic average height Ra of a line to a surface). The surface roughness Sa is indicated by the average value of the absolute values of the height differences of each point from the average plane of the surface. In the following description, the surface roughness Sa is sometimes simply referred to as "Sa", "the arithmetic average height Sa of the surface".

[0024] In addition, in the present specification, the surface roughness Sz (hereinafter, sometimes simply referred to as "Sz") is one of parameters indicating the height of the surface roughness of ISO 25178, and is the maximum height of the surface (obtained by extending the maximum height Rz of a line to a surface). The surface roughness Sz is indicated by the sum of the absolute value of the height of the lowest point of the surface from the average plane and the absolute value of the height of the highest point of the surface from the average plane. In the following description, the surface roughness Sz is sometimes simply referred to as "Sz", "the maximum height Sz of the surface".

[0025] In addition, in the present specification, the surface roughness Sz JIS when observed with an AFM (Atomic Force Microscope) is a value obtained by measuring the Rz JIS value defined in JIS B0601 (2001 edition) and ISO 4287 (1997 edition) for the entire surface within the field of view observed. In the following description, the surface roughness Sz JIS is sometimes simply referred to as "Sz JIS".

[0026] Preferably, the aluminum foil includes a base material layer having aluminum as a mother phase and a surface layer provided on a surface of the base material layer and constituting the concavo-convex structure,

[0027] The area ratio of the second phase particles present on the surface of the base material layer is 0.1% or less.

[0028] An element other than aluminum, such as iron (Fe), can be added to the base material layer of the aluminum foil as an alloying element. Such an element forms an intermetallic compound such as Al3Fe, Al6Fe, and the like with the aluminum metal of the mother phase and is present as a second phase particle dispersed in the mother phase. Since the second phase particle is different in chemical composition from the aluminum metal of the mother phase, it interferes with the formation of a uniform concavo-convex structure when the concavo-convex structure is formed. In particular, in the case where needle-shaped crystals are formed from at least one of aluminum hydroxide and aluminum oxide and the concavo-convex structure is formed from the needle-shaped crystals, either the needle-shaped crystals will not be formed or the needle-shaped crystals will grow abnormally in the vicinity of the second phase particle. In this case, if the area ratio of the second phase particles present on the surface exceeds 0.1%, the uniformity of the concavo-convex structure will be impaired, and in particular, the surface roughness Sa, Sz described above can no longer be obtained in the second rectangular field, and it can not be possible to ensure sufficient smoothness. According to the present configuration, it is possible to ensure sufficient uniformity of the concavo-convex structure formed on the surface of the base material layer, and in particular, it is possible to sufficiently ensure macroscopic smoothness.

[0029] Preferably, the aluminum foil includes a base material layer having aluminum as a mother phase and a surface layer provided on a surface of the base material layer and constituting the concavo-convex structure,

[0030] The content of aluminum in the base material layer is 99.90% by mass or more,

[0031] The content of iron in the base material layer is 0.050% by mass or less.

[0032] In the case where the aluminum in the base material layer is less than 99.9% by mass, the area ratio of the above-described second phase particles increases, and thus the uniformity of the concavo-convex structure can decrease. For example, iron, which is one of the alloying elements, does not form a second phase particle in a state of being solid-solved in aluminum. Furthermore, it is generally known that the solid solubility of iron in aluminum is 0.05% by mass or less. Therefore, if the content of iron exceeds 0.05% by mass, Al-Fe type second phase particles represented by Al3Fe are generated between aluminum and iron, particularly at the time of casting and solidification of the base material layer, and the area ratio of the second phase particles increases. By setting the contents of aluminum and iron in the base material layer to the above-described ranges, it is possible to suppress the generation of second phase particles, and thus it is possible to ensure sufficient uniformity of the concavo-convex structure.

[0033] Preferably, the concavo-convex structure is formed of needle-shaped crystals formed of at least one of aluminum hydroxide and aluminum oxide.

[0034] For example, by performing a boehmite treatment of immersing the surface of an aluminum foil in boiling water or the like, aluminum hydroxide having a needle-shaped concavo-convex shape of a boehmite crystal structure is generated on the surface of the aluminum foil. The needle-shaped crystals of aluminum hydroxide, after a dehydration reaction, can exist as needle-shaped crystals of aluminum oxide. Since the concavo-convex structure is formed of needle-shaped crystals formed of at least one of aluminum hydroxide and aluminum oxide, the needle-shaped crystals have a fine and uniform needle-shaped concavo-convex shape. Therefore, the surface roughness Sa, Sz described above can be easily achieved.

[0035] Preferably, the aluminum foil is used to impart the concavo-convex structure to the surface of a resin substrate.

[0036] By imparting the concavo-convex structure to the surface of a resin substrate using the aluminum foil in the present configuration, a resin substrate having a concavo-convex structure with a height smaller than the depth at which a skin effect can be obtained can be obtained.

[0037] Preferably, the number of peaks is the average of the number of peaks exceeding a threshold value of 0 nm, which is counted for each of the three width direction cross-sectional profile curves observed with the atomic force microscope in each of the three first rectangular fields.

[0038] According to the present configuration, a fine and uniform concavo-convex structure can be obtained.

[0039] Preferably, the aluminum foil includes a base material layer having aluminum as a parent phase and a surface layer provided on the surface of the base material layer and constituting the concavo-convex structure,

[0040] The surface of the base material layer on which the surface layer is provided has a surface roughness Sa of 20 nm or less and a surface roughness Sz of 250 nm or less in the second rectangular field.

[0041] By setting the surface roughness Sa, Sz of the surface of the aluminum base material in the second rectangular field to the above range, the macroscopic smoothness of the surface of the base material layer can be sufficiently ensured, and thus the macroscopic smoothness of the surface layer can also be sufficiently ensured.

[0042] One aspect of the method of manufacturing an aluminum foil disclosed herein is a method of manufacturing the above-described aluminum foil, characterized by,

[0043] The aluminum foil includes a base material layer having aluminum as a parent phase and a surface layer provided on the surface of the base material layer and constituting the concavo-convex structure,

[0044] The manufacturing method of the aluminum foil includes a preparation step and a surface treatment step,

[0045] In the preparation step, an aluminum base material in the form of a foil that forms the base material layer is prepared,

[0046] In the surface treatment step, the surface layer is formed on the surface of the aluminum base material,

[0047] The surface roughness Sa in the second rectangular field of view of the surface of the aluminum base material is 20 nm or less, and the surface roughness Sz is 250 nm or less.

[0048] According to the present configuration, an aluminum foil having a concavo-convex structure that can sufficiently ensure macroscopic smoothness and can impart sufficient adhesion on a microscopic level can be obtained.

[0049] One aspect of the manufacturing method of the laminate disclosed herein is a manufacturing method of a laminate of an aluminum foil and a resin base material, characterized by,

[0050] The surface of the resin base material is brought into contact with the surface having the concavo-convex structure in the aluminum foil, and pressure is applied at a temperature above the softening point or glass transition point of the resin material that forms the resin base material.

[0051] According to the present configuration, the laminate obtained as described above is in a state in which the resin material of the resin base material enters the concavo-convex structure of the surface of the aluminum foil at the interface between the aluminum foil and the resin base material. As a result, a concavo-convex structure that is the inverse of the concavo-convex structure of the surface of the aluminum foil is formed on the surface of the resin base material.

[0052] One aspect of the manufacturing method of the resin base material disclosed herein is characterized by including:

[0053] a step of obtaining a laminate composed of an aluminum layer and a resin layer by bringing the surface of the resin base material into contact with the surface having the concavo-convex structure of the aluminum foil and applying pressure at a temperature above the softening point or glass transition point of the resin material that forms the resin base material; and

[0054] a step of removing the aluminum layer of the laminate to obtain a resin base material in which the shape of the concavo-convex structure of the aluminum foil is transferred to the surface.

[0055] According to the present configuration, it is possible to obtain a resin substrate having a concavo-convex structure on the surface, the concavo-convex structure being in the opposite shape of the concavo-convex structure of the surface of an aluminum foil. In this way, in the case where another material is laminated on the surface of the resin substrate, it is possible to ensure high adhesion between the two. Also, the surface of the resin substrate has sufficient smoothness on a macroscopic scale, and thus in the case where a wiring is formed on the surface of the resin substrate, it is also possible to effectively suppress transmission loss caused by skin effect.

[0056] -Effects of the Invention-

[0057] As described above, according to the present disclosure, it is possible to provide an aluminum foil capable of imparting a concavo-convex structure having a depth smaller than a height at which skin effect can be obtained to the surface of a resin substrate, a manufacturing method of the aluminum foil, a manufacturing method of a laminate of the aluminum foil and the resin substrate, and a manufacturing method of the resin substrate. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is a schematic cross-sectional view of an aluminum foil according to the present embodiment.

[0059] Figure 2 is a flowchart showing one example of a manufacturing method of an aluminum foil.

[0060] Figure 3 is a view showing one example of a surface treatment step.

[0061] Figure 4 is a flowchart showing one example of a manufacturing method of a laminate, a manufacturing method of a resin substrate, and a lamination method of laminating another material on a resin substrate.

[0062] Figure 5 is an SEM image of the surface of the aluminum foil in Example 2.

[0063] Figure 6 is a cross-sectional SEM image at the interface between the surface layer and the substrate layer of the aluminum foil in Example 2.

[0064] Figure 7 is one example of a reflection electron image used to calculate the area ratio of second phase particles.

[0065] Figure 8 shows one example of a first rectangular field (AFM image) of the surface layer of the aluminum foil in Example 1 and one example of a cross-sectional profile curve of the portions indicated by symbols P1 to P3 in the AFM image.

[0066] Figure 9 is one example of a second rectangular field (laser microscope image) of the aluminum foil in Example 2.

[0067] Figure 10 is one example of a cross-sectional SEM image of a copper-plated laminate. DETAILED DESCRIPTION

[0068] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0069] <Aluminum foil>

[0070] like Figure 1 As shown, the aluminum foil 10 involved in this embodiment includes a base layer 11 and a surface layer 12. The base layer 11 has aluminum as a matrix phase, and the surface layer 12 is provided on at least one surface 11a of the base layer 11. The surface layer 12 has a concavo-convex structure. The surface layer 12 can also be provided on another surface 11b of the base layer 11.

[0071] In addition, in this specification, the term "aluminum foil" is used to include not only pure aluminum foil but also aluminum alloy foil.

[0072] [Base material layer]

[0073] As will be described later, the base material layer 11 is formed of an aluminum base material before the surface layer 12 is formed.

[0074] Elements other than aluminum, such as iron (Fe), can be added to the aluminum matrix as alloying elements. In addition, these elements will form intermetallic compounds such as Al3Fe, Al6Fe, etc. with the parent metal aluminum, and dispersed in the parent phase as second phase particles. Since the second phase particles are different from the parent phase of aluminum metal in chemical composition, the formation of a uniform concave-convex structure will be hindered when the concave-convex structure is formed. In particular, when needle-shaped crystals are formed by at least one of aluminum hydroxide and aluminum oxide described later and the concave-convex structure is formed by the needle-shaped crystals, needle-shaped crystals will either not be formed in the second phase particles and their surroundings, or the needle-shaped crystals will grow abnormally. In this case, if the area ratio of the second phase particles present on the surface exceeds 0.1%, the uniformity of the concave-convex structure will be destroyed, especially in the second rectangular field of view, the above-mentioned surface roughness Sa and Sz can no longer be obtained, and sufficient smoothness may not be ensured.

[0075] The area ratio of the second phase particles present on the surface 11a of the aluminum substrate, i.e., the substrate layer 11, is preferably 0.1% or less, more preferably 0.01% or less, and particularly preferably 0.005% or less. This ensures sufficient uniformity of the concavo-convex structure formed on the surface of the substrate layer 11, and in particular, sufficient macroscopic smoothness.

[0076] The aluminum content in the base material layer 11 is preferably 99.90% by mass or more. The iron content in the base material layer 11 is preferably 0.050% by mass or less.

[0077] In the case where the aluminum in the base material layer 11 is less than 99.9 mass%, the area ratio of the second phase particles described above increases, and thus the uniformity of the concavo-convex structure can decrease. For example, iron, one of the alloying elements, does not form second phase particles in a state of being dissolved in aluminum. Also, it is generally known that the solid solubility of iron in aluminum is 0.05 mass% or less. Therefore, if the content of iron exceeds 0.05 mass%, Al-Fe type second phase particles represented by Al3Fe are generated between aluminum and iron particularly at the time of casting and solidification of the base material layer 11, and the area ratio of the second phase particles increases. By setting the contents of aluminum and iron in the base material layer 11 to the ranges described above, generation of the second phase particles can be suppressed, and thus sufficient uniformity of the concavo-convex structure can be ensured.

[0078] Note that the remaining portion of the aluminum base material other than aluminum and iron is composed of impurities. The impurities are, for example, unavoidable impurities, but in addition to the unavoidable impurities, trace amounts of impurities can also be included. The above-described impurities include, for example, at least one element selected from the group consisting of silicon (Si), copper (Cu), manganese (Mn), magnesium (Mg), zinc (Zn), titanium (Ti), chromium (Cr), vanadium (V), gallium (Ga), boron (B), nickel (Ni), lead (Pb), bismuth (Bi), sodium (Na), and zirconium (Zr). The content of each of the impurity elements is 0.01 mass% or less, and the total amount of the impurity elements is 0.10 mass% or less.

[0079] There is no limitation on the thickness of the base material layer 11, and the thickness of the base material layer 11 can be set to, for example, 5 μm or more and 300 μm or less, and preferably the thickness of the base material layer 11 is set to 30 μm or more and 60 μm or less. If the thickness of the base material layer 11 exceeds the upper limit value, a long time can be required when the aluminum layer is removed from the resin base material. If the thickness of the base material layer 11 is less than the lower limit value, the rigidity of the base material layer 11 is insufficient, and it can be difficult to impart the concavo-convex structure to the resin base material.

[0080] The surface roughness Sa of the surface of the base material layer 11, that is, the surface of the aluminum base material in the second rectangular field of view described later is preferably 20 nm or less, and more preferably 5 nm or more and 10 nm or less. Also, the surface roughness Sz of the surface of the aluminum base material in the second rectangular field of view is preferably 250 nm or less, and more preferably 50 nm or more and 200 nm or less, and particularly preferably 50 nm or more and 150 nm or less.

[0081] By setting the surface roughness Sa, Sz of the surface of the aluminum base material in the second rectangular field of view to the ranges described above, the macroscopic smoothness of the surface of the base material layer 11 can be sufficiently ensured, and thus the macroscopic smoothness of the surface layer 12 can also be sufficiently ensured.

[0082] Note that the surface of the aluminum base material is not intended to be limited, but the surface roughness Sa in the first rectangular field described later is preferably 10 nm or less, more preferably 1 nm or more and 10 nm or less, and particularly preferably 1 nm or more and 3 nm or less. The surface roughness SzJIS of the surface of the aluminum base material is preferably 100 nm or less, more preferably 30 nm or more and 50 nm or less.

[0083] By setting the surface roughness Sa, SzJIS of the surface of the aluminum base material in the first rectangular field to the above-described range, the surface of the base material layer 11 also has smoothness on a microscopic level, and thus sufficient uniformity of the concavo-convex structure can be ensured when the surface layer 12 is formed.

[0084] [Surface layer]

[0085] The concavo-convex structure of the surface layer 12 has the following characteristics.

[0086] That is, when the surface of the surface layer 12 is observed with an AFM, the surface roughness Sa is 15 nm or more and 50 nm or less, preferably 16 nm or more and 41 nm or less, and more preferably 20 nm or more and 41 nm or less, in a first rectangular field having a size of 5 μm x 5 μm and a resolution of 256 x 256 pixels.

[0087] Further, the surface roughness SzJIS in the first rectangular field is 150 nm or more and 400 nm or less, and preferably 150 nm or more and 350 nm or less.

[0088] The number of peaks counted in the 5 μm length of the first rectangular field is 25 or more, and preferably 25 or more and 60 or less.

[0089] When the surface of the surface layer 12 is observed with a laser microscope, the surface roughness Sa is 30 nm or less, preferably 5 nm or more and 25 nm or less, and more preferably 10 nm or more and 21 nm or less, in a second rectangular field having a size of 95 μm x 71 μm and a resolution of 1024 x 768 pixels.

[0090] Further, the surface roughness Sz in the second rectangular field is 600 nm or less, preferably 550 nm or less, and more preferably 100 nm or more and 510 nm or less.

[0091] Note that the AFM observation of the first rectangular field means observation of the concavo-convex structure in a microscopic field. Further, the laser microscope observation of the second rectangular field means observation of the concavo-convex structure in a macroscopic field.

[0092] In the present constitution, the concave-convex structure is provided on at least one surface of the aluminum foil 10, and therefore, the resin substrate whose surface has the concave-convex structure transferred thereon can obtain sufficient physical adhesion between the resin substrate and other materials laminated on the surface, and thus can have high peel strength. In particular, the concave-convex structure of the aluminum foil in the present constitution has the surface roughness Sa, Sz JIS in the above range in the first rectangular field of view, and thus has a concave-convex structure whose shape can sufficiently ensure the above adhesion in a microscopic manner. On the other hand, the surface of the aluminum foil 10 in the present constitution has the surface roughness Sa, Sz in the above range in the second rectangular field of view, and thus has sufficient smoothness in a macroscopic manner. That is, according to the aluminum foil 10 in the present constitution, it is possible to impart a concave-convex structure having a height smaller than a depth at which skin effect can be obtained to the surface of the resin substrate, and thus it is possible to both ensure sufficient adhesion between the resin substrate and other materials and sufficiently suppress transmission loss due to skin effect.

[0093] If Sa is less than the above lower limit value or Sz JIS is less than the above lower limit value in the first rectangular field of view in a microscopic manner, it can be difficult to obtain sufficient physical adhesion between the resin substrate and other materials when the concave-convex structure of the aluminum foil has been transferred to the resin substrate. On the other hand, if Sa exceeds the above upper limit value or Sz JIS exceeds the above upper limit value in the first rectangular field of view, although it is possible to sufficiently obtain the above physical adhesion, the height of the concave-convex structure is excessively large, and it can be difficult to obtain surface smoothness that has little influence on electrical characteristics and is suitable for a fine circuit conductor. Furthermore, if the number of peaks counted in a length of 5 μm in the first rectangular field of view is less than the above lower limit value, the above physical adhesion becomes insufficient, and it can be difficult to obtain sufficient peel strength between the resin substrate and materials laminated on the resin substrate.

[0094] If Sa exceeds the above upper limit value or Sz exceeds the above upper limit value in the second rectangular field of view in a macroscopic manner, it is not possible to obtain uniform surface smoothness, and the influence on electrical characteristics due to skin effect can become large.

[0095] The shape of the concave-convex structure of the surface layer 12 is not particularly limited as long as the above surface roughness is satisfied, and can be any shape such as a granular shape, a needle shape, a hair shape, or the like. Furthermore, the arrangement of the concave-convex structure is not particularly limited as long as the above surface roughness is satisfied, and can be random concave-convex structures or patterned concave-convex structures.

[0096] The surface layer 12 is not particularly limited as long as it can constitute the above concave-convex structure, and the material of the surface layer 12 is not particularly limited. Specifically, for example, the surface layer 12 can be a layer formed of the same pure aluminum or aluminum alloy as the base material layer 11, or a layer having a material such as an aluminum hydroxide coating film or an aluminum oxide coating film different from the base material layer 11.

[0097] Note that preferably, the concavo-convex structure is formed of needle-shaped crystals formed of at least one of aluminum hydroxide and aluminum oxide.

[0098] As described later, for example, by performing a boehmite treatment of immersing the surface of an aluminum foil in boiling water or the like, aluminum hydroxide in a needle-shaped concavo-convex structure of boehmite crystals is generated on the surface of the aluminum foil. The needle-shaped crystals of aluminum hydroxide, after a dehydration reaction, can also exist as needle-shaped crystals of aluminum oxide. Since the concavo-convex structure is formed of needle-shaped crystals formed of at least one of aluminum hydroxide and aluminum oxide, the needle-shaped crystals have a fine and uniform needle-shaped concavo-convex shape. Therefore, the surface roughness Sa, Sz, SzJIS of the surface layer 12 described above can be easily achieved.

[0099] The thickness of the surface layer 12 is not particularly limited as long as the concavo-convex structure satisfies the surface roughness and the number of peaks described above, and can be set to, for example, 100 nm or more and 1000 nm or less.

[0100] [Use]

[0101] The aluminum foil according to the present embodiment is most suitable as a manufacturing process paper used for obtaining a surface of a resin substrate having sufficient smoothness on a macroscopic scale but excellent adhesiveness to other materials.

[0102] Specifically, preferably, the aluminum foil according to the present embodiment is used to impart a concavo-convex structure to a surface of a resin substrate used as a substrate of, for example, a semiconductor package substrate and a printed circuit board.

[0103] By imparting a concavo-convex structure to a surface of a resin substrate using the aluminum foil 10 according to the present embodiment, a resin substrate having a concavo-convex structure with a depth smaller than that at which a skin effect can be obtained can be obtained.

[0104] Note that the shape of the resin substrate is not particularly limited, and examples include a film shape, a plate shape, a block shape, and the like.

[0105] The resin material forming the resin substrate is not particularly limited as long as it is a material that can be used as a substrate of, for example, a semiconductor package substrate and a printed circuit board, and generally known materials can be used. Specific examples of the resin material include, for example, an epoxy resin, a polyimide resin, a urethane resin, a liquid crystal polymer resin, a fluororesin, and the like. Note that as the resin substrate, a resin substrate in a semi-cured state (a B-stage state) can also be used.

[0106] <Method for manufacturing aluminum foil>

[0107] Next, one example of a method for manufacturing the aluminum foil 10 will be described.

[0108] As shown in FIG. 1, the manufacturing method of the aluminum foil, for example, includes a preparation step Sll, an optional pretreatment step S12, and a surface treatment step S13. Figure 2

[0109] <Preparation Step>

[0110] The preparation step Sll is a step of preparing an aluminum base material that forms a base material layer 11.

[0111] The preparation step Sll, for example, includes a step of preparing an aluminum ingot, a step of subjecting the ingot to a homogenization treatment, a step of subjecting the ingot to hot rolling, a step of subjecting a hot-rolled material obtained by the hot rolling to cold rolling, and a step of forming an aluminum base material from a cold-rolled material obtained by the cold rolling as final cold finishing (hereinafter, referred to as final cold finishing).

[0112] First, an aluminum ingot is prepared. Specifically, an aluminum melt having a prescribed composition is prepared, and the aluminum melt is solidified, whereby the ingot is cast (for example, semi-continuous casting). The content of iron in the melt is controlled to be within the above numerical range.

[0113] Then, the obtained ingot is subjected to a homogenization heat treatment. The homogenization heat treatment can be performed as long as it is within a general operating condition range, for example, under conditions where the heating temperature is 400°C or higher and 630°C or lower, and the heating time is 1 hour or longer and 20 hours or shorter.

[0114] Next, the ingot is subjected to hot rolling. A hot-rolled material having a prescribed thickness is obtained by this step. The hot rolling can be performed once or a plurality of times. Note that, in the case where a thin-plate-shaped aluminum ingot is manufactured by continuous casting, the thin-plate-shaped ingot can be subjected to cold rolling without going through this step.

[0115] Then, the hot-rolled material obtained by the hot rolling is subjected to cold rolling. By this step, a cold-rolled material (a material to be rolled in the final cold finishing step) having a prescribed thickness is obtained. In this step, the cold rolling can be performed a plurality of times with an intermediate annealing step interposed, for example. For example, first, a first cold rolling step is performed on the hot-rolled material, and a rolled material thinner than the hot-rolled material and thicker than the cold-rolled material is formed. Next, the obtained rolled material is subjected to an intermediate annealing step. The intermediate annealing can be performed as long as it is within a general operating condition range, for example, under conditions where the annealing temperature is 50°C or higher and 500°C or lower, and the annealing time is 1 second or longer and 20 hours or shorter. Then, a second cold rolling step is performed on the rolled material after the annealing. As described above, the cold rolling and the intermediate annealing are repeated a necessary number of times, and the cold-rolled material is obtained.

[0116] ​Finally, the cold-rolled material is subjected to final cold-precision rolling. In this process, the material to be rolled is subjected to final cold-precision rolling using a pair of rolls. The rolls have roll surfaces that come into contact with the material to be rolled to perform rolling. In a pair of rolls arranged with the material to be rolled interposed therebetween, the surface roughness Ra of the roll surface of at least one of the rolls is preferably 50 nm or less. If the material to be rolled is subjected to rolling using a pair of rolls having a surface roughness Ra of more than 50 nm, the surface roughness Sa, Sz, and SzJIS of the aluminum base material obtained can not satisfy the above numerical ranges. The surface roughness Ra of the rolls used in this process is preferably as small as possible, and more preferably 40 nm or less. As described above, the aluminum base material in the form of a foil is ready.

[0117] [Pre-treatment process]

[0118] The pre-treatment process S12 is a process of cleaning at least one surface of the aluminum base material obtained as described above to remove rolling oil components adhering to the surface and aluminum fine powder generated by rolling.

[0119] The cleaning method is not particularly limited, and a generally known method can be employed. Specifically, for example, the aluminum base material can be brought into contact with a metal cleaning agent such as dichloromethane, or the aluminum base material can be brought into contact with an alkaline aqueous solution containing sodium hydroxide, sodium bicarbonate, sodium carbonate, or the like, or an acidic aqueous solution such as phosphoric acid, hydrofluoric acid, or the like. In the case where the alkaline or acidic aqueous solution is brought into contact with the surface of the aluminum base material in the cleaning process, in order not to cause the roughness of the surface of the aluminum base material to become large, it is preferable to use a low-concentration aqueous solution diluted to, for example, about 0.5 to 1.5 mass %.

[0120] The pre-treatment process S12 is an optional process, but from the viewpoint of ensuring the uniformity of the concave-convex structure formed in the surface treatment process S13, it is preferable to provide the pre-treatment process S12.

[0121] [Surface treatment process]

[0122] The surface treatment process S13 is a process of forming a surface layer 12 on the surface of the aluminum base material.

[0123] The surface treatment method in the surface treatment process S13 is not particularly limited as long as it can form a concave-convex structure satisfying the above-mentioned surface roughness Sa, Sz, and SzJIS. Specifically, the surface treatment method is, for example, a wet method and a dry method, and the wet method is, for example, a process of immersing the aluminum base material in an acidic or alkaline solution to perform boehmite treatment on the surface of the aluminum base material, and the dry method is, for example, a process of performing sandblasting treatment on the surface of the aluminum base material to transfer the concave-convex structure formed on the surface of the roll, or the like.

[0124] As a surface treatment method, a method of performing boehmite treatment on the surface of the aluminum substrate is preferred. By boehmite treatment, a concave-convex structure formed by needle-shaped crystals can be formed on the surface of the aluminum substrate, and the needle-shaped crystals are formed by at least one of aluminum hydroxide and aluminum oxide. Boehmite treatment is carried out, for example, by bringing any one of warm water, boiling water and water vapor at 50°C to 100°C into contact with the aluminum substrate. From the viewpoint of reducing the impurity concentration, it is preferred that the water used for boehmite treatment has an electrical conductivity of 1μS / cm or less. More preferably, pure water such as ion exchange water, distilled water, etc. with an electrical conductivity of 0.5μS / cm or less. If the electrical conductivity becomes higher, the impurity concentration becomes higher, and the uniformity of the boehmite needle-shaped crystals may be reduced. Specifically, for example, if the water contains silicon and calcium, compounds such as SiO2 and CaCO3 will precipitate on the surface of the aluminum substrate during boehmite treatment. In particular, SiO2 is adsorbed on the surface of the aluminum substrate, hindering the reaction between the aluminum substrate and water and inhibiting the growth of boehmite needle-shaped crystals.

[0125] For example, 0.1% to 1% by mass of triethanolamine can be added to such low-conductivity water. The addition of triethanolamine increases the hydroxide ions in the solution and promotes the formation of boehmite needle crystals.

[0126] For example, Figure 3 As shown, the boehmite treatment can be performed by continuously immersing the aluminum substrate forming the substrate layer 11 in a warm water bath containing warm water 21 while being conveyed by rollers. In this case, the immersion time can be set in relation to the conveying speed.

[0127] [Method for producing laminate]

[0128] An example of a method for producing a laminate of the aluminum foil 10 and the resin base material will be described.

[0129] Figure 4 This is a flowchart showing an example of a method for producing a laminate, a method for producing a resin substrate described later, and a method for laminating other materials on the resin substrate.

[0130] like Figure 4 As shown, the aluminum foil 10 and the resin base material are thermally compressed (step S21 ), thereby producing a laminate.

[0131] The hot pressing step S21 is specifically carried out, for example, by bringing the surface of the resin substrate into contact with the surface having a concave-convex structure in the aluminum foil, and applying a pressure of, for example, 10 kN or more and 20 kN or less at a temperature above the softening point or glass transition point of the resin material forming the resin substrate.

[0132] The conditions for thermocompression bonding are not particularly limited and can be appropriately changed depending on the type of resin material and the like.

[0133] According to the present configuration, the laminate obtained as described above is in a state where the resin material of the resin substrate enters the concave-convex structure of the surface of the aluminum foil at the interface between the aluminum foil and the resin substrate. In this way, a concave-convex structure is formed on the surface of the resin substrate, which is in the opposite shape of the concave-convex structure of the surface of the aluminum foil.

[0134] Note that the method of manufacturing the laminate is not limited to the above-described method, and for example, an injection molding method or the like can be used to flow molten resin into the surface of the aluminum foil to form the laminate.

[0135] <Method of manufacturing resin substrate>

[0136] One example of a method of manufacturing a resin substrate having a concave-convex structure on the surface using an aluminum foil 10 will be described.

[0137] As shown in FIG. 1, the method of manufacturing a resin substrate according to the present embodiment includes a step S21 of obtaining the above-described laminate and a step S22 of removing the aluminum layer of the laminate. Figure 4

[0138] The method of removing the aluminum layer of the laminate is not particularly limited, and a generally known method can be used. Specifically, for example, by immersing in a 5 to 20 mass% or so sodium hydroxide aqueous solution heated to about 30 to 70°C for a prescribed time, the aluminum layer can be removed by dissolution. The immersion time also depends on the thickness of the aluminum layer, and for example, the immersion time can be set to about 30 seconds to 30 minutes.

[0139] In the case where the surface layer 12 of the aluminum foil is formed of a different component from the substrate layer 11, a removal operation of the surface layer 12 is also required. Specifically, for example, in the case where the surface layer 12 is formed of at least one of aluminum hydroxide and aluminum oxide, it cannot be removed with a sodium hydroxide aqueous solution. Therefore, the resin substrate after the aluminum layer is removed can be immersed in a 5 to 15 mass% or so phosphoric acid aqueous solution heated to about 30 to 70°C for about 30 seconds to 30 minutes to remove the aluminum hydroxide layer and the aluminum oxide layer remaining on the surface of the resin substrate by dissolution.

[0140] As described above, a resin substrate in which the shape of the concave-convex structure of the aluminum foil is transferred to the surface can be obtained.

[0141] According to the present configuration, a concave-convex structure is formed on the surface of the resin substrate, which is in the opposite shape of the concave-convex structure of the aluminum foil, and therefore, in the case where another material is laminated on the surface of the resin substrate, high adhesion between the two can be ensured. Also, the surface of the resin substrate has sufficient smoothness on a macroscopic scale, and therefore, in the case where a wiring is formed on the surface of the resin substrate, transmission loss due to skin effect can also be effectively suppressed. ​

[0142] Note that, since the obtained concave-convex structure of the surface of the resin substrate is in the opposite shape of the concave-convex structure of the aluminum foil, it is preferable to satisfy the above conditions of the surface roughness and the number of peaks of the surface layer 12.

[0143] <Adhesion between resin substrate and other materials>

[0144] As shown in FIG. 6, after the process S23 of imparting, for example, a catalyst to the surface of the resin substrate, a chemical copper plating or the like (process S24) can also be performed. Figure 4

[0145] In the case where the surface of the resin substrate on which the concave-convex structure has been formed has been subjected to copper plating, from the viewpoint of ensuring sufficient adhesion between the two, the peeling strength is preferably 0.5 N / 10 mm or more, more preferably 0.6 N / 10 mm or more and 5 N / 10 mm or less, which is measured under the test conditions described in the peeling strength evaluation item in the Examples described later.

[0146] Examples

[0147] Next, specific examples will be described.

[0148] As described below, the test samples of the aluminum foils in the examples and comparative examples of the present disclosure were produced.

[0149] <Aluminum substrate: Production Examples A to J>

[0150] As shown in Tables 1 and 2, aluminum having various chemical compositions was cast, and the aluminum substrates in Production Examples A to J were produced.

[0151] [Table 1]

[0152]

[0153] [Table 2]

[0154]

[0155] The foil production process as a preparation process S11 was performed in the following steps. First, the aluminum ingot obtained by casting was fed into a heating furnace, and homogenization heat treatment was performed at the prescribed temperature and time shown in Table 2. Then, hot rolling was performed until the thickness reached about 6.5 mm. The obtained hot-rolled material was subjected to cold rolling multiple times. Note that, as necessary, intermediate annealing was performed at a prescribed temperature and time during cold rolling, and final cold finish rolling was performed until the thickness reached a prescribed value, and the aluminum substrate was produced.

[0156] <Aluminum foil: Examples 1 to 5 and Comparative Examples 1 to 12> ​

[0157] Next, the obtained aluminum base material was subjected to the pretreatment and surface treatment shown in Table 3, to obtain the aluminum foil in Examples 1 to 5 and Comparative Examples 1 to 12.

[0158] [Table 3]

[0159]

[0160] Specifically, after the final cold-precision rolling, as the pretreatment, the aluminum base material was immersed in a 1 mass% sodium hydroxide solution at 35°C for a prescribed time as shown in Table 3.

[0161] Then, in Examples 1 to 3, 5, Comparative Examples 1 to 7, 10 to 12, the aluminum base material was subjected to boehmite treatment by immersing it in ion-exchanged water at 100°C for a prescribed time as shown in Table 3. The boehmite treatment was performed using an apparatus shown in Figure 3

[0162] In Example 4, the aluminum base material was subjected to boehmite treatment by immersing it in a treatment liquid obtained by adding 1 mM nitric acid as an additive to ion-exchanged water at 100°C for a time shown in Table 3.

[0163] In Comparative Example 8, the aluminum base material was subjected to hydrochloric acid etching by immersing it in a 2 mass% hydrochloric acid aqueous solution at 35°C.

[0164] Note that Comparative Example 9 is an example in which the aluminum base material in Production Example A was subjected to only the pretreatment, and none of the warm water treatment and the hydrochloric acid etching.

[0165] Figure 5 and Figure 6 SEM images of the concave-convex structure and cross-sectional SEM images of the aluminum foil in Example 2 are shown. As shown in Figure 5 and Figure 6 As shown in Figs. 2 and 3, it was found that needle-shaped crystals of aluminum hydroxide having a thickness of about 473 nm were formed.

[0166] <Area ratio of second phase particles in base material layer>

[0167] The surface state of each sample of the obtained aluminum base material after the above pretreatment and before the above surface treatment was observed using a scanning electron microscope (SEM), and the area ratio of the second phase particles was measured.

[0168] Specifically, the observation of the second phase particles using the SEM was performed using a JSM-7200F (acceleration voltage 10 kV) manufactured by JEOL Ltd. and in accordance with the following procedure. First, the reflected electron images of the surface of each sample were observed in ten randomly selected rectangular fields. Each rectangular field was 2673.43 μm 2 ​a rectangular field of view (59.78 μm x 44.72 μm). Figure 7 An example of a reflection electron image is shown. Figure 7 The upper half of the figure shows a reflection electron image of the surface of the aluminum base material in Production Example D (Comparative Example 4), Figure 7 The lower half of the figure shows a reflection electron image of the surface of the aluminum base material in Production Example A (Example 1, etc.). The black portions are the primary phase aluminum, and the white portions are the second phase particles. As can be seen, in Production Example D (Comparative Example 4), the number of second phase particles is large, and in contrast, in Production Example A (Example 1, etc.), almost no second phase particles are observed.

[0169] The reflection electron images of each rectangular field of view were subjected to binary processing using the image processing software WinRoof 2021 manufactured by San-Ei Gen F.F.I., Inc., whereby the second phase particles were extracted. The observation conditions for the reflection electron images were as follows: the brightness, contrast, and voltage current value of the electron beam were set so that, in the brightness extraction by look-up table conversion prior to the binary processing, the brightness of elements other than the second phase particles, such as rolling streaks, oil pits, and pit shapes after surface formation, present in the rectangular field of view image fell within the range of 0 or more and 100 to 255 or less. The extraction by binary processing was carried out specifically as follows. First, in order to remove elements other than the second phase particles, such as rolling streaks, oil pits, and pit shapes after surface formation, present in the obtained rectangular field of view image, brightness extraction by look-up table conversion was carried out with the upper limit value fixed at 255 and the lower limit value fixed at 254. For the particles extracted with the threshold value of the circle equivalent diameter set to 0.1 or less, the area was measured, and the area ratio with respect to the entire field of view was calculated.

[0170] < Surface roughness of base material layer >

[0171] As with the observation of the surface layer described later, the surface state after the above-mentioned pretreatment and before the above-mentioned surface treatment was observed using a laser microscope for the aluminum base material, i.e., each test piece, and the Sa and Sz of the base material layer were calculated from the observation image of the second rectangular field of view.

[0172] < Structure and surface roughness of surface layer >

[0173] The structure, surface roughness, and number of peaks (PC) of the surface layer in Examples 1 to 5 and Comparative Examples 1 to 12 are shown in Table 4.

[0174] [Table 4]

[0175]

[0176] [Surface roughness and number of peaks of surface layer in first rectangular field of view]

[0177] The measurement of surface roughness by AFM was performed using an atomic force microscope AFM5000II manufactured by Hitachi High-Technologies Corporation. The surface of each sample was observed at a scan frequency of 0.83 Hz, a scan range of 5 μm x 5 μm, and a resolution of 256 x 256 pixels to obtain three first rectangular fields selected at random. Each first rectangular field was tilt-corrected using SPM (scanning probe microscope) image correction, and the Sa and SzJIS were calculated using surface roughness analysis processing. Further, the cross-sectional profile curves of three sites selected at random from each rectangular field were extracted using line roughness analysis processing, and the number of peaks exceeding the threshold value of 0 nm was counted after removing components having a wavelength of λc or less. Then, the average of the number of peaks exceeding the threshold value of 0 nm obtained by counting the three cross-sectional profile curves in the width direction of each of the three first rectangular fields observed by AFM was taken as the number of peaks counted in a length of 5 μm.

[0178] Specifically, Figure 8 An example of a first rectangular field (AFM image) of the surface layer of the aluminum foil in Example 1 and an example of the cross-sectional profile curves of the sites shown by P1 to P3 in the AFM image are shown. For example, the number of peaks exceeding the threshold value of 0 nm was counted for each of the cross-sectional profile curves at P1 to P3, and the same operation was performed in the other two first rectangular fields, and the average of the number of peaks counted in the nine cross-sectional profile curves was taken as the number of peaks.

[0179] [Surface roughness of surface layer in second rectangular field]

[0180] The observation of surface irregularities by a laser microscope was performed using a laser microscope VK-X3000 manufactured by Keyence Corporation in a second rectangular field of 95 μm x 71 μm by shape measurement using laser confocal. Figure 9 An example of a second rectangular field of the aluminum foil in Example 2 is shown.

[0181] The arithmetic mean height of surface Sa and the maximum height of surface Sz were measured from the obtained observation results using a VK-X3000 multi-file analysis application program manufactured by Keyence Corporation. First, the obtained shape data was subjected to a corrugation-removed surface shape correction with a cutoff value of 0.1 mm, and then a height cutoff level correction was performed with a cutoff level of 50 to remove noise components due to laser reflection, and the height corresponding to the average of irregularities was set as a reference surface with respect to the finally obtained corrected image. The arithmetic mean height of surface Sa and the maximum height of surface Sz were measured using a VK-X3000 multi-file analysis application program manufactured by Keyence Corporation in accordance with ISO 25178.

[0182] Evaluation of the concave-convex structure of the surface of the resin substrate

[0183] The HR370 resin manufactured by ISOLA GROUP was hot-pressed on the produced aluminum foil using a hot press device MKP-1000D-ST manufactured by Mikado Techno Co., Ltd. at 17.5 kN and 182°C.

[0184] Then, it was immersed in a 10 mass% sodium hydroxide aqueous solution at 60°C to dissolve the aluminum layer.

[0185] Further immersion in a 10 mass% phosphoric acid aqueous solution removed the aluminum hydroxide layer remaining on the surface of the resin by dissolution, and a resin substrate having a surface on which a concave-convex structure in the reverse shape of the concave-convex structure formed by the needle-shaped crystals of aluminum hydroxide was formed was obtained.

[0186] In order to evaluate the concave-convex structure of the surface, the obtained resin substrate was observed using a laser microscope and an atomic force microscope (AFM), a concave-convex image was obtained, and the surface roughness Sa, Sz, and SzJIS were measured from the concave-convex image. The measurement method was the same as that for the aluminum foil. The results are shown in Table 4.

[0187] Evaluation of the peel strength

[0188] A catalyst for causing chemical copper deposition was given to the surface of the resin substrate obtained as described above, and electroless copper plating was performed using THRU-CUP PEA-V4 manufactured by Uchida Industrial Co., Ltd. The thickness of the obtained electroless copper plating was about 0.5 μm.

[0189] Next, electrolytic copper plating was further performed on the electroless copper plating using a copper sulfate electrolyte. The thickness of the copper (total thickness of the electroless copper plating and the electrolytic copper plating) was about 35 μm.

[0190] Figure 10 An example of a cross-sectional SEM image of the copper-plated laminate sheet produced as described above is shown. It is known that a fine concave-convex structure is formed at the interface between the resin substrate and the electroless copper plating.

[0191] The copper-plated laminate sheet was cut into a width of 10 mm, and a test piece for evaluation of the peel strength was produced. The strength at which the test piece was peeled at 90 degrees was measured in accordance with JIS C 6481 and was taken as the peel strength.

[0192] Evaluation results

[0193] In Examples 1 to 5, the aluminum foil had a surface concave-convex structure that was sufficiently fine, and thus the surface concave-convex structure of the resin substrate obtained after the pressing was fine, and a high peel strength between the copper plating layer was obtained.

[0194] On the other hand, the results of the comparative examples were either that the surface of the obtained resin substrate was rough, or that the peeling strength between the copper plating layer was low even if the surface of the resin substrate was fine.

[0195] - Industrial applicability -

[0196] The present disclosure can provide an aluminum foil capable of imparting a concave-convex structure having a height smaller than a depth at which a skin effect can be obtained to a surface of a resin substrate, a method for manufacturing the aluminum foil, a method for manufacturing a laminate of the aluminum foil and the resin substrate, and a method for manufacturing the resin substrate, and is extremely useful.

[0197] - Symbol explanation -

[0198] 10 Aluminum foil

[0199] 11 Substrate layer

[0200] 12 Surface layer

[0201] 21 Warm water.

Claims

1. An aluminum foil having a concave-convex structure provided on at least one surface, characterized in that: When the surface is observed with an atomic force microscope, in a first rectangular field of view having a size of 5 μm×5 μm and a resolution of 256×256 pixels, The surface roughness Sa is 15 nm or more and 50 nm or less, The surface roughness SzJIS is 150nm or more and 400nm or less, The number of peaks counted in a length of 5 μm is 25 or more, When the surface is observed with a laser microscope, in a second rectangular field of view having a size of 95 μm×71 μm and a resolution of 1024×768 pixels, The surface roughness Sa is less than 30nm, The surface roughness Sz is 600 nm or less.

2. The aluminum foil according to claim 1, characterized in that The aluminum foil includes a base layer and a surface layer, wherein the base layer uses aluminum as a parent phase, and the surface layer is arranged on the surface of the base layer and constitutes the concave-convex structure. The area ratio of the second phase particles present on the surface of the base layer is 0.1% or less.

3. The aluminum foil according to claim 1, characterized in that The aluminum foil includes a base layer and a surface layer, wherein the base layer uses aluminum as a parent phase, and the surface layer is arranged on the surface of the base layer and constitutes the concave-convex structure. The content of the aluminum in the base material layer is 99.90 mass % or more, The iron content in the base material layer is 0.050 mass % or less.

4. The aluminum foil according to claim 1, characterized in that The concavo-convex structure is formed of needle-shaped crystals, and the needle-shaped crystals are formed of at least one of aluminum hydroxide and aluminum oxide.

5. The aluminum foil according to claim 1, characterized in that The aluminum foil is used to impart a concavo-convex structure to the surface of the resin substrate.

6. The aluminum foil according to claim 1, characterized in that The number of peaks is the average of the number of peaks exceeding the threshold value of 0 nm, and the number of peaks exceeding the threshold value of 0 nm is obtained by counting the cross-sectional profile curves in the three width directions of each of the three first rectangular fields observed by the atomic force microscope.

7. The aluminum foil according to claim 1, characterized in that The aluminum foil includes a base layer and a surface layer, wherein the base layer uses aluminum as a parent phase, and the surface layer is arranged on the surface of the base layer and constitutes the concave-convex structure. The surface of the base layer provided with the surface layer has a surface roughness Sa of 20 nm or less and a surface roughness Sz of 250 nm or less in the second rectangular field of view.

8. A method for manufacturing aluminum foil, characterized in that: The aluminum foil is the aluminum foil according to any one of claims 1 to 7, The aluminum foil includes a base layer and a surface layer, wherein the base layer uses aluminum as a parent phase, and the surface layer is arranged on the surface of the base layer and constitutes the concave-convex structure. The manufacturing method of the aluminum foil includes a preparation process and a surface treatment process. In the preparation step, a foil-shaped aluminum substrate forming the substrate layer is prepared. In the surface treatment step, the surface layer is formed on the surface of the aluminum substrate. The surface roughness Sa of the aluminum substrate in the second rectangular field of view is less than or equal to 20 nm, and the surface roughness Sz is less than or equal to 250 nm.

9. A method for producing a laminate, characterized in that: The laminate is a laminate of an aluminum foil and a resin substrate, and the aluminum foil is the aluminum foil according to any one of claims 1 to 7. The surface of the resin substrate is brought into contact with the surface of the aluminum foil having the concavo-convex structure, and pressure is applied at a temperature equal to or higher than the softening point or glass transition point of the resin material forming the resin substrate.

10. A method for producing a resin substrate, characterized in that: The method for manufacturing the resin substrate comprises: A step of obtaining a laminate comprising an aluminum layer and a resin layer by applying pressure at a temperature not lower than the softening point or glass transition point of the resin material forming the resin substrate while the surface of the resin substrate is in contact with the surface having the concavo-convex structure of the aluminum foil according to any one of claims 1 to 7; and A step of removing the aluminum layer of the laminate to obtain a resin base material in which the shape of the concavo-convex structure of the aluminum foil is transferred to the surface.

Images