Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/021—After-treatment of oxides or hydroxides
  • C01F7/027—Treatment involving fusion or vaporisation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/021—After-treatment of oxides or hydroxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/30—Particle morphology extending in three dimensions
  • C01P2004/32—Spheres
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/51—Particles with a specific particle size distribution
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/11—Powder tap density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity
  • C01P2006/82—Compositional purity water content
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2227—Oxides; Hydroxides of metals of aluminium
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/001—Conductive additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/005—Additives being defined by their particle size in general
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/006—Additives being defined by their surface area

Definitions

• the present invention relates to spherical alumina particles, in particular spherical alumina particles that combine high thermal conductivity and fluidity, and a method for producing the same.
• heat dissipation sheets, heat dissipation adhesives, and semiconductor encapsulants are composed of thermally conductive inorganic filler and resin.
• 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 resin is generally used as the resin for heat dissipation sheets and heat dissipation adhesives, while epoxy resin is generally used for semiconductor encapsulants.
• fillers have a higher thermal conductivity than resins, so as a means of improving the thermal conductivity of these components, much research has been done on methods that aim to increase thermal conductivity by increasing the amount of filler added to the resin. However, it is also known that increasing the amount of filler can cause problems. First, the fluidity of the resin composition decreases. Also, in semiconductor encapsulation materials, the filler can cause deformation of the wires connected to the semiconductor.
• Patent Document 1 proposes using an alumina powder containing specified alumina particles as a filler. More specifically, it specifies that the alumina particles have a specified circle equivalent diameter and sphericity, that the alumina powder contains the alumina particles at a specified content rate, and that it has a specified particle diameter and moisture content. It states that this provides the appropriate fluidity for the resin composition, and also makes it possible to suppress deformation of the wire during semiconductor encapsulation.
• the present invention aims to provide spherical alumina particles that can improve the thermal conductivity of the resin composition produced when mixed with resin and suppress the viscosity (increase fluidity), as well as a method for producing the same.
• D50 by the laser diffraction scattering method is 0.5 to 10.0 ⁇ m
• particles having a size of 20.0 ⁇ m or more are 0.04% by weight or less
• the specific surface area measured by the BET method is 0.35 m 2 /g or more and 3.50 m 2 /g or less
• the "tap bulk density" specified in the Japanese Industrial Standard JIS R1628:1997 is 1.30 g/cm 3 or more and 2.50 g/cm 3 or less, Spherical alumina particles having a circularity of 0.90 or more.
• [2] The spherical alumina particles according to [1], having an alpha conversion rate of 55% or less.
• [3] The spherical alumina particles according to [1] or [2], wherein the frequency of particles having a size of 10 ⁇ m or more among particles having a size of 1 ⁇ m or more and a size of 30 ⁇ m or less as detected by a Coulter counter is 20 ppm or less.
• [5] A resin composite composition comprising the spherical alumina particles according to any one of [1] to [4].
• at least one inorganic filler selected from amorphous spherical alumina particles, crystalline spherical silica particles, alumina particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers.
• a method for producing spherical alumina particles comprising the steps of: introducing at least one of alumina, boehmite, and aluminum hydroxide into a flame to melt the melted alumina, and then cooling the melted alumina to form spheroids; and, following the spheroidizing step, classifying the melted alumina using a precision air classifier and a sieve in combination.
• the method has a D50 of 0.5 to 10.0 ⁇ m as measured by a laser diffraction scattering method, a particle size distribution measured by a wet particle size test method in which particles of 20.0 ⁇ m or more account for 0.04% by weight or less, a specific surface area measured by a BET method of 0.35 m2 /g to 3.50 m2 /g, a "tap bulk density" as defined in Japanese Industrial Standard JIS R1628:1997 of 1.30 g/ cm3 to 2.50 g/ cm3 , and a circularity of 0.9 or more.
• thermo conductivity it is possible to provide a heat dissipation sheet, heat dissipation adhesive, and semiconductor encapsulant with improved thermal conductivity, and further provide alumina particles and a method for producing the same that can suppress the viscosity of the resin composition that is formed when mixed with resin.
• the inventors conducted extensive research to obtain alumina particles with high thermal conductivity and excellent fluidity (more specifically, alumina particles that, when mixed with a resin, produce a resin mixture with high thermal conductivity and low viscosity).
• alumina particles with high thermal conductivity and excellent fluidity more specifically, alumina particles that, when mixed with a resin, produce a resin mixture with high thermal conductivity and low viscosity.
• the inventors discovered that controlling the particle size, particle size distribution, specific surface area, bulk density, and circularity of spherical alumina particles brings the thermal conductivity and fluidity into suitable ranges. Based on this discovery, the inventors have completed the present invention.
• the inventors have completed the desired spherical alumina particles with high thermal conductivity and excellent fluidity, and a method for producing the same, by controlling the particle size, particle size distribution, specific surface area, bulk density, and circularity of spherical alumina particles within predetermined ranges.
• the spherical alumina particles provided by one embodiment of the present invention are D50 by the laser diffraction scattering method is 0.5 to 10.0 ⁇ m, In the particle size distribution measured by a wet particle size test method, particles having a size of 20.0 ⁇ m or more are 0.04% by weight or less; The specific surface area measured by the BET method is 0.35 m 2 /g or more and 3.50 m 2 /g or less, The "tap bulk density" specified in the Japanese Industrial Standard JIS R1628:1997 is 1.30 g/cm 3 or more and 2.50 g/cm 3 or less, The circularity is 0.9 or more. It is characterized by:
• the spherical alumina particles which are one embodiment of the present invention, have an average particle size of 0.5 to 10.0 ⁇ m. If the average particle size is less than 0.5 ⁇ m, the particles will have a large coagulation tendency, and when used as a filler, the fluidity of the resin composition will be significantly reduced, which is not preferable. If the average particle size exceeds 10.0 ⁇ m, the particles may get caught in the narrow part between the mounting substrate and the chip in a semiconductor package that has been made smaller and thinner, and the fluidity of the encapsulant may be deteriorated, resulting in a decrease in moldability.
• one embodiment of the present invention is spherical alumina particles that exhibit sufficient fluidity even in the range of a small average particle size of 0.5 to 2.0 ⁇ m.
• the average particle size refers to the average particle size (D50), and means 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 is a method in which a dispersion liquid in which spherical alumina particles are dispersed is irradiated with laser light, and the particle size distribution is determined from the intensity distribution pattern of the diffracted/scattered light emitted from the dispersion liquid.
• a laser diffraction/scattering particle size distribution measurement device "Mastersizer 3000" manufactured by Malvern
• the average particle size of the raw material for spherical alumina particles can also be determined in a similar manner.
• the spherical alumina particles according to this embodiment may be mixed with resin and used as a semiconductor encapsulant.
• the semiconductor element to be encapsulated may have many wires wired at high density, and the spacing between the wires may be narrow. If the spherical alumina particles have a particle size distribution in which the particles of 20.0 ⁇ m or more exceed 0.04% by weight, they may not be able to get into the narrow spacing between the wires.
• the weight percentage here is based on the entire spherical alumina particles, i.e., 100% by weight.
• spherical alumina particles are generally mixed with resin and used in heat dissipation components such as heat dissipation sheets and heat dissipation adhesives. These heat dissipation components are sometimes used to facilitate the transfer of heat to another component by being compressed under pressure or the like. If the spherical alumina particles have a particle size distribution in which particles of 20.0 ⁇ m or more account for more than 0.04% by weight, there is a risk that compression will be hindered by the coarse particles of 20.0 ⁇ m or more.
• the spherical alumina particles contain 0.04% by weight or less of particles of 20.0 ⁇ m or more so that they can fit into the narrow gaps between wiring or so that the heat dissipation member can be sufficiently compressed.
• the maximum value of the particle size distribution may be adjusted appropriately depending on the usage environment, such as the wiring spacing and the compression thickness.
• the maximum value of the particle size distribution may be 19.0 ⁇ m or 18.0 ⁇ m.
• particles of 19.0 ⁇ m or more may contain 0.04% by weight or less
• particles of 18.0 ⁇ m or more may contain 0.04% by weight or less.
• the wet particle size test method involves adding 10 g of the spherical alumina particles to be tested and water to a container, and using ultrasound to thoroughly disperse the spherical particles to create a slurry. The slurry is then transferred onto the mesh of a test sieve and sieved. The particles remaining on the mesh of the test sieve are placed in an appropriate container, and the sample is evaporated to dryness using a hot plate or similar device. The weight of the residue is then measured, and the percentage of the weight of the sieved particles in the 10 g of spherical alumina particles to be tested is calculated.
• the spherical alumina particles have a specific surface area, as measured by the BET method, of 0.35 m 2 /g or more and 3.50 m 2 /g or less.
• the specific surface area of the spherical particles is less than 0.35 m 2 /g, the particles are unlikely to form a close-packed structure, and the fluidity of the plugging material containing the particles may decrease.
• the specific surface area of the spherical particles is more than 3.50 m 2 /g, the tendency of the particles to aggregate increases, and the fluidity of the plugging material may also decrease.
• the preferred upper limit is 0.90 m 2 /g.
• the specific surface area is measured by the BET method. Typically, the specific surface area is measured by the following procedure. Approximately 5 g of a sample is weighed out and vacuum dried for 5 minutes at 250° C. Next, the sample is set in an automatic specific surface area measuring device (Macsorb, manufactured by Mountec Co., Ltd.), and the nitrogen gas adsorption amount is measured at a relative pressure P/P0 of 0.291 at a measurement temperature of 77 K using pure nitrogen and a nitrogen-helium mixed gas (mixture ratio: nitrogen 30%, He 70%), and the BET specific surface area is calculated by the one-point method.
• Macsorb manufactured by Mountec Co., Ltd.
• the spherical alumina particles according to one embodiment of the present invention have a tap bulk density of 1.30 g/cm 3 or more and 2.50 g/cm 3 or less.
• the fluidity of the resin composition when the spherical alumina particles are mixed with a resin is in a suitable range.
• the thermal conductivity of the resin composition is also in a suitable range.
• the preferred lower limit is 1.80 m 2 /g.
• the "tap bulk density” is the bulk density when the sample volume stops changing after the sample is dispersed and placed in a container and an impact is applied to the container by tapping, and is measured based on the Japanese Industrial Standard JIS R1628:1997. More specifically, it is measured using a Hosokawa Micron Powder Tester PT-X.
• a stainless steel 50 ml container with a known mass is used as the measurement container.
• the measurement container is filled with powder sample until it overflows.
• the powder that has risen above the top surface of the measurement container is leveled off using a leveling plate.
• the combined mass of the container and the filled powder is measured, and the mass of the filled powder is calculated by subtracting the mass of the container from the measured mass.
• an adapter is attached to the top of the measurement container, and the sample is poured in until it overflows to the top of the adapter.
• the measurement container with the adapter attached is hung on a tapping device and tapped 180 times to compress the powder.
• the adapter is removed, and the powder that has risen above the top surface of the measurement container is leveled off using a leveling plate.
• the combined mass of the container and the filled powder is measured, and the mass of the container is subtracted from the measured mass to determine the mass of the filled powder.
• the sample mass is divided by the volume of the container to obtain the tapped bulk density.
• the sample mass is also divided by the volume of the measurement container (i.e. the volume of the sample before tapping) to obtain the initial bulk density (loose bulk density).
• tapped bulk density (tapped bulk density) is also called “tapped bulk specific gravity (tapped bulk density).”
• Initial bulk density (loose bulk density) is also called “initial bulk specific gravity (loose bulk density).”
• the spherical alumina particles have a circularity of 0.90 or more.
• 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.
• the upper limit of the circularity is theoretically 1.0, but may be 0.98 or less, or 0.97 or less from the viewpoint of manufacturing management.
• Circularity can be measured using an electron microscope or optical microscope and an image analyzer.
• Sysmex FPIA These devices are used to measure the circularity of particles (perimeter of equivalent circle/perimeter of projected image of particle). The circularity of 100 or more particles is measured, and the average value is taken as the circularity of the powder.
• the spherical alumina particles may have a gelatinization rate of 55.0% or less.
• the alpha-alumina ratio refers to the ratio of alpha-alumina crystals in the crystalline phase.
• the spherical alumina particles which are one embodiment of the present invention, have an alpha-alumina ratio of 55.0% or less. It is known that alumina becomes crystalline, and alpha-alumina, ⁇ -alumina, and ⁇ -alumina are known as typical crystalline forms.
• the spherical alumina particles which are one embodiment of the present invention, can be manufactured based on a thermal spraying method in which a raw material is put into a flame, melted, and then cooled, as will be described in detail later.
• the cooling rate typically by performing the cooling by rapid cooling, the obtained alumina can have a high amorphous ratio, and spherical alumina particles with an alpha-alumina ratio of 55.0% or less can be easily obtained.
• the alumina particle surface becomes smooth, and the effect of maintaining high fluidity when mixed with a resin and the amount of hard alpha-alumina particles are small, so that the equipment wear resistance is low.
• the alpha-conversion rate may be appropriately adjusted so as to obtain the desired fluidity and thermal conductivity. Therefore, the lower limit of the alpha-conversion rate is not particularly limited and may be 0.0%, but from the viewpoint of the burden of manufacturing management and the viewpoint of the thermal conductivity characteristics as a resin composite composition, it may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 10.0%.
• the upper limit of the alpha-conversion rate may be 50.0%, 45.0%, or 40.0%.
• the alpha-conversion rate of the alumina particle powder is measured using a powder X-ray diffractometer.
• the integrated area of the obtained diffraction peaks is calculated, and the ratio of the diffraction peak area derived from alpha-alumina to the total is analyzed using the Rietveld method.
• an X-ray diffraction pattern is obtained using a Bruker D2PHASER in the 2 ⁇ range of 10° to 90°.
• the alpha-conversion rate is calculated from the obtained pattern using a Bruker DIFFRAC. TOPAS by the Rietveld method.
• the analysis is performed assuming that only three types of crystal phases, alpha-alumina, delta-alumina, and theta-alumina, are present, and the alpha-alumina content is calculated.
• the frequency of particles 10 ⁇ m or larger is 20 ppm or less.
• the spherical alumina particles may have a particle number frequency of 20 ppm or less of particles having a size of 10 ⁇ m or more among particles having a size of 1 ⁇ m or more and 30 ⁇ m or less detected by a Coulter counter.
• the Coulter Counter measures particles using an electrical resistance method known as the Coulter Principle, which allows for high measurement accuracy without the errors in particle surface morphology, internal structure, refractive index, color, etc. that occur with optical measurement methods.
• the particle size obtained by this method can be expressed as a number distribution (particles/ml and particles/g), making it possible to precisely manage the particle size distribution.
• the spherical alumina particles as the sample and 150 mL of electrolyte were placed in a 200 mL glass beaker and dispersed for 30 seconds using an ultrasonic homogenizer (ULTRA SONIC HOMOGENIZER UH-300, manufactured by SMT). This dispersion was then added to electrolyte prepared in another beaker to adjust the concentration.
• the particle size of each of the spherical alumina particles in the dispersion with the adjusted concentration was measured using a Coulter counter (Multisizer 3, manufactured by Beckman Coulter) with an aperture diameter of 50 ⁇ m. At this time, the number of particles measured per measurement was set to approximately 100,000, and the same sample was measured three times. The number of particles with a particle size of 10 ⁇ m or more was calculated and used as the coarse particle frequency (ppm) relative to the total number measured.
• ppm coarse particle frequency
• the frequency of particles of 10 ⁇ m or more out of the total number of spherical alumina particles of 1 ⁇ m or more and 30 ⁇ m or less measured by this Coulter counter may be 20 ppm or less.
• 20 ppm or less means, for example, that out of 100,000 particles of 1 ⁇ m or more and 30 ⁇ m or less, there are 2 or less particles of 10 ⁇ m or more. If the frequency of coarse particles of 10 ⁇ m or more exceeds 20 ppm, such coarse particles may clog the narrow spaces between the mounting board and the chip, reducing fluidity and, as a result, increasing the defect rate of semiconductor products filled with the particles.
• the number frequency of coarse particles of 10 ⁇ m or more the higher the number frequency of coarse particles of 10 ⁇ m or more, the better the fluidity, and therefore the more preferable it is.
• the number frequency may be 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, or 10 ppm or less.
• the number frequency of coarse particles of 10 ⁇ m or more may be 0 ppm, but completely eliminating the coarse particles, i.e., reducing them to 0 ppm, may be difficult due to the large burden on manufacturing management, so it may be several ppm, specifically 1 ppm or more, 2 ppm or more, 3 ppm or more, 4 ppm or more, or 5 ppm or more.
• the lower limit of the number frequency may be adjusted depending on the actual application and the acceptable range of the target yield.
• Classification may be performed to obtain the desired particle size distribution.
• Conventional methods may be used for classification, such as a method of cutting off the coarse and fine powder sides using a sieve with a specified mesh size and/or a precision air classifier.
• classification control the number frequency may be measured using a Coulter counter, and precise control of the particle size distribution can contribute to the excellent properties of the spherical alumina particles, such as fluidity.
• the spherical alumina particles may have a moisture content of 20 ppm or less as determined by Karl Fischer coulometric measurement (hereinafter also simply referred to as "moisture content").
• Karl Fischer coulometry is a well-known method for quantifying water using the Karl Fischer reaction (one mole of iodine reacts with water).
• iodine is generated by electrolyzing iodine ions in the electrolytic cell anolyte. Iodine is generated in proportion to the amount of electricity, and since iodine and water react in a 1:1 ratio, the amount of water can be calculated from the amount of electricity required for titration.
• the amount of moisture generated by spherical alumina particles is measured at 500°C to 900°C using a Karl Fischer moisture meter for coulometric measurement.
• the moisture content is preferably 20 ppm or less, more preferably 15 ppm or less, even more preferably 10 ppm or less, and even more preferably less than 10 ppm.
• a resin composite composition containing spherical alumina particles is provided. Furthermore, a resin composite can be produced by curing the resin composite composition. The composition of the resin composite composition will be described in more detail below.
• resin composite compositions such as semiconductor encapsulants, interlayer insulating films, etc. (including heat dissipation sheets and heat dissipation adhesives). Furthermore, by curing these resin composite compositions, it is possible to obtain resin composites such as encapsulants (cured bodies) and substrates for semiconductor packages.
• the resin composite composition for example, in addition to the spherical alumina particles and resin, a curing agent, a curing accelerator, a flame retardant, a silane coupling agent, etc. are mixed as necessary, and the mixture is compounded by a known method such as kneading. The mixture is then molded into pellets, films, etc., depending on the application.
• inorganic fillers When producing the resin composite composition, other inorganic fillers may be blended in addition to the spherical alumina particles and resin, which are an embodiment of the present invention.
• the inorganic fillers include amorphous spherical alumina particles, crystalline spherical silica particles, alumina particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers.
• the resin composite composition when the resin composite composition is cured to produce a resin composite, for example, the resin composite composition can be melted by applying heat, processed into a shape according to the intended use, and then completely cured by applying heat higher than that applied when melted.
• known methods such as the transfer molding method and compression molding method can be used.
• epoxy resin is not particularly limited, but for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, naphthalene type epoxy resin, phenoxy type epoxy resin, etc. can be used.
• bisphenol A type epoxy resin bisphenol F type epoxy resin
• biphenyl type epoxy resin phenol novolac type epoxy resin
• cresol novolac type epoxy resin cresol novolac type epoxy resin
• naphthalene type epoxy resin phenoxy type epoxy resin, etc.
• epoxy resins having two or more epoxy groups in one molecule are preferred from the viewpoints of curability, heat resistance, etc.
• 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 and dimer acid with epochlorohydrin, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified polyfunctional epoxy resins, ⁇ -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.
• these epoxy resins having two or more epoxy groups in one molecule
• resins other than epoxy resins can be used in applications other than composite materials for semiconductor encapsulation, such as prepregs for printed circuit boards and various engineering plastics, as resin composite compositions.
• resins that can be used other than epoxy resins include silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimide, polyamideimide, and polyetherimide; 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.
• the curing agent used in the resin composite composition may be any known curing agent for curing the resin, for example, a phenol-based curing agent.
• a phenol-based curing agent phenol novolac resin, alkylphenol novolac resin, polyvinylphenols, etc.
• phenol novolac resin phenol novolac resin, alkylphenol novolac resin, polyvinylphenols, etc.
• phenol novolac resin alkylphenol novolac resin
• polyvinylphenols, etc. may be used alone or in combination of two or more kinds.
• the amount of the phenolic hardener to be 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. This eliminates the residue of unreacted phenolic hardener and improves moisture absorption and heat resistance.
• the amount of the spherical alumina particles of the present invention added to the resin composite composition is preferably large from the viewpoint of heat resistance and thermal expansion coefficient, but is usually appropriate to be 70% by mass or more and 95% by mass or less, preferably 80% by mass or more and 95% by mass or less, and more preferably 85% by mass or more and 95% by mass or less.
• additives such as silane coupling agents, hardeners, colorants, hardening retarders, and other known additives can be used.
• any known coupling agent may be used, but it is preferable to use one that has an epoxy-based functional group.
• a slurry composition containing spherical alumina particles and resin can be used to produce heat dissipation sheets, heat dissipation adhesives (sometimes called heat dissipation greases), etc.
• the spherical alumina particles, resin, and additives are appropriately mixed and compounded using a known method such as kneading.
• the resulting composite is molded into a sheet using a known method.
• known resins can be used as the resin for the resin composite composition, and specific examples include silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, 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.
• silicone resin there are no particular limitations on the silicone resin, but for example, peroxide curing type, addition curing type, condensation curing type, ultraviolet curing type, etc. can be used.
• additives such as silane coupling agents, hardeners, colorants, hardening retarders, and other known additives can be used.
• the spherical alumina particles, resin, and additives are appropriately mixed and compounded by a known method such as kneading.
• the resin used in the heat-dissipating adhesive or heat-dissipating grease is also called the base oil.
• the resin used in the resin composite composition can be any known resin, including silicone resin, phenol 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.
• silicone resin phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin
• polyamides such as polyimide, polyamideimide, and polyetherimide
• additives such as silane coupling agents, colorants, thickeners, and other known additives can be used.
• the thickeners that can be used include known ones such as calcium soap, lithium soap, aluminum soap, calcium complex, aluminum complex, lithium complex, barium complex, bentonite, urea, PTFE, sodium terephthalamate, silica gel, and organic bentonite.
• a method for producing spherical alumina particles which is a method for suitably producing the above-mentioned alumina particles and includes the following steps: (1) a step of introducing at least one of alumina, boehmite, and aluminum hydroxide into a flame to melt the melted material, and then cooling the melted material to form spheroids; and (2) a step of classifying the melted material using a precision air classifier and/or a sieve after the spheroidizing step.
• the spheroidizing process (1) is a process in which the raw materials are fed into a flame, melted, and then cooled to spheroidize. These raw materials can be fed into the flame while suspended in a carrier gas. Air, oxygen, propane gas, etc. can be used as the carrier gas.
• the method of forming the flame is not particularly limited, but the flame can be formed by supplying a fuel (such as propane) that forms a flame to the burner via a route separate from the feed of the raw materials, or by pre-mixing fuel and a combustion support gas (air or oxygen) and supplying it to the burner to form the flame, or by mixing the raw materials, fuel, and a combustion support gas and supplying it to the burner to form the flame.
• a fuel such as propane
• a combustion support gas air or oxygen
• the flame in a heat-resistant furnace. It is preferable to form a flame at the top of the heat-resistant furnace, feed the raw materials into the flame, and collect the alumina particle material formed as it settles due to gravity from below. By preventing the formation of a flame at the bottom of the heat-resistant furnace, the alumina particle material that settles to the bottom is cooled and granulated. If sufficient heat can be applied to the raw material particles during spheroidization to melt them, the amount of irregularly shaped particles that do not become spheroidized can be reduced, and the bulk density can be increased. At this time, the circularity and bulk density can be adjusted by adjusting the amount of material fed into the flame per unit time and the type of fuel gas. In addition, the particle size of the particles after spheroidization can be adjusted by adjusting the particle size of the raw material powder used.
• the raw material for the spherical alumina particles is at least one of alumina, boehmite, and aluminum hydroxide.
• the alumina remains as alumina, and the boehmite or aluminum hydroxide undergoes an oxidation or dehydration reaction to form alumina.
• the ⁇ -alumina content can be increased by maintaining a high temperature in the melting furnace. From the viewpoint of promoting the crystal growth of ⁇ -alumina, the temperature in the melting furnace is preferably 1200°C or higher. The content can be reduced by rapidly cooling the spherical particles immediately after solidification with a refrigerant such as air or water.
• refrigerant there are no particular limitations on the refrigerant, but from the viewpoint of not reducing the purity of the spherical particles, distilled water or ion-exchanged water that does not contain air or impurities such as sodium ions or chlorine ions is preferable.
• the spherical alumina particles obtained in the spheroidization step are passed through a sieve with a specified mesh size and/or a precision air classifier to suitably produce the above-mentioned alumina particles. If necessary, pre- or post-treatment may be added to separate the particles into coarse and fine particles using a cyclone or the like. This step makes it possible to obtain the desired particle size, particle size distribution, specific surface area, and bulk density.
• thermal conductivity or fluidity of spherical alumina particles It is difficult to measure the thermal conductivity and fluidity (viscosity) of the spherical alumina particles themselves. Therefore, for the thermal conductivity, the thermal conductivity of the resin composition obtained by mixing the spherical alumina particles with a resin is measured under a specified condition, and the thermal conductivity of the spherical alumina particles is evaluated based on the measurement results.
• the fluidity (viscosity) of the resin composition obtained by mixing the spherical alumina particles with a resin is measured under a specified condition, and the fluidity (viscosity) of the spherical alumina particles is evaluated based on the measurement results.
• the thermal conductivity is measured by the following procedure. 88 parts by mass of spherical alumina particles, 6 parts by mass of silicone resin A (CY-52-276A manufactured by Toray Dow Corning Co., Ltd.), and 6 parts by mass of silicone resin B (CY-52-276B manufactured by Toray Dow Corning Co., Ltd.) are mixed by a vacuum kneader, and the resulting resin composition is poured into a mold and molded under heat and pressure to an arbitrary thickness.
• the molding conditions are a pressure of 6 MPa and a temperature of 120°C, and heating is performed for 1 hour. After heating, the molded sheet is removed from the mold and post-heated in a dryer at 140°C.
• the post-heated sheet is cooled.
• the prepared sheet is cut into 20 mm squares, and the thermal conductivity is measured using the ASTM-D5470 method under a pressure of 1.25 kgf/ cm2 .
• the lower limit of the thermal conductivity may be 1.40 W/m K, preferably 1.60 W/m K.
• the upper limit of the thermal conductivity may be 2.50, preferably 2.00 W/m K.
• the lower limit of the thermal conductivity may be 1.70 W/m ⁇ K, while the upper limit of the thermal conductivity may be 2.50 W/m ⁇ K.
• the flow rate is measured by the following procedure. 80 parts by mass of spherical alumina particles and 20 parts by mass of epoxy resin (Epicoat 801N) are mixed by a kneader, and the resulting resin composition is cooled in a water bath for 60 minutes, and then measured by a Shimadzu flow tester CFT-500D. The temperature of about 10 ml of the kneaded sample is set to 28.5°C, and it is extruded from a die with a diameter of 2.0 mm and a length of 75.0 mm.
• Epoat 801N epoxy resin
• the extrusion load is 50.0 kgf, and the discharge speed (ml/sec) is measured from the time when about 50% of the sample is extruded to the time when 75% is extruded.
• the lower limit of the flow rate may be 0.2 ml/sec, preferably 0.28 ml/sec.
• the upper limit may be 1.0 ml/s. If the flow rate is too low, it will cause poor sealing when used as a sealing material. Also, when used as a liquid heat dissipation material such as adhesive or grease, it will cause workability to deteriorate due to insufficient fluidity.
• Examples 1 to 12 Alumina particle raw material was fed into a high-temperature flame formed by LPG and oxygen, and spheroidization treatment was carried out. Spherical alumina particles were produced by controlling the particle size of the alumina particle raw material fed. Alumina particles having the physical property values shown in Table 1 were produced by adjusting the flame formation conditions, raw material particle size, raw material supply amount, classification conditions, etc.
• the particle size distribution was adjusted by adjusting the raw material particle size and subjecting the powder after the spheroidization treatment to a multi-stage sieving operation and classification operation, and as the final step, classification was carried out using a sieve with a 20 ⁇ m mesh setting in Examples 1, 2, 4, 5, 6, and 7, and a precision classifier was used for classification in the other cases.
• Table 1 shows the physical properties of the spherical alumina particles used. Note that in all of Examples 1 to 12, the moisture content measured by Karl Fischer coulometric measurement was less than 10 ppm. In addition, in all of Examples 1 to 12, the thermal conductivity at a filler loading of 88 wt% was 1.7 to 2.0 W/m ⁇ K.
• Average particle size D50 The average particle size (D50) is measured using a laser diffraction/scattering particle size distribution measuring device "Mastersizer 3000" (manufactured by Malvern).
• the specific surface area is measured by the BET method. Specifically, the specific surface area is measured by the following procedure. Approximately 5 g of a sample is weighed out and vacuum dried for 5 minutes at 250° C. Next, the sample is set in an automatic specific surface area measuring device (Macsorb, manufactured by Mountec Co., Ltd.), and the nitrogen gas adsorption amount is measured at a relative pressure P/P0 of 0.291 at a measurement temperature of 77 K using pure nitrogen and a nitrogen-helium mixed gas (mixture ratio: nitrogen 30%, He 70%), and the BET specific surface area is calculated by the one-point method.
• Macsorb manufactured by Mountec Co., Ltd.
• the measurement is performed using a Hosokawa Micron Powder Tester PT-X.
• a stainless steel 50 ml container with a known mass is used as the measurement container.
• the measurement container is filled with powder sample until it overflows.
• the powder that has risen above the top surface of the measurement container is leveled off using a leveling plate.
• the combined mass of the container and the filled powder is measured, and the mass of the filled powder is calculated by subtracting the mass of the container from the measured mass.
• an adapter is attached to the top of the measurement container, and the sample is poured in until it overflows to the top of the adapter.
• the measurement container with the adapter attached is placed on a tapping device and tapped 180 times to compress the powder.
• the adapter After compression, the adapter is removed, and the powder that has risen above the top surface of the measurement container is leveled off using a leveling plate.
• the combined mass of the container and the filled powder is measured, and the mass of the filled powder is calculated by subtracting the mass of the container from the measured mass.
• the sample mass is divided by the volume of the container to obtain the tapped bulk density (packed bulk density).
• the mass of the sample is divided by the volume of the measurement container (i.e., the volume of the sample before tapping) to obtain the initial bulk density (loose bulk density).
• the circularity is measured using an electron microscope, an optical microscope, and an image analyzer. In this embodiment and the comparative example, a Sysmex FPIA was used. These devices are used to measure the circularity of the particles (perimeter of the equivalent circle/perimeter of the projected image of the particle). The circularity of 100 or more particles is measured, and the average value is taken as the circularity of the powder.
• the alpha-conversion rate is measured using a powder X-ray diffractometer.
• the integrated area of the obtained diffraction peaks is calculated, and the ratio of the diffraction peak area derived from alpha alumina to the total area is analyzed by the Rietveld method.
• an X-ray diffraction pattern is obtained using a D2PHASER manufactured by Bruker Corporation in the range of 2 ⁇ from 10° to 90°.
• the alpha-conversion rate is calculated by the Rietveld method using the obtained pattern with a DIFFRAC.TOPAS manufactured by Bruker Corporation. During the calculation, analysis is performed assuming that only three types of crystal phases, alpha alumina, delta alumina, and ⁇ alumina, are present, and the content of alpha alumina is calculated.
• a 200 mL glass beaker is filled with spherical alumina particles as a sample and 150 mL of electrolyte, and dispersed for 30 seconds using an ultrasonic homogenizer (Ultra Sonic Homogenizer UH-300, manufactured by SMT). This dispersion is then added to electrolyte prepared in another beaker to adjust the concentration. The concentration-adjusted dispersion is measured using a Coulter counter (Multisizer 3, manufactured by Beckman Coulter) with an aperture diameter of 50 ⁇ m to measure the particle size of each of the spherical alumina particles.
• the number of particles measured per measurement is set to about 100,000, and the same sample is repeatedly measured three times.
• the number of particles with a particle size of 10 ⁇ m or more is calculated and used as the coarse particle frequency (ppm) relative to the total number of particles measured.
• the flow rate is measured by the following procedure. 80 parts by mass of spherical alumina particles and 20 parts by mass of epoxy resin (Epicoat 801N) are mixed by a kneader, and the resulting resin composition is cooled in a water bath for 60 minutes, and then measured by a Shimadzu flow tester CFT-500D. The temperature of about 10 ml of the kneaded sample is set to 28.5°C, and it is extruded from a die with a diameter of 2.0 mm and a length of 75.0 mm. The extrusion load is 50.0 kgf, and the discharge speed (ml/sec) is measured from the time when about 50% of the sample is extruded to the time when 75% is extruded.
• the temperature of about 10 ml of the kneaded sample is set to 28.5°C, and it is extruded from a die with a diameter of 2.0 mm and a length of 75.0 mm.
• the extrusion load is 5
• the thermal conductivity is measured by the following procedure. 88 parts by mass of spherical alumina particles, 6 parts by mass of silicone resin A (CY-52-276A manufactured by Toray Dow Corning Co., Ltd.), and 6 parts by mass of silicone resin B (CY-52-276B manufactured by Toray Dow Corning Co., Ltd.) are mixed by a vacuum kneader, and the resulting resin composition is poured into a mold and heated and pressurized to a desired thickness.
• the molding conditions are a pressure of 6 MPa and a temperature of 120°C, and heating is performed for 1 hour. After heating, the molded sheet is removed from the mold and post-heated in a dryer at 140°C. The post-heated sheet is cooled.
• the prepared sheet is cut into 20 mm squares, and the thermal conductivity is measured using the ASTM-D5470 method under a pressure of 1.25 kgf/ cm2 .
• the moisture content is measured by Karl Fischer coulometric measurement in the following procedure: 0.5 to 1.0 g of spherical alumina particles are placed in a Karl Fischer moisture meter for coulometric measurement (manufactured by Nitto Seiko Analytech Co., Ltd., CA-200 (measuring device), VA-122 (vaporizer)), the temperature is raised from 25°C to 500°C, and the temperature is maintained at 500°C until it is confirmed that no moisture generation is observed. The temperature is then raised further, and the amount of moisture generated is measured at 500°C to 900°C.
• spherical alumina particles within the scope of the present invention provide good fluidity and thermal conductivity.
• the spherical alumina particles of the present invention and the resin composite composition containing the same exhibit good fluidity and thermal conductivity, and can be used for other purposes as well, not limited to semiconductor encapsulation materials. Specifically, they can also be used as heat dissipation sheets, heat dissipation adhesives, etc. Furthermore, the spherical alumina particles can be obtained by the method for producing spherical alumina particles according to the present invention.

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