Low dielectric heat dissipation material

Abstract

A resin-filled boron nitride plate comprising a porous boron nitride sintered plate and an olefin-aromatic vinyl compound-aromatic polyene copolymer filled into the pores of the porous boron nitride sintered plate.

Description

Low dielectric heat dissipation material

[0001] The present invention relates to a low dielectric heat dissipation material.

[0002] As Moore's Law approaches its limits due to increasing interconnect density, in addition to conventional semiconductor device interconnect density, high integration (chipletization) is required through three-dimensional, 3D packaging and functional integration between component devices. As interconnects within devices become multilayered, miniaturized, and denser, insulating materials with low dielectric constants and low dielectric dissipation factors are particularly required for substrates, interposers, and redistribution layer insulation to prevent high-frequency signal delays and noise generation. Furthermore, because temperature changes in insulating materials, not only in various devices but also in various devices, can cause changes in circuit characteristics, efficient removal of heat generated by multilayered, miniaturized, and densely packed devices is required. Furthermore, insulating materials with excellent high-frequency signal transmission and heat dissipation properties are also required for multilayer antenna substrates containing RFICs and high-frequency wiring (antenna feedlines) layered below the antenna structure material of Massive MIMO (phased array antenna / multilayer substrate for transmitter circuit) for 5G / 6G base stations. Furthermore, in next-generation optical interconnect components (switching integrated circuits for optical transceivers in co-packages), there is a demand for efficient removal of the large amounts of heat generated by switching high-frequency signals in switching integrated circuits (ASICs).

[0003] Fluorine-based resins such as perfluoroethylene have traditionally been used as insulating materials for such high-frequency transmission circuits. While these materials possess low dielectric constants, low dielectric loss, and excellent heat resistance, they present challenges in terms of moldability and film formability, making it difficult to achieve multilayer and high-density wiring, and also present issues with adhesion to copper foil. Furthermore, there are also issues with the ability to incorporate heat-dissipating fillers to ensure thermal conductivity. Therefore, attention has been focused on hydrocarbon-based resins with inherently low dielectric properties. Patent Document 1 discloses a cured product obtained from a specific coordination polymerization catalyst and consisting of an ethylene-olefin (aromatic vinyl compound)-aromatic polyene copolymer with a specific composition and blend, and a non-polar vinyl compound. With this technology, only one of the two vinyl groups in the aromatic polyene (divinylbenzene) is selectively copolymerized, preserving the remaining vinyl group. This facilitates the production of cross-linkable hydrocarbon-based copolymer macromonomers with aromatic vinyl groups as functional groups, which exhibit high reactivity (cross-linkability). Cured products obtained from compositions of similar olefin-aromatic vinyl compound-aromatic polyene copolymers and auxiliary materials are characterized by low dielectric constants and low dielectric loss tangents, and a wide range of physical properties from soft to hard can be achieved by selecting the appropriate composition and auxiliary materials (Patent Documents 2 and 3). Furthermore, these copolymers can be filled with a relatively large amount of inorganic filler, and it is said that they can have a variety of properties depending on the type of inorganic filler (Patent Document 4).

[0004] However, the prior art mixture of copolymer and inorganic filler, as described in Patent Document 4, did not adequately resolve the problem of thermal conductivity. Inorganic fillers, such as alumina, silicon nitride, and aluminum nitride, which are typically used to impart thermal conductivity, have an extremely high dielectric constant of approximately 10, resulting in a problem of a particularly high dielectric constant for cured products obtained using such conventional inorganic fillers. Furthermore, while scaly boron nitride according to the prior art is known to have a relatively low dielectric constant and high thermal conductivity, it suffers from the problem of high anisotropy in thermal conductivity and physical properties, making it difficult to achieve high loading in resin. Furthermore, even when scaly boron nitride powder is aggregated to reduce anisotropy, the anisotropy is still high, and due to its low crushing strength, the aggregates tend to disintegrate during molding, potentially resulting in the development of anisotropy.

[0005] Japanese Patent Application Laid-Open No. 2009-161743 International Publication No. 2021 / 112087 International Publication No. 2022 / 014599 Japanese Patent Application Laid-Open No. 2010-280860

[0006] In view of the above background art, therefore, a new method is required that can achieve both low dielectric properties and high thermal conductivity even in applications for multilayered, miniaturized, and highly dense high-frequency transmission wiring.

[0007] In view of the above-mentioned problems, the present invention can provide the following aspects.

[0008] Aspect 1: A resin-filled boron nitride plate comprising: a porous boron nitride sintered plate; and an olefin-aromatic vinyl compound-aromatic polyene copolymer filled into the pores of the porous boron nitride sintered plate.

[0009] Aspect 2: The resin-filled boron nitride plate according to Aspect 1, wherein the porosity of the porous boron nitride sintered plate is in the range of 10 to 70 volume % and the filling rate of the olefin-aromatic vinyl compound-aromatic polyene copolymer is in the range of 10 to 70 volume %.

[0010] Aspect 3: The resin-filled boron nitride plate according to aspect 1 or 2, wherein the porous boron nitride sintered plate has an orientation degree expressed by I.O.P. of 0.6 to 20.

[0011] Aspect 4: The resin-filled boron nitride plate according to any one of Aspects 1 to 3, wherein the olefin-aromatic vinyl compound-aromatic polyene copolymer satisfies all of the following (1) to (5): (1) the number-average molecular weight of the copolymer is 500 to 50,000; (2) the aromatic vinyl compound monomer is an aromatic vinyl compound having from 8 to 20 carbon atoms, and the content of the aromatic vinyl compound monomer unit is from 0.1 to 70 mass%; (3) the olefin monomer unit is one or more selected from an α-olefin monomer unit having from 2 to 30 carbon atoms and a cyclic olefin monomer unit having from 7 to 30 carbon atoms, and the content thereof is from 5 to 95 mass%; (4) the aromatic polyene monomer is one or more selected from polyenes having from 5 to 20 carbon atoms and having multiple vinyl groups and / or vinylene groups in the molecule, and the content of the vinyl groups and / or vinylene groups derived from the aromatic polyene monomer unit is from 2 to 30 per number-average molecular weight. (5) The total amount of the olefin monomer units, aromatic vinyl compound monomer units, and aromatic polyene monomer units is 100% by mass.

[0012] Aspect 5: The resin-filled boron nitride plate according to any one of Aspects 1 to 4, wherein the olefin monomer units constituting the olefin-aromatic vinyl compound-aromatic polyene copolymer include at least a cyclic olefin monomer unit.

[0013] Aspect 6: The resin-filled boron nitride plate according to any one of Aspects 1 to 5, wherein a cured product obtained by solely curing the olefin-aromatic vinyl compound-aromatic polyene copolymer has a dielectric constant of less than 2.5 and a dielectric loss tangent of less than 0.0008, as measured at 40 GHz and 25°C.

[0014] Aspect 7: A cured body of the resin-filled boron nitride plate according to any one of Aspects 1 to 6.

[0015] Aspect 8: The cured product according to aspect 7, having a dielectric constant of 3.0 or more and 5.0 or less, and a dielectric loss tangent of 0.0002 or more and 0.0030 or less.

[0016] Aspect 9: The cured product according to aspect 7 or 8, having a thermal conductivity of 10 W / (m·K) or more.

[0017] Aspect 10: A high-frequency transmission circuit comprising the cured product according to any one of aspects 7 to 9.

[0018] Aspect 11: A single-layer or multi-layer CCL (copper clad laminate) substrate, a single-layer or multi-layer FCCL (flexible copper clad laminate) substrate, an interlayer insulating material, or an antenna, comprising the cured product according to any one of aspects 7 to 9.

[0019] Aspect 12: A three-dimensional highly integrated circuit packaging package or chiplet, comprising the cured product according to any one of aspects 7 to 9.

[0020] According to the present invention, it is possible to provide an insulating and heat-dissipating material that has a low dielectric constant, a low dielectric loss tangent, and high heat dissipation properties and can be suitably used in various high-frequency devices.

[0021] In this specification, the olefin-aromatic vinyl compound-aromatic polyene copolymer may be simply referred to as the copolymer of the present invention or simply as the copolymer. Numerical ranges in this specification include the upper and lower limits unless otherwise specified. In this specification, the term "sheet" also encompasses the concept of a film. Furthermore, the term "film" in this specification also has the same meaning as "sheet." Furthermore, the term "film" in this specification also encompasses the concept of a sheet. In this specification, the term "cured state" is defined as a state in which the gel fraction (gel content) of the olefin-aromatic vinyl compound-aromatic polyene copolymer is 80% by mass or more, more specifically, 90% by mass or more. The gel fraction is a value obtained by measurement in accordance with JIS K6796:1998 or ASTM D2765-84, which corresponds to ISO 10147:1994, which corresponds to JIS.

[0022] In one embodiment of the present invention, there is provided a three-dimensional highly integrated circuit packaging package or chiplet, which includes an insulating material made of a porous boron nitride sintered plate, a resin-filled boron nitride plate made of an olefin-aromatic vinyl compound-aromatic polyene copolymer having its pores filled therein, and a cured body of the resin-filled boron nitride plate.

[0023] The olefin-aromatic vinyl compound-aromatic polyene copolymer used in the present invention may preferably satisfy all of the following (1) to (5): (1) the number-average molecular weight of the copolymer is 500 to 50,000; (2) the aromatic vinyl compound monomer is an aromatic vinyl compound having from 8 to 20 carbon atoms, and the content of the aromatic vinyl compound monomer unit is from 0.1 to 70 mass%, more preferably from 0.1 to less than 60 mass%; (3) the olefin monomer unit is one or more selected from α-olefin monomer units having from 2 to 30 carbon atoms and cyclic olefin monomer units having from 7 to 30 carbon atoms, and the content thereof is from 5 to 95 mass%; (4) the aromatic polyene monomer is one or more selected from polyenes having from 5 to 20 carbon atoms and having multiple vinyl groups and / or vinylene groups in the molecule, and the content of vinyl groups and / or vinylene groups derived from the aromatic polyene monomer units is from 2 to 30 per number-average molecular weight. (5) The total amount of the olefin monomer units, aromatic vinyl compound monomer units, and aromatic polyene monomer units is 100% by mass. The olefin-aromatic vinyl compound-aromatic polyene copolymer is obtained by copolymerizing the olefin, aromatic vinyl compound, and aromatic polyene monomers.

[0024] Here, the olefin monomer (which refers to a monomer that is the basis of the olefin monomer units in the copolymer, but in this specification, the terms "monomer" and "monomer unit" (or "unit") may be used interchangeably depending on the context; the same applies to similar terms hereinafter) refers to a single or multiple monomers selected from α-olefin monomers having from 2 to 20 carbon atoms and cyclic olefin monomers having from 7 to 30 carbon atoms. Examples of α-olefin monomers having from 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, and 3,5,5-trimethyl-1-hexene. Preferably, the α-olefin monomers are a combination of ethylene and an α-olefin other than ethylene, and most preferably ethylene. In the present copolymer, the content of the α-olefin monomer units is arbitrary, but is preferably from 0 to 70% by mass, more preferably from 0 to 60% by mass, and even more preferably from 1 to 60% by mass. The higher the α-olefin monomer unit content (for example, 5% by mass or more), the easier it is to avoid the copolymer and its cured product from becoming brittle, which is preferable.

[0025] As used herein, the term "cyclic olefin monomer" refers to a cyclic olefin having 7 to 30 carbon atoms. Cyclic olefins having 7 to 30 carbon atoms are cyclic olefins having one or more alicyclic structures in the molecule and a polymerizable vinyl group, vinylene group, or vinylidene group. Preferred cyclic olefins are cyclic olefins having a hydrocarbon ring structure without heteroatoms, and more preferred are cyclic olefins having an unsaturated hydrocarbon ring. While such cyclic olefins are characterized by low dielectric properties and high glass transition temperatures, they also have the notable advantage of being easily prepared using inexpensive raw materials and simple processes compared to conventional engineering plastics.

[0026] Examples of such cyclic olefins include norbornenes. Norbornenes are monomers selected from norbornene and substituted norbornenes. Norbornene can be synthesized, for example, by the Diels-Alder reaction of ethylene and cyclopentadiene. Substituted norbornenes are substituted norbornenes containing polymerizable vinyl, vinylene, or vinylidene groups in the molecule, such as dimethanooctahydronaphthalene (DMON) and trimethanododecahydroanthracene (TMDA). These are also Diels-Alder reaction products of norbornenes and cyclopentadiene. These substituted norbornenes are specifically described in, for example, WO 2006 / 118261. In the present invention, more preferred cyclic olefins have a larger number of ring structures and a higher molecular weight, such as dimethanooctahydronaphthalene (DMON) and trimethanododecahydroanthracene (TMDA). Copolymerization of such cyclic olefins allows the production of copolymers with higher glass transition temperatures (Tg) at lower mol% content of the monomer units. This allows the mol% content of other monomer units to be increased while maintaining the high glass transition temperature of the copolymer. Increasing the mol% content of aromatic vinyl compound monomer units as other monomer units enhances the aromatic properties of the copolymer as a whole, which is preferable because it improves the compatibility of the copolymer with other raw materials and resins. These high molecular weight cyclic olefins may be used alone or in mixtures with norbornene, etc., for copolymerization.

[0027] In particular, the above-mentioned DMON and TMDA may be obtained as a mixture with norbornene when produced by the Diels-Alder reaction, and using the mixture as is for polymerization can reduce production costs. Furthermore, in the present invention, more preferred cyclic olefins are norbornenes having aromatic substituents, such as phenylnorbornene (5-phenylbicyclo[2.2.1]hept-2-ene), a Diels-Alder reaction product of cyclopentadiene and styrene, indanylnorbornene (1,4-methano-1,9a,4,4a-tetrahydrofluorene), a Diels-Alder reaction product of cyclopentadiene and indene, and methylphenylnorbornene (MPNB, 5-methyl-5-phenylbicyclo[2.2.1]hept-2-ene), a Diels-Alder reaction product of cyclopentadiene and α-methylstyrene. When copolymerized, norbornenes having such aromatic substituents can impart a higher glass transition temperature (Tg) to the copolymer, and because they exhibit aromaticity, they can exhibit high compatibility with other aromatic raw materials (crosslinkable soft resins and flame retardants). Furthermore, the use of methylphenylnorbornene (5-methyl-5-phenylbicyclo[2.2.1]hept-2-ene) is preferred because it can improve the thermal oxidation resistance of the resulting copolymer, as described in JP-A-2005-239975. Norbornenes having these aromatic substituents are specifically described, for example, in JP-A-11-504669 and JP-A-2005-239975.

[0028] The content of the cyclic olefin monomer units contained in the copolymer is arbitrary. However, when a high glass transition temperature (Tg) of the copolymer is desired, the optimal content of the cyclic olefin monomer contained in the copolymer varies depending on the type of cyclic olefin. For example, it is 50% by mass to 95% by mass, preferably 50% by mass to 95% by mass, more preferably 70% by mass to 95% by mass, and most preferably 80% by mass to 95% by mass. The higher the content of the cyclic olefin monomer units, the higher the Tg of the copolymer. The optimal content of the cyclic olefin monomer units contained in the copolymer may be less than 90% by mass from the viewpoint of imparting a certain degree of toughness to the copolymer. A content within these ranges makes it easier to achieve a preferred high glass transition temperature of the copolymer. The preferred glass transition temperature of the copolymer is 100°C to 350°C, more preferably 130°C to 300°C, and most preferably 180°C to 300°C. On the other hand, when the content of the cyclic olefin monomer units is in the range of 10% by mass to less than 50% by mass, a copolymer with a relatively low Tg is obtained. In particular, in the case of a copolymer that is soft at room temperature, the content of the cyclic olefin monomer unit is in the range of 10% by mass or more to less than 40% by mass. Those skilled in the art can appropriately adjust the type and content of the cyclic olefin to be used in order to achieve this preferred glass transition temperature.

[0029] In a preferred embodiment, the cyclic olefin monomer units contained in the copolymer may include one or more selected from the group consisting of norbornene, methylphenylnorbornene, substituted norbornenes other than methylphenylnorbornene, and dimethanooctahydronaphthalene, and more preferably, may include one or more selected from the group consisting of norbornene, methylphenylnorbornene, and dimethanooctahydronaphthalene.

[0030] The aromatic vinyl compound monomer is an aromatic vinyl compound having from 8 to 20 carbon atoms, such as styrene, paramethylstyrene, ethylvinylbenzene, paraisobutylstyrene, various vinylnaphthalenes, and various vinylanthracenes. The aromatic vinyl compound monomer has one vinyl group within the monomer. The monomer units derived from the aromatic vinyl compound may be contained in the copolymer as a result of copolymerization of an aromatic vinyl component contained as an impurity in the aromatic polyene used in polymerization. The content of the aromatic vinyl compound monomer units contained in the copolymer is optional, but may be preferably from 0.1% by mass to 70% by mass, more preferably from 1% by mass to 60% by mass.

[0031] When the content of aromatic vinyl compound monomer units is 10% by mass or more, the aromaticity of the copolymer can be improved, the compatibility with other resin materials, flame retardants, and fillers is improved, the bleed-out of flame retardants is suppressed, and high filler loading is facilitated, which is preferable. As described above, the glass transition temperature and aromaticity of the copolymer can be adjusted by the content of cyclic olefin monomer units and the content of aromatic vinyl compound monomer units of the copolymer.

[0032] The aromatic polyene monomer is a polyene having 5 to 20 carbon atoms and containing multiple vinyl groups and / or vinylene groups in its molecule, preferably a polyene having 8 to 20 carbon atoms. The aromatic polyene monomer is preferably a polyene having 8 to 20 carbon atoms and containing multiple vinyl groups in its molecule, more preferably various ortho-, meta-, and para-divinylbenzenes or mixtures thereof, divinylnaphthalene, divinylanthracene, p-2-propenylstyrene, p-3-butenylstyrene, or other compounds having an aromatic vinyl structure and consisting essentially of carbon and hydrogen and substantially free of oxygen, nitrogen, and halogens. Furthermore, bifunctional aromatic vinyl compounds such as 1,2-bis(vinylphenyl)ethane (abbreviation: BVPE), as described in JP-A-2004-087639, can also be used. Among these, various ortho-, meta-, and para-divinylbenzenes or mixtures thereof are preferably used, and a mixture of meta- and para-divinylbenzene is most preferably used. In this specification, these divinylbenzenes are referred to as divinylbenzenes. When a divinylbenzene is used as the aromatic polyene, the vinyl group contained in the divinylbenzene unit is preferred because it has high crosslinking efficiency during curing treatment and facilitates curing.

[0033] The number-average molecular weight of the copolymer is preferably 500 to 50,000, more preferably 500 to 30,000 or less than 30,000, even more preferably 500 to 15,000 or less than 15,000, and even more preferably 500 to 12,000 or less than 12,000. A number-average molecular weight of 500 or more improves the mechanical properties of the composition in the uncured state and provides appropriate adhesion, thereby facilitating molding and processing as a thermoplastic resin. A number-average molecular weight of 30,000 or less improves molding processability. A number-average molecular weight of 30,000 or less is particularly advantageous because it allows the viscosity of a varnish containing the copolymer to be kept below a certain value. A varnish viscosity lower than a certain value improves workability and facilitates impregnation of glass fibers and the like with the varnish, improving embeddability in semiconductor devices with uneven surfaces.

[0034] In the copolymer, the content of vinyl groups and / or vinylene groups derived from the aromatic polyene monomer units is 2 to 30, preferably 3 to 20, per number-average molecular weight. The content of vinyl groups and / or vinylene groups derived from the aromatic polyene monomer units may be less than 30, preferably less than 20, per number-average molecular weight. The content of vinyl groups and / or vinylene groups may be collectively referred to as the "vinyl group content" below. Because vinyl groups are superior to vinylene groups in terms of crosslinking efficiency, in the present invention, the content of vinyl groups (excluding vinylene groups in this case) derived from the aromatic polyene monomer units is preferably 2 to 30, preferably 3 to 20, per number-average molecular weight. A vinyl group content of 2 or more results in high crosslinking efficiency and a cured product with sufficient crosslink density. Increasing the vinyl group content facilitates improving the mechanical properties of the final cured product at room temperature and high temperatures. The vinyl group content derived from aromatic polyene monomer units (divinylbenzene monomer units) per number average molecular weight in the copolymer is determined by the ratio of the number average molecular weight (Mn) calculated in terms of standard polystyrene obtained by a GPC (gel permeation chromatography) method known to those skilled in the art to ... 1 H-NMR measurement and / or quantitative mode 13 The composition can be determined by comparing the composition obtained by C-NMR measurement with the vinyl group content derived from aromatic polyene monomer units. Such a method is obvious and well known to those skilled in the art. For example, the composition of an ethylene-norbornene-styrene-ethylvinylbenzene-divinylbenzene copolymer, which is a representative example of the present copolymer, can also be determined by the following method. 1 H-NMR measurement and quantitative mode 13 C-NMR measurement was performed, and the NMR peak area intensity of the aromatic vinyl / vinylene group ( 1 H, 13 C) to determine the proportion (a) of divinylbenzene units contained, and the strength of the ethyl groups connected to the benzene ring ( 1 H, 13C) to determine the proportion (b) of ethylvinylbenzene units contained in small amounts as impurities in divinylbenzene, and calculate the area intensity ( 1 H, 13 The proportion (c) of styrene units is calculated by subtracting the contributions of (a) and (b) from (C), and finally the area intensity of the aliphatic hydrocarbon region ( 1 H, 13 The ratio (d) of olefin units (total of ethylene and norbornene units) is calculated by subtracting the contributions of each of the contents of (a), (b), and (c) from the ratio (c) of the aliphatic hydrocarbon region. 13 From C), the abundance ratio (e) of ethylene and norbornene units can be determined, and the contents of ethylene, norbornene, styrene, divinylbenzene, and ethylvinylbenzene can be calculated by combining (a), (b), (c), (d), and (e).

[0035] The content of aromatic polyene monomer units in the present copolymer is arbitrary, but is preferably less than 30% by mass, more preferably less than 18% by mass, and most preferably less than 15% by mass. At such a content, the number of crosslinking groups is appropriately suppressed, and the effect of improving the stability during the production of the copolymer and the stability during curing is obtained.

[0036] Specific examples of the α-olefin-aromatic vinyl compound-aromatic polyene copolymer as one embodiment of the present copolymer include an ethylene-styrene-divinylbenzene copolymer, an ethylene-ethylvinylbenzene-divinylbenzene copolymer, an ethylene-propylene-styrene-divinylbenzene copolymer, an ethylene-1-octene-styrene-divinylbenzene copolymer, and a propylene-styrene-divinylbenzene copolymer. Specific examples of suitable α-olefin-cyclic olefin-aromatic vinyl compound-aromatic polyene copolymers include one or more members selected from the group consisting of ethylene-norbornene-styrene-divinylbenzene copolymer, propylene-norbornene-styrene-divinylbenzene copolymer, 1-hexene-norbornene-styrene-divinylbenzene copolymer, 1-octene-norbornene-styrene-divinylbenzene copolymer, ethylene-norbornene-ethylvinylbenzene-divinylbenzene copolymer, propylene-styrene-norbornene-divinylbenzene copolymer, 1-hexene-styrene-styrene-norbornene-divinylbenzene copolymer, and 1-octene-norbornene-styrene-divinylbenzene copolymer. Further, copolymers in which the above-mentioned norbornene is replaced with dimethanooctahydronaphthalene (DMON), trimethanododecahydroanthracene (TMDA), phenylnorbornene (5-phenylbicyclo[2.2.1]hept-2-ene), or methylphenylnorbornene (5-methyl-5-phenylbicyclo[2.2.1]hept-2-ene) are also suitable examples of copolymers of the present invention.

[0037] The olefin-aromatic vinyl compound-aromatic polyene copolymer preferably used in the composition of the present invention is a copolymer in which the olefin monomer units contain at least a cyclic olefin monomer component. By including a cyclic olefin monomer unit as a portion of the olefin monomer units, the dielectric dissipation factor of the copolymer itself can be lowered compared to copolymers that do not contain a cyclic olefin. For example, when a copolymer is cured using a minimum amount of curing agent, the dielectric dissipation factor measured at 40 GHz is lower than that of copolymers that do not contain a cyclic olefin monomer unit. Therefore, a copolymer containing a cyclic olefin monomer component is preferred for reducing the dielectric dissipation factor of compositions and their cured products. Furthermore, increasing the cyclic olefin monomer unit content as described above increases the glass transition temperature of the copolymer, thereby hardening the copolymer and its cured product. Considering that insulating materials for CCLs, three-dimensional integrated circuit packaging, or chiplets, which are preferred applications of the present invention, are hard and require a lower linear expansion coefficient similar to that of wiring metals such as silicon and copper, a higher cyclic olefin monomer unit content as described above is preferred. Furthermore, a portion of the olefin monomer units in the olefin-aromatic vinyl compound-aromatic polyene copolymer contains cyclic olefin monomer units, and the higher the content of these cyclic olefin monomer units, i.e., the higher the glass transition temperature of the copolymer, the higher the thermal conductivity of the cured product of the composition tends to be.

[0038] The olefin-aromatic vinyl compound-aromatic polyene copolymer preferably used in the composition of the present invention is an olefin-aromatic vinyl compound-aromatic polyene copolymer that, when cured alone, produces a cured product that exhibits a dielectric constant of less than about 2.5 and a dielectric dissipation factor of less than 0.0008, preferably less than 0.0006, as measured at 40 GHz and 25°C. Preferred olefin-aromatic vinyl compound-aromatic polyene copolymers that satisfy these requirements are copolymers that contain a cyclic olefin component in the olefin component. In this specification, "curing alone" is defined to mean curing the olefin-aromatic vinyl compound-aromatic polyene copolymer using the minimum necessary amount, i.e., 1% by mass or less of an azo-based curing agent or a curing agent consisting of carbon atoms and hydrogen atoms (e.g., 2,3-dimethyl-2,3-diphenylbutane) relative to the mass of the copolymer, under conditions appropriate for the curing agent.

[0039] In an α-olefin-cyclic olefin-aromatic vinyl compound-aromatic polyene copolymer according to an embodiment, the content of α-olefin monomer units may be 0% by mass (i.e., no α-olefin monomer units are included). Such a copolymer is also referred to herein as a "cyclic olefin-aromatic vinyl compound-aromatic polyene copolymer." The composition of the present invention may use a plurality of such olefin-aromatic vinyl compound-aromatic polyene copolymers having different compositions and molecular weights.

[0040] <Resin-Filled Boron Nitride Plate> The resin-filled boron nitride plate containing the olefin-aromatic vinyl compound-aromatic polyene copolymer of the present invention can be cured by itself, or the copolymer of the present invention can be combined with other materials to form a composition, which can then be filled into a "porous boron nitride sintered plate" as described below to form a resin-filled boron nitride plate. Here, the other materials can include the "polyfunctional monomer component," "monofunctional monomer component," "resin component," "solvent," "other additives," and the like. The loading rate of the copolymer or a composition containing the copolymer relative to the porous boron nitride sintered plate can be adjusted as desired depending on the application, but is preferably in the range of 10 to 70% by volume, more preferably 20 to 60% by volume.

[0041] <Polyfunctional Monomer Component> The amount of polyfunctional monomer component that may be contained in the resin-filled boron nitride plate of the present invention is arbitrary, but is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, per 100 parts by mass of the copolymer. Examples of such polyfunctional monomer components include the aromatic polyenes, polyfunctional maleimides, polyfunctional cyanates, polyfunctional (meth)acrylates such as glycidyl (meth)acrylate and trimethylolpropane tri(meth)acrylate, and polyfunctional isocyanurates such as triallyl isocyanurate and tri(meth)acrylic isocyanurate. Among these, aromatic polyenes are preferred from the viewpoint of their excellent low dielectric properties. Among these, ortho-, meta-, and para-divinylbenzenes, or mixtures thereof, are more preferred, and a mixture of meta- and para-divinylbenzene is most preferred.

[0042] <Monofunctional Monomer Component> The resin-filled boron nitride plate of the present invention may contain any amount of monofunctional monomer component, but is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, per 100 parts by mass of the copolymer. Monomers that can be suitably used in the composition of the present invention preferably have a molecular weight of less than 1,000, more preferably less than 500. Monomers that can be suitably used in the composition of the present invention are the aromatic vinyl compound monomers described above and / or the aromatic vinylene monomers described below. As such monomers, monomers that can be polymerized with a radical polymerization initiator are preferred.

[0043] <Aromatic Vinylene Monomer> The aromatic vinylene monomer that may be contained in the resin-filled boron nitride plate of the present invention refers to a compound having both a single aromatic ring or multiple condensed aromatic rings having 9 to 30 carbon atoms and a vinylene group. Examples of such aromatic vinylene compounds include indenes, beta-substituted styrenes, acenaphthylenes, and the like. Examples of indenes include indene, various alkyl-substituted indenes, and phenyl-substituted indenes. Examples of beta-substituted styrenes include beta-alkyl-substituted styrenes such as beta-methylstyrene, and phenyl-substituted styrenes. Examples of acenaphthylenes include acenaphthylene, various alkyl-substituted acenaphthylenes, and various phenyl-substituted acenaphthylenes. The above-exemplified compounds may be used alone or in combination as the aromatic vinylene compound. From the viewpoints of industrial availability and radical polymerizability, acenaphthylene is the most preferred aromatic vinylene compound.

[0044] <Resin Component> The resin-filled boron nitride plate of the present invention may contain any resin component as long as it does not impair the effects of the present invention. Preferably, one or more resins selected from hydrocarbon-based elastomers, polyether-based resins, aromatic polyene-based resins, and olefin-aromatic vinyl compound-aromatic polyene copolymers containing no cyclic olefins are used. Of these, hydrocarbon-based elastomers and olefin-aromatic vinyl compound-aromatic polyene copolymers containing no cyclic olefins are more preferred. Among hydrocarbon-based elastomers, conjugated diene polymers are preferred. Among conjugated diene polymers, 1,2-polybutadiene is preferred. The amount of resin components is preferably 100 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of the olefin-aromatic vinyl compound-aromatic polyene copolymer. If the amount of these resin components added is large, the dielectric constant and dielectric loss tangent of the final cured product may become high. Furthermore, when a resin component is added to the olefin-aromatic vinyl compound-aromatic polyene copolymer, the ratio of the total mass of the olefin-aromatic vinyl compound-aromatic polyene copolymer and the resin component to the mass of the specific boron nitride powder is in the range of 15:85 to 70:30, and preferably in the range of 20:80 to 50:50.

[0045] <Hydrocarbon Elastomer> The hydrocarbon elastomer suitable for use in the present composition may have a number average molecular weight of 20,000 or more, preferably 30,000 or more. Examples of hydrocarbon elastomers include one or more elastomers selected from EPDM, conjugated diene polymers, block or random copolymers of aromatic vinyl compounds and conjugated dienes, and hydrogenated products thereof. These hydrocarbon elastomers may be modified, for example, by introducing functional groups with maleic anhydride or other compounds.

[0046] <Conjugated Diene Polymer> Examples of conjugated diene polymers include polybutadiene and 1,2-polybutadiene. Examples of aromatic vinyl compound-conjugated diene block or random copolymers and their hydrogenated products (hydrogenated products) include SBS, SIS, SEBS, SEPS, SEEPS, and SEEBS. Suitable 1,2-polybutadiene is available, for example, as a product from JSR Corporation, and also available from Nippon Soda Co., Ltd. under the product names of liquid polybutadiene B-1000, 2000, and 3000. Another suitable copolymer containing a 1,2-polybutadiene structure is "Ricon 100" from TOTAL CRAY VALLEY. These conjugated diene polymers and hydrogenated products thereof may be modified, for example, by introducing functional groups with maleic anhydride or other compounds. Among the conjugated diene polymers, conjugated diene copolymers are preferred. Among these conjugated diene copolymers, hydrogenated block copolymers such as SEBS, SEPS, SEEPS, and SEEBS are useful as compatibilizers for the copolymer of the present invention and other resin components. These are available from Asahi Kasei under the trade names Tuftec or SOE-SS, from Kuraray Co., Ltd. under the trade name Septon, and from KRATON under the trade name Kraton.

[0047] <Polyether-Based Resin> Examples of polyether-based resins include polyphenylene ether and polyether. Polyphenylene ethers having functional groups are preferably those in which the molecular terminals are modified with functional groups. Furthermore, when added for the purpose of curing the composition of the present invention, it is preferable that the polyphenylene ether has multiple functional groups in one molecule. For example, modified polyphenylene ether is preferable. Examples of functional groups include radically polymerizable functional groups and epoxy groups, and preferably radically polymerizable functional groups. A vinyl group is preferable as the radically polymerizable functional group. As the vinyl group, one or more of the group consisting of an allyl group, a (meth)acryloyl group, and an aromatic vinyl group are preferable, one or more of the group consisting of a (meth)acryloyl group and an aromatic vinyl group are more preferable, and an aromatic vinyl group is most preferable. In other words, in the composition of the present invention, a bifunctional polyphenylene ether in which both molecular chain terminals are modified with radically polymerizable functional groups is particularly preferable. Examples of such polyphenylene ethers include Noryl (trademark) SA9000 manufactured by SABIC (modified polyphenylene ether having methacryloyl groups at both ends, number average molecular weight 2200) and bifunctional polyphenylene ether oligomer manufactured by Mitsubishi Gas Chemical Company, Inc. (OPE-2St, modified polyphenylene ether having vinylbenzyl groups at both ends, number average molecular weight 1200). Also usable are allylated PPE manufactured by Asahi Kasei Corporation and aromatic polyethers (ELPAC HC-F series) manufactured by JSR Corporation. Of these, the bifunctional polyphenylene ether oligomer (OPE-2St) manufactured by Mitsubishi Gas Chemical Company, Inc. and aromatic polyethers (ELPAC HC-F series) manufactured by JSR Corporation are preferred.

[0048] <Aromatic Polyene Resin> Aromatic polyene resins include divinylbenzene-based reactive hyperbranched copolymers (PDV or ODV) manufactured by Nippon Steel Chemical & Material Co., Ltd. Such copolymers are described, for example, in the literature "Synthesis of Polyfunctional Aromatic Vinyl Copolymers and Development of New IPN-Type Low Dielectric Loss Materials Using the Same" (Kawabe Masanao et al., Journal of the Japan Institute of Electronics Packaging, p. 125, Vol. 12, No. 2 (2009)). The aromatic polyene resin is a resin (copolymer) essentially composed of aromatic polyene monomer units and aromatic monovinyl compound monomer units, and more preferably, the aromatic polyene resin does not contain olefin monomer units. The aromatic polyene resin is preferably a resin obtained by cationic polymerization or anionic polymerization.

[0049] <Solvent> When producing the resin-filled boron nitride plate of the present invention, an appropriate solvent may be added to the copolymer-containing composition as needed. The solvent is used to adjust the viscosity, fluidity, and dispersibility of the composition. Volatile solvents are preferred, such as cyclohexane, toluene, ethylbenzene, and mixed alkanes. The amount of solvent used is preferably 10 to 2,000 parts by mass, more preferably 5 to 500 parts by mass, and even more preferably 10 to 300 parts by mass, per 100 parts by mass of the composition of the present invention. Generally, the solvent is preferably substantially removed by drying or the like from the resin-filled boron nitride plate obtained by emulsion polymerization of the composition described below and then drying or the like.

[0050] <Other Additives> The composition of the present invention may further contain one or more additives selected from the group consisting of a flame retardant and a surface modifier. The composition of the present invention can be used as a matrix for a resin-filled boron nitride plate.

[0051] <Flame Retardant> A known flame retardant can be used in the composition of the present invention. From the viewpoint of maintaining a low dielectric constant and a low dielectric loss tangent, preferred flame retardants are known organic phosphorus-based flame retardants such as phosphate esters or condensates thereof, known bromine-based flame retardants, and red phosphorus. Among phosphate esters, compounds having multiple xylenyl groups in the molecule are particularly preferred from the viewpoint of flame retardancy and a low dielectric loss tangent.

[0052] In addition to the flame retardant, antimony compounds such as antimony trioxide, antimony tetraoxide, antimony pentoxide, and sodium antimonate, or nitrogen-containing compounds such as melamine, triallyl-1,3,5-triazine-2,3,4-(1H,3H,5H)-trione, and 2,4,6-trialyloxy-1,3,5-triazine may be added as a flame retardant aid. The total amount of these flame retardants and flame retardant aids is usually preferably 1 to 100 parts by mass per 100 parts by mass of the composition. Furthermore, a polyphenylene ether (PPE) resin with a low dielectric constant and excellent flame retardancy may be used in an amount of 30 to 200 parts by mass per 100 parts by mass of the flame retardant.

[0053] <Surface Modifier> The composition of the present invention may contain various surface modifiers for the purpose of improving adhesion to fillers, copper plates, and wiring. The amount of the surface modifier used per 100 parts by mass of the composition of the present invention other than the surface modifier is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass. Examples of the surface modifier include various silane coupling agents and titanate coupling agents. Various silane coupling agents and titanate coupling agents may be used singly or in combination.

[0054] The composition that is the raw material for producing the resin-filled boron nitride plate of the present invention is obtained by mixing, dissolving, or melting one or more components selected from "polyfunctional monomer components," "monofunctional monomer components," "resin components," "solvents," "fillers," "other additives," etc., but can also contain general additives that are added to ordinary resins, such as lubricants, stabilizers, antioxidants, weather resistance agents, UV absorbers, etc., to the extent that the object of the present invention is not impaired. Any known method can be used for mixing, dissolving, or melting these components.

[0055] <Porous boron nitride sintered plate> The porous boron nitride sintered plate used in the present invention is a porous boron nitride sintered plate having boron nitride particles and pores formed by sintering primary particles of boron nitride together, and has a sintered boron nitride sintered body of 30 to 90% by volume and a porosity of 10 to 70% by volume. This porous boron nitride sintered plate and its manufacturing method are described in WO 2014 / 196496, WO 2015 / 022956, WO 2017 / 155110, WO 2023 / 038150, WO 2023 / 038151, and JP 2016-103611 A.

[0056] The shape of the boron nitride sintered plate when viewed from above is not particularly limited, but may be, for example, square or rectangular, from the viewpoint of being able to cut the resin-filled plate into pieces for use.

[0057] The area of ​​the main surface of the boron nitride sintered plate is arbitrary, but preferably 1000 mm 2 The lower limit of the area of ​​the main surface is, for example, 4000 mm 2 Over 6000mm 2 Over 8000mm 2 or more, or 10,000 mm 2 The upper limit of the area of ​​the main surface may be, for example, 250,000 mm 2 Below, 200000mm 2 Below, 150000mm 2 or less than 100,000 mm 2 The area of ​​the main surface of the boron nitride sintered plate means the area of ​​the region surrounded by the outer periphery when the boron nitride sintered plate is viewed from above, and is not affected by the presence or absence of surface irregularities or pores.

[0058] The upper limit of the thickness of the boron nitride sintered plate may be, for example, 2.0 mm or less, 1.0 mm or less, 0.5 mm or less, or 0.2 mm or less. When the upper limit of the thickness is within the above range, resin filling becomes easier, thereby further suppressing variations in resin impregnation in the resulting resin-filled plate. The lower limit of the thickness of the boron nitride sintered plate may be, for example, 0.01 mm or more, 0.02 mm or more, 0.05 mm or more, or 0.10 mm or more. The thickness of the boron nitride sintered plate is measured along a direction perpendicular to the main surface. If the thickness is not constant, the thickness is measured at 10 selected locations, and the average value of the measurements may be within the above range. The thickness of the resin-filled plate corresponds to the thickness of the boron nitride sintered plate.

[0059] The upper limit of the median pore diameter of the pores of the boron nitride sintered plate may be, for example, 6.0 μm or less, 5.5 μm or less, 5.0 μm or less, 4.0 μm or less, 3.8 μm or less, 3.6 μm or less, 3.4 μm or less, 3.2 μm or less, or 3.0 μm or less. Since the pore size of such a boron nitride sintered plate is small, the contact area between boron nitride particles is sufficiently large, thereby increasing the thermal conductivity. The lower limit of the median pore diameter of the pores of the boron nitride sintered plate may be, for example, 0.3 μm or more, 0.5 μm or more, 1.0 μm or more, 1.5 μm or more, 1.6 μm or more, 1.7 μm or more, 1.8 μm or more, 1.9 μm or more, or 2.0 μm or more. By having the lower limit of the median pore diameter within the above range, the molten resin sheet can be more easily penetrated. The median pore size of the pores in the boron nitride sintered plate may be adjusted within the above range, for example, 0.3 to 6.0 μm, 1.5 to 4.0 μm, or 2.0 to 3.0 μm.

[0060] The median pore size and total pore volume (total volume of open pores) of a boron nitride sintered plate can be measured by the following procedure. First, a mercury porosimeter is used to measure the boron nitride sintered plate to be measured, and the pore size distribution is determined when the boron nitride sintered plate is pressurized while increasing the pressure from 0.0042 MPa to 206.8 MPa. With the pore size on the horizontal axis and the cumulative pore volume on the vertical axis, the pore size when the cumulative pore volume reaches 50% of the total pore volume is the median pore size. As a mercury porosimeter, for example, one manufactured by Shimadzu Corporation can be used. Note that when a resin-filled plate is the measurement target, the resin-filled plate is first heated to remove the semi-cured thermosetting composition to obtain a boron nitride sintered plate, and then the measurement is performed.

[0061] The upper limit of the porosity of the porous boron nitride sintered plate, i.e., the pore volume ratio, may be, for example, 70 vol% or less, 65 vol% or less, or 60 vol% or less. By ensuring that the upper limit of the porosity of the boron nitride sintered plate is within the above range, the decrease in mechanical strength of the boron nitride sintered plate can be more sufficiently suppressed, and a resin-filled plate with improved handleability can be provided. The lower limit of the porosity of the porous boron nitride sintered plate may be, for example, 10 vol% or more, 20 vol% or more, or 40 vol% or more. By ensuring that the upper limit of the porosity of the porous boron nitride sintered plate is within the above range, the content of the semi-cured thermosetting composition can be increased, and adhesion to an adherend such as a metal plate can be further improved. The porosity of the porous boron nitride sintered plate may be adjusted within the above range, for example, 40 to 65 vol% or 40 to 60 vol%.

[0062] The porosity of the porous boron nitride sintered plate was calculated by calculating the bulk density [Y (kg / m 3 )] was calculated, and the bulk density was compared with the theoretical density of boron nitride [X (kg / m 3 ) )], it can be calculated by the following formula (1). In the case of boron nitride, the theoretical density X is 2280 kg / m 3 In the case of aluminum nitride, the theoretical density X is 3260 kg / m 3 In the case of silicon nitride, the theoretical density X is 3170 kg / m 3Porosity (volume %) = [1 - (Y / X)] x 100 ... Equation (1)

[0063] The bulk density of the porous boron nitride sintered plate is 800 to 1500 kg / m 3 , or 1000 to 1400 kg / m 3 If the bulk density is too small, the strength of the boron nitride sintered plate tends to decrease. Furthermore, by setting the upper limit of the bulk density within the above range, the amount of cured resin filled can be made more sufficient, and the adhesion between the resin-filled plate and the adherend such as a metal plate can be made better.

[0064] The degree of orientation, represented by the I.O.P. (Index of Orientation Performance) of the porous boron nitride sintered plate, may preferably be in the range of 0.6 to 20, and more preferably 0.7 to 10. The degree of orientation, represented by I.O.P., is calculated using the following formula from the intensity ratio of the (002) diffraction line to the (100) diffraction line in X-ray diffraction of a surface measured from a direction parallel to the height direction of the boron nitride sintered body, and the intensity ratio of the (002) diffraction line to the (100) diffraction line in X-ray diffraction of a surface measured from a direction perpendicular to the height direction of the boron nitride sintered body: I.O.P. = (I100 / I002) par. / (I100 / I002) perp.

[0065] The sintered plate preparation process for preparing the boron nitride sintered plate will be described below.

[0066] The ceramic green sheet used in the sintered plate preparation step may be prepared by preparing a compound containing boron nitride as a ceramic raw material and molding the compound into a sheet. The molding method is not particularly limited, and may be, for example, uniaxial pressing or cold isostatic pressing (CIP). The molding pressure may be, for example, 5 to 350 MPa. The pore size, porosity, bulk density, etc. of the boron nitride sintered plate can be adjusted by adjusting the molding method and molding pressure, or the composition of the compound, which will be described later.

[0067] In addition to boron nitride, the above-mentioned compound may contain, for example, a sintering aid, a binder resin, a solvent, and the like.

[0068] Examples of boron nitride include boron carbonitride, boron nitride, silicon nitride, and aluminum nitride. Examples of sintering aids include metal oxides such as yttrium oxide, aluminum oxide, and magnesium oxide, alkali metal carbonates such as lithium carbonate and sodium carbonate, alkaline earth metal carbonates such as calcium carbonate, and boric acid. The use of a sintering aid can promote sintering of the boron nitride.

[0069] When a sintering aid is blended, the blending amount of the sintering aid may be, for example, 0.01 parts by mass or more, or 0.1 parts by mass or more, relative to 100 parts by mass of the total of boron nitride and sintering aid. The blending amount of the sintering aid may be, for example, 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less, relative to 100 parts by mass of the total of boron nitride and sintering aid. By setting the amount of sintering aid added within the above range, it becomes easier to adjust the median pore diameter of the boron nitride sintered body to the range described below. The blending amount of the sintering aid may be adjusted within the above range, and may be, for example, 0.01 to 20 parts by mass, or 0.01 to 10 parts by mass, relative to 100 parts by mass of the total of boron nitride and sintering aid.

[0070] Examples of binder resins include methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and (meth)acrylic resins. The use of a binder resin makes it easier to mold the compound containing boron nitride, allowing it to be molded into various shapes, such as a sheet. Examples of solvents include organic solvents such as ethanol and toluene. The use of a binder resin and a solvent allows the compound to become a slurry, making it easy to adjust the viscosity.

[0071] The area of ​​the main surface of the ceramic green sheet may be adjusted as desired depending on the area of ​​the main surface of the boron nitride sintered body.

[0072] In the sintered plate preparation step, the areas of the main surfaces of the first setter and the second setter are adjusted so that the main surfaces of the ceramic green sheet are within the areas of the main surfaces of the first setter and the second setter. The areas of the main surfaces of the first setter and the second setter may be equal to or greater than the area of ​​the main surfaces of the ceramic green sheet. By setting the areas of the main surfaces of the first setter and the second setter as described above, warping of the resulting boron nitride sintered plate can be further suppressed.

[0073] The first and second setters may be made of a nitride ceramic sintered body, such as a boron nitride sintered body or an aluminum nitride sintered body.

[0074] The heat treatment of the ceramic green sheet in the sintered plate preparation process may be performed in multiple steps, for example, a degreasing step in which heat treatment is performed at a heating temperature of 800°C or less, and a sintering step in which heat treatment is performed at a temperature higher than the heating temperature in the degreasing step. In the degreasing step, the binder resin and the like are mainly burned to degrease the green sheet. Then, in the sintering step, raw materials containing boron nitride and a sintering aid are sintered to obtain a boron nitride sintered plate.

[0075] The heating temperature in the debinding step may be, for example, 400 to 750°C, 500 to 700°C, or 600 to 650°C. By setting the upper limit of the heating temperature within the above range, organic substances such as binder resins can be sufficiently removed before sintering the boron nitride, resulting in a more homogeneous system, which can then be sintered in the subsequent second heat treatment. The heating time in the debinding step may be, for example, 0.5 to 20 hours.

[0076] The heating temperature in the sintering step is higher than the heating temperature in the debinding step. The heating temperature in the sintering step may be, for example, 1600 to 2050°C, 1700 to 1950°C, or 1800 to 1900°C. The heating time in the sintering step may be, for example, 5 to 15 hours. The sintering step may be performed in an atmosphere of a non-oxidizing gas such as nitrogen, argon, ammonia, or hydrogen.

[0077] <Method for producing resin-filled boron nitride plate> The resin-filled boron nitride plate of the present invention can be composited by, for example, impregnating and filling a porous boron nitride sintered plate with a composition consisting of an olefin-aromatic vinyl compound-aromatic polyene copolymer. Impregnation of the porous boron nitride sintered plate with the copolymer composition can be carried out by vacuum impregnation, pressurized impregnation at 1 to 300 MPa (G), or a combination thereof. The pressure during vacuum impregnation is preferably 1000 Pa (abs) or less, more preferably 100 Pa (abs) or less. With pressurized impregnation, pressures of less than 1 MPa (G) may result in the copolymer composition not being sufficiently impregnated into the interior of the porous boron nitride sintered plate, while pressures of more than 300 MPa (G) require large-scale equipment, which is cost-inefficient. In order to easily impregnate the inside of the porous boron nitride sintered plate with the copolymer composition, it is preferable to carry out the impregnation under temperature conditions such that the viscosity of the copolymer composition is minimized during vacuum impregnation and pressure impregnation, and the composition does not substantially cure or does not completely cure, for example, at about 100°C to 180°C. The minimum melt viscosity of the olefin-aromatic vinyl compound-aromatic polyene copolymer within this temperature range is 3000 mPa s or less (1 sec -1 ) is preferred.

[0078] Furthermore, when the melt viscosity of the olefin-aromatic vinyl compound-aromatic polyene copolymer itself or a composition containing it is high, a varnish prepared by dissolving the olefin-aromatic vinyl compound-aromatic polyene copolymer in a solvent can be used for impregnation. In this case, the solvent must be thoroughly removed after impregnation into the porous boron nitride sintered plate. Furthermore, in anticipation of solvent removal, it is necessary to impregnate the porous boron nitride sintered plate with a copolymer amount equal to or greater than the porosity of the plate. When the melt viscosity of the olefin-aromatic vinyl compound-aromatic polyene copolymer is high and impregnation is difficult, the impregnation method using this varnish is preferred. The viscosity of the preferred olefin-aromatic vinyl compound-aromatic polyene copolymer-containing varnish is preferably 3,000 mPa·s or less (1 sec at 25°C). It is preferable to use a varnish prepared by diluting the olefin-aromatic vinyl compound-aromatic polyene copolymer itself or a composition containing it with a solvent to achieve a viscosity below this value.

[0079] <Curing> The resin-filled boron nitride plate can be cured by a known method, taking into consideration the curing conditions (temperature, time, pressure) of the curing agent contained therein. When the curing agent used is a peroxide or azo-based curing agent, the curing conditions can be determined by taking into consideration the half-life temperature and the like disclosed for each curing agent.

[0080] <Resin-Filled Boron Nitride Plate> The dielectric breakdown voltage of the cured resin-filled boron nitride plate of the present invention is 5 kV / mm or more, preferably 10 kV / mm or more. The dielectric constant and dielectric dissipation factor are measured by a known resonator method. In this specification, the resonator method is performed at a measurement frequency of 40 GHz. The dielectric constant of the cured product may be 3.0 or more and 5.0 or less, preferably 3.0 or more and 4.5 or less. The dielectric dissipation factor of the cured product may be 0.0002 or more and 0.0030 or less, preferably 0.0002 or more and 0.0020 or less. These values ​​are preferred for high-frequency electrical insulating materials, for example, at 3 GHz or more. The thermal conductivity of the cured product obtained from the composition of the present invention is preferably 10 W / m·K or more, more preferably 20 W / m·K or more. The coefficient of linear expansion (CTE) of the cured product from the composition of the present invention at 0°C to 180°C is preferably 50 ppm or less, more preferably 30 ppm or less. Those skilled in the art can determine the formulation of a composition having the above physical property parameters and produce a cured resin-filled boron nitride plate by referring to the information in this specification and publicly known documents.

[0081] <Uses of Resin-Filled Boron Nitride Plate Cured Body> The resin-filled boron nitride plate cured body of the present invention is suitable as an insulating material for high-frequency transmission circuits. Specifically, it can be used as a base material or substrate for single-layer or multilayer printed circuit boards, flexible printed circuit boards, so-called single-layer or multilayer CCL (copper clad laminate) boards, and single-layer or multilayer FCCL (flexible copper clad laminate) boards. It can also be used as various electrical insulating materials for high-frequency signal wiring, such as interlayer insulating materials and antennas. It is also useful as an insulating heat dissipation material for interposers and rewiring layers. The present invention also relates to various three-dimensional integrated circuit packaging packages and chiplets that include the resin-filled boron nitride plate cured body of the present invention. It is also useful as an insulating heat dissipation material for multilayer antenna boards that include RFICs and high-frequency wiring (antenna feed lines) layered below the antenna structure material of Massive MIMO (phased array antenna / multilayer board for transmitter circuit) for 5G / 6G base stations. Furthermore, it is useful as an insulating heat dissipation material for switching integrated circuits (ASIC) in next-generation optical interconnect components (switching integrated circuits for optical transceivers in co-packages).

[0082] In one embodiment of the present invention, there is also provided a method for producing the copolymer, which includes copolymerizing an α-olefin, a cyclic olefin, an aromatic vinyl compound, and an aromatic polyene by coordination polymerization.

[0083] Coordination polymerization is a polymerization method using a coordination polymerization catalyst consisting of a transition metal compound and a co-catalyst. As the transition metal compound, transition metal compounds containing zirconium, hafnium, titanium, iron, nickel, cobalt, and palladium are preferred. In particular, for copolymerizing cyclic olefin monomers, transition metal compounds containing zirconium, titanium, nickel, iron, and palladium are preferred. The most preferred coordination polymerization catalyst is a coordination polymerization catalyst consisting of a transition metal compound represented by the following general formula (1) and a co-catalyst. More preferably, the production method may include a step of copolymerizing each monomer of an olefin such as an α-olefin or a cyclic olefin, an aromatic vinyl compound, and an aromatic polyene using a polymerization catalyst consisting of a transition metal compound represented by the following general formula (1) and a co-catalyst:

[0084] General formula (1)

[0085] In the above formula, A and B are each independently a group selected from an unsubstituted or substituted cyclopentaphenanthryl group, an unsubstituted or substituted benzoindenyl group, an unsubstituted or substituted cyclopentadienyl group, or an unsubstituted or substituted indenyl group. Y is bonded to A and B and is a methylene group, silylene group, ethylene group, germylene group, or boron residue having hydrogen or a hydrocarbon group having 1 to 15 carbon atoms (which may contain 1 to 3 nitrogen, oxygen, sulfur, phosphorus, or silicon atoms) as an additional substituent. The substituents may be different or the same. Y may also have a cyclic structure. Most preferably, Y is a methylene group having a bond to A and B and having hydrogen or a hydrocarbon group having 1 to 15 carbon atoms (which may contain 1 to 3 nitrogen, oxygen, sulfur, phosphorus, or silicon atoms) as an additional substituent. X is hydrogen, halogen, an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkylaryl group having 8 to 12 carbon atoms, a silyl group having a hydrocarbon substituent having 1 to 4 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a dialkylamido group having an alkyl substituent having 1 to 6 carbon atoms. M is a transition metal, and may be preferably zirconium, hafnium, or titanium.

[0086] To obtain a copolymer having a relatively low molecular weight and a low viscosity when made into a varnish, preferably, A and B in the above general formula (1) may each independently be a group selected from an unsubstituted or substituted cyclopentadienyl group or an unsubstituted or substituted indenyl group, and it is particularly preferable to use a transition metal compound having both an unsubstituted or substituted cyclopentadienyl group and an unsubstituted or substituted indenyl group. To obtain a copolymer having a high aromatic polyene content, i.e., a copolymer having a high number of vinyl groups and / or vinylene groups derived from aromatic polyene monomer units per number average molecular weight, it is preferable to use a transition metal compound having at least one group selected from an unsubstituted or substituted indenyl group or an unsubstituted or substituted benzoindenyl group. When the copolymer has a high aromatic polyene content, it is possible to increase the crosslink density of the cured product obtained by curing, and for example, a cured product having a storage modulus of 5 MPa or more measured at 280°C can be obtained.

[0087] The cocatalyst in the polymerization catalyst of the present invention may be a known cocatalyst used in combination with a transition metal compound. Preferred examples of such cocatalysts include aluminum compounds and boron compounds. Alumoxanes such as methylaluminoxane (also referred to as methylalumoxane or MAO) are preferably used as the aluminum compound. Alternatively, alkylaluminums such as triisobutylaluminum and triethylaluminum may be used. Furthermore, aluminum compounds and boron compounds may be used together. Examples of such cocatalysts include the cocatalysts and alkylaluminum compounds described in EP 0872492A2, JP 11-130808 A, JP 9-309925 A, WO 00 / 20426 A, EP 0985689A1, and JP 6-184179 A.

[0088] Examples of boron compounds include trispentafluorophenylborane, triphenylcarbenium tetrakis(pentafluorophenyl)borate {trityltetrakis(pentafluorophenyl)borate}, lithium tetrakis(pentafluorophenyl)borate, trimethylammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tri(n-butyl)ammonium tetraphenylborate, tri(n-butyl)ammonium tetra(p-tolyl)phenylborate, tri(n-butyl)ammonium tetra(p-ethylphenyl)borate, tri(n-butyl)ammonium tetra(pentafluorophenyl)borate, trimethylammonium tetra(p-tolyl)borate, trimethylammonium tetrakis-3,5-dimethylphenylborate, and triethylammonium tetrakis-3 ,5-dimethylphenylborate, tributylammonium tetrakis-3,5-dimethylphenylborate, tributylammonium tetrakis-2,4-dimethylphenylborate, anilinium tetrakispentafluorophenylborate, N,N'-dimethylanilinium tetraphenylborate, N,N'-dimethylanilinium tetrakis(p-tolyl)borate, N,N'-dimethylanilinium tetrakis(m-tolyl)borate, N,N'-dimethylanilinium tetrakis(2,4-dimethylphenyl)borate, N,N'-dimethylanilinium tetrakis(3,5-dimethylphenyl)borate, N,N'-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N'-diethylanilinium tetrakis(pentafluorophenyl)borate, N,N'-2,4,5-pentamethylanilinium tetraphenylborate, N,N'-2,4,Examples of such compounds include 5-pentaethylanilinium tetraphenylborate, di-(isopropyl)ammonium tetrakispentafluorophenylborate, di-cyclohexylammonium tetraphenylborate, triphenylphosphonium tetraphenylborate, tri(methylphenyl)phosphonium tetraphenylborate, tri(dimethylphenyl)phosphonium tetraphenylborate, triphenylcarbenium tetrakis(p-tolyl)borate, triphenylcarbenium tetrakis(m-tolyl)borate, triphenylcarbenium tetrakis(2,4-dimethylphenyl)borate, triphenylcarbenium tetrakis(3,5-dimethylphenyl)borate, tropylium tetrakispentafluorophenylborate, tropylium tetrakis(p-tolyl)borate, tropylium tetrakis(m-tolyl)borate, tropylium tetrakis(2,4-dimethylphenyl)borate, and tropylium tetrakis(3,5-dimethylphenyl)borate. Although boron-containing promoters in which the fluorine-substituted aromatic group is a phenyl group have been exemplified herein, boron-containing promoters having a fused aromatic group such as a fluorine-substituted naphthyl group can also be preferably used. Among these, the most preferred boron promoters are those having boron and a fluorine-substituted aromatic group bonded thereto. Examples include trispentafluorophenylborane, triphenylcarbenium tetrakis(pentafluorophenyl)borate {trityl tetrakis(pentafluorophenyl)borate}, lithium tetrakis(pentafluorophenyl)borate, tri(n-butyl)ammonium tetra(pentafluorophenyl)borate, tropylium tetrakispentafluorophenylborate, and N,N'-dimethylanilinium tetrakis(pentafluorophenyl)borate. Particularly preferred are triphenylcarbenium tetrakis(pentafluorophenyl)borate {trityl tetrakis(pentafluorophenyl)borate} and N,N'-dimethylanilinium tetrakis(pentafluorophenyl)borate is used. These most preferred boron-containing cocatalysts are sometimes referred to as TRI-FABA or TRI-FAB, and DAN-FABA or DAN-FAB, respectively, and can be purchased from Tosoh Finechem Co., Ltd. or Kanto Chemical Co., Ltd.

[0089] The co-catalyst is used in an aluminum atom / transition metal atomic ratio relative to the metal of the transition metal compound of 0.1 to 100,000, preferably 10 to 10,000. A ratio of 0.1 or more can effectively activate the transition metal compound, while a ratio of 100,000 or less is economically advantageous. The transition metal compound and co-catalyst may be mixed and prepared outside of a polymerization facility, or may be mixed inside the facility during polymerization.

[0090] In particular, the aluminum atom / transition metal atomic ratio of a promoter such as alumoxane relative to the metal of the transition metal compound is preferably 0.1 to 100,000, and more preferably 10 to 10,000. A ratio of 0.1 or more can effectively activate the transition metal compound, and a ratio of 100,000 or less is economically advantageous. When a boron compound is used as the promoter, the boron atom / transition metal atomic ratio is preferably 0.1 to 100, more preferably 0.1 to 10, and most preferably in the range of 0.8 to 1.2. A ratio of 0.1 or more can effectively activate the transition metal compound, and a ratio of 100 or less is economically advantageous.

[0091] In a preferred embodiment, a co-catalyst may be used that uses a boron compound as an essential component and an aluminum compound as needed. By using a boron compound as a co-catalyst, the amount of metal components such as aluminum derived from the aluminum compound contained in the finally obtained copolymer can be reduced, and the values ​​of the dielectric constant and dielectric loss tangent of the finally obtained uncured copolymer, or the values ​​of the dielectric constant and dielectric loss tangent of the single cured product or composition, can be reduced to particularly preferred ranges. For example, when the copolymer is cured alone, the dielectric constant can be made less than 2.5 and the dielectric loss tangent can be made less than 0.0008, preferably less than 0.0006.

[0092] In one embodiment, an olefin-aromatic vinyl compound-aromatic polyene copolymer can be provided in which the total content of metals derived from the catalyst and co-catalyst is 1500 ppm or less, preferably 1000 ppm or less, and most preferably 500 ppm or less. Here, the metal content derived from the catalyst and co-catalyst is defined as the sum of the respective contents of the transition metal elements (described above) used in the catalyst and the boron and / or aluminum derived from the boron compound and / or aluminum compound used in the co-catalyst, and can be defined as the sum of the respective elemental contents of zirconium, hafnium, titanium, iron, nickel, palladium, cobalt, boron, and aluminum. Particularly preferably, the metal derived from the catalyst may be zirconium, and the metal derived from the co-catalyst may be aluminum and boron, and the metal content derived from the catalyst and co-catalyst may be the sum of the respective contents of zirconium, aluminum, and boron. Note that, in this specification, boron is included in the category of metal. When cured alone, an olefin-aromatic vinyl compound-aromatic polyene copolymer having a total metal content of 1500 ppm or less, preferably 1000 ppm or less, and most preferably 500 ppm or less can satisfy the properties of a dielectric constant of less than 2.5 and a dielectric loss tangent of less than 0.0008, preferably less than 0.0006, particularly at 40 GHz. In other words, it is suitable for the cured product of the composition of the present invention in that it gives a cured product with excellent low dielectric properties.

[0093] The present invention will be described below with reference to examples, but the present invention should not be construed as being limited to the following examples.

[0094] The methods for producing the copolymers used in the present invention are shown in the following Synthesis Examples. The copolymers obtained in the Synthesis Examples were analyzed by the following methods. The contents of ethylene, cyclic olefin, styrene, and ethylvinylbenzene in the copolymers, as well as the content of vinyl group units derived from divinylbenzene, were determined by the following methods: 1 H-NMR measurement and quantitative mode 13C-NMR measurement was performed, and the determination was performed using a known method based on the area intensity of the obtained peaks. The sample was dissolved in heavy 1,1,2,2-tetrachloroethane, and the measurement was performed at 80 to 130°C. In this specification, the copolymer may also be referred to as a "resin."

[0095] The molecular weight was determined as a number average molecular weight (Mn) converted to standard polystyrene using GPC (gel permeation chromatography) under the following conditions:

[0096] Column: Two TSK-GEL Multipore HXL-M φ7.8 × 300 mm (manufactured by Tosoh Corporation) connected in series were used. Column temperature: 40°C. Solvent: THF. Flow rate: 1.0 ml / min. Detector: RI detector.

[0097] <Viscosity> The viscosity of the copolymer obtained in each example was determined as follows: A 25% by mass toluene solution of each copolymer was prepared, and the viscosity was measured at 25°C using a rotational rheometer (MCR302, manufactured by Anton Paar) at a shear rate of 1 sec. -1 The value of was used.

[0098] <Gel content> The gel content was determined as boiling toluene insoluble matter according to ASTM D2765-84.

[0099] <Dielectric constant and dielectric loss (dielectric loss tangent)> The dielectric loss tangent was measured at 23°C and 40 GHz using a cavity resonator perturbation method (Agilent Technologies 8722ES network analyzer, Keysight Technologies split cylinder resonator 40 GHz) using a 0.1 mm × 25 mm × 30 mm sample cut out from the sheet. Measurements were made for both the uncured and cured states.

[0100] <Measurement of storage modulus> Using a dynamic viscoelasticity measuring device (TA Instruments, formerly Rheometrics RSA-G2), measurements were taken in a nitrogen atmosphere at a frequency of 1 Hz while the temperature was raised from -60°C, and the storage modulus at 25°C and 280°C were measured. Measurement samples (3 mm x 40 mm) were cut out from a film approximately 0.1 mm thick and measured, and the storage modulus was measured in both the uncured and cured states. In addition, the glass transition temperature was also determined from the peak top temperature of the loss tangent (tan δ) in the uncured state. The main measurement parameters involved in the measurement were as follows: measurement frequency 1 Hz, heating rate 3°C / min, sample measurement length 10 mm, strain 0.1%

[0101] <Quantification of Metal Content in Copolymer> The metal content (in the example below, the content of transition metal elements used in the metal catalyst, and the content of boron and aluminum used in the cocatalyst) was measured as follows. Furthermore, the contents of hafnium, titanium, iron, nickel, cobalt, and palladium were also quantified. Measurements were performed using ICP atomic emission spectrometry under the following conditions in accordance with JIS K 0116:2014. 0.5 g of the composition to be measured was weighed into a platinum crucible and incinerated on a hot plate, an electric stove, and an electric furnace (gradually heated to 600°C). 0.5 ml of HCl (1+1) (i.e., a 1:1 mixture of hydrochloric acid and water by volume) and ultrapure water were added to the residue, dissolved by heating, and then the volume was adjusted to 5 ml to form the test solution. Quantitative analysis was performed using ICP atomic emission spectrometry (using an Agilent 5110VDV).

[0102] <Copolymer P-1 (ethylene-styrene-divinylbenzene copolymer)> Ethylene-styrene-divinylbenzene copolymer P-1 was produced according to the production method using the catalyst dimethylmethylenebis(cyclopentadienyl)zirconium dichloride described in WO 2022 / 014599 and the production method using a boron compound as a co-catalyst described in the examples of WO 2017 / 122295.

[0103] Copolymer P-2 (ethylene-norbornene-styrene-divinylbenzene copolymer) The raw material divinylbenzene (DVB) was "Divinylbenzene (81%)" manufactured by Nippon Steel Chemical & Material Co., Ltd. (liquid at room temperature, a mixture of meta and para isomers containing 81% by mass of divinylbenzene, with the remainder being ethylvinylbenzene). Norbornene (75% concentration, toluene solution) manufactured by Maruzen Petrochemical Co., Ltd. was used as the raw material. A small amount of triisobutylaluminum (TIBA) was added beforehand, the mixture was stirred at room temperature, and then distilled and purified under nitrogen. A 10-L polymerization vessel equipped with a heating and cooling jacket and a stirrer was used for the polymerization. The interior of the thoroughly dried polymerization vessel was first purged with nitrogen, and 1.4 kg of toluene, 0.23 kg of pure norbornene, 3.0 kg of styrene, and 0.60 kg of divinylbenzene (81% divinylbenzene) were charged. Approximately 20 L of dry nitrogen was bubbled through the vessel at an internal temperature of 60°C. The inside of the polymerization vessel was then purged with ethylene gas, and 6 mmol of TIBA (manufactured by Kanto Chemical Co., Inc.) was added and stirred. The internal temperature was stabilized at 80°C, and the internal pressure of the polymerization vessel was increased to 0.1 MPaG (gauge) with nitrogen and stabilized. Then, from a catalyst tank installed above the polymerization vessel, a catalyst solution was added to the polymerization vessel, which had been prepared by adding 210 μmol of tritylium tetrakis(pentafluorophenyl)borate to 100 g of a toluene solution containing 200 μmol of dimethylmethylenebis(cyclopentadienyl)zirconium dichloride (formula (1)) as a catalyst and 2 mmol of TIBA, and stirring the solution, and the catalyst solution was added to the polymerization vessel to initiate polymerization. The polymerization was continued while maintaining the internal temperature at 60°C and the internal pressure at 0.1 MPaG (ethylene pressure), and when the ethylene consumption reached 100 g, 50 g of isopropanol (a polymerization terminator) was added to the polymerization vessel to terminate the polymerization. The obtained polymerization liquid was poured little by little into a sufficiently large amount of a methanol / acetone mixed solution, and the precipitated polymer was recovered by stirring and filtering, and the polymer was thoroughly dried in vacuum at room temperature to obtain an ethylene-norbornene-styrene-divinylbenzene copolymer P-2.

[0104] Formula (1)

[0105] <Copolymer P-3 (ethylene-norbornene-styrene-divinylbenzene copolymer)> Similar to P-2, except that 2.0 kg of toluene, 2.0 kg of pure norbornene, 0.80 kg of styrene, and 0.20 kg of divinylbenzene (mass of 81% divinylbenzene product) were charged, and polymerization was continued while maintaining the internal temperature at 90°C and the internal pressure at 0.1 MPaG in ethylene pressure. When the ethylene consumption reached 40 g, 50 g of isopropanol as a polymerization terminator was added to the polymerization vessel to terminate the polymerization. The resulting polymerization solution was poured little by little into a sufficiently large amount of methanol / acetone mixed solution, and the precipitated polymer was recovered by stirring and filtration, and thoroughly vacuum dried at room temperature to obtain ethylene-norbornene-styrene-divinylbenzene copolymer P-3.

[0106] Since P-2 and P-3 obtained in each Production Example contained small amounts of residual monomer and solvent, they were redissolved in toluene, and the solution was poured in small amounts into a sufficiently large amount of a methanol / acetone mixed solution. The precipitated polymer was stirred and filtered, and dried at room temperature under vacuum for 24 hours to obtain a purified polymer. The compositions and molecular weights of the obtained P-1 to P-3 are shown in Table 1. The purified polymer was again dissolved in toluene to obtain a 50% by mass toluene solution (varnish).

[0107] <Preparation and Evaluation of Copolymer Monocurd Products> To varnishes containing 50% by mass of each of P-1 to P-3, 0.75% by mass of initiator, relative to the mass of the resin content, was added and dissolved. Perbutyl P was used for P-1, and azo-based initiator VR-110 was used for P-2 and P-3. These varnishes were poured into a Teflon (registered trademark) mold (frame length 7 cm, width 7 cm, thickness 0.2 mm) on a PET sheet placed on a glass plate, thoroughly air-dried at 25°C, and then further dried at 100°C for 3 hours in a vacuum dryer to obtain uncured sheets that were substantially free of solvent. If necessary, multiple uncured sheets were stacked to the required thickness for each measurement. A Teflon sheet was placed on a smooth metal plate, and the uncured sheet was then placed on top of that. A mold of the required thickness, a Teflon sheet, and a smooth metal plate were then placed on top of that. For P-1 and P-2, the sheets were heated in a vacuum press under a load of 5 MPa at 150°C for 30 minutes and then at 200°C for 30 minutes. For P-3, the sheets were heated at 200°C for 30 minutes and then at 250°C for 30 minutes. The Teflon sheet and Teflon mold were then removed to obtain a cured sheet (a sheet cured with the resin alone). The gel fraction, dielectric constant, and dielectric loss tangent of the resulting cured sheet (all measured at 23°C and 40 GHz) were determined. The results are shown in Table 1.

[0108]

[0109] <Preparation of copolymer varnish> 1% by mass of initiator was added to each of varnishes containing 50% by mass of P-1, P-2, and P-3, based on the mass of the resin content, and dissolved. 2,3-dimethyl-2,3-diphenylbutane was used as the initiator. For P-3, an uncured sheet (approximately 0.1 mm thick) was prepared using the same method as above.

[0110] [Porous boron nitride sintered plate] The porous boron nitride sintered plate constituting the examples of the present invention is manufactured by the following method with reference to the methods described in WO 2014 / 196496, WO 2015 / 022956, WO 2017 / 155110, WO 2023 / 038150, WO 2023 / 038151, and JP 2016-103611 A.

[0111] <Measurement of Thermal Conductivity and Bulk Density> The thermal conductivity (H) of the porous boron nitride sintered body in the thickness direction was calculated using the following formula: H = A × B × C In the formula, H is the thermal conductivity (W / (m·K)), A is the thermal diffusivity (m 2 / sec), B is the bulk density (kg / m 3 ), and C indicate the specific heat capacity (J / (kg·K)). The thermal diffusivity A was measured by the laser flash method using a sample of boron nitride sintered body processed to a size of length x width x thickness = 10 mm x 10 mm x 0.40 mm. The measurement device used was a thermal conductivity measurement device (LFA 467 HyperFlash (registered trademark) (NETZSCH)). The bulk density B was calculated from the volume and mass of the boron nitride sintered body.

[0112] <Measurement of average pore diameter> The pore volume distribution of the obtained porous boron nitride sintered body was measured while increasing the pressure from 0.0042 MPa to 206.8 MPa using a mercury porosimeter (device name: Autopore IV9500) manufactured by Shimadzu Corporation. In the cumulative pore volume distribution, the pore diameter at which the cumulative pore volume reached 50% of the total pore volume was defined as the "median pore diameter."

[0113] <Measurement of porosity> The bulk density B calculated as above and the theoretical density of boron nitride (2280 kg / m 3 ) and the porosity was calculated using the following formula: Porosity (volume %) = [1 - (B / 2280)] x 100

[0114] <I.O.P. (The Index of Orientation Performance)> The degree of orientation represented by I.O.P. is calculated using the following formula from the intensity ratio of the (002) diffraction line to the (100) diffraction line in X-ray diffraction of a surface measured from a direction parallel to the height direction of the boron nitride sintered body, and the intensity ratio of the (002) diffraction line to the (100) diffraction line in X-ray diffraction of a surface measured from a direction perpendicular to the height direction of the boron nitride sintered body. I.O.P. = (I100 / I002) par. / (I100 / I002) perp.

[0115] <Measurement of Breakdown Voltage> The resin-filled boron nitride plate was cut out using a cutter so that it was 50 mm from the end, and used as a measurement sample. One of the cut-out measurement samples was placed on a copper plate in a measurement jig (manufactured by Onishi Electronics Co., Ltd.), and a 40 mm square x 1 mm thick copper plate was placed in the center, and insulating oil (manufactured by 3M, product name: Novec 7200) was filled so that the measurement sample was sufficiently immersed. Next, an electrode was lowered from above the measurement sample, creating a situation in which electricity could be passed between the device and the measurement sample, and the breakdown voltage was measured using an ultra-high voltage withstand voltage tester (manufactured by Keisoku Giken Kenkyusho Co., Ltd.) in accordance with JIS C 2110-1:2016.

[0116] <Thermal Conductivity Evaluation> Measurement of the thermal conductivity H (unit: W / (m·K)) of the sheet: The thermal conductivity H is calculated by multiplying the thermal diffusivity A (unit: m 2 / sec), density B (unit: kg / m 3 ), and specific heat capacity C (unit: J / (kg K)) values ​​were calculated based on the formula H = A × B × C. The thermal diffusivity A was measured by the laser flash method after processing the evaluation sheet into a length of 10 mm, a width of 10 mm, and a thickness of 0.3 mm. The measurement device used was a thermal conductivity measurement device (LFA 467 HyperFlash (registered trademark) (NETZSCH)). The density B was measured using the Archimedes method. The specific heat capacity C was measured using a DSC (manufactured by Rigaku Corporation, product name: ThermoPlusEvoDSC8230).

[0117] [Preparation of Porous Boron Nitride Sintered Plate] 100 parts by mass of orthoboric acid manufactured by Nippon Denko Corporation and 35 parts by mass of acetylene black (product name: HS100) manufactured by Denka Co., Ltd. were mixed using a Henschel mixer. The resulting mixture was loaded into a graphite crucible and heated in an arc furnace in an argon atmosphere at 2200°C for 5 hours to obtain lumped boron carbide (BC). The resulting lumps were coarsely crushed using a jaw crusher to obtain coarse powder. This coarse powder was further crushed using a ball mill with silicon carbide balls (φ10 mm) to obtain a crushed powder.

[0118] The prepared pulverized powder was placed in a boron nitride crucible and heated in a resistance heating furnace at 2000°C and 0.85 MPa under a nitrogen gas atmosphere for 10 hours to obtain a fired material containing boron carbonitride (BCN).

[0119] A sintering aid was prepared by blending powdered boric acid and calcium carbonate. 50.0 parts by mass of calcium carbonate was blended with 100 parts by mass of boric acid. The atomic ratio of boron to calcium was 17.5 atomic % of calcium per 100 atomic % of boron. 20 parts by mass of the sintering aid was blended with 100 parts by mass of the above-mentioned short boron nitride-containing fired material, and the mixture was mixed using a Henschel mixer to prepare a powdered blend.

[0120] The compound was pressed at 150 MPa for 30 seconds using a powder press to form a sheet (length x width x thickness = 100 mm x 200 mm x 0.2 mm) to obtain a ceramic green sheet.

[0121] Two boron nitride setters (length x width x thickness = 100 mm x 200 mm x 2.0 mm) were prepared and stacked so that the above-mentioned ceramic green sheet was sandwiched between them to prepare a laminate. The resulting laminate was placed in a boron nitride container and introduced into a batch-type high-frequency furnace. In the batch-type high-frequency furnace, it was heated under conditions of atmospheric pressure, a nitrogen flow rate of 5 L / min, and 2000°C for 5 hours. Thereafter, the porous boron nitride sintered plate was removed from the boron nitride container. The area of ​​the main surface of the porous boron nitride sintered plate was 20,000 mm. 2 The thickness was 0.2 mm, the porosity was 50% by volume, the median pore diameter was 2.4 μm, and the I.O.P. was 6.8.

[0122] [Preparation and Curing of Resin-Filled Boron Nitride Plates] Example 1: The porous boron nitride sintered plate prepared as described above was cut into a 50 mm square. A toluene varnish containing the P-1 was poured into a container (60 mm square, 2 mm deep). The amount of toluene varnish poured was such that the volume of P-1 contained in the varnish was twice the volume of the pores calculated from the porosity of the porous boron nitride sintered plate. The cut-out porous boron nitride sintered plate (50 mm square) was immersed on top of the toluene varnish. The pressure in a vacuum dryer was slowly reduced (500-100 mmHg absolute pressure) to allow the varnish to fully impregnate the pores. The toluene was then thoroughly removed by heating (room temperature to 100°C) while maintaining the reduced pressure. The container was removed from the vacuum dryer, and the resin-filled boron nitride plate, consisting of a porous boron nitride sintered plate impregnated with resin, was carefully removed. The resin-filled boron nitride plate was sandwiched between two Teflon sheets, then sandwiched between two mirror-finished metal plates. The resin was cured by heating and pressurizing in a vacuum press at 5 MPa and 200°C for 30 minutes, followed by 250°C for 1 hour. The metal plates and Teflon sheets were removed, yielding a cured resin-filled boron nitride plate with a smooth main surface. The resin that had spilled onto the periphery of the resin-filled boron nitride plate was then removed by polishing both sides of the plate to remove the thin resin film on the surface. The specific gravity was measured, and the copolymer filling rate was calculated to be 50% by volume. The thermal conductivity of this cured material was 36 W / (m·K). The dielectric constant measured at 40 GHz was 3.8, and the dielectric dissipation factor was 0.00039.

[0123] Example 2 A cured resin-filled boron nitride plate was obtained in the same manner as in Example 1, except that a toluene varnish of copolymer P-2 containing a curing agent was used. The copolymer filling rate was 50% by volume. The thermal conductivity of this cured plate was 47 W / (m K). The dielectric constant measured at 40 GHz was 3.5, and the dielectric dissipation factor was 0.00035.

[0124] Example 3: Two uncured sheets (approximately 0.1 mm thick) of copolymer P-3 containing a curing agent (2,3-dimethyl-2,3-diphenylbutane) were laminated on both main surfaces of a cut-out porous boron nitride sintered plate (50 mm square) in a Teflon® mold (frame length 7 cm, width 7 cm, thickness 0.2 mm) placed on a Teflon® plate. Using a vacuum heating press, the resin sheet was heated under reduced pressure of 2 kPa and left at 250°C for 5 minutes, melting the resin sheet and impregnating the pores of the porous boron nitride sintered plate with the molten material (thermosetting composition) of the uncured sheet via capillary action. After cooling and impregnation, the boron nitride sintered plate was smoothed under atmospheric pressure using a tabletop hot roll press (manufactured by Hosen Co., Ltd., product name: HSRP-60150H) while removing excess molten material remaining on both main surfaces. In this way, a resin-filled boron nitride plate with a smooth main surface was obtained. This resin-filled boron nitride plate was heated in a vacuum heating press at a surface pressure of 5 MPa and 250°C for 2 hours to obtain a cured resin-filled boron nitride plate. The resin that protruded from the periphery of the resin-filled boron nitride plate was removed, and both sides of the resin-filled boron nitride plate were polished to remove the thin resin film on the surface. The thermal conductivity of this cured plate was 53 W / (m·K). The copolymer filling rate was 48% by volume. The dielectric constant measured at 40 GHz was 3.3, and the dielectric dissipation factor was 0.00034.

Claims

1. A resin-filled boron nitride plate comprising: a porous boron nitride sintered plate; and an olefin-aromatic vinyl compound-aromatic polyene copolymer filled into the pores of the porous boron nitride sintered plate.

2. The resin-filled boron nitride plate according to claim 1, wherein the porosity of the porous boron nitride sintered plate is in the range of 10 to 70% by volume, and the filling rate of the olefin-aromatic vinyl compound-aromatic polyene copolymer is in the range of 10 to 70% by volume.

3. A resin-filled boron nitride plate according to claim 1 or 2, wherein the porous boron nitride sintered plate has a degree of orientation, expressed as I.O.P., of 0.6 to 20.

4. The resin-filled boron nitride plate according to any one of claims 1 to 3, wherein the olefin-aromatic vinyl compound-aromatic polyene copolymer satisfies all of the following (1) to (5): (1) the number-average molecular weight of the copolymer is 500 to 50,000; (2) the aromatic vinyl compound monomer is an aromatic vinyl compound having 8 to 20 carbon atoms, and the content of the aromatic vinyl compound monomer unit is 0.1 to 70 mass%; (3) the olefin monomer unit is one or more selected from α-olefin monomer units having 2 to 30 carbon atoms and cyclic olefin monomer units having 7 to 30 carbon atoms, and the content thereof is 5 to 95 mass%; (4) the aromatic polyene monomer is one or more selected from polyenes having 5 to 20 carbon atoms and having multiple vinyl groups and / or vinylene groups in the molecule, and the content of vinyl groups and / or vinylene groups derived from the aromatic polyene monomer units is 2 to 30 per number-average molecular weight. (5) The total amount of the olefin monomer units, aromatic vinyl compound monomer units, and aromatic polyene monomer units is 100% by mass.

5. A resin-filled boron nitride plate according to any one of claims 1 to 4, wherein the olefin monomer units constituting the olefin-aromatic vinyl compound-aromatic polyene copolymer include at least a cyclic olefin monomer unit.

6. A resin-filled boron nitride plate according to any one of claims 1 to 5, in which a cured product obtained by curing the olefin-aromatic vinyl compound-aromatic polyene copolymer alone has a dielectric constant of less than 2.5 and a dielectric loss tangent of less than 0.0008, measured at 40 GHz and 25°C.

7. A hardened resin-filled boron nitride plate according to any one of claims 1 to 6.

8. The cured product according to claim 7, having a dielectric constant of 3.0 or more and 5.0 or less, and a dielectric loss tangent of 0.0002 or more and 0.0030 or less.

9. The cured product according to claim 7 or 8, having a thermal conductivity of 10 W / (m·K) or more.

10. A high-frequency transmission circuit comprising the cured product according to any one of claims 7 to 9.

11. A single-layer or multi-layer CCL (copper clad laminate) substrate, a single-layer or multi-layer FCCL (flexible copper clad laminate) substrate, an interlayer insulating material, or an antenna, comprising the cured product according to any one of claims 7 to 9.

12. A three-dimensional highly integrated circuit packaging package or chiplet comprising the cured body according to any one of claims 7 to 9.

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