Spherical alumina particles, a method for producing the same, and a resin composite composition containing the same

Abstract

The purpose is to provide spherical alumina particles having low surface residual Na level and low agglomeration degree, a production method of the same and a resin composite composition comprising the same.　Spherical alumina particles have an average diameter of 0.4-1.9 um, a specific surface area of 1.0-5.0 m2 / g, a surface residual Na of 200 ppm or less, a Na2O content of 1,000 ppm or less, an agglomeration degree of 1.0% or less and a degree of circularity of 0.9 or more. A production method of the same and a resin composite composition comprising the same are also provided.

Description

Technical Field

[0001] The present invention relates to spherical alumina particles, particularly spherical alumina particles with a reduced surface residual Na concentration and a low degree of aggregation, a method for producing the same, and a resin composite composition containing the same.

Background Art

[0002] In recent years, due to the high functionality and high speed of electronic devices such as mobile phones, the amount of heat generated from electronic components inside the electronic devices has been increasing. For the normal operation of electronic devices, efficiently dissipating the generated heat to the outside has become an important issue. Commonly used for heat dissipation are those called heat dissipation sheets and heat dissipation adhesives. These are pasted or applied between the heat generating body and the heat dissipation fins and crimped to eliminate the gap between the heat generating body and the heat dissipation fins, enabling efficient heat dissipation. Also, inside electronic components, the semiconductor itself also generates significant heat due to the same high functionality and high speed, and there is a demand for imparting heat dissipation properties to the encapsulant that protects the semiconductor.

[0003] Generally, heat dissipation sheets, heat dissipation adhesives, and semiconductor encapsulants are composed of a thermally conductive inorganic filler and a resin. As the thermally conductive inorganic filler, inexpensive aluminum hydroxide, aluminum oxide (hereinafter, alumina), and further materials such as silicon carbide, boron nitride, and aluminum nitride, which are expected to have high thermal conductivity, are used. In particular, alumina is often used as a thermally conductive inorganic filler because it is inexpensive and chemically stable.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The Bayer process is a widely known method for producing alumina. In the Bayer process, bauxite is treated with caustic soda (sodium hydroxide) to dissolve aluminum as sodium aluminate, while impurities such as iron, titanium, and silicon precipitate as red mud. This is filtered off, and hydrated alumina (Al2O3·3H2O) seeds are added to the filtrate (sodium aluminate solution). By stirring for several days, the hydrated alumina precipitates in the solution and is recovered. High-purity alumina (Al2O3) can be obtained by calcining the recovered hydrated alumina.

[0006] In the Bayer process, sodium hydroxide (caustic soda) is used for treatment, so sodium may remain in the alumina product. If a large amount of sodium is present on the filler surface, it reacts with moisture in the resin and air, releasing hydroxide ions. These hydroxide ions react with epoxy groups in the epoxy resin, inhibiting the polymerization reaction between the resins and causing curing failure. Furthermore, if sodium or potassium ions are present in the resin composition created by kneading with epoxy groups, the dielectric strength is impaired. For these reasons, it is desirable to have a small amount of sodium. To remove or reduce this sodium, the alumina is washed with water and then dried.

[0007] Patent Document 1 discloses an apparatus capable of efficiently washing, filtering, and drying a powder such as alumina within the same container. More specifically, it describes a method for washing, filtering, and drying a powder within the same container without the need for stirring blades by introducing compressed gas into the container. It also discloses methods for improving the drying speed, such as using electric or steam heating or microwave irradiation.

[0008] Thus, when drying alumina slurry after washing, heating is often used. However, prolonged heating during the heat drying process can cause sodium ions remaining inside the alumina to move to the outside and potentially leach onto the alumina surface, which has been cleaned by washing. Furthermore, the smaller the particle size of the alumina particles contained in the slurry, the more the particles will aggregate during heat drying, resulting in a hard, aggregated mass of dried material. This aggregated mass necessitates crushing for powdering. Crushing carries the risk of contamination of the final alumina powder product with foreign matter from the crushing machine.

[0009] Furthermore, Patent Document 2 discloses a fine spherical aluminum oxide powder using fine low-soda aluminum oxide as a raw material, with a maximum particle size of 7 μm or less and an average particle size in the range of 0.2 to 0.9 μm. This document discloses that a spherical inorganic oxide powder free of coarse particles and with an average particle size of less than 1 μm can be stably obtained by performing a strong crushing treatment before introducing the raw material powder into the flame, and then continuously introducing it into the flame immediately after the aggregated particles have been sufficiently crushed and dispersed. However, similar to Patent Document 1, there is a risk that foreign matter from the crushing machine may be mixed into the alumina powder product during the crushing process. The concentration of the sodium component in this powder is not disclosed.

[0010] The present invention has been made in view of the above circumstances, and its object is to provide spherical alumina particles with a low surface residual Na concentration and low degree of aggregation, a method for producing the same, and a resin composite composition containing the same. [Means for solving the problem]

[0011] The inventors have discovered that by drying an alumina slurry that has been washed with water using a predetermined method, it is possible to directly dry and powderize the slurry without crushing it.

[0012] Based on the above findings, the gist of the present invention is as follows. [1] Average particle size of 0.4–1.9 μm, specific surface area of ​​1.0–5.0 m² 2Spherical alumina particles with a surface residual Na content of 20 ppm or less, a Na2O content of 1000 ppm or less, a degree of aggregation of 1.0% or less, and a circularity of 0.9 or more per gram. [2] Spherical alumina particles according to [1], characterized in that the alpha-adsorption rate is 10.0% or less.

[0013] [3] A water slurry preparation step of mixing the raw material spherical alumina with water to prepare a water slurry containing the raw material spherical alumina, A drying step for drying the aforementioned aqueous slurry, A method for producing spherical alumina particles having the following characteristics. [4] A raw material spherical alumina washing step, in which the raw material spherical alumina is washed with water before the water slurry preparation step, A method for producing spherical alumina particles according to [3], comprising the above.

[0014] A resin composite composition characterized by containing spherical alumina particles as described in [5] [1] or [2]. [6] The resin composite composition according to [5], further comprising at least one inorganic filler selected from amorphous spherical silica particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fiber. [Effects of the Invention]

[0015] The present invention provides spherical alumina particles with a low surface residual Na concentration and low cohesion, and a resin composite composition containing them. Because the spherical alumina particles have a low surface residual Na concentration, when used as a filler, curing defects and loss of dielectric strength can be avoided. Furthermore, because of their low cohesion, crushing is unnecessary, and contamination by foreign matter due to crushing can be avoided. Moreover, the spherical alumina particles can be easily manufactured by a manufacturing method according to one aspect of the present invention. [Brief explanation of the drawing]

[0016] [Figure 1]FIG. 1 is a diagram schematically showing the state of alumina particles in the case of conventional heat drying and in the case of freeze drying of the present embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0017] [Spherical alumina particles]

[0018] (Average particle size) Spherical alumina particles, which are one embodiment of the present invention, have an average particle size of 0.4 to 1.9 μm. If the average particle size is less than 0.4 μm, the aggregability of the particles increases, and when used as a filler, the fluidity of the resin composition significantly decreases, which is not preferable. If the average particle size exceeds 1.9 μm, in a semiconductor package or the like that has advanced miniaturization and thinning, particles may get caught in the narrow part between the mounting substrate and the chip, and the fluidity of the liquid encapsulant may deteriorate and the moldability may decrease.

[0019] Here, the average particle size refers to the average particle diameter (D50), and in the volume-based particle size distribution measured by the laser diffraction / scattering type particle size distribution measurement method, it means the median diameter D50 with a cumulative volume of 50%. The laser diffraction / scattering type particle size distribution measurement method is a method of irradiating a dispersion liquid in which spherical alumina particles are dispersed with laser light and obtaining the particle size distribution from the intensity distribution pattern of the diffraction / scattering light emitted from the dispersion liquid. In the present invention, a laser diffraction / scattering type particle size distribution measuring device "Mastersizer3000" (manufactured by Malvern) is used. Incidentally, the average particle diameter of the raw material of the spherical alumina particles can also be obtained in the same manner.

[0020] (Specific surface area) In one embodiment of the present invention, the spherical alumina particles have a specific surface area measured by the BET method of 1.0 m 2 / g or more and 5.0 m 2 / g or less.

[0021] The specific surface area of the spherical particles is 1.0 m 2If the particle density is less than 5.0 m² / g, the particles may have difficulty forming a densely packed structure, which can reduce the fluidity of the liquid sealant containing those particles. On the other hand, if the specific surface area of ​​the spherical particles is 5.0 m², 2 If the concentration exceeds [amount] / g, the tendency for particles to aggregate increases, which can similarly reduce the fluidity of the liquid sealant.

[0022] The specific surface area is measured using the BET method. Typically, the specific surface area is measured using the following procedure. Approximately 5g of the sample was weighed and vacuum-dried at 250°C for 5 minutes. Then, the sample was placed in an automatic specific surface area analyzer (Macsorb, manufactured by Mountec), and the amount of nitrogen gas adsorbed was measured at a measurement temperature of 77K using pure nitrogen and a nitrogen-helium mixed gas (mixing ratio 30% nitrogen, 70% helium) with a relative pressure P / P0 of 0.291. The BET specific surface area was then calculated using the single-point method.

[0023] (Surface residual Na) In one embodiment of the present invention, the spherical alumina particles have a surface residual Na content of 20 ppm or less. Surface residual Na, as used here, refers to the Na adhering to and remaining on the alumina surface, and was measured by ion chromatography. When a large amount of sodium is present on the filler surface, i.e., the alumina surface, it reacts with moisture in the resin and air, releasing hydroxide ions. These hydroxide ions react with the epoxy groups present in the epoxy resin, inhibiting the polymerization reaction between the resins and causing curing failure. Furthermore, the presence of sodium or potassium ions in the resin composition created by kneading with epoxy groups impairs the dielectric strength. If the sodium content is 20 ppm or less, curing failure and loss of dielectric strength can be avoided. From the above viewpoint, a lower sodium content is preferable, but since complete removal is costly, it is set at 0.1 ppm or higher. The sodium remaining on the surface is measured by ion chromatography. Typically, the measurement is performed using the following procedure. Add 4g of the sample and 40ml of distilled water to a centrifuge tube, close the lid, and shake well to mix. After mixing, separate the sample from the sample solution using a centrifuge. Take a sample of the sample solution and analyze the sodium ions using an ion chromatograph. The ion chromatograph used was manufactured by Toa Medical Electronics Co., Ltd.

[0024] (Contains Na2O) In one embodiment of the present invention, the spherical alumina particles contain 1000 ppm or less of Na2O. The Na2O content referred to here is the total amount of Na present on the surface and inside the alumina, which has been quantified as the oxide Na2O using an atomic absorption spectrometer. If a large amount of Na2O is present in alumina, sodium will be present not only on the surface but also inside the alumina. When the alumina is heat-treated, the sodium component may be released onto the particle surface, potentially leading to a high level of residual Na on the surface. If the Na2O content is 1000 ppm or less, the sodium content is low, and the release onto the particle surface can be reduced. The lower the Na2O content, the better, but since complete removal is difficult from a manufacturing control standpoint, the lower limit may be set at 50 ppm or higher. The method for measuring the amount of Na2O contained in alumina particles can be performed using elemental analysis methods known to those skilled in the art, for example, by atomic absorption spectrophotometer, and then converted to oxide equivalent.

[0025] (Cohesion degree) In one embodiment of the present invention, the spherical alumina particles have a degree of aggregation of 1.0% or less. The degree of cohesion referred to here is an indicator of whether the particles are cohesive, and it was measured using a sieving method. When an alumina slurry is washed with water and heated and dried, the particles aggregate and form large clumps. This aggregation necessitates crushing to separate the particles. Crushing leads to equipment wear and costs due to contact with the crushing equipment. Furthermore, insufficient dispersion in the resin due to particle aggregation can worsen the fluidity and viscosity of the resin composition. An aggregation degree of 1.0% or less means fewer clumps and eliminates the need for crushing. From the above perspective, a lower aggregation degree is desirable, but since completely preventing aggregation is difficult, the lower limit may be set at 0.0001% or higher. The method for measuring the degree of cohesion is as follows: Standard sieves with two mesh sizes, 4.75 mm and 212 μm, were stacked in sequence. The sieves were stacked with the 212 μm mesh sieve at the bottom, and the mesh sizes gradually increased on top of it. 50 g of the sample was placed on the top 4.75 mm mesh sieve and set in a sieve shaker. The sieve shaker used was an Endecotts OCTAGON200. After setting the sieves, the shaker was set to an amplitude of 5 and a shaking time of 3 minutes. After shaking was complete, the particle weights of the particles remaining on each sieve and the particles that passed through the 212 μm mesh were measured. If the amount of particles on a 4.75 mm mesh is Ag, the amount of particles on a 212 μm mesh is Bg, and the amount of particles that pass through the 212 μm mesh is Cg, then the degree of cohesion is calculated as (A / (B+C)×100(%)).

[0026] (Circularity) In one embodiment of the present invention, the spherical alumina particles have a circularity of 0.90 or higher. The higher the circularity of the spherical particles, the lower the viscosity of the resin composite composition containing the alumina particles and the better the moldability. The circularity may be 0.91 or higher, 0.92 or higher, or 0.93 or higher. Theoretically, the upper limit of circularity is 1.0, but from a manufacturing control perspective, it may be 0.98 or lower, or 0.95 or lower.

[0027] Circularity can be measured using an electron microscope or optical microscope and an image analysis device, such as the FPIA manufactured by Sysmex Corporation. These devices are used to measure the circularity of particles (perimeter of the equivalent circle / perimeter of the projected image of the particle). The circularity is measured for 100 or more particles, and the average value is taken as the circularity of the powder.

[0028] (gelatinization rate) In one embodiment of the present invention, the spherical alumina particles may have an α-conjugation rate of 10.0% or less. Here, the α-conversion rate refers to the proportion of α-alumina crystals in the crystalline phase. Alumina is known to exist in a crystalline state, and typical crystalline forms include α-alumina, θ-alumina, and δ-alumina. One embodiment of the present invention, spherical alumina particles, can be manufactured by a thermal spraying method in which the raw material is melted by pouring it into a flame and then rapidly cooled, as will be described in detail later. In this case, the proportion of amorphous alumina can be increased, and spherical alumina particles with an α-conversion rate of 10.0% or less can be easily obtained. The upper limit of the α-conversion rate may be 5.0%, 3.0%, or 1.0%. The lower limit of the α-conversion rate is not particularly limited and may be 0.0%, but from the viewpoint of the burden of manufacturing control and the thermal conductivity characteristics of the resin composite composition, it may be 0.1% or 0.4%.

[0029] The alpha-alumina 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 α-alumina to the total area is analyzed using the Rietveld method. Specifically, X-ray diffraction patterns are acquired using a Bruker D2PHASER in the range of 2θ from 10° to 90°. The alpha-alumina conversion rate is calculated from the acquired patterns using the Rietveld method with a Bruker DIFFRAC.TOPAS. In the calculation, the analysis is performed assuming that only three types of crystalline phases exist: α-alumina, δ-alumina, and θ-alumina, and the α-alumina content is calculated.

[0030] (purity) It is preferable that the purity of the aluminum oxide in the alumina particles is between 99.99% and 100.00%. If the purity of the aluminum oxide is less than 99.99%, the alumina particles tend to become irregularly shaped.

[0031] Specific examples of devices for measuring the purity of alumina nanoparticles include highly sensitive analytical instruments such as ICP emission spectrometry, AES, and SIMS, which allow for the quantitative determination of impurity levels. In this embodiment, the amount of impurities in the alumina particles was measured by ICP emission spectrometry and atomic absorption spectrometry. The measurements were performed according to the JIS standard measurement methods described below for each metal oxide. • Fe2O3 (%): Sulfuric acid (1+3) pressurized acid hydrolysis, ICP method (JIS R 1649) • SiO2 (%): Sodium carbonate-boric acid fusion, ICP method (JIS H 1901) Na2O (%): Sulfuric acid (1+3) pressurized acid decomposition, atomic absorption spectrophotometric method (JIS R 1649) Furthermore, the purity of the alumina particles was calculated using the following formula. Note that the value is defined as being rounded to the third decimal place.

[0032] Purity of alumina particles [Al2O3(%)] = 100(%)-[Fe2O3(%)]-[SiO2(%)]-[Na2O(%)]

[0033] [Method for producing spherical alumina particles] One embodiment of the present invention provides a method for producing spherical alumina particles. This method is suitable for producing the above-mentioned alumina particles and includes the following steps. (1) Manufacturing process for raw material alumina. (2) A process for producing spherical alumina raw material by spheroidizing the alumina raw material. (3) A water slurry preparation step of mixing the raw material spherical alumina with water to prepare a water slurry containing the raw material spherical alumina, and (4) A drying step of drying the water slurry.

[0034] (raw material: alumina) Alumina, the raw material, is produced using methods such as thermal decomposition of ammonium aluminum carbonate, gas-phase oxidation, deflagration, Bayer process, and hydrolysis of aluminum alkoxide.

[0035] (Raw material: spherical alumina) The raw material alumina can be sphericalized by a flame melting method to produce spherical raw material alumina. The flame melting method is a known thermal spraying method in which particles are injected into a flame to make them spherical. In this method, the average sphericity can be adjusted by controlling the amount of material injected into the flame per unit time and the type of fuel gas used. Furthermore, the particle size of the spherical alumina powder can be adjusted by controlling the particle size of the particles used. While there are no particular restrictions on the refrigerant, from the viewpoint of not reducing the purity of the spherical particles, gases such as air, nitrogen, or argon with few impurities and low activity are desirable. Alternatively, spherical alumina raw material may be produced by a deflagration method, in which a chemical flame is formed by a burner in an oxygen-containing atmosphere, and a quantity of metallic aluminum powder is added to this chemical flame in such an amount that a dust cloud is formed, causing deflagration to obtain spherical alumina particles.

[0036] (Water slurry) A water slurry containing the spherical alumina raw material is prepared by mixing the aforementioned spherical alumina raw material with water. From the viewpoint of not reducing the purity of the spherical particles, distilled water or ion-exchanged water that does not contain impurities such as sodium ions or chloride ions is preferable for the water used in the mixing. The mixing ratio can be adjusted as appropriate, taking into account the viscosity of the slurry.

[0037] (Washing) Before the water slurry preparation step, a raw material spherical alumina washing step may be performed in which the raw material spherical alumina is washed with water. The washing water may be distilled water or deionized water that does not contain impurities such as sodium ions or chloride ions, similar to the slurry water. Alternatively, washing may be performed using a detergent or surfactant, depending on the target to be removed by washing. By appropriately adjusting the washing conditions such as temperature, number of washes, and time, the alumina particles can be made to a desired washing state. Typically, a desired surface residual Na concentration and contained Na2O concentration can be obtained. After washing, dewatering may be performed using a filter or the like until the desired particle concentration is reached. By performing dewatering, dissolved Na and detergents in the water are washed away, preventing re-adhesion after drying. Alternatively, water may be added to the washed raw material spherical alumina to dissolve any remaining impurity components in the water. If water is added, dewatering can be performed again to wash away impurity components adhering to the surface of the alumina particles. In addition to high purity, controlling the particle concentration to an arbitrary level can improve the efficiency of drying in subsequent processes.

[0038] (Drying) To extract spherical alumina from a water slurry containing the raw material spherical alumina, the water is dried and removed. Conventional drying involves heating the slurry for a long period of time to evaporate the water from the slurry. As heating progresses, the water in the slurry evaporates and decreases, so the distance between alumina particles in the slurry decreases. When the water is completely removed from the slurry, the alumina particles are in contact with each other and may form strong aggregates. Furthermore, if the slurry is heated for a long time, sodium may move from inside the spherical alumina particles contained in the slurry to the surface and become free on the particle surface. In contrast, in this embodiment, the water slurry containing the raw material spherical alumina is dried by airflow heating or freeze-drying.

[0039] (Lyophilization) In freeze-drying, water is immobilized by freezing, and consequently, the alumina particles are also immobilized. During freeze-drying, water gradually detaches from the system (slurry) by sublimation, but because the alumina particles are immobilized, a certain distance is maintained between the alumina particles, suppressing contact and aggregation. In other words, when drying is complete and water has completely detached from the slurry, contact between alumina particles is minimized, and aggregation is unlikely to occur. Figure 1 schematically shows the state of alumina particles in the case of conventional heat drying and in the case of freeze-drying according to this embodiment. As shown above, when freeze-drying is performed according to this embodiment, aggregation of the obtained alumina particles is suppressed, and there is no need to crush aggregates of alumina particles. Generally, crushing equipment such as mills is used to crush aggregates, and there is a risk of foreign matter contamination from the crushing equipment. However, in this embodiment, there is no need to crush, so naturally, foreign matter contamination due to crushing is suppressed. Furthermore, because the heating temperature is low (10-90°C, with a more preferable upper limit of 80°C), the leaching of sodium from within the particles is minimized, resulting in less sodium being freed and reattached to the powder surface after drying.

[0040] (Airflow heating drying) Airflow heating and drying is a method for extracting spherical alumina powder from a slurry by evaporating only the water content by spraying the slurry into a high-temperature airflow of 100-300°C. The slurry is sprayed into the high-temperature airflow using a nozzle such as a two-fluid nozzle. The sprayed slurry becomes fine droplets due to the dispersion effect in the airflow. Compared to conventional heating and drying methods, airflow heating and drying has a much larger surface area because the slurry is turned into droplets by the nozzle. Since the amount of heat received by the slurry is proportional to the surface area in contact with the heat source, the water in the droplets evaporates and dries in an instant. Because the drying time is shorter than conventional heating and drying methods (approximately 0.01 to 10 seconds), the leaching of sodium from inside the particles is minimized, resulting in less sodium being released and reattached to the powder after drying. Furthermore, since the spherical alumina powder is sprayed into the airflow, aggregation of the spherical alumina powder particles is suppressed, and there is no need to break up aggregates of alumina particles.

[0041] [Resin composite composition] According to one embodiment of the present invention, a composite composition of spherical alumina particles and resin can be produced. The composition of the resin composite composition will be described in detail below.

[0042] A slurry composition containing spherical alumina particles and resin can be used to obtain resin composite compositions such as semiconductor encapsulants (especially solid encapsulants) and interlayer insulating films. Furthermore, by curing these resin composite compositions, resin composites such as encapsulants (cured bodies) and semiconductor package substrates can be obtained.

[0043] When manufacturing the aforementioned resin composite composition, for example, in addition to spherical alumina particles and resin, a curing agent, curing accelerator, flame retardant, silane coupling agent, etc., are added as needed and compounded by known methods such as kneading. Then, it is molded into pellets, films, etc., according to the application.

[0044] Furthermore, when manufacturing the resin composite composition, other inorganic fillers may be added in addition to spherical alumina particles and resin. Examples of such inorganic fillers include amorphous spherical silica particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fiber. The blending ratio of the inorganic fillers can be appropriately adjusted depending on the application of the resin composite composition.

[0045] Furthermore, when curing the resin composite composition to produce a resin composite, for example, the resin composite composition is heated and melted, processed into a shape according to the application, and then completely cured by applying a higher heat than that used during melting. In this case, known methods such as the transfer molding method can be used.

[0046] For example, when manufacturing semiconductor-related materials such as packaging substrates and interlayer insulating films, known resins can be used as the resin in the resin composite composition, but epoxy resins are preferred. The 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. One of these can be used alone, or two or more with different molecular weights can be used in combination. Among these, epoxy resins having two or more epoxy groups in one molecule are preferred from the viewpoint of curability, heat resistance, etc. Specifically, 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 such as bisphenol A, bisphenol F, and bisphenol S, glycidyl ester epoxy resins obtained by the reaction of 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, 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 in one molecule, bisphenol A-type epoxy resins are particularly preferred.

[0047] Furthermore, resins other than epoxy resins can be used in applications other than composite materials for semiconductor encapsulants, such as prepregs for printed circuit boards and various engineering plastics. Specifically, in addition to epoxy resins, other resins include silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyetherimides and other polyamides; 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.

[0048] As a curing agent used in a resin composite composition, any known curing agent may be used to cure the resin, but for example, a phenolic curing agent can be used. As a phenolic curing agent, phenol novolac resins, alkylphenol novolac resins, polyvinylphenols, etc., can be used individually or in combination of two or more.

[0049] The amount of phenol curing agent blended is preferably such that its 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 phenol curing agent and improves moisture absorption and heat resistance.

[0050] The amount of spherical alumina particles added to the resin composite composition of the present invention is preferably high 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. This is because if the amount of spherical alumina particles is too low, it is difficult to obtain effects such as improving the strength of the sealing material and suppressing thermal expansion, and conversely, if it is too high, segregation due to aggregation of spherical alumina particles is likely to occur in the composite material regardless of the surface treatment of the spherical alumina particles, and the viscosity of the composite material becomes too high, making it difficult to use as a sealing material.

[0051] In addition to resins, known additives such as silane coupling agents, curing agents, colorants, and curing retarders can also be used.

[0052] Furthermore, while any known coupling agent may be used as the silane coupling agent, one having an epoxy functional group is preferred.

[0053] A slurry composition containing spherical alumina particles and resin can be used to obtain heat dissipation sheets, heat dissipation greases, and the like.

[0054] In obtaining the aforementioned heat dissipation sheet, spherical alumina particles and resin are mixed with appropriate additives and compounded using known methods such as kneading. The resulting composite is then molded into a sheet using known methods.

[0055] For example, when manufacturing a heat dissipation sheet, known resins can be used as the resin in the resin composite composition. Specifically, examples include silicone resin, phenolic resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamide-imide, polyetherimide and other polyamides; 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, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin. Among these, silicone resin is preferred. The silicone resin is not particularly limited, but for example, peroxide-curing type, addition-curing type, condensation-curing type, ultraviolet-curing type, etc., can be used.

[0056] In addition to resins, known additives such as silane coupling agents, curing agents, colorants, and curing retarders can also be used.

[0057] In obtaining the aforementioned heat dissipation grease, spherical alumina particles and resin are combined with appropriate additives and compounded by known methods such as kneading. Here, the resin used in the heat dissipation grease is also called the base oil.

[0058] For example, when manufacturing heat dissipation grease, known resins can be used as resins in the resin composite composition, but specifically include silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamideimides, polyetherimides and other polyamides; 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, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, mineral oils, synthetic hydrocarbon oils, ester oils, polyglycol oils, silicone oils, and fluorine oils.

[0059] In addition to the resin, known additives such as silane coupling agents, colorants, and thickeners can be used. Known thickeners such as calcium soap, lithium soap, aluminum soap, calcium complex, aluminum complex, lithium complex, barium complex, bentonite, urea, PTFE, sodium terephthalate, silica gel, and organic bentonite can be used. [Examples]

[0060] The present invention will be described through the following examples and comparative examples. However, the present invention is not limited to the following examples.

[0061] The spherical alumina particles (materials 1 to 4) listed in Table 1 were prepared and mixed with water to make a water slurry. When preparing the water slurry, the mixing ratio of deionized water to particles was as follows: when using materials 1 and 2, 200 kg of particle powder was mixed with 1000 L of water. When using material 3, 300 kg of particle powder was mixed with 1000 L of deionized water. When using material 4, 200 kg of particle powder was mixed with 1000 L of deionized water. After mixing and stirring the water slurry for about 20 minutes to 1 hour, it was filtered using a suitable filter until the moisture content was about 60-80 wt%.

[0062] (Examples 1-3) The prepared slurry was pre-frozen under conditions of -40°C. Then, while vacuum-degassing the apparatus, it was freeze-dried at 80°C for 24 hours.

[0063] (Example 4) The prepared slurry was air-dried at 200°C using a jet turbo dryer manufactured by Hiraiwa Iron Works.

[0064] (Comparative Examples 1-3) The prepared slurry was placed in an oven without airflow and dried by heat drying. The drying conditions were 230°C for 40 hours.

[0065] (Comparative Example 4) The slurry prepared using material 4 was freeze-dried under the same conditions as in Example 1.

[0066] (Comparative Example 5) The slurry prepared using material 1 was pre-frozen under conditions of -40°C. Then, it was freeze-dried at 95°C for 24 hours while the apparatus was vacuum-degassed.

[0067] (Comparative Example 6) The slurry prepared using material 1 was air-dried at 350°C using a jet turbo dryer manufactured by Hiraiwa Iron Works.

[0068] (Example 5) Spherical alumina particles obtained in Example 1 and aluminum nitride particles (D50 = 30 μm) were mixed in a ratio of (weight of spherical alumina particles):(weight of aluminum nitride particles) = 90:10 to prepare spherical alumina particle mixture A. Furthermore, spherical alumina particle mixture A was mixed with Dow Toray silicone resin CY52-276A liquid so that the amount of spherical alumina particle mixture A added to the resin composite composition was 90% by mass. The mixture was then vacuum mixed using a Thinky vacuum mixer "Awatori Rentaro" to obtain a resin composite composition. The mixing conditions were 15 seconds of pre-mixing and 90 seconds of vacuum mixing. After mixing, the plastic container containing the mixture was placed in a water bath adjusted to 25°C and cooled for 1 hour. 10 g of this resin composite composition was placed on a smooth iron plate and tilted 60° to the horizontal to check the flow rate of the resin composite composition. As a result, after tilting the container for 5 hours, the resin composite composition flowed more than 15 cm, demonstrating good fluidity.

[0069] (Example 6) Spherical alumina particles obtained in Example 2 and boron nitride particles (D50 = 20 μm) were mixed in a ratio of (weight of spherical alumina particles):(weight of boron nitride particles) = 90:10 to prepare spherical alumina particle mixture B. Furthermore, spherical alumina particle mixture B was mixed with Dow Toray silicone resin CY52-276A liquid so that the amount of spherical alumina particle mixture B added to the resin composite composition was 90% by mass. The mixture was then vacuum mixed using a Thinky vacuum mixer "Awatori Rentaro" to obtain a resin composite composition. The mixing conditions were 15 seconds of pre-mixing and 90 seconds of vacuum mixing. After mixing, the plastic container containing the mixture was placed in a water bath adjusted to 25°C and cooled for 1 hour. 10 g of this resin composite composition was placed on a smooth iron plate and tilted 60° to the horizontal to check the flow rate of the resin composite composition. As a result, after tilting the container for 5 hours, the resin composite composition flowed more than 15 cm, demonstrating good fluidity.

[0070] Table 2 shows the physical properties of the (dried) spherical alumina particles obtained under each condition.

[0071] [Table 1]

[0072] [Table 2]

[0073] The measurement methods for each physical property are described below.

[0074] (Average particle size calculated by laser diffraction scattering method) The laser diffraction and scattering particle size distribution method is a method for determining particle size distribution from the intensity distribution pattern of diffracted and scattered light emitted from a dispersion of spherical alumina particles, by irradiating the dispersion with laser light. In this invention, the laser diffraction and scattering particle size distribution analyzer "Mastersizer3000" (manufactured by Malvern) was used.

[0075] (specific surface area) The specific surface area (BET value) was determined by applying the BET theory to the adsorption isotherm measured by the gas adsorption method (BET method). The specific surface area was measured using the "Maxsorb Model HM-1208" manufactured by Mountec Co., Ltd.

[0076] (Surface residual Na) The amount of ionic impurities adhering to the surface can be measured using an ion chromatograph. Add 4 g of the sample and 40 ml of distilled water to a centrifuge tube, close the lid, and shake well to mix. After mixing, separate the sample from the sample solution using a centrifuge. Take a sample of the sample solution and analyze the sodium ions using an ion chromatograph. The ion chromatograph used was manufactured by Toa Medical Electronics Co., Ltd.

[0077] (Contains Na2O) 0.5 g of the sample was placed in a pressure vessel, 10 ml of sulfuric acid (1+3) was added, and the lid was closed. The vessel was then heated in a heating and drying oven at 230°C for 16 hours. After the heated solution had cooled, it was diluted to 100 ml and measured using an atomic absorption spectrophotometer. Note that sulfuric acid (1+3) refers to a solution prepared by adding pure water in a volume ratio of 3 to 1 part concentrated sulfuric acid.

[0078] (Cohesion degree) Standard sieves with two mesh sizes, 4.75 mm and 212 μm, were stacked in sequence. The sieves were stacked with the 212 μm mesh sieve at the bottom, and the mesh sizes gradually increased on top of it. 50 g of the sample was placed on the top 4.75 mm mesh sieve and set in a sieve shaker. The sieve shaker used was an Endecotts OCTAGON200. After setting the sieves, the shaker was set to an amplitude of 5 and a shaking time of 3 minutes. After shaking was complete, the particle weights of the particles remaining on each sieve and the particles that passed through the 212 μm mesh were measured. If the amount of particles on a 4.75 mm mesh is Ag, the amount of particles on a 212 μm mesh is Bg, and the amount of particles that pass through the 212 μm mesh is Cg, then the degree of cohesion is calculated as (A / (B+C)×100(%)).

[0079] Through the above examples, it was confirmed that spherical alumina particles with a low surface residual Na concentration and low degree of aggregation can be obtained. Furthermore, it was confirmed that a resin composite composition containing these spherical alumina particles can be obtained. [Industrial applicability]

[0080] The spherical alumina particles of the present invention have a low surface residual Na concentration, which prevents curing defects and loss of dielectric strength when used as a filler. Furthermore, because of their low degree of aggregation, crushing is unnecessary, thus avoiding contamination by foreign matter caused by crushing. Therefore, they can be suitably used as a filler in miniaturized and thin semiconductor packages and the like. Moreover, the spherical alumina particles can be easily manufactured by a manufacturing method according to one aspect of the present invention. The resin composite composition containing the spherical alumina particles exhibits good quality and is not limited to semiconductor encapsulation materials, but can be used for other applications as well. Specifically, it can be used as a prepreg for printed circuit boards, various engineering plastics, and the like.

Claims

1. Average particle size: 0.4–1.9 μm, specific surface area: 1.0–5.0 m² ２ / g, surface residual Na is 20 ppm or less, containing Na ２ Spherical alumina particles having an O content of 1000 ppm or less, a degree of aggregation of 1.0% or less, and a circularity of 0.9 or more.

2. The spherical alumina particles according to claim 1, characterized in that the alpha-adsorption rate is 10.0% or less.

3. A water slurry preparation step involves mixing the raw material spherical alumina with water to prepare a water slurry containing the raw material spherical alumina, A drying step for drying the aforementioned aqueous slurry, It has, The present invention relates to a method for producing spherical alumina particles, wherein the drying step involves freeze-drying at a heating temperature of 10 to 90°C, or air-flow heating drying in an airflow of 100 to 300°C for a drying time of 0.01 to 10 seconds.

4. Prior to the water slurry preparation step, a raw material spherical alumina washing step is performed in which the raw material spherical alumina is washed with water. A method for producing spherical alumina particles according to claim 3, comprising the above.

5. A resin composite composition characterized by containing spherical alumina particles as described in claim 1 or 2.

6. The resin composite composition according to claim 5, further comprising at least one inorganic filler selected from amorphous spherical silica particles, crystalline spherical silica particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fiber.

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