Inorganic particles, inorganic particle manufacturing method, composition, and electronic device manufacturing method

Abstract

The present invention addresses the problem of providing inorganic particles with which superior fluidity is achieved in a composition obtained by combining said inorganic particles with a resin or a precursor thereof, superior thermal conductivity is achieved in a cured product obtained by curing said composition, and superior insulation reliability is achieved in said cured product. In addition, the present invention addresses the problem of providing an inorganic particle manufacturing method, a curable composition, and an electronic device manufacturing method. The inorganic particles according to the present invention each have a core part and a shell part and are spherical, wherein: the core part contains at least one substance selected from the group consisting of silicon dioxide, aluminum oxide, aluminum nitride, and copper; the shell part contains boron nitride; and the iron atom content of the shell part is equal to or less than 10 ppm by mass with respect to the total mass of the shell part.

Description

[Technical Field]

[0001] The present invention relates to inorganic particles, a method for producing inorganic particles, a composition, and a method for producing an electronic device. [Background technology]

[0002] In recent years, electronic devices such as personal computers and smartphones have rapidly become more functional and smaller. As a result, the amount of heat generated by integrated circuits (ICs) in electronic devices has increased, resulting in problems such as reduced IC durability and the risk of fire. ICs are protected by an encapsulant, which is made by curing a compound made by mixing resins such as epoxy resin and phenolic resin with fillers such as silicon dioxide (silica). However, the encapsulant's thermal conductivity is insufficient, resulting in insufficient heat dissipation. Therefore, the processing capacity of the IC is limited to reduce the amount of heat generated by the IC.

[0003] Fillers used in IC encapsulation must be both insulating and highly thermally conductive. Materials that combine these properties include aluminum oxide (alumina), aluminum nitride, silicon nitride, and boron nitride. Among these, boron nitride has particularly excellent thermal conductivity. Here, Patent Document 1 points out that because typical boron nitride is in the form of scaly particles, when it is mixed as a filler in a resin or the like and molded, orientation tends to occur, which can result in anisotropy in thermal conductivity. Therefore, in order to solve this problem, Patent Document 1 discloses the use of core-shell type inorganic particles, which are inorganic particles coated with boron nitride, as a filler. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 189794 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have studied a cured product formed from a composition in which the inorganic particles described in Patent Document 1 are used as a filler and kneaded with a resin or its precursor, and have found that in a humidity bias test simulating a usage environment, dielectric breakdown occurs in a short time, indicating insufficient insulation reliability. Hereinafter, suppression of dielectric breakdown in a humidity bias test is also referred to as excellent insulation reliability. Furthermore, in order to prevent components such as ICs from being destroyed during compression molding, the composition containing the filler and the resin or its precursor (particularly a sheet-shaped composition) is required to have excellent fluidity.

[0006] Therefore, an object of the present invention is to provide inorganic particles that, when combined with a resin or its precursor (particularly a thermosetting resin), result in a composition (particularly a sheet-like composition) that has excellent fluidity, and that, when cured, result in a cured product that has excellent thermal conductivity and that has excellent insulating reliability. Another object of the present invention is to provide a method for producing inorganic particles, a composition, and a method for producing an electronic device. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0008] [1] A spherical inorganic particle having a core and a shell, the core portion contains at least one selected from the group consisting of silicon dioxide, aluminum oxide, aluminum nitride, and copper, the shell portion comprises boron nitride; The inorganic particles have an iron atom content of 10 ppm by mass or less relative to the total mass of the shell. [2] The inorganic particles according to [1], wherein the shell has a thickness of 20 nm to 1 μm. [3] The inorganic particles according to [1] or [2], which satisfy the requirements 1 and 2 described below. [4] The inorganic particles according to [3], wherein the D value is 0.005 or less. [5] The inorganic particles according to [3] or [4], wherein the atomic ratio is 0.15 or more. [6] The inorganic particles according to any one of [3] to [5], wherein the atomic ratio is 0.25 or less. [7] The inorganic particles according to any one of [1] to [6], which have a median diameter of 300 μm or less. [8] The inorganic particles according to any one of [1] to [7], which have a median diameter of 100 μm or less. [9] Inorganic particles according to any one of [1] to [8], which have peaks in the range of 1.0 to 50 μm, the range of 100 to 150 μm, and the range of 200 to 300 μm in a particle size distribution curve representing a volume-based frequency distribution.

[10] The inorganic particles according to any one of [1] to [9], the surface of which is modified with a metal coupling agent.

[11] A method for producing inorganic particles according to any one of [1] to

[10] , A method for producing inorganic particles, comprising the step of forming the shell portion by a vapor deposition method or a sputtering method.

[12] A composition comprising the inorganic particles according to any one of [1] to

[10] and a resin or a precursor thereof.

[13] The composition according to

[12] , wherein the resin or its precursor is a thermosetting compound.

[14] The composition according to

[12] or

[13] , wherein the content of the inorganic particles is 45 to 60% by volume based on the total solid content of the composition.

[15] The composition according to any one of

[12] to

[14] , which is in the form of a sheet.

[16] A method for producing an electronic device, comprising a step of encapsulating a semiconductor member by a compression molding method using the composition according to

[15] . [Effects of the Invention]

[0009] According to the present invention, inorganic particles can be provided which, when combined with a resin or a precursor thereof, result in a composition (particularly a sheet-shaped composition) having excellent fluidity, and which, when cured, result in a cured product having excellent thermal conductivity and excellent insulating reliability. Furthermore, the present invention can provide a method for producing inorganic particles, a composition, and a method for producing an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

[0011] The following describes the meaning of each description in this specification. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, "ppm" is an abbreviation for "parts per million" and is -6 means. In this specification, when two or more types of a component are present, the "content" of that component means the total content of those two or more components.

[0012] The inorganic particles of the present invention are spherical inorganic particles having a core portion and a shell portion, wherein the core portion contains at least one selected from the group consisting of silicon dioxide, aluminum oxide, aluminum nitride, and copper, the shell portion contains boron nitride, and the content of iron atoms contained in the shell portion is 10 mass ppm or less relative to the total mass of the shell portion.

[0013] The mechanism by which the problems of the present invention are solved by using the inorganic particles of the present invention is not entirely clear, but the present inventors speculate as follows. The inorganic particles of the present invention are spherical, which allows the composition obtained by combining the inorganic particles with a resin or its precursor (particularly a sheet-like composition) to have excellent fluidity. Furthermore, the inorganic particles of the present invention have boron nitride, which has excellent thermal conductivity, in the shell, which allows the cured product obtained by curing the composition to have excellent thermal conductivity. Furthermore, the content of iron atoms in the shell of the inorganic particles of the present invention is 10 ppm by mass relative to the total mass of the shell, which allows the cured product to have excellent insulation reliability. Hereinafter, the term "excellent effects of the present invention" refers to the satisfaction of one or more of the following: the fluidity of a composition (particularly a sheet-shaped composition) obtained by combining the inorganic particles of the present invention with a resin or its precursor is superior; the thermal conductivity of a cured product obtained by curing the composition is superior; and the insulating reliability of the cured product is superior. The requirements that the inorganic particles of the present invention must satisfy and the preferred requirements will be described in detail below.

[0014] <Shape and particle size of inorganic particles> The inorganic particles of the present invention (hereinafter also simply referred to as "inorganic particles") are spherical. The term "spherical inorganic particles" means that the inorganic particles have an aspect ratio (ratio of the major axis to the minor axis) of 1.00 to 1.10, and the aspect ratio is preferably 1.00 to 1.08. The aspect ratio of inorganic particles can be measured by observation using a transmission electron microscope or a scanning electron microscope. First, when observing an inorganic particle using the above method, the distance between two parallel lines circumscribing the inorganic particle, selected so that the distance between the two parallel lines is the longest, is taken as the "major axis." Furthermore, the distance between two parallel lines circumscribing the inorganic particle that are perpendicular to the two parallel lines that give the "major axis" and selected so that the distance between the two parallel lines is the shortest is taken as the "minor axis." The aspect ratio (major axis / minor axis) of the inorganic particle is calculated from the obtained major axis and minor axis. The aspect ratio of the inorganic particles is calculated for at least 100 inorganic particles, and the obtained aspect ratios are arithmetically averaged to obtain the aspect ratio of the inorganic particles. In this specification, the aspect ratio of inorganic particles can be measured using a scanning electron microscope "SU3900" manufactured by Hitachi High-Tech Science Corporation.

[0015] The median diameter of the inorganic particles is not particularly limited, but is preferably 300 μm or less, more preferably 100 μm or less, and even more preferably 10 μm or less, in terms of providing superior effects of the present invention. The lower limit of the median diameter is not particularly limited, but is preferably 500 nm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more, in terms of providing superior effects of the present invention. In this specification, the median diameter (D50) of inorganic particles can be measured using a "Mastersizer 3000" manufactured by Malvern Instruments.

[0016] In order to achieve the effects of the present invention more effectively, the inorganic particles preferably have peaks in the ranges of 1.0 to 50 μm, 100 to 150 μm, and 200 to 300 μm in a particle size distribution curve representing a volume-based frequency distribution. When particles of multiple sizes are mixed in this way, the inorganic particles tend to be densely packed in the composition, and the effects of the present invention (particularly thermal conductivity) are more excellent. The content of inorganic particles having a particle diameter of 1.0 to 50 μm relative to the total volume of inorganic particles is preferably 25 to 45 volume %, the content of inorganic particles having a particle diameter of 100 to 150 μm relative to the total volume of inorganic particles is preferably 25 to 45 volume %, and the content of inorganic particles having a particle diameter of 200 to 300 μm relative to the total volume of inorganic particles is preferably 15 to 35 volume %. Inorganic particles having peaks in the above ranges can be obtained by mixing particles having median diameters at the respective peak positions. Specifically, inorganic particles having peaks in the above ranges can be obtained by mixing particles having a median diameter in the range of 1.0 to 50 μm, particles having a median diameter in the range of 100 to 150 μm, and particles having a median diameter in the range of 200 to 300 μm.

[0017] <Core and shell of inorganic particles> The inorganic particles have a core portion and a shell portion. The shell portion is disposed around the core portion so as to cover the core portion. The shell portion may be disposed so as to cover at least a portion of the core portion, or may be disposed so as to cover the entire surface of the core portion.

[0018] (Core part) The core portion contains at least one material (hereinafter also referred to as the specific material) selected from the group consisting of silicon dioxide, aluminum oxide, aluminum nitride, and copper. Among these, the specific material is preferably aluminum oxide, aluminum nitride, or copper, and more preferably aluminum nitride or copper, in terms of achieving a more excellent effect of the present invention. The core preferably contains the above-mentioned specific material as a main component, which means that the content of the specific material is 50% by mass or more based on the total mass of the core. In particular, the content of the specific material is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 99 to 100% by mass, based on the total mass of the core portion, in terms of achieving better effects of the present invention. The core may contain materials other than the specific materials described above as long as the effects of the present invention are not impaired, but the core does not contain boron nitride.

[0019] The core may contain only one of the above specific materials, or may contain two or more of them.

[0020] The core is preferably spherical in shape. The core being spherical means that the aspect ratio of the core (ratio of the major axis to the minor axis) is 1.00 to 1.10, and the aspect ratio is preferably 1.00 to 1.08. As a method for measuring the aspect ratio of the core portion, as will be described later, when a shell portion is formed around a core particle constituting the core portion by a vapor deposition method during the production of inorganic particles, the aspect ratio can be calculated by measuring the major axis and minor axis of the core particle using the core particle as a raw material in the same manner as the aspect ratio of the inorganic particle described above. Alternatively, only the shell portion of the inorganic particle may be dissolved, and the aspect ratio may be calculated using only the obtained core portion in the same manner as the aspect ratio of the inorganic particle described above.

[0021] (shell part) The shell portion includes boron nitride. When the shell contains boron nitride, the cured product obtained by curing the composition containing the inorganic particles has excellent thermal conductivity. The shell preferably contains the above-mentioned boron nitride as a main component, which means that the content of boron nitride is 50 mass % or more relative to the total mass of the shell. In particular, the content of boron nitride is preferably 60 to 100 mass %, more preferably 80 to 100 mass %, and even more preferably 99 to 100 mass %, relative to the total mass of the shell portion, in that the effects of the present invention are more excellent. The crystal structure of boron nitride is preferably hexagonal from the viewpoint of thermal conductivity.

[0022] The content of iron atoms in the shell is 10 ppm by mass or less relative to the total mass of the shell, and is preferably 5 ppm by mass or less in order to provide a cured product with better insulation reliability. The lower limit is not particularly limited, but may be 0 ppm by mass. By setting the content of iron atoms within the above range, the insulating reliability of the cured product is excellent.

[0023] The content of iron atoms contained in the shell can be measured using a gas chromatograph-mass spectrometer (GC-MS). Specifically, the inorganic particles to be measured are dissolved in hydrofluoric acid, and the iron atom content in the resulting solution is analyzed using a gas chromatograph-mass spectrometer (GC-MS). More specifically, as described below, when forming a shell portion around a core particle that constitutes the core portion during inorganic particle manufacturing by a vapor deposition method, the inorganic particles and core particles are each dissolved in hydrofluoric acid, and each solution is measured using a GC-MS ("SCION SQ 400" manufactured by Hitachi High-Tech Science Corporation). In this case, the inorganic particles are measured using the measurement results of the core particles as a baseline, and the iron atom content in the shell portion is measured.

[0024] The shell portion may contain materials other than the above-mentioned boron nitride and iron atoms, as long as the effects of the present invention are not impaired.

[0025] The thickness of the shell portion is not particularly limited, and is preferably from 20 nm to 1 μm, more preferably from 40 to 500 nm, and even more preferably from 60 to 200 nm, in terms of achieving better effects of the present invention. The thickness of the shell portion can be determined, for example, by measuring the particle size distribution. Specifically, when forming a shell portion on a core particle in the production of inorganic particles, the thickness of the shell portion can be calculated by using a Malvern Instruments "Mastersizer 3000" to compare the median diameter of the core particle with the median diameter of the inorganic particle after the shell portion has been formed.

[0026] (Properties of inorganic particles) The inorganic particles of the present invention preferably satisfy requirements 1 and 2 in terms of achieving better effects of the present invention. Requirement 1: The atomic ratio of oxygen atoms to boron atoms on the surface of the inorganic particles is 0.12 or more, as determined by X-ray photoelectron spectroscopy. Requirement 2: The D value calculated by formula (1) is 0.010 or less. Formula (1): D=B(OH)3(002) / BN(002) B(OH)3(002): Peak intensity originating from (002) of boron hydroxide with triclinic space group measured by X-ray diffraction BN(002): Peak intensity originating from (002) of boron nitride with a hexagonal space group measured by X-ray diffraction Requirements 1 and 2 are described in more detail below.

[0027] It is presumed that by satisfying the above requirement 1, the wettability between the inorganic particles and the resin or its precursor contained in the composition can be improved. In particular, the atomic ratio is more preferably 0.15 or more, and even more preferably 0.20 or more, in terms of achieving better effects of the present invention. There is no particular upper limit, but the atomic ratio is preferably 0.50 or less, and more preferably 0.25 or less. The atomic ratio on the surface of the inorganic particle is measured as follows. The inorganic particles are measured using an X-ray photoelectron spectrometer (XPS) (Ulvac-PHI: Versa Probe II). Specific measurement conditions include using a monochromatic Al tube (tube voltage: 15 kV) as the X-ray source and an analysis area of ​​300 μm × 300 μm. The peak area values ​​of oxygen atoms and boron atoms obtained by the measurement are corrected by the sensitivity coefficients of each element, allowing the atomic ratio of oxygen atoms to boron atoms on the surface of the inorganic particles to be calculated. The peak area value for binding energies between 528 eV and 538 eV is used to calculate the oxygen atomic mass, and the peak area value for binding energies between 187 eV and 196 eV is used to calculate the boron atomic mass. The sensitivity coefficient for oxygen atoms is 0.733, and that for boron atoms is 0.171. The method for correcting the peak areas with the sensitivity coefficients is to divide the peak areas for oxygen atoms and boron atoms by their respective sensitivity coefficients.

[0028] By satisfying the above requirement 2, it is possible to prevent a decrease in the thermal conductivity of the inorganic particles. In particular, the D value is preferably 0.005 or less, as this provides a more excellent effect of the present invention. The lower limit is not particularly limited, but may be 0 or more. B(OH)3(002) and BN(002) in formula (1) can be determined by subjecting inorganic particles to X-ray diffraction measurement. B(OH)3(002): Peak intensity (2θ=25°-30°) derived from the (002) plane of boron hydroxide with a triclinic space group measured by X-ray diffraction. BN(002): Peak intensity (2θ=27.5°-28.5°) derived from the (002) plane of boron nitride with a hexagonal space group measured by X-ray diffraction The X-ray diffraction can be measured by a known method. The D value is calculated mainly from the peak intensity resulting from the shell portion containing boron nitride. Therefore, when calculating the peak intensity, it is desirable to eliminate the influence of the core portion. Specifically, as described below, when forming a shell portion around a core particle that constitutes the core portion by a vapor deposition method during production of inorganic particles, X-ray diffraction measurement is performed on the inorganic particles as well as the core particles, and the peak intensity resulting from the boron nitride contained in the shell portion can be calculated by subtracting the result of the X-ray diffraction measurement of the core particle from the result of the X-ray diffraction measurement of the inorganic particle.

[0029] In order to satisfy the above-mentioned requirements 1 and 2, the surfaces of the inorganic particles may be subjected to a surface treatment. The surface treatment method will be described in detail later.

[0030] The inorganic particles may be surface-modified with a metal coupling agent. By modifying the surface of the inorganic particles with a metal coupling agent, the wettability of the inorganic particle surface can be changed, and the dispersibility in the composition can be controlled. Examples of metal coupling agents include aluminate-based coupling agents, silane-based coupling agents, titanate-based coupling agents, and zirconate-based coupling agents, with silane-based coupling agents being preferred. Silane coupling agents have one or more alkoxy groups in their molecules that can bond with inorganic particles and one or more groups that easily bond with organic materials. Examples of alkoxy groups include linear and branched alkoxy groups. Examples of linear alkoxy groups include methoxy, ethoxy, and n-propoxy groups, and examples of branched alkoxy groups include isopropoxy and t-butoxy groups. From the perspective of reactivity, methoxy or ethoxy groups are preferred. The silane coupling agent may be a low molecular weight compound or a polymer compound. The method for modifying the surface of inorganic particles with a metal coupling agent is not particularly limited, and known methods can be used. For example, there is a method in which inorganic particles and a metal coupling agent are reacted in a solution containing an acid or a base and water to modify them, and a method in which a metal coupling agent is reacted in a solution containing an acid or a base and water to form an intermediate having a metal-OH group, and then the intermediate is brought into contact with the surface of inorganic particles to modify them.

[0031] <Method of manufacturing inorganic particles> The method for producing inorganic particles is not particularly limited as long as it can produce inorganic particles having the above-mentioned properties. In particular, in terms of excellent productivity, the method for producing inorganic particles preferably includes a step of forming the shell portion by vapor deposition or sputtering. By forming the shell portion by vapor deposition or sputtering, the content of impurities in the shell portion can be reduced, and as a result, the content of iron atoms can be reduced. Among these, the vapor deposition method is preferred in terms of excellent productivity. The process of forming the shell portion by vapor deposition will be described in detail below.

[0032] When forming a shell portion by vapor deposition using core particles that become the core portion of inorganic particles, the core particles only need to contain the specific material described above, and commercially available powders can be used. For example, the trade names include Sunsphere NP-30 (silicon dioxide, manufactured by AGC), Sumicorundum AA-5 (aluminum oxide, manufactured by Sumitomo Chemical), ANF-A-05-F (aluminum nitride, manufactured by MARUWA), and CP-2500 (copper, manufactured by Aintech).

[0033] The procedure for the vapor deposition method is not particularly limited, and any known method can be used. It is preferable to use a barrel-type chemical vapor deposition apparatus, as this facilitates the production of a uniform shell portion around a core portion. The barrel-type chemical vapor deposition apparatus includes a gas supply system, a vacuum exhaust system, a plasma generation system, and a rotatable barrel-type container. The gas supply system and vacuum exhaust system are connected to the rotatable barrel-type container, allowing gas to be supplied while controlling the degree of vacuum inside the container. A plasma generation system is also disposed inside the rotatable barrel-type container, allowing plasma to be generated inside the container and exciting the gas supplied inside the container. Furthermore, by rotating or rocking the barrel-type container, the particles contained in the barrel-type container can be fluidized. In the above-described device, a compound layer derived from the reaction gas can be formed on powder contained in a rotatable barrel-shaped container, and by rotating or rocking the barrel-shaped container, a compound layer derived from the reaction gas can be formed on the entire surface of the particles. Therefore, by storing the above-mentioned core particles in a barrel-shaped container and rotating or rocking them while supplying a reaction gas capable of forming a boron nitride layer, a shell layer containing boron nitride can be formed on the entire surface of the core particles.

[0034] The gas supply system may be connected to a plurality of gas supply sources and may further include a gas mixing mechanism. The gas supply sources may include a mechanism for vaporizing liquid and solid gas sources. The gas supply system is also preferably equipped with a means for controlling the gas flow rate. The vacuum exhaust system has a means for evacuating the chamber using a vacuum pump, such as a rotary pump, a diffusion pump, a diaphragm pump, or a turbomolecular pump, or a combination of two or more of these pumps. The plasma generation system has a high frequency power supply and a plasma generation electrode disposed in a rotatable barrel-shaped container, and generates plasma in the container. The rotatable barrel-type container is equipped with the gas supply system, vacuum exhaust system, and plasma generation system. The rotatable barrel-type container can accommodate powder therein, and the powder inside can be fluidized by rotating or rocking the container. The container may also be equipped with a heating mechanism. Furthermore, the container is preferably equipped with a means for monitoring the degree of vacuum inside the container. As the barrel-type chemical vapor deposition apparatus, for example, the apparatus described in Japanese Patent Application Laid-Open No. 2005-036275 can be used.

[0035] The reactive gas is preferably a gas containing boron in its molecules. Examples include borane (BH3), diborane (B2H6), and ammonia borane (NH3BH3). The reactive gas may contain other reactive gases and carrier gases in addition to the gas containing boron in its molecules. Examples of other reactive gases include N2 gas, O2 gas, silane (SiH4) gas, methane gas, and metal carbonyl compound gases. Examples of carrier gases include He gas, Ne gas, Ar gas, Kr gas, N2 gas, and H2 gas. Some gases can function as both a reactive gas and a carrier gas. The carrier gas may be a mixture of the above gases. Among these, ammonia borane is preferred as a gas containing boron in its molecules, and a mixed gas of Ar gas and H2 gas is preferred as a carrier gas. When a mixed gas of Ar gas and H2 gas is used as a carrier gas, the content of H2 gas relative to the total volume of Ar gas and H2 gas is preferably 1 to 5 volume %. Furthermore, ammonia borane is a solid at room temperature and normal pressure, and must be gasified in order to be used as a reaction gas. There are no particular limitations on the method for gasifying ammonia borane, but one example is a method in which a gas generation chamber is provided between a gas supply system capable of supplying a carrier gas and a rotatable barrel-type container, and a boat containing ammonia borane is placed in the gas generation chamber. In this case, a mixed gas of carrier gas and ammonia borane gas is supplied into the rotatable barrel-type container.

[0036] The vacuum level inside the barrel-shaped container is 1 x 10 -6 It is preferable to keep the pressure at 10 Pa to 10 Pa. The flow rate of the carrier gas is preferably 1 to 50 mL / min. The output of the high frequency power source in the plasma generation system is preferably 500 to 2000W. The rotation speed of the barrel-type container is preferably 1 to 10 rpm. The conditions for forming the shell portion can be found in JP 2019-040974 A.

[0037] (Surface treatment method for inorganic particles) The surfaces of the inorganic particles may be subjected to a predetermined treatment to adjust various properties. One method for adjusting the D value to a preferred range is plasma treatment. The plasma treatment may be carried out under atmospheric pressure or under reduced pressure (preferably 500 Pa or less, more preferably 0 to 100 Pa).

[0038] In the plasma treatment, gases to be turned into a plasma state include O2 gas, Ar gas, N2 gas, H2 gas, He gas, and mixed gases containing one or more of these. The above gases preferably contain at least O2 gas, more preferably 60 to 100% by volume of the above gas is O2 gas, even more preferably 90 to 100% by volume of the above gas is O2 gas, and particularly preferably substantially O2 gas alone. That is, the plasma treatment is preferably an oxygen plasma treatment.

[0039] The output power in the plasma treatment is preferably 50 to 1000 W, more preferably 70 to 500 W, in order to control the amount of boron hydroxide produced, whether the treatment is carried out under atmospheric pressure or under reduced pressure.

[0040] When the plasma treatment is carried out under atmospheric pressure, the time for the plasma treatment is preferably 0.2 to 30 hours, more preferably 4 to 8 hours. When the plasma treatment is carried out under reduced pressure, the time for the plasma treatment is preferably 0.2 to 10 hours, more preferably 0.2 to 3 hours. The plasma treatment may be carried out continuously or intermittently. When the plasma treatment is carried out intermittently, the total treatment time is preferably within the above range.

[0041] The treatment temperature when performing the plasma treatment is preferably 0 to 200°C, more preferably 15 to 100°C.

[0042] <Composition> The present invention also relates to a composition (hereinafter, also simply referred to as "composition"). As will be described later, the composition may contain a curable compound such as a thermosetting compound, and the composition may be a so-called curable composition.

[0043] The composition includes the inorganic particles described above. The content of the inorganic particles in the composition is not particularly limited, and is preferably 30 to 70% by volume, more preferably 45 to 60% by volume, and even more preferably 50 to 60% by volume, based on the total solid content of the composition. The inorganic particles may be used alone or in combination of two or more kinds. The total solid content refers to the components that form the cured product, but does not include the solvent. The components that form the cured product are considered to be solids even if they are in liquid form.

[0044] (Resin or its precursor) The composition preferably contains a resin or a precursor thereof, which will hereinafter be collectively referred to as a "binder component." The binder component may be a resin itself or a precursor of a resin.

[0045] The resin precursor is a component that polymerizes and / or crosslinks under predetermined conditions to form a resin (polymer and / or crosslinked product) during the process of forming a cured product from the composition. The resin thus formed functions as a binder (binding agent) in the cured product. Examples of resin precursors include curable compounds (for example, thermosetting compounds).

[0046] Examples of the resin include epoxy resin, silicone resin, phenol resin, polyimide resin, polyester resin, bismaleimide resin, melamine resin, phenoxy resin, and isocyanate resin (polyurethane resin, polyurea resin, polyurethane urea resin, etc.).

[0047] Among these, the resin or its precursor is preferably a thermosetting compound, and at least one selected from the group consisting of an epoxy compound and a phenol compound is preferred.

[0048] (epoxy compounds) An epoxy compound is a compound having at least one epoxy group (oxiranyl group) in one molecule. The epoxy resin can be formed by polymerizing an epoxy compound alone or an epoxy compound with other compounds (active hydrogen group-containing compounds such as phenol compounds and amine compounds, and / or acid anhydrides, etc.).

[0049] The epoxy group is a group obtained by removing one or more hydrogen atoms (preferably one hydrogen atom) from an oxirane ring. If possible, the epoxy group may further have a substituent (such as a linear or branched alkyl group having 1 to 5 carbon atoms).

[0050] The number of epoxy groups that the epoxy compound has is preferably 2 or more, more preferably 2 to 40, even more preferably 2 to 10, and particularly preferably 2, in one molecule. The molecular weight of the epoxy compound is preferably 150 to 10,000, more preferably 150 to 1,000, and even more preferably 200 to 290.

[0051] The epoxy group content of the epoxy compound is preferably from 2.0 to 20.0 mmol / g, more preferably from 5.0 to 15.0 mmol / g, and even more preferably from 6.0 to 14.0 mmol / g. The epoxy group content refers to the number of epoxy groups contained in 1 g of the epoxy compound. The epoxy compound also preferably has an aromatic ring group (preferably an aromatic hydrocarbon ring group).

[0052] The epoxy compound may or may not exhibit liquid crystallinity. That is, the epoxy compound may be a liquid crystal compound, or in other words, a liquid crystal compound having an epoxy group. The epoxy compounds may be used alone or in combination of two or more.

[0053] (active hydrogen group-containing compound) The epoxy resin is preferably formed by reacting an epoxy compound with an active hydrogen group-containing compound. The active hydrogen group-containing compound is a compound that has one or more (preferably two or more, more preferably 2 to 10) groups having active hydrogen (active hydrogen groups). Examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a mercapto group, with a hydroxyl group being preferred. The active hydrogen group-containing compound is preferably a polyol having two or more (preferably three or more, more preferably three to six) hydroxyl groups.

[0054] Among these, the active hydrogen group-containing compound used in combination with the epoxy compound is preferably a phenol compound. That is, the composition of the present invention preferably contains an epoxy compound and a phenol compound. The phenol compound is a compound having one or more (preferably two or more, more preferably three or more, and even more preferably three to six) phenolic hydroxyl groups.

[0055] The lower limit of the hydroxyl group content of the phenol compound is preferably 3.0 mmol / g or more, more preferably 7.0 mmol / g or more, and the upper limit is preferably 25.0 mmol / g or less, more preferably 20.0 mmol / g or less. The hydroxyl group content refers to the number of hydroxyl groups (preferably phenolic hydroxyl groups) that 1 g of the phenol compound has.

[0056] The upper limit of the molecular weight of the phenol compound is preferably 600 or less, more preferably 500 or less, even more preferably 450 or less, and particularly preferably 400 or less. The lower limit is preferably 110 or more, more preferably 300 or more. The phenol compounds may be used alone or in combination of two or more.

[0057] The content of the resin or its precursor in the composition is not particularly limited, and is preferably 30 to 70% by volume, more preferably 40 to 55% by volume, and even more preferably 40 to 50% by volume, based on the total solid content of the composition. The resin or its precursor may be used alone or in combination of two or more.

[0058] (Other ingredients) The composition may contain other ingredients in addition to the above ingredients. Examples of other components include a curing accelerator, a solvent, a polymerization initiator, a surface modifier, and a dispersant. Examples of the curing accelerator include tris-orthotolylphosphine, triphenylphosphine, boron trifluoride amine complex, and the compounds described in paragraph 0052 of JP-A No. 2012-067225. Solvents include water and organic solvents.

[0059] <Production method and molding method of composition> The method for producing the composition is not particularly limited, and any known method can be used. For example, the composition can be produced by mixing the various components described above. When mixing, the various components may be mixed all at once or sequentially. The method for mixing the components is not particularly limited, and known methods can be used. The mixing device used for mixing is preferably a submerged disperser, and examples include agitators such as a planetary centrifugal mixer and a high-speed rotary shear agitator, a colloid mill, a roll mill, a high-pressure injection type disperser, an ultrasonic disperser, a bead mill, and a homogenizer. One type of mixing device may be used alone, or two or more types may be used. Degassing treatment may be performed before, after, and / or simultaneously with mixing.

[0060] The composition can be molded into a shape suitable for the intended purpose. The shape and molding method are not particularly limited, and known shapes and methods can be used. The composition is preferably in the form of a sheet. A known method can be used to form the composition into a sheet. The composition may be formed into a sheet on a substrate, or may be formed into a sheet in a state sandwiched between two substrates. When the composition is in the form of a sheet, it is preferable that the content of the solvent in the sheet-like composition is small. Specifically, the content of the solvent is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total mass of the sheet-like composition (composition sheet). There is no particular restriction on the lower limit, but 0% by mass is an example.

[0061] <Method for curing the composition> As described above, the composition of the present invention is preferably a curable composition, and the composition of the present invention can be cured to obtain a thermally conductive material. The method for curing the composition is not particularly limited, but a thermal curing reaction is preferred. The heating temperature during the thermosetting reaction is not particularly limited and may be appropriately selected within the range of, for example, 50 to 250° C. Furthermore, when carrying out the thermosetting reaction, heat treatments at different temperatures may be carried out multiple times. The curing treatment is preferably carried out on the composition in the form of a sheet.

[0062] The curing treatment may be completed when the composition is in a semi-cured state, or after the composition is in a semi-cured state, further curing treatment may be carried out to complete the curing. The curing treatment for bringing the composition into a semi-cured state (also referred to as "semi-curing treatment") and the curing treatment for complete curing (also referred to as "main curing treatment") may be carried out in separate steps. The curing treatment may be carried out while the composition is being pressed. In particular, it is preferable to carry out the curing treatment while the composition is being pressed in the form of a sheet.

[0063] <Uses of the composition> The cured film obtained by curing the composition of the present invention can be used as an encapsulant for semiconductor members of electronic devices. More specifically, the composition of the present invention can be formed into a sheet, placed on a semiconductor member, and shaped by a compression molding method, whereby the composition can be used as an encapsulant with excellent thermal conductivity. The composition of the present invention provides a coating film with excellent fluidity, and therefore can be molded by compression molding without destroying the semiconductor member, other parts on the substrate, or the substrate.

[0064] The composition of the present invention may be used in combination with other components. For example, a sheet-form composition may be combined with a sheet-form support. Examples of the sheet-like support include a plastic film, a metal film, or a glass plate. Examples of the plastic film material include polyesters such as polyethylene terephthalate (PET), polycarbonate, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones. Examples of the metal film include copper films.

[0065] <Thermal conductive materials> A cured product obtained using the above-described composition functions as a heat conductive material. The shape of the thermally conductive material is not particularly limited, and it can be molded into various shapes depending on the application. A typical shape of the molded thermally conductive material is, for example, a sheet shape. The thermally conductive material is preferably insulating (electrically insulating). For example, the volume resistivity of a thermal conductive material at 23°C and 65% relative humidity is 10 10 Ω·cm or more is preferable, and 10 12 Ω·cm or more is preferable, and 10 14 The upper limit is not particularly limited, but it is usually 10 18 Ω·cm or less. [Example]

[0066] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, 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 should not be construed as being limited by the examples shown below.

[0067] <Production of inorganic particles and curable composition> The methods for producing the inorganic particles and curable compositions used in Examples 1 to 15 and Comparative Examples 1 to 4 will be described below. The median diameters shown below were measured using a Malvern "Mastersizer 3000."

[0068] Example 1 Using a barrel-type chemical vapor deposition apparatus, a boron nitride shell was formed by vapor deposition on core particles of "Sunsphere NP-30" (silicon dioxide, median diameter: 4.3 μm, manufactured by AGC Corporation), to produce inorganic particles 1. The thickness of the shell of inorganic particles 1 was 100 nm. The barrel-type chemical vapor deposition apparatus used was the apparatus described in Japanese Patent Application Laid-Open No. 2005-036275. The conditions for forming the shell portion were as follows. Vacuum degree: 1×10 -6 Pa Gas species: ammonia borane

[0069] Next, the following epoxy compound A and the following phenol compound B were mixed so that the molar amounts of the epoxy groups in A and the hydroxyl groups in B were equal, to obtain a curable liquid. A solvent (cyclopentanone), a dispersant (BYK's "DISPERBYK-106"), and a curing accelerator (triphenylphosphine) were mixed with the curable liquid in this order to obtain a mixture. To this mixture, inorganic particles 1 produced by the method described above were added so that the volume ratio of the cured product (components other than the solvent) to inorganic particles 1 in the mixture was as shown in the table below. The mixture with inorganic particles 1 added was treated for 5 minutes in a planetary centrifugal mixer (THINKY's Awatori Rentaro ARE-310) to obtain curable composition 1. The amount of solvent added was such that the solid content of the composition became 75% by mass. The content of the dispersant in the curable composition 1 was 0.2 mass % relative to the content of the inorganic particles. The content of the curing accelerator in the curable composition was 1 mass % relative to the content of the epoxy compound.

[0070] [ka] JPEG0007766081000002.jpg3780

[0071] Example 2 Inorganic particles 2 were produced in the same manner as in Example 1, except that "Sumicorundum AA-5" (aluminum oxide, median diameter: 5.1 μm, manufactured by Sumitomo Chemical Co., Ltd.) was used as the core particles and the deposition conditions were changed so that the shell thickness would be as shown in Table 1. Next, a curable composition 2 was produced in the same manner as in Example 1, except that inorganic particles 2 were used instead of inorganic particles 1.

[0072] Example 3 Inorganic particles 3 were produced in the same manner as in Example 1, except that "ANF-A-05-F" (aluminum nitride, median diameter: 6.4 μm, manufactured by MARUWA) was used as the core particles and the deposition conditions were changed so that the shell thickness would be as shown in Table 1. Next, a curable composition 3 was produced in the same manner as in Example 1, except that inorganic particles 3 were used instead of inorganic particles 1.

[0073] Example 4 Inorganic particles 4 were produced in the same manner as in Example 1, except that "CP-2500" (copper, median diameter: 2.5 μm, manufactured by Aintech) was used as the core particles and the deposition conditions were changed so that the shell thickness would be as shown in Table 1. Next, a curable composition 4 was produced in the same manner as in Example 1, except that inorganic particles 4 were used instead of inorganic particles 1.

[0074] Example 5 Inorganic particles 1 produced in Example 1 were subjected to a vacuum plasma treatment to obtain inorganic particles 5. The vacuum plasma treatment was carried out on inorganic particles 1 (15 g) using a Plasma Cleaner PDC210 manufactured by Yamato Scientific Co., Ltd. The inorganic particles to be treated were stirred every 5 minutes of vacuum plasma treatment, and the vacuum plasma treatment was continued for a total treatment time of 45 minutes. Next, a curable composition 5 was produced in the same manner as in Example 1, except that inorganic particles 5 were used instead of inorganic particles 1.

[0075] (Examples 6 to 8) Inorganic particles 6 to 8 were produced in the same manner as in Example 5, except that inorganic particles 2 to 4 were used instead of inorganic particles 1, respectively. Next, curable compositions 6 to 8 were produced in the same manner as in Example 1, except that inorganic particles 6 to 8 were used instead of inorganic particles 1, respectively.

[0076] Example 9 The inorganic particles 5 produced in Example 5 were further modified with a metal coupling agent to obtain inorganic particles 9. The modification treatment was carried out by stirring the inorganic particles 5 in acetonitrile (100 ml) and adding a hydrolysis adjustment solution (1.25 g) of a silane coupling agent "X12-984S" (manufactured by Shin-Etsu Chemical Co., Ltd.) to the acetonitrile. The acetonitrile was stirred at room temperature for 3 hours to carry out the modification treatment. After the treatment, the inorganic particles in the acetonitrile were filtered, washed with acetonitrile (100 ml), and dried in an oven at 40° C. to obtain inorganic particles 9. The hydrolysis adjustment solution of the silane coupling agent was prepared by mixing the silane coupling agent (1 g), ethanol (500 μl), 2-propanol (500 μl), water (720 μl), and acetic acid (100 μl) and stirring for 1 hour. Next, a curable composition 9 was produced in the same manner as in Example 1, except that inorganic particles 9 were used instead of inorganic particles 1.

[0077] Example 10 Inorganic particles 10 were produced in the same manner as in Example 9, except that inorganic particles 6 were used instead of inorganic particles 5. Next, a curable composition 10 was produced in the same manner as in Example 1, except that inorganic particles 10 were used instead of inorganic particles 1.

[0078] (Examples 11 to 12) Curable compositions 11 and 12 were produced in the same manner as in Example 10, except that the content of inorganic particles 10 was adjusted as shown in Table 1 below.

[0079] Example 13 Inorganic particles 13A-1 were produced in the same manner as in Example 1, except that "spherical alumina powder" (aluminum oxide, median diameter: 122 μm, manufactured by Air Brown) was used as the core particles and the deposition conditions were changed so that the shell thickness would be as shown in Table 1. Inorganic particles 13A-2 were produced in the same manner as in Example 5, except that inorganic particles 13A-1 were used instead of inorganic particles 1. Inorganic particles 13A-3 were produced in the same manner as in Example 9, except that inorganic particles 13A-2 were used instead of inorganic particles 5. Inorganic particles 13B-1 were produced in the same manner as in Example 1, except that "high-purity alumina beads TB" (aluminum oxide, median diameter: 250 μm, manufactured by Taimei Chemical Industry Co., Ltd.) were used as core particles and the deposition conditions were changed so that the shell thickness would be as shown in Table 1. Inorganic particles 13B-2 were produced in the same manner as in Example 5, except that inorganic particles 13B-1 were used instead of inorganic particles 1. Inorganic particles 13B-3 were produced in the same manner as in Example 9, except that inorganic particles 13B-2 were used instead of inorganic particles 5. Next, curable composition 13 was produced in the same manner as in Example 1, except that inorganic particles 10, inorganic particles 13A-3, and inorganic particles 13B-3 were used instead of inorganic particles 1, and the contents of these inorganic particles were adjusted as shown in Table 1 below.

[0080] Example 14 Inorganic particles 14 were produced in the same manner as in Example 9, except that inorganic particles 7 were used instead of inorganic particles 5. Next, a curable composition 10 was produced in the same manner as in Example 1, except that inorganic particles 14 were used instead of inorganic particles 1.

[0081] Example 15 Inorganic particles 15 were produced in the same manner as in Example 9, except that inorganic particles 8 were used instead of inorganic particles 5. Next, a curable composition 10 was produced in the same manner as in Example 1, except that inorganic particles 15 were used instead of inorganic particles 1.

[0082] (Comparative Example 1) A curable composition C1 was produced in the same manner as in Example 1, except that "Sunsphere NP-30" (silicon dioxide, median diameter: 4.3 μm, manufactured by AGC) was used instead of the inorganic particles 1.

[0083] (Comparative Example 2) A curable composition C2 was produced in the same manner as in Example 1, except that "Sumicorundum AA-5" (aluminum oxide, median diameter: 5.1 μm, manufactured by Sumitomo Chemical Co., Ltd.) was used instead of the inorganic particles 1.

[0084] (Comparative Example 3) A curable composition C3 was produced in the same manner as in Example 1, except that "Denka Boron Nitride SP-2" (boron nitride, median diameter: 4.0 μm, manufactured by Denka Corporation) was used instead of the inorganic particles 1.

[0085] Comparative Example 4 Curable composition C4 was produced in the same manner as in Example 1, except that "Sunsphere NP-30" and the above-mentioned "Denka Boron Nitride SP-2" were used in the amounts shown in Table 1 instead of inorganic particles 1.

[0086] <Evaluation> The evaluation methods and evaluation criteria for each item of the inorganic particles and curable compositions produced in the Examples and Comparative Examples are shown below.

[0087] (Median diameter of inorganic particles) The median diameter of the inorganic particles was measured using a "Mastersizer 3000" manufactured by Malvern Instruments.

[0088] (Shell thickness) The shell thickness was calculated using Malvern Instruments' Mastersizer 3000 by subtracting the median diameter of the core particles from the median diameter of the inorganic particles after the shell was formed, and dividing the resulting value by 2.

[0089] (Aspect ratio of inorganic particles) The aspect ratio of the inorganic particles used in each of the examples and comparative examples was calculated by the method described above.

[0090] (Atomic ratio of oxygen atoms to boron atoms) The oxygen atom concentration and boron atom concentration (both in atomic %) on the surface of the inorganic particles were measured using an X-ray photoelectron spectrometer (Versa Probe II manufactured by Ulvac-PHI) under the conditions described above in the specification. From the obtained results, the atomic ratio of oxygen atoms to boron atoms (oxygen atoms / boron atoms) on the inorganic particle surface was calculated. The atomic ratio of the inorganic particles used in Examples 9 to 15 was measured before treatment with the metal coupling agent.

[0091] (D value) The inorganic particles were subjected to X-ray diffraction measurement, and the D value was calculated by the following formula (1). Formula (1): D=B(OH)3(002) / BN(002) B(OH)3(002): Peak intensity (2θ=25°-30°) derived from the (002) plane of boron hydroxide with a triclinic space group measured by X-ray diffraction. BN(002): Peak intensity (2θ=27.5°-28.5°) derived from the (002) plane of boron nitride with a hexagonal space group measured by X-ray diffraction X-ray diffraction measurements were performed using an XRD7000 (manufactured by Shimadzu Corporation). X-ray diffraction measurements of inorganic particles were performed by filling the inorganic particles into a glass holder for powder measurements. Note that B(OH)3(002) and BN(002) were determined by first obtaining an X-ray diffraction chart of the core particles only, then obtaining an X-ray diffraction chart of the inorganic particles, and then subtracting the X-ray diffraction chart of the core particles only from the X-ray diffraction chart of the inorganic particles. The D values ​​of the inorganic particles used in Examples 9 to 15 were measured before treatment with the metal coupling agent.

[0092] (Iron atom content in the shell) The iron atom content in the shell of the inorganic particle was calculated by the above-mentioned method and evaluated according to the following criteria.

[0093] -Evaluation criteria for iron atom content- More than 1:100 mass ppm 2: More than 10 mass ppm but less than 100 mass ppm 3: More than 5 mass ppm but less than 10 mass ppm 4:5 mass ppm or less

[0094] (thermal conductivity) Using an applicator, the prepared curable composition of each Example or Comparative Example was uniformly applied onto the release surface of a release-treated PET film (PET756501, manufactured by Lintec Corporation, film thickness 75 μm), and left to stand at 120°C for 5 minutes to obtain a coating film. Two such coated PET films were prepared, and the two coated PET films were bonded together with the coating surfaces facing each other. A semi-cured film was obtained by heat pressing in air (heat plate temperature 120°C, pressure 20 MPa, 1 minute). The resulting semi-cured film was then heat pressed in air (heat plate temperature 180°C, pressure 20 MPa, 10 minutes, then further treated at 180°C for 90 minutes under normal pressure) to cure the coating and obtain a resin sheet. The PET films on both sides of the resin sheet were peeled off to obtain a thermally conductive sheet with an average thickness of 200 μm.

[0095] The thermal conductivity of each thermally conductive sheet obtained using each composition was evaluated. The thermal conductivity was measured by the following method, and the thermal conductivity was evaluated according to the following criteria. In practical terms, a rating of 2 to 4 is preferable.

[0096] -Measurement of thermal conductivity (W / m·k)- (1) The thermal diffusivity of the thermal conductive sheet in the thickness direction was measured using the laser flash method using the NETZSCH LFA467. (2) Using a Mettler-Toledo balance "XS204," the specific gravity of the thermal conductive sheet was measured using the Archimedes method ("Solid Specific Gravity Measurement Kit"). (3) Using a Seiko Instruments DSC320 / 6200, the specific heat of the thermally conductive sheet at 25°C was measured under a temperature increase rate of 10°C / min. (4) The thermal conductivity of the thermal conductive sheet was calculated by multiplying the obtained thermal diffusivity by the specific gravity and specific heat.

[0097] -Evaluation criteria for thermal conductivity- 1: Less than 1.0W / (K·cm) 2: 1.0W / (K·cm) or more and less than 3.0W / (K·cm) 3: 3.0W / (K·cm) or more and less than 5.0W / (K·cm) 4:5.0W / (K cm) or more

[0098] (Liquidity) Using an applicator, the prepared curable composition of each Example or Comparative Example was uniformly applied onto the release surface of a release-treated PET film (PET756501, manufactured by Lintec Corporation, film thickness 75 μm), and left to stand at 120°C for 5 minutes to obtain a coating film (thickness: 200 μm). The PET film was peeled off from the resulting coating film, and a 5 cm square coating film test piece was cut out. This test piece was sandwiched between the release surfaces of the PET film and subjected to heat pressing in air (hot plate temperature 175°C, pressure 6 MPa for 5 minutes). The length of extension of the test piece in all directions was measured by comparing the size of the test piece before and after pressing, and the flowability was evaluated by averaging the lengths of extension. The extension length was measured as the maximum length in the direction perpendicular to the direction of extension of each side of the test piece before pressing. The evaluation criteria for fluidity are shown below. In practical terms, a rating of 3 to 5 is preferred.

[0099] -Liquidity evaluation criteria- 1: Less than 0.5cm 2: 0.5cm or more but less than 1.0cm 3: 1.0cm or more and less than 1.5cm 4: 1.5cm or more and less than 2.0cm 5: 2.0cm or more

[0100] (Insulation reliability) A semi-cured film was obtained in the same manner as in the thermal conductivity evaluation. The semi-cured film was peeled off from the PET film, clamped between copper electrodes with a diameter of 2.0 cm, and heat-pressed in air (heat plate temperature 180°C, pressure 20 MPa for 10 minutes, then further treated at 180°C for 90 minutes under normal pressure) to cure the coating, and a test specimen was obtained. The electrodes of a DC power supply (AEM, manufactured by Espec Corp.) were connected to each electrode of the test specimen, and the specimen was placed in a thermo-hygrostat (PL, manufactured by Espec Corp.) The temperature and humidity of the thermo-hygrostat were maintained at 85°C and 85%, respectively, and a DC voltage of 1.5 kV was continuously applied between the electrodes of the specimen. The voltage is applied at a resistance of 1.0 x 10 7 Continue until the resistance is 1.0 x 10 7 The time when the resistance became 0.02Ω or less was recorded. This time was taken as the leakage time and was used to evaluate the insulation reliability. The evaluation criteria for insulation reliability are as follows: In practical terms, a rating of 3 is preferable.

[0101] -Insulation reliability evaluation criteria- Less than 1:50 hours 2: Between 50 and 100 hours 3: Over 100 hours

[0102] In the table, the "Type" column indicates the type of inorganic particle. For example, "1" in the "Type" column for Example 1 indicates that the above-mentioned inorganic particle 1 was used. In the table, the "Core Material" column indicates the material contained in the core. "Silica" stands for silicon dioxide, "Alumina" for aluminum oxide, "BN" for boron nitride, "AlN" for aluminum nitride, and "Copper" for copper. In the table, the column "Core diameter" indicates the median diameter of the core particles. In the table, the "shell thickness" column indicates the thickness of the shell portion. In the table, the column "Inorganic particle diameter" indicates the median diameter of the inorganic particles. In the table, the column "major axis / minor axis" indicates the aspect ratio of the inorganic particles. In the table, the column "iron atom content" indicates the content of iron atoms (ppm by mass) relative to the total mass of the shell portion. In the table, the "vacuum plasma treatment" column indicates that the vacuum plasma treatment was performed during the production of the inorganic particles, with "A" indicating that it was not performed, and "B" indicating that it was not performed. In the table, the "metal coupling agent" column indicates that the inorganic particles were treated with a metal coupling agent during production, with "A," and that the inorganic particles were not treated with a metal coupling agent, with "B." In the table, the column "Surface O / B" indicates the atomic ratio of oxygen atoms to boron atoms on the surface of the inorganic particle, determined by X-ray photoelectron spectroscopy. In the table, the "D value" column indicates the D value calculated by formula (1). In the table, the column "Inorganic particles (vol %)" indicates the content (vol %) of inorganic particles relative to the total solid content of the curable composition. In the table, the column "Cured product (vol %)" indicates the content (vol %) of solids other than inorganic particles relative to the total solids content of the curable composition.

[0103] [Table 1]

[0104] The results in Table 1 confirm that the inorganic particles of the present invention exhibit the desired effects. From a comparison of Examples 5 to 15 with Examples 1 to 4, it was confirmed that when the inorganic particles satisfy the above requirements 1 and 2, the effects of the present invention are more excellent. From a comparison of Examples 9 to 15 with Examples 1 to 8, it was confirmed that the effects of the present invention are more excellent when the surfaces of the inorganic particles are modified with a metal coupling agent. Comparison of Example 10 with Examples 11 and 12 confirmed that the effects of the present invention are more excellent when the content of inorganic particles relative to the total solid content of the composition is 45% by volume to 60% by volume.

Claims

1. A spherical inorganic particle having a core portion and a shell portion, the core portion contains at least one selected from the group consisting of silicon dioxide, aluminum oxide, aluminum nitride, and copper, the shell portion comprises boron nitride; Inorganic particles, wherein the content of iron atoms contained in the shell portion is 10 ppm by mass or less with respect to the total mass of the shell portion.

2. 2. The inorganic particle according to claim 1, wherein the shell portion has a thickness of 20 nm to 1 μm.

3. The inorganic particles according to claim 1 or 2, which satisfy requirements 1 and 2. Requirement 1: The atomic ratio of oxygen atoms to boron atoms on the surface of the inorganic particles is 0.12 or more, as determined by X-ray photoelectron spectroscopy. Requirement 2: The D value calculated by formula (1) is 0.010 or less. Equation (1): D = B(OH) ３ (002) / BN (002) B(OH) ３ (002): Peak intensity derived from (002) of boron hydroxide having a triclinic space group as measured by X-ray diffraction BN(002): Peak intensity derived from (002) of boron nitride having a hexagonal space group as measured by X-ray diffraction

4. The inorganic particles according to claim 3 , wherein the D value is 0.005 or less.

5. The inorganic particles according to claim 3 or 4, wherein the atomic ratio is 0.15 or more.

6. The inorganic particles according to any one of claims 3 to 5, wherein the atomic ratio is 0.25 or less.

7. The inorganic particles according to any one of claims 1 to 6, having a median diameter of 300 µm or less.

8. The inorganic particles according to any one of claims 1 to 7, having a median diameter of 100 µm or less.

9. The inorganic particles according to any one of claims 1 to 8, wherein a particle size distribution curve representing a volume-based frequency distribution has peaks in the ranges of 1.0 to 50 µm, 100 to 150 µm, and 200 to 300 µm.

10. 10. The inorganic particles according to claim 1, wherein the surface of the inorganic particles is modified with a metal coupling agent.

11. The method for producing inorganic particles according to any one of claims 1 to 10, A method for producing inorganic particles, comprising the step of forming the shell portion by a vapor deposition method or a sputtering method.

12. A composition comprising the inorganic particles according to any one of claims 1 to 10 and a resin or a precursor thereof.

13. The composition of claim 12, wherein the resin or precursor thereof is a thermosetting compound.

14. The composition according to claim 12 or 13, wherein the content of the inorganic particles is 45 to 60% by volume based on the total solid content of the composition.

15. The composition according to any one of claims 12 to 14, which is in the form of a sheet.

16. A method for producing an electronic device, comprising a step of encapsulating a semiconductor member by compression molding using the composition according to claim 15.

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