Alumina powder, resin composition and method for producing alumina powder

Abstract

Alumina powder according to the present invention has at least a first peak and a second peak in a volume frequency particle size distribution measured by a wet laser diffraction / scattering method. When the particle diameter of the first peak is represented by d1 and the particle diameter of the second peak is represented by d2, the followings are satisfied: d1 is 1-20 μｍ inclusive; d2 is 0.2 μｍ or more and less than 1 μｍ; and the BET specific surface area is 1.05 m2 / g to 5.00 m2 / g inclusive.

Description

Alumina powder, resin composition, and method for producing alumina powder

[0001] The present invention relates to alumina powder, resin compositions, and methods for producing alumina powder.

[0002] Various developments have been made regarding alumina powder. As an example of this type of technology, the technology described in Patent Document 1 is known. Patent Document 1 describes alumina powder having an average particle size (D50) of 50 μm or less.

[0003] Japanese Patent Publication No. 2015-193493

[0004] However, as a result of our investigation, we found that there is room for improvement in the alumina powder described in Patent Document 1 above, in terms of suppressing burrs when it is blended into a resin composition.

[0005] Further investigations by the inventors revealed that by adding inorganic ultrafine powder, which has an even smaller particle size, to alumina powder containing alumina fine powder and alumina semi-fine powder with a smaller particle size than alumina fine powder, burrs that occur when a resin composition containing such alumina is used in a molding process can be suppressed. However, while the particle size of powder is measured by known methods such as laser diffraction scattering, in the case of inorganic ultrafine powder, a peak corresponding to its particle size may not be detected. Based on this finding, further intensive research revealed that the BET specific surface area of ​​alumina powder is useful as an indicator reflecting the particle size and content of inorganic ultrafine powder contained in the alumina powder, and that by setting the BET specific surface area of ​​the alumina powder to a predetermined value or higher, an alumina powder capable of realizing the aforementioned burr suppression resin composition can be obtained, thus completing the present invention.

[0006] According to one aspect of the present invention, the following alumina powder, resin composition, and method for producing alumina powder are provided.

[0007] 1. In the volume frequency particle size distribution measured by wet laser diffraction scattering, at least a first peak and a second peak are present, and when the particle diameter of the first peak is d1 and the particle diameter of the second peak is d2, d1 is 1 μm or more and 20 μm or less, d2 is 0.2 μm or more and less than 1 μm, and the BET specific surface area is 1.05 m². ２ / g or more 5.00m ２Alumina powder satisfying the requirement of / g or less. 2. Alumina powder according to 1, comprising: alumina fine powder having the first peak in the volume frequency particle size distribution; alumina semi-fine powder having the second peak in the volume frequency particle size distribution; and inorganic ultrafine powder having a BET diameter of 0.001 μm or more and less than 0.2 μm calculated from [6 / (true specific gravity × BET specific surface area)]. 3. Alumina powder according to 2, wherein the inorganic ultrafine powder comprises at least one of alumina ultrafine powder and silica ultrafine powder. 4. Alumina powder according to 2 or 3, wherein the content of the inorganic ultrafine powder is 0.1% by mass or more and 5.0% by mass or less in 100% by mass of the total of the alumina fine powder, alumina semi-fine powder, and inorganic ultrafine powder. 5. 1. to 4. Alumina powder according to any one of the above, wherein the viscosity of the evaluation resin varnish containing the alumina powder, measured according to the following procedure, is 1.5 kPa·s or more and 10.0 kPa·s or less. (Procedure) The alumina powder is mixed with liquid epoxy resin (JER807, manufactured by Mitsubishi Chemical Corporation) at 25°C to obtain the evaluation resin varnish described above. The viscosity of the obtained evaluation resin varnish is measured using a rheometer at 25°C and a shear rate of 0.17 [1 / s]. 6. Alumina powder according to any one of 1 to 5, wherein when the frequency of the first peak is P1, the frequency of the second peak is P2, and the smallest frequency between the first peak and the second peak is P3, (P1 + P2) / P3 is 9.0 or less. 7. A resin composition containing the alumina powder and resin according to any one of 1 to 6. 8. A method for producing alumina powder, comprising the step of mixing: alumina fine powder having a first peak in the range of 1 μm to 20 μm in the volume frequency particle size distribution measured by a wet laser diffraction scattering method; alumina semi-fine powder having a second peak in the range of 0.2 μm to less than 1 μm in the volume frequency particle size distribution; and inorganic ultrafine powder having a BET diameter of 0.001 μm to less than 0.2 μm calculated from [6 / (true specific gravity × BET specific surface area)].

[0008] The present invention provides an alumina powder, a resin composition, and a method for producing alumina powder that are excellent at suppressing burrs when incorporated into a resin composition.

[0009] This is a schematic cross-sectional view showing the configuration of a thermal spraying apparatus.

[0010] The outline of the alumina powder in this embodiment will be described.

[0011] The alumina powder of this embodiment has at least a first peak and a second peak in its volume frequency particle size distribution, measured by a wet laser diffraction scattering method, where d1 is the particle size of the first peak and d2 is the particle size of the second peak, with d1 being 1 μm or more and 20 μm or less, d2 being 0.2 μm or more and less than 1 μm, and the BET specific surface area being 1.05 m². ２ / g or more 5.00m ２ The condition is less than or equal to / g.

[0012] In this specification, powders are referred to as follows according to their particle size: • Powders with a particle diameter of 1 μm or more and 20 μm or less are called "fine powders". • Powders with a particle diameter of 0.2 μm or more and less than 1 μm are called "semi-fine powders". • Powders with a particle diameter of less than 0.2 μm are called "ultrafine powders". The particle diameters of fine powders and semi-fine powders can be determined based on the volume frequency particle size distribution measured by the wet laser diffraction scattering method. If measurement by the wet laser diffraction scattering method is difficult, the particle diameter of ultrafine powders may be defined by the "BET diameter" described below. The BET diameter refers to the specific surface area measured by the BET method (BET specific surface area) and the hypothetical average diameter of the particles (representative diameter) converted based on a spherical model. The "BET diameter" can be calculated by substituting the BET specific surface area and true specific gravity of ultrafine powder into the following formula. In this case, the true specific gravity is ρ (g / cm³). ３ Using the numerical value "ρ" defined as ), the BET specific surface area is calculated as S(m ２ When the value "S" is defined as ( / g), the unit of the BET diameter is set to μm. BET diameter (μm) = [6 / (True specific gravity × BET specific surface area)]

[0013] According to the findings of the present inventors, in alumina powder, although the viscosity in the high shear region can be reduced by blending fine powder and sub-fine powder, which can enhance the narrow gap filling property, it has been found that burrs may occur. By further blending ultra-fine powder with the alumina powder containing fine powder and sub-fine powder, it has been found that while maintaining the low viscosity in the high shear region, the viscosity in the low shear region can be increased, thus realizing burr suppression.

[0014] Although the detailed mechanism is not clear, by blending ultra-fine powder in addition to fine powder and sub-fine powder, the specific surface area of the entire alumina powder can be precisely controlled. Therefore, it is considered that the coexistence of low viscosity in the high shear region and high viscosity in the low shear region can be realized, so that the fluidity into the narrow gap in the resin composition can be enhanced while excellent burr suppression can be achieved.

[0015] Hereinafter, each component of the alumina powder of the present embodiment will be described in detail.

[0016] The alumina powder of the present embodiment has at least a first peak existing in the range of particle diameter of 1 μm or more and 20 μm or less, and a second peak existing in the range of particle diameter of 0.2 μm or more and less than 1 μm in the volume frequency particle size distribution measured by the wet laser diffraction scattering method.

[0017] Here, let the particle diameter of the first peak be d1 and the particle diameter of the second peak be d2. d1 is 1 μm or more and 20 μm or less, preferably 2 to 15 μm, more preferably 3 to 12 μm. d2 is 0.2 μm or more and less than 1 μm, preferably 0.3 to 0.9 μm, more preferably 0.35 to 0.8 μm. In this specification, "~" represents including the upper limit value and the lower limit value unless otherwise specified.

[0018] Further, the BET specific surface area of the alumina powder of the present embodiment is 1.05 m ２ / g or more and 5.00 m ２ / g or less, preferably 1.25 to 4.50 m ２ / g, more preferably 1.35 to 4.00 m ２ / g.

[0019] An example of alumina powder may include alumina fine powder having the first peak described above, alumina semi-fine powder having the second peak described above, and inorganic ultrafine powder having a BET diameter of 0.001 μm or more and less than 0.2 μm calculated from [6 / (true specific gravity × BET specific surface area)]. The BET diameter of the inorganic ultrafine powder is 0.001 μm or more and less than 0.2 μm, preferably 0.005 to 0.18 μm, and more preferably 0.01 to 0.15 μm.

[0020] The inorganic ultrafine powder may contain at least one of alumina ultrafine powder and silica ultrafine powder. When the inorganic ultrafine powder contains alumina ultrafine powder, it becomes possible to suppress burrs in the resin composition and improve thermal conductivity.

[0021] The lower limit of the inorganic ultrafine powder content is, for example, 0.1% by mass or more, preferably 0.2% by mass or more, and more preferably 0.3% by mass or more, out of 100% by mass of the total of alumina fine powder, alumina semi-fine powder, and inorganic ultrafine powder. This allows for a relatively high viscosity in the low-shear region of the resin composition. It also improves the thixotropy of the resin composition. The upper limit of the inorganic ultrafine powder content is, for example, 5.0% by mass or less, preferably 4.5% by mass or less, and more preferably 4.0% by mass or less, out of 100% by mass of the total of alumina fine powder, alumina semi-fine powder, and inorganic ultrafine powder. By keeping it below the upper limit, the increase in viscosity can be suppressed.

[0022] The viscosity of the evaluation resin varnish containing the above alumina powder, measured according to the following procedure, is, for example, 1.5 kPa·s or more and 10.0 kPa·s or less, preferably 1.8 to 9.0 kPa·s, and more preferably 2.0 to 8.0 kPa·s. (Procedure) The above alumina powder is mixed with liquid epoxy resin (JER807, manufactured by Mitsubishi Chemical Corporation) at 25°C to obtain the evaluation resin varnish. The viscosity of the obtained evaluation resin varnish is measured using a rheometer at 25°C and a shear rate of 0.17 [1 / s].

[0023] The volume frequency distribution related to particle size of alumina powder can be measured by laser diffraction scattering, for example, using the "MT-3300EX" manufactured by Nikkiso Co., Ltd. For the measurement target, water was used as the solvent, and as a pretreatment, the alumina powder was dispersed using a homogenizer at a power output of 200W for 1 minute to obtain a dispersion. Furthermore, the PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55%. A refractive index of 1.33 was used for water, and the refractive index of the powder material was considered. For example, a refractive index of 1.50 was used for amorphous silica, and a refractive index of 1.76 was used for alumina.

[0024] In the volume frequency particle size distribution described above, the frequency of the first peak located in the particle size range of 1 μm to 20 μm is defined as P1 (%), the frequency of the second peak located in the particle size range of 0.2 μm to less than 1 μm is defined as P2 (%), and the smallest frequency between the first and second peaks is defined as P3 (%). In this case, the upper limit of (P1 + P2) / P3 in the alumina powder may be configured to satisfy, for example, 9.0 or less, preferably 8.5 or less, and more preferably 8.0 or less. This further suppresses the generation of burrs. The lower limit of (P1 + P2) / P3 is not particularly limited, but may be 3.0 or more.

[0025] Alumina powder is made from alumina (Al ２ 0 ３ Any product that contains alumina (Al) as its main component is acceptable. The main component is defined as alumina (Al) as the mass of the total alumina powder. ２ 0 ３ This means that it contains 90% or more by mass of ). While a higher purity is preferable for alumina powder, the presence of impurities that inevitably get mixed in during the raw material or manufacturing process is acceptable.

[0026] Furthermore, the lower limit of the gelatinization rate of the alumina powder is, for example, 50% or more, preferably 70% or more. The upper limit of the gelatinization rate of the alumina powder is, for example, not particularly limited, but may be 99.5% or less.

[0027] The alumina powder has a lower limit of sphericity measured using a wet flow-type image analysis device, for example, 0.90 or higher, preferably 0.91 or higher, and more preferably 0.92 or higher. This improves packing performance. On the other hand, there is no particular upper limit to the sphericity.

[0028] The alumina powder may be surface-treated with a silane coupling agent, or it may be untreated with no silane coupling agent adhering to the surface.

[0029] The method for producing the alumina powder of this embodiment will now be described.

[0030] An example of a method for producing alumina powder according to this embodiment includes a step of mixing the above-mentioned fine powder, semi-fine powder, and ultra-fine powder. A specific example of the alumina powder production process may include a step of mixing the above-mentioned alumina fine powder having a first peak in the range of 1 μm to 20 μm in the volume frequency particle size distribution measured by wet laser diffraction scattering, the above-mentioned alumina semi-fine powder having a second peak in the range of 0.2 μm to less than 1 μm in the volume frequency particle size distribution, and the above-mentioned inorganic ultra-fine powder having a BET diameter of 0.001 μm to less than 0.2 μm calculated from [6 / (true specific gravity × BET specific surface area)].

[0031] Alumina powder is produced, for example, by supplying alumina raw material powder into a high-temperature flame formed by the combustion reaction of a combustible gas and a combustion-supporting gas, and melting it into spheres above its melting point. As the raw material powder, alumina powder with an average particle size of about 1 to 25 μm may be used. Multiple raw material powders with different particle sizes may be used for the alumina raw material powder. The supply of aluminum hydroxide powder into the high-temperature flame may be dry or wet, by slurring it with water or the like. The obtained molten spheres may be further subjected to classification and sieving treatment as needed. As a classification treatment, it is preferable to remove coarse particles contained in the powder. Alumina powder can be obtained by blending the obtained alumina fine powder with the above-mentioned alumina semi-fine powder and the above-mentioned inorganic ultrafine powder.

[0032] The alumina powder of the present invention, when incorporated into a resin composition, can be suitably used as a resin molding material.

[0033] The resin composition of this embodiment contains the alumina powder of the present invention and a resin. The resin composition may contain, if necessary, inorganic powders described below, known resin additives, and the like.

[0034] In the resin composition, the alumina powder may be used alone or may be used in combination with other fillers. The resin composition may contain 10 to 99% by mass of the alumina powder, or may contain 10 to 99% by mass of an inorganic powder containing the alumina powder and other inorganic fillers. Further, in the inorganic powder, the content of other inorganic fillers may be, for example, 1 to 20% by mass, 3 to 15% by mass with respect to 100% by mass of the alumina powder. In the present specification, "~" represents including the upper limit value and the lower limit value unless otherwise specified.

[0035] Examples of the above other inorganic fillers include alumina powders other than the alumina powder of the present invention, crystalline silica, fused silica, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, and the like. The average particle diameter of other inorganic fillers is, for example, about 0.1 to 100 μm, and there are no particular restrictions on the particle size composition and shape.

[0036] Examples of the above resins include polyamides such as epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamideimides, polyetherimides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile - acrylic rubber - styrene) resin, AES (acrylonitrile - ethylene - propylene - diene rubber - styrene) resin, and the like. These may be used alone or in combination of two or more.

[0037] The resin composition can be manufactured, for example, by blending raw material components in predetermined ratios using a blender or Henschel mixer, then kneading the mixture using a heated roll, kneader, single-screw or twin-screw extruder, cooling, and then grinding it.

[0038] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention.

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0040] <Manufacturing of Alumina Powder> Spherical alumina powder was manufactured using the thermal spraying apparatus 100 shown in Figure 1. The thermal spraying apparatus 100 shown in Figure 1 comprises a melting furnace 2, a burner 1 installed at the top of the melting furnace 2, and a collection system line consisting of a cyclone 4 and a bag filter 8 installed directly connected to the bottom of the melting furnace 2. The burner 1 has a double-tube structure that can form an inner flame and an outer flame, and is installed at the top of the melting furnace 2, to which the combustible gas supply pipe 11, the auxiliary combustion gas supply pipe 12, and the raw material supply pipe 13 are connected. Inside the melting furnace 2, raw material powder is supplied into the high-temperature flame from the raw material supply pipe 13 and melted to form spherical molten spherical particles. The molten spherical particles that have passed through the melting furnace 2 are sucked in by a blower 9 along with the combustion exhaust gas, move through the pipes 3 and 5 by air, and are classified and collected by the cyclone 4 or the bag filter 8.

[0041] - Alumina Fine Powder A1 Using the above-described thermal spraying apparatus 100, alumina powder was manufactured under the following conditions and using the raw material powder, and this was designated as Alumina Fine Powder A1. LPG was supplied as the flammable gas from the flammable gas supply pipe 11, and oxygen was supplied as the auxiliary combustion gas from the auxiliary combustion gas supply pipe 12, and a high-temperature flame was formed in the burner 1 by the combustion of LPG and oxygen. Secondary air was supplied to the cyclone 4 by a rotary valve (not shown) installed in the piping 3. Air from the atmosphere was used as the secondary air. In addition, the degree of opening and closing of the lower valve in the cyclone 4 (lower opening) was set to 100%. As the raw material powder, the average particle size (D ５０ Multiple alumina powders having maximum values ​​in the range of 1 to 25 μm were used.

[0042] (Semi-fine alumina powder) ・Semi-fine alumina powder B1: ASFP-03S manufactured by Denka Co., Ltd. (BET specific surface area: 6.0 m²) ２ The amount ( / g) was defined as semi-fine alumina B1.

[0043] (Inorganic ultrafine powder) ・Ultrafine alumina C1: Nippon Light Metals Alumina A13 (BET specific surface area: 15 m²) ２ Ultrafine alumina C1 was defined as ( / g, BET diameter: 0.10 μm). Ultrafine alumina C2: ASFP-20 manufactured by Denka Co., Ltd. (BET specific surface area: 10.8 m²) ２ / g) and AluC (BET specific surface area: 100m²) manufactured by Nippon Aerosil ２ A mixture of ( / g) in a weight ratio of 80:20 is used to make ultrafine alumina C2 (BET specific surface area: 29 m²). ２ The values ​​were set as follows: ( / g, BET diameter: 0.05 μm). • Ultrafine alumina C3: Manufactured by Nippon Aerosil AluC (BET specific surface area: 100 m²) ２ Ultrafine alumina C3 was defined as ( / g, BET diameter: 0.02 μm). Ultrafine silica C4: AEROSIL 50 manufactured by Nippon Aerosil (BET specific surface area: 38 m²). ２ Ultrafine silica C4 was defined as (g / g, BET diameter: 0.07 μm). The above BET diameter (μm) was calculated based on the formula defined above: [6 / (True specific gravity × BET specific surface area)]. The true specific gravity of alumina is 3.6 g / cm³. ３ The true specific gravity of silica is 2.2 g / cm³. ３ That's what I decided.

[0044] (Examples 1-3, Comparative Examples 1-3, Reference Example 1) Alumina powder was prepared by blending the alumina fine powder, alumina semi-fine powder, and inorganic ultrafine powder shown in Table 1 according to the blending ratios shown in Table 1.

[0045] <Particle Size Distribution> The volume frequency particle size distribution related to the particle size of the powder was determined by wet laser diffraction scattering using a particle size distribution analyzer (MT-3300EX, manufactured by Nikkiso Co., Ltd.). Water was used as the solvent, and as a pretreatment, the powder was dispersed in the solvent using a homogenizer at an output of 200 W for 1 minute, and the resulting dispersion was used as the measurement target. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55% for measurement. In the volume frequency particle size distribution of each alumina powder, the presence of a first peak in the particle size range of 1 μm to 20 μm and a second peak in the particle size range of 0.2 μm to less than 1 μm was confirmed, and when each peak was present, the particle sizes corresponding to each peak were shown as d1 and d2 in Table 1. Furthermore, in the same volume frequency particle size distribution, the frequency of the first peak is defined as P1, the frequency of the second peak as P2, and the smallest frequency between the first and second peaks as P3. The value of (P1 + P2) / P3 is calculated and shown in Table 1. Note that the particle size of the first peak (d1) corresponds to alumina fine powder A1, and the particle size of the second peak (d2) corresponds to semi-fine alumina B1.

[0046] <Specific Surface Area> The specific surface area of ​​the powder was measured by the BET single-point method using nitrogen gas adsorption. Specifically, a specific surface area measuring device (Yuasa Ionics, device name: MONOSORB) was used, with nitrogen gas as the adsorption gas and helium gas as the carrier gas. 1 g of the sample was dried and degassed at 300°C for 30 minutes before measurement. Table 1 shows the BET specific surface area for each alumina powder.

[0047]

[0048] The following items were evaluated for the alumina powder in each example and comparative example.

[0049] <Method for measuring thermal conductivity> The 78 vol% alumina powder obtained above, 12 vol% liquid silicone resin (DOWSIL SE1885A), and 10 vol% liquid silicone resin (DOWSIL SE1885B) were mixed using a rotation-revolution mixer. The resulting mixture was processed into a 3 mm thick sheet and heat-treated in a dryer at 120°C for 2 hours to obtain a sample. The obtained sample was cut to a length of 20 mm x width of 20 mm x thickness of 3 mmt, and the thermal conductivity was measured by the heat flow meter method in accordance with ASTM E 1530 with the upper heater, sample (cut sample), heat flux meter, lower heater, and heat sink stacked in that order. The average value of the thermal conductivity of 10 samples is shown in Table 1.

[0050] <Method for measuring viscosity> The alumina powder obtained above was mixed with liquid bisphenol F epoxy (JER807, manufactured by Mitsubishi Chemical Corporation) at 25°C to a content of 83% by mass, to prepare an evaluation resin varnish. The viscosity (kPa·s) of the obtained evaluation resin varnish was measured using a rheometer at 25°C and a shear rate of 0.17 [1 / s]. The results are shown in Table 1.

[0051] To evaluate the properties of the obtained inorganic powder as a semiconductor encapsulating material, 27 vol% of a resin component, prepared in the following proportions: 44.2 mass% of 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl type epoxy resin, 45.2 mass% of phenolic resin, 1.9 mass% of triphenylphosphine, 2.9 mass% of carbon black, and 5.8 mass% of carnauba wax, was mixed with 73 vol% of the alumina powder obtained above. Further, 0.5 mass% of γ-glycidoxypropyltrimethoxysilane was added to the alumina powder and dry-blended in a Henschel mixer. The resulting mixture was then heated and kneaded in a co-screw twin-screw extruder (screw diameter D = 25 mm, kneading disc length 10 D mm, paddle rotation speed 100-150 rpm, discharge rate 3.5 kg / hr, kneaded material temperature 98-100°C). After cooling the extruded material in a cooling press, it was crushed to form a encapsulant, and the burr length was evaluated according to the following method. <Evaluation of Burr Length> 48 semiconductor packages with a 32-pin LOC (Lead on Chip) structure TSOP (Thin Small Outline Package; 10 mm x 21 mm, thickness 1.0 mm, simulated IC chip size 9 mm x 18 mm, lead frame made of 42 alloy) were manufactured using a transfer molding machine according to the following molding conditions, and the average burr length (mm) was measured. The results are shown in Table 1. The transfer molding conditions were a mold temperature of 175°C, a molding pressure of 7.4 MPa, and a holding pressure time of 90 seconds.

[0052] The results in Table 1 show that the alumina powders of Examples 1-3 and Reference Example 1 suppressed the generation of burrs in the resin composition when compounded with the resin, compared to Comparative Example 1. Furthermore, the alumina powders of Examples 1-3 improved the thermal conductivity of the resin composition compared to Reference Example 1.

[0053] This application claims priority based on Japanese Patent Application No. 2024-176363, filed on 8 October 2024, and incorporates all of its disclosures herein.

[0054] 1. Burner 2. Melting furnace 3. Piping 4. Cyclone 5. Piping 8. Bag filter 9. Blower 11. Combustible gas supply pipe 12. Auxiliary gas supply pipe 13. Raw material supply pipe 100. Thermal spraying equipment

Claims

1. In the volume frequency particle size distribution measured by wet laser diffraction scattering, at least a first peak and a second peak are present, and when the particle diameter of the first peak is d1 and the particle diameter of the second peak is d2, d1 is 1 μm or more and 20 μm or less, d2 is 0.2 μm or more and less than 1 μm, and the BET specific surface area is 1.05 m². ２ / g or more 5.00m ２ Alumina powder that satisfies the requirement of less than or equal to / g.

2. Alumina powder according to claim 1, comprising: alumina fine powder having the first peak in the volume frequency particle size distribution; alumina semi-fine powder having the second peak in the volume frequency particle size distribution; and inorganic ultrafine powder with a BET diameter of 0.001 μm or more and less than 0.2 μm, calculated from [6 / (true specific gravity × BET specific surface area)].

3. Alumina powder according to claim 2, wherein the inorganic ultrafine powder comprises at least one of alumina ultrafine powder and silica ultrafine powder.

4. Alumina powder according to claim 2, wherein the content of the inorganic ultrafine powder is 0.1% by mass or more and 5.0% by mass or less in 100% by mass of the total of the alumina fine powder, the alumina semi-fine powder, and the inorganic ultrafine powder.

5. Alumina powder according to claim 1 or 2, wherein the viscosity of the evaluation resin varnish containing the alumina powder, measured according to the following procedure, is 1.5 kPa·s or more and 10.0 kPa·s or less. (Procedure) The alumina powder is mixed with liquid epoxy resin (JER807, manufactured by Mitsubishi Chemical Corporation) at 25°C to obtain the evaluation resin varnish described above. The viscosity of the obtained evaluation resin varnish is measured using a rheometer at 25°C and a shear rate of 0.17 [1 / s].

6. Alumina powder according to claim 1 or 2, wherein when the frequency of the first peak is P1, the frequency of the second peak is P2, and the smallest frequency between the first peak and the second peak is P3, (P1 + P2) / P3 is 9.0 or less.

7. A resin composition comprising the alumina powder and resin according to claim 1 or 2.

8. A method for producing alumina powder, comprising the step of mixing: alumina fine powder having a first peak in the range of 1 μm to 20 μm in the volume frequency particle size distribution measured by a wet laser diffraction scattering method; alumina semi-fine powder having a second peak in the range of 0.2 μm to less than 1 μm in the volume frequency particle size distribution; and inorganic ultrafine powder having a BET diameter of 0.001 μm to less than 0.2 μm calculated from [6 / (true specific gravity × BET specific surface area)].

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