Boron nitride powder, thermosetting resin composition, heat-conductive member, metal base substrate, circuit board, electronic device, and method for producing heat-conductive member

Abstract

A boron nitride powder containing boron nitride particles, and having a plastic deformation start equivalent pressure of 5.0 MPa or more as calculated by fitting based on the Cooper-Eaton equation.

Description

Boron nitride powder, thermosetting resin composition, thermally conductive member, metal base substrate, circuit board, electronic device, and method for manufacturing thermally conductive member

[0001] The present invention relates to boron nitride powder, a thermosetting resin composition, a thermally conductive member, a metal base substrate, a circuit board, an electronic device, and a method for producing a thermally conductive member.

[0002] Boron nitride powder has excellent thermal conductivity and is therefore used, for example, in thermally conductive members.

[0003] Patent Document 1 aims to provide a heat dissipation sheet with excellent thermal conductivity and electrical insulation, and a method for manufacturing the heat dissipation sheet with excellent thermal conductivity and electrical insulation. The heat dissipation sheet is formed by molding a thermally conductive resin composition containing a resin and boron nitride powder that contains at least agglomerated boron nitride particles formed by agglomeration of hexagonal boron nitride primary particles, and discloses a heat dissipation sheet with a partial discharge inception voltage of 2800 to 5000 kV / mm.

[0004] International Publication No. 2022 / 149434

[0005] According to the investigations of the present inventors, it has become clear that there are cases where variations occur in the thermal conductivity of thermally conductive members containing boron nitride powder.

[0006] The present invention provides a boron nitride powder that can be used to stably produce thermally conductive members with improved thermal conductivity.

[0007] The present inventors conducted extensive research to achieve the above object, and as a result, they discovered that by using boron nitride powder with a plastic deformation initiation equivalent pressure of 5.0 MPa or more, calculated by fitting using the Cooper-Eaton equation, it is possible to stably manufacture a thermally conductive sheet with improved thermal conductivity, and thus completed the present invention.

[0008] According to the present invention, there are provided the following boron nitride powder, thermosetting resin composition, thermally conductive member, metal base substrate, circuit board, electronic device, and method for producing a thermally conductive member.

[0009] [1] A boron nitride powder containing boron nitride particles, wherein the pressure equivalent to the onset of plastic deformation calculated by fitting using the Cooper-Eaton equation is 5.0 MPa or more. [2] The boron nitride powder according to [1] above, wherein the degree of orientation A after compression is 0.120 or more, as measured by the following (Method 1). (Method 1) A compressed body of the boron nitride powder is produced by applying a load of 500 N at a pressing speed of 0.2 mm / s to 0.85±0.15 g of boron nitride powder packed into a cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm, twice in total, and the load is then applied at a pressing speed of 0.2 mm / s to 0.85±0.15 g of boron nitride powder. In the X-ray diffraction spectrum of the compressed body obtained by the following <X-ray diffraction measurement method>, the diffraction peak intensity I of the 002 plane is ００２ and the diffraction peak intensity I of the 100 plane １００ and the degree of orientation A after compression is calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２ <X-ray diffraction measurement method> X-ray diffraction is performed by irradiating the compressed body with X-rays in the thickness direction under the conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min using CuKα radiation as a radiation source. [3] The volume-based median diameter D of the boron nitride powder measured by a laser diffraction scattering method ５０The boron nitride powder according to [1] or [2], wherein the particle size is 0.1 μm or more and 100 μm or less. [4] The boron nitride powder according to any of [1] to [3], wherein the boron nitride powder comprises scaly boron nitride particles. [5] The boron nitride powder according to any of [1] to [4], wherein the boron nitride particles comprise secondary particles constituted by scaly primary particles of boron nitride. [6] The boron nitride powder according to any of [1] to [5], wherein the boron nitride powder can be used for thermally conductive members. [7] The boron nitride powder according to any of [1] to [6], wherein the packing ratio after compression at 10 MPa is less than 0.74. [8] A thermosetting resin composition comprising the boron nitride powder according to any of [1] to [7], and a thermosetting resin. [9] The thermosetting resin composition according to [8], wherein the content of the boron nitride powder is 50% by mass or more and 95% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[10] The thermosetting resin composition according to [8] or [9], wherein the thermosetting resin comprises an epoxy resin.

[11] The thermosetting resin composition according to any one of [8] to

[10] , wherein the content of the thermosetting resin is 5% by mass or more and 50% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[12] The thermosetting resin composition according to any one of [8] to

[11] , further comprising a curing agent.

[13] The thermosetting resin composition according to

[12] , wherein the content of the curing agent is 0.01% by mass or more and 10% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[14] The thermosetting resin composition according to any one of [8] to

[13] above, further comprising a solvent, and being in the form of a varnish as a whole.

[15] A thermally conductive member comprising a resin composition layer made of the thermosetting resin composition according to any one of [8] to

[14] above.

[16] The thermally conductive member according to

[15] above, being in the form of a sheet as a whole.

[17] The thermally conductive member according to

[15] or

[16] above, further comprising a substrate.

[18] The thermally conductive member according to any one of

[15] to

[17] , wherein the resin composition layer is in an uncured state, a B-stage state, or a C-stage state.

[19] The thermally conductive member according to any one of

[15] to

[18] , wherein the thermal conductivity of the cured product of the resin composition layer in the thickness direction, as measured by a laser flash method, is 10.0 W / (m·K) or more.

[20] A metal base substrate comprising, in this order, a metal substrate, an insulating layer, and a metal layer, wherein the insulating layer comprises a resin composition layer made of the thermosetting resin composition according to any one of [8] to

[14] , or a cured product of the resin composition layer.

[21] A circuit board comprising the metal base substrate according to

[20] , wherein the metal layer comprises a circuit layer.

[22] An electronic device comprising the circuit board according to

[21] , and an electronic component on the circuit board.

[23] An electronic device comprising: a metal layer; an electronic component on a first surface of the metal layer; a thermally conductive member on a second surface of the metal layer opposite the first surface; and an encapsulating resin layer encapsulating the electronic component and the metal layer, wherein the thermally conductive member comprises a resin composition layer made of the thermosetting resin composition described in any of [8] to

[14] above, or a cured product of the resin composition layer.

[24] A method for manufacturing a thermally conductive member, comprising the step of selecting boron nitride powder having a plastic deformation initiation equivalent pressure of 5.0 MPa or more, calculated by fitting using the Cooper-Eaton equation.

[25] A method for manufacturing a thermally conductive member according to any of

[24] above, further comprising the step of selecting boron nitride powder having a degree of orientation A after compression of 0.120 or more, using the following (Method 1). (Method 1) A cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm is filled with 0.85±0.15 g of boron nitride powder, and a load of 500 N is applied at a pressing speed of 0.2 mm / s. This operation is repeated twice in total to produce a compressed body of the boron nitride powder. In the X-ray diffraction spectrum of the compressed body obtained by the <X-ray diffraction measurement method> described below, a diffraction peak intensity I of the 002 plane is measured. ００２ and the diffraction peak intensity I of the 100 plane １００ and the degree of orientation A after compression is calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I００２

[26] The method for producing a thermally conductive member according to

[24] or

[25] , further comprising a step of applying, onto a substrate, a resin composition layer made of a thermosetting resin composition containing the boron nitride powder and a thermosetting resin, using CuKα radiation as a radiation source and irradiating X-rays in the thickness direction of the compressed body under conditions of a scanning axis 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min.

[0010] According to the present invention, there are provided a thermally conductive member, a metal base substrate, a circuit board, an electronic device, and a method for manufacturing a thermally conductive member, as shown below.

[0011] [1] A thermally conductive member comprising a resin composition layer made of a thermosetting resin composition containing a thermosetting resin and a boron nitride powder containing boron nitride particles, the boron nitride powder having a plastic deformation initiation equivalent pressure of 5.0 MPa or more as calculated by fitting using the Cooper-Eaton equation, wherein the thermal conductivity of a cured product of the resin composition layer in the thickness direction is 10.0 W / (m·K) or more as measured by a laser flash method. [2] The thermally conductive member according to claim 1, wherein the degree of orientation A after compression of the boron nitride powder is 0.120 or more as measured by the following (Method 1). (Method 1) A cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm is filled with 0.85±0.15 g of boron nitride powder. A load of 500 N is applied to the compressed body of boron nitride powder at a pressing speed of 0.2 mm / s twice in total. The X-ray diffraction spectrum of the compressed body obtained by the <X-ray diffraction measurement method> described below shows that the diffraction peak intensity I of the 002 plane is ００２ and the diffraction peak intensity I of the 100 plane １００ and the degree of orientation A after compression is calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２ <X-ray diffraction measurement method> X-ray diffraction is performed by irradiating the compressed body with X-rays in the thickness direction under the conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min using CuKα radiation as a radiation source. [3] The volume-based median diameter D of the boron nitride powder measured by a laser diffraction scattering method ５０The thermally conductive member according to [1] or [2], wherein the diameter of the boron nitride powder is 0.1 μm or more and 100 μm or less. [4] The thermally conductive member according to any one of [1] to [3], wherein the boron nitride powder comprises scaly boron nitride particles. [5] The thermally conductive member according to any one of [1] to [4], wherein the boron nitride particles comprise secondary particles composed of scaly primary particles of boron nitride. [6] The thermally conductive member according to any one of [1] to [5], wherein the boron nitride powder has a packing fraction of less than 0.74 after compression at 10 MPa. [7] The thermally conductive member according to any one of [1] to [6], wherein the content of the boron nitride powder in the thermosetting resin composition is 50% by mass or more and 95% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is 100% by mass. [8] The thermally conductive member according to any one of [1] to [7], wherein the thermosetting resin comprises an epoxy resin. [9] The thermally conductive member according to any one of [1] to [8], wherein the content of the thermosetting resin in the thermosetting resin composition is 5% by mass or more and 50% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[10] The thermally conductive member according to any one of [1] to [9], wherein the thermosetting resin composition further contains a curing agent.

[11] The thermally conductive member according to

[10] , wherein the content of the curing agent in the thermosetting resin composition is 0.01% by mass or more and 10% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[12] The thermally conductive member according to any one of [1] to

[11] , wherein the entire member is in a sheet form.

[13] The thermally conductive member according to any one of [1] to

[12] , further comprising a substrate.

[14] The thermally conductive member according to any one of [1] to

[13] , wherein the resin composition layer is in an uncured state, a B-stage state, or a C-stage state.

[15] A metal base substrate comprising a metal substrate, an insulating layer, and a metal layer in this order, wherein the insulating layer includes the thermally conductive member according to any one of [1] to

[14] .

[16] A circuit board comprising the metal base substrate according to

[15] , wherein the metal layer includes a circuit layer.

[17] An electronic device comprising the circuit board according to

[16] and an electronic component on the circuit board.

[18] An electronic device comprising: a metal layer; an electronic component on a first surface of the metal layer; a thermally conductive member according to any one of [1] to

[14] on a second surface of the metal layer opposite the first surface; and an encapsulating resin layer encapsulating the electronic component and the metal layer.

[19] A method for producing a thermally conductive member, comprising: selecting boron nitride powder having a plastic deformation initiation equivalent pressure of 5.0 MPa or more as calculated by fitting using the Cooper-Eaton equation; and applying to a substrate a resin composition layer made of a thermosetting resin composition containing the selected boron nitride powder and a thermosetting resin, wherein the cured resin composition layer has a thermal conductivity in the thickness direction of 10.0 W / (m·K) or more as measured by a laser flash method.

[20] A method for producing a thermally conductive member according to

[19] , further comprising: selecting boron nitride powder having a degree of orientation A after compression of 0.120 or more as determined by (Method 1) below. (Method 1) A cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm is filled with 0.85±0.15 g of boron nitride powder, and a load of 500 N is applied at a pressing speed of 0.2 mm / s. This operation is repeated twice in total to produce a compressed body of the boron nitride powder. In the X-ray diffraction spectrum of the compressed body obtained by the <X-ray diffraction measurement method> described below, a diffraction peak intensity I of the 002 plane is measured. ００２ and the diffraction peak intensity I of the 100 plane １００ and the degree of orientation A after compression is calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２ <X-ray diffraction measurement method> X-ray diffraction is performed by irradiating the compressed body with X-rays in the thickness direction using CuKα radiation as a radiation source under conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min.

[0012] According to the present invention, it is possible to provide boron nitride powder that can be used to stably produce thermally conductive members with improved thermal conductivity.

[0013] 1 is a schematic cross-sectional view showing an example of the configuration of a metal base substrate according to an embodiment of the present invention;

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are given similar reference numerals and their description will be omitted where appropriate. The drawings are schematic and do not correspond to actual dimensional proportions. Furthermore, "to" indicating a numerical range means "greater than or equal to" to "less than or equal to" unless otherwise specified.

[0015] [Boron nitride powder] The boron nitride powder of this embodiment (hereinafter also referred to simply as "powder") contains boron nitride. The boron nitride powder of this embodiment has a plastic deformation initiation equivalent pressure of 5.0 MPa or more, calculated by fitting using the Cooper-Eaton equation. Because the boron nitride powder of this embodiment has the above-mentioned configuration, when used, thermally conductive members with improved thermal conductivity can be stably produced.

[0016] The reason for this is not entirely clear, but the following reason is presumed. Because the boron nitride powder of this embodiment has the aforementioned equivalent pressure at the onset of plastic deformation of 5.0 MPa or more, it is believed that the particles of the boron nitride powder are less likely to break even when a compressive pressure is applied. Therefore, it is believed that by reducing the breakage of boron nitride powder particles during the manufacturing process of a thermally conductive member, the thermal conductivity due to heat conduction through the boron nitride powder particles is less likely to decrease even after the manufacturing process of the thermally conductive member. As a result, it is believed that when the boron nitride powder of this embodiment is used, thermally conductive members with improved thermal conductivity can be stably manufactured.

[0017] Next, each component of the boron nitride powder of this embodiment will be described with specific examples.

[0018] <Boron Nitride Powder> The boron nitride powder of the present embodiment contains boron nitride.

[0019] The boron nitride powder of this embodiment preferably contains scaly boron nitride particles, from the viewpoint of enabling more stable production of thermally conductive members with improved thermal conductivity.

[0020] From the viewpoint of enabling more stable production of thermally conductive members with improved thermal conductivity, the boron nitride particles of this embodiment preferably contain secondary particles composed of scaly primary particles of boron nitride. The secondary particles are, for example, spherical particles. Note that the term "spherical" does not necessarily mean a perfect sphere, but also includes ellipsoids of revolution and rounded shapes formed by sphericalizing aggregates of primary particles. Furthermore, as long as the particles are rounded overall, they may have uneven surfaces. The secondary particles may be, for example, particles formed by sintering primary particles.

[0021] <Physical Properties of Boron Nitride Powder> The volume-based median diameter D of the boron nitride powder of this embodiment measured by a laser diffraction scattering method ５０ From the viewpoint of enabling more stable production of a thermally conductive member having improved thermal conductivity, the median diameter D on a volume basis measured by a laser diffraction scattering method is preferably 0.1 μm or more and 100 μm or less, more preferably 1 μm or more and 70 μm or less, even more preferably 5 μm or more and 50 μm or less, even more preferably 10 μm or more and 40 μm or less, and even more preferably 15 μm or more and 35 μm or less. ５０ More specifically, the method described in the Examples can be used as the measurement method.

[0022] The pressure equivalent to the onset of plastic deformation of the boron nitride powder of this embodiment, calculated by fitting using the Cooper-Eaton equation, is 5.0 MPa or more, preferably 5.5 MPa or more, more preferably 6.0 MPa or more, even more preferably 6.3 MPa or more, even more preferably 6.5 MPa or more, even more preferably 7.0 MPa or more, even more preferably 7.5 MPa or more, even more preferably 8.0 MPa or more, and even more preferably 8.5 MPa or more, from the viewpoint of being able to stably produce thermally conductive members with improved thermal conductivity. The upper limit of the pressure equivalent to the onset of plastic deformation is not particularly limited, but may be, for example, 15.0 MPa or less, 14.0 MPa or less, 13.0 MPa or less, 12.0 MPa or less, 11.0 MPa or less, 10.0 MPa or less, or 9.5 MPa or less. The pressure equivalent to the onset of plastic deformation of the boron nitride powder of this embodiment, calculated by fitting using the Cooper-Eaton equation, is preferably 5.0 MPa to 15.0 MPa, more preferably 5.5 MPa to 14.0 MPa, even more preferably 6.0 MPa to 13.0 MPa, even more preferably 6.3 MPa to 12.0 MPa, even more preferably 6.5 MPa to 11.0 MPa, even more preferably 7.0 MPa to 10.0 MPa, even more preferably 7.5 MPa to 10.0 MPa, even more preferably 8.0 MPa to 10.0 MPa, and even more preferably 8.5 MPa to 9.5 MPa, from the viewpoint of being able to stably produce thermally conductive members with improved thermal conductivity. The pressure equivalent to the onset of plastic deformation can be adjusted, for example, by adjusting the blending composition of small-diameter particles and coarse-diameter particles used when producing the boron nitride powder. Here, small-diameter particles are particles having a particle diameter equal to or less than a predetermined value. Coarse particles are particles whose particle diameter is larger than a predetermined value. Small particles are particles whose median diameter is, for example, D ５０ When boron nitride powder having a median diameter D of 20 μm or more and 40 μm or less is sieved through a sieve having an opening of 50 μm or more and 100 μm or less, particles that pass through the sieve can be used. ５０The particles remaining on a sieve when boron nitride powder having a particle size of 20 μm or more and 40 μm or less is sieved through a sieve having an opening of 50 μm or more and 100 μm or less can be used. The method for measuring the pressure equivalent to the onset of plastic deformation can be specifically the method described in the Examples.

[0023] The degree of orientation A of the boron nitride powder of this embodiment after compression by the following <Method 1> is preferably 0.120 or more, more preferably 0.125 or more, even more preferably 0.128 or more, even more preferably 0.130 or more, and even more preferably 0.132 or more, from the viewpoint of being able to more stably produce a thermally conductive member with improved thermal conductivity. The upper limit of the degree of orientation A after compression is not particularly limited, but may be, for example, 0.200 or less, 0.180 or less, or 0.150 or less. From the viewpoint of being able to more stably produce a thermally conductive member with improved thermal conductivity, the degree of orientation A after compression is preferably 0.120 or more and 0.200 or less, more preferably 0.125 or more and 0.200 or less, even more preferably 0.128 or more and 0.200 or less, even more preferably 0.130 or more and 0.180 or less, and even more preferably 0.132 or more and 0.150 or less. The degree of orientation A after compression can be adjusted, for example, by adjusting the blending composition of small particles and coarse particles used when producing the boron nitride powder. More specifically, the method described in the Examples can be used to measure the degree of orientation A after compression.

[0024] <Method 1> A cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm is filled with 0.85±0.15 g of boron nitride powder, and a load of 500 N is applied at a pressing speed of 0.2 mm / s. This operation is repeated twice in total to produce a compressed body of boron nitride powder. In the X-ray diffraction spectrum of the compressed body obtained by the <X-ray diffraction measurement method> described below, the diffraction peak intensity I of the 002 plane is ００２ and the diffraction peak intensity I of the 100 plane １００ The degree of orientation A after compression is calculated using the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２<X-ray diffraction measurement method> Using CuKα radiation as a radiation source, X-rays are irradiated in the thickness direction of the compressed body under the conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min to perform X-ray diffraction.

[0025] The packing fraction of the boron nitride powder of this embodiment after compression at 10 MPa (hereinafter also referred to as the packing fraction after compression) is preferably less than 0.74, more preferably 0.50 to 0.70, even more preferably 0.53 to 0.68, even more preferably 0.55 to 0.65, and even more preferably 0.57 to 0.63, from the viewpoint of more stable production of thermally conductive members with improved thermal conductivity. The packing fraction after compression can be adjusted, for example, by adjusting the blending composition of small particles and coarse particles used when producing the boron nitride powder. More specifically, the method described in the Examples can be used to measure the packing fraction after compression.

[0026] <Uses of Boron Nitride Powder> Next, uses of the boron nitride powder of this embodiment will be described.

[0027] The boron nitride powder of this embodiment can be used for thermally conductive members because it allows for more stable production of thermally conductive members with improved thermal conductivity. The thermally conductive member may further include, for example, a metal member. The shape of the thermally conductive member is not particularly limited and may be any shape.

[0028] [Thermosetting resin composition] The thermosetting resin composition of this embodiment contains the boron nitride powder of this embodiment and a thermosetting resin (A). The thermosetting resin composition of this embodiment may contain components other than the boron nitride powder of this embodiment and the thermosetting resin (A).

[0029] From the viewpoint of enabling more stable production of thermally conductive members with improved thermal conductivity, the content of boron nitride powder in the thermosetting resin composition of this embodiment is preferably 50% by mass or more and 95% by mass or less, more preferably 55% by mass or more and 90% by mass or less, even more preferably 60% by mass or more and 85% by mass or less, even more preferably 65% ​​by mass or more and 82% by mass or less, and even more preferably 70% by mass or more and 80% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[0030] <Thermosetting resin (A)> Examples of the thermosetting resin (A) of the present embodiment include epoxy resins, cyanate resins, polyimide resins, benzoxazine resins, unsaturated polyester resins, phenolic resins, melamine resins, silicone resins, bismaleimide resins, acrylic resins, etc. The thermosetting resin (A) preferably includes an epoxy resin.

[0031] Examples of the epoxy resin (A1) of this embodiment include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol E-type epoxy resins, bisphenol S-type epoxy resins, bisphenol M-type epoxy resins (4,4'-(1,3-phenylenediisopridiene)bisphenol-type epoxy resins), bisphenol P-type epoxy resins (4,4'-(1,4-phenylenediisopridiene)bisphenol-type epoxy resins), and bisphenol Z-type epoxy resins (4,4'-cyclohexidienebisphenol-type epoxy resins); phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, trisphenol methane novolac-type epoxy resins, tetraphenol novolac-type epoxy resins, and the like. aryl alkylene type epoxy resins such as xylylene type epoxy resins and biphenyl aralkyl type epoxy resins; naphthalene type epoxy resins such as naphthylene ether type epoxy resins, naphthol type epoxy resins, naphthalene diol type epoxy resins, difunctional to tetrafunctional epoxy type naphthalene resins, binaphthyl type epoxy resins, and naphthalene aralkyl type epoxy resins; anthracene type epoxy resins; phenoxy type epoxy resins; dicyclopentadiene type epoxy resins; norbornene type epoxy resins; adamantane type epoxy resins; and fluorene type epoxy resins.

[0032] The epoxy resin (A1) of the present embodiment preferably contains one or more resins selected from the group consisting of bisphenol-type epoxy resins, novolac-type epoxy resins, biphenyl-type epoxy resins, aryl alkylene-type epoxy resins, naphthalene-type epoxy resins, anthracene-type epoxy resins, and dicyclopentadiene-type epoxy resins, and more preferably contains one or more resins selected from the group consisting of bisphenol-type epoxy resins and dicyclopentadiene-type epoxy resins.

[0033] From the viewpoint of enabling more stable production of a thermally conductive member with improved thermal conductivity, the content of the thermosetting resin (A) in the thermosetting resin composition of this embodiment is preferably 5% by mass or more and 50% by mass or less, more preferably 7% by mass or more and 45% by mass or less, even more preferably 9% by mass or more and 40% by mass or less, even more preferably 11% by mass or more and 35% by mass or less, even more preferably 13% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[0034] <Curing Agent (B)> The thermosetting resin composition of this embodiment preferably contains one or more selected from the group consisting of a curing agent (B) and a curing catalyst (C), and more preferably contains a curing agent (B). Examples of the curing agent (B) of this embodiment include amine compounds such as aliphatic polyamines, aromatic polyamines, aromatic diamines, and dicyandiamide, acid anhydrides such as alicyclic acid anhydrides and aromatic acid anhydrides, phenolic compounds such as novolac phenolic resins (phenolic curing agents (B1)), and imidazole compounds. The thermosetting resin composition of this embodiment further preferably contains one or more selected from the group consisting of a phenolic curing agent (B1) and a curing catalyst (C), and even more preferably contains both a phenolic curing agent (B1) and a curing catalyst (C).

[0035] <Phenol-Based Curing Agent (B1)> Examples of the phenol-based curing agent (B1) of this embodiment include novolac-type phenolic resins such as phenol novolac resins, cresol novolac resins, trisphenolmethane novolac resins, naphthol novolac resins, and aminotriazine novolac resins; modified phenolic resins such as terpene-modified phenolic resins and dicyclopentadiene-modified phenolic resins; aralkyl-type resins such as phenol aralkyl resins having a phenylene skeleton and / or biphenylene skeleton and naphthol aralkyl resins having a phenylene skeleton and / or biphenylene skeleton; bisphenol compounds such as bisphenol A and bisphenol F; and resole-type phenolic resins. The phenol-based curing agent (B1) of this embodiment preferably contains one or more phenolic resins selected from the group consisting of novolac-type phenolic resins and resole-type phenolic resins, and more preferably contains a novolac-type phenolic resin.

[0036] The content of the curing agent (B) in the thermosetting resin composition of the present embodiment is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 9% by mass or less, even more preferably 1% by mass or more and 8% by mass or less, even more preferably 2% by mass or more and 7% by mass or less, even more preferably 3% by mass or more and 6% by mass or less, and even more preferably 4% by mass or more and 6% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[0037] <Curing Catalyst (C)> Examples of the curing catalyst (C) of the present embodiment include organic metal salts such as zinc naphthenate, cobalt naphthenate, tin octoate, cobalt octoate, bisacetylacetonate cobalt(II), and trisacetylacetonate cobalt(III); tertiary amines such as triethylamine, tributylamine, and 1,4-diazabicyclo[2.2.2]octane; 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, and 2-phenyl-4-methyl-5-hydroxyimidazole; imidazoles such as midazole and 2-phenyl-4,5-dihydroxymethylimidazole; organic phosphorus compounds such as triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, and 1,2-bis-(diphenylphosphino)ethane; phenolic compounds such as phenol, bisphenol A, and nonylphenol; organic acids such as acetic acid, benzoic acid, salicylic acid, and p-toluenesulfonic acid; and the like, or mixtures thereof.

[0038] From the viewpoint of improving the glass transition temperature and reducing the linear expansion coefficient, the content of the curing catalyst (C) in the thermosetting resin composition of the present embodiment is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.005% by mass or more and 0.8% by mass or less, even more preferably 0.01% by mass or more and 0.5% by mass or less, even more preferably 0.05% by mass or more and 0.4% by mass or less, and still more preferably 0.1% by mass or more and 0.3% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is taken as 100% by mass.

[0039] <Other Components> The thermosetting resin composition of this embodiment may contain components other than the boron nitride powder of this embodiment, the thermosetting resin (A), the curing agent (B), and the curing catalyst (C). Examples of other components include fillers, coupling agents, phenoxy resins, antioxidants, leveling agents, defoamers, and dispersants. Examples of fillers include silica, alumina, aluminum nitride, and silicon carbide. Examples of coupling agents include epoxy silane coupling agents, cationic silane coupling agents, amino silane coupling agents, titanate-based coupling agents, and silicone oil-type coupling agents. Examples of phenoxy resins include phenoxy resins having a bisphenol skeleton, phenoxy resins having a naphthalene skeleton, phenoxy resins having an anthracene skeleton, and phenoxy resins having a biphenyl skeleton.

[0040] <Solvent> The thermosetting resin composition of the present embodiment may further contain a solvent. In this case, the entire thermosetting resin composition is in a varnish state. Examples of the solvent include methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, and cyclohexanone.

[0041] The content of the solvent in the thermosetting resin composition of this embodiment is, for example, 40 parts by mass or more and 85 parts by mass or less, when the total content of the boron nitride powder and the thermosetting resin (A) in the thermosetting resin composition is 100 parts by mass.

[0042] <Method for producing thermosetting resin composition> The method for producing the thermosetting resin composition of the present embodiment is not particularly limited, and a known method can be used. For example, more specifically, the method described in the examples can be used as the method for producing the thermosetting resin composition of the present embodiment.

[0043] [Resin Sheet] The resin sheet of this embodiment includes a resin composition layer made of the thermosetting resin composition of this embodiment. The resin composition layer is preferably in a B-stage state. The resin sheet has, for example, a base material and a resin composition layer made of the thermosetting resin composition of this embodiment provided on the base material.

[0044] The resin sheet of this embodiment can be obtained, for example, by applying a varnish-like thermosetting resin composition to a substrate and then subjecting the resulting coating film to a solvent removal treatment. The solvent content in the resin sheet is preferably 10% by mass or less based on the total thermosetting resin composition. For example, the solvent removal treatment can be performed at 80°C to 200°C for 1 minute to 30 minutes.

[0045] The planar shape of the resin sheet of this embodiment is not particularly limited and can be appropriately selected according to the shape of the heat sink, heat generator, etc., but can be, for example, rectangular. The film thickness of the resin composition layer of the resin sheet of this embodiment is, for example, 50 μm or more and 500 μm or less from the viewpoint of further improving the balance between mechanical strength, heat resistance, insulation properties, and heat dissipation properties.

[0046] The substrate may include, for example, one or more materials selected from the group consisting of resin films and metal foils. Examples of resin films include polyolefin films such as polyethylene films and polypropylene films; polyester films such as polyethylene terephthalate films and polybutylene terephthalate films; polycarbonate films; fluorine-based resin films; and polyimide resin films. Examples of metal foils include copper foil, copper-based alloy foil, aluminum foil, aluminum-based alloy foil, iron foil, iron-based alloy foil, silver foil, silver-based alloy foil, gold foil, gold-based alloy foil, zinc foil, zinc-based alloy foil, nickel foil, nickel-based alloy foil, tin foil, and tin-based alloy foil. The thickness of the substrate is, for example, 10 μm or more and 500 μm or less.

[0047] The resin sheet of this embodiment can be used for various substrate applications. From the viewpoint of the balance between thermal conductivity and heat resistance, the resin sheet can be preferably used as a material for a power module substrate.

[0048] [Thermal Conductive Member] The thermal conductive member of this embodiment includes a resin composition layer made of the thermosetting resin composition of this embodiment.

[0049] The thermally conductive member of this embodiment is preferably entirely in a sheet form, from the viewpoint of improving ease of handling. The thermally conductive member is, for example, a thermally conductive sheet.

[0050] The thermally conductive member of this embodiment further includes a substrate. Such a thermally conductive member is, for example, the resin sheet of this embodiment before the substrate is peeled off.

[0051] The resin composition layer contained in the thermally conductive member of this embodiment may be in an uncured state, a B-stage state, or a C-stage state. The resin composition layer is preferably in a B-stage state or a C-stage state.

[0052] In the thermally conductive member of this embodiment, the thermal conductivity in the thickness direction of the cured resin composition layer (i.e., the resin composition layer in a C-stage state), as measured by the laser flash method, is, from the viewpoint of further improving thermal conductivity, preferably 10.0 W / (m·K) or more, more preferably 10.5 W / (m·K) or more, even more preferably 11.0 W / (m·K) or more, even more preferably 11.5 W / (m·K) or more, even more preferably 12.0 W / (m·K) or more, even more preferably 12.5 W / (m·K) or more, and even more preferably 13.0 W / (m·K) or more.

[0053] The upper limit of the thermal conductivity in the thickness direction of the cured resin composition layer is not particularly limited, but may be, for example, 20.0 W / (m·K) or less, 18.0 W / (m·K) or less, or 15.0 W / (m·K) or less.

[0054] From the viewpoint of further improving thermal conductivity, the thermal conductivity in the thickness direction of the cured resin composition layer is preferably 10.0 W / (m K) or more and 20.0 W / (m K) or less, more preferably 10.5 W / (m K) or more and 20.0 W / (m K) or less, even more preferably 11.0 W / (m K) or more and 20.0 W / (m K) or less, even more preferably 11.5 W / (m K) or more and 20.0 W / (m K) or less, even more preferably 12.0 W / (m K) or more and 18.0 W / (m K) or less, even more preferably 12.5 W / (m K) or more and 15.0 W / (m K) or less, even more preferably 13.0 W / (m K) or more and 15.0 W / (m K) or less. More specifically, the method for measuring thermal conductivity can be adopted as described in the examples.

[0055] The thermally conductive member of this embodiment is used, for example, as a thermally conductive material interposed between a heat generating body and a heat dissipating body. Examples of the heat generating body include a semiconductor element, an LED element, a substrate on which a semiconductor element or an LED element is mounted, a central processing unit (CPU), a power semiconductor, a lithium-ion battery, and a fuel cell. Examples of the heat dissipating body include a heat sink, a heat spreader, and a heat dissipating (cooling) fin.

[0056] Furthermore, the thermally conductive member of this embodiment can be provided, for example, at a bonding interface within an electronic device where high thermal conductivity is required, to promote heat conduction from a heat generating element to a heat sink, thereby suppressing failures caused by fluctuations in the characteristics of semiconductor chips and improving the stability of the electronic device.

[0057] The thermally conductive member of this embodiment can be used for various substrate applications, and from the viewpoint of the balance between thermal conductivity and heat resistance, it can be preferably used as a material for a power module substrate.

[0058] <Method for manufacturing thermally conductive member> Hereinafter, each step of the method for manufacturing a thermally conductive member of the present embodiment will be described. Note that the thermosetting resin composition used in the method for manufacturing a thermally conductive member of the present embodiment preferably contains the thermosetting resin composition of the present embodiment.

[0059] The method for manufacturing a thermally conductive member of this embodiment includes the following steps: Step 1: Select boron nitride powder having a plastic deformation initiation equivalent pressure of 5.0 MPa or more, calculated by fitting using the Cooper-Eaton equation. The method for manufacturing a thermally conductive member of this embodiment, having the above-described configuration, can stably manufacture thermally conductive members with improved thermal conductivity.

[0060] <Step 1> In step 1, boron nitride powder is selected based on the pressure equivalent to the onset of plastic deformation calculated by fitting using the Cooper-Eaton equation. From the viewpoint of being able to stably produce thermally conductive members with improved thermal conductivity, the pressure equivalent to the onset of plastic deformation of the boron nitride powder is 5.0 MPa or more, preferably 5.0 MPa to 15.0 MPa, more preferably 5.5 MPa to 14.0 MPa, even more preferably 6.0 MPa to 13.0 MPa, even more preferably 6.3 MPa to 12.0 MPa, even more preferably 6.5 MPa to 11.0 MPa, even more preferably 7.0 MPa to 10.0 MPa, even more preferably 7.5 MPa to 10.0 MPa, even more preferably 8.0 MPa to 10.0 MPa, even more preferably 8.5 MPa to 9.5 MPa. Specific methods for measuring the pressure equivalent to the onset of plastic deformation include those described in the examples.

[0061] The method for producing a thermally conductive member of this embodiment may further include the following step 2: Step 2: Select boron nitride powder having a degree of orientation A after compression of 0.120 or more according to the above-mentioned <Method 1>.

[0062] <Step 2> In step 2, boron nitride powder is selected based on the degree of orientation A after compression obtained by the above-mentioned <Method 1>. From the viewpoint of enabling more stable production of thermally conductive members with improved thermal conductivity, the degree of orientation A of the boron nitride powder after compression is preferably 0.120 or more and 0.200 or less, more preferably 0.125 or more and 0.200 or less, even more preferably 0.128 or more and 0.200 or less, even more preferably 0.130 or more and 0.180 or less, and even more preferably 0.132 or more and 0.150 or less.

[0063] The method for producing a thermally conductive member of this embodiment may further include the following step 3. Step 3: Applying a resin composition layer made of a thermosetting resin composition containing boron nitride powder and a thermosetting resin to a substrate. The method for producing a thermally conductive member of this embodiment, having the above-mentioned configuration, can more stably produce a thermally conductive member with improved thermal conductivity. Step 3 can be performed, for example, by applying a varnish-like thermosetting resin composition to a substrate and performing a solvent removal treatment on the coating film obtained.

[0064] 1 is a schematic cross-sectional view showing an example of the configuration of a metal base substrate 100 of this embodiment. The metal base substrate 100 of this embodiment includes, in this order, a metal substrate 101, an insulating layer 102, and a metal layer 103. The insulating layer 102 includes a resin composition layer made of the thermosetting resin composition of this embodiment, or a cured product of the resin composition layer.

[0065] The thickness of the insulating layer 102 is preferably 10 μm or more and 400 μm or less, more preferably 30 μm or more and 350 μm or less, even more preferably 50 μm or more and 300 μm or less, and even more preferably 100 μm or more and 250 μm or less, from the viewpoint of improving mechanical strength, heat resistance, and insulation properties, as well as improving heat dissipation properties throughout the metal base substrate 100.

[0066] The metal layer 103 is a layer used for circuit processing, provided on the insulating layer 102. Examples of metals that form the metal layer 103 include copper, copper alloys, aluminum, aluminum alloys, nickel, iron, and tin.

[0067] The thickness of the metal layer 103 is preferably 0.01 mm or more and 10.0 mm or less, more preferably 0.025 mm or more and 5.0 mm or less, even more preferably 0.05 mm or more and 3.0 mm or less, even more preferably 0.10 mm or more and 2.0 mm or less, and even more preferably 0.25 mm or more and 1.0 mm or less, from the viewpoint of reducing heat generation in the circuit pattern even in applications requiring high current, improving circuit processability, and making the entire substrate thinner.

[0068] The metal substrate 101 has a role of dissipating heat accumulated in the metal base substrate 100. The metal substrate 101 is not particularly limited as long as it is a heat-dissipating metal substrate.

[0069] The thickness of the metal substrate 101 is preferably 0.01 mm or more and 20.0 mm or less, more preferably 0.1 mm or more and 15.0 mm or less, even more preferably 1.0 mm or more and 7.5 mm or less, and even more preferably 2.0 mm or more and 5.0 mm or less, from the viewpoints of improving processability in contour processing, cutting processing, etc., making the entire substrate thinner, and improving heat dissipation properties.

[0070] The metal base substrate 100 can have a metal layer 103 that has been processed into a circuit pattern by etching or the like. In the metal base substrate 100, a solder resist layer (not shown) may be formed on the outermost layer, thereby exposing connection electrodes so that electronic components can be mounted by exposure and development.

[0071] [Circuit Board] The circuit board of this embodiment includes the metal base substrate 100 of this embodiment. In the circuit board of this embodiment, the metal layer 103 includes a circuit layer. The circuit layer can be obtained by processing the metal layer 103 of the metal base substrate 100 into a circuit pattern by etching or the like.

[0072] The circuit board of this embodiment can be used for various substrate applications, and from the viewpoint of the balance between thermal conductivity and heat resistance, it can be preferably used as a power module substrate.

[0073] [Electronic Device] The metal base substrate 100 and circuit board of this embodiment can be used in various applications requiring heat dissipation and insulation, for example, in electronic devices such as semiconductor devices. Figure 2 is a schematic cross-sectional view showing an example of the configuration of an electronic device 200 of this embodiment. The electronic device 200 of this embodiment includes the circuit board of this embodiment and electronic components 201 on the circuit board. The circuit-processed metal base substrate 100 (circuit board) can function as a heat spreader for heat from the electronic components 201 (various heat-generating elements) that generate heat during operation.

[0074] The electronic device 200 of this embodiment includes a metal layer 103, an electronic component 201 on a first surface of the metal layer 103, a thermally conductive member on a second surface opposite the first surface, and an encapsulating resin layer 205 that encapsulates the electronic component 201 and the metal layer 103. In the electronic device 200 of this embodiment, the thermally conductive member includes a resin composition layer made of the thermosetting resin composition of this embodiment, or a cured product of the resin composition layer. In the electronic device 200 of this embodiment, the thermally conductive member may be, for example, an insulating layer 102 included in the metal base substrate 100. Note that the first surface of the metal layer 103 of the metal base substrate 100 of this embodiment is the upper surface of the metal layer 103 in FIG. 2. Furthermore, the second surface of the metal layer 103 of the metal base substrate 100 of this embodiment is the lower surface of the metal layer 103 in FIG. 2.

[0075] 2 has an electronic component 201 such as a semiconductor element mounted on a metal layer 103 of a metal base substrate 100 via an adhesive layer 202 such as a die attach material. The electronic component 201 is connected to a connection electrode portion formed on the metal base substrate 100 via a bonding wire 203, and is mounted on the metal base substrate 100. The electronic component 201 is then encapsulated on the metal base substrate 100 by an encapsulating resin layer 205.

[0076] A heat sink 207 is provided on the metal substrate 101 side of the metal base substrate 100 via a thermally conductive layer 209 (thermal interface material (TIM)). From the viewpoint of thermal conductivity, examples of materials for the heat sink 207 include metals such as aluminum, iron, and copper.

[0077] The electronic component is preferably, but not limited to, a semiconductor element. Examples of the semiconductor element include, but are not limited to, an integrated circuit, a large-scale integrated circuit, a transistor, a thyristor, a diode, a solid-state imaging device, an LED, and a power semiconductor element. Examples of the power semiconductor element include a rectifier diode, a power transistor, a power MOSFET, an insulated gate bipolar transistor (IGBT), a thyristor, a gate turn-off thyristor (GTO), and a triac.

[0078] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements that do not impair the effects of the present invention are included in the present invention.

[0079] The present embodiment will be described in detail below with reference to examples, etc. However, the present embodiment is not limited to the descriptions of these examples.

[0080] First, the materials used to prepare the boron nitride powder in each example are listed.

[0081] Coarse particles: Prepared according to the method described below for <Preparation of coarse particles>. Small particles: Prepared according to the method described below for <Preparation of small particles>.

[0082] <Preparation of Coarse Particles> Boron nitride 1 (product name: HP-40MF100, manufactured by JFE Mineral Co., Ltd., median diameter D ５０ Boron nitride 1 was passed through a sieve with a mesh size of 75 μm. The particles remaining on the sieve were collected to obtain coarse particles.

[0083] <Preparation of small-diameter particles> Boron nitride 1 (product name: HP-40MF100, manufactured by JFE Mineral Co., Ltd., median diameter D ５０ Boron nitride 1 was passed through a sieve with an opening of 75 μm. The particles that passed through the sieve were collected to obtain small diameter particles.

[0084] [Examples 1 to 5, Comparative Examples 1 and 2] <Preparation of Boron Nitride Powder> Coarse particles and small particles were mixed according to the formulation shown in Table 1 to obtain boron nitride powder for each example. Next, the physical properties of the boron nitride powder for each example and the physical properties of the thermosetting resin composition containing the boron nitride powder for each example were measured by the following methods. The results are shown in Table 1.

[0085] <Volume-based median diameter D measured by laser diffraction scattering method ５０ > Using a laser diffraction particle size distribution analyzer (product name: LA-950V2, manufactured by Horiba, Ltd.), the volume-based median diameter D of each boron nitride powder was measured by laser diffraction scattering method.５０ Here, the median diameter D of the boron nitride powder was measured. ５０ was calculated using the following procedure. 0.1 g of boron nitride powder and 1.5 mL of water were placed in a 2 mL cylindrical container. Next, a detergent (product name: Mama Lemon, manufactured by Lion Corporation) was mixed with pure water at a detergent:pure water volume ratio of 1:100 to prepare a dispersant. Next, three drops of the dispersant were dropped into the cylindrical container using a dropper, and the container was shaken to prepare a sample. The prepared sample was added to pure water (with ultrasonic waves and stirring) circulating in the measuring device, and the particle size distribution of the boron nitride powder was measured. From the particle size distribution of the boron nitride powder, the median diameter D of the boron nitride powder was calculated. ５０ was calculated.

[0086] <Pressure equivalent to the onset of plastic deformation> For each boron nitride powder, the pressure equivalent to the onset of plastic deformation was calculated by fitting with the Cooper-Eaton equation according to the <Method for calculating the pressure equivalent to the onset of plastic deformation> below. The calculation of the pressure equivalent to the onset of plastic deformation was performed twice in total. The average of the two calculations was taken as the pressure equivalent to the onset of plastic deformation for each boron nitride powder.

[0087] <Method of calculating pressure equivalent to the start of plastic deformation> First, the Cooper-Eaton equation is expressed by the following equation (3): [{V(0)-V(P)} / {V(0)-V(∞)}]=A １ exp(-k １ / P) + (1-A １ ) exp(-k ２ / P) In the above formula (3), pressure P represents the pressure applied to the boron nitride powder. Apparent volume V(0) represents the apparent volume of the boron nitride powder before compression. Apparent volume V(P) represents the apparent volume of the boron nitride powder in a state compressed at pressure P [MPa]. Apparent volume V(∞) represents the apparent volume of the boron nitride powder when it is assumed that there are no voids in the boron nitride powder. Coefficient A １ represents a constant between 0 and 1. １ represents a constant greater than or equal to 0. ２ represents a constant greater than or equal to 0, and is also called the pressure equivalent to the start of plastic deformation.

[0088] For the above formula (3), the value of {V(0) - V(P)} / {V(0) - V(∞)} was calculated for each of P = 0, 0.6, 1.2, 1.8, 3.0, 8.0, and 10.0 [MPa]. Then, the value of {V(0) - V(P)} / {V(0) - V(∞)} was plotted against the value of pressure P [MPa]. The coefficient A was calculated from the plotted results using the least squares method. １ , coefficient k １ , and coefficient k ２ The coefficient k ２ The results of (the pressure equivalent to the start of plastic deformation) are shown in Table 1. The method for calculating each apparent volume will be specifically described below.

[0089] Calculation of apparent volume V(0) First, the apparent volume V(0) of the boron nitride powder of each example was calculated according to the following method.

[0090] 0.85 g ± 0.15 g of boron nitride powder from each example was weighed out and placed in a cylindrical container (inner diameter 8.0 mm x height 40 mm) attached to a powder bed shear force measuring device (product name: NS-S500, manufactured by Nano Seeds Corporation). The thickness of the boron nitride powder was made uniform within the cylindrical container. Hereinafter, the radius of the inner diameter of the cylindrical container may be referred to as the radius r.

[0091] Next, the thickness T(0) of the boron nitride powder before compression was measured using a laser displacement meter attached to the powder bed shear force measuring device. The thickness T(0) was the value of the thinnest part of the boron nitride powder before compression. The apparent volume V(0) was calculated using the following formula (4). Formula (4): apparent volume V(0) = (pi) × (radius r) ２ ×T(0)

[0092] Calculation of apparent volume V(P) Next, the apparent volume V(P) of each boron nitride powder was calculated according to the following method: Specifically, the apparent volumes V(P) were calculated as V(0.6), V(1.2), V(1.8), V(3.0), V(8.0), and V(10.0).

[0093] 0.85 g±0.15 g of the boron nitride powder of each example was weighed out and placed in the cylindrical container, with the thickness of the boron nitride powder being made uniform within the cylindrical container.

[0094] Next, the boron nitride powder of each example was subjected to the following (V(P) measurement operation). At this time, the predetermined load was changed for each pressure P applied to the boron nitride powder, and the following (V(P) measurement operation) was performed. The predetermined load for each pressure P was set to 30 N at 0.6 MPa, 60 N at 1.2 MPa, 90 N at 1.8 MPa, 150 N at 3.0 MPa, 400 N at 8.0 MPa, and 500 N at 10.0 MPa.

[0095] (V(P) measurement procedure) With boron nitride powder placed in the cylindrical container, a load was applied to the entire upper surface of the boron nitride powder at a pressing speed of 0.2 mm / s until the load on the boron nitride powder reached a predetermined load. Thereafter, using the laser displacement meter, the thickness T(P) of the boron nitride powder in a state compressed with the predetermined load (pressure P) was measured. The thickness T(P) was the value of the smallest thickness of the boron nitride powder in a state compressed with the predetermined load (pressure P). The apparent volume V(P) was calculated from the following formula (5). Formula (5): apparent volume V(P) = (pi) × (radius r) ２ ×T(P)

[0096] Calculation of apparent volume V(∞) Next, the apparent volume V(∞) of the boron nitride powder of each example was calculated using the following formula (6): Apparent volume V(∞) = (mass of boron nitride powder in cylindrical container) / (true density of boron nitride powder)

[0097] <Filling ratio after compression at 10 MPa> The filling ratio of each boron nitride powder after compression at 10 MPa (hereinafter also referred to as "filling ratio after compression") was calculated using the following formula (8). The results are shown in Table 1. Formula (8): Filling ratio after compression = V(∞) / V(10.0)

[0098] <X-ray diffraction measurement method> CuKα radiation was used as the radiation source. X-ray diffraction was performed by irradiating X-rays onto the boron nitride powder under the conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min. The details of the measurement were as follows.

[0099] X-ray diffraction apparatus: Ultima IV (manufactured by Rigaku Corporation) Radiation source: CuKα radiation Measurement optical system: focusing method Scan axis: 2θ / θ Sampling width: 0.02° Scan speed: 4° / min Divergence slit: 2 / 3° Divergence vertical limiting slit: 10 mm Scattering slit: 1.17 mm Receiving slit: 0.3 mm Offset angle 0° Voltage: 40 kV Current: 40 mA

[0100] <Degree of orientation after compression> A cylindrical container with an inner diameter of 8.0 mm and a height of 40 mm was filled with 0.85±0.15 g of boron nitride powder. A load of 500 N was applied to the entire upper surface of the filled boron nitride powder at a pressing speed of 0.2 mm / s, and this operation was repeated twice in total to produce a compressed body of boron nitride powder. In the X-ray diffraction spectrum of the compressed body obtained by the above <X-ray diffraction measurement method>, the diffraction peak intensity I of the 002 plane was measured. ００２ and the diffraction peak intensity I of the 100 plane １００ The degree of orientation A after compression was calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２ The degree of orientation A after compression was calculated three times in total, and the average value of the three calculations was taken as the degree of orientation A after compression of the boron nitride powder of each example.

[0101] <Evaluation of Thermal Conductivity> A thermosetting resin composition was prepared using the boron nitride powder of each example according to the <Preparation of Thermosetting Resin Composition> described below. Then, the thermal conductivity of the prepared cured product was measured according to the <Method for Measuring Thermal Conductivity> described below. After the measurement, the thermal conductivity of the cured product of each thermosetting resin composition was evaluated.

[0102] <Preparation of Thermosetting Resin Composition> In addition to the boron nitride powder of each example, the following <Materials for Thermosetting Resin Composition> were used for the thermosetting resin composition. The formulation of the thermosetting resin composition was in accordance with the following <Formulation of Thermosetting Resin Composition>.

[0103] <Materials of Thermosetting Resin Composition> Thermosetting resin (A) (Epoxy resin (A1)) Epoxy resin 1: Epoxy resin having a dicyclopentadiene skeleton (XD-1000, manufactured by Nippon Kayaku Co., Ltd.) Epoxy resin 2: Bisphenol A type epoxy resin (828, manufactured by Mitsubishi Chemical Corporation) Curing agent (B) (Phenol-based curing agent (B1)): Trisphenylmethane type phenol novolac resin (MEH-7500, manufactured by Meiwa Chemical Industry Co., Ltd.) Curing catalyst (C): 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW, manufactured by Shikoku Chemical Industry Co., Ltd.) Solvent: Methyl ethyl ketone

[0104] <Composition of thermosetting resin composition> Boron nitride powder: 74.8 parts by mass Epoxy resin 1: 10.0 parts by mass Epoxy resin 2: 10.0 parts by mass Phenol-based curing agent: 5.0 parts by mass Curing catalyst: 0.2 parts by mass

[0105] First, the epoxy resin, phenolic curing agent, and curing catalyst were weighed according to the above-mentioned <Composition of Thermosetting Resin Composition> and added to a solvent. This was stirred to obtain a mixed solution. Next, the boron nitride powder of each example was added to the mixed solution and premixed. After that, the mixture was stirred and mixed using a stirring blade to obtain a varnish-like thermosetting resin composition in which the boron nitride powder was uniformly dispersed.

[0106] <Preparation of Cured Thermosetting Resin Composition (Cured Thermally Conductive Sheet)> Next, the obtained thermosetting resin composition of each example was aged under the conditions of air atmosphere at a temperature of 60°C for 15 hours. The obtained thermosetting resin composition was heat-treated at 100°C for 30 minutes to prepare a B-stage thermally conductive sheet with a film thickness of 400 μm. Next, the above thermally conductive sheet was heat-treated at 180°C and 10 MPa for 40 minutes to obtain a cured thermally conductive sheet with a thickness of 200 μm.

[0107] <Method for measuring thermal conductivity> The thermal diffusion coefficient (α), specific heat (Cp), and density (ρ) of the cured thermal conductive sheet of each example were measured using the method described below. The thermal conductivity of the cured thermal conductive sheet was calculated from the thermal diffusion coefficient (α), specific heat (Cp), and density (ρ) according to the following formula (9). The unit of thermal conductivity is W / (m·K). Formula (9): Thermal conductivity [W / (m·K)] = α [m ２ / s]×Cp[J / (kg・K)]×ρ[kg / m ３ ]

[0108] <Measurement of Thermal Diffusion Coefficient (α)> The thermal diffusion coefficient (α) of the cured thermal conductive sheet of each example was measured by the laser flash method (half-time method). The unit of the thermal diffusion coefficient (α) is m ２ / s. A test piece measuring 10 mm long x 10 mm wide was cut out from the cured thermally conductive sheet to obtain a test piece for measurement in the thickness direction. Next, the thermal diffusion coefficient (α) of the test piece in the thickness direction was measured by a transient method using a thermal conductivity measuring device (product name: LFA467, manufactured by NETZSCH). The measurement was performed under atmospheric conditions at 25°C.

[0109] <Measurement of Specific Heat (Cp)> The specific heat (Cp) of the cured thermally conductive sheet of each example was measured by a DSC method. The unit of specific heat (Cp) is J / (kg·K).

[0110] <Measurement of Density (ρ)> The density (ρ) of the cured thermal conductive sheet of each example was measured in accordance with JIS K 6911:2006. Test pieces were cut out from the cured product of the thermosetting resin composition to a size of 20 mm length x 20 mm width. The unit of density (ρ) is kg / m ３ is.

[0111]

[0112] This application claims priority based on Japanese Patent Application No. 2024-102758, filed June 26, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0113] REFERENCE SIGNS LIST 100 Metal base substrate 101 Metal substrate 102 Insulating layer 103 Metal layer 200 Electronic device 201 Electronic component 202 Adhesive layer 203 Bonding wire 205 Sealing resin layer 207 Heat sink 209 Thermally conductive layer

Claims

1. A boron nitride powder containing boron nitride particles, in which the pressure equivalent to the onset of plastic deformation calculated by fitting using the Cooper-Eaton equation is 5.0 MPa or more.

2. The boron nitride powder according to claim 1, having a degree of orientation A of 0.120 or more after compression by the following (Method 1): (Method 1) A cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm is filled with 0.85±0.15 g of boron nitride powder, and a load of 500 N is applied at a pressing speed of 0.2 mm / s, this operation being repeated twice in total to produce a compressed body of the boron nitride powder; and the X-ray diffraction spectrum of the compressed body obtained by the following <X-ray diffraction measurement method> shows that the diffraction peak intensity I of the 002 plane is ００２ and the diffraction peak intensity I of the 100 plane １００ and the degree of orientation A after compression is calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２ <X-ray diffraction measurement method> X-ray diffraction is performed by irradiating the compressed body with X-rays in the thickness direction using CuKα radiation as a radiation source under conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min.

3. The volume-based median diameter D of the boron nitride powder measured by a laser diffraction scattering method ５０ 3. The boron nitride powder according to claim 1, wherein the particle size is 0.1 μm or more and 100 μm or less.

4. The boron nitride powder according to any one of claims 1 to 3, wherein the boron nitride powder contains scaly boron nitride particles.

5. Boron nitride powder according to any one of claims 1 to 4, wherein the boron nitride particles include secondary particles composed of scaly primary particles of boron nitride.

6. The boron nitride powder according to any one of claims 1 to 5, which can be used in thermally conductive members.

7. The boron nitride powder according to any one of claims 1 to 6, having a packing ratio of less than 0.74 after compression at 10 MPa.

8. A thermosetting resin composition comprising the boron nitride powder according to any one of claims 1 to 7 and a thermosetting resin.

9. The thermosetting resin composition according to claim 8, wherein the content of the boron nitride powder is 50% by mass or more and 95% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is 100% by mass.

10. The thermosetting resin composition according to claim 8 or 9, wherein the thermosetting resin comprises an epoxy resin.

11. A thermosetting resin composition according to any one of claims 8 to 10, wherein the content of the thermosetting resin is 5% by mass or more and 50% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is 100% by mass.

12. The thermosetting resin composition according to any one of claims 8 to 11, further comprising a curing agent.

13. The thermosetting resin composition according to claim 12, wherein the content of the curing agent is 0.01% by mass or more and 10% by mass or less, when the total amount of the thermosetting resin composition (excluding the solvent) is 100% by mass.

14. The thermosetting resin composition according to any one of claims 8 to 13, further comprising a solvent, and which is entirely in the form of a varnish.

15. A thermally conductive member comprising a resin composition layer made of the thermosetting resin composition according to any one of claims 8 to 14.

16. The thermally conductive member according to claim 15, which is entirely in the form of a sheet.

17. The thermally conductive member according to claim 15 or 16, further comprising a substrate.

18. The thermally conductive member according to any one of claims 15 to 17, wherein the resin composition layer is in an uncured state, a B-stage state, or a C-stage state.

19. A thermally conductive member according to any one of claims 15 to 18, wherein the thermal conductivity of the cured resin composition layer in the thickness direction, as measured by a laser flash method, is 10.0 W / (m·K) or more.

20. A metal base substrate comprising a metal substrate, an insulating layer, and a metal layer in this order, wherein the insulating layer comprises a resin composition layer made of a thermosetting resin composition according to any one of claims 8 to 14, or a cured product of the resin composition layer.

21. A circuit board comprising the metal base substrate of claim 20, wherein the metal layer comprises a circuit layer.

22. An electronic device comprising: the circuit board according to claim 21; and an electronic component on said circuit board.

23. An electronic device comprising: a metal layer; an electronic component on a first surface of the metal layer; a thermally conductive member on a second surface of the metal layer opposite the first surface; and an encapsulating resin layer that encapsulates the electronic component and the metal layer, wherein the thermally conductive member comprises a resin composition layer made of a thermosetting resin composition according to any one of claims 8 to 14, or a cured product of the resin composition layer.

24. A method for manufacturing a thermally conductive member, comprising the step of selecting boron nitride powder having a plastic deformation initiation equivalent pressure of 5.0 MPa or more, calculated by fitting using the Cooper-Eaton equation.

25. A method for producing a thermally conductive member according to claim 24, further comprising the step of selecting boron nitride powder having a degree of orientation A of 0.120 or more after compression by the following (Method 1): (Method 1) A cylindrical container having an inner diameter of 8.0 mm and a height of 40 mm is filled with 0.85±0.15 g of boron nitride powder, and a load of 500 N is applied at a pressing speed of 0.2 mm / s, this operation being repeated twice in total to produce a compressed body of the boron nitride powder, and in the X-ray diffraction spectrum of the compressed body obtained by the <X-ray diffraction measurement method> described below, a diffraction peak intensity I of the 002 plane is obtained. ００２ and the diffraction peak intensity I of the 100 plane １００ and the degree of orientation A after compression is calculated from the following formula (1): Formula (1): Degree of orientation A after compression = I １００ / I ００２ <X-ray diffraction measurement method> X-ray diffraction is performed by irradiating the compressed body with X-rays in the thickness direction using CuKα radiation as a radiation source under conditions of a scanning axis of 2θ / θ, a sampling width of 0.02°, and a scanning speed of 4° / min.

26. A method for producing a thermally conductive member according to claim 24 or 25, further comprising the step of applying a resin composition layer onto a substrate, the resin composition layer being made of a thermosetting resin composition containing the boron nitride powder and a thermosetting resin.

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