Spherical alumina powder

Abstract

To provide spherical alumina powder with which a resin composition having a high heat conductivity can be provided despite the spherical alumina powder having a D50 of 0.1 to 40 μm.SOLUTION: Spherical alumina powder has a D50 of 0.1 to 40 μm, a circularity of 0.90 or more and 1.00 or less, an α-conversion ratio of 60% or more and 100% or less, and a particle surface roughness shown as the following equation (1) of 1.14 or more and 1.35 or less. Equation (1): the particle surface roughness=BET specific surface area A / sphere-equivalent specific surface area Sa calculated from particle size distribution.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a spherical alumina powder and a method for producing the same. [Background technology]

[0002] In recent years, mobile devices such as smartphones and electronic devices installed in vehicles have become significantly smaller, lighter, and thinner. As a result, the density of electronic components such as IC chips and memory mounted on printed circuit boards inside electronic devices has increased, leading to an ever-increasing heat density inside electronic devices. As the heat density inside electronic devices increases, the temperature rise caused by the heat generated inside the electronic devices becomes significant, leading to a decrease in the operating performance and reliability of the electronic components. Therefore, there is a need to quickly transfer and dissipate the heat generated by electronic components to the outside. Therefore, there is an increasing need to improve the thermal conductivity of packaging materials and substrate materials for electronic devices.

[0003] The mainstream method for solving the above problems is to fill insulating resin materials constituting packaging materials and substrate materials for electronic devices with a highly thermally conductive inorganic material powder as a filler at a high filling rate. Known highly thermally conductive inorganic material powders include alumina, magnesia, boron nitride, and aluminum nitride, but alumina powder is generally used from the viewpoints of chemical resistance, moisture absorption stability, etc.

[0004] The inorganic material powder preferably has a spherical shape, which allows for easy kneading with resin at a high filling rate. Spherical alumina powder is generally known to be produced by a thermal spraying method, in which Bayer process alumina, the raw material, is sprayed into a flame and rapidly cooled while melting to form spherical particles. The thermal spraying method is described in Patent Document 1.

[0005] However, with conventional thermal spraying methods, when the particle size is large, around 50 μm, spherical alumina with a high content of α-alumina (hereinafter also referred to as the α-phase ratio) can be obtained, but as the particle size becomes smaller, the content of low-temperature phases such as δ-alumina increases, resulting in a problem of reduced thermal conductivity of the spherical alumina. Therefore, studies have been conducted to increase the α-phase ratio by subjecting spherical alumina to heat treatment (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-147711 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-9140 Summary of the Invention [Problem to be solved by the invention]

[0007] When the degree of gelatinization is increased by heat treatment of spherical alumina, the heat treatment increases the surface roughness of the spherical alumina, reducing its ability to be mixed with resin. This has led to the problem of the thermal conductivity of resin materials filled with spherical alumina not being increased. On the other hand, because conventional spherical alumina has excellent filling and flow properties, it tends to settle in the mixed and filled resin composition, which can lead to segregation between the resin layer with lower thermal conductivity and the layer where the spherical alumina powder is packed. This leads to further reductions in thermal conductivity and performance variations.

[0008] The present disclosure provides a spherical alumina powder having a D50 of 0.1 to 40 μm that can provide a resin composition with high thermal conductivity. The present disclosure also provides a resin composition and a prepreg that contain the spherical alumina powder. [Means for solving the problem]

[0009] The contents of the present disclosure relate to the following: [1] D50 is 0.1 to 40 μm, Circularity is 0.90 or more and 1.00 or less, The alpha conversion rate is between 60% and 100%, A spherical alumina powder having a particle surface roughness, as expressed by the following formula (1), of 1.14 or more and 1.35 or less. Equation (1); Particle surface roughness = BET specific surface area A / sphere-equivalent specific surface area Sa calculated from particle size distribution [2] Specific gravity is 3.80g / cm 3 The spherical alumina powder according to [1] above. [3] The spherical alumina powder according to [1] or [2], having a BET specific surface area A of 0.1 or more and 2.0 or less. [4] The spherical alumina powder according to any one of [1] to [3], which has an oil absorption rate of 30% or more and 50% or less. [5] A resin composition comprising the spherical alumina powder according to any one of [1] to [4] and a resin. [6] A prepreg in which a substrate is impregnated with the resin composition according to [5]. [7] A cured product of the prepreg or laminate thereof according to [6]. [8] [7] The cured product according to [7], A metal-clad laminate comprising: a metal foil disposed on at least one main surface of the cured product. [9] The resin composition according to [5], which is used as a sealing material for electronic component devices.

[10] An electronic component device comprising an element and a cured product of the resin composition according to [5] that encapsulates the element.

[11] a high-temperature process in which a high-temperature region is formed inside the furnace by a burner that forms a flame; a spheroidizing step of producing a pre-heat-treated spherical alumina powder by charging raw alumina powder into the furnace and heating and melting it; a cooling and washing step in which the pre-heat-treated spherical alumina powder is cooled and washed by putting the pre-heat-treated spherical alumina powder into cooling and washing water in a water tank; a recovery step of separating the pre-heat-treated spherical alumina powder from the cooling and washing water and recovering the pre-heat-treated spherical alumina powder; a heat treatment step of heat treating the recovered unheat-treated spherical alumina powder at 1100 to 1300°C in an air atmosphere to obtain spherical alumina powder; A method for producing a spherical alumina powder, comprising: [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a spherical alumina powder having a D50 of 0.1 to 40 μm that can give a resin composition with high thermal conductivity. Furthermore, according to the present disclosure, it is possible to provide a resin composition and a prepreg that contain the spherical alumina powder. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a process flow of a method for producing a pre-heat-treated spherical alumina powder according to one embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a manufacturing device applicable to the process flow of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described. Note that the embodiments described below are representative examples of the present invention, and the present invention is not limited thereto.

[0013] In this specification, when multiple upper or lower limits are listed, numerical ranges can be created from all combinations of the upper and lower limits. Similarly, when multiple numerical ranges are listed, separate numerical ranges can be created by individually selecting and combining the upper and lower limits from those numerical ranges.

[0014] [Spherical alumina powder] In one embodiment, the spherical alumina powder has a D50 of 0.1 to 40 μm, a circularity of 0.90 to 1.00, a gelatinization rate of 60% to 100%, and a particle surface roughness of 1.14 to 1.35 as expressed by the following formula (1): Equation (1); Particle surface roughness = BET specific surface area A / sphere-equivalent specific surface area Sa calculated from particle size distribution The spherical alumina powder has a high gelatinization rate and a particle surface roughness that is within an appropriate range from the viewpoint of packing property, and therefore has high thermal conductivity itself, is less likely to cause segregation in the resin composition, and easily forms uniform particle contact points, so that the spherical alumina powder can provide a resin composition with high thermal conductivity.

[0015] (D50) The D50 of the spherical alumina powder is 0.1 μm or more, preferably 0.5 μm or more, and more preferably 1.0 μm or more. The D50 of the spherical alumina powder is 40 μm or less, preferably 10 μm or less, and more preferably 5.0 μm or less. When the D50 is 0.1 μm or more, the thermal conductivity can be increased. When the D50 is 40 μm or less, the fillability into resin can be improved.

[0016] D50 is the 50% particle size in the volume-based cumulative particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer, and is measured by the method described in the examples.

[0017] (gelatinization rate) The gelatinization rate of the spherical alumina powder is 60% or more, preferably 70% or more, and more preferably 80% or more. The higher the gelatinization rate, the more improved the thermal conductivity can be expected. The gelatinization rate of the spherical alumina powder may be 100% or less, 99% or less, or 98% or less.

[0018] The alpha conversion rate is calculated by the following formula (2), where X is the maximum peak intensity of the α-alumina crystal phase at a diffraction angle 2θ=35.2°±0.2° in X-ray diffraction measurement, and Y is the maximum peak intensity of the crystal phase other than α-alumina at a diffraction angle 2θ=67.3°±0.2°. Formula (2); alpha conversion rate=(X / (X+Y))×100(%)

[0019] (Particle surface roughness A / Sa) In this specification, the particle surface roughness is a value calculated by the following formula (1). Equation (1); Particle surface roughness = BET specific surface area A / sphere-equivalent specific surface area Sa calculated from particle size distribution The particle surface roughness of the spherical alumina powder is 1.14 or more, preferably 1.16 or more, and more preferably 1.20 or more. The particle surface roughness of the spherical alumina is 1.35 or less, preferably 1.31 or less, and more preferably 1.29 or less. When the particle surface roughness is 1.14 or more, settling of the alumina particles in the resin composition is suppressed. When the particle surface roughness is 1.35 or less, the fillability into the resin can be improved.

[0020] (BET specific surface area A) The BET specific surface area A of the spherical alumina powder is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1.0 or more. The BET specific surface area A of the spherical alumina powder is preferably 2.0 or less, more preferably 1.7 or less, and even more preferably 1.5 or less. When the BET specific surface area A is 0.1 or more, excellent heat dissipation properties are achieved. When the BET specific surface area A is 2.0 or less, the fillability into resin can be improved.

[0021] In this specification, the BET specific surface area A is a value measured and calculated in accordance with "6.2 Fluidized Method (3.5) Single Point Method" of JIS R 1626:1996 (Method for measuring the specific surface area of ​​fine ceramic powders by the gas adsorption BET method). The measurement is performed by heating the sample to 180°C as a pretreatment, passing nitrogen gas through it for 20 minutes, and then using nitrogen gas as the adsorbate.

[0022] (Sphere-equivalent specific surface area Sa calculated from particle size distribution) In this specification, the spherical equivalent specific surface area Sa calculated from the particle size distribution (also referred to as the spherical equivalent specific surface area Sa) can be determined by the method described in the Examples.

[0023] The spherical alumina powder has a sphere-equivalent specific surface area Sa of preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1.0 or more. The spherical alumina powder has a sphere-equivalent specific surface area Sa of preferably 2.0 or less, more preferably 1.7 or less, and even more preferably 1.5 or less. When the sphere-equivalent specific surface area Sa is 0.1 or more, excellent heat dissipation properties are achieved. When the sphere-equivalent specific surface area Sa is 2.0 or less, fillability into resin can be improved.

[0024] (specific gravity) The specific gravity of the spherical alumina powder is preferably 3.80 g / cm 3 More preferably, 3.85 g / cm 3 The specific gravity of the spherical alumina powder is preferably 4.00 g / cm 3 or less, more preferably 3.97 g / cm 3 The specific gravity is 3.80 g / cm 3 If the specific gravity is 4.00 g / cm or more, the content of α-alumina is high and the thermal conductivity is excellent. 3 When the specific gravity is less than 100%, the content of α-alumina is high and the thermal conductivity is excellent. The specific gravity can be determined by the method described in the examples.

[0025] (Circularity) The circularity of the spherical alumina powder is 0.90 or more, preferably 0.92 or more, more preferably 0.93 or more, and even more preferably 0.95 or more. By definition, the circularity of the spherical alumina powder is 1.00 or less, but may be 0.99 or less from the viewpoint of productivity. The circularity is measured by the method described in the Examples.

[0026] (Oil absorption rate) The oil absorption rate of the spherical alumina powder is preferably 30% or more, more preferably 35% or more, and even more preferably 38% or more. The oil absorption rate of the spherical alumina powder is preferably 50% or less, more preferably 45% or less, and even more preferably 43% or less. When the oil absorption rate is 30% or more, sedimentation of the alumina particles in the resin composition is suppressed. When the oil absorption rate is 50% or less, the fillability into the resin can be improved. The oil absorption rate is measured by the method described in the examples.

[0027] [Method for producing spherical alumina powder] Spherical alumina powders produced by a typical flame fusion method are produced by a known method in which raw material powders that can serve as aluminum sources, such as aluminum oxide powder, aluminum hydroxide powder, or aluminum metal powder, are introduced into a high-temperature flame, melted, and spheroidized by surface tension. The raw material powders are then cooled by air to a temperature at which they can be collected, and the resulting powder is then collected in a collection device. In this method, the cooling after melting is gradual, which causes the alumina particles to crystallize during the cooling process, resulting in increased particle surface roughness. In addition, the temperature profile from spheroidization to cooling is not controlled, resulting in variations in the degree of crystallization during the cooling process. Therefore, when such conventional spherical alumina powders are heat-treated, it is difficult to control the alpha conversion rate and particle surface roughness within the desired ranges.

[0028] On the other hand, the present inventors have discovered that spherical alumina powder with a controlled alpha conversion rate and particle surface roughness within a desired range can be obtained by spheroidizing raw material powder using the above-mentioned known method, immediately cooling the hot powder in a water tank, and then washing out impurities that may induce particle fusion and sintering, such as soda components and calcium components that have seeped out from the interior of the particles and onto the surface, and then heat-treating the resulting spherical alumina powder. Hereinafter, the spherical alumina powder before heat treatment will be referred to as the pre-heat-treated spherical alumina powder, and the spherical alumina powder after heat treatment will be referred to as the spherical alumina powder, and exemplary production methods thereof will be described.

[0029] (Method for producing spherical alumina powder before heat treatment) A method for producing a pre-heat-treated spherical alumina powder according to one embodiment includes a heating step of forming a high-temperature region inside a furnace using a burner that generates a flame, a spheroidizing step of producing a pre-heat-treated spherical alumina powder by introducing a raw alumina powder into the furnace and heating and melting it, a cooling and washing step of introducing the pre-heat-treated spherical alumina powder into cooling and washing water in a water tank to cool and wash the pre-heat-treated spherical alumina powder, and a recovery step of separating the pre-heat-treated spherical alumina powder from the cooling and washing water and recovering the pre-heat-treated spherical alumina powder. Figure 1 shows a process flow for the method for producing a pre-heat-treated spherical alumina powder according to one embodiment. By simultaneously cooling and washing the pre-heat-treated spherical alumina powder, Na, which may induce particle fusion and sintering on the particle surfaces, can be removed at low cost and in a short time. + It is possible to produce a pre-heat-treated spherical alumina powder having reduced amounts of SiO 2 and other ionic impurities.

[0030] <Raw alumina powder> There are no particular restrictions on the raw alumina powder, but Na + It is preferable to use a small amount. + A specific example of alumina powder with a small amount of content is low soda alumina powder produced by the Bayer process.

[0031] The shape of the raw alumina powder is not limited, but a non-spherical shape is preferred for the purpose of obtaining spherical alumina powder before heat treatment. The circularity of the raw alumina powder is, for example, less than 0.90, 0.86 or less, or 0.84 or less.

[0032] The D50 of the raw alumina powder is preferably 0.1 μm or more and 40 μm or less from the viewpoint of obtaining spherical alumina powder before heat treatment having a size suitable for a thermally conductive filler, more preferably 0.5 μm or more and 10 μm or less, and even more preferably 1.0 μm or more and 5 μm or less from the same viewpoint.

[0033] <Furnace> Examples of the furnace include a vertical furnace and a horizontal furnace. The shape of the furnace is not limited, and examples include a cylindrical shape and a polygonal prism shape such as a hexagonal prism. A cylindrical shape is preferred because it is easy to uniformly control the temperature inside the furnace. A cylindrical shape means that at least a portion of the furnace is cylindrical, and may include portions of other shapes. A polygonal prism shape means that at least a portion of the furnace is polygonal prism, and may include portions of other shapes. From the viewpoint of improving collection efficiency, the downstream portion of the furnace is preferably an inverted cone shape that narrows toward the discharge hole.

[0034] Although the material of the furnace is not limited, the inner wall is preferably made of stainless steel in order to reduce contamination of the spherical alumina powder with impurities before heat treatment. A water-cooling jacket may be provided around the periphery of the furnace to cool it.

[0035] <High temperature process> The high temperature process is a process in which a high temperature region is formed inside the furnace by a burner that forms a flame.

[0036] A burner is a device that mixes a suitable amount of a combustion-sustaining gas with a combustible gas to form a flame in a furnace. The burner is supplied with a combustible gas from a combustible gas supply source, and a combustion-sustaining gas from a combustion-sustaining gas supply source. Examples of combustible gases include liquefied natural gas (LNG) and LPG. Examples of combustion-sustaining gases include air, oxygen gas, and oxygen-enriched air.

[0037] The temperature of the high temperature region is preferably 2100°C or higher. The temperature of the high temperature region is preferably 2500°C or lower, more preferably 2300°C or lower. If the temperature is 2100°C or higher, it is above the melting point of alumina, making it easy to increase the circularity of the resulting alumina powder. If the temperature is 2500°C or lower, it is within the heat resistance range of a general burner, which is advantageous in terms of cost.

[0038] <Spheroidization process> The spheroidizing step is a step of producing a pre-heat-treated spherical alumina powder by heating and melting a raw alumina powder in a furnace. In the spheroidizing step, a carrier gas for supplying the raw alumina powder may be used as needed. Examples of the carrier gas include at least one selected from air, nitrogen, oxygen, and carbon dioxide.

[0039] <Pre-cooling process> The method for producing the pre-heat-treated spherical alumina powder preferably includes a pre-cooling step of pre-cooling the pre-heat-treated spherical alumina powder. The pre-cooling step is carried out after the spheroidizing step and before the cooling and washing step. The equipment for pre-cooling is preferably provided outside the high-temperature region of the furnace or between the furnace and the water tank used in the cooling and washing step. This allows the pre-heat-treated spherical alumina powder to be cooled to a desired temperature in a short period of time before being poured into the cooling and washing water in the water tank in the cooling and washing step.

[0040] Pre-cooling is preferably carried out by spraying water onto the spherical alumina powder before heat treatment, using equipment such as a shower.

[0041] <Cooling and washing process> The cooling and washing step involves placing the pre-heat-treated spherical alumina powder in cooling and washing water in a water tank to simultaneously cool and wash the pre-heat-treated spherical alumina powder. By simultaneously cooling and washing, the equipment can be made smaller and the overall process time can be shortened compared to when cooling and washing are performed as separate steps, such as when the pre-heat-treated spherical alumina powder is air-cooled after the spheroidizing step while being collected in a collector such as a cyclone, and the collected pre-heat-treated spherical alumina powder is then washed. In addition, the variation in crystallinity can be reduced. This method for producing pre-heat-treated spherical alumina powder allows for the production of pre-heat-treated spherical alumina powder with a low BET specific surface area due to the minimal thermal history.

[0042] The water tank contains cooling and washing water for cooling and washing the pre-heat-treated spherical alumina powder. To improve the washing efficiency, it is preferable to stir the cooling and washing water with a stirrer. The cooling and washing water is not limited to, but may be, for example, city water.

[0043] The temperature of the cooling and washing water is preferably 50° C. or higher, more preferably 70° C. or higher, from the viewpoint of efficiently reducing ionic impurities present on the surface of the spherical alumina powder before heat treatment. The temperature of the cooling and washing water is preferably 80° C. or lower, from the viewpoint of suppressing damage to the furnace body due to heat load.

[0044] In the cooling and washing step, it is preferable that the pre-heat-treated spherical alumina powder be put into the cooling and washing water within 5 seconds after leaving the furnace. By putting it into the water within 5 seconds, the BET specific surface area of ​​the pre-heat-treated spherical alumina powder can be kept low. By putting it into the water within 5 seconds, it is possible to reduce the variation in the crystallinity of the pre-heat-treated spherical alumina powder.

[0045] In the cooling and washing step, the temperature of the pre-heat-treated spherical alumina powder introduced into the cooling and washing water is preferably 200° C. or lower, and more preferably 100° C. or lower. More preferably, the temperature of the pre-heat-treated spherical alumina powder from the time it leaves the furnace until it is introduced into the cooling and washing water is 200° C. or lower, and particularly preferably 100° C. or lower. If the temperature is 200° C. or lower, there is little risk of the cooling and washing water in the water tank overheating and evaporating, which facilitates stable production.

[0046] The temperature of the spherical alumina powder before heat treatment can be determined using simulation software Ansys Fluent (Ansys, Inc.).

[0047] <Recovery process> The recovery step is a step of separating the pre-heat-treated spherical alumina powder from the cooling and washing water, and recovering the pre-heat-treated spherical alumina powder. The recovery method is not limited to, but includes a method of settling the pre-heat-treated spherical alumina powder dispersed in the cooling and washing water, and removing the supernatant water with a pump or the like. This method removes Na adhering to the particle surface.+ , Ca 2+ This is preferable because it is possible to wash away ionic impurities such as ammonium hydroxide and the like.

[0048] <Drying process> The method for producing the pre-heat-treated spherical alumina powder preferably includes a drying step. The drying step is a step of drying the pre-heat-treated spherical alumina powder from which the cooling and washing water has been separated. In the drying step, the moisture remaining after the recovery step is removed. The drying method is not limited, and may be natural drying or heat drying.

[0049] <Pre-heat-treated spherical alumina powder manufacturing equipment> Hereinafter, a preferred embodiment of a manufacturing apparatus used in a method for manufacturing a spherical alumina powder before heat treatment according to the present invention and its configuration will be described in detail with reference to the drawings. Note that the drawings used in the following description focus on the characteristic parts for the sake of convenience in order to make the characteristics easier to understand, and the dimensional ratios of the respective components may not necessarily be the same as those of an actual apparatus.

[0050] The pre-heat-treated spherical alumina powder manufacturing apparatus will be described with reference to Figure 2. As shown in Figure 2, the pre-heat-treated spherical alumina powder manufacturing apparatus is generally composed of a hopper 1 for storing and charging raw materials, a spheroidizing burner 2, a water-cooled jacket-type spheroidizing furnace 3 (also referred to as the spheroidizing furnace 3) for spheroidizing, a stirring and cooling tank 4 for washing and cooling the pre-heat-treated spherical alumina powder, a separation tank 5 for separating the collected pre-heat-treated spherical alumina powder from a large amount of moisture and extracting the pre-heat-treated spherical alumina powder, and a drying device 6 for drying the pre-heat-treated spherical alumina powder that still retains moisture to obtain a dry pre-heat-treated spherical alumina powder.

[0051] The raw material hopper 1 is equipped with a feeder device and the like, which allows the raw material alumina powder to be quantitatively supplied to the spheroidizing burner 2. This spheroidizing burner 2 supplies the raw material alumina powder supplied from the raw material hopper 1 into the spheroidizing furnace 3. It is also possible to supply the inorganic oxide powder to the spheroidizing burner 2 using a carrier gas for transporting the powder.

[0052] The spheroidizing burner 2 is provided in the spheroidizing furnace 3. A combustible gas is supplied to the spheroidizing burner 2 from a combustible gas supply source (not shown), and a combustion-sustaining gas is supplied to the spheroidizing burner 2 from a combustion-sustaining gas supply source (not shown). The spheroidizing burner 2 can form a flame in the spheroidizing furnace 3.

[0053] The spheroidizing furnace 3 is a cylindrical vertical furnace, and the lower part of the furnace is inverted cone shape, narrowing towards the discharge hole side. In the spheroidizing furnace 3, raw alumina powder is fed into a high-temperature region formed by a flame and melted, producing pre-heat-treated spherical alumina powder.

[0054] A shower 10 is provided inside the spheroidizing furnace 3. The shower 10 sprays water onto the pre-heat-treated spherical alumina powder that has left the high-temperature region, thereby pre-cooling the pre-heat-treated spherical alumina powder. In Fig. 2, the shower is provided inside the spheroidizing furnace 3, but the shower may be provided at any location on the path that the pre-heat-treated spherical alumina powder takes from when it leaves the high-temperature region until it comes into contact with the cooling wash water.

[0055] The spheroidizing furnace 3 is connected to the stirring and cooling tank 4 via a short pipe. The short pipe is equipped with a duct or the like, which is connected to a scrubber-type collector 8 and an exhaust device 9, allowing the combustion exhaust gas to be discharged outside the system. Since the combustion exhaust gas contains fine particles of pre-heat-treated spherical alumina powder, it is desirable to pass the gas through the scrubber-type collector 8 to separate and remove the fine particles from the gas, and then discharge the purified combustion exhaust gas via the exhaust device 9. In FIG. 2, there are no gaps between the spheroidizing furnace 3, the short pipe, and the stirring and cooling tank 4, but gaps may be present between them.

[0056] Cooling and washing water for cooling and washing the pre-heat-treated spherical alumina powder is stored in the stirring and cooling tank 4. The cooling and washing water in the stirring and cooling tank 4 is stirred by an agitator to improve washing efficiency. A cooling water pump 7 is connected to the stirring and cooling tank 4, and the cooling water pump 7 is connected to a shower 10, and piping is provided so that the cooling and washing water in the tank can be recycled and reused.

[0057] A separation tank 5 is connected to the stirring and cooling tank 4 to separate the collected pre-heat-treated spherical alumina powder from the cooling and washing water, and a slurry containing the pre-heat-treated spherical alumina powder is supplied from the stirring and cooling tank 4 to the separation tank 5. In the separation tank 5, the cooling and washing water is separated from the solid matter, and the water is returned to the system via the cooling water pump 7 and circulated. At this time, Na adhering to the particle surfaces is + The solid matter is fed to a drying device 6, where the remaining moisture adhering thereto is dried, thereby obtaining a pre-heat-treated spherical alumina powder with a small amount of ionic impurities.

[0058] This manufacturing apparatus does not require the installation of expensive, large-scale equipment such as an ion-exchange water unit, and allows the production of pre-heat-treated spherical alumina powder with low ionic impurities using a small-scale spheroidizing facility.

[0059] (Method for producing spherical alumina powder) Spherical alumina powder can be obtained by heat-treating unheat-treated spherical alumina powder in an air atmosphere at 1100-1300°C. Heat-treating at 1100°C or higher can promote the transition from phases other than the α-crystalline phase, which have low thermal conductivity, such as amorphous phase, γ-crystalline phase, δ-crystalline phase, and θ-crystalline phase, to the α-crystalline phase, which has high thermal conductivity. Heat-treating at 1300°C or lower can suppress surface roughness. Heat-treating at 1300°C or lower can suppress particle size increase due to fusion between particles.

[0060] The heat treatment time is preferably 1 hour or more, and more preferably 1 hour to 4 hours. If it is 1 hour or more, the transition time to the target α crystal phase is sufficient, making it easier to reach the target α conversion rate. If it is 4 hours or less, sintering between particles is suppressed, making it easier to obtain powder with the target particle size.

[0061] The heat treatment apparatus may be a general apparatus, specific examples of which include a bogie furnace, a tunnel furnace, and a rotary kiln. The heat treatment atmosphere is not particularly limited, but is preferably an air atmosphere.

[0062] The method for producing spherical alumina powder may optionally include a crushing step of crushing agglomerated particles formed by the heat treatment. The method for producing spherical alumina powder may optionally include a classification step of performing a classification treatment. The heat treatment may result in agglomerated particles in which some particles are sintered together. In this case, it is preferable to perform at least one treatment selected from a crushing treatment and a classification treatment. The crushing treatment may be wet or dry. Examples of the crushing treatment include methods using a roll mill, a ball mill, a small-diameter ball mill (also called a bead mill), a pot mill, a media stirring mill, an airflow crusher, a mortar, an automatic kneading mortar, a tank crusher, or a jet mill.

[0063] The spherical alumina powder is preferably used in applications requiring high thermal conductivity, such as heat dissipation materials and semiconductor encapsulation materials, as a filler in materials requiring high thermal conductivity.

[0064] [Resin composition] In one embodiment, the resin composition contains spherical alumina powder and a resin. The resin composition can be used as a heat dissipation and insulation resin composition or a sealing material, for example, a sealing material for electronic component devices. The resin composition is suitable for semiconductor packages and printed wiring boards, which require high thermal conductivity.

[0065] Examples of the resin include thermosetting resins and thermoplastic resins, with thermosetting resins being preferred. Examples of the thermosetting resin include epoxy resins, phenolic resins, unsaturated imide resins, amino resins such as melamine resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, and triazine resins. Among these, epoxy resins are preferred because of their excellent moldability and electrical insulation properties. The resins may be used alone or in combination of two or more.

[0066] Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, biphenyl type epoxy resins, alicyclic epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, bisphenol F novolac type epoxy resins, dicyclopentadiene type epoxy resins, naphthalene type epoxy resins, and anthracene type epoxy resins.

[0067] Examples of thermoplastic resins include polyethylene, polypropylene, polystyrene, polyphenylene ether resin, phenoxy resin, polycarbonate resin, polyester resin, polyamide resin, polyamideimide resin, polyimide resin, xylene resin, polyphenylene sulfide resin, polyetherimide resin, polyetheretherketone resin, and polyetherimide resin.

[0068] The content of the spherical alumina powder in the resin composition is preferably 50 to 90% by volume, more preferably 60 to 85% by volume. When the content is 50% by volume or more, the spherical alumina powder has a sufficient effect of improving thermal conductivity. When the content is 90% by volume or less, the moldability of the resin composition is good.

[0069] The resin composition may contain other inorganic fillers besides spherical alumina. Examples of other inorganic fillers include aluminum hydroxide, zinc oxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, titanium oxide, silicon oxide, and boron nitride. Among these, at least one selected from aluminum hydroxide, zinc oxide, magnesium oxide, and boron nitride is preferred from the viewpoint of improving thermal conductivity.

[0070] The resin composition may contain optional components other than the above components, such as a curing agent, a curing accelerator, a flame retardant, an ultraviolet absorber, an antioxidant, an organic solvent, and a surface treatment agent.

[0071] When an epoxy resin is used, examples of the curing agent include polyfunctional phenolic compounds such as phenol novolac and cresol novolac; amine compounds such as dicyandiamide, diaminodiphenylmethane and diaminodiphenylsulfone; and acid anhydrides such as phthalic anhydride, pyromellitic anhydride, maleic anhydride and maleic anhydride copolymer. The curing agents may be used alone or in combination of two or more.

[0072] When an epoxy resin is used, examples of the curing accelerator include imidazole compounds and derivatives thereof; organic phosphorus compounds; secondary amines; tertiary amines; and quaternary ammonium salts.

[0073] Examples of imidazole compounds and derivatives thereof include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole, 4,5-diphenylimidazole, 2-methylimidazoline, 2-phenylimidazoline, 2-undecylimidazole, 2-heptadecylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, 2-ethylimidazoline, 2-isopropylimidazoline, 2,4-dimethylimidazoline, and 2-phenyl-4-methylimidazoline. The imidazole compounds and derivatives thereof may be masked with a masking agent. Examples of masking agents include acrylonitrile, phenylene diisocyanate, toluidine isocyaninate, naphthalene diisocyanate, methylene bisphenyl isocyanate, and melamine acrylate.

[0074] Examples of organic phosphorus compounds include ethylene phosphine, propyl phosphine, butyl phosphine, phenyl phosphine, trimethyl phosphine, triethyl phosphine, tributyl phosphine, trioctyl phosphine, triphenyl phosphine, tricyclohexyl phosphine, triphenyl phosphine / triphenyl borane complex, and tetraphenyl phosphonium tetraphenyl borate.

[0075] Secondary amines include, for example, morpholine, piperidine, pyrrolidine, dimethylamine, diethylamine, dicyclohexylamine, N-alkylarylamines, piperazine, diallylamine, thiazoline, and thiomorpholine.

[0076] Tertiary amines include, for example, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, and 2,4,6-tris(dimethylaminomethyl)phenol.

[0077] Examples of quaternary ammonium salts include tetrabutylammonium iodide, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium fluoride, benzalkonium chloride, benzyldi(2-hydroxyethyl)ethylammonium chloride, and decyldi(2-hydroxyethyl)methylammonium bromide.

[0078] The curing accelerators may be used alone or in combination of two or more.

[0079] The organic solvent can be used for the purpose of adjusting the viscosity of the resin composition. For example, when a prepreg is produced by impregnating a substrate with the resin composition, or when the resin composition is applied, it is preferable to use an organic solvent to adjust the viscosity of the resin composition to an appropriate range. The organic solvent may be removed after the impregnation treatment or application treatment.

[0080] Examples of organic solvents include alcohols such as methanol, ethanol, propanol, and butanol; glycol ethers such as methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as butyl acetate and propylene glycol monomethyl ether acetate; ethers such as tetrahydrofuran; aromatic hydrocarbons such as toluene and xylene; nitrogen-containing solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and sulfur-containing solvents such as dimethyl sulfoxide. The organic solvents may be used alone or in combination of two or more.

[0081] Among these, methyl isobutyl ketone, methyl ethyl ketone, propylene glycol monomethyl ether, and methyl cellosolve are preferred from the viewpoint of solubility, and methyl isobutyl ketone and propylene glycol monomethyl ether are more preferred from the viewpoint of low toxicity.

[0082] When dispersing the spherical alumina powder in an organic solvent, a dispersing machine such as a bead mill, homogenizer, jet mill, etc. can be used to improve dispersibility. It is also preferable to pretreat the spherical alumina powder with a surface treatment agent described below or to subject it to integral blending treatment.

[0083] Examples of the surface treatment agent include coupling agents such as silane coupling agents and titanate coupling agents, and silicone oligomers. The spherical alumina powder may be pretreated with a surface treatment agent.

[0084] When a prepreg is produced by impregnating a substrate with the resin composition, the total content of components other than the organic solvent (also referred to as solid content) in the resin composition is preferably 40 to 90 mass %, more preferably 50 to 85 mass %, based on the total resin composition.

[0085] [Method of producing resin composition] The method for producing the resin composition is not particularly limited. Examples of the method for producing the resin composition include a method in which predetermined amounts of components are thoroughly mixed using a mixer or the like, kneaded using a mixing roll, extruder, or the like, and cooled. More specifically, examples include a method in which predetermined amounts of components are stirred and mixed, and the mixture is kneaded using a kneader, roll, extruder, or the like that has been preheated to 70 to 140°C, and cooled.

[0086] [Prepreg] The prepreg of one embodiment is obtained by impregnating a base material with a resin composition.

[0087] Examples of substrate materials include inorganic fibers such as E-glass, D-glass, S-glass, and Q-glass. Examples of substrate forms include woven fabric, nonwoven fabric, roving, chopped strand mat, and surfacing mat. The material and form of the substrate are selected depending on the intended use and performance, and a single material or a combination of two or more materials and forms can be used as needed. From the viewpoints of heat resistance, moisture resistance, and processability, the substrate may be surface-treated. Examples of surface treatments include surface treatment with a silane coupling agent and mechanical fiber-opening treatment. The thickness of the substrate is, for example, 0.01 to 0.2 mm.

[0088] The prepreg can be produced, for example, by impregnating a substrate with a resin composition containing an organic solvent and then removing the organic solvent. The impregnated resin composition may be semi-cured by heating.

[0089] Prepregs are suitable for semiconductor packages and printed wiring boards, which require high thermal conductivity.

[0090] [Cured product of prepreg or laminate thereof] A cured product of a prepreg or a laminate thereof can be produced by heating and pressurizing one or more prepregs. The number of prepregs stacked is not particularly limited, but is, for example, 2 to 20. Examples of devices for heating and pressurizing include multi-stage presses, multi-stage vacuum presses, continuous molding machines, and autoclave molding machines. The heating and pressurizing conditions may be selected depending on the thermosetting resin, curing agent, etc. used. For example, the temperature is 100 to 250°C, the pressure is 0.2 to 10 MPa, and the time is 0.1 to 5 hours.

[0091] [Metal-clad laminate] A metal-clad laminate in one embodiment includes a cured product of a prepreg or a laminate thereof, and a metal foil disposed on at least one main surface of the cured product. The metal-clad laminate can be produced, for example, by stacking 1 to 20 prepregs and disposing metal foil on one or both surfaces of the stack, followed by heating and pressing. The heating and pressing apparatus and heating and pressing conditions are the same as those described above. The metal foil is not particularly limited as long as it is used for electronic components. Examples of metal foil include copper foil and aluminum foil.

[0092] [Electronic component equipment] An electronic component device according to one embodiment includes an element and a cured resin composition encapsulating the element, such as an active element (e.g., a semiconductor chip, transistor, diode, or thyristor) or a passive element (e.g., a capacitor, resistor, or coil).

[0093] Examples of electronic component devices include those in which an element is mounted on a support member such as a lead frame, a pre-wired tape carrier, a wiring board, glass, a silicon wafer, or an organic substrate, and the resulting element portion is sealed with a resin composition. More specifically, typical resin-sealed ICs such as DIP (Dual Inline Package), PLCC (Plastic Leaded Chip Carrier), QFP (Quad Flat Package), SOP (Small Outline Package), SOJ (Small Outline J-lead package), TSOP (Thin Small Outline Package), and TQFP (Thin Quad Flat Package) have a structure in which an element is fixed on a lead frame, and terminal portions of the element such as bonding pads and lead portions are connected by wire bonding, bumps, or the like, and then sealed using a resin composition by transfer molding or the like; TCP (Tape Carrier Package) has a structure in which an element connected to a tape carrier by bumps is sealed with a resin composition; and COB (Chip On Board) has a structure in which an element connected to wiring formed on a support member by wire bonding, flip chip bonding, solder, or the like, is sealed with a resin composition. Examples of such modules include BGA (Ball Grid Array), CSP (Chip Size Package), and MCP (Multi Chip Package), which have a structure in which elements are mounted on the surface of a support member having terminals for connecting a wiring board formed on the back surface thereof, the elements are connected to wiring formed on the support member by bump or wire bonding, and then the elements are sealed with a resin composition.

[0094] Methods for encapsulating electronic component devices using a resin composition include, for example, low-pressure transfer molding, injection molding, and compression molding. Of these, low-pressure transfer molding is the most common. [Example]

[0095] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0096] <Evaluation method> (D10, D50, D90) A 40 mg sample was placed in 50 mL of water containing two drops of a nonionic surfactant (TRITON-X; Roche Applied Science) and dispersed ultrasonically for 3 minutes. This dispersion was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac-Bell, MT3300II). The 10%, 50%, and 90% particle sizes in the resulting volume-based cumulative particle size distribution were determined as D10, D50, and D90, respectively.

[0097] (gelatinization rate) The alpha conversion rate was calculated from the relationship: alpha conversion rate (%) = (X / (X + Y)) × 100, where X is the maximum peak intensity of the alpha alumina crystal phase at a diffraction angle 2θ = 35.2° ± 0.2° in X-ray diffraction measurement, and Y is the maximum peak intensity of a crystal phase other than alpha alumina at a diffraction angle 2θ = 67.3° ± 0.2°. X-ray diffraction measurements of the alumina powder were performed using an X-ray diffractometer PW3040 / 60X'Pert-MRD (Malvern Panalytical) with a copper X-ray tube at a tube voltage of 45 kV and a tube current of 40 mA.

[0098] (BET specific surface area A) The BET specific surface area A was measured and calculated in accordance with "6.2 Fluidized Method (3.5) Single-Point Method" of JIS R 1626:1996 (Method for measuring the specific surface area of ​​fine ceramic powders by the gas adsorption BET method). Specifically, approximately 2 g of sample was weighed out and pre-degassed at 180°C for 20 minutes, after which the sample was placed in an automatic specific surface area measuring device (Mountec Co., Ltd., Macsorb). The nitrogen gas adsorption amount was measured using pure nitrogen and a nitrogen-helium mixed gas (mixture ratio: 30 mol% nitrogen, 70 mol% helium), and the BET specific surface area A was calculated using the single-point method.

[0099] (Sphere-equivalent specific surface area Sa calculated from particle size distribution) The spherical equivalent specific surface area (Sa) calculated from the particle size distribution was calculated using the following formula based on particle size distribution data obtained using a laser diffraction / scattering particle size distribution analyzer (Microtrac Bell, MT3300II). The sample preparation method was the same as that used for measuring D10, D50, and D90.

number

[0100] (specific gravity) 5 mg of sample was placed in a measurement sample cell, and the specific gravity was measured by the gas (helium) substitution method using a dry density meter (Shimadzu Corporation, product name: Accupyc II 1340). Specifically, the measurement sample cell was set in the dry density meter, and the volume of the sample was determined by substituting helium gas, and the specific gravity was calculated by dividing the sample mass by the volume.

[0101] (Circularity) The circularity is the average value of values ​​calculated from the following formula (3) for 2000 or more particles, where S is the area of ​​the projection of the particle and L is the perimeter. Equation (3); (4×π×S) / L 2 Measurements of area S and perimeter L were performed using an FPIA-3000 (Malvern Panalytical). As a pretreatment step, due to the instrument's measurement range, approximately 10 g of sample was placed on a 200 mm diameter, 25 μm mesh gold sieve, and particles larger than 25 μm were removed with shower water. The sample that passed through the sieve was transferred to a plastic container and used as the measurement sample. Measurement conditions were LPF / HPF standard (20x lens) and bright field, and ParticleSheath (Malvern Panalytical) was used as the measurement solvent. Two grams of sample were weighed into a 50 mL beaker, filled with 50 mL of pure water, and dispersed in a 200 W ultrasonic disperser for 3 minutes, with the effective particle count at 2000 or more and the effective particle count / total particle count ratio at 55–70%. The sample was then placed in the instrument and measured. For post-measurement data processing, multiple particles on a single screen were removed, and the circularity was calculated.

[0102] (Oil absorption rate) 10 g of sample was placed in a mortar with a diameter of 10 cm, and a small amount of liquid epoxy resin was dropped onto it and mixed thoroughly with the sample. Small amounts of resin were repeatedly dropped until the sample and epoxy resin formed a single mass. The volume of the dropped resin was calculated from the weight of the resin when the sample and resin formed a single mass, and the oil absorption rate was calculated using the following formula. The volume of the sample was calculated from the specific gravity measured above. Oil absorption rate (%) = (volume of dripped resin / (volume of sample + volume of dripped resin)) x 100

[0103] (thermal conductivity) Alumina powder was mixed with an epoxy molding compound resin containing an epoxy resin, a polyfunctional phenolic compound as a curing agent, and an organic phosphorus compound as a curing accelerator at the volumetric filling ratio (%) shown in Table 1. The mixture was diluted with methyl ethyl ketone and stirred using a mixer rotor to produce a varnish with a solids concentration of 75% by mass. The resulting varnish was coated onto a release PET film to a thickness of 200 μm and dried at 110°C for 10 minutes. The dried resin composition was then pulverized. To mold the pulverized resin composition into a composite for measurement, the pressure was increased to 10 kN in a heated vacuum press at 80°C for 3 minutes. Once the pressure reached 10 kN, the temperature was increased to 160°C at a rate of 20°C / 3 minutes. When the temperature reached 100°C, the pressure was increased from 10 kN to 40 kN. After the temperature reached 160°C, the pressure was held for 16 minutes to produce a 1 mm-thick resin composite. The resin composite was post-cured at 175°C for 6 hours to obtain a composite for measurement. Thermal conductivity was measured using this composite for measurement.

[0104] Thermal conductivity is calculated as the product of thermal diffusivity, low-pressure specific heat capacity, and density. Thermal diffusivity was measured using a xenon flash analyzer (NETZSCH JAPAN Co., Ltd., LFA647 HyperFlash). Constant-pressure specific heat capacity was calculated from the specific heat capacity of each material and its blend ratio. Density was measured using an electronic hydrometer (Alpha Mirage Co., Ltd., MDS-3000). Thermal conductivity was calculated from these products. Thermal diffusivity and density were measured at 23°C, and the constant-pressure specific heat capacity value was calculated using the specific heat capacity at 25°C.

[0105] (Comparative Example 1) The raw alumina powder (D50: 1.8 μm) was placed in a 2200°C high-temperature zone created in the furnace by a flame formed from LPG and oxygen, and subjected to spheroidization. The pre-heat-treated spherical alumina powder was placed in a water bath with cooled wash water at 80°C within 5 seconds of leaving the furnace, where it was cooled and washed. The resulting slurry containing the pre-heat-treated spherical alumina powder was separated into a high-concentration slurry and a supernatant liquid in the recovery process, and the high-concentration slurry was dried in a dryer at an ambient temperature of 180°C in an air atmosphere in the drying process to obtain pre-heat-treated spherical alumina powder 1.

[0106] (Comparative Example 2) The raw alumina powder (D50: 1.2 μm) was placed in a high-temperature zone of 2200°C created in the furnace by a flame formed from LPG and oxygen, and subjected to spheroidization. The pre-heat-treated spherical alumina powder was placed in a water bath with cooled wash water at 80°C within 5 seconds of leaving the furnace, where it was cooled and washed. The resulting slurry containing the pre-heat-treated spherical alumina powder was separated into a high-concentration slurry and a supernatant liquid in the recovery process, and the high-concentration slurry was dried in a dryer at an ambient temperature of 180°C in an air atmosphere in the drying process to obtain pre-heat-treated spherical alumina powder 2.

[0107] (Comparative Example 3) Sumitomo Chemical Co., Ltd. Advanced Alumina AA-2

[0108] Example 1 The pre-heat-treated spherical alumina powder 1 was heat-treated in an air atmosphere at 1250°C for 4 hours in a muffle furnace. After cooling, the powder was crushed using a wet shear crusher called a Nanomizer, and then dispersed and classified using a high-speed rotating thin film classifier called a Filmix to obtain spherical alumina powder.

[0109] Example 2 The pre-heat-treated spherical alumina powder 2 was heat-treated in an air atmosphere at 1250° C. for 4 hours in a muffle furnace. After cooling, the powder was crushed and classified using a swirling jet mill to obtain spherical alumina powder.

[0110] [Table 1] As shown in Table 1, the thermal conductivities of the resin compositions containing the heat-treated spherical alumina powder in Examples 1 and 2 were 2.1 W / m·K and 1.9 W / m·K, respectively. These values ​​demonstrate superior thermal conductivity to the resin compositions containing the unheat-treated spherical alumina powder in Comparative Examples 1 and 2. On the other hand, the non-spherical alumina in Comparative Example 3, although not heat-treated, had a high degree of gelatinization, and is presumed to have high thermal conductivity. However, the thermal conductivity of the resin composition containing the non-spherical alumina in Comparative Example 3 was lower than that of Examples 1 and 2. This is presumably due to the non-spherical alumina having an excessively high particle surface roughness, resulting in poor packing. Specifically, this is presumably due to poor packing, which prevents the formation of uniform and sufficient particle contact points that serve as heat conduction paths. [Explanation of symbols]

[0111] 1 Hopper 2 Spheroidizing Burner 3. Water-cooled jacket type spheroidizing furnace 4. Stirring and cooling tank 5 Separation tank 6 Drying equipment 7 Cooling water pump 8 Scrubber-type collection device 9 Exhaust system 10. Shower

Claims

1. D50 is 0.1 to 40 μm, Circularity is 0.90 or more and 1.00 or less, The gelatinization rate is 60% or more and 100% or less, A spherical alumina powder having a particle surface roughness, as expressed by the following formula (1), of 1.14 or more and 1.35 or less. Formula (1); Particle surface roughness = BET specific surface area A / spherical equivalent specific surface area Sa calculated from particle size distribution

2. Specific gravity is 3.80 g / cm ３ 2. The spherical alumina powder according to claim 1, wherein the spherical alumina powder is a spherical alumina powder having the above structure.

3. 3. The spherical alumina powder according to claim 1, wherein the BET specific surface area A is 0.1 or more and 2.0 or less.

4. 3. The spherical alumina powder according to claim 1, having an oil absorption rate of 30% or more and 50% or less.

5. A resin composition comprising the spherical alumina powder according to claim 1 or 2 and a resin.

6. A prepreg, comprising a substrate impregnated with the resin composition according to claim 5.

7. A cured product of the prepreg or laminate thereof according to claim 6.

8. The cured product according to claim 7, A metal-clad laminate comprising: a metal foil disposed on at least one main surface of the cured product.

9. The resin composition according to claim 5, which is used as a sealing material for electronic component devices.

10. An electronic component device comprising: an element; and a cured product of the resin composition according to claim 5 that encapsulates the element.

11. a high temperature process in which a high temperature region is formed inside the furnace by a burner that forms a flame; a spheroidizing step of producing a pre-heat-treated spherical alumina powder by charging raw alumina powder into the furnace and heating and melting it; a cooling and washing step in which the pre-heat-treated spherical alumina powder is cooled and washed by putting the pre-heat-treated spherical alumina powder into cooling and washing water in a water tank; a recovery step of separating the pre-heat-treated spherical alumina powder from the cooling and washing water and recovering the pre-heat-treated spherical alumina powder; a heat treatment step of heat treating the recovered unheat-treated spherical alumina powder at 1100 to 1300°C in an air atmosphere to obtain spherical alumina powder; A method for producing a spherical alumina powder, comprising:

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