Spherical aluminum oxide particle mixture and resin composite composition containing same

Abstract

Provided are: a spherical aluminum oxide particle mixture in which, upon limiting the maximum particle diameter in a particle size distribution, the thermal conductivity of a resin composition that is obtained by kneading the spherical aluminum oxide particle mixture with a resin can be improved and viscosity can be suppressed (fluidity can be enhanced); and a resin composition containing the spherical aluminum oxide particle mixture.　Specifically provided are: a spherical aluminum oxide particle mixture characterized in that the average particle diameter (D50) is 0.5-10.0 μm according to the laser diffraction / scattering method, particles of at least 25.0 μm make up no more than 0.04 wt% in a particle size distribution as measured by a wet particle size test, the specific surface area is 0.30-2.00 m2 / g, the circularity is 0.85 or more, and the pregelatinization rate is less than 50.0%; and a resin composition containing the spherical aluminum oxide particle mixture.

Description

Spherical alumina particle mixture and resin composite composition containing the same

[0001] The present invention relates to a spherical alumina particle mixture, particularly a spherical alumina particle mixture having both high thermal conductivity and flowability, and a resin composite composition and resin composite containing the spherical alumina particle mixture.

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

[0003] Generally, heat dissipation sheets, heat dissipation adhesives, and semiconductor encapsulants are composed of thermally conductive inorganic fillers and resins. Thermally conductive inorganic fillers, such as alumina fillers, combine multiple particle sizes to form a particle size distribution. It is known that forming a particle size distribution reduces the gaps between filler particles (porosity), thereby improving fluidity and thermal conductivity.

[0004] Patent Documents 1 to 3 disclose compositions of inorganic particles such as alumina having a particle size distribution that combines multiple particle sizes. In typical examples, the particle size distribution ranges from a few micrometers to a few hundred micrometers.

[0005] On the other hand, in recent years, the gaps between heat-dissipating sheets and adhesives have become smaller. Furthermore, semiconductors have become increasingly miniaturized, narrowing the spacing between the wiring connecting the semiconductor to the outside world. Therefore, when filler mixtures containing coarse particles are used as fillers for heat-dissipating sheets or adhesives, they may not be able to be compressed to the desired thickness. Furthermore, when such coarse filler mixtures are used as encapsulants, the filler cannot pass through the gaps between the wiring, potentially destroying the internal structure of the semiconductor. Therefore, there is a demand for smaller particle sizes for the filler itself.

[0006] Patent Document 4 discloses a spherical amorphous silica powder having a maximum particle size of several micrometers or less, and states that the silica powder satisfies high loading properties, low viscosity characteristics, and high permeability.

[0007] However, amorphous silica has very low thermal conductivity and is therefore unsuitable for sealing modern power semiconductors or for heat dissipation in highly integrated IC chips. Furthermore, the particle size distribution described in Patent Document 4 increases the viscosity of the compound when kneaded with resin, making various molding processes difficult.

[0008] Patent Document 5 proposes using an alumina powder containing predetermined alumina particles as a filler. More specifically, it specifies that the alumina particles have a predetermined particle size distribution, a predetermined particle diameter, and a predetermined moisture content. It states that this provides appropriate fluidity for the resin composition and can suppress wire deformation during semiconductor encapsulation.

[0009] Patent No. 7325670 International Publication No. 2020 / 153505 International Publication No. 2022 / 071140 Patent No. 4112470 International Publication No. 2021 / 200485

[0010] As in Patent Documents 1 to 3, controlling the particle size distribution of particle compositions has been studied to improve fluidity and thermal conductivity. In addition, semiconductor technology is constantly evolving, resulting in increased heat dissipation from semiconductors and further miniaturization. Therefore, as in Patent Document 4, limiting the maximum particle size has also been studied. Furthermore, as in Patent Document 5, there is a proposal to control the water content, etc., in addition to the particle size distribution, to obtain appropriate fluidity. However, there is still a demand for materials with high heat dissipation and fluidity.

[0011] Therefore, an object of the present invention is to provide a spherical alumina particle mixture and a resin composition containing the same, which can improve the thermal conductivity of a resin composition formed when kneaded with a resin and suppress viscosity (increase fluidity), while limiting the maximum particle diameter in the particle size distribution so as to accommodate the miniaturization of semiconductors and the like.

[0012] The present invention has been made as a result of extensive research to solve the above-mentioned problems, and the gist of the present invention is as follows as described in the claims: [1] An average particle size (D50) measured by a laser diffraction scattering method is 0.5 μm or more and 10.0 μm or less, and in the particle size distribution measured by a wet particle size test method, particles of 25.0 μm or more account for 0.04 wt % or less, and a specific surface area of ​​0.30 m ２ / g or more 2.00m ２[1] The spherical alumina particle mixture according to [1], characterized in that the particle size is 1 μm or more and the particle size is 10 μm or less, the circularity is 0.85 or more, and the gelatinization rate is less than 50%. [2] The spherical alumina particle mixture according to [1], wherein, among the number of particles of 1 μm or more and 30 μm or less, the number frequency of particles of 10 μm or more is 100 ppm or less. [3] The spherical alumina particle mixture according to [1] or [2], wherein the water content measured by Karl Fischer coulometry is less than 20 ppm. [4] The spherical alumina particle mixture according to any one of [1] to [3], comprising: spherical alumina particles (a) having an average particle size (D50) of 7.0 μm or more and 10.0 μm or less and a circularity of 0.85 or more; and spherical alumina particles (b) having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more; wherein the spherical alumina particles (a) account for 50 wt % or more and 95 wt % or less of the spherical alumina particles (a); and the spherical alumina particles (b) account for 5 wt % or more and 45 wt % or less of the spherical alumina particles (b); and the total amount of the spherical alumina particles (a) and the spherical alumina particles (b) is 90 wt % or more. [5] The spherical alumina particle mixture according to any one of [1] to [4], comprising: spherical alumina particles (b) having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more; and spherical alumina particles (c) having an average particle size (D50) of 0.4 μm or more and 2.2 μm or less and a circularity of 0.85 or more; the spherical alumina particles (b) are contained in an amount of 50 wt % to 90 wt % and the spherical alumina particles (c) are contained in an amount of 5 wt % to 20 wt %; and the total amount of the spherical alumina particles (b) and the spherical alumina particles (c) is 90 wt % or more.[6] A spherical alumina particle (a) having an average particle size (D50) of 7.0 μm or more and 10.0 μm or less and a circularity of 0.85 or more, a spherical alumina particle (b) having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more, and a spherical alumina particle (c) having an average particle size (D50) of 0.4 μm or more and 2.2 μm or less and a circularity of 0.85 or more, wherein the spherical alumina particle (a) is contained in an amount of 50 wt% to 90 wt%, the spherical alumina particle (b) is contained in an amount of 5 wt% to 20 wt%, and the spherical alumina particle (c) is contained in an amount of 5 wt% to 30 wt%, and the total of the spherical alumina particle (a), the spherical alumina particle (b), and the spherical alumina particle (c) is 90 wt% or more. [1] The spherical alumina particle mixture according to any one of [1] to [5]. [7] A resin composite composition, characterized by containing, in a resin, the spherical alumina particle mixture according to any one of [1] to [6]. [8] The resin composite composition according to [7], further containing at least one inorganic filler selected from amorphous spherical alumina particles, crystalline spherical silica particles, alumina particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers.

[0013] According to one embodiment of the present invention, there is provided a spherical alumina particle mixture and a resin composition containing the same, which can improve the thermal conductivity and suppress the viscosity (increase fluidity) of the resin composition formed when kneaded with a resin, while limiting the maximum particle diameter in the particle size distribution to accommodate the miniaturization of semiconductors, etc. Furthermore, according to one embodiment of the present invention, there is provided spherical alumina particles and a resin composition containing the same, which have a good hue index, and can contribute to improving the design and visibility of products containing them.

[0014] The spherical alumina particle mixture provided by one embodiment of the present invention has an average particle size (D50) of 0.5 μm or more and 10.0 μm or less as measured by a laser diffraction scattering method, and in the particle size distribution measured by a wet particle size test method, particles of 25.0 μm or more account for 0.04% by weight or less, and a specific surface area of ​​0.30 m ２ / g or more 2.00m ２ / g or less, a circularity of 0.85 or more, and a gelatinization rate of less than 50%.

[0015] (Spherical Alumina Particle Mixture) The spherical alumina particle mixture in this embodiment contains a mixture of spherical alumina particles having a plurality of particle sizes, and has the properties described below.

[0016] (Average particle size (D50) measured by laser diffraction scattering method is 0.5 μm or more and 10.0 μm or less) The spherical alumina particle mixture according to one embodiment of the present invention has an average particle size of 0.5 μm or more and 10.0 μm or less. If the average particle size is less than 0.5 μm, the particles will tend to aggregate more, which is undesirable as it significantly reduces the fluidity of the resin composition when used as a filler, etc. If the average particle size exceeds 10.0 μm, the particles may get caught in the narrow space between the mounting substrate and the chip in semiconductor packages, which have become increasingly smaller and thinner, which may reduce the fluidity of the encapsulant and reduce moldability.

[0017] <Measurement of average particle size (D50)> Here, the average particle size refers to the average particle size (D50), and means the median diameter D50 at 50% cumulative volume in a volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method. The laser diffraction / scattering particle size distribution measurement method involves irradiating a dispersion in which a spherical alumina particle mixture is dispersed with laser light, and determining the particle size distribution from the intensity distribution pattern of the diffracted / scattered light emitted from the dispersion. In the present invention, a laser diffraction / scattering particle size distribution measurement device "Mastersizer 3000" (manufactured by Malvern) is used. The average particle size of alumina particles, which are the raw material for the spherical alumina particle mixture, can also be determined in a similar manner.

[0018] (In the particle size distribution measured by a wet particle size test, particles of 25.0 μm or larger are 0.04% by weight or less) In the spherical alumina particle mixture according to this embodiment, particles of 25.0 μm or larger are 0.04% by weight or less. The reason for this will be explained below.

[0019] Spherical alumina particle mixtures are generally mixed with resins and may also be used as semiconductor encapsulants. The semiconductor elements to be encapsulated may have many wires densely wired, and the spacing between the wires may be narrow. If the spherical alumina particle mixture contains more than 0.04 wt % of particles of 25.0 μm or larger in particle size distribution, the particles may not be able to penetrate the narrow spacing between the wires. The weight percentages here are based on the entire spherical alumina particle mixture, i.e., 100 wt %. It is more preferable that the content of particles of 20.0 μm or larger is 0.04 wt % or less.

[0020] Similarly, spherical alumina particle mixtures are generally mixed with resins and used in heat dissipation components such as heat dissipation sheets and heat dissipation adhesives. These heat dissipation components are sometimes used to facilitate heat transfer to another component by being compressed under pressure or the like. If the spherical alumina particle mixture has more than 0.04 wt % of particles of 25.0 μm or more in its particle size distribution, there is a risk that compression will be hindered by the coarse particles of 25.0 μm or more.

[0021] Therefore, in this embodiment, the spherical alumina particle mixture contains 0.04 wt % or less of particles of 25.0 μm or larger so that the particles can be inserted into narrow spaces between wirings or the heat dissipation component can be sufficiently compressed. Alternatively, the particle size distribution does not substantially have a distribution of particles of 25.0 μm or larger. The maximum value of the particle size distribution may be adjusted appropriately depending on the usage environment, such as the wiring spacing and the compression thickness. For example, the maximum value of the particle size distribution may be 20.0 μm, 19.0 μm, or 18.0 μm. In other words, the particle size distribution may contain 0.04 wt % or less of particles of 20.0 μm or larger, 0.04 wt % or less of particles of 19.0 μm or larger, and 0.04 wt % or less of particles of 18.0 μm or larger.

[0022] <Wet Particle Size Test Method> The wet particle size test method is explained below. In this test method, 10 g of the spherical alumina particle mixture to be tested and water are added to a container, and the spherical particles are thoroughly dispersed using ultrasound to create a slurry. The slurry is then transferred onto the mesh of a test sieve and sieved. The particles remaining on the mesh of the test sieve are placed in an appropriate container, and the sample is evaporated to dryness using a hot plate or the like. The weight of the residue is measured, and the proportion of the weight of the sieved particles in 10 g of the spherical alumina particle mixture to be tested is calculated.

[0023] (The alpha conversion rate is less than 50.0%) It is known that the thermal conductivity of alumina varies depending on the crystal system, with α-alumina being the crystal with the highest thermal conductivity. Therefore, the thermal conductivity of the insulating resin composition can be improved by using an alumina powder containing a large amount of α-alumina. In this regard, the higher the alpha conversion rate of the spherical alumina particle mixture itself (the proportion of α-alumina in the crystals contained in the alumina particle mixture), the higher the thermal conductivity of the alumina particle mixture, which is preferable.

[0024] On the other hand, α-alumina is obtained by subjecting a starting material to high-temperature treatment to cause crystal growth, typically by heating aluminum hydroxide or alumina at high temperatures. Heating methods include calcination in a furnace and heating with high-temperature hot water. Furthermore, in order to efficiently obtain α-particles with the desired particle size, it is common to crush or disintegrate the coarsened α-particles after heating. Therefore, α-alumina particles with small particle sizes are often non-spherical particles with low circularity. In other words, it is difficult to select and collect only spherical particles with a desired circularity from small α-alumina particles, and attempting to do so requires high costs.

[0025] The present inventors have found that desired thermal conductivity and excellent fluidity can be obtained by controlling the specific surface area, circularity, and other factors of the spherical alumina particle mixture itself within specific ranges, in addition to the gelatinization rate.

[0026] The upper limit of the gelatinization rate is preferably less than 50.0% from the viewpoint of controlling the specific surface area and the unevenness (or circularity) of the particle surface of the spherical alumina particle mixture and improving its affinity with the resin. This allows the resin composition containing the spherical alumina particle mixture to have sufficiently high thermal conductivity. The gelatinization rate may be appropriately adjusted to obtain a desired thermal conductivity. For example, the upper limit of the gelatinization rate may be set to 45% or less, 40% or less, 38% or less, or 36% or less. The lower limit of the gelatinization rate may be set to 20% or more, or 30% or more. When appropriately adjusting the gelatinization rate to a desired level, the gelatinization rate of the spherical alumina particles to be mixed can be measured in advance, and the desired gelatinization rate can be adjusted by calculating using the measured gelatinization rate and the blending ratio.

[0027] <Measurement of alpha-conversion ratio> The alpha-conversion ratio is measured using a powder X-ray diffractometer. The integrated area of ​​the obtained diffraction peaks is determined, and the ratio of the diffraction peak area derived from alpha-alumina to the total area is analyzed by the Rietveld method. Specifically, an X-ray diffraction pattern is obtained using a D2PHASER manufactured by Bruker in the 2θ range of 10° to 90°. The alpha-conversion ratio is calculated from the obtained pattern by the Rietveld method using a DIFFRAC.TOPAS manufactured by Bruker. During the calculation, analysis is performed assuming the presence of only three types of crystalline phases, alpha-alumina, delta-alumina, and theta-alumina, and the alpha-alumina content is calculated.

[0028] (specific surface area is 0.30 m ２ / g or more 2.00m ２ / g or less) The spherical alumina particle mixture has a specific surface area of ​​0.30 m as measured by the BET method. ２ / g or more 2.00m ２ / g or less.

[0029] The specific surface area of ​​the spherical particles is 0.30 m ２ If the specific surface area of ​​the spherical particles is less than 2.00 m / g, the particles will be less likely to form a close-packed structure, which may reduce the fluidity of the sealing material containing the particles. ２If the particle size exceeds 0.90 m / g, the tendency for particles to aggregate increases, which may reduce the fluidity of the sealing material. ２ / g.

[0030] <BET Method> The specific surface area is measured by the BET method. Typically, the specific surface area is measured by the following procedure. Approximately 5 g of a sample is weighed out and vacuum dried at 250°C for 5 minutes. Next, the sample is placed in an automatic specific surface area measuring device (Macsorb, manufactured by Mountec Co., Ltd.), and the nitrogen gas adsorption amount is measured at a relative pressure P / P0 of 0.291 at a measurement temperature of 77 K using pure nitrogen and a nitrogen-helium mixed gas (mixture ratio: 30% nitrogen, 70% He), and the BET specific surface area is calculated by the single-point method.

[0031] (Circularity of 0.85 or More) The spherical alumina particle mixture in this embodiment is spherical. By spherical, we mean that the spherical alumina particle mixture has a circularity of 0.85 or more. It is preferably 0.9 or more. If the circularity of the alumina particle mixture is less than 0.85, the hardness of the molded body and the viscosity of the liquid mixture obtained by kneading the alumina particle mixture with a resin may be significantly reduced. Particles with low circularity, such as angular particles, are more likely to have flat surfaces on their surfaces than spherical particles. Therefore, when particles come into contact with each other, spherical particles form point contact, whereas particles with low circularity, such as angular particles, form surface contact, which is more likely to generate friction. Therefore, when particles attempt to flow, the angular particles, which have high friction, are less likely to move, resulting in a deterioration in the hardness and viscosity of the molded body. The higher the circularity, the less likely these problems are to occur. Therefore, a higher circularity is preferable, and it may be 0.90 or more, or even 0.91 or more. On the other hand, although the theoretical upper limit of the circularity is 1.0, achieving a circularity of 1.0 is practically difficult. Furthermore, from the viewpoint of controlling the specific surface area and the irregularities on the particle surfaces of the spherical alumina particle mixture and improving affinity with resin, the upper limit of the circularity may be set to 0.99 or less, 0.98 or less, or 0.97 or less. The circularity of the spherical alumina particle mixture (or the spherical alumina particles constituting the spherical alumina particle mixture) can be adjusted using thermal spraying (flame fusion method) or the like. Specifically, it can be adjusted by maintaining the temperature of the flame at or above the melting point of alumina. If the temperature is below the melting point of alumina, the alumina raw material will no longer melt, and the circularity will deteriorate. The flame temperature can be adjusted by, for example, the flow rate of the fuel gas used. It is preferable that the spherical alumina particles constituting the spherical alumina particle mixture have a circularity of 0.85 or more, and more preferably 0.9 or more, regardless of particle size.

[0032] <Measurement of circularity> The circularity can be measured using an electron microscope, an optical microscope, and an image analyzer. For example, Sysmex FPIA. These devices are used to measure the circularity of particles (perimeter of a circle equivalent to the area / perimeter of a projected image of the particle). The circularity of 100 or more particles is measured, and the average value is taken as the circularity of the powder.

[0033] (Among the number of particles of 1 μm or more and 30 μm or less detected by a Coulter counter, the number frequency of particles of 10 μm or more is 100 ppm or less) In one embodiment of the present invention, the spherical alumina particle mixture may have a number frequency of particles of 10 μm or more of 100 ppm or less among the number of particles of 1 μm or more and 30 μm or less detected by a Coulter counter.

[0034] The Coulter Counter, which will be described in detail later, measures particles using an electrical resistance method known as the Coulter principle, and is free from errors in particle surface morphology, internal structure, refractive index, color, etc., which are seen in optical measurement methods, resulting in high measurement accuracy. In particular, the particle size obtained by this method can be expressed as a number distribution (particles / ml and particles / g), enabling precise control of particle size distribution.

[0035] For example, 100 ppm or less means that, when there are 100,000 particles of 1 μm or more and 30 μm or less, the number of particles of 10 μm or more is 10 or less. If the number frequency of coarse particles of 10 μm or more exceeds 100 ppm, such coarse particles may clog the narrow spaces between the mounting substrate and the chip, reducing fluidity and, as a result, increasing the defect rate of semiconductor products filled with such particles.

[0036] The higher the number frequency of coarse particles of 10 μm or more, the better the fluidity, which is preferable. On the other hand, as mentioned above, a large number of coarse particles increases the defect rate of semiconductor products. Therefore, the number frequency may be 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, or 10 ppm or less. The number frequency of coarse particles of 10 μm or more may be 0 ppm, but completely eliminating the coarse particles, i.e., achieving 0 ppm, may be difficult due to the large burden on production management, so the number frequency may be set to several ppm, specifically 1 ppm or more, 2 ppm or more, 3 ppm or more, 4 ppm or more, or 5 ppm or more. The lower limit of the number frequency may be adjusted depending on the actual application and the allowable range of the target yield.

[0037] Classification may be performed to obtain a desired particle size distribution. Classification may be performed by a conventionally known method, such as a method of separating coarse particles and fine particles using a sieve with a predetermined mesh size and / or a precision air classifier. In classification control, the number frequency may be measured using a Coulter counter, and precise control of the particle size distribution can contribute to excellent properties of the spherical alumina particle mixture, such as fluidity.

[0038] <Measurement by Coulter Counter> A Coulter counter measures particles using an electrical resistance method known as the Coulter principle, which allows for high measurement accuracy without errors in particle surface morphology, internal structure, refractive index, color, etc., which are seen in optical measurement methods. In particular, the particle size obtained by this method can be expressed as a number distribution (particles / ml and particles / g), allowing for precise control of particle size distribution.

[0039] Specifically, a spherical alumina particle mixture (sample) and 150 mL of electrolyte were placed in a 200 mL glass beaker and dispersed for 30 seconds using an ultrasonic homogenizer (ULTRA SONIC HOMOGENIZER UH-300, manufactured by SMT Corporation). This dispersion was then added to electrolyte prepared in another beaker to adjust the concentration. The concentration-adjusted dispersion was measured using a Coulter counter (Multisizer 3, manufactured by Beckman Coulter) with an aperture diameter of 50 μm to measure the particle size of each particle in the spherical alumina particle mixture. The number of particles measured per measurement was approximately 100,000, and the same sample was measured three times. The number of particles with a particle size of 10 μm or more was calculated and used as the coarse particle frequency (ppm) relative to the total number of particles measured.

[0040] (Water content of less than 20 ppm as measured by Karl Fischer coulometry) In one embodiment of the present invention, the spherical alumina particle mixture may have a water content of less than 20 ppm as measured by Karl Fischer coulometry (hereinafter also simply referred to as "water content").

[0041] Karl Fischer coulometry, the details of which will be described later, is a known method for quantifying water by utilizing the Karl Fischer reaction (in which iodine reacts with water in amounts of one mole).

[0042] The lower the water content measured by Karl Fischer coulometry, the more suppressed the aggregation of particles, which improves the dispersibility of the filler when mixed into the resin. Therefore, the water content is preferably less than 20 ppm, more preferably 15 ppm or less, even more preferably 10 ppm or less, and even more preferably less than 10 ppm.

[0043] Karl Fischer Coulometry Karl Fischer Coulometry is a known method for quantifying water using the Karl Fischer reaction (in which iodine reacts with water in 1 mole increments). In coulometric titration, iodine ions in the anolyte of an electrolytic cell are electrolyzed to generate iodine. Iodine is generated in proportion to the amount of electricity, and since iodine and water react in a 1:1 ratio, the amount of water can be determined from the amount of electricity required for titration.

[0044] As a specific example, the spherical alumina particle mixture is placed in a Karl Fischer moisture meter for coulometric measurement (manufactured by Nitto Seiko Analytech Co., Ltd., CA-200 (measuring device), VA-122 (vaporizer)), heated from 25°C to 500°C, and held at 500°C until it is confirmed that no moisture generation is observed.The temperature is then further raised, and the amount of moisture generated is measured at 500°C or higher and 900°C or lower.

[0045] (Blending of Spherical Alumina Particle Mixture) A spherical alumina particle mixture can be obtained by blending spherical alumina particles having different average particle sizes. By appropriately adjusting the blending ratio depending on the properties (specific surface area, gelatinization rate, etc.) of the spherical alumina particles to be blended, the spherical alumina particle mixture itself can have the desired properties.

[0046] The spherical alumina particles to be blended may be spherical alumina particles (a) to (c) having the following average particle sizes. Spherical alumina particles (a): spherical alumina particles having an average particle size (D50) of 7.0 μm or more and 10.0 μm or less and a circularity of 0.85 or more. Spherical alumina particles (b): spherical alumina particles having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more. Spherical alumina particles (c): spherical alumina particles having an average particle size (D50) of 0.4 μm or more and 2.2 μm or less and a circularity of 0.85 or more. The spherical alumina particles (a) to (c) can be classified in descending order of average particle size. For convenience, the spherical alumina particles (a) to (c) may also be referred to as large particles (or coarse powder), medium particles (or medium powder), and fine particles (or fine powder), respectively.

[0047] <Measurement of average particle size> The average particle size of alumina particles was measured by a laser diffraction / scattering method. A Malvern MS3000 was used as the device, and measurements were performed using water as a dispersion medium. The average particle size referred to in this specification is called the median diameter unless otherwise specified. The particle size distribution is measured by a method such as laser diffraction, and the particle size at which the cumulative frequency of the particle size is 50% is defined as the average particle size (D50).

[0048] The spherical alumina particle mixture preferably contains at least two types selected from the group consisting of the spherical alumina particles (a) to (c). The spherical alumina particles (a) to (c) have different average particle sizes, and particles with smaller average particle sizes can enter the gaps between particles with larger average particle sizes, improving the thermal conductivity of the gaps. This is because heat can be transferred not through the gaps, i.e., the spaces, but through the small particles that have entered.

[0049] Furthermore, since the spherical alumina particles (a) to (c) all have a circularity of 0.85 or more, the spherical alumina particle mixture obtained by blending these particles can also have a circularity of 0.85 or more. By having a circularity of 0.85 or more, it is possible to avoid a significant deterioration in the hardness of a molded body obtained by kneading the alumina particle mixture with a resin and in the viscosity of a liquid kneaded product, as described above.

[0050] The compounding ratio (composition ratio) of the spherical alumina particles (a) to (c) can be adjusted appropriately so that the spherical alumina particle mixture itself can have the desired properties. As typical compounding ratios, the following compounding ratios (composition ratios) 1 to 3 may be used.

[0051] Blending ratio 1: Contains 50% by weight or more and 95% by weight or less of spherical alumina particles (a) and 5% by weight or more and 45% by weight or less of spherical alumina particles (b), and the total of the spherical alumina particles (a) and the spherical alumina particles (b) is 90% by weight or more. Preferably, the total of the spherical alumina particles (a) and the spherical alumina particles (b) is 95% by weight or more, more preferably 98% by weight or more, and even more preferably 100% by weight. To obtain desired properties, the spherical alumina particles (a) may be 55% by weight or more, or 60% by weight or more, and 85% by weight or less, or 80% by weight or less; and the spherical alumina particles (b) may be 10% by weight or more, 20% by weight or more, or 30% by weight or more, and 35% by weight or less, or 30% by weight or less.

[0052] Blending ratio 2: The spherical alumina particles (b) are contained in an amount of 50% by weight or more and 90% by weight or less, and the spherical alumina particles (c) are contained in an amount of 5% by weight or more and 20% by weight or less, and the total amount of the spherical alumina particles (b) and the spherical alumina particles (c) is 90% by weight or more. Preferably, the total amount of the spherical alumina particles (b) and the spherical alumina particles (c) is 95% by weight or more, more preferably 98% by weight or more, and even more preferably 100% by weight. To obtain desired properties, the spherical alumina particles (b) may be 55% by weight or more, or 60% by weight or more, and 85% by weight or less, or 80% by weight or less; and the spherical alumina particles (c) may be 10% by weight or more, or 12% by weight or more, and 18% by weight or less, or 16% by weight or less.

[0053] Blending ratio 3: Contains 50% by weight or more and 90% by weight or less of spherical alumina particles (a), 5% by weight or more and 20% by weight or less of spherical alumina particles (b), and 5% by weight or more and 30% by weight or less of spherical alumina particles (c), and the total of the spherical alumina particles (a), the spherical alumina particles (b), and the spherical alumina particles (c) is 90% by weight or more. Preferably, the total of the spherical alumina particles (a), the spherical alumina particles (b), and the spherical alumina particles (c) is 95% by weight or more, more preferably 98% by weight or more, and even more preferably 100% by weight. In order to obtain the desired properties, the amount of the spherical alumina particles (a) may be 55% by weight or more, or 60% by weight or more, and 85% by weight or less, or 80% by weight or less; the amount of the spherical alumina particles (b) may be 10% by weight or more, or 12% by weight or more, and 18% by weight or less, or 15% by weight or less; and the amount of the spherical alumina particles (c) may be 10% by weight or more, 12% by weight or more, or 15% by weight or more, and 25% by weight or less, or 20% by weight or less.

[0054] The spherical alumina particle mixture blended in the above blending ratios 1 to 3 can have desired properties such as specific surface area. More specifically, the specific surface area of ​​the spherical alumina particle mixture itself is 0.30 m ２ / g or more 2.00m ２ / g or less, preferably 0.90m ２ / g or less.

[0055] The effects of blending each particle with the above blending ratios 1 to 3 are shown below.

[0056] The inventors have confirmed that the blending ratio of the alumina spherical particles (a) has two effects: forming a heat transfer path through the filler and reducing viscosity. This is because a low blending ratio of the alumina spherical particles (a) results in a relatively large amount of small particles, forming heat transfer paths due to contact between the small particles and reducing thermal conductivity. Furthermore, the specific surface area unnecessarily increases, causing a deterioration in viscosity. Furthermore, an excessive blending ratio of the alumina spherical particles (a) results in a relatively small amount of small particles, which tends to form large gaps between the filler particles, causing the resin to be trapped in these gaps and resulting in a deterioration in viscosity.

[0057] The blending ratio of spherical alumina particles (b) has the effect of filling the large gaps between large particles, increasing the number of contact points between fillers, and improving thermal conductivity. Since the specific surface area of ​​spherical alumina particles (b) is smaller than that of spherical alumina particles (c), increasing the blending amount has almost no adverse effect on viscosity. However, when blended in amounts exceeding a certain level, the gaps between the large spherical alumina particles (a) are almost completely filled, and the excess medium-sized spherical alumina particles (b) increase the specific surface area, worsening viscosity.

[0058] The spherical alumina particles (c) have the effect of adjusting the specific surface area of ​​the spherical alumina particle mixture itself and filling small gaps, thereby reducing viscosity. However, as mentioned above, if the compounding ratio is too high, the specific surface area becomes too large, which causes the viscosity to deteriorate.

[0059] In the blending ratios 1 to 3, particles other than those constituting the compositions constituting the blending ratios 1 to 3 (hereinafter referred to as "other particles") may be contained to the extent that the blending effect of each of the spherical alumina particles (a) to (c) or the properties of the spherical alumina mixture blended at the blending ratios 1 to 3 are not impaired. As the other particles, known inorganic particles can be used, and examples thereof include CaCO ３ , BaSO ４Examples of suitable inorganic fillers include talc, mica, kaolin clay, wollastonite, sepiolite, hydrotalcite, montmorillonite, potassium titanate, aluminum borate, silica, titanium oxide, zinc oxide, alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, boron nitride, aluminum nitride, carbon black, and graphite. Preferred are silica, zinc oxide, alumina, magnesium oxide, boron nitride, and aluminum nitride, which are expected to have excellent dimensional stability or thermal conductivity when formed into a resin composite, and more preferred is alumina.

[0060] From the viewpoint of not impairing the properties of the spherical alumina mixture, the amount of other particles to be blended is preferably 10% by weight or less of the spherical alumina mixture, or less than 10% by weight, more preferably less than 5% by weight, even more preferably less than 2% by weight, and even more preferably 0% by weight.

[0061] The average particle size D50 of the other particles is not limited as long as it is within a range that does not impair the properties of the spherical alumina mixture, but is preferably 0.1 to 150 μm.

[0062] (Raw material for spherical alumina particles) The raw material for spherical alumina particles is alumina powder, aluminum hydroxide powder, etc. Metallic aluminum may also be used.

[0063] (Method for Producing Spherical Alumina Particles) Spherical alumina particles can be produced by a flame fusion method or a VMC method. The flame fusion method is a known thermal spraying method in which raw material particles are sprayed into a flame to spheroidize the raw material. The average sphericity can be adjusted by adjusting the amount of material fed into the flame per unit time and the type of fuel gas. The particle size of the spherical alumina particles can also be adjusted by adjusting the particle size of the raw material powder used. The α-alumina content can be increased by maintaining a high temperature in the melting furnace. From the viewpoint of promoting crystal growth of α-alumina, the temperature in the melting furnace is preferably 1200°C or higher. The content can also be reduced by rapidly cooling the spherical particles immediately after solidification with a refrigerant such as air or water. While the refrigerant is not particularly limited, distilled water or ion-exchanged water, which does not contain air or impurities such as sodium ions or chlorine ions, is preferred from the viewpoint of not reducing the purity of the spherical particles.

[0064] The VMC method is a method in which a chemical flame is formed by a burner in an oxygen-containing atmosphere, and a metal powder is introduced into the chemical flame in an amount sufficient to form a dust cloud, causing a deflagration to produce spherical oxide particles.The VMC method (deflagration method) allows a metal material such as aluminum to react with oxygen to produce metal oxides such as alumina.

[0065] The 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 be passed through a sieve with a specified mesh size or using an air classifier to remove particles of 10.0 μm or larger and classify particles of the desired average particle size. There are no particular restrictions on the mesh size used, as long as it is 10.0 μm or smaller.

[0066] (Mixing) A spherical alumina particle mixture can be obtained by mixing spherical alumina particles of a plurality of particle sizes. Mixing is performed by a known method such as a rocking mixer, a V-type mixer, or an air blender. During mixing, the mixing conditions may be appropriately adjusted to avoid a decrease in the circularity of the spherical alumina particles, resulting in a spherical alumina particle mixture with a desired circularity. Typically, the mixing time, the mixed density, and the like may be adjusted.

[0067] It is difficult to measure the thermal conductivity and fluidity (viscosity) of the spherical alumina particle mixture itself. Therefore, for thermal conductivity, the thermal conductivity of a resin composition obtained by mixing the spherical alumina particle mixture with a resin under specified conditions is measured, and the thermal conductivity of the spherical alumina particle mixture is evaluated based on the measurement results. Furthermore, for fluidity (viscosity), the fluidity (viscosity) of a resin composition obtained by mixing the spherical alumina particle mixture with a resin under specified conditions is measured, and the fluidity (viscosity) of the spherical alumina particle mixture is evaluated based on the measurement results.

[0068] <Measurement of Thermal Conductivity> More specifically, the thermal conductivity is measured by the following procedure. 92 parts by mass of the spherical alumina particle mixture, 4 parts by mass of silicone resin A (CY-52-276A manufactured by Toray Dow Corning Co., Ltd.), and 4 parts by mass of silicone resin B (CY-52-276B manufactured by Toray Dow Corning Co., Ltd.) are mixed in a vacuum kneader, and the resulting resin composition is poured into a mold and molded under heat and pressure to a desired thickness. The molding conditions are a pressure of 6 MPa and a temperature of 120°C for 1 hour. After heating, the molded sheet is removed from the mold and post-heated in a dryer at 140°C. The post-heated sheet is then cooled. The prepared sheet is cut into 20 mm squares and molded under a pressure of 1.25 kgf / cm using the ASTM-D5470 method. ２The thermal conductivity is measured under the following conditions. In an example using a spherical alumina particle mixture according to this embodiment, when the filler is at its maximum filling amount, the lower limit of the thermal conductivity may be 2.40 W / m·K, 2.60 W / m·K, 2.80 W / m·K, 3.00 W / m·K, 3.10 W / m·K, 3.20 W / m·K, 3.30 W / m·K, 3.40 W / m·K, or 3.50 W / m·K. On the other hand, the upper limit of the thermal conductivity may be 8.00 W / m·K, 4.00 W / m·K, or 3.50 W / m·K. Furthermore, when the maximum filler filling amount is 91 wt%, the lower limit of the thermal conductivity may be 2.9 W / mK, preferably 3.0 W / mK. On the other hand, the upper limit of the thermal conductivity may be 3.5 W / mK.

[0069] <Maximum Filler Loading Amount> The maximum filler loading amount can be determined as follows. A spherical alumina particle mixture and silicone resin A (CY-52-276A manufactured by Toray Dow Corning Co., Ltd.) blended at a given ratio are vacuum kneaded at an arbitrary blending ratio, and visual inspection is performed to determine whether any unblended filler (spherical alumina particle mixture) remains in the blend. If the visual inspection reveals that no filler remains, it is assumed that the filler has been successfully loaded into the resin, and the maximum filler loading amount is determined by increasing the amount of filler blended until it can no longer be loaded. A filler with a higher maximum filler loading amount can be loaded with a smaller amount of resin, and therefore can be said to have good loading properties.

[0070] <Flow Rate Measurement> The flow rate is measured using the following procedure. 87 parts by mass of the spherical alumina particle mixture and 13 parts by mass of epoxy resin (Epicoat 801N) are mixed in a kneader, and the resulting resin composition is cooled in a water bath for 60 minutes. Then, the flow rate is measured using a Shimadzu CFT-500D flow tester. Approximately 10 ml of the kneaded sample is extruded through a die with a diameter of 2.0 mm and a length of 75.0 mm at a temperature of 28.5°C. The extrusion load is 50.0 kgf, and the discharge rate (ml / sec) is measured from the time when approximately 50% of the sample has been extruded to the time when 75% has been extruded. In an example using the spherical alumina particle mixture according to this embodiment, the lower limit of the flow rate may be 0.2 ml / sec, preferably 0.40 ml / sec. Meanwhile, the upper limit may be 1.0 ml / sec. This is because a flow rate that is too low can cause poor sealing when used as a sealing material. Furthermore, when used as a liquid heat dissipation material such as an adhesive or grease, the lack of fluidity can lead to poor workability. On the other hand, if the flow rate is too high, when used as a sealing material, the material can leak from gaps in the mold, causing burrs. When used as a liquid heat dissipation material, the material can leak from the object to be coated, leading to poor workability.

[0071] (Hue Index (L* Value) / (C* Value) is 100 or More and 300 or Less) The spherical alumina particle mixture according to one embodiment of the present invention preferably has a hue index of 100 or more and 300 or less. This can contribute to improving the design and visibility of products containing the spherical alumina particle mixture.

[0072] The hue index is defined as the ratio of the lightness (L*) value to the chroma (C*) value, i.e., (L* value) / (C* value). The lightness (L*) value and the chroma (C*) value are determined in accordance with JIS Z8729. The L* value and the C* value are indices used to represent the color of an object to be measured according to the L*a*b* color system (CIE 1976). In this color system, the L* value represents lightness, the C* value represents chroma, and the a* value and b* value are used to calculate the hue index using the formula (a ２ +b ２ ) １／２ It is expressed as:

[0073] The lightness L* value indicates that the whiteness of the hue of the measured substance increases as the value increases, and the blackness increases as the value decreases. The saturation C* value indicates that the color of the measured substance is more vivid as the value increases. On the other hand, a small C* value indicates that the measured substance is close to an achromatic color with no color tint.

[0074] The chroma C* value is expressed using the a* value and the b* value. The a* value and the b* value are called chromaticness indices and represent the direction of the color. The a* value is based on 0, and a negative value indicates an increase in greenness in the hue of the measured substance, and a positive value indicates an increase in redness. The b* value is based on 0, and a negative value indicates an increase in blueness in the hue of the measured substance, and a positive value indicates an increase in yellowness. When both the a* value and the b* value are 0, the result is an achromatic color with no hue. The C* value represents chroma and is calculated using the formula (a ２ +b ２ ) １／２ It is expressed as:

[0075] The alumina particle mixture according to one embodiment of the present invention preferably has a hue index (L* value) / (C* value) of 100 or more and 300 or less. This generally corresponds to a high lightness L* value and a low chroma C* value. The higher the lightness (L*), the higher the whiteness and brilliance, which can contribute to improving the design and visibility of products containing the alumina particle mixture. On the other hand, the lower the chroma (C*), the less likely it is to interfere with the color of the color pigment contained in the final product.

[0076] The hue index (L* value) / (C* value) may be adjusted appropriately depending on the design and visibility desired in a product containing the alumina particle mixture. For example, the upper limit of the hue index (L* value) / (C* value) may be set to 250 or less, or 200 or less. The lower limit of the hue index (L* value) / (C* value) may be set to 130 or more, or 160 or more. When adjusting the hue index (L* value) / (C* value) appropriately, the hue index (L* value) / (C* value) of the spherical alumina particles to be mixed can be measured in advance, and the desired hue index (L* value) / (C* value) can be adjusted by adjusting the compounding ratio.

[0077] <Method of measuring lightness (L*) and chroma (C*)> Lightness (L*) and chroma (C*) are measured using a whiteness meter (Nippon Denshoku, NW-12). Specifically, the lightness (L*) value, ＊ value, b ＊ The value was measured, and the chroma (C*) was ２ +b ２ ) １／２ Calculated as follows.

[0078] (Resin composite composition containing a spherical alumina particle mixture) One aspect of the present invention provides a resin composite composition containing a spherical alumina particle mixture. Furthermore, a resin composite can be produced by curing the resin composite composition. The composition of the resin composite composition will be described in more detail below.

[0079] A slurry composition containing a spherical alumina particle mixture and a resin can be used to obtain a resin composite composition such as a semiconductor encapsulant, an interlayer insulating film (including a heat dissipation sheet or a heat dissipation adhesive), etc. Furthermore, by curing these resin composite compositions, a resin composite such as an encapsulant (cured product), a substrate for a semiconductor package, etc. can be obtained.

[0080] When producing the resin composite composition, for example, in addition to the spherical alumina particle mixture and resin, a curing agent, a curing accelerator, a flame retardant, a silane coupling agent, etc. are blended as needed, and the resulting mixture is composited by a known method such as kneading, etc. Then, the resulting mixture is molded into pellets, films, etc. depending on the intended use.

[0081] Furthermore, when producing the resin composite composition, in addition to the spherical alumina particle mixture of one embodiment of the present invention and the resin, other inorganic fillers may be blended. Examples of the inorganic fillers include amorphous spherical alumina particles, crystalline spherical silica particles, alumina particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers. The blending ratio of the inorganic fillers can be adjusted appropriately depending on the application of the resin composite composition, but from the viewpoint of exerting the effects of the spherical alumina particle mixture of the present invention, it is preferable that the blending ratio of the spherical alumina particle mixture to the other inorganic fillers is 95:5 to 60:40.

[0082] Furthermore, when the resin composite composition is cured to produce a resin composite, for example, the resin composite composition can be melted by applying heat, processed into a shape according to the intended use, and then completely cured by applying heat higher than that used for melting. In this case, known methods such as transfer molding and compression molding can be used.

[0083] For example, when manufacturing semiconductor-related materials such as package substrates and interlayer insulating films, known resins can be used as the resin for the resin composite composition, but epoxy resins are preferred. The epoxy resin is not particularly limited, but examples include bisphenol A epoxy resins, bisphenol F epoxy resins, biphenyl epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, naphthalene epoxy resins, and phenoxy epoxy resins. One of these resins can be used alone, or two or more resins with different molecular weights can be used in combination. Among these, epoxy resins having two or more epoxy groups per molecule are preferred from the viewpoints of curability, heat resistance, and the like. Specific examples include biphenyl-type epoxy resins, phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, epoxidized novolac resins of phenols and aldehydes, glycidyl ethers of bisphenol A, bisphenol F, bisphenol S, etc., glycidyl ester acid epoxy resins obtained by reacting polybasic acids such as phthalic acid or dimer acid with epochlorohydrin, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified 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 per molecule, bisphenol A-type epoxy resins are particularly preferred.

[0084] Furthermore, resins other than epoxy resins can also be used as resin composite compositions for applications other than semiconductor encapsulation composite materials, such as prepregs for printed circuit boards and various engineering plastics. Specific examples of resins that can be used in addition to epoxy resins include silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimides, polyamideimides, and polyetherimides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins.

[0085] The curing agent used in the resin composite composition may be any known curing agent for curing the resin, such as a phenol-based curing agent, such as a phenol novolac resin, an alkylphenol novolac resin, or a polyvinylphenol, which may be used alone or in combination.

[0086] The amount of the phenolic curing agent blended is preferably such that the equivalent ratio to the epoxy resin (phenolic hydroxyl group equivalent / epoxy group equivalent) is 0.1 or more and less than 1.0, thereby eliminating any unreacted phenolic curing agent from remaining and improving moisture absorption and heat resistance.

[0087] The amount of the spherical alumina particle mixture of the present invention added to the resin composite composition is preferably large from the viewpoints of heat resistance and thermal expansion coefficient, but is typically 70% by mass to 95% by mass, preferably 80% by mass to 95% by mass, and more preferably 85% by mass to 95% by mass. This is because if the amount of the alumina particle mixture is too small, it is difficult to obtain effects such as improving the strength of the sealing material and suppressing thermal expansion, and conversely, if the amount is too large, segregation due to aggregation of the alumina particle mixture is likely to occur in the composite material regardless of the surface treatment of the alumina particle mixture, and the viscosity of the composite material will also become too high, making it difficult to use as a sealing material.

[0088] In addition to the resin, known additives such as a silane coupling agent, a curing agent, a colorant, and a hardening retarder can be used.

[0089] As for the silane coupling agent, any known coupling agent may be used, but those having an epoxy-based functional group are preferred.

[0090] A slurry composition containing a spherical alumina particle mixture and a resin can be used to obtain a heat-dissipating sheet, a heat-dissipating adhesive (also sometimes called heat-dissipating grease), and the like.

[0091] To obtain the heat dissipation sheet, the spherical alumina particle mixture, resin, and additives are appropriately blended and compounded by a known method such as kneading, etc. The resulting composite is molded into a sheet by a known method.

[0092] For example, when producing a heat dissipation sheet, known resins can be used in the resin composite composition, including silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimides, polyamideimides, and polyetherimides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. Among these, silicone resins are preferred. The silicone resin is not particularly limited, but examples include peroxide-curable, addition-curable, condensation-curable, and ultraviolet-curable resins.

[0093] In addition to the resin, known additives such as a silane coupling agent, a curing agent, a colorant, and a hardening retarder can be used.

[0094] When obtaining the thermally conductive adhesive or thermally conductive grease, the spherical alumina particle mixture, resin, and additives are appropriately blended and compounded by a known method such as kneading. Here, the resin used in the thermally conductive adhesive or thermally conductive grease is also called the base oil.

[0095] For example, when producing a heat-dissipating adhesive or heat-dissipating grease, known resins can be used in the resin composite composition, and specific examples include silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimide, polyamideimide, and polyetherimide; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, mineral oils, synthetic hydrocarbon oils, ester oils, polyglycol oils, silicone oils, and fluorine oils.

[0096] In addition to the resin, known additives such as a silane coupling agent, a colorant, a thickener, etc. Known thickeners that can be used include calcium soap, lithium soap, aluminum soap, calcium complex, aluminum complex, lithium complex, barium complex, bentonite, urea, PTFE, sodium terephthalamate, silica gel, and organic bentonite.

[0097] The present invention will be described below through examples and comparative examples, but the present invention should not be construed as being limited to the following examples.

[0098] (Examples 1 to 14, Comparative Examples A to G) Alumina particle raw material was introduced into a high-temperature flame formed by LPG and oxygen, and a spheroidizing treatment was performed. Spherical alumina particles were produced by controlling the particle size of the introduced alumina particle raw material. Furthermore, after the temperature in the melting furnace was raised to 1200°C or higher, the cooling rate was controlled to obtain spherical alumina particles with a predetermined alpha conversion rate. The obtained spherical alumina particles were separated into coarse particles and fine particles using a cyclone, and both the coarse particles and the fine particles were passed through a sieve with a desired mesh size, and only the undersieve particles were collected to obtain the spherical alumina particles shown in Table 1. The physical properties of the obtained spherical alumina particles and the silica fine powder used in some of the examples are summarized in Table 1. The spherical alumina particles and silica fine powder shown in Table 1 were mixed at the blending ratios shown in Table 2 to obtain the spherical alumina particle mixtures of Examples 1 to 14 and Comparative Examples A to G.

[0099] Table 2 shows the physical properties of the obtained spherical alumina particle mixture. The moisture content measured by Karl Fischer coulometry was less than 20 ppm in all of Examples 1 to 14. The thermal conductivity at a filler loading of 88 wt % was 1.7 to 2.0 W / m K in all of Examples 1 to 14. The thermal conductivity at the maximum filler loading was 2.4 to 3.0 W / m K in each of Examples 1 to 14.

[0100] The methods for measuring the various physical properties are described below.

[0101] (Average particle size D50) The average particle size (D50) is measured using a laser diffraction / scattering particle size distribution measuring device "Mastersizer 3000" (manufactured by Malvern).

[0102] (Specific Surface Area) The specific surface area is measured by the BET method. Specifically, the specific surface area is measured by the following procedure. Approximately 5 g of a sample is weighed out and vacuum dried at 250°C for 5 minutes. Next, the sample is placed in an automatic specific surface area measuring device (Macsorb, manufactured by Mountec Co., Ltd.), and the nitrogen gas adsorption amount is measured at a measurement temperature of 77 K using pure nitrogen and a nitrogen-helium mixed gas (mixture ratio: 30% nitrogen, 70% He) at a relative pressure P / P0 of 0.291, and the BET specific surface area is calculated by the one-point method.

[0103] (Particle size distribution measured by wet particle size testing method) In the wet particle size testing method, 10 g of spherical alumina particles to be tested and water are added to a container, and the spherical particles are thoroughly dispersed using ultrasound to create a slurry. The slurry is then transferred onto the mesh of a test sieve and sieved. The particles remaining on the mesh of the test sieve are placed in an appropriate container, and the sample is evaporated to dryness using a hot plate or the like. The weight of the residue is measured, and the proportion of the weight of the sieved particles in 10 g of the spherical alumina particle mixture to be tested is calculated.

[0104] (Measurement by Coulter Counter Method) A spherical alumina particle mixture (sample) and 150 mL of electrolyte were placed in a 200 mL glass beaker and dispersed for 30 seconds using an ultrasonic homogenizer (ULTRA SONIC HOMOGENIZER UH-300, manufactured by SMT Corporation). This dispersion was then added to electrolyte prepared in another beaker to adjust the concentration. The concentration-adjusted dispersion was measured using a Coulter counter (Multisizer 3, manufactured by Beckman Coulter) with an aperture diameter of 50 μm to measure the individual particle diameters of the spherical alumina particles. At this time, the number of particles measured per measurement was set to approximately 100,000, and the same sample was measured three times. The number of particles with a particle size of 10 μm or more was calculated and used as the coarse particle frequency (ppm) relative to the total number of particles measured.

[0105] (Gallitic Ratio) The alpha-phase ratio is measured using a powder X-ray diffractometer. The integrated area of ​​the obtained diffraction peaks is determined, and the ratio of the diffraction peak area derived from alpha-alumina to the total area is analyzed by the Rietveld method. Specifically, an X-ray diffraction pattern is obtained using a D2PHASER manufactured by Bruker in the 2θ range of 10° to 90°. The alpha-phase ratio is calculated from the obtained pattern by the Rietveld method using a DIFFRAC.TOPAS manufactured by Bruker. During the calculation, analysis is performed assuming the presence of only three types of crystalline phases, alpha-alumina, delta-alumina, and theta-alumina, and the alpha-alumina content is calculated.

[0106] (Circularity) The circularity is measured using an electron microscope, an optical microscope, and an image analyzer. In the present examples and comparative examples, an FPIA manufactured by Sysmex Corporation was used. 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 of 100 or more particles is measured, and the average value is taken as the circularity of the powder.

[0107] <Flow Rate Measurement> The flow rate was measured using the following procedure. 87 parts by mass of the spherical alumina particle mixture and 13 parts by mass of epoxy resin (Epicoat 801N) were mixed in a kneader, and the resulting resin composition was cooled in a water bath for 60 minutes. The flow rate was then measured using a Shimadzu CFT-500D flow tester. Approximately 10 ml of the kneaded sample was set to a temperature of 28.5°C and extruded through a die with a diameter of 2.0 mm and a length of 75.0 mm. The extrusion load was 50.0 kgf, and the discharge rate (ml / sec) was measured from the point when approximately 50% of the sample had been extruded to the point when 75% had been extruded.

[0108] <Measurement of Thermal Conductivity> Thermal conductivity is measured by the following procedure. 92 parts by mass of the spherical alumina particle mixture, 4 parts by mass of silicone resin A (CY-52-276A manufactured by Toray Dow Corning Co., Ltd.), and 4 parts by mass of silicone resin B (CY-52-276B manufactured by Toray Dow Corning Co., Ltd.) are mixed in a vacuum kneader, and the resulting resin composition is poured into a mold and molded under heat and pressure to a desired thickness. Molding conditions are a pressure of 6 MPa and a temperature of 120°C for 1 hour. After heating, the molded sheet is removed from the mold and post-heated in a dryer at 140°C. The post-heated sheet is then cooled. The prepared sheet is cut into 20 mm squares and molded under a pressure of 1.25 kgf / cm using the ASTM-D5470 method. ２ The thermal conductivity is measured under the following conditions.

[0109] <Measurement of Moisture Content by Karl Fischer Coulometry> The moisture content is measured by Karl Fischer Coulometry according to the following procedure. 0.5 to 1.0 g of the spherical alumina particle mixture is placed in a Karl Fischer moisture meter for coulometry (manufactured by Nitto Seiko Analytech Co., Ltd., CA-200 (measuring device), VA-122 (vaporizer)), heated from 25°C to 500°C, and held at 500°C until it is confirmed that no moisture is being generated. The temperature is then further increased, and the amount of moisture generated is measured at a temperature between 500°C and 900°C.

[0110] The spherical alumina particle mixture within the scope of the present invention has a particle size distribution measured by a wet particle size test method in which particles of 25.0 μm or larger account for 0.04 wt % or less. Furthermore, it has been confirmed that the spherical alumina particle mixture exhibits good fluidity and thermal conductivity. Furthermore, it has been confirmed that the spherical alumina particle mixture exhibits a good color index.

[0111]

[0112]

[0113]

[0114] The spherical alumina particle mixture of the present invention and the resin composite composition containing the same can exhibit good fluidity, thermal conductivity, and a good color index. The spherical alumina particle mixture and the resin composite composition containing the same can be used for other purposes as well, without being limited to semiconductor encapsulation materials. Specifically, they can also be used as heat dissipation sheets, heat dissipation adhesives, etc.

Claims

1. The average particle size (D50) measured by the laser diffraction scattering method is 0.5 μm or more and 10.0 μm or less, and in the particle size distribution measured by the wet particle size test method, particles of 25.0 μm or more are 0.04% by weight or less, and the specific surface area is 0.30 m ２ / g or more 2.00m ２ / g or less; a circularity of 0.85 or more; and a gelatinization rate of less than 50.0%.

2. The spherical alumina particle mixture according to claim 1, wherein the frequency of particles 10 μm or larger among the number of particles 1 μm or larger and 30 μm or smaller as detected by a Coulter counter is 100 ppm or less.

3. The spherical alumina particle mixture according to claim 1, wherein the water content measured by Karl Fischer coulometry is less than 20 ppm.

4. The spherical alumina particle mixture according to claim 1, comprising: spherical alumina particles (a) having an average particle size (D50) of 7.0 μm or more and 10.0 μm or less and a circularity of 0.85 or more; and spherical alumina particles (b) having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more; the spherical alumina particles (a) are contained in an amount of 50 wt% or more and 95 wt% or less; and the spherical alumina particles (b) are contained in an amount of 5 wt% or more and 45 wt% or less; and the total amount of the spherical alumina particles (a) and the spherical alumina particles (b) is 90 wt% or more.

5. The spherical alumina particle mixture according to claim 1, comprising: spherical alumina particles (b) having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more; and spherical alumina particles (c) having an average particle size (D50) of 0.4 μm or more and 2.2 μm or less and a circularity of 0.85 or more; the spherical alumina particle mixture contains 50% by weight or more and 90% by weight or less of the spherical alumina particles (b) and 5% by weight or more and 20% by weight or less of the spherical alumina particles (c); and the total of the spherical alumina particles (b) and the spherical alumina particles (c) is 90% by weight or more.

6. The spherical alumina particle mixture according to claim 1, comprising: spherical alumina particles (a) having an average particle size (D50) of 7.0 μm or more and 10.0 μm or less and a circularity of 0.85 or more; spherical alumina particles (b) having an average particle size (D50) of 2.4 μm or more and 6.0 μm or less and a circularity of 0.85 or more; and spherical alumina particles (c) having an average particle size (D50) of 0.4 μm or more and 2.2 μm or less and a circularity of 0.85 or more; the spherical alumina particle mixture contains 50% by weight or more and 90% by weight or less of the spherical alumina particles (a), 5% by weight or more and 20% by weight or less of the spherical alumina particles (b), and 5% by weight or more and 30% by weight or less of the spherical alumina particles (c); and the total of the spherical alumina particles (a), the spherical alumina particles (b), and the spherical alumina particles (c) is 90% by weight or more.

7. A resin composite composition comprising a resin containing the spherical alumina particle mixture according to any one of claims 1 to 6.

8. The resin composite composition according to claim 7, further comprising at least one inorganic filler selected from the group consisting of amorphous spherical alumina particles, crystalline spherical silica particles, alumina particles, titania particles, magnesia particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers.

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