Boron nitride agglomerated powder, composite composition, heat dissipation component, and semiconductor device

Abstract

To provide a boron nitride agglomerated powder that has extremely high density and excellent packing properties.SOLUTION: There is provided a boron nitride agglomerated powder in which, in a pore size distribution measured by mercury intrusion porosimetry, there is no second peak corresponding to pores within agglomerated particles on the smaller pore size side of a first peak corresponding to interparticle gaps.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a boron nitride agglomerated powder, a composite composition containing the boron nitride agglomerated powder, a heat dissipation member using the composite composition, and a semiconductor device using the heat dissipation member. [Background technology]

[0002] Boron nitride (BN) is an insulating ceramic and is known to have various crystal forms, such as c-BN with a diamond structure, h-BN with a graphite structure, and α-BN and β-BN with turbostratic structures. Among these, h-BN has the same layered structure as graphite, is relatively easy to synthesize, and has excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance, making it widely used in the electrical and electronic materials field.

[0003] In recent years, heat generation due to the increasing density of integrated circuits has become a major problem, particularly in the electrical and electronics fields, and how to dissipate heat has become an urgent issue. h-BN, which has high thermal conductivity despite being an insulator, has attracted attention as a thermally conductive filler for such heat dissipation components.

[0004] Various efforts have been made to obtain fillers with high thermal conductivity by increasing the density through control of the intraparticle pores in agglomerated particles. Patent Document 1 describes that boron nitride agglomerated particles are typically divided into a peak representing the pores within the agglomerated particles (pore size) and a peak representing the gap between the agglomerated particles (particle gap) using a mercury porosimeter method evaluated in accordance with ISO 15901-1, and describes a preferred range of intraparticle pore size. Patent Document 2 also describes the average pore size of boron nitride agglomerated particles. Patent Document 3 describes that in a boron nitride sintered body, the average pore size can be reduced and thermal conductivity improved by filling the pores with acicular particles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 203164 [Patent Document 2] International Publication No. 2022 / 202827 [Patent Document 3] International Publication No. 2022 / 163650 Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 1, the occurrence of micropores between the constituent boron nitride primary particles in boron nitride agglomerated particles typically leads to a decrease in the particle density of the agglomerated particles. This can be evaluated by separating the peak representing the pores within the agglomerated particles (pore diameter) from the peak representing the inter-agglomerated particles (particle gap) using mercury porosimetry according to ISO 15901-1. Patent Document 2 attempts to reduce the average pore diameter, but the average pore diameter merely indicates the size of the pores. A large number of dense pores reduces the average pore diameter but does not result in high density. While particles always have peaks representing inter-particle gaps, eliminating the pores within the agglomerated particles and increasing the density of the agglomerated particles eliminates the peak representing the intra-particle pores. Therefore, from the perspective of high-density agglomerated particles, it is important that the agglomerated particles do not have specific peaks corresponding to the intra-particle pores. Patent Document 3 is characterized by its molding synthesis process, making it difficult to apply to boron nitride agglomerated particles. The present invention aims to provide a boron nitride agglomerated powder that has extremely high density and excellent packing ability, by attempting to reduce the intraparticle pores of boron nitride agglomerated particles as much as possible, and that does not have a second peak indicating intraparticle pores on the smaller pore diameter side of the first peak indicating interparticle gaps in the pore distribution peak. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A boron nitride agglomerated powder that does not have a second peak corresponding to the pores within the agglomerated particles on the smaller pore diameter side of the first peak corresponding to the interparticle gaps in the pore distribution measured by mercury intrusion porosimetry. [2] The boron nitride agglomerated powder according to [1], having a circularity of 82% or more in a projected image. [3] The boron nitride agglomerated powder according to [1] or [2], wherein the intraparticle porosity is 40% or less as measured by mercury intrusion porosimetry. [4] The agglomerated powder of boron nitride according to any one of [1] to [3], which contains 0.1 mass % or more of aluminum element relative to the agglomerated powder of boron nitride. [5] A composite composition comprising the boron nitride agglomerated powder according to any one of [1] to [4] above and a matrix material. [6] The composite composition according to [5], wherein the matrix material comprises a resin. [7] A heat dissipation member obtained by molding the composite material composition according to [5] or [6] above. [8] A semiconductor device comprising the heat dissipation member according to [7]. [Effects of the Invention]

[0008] According to the present invention, the pore distribution peak does not have a second peak indicating intra-particle pores on the smaller pore diameter side of the first peak indicating inter-particle gaps, and therefore a boron nitride agglomerated powder with extremely high density and excellent packing properties can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows the pore size distribution of the BN agglomerated powders of Examples 1 to 3 and Comparative Examples 1 to 3, measured by mercury intrusion pore size distribution measurement method. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be implemented in various modified forms within the scope of the gist thereof.

[0011] <Boron nitride agglomerated particles / Boron nitride agglomerated powder> In this specification, boron nitride agglomerated particles (hereinafter also referred to as "BN agglomerated particles") refer to particles formed by agglomeration of boron nitride primary particles (hereinafter also referred to as "BN primary particles"). In this specification, boron nitride agglomerated powder (hereinafter also referred to as "BN agglomerated powder") refers to a collection of agglomerated particles of boron nitride.

[0012] The BN agglomerated powder of the present invention (hereinafter also referred to as "the present BN agglomerated powder") is an agglomerated powder that does not have a second peak corresponding to the pores within the agglomerated particles on the smaller pore diameter side of the first peak corresponding to the interparticle gaps in a pore distribution measured by mercury intrusion porosimetry. The term "peak" here refers to the presence of a maximum point where a continuous monotonic increase in a specific range switches to a monotonic decrease. To exclude unusual shapes, a "peak" is defined as a shape in which the pore volume (vertical axis of the pore distribution) before and after the maximum point drops to 90% or less of the pore volume (vertical axis of the pore distribution) at the maximum point.

[0013] The agglomerated shape of the BN agglomerated particles in the present BN agglomerated powder is not particularly limited, and may be, for example, a shape in which BN primary particles are aggregated to form agglomerated particles having a spherical, ellipsoidal, cylindrical, hexagonal prism, or other shape.

[0014] In particular, an agglomeration form forming house-of-card BN agglomerated particles having a house-of-card structure is preferred in that it is easy to obtain high thermal conductivity. The house-of-card structure is described, for example, in Ceramics 43 No. 2 (published by the Ceramic Society of Japan in 2008), and is a structure in which plate-like particles are layered in a complex manner without being oriented. More specifically, BN agglomerated particles having a house-of-card structure are aggregates of BN primary particles, and are BN agglomerated particles having a structure in which the flat surfaces and edge surfaces of the BN primary particles are in contact with each other, and are preferably spherical. It is also preferable that the house-of-card structure is the same structure inside the particles. The agglomeration form and internal structure of these BN agglomerated particles can be confirmed using a scanning electron microscope (SEM).

[0015] [Pore distribution] The pore size distribution in this specification was determined by measuring the mercury intrusion / extrusion curve after degassing the sample under reduced pressure (50 μmHg or less) for 10 minutes using a Micromeritics Autopore IV9520. Methods for producing agglomerated powder that does not have a second peak corresponding to the pores within the agglomerated particles in the pore distribution measured by mercury intrusion porosimetry include adjusting the amount of binder and adjusting the amount of B2O3 volatilized during high-temperature firing by changing the firing vessel and firing conditions.

[0016] [Intraparticle porosity] In this specification, the intraparticle porosity is the ratio of the intraparticle pore volume, which represents the volume of pores within a particle, to the particle volume, calculated by assuming that the pores are cylindrical in mercury intrusion measurements and measuring the pore size in the region smaller than the pore size (division size) where the volume is smallest around 1.0 μm. For powders that do not have a pore size where the volume is smallest around 1.0 μm, the intraparticle porosity can be evaluated by adjusting the pore size to the division size of a powder with a particle size equivalent to that of a BN agglomerated powder. The intraparticle pore volume is measured using the method described in the Examples section below.

[0017] The porosity of the BN agglomerated particles tends to increase due to the evaporation of impurities in the BN raw material during the heat treatment process.

[0018] The intraparticle porosity of the BN agglomerated powder of the present invention is preferably 40% or less, more preferably 38% or less, even more preferably 36% or less, particularly preferably 34% or less, particularly preferably 32% or less, and most preferably 30% or less. When it is less than the above upper limit, excellent thermal conductivity is achieved within the particles. The lower limit of the intra-particle porosity is preferably 1% or more, more preferably 3% or more, even more preferably 5% or more, particularly preferably 7% or more, and most preferably 9% or more, from the viewpoint of volatilization and removal of impurities. Methods for adjusting the intraparticle porosity of the BN agglomerated powder of the present invention to fall within the above range include adjusting the amount of binder, the size of the firing vessel, and the firing conditions so as to maintain the growth-promoting components such as B2O3 of BN crystals during high-temperature firing.

[0019] Circularity The circularity in the present invention is a value obtained by measuring the perimeter of a BN agglomerated particle from a projected image of the particle and calculating the perimeter as follows: (perimeter of a circle having the same projected area) / (perimeter of particle) × 100. The measurement is performed by the method shown in the Examples section below. High circularity indicates that the BN agglomerate particles are nearly spherical. When BN agglomerate powder is used as a composite material containing a matrix material, circularity is an important indicator from the viewpoints of ensuring fluidity in the slurry during processing and achieving closest packing in the composite material.

[0020] The circularity of the BN agglomerated powder of the present invention is preferably 82% or more, more preferably 84% or more, even more preferably 85% or more, particularly preferably 86% or more, and most preferably 87% or more. When the circularity is equal to or greater than the lower limit, the powder has excellent fluidity in the slurry during processing, and the packing density in the composite composition is easily increased. On the other hand, excessively high circularity means that the crystal growth of BN constituting the BN agglomerate particles has not progressed. From this viewpoint, the circularity is preferably 99% or less, more preferably 98% or less, even more preferably 97% or less, particularly preferably 95% or less, and most preferably 93% or less. Methods for adjusting the circularity of the BN agglomerated powder of the present invention to fall within the above range include adjusting the amount of carbon powder added before heat treatment or the firing conditions so as to suppress adhesion of agglomerated particles to each other during high-temperature firing.

[0021] [Aluminum element concentration (Al concentration)] The Al concentration in the present invention is a value measured by the fundamental parameter method using a wavelength dispersive X-ray fluorescence analyzer, more specifically, by the method shown in the Examples section below.

[0022] The aluminum element content of the BN agglomerated powder of the present invention is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, particularly preferably 0.4 mass% or more, and most preferably 0.5 mass% or more, relative to the BN agglomerated powder (100 mass%). If the content is above the lower limit, aluminum will easily contribute to promoting the growth of BN flakes during synthesis. On the other hand, from the viewpoint of cutting the heat transfer path at the BN flake joint portion by the aluminum compound, the aluminum element content relative to the BN agglomerated powder is preferably 50 mass% or less, more preferably 40 mass% or less, even more preferably 30 mass% or less, particularly preferably 20 mass% or less, and most preferably 10 mass% or less. Methods for adjusting the Al concentration of the BN agglomerated powder of the present invention to fall within the above range include adjusting the amount of binder and adjusting the amount of volatilization during high-temperature firing.

[0023] [Particle size] The particle size in the present invention is measured by the method shown in the Examples section below. The particle size of the BN agglomerated powder of the present invention is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. When the particle size is equal to or greater than the lower limit, the slurry viscosity during the processing of the composite composition can be reduced. The upper limit of the particle size is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less, from the viewpoint of thinning the composite material composition. The particle size of the BN agglomerated powder of the present invention can be adjusted to fall within the above range by adjusting the spraying conditions during granulation.

[0024] In various measurements, the method for randomly sampling the BN agglomerated particles to be measured from the BN agglomerated powder is not particularly limited, but it is preferable to sample the BN agglomerated particles after uniformly mixing the BN agglomerated powder.

[0025] <Production method of BN agglomerated powder> The BN agglomerated powder of the present invention is preferably prepared by pulverizing the raw material boron nitride (hereinafter, together with the pulverized product thereof, also referred to as "raw material BN powder") in a pulverization step, agglomerating the resulting powder to form granules in a granulation step, and then subjecting the powder to a heating step for heat treatment. More specifically, a preferred method includes the steps of dispersing raw BN powder in a medium to form a slurry of the raw BN powder (hereinafter also referred to as "BN slurry"), then subjecting the slurry to a pulverization treatment, granulating the resulting slurry into spherical particles, and then heat-treating the granulated BN powder to crystallize it.

[0026] The present BN agglomerated powder can be obtained by heat treatment in the presence of carbon as a reducing agent. Specifically, it is preferable to add carbon powder to the BN granulated powder before heat treatment. Heat treatment in the presence of carbon prevents the fusion of agglomerated particles, which causes sintering. As a result, the resulting BN agglomerated powder has an extremely high density, and the pore size distribution measured by mercury intrusion porosimetry does not have a second peak corresponding to the pores within the agglomerated particles on the smaller pore size side than the first peak corresponding to the gaps between particles. The average particle size of the carbon powder is preferably 0.01 μm or more and 50 μm or less, more preferably 0.05 μm or more and 40 μm or less, and even more preferably 0.1 μm or more and 30 μm or less. When the average particle size of the carbon powder is equal to or more than the lower limit of the above range, the carbon powder is likely to be mixed uniformly with the BN granulated powder, and when the average particle size is equal to or less than the upper limit of the above range, the risk of carbon powder remaining can be reduced. In this specification, the average particle size of the carbon powder is the volume-based median diameter in the particle size distribution measured by a laser diffraction particle size distribution measuring device. The amount of carbon powder added is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less, relative to the mass of the BN granulated powder. When the amount is equal to or more than the lower limit of the above range, the uniformity of the effect due to the addition of carbon powder is excellent, and when the amount is equal to or less than the upper limit, the risk of carbon powder remaining can be reduced.

[0027] <Raw material BN powder> Any of commercially available h-BN, commercially available α- and β-BN, BN produced by the reduction-nitridation method of a boron compound and ammonia, BN synthesized from a boron compound and a nitrogen-containing compound such as melamine, etc. can be used as the raw BN powder without limitation. h-BN is particularly preferred as it more effectively exhibits the effects of the present invention.

[0028] The preferred form of raw BN powder is powdered boron nitride with a wide half-width peak obtained by powder X-ray diffraction measurement and low crystallinity. While flake h-BN can be used as the raw material, non-flake nanoparticles are also suitable. The raw BN powder contains at least flake h-BN. The proportion of flake h-BN relative to the total mass of the raw BN powder is preferably 20% by mass or more, more preferably 50% by mass or more, and particularly preferably 100% by mass. As a measure of the crystallinity of the raw BN powder, the peak half-width of the (002) plane obtained by powder X-ray diffraction measurement is typically 0.4° or more, preferably 0.45° or more, and more preferably 0.5° or more, in terms of 2θ angle. Furthermore, this peak half-width of the (002) plane is typically 2.0° or less, preferably 1.5° or less, and even more preferably 1° or less. When the peak half-width of the (002) plane is below the upper limit, crystallite growth tends to be facilitated and productivity tends to be sufficiently improved. When the peak half-width of the (002) plane is above the lower limit, the crystallinity falls within an appropriate range, crystal growth becomes easy, and dispersion stability during slurry preparation tends to be improved.

[0029] The method for producing the raw material BN powder is not particularly limited, but examples thereof include the method described in Microstructural Development with Crystallization of Hexagonal Boron Nitride (TSUYOSHI TAGIO, et al., Journal of Materials Science Letters 16, 795-798 (1997)).

[0030] From the viewpoint of BN crystal growth, it is preferable that a certain amount of oxygen atoms are present in the raw BN powder. In the present invention, the total oxygen concentration in the raw BN powder is preferably 1 mass% or more, more preferably 2 mass% or more, even more preferably 3 mass% or more, particularly preferably 4 mass% or more, and preferably 10 mass% or less, more preferably 9 mass% or less. When the total oxygen concentration is below the above upper limit, residual oxygen after heat treatment is suppressed, and the effect of improving thermal conductivity tends to be enhanced. When the total oxygen concentration is above the above lower limit, crystal growth tends to be achieved without excessive crystallinity.

[0031] Methods for adjusting the total oxygen concentration of the raw BN powder to fall within the above range include, for example, synthesizing BN at a low temperature of 1500°C or less, or heat-treating the raw BN powder in an oxidizing atmosphere at a low temperature of 500 to 900°C. The total oxygen concentration of the raw material BN powder can be measured by the inert gas fusion-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba, Ltd.

[0032] The total pore volume of the raw BN powder is preferably 1.5 cm 3 / g or less. The total pore volume is 1.5 cm 3 When the total pore volume is 0.3 cm3 / g or less, the raw BN powder is dense, and granulation with high sphericity is possible. Although there is no particular lower limit for the total pore volume, it is preferably 0.3 cm3 / g or less. 3 / g or more, more preferably 0.5 cm 3 / g or more.

[0033] The specific surface area of ​​the raw BN powder is preferably 50m 2 / g or more, more preferably 60m 2 / g or more, more preferably 70m 2 / g or more, preferably 1000m 2 / g or less, more preferably 500m 2 / g or less, more preferably 300m 2 / g or less. The specific surface area of ​​the raw BN powder is 50m 2 / g or more, the dispersed particle size in the BN slurry used for spheroidization by granulation can be made small, which is preferable. 2 / g or less is preferable because it is possible to suppress an increase in the viscosity of the slurry.

[0034] The total pore volume of the raw BN powder can be measured by nitrogen adsorption and mercury intrusion porosimetry. The specific surface area of ​​the raw BN powder can be measured by the BET one-point method (adsorption gas: nitrogen). The nitrogen adsorption method was performed in accordance with JIS Z 8830, and the measurement temperature was -196°C (liquid nitrogen temperature). The mercury intrusion method was performed in accordance with JIS R 1655, and the surface tension of BN was 485 dyn / cm. 2 The contact angle is 140° and the measurement temperature is 23 to 26°C.

[0035] <medium> The medium used to prepare the BN slurry is not particularly limited, and water and / or various organic solvents can be used. From the viewpoints of ease of spray drying and simplification of the equipment, it is preferable to use water as the medium, and pure water is more preferable.

[0036] The medium used in preparing the BN slurry is preferably added in an amount that results in a viscosity of the BN slurry of 50 to 5,000 mPa·s. The viscosity of the BN slurry refers to the viscosity when the slurry temperature is 10°C or higher and 60°C or lower, and is preferably 15°C or higher and 50°C or lower, more preferably 15°C or higher and 40°C or lower, and even more preferably 15°C or higher and 35°C or lower. Specifically, the amount of medium used in preparing the BN slurry is preferably 10% by mass or higher, more preferably 20% by mass or higher, even more preferably 30% by mass or higher, and preferably 70% by mass or lower, more preferably 65% ​​by mass or lower, and even more preferably 60% by mass or lower, relative to the BN slurry. When the amount of medium used is below the upper limit, the slurry viscosity does not become too low, which tends to suppress sedimentation and result in a more uniform BN slurry. When the amount of medium used is above the lower limit, the slurry viscosity does not become too high, which tends to facilitate granulation.

[0037] <Surfactant> Various surfactants may be added to the BN slurry to adjust the viscosity of the slurry and to improve the dispersion stability (suppression of aggregation) of the raw BN powder in the slurry. The surfactant may be an anionic surfactant, a cationic surfactant, a nonionic surfactant, etc. These may be used alone or in combination of two or more.

[0038] Generally, surfactants can change the viscosity of a slurry. Therefore, when adding a surfactant to a BN slurry, the amount is adjusted so that the viscosity of the BN slurry is 50 to 5,000 mPa·s. Note that the viscosity of the BN slurry refers to the viscosity within the temperature range described above for the medium used to prepare the BN slurry. For example, when preparing a slurry with a solid content of 50% by mass using BN powder having a (002) plane peak half-width 2θ of 0.67° as measured by powder X-ray diffraction and a total oxygen concentration of 7.5% by mass, an anionic surfactant is typically added as an active ingredient in an amount of preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, based on the total amount of the slurry. By keeping the amount added below the upper limit, a decrease in the slurry viscosity is suppressed and carbon components derived from the surfactant tend to be less likely to remain in the resulting BN agglomerated particles. By keeping the amount added above the lower limit, an excessive increase in the slurry viscosity is suppressed, and granulation tends to be easier.

[0039] <Binder> The BN slurry may contain a binder to effectively granulate the raw BN powder into particles. The binder acts to firmly bind the BN primary particles together and stabilize the granulated particles that make up the BN granulated powder.

[0040] As the binder used for the BN slurry, any binder can be used as long as it can enhance the adhesiveness between BN primary particles. In the present invention, since the granulated particles are heat-treated after granulation, a binder having heat resistance against the high-temperature conditions in this heat-treatment step is preferred.

[0041] As such a binder, metal oxides such as aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, titanium oxide, etc. are preferably used. Among these, aluminum oxide and yttrium oxide are preferred from the viewpoints of thermal conductivity and heat resistance as oxides, and the binding force for binding BN primary particles to each other. The binder may be a liquid binder such as alumina sol, or may be a substance that reacts during heat treatment and is converted into other inorganic components. These binders may be used alone or in combination of two or more.

[0042] The binder may or may not be contained, and may be 0% by mass with respect to the raw material BN powder in the BN slurry. Also, when the binder is contained, the usage amount (in the case of a liquid binder, the usage amount as a solid content) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less with respect to the raw material BN powder in the BN slurry. When the usage amount of the binder is below the above upper limit, crystal growth can be obtained, and a tendency to obtain an effect of improving thermal conductivity when used as a filler for thermal conductivity is obtained.

[0043] <BN Slurry Preparation Method> [[ID=??]] The method for preparing the BN slurry is not particularly limited as long as the raw material BN powder, the medium, and further, if necessary, the binder and the surfactant are uniformly dispersed and adjusted to a desired viscosity range. When using the raw material BN powder, the medium, and further, if necessary, the binder and the surfactant, the BN slurry is preferably prepared as follows.

[0044] A predetermined amount of raw BN powder is weighed into a resin bottle, and then a predetermined amount of binder is added. If necessary, a predetermined amount of surfactant is added, and then ceramic balls made of alumina or the like are added, and the mixture is stirred on a pot mill rotating table for about 0.5 to 5 hours until the desired viscosity is reached.

[0045] There are no particular restrictions on the order of addition, but when a large amount of raw BN powder is made into a slurry, agglomerates such as lumps are likely to form. Therefore, an aqueous solution may be prepared by adding a surfactant and a binder to water as needed, and then a predetermined amount of raw BN powder may be added little by little. Ceramic balls made of alumina or the like may then be added to the aqueous solution, which is then dispersed and slurried on a pot mill rotating table. For dispersion, a dispersing device such as a bead mill or a planetary mixer may be used in addition to a pot mill.

[0046] When forming the slurry, the temperature of the slurry is preferably 10° C. or higher and 60° C. or lower. When the slurry temperature is equal to or higher than the lower limit, an increase in the viscosity of the slurry tends to be suppressed, and when the slurry temperature is equal to or lower than the upper limit, decomposition of the raw material BN powder into ammonia in the slurry tends to be suppressed. The temperature of the slurry is more preferably 15°C or higher and 50°C or lower, even more preferably 15°C or higher and 40°C or lower, and particularly preferably 15°C or higher and 35°C or lower.

[0047] <Granulation> To obtain granulated powder from the BN slurry, a general granulation method such as spray drying, tumbling, fluidized bed, stirring, etc. can be used, of which spray drying is preferred.

[0048] In the spray drying method, it is possible to produce granulated powder of a desired size by adjusting the concentration of the raw material slurry, the amount of liquid fed into the device per unit time, and the compressed air pressure and amount of compressed air used to spray the fed slurry. The spray drying method also makes it possible to obtain spherical granulated powder. There are no restrictions on the spray drying equipment that can be used, but to produce larger spherical granulated powder, a rotary disk type is optimal. Examples of such equipment include the F series spray dryer manufactured by Okawara Kakoki Co., Ltd., the MDL-050M spray dryer manufactured by GF Co., Ltd. (formerly Fujisaki Electric Co., Ltd.), and the PRIS spray dryer P260.

[0049] <Heat treatment> The above-mentioned BN granulated powder can be further heat-treated in a non-oxidizing gas atmosphere to produce BN agglomerated powder. The non-oxidizing gas atmosphere includes nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas, etc. The crystallization speed of the BN agglomerated particles varies depending on the type of atmospheric gas used. In order to perform crystallization in a short time, nitrogen gas or a mixed gas containing nitrogen gas and other gases is particularly suitable.

[0050] The heat treatment temperature is preferably 1600°C or higher, more preferably 1800°C or higher, and preferably 2300°C or lower, more preferably 2200°C or lower. When the heat treatment temperature is above the lower limit, sufficient crystallite growth of the BN primary particles can be obtained, and high-density BN agglomerated particles with reduced fine pores can be formed. When the heat treatment temperature is below the upper limit, decomposition of the BN agglomerated powder tends to be suppressed.

[0051] The rate of temperature rise until the heat treatment temperature is reached is preferably 1° C. / min or more, more preferably 2° C. / min or more, even more preferably 3° C. / min or more, and particularly preferably 4° C. / min or more. If the rate of temperature rise is equal to or greater than the above lower limit, the temperature can be raised to a high temperature before the boron oxide or aluminum compound volatilizes, and the BN primary particles grow large, facilitating the formation of high-density BN agglomerated particles with reduced fine pores. On the other hand, if the temperature increase rate is too fast, the load on the furnace increases. From this viewpoint, the upper limit of the temperature increase rate is preferably 35°C / min or less, more preferably 30°C / min or less, even more preferably 25°C / min or less, and particularly preferably 20°C / min or less.

[0052] The heat treatment time is preferably 1 hour or more and 20 hours or less, more preferably 2 hours or more and 10 hours or less. When the heat treatment time is equal to or more than the lower limit, the BN primary particles grow large, and high-density BN aggregate particles with reduced fine pores are likely to be formed. When the heat treatment time is equal to or less than the upper limit, decomposition of BN tends to be suppressed.

[0053] Since the heat treatment is carried out under a non-oxidizing gas atmosphere, it is preferable that the inside of the calcination furnace is evacuated using a vacuum pump, and then the temperature is raised to the desired temperature while introducing a non-oxidizing gas. If the atmosphere inside the calcination furnace can be sufficiently replaced with a non-oxidizing gas, the temperature may be raised by heating while introducing a non-oxidizing gas under normal pressure. Examples of calcination furnaces include batch furnaces such as muffle furnaces, tubular furnaces, and atmosphere furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces, and these are used depending on the purpose.

[0054] Typically, the BN granulated powder to be heat-treated is placed in a circular crucible with a lid and heated and fired to reduce non-uniformity in the composition during the heat treatment. The crucible can be made of boron nitride, graphite, or the like. Boron nitride is preferred to reduce the risk of carbon contamination. The size of the crucible is not particularly limited, but a large crucible is preferred from the viewpoint of suppressing volatilization of boron oxide and aluminum compounds, growing large BN primary particles, and forming high-density BN agglomerated particles with reduced fine pores.

[0055] <Classification> The BN agglomerated powder after the heat treatment is preferably classified to narrow the particle size distribution and suppress an increase in viscosity when blended into a resin composition containing the BN agglomerated powder. This classification is usually performed after the heat treatment of the BN granulated powder, but it may also be performed on the BN granulated powder before the heat treatment and then subjected to the heat treatment.

[0056] The classification may be either wet or dry, but dry classification is preferred from the viewpoint of suppressing the decomposition of BN, especially when the binder is water-soluble.

[0057] Dry classification includes sieving and air classification, which classifies particles based on the difference between centrifugal force and fluid drag. Dry classification can also be performed using a classifier such as a swirling air classifier, a forced vortex centrifugal classifier, or a semi-free vortex centrifugal classifier. These classifiers can be used appropriately depending on the particle size of the particles to be classified, such as using a swirling air classifier to classify small particles in the submicron to single micron range, and using a semi-free vortex centrifugal classifier to classify larger particles.

[0058] <Composite composition> The above-mentioned BN agglomerated powder can be suitably used as an inorganic filler. Another embodiment of the present invention is a composite composition comprising the BN agglomerated powder described above and a matrix material. The matrix material preferably has high thermal conductivity. The thermal conductivity of the matrix material is preferably 0.2 W / mK or higher, and particularly preferably 0.22 W / mK or higher. The thermal conductivity of the matrix material is measured using the following equipment to measure the thermal diffusivity, specific gravity, and specific heat, and then calculated by multiplying these three measured values. (1) Thermal diffusivity: iPhase Mobile 1u manufactured by iPhase (2) Specific gravity: Mettler-Toledo XS-204 balance (using a solid specific gravity measurement kit) (3) Specific heat: Seiko Instruments Inc. "DSC320 / 6200"

[0059] Resins are usually used as the matrix material, and either curable resins or thermoplastic resins can be used without any restrictions. The curable resin may be any crosslinkable resin, such as a thermosetting, photocurable, or electron beam curable resin. Thermosetting resins are preferred in terms of heat resistance, water absorption, and dimensional stability. Examples of thermosetting and photocurable resins that can be used include those exemplified in International Publication No. 2013 / 081061. Among these, thermosetting resins are preferred, and epoxy resins are particularly preferred. As epoxy resins, phenoxy resins having at least one skeleton selected from the group consisting of a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton, and a dicyclopentadiene skeleton are preferred. Among these, phenoxy resins having a fluorene skeleton and / or a biphenyl skeleton are particularly preferred because they further enhance heat resistance. Phenoxy resins having at least one skeleton selected from the group consisting of a bisphenol A skeleton, a bisphenol F skeleton, and a biphenyl skeleton are particularly preferred.

[0060] The content of the matrix material relative to the total mass of the composite composition is usually 2 mass% or more, preferably 5 mass% or more, more preferably 7 mass% or more, and usually 70 mass% or less, preferably 60 mass% or less, more preferably 40 mass% or less. The content of the BN agglomerated powder relative to the total mass of the composite composition is usually 30 mass% or more, preferably 40 mass% or more, more preferably 50 mass% or more, and usually 99 mass% or less, preferably 98 mass% or less, more preferably 95 mass% or less.

[0061] An organic solvent can be used to prepare the composite material composition. The organic solvent can be suitably selected from alcohol-based solvents, aromatic solvents, amide-based solvents, alkane-based solvents, ethylene glycol ether and ether-ester-based solvents, propylene glycol ether and ether-ester-based solvents, ketone-based solvents, and ester-based solvents, taking into consideration the solubility of the resin. Specific examples of organic solvents include those exemplified in International Publication No. 2013 / 081061. One organic solvent may be used alone, or two or more organic solvents may be used in any combination and ratio.

[0062] The composite composition may contain a curing agent as needed. A curing agent is a substance that contributes to a crosslinking reaction between crosslinking groups of a matrix material, such as the epoxy groups of an epoxy resin. In the case of an epoxy resin, a curing agent and a curing accelerator for the epoxy resin are used together as needed. Furthermore, for the purpose of further improving functionality, various additives (other additives) may be contained within the range that does not impair the effects of the present invention. Examples of other additives include functional resins that impart functionality to the matrix material, such as liquid crystalline epoxy resins, nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, insulating metal oxides such as alumina, fibrous alumina, zinc oxide, magnesium oxide, beryllium oxide, and titanium oxide, insulating carbon components such as diamond and fullerene, resin curing agents, resin curing accelerators, viscosity modifiers, and dispersion stabilizers.

[0063] Further, other additives include coupling agents such as silane coupling agents and titanate coupling agents, which are added components for improving the adhesion between the matrix material and the BN agglomerated powder, ultraviolet inhibitors for improving storage stability, antioxidants, plasticizers, flame retardants, colorants, dispersants, flow improvers, etc.

[0064] In addition, surfactants, emulsifiers, elasticity reducing agents, diluents, antifoaming agents, ion trapping agents, etc., which improve the dispersibility of each component in the composition, can also be added. These may be used alone or in any combination and ratio of two or more. Specific examples of additives include those exemplified in WO 2013 / 081061, and the amount added can be within the range described in WO 2013 / 081061.

[0065] The composite composition is preferably prepared by mixing the BN agglomerated powder, matrix material, and, if necessary, solvent and other additives using a general mixing device such as a paint shaker, bead mill, planetary mixer, agitator disperser, planetary mixer, rotary and revolutionary mixer, three-roll mill, kneader, single-screw or twin-screw mixer, etc. The order of mixing the components of the composite composition is also arbitrary as long as there are no particular problems, such as the occurrence of reactions or precipitation. Two or more of the components constituting the composition may be mixed in advance, and then the remaining components may be mixed, or all of the components may be mixed at once.

[0066] <Heat dissipation materials> The BN agglomerated powder can be suitably used as a thermally conductive filler for heat dissipation members. The composite composition can be molded into a heat dissipation component by forming it into a molded article. The molded article can be formed using a method commonly used for molding resin compositions. For example, the composite composition can be molded into a desired shape, for example, by filling it into a mold and curing it. Examples of methods for producing such molded articles include injection molding, injection compression molding, extrusion molding, and compression molding. Furthermore, when the composite composition contains a thermosetting resin composition such as an epoxy resin or a silicone resin, molding of the molded article, i.e., curing, can be performed under curing temperature conditions appropriate for the respective compositions.

[0067] When the composite composition contains a thermoplastic resin composition, the molding can be performed at a temperature equal to or higher than the melting point of the thermoplastic resin, at a predetermined molding speed and pressure. Alternatively, the composite composition can be molded and hardened into a solid material, and then cut into a desired shape to obtain a molded article.

[0068] <Semiconductor devices> The semiconductor device of the present invention is mounted with the heat dissipation member of the present invention as a heat dissipation material, and its high thermal conductivity provides a heat dissipation effect and voltage resistance characteristics, enabling high reliability and high output and high density. In the semiconductor device, conventionally known materials can be used as appropriate for the substrate, aluminum wiring, sealing material, packaging material, heat sink, thermal paste, and solder other than the heat dissipation member of the present invention.

[0069] <Action and effect> The mechanism by which a composite composition with excellent thermal conductivity can be obtained from the BN agglomerated powder of the present invention is presumed to be as follows. Thermal conduction in heat dissipation components and the like is mediated by a substance called boron nitride, and voids reduce thermal conduction. Furthermore, because the thermal conductivity of boron nitride varies significantly depending on the crystal orientation, there is concern that the crystal orientation may significantly reduce thermal conduction. In contrast, the present BN agglomerated powder maintains randomly oriented growth of BN primary particles and has extremely small intraparticle voids. The absence of a peak (second peak) corresponding to the intraparticle distribution in the pore size distribution is important from the perspective of reducing intraparticle porosity. Because the intraparticle pores in BN agglomerated particles are formed by the BN primary particles surrounded by them, the absence of micropores within the particles indicates that the surrounding BN primary particles have grown sufficiently large. Due to the nature of crystal growth, junctions between scaly BN primary particles may contain defects, which can reduce thermal conduction due to phonon scattering. In the present BN agglomerated powder, the BN primary particles are grown to a large crystal size, thereby reducing the number of junctions and improving thermal conductivity. When densification is achieved by particle growth with reduced volatile components such as B2O3, the nitridation of B2O3 also suppresses the growth of BN crystals outside the agglomerated particles, such as on the surfaces of the agglomerated particles, which corresponds to the spaces between the agglomerated particles, and therefore improves the packing properties when the composite material is made. Therefore, the BN agglomerated powder of the present invention is expected to have excellent thermal conductivity when used in a composite composition. [Example]

[0070] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

[0071] ≪Measurement method≫ [Pore distribution] The BN agglomerated powder obtained in each example was used as a sample, and the pore size distribution was measured by mercury intrusion pore size distribution measurement method. The mercury porosimeter used was an Autopore IV manufactured by Micromeritics. 200 mg of sample was filled into the measurement cell and subjected to a reduced pressure treatment (50 μmHg or less) for 10 minutes. After that, the powder density and total pore volume were measured, and the mercury intrusion / extrusion curve was also measured. Assuming that the pores are cylindrical, a pore size distribution curve was created with the pore size on the horizontal axis and the pore volume on the vertical axis. The first peak from the larger pore size side was designated as the first peak, and the second peak from the larger pore size side as the second peak.

[0072] [Measurement of intra-particle void ratio] The BN agglomerated powder obtained in each example was used as a sample, and the intra-particle porosity was measured by mercury intrusion pore distribution measurement method. The mercury porosimeter used was an Autopore IV manufactured by Micromeritics. 200 mg of sample was filled into the measurement cell and subjected to a reduced pressure treatment (50 μmHg or less) for 10 minutes. After that, the powder density and total pore volume were measured, and the mercury intrusion / extrusion curve was also measured. Assuming the pores are cylindrical, a pore size distribution curve was created with pore size on the horizontal axis and pore volume on the vertical axis. The pore size (division size) at which the pore volume was smallest near 1.0 μm was read. The total pore volume in the region where the pore size was smaller than the obtained division size was calculated as the intraparticle pore volume. For powders that did not have a pore size with the smallest volume near 1.0 μm, the intraparticle porosity was evaluated by aligning the pore size with the division size of a powder with a comparable particle size of BN agglomerated powder. The ratio of the intraparticle pore volume to the sample volume (1 / powder density) was calculated as the intraparticle porosity (unit: %) of the BN agglomerated powder.

[0073] [Circularity measurement] The BN agglomerated powder obtained in each example was used as a sample, and the circularity of the BN agglomerated particles was measured using a particle image analyzer (Malvern product name "Morphologi G3S"). After dispersing the BN agglomerated powder using a pressure pulse sample dispersion unit, image analysis was performed to measure circularity. Circularity was measured using Morphologi by measuring and calculating the particle perimeter and the perimeter of a circle with an area equal to the particle area, with the former used as the denominator and the latter used as the numerator. Measurements were performed on approximately 10,000 randomly selected BN agglomerated particles, and the average value was used as the circularity of the BN agglomerated powder.

[0074] [Particle size measurement] The BN agglomerated powder obtained in each example was used as a sample, and the particle size of the BN agglomerated particles was measured using a particle image analyzer (Malvern product name "Morphologi G3S"). After dispersing the BN agglomerated powder using a pressure pulse sample dispersion unit, image analysis was performed to measure the particle size. Measurements were taken of approximately 10,000 randomly selected BN agglomerated particles, and the average value was taken as the particle size of the BN agglomerated powder.

[0075] [Measurement of Al concentration] Measurements were performed using a wavelength dispersive X-ray fluorescence analyzer (Rigaku Corporation, ZSX100e) with a 20 mm diameter, a rotating sample holder, and a vacuum atmosphere. The aluminum content was quantified using the fundamental parameter method. A 0.5–2 g sample was placed in a 25 mm inner diameter, 5 mm thick PVC ring. The sample powder was then compacted using a hydraulic press (MAEKAWA TESTING MACHINE MFG. CO., LTD, BRIQUETING PRESS TYPE. M. No. 50) at 20 tf (ram diameter 129 mm) for 3 min, followed by 30 tf (ram diameter 129 mm) for 3 min.

[0076] Example 1 [Preparation of BN granulated powder] (raw materials) Raw material BN powder: scaly h-BN powder, with a half-width of the (002) plane peak obtained by powder X-ray diffraction measurement of 2θ = 0.67°, a total oxygen concentration of 7.5 mass%, and a specific surface area of ​​116 m 2 / g, total pore volume 0.754 cm 3 / g. Binder: Taki Chemical Co., Ltd. product name "Taxeram M160L", basic aluminum lactate aqueous solution, solids concentration 21% by mass. Medium: Demineralized water.

[0077] The raw BN powder, binder, and demineralized water were mixed to prepare a BN slurry. The raw material BN powder accounts for 43 mass% of the total mass of the BN slurry. The binder content, converted to Al2O3, was 20 mass% relative to the mass of the raw BN powder.

[0078] Specifically, a predetermined amount of raw BN powder was weighed into a resin bottle, and then a predetermined amount of binder was added. After that, alumina ceramic balls were added and the mixture was stirred on a pot mill rotating table for 2 hours to obtain a BN slurry (25°C). The obtained BN slurry was spray-dried at a drying temperature of 85°C using a spray dryer (Pris Spray Dryer "P260") to obtain a BN granulated powder with a particle size of about 10 to 50 µm.

[0079] [Production of BN agglomerated powder] (heat treatment) Carbon powder (type: carbon black, average particle size: 0.5 μm) was added to 35 g of the BN granulated powder obtained above and mixed to form a mixed powder, which was placed in a firing vessel and heat-treated at 2000°C for 5 hours while introducing nitrogen gas. The amount of carbon powder added was 5 mass % relative to the mass of the BN granulated powder. The firing vessel used was a circular crucible made of boron nitride with a lid (internal volume: diameter φ55 mm, height H30 mm). The temperature was raised from room temperature (25°C) to 2000°C at a rate of 7°C / min. After the heat treatment, the mixture was cooled to room temperature, and the fired cake was removed from the crucible.

[0080] (Crushing) The obtained baked cake was crushed and passed through a metal mesh with an opening of 90 μm, and the particle group (powder) that passed through the metal mesh was obtained as a BN agglomerated powder.

[0081] (evaluation) The BN agglomerated powder obtained in this example was measured for pore size distribution, Al concentration, particle size, intra-particle porosity, and circularity using the methods described above. The main production conditions and evaluation results are shown in Table 1 (the same applies hereinafter). As shown in FIG. 1, the pore size distribution of the BN agglomerated powder obtained in this example did not have any clear peaks corresponding to intra-particle pores other than the first peak indicating inter-particle gaps. SEM observation revealed that the BN agglomerated particles obtained in this example had a house-of-cards structure in which the scaly BN primary particles were not oriented and were stacked in a complex pattern. In other words, the BN agglomerated powder obtained in this example had a house-of-cards structure.

[0082] <Example 2> In this example, the amount of binder calculated as Al2O3 was changed as shown in Table 1. Apart from that, BN agglomerated powder was produced in the same manner as in Example 1 and evaluated. As shown in FIG. 1, the pore size distribution of the BN agglomerated powder obtained in this example did not have any clear peaks corresponding to intra-particle pores other than the first peak indicating inter-particle gaps. SEM observation revealed that the BN agglomerated particles had a house-of-cards structure in which the scale-like BN primary particles were layered in a complex manner without being oriented. In other words, this BN agglomerated powder had a house-of-cards structure.

[0083] Example 3 In this example, the amount of BN granulated powder and the amount of carbon powder added before heat treatment were changed as shown in Table 1. Otherwise, BN agglomerated powder was produced and evaluated in the same manner as in Example 1. As shown in FIG. 1, the pore size distribution of the BN agglomerated powder obtained in this example did not have any clear peaks corresponding to intra-particle pores other than the first peak indicating inter-particle gaps. SEM observation revealed that the BN agglomerated particles had a house-of-cards structure in which the scale-like BN primary particles were layered in a complex manner without being oriented. In other words, this BN agglomerated powder had a house-of-cards structure.

[0084] <Comparative Example 1> In this example, no binder was added to the BN slurry, and no carbon powder was added before the heat treatment. In addition, the firing conditions (heat treatment conditions) were changed as shown in Table 1. Otherwise, BN agglomerated powder was produced and evaluated in the same manner as in Example 1. As shown in FIG. 1, the pore size distribution of the BN agglomerated powder obtained in this example had a first peak indicating interparticle gaps, as well as a second peak corresponding to intraparticle pores. SEM observation revealed that the BN agglomerated particles had a house-of-cards structure in which the scale-like BN primary particles were layered in a complex manner without being oriented. In other words, the BN agglomerated powder had a house-of-cards structure.

[0085] In Examples 1 to 3, BN agglomerated powders with low intra-particle porosity were obtained. In the heat treatment of Examples 1 to 3, the temperature was raised suddenly to a high temperature range that would normally cause sintering. However, by adding carbon powder before the heat treatment, the fusion of agglomerated particles, which causes sintering, was suppressed, and it is believed that a high-density BN agglomerated powder was obtained in which fine pores, which do not have any clear peaks corresponding to intra-particle pores other than the first peak indicating inter-particle gaps in the pore distribution, were reduced. On the other hand, in Comparative Example 1, no binder was added, and the contribution of boron oxide and aluminum compounds, which are important for the particle growth of boron nitride at high temperatures, was small. This is thought to be why BN primary particles did not grow, and a clear second peak corresponding to intra-particle pores appeared in the pore distribution in addition to the first peak indicating inter-particle gaps.

[0086] <Comparative Example 2> In this example, PTX60 (manufacturing conditions unknown) manufactured by Momentive, which is a commonly available agglomerated powder of boron nitride, was evaluated in the same manner as in Example 1. 1, the pore size distribution of the BN agglomerated powder of this example had a first peak indicating interparticle gaps and a second peak corresponding to intraparticle pores. The intraparticle porosity was clearly higher than in Examples 1 to 3.

[0087] <Comparative Example 3> In this example, CTS7M (manufacturing conditions unknown) manufactured by SAINT-GOBAIN, which is a commonly available agglomerated powder of boron nitride, was evaluated in the same manner as in Example 1. 1, the pore size distribution of the BN agglomerated powder of this example had a first peak indicating interparticle gaps and a second peak corresponding to intraparticle pores. The intraparticle porosity was clearly higher than in Examples 1 to 3.

[0088] [Table 1] [Industrial Applicability]

[0089] The use of the boron nitride agglomerated powder of the present invention makes it possible to provide a heat dissipation member with excellent thermal conductivity. Furthermore, the use of a heat dissipation member containing the boron nitride agglomerated powder of the present invention makes it possible to realize a semiconductor device with good heat dissipation performance, high quality, excellent thermal conductivity, and high reliability.

Claims

1. A boron nitride agglomerated powder in which, in a pore size distribution measured by mercury intrusion porosimetry, there is no second peak corresponding to pores within agglomerated particles on the smaller pore size side of a first peak corresponding to interparticle gaps.

2. 2. The boron nitride agglomerated powder according to claim 1, wherein the circularity in a projected image is 82% or more.

3. 3. The boron nitride agglomerated powder according to claim 1, wherein the intraparticle porosity measured by mercury intrusion porosimetry is 40% or less.

4. 3. The boron nitride agglomerated powder according to claim 1, which contains 0.1 mass % or more of aluminum element relative to the boron nitride agglomerated powder.

5. A composite composition comprising the boron nitride agglomerated powder of claim 1 or 2 and a matrix material.

6. The composite composition of claim 5 , wherein the matrix material comprises a resin.

7. A heat dissipation component obtained by molding the composite material composition according to claim 5.

8. A semiconductor device comprising the heat dissipation member according to claim 7 .

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