Resin composition, resin-coated copper foil, and printed wiring board

Abstract

This invention provides a resin composition that not only exhibits excellent dielectric properties and high adhesion to surfaces with low roughness, but also stably maintains its high adhesion even after thermal loading. The resin composition comprises at least one of: an aryl ether compound with a weight average molecular weight of 30,000 or more, and a styrene-based copolymer having reactive unsaturated bonds in its molecule that exhibit reactivity upon heat or ultraviolet light; and an organic filler composed of a liquid crystal polymer.

Description

Technical Field

[0001] The present invention relates to a resin composition, a copper foil with resin, and a printed wiring board. Prior Art

[0002] Printed wiring boards have long been widely used in electronic devices and other applications. In particular, with the recent advancements in the functionality of electronic devices, signals are becoming increasingly high-frequency, making high-speed, high-capacity communications increasingly possible. Examples of such applications include communication servers, autonomous vehicles, and 5G-enabled mobile phones. There is a growing demand for printed wiring boards suitable for these high-frequency applications. For high-frequency printed wiring boards, low transmission loss is desirable to ensure that high-frequency signals can be transmitted without degrading their quality. Printed wiring boards consist of copper foil processed into a wiring pattern and an insulating resin substrate. Transmission loss primarily consists of conductor loss due to the copper foil and dielectric loss due to the insulating resin substrate. Therefore, in resin-coated copper foil suitable for high-frequency applications, it is desirable to suppress dielectric loss due to the resin layer. Therefore, the resin layer must possess excellent dielectric properties, particularly a low dielectric loss tangent.

[0003] Meanwhile, various resin compositions with excellent dielectric properties and adhesion have been proposed for use in applications such as printed wiring boards. For example, Patent Document 1 (International Publication No. 2013 / 105650) discloses an adhesive-coated copper foil having an adhesive layer on one side of the copper foil. This adhesive layer is formed from a resin composition containing 5 to 65 parts by mass of a styrene-butadiene block copolymer per 100 parts by mass of a polyphenylene ether compound. Furthermore, Patent Document 2 (International Publication No. 2016 / 175326) discloses a resin composition comprising: a polyphenylene ether derivative (A) containing a group containing an N-substituted maleimide structure in one molecule; a thermosetting resin (B) containing at least one member selected from the group consisting of epoxy resins, cyanate resins, and maleimide compounds; and a styrene-based thermoplastic elastomer (C). Patent Document 3 (Japanese Patent Application Publication No. 2011-225639) discloses a thermosetting resin composition comprising an uncured semi-IPN composite and (D) a radical reaction initiator. The uncured semi-IPN composite is believed to be an uncured product formed by the dissolution of a prepolymer comprising (A) polyphenylene ether, (B) a butadiene polymer containing at least 40% 1,2-butadiene units with 1,2-vinyl groups in its side chains, and (C) a crosslinking agent. [Prior Art Literature] [Patent Document]

[0004] [Patent Document 1] International Publication No. 2013 / 105650 [Patent Document 2] International Publication No. 2016 / 175326 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-225639 Summary of the Invention

[0005] The inventors have examined products formed by attaching a base layer (adhesive layer) of a resin composition having excellent dielectric properties to a substrate such as a prepreg. Furthermore, the resin composition layer can be provided in the form of a resin-coated copper foil, which can be used as copper foil for circuit formation. Resin compositions suitable for these applications are desired to have not only excellent dielectric properties but also excellent adhesion to low-roughness surfaces (such as the surface of low-roughness copper foil). In particular, when forming high-frequency dedicated circuits, it is desirable to use low-roughness copper foil from the perspective of reducing transmission loss. However, due to its low roughness, such copper foil tends to have reduced adhesion to the resin composition. In particular, during the substrate manufacturing process, when heat treatment is performed, the adhesion between the copper foil and the resin composition tends to be further reduced. Therefore, it is desirable for a resin composition suitable for the above-mentioned applications to not only exhibit excellent dielectric properties and high adhesion to low-roughness surfaces (e.g., the surface of low-roughness copper foil), but also to stably maintain its high adhesion even after thermal loading.

[0006] The present inventors have discovered that by blending a predetermined aryl ether compound and / or a predetermined styrene-based copolymer with an organic filler composed of a liquid crystal polymer, a resin composition can be provided that exhibits excellent dielectric properties (e.g., a low dielectric loss tangent at 10 GHz) and high adhesion to low-roughness surfaces (e.g., the surface of low-roughness copper foil), and that can stably maintain this high adhesion even after thermal loading.

[0007] Therefore, an object of the present invention is to provide a resin composition that not only exhibits excellent dielectric properties and high adhesion to low-roughness surfaces, but can also stably maintain its high adhesion after thermal loading.

[0008] According to the present invention, the following aspects can be provided. [Aspect 1] A resin composition comprising: At least one of an arylene ether compound having a weight average molecular weight of 30,000 or more, and a styrene copolymer having a reactive unsaturated bond in the molecule that becomes reactive with heat or ultraviolet light; and Organic fillers composed of liquid crystal polymers. [Aspect 2] The resin composition of aspect 1, wherein the reactive unsaturated bond is at least one selected from the group consisting of a cyanate group, a maleimide group, a terminal vinyl group, a (meth)acryl group, an acetylene group, and a styryl group. [Aspect 3] The resin composition of aspect 1 or 2, wherein the styrene-based copolymer has a styrene group as the reactive unsaturated bond. [Aspect 4] The resin composition of any one of Aspects 1 to 3, wherein the resin composition comprises both the arylene ether compound and the styrene copolymer. [Aspect 5] The resin composition of any one of Aspects 1 to 4, wherein the organic filler has a dielectric loss tangent of 0.001 or less at a frequency of 10 GHz. [Aspect 6] A resin-coated copper foil comprising: a copper foil; and a resin layer disposed on at least one surface of the copper foil and comprising the resin composition of any one of Aspects 1 to 5. [Aspect 7] The resin-coated copper foil according to Aspect 6, wherein the surface of the copper foil on the resin layer side has a ten-point average roughness Rzjis of 2.0 μm or less as measured in accordance with JIS B0601-2001. [Aspect 8] A printed wiring board made using the resin-coated copper foil of aspect 6 or 7. Implementation Method

[0009] Resin composition

[0010] The resin composition of the present invention comprises: at least one of an arylene ether compound and a styrene copolymer; and an organic filler. The arylene ether compound has a weight-average molecular weight of 30,000 or greater, while the styrene copolymer has reactive unsaturated bonds in its molecules that become reactive with heat or ultraviolet light. The organic filler is composed of a liquid crystal polymer. By blending a predetermined arylene ether compound and / or a predetermined styrene copolymer with an organic filler composed of a liquid crystal polymer, a resin composition can be provided that exhibits excellent dielectric properties (e.g., a low dielectric loss tangent at 10 GHz) and high adhesion to low-roughness surfaces (e.g., low-roughness copper foil surfaces), while also maintaining this adhesion even after thermal stress.

[0011] As described above, the present inventors have examined products formed by attaching a base layer (adhesive layer) of a resin composition with excellent dielectric properties to a substrate such as a prepreg. Furthermore, the resin composition layer can be provided in the form of a resin-coated copper foil, which can be used as copper foil for circuit formation. Resin compositions suitable for these applications are desired to have not only excellent dielectric properties but also excellent adhesion to low-roughness surfaces (such as those of low-roughness copper foil). In particular, when forming high-frequency circuits, low-roughness copper foil is desirable from the perspective of reducing transmission loss. However, due to its low roughness, such copper foil tends to have poor adhesion to the resin composition. In particular, during the substrate manufacturing process, when heat treatment is performed, the adhesion between the copper foil and the resin composition tends to be further reduced. The resin composition of the present invention can address this issue.

[0012] The resin composition of the present invention comprises at least one of an arylene ether compound having a weight-average molecular weight of 30,000 or greater and a styrene copolymer having reactive unsaturated bonds in its molecule that become reactive with heat or ultraviolet light. Preferably, the composition comprises both the arylene ether compound and the styrene copolymer. This allows for more effective realization of the aforementioned effects of the present invention.

[0013] The resin composition of the present invention preferably has a dielectric loss tangent of less than 0.0035, more preferably less than 0.0020, and even more preferably less than 0.0015 at a frequency of 10 GHz after curing. A lower dielectric loss tangent is preferred; the lower limit is not particularly limited, but is typically greater than 0.0001.

[0014] The resin composition of the present invention preferably contains an arylene ether compound. The weight-average molecular weight of the arylene ether compound is 30,000 or greater, preferably 30,000 or greater and 300,000 or less, more preferably 40,000 or greater and 200,000 or less, and particularly preferably 45,000 or greater and 120,000 or less. The arylene ether compound having a weight-average molecular weight of 30,000 or greater is preferably a phenylene ether compound, such as polyphenylene ether. The arylene ether compound or phenylene ether compound comprises the following formula in its molecule: (wherein R1, R2, R3 and R4 are each independently a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms) Compounds having a skeleton represented by are preferred. Examples of phenylene ether compounds include styrene derivatives of phenylene ether compounds, phenylene ether compounds containing a maleic anhydride structure in the molecule, terminal hydroxyl-modified phenylene ether compounds, terminal methacrylic acid-modified phenylene ether compounds, and terminal glycidyl ether-modified phenylene ether compounds. Examples of arylene ether compounds containing a maleic anhydride structure in the molecule and having a weight-average molecular weight of 30,000 or greater include PME-80 and PME-82 manufactured by Mitsubishi Engineering Plastics Co., Ltd.

[0015] The arylene ether compound of the present invention preferably has a reactive unsaturated bond. Alternatively, the resin composition may further contain an additional arylene ether compound having a reactive unsaturated bond. In this case, the weight-average molecular weight of the additional arylene ether compound does not necessarily have to be greater than 30,000. That is, the weight-average molecular weight of the additional arylene ether compound may be less than 30,000 (although the weight-average molecular weight may be greater than 30,000). For example, the number-average molecular weight may be between 500 and 10,000. A reactive unsaturated bond is defined as an unsaturated bond that becomes reactive with heat or ultraviolet light. Suitable examples of reactive unsaturated bonds include cyanate groups, maleimide groups, vinyl groups, (meth)acryloyl groups, ethynyl groups, styryl groups, and combinations thereof. Styryl groups are particularly preferred due to their high reactivity and controllable reaction (resistance to temporal reaction fluctuations, resin preservation, and a long product life).

[0016] The reactive unsaturated bond in an arylene ether compound is preferably located at a terminal or adjacent position in the molecular structure for high reactivity. For example, 1,2-vinyl is an example of a functional group with an unsaturated bond at a terminal. However, due to its high reactivity, 1,2-vinyl is generally used as a functional group for free radical polymerization. In contrast, when the ethylenically unsaturated bond is present in the molecular chain (the vinyl group is not located at a terminal end of the molecular structure), its reactivity decreases. Furthermore, when the unsaturated bond is adjacent to a benzene ring (such as in the case of a styryl group), it exhibits exceptional reactivity. Therefore, the location of the reactive unsaturated bond can be: a) at a terminal end of the molecular structure (either in the main chain or in a side chain), or b) adjacent to a terminal benzene ring if the benzene ring is located at a terminal end of the molecular structure (either in the main chain or in a side chain). For example, an arylene ether compound can have styryl groups as reactive unsaturated bonds at both ends of the molecular structure. Examples of arylene ether compounds having styryl groups at both molecular ends include OPE-2St-1200 and OPE-2St-2200 manufactured by Mitsubishi Gas Chemical Co., Ltd. (however, the weight average molecular weight of the arylene ether compounds of these products is less than 30,000).

[0017] When the resin composition of the present invention includes an arylene ether compound having a weight-average molecular weight of 30,000 or greater, its content is not particularly limited. From the perspective of achieving a balance between compatibility (which is related to peel strength) and dielectric properties, the content is preferably 10 parts by weight to 90 parts by weight, more preferably 15 parts by weight to 80 parts by weight, and even more preferably 20 parts by weight to 60 parts by weight, relative to 100 parts by weight of the total resin component (solids). In this specification, 100 parts by weight of the total resin component (solids) includes not only the polymer or resin, reaction initiator, etc., but also the weight of additives that constitute part of the resin, and excludes organic fillers.

[0018] The resin composition of the present invention preferably includes a styrene-based copolymer having reactive unsaturated bonds in its molecules that become reactive with heat or ultraviolet light. The styrene-based copolymer may be either hydrogenated or non-hydrogenated. Specifically, the styrene-based copolymer is a polymer of a compound containing a moiety derived from styrene and, in addition to styrene, a moiety derived from a compound having a polymerizable unsaturated group, such as an olefin. If the moiety derived from the compound having a polymerizable unsaturated group in the styrene-based copolymer further contains a double bond, the double bond may be hydrogenated or unhydrogenated. Examples of styrene-based copolymers include acrylonitrile-butadiene-styrene copolymers (ABS), methacrylate-butadiene-styrene copolymers (MBS), acrylonitrile-acrylate-styrene copolymers (AAS), acrylonitrile-ethylene-styrene copolymers (AES), styrene-butadiene copolymers (SBR), styrene-butadiene-styrene copolymers (SBS), styrene-ethylene-butadiene-styrene copolymers (SEBS), styrene-4-methylstyrene-isoprene-butadiene block copolymers, and combinations thereof. Preferred are styrene-butadiene block copolymers (SBR), styrene-4-methylstyrene-isoprene-butadiene block copolymers, and combinations thereof. Styrene-4-methylstyrene-isoprene-butadiene block copolymers are particularly preferred. The weight-average molecular weight of the styrene-based copolymer is not particularly limited, but is preferably 40,000 to 400,000, more preferably 60,000 to 370,000, and particularly preferably 80,000 to 340,000.

[0019] The styrene copolymer used in the present invention has reactive unsaturated bonds in its molecules that become reactive with heat or ultraviolet light. Suitable examples of these reactive unsaturated bonds include cyanate groups, maleimide groups, terminal vinyl groups, (meth)acryloyl groups, ethynyl groups, styryl groups, and combinations thereof. Styryl groups are particularly preferred due to their high reactivity and controllable reaction (resistance to temporal reaction fluctuations, resin preservation, and long product life).

[0020] Reactive unsaturated bonds in styrene-based copolymers are preferably located at or adjacent to the molecular terminal for high reactivity. For example, 1,2-vinyl groups are examples of functional groups with unsaturated bonds at the molecular terminal. However, because 1,2-vinyl groups (terminal vinyl groups) exhibit high reactivity, they are generally used as functional groups for free radical polymerization. Therefore, styrene-based copolymers with such functional groups are considered to have reactive unsaturated bonds in their molecules that become reactive with heat or ultraviolet light. In contrast, when ethylenically unsaturated bonds are present in the molecular chain (vinyl groups are not located at the molecular terminal), their reactivity decreases. Therefore, styrene-based copolymers with such unsaturated bonds are not considered to have reactive unsaturated bonds in their molecules that become reactive with heat or ultraviolet light. An example of a styrene-based copolymer without unsaturated bonds at the molecular terminal is TR2003 manufactured by JSR Corporation. In addition, when the unsaturated bond is adjacent to a benzene ring (such as in the case of a styryl group), it exhibits exceptional reactivity, and is therefore considered a styrene-based copolymer containing reactive unsaturated bonds in the molecule that become reactive with heat or ultraviolet light. Therefore, the location of the reactive unsaturated bond can be: a) at the terminal end of the molecular structure (whether in the main chain or a side chain); b) when the benzene ring is located at the terminal end of the molecular structure (whether in the main chain or a side chain), it can be adjacent to the terminal benzene ring. Examples of styrene-based copolymers containing reactive unsaturated bonds include Septon(R) V9461 (containing a styryl group) manufactured by Kuraray Co., Ltd.; Ricon(R) 100, 181, and 184 (styrene-butadiene copolymers containing a 1,2-vinyl group) manufactured by Cray Valley Co., Ltd.; and EPOFRIEND AT501 and CT310 (styrene-butadiene copolymers containing a 1,2-vinyl group) manufactured by Daicel Co., Ltd. Furthermore, "reactive with heat or ultraviolet light" means that the resin composition of the present invention is reactive under heating conditions or ultraviolet light irradiation conditions to the extent that a substrate (e.g., a prepreg) suitable for use in combination with the resin composition of the present invention is cured. The heating temperature under such conditions is typically around 160-230°C.

[0021] The styrene-based copolymer preferably contains modified styrene butadiene. Alternatively, the resin composition may further contain an additional styrene-based copolymer containing modified styrene butadiene. In this case, the additional styrene-based copolymer may be the same as the above-mentioned styrene-based copolymer, except that it does not necessarily have a reactive unsaturated bond. In other words, the additional styrene-based copolymer may not have a reactive unsaturated bond (however, it may have a reactive unsaturated bond). The modified styrene butadiene may be styrene butadiene that has been chemically modified by introducing various functional groups, such as amine modification, pyridine modification, and carboxyl modification, preferably amine modification. An example of a styrene-based copolymer containing modified styrene butadiene is Tuftec (R) MP10 manufactured by Asahi Kasei Corporation, which is an amine-modified hydrogenated styrene butadiene block copolymer. Another example of an unmodified styrene-based copolymer is TR2003 manufactured by JSR Corporation, which is a styrene-butadiene block copolymer (however, MP10 and TR2003 are not styrene-based copolymers having reactive unsaturated bonds in their molecules that become reactive with heat or ultraviolet rays).

[0022] In the resin composition of the present invention, the content of the styrene-based copolymer having reactive unsaturated bonds that become reactive with heat or ultraviolet light is not particularly limited. However, from the perspective of achieving a balance between compatibility and dielectric properties, the content is preferably from 20 parts by weight to 99.5 parts by weight, more preferably from 30 parts by weight to 90 parts by weight, and even more preferably from 40 parts by weight to 70 parts by weight, based on 100 parts by weight of the total amount of the resin components (solid content).

[0023] In the resin composition of the present invention, the combined content of the arylene ether compound having a weight-average molecular weight of 30,000 or greater and the styrene copolymer having a reactive unsaturated bond in the molecule that becomes reactive with heat or ultraviolet light is not particularly limited, but is preferably from 30 parts by weight to 99.5 parts by weight, more preferably from 40 parts by weight to 90 parts by weight, and even more preferably from 50 parts by weight to 85 parts by weight, based on 100 parts by weight of the total amount of the resin components (solid content).

[0024] The resin composition of the present invention includes an organic filler composed of a liquid crystal polymer (LCP). The addition of a liquid crystal polymer as a filler not only imparts excellent dielectric properties to the resin composition but also significantly reduces degradation of its high adhesion to low-roughness surfaces even after thermal loading. This ability to suppress thermal degradation is an advantage not achieved with inorganic fillers. Furthermore, fillers composed of liquid crystal polymers exhibit excellent dispersibility in other resin components. For example, organic fillers made from polytetrafluoroethylene (PTFE) are extremely difficult to disperse in resin components, while organic fillers made from liquid crystal polymers are advantageous in that they do not suffer from this drawback. The organic filler is preferably in the form of liquid crystal polymer particles. Commercially available liquid crystal polymer particles can be used; for example, XYDAR (R) LF-31P (manufactured by ENEOS Co., Ltd.) is a suitable powder-grade liquid crystal polymer. The particle size of the liquid crystal polymer particles is not particularly limited, as long as they can be dispersed in the resin composition as an organic filler and exhibit the desired properties. The average particle size D50 of the liquid crystal polymer particles is preferably 0.1-10 μm, more preferably 0.5-9 μm, and even more preferably 1-8 μm. The average particle size D50 of the liquid crystal polymer particles can be measured using a laser diffraction scattering particle size distribution analyzer.

[0025] The content of the organic filler is not particularly limited. From the viewpoint of ease of filler dispersion and fluidity of the resin composition, the content is preferably from 5 parts by weight to 300 parts by weight, more preferably from 10 parts by weight to 200 parts by weight, more preferably from 15 parts by weight to 200 parts by weight, particularly preferably from 15 parts by weight to 150 parts by weight, and most preferably from 25 parts by weight to 75 parts by weight, based on 100 parts by weight of the total amount of the resin component (solid content).

[0026] The dielectric loss tangent of the organic filler at a frequency of 10 GHz is preferably 0.001 or less, more preferably 0.0009 or less, and even more preferably 0.0008 or less. A lower dielectric loss tangent is preferred, and the lower limit is not particularly limited, but is typically 0.0001 or greater.

[0027] The resin composition of the present invention may contain additives commonly added to resins or polymers. Examples of additives include reaction initiators, reaction accelerators, flame retardants, silane coupling agents, dispersants, and antioxidants.

[0028] Copper foil with resin The resin composition of the present invention is preferably used as the resin for a resin-coated copper foil. Specifically, a preferred embodiment of the present invention provides a resin-coated copper foil comprising: a copper foil; and a resin layer comprising the resin composition, disposed on at least one surface of the copper foil. Typically, the resin composition is in the form of a resin layer, and the resin composition is applied to the copper foil using a gravure coating method to a predetermined thickness after drying, followed by drying to obtain the resin-coated copper foil. The coating method is arbitrary; in addition to gravure coating, die coating, blade coating, and the like can also be employed. Alternatively, coating can be performed using a doctor blade or rod coater.

[0029] As described above, the resin composition of the present invention not only exhibits excellent dielectric properties (e.g., a low dielectric loss tangent at 10 GHz) and high adhesion to low-roughness surfaces (e.g., low-roughness copper foil surfaces), but also maintains this high adhesion to low-roughness surfaces even after thermal loading. Therefore, resin-coated copper foil exhibits various advantages provided by this resin composition. For example, the lower limit of the peel strength between the resin layer and the copper foil (i.e., normal peel strength), measured in accordance with JIS C 6481-1996 after the resin layer has cured, is preferably 0.5 kgf / cm or greater, more preferably 0.8 kgf / cm or greater, more preferably 1.0 kgf / cm or greater, and particularly preferably 1.2 kgf / cm or greater. While a higher peel strength is preferred, the upper limit is not particularly limited, but is typically 2.0 kgf / cm or less.

[0030] The thickness of the resin layer is not particularly limited; however, to ensure peel strength, a thicker layer is preferred, while a thinner layer is preferred for laminated substrates. Therefore, there is an appropriate thickness. The thickness of the resin layer is preferably 1 μm to 50 μm, more preferably 1.5 μm to 30 μm, particularly preferably 2 μm to 20 μm, and most preferably 2.5 μm to 10 μm. Within this range, the various characteristics of the present invention described above can be more effectively achieved, and the resin layer can be easily formed by applying the resin composition.

[0031] Copper foil can be electrolytically or rolled (so-called raw foil), or it can be surface-treated foil with at least one surface treated. Surface treatments include various treatments applied to the surface of the metal foil to enhance or impart specific properties (such as rust resistance, moisture resistance, chemical resistance, acid resistance, heat resistance, and adhesion to substrates). Surface treatments can be applied to one or both sides of the foil. Examples of surface treatments for copper foil include rust prevention, silane treatment, roughening, and protective film formation.

[0032] The ten-point average roughness Rzjis of the copper foil's resin layer-side surface, measured in accordance with JIS B0601-2001, is preferably 2.0 μm or less, more preferably 1.5 μm or less, more preferably 1.0 μm or less, particularly preferably 0.7 μm or less, and most preferably 0.5 μm or less. Within this range, transmission loss in high-frequency applications can be effectively reduced. This means that conductor loss due to the copper foil's skin effect, which becomes more pronounced at higher frequencies, can be reduced, further reducing transmission loss. While the lower limit of the ten-point average roughness Rzjis of the copper foil's resin layer-side surface is not particularly limited, from the perspective of improving adhesion to the resin layer and heat resistance, Rzjis is preferably 0.01 μm or greater, more preferably 0.03 μm or greater, and even more preferably 0.05 μm or greater.

[0033] The thickness of the copper foil is not particularly limited, but is preferably 0.1 μm to 100 μm, more preferably 0.5 μm to 70 μm, more preferably 1 μm to 50 μm, particularly preferably 1.5 μm to 30 μm, and most preferably 2 μm to 20 μm. A thickness within this range offers the advantage of enabling the formation of fine circuits. In particular, for copper foil thicknesses of 10 μm or less, for example, to improve handling, the resin-coated copper foil of the present invention may be a copper foil with a carrier having a release layer and a carrier and having a resin layer formed on the surface of the copper foil.

[0034] From the perspective of ensuring adhesion with the resin layer, the base material of the prepreg, etc., preferably contains a resin having a reactive unsaturated bond in the molecule. From the perspective of compatibility with the resin layer, it is preferably contained a polyphenylene ether resin. Commercially available examples of base materials that meet both the requirements of containing a resin having a reactive unsaturated bond in the molecule and containing a polyphenylene ether resin include the MEGTRON 6 series manufactured by Panasonic Co., Ltd., MEGTRON 7 series, MEGTRON 8 series, etc. The low dielectric constant and low dielectric loss tangent substrates exemplified here have difficulty maintaining adhesion with conventional resin layers or even low-roughness copper foils. However, the resin composition of the present invention ensures sufficient adhesion. In particular, high adhesion can be stably maintained even with low-roughness copper foils after thermal loading. Therefore, a suitable aspect of the present invention provides a laminate comprising: a substrate (e.g., a prepreg) and a resin layer (or the resin-coated copper foil of the present invention) disposed on one or both surfaces of the substrate and comprising the resin composition of the present invention.

[0035] Printed wiring boards The resin composition or resin-coated copper foil of the present invention is preferably used for the production of printed wiring boards. That is, according to a suitable embodiment of the present invention, a printed wiring board having the above-mentioned resin-coated copper foil or a printed wiring board produced using the above-mentioned resin-coated copper foil can be provided. In this case, the resin layer of the resin-coated copper foil is cured. The printed wiring board obtained by this embodiment has a layer structure comprising an insulating resin layer and a copper layer laminated in this order. The printed wiring board can adopt a well-known layer structure. Specific examples of printed wiring boards include single-sided or double-sided printed wiring boards in which a circuit is formed by bonding the resin-coated copper foil of the present invention to one or both sides of a prepreg and curing the prepreg to produce a laminate, or multilayer printed wiring boards in which the prepreg is multilayered. Other specific examples include flexible printed wiring boards, COFs, TAB tapes, build-up multilayer wiring boards, and direct wafer build-up boards in which the resin-coated copper foil of the present invention is formed on a resin film and then a circuit is formed. The resin-coated copper foil of the present invention is particularly suitable for use as insulating and conductive layers on printed wiring boards for high-frequency digital communications in network equipment. Examples of such network equipment include (i) servers and routers within base stations, (ii) enterprise networks, and (iii) high-speed mobile communication backbone systems. [Example]

[0036] The present invention is further described in detail by the following examples.

[0037] Examples 1~12 (1) Preparation of resin varnish First, the following arylene ether compound, styrene copolymer, additives, organic filler, and inorganic filler are prepared as raw material components for a resin varnish. <Arylene Ether Compound> -OPE-2St-1200 (Mitsubishi Gas Chemical Co., Ltd., a phenylene ether compound with styryl groups at both ends of the molecule, number average molecular weight approximately 1200) -OPE-2St-2200 (Mitsubishi Gas Chemical Co., Ltd., a phenylene ether compound with styryl groups at both molecular ends, number average molecular weight approximately 2200) -PME-82 (Mitsubishi Engineering Plastics Co., Ltd., a phenyl ether compound containing a maleic anhydride structure in its molecule, with a weight-average molecular weight of approximately 56,000) <Styrene Copolymer> -Septon (R) V9461 (Kuraray Co., Ltd., a hydrogenated styrene, 4-methylstyrene, isoprene, and butadiene block copolymer containing styrene groups, weight-average molecular weight approximately 296,000) -TR2003 (manufactured by JSR Co., Ltd., styrene-butadiene block copolymer, weight-average molecular weight approximately 95,700) -Tuftec (R) MP10 (manufactured by Asahi Kasei Co., Ltd., hydrogenated styrene-butadiene block copolymer, amine-modified, weight-average molecular weight approximately 60,000) <Additives (Reaction Initiators)> -PERBUTYL P (peroxide, manufactured by NOF Corporation) <Inorganic filler> -SC4050-MOT (Admatechs, Inc., silica slurry, average particle size D50: 1.0 μm, surface vinyl silane treatment) <Organic fillers> -XYDAR (R) LF-31P (manufactured by ENEOS Co., Ltd., liquid crystal polymer (LCP) powder, average particle size D50: 5-7 μm, dielectric loss tangent at 10 GHz: 0.0007)

[0038] The number average molecular weight and weight average molecular weight of the arylene ether compound and styrene copolymer are values ​​measured using GPC (gel permeation chromatography) under the following conditions. The molecular weights are relative to polystyrene standards. Detector: Differential refractive index detector RI (manufactured by Tosoh Co., Ltd., RI-8020, sensitivity 32) Column: TSKgel GMH HR-M, 2 tubes (7.8 mm × 30 cm, manufactured by Tosoh Corporation) ･Solvent:Chloroform Flow rate: 1.0 mL / min Column temperature: 40°C ･Injection volume: 0.2mL ･Standard sample: Monodisperse polystyrene manufactured by Tosoh Corporation ･Data processing: GPC data processing system manufactured by Toray Research Center Co., Ltd.

[0039] The raw materials were weighed into a round-bottom flask according to the blending ratios (weight ratios) listed in Tables 1 and 2. A mixed solvent was added to achieve the solids concentrations from the raw materials as shown in Tables 1 and 2. The mixed solvent was a mixture of methyl ethyl ketone (MEK) and toluene at the MEK ratios (weight %) listed in Tables 1 and 2. The round-bottom flask containing the raw materials and the mixed solvent was equipped with a heating pack, a stirring blade, and a flask cap with a reflux condenser. The temperature was raised to 60°C while stirring, and then stirred at 60°C for 2 hours to dissolve or disperse the raw materials. The resulting resin varnish was cooled. This yielded a resin varnish having the solids concentrations listed in Tables 1 and 2.

[0040] (2) Production of electrolytic copper foil Electrolytic copper foil was produced using the following method. Electrolysis was performed in a copper sulfate solution at a solution temperature of 45°C and a current density of 55 A / dm², using a titanium rotating electrode (surface roughness Ra: 0.20 μm) as the cathode and a dimensional stability anode (DSA) as the anode. The raw copper foil was produced. The composition of the copper sulfate solution was 80 g / L copper, 140 g / L free sulfuric acid, 30 mg / L bis(3-sulfopropyl) disulfide, 50 mg / L diallyldimethylammonium chloride polymer, and 40 mg / L chlorine. Particle-shaped protrusions were formed on the surface of the raw foil facing the electrolyte. The particle-like protrusions were formed by electrolysis in a copper sulfate solution (copper concentration: 13 g / L, free sulfuric acid concentration: 55 g / L, 9-phenylacridine concentration: 140 mg / L, chlorine concentration: 35 mg / L) at a solution temperature of 30°C and a current density of 50 A / dm2.

[0041] On the electrolyte surface side of the raw foil obtained in this manner, a zinc-nickel film formation, a chromate layer formation, and a silane layer formation were sequentially performed under the conditions disclosed below. <Zinc-Nickel Film Formation> ･Potassium pyrophosphate concentration: 80g / L ･Zinc concentration: 0.2g / L ･Nickel concentration: 2g / L ･Liquid temperature: 40℃ Current density: 0.5A / dm2 <Chromate Layer Formation> ･Chromic acid concentration: 1g / L, pH 11 ･Solution temperature: 25℃ Current density: 1A / dm2 <Silane Layer Formation> Silane coupling agent: 3-aminopropyltrimethoxysilane (3g / L aqueous solution) Liquid treatment method: shower treatment

[0042] The ten-point average roughness Rzjis of the treated surface of the electrolytic copper foil was 0.5 μm (according to JIS B0601-2001). The average particle size of the granular protrusions, as measured by scanning electron microscopy, was 100 nm, with a particle density of 205 particles / μm². The total thickness of the electrolytic copper foil, including the treated surface, was 18 μm.

[0043] (3) Preparation of resin film The resin varnish obtained in (1) was applied to the surface of a release film ("AFLEX (R)" manufactured by AGC Co., Ltd.) using a notch wheel coater to a thickness of 20 μm after drying. The resin was then dried in an oven at 150°C for 3 minutes to obtain a B-stage resin. The release film was peeled off from the obtained B-stage resin, and only two sheets of the B-stage resin were laminated. Vacuum press molding was performed at 200°C for 90 minutes at 20 kgf / cm2 to obtain a resin film having a thickness of 40 μm.

[0044] (4) Fabrication of single-sided laminated substrates The resin varnish obtained in (1) was applied to the surface of the electrolytic copper foil using a gravure coater to a resin thickness of 4 μm after drying. The resin was then dried in an oven at 150°C for 2 minutes to obtain a resin-coated copper foil. A plurality of prepregs (manufactured by Panasonic Corporation, MEGTRON7 series "R-5680") were stacked to a thickness of 0.2 mm, and the resin-coated copper foil was laminated thereon so that the resin contacted the prepreg. Vacuum press molding was performed at 190°C for 90 minutes at 30 kgf / cm2 to obtain a single-sided laminated substrate.

[0045] (5) Various assessments The following evaluations were performed on the produced resin films and single-sided laminated substrates.

[0046] Normal peel strength Copper wiring with a 10mm width and 18μm thickness was formed on a single-sided laminate using a subtractive process. The peel strength (kgf / cm) was measured at room temperature (e.g., 25°C) in accordance with JIS C 6481-1996. Five measurements were performed, and the average value was used as the peel strength. The peel strength measured here reflects four peeling modes: interfacial peeling between the prepreg and resin, cohesive failure of the resin, interfacial peeling within the resin layer, and interfacial peeling between the resin and copper foil. Higher values ​​indicate superior adhesion of the substrate to the prepreg, resin layer strength, and resin adhesion to the low-roughness foil. As shown in Tables 1 and 2, the normal peel strengths of Examples 1-12 were all above 0.5kgf / cm, confirming high adhesion to low-roughness surfaces.

[0047] <Heat-resistant peel strength maintenance rate> The post-heat peel strength (kgf / cm) was measured using the same procedure as the normal peel strength test, except that copper wiring with a 10mm width and 18μm thickness was formed on a single-sided laminate substrate using a subtractive process and then floated in a 288°C solder bath for 5 minutes for heat treatment. The post-heat peel strength (kgf / cm) was then divided by the normal peel strength and multiplied by 100 to calculate the heat-resistant peel strength retention rate (%). The results, shown in Tables 1 and 2, show that the resin compositions of Examples 1-7 achieved heat-resistant peel strength retention rates exceeding 95%, even higher than those of Examples 8-12 (Comparative Examples), demonstrating that they can maintain high adhesion to low-roughness surfaces even after thermal loading.

[0048] <Dielectric loss tangent> The dielectric loss tangent of the resin film at 10 GHz was measured using the cavity resonator perturbation method. The film was cut into sections corresponding to the resonator sample size and then measured using a measuring instrument (Keycom resonator and Keysight network analyzer) in accordance with JIS R 1641. The results are shown in Tables 1 and 2.

[0049]

[0050]

Claims

1. A thermosetting resin composition comprising: at least one of an aryl ether compound with a weight average molecular weight of 30,000 or more, and a styrene copolymer having reactive unsaturated bonds in its molecule that exhibit reactivity by heat or ultraviolet light; and an organic filler composed of a liquid crystal polymer.

2. The thermosetting resin composition of claim 1, wherein the aforementioned reactive unsaturated bond is selected from at least one of the group consisting of cyanate group, maleimide group, terminal vinyl group, (meth)acrylyl group, ethynyl group and styryl group.

3. The thermosetting resin composition of claim 1 or 2, wherein the aforementioned styrene copolymer has styrene groups as the aforementioned reactive unsaturated bonds.

4. The thermosetting resin composition of claim 1 or 2, wherein the resin composition comprises both the aforementioned aryl ether compound and the aforementioned styrene copolymer.

5. The thermosetting resin composition of claim 1 or 2, wherein the aforementioned organic filler has a dielectric loss tangent of 0.001 or less at a frequency of 10 GHz.

6. A copper foil coated with resin, comprising: a copper foil, and a resin layer disposed on at least one surface of the copper foil and comprising a thermosetting resin composition as claimed in any one of claims 1 to 5.

7. The copper foil with resin as claimed in claim 6, wherein the surface of the copper foil on the side of the resin layer has a ten-point average roughness Rzjis of 2.0 μm or less, as measured according to JIS B0601-2001.

8. A printed wiring board made using resin-coated copper foil as claimed in claim 6.