Metal-clad laminate and wiring board

Abstract

One aspect of the present invention provides a metal-clad laminate comprising: a first insulating layer containing a cured product of a first resin composition and a fibrous substrate containing liquid-crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one surface or both surfaces of the first insulating layer; and a metal foil laminated on the second insulating layer. The second insulating layer has a thickness of 1-60 μm, and the second resin composition contains a polyphenylene ether compound and / or a hydrocarbon compound.

Description

Metal-clad laminates and wiring boards

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

[0002] As the amount of information processed in various electronic devices increases, advances in packaging technologies, such as higher integration, higher wiring density, and multi-layering of semiconductor devices, are being made. Furthermore, wiring boards used in various electronic devices are required to be high-frequency compatible, such as server boards for communication infrastructure equipment and millimeter-wave radar boards for automotive applications. The insulating layers of wiring boards used in various electronic devices are required to have excellent dielectric properties, such as low dielectric constant and dielectric loss tangent, in order to increase signal transmission speed and reduce signal transmission loss. To meet this requirement, metal-clad laminates used to manufacture such wiring boards are sometimes used, which include an insulating layer containing a resin component with a low dielectric constant and dielectric loss tangent, and which further contains not only the resin component but also a fibrous substrate such as glass cloth. While glass cloth is often used as the fibrous substrate, the use of substrates containing fibers other than glass cloth has also been considered. Examples of metal-clad laminates using substrates containing fibers other than glass cloth as the fibrous substrate include the laminate described in Patent Document 1 and the copper-clad laminate described in Patent Document 2.

[0003] Patent Document 1 describes a laminate formed by laminating a metal foil and a prepreg obtained by impregnating a nonwoven fabric made of wholly aromatic polyester fibers and having a predetermined tensile strength with a resin. Patent Document 1 discloses that a laminate having high moisture absorption properties can be provided.

[0004] Patent Document 2 describes a copper-clad laminate in which copper foil is laminated on at least one side of a resin laminate made by impregnating a woven or nonwoven fabric made of a liquid crystal polyester resin having a dielectric constant of 2.5 to 3.0 and a liquid crystal transition temperature of 260 to 350° C. with a liquid crystal polyester resin having a liquid crystal transition temperature of 280 to 360° C. Patent Document 2 discloses that the dielectric constant and loss value are low, making it usable in high frequency bands, and the thermal expansion coefficient after Tg is low, making it easy to process, and achieving high reliability.

[0005] Metal-clad laminates used in manufacturing wiring boards and the like include not only an insulating layer but also a metal foil 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 foil provided on the metal-clad laminate.

[0006] Electronic devices, particularly small portable devices such as mobile communication terminals and laptops, are rapidly becoming more diverse, more powerful, thinner, and smaller. Accordingly, wiring boards used in these products are also required to have even higher performance, such as finer conductor wiring, more multi-layered conductor wiring layers, thinner wiring, and improved mechanical properties. Therefore, even if the wiring provided on the wiring board is finer, it is required that the wiring does not peel off from the insulating layer. To meet this requirement, the wiring board is required to have high adhesion between the wiring and the insulating layer. Therefore, metal-clad laminates used to manufacture wiring boards are required to have high adhesion between the metal foil and the insulating layer.

[0007] When manufacturing wiring boards for use in various electronic devices, metal-clad laminates are sometimes cut with a router or drilled with a drill to form through holes and via holes. Metal-clad laminates are required to minimize defects even when subjected to such processing. Specifically, metal-clad laminates used to manufacture wiring boards are required to minimize burrs on the cut edges, even when drilling holes or cutting with a router, and to minimize peeling between the wiring and the insulating layer. Therefore, metal-clad laminates used to manufacture wiring boards are required to have excellent processability that can sufficiently suppress defects that may occur during processing in manufacturing wiring boards. Furthermore, to suppress peeling between the wiring and the insulating layer that may occur when processing a metal-clad laminate to manufacture a wiring board, the wiring board is required to have high adhesion between the wiring and the insulating layer. For this reason, the metal-clad laminate is also required to have high adhesion between the metal foil and the insulating layer.

[0008] The wiring board is also required to have minimal warpage that may occur during chip mounting. In particular, as wiring boards become thinner and larger, there is a problem that warpage occurs in semiconductor packages in which semiconductor chips are mounted on wiring boards, making mounting defects more likely to occur. In order to suppress warpage in semiconductor packages in which semiconductor chips are mounted on wiring boards, the insulating layer is required to have a low thermal expansion coefficient. Therefore, the metal-clad laminate is required to have a low thermal expansion coefficient.

[0009] Japanese Patent Laid-Open No. 10-182857 Japanese Patent Laid-Open No. 2006-319324

[0010] The present invention has been made in view of the above circumstances, and aims to provide a metal-clad laminate that maintains excellent low dielectric properties, has a low coefficient of thermal expansion, and is excellent in processability and metal foil adhesion. Another aim of the present invention is to provide a wiring board that maintains excellent low dielectric properties, has a low coefficient of thermal expansion, and is excellent in wiring adhesion, and that sufficiently suppresses the occurrence of defects during wiring board manufacturing.

[0011] One aspect of the present invention is a metal-clad laminate comprising: a first insulating layer containing a cured product of a first resin composition and a fibrous base material including liquid crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer; and a metal foil laminated on the second insulating layer, wherein the thickness of the second insulating layer is 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

[0012] Another aspect of the present invention is a wiring board comprising: a first insulating layer containing a cured product of a first resin composition and a fibrous base material including liquid crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer; and wiring formed on the second insulating layer, wherein the thickness of the second insulating layer is 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

[0013] These and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0014] 1 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing an example of a wiring board according to an embodiment of the present invention.

[0015] The inventors have found that using an insulating layer containing a liquid crystal polymer fiber substrate, such as a fiber substrate containing liquid crystalline aromatic polyester fiber, as an insulating layer in a metal-clad laminate results in a metal-clad laminate with a low thermal expansion coefficient. That is, they have found that a metal-clad laminate with a metal foil on an insulating layer containing a liquid crystal polymer fiber substrate results in a metal-clad laminate with a low thermal expansion coefficient. On the other hand, they have found that such metal-clad laminates are prone to metal foil peeling and are prone to defects (e.g., burrs on the cut edge when drilling or cutting with a router) when using them to manufacture wiring boards.

[0016] Therefore, the present inventors have conducted various studies on the configuration of a metal-clad laminate that maintains a low coefficient of thermal expansion while improving the adhesion of the metal foil and is less likely to cause the above-mentioned problems during the manufacture of wiring boards. As a result, the present inventors have found that by providing a metal-clad laminate with an insulating layer (second insulating layer) separate from the first insulating layer between the first insulating layer and the metal foil and adjusting the thickness and composition of this second insulating layer, it is possible to maintain a low coefficient of thermal expansion while improving the adhesion of the metal foil and to exhibit high processability that sufficiently suppresses the occurrence of the above-mentioned problems during the manufacture of wiring boards. That is, after various studies, the present inventors have found that the above-mentioned object of providing a metal-clad laminate that maintains excellent low dielectric properties while having a low coefficient of thermal expansion, excellent processability, and excellent adhesion of the metal foil, can be achieved by the present invention described below.

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0018] [Metal-Clad Laminate] As shown in Fig. 1, a metal-clad laminate 10 according to an embodiment of the present invention includes a first insulating layer 11 containing a cured product of a first resin composition and a fibrous base material containing liquid crystalline aromatic polyester fibers, a second insulating layer 12 containing a cured product of a second resin composition and laminated on the first insulating layer 11, and a metal foil 13 laminated on the second insulating layer 12. The metal-clad laminate 10 may include the second insulating layer 12 laminated on one side of the first insulating layer 11, or may include the second insulating layer 12 laminated on both sides of the first insulating layer 11 as shown in Fig. 1. When the second insulating layer 12 is laminated on both sides of the first insulating layer 11, the metal foil 13 may be laminated on one of the second insulating layers 12 laminated on both sides of the first insulating layer 11, or the metal foil 13 may be laminated on both second insulating layers 12 laminated on both sides of the first insulating layer 11 as shown in Fig. 1. In the metal-clad laminate 10, the second insulating layer 12 has a thickness of 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound. This metal-clad laminate has a low coefficient of thermal expansion, excellent processability, and excellent metal foil adhesion (adhesion between the metal foil and the insulating layer) while maintaining excellent low dielectric properties. This is believed to be due to the following.

[0019] First, by providing a first insulating layer containing not only the cured product of the first resin composition but also a fibrous base material containing the liquid crystalline aromatic polyester fiber, it is believed that the thermal expansion coefficient of the resulting metal-clad laminate can be reduced. Instead of providing a metal foil on such a first insulating layer, by providing a second insulating layer containing the cured product of the second resin composition and having a thickness of 1 to 60 μm between the first insulating layer and the metal foil, it is believed that the adhesion of the metal foil can be improved while maintaining a low thermal expansion coefficient. Furthermore, by providing the second insulating layer between the first insulating layer and the metal foil, it is possible to sufficiently suppress the occurrence of burrs on the cut edge when drilling with a drill or cutting with a router. Furthermore, due to the high adhesion of the metal foil, it is believed that peeling of the metal foil can be sufficiently suppressed even when drilling and cutting are performed. Therefore, it is believed that this metal-clad laminate can also exhibit excellent processability that can sufficiently suppress problems that may occur when manufacturing wiring boards using this metal-clad laminate. From the above, it is believed that by using the above-mentioned configuration, a metal-clad laminate can be obtained that maintains excellent low dielectric properties, has a low thermal expansion coefficient, and is excellent in processability and adhesion to the metal foil.

[0020] <First Insulating Layer> The first insulating layer is not particularly limited as long as it is an insulating layer that contains not only the cured product of the first resin composition but also a fibrous base material containing liquid crystalline aromatic polyester fibers.

[0021] (Fibrous substrate) The fibrous substrate is not particularly limited as long as it is a fibrous substrate containing a liquid crystalline aromatic polyester fiber. Examples of the fibrous substrate include a fibrous substrate containing a liquid crystalline aromatic polyester fiber, and a fibrous substrate in which, on the surface of the fibrous substrate, the ratio of the total amount of groups represented by the following formula (3), the total amount of groups represented by the following formula (4), and the total amount of groups represented by the following formula (5) to the total amount of groups represented by the following formula (1) and the total amount of groups represented by the following formula (2), as measured by X-ray photoelectron spectroscopy (XPS), is 0.3 or more and less than 0.55.

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] Examples of the liquid crystalline aromatic polyester fiber include fibers containing a wholly aromatic polyester polymer. Examples of the liquid crystalline aromatic polyester fiber include fibers obtained by melt-spinning a liquid crystalline aromatic polyester. The liquid crystalline aromatic polyester contains structural units (e.g., repeating units) derived from acids such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids. The structural units derived from acids such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids are not particularly limited as long as they do not impair the effects of the present invention. Furthermore, the liquid crystalline aromatic polyester may further contain other structural units derived from aromatic diamines, aromatic hydroxyamines, aromatic aminocarboxylic acids, and the like, as long as they do not impair the effects of the present invention. The structural units are preferably structural units represented by the following formulas (6) to (9).

[0028]

[0029]

[0030]

[0031] In formulas (6) to (9), X represents at least one selected from the groups represented by formulas (10) to (17).

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040] In formulas (10), (13), and (16), m represents 0 to 2. In formulas (10) to (12), (16), and (17), Y represents a hydrogen atom or a substituent of an aromatic ring. When Y represents a substituent, the number of Y's (number of substituents) is in the range of 1 or more and the maximum number of substituents that can be introduced into the aromatic ring. Examples of the substituent include a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an aryloxy group, or an aralkyloxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include an alkyl group having 1 to 4 carbon atoms, more specifically, a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, and an n-butoxy group. Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the aralkyl group include a benzyl group (phenylmethyl group) and a phenethyl group (phenylethyl group). Examples of the aryloxy group include a phenoxy group. Examples of the aralkyloxy group include a benzyloxy group.

[0041] Examples of the combination of the structural units in the liquid crystalline aromatic polyester include combinations of structural units represented by the following formulas (18) to (34). When a structural unit represented by one formula can have multiple structures, multiple structural units represented by one formula may be used in combination.

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] In formula (19), formula (21) to formula (25), formula (28) to formula (30), and formula (32) to formula (34), n represents 1 or 2, and multiple constitutional units represented by the same formula but with different n numbers may be used in combination.

[0060] In formula (31), Y １ and Y ２ Each of Y independently represents a hydrogen atom or a substituent. Examples of the substituent include the same groups as those listed for Y. １ and Y ２ Preferred examples of include a hydrogen atom, a chlorine atom, a bromine atom, and a methyl group.

[0061] In formula (31), Z represents a group represented by the following formulas (35) to (39). That is, Z is at least one selected from the group consisting of groups represented by the following formulas (35) to (39).

[0062]

[0063]

[0064]

[0065]

[0066]

[0067] The liquid crystalline aromatic polyester preferably contains a naphthalene skeleton as the structural unit, and more preferably contains both a structural unit (A) derived from hydroxybenzoic acid and a structural unit (B) derived from hydroxynaphthoic acid. Examples of the structural unit (A) include a structural unit represented by the following formula (40). Examples of the structural unit (B) include a structural unit represented by the following formula (41). From the viewpoint of improving melt moldability, the molar ratio of the structural unit (A) to the structural unit (B) in the liquid crystalline aromatic polyester is preferably 9:1 to 1:1, more preferably 7:1 to 1:1, and even more preferably 5:1 to 1:1. The total amount of the structural unit (A) and the structural unit (B) in the liquid crystalline aromatic polyester is preferably 65 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more. It is also preferable that the content of the structural unit (A) in the liquid crystalline aromatic polyester is 50 to 70 mol %, and the content of the structural unit (B) is 4 to 45 mol %.

[0068]

[0069]

[0070] The melting point of the liquid crystalline aromatic polyester is not particularly limited, and is preferably 250 to 360°C, and more preferably 260 to 320°C. The melting point referred to here is the main endothermic peak temperature observed when measured using a differential scanning calorimeter (DSC; Mettler "TA3000") in accordance with JIS K7121. In this method, the DSC apparatus is used, and 10 to 20 mg of sample is placed in an aluminum pan. Nitrogen is flowed as a carrier gas at 100 cc / min, and the endothermic peak is measured when the temperature is increased at a rate of 20°C / min. Depending on the type of polymer, a clear peak may not appear during the first heating run (1st run) in the DSC measurement. In this case, the sample is first heated at a heating rate of 50°C / min to a temperature 50°C higher than the expected flow temperature, and then held at that temperature for 3 minutes until it is completely melted. Thereafter, the sample is cooled to 50°C at a heating rate of -80°C / min, and then the endothermic peak is measured at a heating rate of 20°C / min.

[0071] The liquid crystalline aromatic polyester fiber contains the liquid crystalline aromatic polyester and may further contain other thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin, as long as the effects of the present invention are not impaired. The liquid crystalline aromatic polyester fiber may also contain various additives such as inorganic substances, colorants such as carbon black, dyes and pigments, antioxidants, ultraviolet absorbers, and light stabilizers. Examples of inorganic substances include titanium oxide, kaolin, silica, and barium oxide.

[0072] The fibrous substrate is not particularly limited, but examples thereof include, as described above, fibrous substrates in which the ratio (b / a) of the total amount (b) of the groups represented by formula (3), the groups represented by formula (4), and the groups represented by formula (5) to the total amount (a) of the groups represented by formula (1) and the groups represented by formula (2) on the surface thereof, as measured by X-ray photoelectron spectroscopy, is 0.3 or more and less than 0.55. The ratio (b / a) is preferably 0.3 or more and less than 0.55, more preferably 0.35 to 0.53, and even more preferably 0.45 to 0.5. The groups represented by formula (3), the groups represented by formula (4), and the groups represented by formula (5) are more polar than the groups represented by formula (1) and the groups represented by formula (2). Therefore, the ratio (b / a) represents the ratio of relatively highly polar groups to relatively low polar groups on the surface of the fibrous substrate. When the ratio (b / a) is within the above range, the fibrous substrate tends to have high adhesion to the cured product of the first resin composition. That is, on the surface of the fibrous substrate, the group with relatively high polarity so that the ratio (b / a) is within the above range is considered to favorably contribute to improving the adhesion between the cured product of the first resin composition and the fibrous substrate. For this reason, if the fibrous substrate contained in the first insulating layer is the fibrous substrate, even if an insulating layer containing a fibrous substrate containing liquid crystalline aromatic polyester fibers is provided, peeling is unlikely to occur between the cured product of the first resin composition and the fibrous substrate in the first insulating layer. For this reason, the occurrence of problems that may occur when cutting the metal-clad laminate can be suppressed. Therefore, a metal-clad laminate with excellent processability and metal foil adhesion can be obtained.

[0073] The X-ray photoelectron spectroscopy can be measured using a general X-ray photoelectron spectroscopy. The ratio (b / a) can be measured, for example, as follows. The surface of the fibrous substrate is subjected to surface X-ray analysis using an X-ray photoelectron spectroscopy analyzer. The spectrum resulting from the carbon peak obtained by this surface X-ray analysis is then subjected to peak separation analysis using predetermined analysis software, and the peak area derived from each bond is calculated by analyzing the spectrum using a relative sensitivity coefficient. The ratio (b / a) is then calculated using the calculated peak areas derived from each bond. Here, when calculating the ratio (b / a), a is used as the sum of the peak area derived from the group represented by formula (1) with a bond energy of 284 eV (i.e., the —C—C— bond) and the peak area derived from the group represented by formula (2) with a bond energy of 285 eV (i.e., the —C—H bond). Furthermore, when calculating the ratio (b / a), b is the sum of the peak area derived from the group represented by formula (3) with a binding energy of 288 eV (i.e., a —C═O bond), the peak area derived from the group represented by formula (4) with a binding energy of 289 eV (i.e., a —COO bond), and the group represented by formula (5) with a binding energy of 286 eV (i.e., a —C—O— bond). Based on these values, the ratio (b / a) measured by XPS can be calculated. The X-ray photoelectron spectrometer is not particularly limited as long as it can perform measurements by X-ray photoelectron spectroscopy, and examples thereof include a scanning X-ray photoelectron spectrometer (PHI 5000 VersaProbe manufactured by ULVAC-PHI, Inc.). X-ray photoelectron spectroscopy can be performed by irradiating a sample with X-rays under vacuum using a scanning X-ray photoelectron spectrometer such as the PHI 5000 Versaprobe manufactured by ULVAC-PHI, Inc. The measurement conditions for the surface X-ray analysis are not particularly limited as long as they allow the ratio (b / a) to be measured. For example, the measurement conditions include a condition in which monochromatic Al-Kα rays are used as X-rays and the X-ray beam diameter is about 100 μmφ (25 W, 15 kV).

[0074] The fibrous substrate may be, for example, a fibrous substrate that has been subjected to a surface treatment on the surface of the fibrous substrate containing the liquid crystalline aromatic polyester fiber, such that the ratio (b / a) is 0.3 or more and less than 0.55. The surface treatment is not particularly limited as long as it is a surface treatment that makes the ratio (b / a) 0.3 or more and less than 0.55, and may be, for example, a plasma treatment. The plasma treatment may be, for example, an oxygen gas plasma treatment (a surface treatment using plasma generated by using oxygen gas as raw material gas), an oxygen and carbon tetrafluoride mixed gas plasma treatment (a surface treatment using plasma generated by using oxygen and carbon tetrafluoride mixed gas as raw material gas), and an argon, hydrogen, and nitrogen mixed gas plasma treatment (a surface treatment using plasma generated by using argon, hydrogen, and nitrogen mixed gas as raw material gas). That is, the fibrous substrate may be, for example, a fibrous substrate whose surface has been subjected to plasma treatment. More specifically, examples include fibrous substrates whose surface has been subjected to at least one plasma treatment selected from the group consisting of oxygen gas plasma treatment, oxygen and carbon tetrafluoride mixed gas plasma treatment, and argon, hydrogen, and nitrogen mixed gas plasma treatment. By subjecting the surface of the fibrous substrate to plasma treatment, a fibrous substrate having the ratio (b / a) of 0.3 or more and less than 0.55 can be obtained. Therefore, by using such a fibrous substrate, an insulating layer excellent in processability and metal foil adhesion can be obtained while maintaining excellent dielectric properties. Specifically, by subjecting the fibrous substrate to plasma treatment, the affinity of the fibrous substrate with the cured product of the first resin composition contained in the first insulating layer is improved, thereby improving adhesion to the cured product of the first resin composition. Therefore, a metal-clad laminate excellent in processability and metal foil adhesion can be obtained. Among the plasma treatments, the oxygen and carbon tetrafluoride mixed gas plasma treatment is preferred because it can produce a chemical surface modification effect in a shorter time than the oxygen gas plasma treatment. Of the plasma treatments, the oxygen gas plasma treatment is preferred because it mainly produces a chemical surface modification rather than a physical etching effect and is environmentally friendly.The oxygen and carbon tetrafluoride mixed gas plasma treatment raises concerns about environmental regulations due to the extremely high global warming potential of carbon tetrafluoride. The argon, hydrogen, and nitrogen mixed gas plasma treatment has a stronger physical etching effect than chemical surface modification. These plasma treatments may be used alone or in combination of two or more.

[0075] The conditions for the plasma treatment include, for example, a condition in which the ratio (b / a) is 0.3 or more and less than 0.55. The plasma irradiation amount in the plasma treatment is 0.35 to 0.65 W / cm in watt density. ２ is preferably 0.45 to 0.55 W / cm ２ The time for which the plasma treatment is carried out varies depending on the amount of raw material gas, plasma density, etc., but is preferably 10 to 40 minutes, and more preferably 20 to 30 minutes, for example.

[0076] The plasma treatment may be a treatment using microwave plasma (plasma excited by microwaves) or RF (Radio Frequency) plasma (plasma excited by RF). These plasmas may be pulse-excited or DC-excited. The microwaves may be, for example, microwaves with a frequency of 1 GHz or higher, which is an industrially usable frequency band and capable of generating high-density non-equilibrium plasma. Microwaves with a frequency of 2.45 GHz are preferred. In the case of microwave plasma, the microwave power used to generate the plasma atmosphere may be, for example, 300 W or higher. RF plasma is widely used in industry, and the excitation frequency used to generate RF plasma is generally 13.56 MHz in Japan due to legal regulations.

[0077] (Cured Product of First Resin Composition) The cured product of the first resin composition is not particularly limited, as long as it is a cured product that can be used as the cured product contained in the first insulating layer provided in a metal-clad laminate. That is, the first resin composition is not particularly limited, as long as it is a resin composition that can constitute the cured product contained in the first insulating layer provided in a metal-clad laminate, and examples thereof include resin compositions containing thermosetting resins. More specifically, examples thereof include resin compositions containing a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule, resin compositions containing a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in the molecule, and resin compositions containing the polyphenylene ether compound and the hydrocarbon-based compound. Furthermore, the first resin composition may or may not contain an inorganic filler, but preferably contains an inorganic filler, and more preferably contains a silica filler.

[0078] (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 double bond in the molecule. Examples of the polyphenylene ether compound include polyphenylene ether compounds having a carbon-carbon unsaturated double bond at a terminal, and more specifically, polyphenylene ether compounds having a substituent having a carbon-carbon unsaturated double bond at a molecular terminal, such as modified polyphenylene ether compounds whose terminals are modified with a substituent having a carbon-carbon unsaturated double bond.

[0079] Examples of the substituent having a carbon-carbon unsaturated double bond include a group represented by the following formula (42) and a group represented by the following formula (43). That is, examples of the polyphenylene ether compound include a polyphenylene ether compound having at least one selected from a group represented by the following formula (42) and a group represented by the following formula (43) in the molecule.

[0080]

[0081] In formula (42), p represents 0 to 10. Ar represents an arylene group. １ ~R ３are 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. In the formula (42), when p is 0, this indicates that Ar is directly bonded to the polyphenylene ether.

[0082] 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 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.

[0083] 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.

[0084] In formula (43), 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.

[0085] Examples of the group represented by the formula (42) include a vinylbenzyl group (ethenylbenzyl group) represented by the following formula (44): Furthermore, examples of the group represented by the formula (43) include an acryloyl group and a methacryloyl group.

[0086]

[0087] More specifically, examples of the substituent include vinylbenzyl groups (ethenylbenzyl groups) such as o-ethenylbenzyl groups, m-ethenylbenzyl groups, and p-ethenylbenzyl groups, vinylphenyl groups, acryloyl groups, and methacryloyl groups. The polyphenylene ether compound may have one type of substituent, or two or more types. The polyphenylene ether compound may have, for example, any one of an o-ethenylbenzyl group, an m-ethenylbenzyl group, and a p-ethenylbenzyl group, or may have two or three types of these.

[0088] 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 (45) in the molecule.

[0089]

[0090] In formula (45), 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.

[0091] R ５ ~R ８ Specific examples of the functional groups mentioned in the above include the following:

[0092] 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.

[0093] 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.

[0094] 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).

[0095] 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.

[0096] 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.

[0097] 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.

[0098] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polyphenylene ether compound are not particularly limited, and specifically, are 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 and number-average molecular weight may be measured by a general molecular weight measurement method, specifically, values ​​measured using gel permeation chromatography (GPC) may be used. Furthermore, when the polyphenylene ether compound has a repeating unit represented by formula (45) in the molecule, t is preferably a value such that the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound fall within the above ranges. Specifically, t is preferably 1 to 50.

[0099] When the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound are within the above ranges, the compound has the excellent low dielectric properties of polyphenylene ether, and the cured product not only has excellent heat resistance but also has excellent moldability. This is believed to be due to the following reasons. When the weight-average molecular weight and number-average molecular weight of a typical polyphenylene ether are within the above ranges, the compound has a relatively low molecular weight, which tends to reduce heat resistance. In contrast, the polyphenylene ether compound has one or more unsaturated double bonds at its terminals, and therefore, as the curing reaction progresses, a cured product with sufficiently high heat resistance is believed to be obtained. Furthermore, when the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound are within the above ranges, the compound has a relatively low molecular weight, which is believed to result in excellent moldability. Therefore, it is believed that such a polyphenylene ether compound not only has excellent heat resistance but also provides a cured product with excellent moldability.

[0100] The average number of the substituents (number of terminal functional groups) at the molecular terminals per molecule of the polyphenylene ether compound is not particularly limited. Specifically, it is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1.5 to 3. If the number of terminal functional groups is too small, it tends to be difficult to obtain a cured product with sufficient heat resistance. On the other hand, if the number of terminal functional groups is too large, the reactivity becomes too high, which may cause problems such as reduced shelf life and reduced fluidity of the resin composition. In other words, when such a polyphenylene ether compound is used, insufficient fluidity may cause molding defects such as the generation of voids during multilayer molding, making it difficult to obtain a highly reliable wiring board.

[0101] 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.

[0102] The intrinsic viscosity of the polyphenylene ether compound is not particularly limited. Specifically, it may be 0.03 to 0.12 dl / g, preferably 0.04 to 0.11 dl / g, and more preferably 0.06 to 0.095 dl / g. If the intrinsic viscosity is too low, the molecular weight tends to be low, and it tends to be difficult to achieve low dielectric properties such as a low dielectric constant and a low dielectric loss tangent. On the other hand, if the intrinsic viscosity is too high, the viscosity tends to be high, sufficient fluidity cannot be achieved, and the moldability of the cured product tends to be reduced. Therefore, if the intrinsic viscosity of the polyphenylene ether compound is within the above range, excellent heat resistance and moldability of the cured product can be achieved.

[0103] The intrinsic viscosity here is the intrinsic viscosity measured in methylene chloride at 25° C., and more specifically, it is the value measured, for example, with a viscometer using a 0.18 g / 45 ml methylene chloride solution (liquid temperature: 25° C.). Examples of such viscometers include the AVS500 Visco System manufactured by Schott.

[0104] Examples of the polyphenylene ether compound include a polyphenylene ether compound represented by the following formula (46) and a polyphenylene ether compound represented by the following formula (47). 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.

[0105]

[0106]

[0107] In formula (46) and formula (47), R ９ ~R １６ and R １７ ~R ２４ are independent of each other. That is, R ９ ~R １６ and R １７ ~R ２４ may be the same group or different groups. ９ ~R １６ and R １７ ~R ２４represents 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 are independent of each other. １ and X ２ and may be the same group or different groups. １ and X ２ represents a substituent having a carbon-carbon unsaturated double bond. A and B represent repeating units represented by the following formulas (48) and (49), respectively. In addition, in formula (47), Y Ａ represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

[0108]

[0109]

[0110] In formula (48) and formula (49), t1 and t2 each represent an integer of 0 to 20. 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.

[0111] The polyphenylene ether compound represented by the formula (46) and the polyphenylene ether compound represented by the formula (47) are not particularly limited as long as they satisfy the above-mentioned constitution. ９ ~R １６ and R １７ ~R ２４As described above, each of R is independent. ９ ~R １６ and R １７ ~R ２４ may be the same or different groups. R9 to R16 and R17 to R24 each represent 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 these, a hydrogen atom and an alkyl group are preferred.

[0112] In formula (48) and formula (49), t1 and t2 preferably represent 0 to 20, as described above. Furthermore, t1 and t2 preferably represent a numerical value such that the sum of t1 and t2 is 1 to 30. Therefore, it is more preferable that t1 represents 0 to 20, t2 represents 0 to 20, and the sum of t1 and t2 represents 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.

[0113] R ９ ~R ３２ is R in the above formula (45). ５ ~R ８ is the same as

[0114] In the formula (47), Y Ａ As described above, Y is a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms. Ａ Examples of the group include a group represented by the following formula (50).

[0115]

[0116] In the formula (50), 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 (50) include a methylene group, a methylmethylene group, and a dimethylmethylene group, and among these, a dimethylmethylene group is preferred.

[0117] In the formula (46) and the formula (47), X １ and X ２ are each independently a substituent having a carbon-carbon double bond. In the polyphenylene ether compound represented by the formula (46) and the polyphenylene ether compound represented by the formula (47), X １ and X ２ may be the same group or different groups.

[0118] More specific examples of the polyphenylene ether compound represented by the formula (46) include polyphenylene ether compounds represented by the following formula (51).

[0119]

[0120] More specific examples of the polyphenylene ether compound represented by the formula (47) include a polyphenylene ether compound represented by the following formula (52) and a polyphenylene ether compound represented by the following formula (53).

[0121]

[0122]

[0123] In the above formulas (51) to (53), t1 and t2 are the same as t1 and t2 in the above formulas (48) and (49). １ ~R ３ , p and Ar are R in the above formula (42). １ ~R ３, p and Ar. In addition, in the above formula (52) and the above formula (53), Y Ａ is Y in the above formula (47). Ａ In addition, in the above formula (53), R ４ is R in the above formula (43). ４ is the same as

[0124] The method for synthesizing the polyphenylene ether compound used in the present embodiment is not particularly limited as long as it is possible to synthesize a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule. Specific examples of this method include a method of reacting polyphenylene ether with a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded.

[0125] (Hydrocarbon Compound) The hydrocarbon compound is not particularly limited as long as it is a hydrocarbon compound having a carbon-carbon unsaturated double bond in the molecule, and examples thereof include polyfunctional vinyl aromatic compounds. The polyfunctional vinyl aromatic compound, for example, contains a repeating unit (c) derived from a divinyl aromatic compound and a repeating unit (d) derived from a monovinyl aromatic compound, and contains a structural unit (c1) represented by the following formula (54) as part of the repeating unit (c) derived from the divinyl aromatic compound:

[0126]

[0127] In formula (54), R ３５ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.

[0128] In the polyfunctional vinyl aromatic copolymer, when the sum of the repeating units (c) and (d) is taken as 100 mol %, it is preferable that the repeating unit (c) is contained in an amount of 2 mol % or more and less than 95 mol % and the repeating unit (d) is contained in an amount of 5 mol % or more and less than 98 mol %. When the sum of the repeating units (c) and (d) is taken as 100 mol %, it is preferable that the repeating unit (c1) is contained in an amount of 2 to 80 mol %.

[0129] The polyfunctional vinyl aromatic copolymer preferably has a number average molecular weight Mn of 300 to 100,000 and a molecular weight distribution (Mw / Mn) expressed as the ratio of the weight average molecular weight Mw to the number average molecular weight of 100.0 or less. The polyfunctional vinyl aromatic copolymer is also preferably soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform.

[0130] The polyfunctional vinyl aromatic copolymer is not particularly limited, and examples thereof include a copolymer containing a repeating unit (c) derived from a divinyl aromatic compound and a repeating unit (d) derived from a monovinyl aromatic compound, as represented by the following formula (55): These repeating units may be arranged regularly or randomly.

[0131]

[0132] In formula (55), R ３６ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from a monovinyl aromatic compound, and R ３７ and R ３８ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from a divinyl aromatic compound. h, i, j, and k each independently represent an integer of 0 to 200, provided that the total of these is 2 to 20,000.

[0133] The polyfunctional vinyl aromatic copolymer is a copolymer represented by the formula (55), ３６ ~R ３８ are each independently an aromatic hydrocarbon group selected from the group consisting of a phenyl group which may have a substituent, a biphenyl group which may have a substituent, a naphthalene group which may have a substituent, and a terphenyl group which may have a substituent.

[0134] The polyfunctional vinyl aromatic copolymer is preferably solvent-soluble. In addition, the repeating unit referred to in this specification is derived from a monomer and includes a unit that is present in the main chain of the copolymer and appears repeatedly, and a unit or terminal group that is present at the end or side chain. The repeating unit is also referred to as a structural unit.

[0135] The structural unit (c) derived from the divinylaromatic compound is preferably contained in an amount of 2 mol% or more but less than 95 mol% of the total of the structural unit (c) derived from the divinylaromatic compound and the structural unit (d) derived from the monovinyl aromatic compound. The structural unit (c) derived from the divinylaromatic compound can have a variety of structures, such as one in which only one of two vinyl groups has reacted or two in which two have reacted. Among these, the repeating unit in which only one vinyl group has reacted, represented by formula (54), is preferably contained in an amount of 2 to 80 mol%, more preferably 5 to 70 mol%, even more preferably 10 to 60%, and particularly preferably 15 to 50%, relative to the total. By keeping the repeating unit in which only one vinyl group has reacted, represented by formula (54), within the above range (e.g., 2 to 80 mol%), it is believed that the dielectric loss tangent is low, heat resistance is excellent, and compatibility with other resins is excellent. If the repeating unit in which only one vinyl group represented by the formula (54) has reacted is too small (for example, less than 2 mol%), the heat resistance tends to decrease, whereas if the repeating unit in which only one vinyl group represented by the formula (54) has reacted is too large (for example, more than 80 mol%), the adhesion strength tends to decrease.

[0136] The vinyl group present in the formula (54) acts as a cross-linking component, and is thought to contribute to the development of heat resistance of the polyfunctional vinyl aromatic copolymer.On the other hand, the structural unit (d) derived from the monovinyl aromatic compound does not have a vinyl group, since it is thought that polymerization usually proceeds through a 1,2-addition reaction of the vinyl group.In other words, the structural unit (d) derived from the monovinyl aromatic compound does not act as a cross-linking component, but is thought to contribute to the development of moldability.

[0137] Styrene is a preferred example of the monovinyl aromatic compound. Furthermore, as the monovinyl aromatic compound, a monovinyl aromatic compound other than styrene can also be used together with styrene. When the structural unit (d) derived from the monovinyl aromatic compound contains a structural unit (d1) derived from styrene and a structural unit (d2) derived from a monovinyl aromatic compound other than styrene, the content of the structural unit (d1) derived from styrene is preferably 99 to 20 mol%, more preferably 98 to 30 mol%, when the total content of the structural unit (d1) derived from styrene and the structural unit (d2) derived from the monovinyl aromatic compound other than styrene is taken as 100 mol%. A content of the structural unit (d1) derived from styrene within the above range is preferred because it combines thermal oxidative degradation resistance and moldability. If the structural unit (d1) derived from styrene is too high (e.g., greater than 99 mol%), heat resistance tends to decrease. Furthermore, if the structural unit (d2) derived from a monovinyl aromatic compound other than styrene is too high (e.g., greater than 80 mol%), moldability tends to decrease.

[0138] The number average molecular weight of the polyfunctional vinyl aromatic copolymer (number average molecular weight measured using GPC in terms of standard polystyrene) is preferably 300 to 100,000, more preferably 400 to 50,000, and even more preferably 500 to 10,000. If the molecular weight of the polyfunctional vinyl aromatic copolymer is too low (for example, Mn is less than 300), the amount of monofunctional copolymer component contained in the polyfunctional vinyl aromatic copolymer increases, which tends to reduce the heat resistance of the cured product. On the other hand, if the molecular weight of the polyfunctional vinyl aromatic copolymer is too high (for example, Mn is more than 100,000), gel tends to be easily formed and the viscosity increases, which tends to reduce moldability. The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (weight average molecular weight measured using GPC in terms of standard polystyrene) to Mn of the polyfunctional vinyl aromatic copolymer, is preferably 100.0 or less, more preferably 50.0 or less, even more preferably 1.5 to 30.0, and particularly preferably 2.0 to 20.0. If the molecular weight distribution (Mw / Mn) is too large (for example, if Mw / Mn exceeds 100.0), the processing characteristics of the polyfunctional vinyl aromatic copolymer (B) tend to deteriorate, and gel tends to form.

[0139] The divinylaromatic compound is thought to play a role in forming a branched structure to impart multifunctionality, and also to function as a cross-linking component to impart heat resistance when the resulting multifunctional vinyl aromatic copolymer is thermally cured. Examples of the divinylaromatic compound are not limited as long as they are aromatic compounds having two vinyl groups, but preferred examples include divinylbenzene (including positional isomers or mixtures thereof), divinylnaphthalene (including positional isomers or mixtures thereof), and divinylbiphenyl (including positional isomers or mixtures thereof). These compounds may be used alone or in combination of two or more. From the viewpoint of moldability, the divinylaromatic compound is more preferably divinylbenzene (m-isomer, p-isomer, or a mixture of positional isomers thereof).

[0140] Examples of the monovinyl aromatic compound include styrene and monovinyl aromatic compounds other than styrene. As the monovinyl aromatic compound, for example, it is desirable to use styrene as an essential component and a monovinyl aromatic compound other than styrene in combination.

[0141] It is believed that the styrene, as a monomer component, serves to impart excellent low dielectric properties and thermal oxidative degradation resistance to the polyfunctional vinyl aromatic copolymer, and also serves as a chain transfer agent to control the molecular weight of the polyfunctional vinyl aromatic copolymer. In addition, the monovinyl aromatic compound other than styrene is believed to improve the solvent solubility and processability of the polyfunctional vinyl aromatic copolymer.

[0142] Examples of the monovinyl aromatic compound other than styrene are not limited as long as they are aromatic compounds other than styrene having one vinyl group, but include vinyl aromatic compounds such as vinylnaphthalene and vinylbiphenyl; and nuclear alkyl-substituted vinyl aromatic compounds such as o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylvinylbenzene, m-ethylvinylbenzene, and p-ethylvinylbenzene. The monovinyl aromatic compound other than styrene is preferably ethylvinylbenzene (including each positional isomer or a mixture thereof), ethylvinylbiphenyl (including each positional isomer or a mixture thereof), or ethylvinylnaphthalene (including each positional isomer or a mixture thereof) because they prevent gelation of the polyfunctional vinyl aromatic copolymer, are highly effective in improving solvent solubility and processability, are low cost, and are easily available. Furthermore, the monovinyl aromatic compound other than styrene is preferably ethylvinylbenzene (m-isomer, p-isomer, or a mixture of these positional isomers) from the viewpoints of dielectric properties and cost.

[0143] In addition to the divinyl aromatic compound and the monovinyl aromatic compound, one or more other monomer components such as a trivinyl aromatic compound, a trivinyl aliphatic compound, a divinyl aliphatic compound, or a monovinyl aliphatic compound may be used in the polyfunctional vinyl aromatic copolymer, and structural units (e) derived therefrom may be introduced within a range that does not impair the effects of the present invention.

[0144] Examples of the other monomer components include 1,3,5-trivinylbenzene, 1,3,5-trivinylnaphthalene, 1,2,4-trivinylcyclohexane, ethylene glycol diacrylate, butadiene, 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, and triallyl isocyanurate. These can be used alone or in combination of two or more.

[0145] The molar fraction of the other monomer component relative to the sum of all monomer components is preferably less than 30 mol %. That is, the molar fraction of the structural unit (e) derived from the other monomer component relative to the sum of all monomer components constituting the copolymer [the sum of the structural unit (c) derived from the divinyl aromatic compound, the structural unit (d) derived from the monovinyl aromatic compound, and the structural unit (e) derived from the other monomer components] is preferably less than 30 mol %.

[0146] (Inorganic Filler) As described above, the first resin composition may contain an inorganic filler. The inorganic filler is not particularly limited, and examples thereof include metal oxide fillers, metal hydroxide fillers, molybdate fillers, nitride fillers, titanate fillers, magnesium carbonate fillers such as anhydrous magnesium carbonate fillers, calcium carbonate fillers, quartz glass fillers, talc fillers, aluminum borate fillers, and barium sulfate fillers. Examples of the metal oxide fillers include silica fillers, alumina fillers, titanium oxide fillers, magnesium oxide fillers, and mica fillers. Examples of the silica fillers include crushed silica, spherical silica such as fused spherical silica, and silica particles, with spherical silica being preferred. Examples of the metal hydroxide fillers include magnesium hydroxide fillers and aluminum hydroxide fillers. Examples of the molybdate fillers include zinc molybdate fillers, calcium molybdate fillers, and magnesium molybdate fillers. Examples of the nitride filler include aluminum nitride filler and boron nitride filler. Examples of the titanate filler include barium titanate filler, strontium titanate filler, calcium titanate filler, and aluminum titanate filler. Among these, silica filler, quartz glass filler, and magnesium oxide filler are preferred as the inorganic filler, silica filler is more preferred, and spherical silica such as fused spherical silica is even more preferred. The inorganic filler may be used alone or in combination of two or more. The inorganic filler may be, for example, a talc filler supporting molybdate in the molybdate filler.

[0147] The inorganic filler may be a surface-treated or untreated inorganic filler. Examples of the surface treatment include treatment with a silane coupling agent.

[0148] The silane coupling agent is not particularly limited, and examples thereof include silane coupling agents having at least one functional group selected from the group consisting of vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group. That is, the silane coupling agent has at least one reactive functional group selected from vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group, and further includes compounds having a hydrolyzable group such as a methoxy group or an ethoxy group.

[0149] Examples of the silane coupling agent include those having a vinyl group, such as vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the silane coupling agent include those having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane. Examples of the silane coupling agent include those having a methacryloyl group, such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. Examples of the silane coupling agent include those having an acryloyl group, such as 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent include those having a phenylamino group, such as N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane.

[0150] The average particle size of the inorganic filler is not particularly limited, and is preferably 0.05 to 10 μm, and more preferably 0.1 to 8 μm. Here, the average particle size refers to the volume average particle size. The volume average particle size can be measured, for example, by a laser diffraction method.

[0151] (Content) The content of the inorganic filler is preferably 30 to 200 parts by mass, more preferably 70 to 150 parts by mass, and even more preferably 80 to 130 parts by mass, relative to 100 parts by mass of the resin components contained in the first resin composition (e.g., the sum of the polyphenylene ether compound and the hydrocarbon-based compound). Furthermore, the content of the inorganic filler is preferably 0 to 67% by mass, more preferably 41 to 60% by mass, and even more preferably 44 to 57% by mass, relative to the total amount of the resin composition. When the content of the inorganic filler is within the above range, a metal-clad laminate having a low thermal expansion coefficient, excellent processability, and excellent metal foil adhesion can be obtained while maintaining excellent dielectric properties.

[0152] (Other Components) The first resin composition may contain, as necessary, components (other components) other than the polyphenylene ether compound, the hydrocarbon compound, and the inorganic filler, as long as the effects of the present invention are not impaired. Examples of the other components contained in the first resin composition include a reactive compound capable of reacting with the polyphenylene ether compound and the hydrocarbon compound, a thermoplastic resin (thermoplastic elastomer), a reaction initiator, a curing accelerator, a catalyst, a polymerization retarder, a polymerization inhibitor, a dispersant, a leveling agent, a silane coupling agent, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a dye or pigment, and additives such as a lubricant.

[0153] The first resin composition may contain the reactive compound. The reactive compound is a compound different from the polyphenylene ether compound and the hydrocarbon-based compound, and examples thereof include compounds that react with the polyphenylene ether compound and the hydrocarbon-based compound. Examples of the reactive compound include, but are not limited to, styrene, styrene derivatives, acrylate compounds having an acryloyl group in the molecule, methacrylate compounds having a methacryloyl group in the molecule, vinyl compounds having a vinyl group in the molecule, maleimide compounds having a maleimide group in the molecule, modified maleimide compounds, alkenyl isocyanurate compounds, acenaphthylene compounds, cyanate ester compounds, and active ester compounds. The reactive compounds may be used alone or in combination of two or more.

[0154] Examples of the styrene derivatives include bromostyrene and dibromostyrene.

[0155] Examples of the acrylate compound include polyfunctional acrylate compounds having two or more acryloyl groups in the molecule, such as tricyclodecane dimethanol diacrylate.

[0156] Examples of the methacrylate compound include polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule, such as tricyclodecane dimethanol diacrylate.

[0157] Examples of the vinyl compound include polyfunctional vinyl compounds having two or more vinyl groups in the molecule, such as divinylbenzene and polybutadiene.

[0158] Examples of the maleimide compound include a monofunctional maleimide compound having one maleimide group in the molecule and a polyfunctional maleimide compound having two or more maleimide groups in the molecule. Examples of the modified maleimide compound include a modified maleimide compound in which a portion of the molecule is modified with an amine, a modified maleimide compound in which a portion of the molecule is modified with a silicone, and a modified maleimide compound in which a portion of the molecule is modified with both an amine and a silicone.

[0159] The alkenyl isocyanurate compound may be any compound having an isocyanurate structure and an alkenyl group in the molecule, and examples thereof include trialkenyl isocyanurate compounds such as triallyl isocyanurate (TAIC).

[0160] The acenaphthylene compound is a compound having an acenaphthylene structure in the molecule. 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.

[0161] The cyanate ester compound is a compound having a cyanate group in the molecule, and examples thereof include 2,2-bis(4-cyanatephenyl)propane, bis(3,5-dimethyl-4-cyanatephenyl)methane, and 2,2-bis(4-cyanatephenyl)ethane.

[0162] The active ester compound is a compound having an ester group with high reactivity in the molecule, and examples thereof include benzenecarboxylic acid active ester, benzenedicarboxylic acid active ester, benzenetricarboxylic acid active ester, benzenetetracarboxylic acid active ester, naphthalenecarboxylic acid active ester, naphthalenedicarboxylic acid active ester, naphthalenetricarboxylic acid active ester, naphthalenetetracarboxylic acid active ester, fluorenecarboxylic acid active ester, fluorenedicarboxylic acid active ester, fluorenetricarboxylic acid active ester, and fluorenetetracarboxylic acid active ester.

[0163] As described above, the first resin composition may contain a reaction initiator. The curing reaction can proceed even if the first 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 accelerate the curing reaction of the first resin composition, and examples thereof include peroxides and organic azo compounds. Examples of peroxides include dicumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, and benzoyl peroxide. Examples of organic azo compounds include azobisisobutyronitrile. Furthermore, if necessary, a metal carboxylate or the like can be used in combination. This can further accelerate the curing reaction. Among these, α,α'-bis(t-butylperoxy-m-isopropyl)benzene is preferably used. Because α,α'-bis(t-butylperoxy-m-isopropyl)benzene has a relatively high reaction initiation temperature, 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, because α,α'-bis(t-butylperoxy-m-isopropyl)benzene has low volatility, 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.

[0164] As described above, the first resin composition may contain a thermoplastic elastomer. Examples of the thermoplastic elastomer include styrene-based copolymers. Examples of the styrene-based copolymer include 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 versions thereof. When the first resin composition contains the thermoplastic elastomer, the thermoplastic elastomer preferably has a number average molecular weight (measured using GPC in terms of standard polystyrene) of more than 100,000. The thermoplastic elastomers listed above may be used alone or in combination of two or more.

[0165] As described above, the first resin composition may contain a curing accelerator. The curing accelerator is not particularly limited as long as it can accelerate the curing reaction of the first resin composition. Specific examples of the curing accelerator include imidazoles and their derivatives, organophosphorus compounds, amines such as secondary amines and tertiary amines, quaternary ammonium salts, organoboron compounds, and metal soaps. Examples of the imidazoles include 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenyl-4-methylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole. Examples of the organophosphorus compounds include triphenylphosphine, diphenylphosphine, phenylphosphine, tributylphosphine, and trimethylphosphine. Examples of the amines include dimethylbenzylamine, triethylenediamine, triethanolamine, and 1,8-diaza-bicyclo(5,4,0)undecene-7 (DBU). Examples of the quaternary ammonium salts include tetrabutylammonium bromide. Examples of the organoboron compounds include tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate, and tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium ethyltriphenylborate. The metal soap refers to a fatty acid metal salt, and may be either a linear fatty acid metal salt or a cyclic fatty acid metal salt. Specific examples of the metal soap include linear fatty acid metal salts and cyclic fatty acid metal salts having 6 to 10 carbon atoms. More specifically, examples of the curing accelerator include aliphatic metal salts composed of linear fatty acids such as stearic acid, lauric acid, ricinoleic acid, and octylic acid, or cyclic fatty acids such as naphthenic acid, and metals such as lithium, magnesium, calcium, barium, copper, and zinc. For example, zinc octylate is included. The curing accelerators may be used alone or in combination of two or more.

[0166] As described above, the first resin composition may contain a silane coupling agent. The silane coupling agent may be contained in the first resin composition, or may be contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler contained in the first resin composition. Among these, it is preferable that the silane coupling agent be contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler. It is more preferable that the silane coupling agent be contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler, and that the silane coupling agent be further contained in the first resin composition. In addition, in the case of a prepreg, the prepreg may contain the silane coupling agent that has been surface-treated in advance on a fibrous substrate. Examples of the silane coupling agent include the same silane coupling agents as those used in the surface treatment of the inorganic filler described above.

[0167] As described above, the first resin composition may contain a flame retardant. The inclusion of a flame retardant can enhance the flame retardancy of the cured product of the first resin composition. The flame retardant is not particularly limited. Specifically, in fields where halogen-based flame retardants such as bromine-based flame retardants are used, for example, ethylene dipentabromobenzene, ethylene bistetrabromoimide, decabromodiphenyl oxide, tetradecabromodiphenoxybenzene, and bromostyrene-based compounds that react with the polymerizable compound, which have melting points of 300°C or higher, are preferred. It is believed that the use of a halogen-based flame retardant can suppress halogen elimination at high temperatures and reduce deterioration in heat resistance. Furthermore, in fields requiring halogen-free materials, phosphorus-containing flame retardants (phosphorus-based flame retardants) are sometimes used. Examples of the phosphorus-based flame retardant include, but are not limited to, phosphate ester-based flame retardants, phosphazene-based flame retardants, bisdiphenylphosphine oxide-based flame retardants, and phosphinate-based flame retardants. A specific example of a phosphate ester-based flame retardant is a condensed phosphate ester of dixylenyl phosphate. A specific example of a phosphazene-based flame retardant is phenoxyphosphazene. A specific example of a bisdiphenylphosphine oxide-based flame retardant is xylylenebisdiphenylphosphine oxide. A specific example of a phosphinate-based flame retardant is, for example, a metal phosphinate salt of an aluminum dialkylphosphinate. As the flame retardant, each of the exemplified flame retardants may be used alone or in combination of two or more.

[0168] <Second Insulating Layer> The second insulating layer is not particularly limited as long as it is an insulating layer containing a cured product of a second resin composition containing at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

[0169] The second resin composition is not particularly limited as long as it is a resin composition containing at least one of a polyphenylene ether compound and a hydrocarbon-based compound, as described above. The second resin composition may be a thermoplastic resin composition or a thermosetting resin composition, as long as it contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

[0170] The polyphenylene ether compound is not particularly limited as long as it has a polyphenylene ether chain in the molecule. The polyphenylene ether compound may be, for example, a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule, or a polyphenylene ether compound not having a carbon-carbon unsaturated double bond in the molecule (such as an unmodified polyphenylene ether compound). The polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule is not particularly limited as long as it has a carbon-carbon unsaturated double bond in the molecule. Examples of the polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule include those exemplified as the polyphenylene ether compounds contained in the first resin composition.

[0171] The hydrocarbon-based compound is not particularly limited, and may be a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in the molecule, or may be a hydrocarbon-based compound not having a carbon-carbon unsaturated double bond in the molecule. The hydrocarbon-based compound having a carbon-carbon unsaturated double bond in the molecule is not particularly limited, as long as it is a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in the molecule, and examples thereof include those exemplified as the hydrocarbon-based compounds contained in the first resin composition. The hydrocarbon-based compound not having a carbon-carbon unsaturated double bond in the molecule is not particularly limited, as long as it is a hydrocarbon-based compound not having a carbon-carbon unsaturated double bond in the molecule. Examples of the hydrocarbon-based compound include those exemplified as the thermoplastic resin (thermoplastic elastomer) contained in the first resin composition. The thermoplastic resin may be one having a carbon-carbon unsaturated double bond in the molecule, or one not having a carbon-carbon unsaturated double bond in the molecule. Among the thermoplastic resins, those having a carbon-carbon unsaturated double bond in the molecule are examples of hydrocarbon compounds having the carbon-carbon unsaturated double bond in the molecule, and among the thermoplastic resins, those not having a carbon-carbon unsaturated double bond in the molecule (for example, fully hydrogenated ones) are examples of hydrocarbon compounds not having a carbon-carbon unsaturated double bond in the molecule. The hydrocarbon compounds preferably include both hydrocarbon compounds having a carbon-carbon unsaturated double bond in the molecule and hydrocarbon compounds not having a carbon-carbon unsaturated double bond in the molecule.

[0172] The second resin composition may contain an inorganic filler. When the second resin composition contains an inorganic filler, the inorganic filler is not particularly limited, and examples thereof include those exemplified as the inorganic fillers contained in the first resin composition.

[0173] The second resin composition may contain components (other components) other than the polyphenylene ether compound, the hydrocarbon compound, and the inorganic filler. Specifically, the second resin composition preferably further contains a thermoplastic elastomer.

[0174] When the second resin composition contains the inorganic filler, the content of the inorganic filler is preferably 250 parts by mass or less, more preferably 30 to 170 parts by mass, and even more preferably 60 to 150 parts by mass, relative to 100 parts by mass of the resin components contained in the second resin composition (e.g., the total of the polyphenylene ether compound, the hydrocarbon compound, and the thermoplastic resin). Furthermore, the content of the inorganic filler is preferably 72% by mass, more preferably 23 to 63% by mass, and even more preferably 37 to 60% by mass, relative to the total amount of the resin composition. When the content of the inorganic filler is within the above range, a metal-clad laminate having a low coefficient of thermal expansion, excellent processability, and excellent metal foil adhesion can be obtained while maintaining excellent dielectric properties.

[0175] <Metal Foil> The metal foil 13 may be any metal foil capable of being used as wiring for a wiring board, and examples thereof include copper foil and aluminum foil. Copper foil is preferred for purposes such as increasing signal transmission speed. When the metal foil is thin, it may be a carrier-attached copper foil equipped with a release layer and a carrier to improve handling. The copper foil may contain copper, and may be made of, for example, copper or a copper alloy. Examples of copper alloys include alloys containing copper and at least one element selected from the group consisting of nickel, phosphorus, tungsten, arsenic, molybdenum, chromium, cobalt, and zinc. The metal foil 13 may be a surface-treated metal foil. The surface-treated metal foil may be surface-treated on both sides or on one side. Furthermore, if one side of the metal foil is surface-treated, it is preferable that the surface-treated surface contacts the second insulating layer. Examples of surface treatments include silane coupling agent treatment, roughening treatment, heat-resistant treatment, and rust-proofing treatment. The metal foil 13 may be subjected to one of these surface treatments alone, or to a combination of two or more of them. The silane coupling agent used in the silane coupling agent treatment is not particularly limited, and examples thereof include the same silane coupling agent as that contained in the first resin composition. Examples of the roughening treatment, heat resistance treatment, and rust prevention treatment include those generally used for roughening treatment, heat resistance treatment, and rust prevention treatment, respectively, on metal foils.

[0176] <Thickness> The thickness of the first insulating layer 11 is not particularly limited, but is preferably 20 to 1600 μm, more preferably 40 to 1000 μm. The thickness of the second insulating layer 12 is 1 to 60 μm, preferably 1 to 50 μm, and more preferably 5 to 30 μm. The thickness of the metal foil 13 varies depending on the performance required of the final wiring board, and is not particularly limited. The thickness of the metal foil 13 can be appropriately set depending on the desired purpose, and is preferably, for example, 0.2 to 70 μm. The thickness of the metal-clad laminate 10 is not particularly limited, but is preferably 30 to 1700 μm, more preferably 50 to 1100 μm. The thickness of the second insulating layer 12 is preferably 7% or less of the thickness of the metal-clad laminate 10. The thickness of the second insulating layer 12 is preferably 6.6% or less of the thickness of the first insulating layer 11. If the first insulating layer 11 is too thin, it tends to be difficult to maintain a low coefficient of thermal expansion. This is thought to be due to the fact that the first insulating layer 11 is relatively thin compared to the thickness of the second insulating layer 12. Furthermore, if the first insulating layer 11 is too thick, even if the thermal expansion coefficient is low, it tends to be difficult to fully achieve the effects of providing the second insulating layer 12. Specifically, it tends to be difficult to sufficiently improve processability and adhesion to the metal foil. Furthermore, if the second insulating layer 12 is too thin, it tends to be difficult to fully achieve the effects of providing the second insulating layer 12, as in the case where the first insulating layer 11 is too thick. Specifically, it tends to be difficult to sufficiently improve processability and adhesion to the metal foil. If the second insulating layer 12 is too thick, although it is possible to sufficiently improve processability and adhesion to the metal foil, the metal-clad laminate tends to become too thick and it tends to be difficult to maintain a low coefficient of thermal expansion. Therefore, in a metal-clad laminate such as the metal-clad laminate 10, in which the second insulating layer 12 is laminated on the first insulating layer 11 and the metal foil 13 is further laminated on top of it, by setting the thickness of each layer within the above range, it is possible to improve processability and adhesion of the metal foil while maintaining low dielectric constant.

[0177] <Manufacturing Method> The method for manufacturing the metal-clad laminate 10 is not particularly limited as long as it can produce the metal-clad laminate 10. For example, the method for manufacturing the metal-clad laminate 10 includes first heating and curing a prepreg containing the first resin composition or a semi-cured product of the first resin composition to form the first insulating layer 11. Then, a film containing the second resin composition or a semi-cured product of the second resin composition is laminated on one or both sides of the first insulating layer 11. Then, a metal foil 13 is laminated on this film. The resulting laminate is then heated and pressure molded to form an integrated laminate. This results in the metal-clad laminate 10. The film becomes the second insulating layer 12 in the metal-clad laminate 10. In addition, in the method for manufacturing the metal-clad laminate 10, instead of laminating a film and then laminating a metal foil, a film with a metal foil (metal foil with resin) may be used. Specifically, a resin-coated metal foil is first prepared, comprising a prepreg containing the first resin composition or a semi-cured product of the first resin composition, a resin layer containing the second resin composition or a semi-cured product of the second resin composition, and a metal foil. Then, the resin-coated metal foil, each in a semi-cured state, is placed on one or both sides of the prepreg so that the resin layer of the resin-coated metal foil contacts the prepreg. The resulting laminate is then heated and pressurized to form an integrated laminate. This process yields the metal-clad laminate 10. The prepreg becomes the first insulating layer 11 of the metal-clad laminate 10, the resin layer of the resin-coated metal foil becomes the second insulating layer 12 of the metal-clad laminate 10, and the metal foil (copper foil) of the resin-coated metal foil becomes the metal foil 13 of the metal-clad laminate 10. The semi-cured product refers to a resin composition that has been partially cured to the extent that it can be further cured. In other words, the semi-cured product refers to a resin composition that has been semi-cured (B-staged). For example, when a resin composition is heated, the viscosity initially gradually decreases as it melts, and then hardening begins and the viscosity gradually increases. In such a case, the semi-cured state may be the state between when the viscosity starts to gradually decrease and when the composition is completely hardened.The method for producing the prepreg is not particularly limited, and examples thereof include a method in which the first resin composition, for example, the first resin composition prepared in a varnish form, is impregnated into the fibrous substrate, and then drying. The method for producing the resin-coated metal foil is not particularly limited, and examples thereof include a method in which the second resin composition, for example, the second resin composition prepared in a varnish form, is applied to a metal foil (such as a copper foil), and then heating and drying.

[0178] [Wiring Board] A wiring board 20 according to another embodiment of the present invention includes the first insulating layer 11, the second insulating layer 12, and the wiring 14, as shown in Fig. 2. The wiring board 20 may include the second insulating layer 12 laminated on one side of the first insulating layer 11, or may include the second insulating layer 12 laminated on both sides of the first insulating layer 11, as shown in Fig. 2. That is, the wiring board 20 includes the first insulating layer 11 containing a cured product of a first resin composition and a fibrous base material containing liquid crystalline aromatic polyester fibers, the second insulating layer 12 containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer 11, and the wiring 14 formed on the second insulating layer 12. In the wiring board 20, similarly to the metal-clad laminate 10, the thickness of the second insulating layer 12 is 1 to 60 μm, and the second resin composition includes at least one of a polyphenylene ether compound having a carbon-carbon unsaturated double bond in its molecule and a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in its molecule. Examples of the wiring 14 include wiring formed by partially removing the metal foil 13 provided in the metal-clad laminate 10. That is, examples of the wiring board 20 include wiring 14 formed by processing the metal foil 13 provided in the metal-clad laminate 10, the second insulating layer 12, and the first insulating layer 11. The wiring board 20 according to this embodiment is a wiring board that maintains excellent low dielectric properties, has a low coefficient of thermal expansion, and exhibits excellent wiring adhesion (adhesion between the wiring and the insulating layer), and is a wiring board in which the occurrence of defects during wiring board manufacturing is sufficiently suppressed.

[0179] The method for manufacturing the wiring board 20 is not particularly limited as long as it can manufacture the wiring board 20. Examples of methods for manufacturing the wiring board 20 include a method of manufacturing a wiring board in which wiring is provided as a circuit on the surface of the second insulating layer 12 by forming wiring by etching the metal foil 13 on the surface of the metal-clad laminate 10, etc. That is, the wiring board 20 is obtained by forming a circuit by partially removing the metal foil 13 on the surface of the metal-clad laminate 10. In addition to the above methods, examples of methods for forming a circuit include circuit formation by a semi-additive process (SAP) or a modified semi-additive process (MSAP).

[0180] As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

[0181] A metal-clad laminate according to a first aspect of the present invention comprises a first insulating layer containing a cured product of a first resin composition and a fibrous base material including liquid crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer; and a metal foil laminated on the second insulating layer, wherein the thickness of the second insulating layer is 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

[0182] A metal-clad laminate according to a second aspect of the present invention is a metal-clad laminate according to the first aspect of the present invention, wherein the first resin composition contains at least one of a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule and a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in the molecule.

[0183] A metal-clad laminate according to a third aspect of the present invention is a metal-clad laminate according to the first or second aspect of the present invention, in which the thickness of the second insulating layer is 7% or less of the thickness of the metal-clad laminate.

[0184] A metal-clad laminate according to a fourth aspect of the present invention is a metal-clad laminate according to any one of the first to third aspects of the present invention, wherein the first resin composition contains a silica filler.

[0185] A metal-clad laminate according to a fifth aspect of the present invention is a metal-clad laminate according to any one of the first to fourth aspects of the present invention, wherein the fibrous base material has been subjected to a surface treatment by plasma treatment.

[0186] A wiring board according to a sixth aspect of the present invention comprises a first insulating layer containing a cured product of a first resin composition and a fibrous base material including liquid crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer; and wiring formed on the second insulating layer, wherein the thickness of the second insulating layer is 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

[0187] According to the present invention, it is possible to provide a metal-clad laminate and a wiring board that maintain excellent low dielectric properties, have a low coefficient of thermal expansion, and are excellent in processability and metal foil adhesion. Furthermore, according to the present invention, it is possible to provide a wiring board that maintains excellent low dielectric properties, has a low coefficient of thermal expansion, and is excellent in wiring adhesion, and in which the occurrence of defects during wiring board manufacturing is sufficiently suppressed.

[0188] 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.

[0189] Examples 1 to 10 and Comparative Examples 1 to 3 The first resin composition and the second resin composition used in the examples and comparative examples will now be described.

[0190] <First Resin Composition> First, each component used in preparing the first resin composition used to form the first insulating layer will be described.

[0191] (Hydrocarbon Compound) Hydrocarbon compound: A polyfunctional vinyl aromatic copolymer obtained by the following reaction.

[0192] 3.0 mol (390.6 g) of divinylbenzene, 1.8 mol (229.4 g) of ethylvinylbenzene, 10.2 mol (1066.3 g) of styrene, and 15.0 mol (1532.0 g) of n-propyl acetate were charged into a 5.0 L reactor, and 600 mmol of a boron trifluoride diethyl ether complex was added at 70 ° C., followed by a reaction for 4 hours. Thereafter, to terminate the reaction, an aqueous sodium bicarbonate solution was added to the resulting reaction solution, and the oil layer was washed three times with pure water. The mixture was then subjected to vacuum degassing at 60 ° C., and a solid (polymer) was recovered. The resulting solid was weighed, confirming that 896.7 g was obtained.

[0193] The structure of the solid (polymer) obtained above was analyzed using a nuclear magnetic resonance spectrometer, JNM-LA600, manufactured by JEOL Ltd. １３ C-NMR and １ The measurement was carried out by H-NMR analysis. １ was used, and the resonance line of tetramethylsilane was used as an internal standard. １３ C-NMR and １ In addition to the H-NMR measurement results, the amount of a specific structural unit introduced was calculated from data on the total amount of each structural unit introduced into the copolymer obtained by gas chromatography (GC) analysis, and the amount of pendant vinyl group units contained in the polyfunctional vinyl aromatic copolymer was calculated from the amount of the specific structural unit introduced at the terminal and the number average molecular weight obtained by the GPC measurement.

[0194] The resulting solid was subjected to the above-mentioned １３ C-NMR and １By performing H-NMR analysis, resonance lines derived from each monomer unit were observed. Furthermore, based on the results of NMR measurement and GC analysis, it was found that this solid was the polyfunctional vinyl aromatic copolymer. Based on the results of NMR measurement and GC analysis, the constituent units of this polyfunctional vinyl aromatic copolymer were calculated as follows: structural units derived from divinylbenzene: 30.4 mol% (33.1 mass%), structural units derived from styrene: 57.4 mol% (52.7 mass%), structural units derived from ethylvinylbenzene: 12.2 mol% (14.2 mass%), and structural units with residual vinyl groups derived from divinylbenzene: 23.9 mol% (25.9 mass%).

[0195] The molecular weight and molecular weight distribution of the obtained solid (polyfunctional vinyl aromatic copolymer) were measured using GPC (HLC-8120GPC manufactured by Tosoh Corporation) with tetrahydrofuran as the solvent, a flow rate of 1.0 ml / min, a column temperature of 38°C, and a calibration curve based on monodisperse polystyrene. As a result, the number average molecular weight Mn of the obtained solid was 2980, the weight average molecular weight Mw was 41300, and Mw / Mn was 13.9.

[0196] PPE (polyphenylene ether compound): A polyphenylene ether compound having a vinylbenzyl group (ethenylbenzyl group) at the end (a modified polyphenylene ether compound obtained by reacting polyphenylene ether with chloromethylstyrene).

[0197] Specifically, it is a modified polyphenylene ether compound obtained by the following reaction.

[0198] First, 200 g of polyphenylene ether (SA90 manufactured by SABIC Innovative Plastics, 2 terminal hydroxyl groups, weight average molecular weight Mw 1700), 30 g of a 50:50 mass ratio mixture of p-chloromethylstyrene and m-chloromethylstyrene (chloromethylstyrene: CMS manufactured by Tokyo Chemical Industry Co., Ltd.), 1.227 g of tetra-n-butylammonium bromide as a phase transfer catalyst, and 400 g of toluene were charged into a 1-liter three-neck flask equipped with a temperature controller, a stirrer, a cooling device, and a dropping funnel, and the mixture was stirred. The polyphenylene ether, chloromethylstyrene, and tetra-n-butylammonium bromide were stirred until they were dissolved in toluene. The mixture was gradually heated, and finally heated until the liquid temperature reached 75 ° C. Then, an aqueous sodium hydroxide solution (20 g sodium hydroxide / 20 g water) was added dropwise to the solution as an alkali metal hydroxide over 20 minutes. The mixture was then stirred at 75°C for an additional 4 hours. Next, the contents of the flask were neutralized with 10% by mass hydrochloric acid, and a large amount of methanol was added. This caused a precipitate to form in the liquid in the flask. That is, the product contained in the reaction solution in the flask was reprecipitated. The precipitate was then filtered, washed three times with a mixture of methanol and water in a mass ratio of 80:20, and then dried under reduced pressure at 80°C for 3 hours.

[0199] The obtained solid is １ H-NMR (400MHz, CDCl ３ , TMS). As a result of NMR measurement, a peak derived from a vinylbenzyl group (ethenylbenzyl group) was confirmed at 5 to 7 ppm. This confirmed that the obtained solid was a modified polyphenylene ether compound having a vinylbenzyl group (ethenylbenzyl group) as the substituent at the molecular end in the molecule. Specifically, it was confirmed that it was an ethenylbenzylated polyphenylene ether. This modified polyphenylene ether compound obtained was represented by the above formula (52), in which Y in formula (52) is a dimethylmethylene group (represented by formula (50), and R in formula (50) is a methyl group. ３３ and R ３４ is a methyl group), Ar is a phenylene group, and R１ ~R ３ was a hydrogen atom and p was 1.

[0200] The number of terminal functional groups of the modified polyphenylene ether was measured as follows.

[0201] First, the modified polyphenylene ether was accurately weighed. The weight at that time was designated X (mg). Then, this weighed modified polyphenylene ether was dissolved in 25 mL of methylene chloride, and 100 μL of a 10 mass% ethanol solution of tetraethylammonium hydroxide (TEAH) (TEAH:ethanol (volume ratio) = 15:85) was added to the solution, and the absorbance (Abs) at 318 nm was measured using a UV spectrophotometer (UV-1600 manufactured by Shimadzu Corporation). Then, from the measurement results, the number of terminal hydroxyl groups of the modified polyphenylene ether was calculated using the following formula.

[0202] Residual OH amount (μmol / g) = [(25×Abs) / (ε×OPL×X)]×10 ６ Here, ε is the extinction coefficient and is 4700 L / mol·cm, and OPL is the cell optical path length and is 1 cm.

[0203] The calculated residual OH amount (number of terminal hydroxyl groups) of the modified polyphenylene ether was almost zero, which indicated that the hydroxyl groups of the polyphenylene ether before modification were almost entirely modified. This indicated that the decrease from the number of terminal hydroxyl groups of the polyphenylene ether before modification was the number of terminal hydroxyl groups of the polyphenylene ether before modification. In other words, it was found that the number of terminal hydroxyl groups of the polyphenylene ether before modification was the number of terminal functional groups of the modified polyphenylene ether. In other words, the number of terminal functional groups was two.

[0204] The intrinsic viscosity (IV) of the modified polyphenylene ether was measured in methylene chloride at 25° C. Specifically, the intrinsic viscosity (IV) of the modified polyphenylene ether was measured by using a viscometer (AVS500 Visco System manufactured by Schott) to measure a 0.18 g / 45 ml methylene chloride solution (liquid temperature 25° C.). As a result, the intrinsic viscosity (IV) of the modified polyphenylene ether was 0.086 dl / g.

[0205] The molecular weight distribution of the modified polyphenylene ether was measured using GPC. The weight average molecular weight (Mw) was calculated from the molecular weight distribution. The Mw was found to be 1,900.

[0206] (Inorganic filler) Inorganic filler: fused spherical silica (GT grade 3 μm product manufactured by Denka Co., Ltd.)

[0207] (Fibrous substrate) Fibrous substrate: A fibrous substrate containing liquid crystalline aromatic polyester fiber (HT0150 manufactured by Kuraray Co., Ltd.) was irradiated with oxygen gas as a raw material gas at a plasma irradiation dose of 0.5 W / cm in watt density. ２ The fibrous substrate was subjected to an oxygen gas plasma treatment for 10 minutes. The ratio (b / a) of this fibrous substrate was measured by the method described below and was found to be 0.32.

[0208] The ratio (b / a) of the fibrous substrate was measured as follows. First, a surface X-ray analysis was performed on the surface of the fibrous substrate using an X-ray photoelectron spectrometer (XPS, PHI 5000 Versaprobe manufactured by ULVAC-PHI, Inc.). This surface X-ray analysis was performed by irradiating the surface of the fibrous substrate with X-rays under the following conditions from a direction perpendicular to the surface under vacuum, adjusting the irradiation height, and performing the analysis at a position where photoelectrons emitted due to ionization of the sample could be detected with the strongest intensity.

[0209] X-ray used: Monochrome Al-Kα ray X-ray beam diameter: Approximately 100 μmφ (25 W, 15 kV) Analysis area: Approximately 100 μmφ The spectrum obtained by the surface X-ray analysis was analyzed using analysis software provided with the apparatus (quantitative conversion using a relative sensitivity coefficient incorporated in the analysis software, etc.), to measure the ratio (b / a).

[0210] <Prepreg> First, the hydrocarbon compound was added to toluene to a solids concentration of 30% by mass, and mixed. The mixture was stirred for 60 minutes. Thereafter, an inorganic filler was added to the resulting liquid to obtain the composition (parts by mass) shown in Table 1, and the inorganic filler was dispersed using a bead mill. This resulted in a varnish-like composition (varnish).

[0211] Next, the fibrous base material was impregnated with the obtained varnish and then heated and dried at 100 to 160°C for about 2 to 8 minutes to obtain a prepreg. The thickness of the prepreg after curing was adjusted to about 125 μm (the content of hydrocarbon compounds was about 74% by mass). This prepreg will become the insulating layer in the metal-clad laminate.

[0212] <Second Resin Composition> Hydrocarbon compound: the hydrocarbon compound in the first resin composition (the polyfunctional vinyl aromatic copolymer obtained by the reaction as described above). PPE (polyphenylene ether compound): the PPE in the first resin composition (the modified polyphenylene ether obtained by the reaction as described above).

[0213] (Thermoplastic Resin) Thermoplastic Resin: Thermoplastic elastomer [styrene (ethylene / butylene) styrene copolymer (SEBS), DYNARON 9901P manufactured by JSR Corporation]

[0214] (Inorganic filler) Inorganic filler: fused spherical silica (GT grade 3 μm product manufactured by Denka Co., Ltd.)

[0215] <Resin-Coated Metal Foil> First, the components other than the inorganic filler were mixed to obtain the composition shown in Table 1, and then the mixture was added to toluene and mixed so that the solids concentration of the mixture became 30% by mass. The mixture was stirred for 60 minutes. Thereafter, the inorganic filler was added to the resulting liquid to obtain the composition (parts by mass) shown in Table 1, and the inorganic filler was dispersed using a bead mill. This resulted in a varnish-like composition (varnish).

[0216] Next, a resin-coated metal foil was obtained as follows.

[0217] The obtained varnish was applied to an 18 μm thick copper foil (CF-T4X-SV-18 manufactured by Fukuda Metal Foil & Powder Co., Ltd.) so that the thickness after curing would be the thickness of the second insulating layer shown in Table 1, and then heated and dried at 120° C. for 5 minutes to obtain a resin-coated metal foil (resin-coated copper foil) in which a resin layer was formed on the copper foil. The resin layer in this resin-coated metal foil becomes the second insulating layer in the metal-clad laminate, and the metal foil (copper foil) in the resin-coated metal foil becomes the metal foil in the metal-clad laminate.

[0218] <Metal-clad laminate> Evaluation substrates (metal-clad laminates) were obtained as follows.

[0219] Eight sheets of the resulting prepreg were stacked, and the resulting resin-coated metal foil was placed on both sides of the stack so that the resin layer of the resin-coated metal foil was in contact with the prepreg. This was used as a pressure body and heated to 200°C at a temperature increase rate of 3°C / min, and then heated and pressurized at 200°C for 120 minutes at a pressure of 3 MPa to obtain a metal-clad laminate. The prepreg became the first insulating layer of the metal-clad laminate, and the resin layer of the resin-coated metal foil became the second insulating layer of the metal-clad laminate. The thickness of the second insulating layer in this metal-clad laminate was as shown in Table 1. The thickness of the first insulating layer was 1000 μm.

[0220] The metal-clad laminate according to Comparative Example 1 was a metal-clad laminate not provided with a second insulating layer.

[0221] The metal-clad laminate (evaluation substrate) manufactured as described above was evaluated by the following method.

[0222] (Thermal Expansion Coefficient) An unclad plate obtained by etching the copper foil from the evaluation substrate was used as a test specimen, and the thermal expansion coefficient (%) of the test specimen in the thickness direction (Z direction) was measured by the TMA method (Thermo-mechanical analysis) in accordance with IPC TM-650. Specifically, using a TMA device (TMA7100 manufactured by Hitachi High-Tech Corporation), first, with a load of 98 mN applied to the test specimen, the test specimen was heated from 30 ° C. to 350 ° C. at a heating rate of 20 ° C. / min, and then cooled to room temperature. The test specimen was then heated from 30 ° C. to 350 ° C. at a heating rate of 10 ° C. / min. The average thermal expansion coefficient from 50 to 260 ° C. was calculated from the temperature displacement chart obtained during this second heating. If this average thermal expansion coefficient was 3.5% or less, it was determined to be "passed."

[0223] [Copper Foil Peel Strength] The metal foil (copper foil) was peeled from the evaluation substrate (metal-clad laminate), and the peel strength at this time was measured in accordance with JIS C 6481 (1996). Specifically, the copper foil was peeled from the evaluation substrate at a rate of 50 mm / min using a tensile tester, and the peel strength (N / mm) at this time was measured. This peel strength is the copper foil peel strength, and the higher this is, the higher the adhesion of the metal foil (copper foil). If the measured copper foil peel strength was 0.3 N / mm or more, it was judged to be "passed."

[0224] [Dielectric Properties (Dielectric Loss Tangent Df)] The copper foil was removed from the evaluation board by etching. The resulting board was used as a test piece, and the dielectric loss tangent at 10 GHz was measured using a cavity resonator perturbation method (split cylinder method). Specifically, the dielectric loss tangent (Df) of the test piece at 10 GHz was measured using a network analyzer (N5230A manufactured by Keysight Technologies, Inc.). If the measured dielectric loss tangent was 0.0025 or less, it was determined to have excellent low dielectric properties and was judged to be "passed."

[0225] [Processability] The evaluation board was subjected to router processing using a drill pit (RHM FT, diameter 2.0 mm, length 9.5 mm, manufactured by Union Tool Co., Ltd.) at a rotation speed of 50,000 rpm and a cutting speed (drill movement speed) of 10 mm / sec. The processed surface was visually observed. As a result, if no burrs or copper foil peeling were observed, the board was evaluated as "excellent." If a small amount of burrs was observed but no copper foil peeling was observed, the board was evaluated as "good." If a larger amount of burrs than in the "good" case was observed but no copper foil peeling was observed, the board was evaluated as "passable." If both burrs and copper foil peeling were observed, the board was evaluated as "failable." Processability was evaluated based on the presence or absence of burrs or copper foil peeling on the end surface after such processing, and a result of "excellent," "good," or "passable" was judged to be "pass."

[0226] The results of the above evaluations are shown in Table 1.

[0227]

[0228] Table 1 shows that when a metal-clad laminate (metal-clad laminate according to Examples 1 to 10) is formed by laminating a 1-60 μm thick second insulating layer containing a cured resin composition containing at least one of the polyphenylene ether compound and the hydrocarbon-based compound on a first insulating layer containing a fibrous base material containing liquid crystalline aromatic polyester fibers, and then laminating a metal foil on the second insulating layer, it is possible to obtain a metal-clad laminate with a low coefficient of thermal expansion, excellent processability, and excellent metal foil adhesion while maintaining excellent low dielectric properties. Specifically, the metal-clad laminate according to Examples 1 to 10 has a low dielectric loss tangent and, compared to a laminate without a second insulating layer (Comparative Example 1), it has high copper foil peel strength and high processability. Furthermore, Examples 1 to 10 show that when the second insulating layer is provided, the copper foil peel strength and processability increase as its thickness increases. Furthermore, the metal-clad laminates according to Examples 1 to 10 were found to have low dielectric loss tangents, high copper foil peel strength, and excellent processability compared to the case where the second insulating layer was 0.5 μm (less than 1 μm) (Comparative Example 3). On the other hand, it was also found that as the thickness of the second insulating layer increased, it became difficult to maintain a low thermal expansion coefficient. Specifically, the metal-clad laminates according to Examples 1 to 10 were found to have a lower thermal expansion coefficient compared to the case where the second insulating layer was 70 μm (more than 50 μm) (Comparative Example 2). From these findings, it was found that the metal-clad laminates according to Examples 1 to 10 were able to obtain metal-clad laminates with low thermal expansion coefficients, excellent processability, and excellent metal foil adhesion while maintaining excellent low dielectric properties.

[0229] It was found from Examples 1 to 10 that increasing the amount of inorganic filler contained in the second resin composition, i.e., increasing the amount of inorganic filler contained in the second insulating layer, increased the copper foil peel strength and also improved the processability. Therefore, it was found that the content of the inorganic filler is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, and even more preferably 130 parts by mass or more, per 100 parts by mass of resin components such as the hydrocarbon compound, the polyphenylene ether compound, and the thermoplastic resin.

[0230] This application is based on Japanese Patent Application No. 2024-011283 filed on January 29, 2024, the contents of which are incorporated herein by reference.

[0231] In order to express the present invention, the present invention has been properly and sufficiently described through the embodiments in the above, 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.

[0232] According to the present invention, a metal-clad laminate is provided that maintains excellent low dielectric properties, has a low coefficient of thermal expansion, and is excellent in processability and metal foil adhesion. Also, according to the present invention, a wiring board is provided that maintains excellent low dielectric properties, has a low coefficient of thermal expansion, and is excellent in wiring adhesion, and the occurrence of defects during wiring board production is sufficiently suppressed.

Claims

1. A metal-clad laminate comprising: a first insulating layer containing a cured product of a first resin composition and a fibrous base material containing liquid crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer; and a metal foil laminated on the second insulating layer, wherein the thickness of the second insulating layer is 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

2. The metal-clad laminate according to claim 1, wherein the first resin composition contains at least one of a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule and a hydrocarbon-based compound having a carbon-carbon unsaturated double bond in the molecule.

3. The metal-clad laminate according to claim 1, wherein the thickness of said second insulating layer is 7% or less of the thickness of said metal-clad laminate.

4. The metal-clad laminate according to claim 1, wherein the first resin composition contains a silica filler.

5. The metal-clad laminate according to claim 1, wherein the fibrous substrate has been subjected to a surface treatment by plasma treatment.

6. A wiring board comprising: a first insulating layer containing a cured product of a first resin composition and a fibrous base material containing liquid crystalline aromatic polyester fibers; a second insulating layer containing a cured product of a second resin composition and laminated on one or both sides of the first insulating layer; and wiring formed on the second insulating layer, wherein the thickness of the second insulating layer is 1 to 60 μm, and the second resin composition contains at least one of a polyphenylene ether compound and a hydrocarbon-based compound.

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