Metal foil with resin, metal-clad laminate, and wiring board

Abstract

[Problem] The objective of the present invention is to provide a metal foil with a resin capable of manufacturing a wiring board having high adhesion between a resin layer and a metal layer, excellent laser processability, and reduced loss during signal transmission. [Solution] Provided is a metal foil with a resin comprising a resin layer containing a resin composition or a semi-cured product of the resin composition, and a metal layer on at least one surface of the resin layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in a molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, the metal layer has a copper foil in contact with the surface of the resin layer, the copper foil has a thickness of 5.0 μm or less, the surface of the copper foil in contact with the resin layer has an arithmetic average roughness (Ra) of 0.6 μm or less and a ten-point average roughness (Rzjis) of 3.0 μm or less.

Description

Resin-coated metal foil, metal-clad laminate, and wiring board

[0001] The present invention relates to a resin-coated metal foil, a metal-clad laminate, and a wiring board.

[0002] As the amount of information processed increases in various electronic devices, packaging technologies such as higher integration of semiconductor devices, higher density wiring, and multi-layering are advancing. Furthermore, wiring boards used in various electronic devices are required to be high-frequency compatible, for example, millimeter-wave radar boards for automotive applications. Substrate materials for constituting the insulating layers of wiring boards used in various electronic devices are required to increase signal transmission speed and reduce loss during signal transmission. To reduce loss during signal transmission, low dielectric constants and dielectric loss tangents are required.

[0003] Polyphenylene ether is known to have excellent low dielectric properties, such as a low dielectric constant and a low dielectric loss tangent, even in high frequency bands (high frequency regions) from the MHz band to the GHz band. For this reason, polyphenylene ether is being considered for use as, for example, a molding material for high frequencies. More specifically, it is preferably used as a substrate material for constituting an insulating layer of a wiring board included in an electronic device that uses high frequencies.

[0004] Here, resin-coated metal foils and metal-clad laminates used in manufacturing wiring boards and the like include not only an insulating layer but also a metal foil (metal layer) on the insulating layer. Similarly, wiring boards also include not only an insulating layer but also wiring on the insulating layer. Examples of the wiring include wiring derived from the metal layer provided on the metal-clad laminate and the like.

[0005] As wiring boards become thinner, finer wiring is required, resulting in thinner wiring. Therefore, it is increasingly important for the wiring board to prevent peeling of the wiring from the insulating layer. Therefore, wiring boards are required to have high adhesion between the wiring and the insulating layer, and metal-clad laminates and resin-coated metal foils are required to have high adhesion between the metal layer and the insulating layer. Therefore, substrate materials for constituting the insulating layer of wiring boards are required to produce cured products that have high adhesion to the metal layer.

[0006] Furthermore, as the thickness of wiring becomes thinner, the insulating layer provided on the wiring board is required to have a lower dielectric constant in order to match the impedance of the wiring board and to suppress losses due to increased resistance as the wiring becomes finer.

[0007] Patent Document 1 discloses a resin composition containing a polyphenylene ether compound, a polybutadiene compound, a styrene-based block copolymer, and a curing agent. It is disclosed that the technology described in Patent Document 1 can provide a resin composition that can give a cured product having low dielectric properties and high adhesion to a metal layer.

[0008] Recently, design patterns of semiconductor package substrates have become more complex, and materials used in wiring boards are required to have high laser processability in the process of forming vias. In particular, as wiring boards become thinner, when circuits are formed using ultrathin metal foils (e.g., thickness of 5 μm or less), there is a growing need to perform laser processing in the process of forming vias for interlayer connections.

[0009] However, when the metal foil (metal layer) is thin, it is difficult to perform laser processing while maintaining adhesion between the insulating layer and the metal layer, and improving laser processability is an issue. In this regard, the technology described in Patent Document 1 does not mention laser processability for ultra-thin metal foils.

[0010] International Publication No. 2021 / 010431

[0011] The present invention has been made in consideration of the above circumstances, and aims to provide a resin-coated metal foil that has high adhesion between the resin layer and the metal layer, excellent laser processability, and can be used to manufacture wiring boards with reduced loss during signal transmission; a metal-clad laminate that has high adhesion between the insulating layer and the metal layer, excellent laser processability, and can be used to manufacture wiring boards with reduced loss during signal transmission; and a wiring board that has high adhesion between the insulating layer and the metal layer, excellent laser processability, and reduced loss during signal transmission.

[0012] In one aspect of the present invention, the resin-coated metal foil comprises a resin layer containing a resin composition or a semi-cured product of the resin composition, and a metal layer on at least one surface of the resin layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, and the metal layer has copper foil in contact with the surface of the resin layer, the copper foil having a thickness of 5.0 μm or less, and the surface of the copper foil in contact with the resin layer has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less.

[0013] Fig. 1 is a schematic cross-sectional view showing an example of a resin-coated metal foil according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing another example of a resin-coated metal foil according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing an example of a wiring board according to an embodiment of the present invention.

[0014] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0015] The resin-coated metal foil according to this embodiment is a resin-coated metal foil comprising a resin layer containing a resin composition or a semi-cured product of the resin composition, and a metal layer on at least one surface of the resin layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, and the metal layer has copper foil in contact with the surface of the resin layer, the copper foil having a thickness of 5.0 μm or less, and the surface of the copper foil in contact with the resin layer has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less.

[0016] This configuration provides a resin-coated metal foil that has high adhesion between the resin layer and the metal layer and excellent laser processability. The resin-coated metal foil also has excellent heat resistance. Furthermore, when such a resin-coated metal foil is used in a wiring board, signal transmission loss can be reduced.

[0017] In this specification, the term "laser processability" refers particularly to the laser processability for forming via holes. More specifically, "excellent laser processability" means, for example, that the metal layer is unlikely to peel off from the insulating layer even when the distance between vias to be formed is narrow, and further, that vias can be formed even when vias with smaller hole diameters are formed.

[0018] <Resin-Coated Metal Foil> Figures 1 and 2 are schematic cross-sectional views showing the configuration of a resin-coated metal foil according to this embodiment. The resin-coated metal foil 1 has a resin layer 2 containing a resin composition or a semi-cured product of the resin composition, and a metal layer 3. In Figures 1 and 2, the respective reference numerals 1 and 1' indicate the resin-coated metal foil, 2 the resin layer, 3 the metal layer, and 4 the surface of the copper foil that comes into contact with the resin layer 2 (hereinafter also referred to as the contact surface).

[0019] The resin-coated metal foil 1 may be provided with a cover film or the like as needed. By providing a cover film, it is possible to prevent the inclusion of foreign matter, etc. The cover film is not particularly limited, but examples thereof include polyolefin films, polyester films, polymethylpentene films, and films formed by providing these films with a release agent layer.

[0020] [Metal Layer] The metal layer 3 is laminated on at least one surface of the resin layer 2. The resin-coated metal foil 1 may have a configuration in which the metal layer 3 is laminated on only one surface of the resin layer 2 as shown in FIG. 1, or may have a configuration in which the metal layer 3 is laminated on both surfaces of the resin layer 2 as shown in FIG. 2' as shown in FIG. 2. The metal layer 3 also has copper foil in contact with the surface of the resin layer 2. The copper foil may be in contact with only one surface of the resin layer 2 as shown in FIG. 1, or may be in contact with both surfaces of the resin layer 2 as shown in FIG. 2.

[0021] In the metal layer 3, the thickness of the copper foil is 5.0 μm or less. Even when the copper foil thickness is this thin, the resin-coated metal foil of this embodiment is excellent in adhesion between the resin layer and the metal layer and in laser processability. The thickness of the copper foil is preferably 4.0 μm or less, and more preferably 3.0 μm or less. There is no particular restriction on the lower limit of the copper foil thickness, but it is preferably 0.2 μm or more, and more preferably 0.5 μm or more.

[0022] Furthermore, the copper foil surface 4 in contact with the resin layer 2 (contact surface) has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less. When a wiring board is fabricated using a resin-coated metal foil of this configuration, signal transmission loss in the wiring board can be reduced. The arithmetic mean roughness (Ra) of the contact surface 4 is preferably 0.5 μm or less, more preferably 0.35 μm or less. The ten-point mean roughness (Rzjis) of the contact surface 4 is preferably 2.5 μm or less, more preferably 2.0 μm or less.

[0023] The arithmetic mean roughness (Ra) of the contact surface 4 is preferably 0.03 μm or more. Furthermore, the ten-point mean roughness (Rzjis) of the contact surface 4 is preferably 0.1 μm or more. By having the arithmetic mean roughness (Ra) and ten-point mean roughness (Rzjis) of the contact surface 4 within these ranges, the adhesion between the metal layer and the resin layer can be more reliably improved. In particular, when laser processing is performed on a wiring board using the resin-coated metal foil, there is an advantage that the metal layer is less likely to peel off from the insulating layer even when the spacing between the formed vias is narrow. The arithmetic mean roughness (Ra) of the contact surface 4 is more preferably 0.04 μm or more, and even more preferably 0.05 μm or more. The ten-point mean roughness (Rzjis) of the contact surface 4 is more preferably 0.3 μm or more, and even more preferably 0.4 μm or more.

[0024] The arithmetic mean roughness (Ra) conforms to JIS B 0601-2001 and can be measured using a general arithmetic mean roughness measuring instrument or the like. Specifically, it can be measured using, for example, a laser microscope (VK-X1000 manufactured by Keyence Corporation). The ten-point mean roughness (Rzjis) conforms to JIS B 0601-2001 and can be measured using a general ten-point mean roughness measuring instrument or the like. Specifically, it can be measured using, for example, a laser microscope (VK-X1000 manufactured by Keyence Corporation).

[0025] The copper foil may contain copper, and may be made of, for example, copper or a copper alloy. Examples of the copper alloy include an alloy containing copper and at least one selected from the group consisting of nickel, phosphorus, tungsten, arsenic, molybdenum, chromium, cobalt, and zinc. Commercially available copper foils may be used. Examples of commercially available copper foils that can be used include MT18FL (Ra: 0.2 μm, RzJIS: 1.3 μm) manufactured by Mitsui Mining & Smelting Co., Ltd., and MT18Ex (Ra: 0.3 μm, RzJIS: 2.0 μm) manufactured by Mitsui Mining & Smelting Co., Ltd.

[0026] It is also preferable that at least one surface of the copper foil is surface-treated. That is, the copper foil may be surface-treated on both surfaces or on one surface. When one surface of the copper foil is surface-treated, the copper foil is disposed so that the surface that has been surface-treated is in contact with the resin layer 2. That is, the surface that has been surface-treated becomes the contact surface 4.

[0027] Examples of the surface treatment include silane coupling agent treatment, roughening treatment, heat resistance treatment, and rust prevention treatment. Of these, the copper foil is preferably surface-treated with a silane coupling agent. Surface-treating the copper foil with a silane coupling agent has the advantage of improving adhesion between the copper foil and the resin layer. The copper foil may be subjected to any one of these treatments, or may be subjected to a combination of two or more treatments.

[0028] The surface treatment with the silane coupling agent may be a rust prevention treatment generally performed when manufacturing copper foil, and is not particularly limited, but may include, for example, a treatment in which a silane coupling agent is applied to the surface of the copper foil to be treated. The silane coupling agent treatment may involve drying or heating after applying the silane coupling agent.

[0029] Examples of the silane coupling agent include silane coupling agents having at least one functional group selected from the group consisting of a vinyl group, a styryl group, a methacryl group, an acrylic group, a phenylamino group, and a glycidyl group. That is, the silane coupling agent includes compounds having at least one reactive functional group selected from the group consisting of a vinyl group, a styryl group, a methacryl group, an acrylic group, a phenylamino group, and a glycidyl group, and further having a hydrolyzable group such as a methoxy group or an ethoxy group.

[0030] Examples of the silane coupling agent having a vinyl group include vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the silane coupling agent having a styryl group include p-styryltrimethoxysilane and p-styryltriethoxysilane. Examples of the silane coupling agent having a methacryl group include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. Examples of the silane coupling agent having an acrylic group include 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent having a phenylamino group include N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane. Examples of the silane coupling agent having a glycidyl group include 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane.

[0031] As the silane coupling agent, only one of the exemplified silane coupling agents may be used, or two or more of them may be used.

[0032] The roughening treatment may be a roughening treatment generally performed when manufacturing copper foil, and is not particularly limited, but examples thereof include a treatment for forming roughening particles on the surface of the copper foil, which is the object to be treated, etc. By this roughening treatment, the surface of the copper foil is covered with roughening particles made of copper or a copper alloy.

[0033] The heat-resistant treatment may be a heat-resistant treatment generally performed when manufacturing copper foil, and is not particularly limited, but examples thereof include treatments that form a heat-resistant layer containing nickel, cobalt, copper, and zinc, either alone or as an alloy.

[0034] The anti-rust treatment may be any anti-rust treatment commonly performed in the production of copper foil, and is not particularly limited, but is preferably a treatment that forms an anti-rust layer containing nickel. Examples of the anti-rust treatment include chromate treatment.

[0035] The metal layer 3 may include only the copper foil described above. Furthermore, as long as the metal layer 3 includes the copper foil described above, it may further include a metal foil that can be used as the metal layer of a resin-coated metal foil. Specifically, the metal layer 3 may further include, for example, a copper foil other than the copper foil described above, an aluminum foil, a nickel foil, or the like. Furthermore, when the metal foil is thin, a carrier-attached metal foil having a release layer and a carrier may be used as the metal layer 3 from the viewpoint of improving handleability.

[0036] The thickness of the metal layer 3 is not particularly limited, but is preferably 0.5 to 5 μm, and more preferably 1.5 to 3.0 μm.

[0037] [Resin Layer] The resin layer 2 may contain a semi-cured product of the resin composition, or may contain the uncured resin composition. That is, the resin-coated metal foil 1 may include a resin layer 2 containing a semi-cured product of the resin composition (the resin composition in B stage) and a metal layer 3, or may include a resin layer 2 containing a resin composition before curing (the resin composition in A stage) and a metal layer 3. Furthermore, the resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried.

[0038] The thickness of the resin layer 2 varies depending on the performance required of the printed wiring board obtained using the resin-coated metal foil 1, and is not particularly limited. The thickness of the resin layer 2 is preferably, for example, 5 μm or more and 200 μm or less. When the thickness of the resin layer 2 is within this range, resin extrusion during heating and pressure application can be suppressed. Furthermore, it becomes easy to adjust the thickness of the printed wiring board when it is finished.

[0039] The resin layer 2 may contain a resin composition or a semi-cured product of the resin composition, and may or may not contain a fibrous substrate. Specific examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. The use of glass cloth results in a resin layer with excellent mechanical strength, and flattened glass cloth is particularly preferred. A specific example of the flattening process is a method in which glass cloth is continuously pressed with a press roll at an appropriate pressure to compress the yarns flat. The thickness of commonly used fibrous substrates is, for example, 0.01 mm or more and 0.3 mm or less.

[0040] As described above, the resin layer 2 contains a resin composition or a semi-cured product of the resin composition. Each component contained in this resin composition will be described below.

[0041] The resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent.

[0042] First, it is believed that the resin composition can obtain a cured product that maintains the excellent low dielectric properties of polyphenylene ether even when it contains the polybutadiene compound and the styrene-based block copolymer by curing the polyphenylene ether compound together with the curing agent. Furthermore, since the resin composition contains a polybutadiene compound having an epoxy group in the molecule in addition to the styrene-based block copolymer, a cured product that has high adhesion to a metal layer can be obtained.

[0043] From the above, a resin-coated metal foil having a resin layer containing the resin composition or a semi-cured product of the resin composition has low dielectric properties and excellent adhesion between the resin layer and the metal layer when cured.

[0044] (Polybutadiene Compound) The polybutadiene compound is not particularly limited as long as it is a polybutadiene compound having an epoxy group in the molecule. When the resin composition contains the polybutadiene compound, the adhesion between the resin layer and the metal layer can be improved when the resin layer is cured. More specifically, when the polybutadiene compound has an epoxy group in the molecule, the adhesion between the resin layer and the metal layer can be improved.

[0045] Examples of the polybutadiene compound include epoxidized polybutadiene, i.e., a compound in which epoxy groups are introduced into the molecule by epoxidizing at least a portion of the carbon-carbon double bonds contained in polybutadiene, and a compound in which both terminals of polybutadiene are glycidyl etherified. The epoxidation is carried out, for example, by adding one oxygen atom to the carbon-carbon double bonds contained in polybutadiene (non-epoxidized polybutadiene) using an epoxidizing agent to form a three-membered ring epoxy group. A compound in which both terminals of polybutadiene are glycidyl etherified can be obtained by adding epichlorohydrin to polybutadiene having hydroxyl groups at both terminals.

[0046] The polybutadiene (non-epoxidized polybutadiene) may have a stereostructure of carbon-carbon double bonds of any of cis-1,4, trans-1,4, cis-1,2, and trans-1,2, and the ratio thereof is not particularly limited.

[0047] The epoxidizing agent is not particularly limited as long as it can epoxidize the carbon-carbon double bonds contained in polybutadiene, and examples of the epoxidizing agent include percarboxylic acids such as peracetic acid, performic acid, perbenzoic acid, trifluoroperacetic acid, and perpropionic acid, organic hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, and hydrogen peroxide.

[0048] The concentration of oxirane oxygen in the polybutadiene compound is preferably 1 to 10% by mass, and more preferably 5 to 9% by mass. If the concentration of oxirane oxygen is too low, the effect of adding the polybutadiene compound, that is, the effect of improving the adhesion between the resin layer and the metal layer when the resin layer is cured, tends to be insufficient. On the other hand, if the concentration of oxirane oxygen is too high, the amount of epoxy groups tends to be too large, which tends to deteriorate the low dielectric properties. By using a polybutadiene compound whose concentration of oxirane oxygen is within the above range, when cured, it is possible to more reliably obtain a resin-coated metal foil that has low dielectric properties and high adhesion between the resin layer and the metal layer.

[0049] The concentration of oxirane oxygen is an index of the content of epoxy groups contained in the polybutadiene compound, and can be measured, for example, by a hydrogen bromide-glacial acetic acid solution method.

[0050] (Polyphenylene ether compound) The polyphenylene ether compound is not particularly limited as long as it is a polyphenylene ether compound having a carbon-carbon unsaturated bond. Examples of the polyphenylene ether compound include polyphenylene ether compounds having at least one of a group represented by the following formula (1) and a group represented by the following formula (2) in the molecule, and it is preferable to include a polyphenylene ether compound having a group represented by the following formula (2) in the molecule.

[0051] Specific examples of the polyphenylene ether compound include polyphenylene ether compounds having at least one of a group represented by the following formula (1) and a group represented by the following formula (2) at the molecular terminal. More specific examples of the polyphenylene ether compound include modified polyphenylene ether compounds whose terminals are modified with at least one of a group represented by the following formula (1) and a group represented by the following formula (2).

[0052]

[0053] In formula (1), p represents 0 to 10, Z represents an arylene group, and R １ ~R３ each independently represents a hydrogen atom or an alkyl group.

[0054]

[0055] In formula (2), R ４ represents a hydrogen atom or an alkyl group.

[0056] In the formula (1), p represents 0 to 10. Z represents an arylene group. １ ~R ３ are independent of each other. That is, R １ ~R ３ may be the same group or different groups. １ ~R ３ represents a hydrogen atom or an alkyl group.

[0057] In the formula (1), when p is 0, this indicates that Z is directly bonded to the end of the polyphenylene ether.

[0058] The arylene group is not particularly limited. Examples of the arylene group include monocyclic aromatic groups such as a phenylene group, and polycyclic aromatic groups in which the aromatic ring is not monocyclic but is polycyclic, such as a naphthalene ring. The arylene group also includes derivatives in which a hydrogen atom bonded to the aromatic ring is substituted with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. The alkyl group is not particularly limited, and is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0059] In the formula (2), R ４ represents a hydrogen atom or an alkyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0060] Preferred specific examples of the group represented by formula (1) include a vinylbenzyl group (ethenylbenzyl group) and a vinylphenyl group represented by formula (3) below. Examples of the vinylbenzyl group include an o-ethenylbenzyl group, a p-ethenylbenzyl group, and an m-ethenylbenzyl group. Examples of the group represented by formula (2) include an acryloyl group and a methacryloyl group.

[0061]

[0062] The polyphenylene ether compound has at least one of the group represented by formula (1) and the group represented by formula (2) in the molecule, and may have one type or two or more types of these groups. The polyphenylene ether compound may have, for example, any one of an o-ethenylbenzyl group, a p-ethenylbenzyl group, and an m-ethenylbenzyl group, or may have two or three types of these groups.

[0063] The polyphenylene ether compound has a polyphenylene ether chain in the molecule, and preferably has, for example, a repeating unit represented by the following formula (4) in the molecule.

[0064]

[0065] In formula (4), t represents 1 to 50. ５ ~R ８ are independent of each other. That is, R ５ ~R ８ may be the same group or different groups. ５ ~R ８ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0066] R ５ ~R ８ Specific examples of the functional groups mentioned in the above include the following:

[0067] The alkyl group is not particularly limited, but is preferably an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0068] The alkenyl group is not particularly limited, but is preferably an alkenyl group having 2 to 18 carbon atoms, and more preferably an alkenyl group having 2 to 10 carbon atoms. Specific examples include a vinyl group, an allyl group, and a 3-butenyl group.

[0069] The alkynyl group is not particularly limited, but is preferably an alkynyl group having 2 to 18 carbon atoms, and more preferably an alkynyl group having 2 to 10 carbon atoms. Specific examples include an ethynyl group and a prop-2-yn-1-yl group (propargyl group).

[0070] The alkylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkyl group, but for example, an alkylcarbonyl group having 2 to 18 carbon atoms is preferred, and an alkylcarbonyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, and a cyclohexylcarbonyl group.

[0071] The alkenylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkenyl group, but for example, an alkenylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkenylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include an acryloyl group, a methacryloyl group, and a crotonoyl group.

[0072] The alkynylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkynyl group, but for example, an alkynylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkynylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include a propioloyl group.

[0073] The weight-average molecular weight (Mw) of the polyphenylene ether compound is not particularly limited. Specifically, it is preferably 500 to 5,000, more preferably 800 to 4,000, and even more preferably 1,000 to 3,000. The weight-average molecular weight may be measured by a general molecular weight measurement method, specifically, a value measured using gel permeation chromatography (GPC), etc. Furthermore, when the polyphenylene ether compound has a repeating unit represented by the formula (4) in the molecule, t is preferably a value such that the weight-average molecular weight of the polyphenylene ether compound falls within this range. Specifically, t is preferably 1 to 50.

[0074] When the weight-average molecular weight of the polyphenylene ether compound is within this range, the compound has the excellent low dielectric properties of polyphenylene ether, and the cured product not only has excellent heat resistance but also excellent moldability. This is believed to be due to the following reasons. Ordinary polyphenylene ethers, when their weight-average molecular weight is within this range, tend to have a relatively low molecular weight, resulting in a cured product with reduced heat resistance. In this regard, when the polyphenylene ether compound has at least one of the group represented by formula (1) and the group represented by formula (2) in its molecule, it is believed that a cured product with sufficiently high heat resistance can be obtained. Furthermore, when the weight-average molecular weight of the polyphenylene ether compound is within this range, it is believed that the compound has a relatively low molecular weight, resulting in excellent moldability. Therefore, it is believed that such a polyphenylene ether compound not only has excellent heat resistance but also excellent moldability can be obtained as a cured product. Therefore, when the weight-average molecular weight of the polyphenylene ether compound is within this range, a resin-coated metal foil with excellent heat resistance and moldability can be more reliably obtained upon curing.

[0075] The polyphenylene ether compound has, per molecule thereof, an average number (number of terminal functional groups) of at least one (substituent) of the group represented by formula (1) and the group represented by formula (2), and the average number of terminal functional groups is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1.5 to 3.

[0076] The number of terminal functional groups of a polyphenylene ether compound can be exemplified by a numerical value representing the average number of the substituents per molecule of all polyphenylene ether compounds present in 1 mole of the polyphenylene ether compound. The number of terminal functional groups can be measured, for example, by measuring the number of hydroxyl groups remaining in the obtained polyphenylene ether compound and calculating the difference from the number of hydroxyl groups in the polyphenylene ether before it has the substituents (before modification). This difference from the number of hydroxyl groups in the polyphenylene ether before modification is the number of terminal functional groups. The number of hydroxyl groups remaining in the polyphenylene ether compound can be measured by adding a quaternary ammonium salt (tetraethylammonium hydroxide) that associates with hydroxyl groups to a solution of the polyphenylene ether compound and measuring the UV absorbance of the resulting mixed solution.

[0077] Examples of the polyphenylene ether compound include a polyphenylene ether compound represented by the following formula (5) and a polyphenylene ether compound represented by the following formula (6). As the polyphenylene ether compound, these polyphenylene ether compounds may be used alone, or these two types of polyphenylene ether compounds may be used in combination.

[0078]

[0079]

[0080] In formula (5) and formula (6), R ９ ~R １６ and R １７ ~R ２４each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. １ and X ２ each independently represents a group represented by the above formula (1) or a group represented by the above formula (2). A and B represent repeating units represented by the following formula (7) and formula (8), respectively. In addition, in formula (6), Y represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

[0081]

[0082]

[0083] In formula (7) and formula (8), m and n each represent an integer of 0 to 20. ２５ ~R ２８ and R ２９ ~R ３２ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0084] The polyphenylene ether compound represented by the formula (5) and the polyphenylene ether compound represented by the formula (6) are not particularly limited as long as they satisfy the above-mentioned constitution. Specifically, in the formulas (5) and (6), R ９ ~R １６ and R １７ ~R ２４ As described above, each of R is independent. ９ ~R １６ and R １７ ~R ２４ may be the same group or different groups. ９ ~R １６ and R １７ ~R ２４ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0085] In the formula (7) and the formula (8), m and n each preferably represent a value of 0 to 20, as described above. Furthermore, it is preferable that m and n represent a numerical value such that the sum of m and n is 1 to 30. Therefore, it is more preferable that m represents a value of 0 to 20, n represents a value of 0 to 20, and the sum of m and n represents a value of 1 to 30. Furthermore, R ２５ ~R ２８ and R ２９ ~R ３２ are independent of each other. That is, R ２５ ~R ２８ and R ２９ ~R ３２ may be the same group or different groups. ２５ ~R ２８ and R ２９ ~R ３２ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0086] R ９ ~R ３２ is R in the above formula (4). ５ ~R ８ is the same as

[0087] In the formula (6), as described above, Y is a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms. Examples of Y include a group represented by the following formula (9).

[0088]

[0089] In the formula (9), R ３３ and R ３４ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include a methyl group. Examples of the group represented by formula (9) include a methylene group, a methylmethylene group, and a dimethylmethylene group, and among these, a dimethylmethylene group is preferred.

[0090] In the formula (5) and the formula (6), X １and X ２ are each independently a group represented by the above formula (1) or a group represented by the above formula (2). In the polyphenylene ether compound represented by the above formula (5) and the polyphenylene ether compound represented by the above formula (6), X １ and X ２ may be the same group or different groups.

[0091] More specific examples of the polyphenylene ether compound represented by the formula (5) include polyphenylene ether compounds represented by the following formula (10).

[0092]

[0093] More specific examples of the polyphenylene ether compound represented by the formula (6) include a polyphenylene ether compound represented by the following formula (11) and a polyphenylene ether compound represented by the following formula (12).

[0094]

[0095]

[0096] In the above formulas (10) to (12), m and n are the same as m and n in the above formulas (7) and (8). １ ~R ３ , p and Z are R in the above formula (1). １ ~R ３ , p and Z. In the formulas (11) and (12), Y is the same as Y in the formula (6). In the formula (12), R ４ is R in the above formula (2). １ is the same as

[0097] The synthesis method of the polyphenylene ether compound that can be used in the present embodiment is not particularly limited as long as it can synthesize a polyphenylene ether compound having a carbon-carbon unsaturated bond. Here, a method for synthesizing a modified polyphenylene ether compound that is terminally modified with at least one of the group represented by formula (1) and the group represented by formula (2) will be described. Specific examples of this method include reacting a polyphenylene ether with a compound in which at least one of the group represented by formula (1) and the group represented by formula (2) is bonded to a halogen atom. Specific examples of the halogen atom include chlorine, bromine, iodine, and fluorine atoms, with chlorine being preferred. More specific examples of compounds in which at least one of the group represented by formula (1) and the group represented by formula (2) is bonded to a halogen atom include o-chloromethylstyrene, p-chloromethylstyrene, and m-chloromethylstyrene. The compounds in which at least one of the group represented by formula (1) and the group represented by formula (2) is bonded to a halogen atom may be used alone or in combination of two or more. For example, o-chloromethylstyrene, p-chloromethylstyrene, and m-chloromethylstyrene may be used alone or in combination of two or three kinds.

[0098] The polyphenylene ether used as a raw material is not particularly limited as long as it can ultimately synthesize a predetermined modified polyphenylene ether compound. Specific examples include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a bifunctional phenol and a trifunctional phenol, and compounds containing polyphenylene ether as a main component, such as poly(2,6-dimethyl-1,4-phenylene oxide). A bifunctional phenol is a phenolic compound having two phenolic hydroxyl groups per molecule, such as tetramethylbisphenol A. A trifunctional phenol is a phenolic compound having three phenolic hydroxyl groups per molecule.

[0099] (Styrene-Based Block Copolymer) The styrene-based block copolymer is not particularly limited, as long as it is a styrene-based block copolymer that can be used as a resin contained in a resin composition used to form a resin layer provided on a resin-coated metal foil, an insulating layer provided on a metal-clad laminate, a wiring board, or the like.

[0100] Examples of the styrene-based block copolymer include those containing at least one selected from the group consisting of methylstyrene (ethylene / butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene / butylene) styrene copolymer, styrene (ethylene-ethylene / propylene) styrene copolymer, styrene-butadiene styrene copolymer, styrene (butadiene / butylene) styrene copolymer, styrene-isobutylene styrene copolymer, and hydrogenated products thereof.

[0101] The styrene-based block copolymer preferably includes a styrene-butadiene-styrene copolymer, a styrene-(ethylene / butylene)-styrene copolymer, a methylstyrene-(ethylene / butylene)-methylstyrene copolymer, or a hydrogenated product thereof. The styrene-based block copolymer may be used alone or in combination of two or more thereof.

[0102] By including the styrene-based block copolymer in the resin composition, when the resin layer is cured, a resin-coated metal foil having excellent adhesion to the metal layer can be obtained.

[0103] (Curing Agent) The curing agent is a curing agent that can react with the polyphenylene ether compound to cure a resin composition containing the polyphenylene ether compound. The curing agent is not particularly limited as long as it can cure a resin composition containing the polyphenylene ether compound. Examples of the curing agent include styrene, styrene derivatives, compounds having an acryloyl group in the molecule, compounds having a methacryloyl group in the molecule, compounds having a vinyl group in the molecule, compounds having an allyl group in the molecule, compounds having an acenaphthylene structure in the molecule, compounds having a maleimide group in the molecule, and isocyanurate compounds having an isocyanurate group in the molecule.

[0104] Examples of the styrene derivatives include bromostyrene and dibromostyrene.

[0105] The compound having an acryloyl group in the molecule is an acrylate compound. Examples of the acrylate compound include monofunctional acrylate compounds having one acryloyl group in the molecule and polyfunctional acrylate compounds having two or more acryloyl groups in the molecule. Examples of the monofunctional acrylate compound include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of the polyfunctional acrylate compound include diacrylate compounds such as tricyclodecane dimethanol diacrylate.

[0106] The compound having a methacryloyl group in the molecule is a methacrylate compound. Examples of the methacrylate compound include monofunctional methacrylate compounds having one methacryloyl group in the molecule and polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compound include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compound include dimethacrylate compounds such as tricyclodecane dimethanol dimethacrylate, and trimethacrylate compounds such as trimethylolpropane trimethacrylate.

[0107] The compound having a vinyl group in the molecule is a vinyl compound. Examples of the vinyl compound include a monofunctional vinyl compound (monovinyl compound) having one vinyl group in the molecule, and a polyfunctional vinyl compound having two or more vinyl groups in the molecule. Examples of the polyfunctional vinyl compound include divinylbenzene and polybutadiene.

[0108] The compound having an allyl group in the molecule is an allyl compound. Examples of the allyl compound include monofunctional allyl compounds having one allyl group in the molecule and polyfunctional allyl compounds having two or more allyl groups in the molecule. Examples of the polyfunctional allyl compound include triallyl isocyanurate compounds such as triallyl isocyanurate (TAIC), diallyl bisphenol compounds, and diallyl phthalate (DAP).

[0109] The compound having an acenaphthylene structure in the molecule is an acenaphthylene compound. Examples of the acenaphthylene compound include acenaphthylene, alkylacenaphthylenes, halogenated acenaphthylenes, and phenylacenaphthylenes. Examples of the alkylacenaphthylenes include 1-methylacenaphthylene, 3-methylacenaphthylene, 4-methylacenaphthylene, 5-methylacenaphthylene, 1-ethylacenaphthylene, 3-ethylacenaphthylene, 4-ethylacenaphthylene, and 5-ethylacenaphthylene. Examples of the halogenated acenaphthylenes include 1-chloroacenaphthylene, 3-chloroacenaphthylene, 4-chloroacenaphthylene, 5-chloroacenaphthylene, 1-bromoacenaphthylene, 3-bromoacenaphthylene, 4-bromoacenaphthylene, and 5-bromoacenaphthylene. Examples of the phenylacenaphthylenes include 1-phenylacenaphthylene, 3-phenylacenaphthylene, 4-phenylacenaphthylene, and 5-phenylacenaphthylene. The acenaphthylene compound may be a monofunctional acenaphthylene compound having one acenaphthylene structure in the molecule, as described above, or a polyfunctional acenaphthylene compound having two or more acenaphthylene structures in the molecule.

[0110] The compound having a maleimide group in the molecule is a maleimide compound. Examples of the maleimide compound include a monofunctional maleimide compound having one maleimide group in the molecule, a polyfunctional maleimide compound having two or more maleimide groups in the molecule, and a modified maleimide compound. Examples of the modified maleimide compound include a modified maleimide compound in which a portion of the molecule is modified with an amine compound, a modified maleimide compound in which a portion of the molecule is modified with a silicone compound, and a modified maleimide compound in which a portion of the molecule is modified with an amine compound and a silicone compound.

[0111] The compound having an isocyanurate group in the molecule is an isocyanurate compound. Examples of the isocyanurate compound include compounds further having an alkenyl group in the molecule (alkenyl isocyanurate compounds), such as triallyl isocyanurate (TAIC).

[0112] Among the above, the curing agent preferably contains, for example, an allyl compound having an allyl group in the molecule. As the allyl compound, an allyl isocyanurate compound having two or more allyl groups in the molecule is preferred, and triallyl isocyanurate (TAIC) is more preferred.

[0113] The curing agent may be used alone or in combination of two or more thereof. The curing agent preferably contains the allyl compound, and more preferably the allyl compound contains an allyl isocyanurate compound having two or more allyl groups in the molecule.

[0114] (Content) The content of the polybutadiene compound is preferably 5 to 38% by mass, more preferably 5 to 32% by mass, and even more preferably 5 to 15% by mass, based on the total mass (total) of the polybutadiene compound, the polyphenylene ether compound, and the curing agent. The content of the polybutadiene compound is preferably 3 to 25% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, based on the total mass (total) of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent. The content of the polyphenylene ether compound is preferably 10 to 70% by mass, and even more preferably 20 to 50% by mass, based on the total mass (total) of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent. The content of the styrene-based block copolymer is preferably 5 to 60% by mass, and more preferably 10 to 50% by mass, based on the total mass (total) of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent. The content of the curing agent is preferably 3 to 30% by mass, and more preferably 5 to 20% by mass, based on the total mass (total) of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent. When the contents of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent are each within the above ranges, a resin-coated metal foil can be obtained that maintains excellent low dielectric properties upon curing and has higher adhesion between the resin layer and the metal layer.

[0115] (Other Components) The resin composition may contain other components (other components) in addition to the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent, as necessary, as long as the effects of the present invention are not impaired. Examples of other components contained in the resin composition include additives such as silane coupling agents, flame retardants, initiators, curing accelerators, antifoaming agents, antioxidants, polymerization inhibitors, polymerization retarders, dispersants, leveling agents, heat stabilizers, antistatic agents, UV absorbers, dyes and pigments, lubricants, and fillers. In addition to the polyphenylene ether compound, the resin composition may also contain thermosetting resins such as epoxy resins, unsaturated polyester resins, and thermosetting polyimide resins.

[0116] As described above, the resin composition may contain an initiator (reaction initiator). The curing reaction can proceed even if the resin composition does not contain a reaction initiator. However, depending on the process conditions, it may be difficult to raise the temperature high enough for curing to proceed, so a reaction initiator may be added. The reaction initiator is not particularly limited as long as it can promote the curing reaction between the polyphenylene ether compound and the curing agent. Specific examples include oxidizing agents such as α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, t-butylperoxyisopropyl monocarbonate, and azobisisobutyronitrile. Furthermore, a metal carboxylate or the like can be used in combination, if necessary. This can further promote the curing reaction. Among these, α,α'-bis(t-butylperoxy-m-isopropyl)benzene is preferably used. α,α'-bis(t-butylperoxy-m-isopropyl)benzene has a relatively high reaction initiation temperature, so it can suppress the acceleration of the curing reaction when curing is not necessary, such as during prepreg drying, and can suppress a decrease in the shelf life of the resin composition. Furthermore, α,α'-bis(t-butylperoxy-m-isopropyl)benzene has low volatility, so it does not volatilize during prepreg drying or storage, and has good stability. Furthermore, the reaction initiators may be used alone or in combination of two or more.

[0117] As described above, the resin composition may contain a filler such as an inorganic filler. Examples of fillers include those added to enhance heat resistance and flame retardancy when the resin layer is cured, and are not particularly limited. Furthermore, the inclusion of a filler can further enhance heat resistance, flame retardancy, and the like. Specifically, the filler preferably contains a filler made of at least one material selected from the group consisting of silica (e.g., spherical silica), metal oxides (e.g., alumina, titanium oxide, and mica), metal hydroxides (e.g., aluminum hydroxide and magnesium hydroxide), talc, aluminum borate, barium sulfate, and calcium carbonate. Among these, the filler preferably contains a filler made of at least one material selected from the group consisting of silica, mica, and talc, and even more preferably a filler made of spherical silica. The fillers may be used alone or in combination of two or more. The fillers may be used as they are, or may be surface-treated with the silane coupling agent. When a filler is contained, the content thereof (filler content) is preferably 20 to 270 parts by mass, and more preferably 30 to 250 parts by mass, per 100 parts by mass of the resin composition.

[0118] The method for producing the resin composition is not particularly limited, and examples thereof include a method in which the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent are mixed to achieve predetermined contents.

[0119] [Manufacturing Method] The method for manufacturing the resin-coated metal foil according to this embodiment is not particularly limited as long as it can produce the resin-coated metal foils 1, 1' described above. For example, as shown in Figure 1, a method for manufacturing a resin-coated metal foil 1 in which a copper foil is in contact with only one surface of a resin layer 2 includes preparing the resin composition in a varnish form, applying this varnish-like resin composition to the contact surface 4 of the copper foil, and heating the resin composition.

[0120] A varnish-like resin composition (resin varnish) can be prepared, for example, as follows. First, each component soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be performed as necessary during this process. Then, components that are insoluble in the organic solvent are added as needed, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until a predetermined dispersion state is achieved, thereby preparing a varnish-like composition. The organic solvent used here is not particularly limited as long as it dissolves each component soluble in the organic solvent and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0121] The varnish-like resin composition is applied to the contact surface 4 of the copper foil, for example, by using a bar coater. The applied resin composition is heated, for example, at 40°C or higher and 180°C or lower for 0.1 minutes or longer and 10 minutes or shorter. By heating, a resin layer 2 in an uncured (A-stage) or semi-cured (B-stage) state is obtained. That is, the heated resin composition is formed on the contact surface 4 of the copper foil as a resin layer 2 in an uncured or semi-cured state. Note that the heating volatilizes the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

[0122] 2, a method for producing a resin-coated metal foil 1' in which copper foil is in contact with both surfaces of the resin layer 2 includes, for example, producing the resin-coated metal foil 1 shown in FIG. 1 by the method described above, stacking two of the resin-coated metal foils 1 so that their resin layers 2 are in contact with each other, and heating the resulting foil. The heating temperature is preferably, for example, 180° C. or higher and 230° C. or lower, and the heating time is preferably 60 minutes or higher and 150 minutes or lower.

[0123] The resin-coated metal foil according to the present embodiment can be suitably used to manufacture wiring boards that have low dielectric properties, an insulating layer that has high adhesion to wiring, excellent laser processability, and reduced loss during signal transmission. Furthermore, for example, by laminating the resin-coated metal foil on a wiring board, a multilayer wiring board can be manufactured.

[0124] <Metal-clad laminate> Fig. 3 is a schematic cross-sectional view showing an example of a metal-clad laminate 11 according to an embodiment of the present invention. In Fig. 3, the respective symbols indicate 11: metal-clad laminate, 12: insulating layer, 13: metal layer, and 14: surface where the copper foil contacts the insulating layer 12 (hereinafter also referred to as contact surface).

[0125] As shown in FIG. 3, the metal-clad laminate 11 includes an insulating layer 12 containing a cured resin composition and a metal layer 13. While the metal layer 13 is shown laminated on both surfaces of the insulating layer 12 in FIG. 3, it may be laminated on only one surface of the insulating layer 12. The metal layer 13 has copper foil in contact with the surface of the insulating layer 12, the copper foil having a thickness of 5.0 μm or less, and the surface (contact surface) 14 of the copper foil in contact with the insulating layer 12 has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less. The resin composition contains a polybutadiene compound having an epoxy group in its molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent. A metal-clad laminate having such a configuration has an insulating layer with low dielectric properties and high adhesion to the metal layer, excellent laser processability, and can reduce signal transmission loss in the resulting wiring board. The resin composition and metal layer 13 can be the same as those in the resin-coated metal foil 1 and the metal layer 3, and therefore a detailed description thereof will be omitted.

[0126] The insulating layer 12 may be made of a cured resin composition or a cured prepreg, which will be described later. The thickness of the insulating layer 12 is preferably 5 μm or more and 400 μm or less.

[0127] The method for producing the metal-clad laminate 11 is not particularly limited as long as it is possible to produce the metal-clad laminate 11. Specifically, there is mentioned a method for producing the metal-clad laminate 11 using a prepreg including a resin layer containing the resin composition or a semi-cured product of the resin composition and a fibrous base material.

[0128] The prepreg includes a resin layer containing the resin composition or a semi-cured product of the resin composition, and a fibrous base material present in the resin layer. As the fibrous base material, any fibrous base material that can be used for the resin-coated metal foil 1 can be used without limitation.

[0129] When producing the prepreg, the resin composition is often a resin varnish prepared in a varnish form as described above, in order to impregnate a fibrous base material that is a base material for forming the prepreg.

[0130] The method for producing the prepreg is not particularly limited as long as it can produce the prepreg. Examples of the method for producing the prepreg include a method of impregnating the fibrous substrate with the varnish-like resin composition and then drying it. The resin composition is impregnated into the fibrous substrate by immersion, coating, or the like. Impregnation can be repeated multiple times as needed. Furthermore, by repeating the impregnation using multiple resin compositions with different compositions and concentrations, it is possible to adjust the final composition and impregnation amount to the desired one.

[0131] The fibrous substrate impregnated with the resin composition (resin varnish) is heated under desired conditions, for example, at 80°C to 180°C for 1 minute to 10 minutes. This heating results in a prepreg in an uncured (A-stage) or semi-cured (B-stage) state. The heating also volatilizes the organic solvent from the resin varnish, reducing or eliminating the organic solvent.

[0132] A prepreg is prepared as described above, one or more prepregs are stacked, and then metal layers 13 are stacked on both the top and bottom surfaces or on one surface of the prepreg so that the copper foil contacts the prepreg. The metal layers 13 and the prepreg are then heated and pressurized to form an integrated laminate, thereby producing a double-sided or single-sided metal foil laminate 11.

[0133] That is, the metal-clad laminate 11 is obtained by laminating a metal layer 13 on a prepreg and then hot-pressing and molding. The conditions for hot-pressing and pressing can be appropriately set depending on the thickness of the metal-clad laminate 11 to be produced, the type of prepreg composition, and the like. For example, the temperature can be 170 to 230°C, the pressure can be 2 to 5 MPa, and the time can be 60 to 150 minutes. The metal-clad laminate may also be produced without using a prepreg. For example, a method can be used in which a varnish-like resin composition is applied to the surface of a copper foil to form a layer containing the resin composition on the surface of the copper foil, followed by hot-pressing and pressing.

[0134] <Wiring Board> Fig. 4 is a schematic cross-sectional view showing an example of a wiring board 21 according to an embodiment of the present invention. In Fig. 4, the reference symbols indicate 21: wiring board, 23: first copper conductor layer, 24: surface where the first copper conductor layer 23 contacts the insulating layer 12 (hereinafter also referred to as contact surface), 25: second copper conductor layer, and 26: wiring.

[0135] 4, wiring board 21 according to this embodiment is composed of insulating layer 12 containing a cured resin composition, and wiring 26 formed by partially removing a metal layer laminated on one or both sides of insulating layer 12 and then plating the surface of this metal layer on the side not in contact with insulating layer 12. Note that the metal layer can be the same as metal layer 3 in resin-coated metal foil 1, and therefore a detailed description thereof will be omitted.

[0136] The wiring board 21 includes an insulating layer 12 containing a cured product of the resin composition, and wiring 26. The resin composition contains a polybutadiene compound having an epoxy group in its molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent. The wiring 26 includes a first copper conductor layer 23 in contact with the surface of the insulating layer 12 and a second copper conductor layer 25 laminated on the first copper conductor layer 23. The thickness of the first copper conductor layer 23 is 5.0 μm or less, and the arithmetic mean roughness (Ra) of a surface 24 of the first copper conductor layer 23 in contact with the insulating layer 12 is 0.6 μm or less and the ten-point mean roughness (Rzjis) is 3.0 μm or less. The wiring board 21 may be configured such that the wiring 26 is formed on both surfaces of the insulating layer 12 as shown in FIG. 4, or may be configured such that the wiring 26 is formed on only one surface of the insulating layer 12. The resin composition can be the same as the resin composition in the resin-coated metal foil 1, and therefore a detailed description thereof will be omitted.

[0137] The first copper conductor layer 23 can be the same copper foil as in the resin-coated metal foil 1. The second copper conductor layer 25 is formed, for example, by plating the surface of the first copper conductor layer 23 opposite the contact surface 24. This plating process is not particularly limited, but examples include electroless copper plating and electrolytic copper plating. The thickness of the second copper conductor layer 25 is preferably 0.1 to 100 μm.

[0138] A wiring board having such a configuration has an insulating layer with low dielectric properties and high adhesion to wiring. Furthermore, such a wiring board has the advantage that the wiring is less likely to peel off from the insulating layer when vias are formed by laser processing during circuit formation using fine circuit processing, such as semi-additive process (SAP) and modified semi-additive process (MSAP). Another advantage is that vias can be formed even when vias with smaller hole diameters are formed. Therefore, the wiring board has excellent laser processability. Furthermore, the wiring board is expected to reduce loss during signal transmission, making it suitable for use in electronic devices that transmit and receive electrical signals at high speeds, for example.

[0139] The method for manufacturing the wiring board according to the present embodiment is not particularly limited as long as it can manufacture wiring board 21. Specifically, a method for manufacturing wiring board 21 using the prepreg can be mentioned. Examples of such a method include a method for manufacturing wiring board 21 by etching metal layer 13 on the surface of metal-clad laminate 11 manufactured as described above, and then laminating a plated layer on the etched metal layer 13 by plating to form wiring 26, thereby manufacturing wiring board 21 having wiring 26 provided as a circuit on the surface of insulating layer 12. In addition to the above-mentioned methods, examples of methods for forming circuits include circuit formation by a semi-additive process (SAP) or a modified semi-additive process (MSAP).

[0140] This specification discloses various aspects of the technology as described above, but the main technologies among them are summarized below.

[0141] The resin-coated metal foil in a first aspect is a resin-coated metal foil comprising a resin layer containing a resin composition or a semi-cured product of the resin composition, and a metal layer on at least one surface of the resin layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, and the metal layer has copper foil in contact with the surface of the resin layer, the copper foil having a thickness of 5.0 μm or less, and the surface of the copper foil in contact with the resin layer has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less.

[0142] The resin-coated metal foil in the second aspect is the resin-coated metal foil in the first aspect, wherein the polyphenylene ether compound contains a polyphenylene ether compound having at least one of a group represented by the following formula (1) and a group represented by the following formula (2) in the molecule:

[0143]

[0144] (In formula (1), p represents 0 to 10, Z represents an arylene group, and R1 to R3 each independently represent a hydrogen atom or an alkyl group.)

[0145]

[0146] (In formula (2), R4 represents a hydrogen atom or an alkyl group.)

[0147] The resin-coated metal foil in a third aspect is the resin-coated metal foil in the first or second aspect, wherein the content of the polybutadiene compound is 5 to 38 mass % based on the total amount of the polybutadiene compound, the polyphenylene ether compound, and the curing agent.

[0148] The resin-coated metal foil in a fourth aspect is the resin-coated metal foil in any one of the first to third aspects, wherein the content of the polybutadiene compound is 3 to 25 mass% based on the total amount of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent.

[0149] A resin-coated metal foil in a fifth aspect is the resin-coated metal foil in any one of the first to fourth aspects, wherein the curing agent contains an allyl compound.

[0150] A resin-coated metal foil in a sixth embodiment is the resin-coated metal foil in the fifth embodiment, wherein the allyl compound contains an allyl isocyanurate compound having two or more allyl groups in the molecule.

[0151] A seventh aspect of the resin-coated metal foil is the resin-coated metal foil of any one of the first to sixth aspects, wherein the concentration of oxirane oxygen in the polybutadiene compound is 1 to 10 mass %.

[0152] The resin-coated metal foil in an eighth aspect is the resin-coated metal foil in any one of the first to seventh aspects, wherein the styrene-based block copolymer comprises at least one selected from the group consisting of methylstyrene (ethylene / butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene / butylene) styrene copolymer, styrene (ethylene-ethylene / propylene) styrene copolymer, styrene-butadiene styrene copolymer, styrene (butadiene / butylene) styrene copolymer, styrene-isobutylene styrene copolymer, and hydrogenated products thereof.

[0153] A resin-coated metal foil in a ninth aspect is the resin-coated metal foil in the second aspect, wherein the polyphenylene ether compound contains a polyphenylene ether compound having a group represented by formula (2) in the molecule.

[0154] In a tenth aspect, the metal-clad laminate is a metal-clad laminate comprising an insulating layer containing a cured product of a resin composition and a metal layer on at least one surface of the insulating layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, and the metal layer has copper foil in contact with the surface of the insulating layer, the copper foil having a thickness of 5.0 μm or less, and the surface of the copper foil in contact with the insulating layer has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less.

[0155] In an eleventh aspect, the wiring board comprises an insulating layer containing a cured product of a resin composition and wiring on at least one surface of the insulating layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, and the wiring has a first copper conductor layer in contact with the surface of the insulating layer and a second copper conductor layer laminated on the first copper conductor layer, the thickness of the first copper conductor layer being 5.0 μm or less, and the arithmetic mean roughness (Ra) of the surface of the first copper conductor layer in contact with the insulating layer being 0.6 μm or less and the ten-point mean roughness (Rzjis) being 3.0 μm or less.

[0156] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0157] Examples 1 to 7 and Comparative Examples 1 to 4 In these examples, each component used in preparing the resin composition will be described.

[0158] (Epoxy group-containing polybutadiene) Epoxy group-containing polybutadiene: a polybutadiene compound having an epoxy group in the molecule (JP-100 manufactured by Nippon Soda Co., Ltd., oxirane concentration: 7.7% by mass)

[0159] (Polyphenylene ether compound: PPE) Modified PPE: a polyphenylene ether compound having a methacryloyl group at its terminal (a modified polyphenylene ether in which the terminal hydroxyl group of polyphenylene ether is modified with a methacryloyl group, represented by the above formula (12), in which Y in formula (12) is a dimethylmethylene group (represented by formula (9), in which R ３３ and R ３４ a modified polyphenylene ether compound (SA9000 manufactured by SABIC Innovative Plastics, weight average molecular weight Mw 2000, number of terminal functional groups 2)

[0160] (Styrene-based block copolymer) Tuftec H1221: Hydrogenated styrene-based thermoplastic elastomer (SEBS) (H1221 manufactured by Asahi Kasei)

[0161] (Curing agent: allyl compound) TAIC: triallyl isocyanurate (TAIC manufactured by Nippon Kasei Chemical Co., Ltd.)

[0162] (Others) Initiator: α,α'-di(t-butylperoxy)diisopropylbenzene (Perbutyl P (PBP) manufactured by NOF Corporation) Filler: Spherical silica filler (dry powder) SC2500SQ (2500SQ manufactured by Admatechs Co., Ltd., average particle size 0.6 μm)

[0163] [Method for preparing resin composition] First, each component other than the filler was added to toluene and mixed in the composition (parts by mass) shown in Table 1 so that the solid content concentration was 50 mass%. The mixture was stirred for 60 minutes. Thereafter, the filler was added to the resulting liquid, and the filler was dispersed using a bead mill. This resulted in a varnish-like resin composition (varnish).

[0164] [Method for producing resin-coated metal foil] Next, the obtained varnish was applied to one of the copper foils described below (copper foils 1 to 5) to a thickness of 30 μm, and heated at 100° C. for 1 minute to produce a resin-coated metal foil in which the copper foil was bonded to one side of a resin layer. Note that the Ra and Rzjis of copper foils 1 to 5 described below are the Ra and Rzjis values ​​of the copper foil on the side in contact with the resin layer.

[0165] (Metal layer: copper foil) - Copper foil 1: MT18FL (manufactured by Mitsui Metal Mining Co., Ltd., Ra: 0.2 μm, Rzjis: 1.3 μm) - Copper foil 2: MT18Ex (manufactured by Mitsui Metal Mining Co., Ltd., Ra: 0.3 μm, Rzjis: 2.0 μm)・Copper foil 3: GTH-MP (Taiwan Furukawa Copper Foil Co., Ltd., Ra: 1.2 μm, Rzjis: 6.5 μm) ・Copper foil 4: 3EC-VLP (Mitsui Mining & Mining Co., Ltd., Ra: 0.6 μm, Rzjis: 3.5 μm)・Copper foil 5: TLC-V1 (manufactured by Nan-ya Plastic Industry Co., Ltd., Ra: 0.2 μm, Rzjis: 1.3 μm)

[0166] [Method for producing cured resin-coated metal foil (metal-clad laminate)] Two sheets of the resin-coated metal foil obtained above were stacked so that the resin layers were in contact with each other, and this was heated and pressurized at a temperature of 200°C and a pressure of 3 MPa for 100 minutes to produce a cured resin-coated metal foil (metal-clad laminate).

[0167] [Evaluation] The resin-coated metal foil (evaluation substrate 1) and the cured resin-coated metal foil (evaluation substrate 2) prepared as described above were used to evaluate the properties by the methods described below.

[0168] (Dielectric Properties (Relative Permittivity and Dielectric Loss Tangent)) A substrate obtained by removing the copper foil from the evaluation substrate 2 was used as a test piece, and the relative permittivity and dielectric loss tangent at 10 GHz were measured by a cavity resonator perturbation method. Specifically, the relative permittivity and dielectric loss tangent of the test piece at 10 GHz were measured using a network analyzer (N5230A manufactured by Agilent Technologies, Inc.).

[0169] (Copper Foil Peel Strength) The copper foil was peeled off from the evaluation substrate 2, and the peel strength (copper foil peel strength) at this time was measured in accordance with JIS C 6481. Specifically, the copper foil was peeled off from the evaluation substrate 2 at a rate of 50 mm / min using a tensile tester, and the peel strength (N / mm) at this time was measured. The pass criterion in this test was 0.40 N / mm or more.

[0170] (Laser Processability) First, a test piece (four-layer board) for evaluating laser processability was obtained as follows. Evaluation substrates 1 were placed on both sides of a core material (manufactured by Panasonic Industries Co., Ltd., "R-1515A," thickness 0.4 mm, copper foil thickness 12 μm) so that the copper foil of the core material and the resin layer of the resin-coated metal foil were in contact, and the test piece (four-layer board) was produced by heating and pressing at a temperature of 200°C and a pressure of 3 MPa for 100 minutes. This test piece (four-layer board) was evaluated by the method shown below.

[0171] Copper foil peeling due to via formation A laser was irradiated onto a test piece (four-layer board) to form multiple via openings at 30 μm intervals between the vias. Specifically, a Mitsubishi Electric Corporation "ML605GTWV(-P)-5350U" laser device was used, and processing was performed with a 0.8 mm mask, 6 usec pulse, 2.2 mJ energy, and 1 shot. The test piece after laser processing was then observed from directly above with a microscope to check for copper foil peeling between the vias. Specifically, observation was performed using an optical microscope (Keyence Corporation VHX-7000).

[0172] Via top diameter A laser was irradiated onto a test piece (four-layer board). Specifically, the laser device used was the "ML605GTWV(-P)-5350U" manufactured by Mitsubishi Electric Corporation, and processing was performed with a mask of 0.8 mm, a pulse of 6 usec, an energy of 2.2 mJ, and one shot. The via opening was observed from directly above with a microscope, and the hole diameter was measured. Specifically, the observation was performed using an MF-UJ4020D manufactured by Mitutoyo Corporation. The pass criterion for this test was 15 μm or more.

[0173] (Transmission Loss Evaluation Test) A test piece was obtained by processing one surface of the evaluation substrate 2 with a line width of 100 to 200 μm. The line width was adjusted so that the characteristic impedance of the circuit after finishing was 50Ω.

[0174] To evaluate the transmission characteristics, the test pieces were measured for their transmission loss (transmission loss) using a network analyzer (Keysight Technologies N5222B). The evaluation frequency was 60 GHz. The pass criterion for this test was an absolute value of transmission loss of 1.38 dB / inch or less.

[0175] The results of the above evaluations are shown in Table 1.

[0176]

[0177] [Discussion] As can be seen from Table 1, in the resin compositions containing the polyphenylene ether compound, the styrene-based block copolymer, and the cured product, when a polybutadiene compound having an epoxy group in the molecule was included (Examples 1 to 7), the dielectric properties were lower and the copper foil peel strength was higher compared to when a polybutadiene compound having an epoxy group in the molecule was not included (Comparative Example 1). Furthermore, when laser processing was performed to form vias in Examples 1 to 7, there was no peeling of the copper foil between the vias, and laser processability was excellent. Furthermore, when copper foils having a thickness of 5.0 μm or less were used (Examples 1 to 7), the via top diameter was 15 μm or more. On the other hand, when thicker copper foils were used (Comparative Examples 2 to 4), the via top diameter did not reach 15 μm or more. In other words, when copper foils having a thickness of 5.0 μm or less were used (Examples 1 to 7), laser processability was superior compared to when thicker copper foils were used (Comparative Examples 2 to 4), and vias with small hole diameters could be formed.

[0178] Furthermore, it was found that the transmission loss in Examples 1 to 7, in which the arithmetic mean roughness (Ra) of the copper foil surface in contact with the resin layer was 0.6 μm or less and the ten-point mean roughness (Rzjis) was 3.0 μm or less, was smaller (the absolute value of the transmission loss was smaller) than in Comparative Examples 2 and 3, in which the arithmetic mean roughness (Ra) exceeded 0.6 μm and / or the ten-point mean roughness (Rzjis) exceeded 3.0 μm.

[0179] This application is based on Japanese Patent Application No. 2023-170485 filed on September 29, 2023, the contents of which are incorporated herein by reference.

[0180] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims.

[0181] According to the present invention, it is possible to provide a resin-coated metal foil that has high adhesion between the resin layer and the metal layer, excellent laser processability, and can be used to manufacture wiring boards with reduced loss during signal transmission; a metal-clad laminate that has high adhesion between the insulating layer and the metal layer, excellent laser processability, and can be used to manufacture wiring boards with reduced loss during signal transmission; and a wiring board that has high adhesion between the insulating layer and the metal layer, excellent laser processability, and reduced loss during signal transmission.

Claims

1. A resin-coated metal foil comprising a resin layer containing a resin composition or a semi-cured product of the resin composition, and a metal layer on at least one surface of the resin layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, the metal layer has copper foil in contact with the surface of the resin layer, the copper foil has a thickness of 5.0 μm or less, and the surface of the copper foil in contact with the resin layer has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less.

2. The resin-coated metal foil according to claim 1, wherein the polyphenylene ether compound contains a polyphenylene ether compound having at least one of a group represented by the following formula (1) and a group represented by the following formula (2) in the molecule: In formula (1), p represents 0 to 10, Z represents an arylene group, and R １ ~R ３ each independently represents a hydrogen atom or an alkyl group. (In formula (2), R ４ represents a hydrogen atom or an alkyl group.

3. The resin-coated metal foil according to claim 1 or 2, wherein the content of the polybutadiene compound is 5 to 38 mass% based on the total amount of the polybutadiene compound, the polyphenylene ether compound, and the curing agent.

4. The resin-coated metal foil according to claim 1 or 2, wherein the content of the polybutadiene compound is 3 to 25 mass% based on the total amount of the polybutadiene compound, the polyphenylene ether compound, the styrene-based block copolymer, and the curing agent.

5. The resin-coated metal foil according to claim 1 or 2, wherein the curing agent contains an allyl compound.

6. The resin-coated metal foil according to claim 5, wherein the allyl compound comprises an allyl isocyanurate compound having two or more allyl groups in the molecule.

7. The resin-coated metal foil according to claim 1 or 2, wherein the concentration of oxirane oxygen in the polybutadiene compound is 1 to 10 mass %.

8. The resin-coated metal foil according to claim 1 or 2, wherein the styrene-based block copolymer comprises at least one selected from the group consisting of methylstyrene (ethylene / butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene / butylene) styrene copolymer, styrene (ethylene-ethylene / propylene) styrene copolymer, styrene-butadiene styrene copolymer, styrene (butadiene / butylene) styrene copolymer, styrene-isobutylene styrene copolymer, and hydrogenated products thereof.

9. The resin-coated metal foil according to claim 2, wherein the polyphenylene ether compound comprises a polyphenylene ether compound having a group represented by formula (2) in the molecule.

10. A metal-clad laminate comprising an insulating layer containing a cured product of a resin composition and a metal layer on at least one surface of the insulating layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in its molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, the metal layer has copper foil in contact with the surface of the insulating layer, the copper foil having a thickness of 5.0 μm or less, and the surface of the copper foil in contact with the insulating layer has an arithmetic mean roughness (Ra) of 0.6 μm or less and a ten-point mean roughness (Rzjis) of 3.0 μm or less.

11. A wiring board comprising an insulating layer containing a cured product of a resin composition and wiring on at least one surface of the insulating layer, wherein the resin composition contains a polybutadiene compound having an epoxy group in the molecule, a polyphenylene ether compound having a carbon-carbon unsaturated bond, a styrene-based block copolymer, and a curing agent, and the wiring has a first copper conductor layer in contact with the surface of the insulating layer and a second copper conductor layer laminated on the first copper conductor layer, wherein the thickness of the first copper conductor layer is 5.0 μm or less, and the arithmetic mean roughness (Ra) of the surface of the first copper conductor layer in contact with the insulating layer is 0.6 μm or less, and the ten-point mean roughness (Rzjis) is 3.0 μm or less.

Images