Hexagonal boron nitride-fine particle aggregate, resin composition, resin sheet, multilayer body, semiconductor element, and method for producing hexagonal boron nitride-fine particle aggregate

Abstract

A purpose of the present invention is to provide a hexagonal boron nitride-fine particle aggregate, a resin composition, a resin sheet, a multilayer body, a semiconductor element, and a method for producing the hexagonal boron nitride-fine particle aggregate. A hexagonal boron nitride-fine particle aggregate according to the present invention includes an aggregate of primary particles of hexagonal boron nitride and fine particles. At least a portion of the fine particles are present in voids in the aggregate of the primary particles of hexagonal boron nitride. The ratio of the average particle size (D50A) of the aggregate of primary particles of hexagonal boron nitride to the average particle size (D50B) of the fine particles, (D50A / D50B), is 20 to 10,000. The mass ratio of the aggregate of the primary particles of hexagonal boron nitride to the fine particles is 1:0.01 to 1:0.1. The porosity of the hexagonal boron nitride-fine particle aggregate is 56 to 80%.

Description

Hexagonal boron nitride-fine particle aggregate, resin composition, resin sheet, multilayer body, semiconductor element, and method for producing hexagonal boron nitride-fine particle aggregate

[0001] The present invention relates to a hexagonal boron nitride-fine particle aggregate, a resin composition, a resin sheet, a multilayer body, a semiconductor device, and a method for producing the hexagonal boron nitride-fine particle aggregate.

[0002] In recent years, the heat generation density inside electronic devices has been increasing year by year due to the increasing speed and integration of circuits in electrical and electronic devices and the increased mounting density of electronic components on printed wiring boards. As a result, there is a demand for materials with high thermal conductivity and electrical insulation properties that can efficiently dissipate the heat generated by electronic components.

[0003] Hexagonal boron nitride, which has a hexagonal crystal structure, is relatively easy to synthesize and has excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance. As a result, it is used in a wide range of applications, including thermally conductive insulating sheets, highly flexible thermally conductive rubber, heat-dissipating grease, heat-dissipating sealants, fillers for semiconductor sealing resins, release agents for molten metal and molten glass molding dies, solid lubricants, and cosmetic ingredients.

[0004] In recent years, in high-performance electronic devices, the amount of heat generated by various electronic components has increased due to higher integration, speed, miniaturization, and weight reduction, and there is a demand for thermally conductive sheets with even higher thermal conductivity than before.To this end, various thermally conductive sheets have been proposed in which hexagonal boron nitride, which has excellent thermal conductivity and electrical insulation properties, is dispersed in an organic matrix material as a thermally conductive filler.

[0005] More specifically, hexagonal boron nitride is generally flaky due to its hexagonal crystal shape, and its thermal conductivity is known to be anisotropic. Ordinary flaky hexagonal boron nitride has higher thermal conductivity in its plane direction (a-axis direction) than in its thickness direction (c-axis direction). In resin sheets incorporating such flaky hexagonal boron nitride, the a-axis direction of the hexagonal boron nitride tends to be oriented in the thickness direction of the resin sheet, resulting in a problem of inferior thermal conductivity in the thickness direction of the resin sheet compared to the plane direction.

[0006] For example, Patent Document 1 discloses a hexagonal boron nitride particle aggregate having a porosity of 65% or less, in which hexagonal boron nitride primary particles are randomly assembled, in order to improve the thermal anisotropy of hexagonal boron nitride.

[0007] Furthermore, Patent Document 2 discloses a hexagonal boron nitride composite powder, which is hexagonal boron nitride in which hexagonal boron nitride primary particles are bonded together, and which is a composite powder obtained by combining hexagonal boron nitride powder, which is an aggregate of the hexagonal boron nitride, with a ceramic powder having an average particle size of 0.1 to 10 μm, and which is characterized in that the porosity of the composite powder is 5 to 55%, the average particle size is 20 to 100 μm, and the peak intensity ratio I(002) / I(100) of the (002) plane to the (100) plane of the hexagonal boron nitride, measured by powder X-ray diffraction, is 9.0 or less.

[0008] As shown in Patent Documents 1 and 2, in order to improve the thermal anisotropy of hexagonal boron nitride, a hexagonal boron nitride particle aggregate with low porosity, in which hexagonal boron nitride primary particles are randomly assembled, is disclosed. By using such a hexagonal boron nitride particle aggregate with low porosity, the aggregate can be made less likely to be crushed during press molding. As a result, when made into a resin sheet, the thermal conductivity in the thickness direction of the resin sheet can be increased.

[0009] On the other hand, as shown in Patent Documents 3 and 4, resin compositions containing a mixture of hexagonal boron nitride particle aggregates and fine particles have been widely studied for the purpose of improving high thermal conductivity and peel strength.

[0010] Japanese Patent Publication No. 2022-97544 Japanese Patent Publication No. 6125282 Japanese Patent Publication No. 2012-219251 International Publication No. 2023 / 068024

[0011] However, resin sheets with a high hexagonal boron nitride filling rate, as described in Patent Documents 1 and 2, tend to have improved thermal conductivity but reduced insulation reliability and a thermal expansion coefficient that is too low compared to surrounding materials. Furthermore, a high hexagonal boron nitride filling rate leads to brittleness and reduced peel strength. On the other hand, when a cured molded product is produced using a hexagonal boron nitride particle aggregate with a high porosity, the voids in the thermal conductive sheet increase, reducing the dielectric breakdown strength. Press molding under high pressure to reduce the voids in the sheet causes the hexagonal boron nitride particle aggregate to collapse, resulting in a failure to improve the thermal conductivity of the thermal conductive sheet through its thickness. Patent Documents 3 and 4 also disclose resin compositions that combine hexagonal boron nitride particle aggregates and fine particles. However, the high fine particle filling rate reduces the thermal expansion coefficient of the sheet, making it difficult to match the thermal expansion coefficient of the sheet to that of copper or aluminum to be bonded to the thermal conductive sheet. Furthermore, all of the documents mainly focus on improving thermal conductivity and peel strength by interposing inorganic fine particles between the hexagonal boron nitride particle agglomerates, and do not pay attention to the effect obtained by retaining fine particles in the voids within the hexagonal boron nitride particle agglomerates.

[0012] As described above, various materials have been studied that focus on the thermal conductivity and electrical insulation properties of hexagonal boron nitride, but there is a need for further improvements in hexagonal boron nitride or for the provision of a new hexagonal boron nitride.The present invention aims to solve these problems and provides a hexagonal boron nitride-fine particle aggregate, a resin composition, a resin sheet, a multilayer body, a semiconductor device, and a method for producing a hexagonal boron nitride-fine particle aggregate that are superior in thermal conductivity and electrical insulation properties.

[0013] Under these circumstances, the present inventors have conducted research and found that the above-mentioned problems can be solved by having fine particles present in the voids of the aggregates of primary particles of hexagonal boron nitride. Specifically, the above-mentioned problems have been solved by the following means: [1] A hexagonal boron nitride-fine particle aggregate comprising an aggregate of primary particles of hexagonal boron nitride and fine particles, wherein at least a portion of the fine particles are present in the voids of the aggregates of primary particles of hexagonal boron nitride, and the average particle diameter (D50 Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ [2] A hexagonal boron nitride-fine particle aggregate, wherein the average particle diameter (D50 Ａ [3] The hexagonal boron nitride-fine particle aggregate according to [1], wherein the average particle diameter (D50 Ｂ ) is 0.01 to 0.5 μm. [4] The hexagonal boron nitride-particle aggregate according to any one of [1] to [3], wherein the void ratio of the hexagonal boron nitride-particle aggregate is 60 to 75%. [5] The hexagonal boron nitride-particle aggregate according to any one of [1] to [4], wherein the particles contain aluminum oxide and / or zinc oxide. [6] The average particle size (D50 Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ [7] The hexagonal boron nitride-fine particle aggregate according to any one of [1] to [5], wherein the average particle diameter (D50 Ａ ) is 10 to 100 μm, and the average particle diameter (D50 Ｂ) is 0.01 to 0.5 μm, the void ratio of the hexagonal boron nitride-fine particle aggregate is 60 to 75%, the fine particles contain aluminum oxide and / or zinc oxide, and the average particle diameter (D50 Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ ) is 100 to 950. [8] A resin composition comprising a thermosetting resin and the hexagonal boron nitride-fine particle aggregate according to any one of [1] to [7]. [9] A resin sheet comprising a resin and the hexagonal boron nitride-fine particle aggregate according to any one of [1] to [7].

[10] A multilayer body having a metal substrate and the resin sheet according to [9] provided on the metal substrate.

[11] A multilayer body having a metal substrate, the resin sheet according to [9] provided on the metal substrate, and a heat spreader provided on the resin sheet.

[12] A semiconductor device having the multilayer body according to

[10] or

[11] .

[13] A method for producing the hexagonal boron nitride-fine particle aggregate according to any one of [1] to [7], comprising dispersing hexagonal boron nitride and fine particles in a slurry containing hexagonal boron nitride, a dispersant, and fine particles, followed by drying.

[14] The method for producing a hexagonal boron nitride-fine particle aggregate according to

[13] , wherein the hexagonal boron nitride is an aggregate of primary particles of hexagonal boron nitride.

[15] The method for producing a hexagonal boron nitride-fine particle aggregate according to

[13] or

[14] , wherein the dispersant contains at least one selected from the group consisting of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

[0014] The present invention makes it possible to provide a hexagonal boron nitride-fine particle aggregate, a resin composition, a resin sheet, a multilayer body, a semiconductor device, and a method for producing a hexagonal boron nitride-fine particle aggregate that are superior in thermal conductivity and electrical insulation.

[0015] 1 shows an SEM image (one entire image) of the hexagonal boron nitride-fine particle aggregate obtained in Example 1. 2 shows an SEM image (an image of a portion of the surface) of the hexagonal boron nitride-fine particle aggregate obtained in Example 1. 3 shows an SEM image (an image of a portion of the surface) of the resin sheet obtained in Example 1. 4 shows an SEM image (one entire image) of the hexagonal boron nitride-fine particle aggregate obtained in Example 3. 5 shows an SEM image (an image of a portion of the surface) of the hexagonal boron nitride-fine particle aggregate obtained in Example 5. 6 shows an SEM image (an image of a portion of the surface) of the hexagonal boron nitride-fine particle aggregate obtained in Example 5. 7 shows an SEM image (one entire image) of the hexagonal boron nitride-fine particle aggregate used in Comparative Example 1. 1 shows an SEM image (an image of a portion of the surface) of the hexagonal boron nitride aggregate used in Comparative Example 1. FIG. 2 shows an image illustrating the structure of the hexagonal boron nitride-fine particle aggregate of the present embodiment.

[0016] Hereinafter, a detailed description will be given of an embodiment of the present invention (hereinafter simply referred to as "the present embodiment"). Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, the term "to" is used to mean that the numerical values ​​before and after it are included as upper and lower limits. "A to B" means A or greater and B or less. Furthermore, any combination of the upper and lower limits of numerical values ​​in this specification is also included as an example of this embodiment. In this specification, various physical property values ​​and characteristic values ​​are those at 23°C unless otherwise specified. If the measurement methods, etc. described in the standards shown in this specification vary from year to year, they shall be based on the standards in effect as of January 1, 2024, unless otherwise specified. If the measurement methods, etc. described in the standards shown in this specification are discontinued as of January 1, 2024, they shall be based on the standards in effect at the time of discontinuation.

[0017] The hexagonal boron nitride-fine particle aggregate of this embodiment is a hexagonal boron nitride-fine particle aggregate containing an aggregate of primary particles of hexagonal boron nitride (sometimes referred to herein as a "hexagonal boron nitride aggregate" or "raw hexagonal boron nitride") and fine particles, wherein at least a portion of the fine particles are present in voids in the aggregate of the primary particles of hexagonal boron nitride, and the average particle diameter (D50 Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ ) is 20 to 10,000, the mass ratio of the aggregates of primary particles of hexagonal boron nitride to the fine particles is 1:0.01 to 1:0.1, and the void ratio of the hexagonal boron nitride-fine particle aggregate is 56 to 80%. By adopting such a configuration, a hexagonal boron nitride-fine particle aggregate, a resin composition, and a resin sheet having superior thermal conductivity and insulating properties can be obtained.

[0018] Ceramic substrates are known as insulating substrates used for semiconductor materials and the like. However, ceramic substrates have a thermal expansion coefficient of approximately several ppm / °C, which is significantly different from the thermal expansion coefficients of their surrounding materials, such as copper (thermal expansion coefficient of approximately 17 ppm / °C) and aluminum (thermal expansion coefficient of approximately 23 ppm / °C). Therefore, an insulating resin sheet with high thermal conductivity and a small difference in thermal expansion coefficient from surrounding materials is desired. As one example, an insulating resin sheet containing hexagonal boron nitride (e.g., hexagonal boron nitride particles) has been developed. However, resin sheets with a high hexagonal boron nitride filling rate (e.g., 60 volume % or more) tend to have improved thermal conductivity but reduced insulation reliability and a thermal expansion coefficient that is too low compared to surrounding materials. Furthermore, a high hexagonal boron nitride filling rate leads to brittleness and reduced peel strength. Under these circumstances, the present invention has succeeded in obtaining a resin sheet containing hexagonal boron nitride-fine particle aggregates with superior thermal conductivity and insulation properties. That is, because the hexagonal boron nitride-fine particle aggregate of this embodiment has a high porosity, it tends to be able to achieve high thermal conductivity even when the filling rate of hexagonal boron nitride is low. Furthermore, because the hexagonal boron nitride-fine particle aggregate of this embodiment has fine particles present in the voids of the hexagonal boron nitride aggregate, the hexagonal boron nitride-fine particle aggregate is less likely to be crushed during press molding. As a result, when it is made into a resin sheet, the thermal conductivity in the thickness direction of the resin sheet can be increased.

[0019] More specifically, hexagonal boron nitride is generally flaky due to its hexagonal crystal shape, and its thermal conductivity is known to be anisotropic. Ordinary flaky hexagonal boron nitride has higher thermal conductivity in its plane direction (a-axis direction) than in its thickness direction (c-axis direction). In resin sheets incorporating such flaky hexagonal boron nitride, the a-axis direction of the hexagonal boron nitride tends to be oriented in the thickness direction of the resin sheet, resulting in a problem of inferior thermal conductivity in the thickness direction of the resin sheet compared to the plane direction.

[0020] To address this issue, agglomerates (secondary particles) of hexagonal boron nitride primary particles, in which primary particles of hexagonal boron nitride are randomly assembled, have been proposed. Resin sheets using hexagonal boron nitride aggregates with low porosity are resistant to crushing during press molding, but unless the filler density of hexagonal boron nitride is high (e.g., 60% by volume or higher), no inter-filler thermal conduction paths are formed within the resin sheet, resulting in low thermal conductivity. Furthermore, a high filler density of hexagonal boron nitride improves thermal conductivity, but also reduces insulation reliability and tends to result in a thermal expansion coefficient that is too low compared to surrounding materials. Furthermore, a high filler density of hexagonal boron nitride results in brittleness and low peel strength. On the other hand, in a resin sheet using hexagonal boron nitride aggregates with a high porosity, the filling rate of hexagonal boron nitride is low (for example, 40 volume % or more), and although heat conduction paths are formed between fillers within the resin sheet, the resin sheet is easily crushed during press molding, and the thermal conductivity in the thickness direction tends not to improve.

[0021] In this embodiment, in order to improve the anisotropy of the thermal conductivity of hexagonal boron nitride, a hexagonal boron nitride-fine particle aggregate is used, in which fine particles exist in the voids of the aggregate of primary particles of hexagonal boron nitride. By adopting this configuration, it is presumed that the primary particles of hexagonal boron nitride are oriented so as to stand in the thickness direction of the resin sheet, increasing the orientation strength ratio within the resin sheet and thereby increasing the thermal conductivity in the thickness direction of the resin sheet.

[0022] Hereinafter, the embodiments of the present invention will be described in detail. However, the explanation of the constituent elements described below is an example of an embodiment of the present invention, and the present invention is not limited to these contents.

[0023] <Hexagonal Boron Nitride-Particle Aggregate> As described above, the hexagonal boron nitride-particle aggregate of this embodiment is a hexagonal boron nitride-particle aggregate containing primary particles of hexagonal boron nitride and fine particles present in the voids of the hexagonal boron nitride aggregate. Fig. 10 is a conceptual diagram showing the structure of the hexagonal boron nitride-particle aggregate of this embodiment. In Fig. 10, 1 indicates primary particles of hexagonal boron nitride, 2 indicates an aggregate of primary particles of hexagonal boron nitride (hexagonal boron nitride aggregate), 3 indicates fine particles, and 4 indicates the hexagonal boron nitride-particle aggregate. Here, the presence of fine particles in the voids of the hexagonal boron nitride aggregate includes the presence of at least some of the fine particles between the primary particles of hexagonal boron nitride and the primary particles of hexagonal boron nitride, and does not necessarily mean that all of the fine particles are present in the voids of the hexagonal boron nitride aggregate. For example, some of the fine particles may be present on the surface of the hexagonal boron nitride aggregates.

[0024] In this embodiment, the average particle diameter (D50 Ａ ) and the average particle size of the fine particles (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ ) is 20 to 10,000. Ａ By making the average particle diameter (D50) equal to or greater than the lower limit, the fine particles become sufficiently small relative to the hexagonal boron nitride aggregates, and the fine particles tend to easily enter the gaps between the primary particles of hexagonal boron nitride. Ａ By making the ratio (D50) equal to or less than the upper limit, the specific surface area of ​​the fine particles tends to be small, and the interfacial thermal resistance tends to be reduced. Ａ / D50 Ｂ) is preferably 100 or more, more preferably 150 or more, even more preferably 200 or more, even more preferably 250 or more, and even more preferably 300 or more, and is preferably 1000 or less, more preferably 950 or less, even more preferably 900 or less, even more preferably 850 or less, and even more preferably 800 or less. Ａ ) and average particle size (D50 Ｂ ) is the median diameter, and is measured according to the method described in the Examples below. The hexagonal boron nitride-microparticle aggregate of this embodiment exists in the form of a composition (aggregate) of a plurality of hexagonal boron nitride-microparticle aggregates, for example, when incorporated into a resin sheet. In this case, the composition may contain two or more types of hexagonal boron nitride-microparticle aggregates, each hexagonal boron nitride-microparticle aggregate being composed of different materials. An example of two or more types of hexagonal boron nitride-microparticle aggregates, each hexagonal boron nitride-microparticle aggregate being composed of different materials, is, for example, a mixture of the hexagonal boron nitride-microparticle aggregate obtained in Example 1 and the hexagonal boron nitride-microparticle aggregate obtained in Example 2, which will be described later. Alternatively, the hexagonal boron nitride-microparticle aggregate may have multiple types of microparticles present in the voids in different proportions, as in Example 6, which will be described later. When the hexagonal boron nitride-fine particle aggregate of this embodiment is present in the state of a composition containing the two or more types of hexagonal boron nitride-fine particle aggregate, the ratio (D50 Ａ / D50 Ｂ ) is the ratio (D50) in each hexagonal boron nitride-fine particle aggregate. Ａ / D50 Ｂ ) by the mass fraction of each hexagonal boron nitride-fine particle aggregate (weighted average value).

[0025] In this embodiment, the mass ratio of the aggregates of hexagonal boron nitride primary particles (raw hexagonal boron nitride) to the fine particles is 1:0.01 to 1:0.1. By setting the mass ratio at or above the lower limit, the fine particles can adequately enter the voids of the hexagonal boron nitride aggregates, thereby further improving the thermal conductivity of the resin sheet. By setting the mass ratio at or below the upper limit, the fine particles are present in a more appropriate amount in the voids of the hexagonal boron nitride aggregates, which tends to make the aggregates less susceptible to crushing during press molding. The mass ratio of the aggregates of hexagonal boron nitride primary particles to the fine particles is preferably at least 0.015, and is preferably at or below 0.08, more preferably at or below 0.06, even more preferably at or below 0.05, even more preferably at or below 0.048, and even more preferably at or below 0.045, relative to 1 aggregate of hexagonal boron nitride primary particles.

[0026] On the other hand, the porosity of the hexagonal boron nitride-fine particle aggregate of this embodiment is 56 to 80%. By setting the porosity at or above the lower limit, the thermal expansion coefficient when incorporated into a resin sheet tends to be lower. Furthermore, by setting the porosity at or below the upper limit, the aggregates are less likely to be crushed when press-molding the resin sheet, and the thermal conductivity of the resulting resin sheet tends to be further improved. As described above, the hexagonal boron nitride-fine particle aggregate of this embodiment has a high porosity, so that even if the filling rate of hexagonal boron nitride is low, inter-filler thermal conduction paths are generated within the resin sheet, enabling the resulting resin sheet to have high thermal conductivity. The porosity is preferably 60% or more, more preferably 61% or more, even more preferably 62% or more, even more preferably 63% or more, and even more preferably 64% or more. It is also preferably 75% or less, more preferably 74% or less, even more preferably 73% or less, even more preferably 72% or less, and even more preferably 71% or less. When the hexagonal boron nitride-fine particle aggregate of this embodiment is present in the form of a composition containing two or more types of hexagonal boron nitride-fine particle aggregates, the porosity is the sum (weighted average) of the values ​​obtained by multiplying the porosity of each hexagonal boron nitride-fine particle aggregate by the mass fraction of each hexagonal boron nitride-fine particle aggregate. The porosity is measured as described in the Examples below.

[0027] As described above, the hexagonal boron nitride aggregate of this embodiment contains primary particles of hexagonal boron nitride. By using a random aggregation of anisotropic, scaly hexagonal boron nitride primary particles, a resin sheet with high thermal conductivity can be obtained when blended with a resin. Hexagonal boron nitride is usually in the form of scaly primary particles that aggregate to form secondary particles.

[0028] The average particle size (D50) of the aggregates of the primary particles of hexagonal boron nitride in this embodiment Ａ) (for example, the average particle diameter of reference numeral 2 in FIG. 10) is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, even more preferably 25 μm or more, even more preferably 26 μm or more, even more preferably 30 μm or more, and is preferably 100 μm or less, more preferably 90 μm or less, even more preferably 80 μm or less, even more preferably 75 μm or less, even more preferably 70 μm or less, and even more preferably 65 μm or less. Ａ By making the average particle diameter (D50) equal to or greater than the lower limit, the thermal conductivity in the thickness direction of the resin sheet tends to be further improved. Ａ ) to be equal to or less than the upper limit, a thin resin sheet can be easily produced, and the thermal resistance tends to be reduced.

[0029] In this embodiment, it is preferable that the tap density of the raw material hexagonal boron nitride is low. Specifically, the tap density of the raw material hexagonal boron nitride is 0.5 g / cm ３ It is preferable that the density is 0.45 g / cm or less. ３ It is more preferable that the density is 0.1 g / cm or less. ３ By setting the density to the upper limit or less, the bulk density of the raw material hexagonal boron nitride increases, and therefore even if the filling rate of hexagonal boron nitride is low, heat conduction paths are formed between the fillers within the resin sheet, and the thermal conductivity in the thickness direction tends to be further improved. The tap density of the raw material hexagonal boron nitride represents the bulk density of the filler, and is the density of the powder obtained by tapping a container, as described in JIS Z 2512.

[0030] The hexagonal boron nitride-fine particle aggregate of this embodiment contains fine particles. In this embodiment, by including fine particles in the voids of the raw hexagonal boron nitride (aggregates of primary particles of hexagonal boron nitride), the resulting resin sheet tends to have a high thermal conductivity in the thickness direction. Furthermore, by compounding the raw hexagonal boron nitride with fine particles, the hexagonal boron nitride-fine particle aggregate is less likely to be crushed during press molding, etc., resulting in a resin sheet with high thermal conductivity in the thickness direction and excellent voltage resistance and insulation properties when formed into a resin sheet. In this embodiment, at least a portion of the fine particles are present in the voids of the hexagonal boron nitride aggregate. The hexagonal boron nitride-fine particle aggregate is obtained by blending a dispersant and fine particles into hexagonal boron nitride (preferably aggregates of primary particles of hexagonal boron nitride), dispersing the mixture, and then drying. The fine particles are usually retained in the hexagonal boron nitride aggregate by chemical adsorption and / or physical adsorption. Furthermore, some of the fine particles may be present on the surface of the hexagonal boron nitride aggregates. Details of this will be described later.

[0031] The type of the fine particles used in this embodiment is not particularly limited as long as they can be present in the voids of the raw hexagonal boron nitride (aggregates of primary particles of hexagonal boron nitride), but a wide variety of insulators with high thermal conductivity other than boron nitride can be used. Specifically, the fine particles used in this embodiment preferably contain a metal, more preferably contain a metal oxide, and even more preferably contain at least one selected from the group consisting of aluminum oxide, zinc oxide, magnesium oxide, silica, aluminum hydroxide, magnesium hydroxide, silicon nitride, silicon carbide, gallium nitride, and talc, and even more preferably contain aluminum oxide and / or zinc oxide, and even more preferably contain aluminum oxide.

[0032] The average particle diameter (D50 ＢThe average particle diameter (D50) is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.08 μm or more. Depending on the application, it may be 0.1 μm or more, 0.2 μm or more, or 0.35 μm or more, and is preferably 0.5 μm or less. Ｂ By making the average particle diameter (D50) equal to or greater than the lower limit, the specific surface area of ​​the fine particles becomes smaller, and the interfacial thermal resistance tends to be further reduced. Ｂ By making the average particle size (D50) of each particle smaller than the upper limit, the particles tend to be more easily present in the fine voids of the raw hexagonal boron nitride. The hexagonal boron nitride-particle aggregate of this embodiment may contain only one type of particle, or may contain two or more types. When two or more types are contained, the average particle size (D50) of each particle is Ｂ ) multiplied by the mass fraction of each particle, and the sum is taken as the weighted average value.

[0033] The hexagonal boron nitride-microparticle aggregate of this embodiment contains hexagonal boron nitride primary particles and microparticles, but may or may not contain other components. The hexagonal boron nitride-microparticle aggregate of this embodiment typically contains a dispersant or the like used in its production. Furthermore, from the viewpoint of improving the robustness of the hexagonal boron nitride-microparticle aggregate, it may contain a binder as another component. Details of the dispersant and binder are described in the section <Method for producing hexagonal boron nitride-microparticle aggregate> below. In the hexagonal boron nitride-microparticle aggregate of this embodiment, the total amount of the hexagonal boron nitride primary particles and microparticles preferably accounts for 90 mass% or more of the hexagonal boron nitride-microparticle aggregate, more preferably 95 mass% or more, and may even account for 98 mass% or more, or even 99 mass% or more, or is 100 mass% or less. Furthermore, in the hexagonal boron nitride-fine particle aggregate of this embodiment, the total amount of the hexagonal boron nitride primary particles, fine particles, and the dispersant and binder contained as needed accounts for preferably 93 mass % or more of the hexagonal boron nitride-fine particle aggregate, more preferably 97 mass % or more, and may even account for 99 mass % or more, or even 99.5 mass % or more, and is 100 mass % or less.

[0034] <Method for Producing Hexagonal Boron Nitride-Fine Particle Aggregates> The method for producing the hexagonal boron nitride-fine particle aggregates of this embodiment is not particularly limited, but is preferably produced by dispersing hexagonal boron nitride (preferably, primary particles of hexagonal boron nitride) and the fine particles in a slurry containing hexagonal boron nitride (preferably, aggregates of primary particles of hexagonal boron nitride), a dispersant, and the fine particles, followed by drying. In particular, it is preferable to mix the fine particles with hexagonal boron nitride after sufficiently dispersing them (preferably, after monodispersing them), and further disperse them. By undergoing such a process, it becomes possible to highly disperse the fine particles, and the fine particles tend to be more likely to exist in the voids of the hexagonal boron nitride (preferably, aggregates of primary particles of hexagonal boron nitride). It is preferable to mix the hexagonal boron nitride (preferably, aggregates of primary particles of hexagonal boron nitride) with a dispersant and stir the hexagonal boron nitride (preferably, aggregates of primary particles of hexagonal boron nitride) in advance. Furthermore, the aggregate of hexagonal boron nitride (preferably primary particles of hexagonal boron nitride) is preferably heated after stirring, and the heating temperature is preferably 80°C or higher and 140°C or lower. By carrying out such advance stirring, it becomes possible to uniformly attach the dispersant to the hexagonal boron nitride. Furthermore, by carrying out heating, the dispersant such as a silane coupling agent tends to undergo hydrolysis and dehydration condensation, and to be attached more effectively to the hexagonal boron nitride. The hexagonal boron nitride is preferably a hexagonal boron nitride aggregate as described in the section on hexagonal boron nitride-fine particle aggregate of this embodiment.

[0035] The fine particles are usually single particles, and are preferably dispersed uniformly in a solvent by blending a dispersant in advance. Specifically, the fine particles are preferably blended with a dispersant and then dispersed using an ultrasonic disperser.

[0036] In this embodiment, it is preferable to prepare a slurry containing hexagonal boron nitride (preferably aggregates of primary particles of hexagonal boron nitride) mixed with a dispersant and stirred, and fine particles dispersed by mixing with a dispersant and ultrasonic treatment, and then further disperse the slurry. In this case, the blending ratio of hexagonal boron nitride and fine particles can be appropriately determined depending on the ratio of the two in the final aggregate. Dispersion of hexagonal boron nitride and fine particles in the slurry is preferably performed by ultrasonic treatment. During the dispersion, the uniformly dispersed fine particles enter the voids present inside the hexagonal boron nitride aggregates, forming aggregates in which the fine particles are trapped. After the dispersion, it is preferable to filter the dispersion liquid from the slurry and dry the slurry. During the drying, the fine particles present in the voids of the hexagonal boron nitride aggregates aggregate, forming hexagonal boron nitride-fine particle aggregates containing the fine particles. The drying may be performed at room temperature or by heating. For example, drying at a temperature of 20 to 40°C, followed by drying at a temperature of 100 to 160°C, is preferable. Drying at such a temperature tends to promote re-aggregation more effectively, as the organic molecular structure formed on the particle surface of the fine particles forms interparticle cross-links. The drying time is preferably 2 hours to 5 days. In particular, it is preferable to dry at a temperature of 20 to 40°C for 5 hours to 3 days, and then dry at a temperature of 100 to 160°C for 1 to 5 hours.

[0037] The dispersant typically improves the dispersibility of the inorganic powder. While the type of dispersant is not particularly limited, it is preferably one that improves the dispersibility of the hexagonal boron nitride aggregates and microparticles in the slurry, and more preferably one that uniformly and singly disperses the hexagonal boron nitride aggregates and microparticles. Specific examples of dispersants include silane coupling agents, titanate coupling agents, aluminate coupling agents, polycarboxylic acid-based dispersants, acrylic-based dispersants, and urethane-based dispersants. The dispersant preferably contains at least one selected from the group consisting of silane coupling agents, titanate coupling agents, and aluminate coupling agents, with silane coupling agents being more preferred. The amount of dispersant used is preferably 0.0 to 10 parts by mass per 100 parts by mass of the final hexagonal boron nitride-microparticle aggregate. Only one type of dispersant may be used, or two or more types may be used. In particular, the dispersant blended with the hexagonal boron nitride and the dispersant blended with the microparticles may be different.

[0038] The slurry may contain a solvent. The type of solvent is not particularly limited, but examples include water, ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), cellosolves (e.g., propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, etc.), esters (e.g., ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, isoamyl acetate, ethyl lactate, methyl methoxypropionate, methyl hydroxyisobutyrate, etc.), amides (e.g., dimethoxyacetamide, dimethylformamides, etc.), and aromatic hydrocarbons (e.g., toluene, xylene, etc.). When the slurry contains a solvent, the solids concentration is preferably 0.001 to 10% by mass. The solvent may be used alone or in combination of two or more. When two or more solvents are used, the total amount falls within the above range.

[0039] The hexagonal boron nitride-fine particle aggregate in this embodiment may contain a binder from the viewpoint of improving the robustness of the raw material hexagonal boron nitride. The binder essentially acts to firmly bind the primary particles of hexagonal boron nitride together and stabilize the shape of the raw material hexagonal boron nitride.

[0040] As such a binder, a metal oxide is preferred, and specifically, aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, titanium oxide, etc. are preferably used. Among these, aluminum oxide and yttrium oxide are preferred from the viewpoints of thermal conductivity and heat resistance as oxides, and the bonding strength that bonds primary particles of hexagonal boron nitride together. The binder may be a liquid binder such as alumina sol, or may be one that is converted into a metal oxide by firing, such as an organometallic compound. These binders may be used alone or in combination of two or more.

[0041] The hexagonal boron nitride fine particle aggregates obtained by these methods may be further treated after production. In this case, for example, surface oxidation by heat treatment in the presence of oxygen, steam treatment, surface modification with an organometallic compound or polymer using a carrier or reactive gas at room temperature or under heat, or a sol-gel method using boehmite or silica can be used. These treatments may be used alone or in combination of two or more.

[0042] The hexagonal boron nitride-particle agglomerates produced as described above may be subjected to typical post-processing steps such as scrubbing, grinding, classification, purification, washing, and drying, if necessary. Fine particles, if present, may be removed first. As an alternative to sieving, the grinding of the hexagonal boron nitride-particle agglomerates may be carried out using a sieve screen, a classification mill, a structured roller crusher, or a cutting wheel. Dry milling, for example in a ball mill, is also possible.

[0043] <Resin composition, resin sheet, and uses thereof> The uses of the hexagonal boron nitride-fine particle aggregate of this embodiment are not particularly limited, and it can be used in various uses known for hexagonal boron nitride powder. Among these, a particularly suitable use is as a filler for resins to be filled into resins to improve electrical insulation, impart thermal conductivity, etc. The hexagonal boron nitride-fine particle aggregate of this embodiment may also be used for other purposes, for example, to produce a sintered body.

[0044] The resin composition of this embodiment contains a resin and the hexagonal boron nitride-fine particle aggregate of this embodiment. Furthermore, the resin sheet of this embodiment contains a resin and the hexagonal boron nitride-fine particle aggregate of this embodiment. By including the hexagonal boron nitride-fine particle aggregate of this embodiment, a resin sheet with excellent electrical insulation and thermal conductivity can be obtained. The resin may be a thermosetting resin or a thermoplastic resin, with a thermosetting resin being preferred. Other resins such as synthetic rubber and liquid gels can also be used. Thermoplastic resins are not particularly limited, and examples include polyolefins, vinyl chloride resins, acrylic resins, methacrylic acid ester resins, nylons, and fluororesins. Examples of thermosetting resins include compounds having a terminal carbon-carbon unsaturated double bond, maleimide compounds, nadimide compounds, phenolic compounds, oxetane resins, benzoxazine compounds, arylcyclobutene compounds, perfluorovinyl ether resins, polyimide compounds, compounds having a vinylene group, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, and silicone resins. As the thermosetting resin, the descriptions in paragraphs 0012 to 0085 of WO 2023 / 026829 and paragraphs 0017 to 0034 of JP 2016-10964 A can also be taken into consideration, and the contents of these can be incorporated into this specification.

[0045] One embodiment of the resin composition of the present embodiment contains a thermosetting resin and the hexagonal boron nitride-fine particle aggregate of the present embodiment. In this embodiment of the resin composition, the thermosetting resin is usually in an uncured or semi-cured state, but is not limited thereto.

[0046] One form of the resin sheet of this embodiment includes a thermosetting resin and the hexagonal boron nitride-fine particle aggregate of this embodiment. In another form of the resin sheet of this embodiment, the thermosetting resin is typically in a semi-cured state or in a state where it has been further cured from the semi-cured state, but this is not limiting. As an example of the resin sheet, a resin sheet in which the thermosetting resin is in an uncured state can be obtained by applying the resin composition of this embodiment to a substrate and drying it. As another example, a resin sheet can be obtained by applying the resin composition of this embodiment to a substrate and heating it to cure the thermosetting resin (semi-cured or further cured from the semi-cured state).

[0047] An example of the thermosetting resin contained in one embodiment of the resin composition or resin sheet is a cyanate ester compound and / or an epoxy compound. Furthermore, because the hexagonal boron nitride-fine particle aggregate of this embodiment has a high porosity, high thermal conductivity can be achieved even if the filling rate of hexagonal boron nitride in the resin composition or resin sheet is low. Furthermore, because the resin composition or resin sheet of this embodiment is formed by compounding raw material hexagonal boron nitride with fine particles, the hexagonal boron nitride-fine particle aggregate is less likely to be crushed during processing or molding, such as press molding. As a result, the resulting resin composition and resin sheet tend to have high thermal conductivity in the thickness direction and excellent voltage resistance and insulation properties.

[0048] Generally, thermosetting resins have low thermal conductivity (approximately 0.2 W / mK), while hexagonal boron nitride-fine particle aggregates have higher thermal conductivity (approximately 200 W / mK). Therefore, the thermal conductivity of resin compositions and resin sheets tends to improve in accordance with the blending amount of hexagonal boron nitride-fine particle aggregates.

[0049] In addition to the above, the resin composition or resin sheet of this embodiment can also contain fillers other than hexagonal boron nitride-fine particle aggregates, various polymeric compounds such as elastomers, and various additives. These are not particularly limited as long as they are commonly used. Examples of various additives include flame retardants, curing accelerators (curing catalysts), ultraviolet absorbers, antioxidants, photopolymerization initiators, fluorescent brighteners, photosensitizers, dyes, pigments, thickeners, flow adjusters, lubricants, antifoaming agents, dispersants, leveling agents, gloss agents, and polymerization inhibitors. These can be used alone or in combination of two or more, as desired.

[0050] Furthermore, the resin composition of this embodiment may contain one or more fillers other than the hexagonal boron nitride-fine particle aggregate within a range that does not impair the effects of this embodiment. For example, a thermally conductive filler other than the hexagonal boron nitride-fine particle aggregate of this embodiment may also be used.

[0051] Examples of such thermally conductive fillers include silica, alumina, aluminum nitride, boron nitride other than the hexagonal boron nitride-fine particle aggregate of this embodiment, silicon nitride, magnesium oxide, etc. These thermally conductive fillers can be used alone or in appropriate combination of two or more.

[0052] When using a filler, a silane coupling agent may be used in combination. Silane coupling agents generally used for surface treatment of inorganic materials can be suitably used, and the type is not particularly limited. Specific examples include aminosilane-based agents such as γ-aminopropyltriethoxysilane and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane; epoxysilane-based agents such as γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinylsilane-based agents such as γ-methacryloxypropyltrimethoxysilane and vinyl-tri(β-methoxyethoxy)silane; cationic silane-based agents such as N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride; and phenylsilane-based agents. Silane coupling agents can be used alone or in combination of two or more.

[0053] The content of hexagonal boron nitride-fine particle aggregates in the resin composition or resin sheet of this embodiment is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, even more preferably 45% by mass or less, and even more preferably 40% by mass or less, when the mass of the components excluding the solvent in the resin composition or resin sheet is taken as 100% by mass. By setting the content at or above the lower limit, the thermal conductivity of the resin composition or resin sheet tends to be improved, and the loss modulus (DMA, viscosity) and tan δ (loss tangent, vibration absorption) tend to be lower. Furthermore, the adhesion of the resin sheet to metals (e.g., metal foil, metal substrate, etc.) tends to be improved. On the other hand, by setting the content at or below the upper limit, the generation of voids in the resin sheet tends to be effectively suppressed, and the voltage resistance tends to be further improved. The resin composition or resin sheet of this embodiment may contain only one type of hexagonal boron nitride-fine particle aggregate, or may contain two or more types. When two or more types are contained, it is preferable that the total amount is in the above range.

[0054] The resin sheet of this embodiment also preferably satisfies the following requirements. (1) Thermal Expansion Coefficient The resin sheet of this embodiment preferably has a thermal expansion coefficient of 16 ppm / K or more and 23 ppm / K or less, measured along the x-y direction of the resin sheet. It is also preferable that the thermal expansion coefficient be close to that of the metal substrate to which the resin sheet is bonded. For example, the difference between the thermal expansion coefficient of the resin sheet and that of the metal substrate is preferably ±2 ppm / K or less (preferably ±1 ppm / K or less). For example, when the resin sheet is bonded to a copper substrate, the thermal expansion coefficient of the resin sheet is preferably 17±2 ppm / K (preferably 17±1 ppm / K). It is also preferable that the thermal expansion coefficient of the resin sheet is 23±2 ppm / K (preferably 23±1 ppm / K) when the resin sheet is bonded to an aluminum substrate.

[0055] (2) Thermal Conductivity The resin sheet of this embodiment preferably has a thermal conductivity of 10 W / m K or more, more preferably 15 W / m K or more, and even more preferably 17 W / m K or more, measured at 25° C. in the thickness direction of the resin sheet. There is no particular upper limit to the thermal conductivity, but a value of 25 W / m K or less is practical.

[0056] (3) Orientation Intensity Ratio The orientation of hexagonal boron nitride primary particles in a resin sheet is measured by the ratio (I(002) / I(100)) of the intensity of the I(002) diffraction line (2θ=26.5°) to the intensity of the I(100) diffraction line (2θ=41.5°) by X-ray diffraction. The thickness direction of the hexagonal hexagonal boron nitride primary particles corresponds to the crystallographic I(002) diffraction line, i.e., the c-axis direction, and the in-plane direction corresponds to the I(100) diffraction line, i.e., the a-axis direction. When the hexagonal boron nitride primary particles constituting the hexagonal boron nitride aggregates are completely randomly oriented (non-oriented), (I(002) / I(100)) is approximately 6.7 (the crystal density value [Dx] of "JCPDS [Powder X-ray Diffraction Database]" No. 34-0421 [BN]). When (I(002) / I(100)) is small, the a-axis direction of the hexagonal hexagonal boron nitride particles is oriented in the thickness direction, and the thermal conductivity in the thickness direction increases. There is no particular lower limit, but a value of 1 or more is practical. In the resin sheet of this embodiment, the peak intensity ratio (I<002> / I<100>) of the <002> diffraction line intensity to the <100> diffraction line obtained by irradiating the resin composition sheet with X-rays in the thickness direction, i.e., at an angle of 90° with respect to the length direction of the sheet, is preferably 30 or less, more preferably 25 or less, even more preferably 20 or less, and even more preferably 15 or less. There is no particular lower limit, but a value of 1 or more is practical, and even a value of 2 or more sufficiently satisfies the required performance.

[0057] (4) Dielectric Breakdown Strength (Dielectric Breakdown Voltage) The resin sheet of this embodiment preferably has a dielectric breakdown voltage measured in the thickness direction of the resin sheet of 35 kV / mm or more, more preferably 40 kV / mm or more, and even more preferably 50 kV / mm or more. The upper limit of the dielectric breakdown voltage is not particularly specified, but a practical upper limit is 100 kV / mm or less.

[0058] (5) Thickness of Resin Sheet The resin sheet of this embodiment preferably has a thickness of 50 μm or more, more preferably 75 μm or more, and even more preferably 100 μm or more, and is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less.

[0059] In particular, the resin sheet of this embodiment preferably satisfies the above (1) to (3). Also, the resin sheet of this embodiment preferably satisfies the above (1) to (4). Also, the resin sheet of this embodiment preferably satisfies the above (1) to (3) and (5). Furthermore, the resin sheet of this embodiment preferably satisfies the above (1) to (5).

[0060] The resin sheet of this embodiment has heat dissipation and insulation properties, and is therefore preferably used as a highly thermally conductive insulating sheet incorporated for the purpose of heat dissipation and insulation of semiconductor elements. One example of the use of the resin sheet of this embodiment is a highly thermally conductive resin sheet provided on (preferably on) a metal substrate.

[0061] That is, an example of the multilayer body of this embodiment is a multilayer body having a metal substrate and a resin sheet of this embodiment provided on (preferably on) the metal substrate. Furthermore, the multilayer body of this embodiment is preferably a multilayer body having a metal substrate, a resin sheet of this embodiment provided on (preferably on) the metal substrate, and a heat spreader provided on (preferably on) the resin sheet. Examples of the metal substrate include a copper substrate and an aluminum substrate. A heat spreader is a highly thermally conductive metallic structural member used in a semiconductor device to efficiently dissipate heat from an IC chip. Therefore, the semiconductor device of this embodiment has the multilayer body of this embodiment.

[0062] Other uses of the resin sheet of this embodiment include prepregs and build-up materials for semiconductor elements. For details, see paragraphs 0114 to 0125 of International Publication No. 2023 / 026829 and paragraphs 0051 to 0064 of Japanese Patent Laid-Open Publication No. 2016-010964, the contents of which are incorporated herein by reference.

[0063] The resin composition of this embodiment is also used as a cured product. Specifically, the resin composition of this embodiment can be suitably used as a resin composition for electronic materials such as an insulating layer for a printed wiring board or a material for a semiconductor package. The resin composition of this embodiment can be suitably used as a material for prepregs, metal foil-clad laminates using prepregs, and printed wiring boards. The printed wiring board referred to here is not particularly limited and includes, for example, rigid substrates, flexible substrates, semiconductor package substrates (substrates for mounting semiconductor elements), and organic interposers. For details of these, please refer to the descriptions in paragraphs 0152 to 0167 of WO 2024 / 024664, as well as the descriptions in JP 2022-99579 A and JP 2022-089837 A, the contents of which are incorporated herein by reference.

[0064] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

[0065] 1. Raw material PTX60: Raw material hexagonal boron nitride, manufactured by Momentive Performance, tap density 0.4 g / cm ３ , average particle diameter (D50 Ａ ) 60 μm PTX25: Raw hexagonal boron nitride, manufactured by Momentive Performance, tap density 0.3 g / cm ３ , average particle diameter (D50 Ａ ) 25 μm HT40MF: raw material hexagonal boron nitride, manufactured by JFE Mineral, tap density 0.8 g / cm ３ , average particle diameter (D50 Ａ ) 36 μm

[0066] AA03: Aluminum oxide, manufactured by Sumitomo Chemical, average particle size (D50 Ｂ ) 0.35 μm ZnO: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., average particle diameter (D50 Ｂ NXA-100: Aluminum oxide, manufactured by Sumitomo Chemical, average particle size (D50 Ｂ AA3: Aluminum oxide, manufactured by Sumitomo Chemical, average particle size (D50 Ｂ ) 3.5 μm

[0067] Phenyltrimethoxysilane: manufactured by Tokyo Chemical Industry Co., Ltd. 3-Glycidylpropyltrimethoxysilane: manufactured by Tokyo Chemical Industry Co., Ltd. TTS: Titanate coupling agent, manufactured by Ajinomoto Fine-Techno Co., Ltd., PLENACT TTS AL-M: Aluminate coupling agent, manufactured by Ajinomoto Fine-Techno Co., Ltd., PLENACT AL-M

[0068] Cyanate resin: P-201 manufactured by Mitsubishi Gas Chemical Co., Ltd. Epoxy resin: NC-3000-L manufactured by Nippon Kayaku Co., Ltd. Curing catalyst: Zinc bis(2-ethylhexanoate)-mineral spirit solution (Zn: 15% by mass) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0069] 2. Example 1 <Preparation of hexagonal boron nitride fine particle aggregate> Tap density 0.4 g / cm ３ The average particle diameter (D50 Ａ Phenyltrimethoxysilane was added dropwise to a raw material hexagonal boron nitride (PTX-60) having an average particle diameter (D50) of 60 μm in an amount of 0.5 mass % based on the raw material hexagonal boron nitride, and the mixture was stirred in a planetary mixer, heated to 110°C, and then allowed to stand at room temperature for 2 days. Subsequently, the average particle diameter (D50) was measured in methyl ethyl ketone. Ｂ ) 0.35 μm alumina fine particles (AA-03) and 3-glycidylpropyltrimethoxysilane were mixed in an amount of 0.5 mass% relative to the fine particles, and the mixture was dispersed using an ultrasonic disperser. Next, the raw hexagonal boron nitride and alumina fine particles that had been subjected to the above treatment were mixed so that the mass ratio of raw hexagonal boron nitride to alumina fine particles was 1:0.044, and the mixture was dispersed using an ultrasonic disperser. This dispersion was filtered, dried in the air for 12 hours, and then further dried at 130°C for 2 hours to obtain a hexagonal boron nitride-fine particle aggregate. The obtained hexagonal boron nitride-fine particle aggregate was observed using a scanning electron microscope (SEM), and the results are shown in Figures 1 and 2. Figure 1 shows the results of observing one of the hexagonal boron nitride-fine particle aggregates, and Figure 2 shows the results of observing a portion of the surface of the hexagonal boron nitride-fine particle aggregate.

[0070] <Measurement of average particle diameter D50> The average particle diameter (D50) of raw material hexagonal boron nitride Ａ ) and the average particle size of the fine particles (D50 Ｂ ) is a median diameter based on JIS Z8825 "Laser diffraction distribution curve", and in the test example, it was measured using "Microtrac MT3000EXII" (manufactured by Microtrap Bell Co., Ltd.).

[0071] <Measurement of porosity of hexagonal boron nitride-fine particle aggregate> The porosity of the hexagonal boron nitride-fine particle aggregate was determined by measuring the pore volume using a mercury porosimeter. The pore volume using the mercury porosimeter was measured using an "Autopore V 9620 pore distribution measuring device" (manufactured by Micromeritics). From the obtained data, a distribution curve showing the pore volume per unit interval of pore diameter was obtained. From the obtained distribution curve, voids with pore diameters of 5 μm or more were determined to be interparticle voids. The principle of porosity measurement is based on ε = V / (V + 1 / p) × 100. In the formula, ε is the porosity of the aggregate, V is the value obtained by subtracting the interparticle voids from the pore volume, and p is the density of the primary particles of hexagonal boron nitride, 2.34 (g / cm ３ )

[0072] <Preparation of Resin Sheet> A resin sheet was prepared using the obtained hexagonal boron nitride-fine particle aggregate. The resin component was a mixture of 50 parts by mass of cyanate resin (P-201), 50 parts by mass of epoxy resin (NC-3000-L), and 0.05 parts by mass of curing catalyst. The resin component and the hexagonal boron nitride-fine particle aggregate (raw material hexagonal boron nitride:fine particles = 1:0.025) were mixed using methyl ethyl ketone as a solvent so that the volume ratio of the two was 61:39. The resulting mixture was applied to the surface of a release PET sheet (thickness 38 μm) and dried at room temperature for 12 hours or more at 110°C to prepare a semi-cured resin sheet. This was laminated and cured using a vacuum press at 180°C and 1.5 MPa using a 1 mm or 0.3 mm thick mold to prepare a resin sheet.

[0073] <Thermal Conductivity in the Thickness Direction> The thermal conductivity in the thickness direction of the resin sheet obtained above was measured by the following method. Thermal Conductivity in the Thickness Direction: A plate-shaped sample of 10 mm × 10 mm × 1 mm thick was cut out, and the thermal conductivity of the test piece was measured at 23°C with a laser flash using a Xenon Flash Analyzer LFA447 type thermal conductivity meter manufactured by NETZSCH.

[0074] <Orientation Intensity Ratio> The orientation intensity ratio of the resin sheet obtained above after curing was measured by the following method. Using a "Fully Automatic Horizontal Multipurpose X-ray Diffraction Device SmartLab" (manufactured by Rigaku Corporation), X-rays were irradiated perpendicularly to the normal to the in-plane direction of a 10 mm x 10 mm x 1 mm thick resin sheet. During the measurement, CuKα rays were used as the X-ray source, the tube voltage was 45 kV, and the tube current was 360 mA.

[0075] <Thermal expansion coefficient (x-y direction)> The thermal expansion coefficient of the resin sheet obtained above was measured by the following method. In accordance with JIS-K-7197-2012 (JIS C6481), a thermomechanical analyzer (trade name "TMA7100" manufactured by Hitachi High-Technologies Corporation) was used to perform thermomechanical analysis in a tensile mode on a 20 mm x 5 mm x 0.3 mm test piece of the cured product at a starting temperature of 30°C, an ending temperature of 250°C, a heating rate of 10°C / min, and a load of 0.05 N (49 mN), and the average thermal expansion per 1°C from 30 to 100°C was measured.

[0076] <Dielectric Breakdown Strength> The dielectric breakdown strength of the resin sheet obtained above when cured was evaluated by the following method. Using a dielectric breakdown tester YST-243-100RHO (manufactured by Yamayo Test Instruments Co., Ltd.), a dielectric breakdown test was performed on a 100 mm × 100 mm × 0.3 mm test piece of the cured product using a short-time heating method and silicone oil as the ambient medium, and the average dielectric breakdown voltage at room temperature was measured. 35 kV / mm or more was marked "A", and less than 35 kV / mm was marked "B".

[0077] <Observation of Particle Images> The morphology of the aggregates was observed by SEM observation images using a scanning electron microscope (FE-SEM-EDX (SU8220): manufactured by Hitachi High-Technologies Corporation).

[0078] 3. Examples 2 to 8, Comparative Examples 1 to 9 The same procedures were carried out as in Example 1, except that the hexagonal boron nitride-fine particle aggregate was changed as shown in Table 1 and the resin sheet was changed as shown in Table 2. The results of observation using a scanning electron microscope (SEM) of the hexagonal boron nitride-fine particle aggregate obtained in Example 3 are shown in Figs. 4 and 5. Fig. 4 shows the result of observation of one of the hexagonal boron nitride-fine particle aggregates, and Fig. 5 shows the result of observation of a portion of the surface of the hexagonal boron nitride-fine particle aggregate. The results of observation using a scanning electron microscope (SEM) of the hexagonal boron nitride-fine particle aggregate obtained in Example 5 are shown in Figs. 6 and 7. Fig. 6 shows the result of observation of one of the hexagonal boron nitride-fine particle aggregates, and Fig. 7 shows the result of observation of a portion of the surface of the hexagonal boron nitride-fine particle aggregate. The results of observation using a scanning electron microscope (SEM) of the hexagonal boron nitride-fine particle aggregate of Comparative Example 1, in which no fine particles were compounded, are shown in Figs. 8 and 9. FIG. 8 shows the results of observing one of the hexagonal boron nitride aggregates not compounded with fine particles, and FIG. 9 shows the results of observing a portion of the surface of a hexagonal boron nitride aggregate not compounded with fine particles.

[0079] The ratio of raw material hexagonal boron nitride to fine particles in Table 1 above is a mass ratio. Ａ is the average particle size of the raw material hexagonal boron nitride, and D50 Ｂ indicates the average particle size of the fine particles, and the porosity indicates the porosity of the hexagonal boron nitride-fine particle aggregate.

[0080]

[0081] 4. Examples 9 to 15 Hexagonal boron nitride-fine particle aggregates were produced in the same manner as in Example 1, and a resin sheet was also produced, except that in the <Production of hexagonal boron nitride-fine particle aggregate> of Example 1, when phenyltrimethoxysilane was dropped onto the raw material hexagonal boron nitride (PTX-60), a dispersant shown in Table 3 was dropped in the ratio shown in Table 3, and when 3-glycidylpropyltrimethoxysilane was mixed with the alumina fine particles (AA-03), a dispersant shown in Table 3 was mixed in the ratio shown in Table 3.

[0082] 5. Comparative Example 11 The same procedure as in Example 1 was carried out except that 3-glycidylpropyltrimethoxysilane (dispersant) was not mixed with the alumina fine particles (AA-03).

[0083]

[0084] The resin sheets obtained from the hexagonal boron nitride-fine particle aggregates of this embodiment were excellent in thermal conductivity and electrical insulation (Examples 1 to 15). More specifically, the resin sheets obtained from the hexagonal boron nitride-fine particle aggregates of Examples 1 to 6 were excellent in thermal conductivity and had good electrical insulation compared to the resin sheets of Comparative Examples 1 to 4. Furthermore, the resin sheets obtained from the hexagonal boron nitride-fine particle aggregates of Examples 7 and 8 were excellent in thermal conductivity and had good electrical insulation compared to the resin sheets of Comparative Examples 5 to 8.

[0085] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.

[0086] 1 Primary particles of hexagonal boron nitride 2 Aggregates of primary particles of hexagonal boron nitride (raw hexagonal boron nitride) 3 Fine particles 4 Hexagonal boron nitride-fine particle aggregates

Claims

1. A hexagonal boron nitride-fine particle aggregate comprising an aggregate of primary particles of hexagonal boron nitride and fine particles, wherein at least a portion of the fine particles are present in voids in the aggregate of primary particles of hexagonal boron nitride, and the average particle diameter (D50 Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ ) is 20 to 10,000, a mass ratio of the aggregates of primary particles of hexagonal boron nitride to the fine particles is 1:0.01 to 1:0.1, and the void ratio of the hexagonal boron nitride-fine particle aggregate is 56 to 80%.

2. The average particle size (D50) of the aggregates of the primary particles of the hexagonal boron nitride Ａ 2. The hexagonal boron nitride-fine particle aggregate according to claim 1, wherein the particle size is 10 to 100 μm.

3. The average particle diameter (D50 Ｂ 2. The hexagonal boron nitride-fine particle aggregate according to claim 1, wherein the particle size is 0.01 to 0.5 μm.

4. The hexagonal boron nitride-fine particle aggregate according to claim 1, wherein the void ratio of the hexagonal boron nitride-fine particle aggregate is 60 to 75%.

5. The hexagonal boron nitride-particle aggregate of claim 1, wherein the particles comprise aluminum oxide and / or zinc oxide.

6. The average particle size (D50) of the aggregates of the primary particles of the hexagonal boron nitride Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ 2. The hexagonal boron nitride-fine particle aggregate according to claim 1, wherein the molecular weight of the hexagonal boron nitride-fine particle aggregate is 100 to 950.

7. The average particle size (D50) of the aggregates of the primary particles of the hexagonal boron nitride Ａ ) is 10 to 100 μm, and the average particle diameter (D50 Ｂ ) is 0.01 to 0.5 μm, the void ratio of the hexagonal boron nitride-fine particle aggregate is 60 to 75%, the fine particles contain aluminum oxide and / or zinc oxide, and the average particle diameter (D50 Ａ ) and the average particle diameter (D50 Ｂ ) is the ratio of (D50 Ａ / D50 Ｂ 2. The hexagonal boron nitride-fine particle aggregate according to claim 1, wherein the molecular weight of the hexagonal boron nitride-fine particle aggregate is 100 to 950.

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

9. A resin sheet comprising a resin and the hexagonal boron nitride fine particle aggregate according to any one of claims 1 to 7.

10. A multilayer body having a metal substrate and the resin sheet according to claim 9 provided on the metal substrate.

11. A multilayer body having a metal substrate, the resin sheet according to claim 9 provided on the metal substrate, and a heat spreader provided on the resin sheet.

12. A semiconductor device comprising the multilayer body according to claim 10.

13. A method for producing the hexagonal boron nitride-fine particle aggregate according to any one of claims 1 to 7, comprising dispersing hexagonal boron nitride and fine particles in a slurry containing hexagonal boron nitride, a dispersant, and fine particles, and then drying the resulting mixture.

14. A method for producing a hexagonal boron nitride fine particle aggregate according to claim 13, wherein the hexagonal boron nitride is an aggregate of primary particles of hexagonal boron nitride.

15. The method for producing a hexagonal boron nitride fine particle aggregate according to claim 13, wherein the dispersing agent comprises at least one selected from the group consisting of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

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