Method for producing oxide particles and method for producing resin composition for electronic devices

Abstract

Provided are: a method for producing oxide particles which achieves a reduction in the amount of impurities contained in oxide particles that will serve as filler for addition to sealing materials; and a method for producing a resin composition for electronic devices, that uses the oxide particles. The method comprises: a dissolution step of dissolving a metal starting material of an amphoteric element in a basic solution to obtain a starting material solution; a solidification step of solidifying a dissolved component of the starting material solution to obtain a solidified product; a firing step of firing the solidified product to obtain a fired product; a pulverizing step of pulverizing the fired product to obtain a pulverized product; and a melting spheroidizing step of introducing the pulverized product into a flame to obtain spherical particles spheroidized by melting.

Description

Method for producing oxide particles and method for producing resin composition for electronic devices

[0001] The present invention relates to a method for producing oxide particles and a method for producing a resin composition for electronic devices, and more particularly to a method for producing oxide particles that reduce the content of impurities, and a method for producing a resin composition for electronic devices using the oxide particles.

[0002] Inorganic fillers are added to resin compositions to seal precision electronic components such as semiconductors. Fillers are required to have insulating properties and a low coefficient of thermal expansion. Silica (silicon oxide) and alumina (aluminum oxide) are commonly used.

[0003] Silica and alumina are processed into fillers by crushing natural high-purity ores to a predetermined particle size. That is, even if they are highly pure, because they are derived from natural ores, the presence of impurities other than silicon oxide and aluminum oxide is inevitable. In particular, in the case of silica and alumina derived from natural products, uranium and thorium elements are present. To reduce these impurities, a method for producing spherical silica powder that combines crushing and exposure to flame has been proposed (see Patent Document 1).

[0004] According to the manufacturing method of Patent Document 1, pulverization and exposure to flame contribute to the reduction of uranium elements. Here, processing precision and integration are further promoted in order to improve the processing speed of semiconductors. Therefore, the influence of external electromagnetic noise on semiconductors is becoming a greater problem than ever before. In the case of silica and alumina derived from natural products, it is known that alpha rays and the like are generated by the radioactive decay of uranium and thorium elements, which are thought to be the cause of malfunctions.

[0005] JP 2012-206870 A

[0006] After further research, the inventors have discovered a method that makes it possible to more effectively remove uranium and thorium elements from natural high-purity ores or low-grade metal materials, thereby reducing alpha rays and other radiation emitted from the sealing material.

[0007] The present invention has been made in consideration of the above points, and provides a method for producing oxide particles that reduce the amount of impurities contained in oxide particles that serve as filler to be added to an encapsulant, and a method for producing a resin composition for electronic devices using the oxide particles.

[0008] That is, the method for producing oxide particles of the embodiment is characterized by comprising a dissolving step of dissolving a metal raw material of an amphoteric element in a basic solution to obtain a raw material solution, a solidification step of solidifying the dissolved components of the raw material solution to obtain a solidified material, a firing step of firing the solidified material to obtain a fired material, a grinding step of grinding the fired material to obtain a ground material, and a melting and spheroidizing step of throwing the ground material into a flame to obtain spherical particles by melting.

[0009] Furthermore, in the method for producing oxide particles, the basic solution may be an aqueous solution of an amine compound.

[0010] Furthermore, in the solidification step of the method for producing oxide particles, when solidifying the dissolved components of the raw material solution, an acidic solution may be added to obtain a solidified product.

[0011] Furthermore, in the solidification step of the method for producing oxide particles, when the dissolved components of the raw material solution are solidified, the raw material solution may be heated to obtain a solidified product.

[0012] Furthermore, when solidifying the dissolved components of the raw material solution in the solidification step of the method for producing oxide particles, the raw material solution may be heated to a liquid temperature of 40 to 60°C.

[0013] Furthermore, in the method for producing oxide particles, the metal raw material of the amphoteric element may be metallic silicon or metallic aluminum.

[0014] Furthermore, in the method for producing oxide particles, the total amount of uranium and thorium contained in the spherical particles may be reduced to 1 / 10 or less of the total amount of uranium and thorium contained in the metal raw material of the amphoteric element.

[0015] The method for producing a resin composition for electronic devices according to an embodiment is characterized by comprising a dissolving step of dissolving a metal raw material of an amphoteric element in a basic solution to obtain a raw material solution, a solidification step of solidifying the dissolved components of the raw material solution to obtain a solidified product, a firing step of firing the solidified product to obtain a fired product, a grinding step of grinding the fired product to obtain a ground product, a melting and spheroidizing step of introducing the ground product into a flame to obtain spherical particles by melting, and a resin dispersion step of dispersing the spherical particles in a resin composition to obtain a resin dispersion.

[0016] The method for producing oxide particles of the present invention includes a dissolving step of dissolving a metal raw material of an amphoteric element in a basic solution to obtain a raw material solution, a solidification step of solidifying the dissolved components of the raw material solution to obtain a solidified product, a firing step of firing the solidified product to obtain a fired product, a grinding step of pulverizing the fired product to obtain a pulverized product, and a melting and spheroidizing step of introducing the pulverized product into a flame to obtain spherical particles by melting.This makes it possible to obtain oxide particles that reduce the amount of impurities contained in the oxide particles that will be used as a filler to be added to a sealing material.

[0017] Furthermore, the method for producing a resin composition for electronic devices makes it possible to reduce the dose of particle rays and electromagnetic waves emitted from the spherical particles contained in the resin composition, which is expected to suppress external disturbance factors such as noise and reduce malfunctions and other problems with the equipment.

[0018] (A) is an electron microscope photograph of a pulverized product that has undergone a pulverization process, and (B) is an electron microscope photograph of spherical particles that have undergone a melt-spheroidization process in Test Example 4. (A) is an electron microscope photograph of a pulverized product that has undergone a pulverization process, and (B) is an electron microscope photograph of spherical particles that have undergone a melt-spheroidization process in Test Example 16. (A) is an electron microscope photograph of a pulverized product that has undergone a pulverization process, and (B) is an electron microscope photograph of spherical particles that have undergone a melt-spheroidization process in Test Example 17. (A) is an electron microscope photograph of a pulverized product that has undergone a pulverization process, and (B) is an electron microscope photograph of spherical particles that have undergone a melt-spheroidization process in Test Example 18.

[0019] The method for producing oxide particles according to the embodiment involves sequentially treating a metal raw material with the following steps: Furthermore, the method for producing a resin composition for electronic devices includes a final step of dispersing the metal raw material in a resin composition.

[0020] First, a metal source of an amphoteric element is prepared and dissolved in a basic solution to prepare a raw material solution in which the metal source of the amphoteric element is dissolved (the "dissolving step").

[0021] In the embodiment, suitable amphoteric elements are primarily metallic Si and Al, and further include metallic elements such as Zn, Pb, Sn, Be, Ti, V, Fe, Co, Ge, Zr, Ag, and Sn. Amphoteric elements are characterized by their ability to react with both acids and bases. When the amphoteric element is metallic Si, the oxide particles produced by the production method are high-purity silica (silicon oxide). When the amphoteric element is Al, the oxide particles produced by the production method are high-purity alumina (aluminum oxide). The other amphoteric elements mentioned above can also be used as raw materials for metallic elements.

[0022] When dissolving a metal raw material of an amphoteric element in a basic solution, the basic solution is a solution that does not contain alkali metals. Generally, aqueous solutions of alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide are strongly basic. However, if alkali metals remain in the basic solution, this undesirably reduces the purity of the final oxide particles.

[0023] Therefore, an aqueous solution of an amine compound is used as a solution that does not contain an alkali metal, and examples of the amine compound include ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium hydroxides (ammonium salts), arylamines, silazanes, and hydrazines.

[0024] More specifically, the amine compound is one or more compounds selected from ammonia, methylamine, ethylamine, propylamine, dimethylamine, diethylamine, pyrrolidine, trimethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, methyltriamylammonium hydroxide, methyltributylammonium hydroxide, pyrrolidine, piperidine, pyridine, quinoline, imidazole, indole, pyrimidine, hexamethyldisilazane, hydrazine, diazabicycloundecene, diazabicyclononene, etc. When preparing the aqueous solution, the amine compound may be a single type or a mixture of two or more types.

[0025] When an organic amine compound is used, the compound molecules volatilize and decompose during subsequent processing. Therefore, it is desirable to use an amine compound so that almost no residue remains in the final oxide particles. Of course, the concentration of the amine compound in the aqueous solution is set to an optimum concentration and pH depending on the type of metal raw material of the amphoteric element to be dissolved, and the solution is stirred. Furthermore, the liquid temperature during dissolution is also adjusted. Since some of the compound remains undissolved during dissolution, filtration is also performed as necessary.

[0026] Here, the blending amount of the base and the metal raw material of the amphoteric element to be dissolved can be expressed as the ratio between the following molar amounts. The "ratio of the base amount (mol) / metallic silicon (Si) amount (mol)" is preferably in the range of 0.3 to 1.5, and more preferably in the range of 0.5 to 1.1. Furthermore, the "ratio of the base amount (mol) / metallic aluminum (Al) amount (mol)" is preferably in the range of 1.0 to 5.0, and more preferably in the range of 1.3 to 4.5.

[0027] The dissolved components of the raw material solution prepared by dissolving them in a basic solution are solidified to prepare a solidified product ("solidification step"). Here, the methods for preparing a solidified product are roughly divided into the following two types.

[0028] First, in the solidification process, an acidic solution is added to prepare a solidified product. The raw material solution is basic, and adding an acidic solution to it promotes neutralization of the acid and base, resulting in the formation of a precipitate. This precipitate becomes the target solidified product. The resulting solidified product is washed with water and dried. Examples of acidic solutions that can be used include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, and organic acids such as citric acid. Among these, acetic acid is preferred as the acidic solution because of its tendency to volatilize and decompose in subsequent processes.

[0029] After drying, the solidified material is calcined to form a calcined product, and excess moisture such as bound water is removed ("calcination step"). The calcination temperature is 300 to 1200°C, and the calcination time is 1 to 3 hours. Specifically, silicon hydroxide produced by precipitation is oxidized to silicon oxide (silica) through calcination.

[0030] Second, in the solidification step, the raw material solution is heated to prepare a solidified product. In this preparation, heating the raw material solution causes precipitation and sedimentation in the solution. Heating is carried out under liquid temperature conditions of approximately 40 to 60°C. The resulting precipitate becomes the target solidified product. If the temperature is below 40°C, it takes a long time for precipitation to occur. Also, if the temperature exceeds 60°C, precipitation becomes difficult due to the influence of the liquid temperature. Here, the preparation method of heating the raw material solution is mainly used when the metal raw material of the amphoteric element is aluminum.

[0031] The resulting solidified material is washed with water and dried. After drying, the solidified material is calcined to form a calcined material, and excess moisture such as bound water is removed (the "calcination step"). The calcination temperature is 300 to 1200°C, and the calcination time is 1 to 3 hours. The heating temperature range of the raw material solution is set so that the crystal grains of aluminum hydroxide formed during the process are relatively fine. Specifically, in the solidification step, the aluminum hydroxide formed by precipitation is calcined and oxidized to aluminum oxide (alumina).

[0032] The fired product produced in the firing step is pulverized to prepare a pulverized product ("pulverization step"). Either wet pulverization or dry pulverization may be used for pulverization. Furthermore, known devices for pulverizing solids, such as a ball mill, vibration mill, jet mill, or atomizer, are used as the pulverizer. In this embodiment, the solidified product and alumina balls are placed in a pulverization pod, and the pod is rotated to perform wet pulverization. The rotation time of the pod (pulverization time) is adjusted depending on the target particle size. After wet pulverization, the pulverized product recovered from the pod is dried by spray drying or the like.

[0033] The purpose of the pulverization process is to control the particle size prior to the subsequent melt-spheroidization process. At the stage of the calcination process, the calcined product is irregular in shape and not uniform in size due to the fusion of particles. If the product is directly subjected to the melt-spheroidization process, particles with varying particle sizes will be produced. Furthermore, the non-uniform shape makes it difficult to obtain a spherical shape. This results in a high yield during the process (a decrease in yield).

[0034] Here, the average particle size of the pulverized material is the median diameter (D) measured by a known particle size measurement method such as a laser diffraction scattering method or a dynamic scattering method. ５０ ) and the average particle diameter (D ５０ The particle size is preferably 30 μm or less, more preferably 20 μm or less. By making the particle size smaller, melting in the melt-spheroidizing step becomes easier.

[0035] The pulverized material prepared in the pulverization step is thrown into a flame, and the pulverized material flies through the flame. The pulverized material melts when exposed to the flame, and the surface tension during melting promotes spheroidization, resulting in spherical particles ("melt-spheroidization step"). The spherical particles thus obtained are the target oxide particles. A suitable particle size is also specified for the spherical particles. Specifically, the average particle size (D ５０ The average particle diameter (D) of the spherical particles is 30 μm or less, and more preferably 20 μm or less. ５０ ) is also a median diameter (D) measured by a known particle size measurement method such as a laser diffraction scattering method or a dynamic scattering method. ５０ ) means

[0036] The flame in the melting and spheroidizing process is formed by mixing a combustible gas with a combustion supporting gas containing oxygen and burning it. As an indicator of the furnace temperature, the temperature of the furnace's refractory structure at its highest point (furnace body temperature) is in the range of 900°C to 1500°C. The furnace body temperature preferably has a lower limit of 900°C to 1100°C and an upper limit of 1300°C to 1500°C. Air or oxygen is used as the combustion supporting gas. When the combustible gas and the combustion supporting gas are supplied to the furnace, they may be supplied separately or in a pre-mixed state.

[0037] The flow velocity of the combustible gas is preferably 10 m / s or more, more preferably 15 m / s or more, and even more preferably 20 m / s or more. The flow velocity of the combustion supporting gas is preferably 10 m / s or more, more preferably 15 m / s or more, and even more preferably 20 m / s or more. The flow velocity ratio of combustible gas / combustion supporting gas is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. The supply amounts of combustible gas and combustion supporting gas are determined by the amount of combustible gas that can form a flame large enough to sufficiently heat the raw material particles being supplied, and the amount of combustion supporting gas that can sufficiently combust the combustible gas. For example, the amount of combustible gas per unit weight of the pulverized material to be processed is 0.5 Nm ３ / kg to 5Nm ３ / kg, and oxygen as a combustion support gas is 1 Nm ３ / kg to 5Nm ３ It is said to be about / kg.

[0038] The method for supplying the raw material particles into the flame is not particularly limited, but the raw material particles can be supplied to the flame in a dispersed state in a carrier gas, such as air, oxygen, or nitrogen.

[0039] After the pulverization step and the melt-spheroidization step, the mixture is sieved to obtain particles of a desired size. For sieving, a method of centrifugal separation using a cyclone or the like is used.

[0040] As explained above, the spherical particles produced from an amphoteric element metal raw material through the melting, solidifying, firing, pulverizing, and melt-spheroidizing processes have a significantly reduced total amount of uranium and thorium compared to the amphoteric element metal raw material stage. As will be apparent from the examples described below, the total amount of uranium and thorium contained in the spherical particles is reduced to 1 / 10 or less, or even 6 / 100 or less, of the total amount of uranium and thorium contained in the amphoteric element metal raw material. This makes it possible to further reduce the dose of particle rays such as alpha rays and beta rays, and electromagnetic waves such as gamma rays, emitted from the spherical particles, thereby reducing the impact on electronic components, etc.

[0041] When the amphoteric element metal source is dissolved in the basic solution, the original amphoteric element metal source changes from a metallic state to a hydroxide. At this point, the amount of impurities contained in the amphoteric element metal source is thought to be less than the amount of the amphoteric element in its metallic state that dissolves in the basic solution. Heavy elements such as U (uranium) and Th (thorium) are not amphoteric elements, so they are less likely to dissolve in the basic solution and remain as insoluble components. This ease of solubility in the basic solution makes it possible to separate impurities such as uranium and thorium. Therefore, it is possible to further reduce impurities compared to conventional methods for preparing oxides for fillers.

[0042] The oxide particles prepared by the oxide particle manufacturing method of the embodiment described above are mainly used as fillers for electronic materials. The oxide particles are added to resins to prepare resin compositions for electronic devices (filler-containing resin compositions for electronic materials) (method for manufacturing resin compositions for electronic devices). Examples of resins to which the oxide particles can be added include thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polystyrene, other olefin resins, polyimide resins, and liquid crystal polymers; fluororesins, urea resins, phenolic resins, and thermosetting resins such as polyphenylene ether and bismaleimide. The oxide particles can also be added to elastic resins such as styrene-butadiene rubber and isoprene rubber, silicone resins, and the like. For example, epoxy resins are used as resins when manufacturing resin substrates such as electronic component packaging substrates and interlayer insulating films.

[0043] Examples of epoxy resins used in the resin composition include bisphenol A epoxy resins, bisphenol F epoxy resins, biphenyl epoxy resins, phenol novolac epoxy resins, naphthalene epoxy resins, and phenoxy epoxy resins. The weight of the oxide particles incorporated into the resin composition is preferably large from the viewpoints of heat resistance and thermal expansion coefficient. It is desirable to add 80% by mass or more of the oxide particles (filler for electronic materials) to the total mass of the resin composition.

[0044] Furthermore, the oxide particles (filler for electronic materials) of the embodiment can be dispersed in a liquid dispersion medium substantially free of water to prepare a slurry for electronic materials. Examples of the dispersion medium include methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, toluene, N-methylpyrrolidone, γ-butyrolactone, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. The dispersion medium can be used alone or in combination. An appropriate dispersant can also be used.

[0045] As explained above, a characteristic property of the resin composition for electronic devices (resin composition containing a filler for electronic materials) is that it can reduce the dose of particle radiation and electromagnetic waves emitted from the spherical particles contained in the resin composition. This reduces the impact of particle radiation and electromagnetic waves on electronic components and the like from the processed portion of the resin composition. As a result, external disturbance factors such as noise can be suppressed, and malfunctions and other problems with the equipment can be reduced.

[0046] To demonstrate the method for producing oxide particles, Test Examples 1 to 31 were prepared and the physical properties of each Test Example were evaluated. Hereinafter, the raw materials used, the production method, and the measurement and evaluation methods will be described in that order. For details of each test example, see Tables 1 to 6 below.

[0047] [Raw materials used] Metallic silicon powders with an average particle size of 20 μm were used in Test Examples 1 to 10 and 30 to 33. Crystalline silica powders with an average particle size of 30 μm were used in Test Examples 11 to 15. Alumina powders with an average particle size of 20 μm were used in Test Examples 16 to 27.

[0048] The following amine compounds were used in preparing the basic solution: Dimethylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Tetramethylammonium hydroxide (hereinafter referred to as TMAH): manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Diazabicycloundecene (hereinafter referred to as DBU): manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Diazabicyclononene (hereinafter referred to as DBN): manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Ammonia: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Butylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Diethylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Triethylamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Ethylenediamine: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0049] [Preparation of oxide particles] Test Examples 1 to 8 9.0 g of metallic silicon powder (Si powder in the tables below), 315 g of ion-exchanged water, and 32 g of a 50 wt % aqueous dimethylamine solution were mixed and stirred for 48 hours while heating to 40° C. As a result, a 6.0 wt % aqueous solution of basic silicic acid was obtained in terms of oxide.

[0050] A 90% aqueous acetic acid solution was added dropwise to the basic silicic acid solution while stirring to adjust the pH, and stirring was continued. The precipitate was recovered, dried at 120°C, and calcined at 800°C for 2 hours. Note that calcination was omitted for Test Example 3. The resulting calcined product, an appropriate amount of silica powder and water, and high-purity alumina balls with a particle size of 5 mm were placed in a high-purity alumina milling pod and milled until the target particle size was reached. The milled product was then collected through a 4 mm sieve and appropriately dried. The difference between each test example was the particle size during milling, which was achieved by adjusting the milling time.

[0051] 5Nm in a furnace lined with fireproof material (cylindrical, 5m high x 0.5m inner diameter) ３ / hour and 25 Nm３ The pulverized material of each test example was dispersed in air at a rate of 10 kg / hour into a flame generated by combustion with oxygen gas supplied at a rate of 10 kg / hour, heated and melted, and then collected. In this way, the oxide powder (silica powder) of each test example was prepared.

[0052] Test Examples 9, 10, 30 to 33 In Test Example 9, dimethylamine was replaced with TMAH, and the amounts of reagents and treatment were the same as in Test Example 6. In Test Example 10, dimethylamine was replaced with DBU, and the amounts of reagents and treatment were the same as in Test Example 6. In Test Example 30, dimethylamine was replaced with butylamine, and the amounts of reagents and treatment were the same as in Test Example 6. In Test Example 31, dimethylamine was replaced with diethylamine, and the amounts of reagents and treatment were the same as in Test Example 6. In Test Example 32, dimethylamine was replaced with triethylamine, and the amounts of reagents and treatment were the same as in Test Example 6. In Test Example 33, dimethylamine was replaced with ethylenediamine, and the amounts of reagents and treatment were the same as in Test Example 6.

[0053] Test Examples 11 to 15 Test Examples 11 to 15 are control groups in which crystalline silica was crushed as a raw material and exposed to flame, unlike the above-mentioned Test Examples 1 to 10. The crushing method was the same as when using the high-purity alumina pot described above, and the crushing time was adjusted to create different samples. The exposure to flame was also the same.

[0054] Test Examples 16 to 22 and 27 20.0 g of metallic aluminum powder (Al powder in the tables below), 3,366 g of ion-exchanged water, and 300 g of a 50 wt % aqueous dimethylamine solution were mixed, stirred for 0.5 to 2 hours while maintaining the liquid temperature at 20° C., and filtered through a 5 μm mesh. As a result, a basic aluminum aqueous solution with a concentration of 1.0 wt % in terms of alumina oxide was obtained.

[0055] The basic aluminum aqueous solution was heated to 50°C and stirred for approximately 8 hours to obtain a precipitate. The precipitate was filtered and washed with ion-exchanged water. After recovery, the precipitate was dried at 120°C and calcined for 2 hours at 1100°C (Test Examples 16, 17, and 18), 800°C (Test Examples 19, 20, 21, and 22), and 300°C (Test Example 27).

[0056] The grinding method was the same as when using the high-purity alumina pot described above, but the grinding time was adjusted accordingly. The flame exposure was also the same. Thus, the oxide powders (alumina powders) for each test example were prepared.

[0057] Test Examples 23 to 26 In Test Example 23, dimethylamine was replaced with DBU, and the amounts of reagents and treatment were the same as in Test Example 19. In Test Example 24, dimethylamine was replaced with TMAH, and the amounts of reagents and treatment were the same as in Test Example 19. In Test Example 25, dimethylamine was replaced with DBN, and the amounts of reagents and treatment were the same as in Test Example 19. In Test Example 26, dimethylamine was replaced with ammonia, and the amounts of reagents and treatment were the same as in Test Example 19.

[0058] [Measurement and evaluation methods] Particle size distribution For each test example, the particle size after pulverization and after melting was measured in an aqueous solvent using a laser diffraction particle size distribution analyzer SALD-7500 nano manufactured by Shimadzu Corporation. １０ , D ５０ (Median diameter), D ９０ The particle size distribution was calculated.

[0059] Measurement of BET specific surface area 1.0 g of each test example was weighed and placed in a measurement cell. After pretreatment, the BET specific surface area was measured by nitrogen adsorption. For the measurement, an automatic specific surface area and pore distribution measuring device TriStar (registered trademark)-II3020 manufactured by Shimadzu Corporation was used. The pretreatment conditions were as follows: Degassing temperature: 200°C Degassing time: 30 minutes Cooling time: 4 minutes

[0060] ・Component analysis When analyzing the atomic composition contained in the oxide powder, ICP (inductively coupled plasma atomic emission spectroscopy) devices ICP-MS (measuring U and Th), ICP-OES (measuring silica and other impurities), and ICP-AES (measuring alumina and other impurities) manufactured by Shimadzu Corporation were used. For the measurement, the oxide powder of the silica powder of each test example was completely dissolved in a mixed solution of nitric acid and hydrofluoric acid to form a solution, and the oxide powder of the alumina powder of each test example was completely dissolved in sulfuric acid to form a solution, and then subjected to the device.

[0061] [Results] The results of Test Examples 1 to 31 are shown in Tables 1 to 6. In each table, from the top to bottom, the raw material type, the amount of uranium and thorium in the raw material (ppb), the type of base, the ratio of base to element (mol), the yield (%), the firing temperature (°C), the particle diameter after grinding and after melting (D １０ , D ５０ , D ９０ μm), specific surface area (m ２ / g), and the amount of uranium and thorium after melting (ppb). Tables 7 and 8 show the compositional analysis of the contained elements. Test Examples 1, 11, and 16 are examples conforming to the manufacturing method of the embodiment, and Test Examples 28 and 29 are the results of oxide particles produced by the VMC method (Vaporized Metal Combustion Method) using metal powders implemented as control examples. The VMC method is a method for producing spherical oxide microparticles by utilizing the deflagration phenomenon of metal powder.

[0062] Additionally, photographs taken with an electron microscope (SEM) are presented. Figure 1 shows enlarged photographs of Test Example 4 after pulverization (5,000x magnification) and after melting (10,000x magnification), Figure 2 shows enlarged photographs of Test Example 16 after pulverization (5,000x magnification) and after melting (2,500x magnification), Figure 3 shows enlarged photographs of Test Example 17 after pulverization (5,000x magnification) and after melting (1,000x magnification), and Figure 4 shows enlarged photographs of Test Example 18 after pulverization (5,000x magnification) and after melting (2,500x magnification).

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] 1 to 4, it was confirmed that even if the crushed material was irregular in shape after crushing, it was converted into spherical particles by exposure to flame. Test Example 1 was silica, and Test Examples 16 to 18 were alumina, and in both cases, they were reconstituted into spherical oxide particles after dissolution in a basic solution.

[0072] Focusing on the amounts (ppb) of uranium and thorium elements in Test Examples 1 to 10 and 16 to 27, a comparison of the amounts in the raw material stage and after melting showed a significant reduction of 1 / 10 or less and 6 / 100 or less, respectively. In addition, a comparison of all components in Tables 7 and 8 confirmed a reduction in not only uranium and thorium but also other impurity components. This demonstrates that a method combining dissolution in a basic solution and exposure to a flame is effective in reducing impurity components.

[0073] Test Examples 1 to 10, 23 to 27, and 30 to 33 show that the types of amine compounds that can be used in preparing the basic solution can be expanded. The selection can be made taking into consideration the type of metal raw material of the amphoteric element to be dissolved, its ease of solubility (reactivity), etc.

[0074] Test Examples 1 to 8 and 16 to 20 are examples in which the particle size during pulverization was increased or decreased. Regardless of the particle size, it is possible to reduce impurity components, including uranium and thorium elements, making it possible to prepare fillers with particle sizes suited to specific applications and purposes. In addition, because impurity components can be reduced from the metal raw material to prepare oxide particles, not only can high-purity natural products be used as metal raw materials, but also commercially available low-grade metal raw materials can be used as raw materials, broadening the range of raw material options available when producing oxide particles.

Claims

1. A method for producing oxide particles, comprising: a dissolving step of dissolving a metal raw material of an amphoteric element in a basic solution to obtain a raw material solution; a solidification step of solidifying the dissolved components of the raw material solution to obtain a solidified product; a firing step of firing the solidified product to obtain a fired product; a grinding step of pulverizing the fired product to obtain a pulverized product; and a melting and spheroidizing step of introducing the pulverized product into a flame to obtain spherical particles by melting.

2. The method for producing oxide particles according to claim 1, wherein the basic solution is an aqueous solution of an amine compound.

3. The method for producing oxide particles according to claim 1, wherein when the dissolved components of the raw material solution are solidified in the solidification step, an acidic solution is added to obtain the solidified material.

4. The method for producing oxide particles according to claim 1, wherein when the dissolved components of the raw material solution are solidified in the solidification step, the raw material solution is heated to obtain the solidified material.

5. The method for producing oxide particles according to claim 4, wherein when the dissolved components of the raw material solution are solidified in the solidification step, the raw material solution is heated to a liquid temperature of 40 to 60°C.

6. The method for producing oxide particles according to claim 3, wherein the metal source of the amphoteric element is metallic silicon.

7. The method for producing oxide particles according to claim 4, wherein the metal source of the amphoteric element is metallic aluminum.

8. The method for producing oxide particles described in claim 1, wherein the total amount of uranium and thorium contained in the spherical particles is reduced to 1 / 10 or less of the total amount of uranium and thorium contained in the metal raw material of the amphoteric element.

9. A method for producing a resin composition for electronic devices, comprising: a dissolving step of dissolving a metal raw material of an amphoteric element in a basic solution to obtain a raw material solution; a solidifying step of solidifying the dissolved components of the raw material solution to obtain a solidified product; a firing step of firing the solidified product to obtain a fired product; a grinding step of pulverizing the fired product to obtain a pulverized product; a melt-spheroidizing step of introducing the pulverized product into a flame to obtain spherical particles by melting; and a resin dispersing step of dispersing the spherical particles in a resin composition to obtain a resin dispersion.

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