Fullerene-coated boron nitride particles, resin composition, resin sheet, semiconductor device, and method for producing fullerene-coated boron nitride particles

Abstract

To provide fullerene-coated boron nitride particles capable of improving voltage-resistant performance with no loss of heat radiation performance when applied to a heat radiation member of a semiconductor device, that are easily manufacturable at low cost; and to provide a resin composition using the same, a resin sheet, a semiconductor device and a manufacturing method of the fullerene-coated boron nitride particles thereof.SOLUTION: Fullerene-coated boron nitride particles comprise hexagonal boron nitride particles, and fullerene covering at least part of a surface made of the hexagonal boron nitride particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to fullerene-coated boron nitride particles, and to a resin composition, a resin sheet, a semiconductor device, and a method for producing fullerene-coated boron nitride particles, which use the same. [Background technology]

[0002] In recent years, power semiconductor devices have been used in a variety of fields, including railways, automobiles, and general home appliances. To achieve further miniaturization, lower cost, and higher efficiency, there has been a shift from conventional silicon power semiconductors to power semiconductors using silicon carbide (SiC), aluminum nitride (AlN), gallium nitride (GaN), and other materials. In such power semiconductor devices, the amount of heat generated increases as the current value increases. There are concerns that this heat generated by power semiconductor devices may affect their reliability.

[0003] As a method for dissipating heat, a heat-dissipating resin sheet in which a heat-dissipating filler is dispersed is being considered. For example, Patent Document 1 discloses a sheet containing heat-dissipating boron nitride secondary particles in which boron nitride secondary particles contain a specific resin, thereby eliminating voids within the secondary particles and achieving excellent thermal conductivity, voltage resistance, adhesive strength, and flex resistance.

[0004] Patent Document 2 also discloses a laminate sheet having a layer (layer A) made of a thermoplastic resin and a resin layer (layer B) containing a filler, and by making the thickness of the laminate sheet 100 μm or less, it is possible to achieve both heat dissipation and insulation properties even though it is a thin film.

[0005] Patent Document 3 discloses a polyimide resin film in which the concentration of boron nitride particles is dispersed in a moderately dispersed manner without being too high locally, and is said to achieve high voltage resistance and heat dissipation.

[0006] Furthermore, Patent Document 4 discloses a thermosetting resin composite material having improved wear resistance, in which fullerene particles are uniformly and finely dispersed in a thermosetting resin matrix. Furthermore, it is said that fillers treated with organic compounds may be contained as optional components depending on the application, and examples thereof include calcium carbonate, barium sulfate, magnesia, alumina, zirconia, silica, aluminum powder, and copper powder.

[0007] Furthermore, Patent Document 5 discloses that a composition in which 0.1 to 3 mass % of fullerene is uniformly dispersed in an epoxy resin has an improved breakdown voltage compared to an epoxy resin containing no fullerene. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2018-165344 [Patent Document 2] Japanese Patent Application Publication No. 2017-226213 [Patent Document 3] Japanese Patent Application Publication No. 2018-002843 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-242529 [Patent Document 5] Japanese Patent Application Publication No. 2018-177895 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the invention of Patent Document 1 does not have a high breakdown voltage, and the process of encapsulating a specific resin in secondary particles of boron nitride is complicated, requiring mixing the resin and boron nitride and then vacuuming, making efficient production difficult. Furthermore, the withstand voltage is insufficient for use in power semiconductor devices. The invention of Patent Document 2 involves a complicated process of laminating a film containing no thermally conductive filler with a film containing a thermally conductive filler. Furthermore, laminating resin films with different expansion coefficients can easily cause warping and peeling of the laminated sheet. The invention of Patent Document 3 also has limited heat dissipation properties, making it difficult to dissipate heat from power semiconductor devices that generate a large amount of heat. The invention of Patent Document 4 improves wear resistance by finely dispersing fullerenes in the resin, but does not take into account heat dissipation properties or withstand voltage. The invention of Patent Document 5 focuses only on the withstand voltage performance of the resin containing dispersed fullerenes, and does not consider its properties as a heat dissipation component.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide fullerene-coated boron nitride particles that, when applied to heat dissipation components of semiconductor devices, can improve voltage resistance performance without impairing heat dissipation characteristics, and that can be easily produced at low cost, as well as resin compositions, resin sheets, and semiconductor devices using the same. [Means for solving the problem]

[0011] In order to solve the above problems, the present inventors have discovered that by coating the surfaces of hexagonal boron nitride particles, which are a heat-dissipating filler, with fullerenes to create fullerene-coated boron nitride particles, it is possible to suppress dielectric breakdown at the interface between the resin and the fullerene-coated boron nitride particles due to the electron-accepting function of the fullerenes.

[0012] The present invention has been made based on the above-mentioned findings, and the fullerene-coated boron nitride particles of the present invention comprise hexagonal boron nitride particles and fullerenes that cover at least a part of the surface of the hexagonal boron nitride particles. The mass ratio of the fullerene contained in the fullerene-coated boron nitride particles is in the range of 0.001 mass % or more and 0.1 mass % or less with respect to 100 mass % of the hexagonal boron nitride particles. .

[0013] According to the present invention, by covering at least a portion of the surface of hexagonal boron nitride particles with fullerenes, it is possible to improve the voltage resistance performance without impairing the heat dissipation characteristics when applied to, for example, heat dissipation components of semiconductor devices.

[0015] The resin composition of the present invention contains a resin and the fullerene-coated boron nitride particles described in the above sections.

[0016] In the present invention, the resin may include an epoxy resin.

[0017] The resin sheet of the present invention contains the resin composition described above.

[0018] The semiconductor device of the present invention comprises the resin composition described above and a semiconductor element.

[0019] The method for producing fullerene-coated boron nitride particles of the present invention comprises a dissolving step of dissolving fullerenes in an organic solvent to prepare a fullerene solution, a mixing step of adding hexagonal boron nitride particles to the fullerene solution to prepare a dispersion, and subjecting the dispersion to a wet ball mill treatment, and a solvent removal step of distilling off the solvent from the dispersion after the ball mill treatment. The fullerene added to the organic solvent is in the range of 0.001% by mass or more and 0.1% by mass or less with respect to 100% by mass of the hexagonal boron nitride particles. . [Effects of the Invention]

[0021] According to the present invention, it is possible to provide fullerene-coated boron nitride particles that, when applied to heat dissipation components of semiconductor devices, can improve voltage resistance performance without impairing heat dissipation characteristics and can be easily produced at low cost, as well as resin compositions, resin sheets, semiconductor devices, and methods for producing fullerene-coated boron nitride particles that use the same. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic cross-sectional view showing an example of a resin composition of the present invention. [Figure 2]1 is a graph showing the relationship between the amount of fullerene relative to hexagonal boron nitride and the breakdown voltage. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, fullerene-coated boron nitride particles according to one embodiment of the present invention, as well as a resin composition and a semiconductor device using the same, will be described with reference to the drawings. The following embodiments are specifically described to provide a better understanding of the gist of the invention, and unless otherwise specified, do not limit the present invention. Furthermore, the drawings used in the following description may show essential parts enlarged for the sake of clarity, and the dimensional proportions of each component may not necessarily be the same as those in reality.

[0024] In the following description, the breakdown voltage refers to the lower limit voltage at which breakdown occurs, and the withstand voltage performance refers to the performance of suppressing breakdown.

[0025] (Hexagonal boron nitride particles) Hexagonal boron nitride particles 13, which exhibit high heat dissipation properties, are selected as boron nitride particles for use in heat dissipation components. The particle size of the hexagonal boron nitride particles 13 is not particularly limited, but for example, particles with a particle size (diameter) of approximately 0.1 μm to 100 μm are used. In this case, the particles may be primary or secondary particles. In this specification, particle size refers to the average particle size, meaning the particle size at 50% of the cumulative value (d50) in the particle size distribution determined by laser diffraction / scattering. Such particle size is selected depending on the intended use of the fullerene-coated boron nitride particles 12. For example, in the case of a gap filler, the particle size must be smaller than the gap to be used, so the particle size is adjusted to be smaller than the intended size.

[0026] It is also possible to adjust the overall particle size distribution in order to reduce the viscosity of the resin material constituting the resin 11 or to consider optimal thermal conductivity. In such cases, fullerene-coated boron nitride particles 12 having hexagonal boron nitride particles 13 with several different particle sizes can be mixed and used.

[0027] The presence of fullerenes 14 at the interface between resin 11 and hexagonal boron nitride particles 13 is believed to be important for the effect of resin composition 10 in suppressing dielectric breakdown.

[0028] The hexagonal boron nitride particles 13 may be composed of a material having one type of particle diameter, or may be composed of a mixture of materials having two or more types of particle diameters. Furthermore, the hexagonal boron nitride particles 13 not coated with fullerenes 14 may be mixed with fullerene-coated boron nitride particles 12 coated with fullerenes 14, as long as the voltage resistance and heat dissipation properties are not affected.

[0029] (fullerene) The fullerenes 14 that cover the hexagonal boron nitride particles 13 are electron acceptors, and this property contributes to improving the voltage resistance performance of the resin composition 10 containing fullerene-coated boron nitride particles 12 in which the hexagonal boron nitride particles 13 are coated with fullerenes 14. Since fullerenes have electron acceptor properties, any type of fullerene can be used. For example, C 60 Even if C 70 and C 70 It may also be a higher fullerene. 60 Or C 70 It may be a fullerene in which a substituent has been introduced, or a mixture thereof.

[0030] Generally, fullerenes are 60 or C 70 The fullerene mixture obtained without excessive purification is relatively inexpensive, and the resin composition 10 can be produced at low cost by using the fullerene mixture.

[0031] In addition, as long as the voltage resistance and heat dissipation properties are not affected, fullerene-coated boron nitride particles 12 in which hexagonal boron nitride particles 13 are coated with fullerenes 14 can be added, and fullerenes 14 can be dispersed alone in resin 11.

[0032] (Fullerene-coated boron nitride particles) In the fullerene-coated boron nitride particles 12, the amount of fullerene 14 coated on the hexagonal boron nitride particles 13 is appropriately selected depending on the thickness of the resin composition 10, the blending ratio of the fullerene-coated boron nitride particles 12 to the resin 11, the insulating properties of the resin 11, etc. Therefore, the amount of fullerene 14 coated on the hexagonal boron nitride particles 13 is not particularly limited, but it is preferable to use, for example, between 0.00001% by mass and 10% by mass of fullerene 14 relative to 100% by mass of the hexagonal boron nitride particles 13.

[0033] For example, in the case of a 0.2 mm-thick resin composition 10 formed by mixing hexagonal boron nitride particles 13 with epoxy resin in a range of 30 to 80% by weight relative to 100% by weight of the epoxy resin, fullerenes 14 can be used in a range of 0.00001 to 10% by weight relative to 100% by weight of the hexagonal boron nitride particles 13. The range is preferably 0.0001 to 5% by weight, more preferably 0.0005 to 1% by weight, and even more preferably 0.001 to 0.3% by weight. If the mass of fullerenes is 0.00001% by weight or more relative to 100% by weight of the hexagonal boron nitride particles 13, the effect of coating the hexagonal boron nitride particles with fullerenes improves the breakdown voltage. Furthermore, if the mass is 10% by weight or less, the thermal conductivity can be used without significantly decreasing.

[0034] In resin composition 10 containing resin 11 and fullerene-coated boron nitride particles 12 having the above-described configuration, the total content of fullerene-coated boron nitride particles 12 in which hexagonal boron nitride particles 13 are coated with fullerenes 14 and hexagonal boron nitride particles 13 that are not coated with fullerenes 14 is preferably in the range of 45 to 95 mass%, more preferably in the range of 45 to 85 mass%, and even more preferably in the range of 50 to 85 mass%, when resin composition 10 is taken as 100 mass%.

[0035] In addition, in the resin composition 10, the total content of the fullerene-coated boron nitride particles 12 in which the hexagonal boron nitride particles 13 are coated with fullerenes 14 and the hexagonal boron nitride particles 13 that are not coated with fullerenes 14 is preferably in the range of 30 to 85 volume %, more preferably in the range of 30 to 70 volume %, and even more preferably in the range of 35 to 70 volume %, of the volume of the resin composition 10. Note that this content can be calculated at room temperature (25°C) from the density and mass of the fullerene-coated boron nitride particles 12 and the hexagonal boron nitride particles 13 that are not coated with fullerenes 14.

[0036] The mass-based contents of fullerene-coated boron nitride particles 12, hexagonal boron nitride particles 13 not coated with fullerenes 14, and fullerenes 14 in resin composition 10 can be calculated from the masses of hexagonal boron nitride, fullerene-coated boron nitride, and fullerenes obtained by dissolving resin composition 10 in a solvent, and resin composition 10 before dissolution. Similarly, the density of the fullerene-coated boron nitride particles can be calculated from the mass of fullerene-coated boron nitride particles 12 obtained at room temperature (25°C) using the density of the hexagonal boron nitride particles (2.27 g / cm 3 ) and, for example, in the case of a liquid hardening epoxy resin used as the resin 11, its density (1.17 g / cm 3 ) the volumetric content of the fullerene-coated boron nitride particles 12, the hexagonal boron nitride particles 13 not coated with fullerenes 14, and the fullerenes 14 in the resin composition 10 can be calculated.

[0037] When the total content of the fullerene-coated boron nitride particles 12 and the hexagonal boron nitride particles 13 not coated with fullerenes 14 is 30% by volume or more, thermal conductivity can be ensured, and when it is 85% by volume or less, the fluidity of the resin composition 10 can be well ensured. Furthermore, when the total content of the fullerene-coated boron nitride particles 12 and the hexagonal boron nitride particles 13 not coated with fullerenes 14 is 45% by mass or more, thermal conductivity can be ensured, and when it is 95% by mass or less, the fluidity of the resin composition 10 can be well ensured.

[0038] Furthermore, in order to improve the fluidity of the resin composition 10, multiple fullerene-coated boron nitride particles 12 with different particle size distributions can be added to increase the content of all fullerene-coated boron nitride particles 12, thereby improving heat dissipation properties.

[0039] (Resin composition) FIG. 1 is a schematic cross-sectional view showing a resin composition containing fullerene-coated boron nitride particles according to one embodiment of the present invention. Resin composition 10 is formed, for example, in the shape of a sheet, and includes resin 11 and fullerene-coated boron nitride particles 12 dispersed in this resin 11. Fullerene-coated boron nitride particles 12 are composed of hexagonal boron nitride particles 13 and fullerenes 14 that cover at least a portion of the surface of these hexagonal boron nitride particles 13.

[0040] In the following embodiments, a sheet-shaped resin composition 10 (also referred to as a resin sheet) will be described. However, the resin composition 10 may be in the form of a gap filler, which is a composition comprising a resin 11 and fullerene-coated boron nitride particles 12 that is deformed to fill the necessary space between adherends and harden, or a heat-dissipating grease, which is a liquid composition containing the resin 11 and fullerene-coated boron nitride particles 12 and does not harden but fills the necessary space between adherends. The resin composition 10 may also be used for sealing or bonding depending on the purpose. It may also be used as a component of electrical and electronic components that require high voltage resistance.

[0041] (resin) Examples of resin materials used for the resin 11 constituting the resin composition 10 of this embodiment include epoxy resin, silicone resin, acrylic resin, and polyimide resin. These can be used alone or as a mixture or copolymer of two or more types. Among these, it is preferable to use epoxy resin, which has high heat dissipation properties.

[0042] Examples of epoxy resins used in the resin 11 include epoxy monomers having a bisphenol skeleton, epoxy monomers having a dicyclopentadiene skeleton, epoxy monomers having a naphthalene skeleton, epoxy monomers having an adamantene skeleton, epoxy monomers having a fluorene skeleton, epoxy monomers having a biphenyl skeleton, epoxy monomers having a bi(glycidyloxyphenyl)methane skeleton, epoxy monomers having a xanthene skeleton, epoxy monomers having an anthracene skeleton, and epoxy monomers having a pyrene skeleton. These may be used alone or in combination of two or more.

[0043] Examples of the epoxy monomer having a bisphenol skeleton include epoxy monomers having a bisphenol skeleton of bisphenol A type, bisphenol F type, or bisphenol S type.

[0044] Examples of the epoxy monomer having a naphthalene skeleton include 1-glycidylnaphthalene, 2-glycidylnaphthalene, 1,2-diglycidylnaphthalene, 1,5-diglycidylnaphthalene, 1,6-diglycidylnaphthalene, 1,7-diglycidylnaphthalene, 2,7-diglycidylnaphthalene, triglycidylnaphthalene, and 1,2,5,6-tetraglycidylnaphthalene.

[0045] Examples of the epoxy monomer having an adamantene skeleton include 1,3-bis(4-glycidyloxyphenyl)adamantene and 2,2-bis(4-glycidyloxyphenyl)adamantene.

[0046] Examples of the epoxy monomer having a fluorene skeleton include 9,9-bis(4-glycidyloxyphenyl)fluorene, 9,9-bis(4-glycidyloxy-3-methylphenyl)fluorene, 9,9-bis(4-glycidyloxy-3-chlorophenyl)fluorene, 9,9-bis(4-glycidyloxy-3-bromophenyl)fluorene, 9,9-bis(4-glycidyloxy-3-fluorophenyl)fluorene, 9,9-bis(4-glycidyloxy-3-methoxyphenyl)fluorene, 9,9-bis(4-glycidyloxy-3,5-dimethylphenyl)fluorene, 9,9-bis(4-glycidyloxy-3,5-dichlorophenyl)fluorene, and 9,9-bis(4-glycidyloxy-3,5-dibromophenyl)fluorene.

[0047] Examples of the above-mentioned epoxy monomer having a biphenyl skeleton include 4,4'-diglycidylbiphenyl and 4,4'-diglycidyl-3,3',5,5'-tetramethylbiphenyl.

[0048] Examples of the epoxy monomer having the bi(glycidyloxyphenyl)methane skeleton include 1,1'-bi(2,7-glycidyloxynaphthyl)methane, 1,8'-bi(2,7-glycidyloxynaphthyl)methane, 1,1'-bi(3,7-glycidyloxynaphthyl)methane, 1,8'-bi(3,7-glycidyloxynaphthyl)methane, 1,1'-bi(3,5-glycidyloxynaphthyl)methane, 1,8'-bi(3,5-glycidyloxynaphthyl)methane, 1,2'-bi(2,7-glycidyloxynaphthyl)methane, 1,2'-bi(3,7-glycidyloxynaphthyl)methane, and 1,2'-bi(3,5-glycidyloxynaphthyl)methane.

[0049] Examples of the epoxy monomer having a xanthene skeleton include 1,3,4,5,6,8-hexamethyl-2,7-bis-oxiranylmethoxy-9-phenyl-9H-xanthene.

[0050] Epoxy resins having a tertiary amine structure can also be used, such as N,N-dimethylaminoethyl glycidyl ether, N,N-dimethylaminotrimethyl glycidyl ether, N,N-dimethylaminophenyl glycidyl ether, N,N-diglycidyl-4-glycidyloxyaniline, and 1,3,5-triglycidyl isocyanurate.

[0051] Examples of polyfunctional aliphatic epoxy resins include 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane polymethyl ether, diethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, and sorbitol polyglycidyl ether.

[0052] The above-mentioned epoxy resins can be used alone or in combination of two or more. When using epoxy resins, curing agents and curing accelerators may be added. Examples of curing agents include alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and himic anhydride; aliphatic acid anhydrides such as dodecenyl succinic anhydride; aromatic acid anhydrides such as phthalic anhydride and trimellitic anhydride; bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenolic resins such as phenol-formaldehyde resin, phenol-aralkyl resin, naphthol-aralkyl resin, and phenol-dicyclopentadiene copolymer resin; and organic dihydrazides such as dicyandiamide and adipic dihydrazide.

[0053] Examples of curing catalysts include amines such as tris(dimethylaminomethyl)phenol, dimethylbenzylamine, 1,8-diazabicyclo(5,4,0)undecene and derivatives thereof, and imidazoles and derivatives thereof such as 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole. These may be used alone or in combination of two or more.

[0054] Furthermore, other resins can be added to the epoxy resins described above to maintain the shape of the resin composition 10. Examples of such resins include phenoxy resins, polyimide resins, polyamide resins, polycarbodiimide resins, cyanate ester resins, (meth)acrylic resins, polyester resins, polyethylene resins, polyethersulfone resins, polyetherimide resins, polyvinyl acetal resins, urethane resins, and acrylic rubber. Among these, phenoxy resins, polyimide resins, (meth)acrylic resins, acrylic rubber, cyanate ester resins, and polycarbodiimide resins are preferred from the viewpoint of excellent heat resistance and film formability, with phenoxy resins, polyimide resins, (meth)acrylic resins, and acrylic rubber being more preferred. These resins can be used alone or as a mixture or copolymer of two or more types.

[0055] Furthermore, as necessary, constituent materials of the resin composition 10 may include a flexibility imparting agent, a silane coupling agent, a titanium coupling agent, an inorganic ion scavenger, a pigment, a dye, a diluent, a solvent, and the like.

[0056] The solvent as the additive described above is not particularly limited, and examples thereof include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; ether solvents such as 1,4-dioxane, tetrahydrofuran, and diglyme; glycol ether solvents such as methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and diethylene glycol methyl ethyl ether; and other solvents such as benzyl alcohol, N-methylpyrrolidone, γ-butyrolactone, ethyl acetate, and N,N-dimethylformamide, which can be used alone or in combination.

[0057] (Semiconductor Devices) The semiconductor device may be formed by laminating the resin composition 10 on a support as a component of the semiconductor device. The support is not particularly limited, but in order to increase thermal conductivity, for example, a metal foil or metal plate, particularly a copper foil or copper plate, or an aluminum foil or aluminum plate, can be used.

[0058] The thickness of the metal foil or metal plate constituting the support on which the resin composition 10 is laminated is usually preferably 0.03 to 5 mm, particularly 0.1 to 5 mm, in order to ensure sufficient heat dissipation. These are used as wiring layers by attaching the metal foil or metal plate to both sides of the resin composition 10.

[0059] (Method for producing fullerene-coated boron nitride particles) A method for producing fullerene-coated boron nitride particles according to one embodiment of the present invention will be described. First, fullerene-coated boron nitride particles 12 can be produced by adding hexagonal boron nitride particles 13 to a solvent in which fullerenes 14 have been dissolved, and then subjecting the mixture to, for example, wet ball milling, followed by distilling off the solvent (fullerene-coated boron nitride particle production process).

[0060] Specifically, first, fullerene is dissolved in an organic solvent to prepare a fullerene solution (dissolving step). In this embodiment, the organic solvent used for the fullerene solution is not particularly limited, and a solvent in which fullerene dissolves and in which hexagonal boron nitride particles 13 do not easily aggregate is preferably used. Specifically, a solvent containing an aromatic hydrocarbon can be preferably used as the solvent. Aromatic hydrocarbons are hydrocarbon compounds having at least one benzene nucleus in the molecule, and specific examples include alkylbenzenes such as benzene, toluene, xylene, ethylbenzene, n-propylbenzene, isopropylbenzene, n-butylbenzene, sec-butylbenzene, tert-butylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene, diethylbenzene, and cymene; alkylnaphthalenes such as 1-methylnaphthalene; and halogenated aromatic hydrocarbons such as decahydronaphthalene, tetralin, and o-dichlorobenzene. Among these, it is preferable to use one of toluene, 1,2,4-trimethylbenzene, and tetralin as the solvent used for the fullerene mixed solution. It is preferable to dissolve the fullerene by stirring thoroughly.

[0061] Next, this fullerene solution is placed in a sealed container, and hexagonal boron nitride particles 13 and zirconia balls are added, followed by stirring using a stirring device (mixing step). It is particularly preferable to use a wet ball mill treatment. Zirconia balls, alumina balls, natural silica, nylon balls with iron cores, etc. can be used in a wet ball mill, with zirconia balls being the most preferable. The balls used in the ball mill treatment are set aside after mixing. Therefore, it is preferable to use balls that are at least 10 times larger than the secondary particle diameter of the boron nitride.

[0062] Next, after removing the balls from the solution that has been subjected to the mixing step, the solvent is distilled off (solvent distillation step). The solvent distillation can be carried out, for example, by using a pressure reducing device such as an evaporator while heating to a temperature lower than the boiling point of the solvent used.

[0063] The fullerene-coated boron nitride particles thus obtained are slightly reddish-brown in color, and when observed under an optical microscope, the black fullerene particles are not visible, and the white boron nitride surface is seen to be colored light purple to pink. These observation results confirm that the surfaces of the hexagonal boron nitride particles are coated with fullerenes.

[0064] More specifically, the absence or reduction of fullerene particles can be confirmed at high magnification using scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX). If fullerene particles are present, the carbon element mapping function of EDX can be used to confirm that the observed particles are fullerene particles. On the other hand, the amount of fullerenes coating the hexagonal boron nitride particles can be confirmed by confirming the presence of carbon atoms.

[0065] Generally, carbon atoms can be detected in fullerene-coated boron nitride particles if they contain a few mass percent or more of carbon atoms relative to the total amount of nitrogen, boron, and carbon atoms. Therefore, if fullerenes are added to hexagonal boron nitride particles at 4 mass percent or more, it may be possible to detect carbon atoms, but if the amount is less than 4 mass percent, it is difficult to detect carbon atoms. When the carbon atom content is 4 mass percent or less, fullerene coating can be confirmed by confirming the presence of fullerenes using the method described below, and then checking whether the initially added fullerene particles are not visible or the amount of visible fullerene particles is reduced using an optical microscope or scanning electron microscope, or by the resulting fullerene-coated boron nitride particles being colored light purple to pink.

[0066] The coating of hexagonal boron nitride particles with fullerenes can be confirmed by placing the fullerene-coated boron nitride in a toluene solution, heating it to 80°C, applying ultrasound, and stirring for 30 minutes or more, and then checking that the fullerenes are eluted into the toluene solution. The fullerene content in the fullerene-coated boron nitride particles can be confirmed by quantifying the fullerenes eluted into the solution in the same manner. The elution and content of fullerenes may be measured by known methods such as high-performance liquid chromatography or ultraviolet absorption spectroscopy.

[0067] The fullerene-coated boron nitride particles 12 thus obtained, in which the hexagonal boron nitride particles 13 are coated with fullerenes 14, can be used to produce, for example, a resin composition 10. When producing a sheet-shaped resin composition 10 (resin sheet), first, a kneaded mixture is produced by kneading resin 11 and fullerene-coated boron nitride particles 12 (kneading step). If necessary, hexagonal boron nitride particles 13 not coated with fullerenes 14 or fullerenes 14 alone can be added. To improve handling, resin 11 may be dissolved in a solvent, and fullerene-coated boron nitride particles 12 may be added to the solution and stirred and mixed. This kneading can be performed by a known method. For example, a paint shaker, planetary mixer, agitator, rotary / revolutionary agitator / mixer, three-roll mill, kneader, or the like can be used. During this kneading, vacuum operation (degassing) can also be performed to remove bubbles.

[0068] Next, the kneaded material thus obtained is coated to form a sheet-like resin composition 10 (resin sheet) (molding process). For example, the kneaded material is coated onto a sheet material such as a PET film with a release agent using a coating device such as a slit coater, die coater, or blade coater. If the kneaded material contains a volatile component such as a solvent, a drying process such as blowing hot air can also be performed.

[0069] When the kneaded resin 11 is a thermosetting resin, it is cured at a curing temperature of 80 to 200° C., preferably 100 to 150° C. If the curing temperature is 80° C. or higher, curing proceeds well, and if the curing temperature is 200° C. or lower, there is little concern about deterioration of the molded resin composition 10 or deformation of the sheet material used for molding.

[0070] It is also preferable to apply pressure during curing to ensure a uniform thickness of the molded resin composition 10. The pressure conditions are, for example, 15 to 20 MPa, and preferably 17 to 19 MPa. The resin composition 10 can also be supplied in a semi-cured state to the next step of bonding it to an applicable part or the like.

[0071] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Example]

[0072] The effects of the present invention were verified. Note that the following verification examples do not limit the present invention in any way.

[0073] <Measurement method> (Measurement of resin sheet density) Measurement samples (size: 15 mm x 15 mm x 200 μm) were cut out from the resin sheets of Examples 1 to 3 and Comparative Examples 1 and 2, and the sheet density was measured by the Archimedes method using a specific gravity measurement kit (AD-1653: manufactured by AS ONE Corporation).

[0074] (Measurement of thermal conductivity of resin sheet) The thermal diffusivity of the sheet-shaped resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2 was measured using a heat flow meter (LFA447 NanoFlash, manufactured by Netzsch Japan Co., Ltd.), and the value calculated by multiplying the obtained measurement value by the theoretical values ​​of the specific heat and density of each resin composition was used as the thermal conductivity in the thickness direction of the sheet-shaped resin composition. The specific heat capacities of Examples 1 to 3 and Comparative Examples 1 and 2 were calculated assuming that the theoretical specific heat of fullerene-coated hexagonal boron nitride was 0.8, the same as that of hexagonal boron nitride, and that the theoretical specific heat of the resin component was 1.8.

[0075] (Measurement of dielectric breakdown voltage of resin sheet) For Examples 1 to 3 and Comparative Examples 1 and 2, the breakdown voltage was measured at a voltage rise rate of 0.1 kV / sec using a withstand voltage / insulation resistance measuring device (TOS9201 / 5101: manufactured by Kikusui Electronics Co., Ltd.).

[0076] <Sample> Example 1 "Fullerene-coated boron nitride particles" 240 mL of a toluene solution in which 0.45 mg of fullerene (Nanomumix, manufactured by Frontier Carbon Corporation) was dissolved in toluene as a solvent, and 45 g of hexagonal boron nitride particle powder (UHP-G1H, manufactured by Showa Denko K.K.) were placed in a polypropylene container containing 100 g of beads (zirconia, φ1 mm), and ball milling was carried out at room temperature for 24 hours using a mix rotor (MIX RORTOR VMR-5R, manufactured by AS ONE Corporation).

[0077] The ball-milled contents were then passed through a 0.1 mm sieve to filter out the balls, and the resulting filtrate was heated at 60°C in a rotary evaporator (N-1100, manufactured by Tokyo Rikakikai Co., Ltd.) to remove the toluene. The powder obtained after removing the toluene was dried in a vacuum dryer at 100°C to produce 40 g of fullerene-coated boron nitride particles containing 0.001% by mass of fullerenes relative to 100% by mass of hexagonal boron nitride particles. Because the solvent (toluene) was removed from the resulting filtrate, almost the entire amount of fullerenes added and dissolved in toluene was contained in the produced fullerene-coated boron nitride particles.

[0078] When the obtained fullerene-coated boron nitride particles were observed under an optical microscope, it was confirmed that the surfaces of the hexagonal boron nitride particles were colored pink, and no black fullerene particles were observed, confirming that the hexagonal boron nitride particles were coated with fullerenes.

[0079] "Resin composition" 6.12 parts by mass of liquid epoxy resin (bisphenol A-type epoxy resin (trade name "YD-128" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., epoxy equivalent: 184-194 g / eq)) and 0.68 parts by mass of phenoxy resin (trade name "YP-50S" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., purity: 99.0% by mass or higher) were used as the organic matrix. 13.2 parts by mass of the fullerene-coated boron nitride particles obtained above and 0.2 parts by mass of an imidazole-based curing agent (Curesol 2E4MZ manufactured by Shikoku Chemical Industries Co., Ltd.) were added to this organic matrix, and 2.26 parts by mass of methoxypropanol (trade name "Hisorb MP" manufactured by Toho Chemical Industry Co., Ltd.) were added to adjust the viscosity. The mixture was then stirred and mixed using Mazerustar (registered trademark) manufactured by Kurabo Industries Co., Ltd. to obtain a resin composition.

[0080] The fullerene-coated boron nitride particles were adjusted so that the content of the fullerene-coated boron nitride particles in the total amount of the fullerene-coated boron nitride particles and the organic matrix was 50% by volume. The volume-based content (volume %) of the fullerene-coated boron nitride particle powder was determined by dividing the density of the fullerene-coated boron nitride particles by the density of the hexagonal boron nitride particles (2.27 g / cm 3 ) and the density of the liquid curable epoxy resin used as the organic matrix (1.17 g / cm 3 ) was calculated.

[0081] Resin sheet The resin composition obtained above was applied to a release film (polyethylene terephthalate SP-PET-100-01-BU, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) using a coater (micrometer-equipped filter applicator SA-204, manufactured by Tester Sangyo Co., Ltd.) to a film thickness of 350 μm to form a resin composition layer (10 cm × 10 cm). The resin composition layer was then dried in a hot air dryer at 50°C for 10 minutes, and then vacuum-dried in a vacuum dryer at 50°C for 10 minutes.

[0082] Two of the dried resin composition layers were stacked so that they were in contact with each other and pressed together by passing them through a roll (small tabletop roll press SA602, manufactured by Tester Sangyo Co., Ltd.). The roll pressure was adjusted so that the resulting resin sheet had a film thickness of 200 μm. The resin composition layers were then cured by heat pressing at 120° C. for 30 minutes to produce a resin sheet. The dielectric breakdown voltage and thermal conductivity of the resin sheet obtained as described above were measured and found to be 14 kV / mm and 13 W / mk, respectively.

[0083] (Examples 2 and 3) Fullerene-coated boron nitride particles were prepared in the same manner as in Example 1, except that the content of fullerene relative to 100% by mass of hexagonal boron nitride particles was 0.01% by mass (Example 2) and 0.1% by mass (Example 3), and a resin sheet was obtained in the same manner as in Example 1, and its breakdown voltage and thermal conductivity were measured. The fullerene-coated boron nitride particles were also observed with an optical microscope to observe the state of coating with fullerene.

[0084] (Comparative Example 1) As conventional Comparative Example 1, a resin composition was obtained in the same manner as in Example 1, except that 40 g of hexagonal boron nitride powder (UHP-G1H: manufactured by Showa Denko K.K.) was used instead of the fullerene-coated boron nitride particles of Example 1. Thereafter, a resin sheet was obtained in the same manner as in Example 1, and its breakdown voltage and thermal conductivity were measured.

[0085] (Comparative Example 2) 15 g of hexagonal boron nitride particles not coated with fullerene were dry-mixed with 15 mg of fullerene (0.01 mass % of hexagonal boron nitride particles per 100 mass % of hexagonal boron nitride particles). The specified amounts of each were placed in a 20 mL screw tube and stirred at 100 rpm at room temperature for 24 hours using a mix rotor.

[0086] When the resulting mixture was observed under an optical microscope, white hexagonal boron nitride particles and black fullerene particles were observed, confirming that the hexagonal boron nitride particles were not coated with fullerenes. This mixture was used in place of the fullerene-coated boron nitride particles of Example 1 to obtain a resin composition. Thereafter, a resin sheet was obtained in the same manner as in Example 1, and its breakdown voltage and thermal conductivity were measured.

[0087] The results of the above measurements are shown in Table 1. Figure 2 is a graph showing the relationship between the amount of fullerene (mass %) relative to 100 mass % of hexagonal boron nitride and the breakdown voltage.

[0088] [Table 1]

[0089] According to the results shown in Table 1, Examples 1 to 3, which used fullerene-coated boron nitride particles in which hexagonal boron nitride particles were coated with fullerene, resulted in high thermal conductivity and breakdown voltage, whereas Comparative Examples 1 and 2, in which hexagonal boron nitride particles were used as is without being coated with fullerene, resulted in low breakdown voltage.

[0090] Furthermore, the graph shown in FIG. 2 reveals that when the amount of fullerene added is in the range of 0.00001 mass % or more and 10 mass % or less relative to 100 mass % of hexagonal boron nitride particles, a high breakdown voltage can be maintained.

[0091] Therefore, it was confirmed that a resin sheet molded from a resin composition using the fullerene-coated boron nitride particles of this embodiment can achieve both high thermal conductivity and high breakdown voltage. [Explanation of symbols]

[0092] 10...Resin composition 11...Resin 12...Fullerene-coated boron nitride particles 13...Hexagonal boron nitride particles 14...Fullerene

Claims

1. hexagonal boron nitride particles; and fullerenes covering at least a portion of the surfaces of the hexagonal boron nitride particles, The fullerene-coated boron nitride particles have a mass ratio of the fullerene contained therein in the range of 0.001 mass % or more and 0.1 mass % or less relative to 100 mass % of the hexagonal boron nitride particles.

2. A resin composition comprising a resin and the fullerene-coated boron nitride particles according to claim 1.

3. The resin composition according to claim 2 , wherein the resin comprises an epoxy resin.

4. A resin sheet comprising the resin composition according to claim 2 or 3.

5. A semiconductor device comprising the resin composition according to claim 2 or 3 and a semiconductor element.

6. a dissolving step of dissolving fullerene in an organic solvent to prepare a fullerene solution; a mixing step of adding hexagonal boron nitride particles to the fullerene solution to form a dispersion, and subjecting the dispersion to a wet ball mill treatment; a solvent removal step of distilling off the solvent from the dispersion liquid after the ball mill treatment, The method for producing fullerene-coated boron nitride particles, wherein the fullerene added to the organic solvent is in the range of 0.001 mass % or more and 0.1 mass % or less with respect to 100 mass % of the hexagonal boron nitride particles.

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