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

Abstract

Provided are spherical alumina particles having a low metal Al concentration and a small particle diameter, a method for producing the same, and a resin composite composition containing the spherical alumina particles. Spherical alumina particles having a metal Al concentration of 1000 ppm or less, an average particle diameter of 0.3-2.0 [mu] m, a specific surface area of 2.5-5.0 m2 / g, a circularity of 0.80 or more, and an alpha rate of 5.0% or less, a method for producing the same, and a resin composite composition containing the spherical alumina particles.

Description

Technical Field

[0001] The present invention relates to spherical alumina particles, particularly spherical alumina particles having a reduced metal Al concentration, a method for producing the same, and a resin composite composition containing the spherical alumina particles. Background Art

[0002] In recent years, due to the high functionality and high speed of electronic devices such as mobile phones, the heat generated by the electronic components inside the electronic devices has increased. In order for the electronic devices to work properly, it is an important issue to release the generated heat to the outside efficiently. Those used for heat dissipation are called heat sinks and heat dissipation adhesives. They are attached or coated and crimped between the heating element and the heat dissipation fins, so that the gap between the heating element and the heat dissipation fins can be eliminated and the heat can be dissipated efficiently. In addition, the semiconductors inside the electronic components themselves also generate significant heat due to the same high functionality and high speed, and the sealing materials that protect the semiconductors are also required to have heat dissipation properties.

[0003] Generally, heat sinks, heat dissipation adhesives, and semiconductor sealing materials are composed of thermally conductive inorganic fillers and resins. The thermally conductive inorganic fillers use raw materials such as inexpensive aluminum hydroxide, aluminum oxide (hereinafter referred to as alumina), and silicon carbide, boron nitride, and aluminum nitride that are expected to have high thermal conductivity. In particular, aluminum oxide is often used as a thermally conductive inorganic filler because it is inexpensive and chemically stable.

[0004] Thermally conductive inorganic fillers such as alumina are also required to have a small particle size and a spherical shape. This is because the miniaturization and thinning of semiconductor packages such as ICs and CPUs are progressing, and with this, the diameter and pitch of bonding wires are also becoming thinner. In other words, in order to improve the filling property of the narrow part inside the semiconductor, thermally conductive inorganic fillers such as alumina used for semiconductor packaging are also required to have a small particle size and a spherical shape.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6771078

[0008] Patent Document 2: Japanese Patent No. 5036984

[0009] Patent Document 3: Japanese Patent Application Publication No. 2008-120673 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] Several methods are known for producing spherical alumina particles having a small particle size, typically a particle size of 2.0 μm or less.

[0012] As a general method for preparing spherical alumina, a flame melting method using alumina as a raw material can be cited. The raw material alumina is sprayed into a flame, and the surface of the alumina is heated and melted to form a spheroidal shape, but sometimes the molten particles are fixed to each other to form agglomerated particles with a large particle size, and sometimes the desired small particle size particles cannot be obtained.

[0013] Patent Document 1 discloses a method of suppressing the aggregation of alumina by adding silica particles to alumina as a raw material and then performing thermal spraying. However, in this method, it is inevitable that silica particles are mixed into the spherical alumina particles finally obtained.

[0014] Patent Document 2 discloses a method in which a collision plate is disposed at the front end of a thermal spraying burner, and a thermal spraying step is performed after causing raw material aluminum oxide to collide with the collision plate, thereby suppressing aggregation of aluminum oxide.

[0015] Patent document 3 discloses the following method: in the raw material of micronized low-alkali alumina, after the raw material powder is passed through a device with crushing and dispersing functions and dispersed in a carrier gas, it is immediately and continuously introduced into a flame to obtain spherical alumina with an average particle size of less than 1 μm and very few metal impurities. Here, the metal Al concentration of the obtained spherical alumina is <0.010%. However, in this method, the crushed and dispersed particles re-agglomerate due to the trace amount of moisture in the carrier gas, and spherical alumina with a small particle size cannot be obtained. In addition, since the alumina particles contain a large amount of harder α-alumina, there is a concern that the device will be worn when passing through the device with crushing and dispersing functions. In addition, the basic properties of the obtained spherical alumina, such as the specific surface area and circularity, are not clear.

[0016] As a method other than the flame melting method, the deflagration method (VMC method) is also known. Specifically, the metal aluminum powder is dispersed in a gas flow of oxygen and ignited to oxidize it. The metal and oxide are converted into vapor or liquid by utilizing the reaction heat and cooled, thereby obtaining fine aluminum oxide particles with a particle size of, for example, less than 2.0 μm. However, since an explosive reaction is utilized, there is a risk of dust explosion. In addition, part of the metal aluminum does not react, that is, does not change into aluminum oxide, and there is also the possibility that metal aluminum remains. In particular, when the residual metal aluminum is included in a semiconductor package, etc., it may cause a major accident such as a short circuit of the semiconductor. In addition, there is no record or revelation about the residual metal aluminum in Patent Documents 1 and 2.

[0017] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide spherical alumina particles having a low metal Al concentration, a low alpha conversion rate, and a small particle size, a method for producing the same, and a resin composite composition containing the spherical alumina particles.

[0018] Technical means for solving technical problems

[0019] The present inventors have discovered that in a flame melting method, by spraying a raw material containing at least one of alumina, boehmite or aluminum hydroxide having a specified particle size, agglomeration of the raw material particles can be suppressed, and spherical alumina particles with a low metallic aluminum concentration and a small particle size can be obtained.

[0020] Based on the above findings, the gist of the present invention is as follows.

[0021] [1] A spherical aluminum oxide particle,

[0022] The metal Al concentration is below 1000ppm, the average particle size is 0.3-2.0um, and the specific surface area is 2.5-5.0m 2 / g, the circularity is 0.80 or more, and the alpha conversion rate is 5.0% or less.

[0023] [2] The spherical alumina particles according to [1],

[0024] The alpha conversion rate is 1.0% or less.

[0025] [3] A method for producing spherical alumina particles, comprising the following steps:

[0026] A raw material preparation process for preparing a raw material containing at least one of aluminum oxide, boehmite or aluminum hydroxide and having a particle size of 0.2 to 2.0 μm;

[0027] A surface treatment step of treating the surface of the raw material with a surface treatment agent containing silicon atoms; and

[0028] A spheroidizing step is performed in which the surface-treated raw material is put into a flame to be melted and then rapidly cooled to be spheroidized.

[0029] [4] A resin composite composition, characterized in that:

[0030] Contains the spherical alumina particles described in [1] or [2].

[0031] [5] The resin composite composition according to [4],

[0032] It also contains at least one inorganic filler selected from amorphous spherical silica particles, crystalline spherical silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers.

[0033] Effects of the Invention

[0034] According to the present invention, it is possible to obtain spherical alumina particles with a small particle size, a very low alpha conversion rate, and a controlled specific surface area, and a resin composite composition containing the spherical alumina particles. Since they have a small particle size, they can also be used for miniaturized and thinned semiconductor packages, etc., and since the metal aluminum concentration is low, major accidents such as short circuits can be suppressed. In addition, since the alpha conversion rate is very low, the shape of the surface of the alumina particles is generally smooth, which has the advantages of improving fluidity and reducing equipment wear. Furthermore, according to the manufacturing method as one embodiment of the present invention, the spherical alumina particles can be easily manufactured. DETAILED DESCRIPTION

[0035] [Spherical alumina particles]

[0036] (Metal Al concentration)

[0037] The metal Al concentration of the spherical alumina particles as one embodiment of the present invention is 1000ppm or less. Alumina is an oxide of metal Al, which can be manufactured by oxidizing and dehydrating metal Al or an aluminum compound (aluminum hydroxide, etc.) containing the metal Al. In the manufacturing process of alumina, sometimes the metal Al contained in the raw material is not fully oxidized and remains in the product alumina as metal Al. In particular, the deflagration method (VMC method) utilizes an explosive reaction to oxidize metal Al, so it is not uniformly oxidized, that is, it does not change into alumina, and there is a high possibility that metal Al remains. Metal Al is much more conductive than aluminum oxide (aluminum oxide). If metal Al is contained in an application requiring high insulation, such as semiconductor packaging, sometimes unexpected major accidents such as short circuits may occur. From this point of view, the lower the metal Al concentration, the better. Regarding the spherical alumina particles as one embodiment of the present invention, the metal Al concentration is 1000ppm or less, which can suppress the occurrence of major accidents such as short circuits. More preferably, the metal Al concentration can also be 800ppm or less or 700ppm or less. The lower limit of the metal Al concentration is not particularly limited and may be 0 ppm, but since there is a large burden on manufacturing management and it is difficult, it may be several ppm, specifically, 1 ppm or more, 5 ppm or more. The lower limit of the metal Al concentration is also adjusted according to the actual use and the allowable range of the insulation as the purpose, for example, it may be 10 ppm or more, 20 ppm or more, or 30 ppm or more.

[0038] The analysis of the metal Al concentration is performed as follows. About 1 g of the spherical alumina particle sample is weighed and placed in a beaker. 60 ml of 1 mol / L hydrochloric acid is added to the beaker and stirred at room temperature for 5 hours. The supernatant of the stirred sample solution is taken and fixed to 100 ml, and the Al component of the solution is analyzed by ICP-MS.

[0039] (Particle size)

[0040] The average particle size of the spherical alumina particles as one embodiment of the present invention is 0.3 to 2.0 μm. If the particle size is less than 0.3 μm, the agglomeration of the particles becomes greater, and the fluidity of the resin composition when used as a filler is significantly reduced, so it is not preferred. If the particle size exceeds 2.0 μm, in semiconductor packaging that is becoming smaller and thinner, the particles will get stuck in the narrow part between the mounting substrate and the chip, and sometimes the fluidity of the liquid sealing material will deteriorate and the moldability will be reduced.

[0041] Here, the average particle size refers to the average particle size (D50), which means the median particle size D50 at which the cumulative volume is 50% in the volume-based particle size distribution measured by the laser diffraction / scattering particle size distribution measurement method. In addition, the laser diffraction / scattering particle size distribution measurement method is a method of irradiating a dispersion liquid in which spherical aluminum oxide particles are dispersed with laser light and obtaining the particle size distribution based on the intensity distribution pattern of the diffraction / scattered light emitted from the dispersion liquid. In the present invention, the laser diffraction / scattering particle size distribution measurement device uses the "Mastersizer 3000" (manufactured by Malvern). In addition, the average particle size of the raw material of the spherical aluminum oxide particles can also be obtained in the same manner.

[0042] (α-ratio)

[0043] Here, the alpha conversion rate refers to the proportion of α-alumina crystals in the crystalline phase. The alpha conversion rate of the spherical alumina particles as one embodiment of the present invention is 5.0% or less. It is known that alumina is crystalline, and as typical crystalline forms, α-alumina, θ-alumina, and δ-alumina are known. The details of the spherical alumina particles as one embodiment of the present invention will be described later, but it can be manufactured based on a spraying method in which the raw material is put into a flame to melt it and then quenched. In this case, the alumina obtained can increase the proportion of amorphous, and spherical alumina particles with an alpha conversion rate of less than 5.0% can be easily obtained. By controlling within this range, the surface of the alumina particles becomes smooth, the effect of maintaining a high fluidity when mixed with the resin, and the amount of hard α-alumina particles is small, so it is excellent in terms of low equipment wear. On the other hand, if the alpha conversion rate is low, the amount of α-alumina contained in the alumina particles becomes too small, so the thermal conductivity of the particles is reduced, and the thermal conductivity of the resin composition may also be reduced. The lower limit of the alpha conversion rate is not particularly limited and may be 0.0%, but from the perspective of the burden of manufacturing management and the thermal conductivity characteristics of the resin composition, it may be 0.1% or 0.2%. In addition, the upper limit of the alpha conversion rate may be 3.0%, 1.5%, 1.0%, 0.9%, or 0.8%.

[0044] The alpha rate of the alumina particle powder is measured using a powder X-ray diffraction device. The integral area of ​​the obtained diffraction peak is calculated, and for the total, the ratio of the diffraction peak area from α-alumina is analyzed by the Rietveld method. Specifically, the X-ray diffraction pattern is obtained in the range of 2θ of 10° to 90° using D2PHASER manufactured by Bruker. The alpha rate of the obtained pattern is calculated by the Rietveld method using DIFFRAC.TOPAS manufactured by Bruker. When calculating, it is assumed that only three crystalline phases, α-alumina, δ-alumina, and θ-alumina, are present for analysis, and the content of α-alumina is calculated.

[0045] (Specific surface area)

[0046] The specific surface area of ​​the spherical alumina particles of the present invention measured by the BET method is 2.5 m 2 / g above 5.0m 2 / g or less.

[0047] If the specific surface area of ​​spherical particles is less than 2.5m 2 / g, the particles are difficult to form a close-packed structure, so the fluidity of the liquid sealing material containing the particles may decrease. On the other hand, if the specific surface area of ​​the spherical particles exceeds 5.0 m 2 / g, the tendency of particles to aggregate increases, and similarly, the fluidity of the liquid sealing material may decrease. The preferred lower limit is 3.0 m 2 / g. The preferred upper limit is 4.0m 2 / g.

[0048] The specific surface area of ​​spherical particles can also be measured by the BET method. Typically, the specific surface area is measured according to the following procedure.

[0049] About 5 g of the sample was weighed and vacuum dried at 250°C for 5 minutes. Then, the sample was placed in an automatic specific surface area measuring device (Macsorb, manufactured by Mountech), and the nitrogen adsorption amount at a relative pressure P / P0 of 0.291 was measured at a measuring temperature of 77K using pure nitrogen and nitrogen-helium mixed gas (mixing ratio of nitrogen 30% and He 70%), and the BET specific surface area was calculated by the one-point method.

[0050] (Circularity)

[0051] In one embodiment of the present invention, the circularity of the spherical alumina particles may be 0.80 or more.

[0052] The higher the circularity of the spherical particles, the lower the viscosity of the resin composite composition containing the alumina particles, and the better the moldability. The circularity may be 0.85 or more, 0.90 or more, or 0.93 or more. The upper limit of the circularity is theoretically 1.0, but from the perspective of manufacturing management, it may be 0.98 or less or 0.95 or less.

[0053] The circularity can be measured using an electron microscope or an optical microscope and an image analysis device. For example, FPIA manufactured by Sysmex Corporation, etc. These devices are used to measure the circularity of particles (the circumference of the equivalent circle / the circumference of the projected image of the particle). The circularity is measured for more than 100 particles, and the average value is used as the circularity of the powder.

[0054] (Converted powder resistivity)

[0055] The converted powder resistivity of the spherical alumina particles as one embodiment of the present invention may be 3.0×10 9 Ω·cm or more. Alumina particles are sometimes used for applications that require high insulation, such as semiconductor packaging, and the higher the converted powder resistivity, the better. In this regard, the converted powder resistivity of spherical alumina particles can also be 3.1×10 9 Ω·cm or more, 3.2×10 9 Ω·cm or more, 4.0×10 9 Ω·cm or more, 5.0×10 9 Ω·cm or more. The upper limit is not particularly limited and may be 1.0×10 11 Ω·cm or less, 1.0×10 10 Ω·cm or less.

[0056] The converted powder resistivity of alumina particle powder (hereinafter also referred to as "converted powder resistivity") is obtained by multiplying the powder resistivity by the Na2O content of the particles. That is, it is calculated by the formula (converted powder resistivity) = (powder resistivity of alumina particle powder) × (Na2O content of spherical alumina particles). The powder resistivity of alumina particle powder is measured using the powder resistivity measurement system MCP-PD51. As a pretreatment for the measurement, heat and dry it in the atmosphere at 200°C for 5 hours. The dried powder is introduced into the powder resistivity measurement probe unit, and the sample is gradually pressurized using the attached hydraulic pump. When the load reaches 20kN, the measurement is performed using a high resistivity meter.

[0057] (Na2O content)

[0058] The Na2O content of the spherical alumina particles as one embodiment of the present invention may also be 1000ppm or less. In the case where the spherical alumina particles contain Na2O, in the resin composite composition containing the alumina particles, Na2O acts as an impurity and the desired properties may not be obtained. In this regard, the lower the Na2O content, the more preferred it is, and the upper limit of the Na2O content may also be 750ppm or less or 500ppm or less. The lower limit of the Na2O content is not particularly limited and may also be 0ppm, but due to the burden of manufacturing management and the difficulty, it may also be several ppm, specifically, more than 1ppm, more than 5ppm. The lower limit of the Na2O content may also be adjusted according to the actual use and the intended properties, for example, it may be more than 10ppm, more than 20ppm, or more than 30ppm.

[0059] The Na2O content of the spherical alumina particles is measured using an atomic absorption spectrometer. 0.5 g of the sample is added to a pressurized container, 10 ml of sulfuric acid (1+3) is added and the container is covered, and then heated at 230°C for 16 hours in a heating drying furnace. After the heated solution is cooled, the solution is fixed to 100 ml and then measured using an atomic absorption spectrometer. In addition, sulfuric acid (1+3) refers to a solution obtained by diluting 3 pure water with respect to 1 concentrated sulfuric acid by volume.

[0060] (Liquidity)

[0061] The evaluation of the fluidity of the spherical alumina particles as one embodiment of the present invention based on the following measurement method can also be good, that is, 0 (good). The spherical alumina particles can be used as a filler for a resin composite composition, etc. From the perspective of manufacturing management, the fluidity is preferably within an appropriate range. The fluidity varies depending on conditions such as the matrix resin, and as a benchmark, the evaluation benchmark of the fluidity in this specification is shown.

[0062] The evaluation method of fluidity in this specification is as follows. First, measure 30g of spherical alumina particle sample and put it in a bag. Furthermore, measure 70g of AZ10-75 (alumina powder manufactured by Nippon Steel Chemical Materials Co., Ltd., with an average particle size of 10μm) and put it into the bag previously containing the spherical alumina particles. Then, tie the bag and stir and mix thoroughly. Measure 43.5g of the mixed alumina particle mixed powder and put it in a 200ml plastic container. Add 6.5g of silicone resin CY52-276A liquid manufactured by Dow Toray, and vacuum knead it using a vacuum mixer "Degassing Rentaro" manufactured by THINKY. The kneading conditions are implemented with pre-mixing for 15 seconds and vacuum kneading for 90 seconds. After kneading, place the plastic container containing the mixture in a water bath adjusted to 25°C and cool it for 1 hour. 10g of the composite (resin composite composition) prepared by kneading is placed on a plate with a smooth surface. The material of the plate is not particularly limited, and an iron plate is used in this embodiment. The plate on which the composite is placed is tilted 60° relative to the horizontal direction to confirm the fluidity of the composite. In this test, if the composite flows for more than 15 cm after tilting for 5 hours, the fluidity is evaluated as 0 (good), and if the composite does not flow for more than 15 cm, the fluidity is evaluated as × (poor).

[0063] [Method for producing spherical alumina particles]

[0064] In one embodiment of the present invention, a method for producing spherical alumina particles is provided. The method is a method that can suitably produce the alumina particles, and includes the following steps.

[0065] (1) a raw material preparation step of preparing a raw material containing at least one of aluminum oxide, boehmite or aluminum hydroxide and having a particle size of 0.3 to 2.00 μm;

[0066] (2) a surface treatment step of treating the surface of the raw material with a surface treatment agent containing silicon atoms; and

[0067] (3) A spheroidizing step of melting the raw materials by putting them into a flame and then rapidly cooling them into spheroids.

[0068] Although the order of the steps is reversed, the spheroidization step (3) will be described first.

[0069] The spheroidization process of (3) is a process of putting the raw material into a flame to melt it, and then spheroidizing it by rapid cooling. The raw material can be put into the flame in a state of being suspended in a carrier gas. As the carrier gas, air, oxygen, propane gas, etc. can be used. There is no particular limitation on the method for forming the flame, but the fuel (propane, etc.) for forming the flame can be supplied to the burner in a different path from the input of the raw material to form the flame, or the fuel and the combustion-supporting gas (air, oxygen) can be pre-mixed and supplied to the burner to form the flame, or the raw material, fuel, and combustion-supporting gas are mixed and supplied to the burner to form the flame. The formation of the flame is preferably carried out in a heat-resistant furnace. It is preferred to form a flame at the upper part of the heat-resistant furnace, supply the raw material to the flame, and the formed alumina granular material continuously settles due to gravity, and the material is recovered from the bottom. By setting it so that no flame is formed at the bottom of the heat-resistant furnace, the alumina granular material settled at the bottom is rapidly cooled and granulated.

[0070] In the raw material preparation step (1), a raw material to be fed into the spheroidization step (3) is prepared. The raw material contains at least one of alumina, boehmite, or aluminum hydroxide and is prepared to have a particle size of 0.2 to 2.00 μm.

[0071] Boehmite is aluminum oxide monohydrate, represented by the chemical formula of Al2O3·H2O, and aluminum hydroxide is represented by the chemical formula of Al(OH)3. When both are put into the flame in the spheroidization step (3), first, the hydrated component (H2O) or hydroxyl group (OH) in the raw material is separated as water vapor (H2O), and aluminum oxide (Al2O3) particles are generated. At least the surface of the aluminum oxide (Al2O3) particles melts and spheroidizes.

[0072] In addition, when alumina is used as the raw material, examples include: pre-calcined alumina obtained by sintering aluminum hydroxide, alumina obtained by electromelting aluminum hydroxide, low-alkali alumina produced from aluminum hydroxide, and high-purity alumina produced by ammonia alum thermal decomposition method, aluminum alkoxide hydrolysis method, aluminum water discharge method, or other methods. More preferably, alumina obtained by calcining low-alkali aluminum hydroxide is used from the viewpoint of productivity and cost.

[0073] Among the above raw materials, boehmite or aluminum hydroxide contains sufficient moisture (hydrated water, hydroxyl group). Therefore, as described below, the increase in the particle size of the raw material can be particularly effectively suppressed in the spheroidization step, so spherical alumina particles with an average particle size of less than 1 μm can be efficiently obtained, which is more preferred.

[0074] Conventionally, as a method for producing spherical alumina, a method of spheroidizing alumina particles by placing them into a flame is known, but in the spheroidization step, the alumina particles melted on the surface fuse and agglomerate with each other, which sometimes leads to an increase in the particle size of the obtained particles and a decrease in the circularity. However, in the present embodiment, these disadvantages are eliminated.

[0075] First, since the raw material of this embodiment contains water (hydrated water, hydroxyl group), it takes time for water vapor (H2O) to be separated from the entrance of the flame to the middle of the flame. That is, in the flame, the surface of the alumina particles melts, and there is less chance (short time) for the alumina particles to fuse and condense with each other. As a result, the particle size of the alumina particles after passing through the flame is suppressed from being excessively increased compared with the particle size (0.2 to 2.0 μm) of the raw material.

[0076] Furthermore, the water vapor (H2O) separated from the raw material expands by being heated in the flame, and acts in a manner that the remaining raw materials, that is, the distance between the alumina particles becomes larger. That is, the chance of the alumina particles fusing with each other is further reduced. As a result, the particle size of the alumina particles after passing through the flame is suppressed from being excessively increased compared to the particle size of the raw material (0.2 to 2.0 μm). In addition, since the contact between the particles is small, the spheroidization of each particle is also promoted.

[0077] Next, the surface treatment step (2) will be described.

[0078] In the surface treatment step (2), the raw material obtained in the raw material preparation step (1) is surface treated before the spheroidization step (3). As the surface treatment agent for the raw material, silane compounds (silane coupling agents, etc.), silazanes, Al coupling agents, etc. can be used. The treatment amount of the surface treatment agent can be appropriately adjusted according to the material of the raw material, but it is preferred that by adding 1% by mass or more of these surface treatment agents relative to the raw material, it is possible to make the raw material powders difficult to adsorb each other, thereby effectively preventing blockage caused by adhesion to the burner and piping and deviation in the supply amount. In addition, it is possible to effectively prevent the raw material powders from agglomerating with each other and causing coarsening. On the other hand, if the surface treatment agent exists in excess, the treatment agents react with each other, and the particles are cross-linked via the surface treatment agent, so that the original dispersion effect may not be obtained. In addition, from the viewpoint of economic efficiency, it is not preferred to add the treatment agent in excess. The preferred upper limit of the amount of the surface treatment agent is 10% by mass relative to the raw material.

[0079] Among the above-mentioned surface treatment agents, compounds containing silicon atoms such as silane coupling agents, alkoxysilane compounds, and silazane compounds (also referred to as "silicon atom surface treatment agents") are preferred from the viewpoints of economy and reactivity. These silicon atom surface treatment agents can adopt known substances. As silane coupling agents, vinyl trimethoxysilane and N-phenyl-3-aminopropyl trimethoxysilane can be mentioned. As alkoxysilane compounds, hexyl trimethoxysilane and octyl triethoxysilane can be mentioned. Silazane compounds can include hexamethyldisilazane and trimethylsilane. From the viewpoint of excellent reactivity, silazane compounds are more preferred. More preferred are hexamethyldisilazane and trimethylsilane.

[0080] The surface treatment method includes the following first step (heating step) and second step (surface treatment step).

[0081] First step (heating step)

[0082] A raw material powder containing any one of aluminum oxide, aluminum hydroxide, and boehmite is heated at a temperature of 100°C to 500°C for more than 30 minutes. The preferred heating condition may be heating at 150°C or above for 2 hours or 5 hours. By heating the raw material powder in this step, the excess water present on the surface of the powder particles is removed, and the reactivity of the treatment agent and the particle powder can be improved in the surface treatment step of the subsequent step. This is because if water adheres to the surface of the raw material, the attached water reacts with the surface treatment agent, and the surface treatment agent becomes unable to react properly with the raw material. The method for heating the raw material is not particularly limited, and it is preferred to use a method of drying the raw material powder using a commonly used electric drying furnace, tunnel kiln, shuttle kiln, etc. In order to obtain the effect of inhibiting the coarsening of the particle size brought about by the water generated from the raw material during the above-mentioned spheroidization, the drying temperature is preferably 500°C or less. By heating at more than 500°C, the water is completely separated from the aluminum hydroxide or boehmite, and no water is generated during spheroidization. In order to evaporate the water, the lower limit of the drying temperature is preferably 100°C or above. After heating, it can be cooled and used in the next step, or it can be not cooled. It is preferred to carry out the next surface treatment step without cooling.

[0083] Second process (surface treatment process)

[0084] The raw material powder that has been heat-treated in the previous process is put into any mixer and stirred. During stirring, stirring can be performed at room temperature, or heating and stirring can be performed. In order to improve the reactivity of the silane compound, it is preferably heated to above 50°C, more preferably heated to above 80°C and stirred. After stirring for about 30 seconds to 10 minutes, the surface treatment agent is sprayed while stirring. The type of surface treatment agent is as mentioned above, preferably hexamethyldisilazane and trimethylsilane. In addition, regarding the amount of spray, 1 to 5 times the amount calculated based on the minimum coating area of ​​the surface treatment agent, the specific surface area of ​​the raw material powder to be treated, and the input weight (refer to the following formula) can be sprayed.

[0085] Surface treatment dose of spray = (specific surface area of ​​raw material powder) × (weight of raw material powder input) / (minimum coverage area of ​​surface treatment agent)

[0086] The stirring method of the surface treatment agent is not limited, and preferably a mixer such as a commonly used ball mill, a vibration mill, a planetary pulverizer, a jet mill, a mechanical stirring blade mixer, a container rotary mixer, etc. is used to mix the surface treatment agent such as the above-mentioned silane coupling agent in the raw material powder. In addition, the raw material can also be heated during mixing. The heating method is not limited, and the outside of the mixing container can also be covered with a jacket, and heated with steam or heated water, oil, etc. By heating, the reactivity of the surface treatment agent can be improved, and the raw material can be efficiently surface treated.

[0087] Furthermore, before the surface treatment step (2), the raw material may be auxiliary passed through a device having a crushing and dispersing function.

[0088] In the case of a dry method, the device with crushing and dispersing functions includes a jet mill that causes powders to rotate in a high-speed airflow and collide and crush, and a device that causes dust-containing gases to collide with each other in counter-currents to crush powders. In addition, in the case of a wet method, a high-pressure wet jet mill type crushing device that causes slurry to collide and crush, and an ultrasonic dispersion device that can irradiate strong ultrasonic waves into the slurry liquid feeding pipe, etc., can be cited. In the case of the above-mentioned device with crushing and dispersing functions, in order to prevent the aluminum oxide particles from contacting and wearing the metal part of the device, it is preferred to line the powder receiving part of the device. The components for the lining treatment are not particularly limited, and polyurethane, boron carbide, aluminum oxide, silicon carbide, and Teflon (registered trademark) can be cited, but aluminum oxide particles are very hard substances, so aluminum oxide lining is more preferred as a raw material for lining treatment.

[0089] The raw material of this embodiment may contain at least one of boehmite or aluminum hydroxide, which contains more surface OH groups than aluminum oxide, so it is easy to perform surface treatment and its effect is easy to show. That is, the dispersion effect of the raw materials is high, and as a result, it is easier to obtain the desired spherical aluminum oxide particles with a small particle size and high roundness.

[0090] Furthermore, the raw material of the present embodiment may contain components other than boehmite and aluminum hydroxide, for example, aluminum oxide, within a range not affecting the effects of the present invention.

[0091] In addition, the raw material of the present embodiment is adjusted to a particle size equal to or slightly smaller than the alumina particles to be manufactured, that is, 0.2 to 2.0 μm. Preferably, it can be 0.3 μm or more, or 1.9 μm or less. The particle size can also be adjusted to the target particle size by crushing and classification. As described above, in the manufacturing method of the present embodiment, the particle size distribution of the raw material is roughly continued as the particle size distribution of the alumina particle material to be manufactured.

[0092] [Resin composite composition]

[0093] According to one embodiment of the present invention, a composite composition of spherical alumina particles and a resin can be produced. The composition of the resin composite composition is described in detail below.

[0094] The slurry composition containing spherical alumina particles and a resin can be used to obtain a resin composite composition such as a semiconductor sealing material (especially a solid sealing material) or an interlayer insulating film. Furthermore, by curing these resin composite compositions, a resin composite such as a sealing material (cured body) or a semiconductor packaging substrate can be obtained.

[0095] When manufacturing the resin composite composition, for example, in addition to the spherical alumina particles and the resin, a curing agent, a curing accelerator, a flame retardant, a silane coupling agent, etc. are added as needed, and the composite is prepared by a known method such as kneading. Then, the composite is formed into a granular form, a film form, etc. according to the application.

[0096] In addition, when manufacturing the resin composite composition, in addition to the spherical alumina particles and the resin, other inorganic fillers may be mixed. Examples of the inorganic filler include amorphous spherical silica particles, crystalline spherical silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers. The mixing ratio of the inorganic filler can be appropriately adjusted according to the use of the resin composite composition, but from the viewpoint of showing the effect of the spherical alumina particles of the present invention, it is preferably (mixed weight of spherical alumina particles): (mixed weight of other inorganic fillers) = 95:5 to 60:40.

[0097] Furthermore, when the resin composite composition is cured to produce a resin composite, for example, the resin composite composition is melted by applying heat, processed into a shape corresponding to the application, and completely cured by applying heat higher than that when melted. In this case, a known method such as transfer molding can be used.

[0098] For example, in the case of manufacturing semiconductor-related materials such as a substrate for packaging or an interlayer insulating film, as the resin used in the resin composite composition, a known resin can be used, but an epoxy resin is preferably used. The epoxy resin is not particularly limited, and 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 them, from the viewpoints of curability, heat resistance, etc., an epoxy resin having two or more epoxy groups in one molecule is preferred. Specifically, there can be mentioned: biphenyl type epoxy resin, phenol novolac type epoxy resin, o-cresol novolac type epoxy resin, epoxy resin obtained by epoxidizing novolac resin of phenol and aldehyde, glycidyl ethers such as bisphenol A, bisphenol F and bisphenol S, glycidyl acid epoxy resin obtained by reaction of polyacids such as phthalic acid or dimer acid with epichlorohydrin, linear aliphatic epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, alkyl modified multifunctional epoxy resin, β-naphthol novolac type epoxy resin, 1,6-dihydroxynaphthalene type epoxy resin, 2,7-dihydroxynaphthalene type epoxy resin, bishydroxybiphenyl type epoxy resin, and epoxy resin introduced with halogen such as bromine for imparting flame retardancy, etc. Among these epoxy resins having two or more epoxy groups in one molecule, bisphenol A type epoxy resin is particularly preferred.

[0099] In addition, resins other than epoxy resins can also be used as resins used in resin composite compositions such as prepregs for printed circuit boards and various engineering plastics for uses other than semiconductor sealing materials. Specifically, in addition to epoxy resins, polyamides such as silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, 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 and styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber and styrene) resins can also be mentioned.

[0100] As a curing agent for the resin composite composition, a known curing agent can be used to cure the resin, for example, a phenolic curing agent can be used. As the phenolic curing agent, phenol novolac resin, alkylphenol novolac resin, polyvinylphenol, etc. can be used alone or in combination of two or more.

[0101] The phenolic curing agent is preferably blended in an equivalent ratio (phenolic hydroxyl equivalent / epoxy equivalent) of 0.1 or more and less than 1.0 to the epoxy resin. This eliminates the residual unreacted phenolic curing agent and improves the moisture absorption heat resistance.

[0102] From the viewpoint of heat resistance and thermal expansion coefficient, the amount of spherical alumina particles added to the resin composite composition of the present invention is preferably large, usually appropriately 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 spherical alumina particles is too small, it is difficult to obtain the effects of improving the strength of the sealing material and inhibiting thermal expansion. On the contrary, if it is too much, regardless of the surface treatment of the spherical alumina particles, it is easy to cause segregation due to the agglomeration of the spherical alumina particles in the composite material, and the viscosity of the composite material is too large, so it is difficult to use as a sealing material. In addition, when the "other fillers" are used in combination, the preferred amount added to the resin composite composition is the total amount of the spherical alumina particles and the "other fillers".

[0103] In addition to the resin, additive materials such as a silane coupling agent, a curing agent, a colorant, a curing delay material, and other known additives may be used.

[0104] Moreover, as the silane coupling agent, a known coupling agent may be used, but a silane coupling agent having an epoxy functional group is preferred.

[0105] A heat sink, heat dissipation paste, and the like can be obtained using a slurry composition containing spherical alumina particles and a resin.

[0106] When obtaining the heat sink, in addition to the spherical alumina particles and the resin, an additive is appropriately mixed and compounded by a known method such as kneading. The obtained composite is formed into a sheet by a known method.

[0107] For example, in the case of manufacturing a heat sink, as the resin used in the resin composite composition, a known resin can be used, specifically, polyamides such as silicone resin, phenolic resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamide-imide, and polyetherimide; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber﹒styrene) resin, AES (acrylonitrile﹒ethylene﹒propylene﹒diene rubber-styrene) resin. Among them, silicone resin is preferably used. The silicone resin is not particularly limited, for example, peroxide curing type, addition curing type, condensation curing type, ultraviolet curing type, etc. can be used.

[0108] In addition to the resin, additive materials such as a silane coupling agent, a curing agent, a colorant, a curing delay material, and other known additives may be used.

[0109] When obtaining the heat dissipation paste, in addition to the spherical alumina particles and the resin, an appropriate additive is added and compounded by a known method such as kneading. Here, the resin used in the heat dissipation paste is also referred to as a base oil.

[0110] For example, in the case of manufacturing thermal paste, as the resin used in the resin composite composition, known resins can be used, specifically, polyamides such as silicone resins, phenolic resins, melamine resins, urea-formaldehyde resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, and polyether-imides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, mineral oil, synthetic hydrocarbon oil, ester oil, polyethylene glycol oil, silicone oil, fluoro oil, etc.

[0111] In addition to the resin, additives such as silane coupling agents, colorants, thickeners, and other known additives may be used. Thickeners may be calcium soaps, lithium soaps, aluminum soaps, calcium complex soaps, aluminum complex soaps, lithium complex soaps, barium complex soaps, bentonite, urea, PTFE, sodium terephthalate, silica gel, organic bentonite, and other known thickeners.

[0112] [Example]

[0113] The present invention will be described below with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.

[0114] (Example 1)

[0115] The boehmite raw material (D50 = 0.4 μm) was heated in a heating furnace at 150°C for 5 hours in advance, and the heated raw material was put into a Henschel mixer. After the addition, hexamethyldisilazane was added while stirring to perform surface treatment. The amount of hexamethyldisilazane added was 1.5 wt% relative to the weight of the raw material. Then, oxygen was used as a carrier gas and supplied to a high-temperature flame formed by the combustion of LPG and oxygen, and melted and spheroidized to produce spherical alumina particles described in Example 1 of Table 1.

[0116] (Example 2)

[0117] Spherical alumina particles described in Example 2 in Table 1 were produced by the same operation as in Example 1 except that alumina powder (D50=0.7 μm) was used as a raw material.

[0118] (Example 3)

[0119] Spherical alumina particles described in Example 3 in Table 1 were produced by the same operation as in Example 1 except that boehmite (D50=0.2 μm) was used as the raw material.

[0120] (Comparative Examples 1 to 7)

[0121] Under the conditions described in Table 1, various materials (metal aluminum powder, boehmite or alumina) as raw materials are supplied to a high-temperature flame formed by the combustion of LPG and oxygen using air as a carrier gas, and oxidized and spheroidized to produce spherical alumina particles described in the comparative example of Table 1.

[0122] (Example 4)

[0123] The spherical alumina particles obtained in Example 1 were mixed with aluminum nitride particles (D50 = 30 μm) in a ratio of (blended weight of spherical alumina particles): (blended weight of aluminum nitride particles) = 90:10 to prepare a spherical alumina particle mixture A. Furthermore, the spherical alumina particle mixture A was mixed with silicone resin CY52-276A liquid manufactured by Dow Toray so that the addition amount of the spherical alumina particle mixture A in the resin composite composition was 90 mass %, and vacuum kneading was performed using a vacuum kneading machine "Defoam Rentaro" manufactured by THINKY to obtain a resin composite composition. The kneading conditions were pre-kneading for 15 seconds and vacuum kneading for 90 seconds.

[0124] (Example 5)

[0125] The spherical alumina particles obtained in Example 2 were mixed with boron nitride particles (D50 = 20 μm) in a ratio of (blended weight of spherical alumina particles): (blended weight of boron nitride particles) = 90:10 to prepare a spherical alumina particle mixture B. Furthermore, the spherical alumina particle mixture B was mixed with silicone resin CY52-276A liquid manufactured by Dow Toray so that the addition amount of the spherical alumina particle mixture B in the resin composite composition was 90 mass %, and vacuum kneading was performed using a vacuum kneading machine "Defoam Rentaro" manufactured by THINKY to obtain a resin composite composition. The kneading conditions were pre-kneading for 15 seconds and vacuum kneading for 90 seconds.

[0126] Table 1 shows the physical property values ​​of the produced spherical alumina particles.

[0127] [Table 1]

[0128]

[0129] The measuring methods of the physical property values ​​are as follows.

[0130] (Average particle size by laser diffraction scattering method)

[0131] The laser diffraction / scattering particle size distribution measurement method is a method of irradiating a dispersion liquid in which spherical aluminum oxide particles are dispersed with laser light and obtaining the particle size distribution based on the intensity distribution pattern of the diffracted / scattered light emitted from the dispersion liquid. In the present invention, the laser diffraction / scattering particle size distribution measurement device used is "Mastersizer 3000" (manufactured by Malvern).

[0132] (Specific surface area)

[0133] The specific surface area is measured by the BET method. Typically, the specific surface area is measured according to the following steps.

[0134] About 5 g of the sample was weighed and vacuum dried at 250°C for 5 minutes. Then, the sample was placed in an automatic specific surface area measuring device (Macsorb, manufactured by Mountech), and the nitrogen adsorption amount at a relative pressure P / P0 of 0.291 was measured at a measuring temperature of 77K using pure nitrogen and nitrogen-helium mixed gas (mixing ratio of nitrogen 30% and He 70%), and the BET specific surface area was calculated by the one-point method.

[0135] (Circularity)

[0136] The circularity can be measured using an electron microscope or an optical microscope and an image analysis device. For example, FPIA manufactured by Sysmex Corporation, etc. These devices are used to measure the circularity of particles (the circumference of the equivalent circle / the circumference of the projected image of the particle). The circularity is measured for more than 100 particles, and the average value is used as the circularity of the powder.

[0137] (α-ratio)

[0138] The alpha rate of the alumina particle powder is measured using a powder X-ray diffraction device. The integral area of ​​the obtained diffraction peak is calculated, and for the total, the ratio of the diffraction peak area from α-alumina is analyzed by the Rietveld method. Specifically, the X-ray diffraction pattern is obtained in the range of 2θ of 10° to 90° using D2PHASER manufactured by Bruker. The alpha rate of the obtained pattern is calculated by the Rietveld method using DIFFRAC.TOPAS manufactured by Bruker. When calculating, it is assumed that only three crystalline phases, α-alumina, δ-alumina, and θ-alumina, are present for analysis, and the content of α-alumina is calculated.

[0139] (Metal Al concentration)

[0140] The metal Al remaining in the alumina particles is measured by the following steps. About 1g of spherical alumina particle sample is weighed and placed in a beaker. 60ml of 1mol / L hydrochloric acid is added to the beaker and stirred at room temperature for 5 hours. The supernatant of the stirred sample solution is taken and the volume is fixed to 100ml, and the Al component of the solution is analyzed by ICP-MS.

[0141] (Converted powder resistivity)

[0142] The converted powder resistivity of alumina particle powder (hereinafter also referred to as "converted powder resistivity") is obtained by multiplying the powder resistivity by the Na2O content of the particles. That is, it is calculated by the formula (converted powder resistivity) = (powder resistivity of alumina particle powder) × (Na2O content of spherical alumina particles). The powder resistivity of alumina particle powder is measured using the powder resistivity measurement system MCP-PD51. As a pretreatment for the measurement, heat and dry it in the atmosphere at 200°C for 5 hours. The dried powder is introduced into the powder resistivity measurement probe unit, and the sample is gradually pressurized using the attached hydraulic pump. When the load reaches 20kN, the measurement is performed using a high resistivity meter.

[0143] (Na2O content of particles)

[0144] The Na2O content of the alumina particles was measured using an atomic absorption spectrometer. 0.5 g of the sample was added to a pressurized container, 10 ml of sulfuric acid (1+3) was added, and the container was covered with a lid, and then heated in a heating drying furnace at 230°C for 16 hours. After the heated solution was cooled, the solution was fixed to 100 ml and measured using an atomic absorption spectrometer.

[0145] (Liquidity)

[0146] Measure 30g of the spherical alumina particle sample and put it in a bag. Furthermore, measure 70g of AZ10-75 (alumina powder manufactured by Nippon Steel Chemical Materials Co., Ltd., with an average particle size of 10μm) and put it into the bag where the spherical alumina particles were previously placed. Then, tie the bag and stir and mix thoroughly. Measure 43.5g of the mixed alumina particle mixed powder and put it into a 200ml plastic container. Add 6.5g of silicone resin CY52-276A liquid manufactured by Dow Toray, and use a vacuum mixer "Degassing Rentaro" manufactured by THINKY for vacuum mixing. The mixing conditions are pre-mixing for 15 seconds and vacuum mixing for 90 seconds. After mixing, place the plastic container containing the mixture in a water bath adjusted to 25°C and cool it for 1 hour. 10g of the composite (resin composite composition) prepared by mixing is placed on a plate with a smooth surface. There is no particular restriction on the material of the plate, and an iron plate is used in this embodiment. The plate with the composite was tilted 60° relative to the horizontal direction to confirm the fluidity of the composite. In this test, if the composite flowed more than 15 cm after tilting for 5 hours, the fluidity was evaluated as 0 (good), and if the composite did not flow more than 15 cm, the fluidity was evaluated as × (poor).

[0147] It was confirmed that spherical alumina particles having a low metal aluminum concentration, a low alpha conversion rate, and a small particle size can be obtained. In addition, it was confirmed that a resin composite composition containing the spherical alumina particles can be obtained.

[0148] Industrial Availability

[0149] The spherical alumina particles of the present invention have a small particle size, so they can also be used for miniaturized and thin semiconductor packages, etc. In addition, due to the low concentration of metal aluminum, major accidents such as short circuits can be suppressed. Furthermore, according to a manufacturing method that is one embodiment of the present invention, the spherical alumina particles can be easily manufactured. The resin composite composition containing the spherical alumina particles shows good fluidity and is not limited to semiconductor sealing materials, but can also be used for other purposes. Specifically, it can also be used as a prepreg for printed circuit boards, various engineering plastics, etc.

Claims

1. A spherical alumina particle, characterized in that: The metal Al concentration is below 1000ppm, the average particle size is 0.3-2.0um, and the specific surface area is 2.5-5.0m 2 / g, the circularity is 0.80 or more, and the alpha conversion rate is 5.0% or less.

2. The spherical alumina particles according to claim 1, The alpha conversion rate is less than 1.0%.

3. A method for producing spherical alumina particles, comprising the following steps: A raw material preparation process for preparing a raw material containing at least one of aluminum oxide, boehmite or aluminum hydroxide and having a particle size of 0.2 to 2.0 μm; A surface treatment step of treating the surface of the raw material with a surface treatment agent containing silicon atoms; and The spheroidization step is to put the surface-treated raw material into a flame to melt it and then rapidly cool it into a spheroidized shape.

4. A resin composite composition, characterized in that: Contains the spherical aluminum oxide particles as described in claim 1 or 2.

5. The resin composite composition according to claim 4, It also contains at least one inorganic filler selected from amorphous spherical silica particles, crystalline spherical silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers.

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