Spherical alumina particles and resin composite compositions containing them

Abstract

The present invention provides spherical alumina particles, particularly spherical alumina particles having a specific loose bulk density, and resin composite compositions containing the same. [Solution] Loose bulk density (g / cm³) 3 Spherical alumina particles characterized by having a ratio of 1.80 or higher, and a resin composition characterized by containing the same.

Description

[Technical Field]

[0001] The present invention relates to spherical alumina particles, particularly spherical alumina particles having a specific loose bulk density, and resin composite compositions containing such spherical alumina particles. [Background technology]

[0002] Alumina is an oxide of aluminum and has a wide range of applications. Examples of its uses include its use as a raw material for aluminum in molten salt electrolysis, as well as its addition as a ceramic material in pottery and other ceramic applications. It is also widely used in fields requiring high strength, toughness, and thermal shock resistance, such as abrasives and sandblasting equipment, as a catalyst carrier in automotive exhaust gas purification catalysts, and in dental treatment (restorations and prosthetics such as inlays and crowns). Furthermore, it is used as an abrasive in industrial sandblasting. It is also used as a material in medical applications and cosmetic compositions.

[0003] In recent years, spherical alumina particles have also been used as fillers in encapsulating materials (resin compositions) to protect semiconductor chips. Furthermore, as semiconductor chips require higher functionality and higher speeds, the amount of heat generated from them is increasing. Spherical alumina particles are attracting increasing attention as fillers in encapsulating materials due to their heat dissipation and filling properties.

[0004] Patent Document 1 is a document relating to spherical alumina powder, and proposes setting the difference between the angle of repose and the collapse angle of spherical alumina particles to a specific range in order to improve burr formation and thermal conductivity when mixed with resin (when used as a sealing material).

[0005] Patent Document 2 is a document relating to a powder of an inorganic metal compound containing alumina, and proposes setting the Hausner ratio (tap density / bulk density) of spherical alumina particles to a specific range in order to improve the fluidity when mixed with resin (when used as a sealing material). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2024 / 128321 [Patent Document 2] International Publication No. 2024 / 106403 [Overview of the project] [Problems that the invention aims to solve]

[0007] As described in Patent Documents 1 and 2 above, various studies have been conducted to improve the thermal conductivity, fluidity, etc., of resin compositions (sealants) in which spherical alumina particles are mixed with resin.

[0008] On the other hand, with the development and expansion of the information society, the production volume of semiconductor chips is steadily increasing. Naturally, the amount of encapsulating material and the fillers used therein, such as spherical alumina particles, is also increasing.

[0009] If the amount and applications of spherical alumina particles increase, then the transportation and handling of these particles should also be considered. Therefore, the inventors first conducted various studies with the aim of improving transportation efficiency without increasing the burden of handling. [Means for solving the problem]

[0010] Through detailed studies of spherical alumina particles, the inventors discovered that the loosened bulk density of spherical alumina particles can be set to a specific range through classification operations. They then found that by setting the loosened bulk density to a specific range, in other words, a relatively high range, transportation efficiency can be improved without significantly increasing the burden on handling, leading to the conception of the present invention.

[0011] This invention aims to solve the aforementioned problems based on the above findings, and its gist is as described in the claims below. [1] Loose bulk density (g / cm³) 3 Spherical alumina particles characterized by having a ratio of 1.80 or higher. [2] The spherical alumina particles according to [1], characterized in that the average particle size is 15.0 to 25.0 μm in the particle size distribution measured by the laser diffraction scattering particle size distribution method. [3] The spherical alumina particles according to [1] or [2], characterized in that, when the loose bulk density is A and the hard bulk density is B, the compressibility calculated based on {(BA) / B)} × 100% is 25.0% or less. [4] Spherical alumina particles according to any one of [1] to [3], characterized in that the angle of repose is 30.0° or more and 35.0° or less. [5] A resin composite composition characterized by containing spherical alumina particles as described in any one of [1] to [4], and a resin. [Effects of the Invention]

[0012] While we do not wish to be bound by any particular theory, the following can be considered regarding the ability to control the bulk density of spherical alumina particles within a specific range through classification operations, etc. Classification operations can restrict the particle size distribution to a relatively narrow range. A narrow particle size distribution means that the size of the particles (particle size) is almost uniform, and the size of the gaps between the particles is also almost uniform. In other words, a constant density can be achieved in the spherical alumina particles, and the bulk density is determined accordingly. It is possible to obtain the desired bulk density by utilizing this particle size distribution adjustment.

[0013] When spherical alumina particles have a relatively high bulk density, the amount (weight) loaded into a container of a certain volume increases (becomes heavier). Alternatively, when transporting a certain weight of spherical alumina particles, it is possible to reduce the number of containers or the capacity of the containers required, which also contributes to reducing packaging materials. These lead to an improvement in the transport efficiency of the spherical alumina particles, and it is also expected that, without particularly increasing the burden in handling the spherical alumina particles, the handling load is reduced instead.

[0014] Although Patent Document 1 describes the loose bulk density, it discloses that from the viewpoint of miscibility with a resin, 1.50 cm 3 / g or less is preferable, and the maximum value of the loose bulk density through Examples and Comparative Examples is 1.55 cm 3 / g.

[0015] Also, although Patent Document 2 describes the bulk density, from the viewpoint of achieving a desired Hausner ratio, the bulk density may be 1.60 cm 3 / g or less, but it discloses that 1.00 cm 3 / g or less is preferable, and the maximum value of the loose bulk density through Examples and Comparative Examples is 0.65 cm 3 / g.

[0016] That is, according to the present invention, spherical alumina particles having a higher bulk density can be obtained compared to conventionally known spherical alumina particles. And such spherical alumina particles having a high bulk density can improve the transport efficiency without increasing the burden in handling. Naturally, in the resin composition containing the spherical alumina particles, the advantages such as good handling property and high transport efficiency of the spherical alumina particles can also be enjoyed.

Embodiments for Carrying Out the Invention

[0017] (Loose bulk density (g / cm 3 ) 1.80 or more) The spherical alumina particles provided by one embodiment of the present invention have a loose bulk density (g / cm 3 ) of 1.80 or more.

[0018] The spherical alumina particles according to this embodiment have a loose bulk density (g / cm 3 ) of 1.80 or more, and have a relatively high bulk density compared to conventional spherical alumina particles. Therefore, when loading the spherical alumina particles into a container of a certain volume, their weight can be increased. Alternatively, when transporting spherical alumina particles of a certain weight, the number of containers or the capacity of the containers required can be reduced, which also contributes to the reduction of packaging materials. That is, the spherical alumina particles according to this embodiment lead to an improvement in transportation efficiency, and without particularly increasing the burden in handling the spherical alumina particles, on the contrary, it is expected that the handling load will be reduced.

[0019] Generally, the higher the loose bulk density (g / cm 3 ), the more preferable it is as the transportation efficiency is higher. In that regard, the loose bulk density (g / cm 3 ) may be 1.90 or more, or may be 2.00 or more.

[0020] On the other hand, the upper limit of the loose bulk density is not particularly limited. However, since the true specific gravity of alumina (g / cm 3 ) is about 3.9, the upper limit of the loose bulk specific gravity (g / cm 3 ) may be 3.50 or less, may be 3.00 or less, or may be 2.50 or less.

[0021] The loose bulk density (g / cm 3The method for adjusting the size distribution is not particularly limited as long as it can obtain the desired loose bulk density, but it is possible to obtain the desired loose bulk density by classifying the spherical alumina particles. By classifying the spherical alumina particles, the particle size distribution of the spherical alumina particles can be restricted to a desired narrow range. A narrow particle size distribution means that the size of the particles (particle size) is almost the same and the size of the gaps between the particles is also almost the same. In other words, a constant density can be achieved in the spherical alumina particles, and the bulk density is determined accordingly. It is possible to obtain the desired bulk density by utilizing this particle size distribution adjustment.

[0022] In this embodiment, the loosened bulk density is measured in the following manner. The loosened bulk density is measured using a Hosokawa Micron PT-X powder tester. The device is equipped with a guidance function, and the setup of jigs and processing of samples are performed according to that guidance. More specifically, using a cup and sieve of known volume provided with or specified for the apparatus, the sieve is placed above the cup, and the spherical alumina particles, which are the measurement sample, are placed on the sieve. The mesh size of the sieve was selected according to the particle size of the sample (a sieve that would not allow the sample to fall through if simply placed on it, but would fall through if the sieve was vibrated). In this case, a sieve with a mesh size of 75 μm was used. The sieve is vibrated up and down with an amplitude of 1 mm to dislodge the sample (spherical alumina particles) from the sieve and fill the cup below. After dropping the sample (spherical alumina particles) into the cup until it overflows, use the blade (metal plate) attached to the device to scrape off the sample (spherical alumina particles) so that the top edge of the cup and the surface of the sample (spherical alumina particles) are at the same height. The cup filled with the sample (spherical alumina particles) is weighed, and the loosened bulk density is determined using the following formula. (Loose bulk density) = {(Weight of cup filled with sample) - (Weight of cup only)} / (Volume of cup) Repeat the above procedure twice and use the average value of the measured loosened bulk density.

[0023] (Average particle size 15.0~25.0μm) The spherical alumina particles provided by one embodiment of the present invention may have an average particle size of 15.0 to 25.0 μm in the particle size distribution measured by laser diffraction scattering particle size distribution measurement method.

[0024] The average particle size of spherical alumina particles can be appropriately selected depending on the application and desired properties. If the average particle size is less than 15 μm, the particles will aggregate more, which can significantly reduce the fluidity of the resin composition when used as a filler, and is therefore undesirable. If the average particle size exceeds 25 μm, in increasingly miniaturized and thin semiconductor packages, the particles may get stuck in the narrow space between the mounting substrate and the chip, resulting in unfilled areas and reduced reliability.

[0025] The method for adjusting the average particle size is not particularly limited as long as it can yield the desired average particle size, but it is possible to obtain the desired average particle size by classifying spherical alumina particles. By classifying spherical alumina particles, it is typically possible to obtain the desired average particle size by sieving and removing spherical alumina particles with a particle size larger than the desired average particle size, and also by sieving and removing spherical alumina particles with a particle size smaller than the desired average particle size.

[0026] In this embodiment, the average particle size is measured in the following manner. Average particle size refers to the average particle diameter (D50), which is the median diameter D50 at which the cumulative volume reaches 50% in the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution method. The laser diffraction scattering particle size distribution method is a method in which a laser beam is irradiated onto a dispersion of spherical alumina particles, and the particle size distribution is determined from the intensity distribution pattern of the diffracted and scattered light emitted from the dispersion. In this embodiment, the laser diffraction and scattering particle size distribution analyzer "Mastersizer3000" (manufactured by Malvern) is used.

[0027] (Compression level 25.0% or less) In one embodiment of the present invention, spherical alumina particles may have a compressibility of 25% or less, calculated based on {(BA) / B} × 100%, where A is the loose bulk density and B is the hard bulk density.

[0028] Compression degree is an index that indicates the degree of density change when a loosely bulky powder (bulk density A) is tapped under predetermined conditions to achieve a firm bulky density (bulk density B). In other words, it can be considered an index that indicates how much the density is compressed by tapping.

[0029] The spherical alumina particles according to this embodiment may have a compressibility of 25.0% or less. Generally, the lower the compressibility, the smaller the difference between the loose bulk density A and the hard bulk density B, meaning that the bulk density does not change much even after tapping. This means that the bulk density does not change much even after processes such as transportation, and the bulk density is easily maintained stably. In this respect, the compressibility may be 20.0% or less, 15.0% or less, or 10.0% or less.

[0030] On the other hand, the lower limit of the degree of compression is not particularly limited and may be 3.0% or higher, 5.0% or higher, 7.0% or higher, or 10.0% or higher.

[0031] The method for adjusting the degree of compressibility is not particularly limited as long as it can achieve the desired degree of compressibility, but it is possible to obtain the desired degree of compressibility by classifying spherical alumina particles. By classifying spherical alumina particles, the particle size distribution of the spherical alumina particles can be kept within a desired narrow range. A narrow particle size distribution means that the size of the particles (particle size) is almost the same and the size of the gaps between the particles is also almost the same. In other words, a constant density can be achieved in the spherical alumina particles. That is, the position and size of each void are almost constant, and the size of the particles adjacent to the voids is also almost constant, so once the positional relationship between particles and voids is settled, even if there is vibration such as tapping afterward, it is unlikely that particles will move into the voids and the voids will become smaller. As a result, it is possible to obtain a state in which the overall bulk density of the particles does not change easily, that is, the degree of compressibility does not change easily.

[0032] In this embodiment, the loose bulk density A is measured according to the loose bulk density measurement procedure described above, and the firm bulk density B is measured according to the following procedure. The bulk density is measured using a Hosokawa Micron PT-X powder tester. The device is equipped with a guidance function, and the setup of jigs and processing of samples are performed according to that guidance. More specifically, the apparatus uses a cup of known volume that is attached to or specified by the device, a cylindrical cap that can be fitted onto the cup (for filling the sample, which consists of spherical alumina particles, up to above the upper rim of the cup), and a sieve. The cap is placed over the cup, the sieve is set above it, and the spherical alumina particles, which are the measurement sample, are placed on the sieve. The mesh size of the sieve was selected according to the particle size of the sample (a sieve that would not allow the sample to fall through if simply placed on it, but would fall through if the sieve was vibrated). In this case, a sieve with a mesh size of 75 μm was used. The sieve is vibrated up and down with an amplitude of 1 mm to dislodge the sample (spherical alumina particles) from the sieve and fill the cup below. After dropping the sample (spherical alumina particles) into the cup until it overflows, the cup is lifted 18 mm and then dropped again. This tapping operation is performed 180 times at a speed of 60 times per minute to increase the packing density of the sample (spherical alumina particles). After the tapping operation is complete, remove the cap and then use the blade (metal plate) attached to the device to scrape the sample (spherical alumina particles) so that the top edge of the cup and the surface of the sample (spherical alumina particles) are at the same height. The cup filled with the sample (spherical alumina particles) is weighed, and its bulk density is determined using the following formula. (Compressed bulk density) = {(Weight of cup filled with sample) - (Weight of cup only)} / (Volume of cup) Repeat the above procedure twice and use the average value of the measured bulk density.

[0033] (Angle of repose 30.0° or more and 35.0° or less) The spherical alumina particles provided by one embodiment of the present invention may have an angle of repose of 30.0° or more and 35.0° or less.

[0034] The angle of repose refers to the angle between the slope (ridge) of a powder deposit and the horizontal plane when the powder is deposited on a horizontal plane under certain conditions.

[0035] Generally, the smaller the angle of repose, the higher the fluidity of the powder, while the larger the angle of repose, the higher the viscosity and the less easily the powder flows. The angle of repose may be selected according to the desired fluidity and viscosity. The spherical alumina particles according to this embodiment may have an angle of repose of 30.0° to 35.0°. An angle of repose of 30.0° to 35.0° is preferable as it provides appropriate fluidity as a powder.

[0036] The method for adjusting the angle of repose is not particularly limited as long as it can obtain the desired angle of repose. The angle of repose may be adjusted by the surface properties of the spherical alumina particles, or more specifically, by adjusting various process conditions such as the surface treatment of the spherical alumina particles or the thermal spraying conditions of the spherical alumina particles. It is also possible to adjust the angle of repose by classifying the spherical alumina particles, regardless of the surface properties (coefficient of friction, circularity, etc.) of the spherical alumina particles. By classifying the spherical alumina particles, the particle size distribution of the spherical alumina particles can be kept within a desired narrow range. A narrow particle size distribution means that the size of the particles (particle size) is almost uniform, and the size of the gaps between the particles is also almost uniform. In other words, a constant density can be achieved in the spherical alumina particles. In other words, the position and size of each void are almost constant, and the size of the particles adjacent to the voids is also almost constant. Therefore, once the positional relationship between the particles and voids settles, that is, once a state of rest is reached, it is unlikely that the particles will move afterward, and the state of rest is easily maintained. It is possible to adjust the angle of rest by utilizing this particle size distribution adjustment through classification.

[0037] In this embodiment, the angle of repose is measured in the following manner. The angle of repose is measured using a Hosokawa Micron PT-X powder tester. The device is equipped with a guidance function, and the setup of jigs and processing of samples are performed according to that guidance. More specifically, a circular table and a sieve, provided for or specified with the device, are used for measuring the angle of repose. A circular table for measuring the angle of repose is set up, and the sieve mesh is placed above it. Spherical alumina particles, which are the measurement sample, are then placed on the sieve mesh. The mesh size of the sieve was selected according to the particle size of the sample (a sieve that would not allow the sample to fall through if simply placed on it, but would fall through if the sieve was vibrated). In this case, a sieve with a mesh size of 75 μm was used. The sieve is vibrated up and down to dislodge the sample (spherical alumina particles) from the sieve, which is then deposited onto a circular table below. The vertical amplitude is 0.5 mm, the vibration time is 170 seconds, and the slowdown time is 10 seconds. The pile of deposited sample (spherical alumina particles) is photographed with a camera while shining blue light from behind, and the angle between the top surface of the circular table and the pile (=angle of repose) is measured. Repeat the above procedure twice and use the average value of the measured angles of repose.

[0038] (Method for producing spherical alumina particles) Spherical alumina particles can be manufactured by known methods such as flame melting. The flame melting method is a known thermal spraying method in which raw material particles are sprayed into a flame to spheroidize the raw material. In this method, the average spheroidity 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 particles can be adjusted by controlling the particle size of the raw material powder used.

[0039] Spherical alumina particles can be separated into coarse and fine particles using a cyclone or the like, as needed. The spherical alumina particles thus obtained can then be classified into particles with a desired average particle size and particle size distribution using a sieve or classifier with a predetermined mesh size.

[0040] Spherical alumina particles are alumina particles that have a spherical shape. Spherical may mean that the circularity of the alumina particle is 0.85 or higher. Generally, the higher the circularity of spherical alumina particles, the lower the viscosity of the resin composite composition containing the particles and the better the moldability. The circularity may be 0.90 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. In flame spraying, the circularity can be adjusted by the amount of raw material input to the flame per unit time, the type of fuel gas, the flame temperature, etc.

[0041] 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.

[0042] (Raw material for spherical alumina particles) The raw materials for the spherical alumina particles may include alumina powder or aluminum hydroxide powder. Metallic aluminum may also be used.

[0043] (Resin composite composition containing spherical alumina particles) According to one aspect of the present invention, a resin composite composition containing spherical alumina particles and a resin is provided. Furthermore, a resin composite obtained by curing the resin composite composition can also be manufactured. The composition of the resin composite composition and other details are described in detail below.

[0044] A slurry composition containing spherical alumina particles and resin can be used to obtain resin composite compositions for semiconductor encapsulants, interlayer insulating films, etc. (including heat dissipation sheets and heat dissipation adhesives). Furthermore, by curing these resin composite compositions, resin composites for encapsulants (cured bodies), semiconductor packaging substrates, etc. can be obtained.

[0045] 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.

[0046] Furthermore, when manufacturing the resin composite composition, in addition to the spherical alumina particles and resin which are part of one embodiment of the present invention, other inorganic fillers may be added. 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, but from the viewpoint of exhibiting the effect of the spherical alumina particles which are part of one embodiment of the present invention, it is preferable that (weight of spherical alumina particles):(weight of other inorganic fillers) = 95:5 to 60:40.

[0047] Furthermore, when curing the resin composite composition to produce a resin composite, for example, the resin composite composition can be heated and melted, processed into a shape suitable for 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 or the compression molding method can be used.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In a resin composite composition, the amount of spherical alumina particles, which is one embodiment of the present invention, is preferably high from the viewpoint of heat resistance and thermal expansion coefficient. However, it is generally appropriate for the amount 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. Conversely, if the amount 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.

[0053] In addition to resins, known additives such as silane coupling agents, curing agents, colorants, and curing retarders can also be used.

[0054] Furthermore, while any known coupling agent may be used as the silane coupling agent, one having an epoxy functional group is preferred.

[0055] A slurry composition containing spherical alumina particles and resin can be used to obtain heat dissipation sheets, heat dissipation adhesives (sometimes referred to as heat dissipation grease), and the like.

[0056] 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.

[0057] 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.

[0058] In addition to resins, known additives such as silane coupling agents, curing agents, colorants, and curing retarders can also be used.

[0059] In obtaining the aforementioned heat-dissipating adhesive or heat-dissipating grease, spherical alumina particles and resin are appropriately blended with additives and compounded by known methods such as kneading. Here, the resin used in the heat-dissipating adhesive or heat-dissipating grease is also called the base oil.

[0060] For example, when manufacturing a heat dissipation adhesive or heat dissipation grease, known resins can be used as the resin in the resin composite composition. Specifically, these 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, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, mineral oils, synthetic hydrocarbon oils, ester oils, polyglycol oils, silicone oils, and fluorine oils.

[0061] 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]

[0062] The present invention will be described through the following examples and comparative examples. However, the present invention is not limited to the following examples.

[0063] [Manufacturing of spherical alumina particles] Spherical alumina particles were produced by introducing alumina particle raw material into a high-temperature flame formed by LPG and oxygen, followed by melting, spheroidization, and solidification. The obtained spherical alumina particles were separated into coarse and fine particles using a cyclone, and the recovered coarse particles were used as the raw material before classification. The raw material before classification was classified under various conditions described below to produce the spherical alumina particles of the comparative example and the example.

[0064] For Examples C and D, the particle size of the alumina particle raw material was controlled (details described later), and then classification was performed to produce the spherical alumina particles of Examples C and D.

[0065] (Comparative Example 1) Without any special classification operations, the unclassified material was used as the spherical alumina particles in Comparative Example 1.

[0066] (Comparative Example 2) The raw material was fed into a classifier equipped with a classification rotor, and particles smaller than 7 μm were removed to obtain spherical alumina particles of Comparative Example 2.

[0067] (Comparative Example 3) The raw material was fed into a classifier equipped with a classification rotor, and particles smaller than 5 μm were removed to obtain spherical alumina particles of Comparative Example 3.

[0068] (Example A) The raw material was fed into a classifier equipped with a classification rotor to remove particles smaller than 7 μm. After that, it was passed through a sieve with a mesh size of 25 μm, and the sieved material was collected to obtain the spherical alumina particles of Example A.

[0069] (Example B) The raw material was fed into a classifier equipped with a classification rotor to remove particles smaller than 10 μm. The material was then passed through a sieve with a 32 μm mesh opening, and the residue was collected to obtain the spherical alumina particles of Example B.

[0070] (Example C) Spherical alumina particles, containing almost no particles smaller than 7 μm, were introduced into a high-temperature flame formed by LPG and oxygen. The mixture underwent melting, spheroidization, and solidification to produce spherical alumina particles. The obtained spherical alumina particles were separated into coarse and fine particles using a cyclone. The recovered coarse particles were sieved through a 25 μm mesh sieve, and the sieve residue was collected to obtain the spherical alumina particles of Example C.

[0071] (Example D) Spherical alumina particles, containing almost no particles smaller than 10 μm, were introduced into a high-temperature flame formed by LPG and oxygen. The mixture underwent melting, spheroidization, and solidification to produce spherical alumina particles. The obtained spherical alumina particles were separated into coarse and fine particles using a cyclone. The recovered coarse particles were sieved through a 32 μm mesh sieve, and the sieve residue was collected to obtain the spherical alumina particles of Example D.

[0072] Various physical properties were measured for the obtained spherical alumina particles, and the results are shown in Table 1.

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

[0074] (Average particle size (D50)) The average particle size (D50) was measured using the "Mastersizer3000" laser diffraction / scattering particle size distribution analyzer (manufactured by Malvern).

[0075] (Loose bulk density) The loose bulk density was measured using the following procedure. The loosened bulk density was measured using a Hosokawa Micron PT-X powder tester. The device is equipped with a guidance function, and the jig setup and sample processing were performed according to that guidance. More specifically, using a cup and sieve of known volume provided with or specified for the apparatus, the sieve was placed above the cup, and the spherical alumina particles, which were the measurement sample, were placed on the sieve. The mesh size of the sieve was selected according to the particle size of the sample (a sieve that would not allow the sample to fall through if simply placed on it, but would fall through if the sieve was vibrated). In this case, a sieve with a mesh size of 75 μm was used. The sieve was vibrated up and down with an amplitude of 1 mm to dislodge the sample (spherical alumina particles) from the sieve and fill the cup below. After dropping the sample (spherical alumina particles) into the cup until it overflowed, the sample (spherical alumina particles) was scraped off using the blade (metal plate) attached to the device so that the top edge of the cup and the surface of the sample (spherical alumina particles) were at the same height. The cup filled with the sample (spherical alumina particles) is weighed, and the loosened bulk density is determined using the following formula. (Loose bulk density) = {(Weight of cup filled with sample) - (Weight of cup only)} / (Volume of cup) The above procedure was repeated twice, and the average value of the loosened bulk density was adopted.

[0076] (High bulk density) The bulk density B was measured according to the following procedure. The bulk density was measured using a Hosokawa Micron PT-X powder tester. The device is equipped with a guidance function, and the jig setup and sample processing were performed according to that guidance. More specifically, the apparatus used a cup of known volume, which was either attached to or specified by the device; a cylindrical cap that could be fitted onto the cup (for filling the sample, consisting of spherical alumina particles, up to above the upper rim of the cup); and a sieve. The cap was placed over the cup, the sieve was set above it, and the spherical alumina particles, which were the measurement sample, were placed on the sieve. The mesh size of the sieve was selected according to the particle size of the sample (a sieve that would not allow the sample to fall through if simply placed on it, but would fall through if the sieve was vibrated). In this case, a sieve with a mesh size of 75 μm was used. The sieve was vibrated up and down with an amplitude of 1 mm to dislodge the sample (spherical alumina particles) from the sieve and fill the cup below. After dropping the sample (spherical alumina particles) into the cup until it overflowed, the cup was lifted 18 mm and then dropped again. This tapping operation was performed 180 times at a speed of 60 times per minute to increase the packing density of the sample (spherical alumina particles). After the tapping operation was completed, the cap was removed, and the sample (spherical alumina particles) was scraped off using the blade (metal plate) attached to the device so that the top edge of the cup and the surface of the sample (spherical alumina particles) were at the same height. Cups filled with the sample (spherical alumina particles) were weighed, and the bulk density was determined using the following formula. (Compressed bulk density) = {(Weight of cup filled with sample) - (Weight of cup only)} / (Volume of cup) The above procedure was repeated twice, and the average value of the bulk density was adopted.

[0077] (Degree of compression) When the loose bulk density obtained above is denoted as A and the firm bulk density as B, the value calculated based on {(BA) / B} × 100% was defined as the degree of compression.

[0078] (Angle of repose) The angle of repose was measured as follows: The angle of repose was measured using a Hosokawa Micron PT-X powder tester. The device is equipped with a guidance function, and the jig setup and sample processing were performed according to that guidance. More specifically, a circular table and a sieve, provided for measuring the angle of repose and specified for use with the device, were used. A circular table for measuring the angle of repose was set up, with a sieve mesh placed above it. Spherical alumina particles, which were the measurement sample, were then placed on the sieve mesh. The mesh size of the sieve was selected according to the particle size of the sample (a sieve that would not allow the sample to fall through if simply placed on it, but would fall through if the sieve was vibrated). In this case, a sieve with a mesh size of 75 μm was used. The sieve was vibrated vertically to dislodge the sample (spherical alumina particles) from the sieve, which was then deposited onto a circular table below. The vertical amplitude was 0.5 mm, the vibration time was 170 seconds, and the slowdown time was 10 seconds. The pile of deposited samples (spherical alumina particles) was photographed with a camera while shining blue light from behind, and the angle between the top surface of the circular table and the pile (=angle of repose) was measured. The above procedure was repeated twice, and the average value of the measured angle of repose was adopted.

[0079] [Table 1]

[0080] The spherical alumina particles of Examples A to D have a loose bulk density (g / cm³). 3 The loosened bulk density (g / cm³) of the spherical alumina particles in Comparative Examples 1-3 was 1.80 or higher. 3 The value was less than 1.80.

[0081] The following calculations were made regarding the effects obtained from a looser, higher bulk density. We prepared 1 ton each of the spherical alumina particles for the examples and comparative examples, and assumed a scenario where they were bagged and filled into paper bags for shipment. For the spherical alumina particles of Comparative Example 1, we assumed that each type of spherical alumina particle would be filled into one paper bag with a volume that can hold 25 kg, and the number of paper bags required is shown in Table 2.

[0082] [Table 2]

[0083] In the examples, it was confirmed that the number of paper bag containers required could be reduced due to the higher loose bulk density compared to the comparative example. Furthermore, there were no particular differences in handling the spherical alumina particles in the comparative example and the examples. [Industrial applicability]

[0084] The spherical alumina particles of the present invention can improve transport efficiency without increasing the burden of handling. Furthermore, resin compositions containing these spherical alumina particles can also enjoy the advantages of the spherical alumina particles, such as their good handling properties and high transport efficiency.

[0085] The spherical alumina particles and the resin composite compositions containing them are not limited to semiconductor encapsulation materials but can also be used for other applications. Specifically, they can be used as heat dissipation sheets, heat dissipation adhesives, and the like.

Claims

1. Loose bulk density (g / cm³) ３ Spherical alumina particles characterized in that the ratio of ) is 1.80 or higher.

2. The spherical alumina particles according to claim 1, characterized in that the average particle size is 15.0 to 25.0 μm in the particle size distribution measured by the laser diffraction scattering particle size distribution method.

3. The spherical alumina particles according to claim 2, characterized in that, when the loose bulk density is A and the hard bulk density is B, the compressibility calculated based on {(B-A) / B} × 100% is 25.0% or less.

4. The spherical alumina particles according to claim 3, characterized in that the angle of repose is 30.0° or more and 35.0° or less.

5. A resin composite composition characterized by containing spherical alumina particles as described in any one of claims 1 to 4, and a resin.

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