Gallium-containing alumina particles, and slurry composition and resin composite composition containing the same

Abstract

To provide new alumina particles, particularly, alumina particles having a content of gallium measured by inductively coupled plasma mass spectrometry (ICP-MS) in a specific range, and a slurry composition and a resin composite composition containing the same.SOLUTION: There are provided alumina particles which have an average particle diameter of 0.5 to 30.0 μm, and a content of gallium measured by inductively coupled plasma mass spectrometry (ICP-MS) of 95.0 to 800.0 ppm; and a slurry composition and a resin composite composition containing the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to gallium-containing alumina particles, particularly alumina particles having a gallium content within a specific range as measured by inductively coupled plasma mass spectrometry (ICP-MS), as well as a slurry composition and a resin composite composition containing the alumina particles. [Background technology]

[0002] In recent years, the increasing functionality and speed of electronic devices such as mobile phones has led to an increase in the amount of heat generated by the electronic components inside the devices. To ensure the normal operation of electronic devices, efficiently dissipating the generated heat to the outside has become an important issue. Thermally conductive sheets and thermally conductive adhesives are widely used for heat dissipation. These are attached or applied between the heat-generating element and the heat-dissipating fin and then pressed together to eliminate the gap between the heat-generating element and the heat-dissipating fin, allowing for efficient heat dissipation. Furthermore, the semiconductors inside electronic components also generate significant amounts of heat due to their similarly high functionality and high speed, and the encapsulating materials that protect the semiconductors are also required to have heat dissipation properties.

[0003] Generally, heat-dissipating sheets, heat-dissipating adhesives, and semiconductor encapsulants are composed of thermally conductive inorganic fillers and resins. (Such mixtures of fillers and resins are sometimes called resin compositions or resin composite compositions.) Thermally conductive inorganic fillers include inexpensive aluminum hydroxide and aluminum oxide (hereafter referred to as alumina), as well as silicon carbide, boron nitride, and aluminum nitride, which are expected to have high thermal conductivity. Silicone resins are commonly used as resins for heat-dissipating sheets and heat-dissipating adhesives, while epoxy resins are commonly used for semiconductor encapsulants.

[0004] It is generally known that thermally conductive inorganic fillers with particles having a more symmetrical crystal structure (such as α- and θ-phases in the case of alumina) have higher thermal conductivity because scattering due to lattice imperfections is reduced (e.g., Non-Patent Document 1). On the other hand, a high content of α- and θ-phases results in a loss of surface smoothness (e.g., Patent Document 1). Furthermore, because the α-phase has high hardness, it has been reported that a high content of α-phases can worsen wear characteristics (e.g., Patent Document 2). For example, during the kneading process of filler and resin in the production of heat-dissipating sheets, problems such as wear on the kneading equipment can occur (e.g., Patent Documents 1 and 2). Therefore, designing a thermally conductive inorganic filler that combines high thermal conductivity and surface smoothness has been an important technical challenge.

[0005] Patent Document 2 discloses that aluminum hydroxide powder or a slurry of aluminum hydroxide powder is sprayed into a flame from a feed tube with a strong dispersing function to obtain spherical alumina powder. It is disclosed that this method results in spherical alumina powder with a main crystalline phase consisting of δ and α, which can improve die wear characteristics. However, Patent Document 1 states that the spherical alumina particles obtained by this method, even those with an average sphericity of 0.90 or more, have surface irregularities derived from the aluminum hydroxide raw material, leaving room for improvement.

[0006] Patent Document 1 also discloses a method for obtaining spherical alumina by supplying aluminum hydroxide or alumina as an alumina raw material at a specific feed rate, melting the material at 2050 to 2300°C, and then rapidly cooling it with dry ice. This method achieves a δ-phase peak intensity / θ-phase peak intensity ratio (δ-phase peak intensity / θ-phase peak intensity) of 1.0 or greater in X-ray diffraction, resulting in highly fluid spherical alumina powder with a controlled surface morphology. However, the rapid cooling process, in which low-temperature dry ice is supplied to a high-temperature melting furnace during the flame-melting of the alumina raw material, places a heavy load on the manufacturing equipment, making stable industrial production difficult. Furthermore, there is still room for improvement in terms of surface morphology control and mold wear characteristics. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-102215 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-19425 [Non-patent literature]

[0008] [Non-Patent Document 1] Kittel Introduction to Solid State Physics 5th Edition Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, attempts have been made to design alumina particles with both excellent surface smoothness and high thermal conductivity, but the results have not been sufficient, and further improvements are needed. Also, from the perspective of industrial stable production, a manufacturing method that does not place excessive strain on manufacturing equipment is required. [Means for solving the problem]

[0010] The inventors conducted detailed studies on alumina particles and discovered that controlling the gallium content in the alumina particles within a specific range results in excellent surface smoothness and high thermal conductivity. Furthermore, they discovered that this method can achieve control of these properties without placing an excessive load on the manufacturing equipment.

[0011] Although we do not wish to be bound by any particular theory, it is believed that the smoothness of the surface shape can be improved by controlling the abundance ratio of the α crystalline phase, the θ crystalline phase, and the δ crystalline phase as measured by X-ray diffraction (XRD) and analyzed by the Rietveld method, and in particular by maintaining a constant amount of the θ crystalline phase.

[0012] The present invention is intended to solve the above-mentioned problems based on the above findings, and the gist of the present invention is as follows, as set forth in the claims. [1] Gallium-containing alumina particles, characterized by having an average particle size of 0.5 to 30.0 μm and a gallium content of 95.0 to 800.0 ppm as measured by inductively coupled plasma mass spectrometry (ICP-MS). [2] The gallium-containing alumina particles according to [1], wherein the abundance ratio of the θ crystalline phase and the δ crystalline phase as measured by X-ray diffraction (XRD) and analyzed by the Rietveld method is θ / δ<0.6. [3] Gallium-containing alumina particles according to [1] or [2], wherein the abundance ratio of α crystalline phase, θ crystalline phase and δ crystalline phase as measured by X-ray diffraction (XRD) and analyzed by the Rietveld method is expressed as (α + θ) / δ<0.6. [4] The gallium-containing alumina particles according to any one of [1] to [3], which have a circularity of 0.90 or more. [5] A slurry composition comprising the gallium-containing alumina particles according to any one of [1] to [4]. [6] The slurry composition according to [5], further comprising at least one inorganic filler selected from amorphous spherical alumina particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth basic carbonates (calcium carbonate, magnesium carbonate, etc.). [7] A resin composite composition, characterized by containing the gallium-containing alumina particles according to any one of [1] to [4]. [8] The resin composite composition according to [7], further comprising at least one inorganic filler selected from amorphous spherical alumina particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth basic carbonates (calcium carbonate, magnesium carbonate, etc.). [Effects of the Invention]

[0013] The gallium-containing alumina particles of the present invention, in which the gallium content is controlled within a specific range, are particularly excellent in surface smoothness and also have a high level of thermal conductivity. Furthermore, the gallium-containing alumina particles are extremely excellent in terms of industrially stable productivity, in that these properties can be controlled without placing an excessive load on the production equipment. In addition, by controlling the gallium content in the alumina particles, it is possible to easily control the balance between thermal conductivity and surface smoothness. In other words, the required level of thermal conductivity varies depending on the application, and the required level of wear resistance of kneading equipment varies depending on the equipment, and the balance can be controlled according to these desired required properties. The above-mentioned effect is extremely useful when the gallium-containing alumina particles are used as a filler for products that require thermal conductivity, such as heat-dissipating sheets, heat-dissipating adhesives, and semiconductor encapsulants. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Gallium content measured by inductively coupled plasma mass spectrometry (ICP-MS) is 95.0 to 800.0 ppm) The alumina particles provided by one embodiment of the present invention are The gallium content measured by inductively coupled plasma mass spectrometry (ICP-MS) is 95.0 to 800.0 ppm. The lower limit may be preferably 100.0 ppm. The upper limit may be preferably 500.0 ppm, more preferably 300.0 ppm.

[0015] By controlling the Ga content in the alumina particles within the above range, it is possible to achieve both particularly excellent low wear properties and good thermal conductivity.

[0016] Although the details are unclear, if the gallium content is below 95.0 ppm, the occurrence of surface irregularities associated with crystallization during the production of alumina particles, for example, during the cooling process after melting the alumina raw material, becomes significant. Since cooling of alumina particles is thought to occur from the surface, crystallization occurs from the surface. As a result, the surface irregularities become significant, and the smoothness of the alumina particle surface is thought to be significantly reduced. That is, when the Ga content is less than 95.0 ppm, the content of the α phase and θ phase, which are highly symmetric and tend to exhibit pronounced surface irregularities due to crystal habit during crystallization, increases, resulting in significant particle surface irregularities during cooling and crystallization. Therefore, during the kneading process of alumina particles and resin, the unevenness of the alumina particle surface (due to low smoothness) causes wear on the kneading equipment, i.e., equipment wear. Furthermore, the fluidity of the resin composition is significantly reduced. Therefore, in the kneading process of alumina particles and resin, the unevenness of the alumina particle surface (due to low smoothness) causes wear of the kneading equipment, i.e., equipment wear, and also tends to reduce the fluidity of the resin composition.

[0017] If the gallium content exceeds 800.0 ppm, the content of α-phase and θ-phase decreases, which is thought to tend to decrease thermal conductivity. Also, if the gallium content exceeds 800.0 ppm, impurity phases such as gallium oxide precipitate within the particles, which can cause defects such as poor shape.

[0018] In other words, by controlling the Ga content in the alumina particles within an appropriate range, the ratio of the α phase, δ phase, and θ phase can be appropriately controlled, resulting in achieving both particularly excellent low wear properties and good thermal conductivity.

[0019] To achieve both of the above properties (low equipment wear problems and excellent thermal conductivity), conventionally, the cooling process during particle production required a lot of effort, such as rapid cooling with dry ice. Surprisingly, in the present invention, by controlling the Ga content, particles with both of the above properties (low equipment wear problems and excellent thermal conductivity) were created.

[0020] [Ga content measurement method] The Ga content is measured using ICP-MS, which can ensure quantitative accuracy for trace elements (on the order of ppm). To measure with ICP-MS, the sample must be dissolved to create a solution, but alumina is a difficult substance to dissolve, so it is dissolved using a method such as pressurized acid decomposition. The solution can then be analyzed using ICP-MS.

[0021] (average particle size is 0.5 to 30.0 μm) The alumina particles according to one embodiment of the present invention have an average particle size of 0.5 to 30.0 μm. An average particle size of less than 0.5 μm undesirably increases particle cohesion, resulting in reduced lubricity (fluidity) of compositions containing the alumina particles, typically slurry compositions and resin composite compositions. An average particle size of more than 30.0 μm may result in reduced miscibility with other components in compositions containing the alumina particles, typically slurry compositions and resin composite compositions. The average particle size of the alumina particles can be adjusted appropriately depending on the intended use and properties of the composition containing them. Therefore, the lower limit of the average particle size may be 1.0 μm or 3.0 μm. The upper limit of the average particle size may be 20.0 μm, 15.0 μm, or 10.0 μm. The alumina particles according to one embodiment of the present invention can be produced by a thermal spraying method. In the thermal spraying method, the particle size of the alumina particles after thermal spraying can be adjusted by adjusting the particle size of the raw material used.

[0022] Here, the average particle size refers to the average particle size (D50), which is the median diameter D50 at 50% cumulative volume in the volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method. The laser diffraction / scattering particle size distribution measurement method involves irradiating a dispersion containing dispersed alumina particles with laser light and determining the particle size distribution from the intensity distribution pattern of the diffracted / scattered light emitted from the dispersion. In one embodiment of the present invention, a laser diffraction / scattering particle size distribution measurement device, Mastersizer 3000 (manufactured by Malvern), is used. The average particle size of the raw material alumina particles can also be determined in a similar manner.

[0023] (The ratio of the θ crystalline phase to the δ crystalline phase measured by X-ray diffraction (XRD) and analyzed by the Rietveld method is expressed as θ / δ<0.6.) In one embodiment of the present invention, the alumina particles may have a ratio of the θ crystalline phase to the δ crystalline phase as measured by X-ray diffraction (XRD) and analyzed by the Rietveld method, which is expressed as θ / δ<0.6. The upper limit of θ / δ is preferably 0.5 or less, or less than 0.5, and the lower limit of θ / δ may be 0.1 or more, or more than 0.1.

[0024] By controlling the abundance ratio of the θ crystalline phase and the δ crystalline phase within the above range, the abundance ratio of the δ phase and the θ phase can be appropriately controlled, and as a result, it is possible to achieve both particularly excellent low wear properties and good thermal conductivity.

[0025] [Method for quantifying α phase, θ phase, and δ phase] The α, θ, and δ phases of alumina particles are quantified by Rietveld analysis of the particle's X-ray diffraction data. X-ray diffraction measurements of alumina particles are performed using a Bruker D2PHASER powder X-ray diffraction measurement device. The obtained X-ray diffraction pattern is analyzed using the Rietveld method to quantify each phase and calculate (α + θ) / δ and θ / δ. The PDF-4 2020 database (α: 04-004-2852, θ: 01-086-1410, δ: 04-021-8098) was referenced for the analysis. Other measurement conditions are as follows: <Measurement conditions> Light source: Cu Kα (=0.1541nm) Scanning range: 10~90° Scanning speed: 0.02° / s In addition, the reliability factor Rwp value used as an index of the reliability of the Rietveld analysis should all be less than 10%.

[0026] (The abundance ratio of α, θ, and δ crystalline phases measured by X-ray diffraction (XRD) and analyzed by the Rietveld method is expressed as (α+θ) / δ<0.6.) In one embodiment of the present invention, the alumina particles may have a ratio of theta crystalline phase to delta crystalline phase as measured by X-ray diffraction (XRD) and analyzed by the Rietveld method, expressed as (α + θ) / δ<0.6. The upper limit of (α + θ) / δ is preferably 0.5 or less, and the lower limit of (α + θ) / δ may be 0.1 or more, or greater than 0.1.

[0027] By controlling the abundance ratio of the α-, θ-, and δ-crystalline phases within the above ranges, the abundance ratios of the α-, δ-, and θ-phases can be appropriately controlled, and as a result, it is possible to achieve both excellent low wear properties and good thermal conductivity. The α-, θ-, and δ-phases are quantified by the above-mentioned quantification method.

[0028] (Circularity of 0.90 or more) The alumina particles according to one embodiment of the present invention can be produced by a thermal spraying method, which allows the shape of the resulting alumina particles to be adjusted by adjusting the amount of raw material fed to the flame per unit time and the type of fuel gas, thereby producing spherical alumina particles.

[0029] "Spherical" refers not only to particles that are perfectly spherical, but also to particles that are roughly spherical. Specifically, whether a particle is spherical or not is determined by the following procedure. First, the particle is photographed as a two-dimensional image. The shape of the two-dimensional image (i.e., circular or roughly circular) is noted, and its circularity (perimeter of the equivalent circle / perimeter of the projected image of the particle) is measured. The circularity of 100 or more particles is measured, and the average value is calculated. Particles with an average circularity value of 0.90 or more are considered spherical.

[0030] The spherical alumina particles may have a circularity of 0.90 or more. The higher the circularity of the spherical particles, the lower the abrasion or the higher the lubricity (fluidity) of compositions containing the alumina particles, typically slurry compositions and resin composite compositions, and ultimately the better the feel (texture) of the product. The circularity may be 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, or 0.95 or more. Theoretically, the upper limit of the circularity is 1.0, but from the viewpoint of manufacturing control, it may be 0.98 or less, or 0.97 or less.

[0031] [Method for measuring circularity] Circularity can be measured using an electron microscope or optical microscope and an image analyzer, such as the FPIA manufactured by Sysmex Corporation. These devices are used to obtain a two-dimensional image of the particle. The circularity of the two-dimensional image (perimeter of the equivalent circle / perimeter of the projected image of the particle) is measured. The circularity of 100 or more particles is measured, and the average value is taken as the circularity of that particle.

[0032] (Slurry composition containing gallium-containing alumina particles) According to one embodiment of the present invention, a slurry composition containing gallium-containing alumina particles is provided. The slurry composition can be obtained using a composition containing alumina particles and a dispersion medium. The slurry composition can be used in the resin composite composition described below. The slurry composition according to one embodiment of the present invention can reduce abrasion or increase lubricity (fluidity), and can also provide a resin composite composition with excellent fluidity.

[0033] The dispersion medium in the slurry composition can be water or a known organic solvent, and can be adjusted appropriately depending on the application of the slurry composition. Multiple dispersion mediums may be used in combination. Typically, the dispersion medium is a liquid, and examples thereof include water and organic solvents. Examples of organic solvents include alkane solvents such as hexane, heptane, octane, and decane; alcohol solvents such as methanol, ethanol, and propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and aromatic solvents such as benzene, toluene, ethylbenzene, and xylene. Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone are preferred.

[0034] When producing the slurry composition, for example, in addition to the gallium-containing alumina particles and the dispersion medium, known dispersants, pigments, fragrances, preservatives, purified water, surfactants, etc. may be blended as needed, and the resulting mixture may be compounded by a known method such as kneading.

[0035] The dispersant in the slurry composition may be water or a known organic solvent, and may be appropriately adjusted depending on the intended use of the slurry composition. A plurality of dispersants may be used in combination.

[0036] The dispersant may be, for example, a dispersant containing at least one selected from a nonionic dispersant and a cationic dispersant.

[0037] The nonionic dispersant is not particularly limited, and known dispersants can be used. Examples include polymeric compounds having a polyoxyethylene chain. Examples of polymeric compounds having a polyoxyethylene chain include alkyl polyoxyethylene ethers, alkyl polyoxyethylene-polyoxypropylene ethers, alkyl polyoxypropylene-polyoxyethylene ethers, polyoxyethylene-polyoxypropylene ethers (polyoxyethylene-polyoxypropylene block copolymers), fatty acid polyoxyethylene esters, fatty acid polyoxyethylene sorbitan esters, fatty acid polyoxyethylene sorbitol esters, polyoxyethylene sorbitan monoalkyl ethers, polyoxyethylene alkyl ether sulfate esters, polyoxyethylene castor oil (hydrogenated castor oil), and acetylene glycol ethylene oxide adducts. Examples of alkyl polyoxyethylene ethers include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl ether, polyoxyethylene cetyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene nonylphenyl ether. Examples of fatty acid polyoxyethylene sorbitan esters include polyoxyethylene sorbitan monolaurate.

[0038] The cationic dispersant is not particularly limited, and known dispersants can be used. Examples include alkylamine salts, acylamine salts, quaternary ammonium salts, ammonium salts having an amide bond, an ester bond, or an ether bond, imidazoline, imidazolium salts, and amine derivatives. The cationic dispersant may be a low-molecular-weight compound or a high-molecular-weight compound, but high-molecular-weight compounds are preferred from the viewpoint of the dispersibility of alumina particles. Examples of such high-molecular-weight dispersants include polyethyleneimine, aminoalkyl (meth)acrylate copolymers, polyvinylimidazoline, polyvinylpyridine derivatives, polyoxyethylene alkylamines, and polyoxyethylene alkylamides. Examples of polyvinylpyridine derivatives include copolymers of vinylpyridine and (meth)acrylic acid, and copolymers of vinylpyridine, (meth)acrylic acid, and an oxyethylene group-containing polymer compound. Examples of copolymers of vinylpyridine, (meth)acrylic acid, and an oxyethylene group-containing polymer compound include copolymers of vinylpyridine, (meth)acrylic acid, and polyoxyethylene. Among these, amine-type high-molecular-weight dispersants are preferred from the viewpoint of the dispersibility of alumina particles.

[0039] The dispersant may be a known surface treatment agent. The inclusion of a surface treatment agent improves the dispersibility of alumina particles in a dispersion medium in a slurry composition, and the dispersibility or affinity of the alumina particles with a resin in a resin composite composition. Examples of the surface treatment agent include compounds having at least one functional group selected from alkyl groups such as methyl, ethyl, propyl, and butyl; alkenyl groups such as vinyl, ethenyl, and propenyl; phenyl, amino, phenylamino, acrylic, methacrylic, epoxy, and styryl groups; silane coupling agents; and silazanes. Silane coupling agents having SiH, SiOH, or SiOR (where R is a hydrocarbon group) and silazane containing hexamethylenedisilazane are preferred.

[0040] Examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. Examples of alkoxysilane compounds include hexyltrimethoxysilane, octyltriethoxysilane, and phenyltriethoxysilane. Examples of silazane compounds include hexamethyldisilazane and trimethylsilane. From the viewpoint of excellent reactivity, silazane compounds are more preferred. Hexamethyldisilazane and trimethylsilane are more preferred.

[0041] The content of the gallium-containing alumina particles in the slurry composition (when the slurry composition contains an "inorganic filler" or "other fillers" described below, the total content of these) can be adjusted appropriately depending on the application of the slurry composition. Typically, from the viewpoint of exhibiting the effects of the gallium-containing alumina particles of one embodiment of the present invention, the content is 50 to 95 wt%. A more preferred lower limit is 55 wt%, more preferably 60 wt%, more preferably 65 wt%, and more preferably 70 wt%. A more preferred upper limit is 93 wt%, more preferably 90 wt%, and more preferably 85 wt%.

[0042] (inorganic filler) Furthermore, when producing the slurry composition and the resin composite composition described below, other inorganic fillers may be blended in addition to the gallium-containing alumina particles of one embodiment of the present invention. Examples of the inorganic fillers include amorphous spherical alumina particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth basic carbonates (calcium carbonate, magnesium carbonate, etc.). The blending ratio of the inorganic fillers can be adjusted appropriately depending on the intended use of the slurry composition or resin composite composition. Typically, to achieve the effects of the gallium-containing alumina particles of one embodiment of the present invention, the blending ratio (weight of gallium-containing alumina particles):(weight of other inorganic fillers) may be 5:95 to 90:10.

[0043] (Resin composite composition containing gallium-containing alumina particles) According to one embodiment of the present invention, there is provided a resin composite composition containing gallium-containing alumina particles. The resin composite composition can be obtained using a composition containing gallium-containing alumina particles and a resin.

[0044] For example, the gallium-containing alumina particles can be used to obtain resin composite compositions such as semiconductor encapsulants (particularly solid encapsulants) and interlayer insulating films. Furthermore, by curing these resin composite compositions, resin composites such as encapsulants (cured products) and semiconductor package substrates can be obtained. The gallium-containing alumina particles according to one embodiment of the present invention can also be used in applications such as semiconductor encapsulants, interlayer insulating films, heat dissipation sheets, and heat dissipation greases, because they can be used to obtain resin composite compositions with excellent thermal conductivity.

[0045] When producing the resin composite composition, for example, in addition to the gallium-containing alumina particles and resin, a curing agent, a curing accelerator, a flame retardant, a silane coupling agent, etc. are blended as needed, and the resulting mixture is composited by a known method such as kneading, etc. Then, the resulting mixture is molded into pellets, films, etc. depending on the intended use.

[0046] Furthermore, when producing the resin composite composition, the aforementioned inorganic filler may be blended in addition to the gallium-containing alumina particles and resin. The inorganic filler blended in the resin composite composition (or slurry composition) may be amorphous spherical alumina particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, or carbon fiber. The blending ratio of the inorganic filler can be appropriately adjusted depending on the application of the resin composite composition. However, from the viewpoint of exerting the effects of the gallium-containing alumina particles of one embodiment of the present invention, it is preferable that the blending ratio of the gallium-containing alumina particles to the other inorganic fillers is 95:5 to 60:40.

[0047] Furthermore, when the resin composite composition is cured to produce a resin composite, for example, the resin composite composition is heated to melt it, processed into a shape according to the intended use, and then heated to a temperature higher than that used for melting to completely cure it. In this case, a known method such as a transfer molding method can be used.

[0048] For example, when manufacturing semiconductor-related materials such as package substrates and interlayer insulating films, known resins can be used as the resin for the resin composite composition, but epoxy resins are preferred. The epoxy resin is not particularly limited, but examples include bisphenol A epoxy resins, bisphenol F epoxy resins, biphenyl epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, naphthalene epoxy resins, and phenoxy epoxy resins. One of these resins can be used alone, or two or more resins with different molecular weights can be used in combination. Among these, epoxy resins having two or more epoxy groups per molecule are preferred from the standpoints of curability, heat resistance, and the like. Specific examples include biphenyl-type epoxy resins, phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, epoxidized novolac resins of phenols and aldehydes, glycidyl ethers of bisphenol A, bisphenol F, bisphenol S, etc., glycidyl ester acid epoxy resins obtained by reacting polybasic acids such as phthalic acid or dimer acid with epochlorohydrin, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified multifunctional epoxy resins, β-naphthol novolac-type epoxy resins, 1,6-dihydroxynaphthalene-type epoxy resins, 2,7-dihydroxynaphthalene-type epoxy resins, bishydroxybiphenyl-type epoxy resins, and epoxy resins into which halogens such as bromine have been introduced to impart flame retardancy. Among these epoxy resins having two or more epoxy groups per molecule, bisphenol A-type epoxy resins are particularly preferred.

[0049] In addition, resins other than epoxy resins can also be used in resin composite compositions for applications other than semiconductor encapsulation composites, such as prepregs for printed circuit boards and various engineering plastics. Specific examples of resins that can be used in addition to epoxy resins include silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimides, polyamideimides, and polyetherimides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins.

[0050] The curing agent used in the resin composite composition may be any known curing agent for curing the resin, such as a phenol-based curing agent, such as a phenol novolac resin, an alkylphenol novolac resin, or a polyvinylphenol, which may be used alone or in combination.

[0051] The amount of the phenolic curing agent blended is preferably such that the equivalent ratio to the epoxy resin (phenolic hydroxyl group equivalent / epoxy group equivalent) is 0.1 or more and less than 1.0, thereby eliminating any unreacted phenolic curing agent residue and improving moisture absorption and heat resistance.

[0052] In one embodiment of the present invention, the amount of gallium-containing alumina particles added to the resin composite composition is preferably large from the viewpoint of heat resistance and thermal expansion coefficient, but is typically 70% by mass to 95% by mass, preferably 80% by mass to 95% by mass, and more preferably 85% by mass to 95% by mass. This is because if the amount of gallium-containing alumina particles added is too small, it is difficult to achieve effects such as improving the strength of the sealing material and suppressing thermal expansion. Conversely, if the amount is too large, segregation due to aggregation of the gallium-containing alumina particles is likely to occur in the composite material regardless of the surface treatment of the gallium-containing alumina particles, and the viscosity of the composite material becomes too high, making it difficult to use as a sealing material. Note that when the above-mentioned "other filler" is used in combination, the preferred amount added to the resin composite composition is the total amount of the gallium-containing alumina particles and the "other filler."

[0053] In addition to the resin, known additives such as a silane coupling agent, a curing agent, a colorant, and a hardening retarder can be used.

[0054] As for the silane coupling agent, any known coupling agent may be used, but those having an epoxy-based functional group are preferred.

[0055] Furthermore, the composite resin composition can be used to obtain a heat-dissipating sheet, a heat-dissipating grease, and the like.

[0056] When obtaining the heat dissipation sheet, the gallium-containing alumina particles, the resin, and additives are appropriately blended and compounded by a known method such as kneading, etc. The obtained composite is molded into a sheet by a known method.

[0057] For example, when producing a heat dissipation sheet, known resins can be used in the resin composite composition, including silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimides, polyamideimides, and polyetherimides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. Among these, silicone resins are preferred. The silicone resin is not particularly limited, but examples include peroxide-curable, addition-curable, condensation-curable, and UV-curable types.

[0058] In addition to the resin, known additives such as a silane coupling agent, a curing agent, a colorant, and a hardening retarder can be used.

[0059] When preparing the thermal grease, the gallium-containing alumina particles, the resin, and additives are appropriately blended and compounded by a known method such as kneading. The resin used in the thermal grease is also called the base oil.

[0060] For example, when producing thermally conductive grease, known resins can be used in the resin composite composition, including silicone resin, phenolic resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamides such as polyimide, polyamideimide, and polyetherimide; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, mineral oil, synthetic hydrocarbon oil, ester oil, polyglycol oil, silicone oil, and fluorine oil.

[0061] In addition to the resin, known additives such as silane coupling agents, colorants, thickeners, etc. Examples of the thickener that can be used include calcium soap, lithium soap, aluminum soap, calcium complex, aluminum complex, lithium complex, barium complex, bentonite, urea, PTFE, sodium terephthalamate, silica gel, and organic bentonite.

[0062] [Method of manufacturing alumina particles] The gallium-containing alumina particles according to one embodiment of the present invention are not particularly limited in terms of the manufacturing method, and can be manufactured by the following manufacturing method. The manufacturing method is a method that can suitably manufacture the above-described gallium-containing alumina particles, and can include the following steps. (1) A process for producing alumina particles by introducing at least one of alumina, boehmite, aluminum hydroxide, etc. into a flame, melting the melt, and then cooling the melt; (2) A step of classifying the alumina particles using a sieve or the like after the step of producing the alumina particles.

[0063] The process for producing alumina particles (1) involves injecting raw materials for alumina particles (hereinafter simply referred to as "raw materials") into a flame, melting them, and then cooling them. These raw materials can be injected into the flame while suspended in a carrier gas. Examples of the carrier gas that can be used include air, oxygen, and propane gas.

[0064] The flame is preferably formed in a heat-resistant furnace. The flame is formed in the upper part of the heat-resistant furnace, the raw material is fed into the flame, and the molten alumina particulate material is collected from the bottom of the heat-resistant furnace as it settles due to gravity. By preventing the raw material from forming a flame in the lower part of the heat-resistant furnace, the alumina particulate material that settles to the bottom is cooled and granulated.

[0065] The upper region of the heat-resistant furnace where the raw material is supplied and melted by the flame is called the melting region, and the lower region of the heat-resistant furnace where the molten alumina particles are cooled is called the cooling region.

[0066] The flame formation method is not particularly limited, but may be such that a fuel (a known fuel such as propane, LPG, LNG, hydrogen, or ammonia) and a combustion supporting gas (air or oxygen) are supplied to the melting zone via a burner, a mixture of fuel and combustion supporting gas is supplied to the melting zone via a burner, or a mixture of raw material, fuel, and combustion supporting gas is supplied to the melting zone via a burner to form a flame. In particular, from the viewpoint of increasing the maximum flame temperature and widening the temperature gradient within the heat-resistant furnace, a flame formation method in which a mixture of fuel and combustion supporting gas or a mixture of raw material, fuel, and combustion supporting gas is supplied to the melting zone is preferred.

[0067] Furthermore, if sufficient heat can be applied to the raw material particles in the melting region to melt them, the amount of irregularly shaped particles that do not become spherical can be reduced. This allows the bulk density of the alumina particles to be adjusted. Furthermore, the circularity and bulk density can be adjusted by adjusting the amount of material fed to the flame per unit time and the type of fuel gas. Furthermore, the particle size of the alumina particles after thermal spraying can be adjusted by adjusting the particle size of the raw material powder used.

[0068] The raw material of the alumina particles may be at least one of alumina, boehmite, aluminum hydroxide, etc. When these raw materials are introduced into the flame, the alumina remains as alumina, and the boehmite or aluminum hydroxide undergoes an oxidation or dehydration reaction to form alumina.

[0069] A refrigerant may be used in the cooling region. Although the refrigerant is not particularly limited, distilled water or ion-exchanged water that does not contain air or impurities such as sodium ions or chlorine ions is preferable from the viewpoint of not reducing the purity of the alumina particles.

[0070] In the classification step (2), the alumina particles obtained in the alumina particle production step can be suitably classified using a sieve or the like with a specified mesh size. If necessary, pre-treatment or post-treatment such as separation into coarse particles and fine particles using a cyclone or the like can be added. This step allows the desired particle size, particle size distribution, specific surface area, and bulk density to be obtained.

[0071] The gallium-containing alumina particles according to one embodiment of the present invention may be in a state in which alumina particles having a Ga content specified in the present invention are obtained in the above step (1).

[0072] For example, the raw material for the alumina particles may have a Ga content specified in one embodiment of the present invention, and when the raw material is introduced into the flame, a Ga source such as gallium oxide or gallium hydroxide may also be introduced. [Example]

[0073] An embodiment of the present invention will be described through the following examples and comparative examples, but the embodiment of the present invention should not be construed as being limited to the following examples.

[0074] Alumina particles were produced by thermal spraying, that is, by feeding alumina particle raw material containing a specified amount of gallium into a flame formed by LPG and oxygen. The average particle size of the alumina particles was adjusted by controlling the particle size of the alumina particle raw material fed, and gallium-containing alumina particles having the physical properties shown in Table 1 were produced by adjusting the flame formation conditions, raw material particle size, raw material supply amount, classification conditions, etc. The physical properties of the obtained alumina particles are shown in Table 1.

[0075] [Table 1]

[0076] The methods for measuring the various physical properties are described below.

[0077] [Average particle size] The average particle size (D50) was measured using a laser diffraction / scattering particle size distribution analyzer "Mastersizer 3000" (manufactured by Malvern).

[0078] [Ga content measurement method] The Ga content was measured by ICP-MS. To dissolve the alumina, the sample was dissolved by pressurized acid decomposition to obtain a solution. The Ga content was then measured by ICP-MS to determine the content.

[0079] [Method for quantifying α phase, θ phase, and δ phase] The α, θ, and δ phases of the alumina particles described in the examples and comparative examples were quantified by Rietveld analysis of the particle X-ray diffraction data. X-ray diffraction measurements of the alumina particles were performed using a Bruker D2PHASER powder X-ray diffraction analyzer. The obtained X-ray diffraction patterns were analyzed using the Rietveld method to quantify each phase and calculate (α + θ) / δ and θ / δ. The PDF-4 2020 database (α: 04-004-2852, θ: 01-086-1410, δ: 04-021-8098) was referenced for the analysis. Other measurement conditions were as follows: <Measurement conditions> Light source: Cu Kα (=0.1541nm) Scanning range: 10~90° Scanning speed: 0.02° / s In addition, the reliability factor Rwp value, which is used as an index of the reliability of the Rietveld analysis, was less than 10% in all cases.

[0080] [Thermal conductivity evaluation method] Alumina particles described in the Examples and Comparative Examples, a biphenyl-based epoxy resin "YX-4000H" manufactured by Mitsubishi Chemical Corporation, and a curing agent "2-ethyl-4-methylimidazole" manufactured by Shikoku Chemical Industries Co., Ltd. were weighed into a metal dish in a mass ratio of 80:15:5 and kneaded until the mixture became uniform while heating on a hot plate set to 175°C. The mixture was then held for 5 hours to produce a 5 mm-thick plate-shaped resin composite composition. The plate-shaped resin composition was cooled in a thermostatic oven at 25°C and placed on a hot plate heated to 100°C. Thermal conductivity was evaluated based on the time it took for the surface not touching the hot plate to reach 80°C. The group with the shortest time to reach 80°C was designated ◎, the group with the next shortest time was designated ○, the group with the next shortest time was designated △, and the group with the longest time was designated ×. ◎ indicates particularly excellent thermal conductivity. From an industrial perspective, a rating of ○ to △ indicates sufficiently excellent thermal conductivity.

[0081] [Method for measuring composition hardness] The alumina particles described in the Examples and Comparative Examples and a biphenyl-based epoxy resin "YX-4000H" manufactured by Mitsubishi Chemical were weighed into a metal dish in a mass ratio of 4:1, and the mixture was kneaded while heating on a hot plate set to 175°C until it became uniform. The mixture was cooled in a thermostatic bath at 25°C, and a 5mm-thick plate-shaped resin composite composition was produced. The hardness of the plate-shaped resin composition was measured using an Asker Hardness Tester Type E and used to evaluate abrasion resistance. The group with the lowest hardness was designated as ◎, the next lowest group as ○, the next lowest group as △, and the highest group as ×. ◎ indicates particularly low equipment abrasion resistance and can be said to be industrially excellent.

[0082] Circularity The circularity was measured using an electron microscope, an optical microscope, and an image analyzer. In this example and comparative example, an FPIA manufactured by Sysmex Corporation was used. These devices were used to measure the circularity of particles (perimeter of the equivalent circle / perimeter of the projected image of the particle). The circularity of 100 or more particles was measured, and the average value was taken as the circularity of the powder. [Industrial Applicability]

[0083] The alumina particles of one embodiment of the present invention have excellent surface smoothness and also have high thermal conductivity and high levels of surface smoothness. In one embodiment of the present invention, a slurry composition and a resin composite composition containing the alumina particles are also provided, and depending on the properties of the alumina particles, effects such as excellent wear resistance (less wear on equipment) and thermal conductivity can be obtained.

Claims

1. Gallium-containing alumina particles, characterized in that the average particle size is 0.5 to 30.0 μm and the gallium content measured by inductively coupled plasma mass spectrometry (ICP-MS) is 95.0 to 800.0 ppm.

2. The gallium-containing alumina particles according to claim 1, wherein the abundance ratio of theta crystalline phase and delta crystalline phase measured by X-ray diffraction (XRD) and analyzed by the Rietveld method is expressed as θ / δ<0.

6.

3. The abundance ratio of the α crystalline phase, the θ crystalline phase and the δ crystalline phase measured by X-ray diffraction (XRD) and analyzed by the Rietveld method is (α + θ) / δ < 0.

6. Gallium-containing alumina particles according to claim 1.

4. The gallium-containing alumina particles according to claim 1, having a circularity of 0.90 or more.

5. A slurry composition comprising the gallium-containing alumina particles according to any one of claims 1 to 4.

6. 6. The slurry composition according to claim 5, further comprising at least one inorganic filler selected from amorphous spherical alumina particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth basic carbonates (calcium carbonate, magnesium carbonate).

7. A resin composite composition comprising the gallium-containing alumina particles according to any one of claims 1 to 4.

8. 8. The resin composite composition according to claim 7, further comprising at least one inorganic filler selected from amorphous spherical alumina particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth basic carbonates (calcium carbonate, magnesium carbonate).

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