JP7705609B2 - Resin sheet and printed wiring board - Google Patents

Description

The present invention relates to a resin sheet and a printed wiring board.

In recent years, semiconductor packages, which are widely used in electronic devices, communication devices, personal computers, etc., have become more functional, thinner, and smaller, and the integration and high-density packaging of each component is accelerating. Accordingly, the properties required of printed wiring boards for semiconductor packages are becoming increasingly strict. Examples of properties required of such printed wiring boards include low water absorption, moisture absorption and heat resistance, flame retardancy, low thermal expansion coefficient, chemical resistance, and high plating peel strength.

In addition to these characteristics, suppressing warping of printed wiring boards (achieving low warping) has become an important issue, and various studies have been conducted on this issue. For example, Patent Document 1 describes a resin sheet that has a support and an adhesive layer, and reduces warping in a high-temperature environment when applied to a printed wiring board.

Insulation layers of printed wiring boards are also required to have excellent heat resistance and electrical properties such as low dielectric constant and low dielectric tangent. Cyanate ester compounds are known as resins used in insulation layers, and resin compositions in which cyanate ester compounds are used in combination with epoxy resins and bismaleimide compounds are widely used. For example, Patent Document 2 describes that a resin composition containing a cyanate ester compound of a specific structure and other components has excellent properties such as low water absorption and low thermal expansion coefficient.

A known method for manufacturing printed wiring boards is the build-up method, in which insulating layers and conductor layers are alternately stacked on a core substrate. Resin sheets or build-up materials are usually used to form the insulating layers (see, for example, Patent Document 3).

JP 2016-179564 A International Publication No. 2012/105547 JP 2017-11032 A

However, in Patent Document 1, the warpage of the printed wiring board is reduced by reducing the thermal expansion coefficient, so the warpage is still not sufficiently reduced. For this reason, further improvements in reducing the warpage are desired.

The resin composition described in Patent Document 2 has good physical properties such as low water absorption and low coefficient of thermal expansion, but there is still room for improvement in terms of thermal conductivity. Therefore, when used as a resin sheet for an insulating material in a printed wiring board, the heat resistance is insufficient, making it difficult to apply to insulating materials.

In addition, as semiconductor packages become more functional, thinner, and smaller, the number of layers in the build-up of the printed wiring board increases when the components for the semiconductor package are highly integrated and densely mounted. However, as the number of layers increases, problems arise such as cracks occurring on the surface of the insulating layer, causing the insulating layer to break and circuit distortion. In this regard, Patent Document 3 describes a build-up material that suppresses surface scratch resistance, but the build-up material described in Patent Document 3 contains a large amount of inorganic filler, so the surface has a high hardness (Vickers hardness (HV0.01) of 32.8 or more and 93.9 or less). Therefore, even with this build-up material, cracks occur on the surface of the insulating layer, causing the insulating layer to break and circuit distortion. In addition, the build-up material described in Patent Document 3 contains a large amount of inorganic filler, so it is difficult to make it thinner and smaller. Furthermore, there is also a problem that the surface hardness is high due to the large amount of inorganic filler, and the peel strength is low.

The present invention has been made in consideration of the above-mentioned problems, and aims to provide a resin sheet and a printed wiring board that can sufficiently reduce warping of the printed wiring board (achieve low warping), are less likely to cause cracks in the insulating layer of the printed wiring board, and are therefore less likely to cause cracks in the insulating layer or circuit distortion, and can exhibit excellent heat resistance and high peel strength.

As a result of extensive research into solving the above problems, the inventors have discovered that by using a specific resin sheet, it is possible to sufficiently reduce warping of a printed wiring board, cracks are less likely to occur in the insulating layer of the printed wiring board, and therefore cracks in the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength can be achieved, which has led to the completion of the present invention.

That is, the present invention is as follows.
[1] A resin sheet comprising a support and a layer containing a resin composition disposed on a surface of the support,
The resin composition contains a cyanate ester compound and/or a phenol compound, and an epoxy compound and/or a maleimide compound,
at least one selected from the group consisting of the cyanate ester compound, the phenol compound, the epoxy compound, and the maleimide compound includes a compound having a biphenyl skeleton;
When the resin composition contains an inorganic filler, the content of the inorganic filler is 60 parts by mass or less relative to 100 parts by mass of a resin solid content in the resin composition;
The Vickers hardness (HV0.01) of the cured product of the resin composition is 10 or more and 19 or less,
The resin sheet, wherein the layer containing the resin composition has a thickness of 2 μm or more and 20 μm or less.

[2] The resin sheet according to [1], wherein the content of the compound having a biphenyl skeleton is 15 parts by mass or more per 100 parts by mass of a resin solid content in the resin composition, and when one or more selected from the group consisting of the cyanate ester compound, the phenol compound, the epoxy compound, and the maleimide compound contain a compound having a polycyclic aromatic, the content of the compound having a polycyclic aromatic is less than 40 parts by mass per 100 parts by mass of a resin solid content in the resin composition.
[3] The resin sheet according to [1] or [2], wherein the cyanate ester compound includes a compound represented by the following formula (1a):

(In formula (1a), each R ^1c independently represents a hydrogen atom or a methyl group, and n1 represents an integer of 1 or more and 10 or less).

[4] A resin sheet described in any one of [1] to [3], wherein the phenol compound includes a compound represented by the following formula (2a):

(In formula (2a), each Ar ¹ independently represents a benzene ring or a naphthalene ring. Ar ² independently represents a benzene ring, a naphthalene ring, or a biphenyl ring. Each R ^2a independently represents a hydrogen atom or a methyl group. m independently represents an integer of 1 or more and 50 or less. Each ring may have a substituent other than a hydroxyl group.)

[5] A resin sheet described in any one of [1] to [4], wherein the epoxy compound includes a compound represented by the following formula (3a):

(In formula (3a), each Ar ³ independently represents a benzene ring or a naphthalene ring. Ar ⁴ independently represents a benzene ring, a naphthalene ring, or a biphenyl ring. Each R ^3a independently represents a hydrogen atom or a methyl group. k independently represents an integer of 1 or more and 50 or less. Each ring may have a substituent other than a glycidyloxy group.)

[6] A resin sheet described in any one of [1] to [5], wherein the maleimide compound includes a compound represented by the following formula (4a):

(In formula (4a), R ^4a and R ^5a each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Each R ^4b independently represents a hydrogen atom or a methyl group. s represents an integer of 1 or more).

[7] The resin sheet according to any one of [1] to [6], wherein the layer containing the resin composition has a thickness of 2 μm or more and 15 μm or less.
[8] The resin sheet according to any one of [1] to [7], wherein the thickness of the support is 1 μm or more and 105 μm or less.
[9] The support is a copper foil,
The resin sheet according to any one of [1] to [8], wherein the arithmetic average roughness (Ra) of the copper foil surface in contact with the layer containing the resin composition is 0.05 μm or more and 2 μm or less.
[10] The resin sheet according to [9], wherein the layer containing the resin composition has a copper foil peel strength of 0.5 kgf/cm or more.

[11] A printed wiring board comprising a layer containing a cured product of the resin composition described in any one of [1] to [10] and a conductor layer disposed on the surface of the layer containing the cured product.

According to the present invention, it is possible to provide a resin sheet and a printed wiring board that can sufficiently reduce warping of the printed wiring board, are less likely to cause cracks in the insulating layer of the printed wiring board, and are therefore less likely to cause cracks in the insulating layer or circuit distortion, and can exhibit excellent heat resistance and high peel strength.

Below, we will explain in detail the form for implementing the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this, and various modifications are possible without departing from the gist of the present invention.

As used herein, unless otherwise specified, "resin solids" refers to the components in the resin composition according to this embodiment excluding additives (such as silane coupling agents, wetting and dispersing agents, and curing accelerators), solvents, and fillers (inorganic fillers and organic fillers), and 100 parts by mass of resin solids refers to the total of 100 parts by mass of the components in the resin composition excluding additives (such as silane coupling agents, wetting and dispersing agents, and curing accelerators), solvents, and fillers (inorganic fillers and organic fillers).

[Resin sheet]
The resin sheet of the present embodiment (hereinafter also simply referred to as "resin sheet") includes a support and a layer containing a resin composition disposed on a surface of the support,
The resin composition comprises a cyanate ester compound and/or a phenol compound, and an epoxy compound and/or a maleimide compound,
one or more compounds selected from the group consisting of a cyanate ester compound, a phenol compound, an epoxy compound, and a maleimide compound include a compound having a biphenyl skeleton;
When the resin composition contains an inorganic filler, the content of the inorganic filler is 60 parts by mass or less per 100 parts by mass of the resin solid content in the resin composition;
The Vickers hardness (HV0.01) of the cured product of the resin composition is 10 or more and 19 or less,
The layer containing the resin composition has a thickness of 2 μm or more and 20 μm or less.

The layer containing the resin composition of the resin sheet is a semi-cured (B stage) resin composition that is applied to a support in an uncured state (A stage). The method for manufacturing the resin sheet is generally a method for manufacturing a composite of a layer containing a B-stage resin composition and a support. Specifically, the uncured (A stage) resin composition according to this embodiment is in the form of a varnish, and the varnish is applied to a support such as copper foil using a known method such as a bar coater, and then semi-cured (B stage) by heating in a dryer at 100°C to 200°C for 1 minute to 60 minutes, etc., to manufacture a resin sheet. For specific manufacturing methods, the examples can be referred to.

Here, in this embodiment, the uncured state (A stage) refers to a state in which the resin composition is almost uncured and not gelled. The resin composition before being applied to the support for the resin sheet is, for example, in the form of a mixture of the components of the resin composition (which may or may not contain a solvent) or a varnish in which the mixture is dissolved or dispersed in a solvent, and is in an uncured state (A stage).

In this embodiment, the semi-cured state (B stage) refers to a state in which each component contained in the layer containing the resin composition has not actively started to react (cure), but the layer containing the resin composition is in a dry state, that is, the layer is heated to a degree that is not sticky, and the solvent has been evaporated. It also includes a state in which the solvent has only evaporated without curing even without heating. In this embodiment, the minimum melt viscosity of the semi-cured state (B stage) is usually 20,000 Pa·s or less. The lower limit of the minimum melt viscosity is, for example, 10 Pa·s or more. In this embodiment, the minimum melt viscosity is measured by the following method. That is, 1 g of resin powder collected from the layer containing the resin composition is used as a sample, and the minimum melt viscosity is measured using a rheometer (ARES-G2 (product name) manufactured by TA Instruments). Here, a disposable plate with a diameter of 25 mm is used to measure the minimum melt viscosity of the resin powder under conditions of a temperature rise rate of 2°C/min, a frequency of 10.0 rad/sec, and a distortion of 0.1% in the range of 40°C to 180°C.

In this embodiment, the Vickers hardness is a value measured for the cured product in the cured state (C stage) of the resin composition. The cured state (C stage) refers to a state in which the thermosetting resin contained in the resin composition has been fully cured and has become a cured product, and the curing does not proceed any further. The cured product is obtained by thermally curing an uncured (A stage) resin composition or a semi-cured (B ^stage ) resin composition under conditions of, for example, a heating temperature of 180°C to 270°C, a pressure of ² kgf/cm2 to 100 kgf/cm2, and a heating time of 30 minutes to 210 minutes.

In this embodiment, by using the resin sheet of this embodiment, it is possible to sufficiently reduce warping of the printed wiring board, and cracks are less likely to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion are less likely to occur, and it is possible to achieve excellent heat resistance and high peel strength. The technical reasons for this are believed to be as follows. Note that the following description includes considerations, but these considerations do not limit this embodiment in any way.

In the resin sheet of this embodiment, in a layer containing a resin composition arranged on the surface of a support, the resin composition contains a cyanate ester compound and/or a phenol compound, and an epoxy compound and/or a maleimide compound, and one or more selected from the group consisting of a cyanate ester compound, a phenol compound, an epoxy compound, and a maleimide compound contain a compound having a biphenyl skeleton, and when an inorganic filler is contained, the content of the inorganic filler is 60 parts by mass or less relative to 100 parts by mass of the resin solid content in the resin composition, the Vickers hardness (HV0.01) of the cured product (C stage) of the resin composition is 10 to 19, and the thickness of the layer (B stage) containing the resin composition is 2 μm to 20 μm. Therefore, the obtained insulating layer (cured product) is a thin film, but has high rigidity due to the biphenyl skeleton, and on the other hand, has moderate flexibility due to the single bond between the phenyl groups, so it has a well-balanced rigidity and flexibility, and further, the surface of the insulating layer is considered to have a moderate hardness. Therefore, it is presumed that the insulating layer has resistance to warping and can absorb external forces such as impacts. Furthermore, since the resin composition is composed of specific compounds and contains an inorganic filler in a specific blending amount, it is presumed that the obtained insulating layer also has excellent heat resistance and high peel strength.
For these reasons, the inventors presume that by using the resin sheet of this embodiment, it is possible to sufficiently reduce warping of a printed wiring board, and since cracks are less likely to occur in the insulating layer of the printed wiring board, breakage of the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength can be achieved.

[Layer containing resin composition]
The resin sheet of the present embodiment includes a layer containing a resin composition disposed on the surface of a support described below. The layer containing a resin composition is not particularly limited as long as it contains the resin composition described below.
The thickness of the layer containing the resin composition is from 2 μm to 20 μm, preferably from 2 μm to 15 μm, and more preferably from 3 μm to 15 μm.

(Cured product of resin composition)
In the resin sheet of this embodiment, the Vickers hardness (HV0.01) of the cured product (C stage) obtained by curing the resin composition is 10 or more and 19 or less, and since this has a more appropriate rigidity, it is preferably 11 or more and 19 or less, and more preferably 12 or more and 19 or less.

The cured product for measuring the Vickers hardness (HV0.01) is obtained by thermally curing a semi-cured (B-stage) resin composition under conditions of a heating temperature of 180°C to 270°C, a pressure of 2kgf/ ^cm2 to 100kgf/ ^cm2 , and a heating time of 30 minutes to 210 minutes. The heating temperature is preferably 200°C to 240°C, more preferably 210°C to 230°C, and even more preferably 220°C. The pressure condition is preferably 10kgf/ ^cm2 to 50kgf/ ^cm2 , more preferably 20kgf/ ^cm2 to 40kgf/ ^cm2 , and even more preferably 30kgf/ ^cm2 . The heating time is preferably 60 minutes to 180 minutes, and more preferably 120 minutes. The heating means for curing the resin composition is not particularly limited as long as it does not inhibit the effect of this embodiment, and a normal heating means (e.g., a dryer, etc.) may be used. The specific measurement method is as described in the Examples.

(Constituents of Resin Composition)
(Cyanate ester compounds, phenol compounds, epoxy compounds, and maleimide compounds)
The resin composition according to the present embodiment has high heat resistance, and therefore contains a cyanate ester compound and/or a phenol compound, and an epoxy compound and/or a maleimide compound, and at least one selected from the group consisting of a cyanate ester compound, a phenol compound, an epoxy compound, and a maleimide compound contains a compound having a biphenyl skeleton. In the present embodiment, the compound having a biphenyl skeleton means that at least one compound selected from the group consisting of a cyanate ester compound, a phenol compound, an epoxy compound, and a maleimide compound has a biphenyl skeleton.
Since the resin composition has such a specific composition, cracks are less likely to occur in the insulating layer of the printed wiring board, and cracks in the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength can be achieved. These compounds are used alone or in combination of two or more. Among these, the compound preferably contains a phenol compound and an epoxy compound and/or a maleimide compound, since good flexibility can be obtained.

In this embodiment, the content of the compound having a biphenyl skeleton is preferably 15 parts by mass or more per 100 parts by mass of resin solids in the resin composition, more preferably 15 parts by mass or more and 90 parts by mass or less, and even more preferably 15 parts by mass or more and 80 parts by mass or less, since cracks are less likely to occur in the insulating layer of the printed wiring board, making it less likely that the insulating layer will break or the circuit will be distorted, and excellent heat resistance and high peel strength can be more effectively exhibited.

In this embodiment, when one or more selected from the group consisting of cyanate ester compounds, phenol compounds, epoxy compounds, and maleimide compounds contain a compound having a polycyclic aromatic, the rigidity increases, so that the warping of the printed wiring board tends to increase, and cracks tend to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion tend to occur. Therefore, in this embodiment, the content of the compound having a polycyclic aromatic is preferably less than 40 parts by mass relative to 100 parts by mass of the resin solid content in the resin composition, and from the viewpoint of obtaining better heat resistance, it is more preferable that it is 2 parts by mass or more and less than 40 parts by mass, and even more preferable that it is 3 parts by mass or more and less than 40 parts by mass. In this embodiment, the compound having a polycyclic aromatic means that one or more compounds selected from the group consisting of cyanate ester compounds, phenol compounds, epoxy compounds, and maleimide compounds have a polycyclic aromatic. In this embodiment, the polycyclic aromatic refers to a condensed ring structure in which two or more unsaturated cyclic compounds such as naphthalene, anthracene, indene, and fluorene supply the sides of their rings to each other, and excludes structures in which monocyclic aromatic compounds such as biphenyl and phenylpyridine are directly bonded to each other. In this embodiment, a compound having both a biphenyl skeleton and a polycyclic aromatic is included in the compound having a polycyclic aromatic.

Next, we will describe in detail specific cyanate ester compounds, phenol compounds, epoxy compounds, and maleimide compounds, as well as compounds having a biphenyl skeleton and compounds having a polycyclic aromatic ring.

(Cyanate ester compounds)
In this embodiment, the term "cyanate ester compound" refers to a compound having two or more cyanate groups (cyanate ester groups) in one molecule, and the term "compound" refers to a concept that includes resin. Examples of cyanate ester compounds include aromatic hydrocarbon compounds containing two or more cyanate groups in one molecule, compounds in which two aromatic rings containing two or more cyanate groups are bonded by a linking group, novolac-type cyanate ester compounds, bisphenol-type cyanate ester compounds, diallyl bisphenol-type cyanate ester compounds (e.g., diallyl bisphenol A-type cyanate ester compounds, diallyl bisphenol E-type cyanate ester compounds, diallyl bisphenol F-type cyanate ester compounds, and diallyl bisphenol S-type cyanate ester compounds), aralkyl-type cyanate ester compounds, and prepolymers of these cyanate esters. These cyanate ester compounds can be used alone or in combination of two or more. Among these, from the viewpoints of obtaining a high glass transition temperature and further improving the chemical resistance and peel strength of the resulting cured product, aralkyl cyanate ester compounds are preferred, and α-naphthol aralkyl cyanate ester compounds and biphenyl aralkyl cyanate ester compounds are more preferred.

An example of an aromatic hydrocarbon compound containing two or more cyanato groups in one molecule is a compound represented by formula (I): Ar-(OCN) _p (wherein Ar represents any one of a benzene ring, a naphthalene ring, and a biphenyl ring, and p represents an integer of 2 or more). When Ar in formula (I) contains a biphenyl ring, the compound has a biphenyl skeleton. When Ar in formula (Ia) contains a naphthalene ring, the compound has a polycyclic aromatic ring. Examples of the compound represented by formula (I) include 1,3-dicyanatobenzene, 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene, 1,3-dicyanatonaphthalene, 1,4-dicyanatonaphthalene, 1,6-dicyanatonaphthalene, 1,8-dicyanatonaphthalene, 2,6-dicyanatonaphthalene, 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, and 4,4'-dicyanatobiphenyl.

Examples of compounds in which two aromatic rings containing two or more cyanato groups are linked by a linking group include bis(4-cyanatophenyl) ether, bis(4-cyanatophenyl) thioether, and bis(4-cyanatophenyl) sulfone.

An example of a novolac-type cyanate ester compound is a compound represented by the following formula (1):

In the above formula (1), each R ^1a independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Each R ^1b independently represents a hydrogen atom or a methyl group, preferably a hydrogen atom. n represents an integer of 1 to 10, preferably an integer of 1 to 7.

Examples of compounds represented by the above formula (1) include bis(3,5-dimethyl-4-cyanatophenyl)methane, bis(4-cyanatophenyl)methane, and 2,2'-bis(4-cyanatophenyl)propane.

These cyanate ester compounds may be used alone or in combination of two or more. Among these, the cyanate ester compounds are preferably bisphenol-type cyanate ester compounds and/or aralkyl-type cyanate ester compounds, from the viewpoints of obtaining heat resistance and further excellent low water absorption of the resulting cured product.

(Bisphenol-type cyanate ester compounds)
The bisphenol type cyanate ester compound is not particularly limited, but examples thereof include bisphenol A type cyanate ester compounds, bisphenol E type cyanate ester compounds, bisphenol F type cyanate ester compounds, and bisphenol S type cyanate ester compounds.

The bisphenol-type cyanate ester compound may be a commercially available product, or a preparation prepared by a known method may be used. Commercially available bisphenol-type cyanate ester compounds include, for example, CA210 (product name) manufactured by Mitsubishi Gas Chemical Co., Ltd.

(Aralkyl-type cyanate ester compound)
The aralkyl cyanate ester compound is not particularly limited, but examples thereof include α-naphthol aralkyl cyanate ester compounds and biphenyl aralkyl cyanate ester compounds. In the present embodiment, the α-naphthol aralkyl cyanate ester compound is a compound having a polycyclic aromatic ring. The biphenyl aralkyl cyanate ester compound is a compound having a biphenyl skeleton.

An example of an α-naphthol aralkyl cyanate ester compound is a compound represented by the following formula (1a). Since this further improves the heat resistance of the resin layer of the printed wiring board, it is preferable that the resin composition contains an α-naphthol aralkyl cyanate ester compound.

In the formula (1a), each R ^1c independently represents a hydrogen atom or a methyl group, and preferably represents a hydrogen atom. n1 represents an integer of 1 to 10, and preferably an integer of 1 to 6.

An example of a biphenyl aralkyl type cyanate ester compound is the compound represented by the following formula (1b):

In the above formula (1b), R ^1d each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ^1e each independently represents a hydrogen atom or a methyl group, preferably a hydrogen atom. n2 represents an integer of 1 to 10, preferably an integer of 1 to 6.

The aralkyl cyanate ester compound may be a commercially available product or a product synthesized by a known method. Examples of methods for synthesizing an aralkyl cyanate ester compound include a method of reacting a phenolic resin (hereinafter also referred to as the "corresponding phenolic resin") corresponding to the target aralkyl cyanate ester compound with a cyanogen halide and a basic compound in an inert organic solvent, and a method of reacting a corresponding phenolic resin with a basic compound in an aqueous solution to form a salt and a cyanogen halide at a two-phase interface. In either method, the hydrogen atom of the phenolic hydroxyl group of the corresponding phenolic resin is cyanated to obtain an aralkyl cyanate ester compound. More specifically, for example, the method described in the examples is used.

The content of the cyanate ester compound is preferably 10 parts by mass or more and 45 parts by mass or less per 100 parts by mass of the resin solid content. By having the content within the above range, cracks are less likely to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength tend to be more likely to be exhibited. From the same viewpoint, the lower limit of the content is more preferably 15 parts by mass, even more preferably 20 parts by mass, and even more preferably 30 parts by mass. The upper limit of the content is more preferably 40 parts by mass, and even more preferably 35 parts by mass.

The cyanate equivalent of the cyanate ester compound is preferably 100 g/eq or more and 500 g/eq or less, more preferably 100 g/eq or more and 400 g/eq or less, and even more preferably 100 g/eq or more and 300 g/eq or less. When the cyanate equivalent is within the above range, the rigidity of the obtained cured product is further improved, and the glass transition temperature and warping of the printed wiring board tend to be further suppressed.

(Phenol compounds)
In the present embodiment, the term "phenol compound" refers to a compound having two or more phenolic hydroxyl groups in one molecule, and the term "compound" refers to a concept that includes resins. Examples of the phenolic compound include phenols having two or more phenolic hydroxyl groups in one molecule, bisphenols (e.g., bisphenol A, bisphenol E, bisphenol F, and bisphenol S), diallyl bisphenols (e.g., diallyl bisphenol A, diallyl bisphenol E, diallyl bisphenol F, and diallyl bisphenol S), bisphenol-type phenolic resins (e.g., bisphenol A-type resin, bisphenol E-type resin, bisphenol F-type resin, and bisphenol S-type resin), phenol novolac resins (e.g., phenol novolac resin, naphthol novolac resin, and cresol novolac resin), glycidyl ester-type phenolic resins, naphthalene-type phenolic resins, anthracene-type phenolic resins, dicyclopentadiene-type phenolic resins, biphenyl-type phenolic resins, alicyclic phenolic resins, polyol-type phenolic resins, aralkyl-type phenolic resins, and phenol-modified aromatic hydrocarbon formaldehyde resins. These phenolic compounds may be used alone or in combination of two or more. In this embodiment, when the phenolic compound includes a compound having a biphenyl skeleton, such a compound may be, for example, a biphenyl-type phenolic resin. When the phenolic compound includes a compound having a polycyclic aromatic ring, such a compound may be, for example, a naphthol novolac resin, a cresol novolac resin, a naphthalene-type phenolic resin, and an anthracene-type phenolic resin. Among these, the phenolic compound is preferably an aralkyl-type phenolic resin and/or a phenol-modified aromatic hydrocarbon formaldehyde resin, and more preferably a biphenyl aralkyl-type phenolic resin and/or a phenol-modified xylene resin, from the viewpoint of obtaining a cured product with better heat resistance and low water absorption.

(Aralkyl-type phenolic resin)
An example of the aralkyl phenol resin is a compound represented by the following formula (2a).

In the above formula (2a), Ar ¹ each independently represents a benzene ring or a naphthalene ring. Ar ² represents a benzene ring, a naphthalene ring, or a biphenyl ring. R ^2a each independently represents a hydrogen atom or a methyl group. m represents an integer of 1 to 50. Each ring may have a substituent other than a hydroxyl group (for example, an alkyl group or a phenyl group having 1 to 5 carbon atoms). When Ar ² in formula (2a) contains a biphenyl ring, it becomes a compound having a biphenyl skeleton. In addition, when Ar ¹ and/or Ar ² in formula (2a) contain a naphthalene ring, it becomes a compound having a polycyclic aromatic ring. When a naphthalene ring and a biphenyl ring are contained in formula (2a), it becomes a compound having a polycyclic aromatic ring.

Examples of the compound represented by the formula (2a) include a compound in which Ar ¹ is a naphthalene ring and Ar ² is a benzene ring in the formula (2a) (also referred to as a "naphthol aralkyl type phenolic resin"), and a compound in which Ar ¹ is a benzene ring and Ar ² is a biphenyl ring in the formula (2a) (also referred to as a "biphenyl aralkyl type phenolic resin"). As the compound represented by the formula (2a), a biphenyl aralkyl type phenolic resin is preferable from the viewpoint of obtaining a cured product with better heat resistance and low water absorption.

The naphthol aralkyl type phenolic resin is preferably a compound represented by the following formula (2b).

In the above formula (2b), ^R2a is the same as ^R2a in the above formula (2a) and is preferably a hydrogen atom. m is the same as m in the above formula (2a) and is preferably an integer of 1 to 10, more preferably an integer of 1 to 6.

The biphenyl aralkyl phenol resin is preferably a compound represented by the following formula (2c). The resin composition preferably contains a biphenyl aralkyl phenol resin, since this can further reduce warping of the printed wiring board, is less susceptible to cracking, and results in a resin layer with a more appropriate hardness.

In the above formula (2c), each R ^2b independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a phenyl group, and preferably represents a hydrogen atom. m1 represents an integer of 1 to 20, and preferably an integer of 1 to 6.

The aralkyl phenol resin may be a commercially available product, or a product synthesized by a known method. Commercially available aralkyl phenol resins include SN-495 (trade name) manufactured by Nippon Steel Chemical Co., Ltd. (naphthol aralkyl phenol resin represented by formula (2b)), and KAYAHARD (registered trademark) GPH-65 (trade name), KAYAHARD (registered trademark) GPH-78 (trade name), and KAYAHARD (registered trademark) GPH-103 (trade name) manufactured by Nippon Kayaku Co., Ltd. (all biphenyl aralkyl phenol resins represented by formula (2c)).

(Phenol-modified aromatic hydrocarbon formaldehyde resin)
In this specification, the term "phenol-modified aromatic hydrocarbon formaldehyde resin" refers to a resin obtained by heating an aromatic hydrocarbon formaldehyde resin and a phenol in the presence of an acid catalyst (e.g., paratoluenesulfonic acid, oxalic acid, etc.) to cause a condensation reaction (modification condensation reaction).

The aromatic hydrocarbon formaldehyde resin is not particularly limited, and examples thereof include compounds obtained by a condensation reaction between an aromatic hydrocarbon compound (e.g., toluene, ethylbenzene, xylene, mesitylene, pseudocumene, monocyclic aromatic hydrocarbon compounds having 10 or more carbon atoms, and polycyclic aromatic hydrocarbon compounds such as methylnaphthalene) and formaldehyde. Among these, xylene formaldehyde resin obtained by a condensation reaction between xylene and formaldehyde is preferable.

The phenols are not particularly limited, and examples thereof include phenol, cresols, bisphenolpropane, bisphenolmethane, resorcin, pyrocatechol, hydroquinone, para-tertiary butylphenol, bisphenol sulfone, bisphenol ether, and para-phenylphenol. These phenols may be used alone or in combination of two or more.

The phenol-modified aromatic hydrocarbon formaldehyde resin is preferably a phenol-modified xylene formaldehyde resin obtained by heating a xylene formaldehyde resin and the above-mentioned phenols in the presence of the above-mentioned acid catalyst to cause a condensation reaction, and is more preferably a phenol-modified xylene resin.

The phenol-modified aromatic hydrocarbon formaldehyde resin may be a commercially available product, or a preparation prepared by a known method may be used. Commercially available phenol-modified aromatic hydrocarbon formaldehyde resins include, for example, the Zystar (registered trademark) series manufactured by Fudow Co., Ltd., such as HP-120 (trade name), HP-100 (trade name), HP-210 (trade name), HP-70 (trade name), NP-100 (trade name), GP-212 (trade name), P-100 (trade name), GP-100 (trade name), GP-200 (trade name), and HP-30 (trade name). Known methods include, for example, the method described in JP 2015-174874 A.

The content of the phenol compound is not particularly limited, but is preferably 10 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the resin solid content. By having the content within the above range, cracks are less likely to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength tend to be more likely to be exhibited. From the same viewpoint, the lower limit of the content is more preferably 20 parts by mass, even more preferably 30 parts by mass, and the upper limit of the content is more preferably 55 parts by mass, even more preferably 50 parts by mass, and even more preferably 40 parts by mass.

The phenol equivalent of the phenol compound (hydroxyl equivalent of the phenolic hydroxyl group) is preferably 500 g/eq or less, more preferably 400 g/eq or less, even more preferably 350 g/eq or less, and even more preferably 300 g/eq or less. When the phenol equivalent is within the above range, the rigidity of the obtained cured product is more excellent, and the glass transition temperature and warping of the printed wiring board tend to be further suppressed. The lower limit is not particularly limited, but is 100 g/eq or more.

(Epoxy Compound)
In the present embodiment, the term "epoxy compound" refers to a compound having two or more epoxy groups in one molecule, and the term "compound" refers to a concept that includes resins. Examples of the epoxy compound include bisphenol type epoxy resins (e.g., bisphenol A type epoxy resins, bisphenol E type epoxy resins, bisphenol F type epoxy resins, and bisphenol S type epoxy resins), diallyl bisphenol type epoxy resins (e.g., diallyl bisphenol A type epoxy resins, diallyl bisphenol E type epoxy resins, diallyl bisphenol F type epoxy resins, and diallyl bisphenol S type epoxy resins, etc.), phenol novolac type epoxy resins (e.g., phenol novolac type epoxy resins, bisphenol A novolac type epoxy resins, and cresol novolac type epoxy resins), aralkyl type epoxy resins, biphenyl type epoxy resins containing a biphenyl skeleton, naphthalene type epoxy resins containing a naphthalene skeleton, anthracene type epoxy resins containing anthracene skeleton, glycidyl ester type epoxy resins, polyol type epoxy resins, isocyanurate ring-containing epoxy resins, dicyclopentadiene type epoxy resins, epoxy resins consisting of bisphenol A type structural units and hydrocarbon-based structural units, and halogen compounds thereof. These epoxy compounds may be used alone or in combination of two or more. In this embodiment, when the epoxy resin contains a compound having a biphenyl skeleton, such a compound may be, for example, a biphenyl type epoxy resin. When the epoxy resin contains a compound having a polycyclic aromatic ring, such a compound may be, for example, a naphthalene type epoxy resin containing a naphthalene skeleton and an anthracene type epoxy resin containing an anthracene skeleton. Among these, from the viewpoint of obtaining a cured product with better heat resistance and low water absorption, it is preferable to use one or more selected from the group consisting of aralkyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, and epoxy resins consisting of bisphenol A type structural units and hydrocarbon-based structural units. In this embodiment, cracks are less likely to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength can be more effectively exhibited. Therefore, it is preferable that the epoxy compound contains two or more types, and the two or more types of epoxy compounds contain a naphthalene type epoxy resin and/or an aralkyl type epoxy resin containing a naphthalene skeleton, and it is more preferable that the epoxy compound contains a naphthalene type epoxy resin and an aralkyl type epoxy resin. As the aralkyl type epoxy resin, a biphenyl aralkyl type epoxy resin is more preferable.

(Aralkyl type epoxy resin)
An example of the aralkyl type epoxy resin is a compound represented by the following formula (3a).

In the above formula (3a), Ar ³ each independently represents a benzene ring or a naphthalene ring. Ar ⁴ represents a benzene ring, a naphthalene ring, or a biphenyl ring. R ^3a each independently represents a hydrogen atom or a methyl group. k represents an integer of 1 to 50. Each ring may have a substituent other than a glycidyloxy group (for example, an alkyl group or a phenyl group having 1 to 5 carbon atoms). When Ar ⁴ in formula (3a) contains a biphenyl ring, it becomes a compound having a biphenyl skeleton. In addition, when Ar ³ and/or Ar ⁴ in formula (3a) contain a naphthalene ring, it becomes a compound having a polycyclic aromatic ring. When a naphthalene ring and a biphenyl ring are contained in formula (3a), it becomes a compound having a polycyclic aromatic ring.

From the viewpoint of obtaining a cured product having even better heat resistance and low water absorption, the compound represented by the above formula (3a) is preferably a compound in which Ar ³ is a naphthalene ring and Ar ⁴ is a benzene ring (also referred to as a "naphthalene aralkyl type epoxy resin"), or a compound in which Ar ³ is a benzene ring and Ar ⁴ is a biphenyl ring (also referred to as a "biphenyl aralkyl type epoxy resin"), and more preferably a biphenyl aralkyl type epoxy resin.

The aralkyl type epoxy resin may be a commercially available product, or a preparation prepared by a known method may be used. Commercially available naphthalene aralkyl type epoxy resins include, for example, Epotohto (registered trademark) ESN-155 (trade name), Epotohto (registered trademark) ESN-355 (trade name), Epotohto (registered trademark) ESN-375 (trade name), Epotohto (registered trademark) ESN-475V (trade name), Epotohto (registered trademark) ESN-485 (trade name), and Epotohto (registered trademark) ESN-175 (trade name) manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., NC-7000 (trade name), NC-7300 (trade name), and NC-7300L (trade name) manufactured by Nippon Kayaku Co., Ltd., and HP-5000 (trade name), HP-9900 (trade name), HP-9540 (trade name), and HP-9500 (trade name) manufactured by DIC Corporation. Commercially available biphenylaralkyl epoxy resins include, for example, NC-3000 (trade name), NC-3000L (trade name), and NC-3000FH (trade name) manufactured by Nippon Kayaku Co., Ltd.

From the viewpoint of obtaining a cured product having even better heat resistance and low water absorption, it is preferable that the biphenyl aralkyl type epoxy resin is a compound represented by the following formula (3b).

In the above formula (3b), ka represents an integer of 1 or more, preferably an integer of 1 or more and 20 or less, and more preferably an integer of 1 or more and 6 or less.

It is also preferable that the naphthalene aralkyl type epoxy resin is a compound represented by the following formula (3c). It is preferable that the resin composition contains a naphthalene aralkyl type epoxy resin, since this can further reduce warping of the printed wiring board, makes it less likely for cracks to occur, and results in a resin layer with a more appropriate hardness.

In the above formula (3c), ky represents an integer of 1 or more and 10 or less. Also, Me represents a methyl group.

(Naphthalene type epoxy resin)
Examples of the naphthalene type epoxy resin include epoxy resins other than the above naphthalene aralkyl type epoxy resins, such as naphthalene skeleton-containing polyfunctional epoxy resins having a naphthalene skeleton represented by the following formula (3d) and epoxy resins having a naphthalene skeleton (for example, epoxy resins represented by the following formula (3e)). These resins are compounds having polycyclic aromatic rings. Examples of the naphthalene type epoxy resin include naphthylene ether type epoxy resins. Naphthylene ether type epoxy resins are preferred because the heat resistance and low water absorption of the resulting cured product are even more excellent.

In the above formula (3d), Ar ³¹ each independently represents a benzene ring or a naphthalene ring. Ar ⁴¹ represents a benzene ring, a naphthalene ring, or a biphenyl ring. R ^31a each independently represents a hydrogen atom or a methyl group. p represents an integer of 0 to 2, preferably 0 or 1. kz represents an integer of 1 to 50. Each ring may have a substituent other than a glycidyloxy group (e.g., an alkyl group, an alkoxy group, or a phenyl group having 1 to 5 carbon atoms), and at least one of Ar ³¹ and Ar ⁴¹ represents a naphthalene ring. When Ar ³¹ and/or Ar ⁴¹ in formula (3d) contain a naphthalene ring, the compound has a polycyclic aromatic ring. When Ar ³¹ in formula (3d) contains a benzene ring and Ar ⁴¹ contains a biphenyl ring, the compound has a biphenyl skeleton. When the formula (3d) contains a naphthalene ring and a biphenyl ring, it becomes a compound having a polycyclic aromatic group.

Examples of compounds represented by the above formula (3d) include compounds represented by the following formula (3f).

In the above formula (3f), kz has the same meaning as kz in the above formula (3d).

The naphthalene skeleton-containing multifunctional epoxy resin may be a commercially available product, or a preparation prepared by a known method. Commercially available naphthalene skeleton-containing multifunctional epoxy resins include, for example, HP-9540 (trade name) and HP-9500 (trade name) manufactured by DIC Corporation.

The epoxy resin represented by the above formula (3e) may be a commercially available product or a preparation prepared by a known method. Commercially available products include HP-4710 (product name) manufactured by DIC Corporation.

(Naphthylene ether type epoxy resin)
An example of the naphthylene ether type epoxy resin is a compound represented by the following formula (3g): Since a resin layer having a more appropriate hardness can be obtained, it is preferable that the resin composition contains a naphthylene ether type epoxy resin.

In the above formula (3g), each R ^3b independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aralkyl group, a naphthyl group, or a naphthyl group containing a glycidyloxy group. k1 represents an integer of 1 or more and 10 or less.

In the compound represented by the above formula (3g), the number of glycidyloxy groups containing epoxy groups in the molecule is preferably 2 or more and 6 or less, and more preferably 2 or more and 4 or less.

In the above formula (3g), k1 represents an integer of 0 or more and 10 or less, and from the viewpoint of more effectively and reliably achieving the effect of this embodiment, it is preferable for k1 to represent an integer of 0 or more and 6 or less, more preferably an integer of 0 or more and 4 or less, and even more preferably 2 or 3.

In the above formula (3g), from the viewpoint of more effectively and reliably achieving the effects of the present embodiment, it is preferable that each R ^3b independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aralkyl group, or a naphthyl group.

In addition, when the naphthylene ether type epoxy resin contains a compound represented by the above formula (3g), it may contain multiple types of compounds with the same k1, or multiple types of compounds with different k1. When the naphthylene ether type epoxy resin contains multiple types of compounds with different k1, it is preferable that the naphthylene ether type epoxy resin contains a compound in which k1 in the above formula (3g) is an integer of 0 to 4, and more preferably 2 or 3.

An example of the compound represented by formula (3g) above is the compound represented by formula (3h) below.

The epoxy resin represented by the above formula (3h) may be a commercially available product or a preparation prepared by a known method. Commercially available products include HP-4032 (trade name) manufactured by DIC Corporation.

The naphthylene ether type epoxy resin may be a commercially available product, or a preparation prepared by a known method may be used. Commercially available naphthylene ether type epoxy resins include, for example, HP-4032 (trade name), HP-6000 (trade name), EXA-7300 (trade name), EXA-7310 (trade name), EXA-7311 (trade name), EXA-7311L (trade name), and EXA7311-G3 (trade name), manufactured by DIC Corporation.

(Dicyclopentadiene type epoxy resin)
An example of the dicyclopentadiene type epoxy resin is a compound represented by the following formula (3i): Since a resin layer having a more appropriate hardness can be obtained, it is preferable that the resin composition contains a dicyclopentadiene type epoxy resin.

In the above formula (3i), each R ^3c independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and k2 represents an integer of 0 or more and 10 or less.

In the above formula (3i), k2 represents an integer of 0 or more and 10 or less. From the viewpoint of more effectively and reliably achieving the effect of this embodiment, k2 preferably represents an integer of 0 or more and 6 or less, more preferably an integer of 0 or more and 2 or less, and even more preferably 0 or 1.

In addition, when the dicyclopentadiene type epoxy resin contains a compound represented by the above formula (3i), it may contain multiple types of compounds with the same k2, or multiple types of compounds with different k2. When the dicyclopentadiene type epoxy resin contains multiple types of compounds with different k2, it is preferable that the dicyclopentadiene type epoxy resin contains a compound in which k2 is 0 or more and 2 or less in the above formula (3i).

The dicyclopentadiene type epoxy resin may be a commercially available product, or a preparation prepared by a known method may be used. Commercially available dicyclopentadiene type epoxy resins include EPICRON (registered trademark) HP-7200L (product name), EPICRON (registered trademark) HP-7200 (product name), EPICRON (registered trademark) HP-7200H (product name), and EPICRON (registered trademark) HP-7000HH (product name), manufactured by DIC Corporation.

(Epoxy resin consisting of bisphenol A structural units and hydrocarbon-based structural units)
An epoxy resin consisting of a bisphenol A structural unit and a hydrocarbon-based structural unit (also referred to as a "specific epoxy resin") has one or more bisphenol A structural units and one or more hydrocarbon-based structural units in the molecule. An example of the specific epoxy resin is a compound represented by the following formula (3j). It is preferable that the resin composition contains a specific epoxy resin, since cracks are less likely to occur and a resin layer having a more appropriate hardness can be obtained.

In the formula (3j), R ^1x and R ^2x each independently represent a hydrogen atom or a methyl group. R ^3x to R ^6x each independently represent a hydrogen atom, a methyl group, a chlorine atom, or a bromine atom. X represents an ethyleneoxyethyl group, a di(ethyleneoxy)ethyl group, a tri(ethyleneoxy)ethyl group, a propyleneoxypropyl group, a di(propyleneoxy)propyl group, a tri(propyleneoxy)propyl group, or an alkylene group having 2 to 15 carbon atoms.

In the above formula (3j), k3 represents an integer, and from the viewpoint of more effectively and reliably achieving the effect of this embodiment, k3 is preferably an integer of 1 to 10, more preferably an integer of 1 to 6, even more preferably 1 or 2, and even more preferably 1.

In the above formula (3j), it is preferable that X is an ethylene group in order to more effectively and reliably achieve the effect of this embodiment.

The specific epoxy resin may be a commercially available product or a preparation prepared by a known method. Commercially available products of the specific epoxy resin include EPICLON (registered trademark) EXA-4850-150 (product name) and EPICLON (registered trademark) EXA-4816 (product name) manufactured by DIC Corporation.

The content of the epoxy compound is preferably 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the resin solid content. By having the content within the above range, cracks are less likely to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion are less likely to occur, and there is a tendency for excellent heat resistance and high peel strength to be more exhibited. In addition, by having the content within the above range, the rigidity, heat resistance, and low water absorption of the obtained cured product tend to be further improved. From the same viewpoint, the lower limit of the content is more preferably 20 parts by mass, even more preferably 25 parts by mass, even more preferably 30 parts by mass, and particularly preferably 45 parts by mass, and the upper limit of the content is more preferably 75 parts by mass, even more preferably 70 parts by mass, and even more preferably 64 parts by mass.

The epoxy equivalent of the epoxy compound is preferably 500 g/eq or less, more preferably 400 g/eq or less, and even more preferably 350 g/eq or less. By having the epoxy equivalent within the above range, the rigidity of the obtained cured product is more excellent, and the glass transition temperature and warping of the printed wiring board tend to be further suppressed. The lower limit is preferably 100 g/eq or more.

When the resin composition contains a phenolic compound and/or a cyanate ester compound and an epoxy compound, the ratio of the amount of phenolic groups (parts by mass/phenol equivalent) and/or the amount of cyanate ester groups (parts by mass/cyanate ester equivalent) in the resin composition to the amount of epoxy groups (parts by mass/epoxy equivalent) in the resin composition is preferably 0.5 to 1.5. In addition, when the resin composition contains both a phenolic compound and a cyanate ester compound, the above ratio is the ratio of the total amount of the phenolic groups and the cyanate groups to the amount of epoxy groups. By having the ratio within the above range, cracks are less likely to occur in the insulating layer of the printed wiring board, so that cracks in the insulating layer and circuit distortion are less likely to occur, and excellent heat resistance and high peel strength tend to be more easily expressed. From the same viewpoint, the lower limit of the ratio is preferably 0.5, more preferably 0.6, even more preferably 0.7, and even more preferably 0.9. The upper limit of the ratio is preferably 1.5, more preferably 1.4, even more preferably 1.3, and even more preferably 1.2. When there are multiple types of phenol compounds, the above-mentioned phenol group amount refers to the total value of the phenol group amounts of the respective phenol compounds, when there are multiple types of cyanate ester compounds, the above-mentioned cyanate group amount refers to the total value of the cyanate group amounts of the respective cyanate ester compounds, and when there are multiple types of epoxy compounds, the above-mentioned epoxy group amount refers to the total value of the epoxy group amounts of the respective epoxy compounds.

(Maleimide Compound)
In this embodiment, the term "maleimide compound" refers to a compound having one or more maleimide groups in one molecule, and the term "compound" refers to a concept that includes resins. Examples of maleimide compounds include monomaleimide compounds having one maleimide group in one molecule, polymaleimide compounds having two or more maleimide groups in one molecule, and prepolymers of these maleimide compounds and amine compounds. These maleimide compounds may be used alone or in combination of two or more.

Examples of monomaleimide compounds include N-phenylmaleimide and N-hydroxyphenylmaleimide.

Examples of polymaleimide compounds include compounds represented by the following formula (4a); 2,2-bis(4-(4-maleimidophenoxy)-phenyl)propane, 1,6-bismaleimido-(2,2,4-trimethyl)hexane, and other compounds in which maleimide groups are bonded to both ends of a linear or branched alkyl chain (but not limited to compounds represented by the following formula (4a)); bis(4-maleimidophenoxy)biphenyl; bisphenol A diphenyl ether bismaleimide; imide resins in which maleimide groups have been introduced directly into the naphthalene ring; phenylene bismaleimide such as m-phenylene bismaleimide and 4-methyl-1,3-phenylene bismaleimide; and compounds in which multiple maleimide groups are bonded to a benzene ring.

In the above formula (4a), R ^4a and R ^5a each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom. R ^4b each independently represent a hydrogen atom or a methyl group, preferably a hydrogen atom. s represents an integer of 1 or more. The lower limit of s is preferably an integer of 10 or less, more preferably an integer of 7 or less.

Examples of compounds represented by the above formula (4a) include bis(4-maleimidophenyl)methane, bis(3,5-dimethyl-4-maleimidophenyl)methane, bis(3,5-diethyl-4-maleimidophenyl)methane, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, and polyphenylmethane maleimide compounds. When the maleimide compound contains the maleimide compound represented by the above formula (4a), the thermal expansion coefficient of the obtained cured product tends to be further reduced, and the heat resistance and glass transition temperature (Tg) tend to be further improved.

In the present embodiment, when the maleimide compound includes a compound having a biphenyl skeleton, an example of such a compound is bis(4-maleimidophenoxy)biphenyl.When the maleimide compound includes a compound having a polycyclic aromatic ring, an example of such a compound is an imide resin in which a maleimide group is directly introduced into a naphthalene ring.
Among these, the maleimide compound is preferably a polymaleimide compound in that the heat resistance and glass transition temperature of the resulting cured product are further improved, and is more preferably a compound represented by formula (4a) in that the thermal expansion coefficient of the resulting cured product is further reduced in addition to the excellent heat resistance and glass transition temperature, with bis(3-ethyl-5-methyl-4-maleimidophenyl)methane being even more preferable.

The maleimide compound may be a commercially available product, or a preparation prepared by a known method may be used. Commercially available maleimide compounds include BMI-70 (trade name) and BMI-80 (trade name) manufactured by K.I. Kasei Co., Ltd., and BMI-2300 (trade name), BMI-1000P (trade name), BMI-3000 (trade name), BMI-4000 (trade name), BMI-5100 (trade name), and BMI-7000 (trade name) manufactured by Daiwa Kasei Co., Ltd.

The content of the maleimide compound is not particularly limited, but is preferably 1 part by mass or more and 45 parts by mass or less per 100 parts by mass of the resin solid content. By having the content within the above range, the obtained cured product has better low water absorption and tends to be able to further suppress warping of the printed wiring board. From the same viewpoint, the lower limit of the content is more preferably 4 parts by mass, even more preferably 10 parts by mass, and even more preferably 15 parts by mass, and the upper limit of the content is more preferably 40 parts by mass, even more preferably 30 parts by mass, even more preferably 25 parts by mass, and particularly preferably 20 parts by mass.

(Other resins)
The resin composition according to the present embodiment may contain other resins, but is not limited thereto. Examples of other resins include alkenyl-substituted nadiimide compounds, oxetane resins, benzoxazine compounds, and compounds having a polymerizable unsaturated group. These resins may be used alone or in combination of two or more.

(Alkenyl-substituted nadiimide compounds)
In the present embodiment, the term "alkenyl-substituted nadimide compound" refers to a compound having one or more alkenyl-substituted nadimide groups in the molecule. Examples of the alkenyl-substituted nadimide compound include a compound represented by the following formula (5a).

In the above formula (5a), each R ^6a independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R ^6b represents an alkylene group having 1 to 6 carbon atoms, a phenylene group, a biphenylene group, a naphthylene group, or a group represented by the following formula (5b) or (5c).

In the above formula (5b), R ^6c represents a methylene group, an isopropylidene group, or a divalent substituent represented by CO, O, S, or SO ₂ .

In the above formula (5c), each R ^6d independently represents an alkylene group having 1 to 4 carbon atoms or a cycloalkylene group having 5 to 8 carbon atoms.

Further, the alkenyl-substituted nadiimide compound may be a compound represented by the following formula (6) and/or (7).

The alkenyl-substituted nadimide compound may be a commercially available product, or a product prepared by a known method may be used. Commercially available alkenyl-substituted nadimide compounds include, for example, BANI-M (trade name) and BANI-X (trade name) manufactured by Maruzen Petrochemical Co., Ltd.
These alkenyl-substituted nadimide compounds may be used alone or in combination of two or more.

(Oxetane resin)
Examples of oxetane resins include alkyl oxetanes such as oxetane, 2-methyloxetane, 2,2-dimethyloxetane, 3-methyloxetane, and 3,3-dimethyloxetane, 3-methyl-3-methoxymethyloxetane, 3,3'-di(trifluoromethyl)perfluorooxetane, 2-chloromethyloxetane, 3,3-bis(chloromethyl)oxetane, biphenyl-type oxetane, and OXT-101 (trade name) and OXT-121 (trade name) manufactured by Toagosei Co., Ltd.
These oxetane resins may be used alone or in combination of two or more.

(Benzoxazine Compounds)
The term "benzoxazine compound" in the present embodiment refers to a compound having two or more dihydrobenzoxazine rings in one molecule. Examples of the benzoxazine compound include bisphenol F benzoxazine BF-BXZ (trade name) and bisphenol S benzoxazine BS-BXZ (trade name) manufactured by Konishi Chemical Co., Ltd.
These benzoxazine compounds may be used alone or in combination of two or more.

(Compound having a polymerizable unsaturated group)
Examples of the compound having a polymerizable unsaturated group include vinyl compounds such as ethylene, propylene, styrene, divinylbenzene, and divinylbiphenyl; (meth)acrylates of monohydric or polyhydric alcohols such as methyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; epoxy (meth)acrylates such as bisphenol A type epoxy (meth)acrylate and bisphenol F type epoxy (meth)acrylate; and benzocyclobutene resins.
These compounds having a polymerizable unsaturated group may be used alone or in combination of two or more.

These other resins are not particularly limited as long as they achieve the effect of this embodiment, but are preferably 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of resin solids.

(Elastomer Component)
The resin composition according to the present embodiment may contain, but is not limited to, an elastomer component. When the resin composition contains an elastomer component, the warping of the printed wiring board tends to be further suppressed. Examples of the elastomer component include acrylic rubber, silicone rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, butadiene rubber, polyisoprene rubber, urethane rubber, butyl rubber, and core-shell rubber, which are different from the organic filler and other additives described below. These elastomer components are used alone or in combination of two or more.

Acrylic rubbers include, for example, alkyl acrylates such as ethyl acrylate and butyl acrylate.
Examples of silicone rubbers include copolymers containing dimethylsiloxane groups, methylvinyl groups, methylphenyl groups, and diphenylsiloxane groups, and polydimethylsiloxanes composed only of dimethylsiloxane groups.
Examples of the core-shell rubber include methacrylate ester-styrene/butadiene rubber graft copolymers, acrylonitrile-styrene/butadiene rubber graft copolymers, acrylonitrile-styrene/ethylene-propylene rubber graft copolymers, acrylonitrile-styrene/acrylic acid ester graft copolymers, methacrylate ester/acrylic acid ester rubber graft copolymers, and methacrylate ester-acrylonitrile/acrylic acid ester rubber graft copolymers.

The elastomer content is usually 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of resin solids in the resin composition. By having the content within the above range, the heat resistance and water absorption of the obtained cured product tend to be further improved. The lower limit of the elastomer content is 0 parts by mass or more.

(filling material)
In this embodiment, the filler includes inorganic fillers and organic fillers.
Inorganic filler The resin composition of this embodiment may contain an inorganic filler, but it is preferable that the resin composition does not contain an inorganic filler because the printed wiring board can be thinned and miniaturized, and the resin composition has a high peel strength and a moderate surface hardness. Not containing an inorganic filler means that the content of the inorganic filler is 0 parts by mass relative to 100 parts by mass of the resin solid content in the resin composition. In this embodiment, when the resin composition contains an inorganic filler, the warping of the printed wiring board can be reduced, cracks are unlikely to occur in the insulating layer of the printed wiring board, and cracks and circuit distortion of the insulating layer can be unlikely to occur. Therefore, the content of the inorganic filler is 60 parts by mass or less, preferably 55 parts by mass or less, and more preferably 45 parts by mass or less relative to 100 parts by mass of the resin solid content in the resin composition. When an inorganic filler is contained, the lower limit is not particularly limited, but it is preferable that the content is 1 part by mass or more from the viewpoint of further suppressing the warping of the printed wiring board.

Inorganic fillers include, for example, metal oxides (e.g., silica, alumina, titanium white, zinc oxide, magnesium oxide, zirconium oxide, etc.); metal nitrides (e.g., boron nitride, agglomerated boron nitride, silicon nitride, aluminum nitride, etc.); metal sulfates (e.g., barium sulfate, etc.); metal hydroxides (e.g., aluminum hydroxide, heat-treated aluminum hydroxide (e.g., aluminum hydroxide that has been heat-treated to remove some of the water of crystallization), boehmite, magnesium hydroxide, etc.); molybdenum compounds (e.g., molybdenum oxide, and zinc molybdate, etc.); zinc compounds (e.g., zinc borate, zinc stannate, etc.); clay (e.g., natural clay, and calcined clay); kaolin (e.g., natural kaolin, and calcined kaolin); talc (e.g., natural talc, and calcined talc); mica; glass (e.g., E-glass, A-glass, NE-glass, C-glass, L-glass, D-glass, S-glass, M-glass G20, glass short fiber (including glass fine powders such as E-glass, T-glass, D-glass, S-glass, and Q-glass), hollow glass, and spherical glass). These inorganic fillers may be used alone or in combination of two or more.

Examples of silica include natural silica, fused silica, synthetic silica, amorphous silica, aerosil, hollow silica, and white carbon. Commercially available silica includes SC2050-MB (product name), SC5050-MOB (product name), SC2500-SQ (product name), SC4500-SQ (product name), SC5050-MOB (product name), SO-C2 (product name), and SO-C1 (product name) manufactured by Admatechs Co., Ltd., and SFP-130MC (product name) manufactured by Denka Co., Ltd.

Organic filler The resin composition of the present embodiment may contain an organic filler, but it is preferable that the resin composition does not contain an organic filler because it allows the printed wiring board to be thin and small, and has a high peel strength while also having a moderate surface hardness. "Doing not contain an organic filler" means that the content of the organic filler is 0 parts by mass relative to 100 parts by mass of the resin solid content in the resin composition.
Examples of the organic filler include rubber powders such as styrene type powder, butadiene type powder, and acrylic type powder; core-shell type rubber powder; silicone type powder, etc. These organic fillers may be used alone or in combination of two or more.

Examples of silicone type powders include silicone resin powder, silicone rubber powder, and silicone composite powder. These silicone type powders may be used alone or in combination of two or more.

(Silane coupling agent)
The resin composition according to the present embodiment preferably contains a silane coupling agent. In the present embodiment, by containing the silane coupling agent, the adhesive strength between the components of the resin composition according to the present embodiment and the support and the substrate of the printed wiring board tends to be further improved.

Examples of silane coupling agents include silane coupling agents that are generally used for surface treatment of inorganic substances. Examples include aminosilane compounds (e.g., γ-aminopropyltriethoxysilane, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, etc.), epoxysilane compounds (e.g., γ-glycidoxypropyltrimethoxysilane, etc.), acrylicsilane compounds (e.g., γ-acryloxypropyltrimethoxysilane, etc.), cationic silane compounds (e.g., N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, etc.), and phenylsilane compounds. These silane coupling agents are used alone or in combination of two or more. Among these, the silane coupling agent is preferably an epoxysilane compound because it has excellent reactivity with resin components and excellent adhesion to the substrate in the support and printed wiring board. Examples of epoxysilane-based compounds include KBM-403 (trade name), KBM-303 (trade name), KBM-402 (trade name), and KBE-403 (trade name), all of which are manufactured by Shin-Etsu Chemical Co., Ltd.

The amount of silane coupling agent is not particularly limited, but it is preferable that the amount be 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of resin solids.

(Wetting and dispersing agent)
The resin composition according to the present embodiment preferably contains a wetting dispersant. In the present embodiment, by including the wetting dispersant, the rigidity of the obtained cured product is further improved, and the warpage of the printed wiring board tends to be further reduced.

Examples of wetting and dispersing agents include known dispersing agents (dispersion stabilizers) used to disperse fillers. Examples include DISPERBYK (registered trademark)-110 (trade name), 111 (trade name), 118 (trade name), 180 (trade name), 161 (trade name), W996 (trade name), W9010 (trade name), and W903 (trade name) manufactured by BYK-Chemie Japan Co., Ltd. These wetting and dispersing agents may be used alone or in combination of two or more types.

The content of the wetting dispersant is preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the resin solids. By having the content within the above range, the rigidity of the obtained cured product is further improved, and the warping of the printed wiring board tends to be further reduced. From the same viewpoint, the lower limit of the content is more preferably 1.5 parts by mass, and even more preferably 2 parts by mass.

(Cure Accelerator)
The resin composition according to the present embodiment preferably contains a curing accelerator. Examples of the curing accelerator include imidazoles (e.g., triphenylimidazole, etc.); organic peroxides (e.g., benzoyl peroxide, lauroyl peroxide, acetyl peroxide, parachlorobenzoyl peroxide, and di-tert-butyl-di-perphthalate, etc.); azo compounds (e.g., azobisnitrile, etc.); tertiary amines (e.g., N,N-dimethylbenzylamine, N,N-dimethylaniline, N,N-dimethyltoluidine, N,N-dimethylpyridine, 2-N-ethylanilinoethanol, tri-n-butylamine, pyridine, quinoline, N-methylmorpholine, triethanolamine, triethylenediamine, tetramethylphenyl ... methylbutanediamine, N-methylpiperidine, etc.); phenols (e.g., phenol, xylenol, cresol, resorcin, catechol, etc.); organic metal salts (e.g., lead naphthenate, lead stearate, zinc naphthenate, zinc octylate, tin oleate, dibutyltin maleate, manganese naphthenate, cobalt naphthenate, and iron acetylacetonate, etc.); these organic metal salts dissolved in hydroxyl-containing compounds such as phenol and bisphenol; inorganic metal salts (e.g., tin chloride, zinc chloride, and aluminum chloride, etc.); and organic tin compounds (e.g., dioctyltin oxide, other alkyl tins, and alkyl tin oxides, etc.). These curing accelerators may be used alone or in combination of two or more. Among these, the curing accelerator is preferably 2,4,5-triphenylimidazole from the viewpoint of accelerating the curing reaction and further improving the glass transition temperature (Tg) of the obtained cured product.
The content of the curing accelerator is preferably 0.1 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the resin solid content.

(Other Additives)
The resin composition according to the present embodiment may contain various polymer compounds such as thermosetting resins, thermoplastic resins, oligomers, and elastomers that have not been mentioned so far; additives that have not been mentioned so far, etc., within the scope that does not impair the characteristics of the present embodiment. These are not particularly limited as long as they are commonly used. Examples of additives include ultraviolet absorbers, antioxidants, photopolymerization initiators, fluorescent brighteners, photosensitizers, dyes, pigments, thickeners, flow regulators, lubricants, defoamers, dispersants, leveling agents, gloss agents, and polymerization inhibitors. These other additives are used alone or in combination of two or more.
The content of each of the other additives is usually 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the resin solid content.

(solvent)
The resin composition according to the present embodiment may contain a solvent. By containing a solvent, the resin composition according to the present embodiment tends to have a lower viscosity during preparation of the resin composition, further improve the handleability, and further improve the impregnation property into the support.

The solvent is not particularly limited as long as it can dissolve a part or all of the resin content in the resin composition. Examples of the solvent include ketones (e.g., acetone, methyl ethyl ketone, methyl cellosolve, etc.); aromatic hydrocarbons (e.g., toluene, xylene, etc.); amides (e.g., dimethylformaldehyde, etc.); propylene glycol monomethyl ether and its acetate, etc. These solvents are used alone or in combination of two or more.

(Method for producing resin composition)
Examples of the method for producing the resin composition according to the present embodiment include a method for obtaining the resin composition by mixing the components all at once or successively, and a method for obtaining the resin composition in the form of a varnish by mixing the components all at once or successively in a solvent, stirring the components, and dissolving or dispersing the components in the solvent. In this case, in order to dissolve or disperse the components uniformly, known processes such as stirring, mixing, and kneading are used. The solvent is as described above. For specific production methods, the examples can be referred to.

[Support]
The support according to the present embodiment can be a known one used in various printed wiring board materials, and is preferably a resin sheet or metal foil. The resin sheet is different from the resin sheet of the present embodiment, that is, a resin sheet having a support and a layer containing a resin composition arranged on the surface of the support. Examples of the resin sheet and metal foil include resin sheets such as polyimide film, polyamide film, polyester film, polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, polypropylene (PP) film, and polyethylene (PE) film; and metal foils such as aluminum foil, copper foil, and gold foil. Among these, copper foil and PET film are preferred because they have high heat resistance and flatness, and copper foil is more preferred.

In this embodiment, when a copper foil is used as a support, it is possible to improve the adhesion strength between the copper foil and the layer containing the resin composition, prevent peeling of the layer during long-term use, and have excellent wiring formability. Therefore, the arithmetic mean roughness (Ra) of the copper foil surface in contact with the layer containing the resin composition is preferably 0.05 μm or more and 2 μm or less, more preferably 0.08 μm or more and 1.7 μm or less, and even more preferably 0.2 μm or more and 1.6 μm or less. In this embodiment, by using a copper foil having an arithmetic mean roughness in the above range as a support, a printed wiring board having high-density fine wiring formed thereon can be suitably manufactured. The arithmetic mean roughness can be measured using a commercially available shape measuring microscope (laser microscope, for example, VK-X210 (trade name) manufactured by Keyence Corporation). Specific measurement methods are as described in the Examples.
Examples of the copper foil include electrolytic copper foil, rolled copper foil, and copper alloy film. The copper foil and copper film may be subjected to a known surface treatment such as matte treatment, corona treatment, nickel treatment, and cobalt treatment. As the copper foil, a commercially available product may be used, and examples thereof include 3EC-VLP (product name) manufactured by Mitsui Mining & Smelting Co., Ltd., 3EC-M2S-VLP (product name) manufactured by Mitsui Mining & Smelting Co., Ltd., MT18Ex (product name) manufactured by Mitsui Mining & Smelting Co., Ltd., and JXUT-I (product name) manufactured by JX Nippon Mining & Metals Co., Ltd.

In this embodiment, when copper foil is used as the support, high heat resistance and reliability are obtained, so that the copper foil peel strength of the layer containing the resin composition is preferably 0.5 kgf/cm or more, more preferably 0.55 kgf/cm or more, and even more preferably 0.65 kgf/cm or more and 3 kgf/cm or less. The copper foil peel strength can be measured in accordance with JIS C6481. The specific measurement method is as described in the examples.

For reasons of economy and ease of handling, the thickness of the support is preferably 1 μm or more and 105 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 10 μm or more and 25 μm or less. If the thickness of the support is less than 1 μm, it may be difficult to roughen the surface of the support, and the resin sheet may also be difficult to handle. On the other hand, if the thickness of the support exceeds 105 μm, there is a risk that the cost or hole processing may be disadvantageous.

[Application]
The resin sheet of the present embodiment can sufficiently reduce the warping of the printed wiring board, and since cracks are unlikely to occur in the insulating layer of the printed wiring board, cracks in the insulating layer and circuit distortion are unlikely to occur, and excellent heat resistance and high peel strength can be exhibited. Therefore, the resin sheet of the present embodiment is used, for example, in laminates, metal foil-clad laminates, printed wiring boards, and multilayer printed wiring boards. The resin sheet is suitable for printed wiring boards. The resin composition of the present embodiment is also suitable for use as an insulating layer of a printed wiring board or the like, or as a laminate.

[Laminate]
In this embodiment, the resin sheet of this embodiment may be used for a laminate. The laminate includes one or more layers containing the cured product of the resin composition in the resin sheet of this embodiment, and when multiple layers are included, the layers containing the cured product have a laminated form or a laminated form via a conductive layer such as a metal foil. By using the resin sheet of this embodiment, the laminate has a sufficiently reduced warp, and cracks are unlikely to occur in the layer containing the cured product, so that the layer containing the cured product is unlikely to crack, and has excellent heat resistance and high peel strength.

[Metal foil laminate]
In this embodiment, the resin sheet of this embodiment may be used for a metal foil-clad laminate. The metal foil-clad laminate includes a layer containing a cured product of the resin composition in the resin sheet of this embodiment and a metal foil arranged on one or both sides of the layer containing the cured product. The metal foil-clad laminate includes one or more layers containing a cured product of the resin composition in the resin sheet of this embodiment. When the number of layers containing a cured product is one, the metal foil-clad laminate has a form in which a metal foil is arranged on one or both sides of the layer containing the cured product. When the number of layers containing a cured product is multiple, the metal foil-clad laminate has a form in which a metal foil is arranged on one or both sides of the layer containing the laminated cured product. By using the resin sheet of this embodiment, the metal foil-clad laminate has sufficiently reduced warping, and cracks are unlikely to occur in the layer containing the cured product, so that the layer containing the cured product is unlikely to crack, and has excellent heat resistance and high peel strength.

The metal foil (conductor layer) may be any metal foil used in various printed wiring board materials, such as copper and aluminum foil. Examples of copper foil include rolled copper foil and electrolytic copper foil. The thickness of the conductor layer is, for example, 1 μm or more and 70 μm or less, and preferably 1.5 μm or more and 35 μm or less.

The molding method and molding conditions of the laminate and metal foil-clad laminate can be the same as those of the laminate and multilayer board for printed wiring boards. For example, a multi-stage press machine, a multi-stage vacuum press machine, a continuous molding machine, an autoclave molding machine, etc. can be used when molding the laminate and metal foil-clad laminate. In addition, in molding (lamination molding) the laminate and metal foil-clad laminate, the temperature is generally 100°C or higher and 300°C or lower, the pressure is 2 kgf/ ^cm2 or higher and 100 kgf/cm2 or ^lower , and the heating time is generally 0.05 hours or higher and 5 hours or lower. Furthermore, if necessary, post-curing can be performed at a temperature of 150°C or higher and 300°C or lower. For example, when a multi-stage press is used, from the viewpoint of sufficiently promoting the curing of the resin composition in the resin sheet, the temperature is preferably 200° C. or more and 250° C. or less, the pressure is 10 kgf/cm ² or more and 40 kgf/cm ² or less, and the heating time is preferably 80 minutes or more and 130 minutes or less, and the temperature is more preferably 215° C. or more and 235° C. or less, the pressure is 25 kgf/cm ² or more and 35 kgf/cm ² or less, and the heating time is more preferably 90 minutes or more and 120 minutes or less. In addition, in the resin sheet of this embodiment, a layer containing the cured product of the resin composition and a separately prepared wiring board for an inner layer are combined and laminated to form a multilayer board.

[Printed wiring board]
The printed wiring board of this embodiment includes a layer containing a cured product of the resin composition in the resin sheet of this embodiment, and a conductor layer disposed on the surface of the layer containing the cured product. The printed wiring board of this embodiment can be formed, for example, by etching the metal foil of a metal foil-clad laminate into a predetermined wiring pattern to form a conductor layer. The printed wiring board of this embodiment has sufficient warping reduced by using a resin sheet, and the layer containing the cured product is less likely to crack, so that the layer containing the cured product is less likely to crack, and has excellent heat resistance and high peel strength.

The printed wiring board of this embodiment can also be obtained, for example, by using the resin sheet of this embodiment as a build-up material for a metal foil laminate in which the insulating layer, called a core substrate, has been fully cured.

On the surface of the core board, a conductor circuit is formed by a conductor layer obtained by plating after peeling off the metal foil of a metal foil laminate usually used in the industry. The core board is not particularly limited, but a patterned conductor layer (circuit) is formed on one or both sides of a substrate such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a substrate of bismaleimide triazine resin, and a thermosetting polyphenylene ether substrate. In addition, the inner layer circuit substrate of an intermediate product on which an insulating layer and/or a conductor layer is to be formed when manufacturing a printed wiring board is also included in the circuit substrate in this embodiment. Note that it is preferable that the surface of the conductor layer (circuit) has been roughened in advance by blackening treatment or the like from the viewpoint of adhesion of the insulating layer to the circuit substrate. For example, the above-mentioned metal foil can be referred to as the metal foil. For example, the above-mentioned conductor layer can be referred to as the conductor layer.

In this embodiment, build-up refers to a method of laminating a layer containing a semi-cured resin composition of the resin sheet of this embodiment onto the surface conductor circuit. The semi-cured resin is then usually subjected to a heat treatment or the like to completely cure it, thereby obtaining a printed wiring board.

In the manufacture of printed wiring boards, via holes and/or through holes are drilled as necessary to electrically connect each conductor layer. Drilling is usually performed using a mechanical drill, a carbon dioxide laser, a UV laser, a YAG laser, or the like.

When this hole processing is performed, it is preferable to then perform a roughening process including a desmear process. Note that the roughening process usually consists of a swelling process, a surface roughening process, a smear dissolving process, and a neutralization process.

The swelling process is carried out by swelling the surface of the insulating layer using a swelling agent. There are no particular limitations on the swelling agent, but it is preferable to use one that can improve the wettability of the surface of the insulating layer and swell the surface of the insulating layer to such an extent that oxidative decomposition is promoted in the subsequent surface roughening and smear dissolution processes. Examples of swelling agents include an alkaline solution and a surfactant solution.

The surface roughening and smear dissolution process is carried out using an oxidizing agent. Examples of the oxidizing agent include an alkaline permanganate solution, and an aqueous potassium permanganate solution and an aqueous sodium permanganate solution are preferred. Such an oxidizing agent treatment is called wet desmearing, but in addition to wet desmearing, dry desmearing by plasma treatment and UV treatment, mechanical polishing by buffing, and other known roughening treatments such as sandblasting may be appropriately combined.

In the neutralization step, the oxidizing agent used in the previous step is neutralized with a reducing agent. Examples of the reducing agent include amine-based reducing agents, and preferred are acidic aqueous solutions such as an aqueous solution of hydroxylamine sulfate, an aqueous solution of ethylenediaminetetraacetic acid, and an aqueous solution of nitrilotriacetic acid.

In this embodiment, after providing the via holes and/or through holes, or after desmearing the inside of the via holes and/or through holes, it is preferable to perform a metal plating process to electrically connect each conductor layer.

The method of metal plating is not particularly limited, and a treatment method used in the manufacture of a normal printed wiring board can be used as appropriate. The method of metal plating and the type of chemical used for plating are not particularly limited, and a treatment method and chemical used in the manufacture of a normal printed wiring board can be used as appropriate. The chemical used for metal plating may be a commercially available product.
Examples of metal plating methods include treatment with a degreasing liquid, treatment with a soft etching liquid, acid washing, treatment with a pre-dip liquid, treatment with a catalyst liquid, treatment with an accelerator liquid, treatment with a chemical copper liquid, acid washing, and treatment in which the substrate is immersed in a copper sulfate liquid and an electric current is passed through the substrate.

The metal plating process for forming a conductor layer on a layer containing a resin composition is carried out, for example, by forming a conductor layer on the surface of the layer containing a resin composition on which irregularities have been formed by roughening treatment, using a method that combines electroless plating and electrolytic plating, or by forming a conductor layer only by electroless plating. The conductor layer can be formed from metals such as copper, aluminum, nickel, silver, and gold, as well as alloys of these metals, with copper being more preferred. The copper plating layer can be formed by a method that combines electroless copper plating and electrolytic copper plating, or by forming a plating resist with a reverse pattern to the conductor layer and then forming the conductor layer only by electroless copper plating.

Examples of the circuit formation process include the semi-additive method, the full-additive method, and the subtractive method. Among these, the semi-additive method is preferred from the viewpoint of forming fine wiring patterns.

One example of a method for forming a pattern using the semi-additive method is to form a thin conductor layer on the surface of an insulating layer by electroless plating or the like, then selectively apply electrolytic plating using a plating resist (pattern plating), and then peel off the plating resist and etch the entire surface appropriately to form a wiring pattern.

When forming a wiring pattern by plating, it is preferable to perform a drying process after plating in order to improve the adhesive strength between the insulating layer and the conductor layer. In pattern formation by the semi-additive method, electroless plating and electrolytic plating are performed in combination, and in this case, it is preferable to perform drying after electroless plating and after electrolytic plating, respectively. Drying after electroless plating is preferably performed, for example, at 80°C to 180°C and for 10 minutes to 120 minutes. Drying after electrolytic plating is preferably performed, for example, at 130°C to 220°C and for 10 minutes to 120 minutes. Copper plating is preferable as the plating.

In addition, if an insulating layer is present on the surface of the printed wiring board, this insulating layer can be surface-treated, and a conductor layer can be provided by plating or the like, and a pattern circuit can be formed using this conductor layer. When forming a pattern by plating, it is preferable to roughen the surface of the insulating layer before plating.

A vacuum pressure laminator can be suitably used as a lamination method in the build-up method. In this case, a method of laminating the resin sheet of the present embodiment via an elastic body such as rubber is preferred. The lamination conditions are not particularly limited as long as they are conditions generally used in the industry, but for example, the lamination is performed at a temperature of 70°C to 140°C, a contact pressure of 1 kgf/ ^cm2 to 11 kgf/ ^cm2 , and a reduced pressure atmosphere of 20 hPa or less. After the lamination process, the laminated adhesive film may be smoothed by hot pressing with a metal plate. The lamination process and the smoothing process can be performed continuously by a commercially available vacuum pressure laminator. After the lamination process or the smoothing process, a heat curing process can be performed. The heat curing process completely cures the resin composition. The heat curing conditions vary depending on the type of resin composition, etc., but usually the curing temperature is 170°C to 190°C, and the curing time is 15 minutes to 60 minutes.

In addition, when a metal foil-clad laminate is not used, a printed wiring board may be produced by forming a conductor layer that serves as a circuit on a layer containing the resin composition in the resin sheet of this embodiment. In this case, an electroless plating technique may be used to form the conductor layer.

[Multilayer printed wiring board (multilayer core board)]
In this embodiment, an insulating layer and/or a conductor layer may be further laminated on the printed wiring board to obtain a multilayer printed wiring board. The inner layer of the multilayer printed wiring board may have a circuit board. The multilayer printed wiring board of this embodiment has sufficient warping reduced by using a resin sheet, and the layer containing the cured product is less likely to crack because cracks are unlikely to occur in the layer containing the cured product, and has excellent heat resistance and high peel strength.

The lamination method is not particularly limited, but a method generally used in lamination molding of ordinary printed wiring boards can be used. Examples of lamination methods include a multi-stage press, a multi-stage vacuum press, a laminator, a vacuum laminator, and an autoclave molding machine. The lamination is performed, for example, at a temperature of 100°C to 300°C, a pressure of 0.1 kgf/ ^cm2 to 100 kgf/ ^cm2 (about 9.8 kPa to about 9.8 MPa), and a heating time of 30 seconds to 5 hours. If necessary, post-curing may be performed at a temperature range of, for example, 150°C to 300°C to adjust the degree of curing.

[Multilayer printed wiring board (multilayer coreless substrate)]
In this embodiment, the resin sheet of this embodiment may be used for a multilayer printed wiring board. The multilayer printed wiring board may have, for example, a plurality of insulating layers consisting of a first insulating layer and one or more second insulating layers laminated on one side of the first insulating layer, a first conductor layer arranged between each of the plurality of insulating layers, and a plurality of conductor layers consisting of a second conductor layer arranged on the surface of the outermost layer of the plurality of insulating layers, and the first insulating layer and the second insulating layer are each an insulating layer formed of a cured product of the resin composition in the resin sheet of this embodiment.

The multilayer printed wiring board may be, for example, a so-called coreless type multilayer printed wiring board (multilayer coreless substrate) in which a second insulating layer is laminated only on one side of a first insulating layer. In this embodiment, an insulating layer formed of a cured product of the resin composition in the resin sheet of this embodiment is used, so that the multilayer printed wiring board has sufficiently reduced warping, is less likely to crack in the layer containing the cured product, and has excellent heat resistance and high peel strength. For this reason, in this embodiment, it can be effectively used as a multilayer coreless substrate for semiconductor packages.

The present invention will be further explained below using examples and comparative examples, but the present invention is not limited to these examples in any way.

[Evaluation of copper foil]
(arithmetic mean roughness)
The copper foil surface was photographed with a shape measuring microscope (laser microscope, Keyence Corporation VK-X210 (product name)) at an objective lens magnification of 150 times (magnification on a 15-inch monitor: 3000 times). Next, the height distribution on a straight line of 90 μm length randomly selected from the photographed image was obtained by image processing, and the arithmetic mean roughness (Ra) was calculated.

Synthesis Example 1
The α-naphthol aralkyl cyanate ester compound (SN495VCN) was synthesized according to the following procedure.
0.47 moles (OH group equivalent) of α-naphthol aralkyl resin (SN495V, OH group equivalent: 236 g/eq., manufactured by Nippon Steel Chemical Co., Ltd.: the number of repeating units n of naphthol aralkyl is 1 to 5) was dissolved in 500 mL of chloroform, and 0.7 moles of triethylamine was added to this solution (solution 1). While keeping the temperature at -10°C, the above solution 1 was dropped over 1.5 hours into 300 g of a chloroform solution in which 0.93 moles of cyanogen chloride was dissolved, and after the dropwise addition, the mixture was stirred for 30 minutes. Thereafter, a mixed solution of 0.1 moles of triethylamine and 30 g of chloroform was dropped into the reactor, and the reaction was completed by stirring for 30 minutes. The by-produced triethylamine hydrochloride was filtered out from the reaction solution, and the obtained filtrate was washed with 500 mL of 0.1 N hydrochloric acid, and then washed with 500 mL of water four times. This was dried over sodium sulfate, then dried to dryness at 75° C. under reduced pressure, and further degassed under reduced pressure at 90° C. to obtain a brown solid α-naphthol aralkyl cyanate ester compound represented by the above formula (1a) (wherein all R ^1c 's are hydrogen atoms, and the number of repeating units n1 is 1 or more and 5 or less). When the obtained α-naphthol aralkyl cyanate ester compound was analyzed by infrared absorption spectroscopy, absorption of the cyanate ester group was confirmed at around 2264 cm ⁻¹ .

[Example 1]
Biphenylaralkyl-type phenol compound (KAYAHARD (registered trademark) GPH-103 (trade name), manufactured by Nippon Kayaku Co., Ltd., hydroxyl group equivalent: 231 g/eq., represented by the above formula (2c), in which all of R ^2b are hydrogen atoms, and the number of repeating units m1 is 1 or more and 6 or less), 36 parts by mass; biphenylaralkyl-type epoxy resin (NC-3000FH (trade name), epoxy equivalent: 320 g/eq., manufactured by Nippon Kayaku Co., Ltd., represented by the above formula (3b), the number of repeating units ka is 1 or more and 6 or less), 39 parts by mass; naphthalenearalkyl-type epoxy resin (HP-9900 (trade name), epoxy equivalent: 274 g/eq., manufactured by DIC Corporation, (represented by formula (3c), the number of repeating units ky is 1 or more and 10 or less) 7 parts by mass, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane (BMI-70 (trade name, manufactured by K.I. Chemical Co., Ltd.) 18 parts by mass, wetting and dispersing agent 1 (DISPERBYK (registered trademark)-161 (trade name), manufactured by BYK Japan Co., Ltd.) 1 part by mass, wetting and dispersing agent 2 (DISPERBYK (registered trademark)-111 (trade name), manufactured by BYK Japan Co., Ltd.) A varnish (resin composition) was obtained by blending (mixing) 2 parts by mass of silane coupling agent (KBM-403 (trade name), manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part by mass of silane coupling agent (KBM-403 (trade name), manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.5 parts by mass of 2,4,5-triphenylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.), and then diluting with methyl ethyl ketone. This varnish (resin composition) was diluted with methyl ethyl ketone and coated with a 350 mm x 250 mm x 12 μm thick copper foil (arithmetic average roughness (Ra): A resin sheet having a B-staged layer containing the resin composition and a thickness of 20 μm was obtained by applying the coating solution to the matte surface of a polyester film (0.5 μm, 3EC-M2S-VLP (product name), manufactured by Mitsui Mining & Smelting Co., Ltd.) and drying by heating at 130° C. for 5 minutes. A varnish (resin composition) was prepared in the same manner, and a resin sheet having a B-staged layer containing the resin composition and a thickness of 20 μm was obtained using this varnish.

[Example 2]
In Example 1, 40 parts by mass of slurry silica (SC2050-MB (product name), average particle size 0.7 μm, manufactured by Admatechs Co., Ltd.) was further added to obtain a varnish (resin composition). In the same manner as in Example 1, a resin sheet having a B-staged layer containing the resin composition, the layer containing the resin composition having a thickness of 5 μm or 20 μm, was obtained.

[Example 3]
In Example 1, the amount of biphenyl aralkyl type epoxy resin (NC-3000FH (trade name)) blended was changed from 39 parts by mass to 19 parts by mass, and 20 parts by mass of naphthylene ether type epoxy resin (HP-6000 (trade name), epoxy equivalent: 250 g/eq., manufactured by DIC Corporation, represented by the above formula (3g), in which all R ^3b are hydrogen atoms, and the number of repeating units k1 is 2) was blended. Except for this, a resin sheet having a B-staged layer containing the resin composition, with the layer containing the resin composition having a thickness of 5 μm or 20 μm, was obtained in the same manner as in Example 1.

[Example 4]
The mixture was prepared by the method described in Synthesis Example 1, and contained 34 parts by mass of an α-naphthol aralkyl type cyanate ester compound (cyanate equivalent: 261 g/eq.), 5 parts by mass of bis(3-ethyl-5-methyl-4-maleimidophenyl)methane (BMI-70 (trade name, manufactured by K.I. Kasei Co., Ltd.)), 15 parts by mass of a biphenyl aralkyl type epoxy resin (NC-3000FH (trade name)), 5 parts by mass of a naphthylene ether type epoxy resin (HP-6000 (trade name)), 26 parts by mass of a dicyclopentadiene type epoxy resin (EPICRON (registered trademark) HP-7200L (trade name), epoxy equivalent: 249 g/eq., manufactured by DIC Corporation), and 26 parts by mass of a bisphenone type epoxy resin (EPICRON (registered trademark) HP-7200L (trade name), epoxy equivalent: 249 g/eq., manufactured by DIC Corporation). An epoxy resin consisting of an epoxy A type structural unit and a hydrocarbon-based structural unit (EPICLON (registered trademark) EXA-4816 (trade name), manufactured by DIC Corporation, epoxy equivalent: 403 g/eq., represented by the above formula (3j)) (15 parts by mass), wetting dispersant 1 (DISPERBYK (registered trademark)-161 (trade name)), 2 parts by mass of wetting dispersant 2 (DISPERBYK (registered trademark)-111 (trade name)), 1 part by mass of a silane coupling agent (KBM-403 (trade name)), and 0.5 parts by mass of 2,4,5-triphenylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) were blended (mixed), and then diluted with methyl ethyl ketone to obtain a varnish (resin composition). This varnish (resin composition) was diluted with methyl ethyl ketone and applied to the matte side of a 350 mm x 250 mm x 12 μm thick copper foil (3EC-M2S-VLP (product name)) using a bar coater, and dried by heating at 130° C. for 5 minutes to obtain a resin sheet having an insulating resin layer of a 5 μm thick B-staged layer containing the resin composition. In addition, a varnish (resin composition) was prepared in the same manner, and this varnish was used to obtain a resin sheet having a 20 μm thick B-staged layer containing the resin composition.

[Comparative Example 1]
In Example 1, 80 parts by mass of slurry silica (SC2050-MB (product name), average particle size 0.7 μm) was further added to obtain a varnish (resin composition). In the same manner as in Example 1, a resin sheet having a B-staged layer containing the resin composition, the layer containing the resin composition having a thickness of 5 μm or 20 μm, was obtained.

[Comparative Example 2]
40 parts by mass of an α-naphthol aralkyl type cyanate ester compound (cyanate equivalent: 261 g / eq.) synthesized by the method described in Synthesis Example 1, 20 parts by mass of a polyphenylmethane maleimide compound (BMI-2300 (trade name)), 40 parts by mass of a naphthylene ether type epoxy resin (HP-6000 (trade name)), 1 part by mass of a wetting dispersant 1 (DISPERBYK (registered trademark) -161 (trade name)), 2 parts by mass of a wetting dispersant 2 (DISPERBYK (registered trademark) -111 (trade name)), 1 part by mass of a silane coupling agent (KBM-403 (trade name)), and 0.5 parts by mass of 2,4,5-triphenylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) were blended (mixed), and then diluted with methyl ethyl ketone to obtain a varnish (resin composition). This varnish (resin composition) was diluted with methyl ethyl ketone and applied to the matte side of a 350 mm x 250 mm x 12 μm thick copper foil (3EC-M2S-VLP (product name)) using a bar coater, and dried by heating at 130° C. for 5 minutes to obtain a resin sheet having a B-staged layer containing the resin composition with a thickness of 5 μm. Further, a varnish (resin composition) was prepared in the same manner, and this varnish was used to obtain a resin sheet having a B-staged layer containing the resin composition with a thickness of 20 μm.

[Comparative Example 3]
5 parts by mass of α-naphthol aralkyl type cyanate ester compound (cyanate equivalent: 261 g/eq.) synthesized by the method described in Synthesis Example 1, 50 parts by mass of polyphenylmethane maleimide compound (BMI-2300 (trade name)), 10 parts by mass of biphenyl aralkyl type epoxy resin (NC-3000FH (trade name)), 35 parts by mass of alkenyl-substituted nadiimide compound (BANI-M (trade name), manufactured by Maruzen Petrochemical Co., Ltd.), Amount parts, wetting dispersant 1 (DISPERBYK (registered trademark)-161 (trade name)) 1 part by mass, wetting dispersant 2 (DISPERBYK (registered trademark)-111 (trade name)) 2 parts by mass, silane coupling agent (KBM-403 (trade name)) 1 part by mass, 2,4,5-triphenylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.5 parts by mass were blended (mixed), and then diluted with methyl ethyl ketone to obtain a varnish (resin composition). This varnish (resin composition) was diluted with methyl ethyl ketone and applied to the matte surface side of a 350 mm x 250 mm x 12 μm thick copper foil (3EC-M2S-VLP (trade name)) by a bar coater, and heated and dried at 130 ° C. for 5 minutes to obtain a resin sheet having a layer containing the resin composition and a B-staged layer containing the resin composition with a thickness of 5 μm. Further, a varnish (resin composition) was prepared in the same manner, and this varnish was used to obtain a resin sheet having a B-staged layer containing the resin composition, the layer containing the resin composition being 20 μm thick.

[Physical property measurement and evaluation]
Using the resin sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 3, each having a layer containing the resin composition of 5 μm or 20 μm in thickness, samples for measuring and evaluating physical properties were prepared according to the procedures shown in the following items, and the Vickers hardness, warpage, crack length, heat resistance, and copper foil peel strength were measured and evaluated. The results of the Examples and Comparative Examples are summarized in Table 1.

(Vickers hardness (HV0.01))
First, a copper foil clad laminate 1 (HL832NSR (trade name) T/T 0.1 mmt, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used to etch the copper foil on one side of the copper foil clad laminate 1 to obtain an unclad plate. Next, using one resin sheet having a layer thickness of 5 μm containing the resin composition obtained in Example 1, the layer containing the resin composition of this resin sheet was placed on the resin surface of the unclad plate, and laminate molding (thermal curing) was performed for 120 minutes at a pressure of 30 kgf/cm ² and a temperature of 220 ° C. to obtain a copper foil clad laminate 2 (size: 297 mm × 210 mm) having copper foil on both sides. Next, both copper foils were removed from the obtained copper foil clad laminate 2 by etching to obtain a test piece (cured product). This test piece was placed on a slide glass, and the test piece was fixed to the slide glass with a cyanoacrylate-based instant adhesive (Aron Alpha (registered trademark) 201 (trade name), manufactured by Toagosei Co., Ltd.). Using a micro Vickers hardness tester (HMV-G (trade name), manufactured by Shimadzu Corporation, load 0.01 kgf, holding time 10 seconds), the Vickers hardness was measured at seven arbitrary points on the surface of the test piece, and the average value was calculated.
The Vickers hardness of each of the resin sheets obtained in Examples 2 to 4 and Comparative Examples 1 to 3, each having a layer containing a resin composition and a thickness of 5 μm, was measured in the same manner.

(Warpage: bimetal method)
First, a copper foil clad laminate 1 (HL832NSR (trade name) T/T 0.1 mmt, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used to etch the copper foil on one side of the copper foil clad laminate 1 to obtain an unclad plate. Next, a resin sheet having a thickness of 5 μm containing the resin composition obtained in Example 1 was used to place the layer containing the resin composition of the resin sheet on the resin side of the unclad plate, and laminate molding (thermosetting) was performed for 120 minutes at a pressure of 30 kgf/cm ² and a temperature of 220° C. to obtain a copper foil clad laminate 2 (size: 297 mm x 210 mm) having copper foil on both sides. Next, the copper foil was removed from both sides of the obtained copper foil clad laminate 2 by etching to obtain a laminate. Then, one end of the short side of the laminate was attached to a surface perpendicular to the plane with a magnet, and a straightedge (metal ruler) was placed parallel to the plane to measure the distance between the perpendicular surface and the laminate. In the laminate, the resin surface originating from the copper foil laminate 1 was attached to a vertical surface. Measurements were taken at eight locations in total, including the center locations of the four sides of the laminate and four locations at the corners. The average value was calculated from these measurements, and this average value was used as the "warpage" according to the bimetal method. When the warpage was less than 10 mm, it was rated as "AA," and otherwise it was rated as "CC."
The amount of warping of each of the resin sheets having a resin composition layer thickness of 5 μm obtained in Examples 2 to 4 and Comparative Examples 1 to 3 was similarly measured and evaluated.

(crack length)
Using one resin sheet having a layer containing the resin composition of 20 μm obtained in Example 1, the layer containing the resin composition of this resin sheet was placed on a copper foil (3EC-M2S-VLP (trade name), thickness 12 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.) and laminated (thermosetting) was performed for 120 minutes at a pressure of 30 kgf/cm ² and a temperature of 220° C. to obtain a copper foil-clad laminate. The copper foil was removed from both sides of the obtained copper foil-clad laminate by etching to obtain a test piece (cured product). This test piece was placed on a slide glass, and a load was applied at 10 points using a micro Vickers hardness tester (HMV-G (trade name), manufactured by Shimadzu Corporation, load 2 kgf, holding time 15 seconds). The 10 points were checked for the occurrence of a cross-shaped crack (crack), and if a crack occurred, the vertical and horizontal lengths of the crack were measured. If no crack was observed, the length of the crack was set to 0. The average crack length was calculated from both the vertical and horizontal lengths of the cracks at 10 locations, and if the average was 200 μm or less, it was rated as "AA," and otherwise it was rated as "CC."
Similarly, the average crack length was measured and evaluated for each of the resin sheets obtained in Examples 2 to 4 and Comparative Examples 1 to 3, each having a layer containing a resin composition of 20 μm in thickness.

(heat resistance)
First, a copper foil clad laminate 1 (HL832NSR (trade name) T/T 0.8 mmt, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used, and the copper foil surfaces on both sides of this copper foil clad laminate 1 were etched to about 1 to 3 μm (inner layer roughening treatment, CZ-8100 (trade name), manufactured by MEC Co., Ltd.). Thereafter, the resin sheet having a layer thickness of 5 μm containing the resin composition obtained in Example 1 was arranged on each of the two sides so that the layer surface containing the resin composition was on the inside, and laminate molding (thermal curing) was performed at a pressure of 30 kgf/cm ² and a temperature of 220° C. for 120 minutes to obtain a copper foil clad laminate 2. The obtained copper foil clad laminate 2 was cut (downsized) to a size of 50 mm x 50 mm to obtain a measurement sample. The obtained sample was left in a constant temperature bath at 120° C. for 1 hour as a pretreatment, and then immersed in a solder bath at 260° C. for 30 seconds to evaluate heat resistance. After 30 seconds had elapsed, the presence or absence of delamination between the copper foil on the surface of the copper foil-clad laminate 1 and the cured layer of the layer containing the resin composition in the resin sheet was confirmed for each surface of the copper foil-clad laminate 1. Cases in which no delamination occurred on either side were marked "AA," and cases in which delamination occurred on either side were marked "CC."
Similarly, the resin sheets each having a layer containing the resin composition and a thickness of 5 μm obtained in Examples 2 to 4 and Comparative Examples 1 to 3 were checked for the occurrence of delamination and their heat resistance was evaluated.

(Copper foil peel strength)
First, a copper foil clad laminate 1 (HL832NSR (trade name) T/T 0.1 mmt, manufactured by Mitsubishi Gas Chemical Co., Inc.) was used, and the copper foil surfaces on both sides of this copper foil clad laminate 1 were etched to about 1 to 3 μm (inner layer roughening treatment, CZ-8100 (trade name), manufactured by MEC Co., Ltd.). Thereafter, on each of the both sides, a resin sheet having a layer containing a resin composition and a thickness of 5 μm obtained in Example 1 was arranged so that the layer surface containing the resin composition was on the inner side, and laminate molding (thermosetting) was performed at a pressure of 30 kgf/cm ² and a temperature of 220° C. for 120 minutes to obtain a copper foil clad laminate 2. Using the obtained copper foil clad laminate 2, the peel strength (kgf/cm) of the copper foil in the normal state was measured for three arbitrary points on the outer layer on one side in accordance with JIS C6481. Similarly, the peel strength (kgf/cm) of the copper foil in its normal state was measured at three arbitrary points on the other outer layer. The average value of the peel strength values (6 points) was calculated, and this average value was defined as the copper foil peel strength.
Similarly, the copper foil peel strength (average value) was calculated for each of the resin sheets obtained in Examples 2 to 4 and Comparative Examples 1 to 3, each having a layer containing a resin composition with a thickness of 5 μm.

This application is based on a Japanese patent application (Patent Application No. 2019-227427) filed on December 17, 2019, the contents of which are incorporated herein by reference.

The resin sheet of this embodiment is suitable for, for example, laminates, metal foil-clad laminates, printed wiring boards, and multilayer printed wiring boards.

Claims (10)

A resin sheet comprising a support and a layer containing a resin composition disposed on a surface of the support,
The resin composition comprises:
a cyanate ester compound and/or a phenol compound;
an epoxy compound and/or a maleimide compound,
Including,
at least one selected from the group consisting of the cyanate ester compound, the phenol compound, the epoxy compound, and the maleimide compound includes a compound having a biphenyl skeleton;
the content of the compound having a biphenyl skeleton is 15 parts by mass or more relative to 100 parts by mass of a resin solid content in the resin composition,
when one or more selected from the group consisting of the cyanate ester compound, the phenol compound, the epoxy compound, and the maleimide compound contain a compound having a polycyclic aromatic ring, the content of the compound having a polycyclic aromatic ring is less than 40 parts by mass per 100 parts by mass of a resin solid content in the resin composition,
When the resin composition contains an inorganic filler, the content of the inorganic filler is 60 parts by mass or less relative to 100 parts by mass of a resin solid content in the resin composition;
The Vickers hardness (HV0.01) of the cured product of the resin composition is 10 or more and 19 or less,
The thickness of the layer containing the resin composition is 2 μm or more and 20 μm or less.
Resin sheet. The resin sheet according to claim 1 , wherein the cyanate ester compound comprises a compound represented by the following formula (1a):
(In formula (1a), each R ^1c independently represents a hydrogen atom or a methyl group, and n1 represents an integer of 1 or more and 10 or less). The resin sheet according to claim 1 or 2 , wherein the phenol compound comprises a compound represented by the following formula (2a):
(In formula (2a), each Ar ¹ independently represents a benzene ring or a naphthalene ring. Ar ² independently represents a benzene ring, a naphthalene ring, or a biphenyl ring. Each R ^2a independently represents a hydrogen atom or a methyl group. m independently represents an integer of 1 or more and 50 or less. Each ring may have a substituent other than a hydroxyl group.) The resin sheet according to any one of claims 1 to 3 , wherein the epoxy compound includes a compound represented by the following formula (3a):
(In formula (3a), each ^Ar3 independently represents a benzene ring or a naphthalene ring. ^Ar4 independently represents a benzene ring, a naphthalene ring, or a biphenyl ring. Each ^R3a independently represents a hydrogen atom or a methyl group. k independently represents an integer of 1 or more and 50 or less. Each ring may have a substituent other than a glycidyloxy group.) The resin sheet according to any one of claims 1 to 4 , wherein the maleimide compound includes a compound represented by the following formula (4a):
(In formula (4a), R ^4a and R ^5a each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; R ^4b each independently represent a hydrogen atom or a methyl group; and s represents an integer of 1 or greater). The resin sheet according to any one of claims 1 to 5 , wherein the layer containing the resin composition has a thickness of 2 µm or more and 15 µm or less. The resin sheet according to any one of claims 1 to 6 , wherein the support has a thickness of 1 µm or more and 105 µm or less. The support is a copper foil,
The arithmetic average roughness (Ra) of the copper foil surface in contact with the layer containing the resin composition is 0.05 μm or more and 2 μm or less.
The resin sheet according to any one of claims 1 to 7 . The copper foil peel strength of the layer containing the resin composition is 0.5 kgf/cm or more.
The resin sheet according to claim 8 . A layer comprising a cured product of the resin composition according to any one of claims 1 to 9 ;
A conductor layer disposed on a surface of the layer containing the cured product;
A printed wiring board comprising: