Hexagonal boron nitride powder and method for producing the same

Abstract

[Problem] The present invention aims to provide a hexagonal boron nitride powder that can be used to obtain a resin composition that is excellent in resistance to solder heat. [Solution] With a hexagonal boron nitride powder, the resistance to solder heat of a resin composition can be improved, and the ratio (S W / S N ) of the BET specific surface area (S W ) measured with water as the adsorbate species to the BET specific surface area (S N ) measured with nitrogen as the adsorbate species is 0.07 or less. In addition, with a manufacturing method for a hexagonal boron nitride powder that includes a step of subjecting a crude hexagonal boron nitride powder having a boron elution amount of 60 ppm or less to a heat treatment at 1300°C or higher and 2200°C or lower in a nitrogen atmosphere at a dew point temperature of -85°C or lower, a hexagonal boron nitride powder that can improve the resistance to solder heat of a resin composition can be obtained.

Description

Technical Field

[0001] This invention relates to novel boron nitride powders. More specifically, it relates to hexagonal boron nitride powders capable of producing resin compositions with good resistance to welding heat. Background Technology

[0002] In recent years, the development of 5G (5th generation mobile communication system) and other technologies have led to increasingly sophisticated performance in digital information and communication equipment. This has resulted in the high integration and miniaturization of semiconductor devices, leading to a tendency for increased heat dissipation from these devices. Therefore, as a heat dissipation countermeasure, resin compositions filled with thermally conductive fillers are used as heat dissipation materials. Such resin compositions exhibit excellent thermal conductivity and moldability, and are easy to handle, thus increasing demand. In particular, the development of resin compositions using hexagonal boron nitride powder as a thermally conductive filler has been prevalent in recent years.

[0003] Requirements for resin compositions used as heat dissipation materials are multifaceted, but one notable aspect is resistance to soldering heat. When soldering resin compositions, such as those used in printed circuit boards, high temperatures of around 250°C to 350°C are typically applied. In resin compositions with low soldering heat resistance, this high temperature causes expansion, leading to cracking and breakage at the solder joint. Therefore, improving the soldering heat resistance of resin compositions is desirable.

[0004] In the past, the soldering heat resistance of heat sinks and printed circuit boards has been widely improved by selecting resins with higher heat resistance as the resin in resin compositions. For example, Patent Document 1 reports that in a resin composition containing resin and heat-dissipating fillers such as boron nitride, the soldering heat resistance of the resin composition is improved by using a polyimide copolymer with a high glass transition temperature and a specific structure as the resin.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6758875 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] As mentioned above, in order to improve the welding heat resistance of resin compositions, operations were carried out to control the chemical structure of the resin, but there is a problem that the available resins are limited.

[0010] On the other hand, as a way to improve the weld heat resistance of resin compositions without limitation, it is also possible to control the main components other than the resin, namely fillers. However, the relationship between the properties of fillers and weld heat resistance has not been understood to date, and it is unclear how to control the properties of fillers to improve the weld heat resistance of resin compositions. The present invention was made in view of the above circumstances, and its object is to provide a hexagonal boron nitride powder that can yield resin compositions with excellent weld heat resistance.

[0011] Solution for solving the problem

[0012] The main reason for the decrease in soldering heat resistance is the trace amounts of moisture and low-molecular-weight compounds contained in the resin composition. When high heat is applied during soldering, the moisture in the resin composition vaporizes and expands, causing the resin composition to swell. Previously, it was thought that the substances causing this decrease in soldering heat resistance originated from the resin itself, but the inventors have discovered that these components also adhere to the surface of the hexagonal boron nitride powder, causing a decrease in soldering heat resistance.

[0013] Further research yielded the following insights: Based on the BET specific surface area (S) measured using water as the adsorbent species... W ) and the BET specific surface area (S) measured using nitrogen as the adsorbate species N The ratio of (S) W / S N The value of S can be used to evaluate the adhesion ease of substances that contribute to the reduction in solder heat resistance on the surface of hexagonal boron nitride powder. Furthermore, it was found that by using S... W / S N By controlling the value of hexagonal boron nitride powder to be smaller than that of conventional hexagonal boron nitride, a resin composition with high resistance to welding heat can be obtained.

[0014] That is, the present invention measures the BET specific surface area (S) by using water as the adsorbent species. W ) and the BET specific surface area (S) measured using nitrogen as the adsorbate species N The ratio of (S) W / S N The hexagonal boron nitride powder has a particle size of 0.07 or less. Preferably, the hexagonal boron nitride powder has a boron content of 40 ppm or less, a sodium content of 1 ppm or less, and a calcium content of 50 ppm or less. Furthermore, the hexagonal boron nitride powder preferably has an average particle size of 1–150 μm, and a BET specific surface area (Si) measured using nitrogen as the adsorbate species. N ) is 15m 2 / Below g.

[0015] In addition, the present invention provides a method for manufacturing hexagonal boron nitride powder, which includes a step of calcining crude hexagonal boron nitride powder with a boron content of less than 60 ppm at a temperature of 1300°C or higher and 2200°C or lower.

[0016] The effects of the invention

[0017] By using the hexagonal boron nitride powder of the present invention, a resin composition with high resistance to soldering heat can be obtained. By using the aforementioned resin composition as a heat dissipation resin sheet or heat dissipation substrate, expansion will not occur even when high heat is applied during processing with solder. Therefore, cracking and breakage in the resin composition can be easily prevented, and the yield in semiconductor device manufacturing can be improved. Detailed Implementation

[0018] <Hexagonal boron nitride powder>

[0019] For the hexagonal boron nitride powder of the present invention, the BET specific surface area (S) measured with water as the adsorbate species is... W ) and the BET specific surface area (S) measured using nitrogen as the adsorbate species N The ratio of (S) W / S N The value is below 0.07. Hexagonal boron nitride is composed of boron and nitrogen and consists of particles with a hexagonal crystal structure.

[0020] The hexagonal boron nitride powder of the present invention has S W / S N The value is below 0.07. Therefore, a resin composition with high resistance to welding heat can be obtained. By making S... W / S N The reason why the resistance to welding heat becomes good when the value is below 0.07 is unclear, but the inventors speculate as follows.

[0021] S W / S N It is a parameter dependent on the affinity between hexagonal boron nitride powder and hydrophilic substances. The BET specific surface area (S) is measured using nitrogen as the adsorbate species. N The specific surface area (S) is calculated by adsorbing nitrogen gas, a known adsorbent species, onto the surface of powder particles and then calculating the amount of adsorption. It represents the actual specific surface area of ​​the powder. On the other hand, the BET specific surface area (S) is measured using water vapor as an adsorbent species. W The adsorption area is calculated by adsorbing water vapor, a known adsorbent species, onto the surface of powder particles and then calculating the amount adsorbed. In this case, because water molecules are polar, unlike when nitrogen is used as the adsorbent species, the apparent specific surface area is calculated, taking into account the hydrophilicity of the powder. Therefore, based on S... W / S NIt can evaluate the surface state of powder, especially the ease with which hydrophilic substances adhere to the powder surface.

[0022] Moreover, S W / S N Small hexagonal boron nitride powders are not prone to moisture absorption because it is difficult for hydrophilic substances to adhere to their surface, and therefore do not readily absorb moisture. W / S N Compared to large hexagonal boron nitride powder, it is possible to prevent moisture from mixing into the resin composition, which would be a cause of reduced weld heat resistance. Therefore, it is speculated that a resin composition with good weld heat resistance can be obtained.

[0023] If S W / S N Smaller S-values ​​make it easier to improve the welding heat resistance of the resin composition; therefore, the S-value of hexagonal boron nitride powder is... W / S N More preferably, 0.06 or less. The S content of hexagonal boron nitride powder W / S N When the size is too small, operation and manufacturing become difficult, therefore, S W / S N Preferably 0.01 or higher, more preferably 0.03 or higher.

[0024] When impurities exist on the surface of the hexagonal boron nitride powder of the present invention, these impurities can sometimes contribute to the absorption of water molecules. Therefore, it is preferable that the hexagonal boron nitride powder of the present invention has few impurities; specifically, the amount of dissolved boron is 40 ppm or less, the amount of dissolved sodium is 1 ppm or less, and the amount of dissolved calcium is 50 ppm or less. By keeping the impurities within the aforementioned ranges, it is easy to reduce sulfur content (S). W / S N This readily yields resin compositions with high resistance to welding heat. More preferably, the hexagonal boron nitride powder of the present invention has a boron content of 20 ppm or less, a sodium content of 0.5 ppm or less, and a calcium content of 20 ppm or less.

[0025] The hexagonal boron nitride powder of the present invention can be either single particles or aggregated particles. The particle size of the hexagonal boron nitride powder of the present invention is not particularly limited, but the average particle size is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. By setting the average particle size to 1 μm or more, it becomes easier to improve the thermal conductivity of the resin composition. Furthermore, the average particle size is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 60 μm or less. By setting the average particle size to 150 μm or less, it becomes easier to obtain a resin composition in which the hexagonal boron nitride powder is uniformly dispersed in the resin.

[0026] The BET specific surface area (S) of the hexagonal boron nitride powder of the present invention, measured with nitrogen as the adsorbent species. NNo specific restrictions are specified, but 15m is preferred. 2 / g or less, more preferably 10m 2 / g or less, further preferred 4m 2 / g or less. By S N Set to 15m 2 / g or less, thus making it easier to reduce the viscosity of the resin composition and easily obtain a resin composition with excellent workability. Additionally, S N 0.5m is preferred 2 / g or more, preferably 1.0m 2 / g or more. By S N Set to 0.5m 2 / g or more, thus making it easier to improve the thermal conductivity of the resin composition.

[0027] The tap density of the hexagonal boron nitride powder of the present invention is preferably 0.3–0.9 g / cm³. 3 More preferably, it is 0.4–0.8 g / cm³. 3 By setting the tap density to the aforementioned range, it becomes easier to uniformly disperse the hexagonal boron nitride powder in the resin composition.

[0028] By filling the resin with the hexagonal boron nitride powder of the present invention, a resin composition with high thermal conductivity and high resistance to welding heat, suitable for heat dissipation applications, can be obtained. Therefore, it is preferred to use it as a thermally conductive filler.

[0029] The preferred method for storing the hexagonal boron nitride powder of the present invention is one that prevents the introduction of moisture and impurities. For example, the method of placing the powder in a polypropylene container or a glass container and replacing the gas phase with nitrogen is an example of such a method.

[0030] <Method for Manufacturing Hexagonal Boron Nitride Powder>

[0031] The method for manufacturing hexagonal boron nitride powder of the present invention is not particularly limited. For example, it can be manufactured according to a method for manufacturing hexagonal boron nitride powder including the following steps: a crude hexagonal boron nitride powder with a boron content of 60 ppm or less is subjected to heat treatment at 1300°C or higher and 2200°C or lower in a high-purity nitrogen atmosphere with a dew point temperature of -85°C or lower.

[0032] In the method for manufacturing hexagonal boron nitride powder of the present invention, there are no particular limitations on the method for obtaining the aforementioned crude hexagonal boron nitride powder. For example, boron can be reacted with nitrogen to synthesize nitride powder, and then washed / dried to obtain the aforementioned crude hexagonal boron nitride powder.

[0033] There are no particular restrictions on the process for obtaining nitrided powder. It can be a reduction nitriding method that reacts oxygen-containing boron compounds with nitrogen at high temperatures, or a melamine method based on the thermal decomposition of melamine borate. However, in terms of time and cost in the heating process, the reduction nitriding method is preferred.

[0034] In the reduction nitriding process, a boron-containing compound is typically mixed with an auxiliary agent to obtain a raw material mixture powder. Heating this mixture under a nitrogen atmosphere effectively yields nitrided powder. Examples of the aforementioned boron-containing compounds include boron trioxide, boron dioxide, boron tetraoxide, metaboric acid, perboric acid, orthoboric acid, sodium tetraborate, and sodium perborate. Boric acid, which is readily available, is commonly used. The aforementioned auxiliary agents can be carbon sources and oxygen-containing alkaline earth metal compounds. Examples of carbon sources include carbon black, activated carbon, nano-carbon, and boron carbide. Inexpensive carbon black is commonly used. Examples of oxygen-containing alkaline earth metals include magnesium oxide, calcium oxide, magnesium carbonate, and calcium carbonate. The method of mixing the boron-containing compound and the auxiliary agent is not particularly limited; a vibratory mill, bead mill, ball mill, or other general mixer can be used. The step of heating the aforementioned raw material mixture powder under a nitrogen atmosphere is not particularly limited as long as the nitriding reaction can proceed to obtain nitrided powder. The heating temperature is preferably 1500°C or higher, more preferably 1800°C to 2000°C. By setting the heating temperature to 1500°C or higher, the formation of amorphous boron nitride can be suppressed, making it easier to obtain hexagonal boron nitride.

[0035] The nitriding powder obtained in the aforementioned nitriding reaction is typically obtained as a solidified mass of several millimeters or larger. Therefore, it is preferable to break this solidified mass into a size of 500 μm or smaller before performing the acid-based cleaning described below. By breaking it into smaller pieces, the acid can easily penetrate into the interior of the nitriding powder through the acid cleaning process described later, making cleaning easier and more effective. Furthermore, during the heat treatment described later, nitrogen can flow into the interior of the nitriding powder, effectively producing S... W / S N Small hexagonal boron nitride powder. There are no particular restrictions on the crushing method; examples include mortar and pestle mills, ball mills, and mortars.

[0036] The boron nitride powder contains alkali metal salts and oxygen-containing boron compounds as unreacted substances and byproducts. These components are hygroscopic, and if present on the surface of the hexagonal boron nitride powder, the SW / SN value tends to increase. Therefore, it is preferable to remove them by acid cleaning. There are no particular limitations on the acid used for cleaning; examples include hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. The method of acid cleaning is not particularly limited as long as the aforementioned unreacted substances and byproducts can be sufficiently removed. For example, a method can be used where 100 parts by weight of the boron nitride powder is mixed with 50 to 200 parts by weight of concentrated hydrochloric acid (37% aqueous hydrogen chloride solution) and 200 to 500 parts by weight of pure water and stirred in the form of an acid slurry for at least 6 hours.

[0037] After the acid cleaning process described above, pure water is typically used to remove any remaining acid from the surface of the nitride powder. There are no particular limitations to the use of pure water as long as it effectively removes the acid residue from the nitride powder surface. For example, a possible method is as follows: After filtering the stirred acid slurry to remove the solvent, add nitride powder and an equal or greater volume of pure water to prepare an aqueous slurry. Stir this slurry and repeat the process until the aqueous slurry exhibits a pH of 7.

[0038] After the aforementioned washing with pure water, drying is preferable to remove residual moisture from the surface of the boron nitride powder. The drying conditions are not particularly limited, but heating at 80–250°C under reduced pressure is preferred. At drying temperatures below 80°C, moisture removal is time-consuming; above 250°C, residual moisture reacts with boron nitride and undergoes hydrolysis, sometimes increasing boron dissolution. There is no particular limitation on the lower limit of the reduced pressure, but 100 kPa or less is preferred. By maintaining a reduced pressure of 100 kPa or less, moisture can be effectively removed. The weight moisture content of the boron nitride powder before drying is preferably 40% or less. If the weight moisture content is greater than 40%, the drying time becomes longer, and due to prolonged heating, hydrolysis occurs, sometimes increasing boron dissolution.

[0039] After washing, grading can also be performed to adjust the particle size or remove coarse particles. Grading methods include, for example, grading using sieves and air grading.

[0040] The hexagonal boron nitride powder of the present invention can be obtained by heating the crude hexagonal boron nitride powder with a boron leaching content of less than 60 ppm obtained by the above method at a nitrogen atmosphere with a dew point temperature of less than -85°C and a temperature of 1300°C to less than 2200°C.

[0041] The process of heat-treating crude hexagonal boron nitride powder is not particularly limited as long as the powder is heated at a temperature between 1300°C and 2200°C in a nitrogen atmosphere with a dew point temperature below -85°C, and can be carried out using known methods. Specifically, for example, the crude hexagonal boron nitride powder can be placed in a heating furnace, the furnace can be replaced with nitrogen, and the temperature can be increased to the desired temperature while the nitrogen is flowing.

[0042] The surface of crude hexagonal boron nitride powder before heat treatment contains hydrophilic functional groups such as amino and hydroxyl groups generated during the powder manufacturing process. The presence of hydrophilic functional groups such as amino and hydroxyl groups increases the S... W / S N It will become a large value, but it is speculated that these functional groups can be effectively removed through heat treatment, which can form S. W / S N The powder is hexagonal boron nitride powder with a content of 0.07 g / L or less. The heat treatment temperature is preferably 1300°C or higher, more preferably 1400°C or higher, and even more preferably 1600°C or higher. Furthermore, the heat treatment temperature is preferably 2200°C or lower, more preferably 2000°C or lower, and even more preferably 1800°C or lower. If the heat treatment temperature is below 1300°C, the amino and hydroxyl groups may not be sufficiently removed; if the temperature exceeds 2200°C, the boron nitride may decompose or yellow.

[0043] During heat treatment, using nitrogen with a dew point temperature below -85°C prevents the hydrolysis of hexagonal boron nitride caused by trace amounts of moisture in the nitrogen within the furnace, and inhibits the regeneration of functional groups such as amino and hydroxyl groups. The lower the dew point temperature of the aforementioned nitrogen, the easier it is to inhibit the regeneration of amino and hydroxyl groups. However, nitrogen with a low dew point temperature is difficult to operate and also disadvantageous in terms of cost. Therefore, a lower limit of -100°C and a lower limit of -90°C are preferred. After heat treatment, allowing nitrogen to flow and cooling the furnace to room temperature before opening it is preferable, as this easily inhibits the hydrolysis of hexagonal boron nitride.

[0044] There is no particular limitation on the heat treatment time, but it is generally preferred to be more than 1 hour, and more preferably more than 2 hours. In addition, the treatment time is preferably less than 18 hours, and more preferably less than 12 hours.

[0045] Furthermore, since the crude hexagonal boron nitride powder has a boron leaching content of less than 60 ppm, a sodium leaching content of less than 1 ppm, and a calcium leaching content of less than 50 ppm, the hygroscopicity and hydrolysis during heat treatment of the crude hexagonal boron nitride powder can be suppressed, and the hydrophilic functional groups on the surface of the crude hexagonal boron nitride can be effectively removed through heat treatment. Therefore, S can be obtained. W / S N It is a hexagonal boron nitride powder with a strength of less than 0.07.

[0046] Furthermore, the weight moisture content of the crude hexagonal boron nitride powder is preferably 0.5% or less, more preferably 0%. If the weight moisture content is high, hydrolysis will occur during heat treatment, S W / S N Sometimes it gets bigger.

[0047] After heat treatment, the particles can also be classified to adjust their size or remove large particles. Classification methods include, for example, sieving using sieves and air classification.

[0048] <Resin Composition>

[0049] The resin composition of the present invention comprises at least the hexagonal boron nitride powder and resin of the present invention. The aforementioned resin composition exhibits excellent resistance to soldering heat and is not prone to heat-induced expansion or breakage, making it useful, for example, as a heat dissipation material such as a printed circuit board resin, a semiconductor encapsulation material, and a heat sink.

[0050] The resin constituting the aforementioned resin composition is not particularly limited, and may be, for example, an organosilicon resin or a curable epoxy resin. Examples of curable epoxy resins include bisphenol A type epoxy resin, bisphenol S type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, polypropylene glycol type epoxy resin, polytetramethylene glycol type epoxy resin, naphthalene type epoxy resin, phenylmethane type epoxy resin, tetraphenolmethane type epoxy resin, biphenyl type epoxy resin, phenolic varnish type epoxy resin, tetrafunctional naphthalene type epoxy resin, and cresol varnish. This includes various types of epoxy resins, such as tricyclopentadiene epoxy resin, triphenol epoxy resin, naphthol phenolic varnish epoxy resin, naphthyl ether epoxy resin, aromatic glycidylamine epoxy resin, hydroquinone epoxy resin, uranium epoxy resin, triphenol methane epoxy resin, aralkyl epoxy resin, polypropylene glycol epoxy resin, polysulfide modified epoxy resin, epoxy resin with a triazine core in the skeleton, and bisphenol A epoxy alkyl adduct type epoxy resin. These curable epoxy resins can be used alone or in mixtures of two or more. Additionally, as curing agents, amine resins, anhydride resins, phenol resins, imidazole resins, reactive ester curing agents, cyanate ester curing agents, naphthol curing agents, and benzoxazine curing agents can be used. These curing agents can also be used alone or in mixtures of two or more. The amount of these curing agents mixed with the epoxy resin is 0.5 to 1.5 equivalents, preferably 0.7 to 1.3 equivalents, relative to the epoxy resin. In this specification, these curing agents are also included in the resin.

[0051] Furthermore, as the silicone resin, a mixture of addition-reaction silicone resin and silicone crosslinking agent, i.e., a known curable silicone resin, can be used without limitation. Examples of addition-reaction silicone resins include polyorganosiloxanes such as polydimethylsiloxane, which have alkenyl groups such as vinyl or hexenyl as functional groups in the molecule. Examples of silicone crosslinking agents include dimethylhydrosiloxy-terminated dimethylsiloxane-methylhydrosiloxane copolymers, trimethylsiloxy-terminated dimethylsiloxane-methylhydrosiloxane copolymers, trimethylsiloxane-terminated poly(methylhydrosiloxane), poly(hydrodiene silsesquioxane), and other polyorganosiloxanes having silicon atoms bonded to hydrogen atoms. Additionally, as the curing catalyst, known platinum-based catalysts used in the curing of silicone resins can be used without limitation. Examples include fine-grained platinum, fine-grained platinum supported on carbon powder, platinum chloride, alcohol-modified platinum chloride, olefin complexes of platinum chloride, palladium, and rhodium catalysts.

[0052] In addition, liquid crystal polymers, polyesters, polyamides, polyimides, polyphthalamides, polyphenylene sulfides, polycarbonates, polyaryl ether ketones, polyphenylene ethers, fluoropolymers, cyanate compounds, maleimide compounds, etc., can also be used as resins.

[0053] Liquid crystal polymers include thermotropic liquid crystal polymers that exhibit liquid crystal properties in the molten state and lyotropic liquid crystal polymers that exhibit liquid crystal properties in the solution state; any liquid crystal polymer can be used.

[0054] Examples of thermotropic liquid crystal polymers include polymers synthesized from p-hydroxybenzoic acid (PHB), terephthalic acid and 4,4'-biphenyl, polymers synthesized from PHB and 2,6-hydroxynaphthoic acid, and polymers synthesized from PHB, terephthalic acid and ethylene glycol.

[0055] Examples of fluoropolymers include ethylene tetrafluoride resin (PTFE), ethylene tetrafluoride-propylene hexafluoride copolymer resin (PFEP), and ethylene tetrafluoride perfluoroalkyl vinyl ether copolymer resin (PFA).

[0056] As cyanate compounds, phenolic varnish-type cyanate compounds, naphthol aralkyl-type cyanate compounds, biphenyl aralkyl-type cyanate compounds, naphthalene ether-type cyanate compounds, xylene resin-type cyanate compounds, and adamantane skeleton-type cyanate compounds are preferred. Examples of phenolic varnish-type cyanate compounds, biphenyl aralkyl-type cyanate compounds, and naphthol aralkyl-type cyanate compounds are also mentioned.

[0057] Examples of maleimide compounds include N-phenylmaleimide, N-hydroxyphenylmaleimide, bis(4-maleimidephenyl)methane, 2,2-bis{4-(4-maleimidephenoxy)-phenyl}propane, bis(3,5-dimethyl-4-maleimidephenyl)methane, bis(3-ethyl-5-methyl-4-maleimidephenyl)methane, bis(3,5-diethyl-4-maleimidephenyl)methane, maleimide compounds represented by formula (1) below, and maleimide compounds represented by formula (2) below.

[0058]

[0059] In the above formula (1), R5 independently represents a hydrogen atom or a methyl group, preferably a hydrogen atom.

[0060] In addition, n1 represents an integer greater than or equal to 1, preferably an integer less than or equal to 10, and more preferably an integer less than or equal to 7.

[0061]

[0062] In the above formula (2), each of the multiple Rs independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, etc.), or a phenyl group. From the viewpoint of further improving flame retardancy and peel strength, it is preferable to select a group from the group consisting of hydrogen atoms, methyl and phenyl, more preferably one of hydrogen atoms and methyl, and even more preferably hydrogen atoms.

[0063] The content of the hexagonal boron nitride powder of the present invention in the aforementioned resin composition is preferably 30-80% by weight, more preferably 40-70% by weight. When the content of hexagonal boron nitride powder is less than 30% by weight, the thermal conductivity of the resin composition tends to decrease; if it exceeds 80% by weight, the porosity increases, and the dielectric strength sometimes decreases. It should be noted that the hexagonal boron nitride powder of the present invention can also be mixed with other hexagonal boron nitride powders and filled into the resin composition of the present invention. However, in this case, it is preferable that 50% or more by weight, preferably 80% or more by weight, and more preferably 100% by weight of the total hexagonal boron nitride powder is the hexagonal boron nitride powder of the present invention.

[0064] The resin content in the aforementioned resin composition is equivalent to the value obtained by reducing the content of hexagonal boron nitride powder when the total capacity of the composition is set to 100 capacity%, and also includes the capacity of the curing agent if it is included, preferably 70 to 20 capacity%, more preferably 60 to 30 capacity%.

[0065] Furthermore, the aforementioned resin composition may also contain components other than hexagonal boron nitride powder and resin, and may appropriately include, within a range that does not affect the effects of the present invention, inorganic fillers, anti-discoloration agents, surfactants, dispersants, coupling agents, etc., other than hexagonal boron nitride. Examples of inorganic fillers include alumina, silicon oxide, zinc oxide, magnesium oxide, titanium oxide, silicon nitride, aluminum nitride, aluminum hydroxide, magnesium hydroxide, silicon carbide, calcium carbonate, barium sulfate, talc, etc. When the total volume of the composition is set to 100% by volume, the content of these components is preferably 25% by volume or less, more preferably 15% by volume or less.

[0066] The method for manufacturing the resin composition is not particularly limited. For example, if the resin is a curable epoxy resin, the following method for manufacturing the resin composition can be adopted, which includes: a mixing step of mixing the curable epoxy resin with the hexagonal boron nitride powder of the present invention and other components as needed to obtain a curable composition; a molding step of molding the curable composition into a desired shape; and a curing step of curing the curable composition.

[0067] In the aforementioned mixing process, there are no particular limitations on the method as long as the components can be mixed evenly to obtain a curable composition. For example, a general mixer, planetary mixer, or rotation-revolution mixer can be used.

[0068] In the aforementioned mixing process, to improve the dispersibility of hexagonal boron nitride powder and other components with the resin, and to reduce the viscosity of the curable composition for easy molding into the desired shape, a solvent with high affinity for the resin used can be added. It should be noted that in the molding process described later, when using coating molding, it is particularly preferable to add a solvent to the curable composition. Examples of solvents include ketones such as cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; glycol ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether; and ether alcohols such as 2-methoxyethanol, 1-methoxyethanol, 2-ethoxyethanol, 1-ethoxy-2-propanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, and 2-(2-butoxyethoxy)ethanol. These solvents can be used alone or in mixtures of two or more.

[0069] The aforementioned molding process is not particularly limited as long as the aforementioned curable composition can be molded into the desired shape. For example, it can also be filled into a mold. However, if the desired shape is a plate, it can also be molded by coating the curable composition onto a substrate such as a film or metal foil to make it a uniform thickness.

[0070] When the curable composition contains a solvent, it is preferable to remove the solvent from the curable composition after the aforementioned molding process and before the curing process. If a large amount of solvent remains in the curable composition, pores are easily generated in the resulting resin composition, and the solder heat resistance and dielectric strength of the resin composition tend to decrease. There are no particular limitations on the solvent removal method; examples include ventilation drying in an open system, heating drying in an oven, and ambient / heated vacuum drying in a vacuum dryer. To produce a resin composition with a smooth surface without generating bubbles due to solvent evaporation, it is preferable to remove a constant amount of solvent under ambient vacuum drying followed by heated vacuum drying. The drying time and temperature can be appropriately selected depending on the solvent used, but to ensure sufficient solvent removal, the drying time is typically set to 40 minutes or more, and the drying temperature to 100°C or more.

[0071] The curing process is the process of curing the molded curable composition. In the case of a curable epoxy resin, the curable epoxy resin is cross-linked and forms a three-dimensional network by heating, thereby obtaining a resin composition. It should be noted that, for the aforementioned curing of a heated curable epoxy resin, degassing can be effectively carried out by compression or heating under reduced pressure, making it easier to improve the insulation properties of the resin composition; therefore, this is a preferred method.

[0072] Examples of applications for resin compositions include heat dissipation materials, such as thermally conductive sealing materials, heat dissipation coatings, printed circuit boards, and insulating layers for metal substrates. When using a resin composition as an insulating layer for a metal substrate, a curable composition is coated onto a metal foil and molded into a sheet. A metal foil is then placed on the opposite side of the curable composition, and the metal foil is heated to a high temperature while under pressure, thereby curing the curable composition and bonding the metal foil to the resin composition. This process can produce a metal substrate. There are no particular limitations on the metal foil used in electrical insulation applications; examples include copper foil and aluminum foil. Furthermore, by heating the metal foil under reduced pressure, gaseous components can be effectively removed, making it easy to manufacture a dense resin composition with excellent soldering heat resistance and dielectric strength.

[0073] Example

[0074] Hereinafter, embodiments are described in detail to illustrate the present invention, but the present invention is not limited to these embodiments. It should be noted that the values ​​in the embodiments and comparative examples were measured according to the following methods.

[0075] (1) BET specific surface area ratio (S W / S N )

[0076] The specific surface area S of BET was determined using the following method. W and S N S is calculated from the obtained results. W / S N .

[0077] ·S W Measurement

[0078] Gas adsorption experiments were conducted using a high-precision vapor adsorption capacity measuring device, BELSORP-Aqua3 (manufactured by MicrotracBEL Corp.), with water vapor as the adsorbate. Water vapor adsorption-desorption isotherms were measured, and the specific surface area was calculated from the results. Specifically, hexagonal boron nitride powder, which had been vacuum-dried and degassed at 120°C for 8 hours as a pretreatment, was used. The adsorption conditions were set at 298.15 K, saturated vapor pressure of 3.169 kPa, equilibrium waiting time of 500 seconds, with pure water as the adsorbate, a molecular weight of 18.020, and a cross-sectional area of ​​0.125 nm. 2 Under the specified conditions, the adsorption-desorption isotherms of water vapor gas were determined using the constant volume method, and S was calculated using the BET method. W .

[0079] ·S N Measurement

[0080] Gas adsorption experiments were conducted using a FlowSorb III 2310 (manufactured by Shimadzu Corporation), with nitrogen as the adsorbate species. Nitrogen adsorption isotherms were measured, and the specific surface area was calculated from the results. Specifically, hexagonal boron nitride powder, which had been vacuum-dried and degassed at 200°C for 10 minutes as a pretreatment, was then subjected to a gas flow rate of 15 cm⁻¹. 3 Under conditions of / minute, the adsorption-desorption isotherm of nitrogen was determined using the continuous flow method, and S was calculated according to the BET method. N .

[0081] (2) Average particle size (D50) of hexagonal boron nitride powder

[0082] The particle size distribution was performed using a laser diffraction / scattering particle size analyzer MT3000 (manufactured by MicrotracBEL Corp.) based on the laser diffraction method. Specifically, 0.1 g of hexagonal boron nitride powder was added to a mixing tank attached to the apparatus, which was filled with 50 cc of ethanol. The sample, which was ultrasonically dispersed at 40 W for 20 seconds, was used for measurement, and the average particle size (D50) on a volume basis was calculated.

[0083] (3) Tap packing density of hexagonal boron nitride powder

[0084] The tapped bulk density (g / cm³) was determined using a KYT-5000 tapped density meter (manufactured by SEISHIN ENTERPRISE Co., Ltd.). 3 In detail, 100 mL of hexagonal boron nitride powder was filled into a 100 mL sample cuvette. After compaction at a speed of 120 times / minute, a compaction height of 5 cm, and 500 compaction cycles, the weight was measured and the compacted bulk density was calculated.

[0085] (4) The amount of boron, sodium, and calcium dissolved from crude hexagonal boron nitride powder and hexagonal boron nitride powder.

[0086] In a 50 mL vial, 50 g of 0.5 mol / L sulfuric acid aqueous solution and 2 g of hexagonal boron nitride powder were added. The liquid temperature was adjusted to 25 °C while shaking and stirring for 1 minute. After standing for 120 minutes, the boron, sodium, and calcium content in the liquid were analyzed using an ICP spectrometer (THERMOFISHER iCAP6500). The measured results were divided by the mass of hexagonal boron nitride powder used in the experiment to calculate the amount of dissolved boron, sodium, and calcium per unit mass of hexagonal boron nitride powder (ppm).

[0087] (5) Moisture content of crude hexagonal boron nitride powder and hexagonal boron nitride powder

[0088] The determination was performed using a heated drying moisture meter MS-70 (manufactured by A&D Company). Specifically, 10g of coarse hexagonal boron nitride powder or hexagonal boron nitride powder was measured onto a balance, and the weight change was measured while heating to 200°C. The measurement ended when the weight change was less than 0.01% / minute. The difference between the weight before heating and the weight at the end of the measurement was taken as the moisture content, and the moisture percentage was calculated.

[0089] (6) Fabrication of resin composition / metal base substrate

[0090] 22.5 g (49.2% by volume) of hexagonal boron nitride powder, 7.20 g (30.6% by volume) of liquid-curing epoxy resin (Mitsubishi Chemical JER828, bisphenol A type epoxy resin, epoxy equivalent 184-194 g / eq), 10.1 g (12.6% by volume) of alumina, and 20 g of cyclohexanone as a solvent were mixed with 1.80 g (7.6% by volume) of epoxy resin curing agent (Mitsubishi Chemical JER cure W, modified aromatic amine, amine value 623-639) and mixed using a rotary mixer (Kurashiki Spinning Mazerustar KK-250S) to prepare a curable composition.

[0091] The obtained curable composition was coated onto a release PET film (Nippa PET50×1-FSC6, 50μm thick) using an automatic coating device (TESTER SANGYO CO,.LTD. PI-1210) with a rod applicator to a film thickness of 300μm. After air-drying the coated film in a ventilated chamber for 10 minutes, it was then vacuum-dried at 100°C for 40 minutes to obtain a plate-shaped molded body. Next, the plate-shaped molded body was clamped between two 50×100mm copper foil sheets and pressurized at 100°C and 15MPa for 3 minutes under reduced pressure to perform pressing. Then, the temperature was raised to 150°C, and the mixture was pressurized at 20MPa for 60 minutes under reduced pressure to cure the curable composition, forming a resin composition for fabricating a metal substrate.

[0092] (7) Welding heat resistance test

[0093] The metal substrate obtained in (6) was subjected to a solder heat resistance test and evaluated according to the method of JIS C60068-2-20:2010. Specifically, as an accelerated curing process using a constant temperature and humidity chamber, the metal substrate was kept at 85% relative humidity and 120°C for 4 hours, and then left to stand under standard atmospheric conditions for 2 hours. Afterwards, using a solder bath with a depth of 60 mm and a volume of 730 mL, the metal substrate was immersed in molten solder at 260°C for 10 seconds at an immersion speed of 25 mm / s, and then pulled out at a pull-out speed of 25 mm / s to obtain the test specimen. The appearance of the obtained test specimen was visually inspected; those without expansion were rated as good, and those with expansion were rated as poor.

[0094] (Example 1)

[0095] 700g of boron oxide, 300g of carbon black, 200g of calcium carbonate, and 66g of boron carbide were mixed in a mixer. The mixture was heated to 1500°C in a graphite-based Taman furnace under a nitrogen atmosphere and held at 1500°C for 6 hours. After holding at 1500°C, the temperature was increased to 1880°C, and a reduction nitriding treatment was performed at 1880°C for 2 hours to obtain nitrided powder.

[0096] Next, the obtained nitriding powder was crushed using a mortar and pestle mill and then placed into a polyethylene container. 500g of hydrochloric acid (37% wt HCl) and 1500g of pure water were added per 500g of nitriding powder to adjust the acid slurry. The mixture was stirred for 8 hours to perform acid cleaning. After acid cleaning, the acid slurry was filtered through a Buchner funnel and then added to pure water at least 10 times the mass of the nitriding powder. The water slurry was adjusted for cleaning, and then dehydrated by vacuum filtration until the moisture content of the nitriding powder was below 40% by weight.

[0097] Subsequently, the nitride powder was dried under reduced pressure of 30 kPaA at 200°C for 15 hours until the moisture content was below 0.50%. It was then classified using a 90 μm sieve, and the undersize particles were recovered to obtain coarse hexagonal boron nitride powder. The amount of boron dissolved from the obtained coarse hexagonal boron nitride powder was 46 ppm.

[0098] The obtained coarse hexagonal boron nitride powder was filled into a carbon sintering frame coated with boron nitride and placed in a graphite Taman furnace. The furnace was then depressurized, and a nitrogen atmosphere was created by circulating nitrogen gas at a dew point of -85°C at a flow rate of 40 NL / min. The temperature was raised to 1650°C and heated for 4 hours, followed by cooling to room temperature. The powder was then classified using a 90 μm sieve, and the undersize particles were collected to obtain hexagonal boron nitride powder. The obtained hexagonal boron nitride powder was placed in a 2L covered polypropylene container, and the gas phase was purged with nitrogen and stored. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 1.

[0099] (Example 2)

[0100] 700g of boron oxide, 300g of carbon black, and 200g of calcium carbonate were mixed in a mixer. The mixture was then heated to 1500°C in a graphite-made Taman furnace under a nitrogen atmosphere and held at 1500°C for 6 hours. After holding at 1500°C, the temperature was increased to 1840°C, and a reduction nitriding treatment was performed at 1840°C for 2 hours to obtain nitrided powder.

[0101] Next, the obtained nitriding powder was crushed using a mortar and pestle mill and then placed into a polyethylene container. For every 500g of nitriding powder, 500g of hydrochloric acid (37% wt HCl) and 1500g of pure water were added to adjust the acid slurry. The mixture was stirred for 8 hours to perform acid cleaning. After acid cleaning, the acid slurry was filtered using a Buchner funnel. Then, a water slurry was prepared by adjusting the water slurry with at least 10 times the amount (by weight) of the nitriding powder. Finally, the mixture was dehydrated by vacuum filtration until the moisture content of the nitriding powder was below 40% by weight.

[0102] Subsequently, the sample was dried under reduced pressure at 200°C for 15 hours at 30 kPaA until the moisture content was below 0.50%. It was then classified using a 90 μm sieve, and the undersize particles were recovered to obtain coarse hexagonal boron nitride powder. The amount of boron dissolved from the obtained coarse hexagonal boron nitride powder was 18 ppm.

[0103] The obtained coarse hexagonal boron nitride powder was filled into a carbon sintering frame coated with boron nitride and placed in a graphite Taman furnace. The furnace was then depressurized, and a nitrogen atmosphere was created by circulating nitrogen gas at a dew point of -85°C at a flow rate of 40 NL / min. The temperature was raised to 1650°C and heated for 4 hours, followed by cooling to room temperature. The powder was then classified using a 90 μm sieve, and the undersize particles were collected to obtain hexagonal boron nitride powder. The obtained hexagonal boron nitride powder was placed in a 2L covered polypropylene container, and the gas phase was purged with nitrogen and stored. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 1.

[0104] (Example 3)

[0105] 700g of boron oxide, 300g of carbon black, 200g of calcium carbonate, and 180g of boron carbide were mixed in a mixer. The mixture was heated to 1500°C in a graphite-made Taman furnace under a nitrogen atmosphere and held at 1500°C for 6 hours. After holding at 1500°C, the temperature was increased to 1940°C, and a reduction nitriding treatment was performed at 1940°C for 2 hours to obtain nitrided powder.

[0106] Next, the obtained nitriding powder was crushed using a mortar and pestle mill and then placed into a polyethylene container. For every 500g of nitriding powder, 500g of hydrochloric acid (37% wt HCl) and 1500g of pure water were added to adjust the acid slurry. The mixture was stirred for 8 hours to perform acid cleaning. After acid cleaning, the acid slurry was filtered using a Buchner funnel. Then, a water slurry was prepared using at least 10 times the amount (by weight) of the nitriding powder and washed. Finally, the mixture was dehydrated by vacuum filtration until the moisture content of the nitriding powder was below 40% by weight.

[0107] Subsequently, the sample was dried under reduced pressure at 30 kPaA and 200°C for 15 hours until the moisture content was below 0.50%. It was then classified using a 90 μm sieve, and the undersize particles were recovered to obtain coarse hexagonal boron nitride powder. The amount of boron dissolved from the obtained coarse hexagonal boron nitride powder was 32 ppm.

[0108] The obtained coarse hexagonal boron nitride powder was classified using a 90 μm sieve and then filled into a carbon sintering rack coated with boron nitride, placed in a graphite Taman furnace. The furnace pressure was then reduced, and a nitrogen atmosphere was created by circulating nitrogen gas at a dew point of -85 °C at a flow rate of 40 NL / min. The temperature was raised to 1650 °C and heated for 4 hours, followed by cooling to room temperature. Next, the powder was classified using a 90 μm sieve, and the undersize particles were collected to obtain hexagonal boron nitride powder. The obtained hexagonal boron nitride powder was placed in a 2 L covered polypropylene container, and the gas phase was purged with nitrogen and stored. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 1.

[0109] (Examples 4-7)

[0110] As shown in Table 1, the manufacturing conditions were changed, but otherwise the hexagonal boron nitride powders of Examples 4-7 were prepared in the same manner as in Example 1. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 1.

[0111] (Example 8)

[0112] 80g of anhydrous borax, 50g of boron oxide, and 45g of melamine were mixed to prepare a mixed powder. The mixture was heated to 1250°C in a graphite-made Taman furnace under a nitrogen atmosphere and heated at 1250°C for 2 hours to obtain nitrided powder using the melamine method.

[0113] Next, the obtained nitriding powder was crushed using a mortar and pestle mill and then placed into a polyethylene container. For every 100g of nitriding powder, 100g of hydrochloric acid (37% wt HCl) and 300g of pure water were added to adjust the acid slurry. The mixture was stirred for 8 hours to perform acid cleaning. After acid cleaning, the acid slurry was filtered using a Buchner funnel. Then, a water slurry was prepared using at least 10 times the amount (by weight) of the nitriding powder and washed. Finally, the mixture was dehydrated by vacuum filtration until the moisture content of the nitriding powder was below 40% by weight.

[0114] Subsequently, the sample was dried under reduced pressure at 30 kPaA and 150 °C for 15 hours until the moisture content was below 0.50%. It was then classified using a 90 μm sieve, and the undersize particles were recovered to obtain coarse hexagonal boron nitride powder. The amount of boron dissolved from the obtained coarse hexagonal boron nitride powder was 57 ppm.

[0115] The obtained crude hexagonal boron nitride powder was filled into a carbon sintering frame coated with boron nitride and placed in a graphite Taman furnace. The furnace was then depressurized, and a nitrogen atmosphere was created by circulating nitrogen gas at a dew point of -85°C at a flow rate of 40 NL / min. The temperature was raised to 1350°C and heated for 4 hours, followed by cooling to room temperature. The powder was then classified using a 90 μm sieve, and the undersize particles were collected to obtain hexagonal boron nitride powder. The obtained hexagonal boron nitride powder was placed in a 500 mL capped polypropylene container, and the gas phase was purged with nitrogen and stored. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 2.

[0116] (Compare Examples 1, 2, and 5)

[0117] As shown in Table 1, the manufacturing conditions were changed, but otherwise, the hexagonal boron nitride powders of Comparative Examples 1, 2, and 5 were prepared in the same manner as in Example 1. The evaluation results of the obtained hexagonal boron nitride are shown in Table 3.

[0118] (Comparative Example 3)

[0119] As shown in Table 1, the manufacturing conditions were modified, but otherwise, the hexagonal boron nitride powder was prepared in the same manner as in Example 3. It should be noted that the amount of boron dissolved from the crude hexagonal boron nitride was adjusted by changing the conditions of acid washing. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 3.

[0120] (Comparative Example 4)

[0121] As shown in Table 1, the manufacturing conditions were changed, but otherwise the hexagonal boron nitride powder was prepared in the same manner as in Example 2. The evaluation results regarding the manufacturing conditions and the obtained hexagonal boron nitride are shown in Table 3.

[0122] [Table 1]

[0123]

[0124] [Table 2]

[0125]

[0126] [Table 3]

[0127]

[0128] The BET specific surface area ratio S of the hexagonal boron nitride powders in Examples 1-8 W / S N All values ​​were below 0.07, and the resin compositions using these hexagonal boron nitride powders all showed good weld heat resistance tests. On the other hand, the BET specific surface area ratio S... W / S N Resin compositions containing hexagonal boron nitride powder exceeding 0.07 g / L in Comparative Examples 1-5 all performed poorly in the solder heat resistance test. This indicates that by using S... W / S N Small hexagonal boron nitride powders improve the weld heat resistance of the resin composition.

Claims

1. A hexagonal boron nitride powder, wherein the BET specific surface area (S) measured with water as the adsorbent species is... W ) and the BET specific surface area (S) measured using nitrogen as the adsorbate species N The ratio of (S) W / S N The concentration of 0.07 or less is 0.07, and the amount of dissolved boron is less than 40 ppm, the amount of dissolved sodium is less than 1 ppm, and the amount of dissolved calcium is less than 50 ppm.

2. The hexagonal boron nitride powder according to claim 1, wherein the average particle size is 1-150 μm, and the BET specific surface area (S) measured by using nitrogen as an adsorbent species is... N ) is 15m 2 / g or less.

3. A resin composition comprising the hexagonal boron nitride powder and resin as described in claim 1 or 2.

4. The resin composition according to claim 3, wherein, The resin composition is used as a heat dissipation material.

5. A method for manufacturing hexagonal boron nitride powder, comprising a step of heat-treating crude hexagonal boron nitride powder with a boron content of less than 60 ppm, a sodium content of less than 1 ppm, and a calcium content of less than 50 ppm under a nitrogen atmosphere at a dew point temperature of less than -85°C and a temperature of more than 1300°C and less than 2200°C.

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