Inorganic metal oxide powder with less magnetized foreign matter and its manufacturing method

Abstract

To provide inorganic metal oxide powder which has a small total number (a mean value) of magnetized foreign matters, and whose coagulation is suppressed, and a method for producing the same.SOLUTION: The inorganic metal oxide powder has a content ratio of an agglomerate, obtained by the following measuring method, of not more than 30 ppm (in terms of mass), and has a total number (a mean value) of magnetized foreign matters of not more than 2000 pieces / 100 g. 300 g of ion-exchanged water is fed to 100 g of the inorganic metal oxide powder, and the mixture is treated by an ultrasonic device for 5 minutes. Thereafter, the treated mixture is sieved by a sieve having an opening size of 150 μm, according to JIS Z 8815-1994. The inorganic metal oxide powder remaining on the sieve is dried for 4 hours at 60°C. Subsequently, the mass W (g) of the agglomerate is measured. A value obtained by the following equation (1) is the content ratio of the agglomerate.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an inorganic metal oxide powder containing little magnetized foreign matter, and a method for producing the same. [Background technology]

[0002] In the field of semiconductor encapsulation materials, inorganic metal oxide powders such as silica and alumina are used as fillers to improve the thermal expansion coefficient, thermal conductivity, flame retardancy, etc. Among such inorganic metal oxide powders, for example, silica powder is produced by a dry method (such as a molten flame method) in which raw material powder is thrown into a high-temperature flame to oxidize it and obtain silica powder, or a wet method in which raw material powder is dispersed in a medium such as water or alcohol to form a slurry, and the slurry is sprayed into a flame to obtain silica powder.

[0003] However, inorganic metal oxide powders such as silica powder may be contaminated with fine metal particles as foreign matter during the manufacturing process. This is because a part of the manufacturing equipment for inorganic metal oxide powders is generally made of metals such as iron and stainless steel, and the surface of the equipment is scraped by the inorganic metal oxide powder when the inorganic metal oxide is crushed into powder, transported by air current, classified, sieved, or blended. When inorganic metal oxide powders containing such foreign metal particles (hereinafter referred to as "magnetized foreign matter") are filled as a filler into a semiconductor encapsulant, a short circuit may occur between wiring such as semiconductor wires. Therefore, various attempts to remove the magnetized foreign matter from inorganic metal oxide powders have been considered.

[0004] The above-mentioned dry method can easily produce fine inorganic metal oxide powder with high purity, but magnetized foreign matter is likely to be mixed in. On the other hand, the wet method has the advantage that ionic impurities contained in the inorganic metal oxide powder can be easily removed, but the raw material powder tends to aggregate in a high-concentration slurry, making it difficult to obtain a fine powder. Therefore, there is a demand for fine inorganic metal oxide powder with less magnetized foreign matter.

[0005] To address this issue, for example, Patent Document 1 describes a method in which a material to be treated, such as silica powder or alumina powder, is dispersed in a dispersion medium to prepare a suspension, and then a magnetic force is applied to this suspension to remove magnetized foreign matter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-42347 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the method of Patent Document 1, the silica powder or alumina powder to be treated aggregates during the removal of magnetized foreign matter, making it difficult to obtain inorganic metal oxide powder having the same particle size distribution and particle diameter as before the treatment. SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide an inorganic metal oxide powder having a small total number of magnetized foreign matter and suppressed aggregation, and a method for producing the same. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that by spray drying a slurry containing an inorganic metal oxide powder and a specific alcohol, it is possible to obtain an inorganic metal oxide powder from which magnetized foreign matter, particularly fine magnetized foreign matter adhering to the powder surface, has been effectively removed while suppressing the aggregation of the powder particles. [1] An inorganic metal oxide powder having a content of agglomerates of 30 ppm (by mass) or less, and a total number (average value) of magnetized foreign matter of 2,000 or less per 100 g, as determined by the measurement method described below. (Measurement method) 300g of ion-exchanged water is added to 100g of inorganic metal oxide powder and treated with an ultrasonic device for 5 minutes. After that, the powder is sieved through a sieve with 150μm openings according to JIS Z 8815-1994. The inorganic metal oxide powder remaining on the sieve is dried at 60°C for 4 hours, and then the mass of the aggregates: W (g) is measured. The value calculated by the following formula (1) is taken as the content ratio of the aggregates. Aggregate content (ppm) = (W(g) / 100(g)) x 10 6 (1) [2] The inorganic metal oxide powder according to [1], having a volume-based cumulative diameter (D50) of 1 μm or less. [3] The inorganic metal oxide powder according to [1], having a volume-based cumulative diameter (D50) of more than 1 μm and not more than 100 μm. [4] The inorganic metal oxide powder according to any one of [1] to [3], which contains silica powder. [5] A method for producing an inorganic metal oxide powder according to any one of [1] to [4], comprising spray drying a slurry containing an inorganic metal oxide powder and a dispersion medium containing a monohydric alcohol having a linear or branched alkyl group having 1 to 3 carbon atoms. [6] The method for producing an inorganic metal oxide powder according to [5], wherein the dispersion medium contains the monohydric alcohol and water, and the proportion of the monohydric alcohol relative to the total amount (100 mass%) of the monohydric alcohol and the water is 50 mass% or more. [7] The method for producing an inorganic metal oxide powder according to [5] or [6], wherein the monohydric alcohol comprises isopropyl alcohol. Effect of the Invention

[0009] According to the present invention, it is possible to provide an inorganic metal oxide powder having a small total number (average value) of magnetized foreign matter and suppressed aggregation, and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below, but the present invention is not limited to the following embodiments. In this specification, the symbol "~" means "not less than or equal to." For example, "0.1~1" means "not less than or equal to 0.1 and not more than 1." [Inorganic metal oxide powder] The inorganic metal oxide powder according to the present invention is characterized in that the content of agglomerates, as determined by the following measurement method, is 30 ppm (by mass) or less, and the total number (average value) of magnetized foreign matter is 2,000 or less per 100 g. (Measurement method) 300 g of ion-exchanged water is added to 100 g of inorganic metal oxide powder and treated with an ultrasonic device (manufactured by AS ONE Corporation, product name: ASU CLEANER, model: AUS-20M) at an output of 500 W for 5 minutes. Then, in accordance with JIS Z 8815-1994, the powder is sieved through a sieve with 150 μm openings. The inorganic metal oxide powder remaining on the sieve is dried at 60° C. for 4 hours, and the mass of the aggregates: W (g) is measured. The value calculated by the following formula (1) is taken as the aggregate content ratio. Aggregate content (ppm) = (W(g) / 100(g)) x 10 6 (1)

[0011] The inorganic metal oxide powder according to the present invention has a small total number of magnetized foreign matter and is inhibited from agglomerating. In the present invention, the term "magnetized foreign matter" refers to fine magnetic particles in the inorganic metal oxide powder that can be collected by a magnet. The term "total number (average value) of magnetized foreign matter" refers to a value determined by the following method. (Total number of magnetized foreign objects (average value)) A: 10 g of inorganic metal oxide powder and 40 mL of ion-exchanged water are placed in a centrifuge tube. Next, the centrifuge tube is placed in a φ150 mm container filled with water so that the water level is the same as that of the centrifuge tube, and the tube is dispersed for 2 minutes using a homogenizer (SONICS Corporation, product name: VC-505) at 500 W. The slurry after dispersion is placed in a resin tray with a thickness of 0.2 mm, and magnetized foreign matter is collected using a magnet with a magnetic force of 12,000 gauss. B: Repeat step A 10 times to collect magnetized foreign matter contained in 100 g of inorganic metal oxide powder. The collected slurry containing magnetized foreign matter is suction filtered using a membrane filter (filter diameter: 1 μm, Millipore, model: JAWP04700) to collect the magnetized foreign matter on the filter. After that, observe the entire area on the filter with an optical microscope (magnification: 100 times) and count the total number of magnetized foreign matter. C: Repeat A and B five times, and take the average value as the "total number of magnetized foreign objects (average value)."

[0012] In the inorganic metal oxide powder according to the present invention, the content ratio (mass basis) of the aggregates calculated by the above formula (1) is 30 ppm or less, preferably 25 ppm or less, and more preferably 20 ppm or less. In addition, in consideration of productivity, the content ratio may be 1 ppm or more, 3 ppm or more, or 4 ppm or more. That is, the content ratio (mass basis) of the aggregates may be 1 to 30 ppm, 3 to 25 ppm, or 4 to 20 ppm.

[0013] The fewer the total number of magnetized foreign objects contained in the inorganic metal oxide powder, the better. In general, if the total number (average) of magnetized foreign objects contained in 100 g of inorganic metal oxide powder is 2,000 or less, when the inorganic metal oxide powder is used as a filler, short circuits between wiring such as semiconductor wires are unlikely to occur. In addition, the total number (average) of magnetized foreign objects in the inorganic metal oxide powder is preferably 1,800 or less / 100 g, more preferably 1,700 or less / 100 g. Furthermore, it may be 1,500 or less / 100 g, 1,200 or less / 100 g, 1,000 or less / 100 g, or 800 or less / 100 g. In addition, in consideration of productivity, it may be 50 or more / 100 g, 100 or more / 100 g, or 150 or more / 100 g. That is, the total number (average value) of magnetized foreign objects contained in 100 g of the inorganic metal oxide powder may be 50 to 2,000, 100 to 1,800, or 150 to 1,700.

[0014] The inorganic metal oxide powder according to the present invention may contain other components (additives, etc.) other than the inorganic oxide powder, as long as the effects of the present invention are not impaired. The content of other components including impurities may be 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total mass of the inorganic metal oxide powder. In addition, as described below, according to the present invention, the amount of ionic impurities contained in the inorganic metal oxide powder can be reduced.

[0015] The proportion of ionic impurities (by mass) contained in the inorganic metal oxide powder according to the present invention is preferably 50 ppm or less for Fe ions, more preferably 30 ppm or less. Further preferably, it is 20 ppm or less, and may be 15 ppm or less. Furthermore, it is preferable that the proportion of Na ions is 10 ppm or less. Furthermore, it is desirable that the proportion of chlorine ions is 2 ppm or less, and more preferably 1 ppm or less. The proportion of ionic impurities in the inorganic metal oxide powder can be measured by the following method. (Method for measuring Fe ions) 30mL of aqua regia, which is made by adjusting the volume ratio of concentrated nitric acid, concentrated hydrochloric acid, and water to 1:5:34, and 5g of inorganic metal oxide powder sample are placed in a 100mL beaker and heated. After cooling, the mixture is centrifuged, and the resulting supernatant is used as the measurement solution. This measurement solution is measured using an air-acetylene atomic absorption spectrometer to measure the absorbance at 248.3nm. (Method of measuring sodium ions) 10 g of inorganic metal oxide powder sample and 70 mL of ion-exchanged water are placed in a PE container and shaken for 1 minute. Then, place in a dryer and leave at 95°C for 20 hours, then cool. Add water to make up for the amount that has evaporated and obtain a quantitative amount. Then, centrifuge and collect the supernatant liquid to use as the measurement liquid. This measurement liquid is measured using an air-acetylene atomic absorption spectrophotometer to measure the absorbance at 589.0 nm. (Method of measuring chloride ions) 10 g of inorganic metal oxide powder sample and 70 mL of ion-exchanged water are placed in a PE container and shaken for 1 minute. Then, place in a dryer and leave at 95°C for 20 hours, then cool. Add water to make up for the amount that evaporated and obtain a quantitative amount. Then, centrifuge and collect the supernatant liquid as the measurement liquid. This measurement liquid is measured using an ion chromatograph. For the Fe ions, Na ions, and chlorine ions, standard stock solutions (1,000 ppm) were prepared and then diluted to prepare standard solutions. Calibration curves were created from the relationship between the absorbance and the concentration of each ion.

[0016] <Inorganic metal oxides> Inorganic metal oxides include silica (SiO 2 ), Alumina (Al 2 O 3 ), titania (TiO 2 ), magnesia (MgO), calcia (CaO), etc. The inorganic metal oxide powder according to the present invention preferably contains at least one inorganic metal oxide powder selected from these, and more preferably contains silica powder. The inorganic metal oxide powder is preferably a spherical inorganic metal oxide powder, more preferably a spherical silica powder. From the viewpoint of bringing the thermal expansion coefficients of the semiconductor chip and the liquid encapsulant closer to each other, solder heat resistance, moisture resistance, and low wear of the mold, amorphous silica powder produced by a method of melting crystalline silica at high temperature is more preferable.

[0017] As described above, the inorganic metal oxide powder is preferably spherical. The sphericity of the inorganic metal oxide powder is preferably 0.70 or more, more preferably 0.85 or more. The sphericity refers to the average sphericity value measured in pure water using a flow type particle shape and particle size analyzer (FPIA-3000) manufactured by Sysmex Corporation. Specifically, a sample of the inorganic metal oxide powder is dispersed in pure water, and the liquid is then passed through a planar extensional flow cell, and 100 or more particles of the inorganic metal oxide powder moving through the cell are recorded as images using an objective lens, and the average circularity is calculated from the recorded image and the following formula (2). Average circularity = π HD / PM (2) In formula (2), HD represents the equivalent circle diameter, which is calculated from the ratio of the projected area of ​​the target particle to the area of ​​a perfect circle. PM represents the projected perimeter of the target particle. The average value of 200 particles of inorganic metal oxide powder calculated in this manner is taken as the average circularity. This average circularity is then used to calculate the average sphericity from the formula: average circularity = (average circularity) 2 The average sphericity is calculated by

[0018] In one embodiment of the inorganic metal oxide powder according to the present invention, the inorganic metal oxide powder has a volume-based cumulative diameter (D50) (hereinafter referred to as "D50 particle diameter") of 1 μm or less, more preferably 0.1 to 1.0 μm, and even more preferably 0.2 to 0.7 μm. Hereinafter, the inorganic metal oxide powder having a D50 particle diameter of 1 μm or less will be referred to as "inorganic metal oxide powder of the first embodiment". The inorganic metal oxide powder of the first embodiment is used, for example, in the field of substrates and the like. In the inorganic metal oxide powder used in such fields, if the content ratio of aggregates is 30 ppm (mass basis) or less and the total number of magnetized foreign matter is 2,000 pieces or less / 100 g, the effect of improving voltage resistance is easily obtained. In this specification, the D50 particle diameter of the inorganic metal oxide powder refers to the particle diameter at which the cumulative value corresponds to 50% in the volume-based cumulative particle size distribution measured by a laser diffraction scattering method (refractive index: 1.50). The cumulative particle size distribution is expressed by a distribution curve with the particle size (μm) on the horizontal axis and the cumulative value (%) on the vertical axis. The cumulative particle size distribution on a volume basis measured by the laser diffraction scattering method (refractive index: 1.50) is measured using a laser diffraction scattering type particle size distribution analyzer (manufactured by Beckman Coulter, product name: LS-230) and water (refractive index: 1.33) as the solvent, and is measured by dispersing the particles for 2 minutes as a pretreatment by applying an output of 200 W using an ultrasonic generator UD-200 (with ultra-micro tip TP-040) manufactured by Tommy Seiko Co., Ltd.

[0019] In the inorganic metal oxide powder of the first embodiment, the specific surface area measured by the BET method is 4 to 35 m 2 / g, and 4 to 12m 2 / g is more preferable, and 5.5 to 12m 2 / g is more preferable. Since the inorganic metal oxide powder according to the present invention is inhibited from agglomerating, it is easy to realize a sufficiently high specific surface area. In this specification, the measurement of the specific surface area by the BET method was performed using "Macsorb HM model-1208" (manufactured by Mountec Co., Ltd.).

[0020] In another embodiment of the inorganic metal oxide powder according to the present invention, the D50 particle size is preferably more than 1 μm and not more than 100 μm, more preferably more than 1 μm and not more than 55 μm, and even more preferably 5 to 50 μm. Hereinafter, the inorganic metal oxide powder having a D50 particle size of more than 1 μm and not more than 100 μm will be referred to as the "inorganic metal oxide powder of the second embodiment". The inorganic metal oxide powder of the second embodiment is used, for example, in the field of semiconductor encapsulation materials. In the inorganic metal oxide powder used in such a field, if the content of aggregates is 30 ppm (mass basis) or less and the total number (average value) of magnetized foreign matter is 2,000 pieces or less / 100 g, the effect of reducing the short-circuit defect rate of semiconductors can be easily obtained.

[0021] The inorganic metal oxide powder of the second embodiment preferably contains silica powder, more preferably spherical silica powder. In the second embodiment, when the inorganic metal oxide powder contains silica powder, the silica powder may be produced by either a dry method or a wet method. From the viewpoint of high productivity and lower cost, the silica powder produced by the molten flame method is preferable.

[0022] In the second embodiment, the total number (average value) of magnetized foreign matter having a particle size of 45 μm or more (hereinafter sometimes referred to as "large particle size magnetized foreign matter") contained in 100 g of inorganic metal oxide powder is preferably less than 10% of the total number (average value) of magnetized foreign matter contained in 100 g of inorganic metal oxide powder, more preferably 8.0% or less, and particularly preferably 7.0% or less. If the total number (average value) of large particle size magnetized foreign matter is within the above range, short circuits caused by magnetized foreign matter are less likely to occur. In this specification, the particle size of magnetized foreign matter refers to the diameter of the magnetized foreign matter measured by photographing the magnetized foreign matter with an optical microscope.

[0023] In the inorganic metal oxide powder of the second embodiment, the specific surface area measured by the BET method is 0.1 to 4 m 2 / g, and 0.5 to 4m 2 / g is more preferable, and 1 to 4m 2 / g Since the inorganic metal oxide powder according to the present invention is inhibited from agglomerating, it is easy to realize a sufficiently high specific surface area.

[0024] [Method for removing magnetized foreign matter from inorganic metal oxide powder] The above-mentioned inorganic metal oxide powder can be produced by removing magnetized foreign matter from an inorganic metal oxide powder obtained by a dry method or a wet method, by the method described below. The method for removing magnetized foreign matter according to the present invention is characterized in that it includes spray drying a slurry containing an inorganic metal oxide powder and a dispersion medium containing a monohydric alcohol having a linear or branched alkyl group having 1 to 3 carbon atoms. The method for removing magnetized foreign matter according to the present invention can effectively remove magnetized foreign matter adhering to the surface of a powder while suppressing aggregation of the powder particles.

[0025] <Slurry> In the method for removing magnetized foreign matter according to the present invention, the slurry contains an inorganic metal oxide powder and a dispersion medium. From the viewpoint of viscosity, the slurry concentration (concentration of the inorganic metal oxide powder) is preferably 30 to 70 mass % relative to the total mass of the slurry. From the viewpoint of more effectively suppressing aggregation of the inorganic metal oxide powder, the slurry concentration is preferably low.

[0026] (dispersion medium) In the method for removing magnetized foreign matter according to the present invention, the dispersion medium contains a monohydric alcohol having a linear or branched alkyl group having 1 to 3 carbon atoms. Examples of such monohydric alcohol include methanol, ethanol, n-propyl alcohol, and isopropyl alcohol. Among these, isopropyl alcohol is preferred from the viewpoint of more effectively suppressing aggregation of inorganic metal oxide powder. From the viewpoint of easily suppressing aggregation of the inorganic metal oxide powder, the proportion of the monohydric alcohol in the dispersion medium is preferably 50% by mass or more, more preferably 50 to 75% by mass, and even more preferably 75 to 100% by mass, based on the total mass of the dispersion medium. The dispersion medium may be composed of only isopropyl alcohol. The dispersion medium may contain components other than the monohydric alcohol. Examples of the other components include water (pure water, ion-exchanged water, etc.). When the dispersion medium contains other components, they can be blended in a ratio of 50 mass% or less with respect to the total mass of the dispersion medium. When the dispersion medium contains water and a monohydric alcohol, the ratio of the monohydric alcohol to the total amount (100 mass%) of water and the monohydric alcohol is preferably 50 mass% or more, more preferably 50 to 75 mass%.

[0027] The method for removing magnetized foreign matter according to the present invention includes spray drying the above-mentioned slurry. The temperature during spray drying (spray inlet temperature) is preferably equal to or higher than the boiling point of the solvent, and more preferably equal to or higher than the boiling point of the solvent + 20°C. Furthermore, the method for removing magnetized foreign matter according to the present invention may include a step of recovering the inorganic metal oxide powder after spray drying, as necessary. This recovery step may be a cyclone recovery step.

[0028] Furthermore, the method for removing magnetized foreign matter according to the present invention may include a de-ironizing step using a magnet, if necessary. The de-ironizing step may be, for example, a step of removing magnetized foreign matter from the recovered inorganic metal oxide powder using a natural magnet or an electromagnet. Alternatively, large-sized magnetized foreign matter may be removed by filtration using a magnet, and then spray-dried. When the method includes a de-ironizing step, large-sized magnetized foreign matter can be removed more effectively.

[0029] The method for removing magnetized foreign matter according to the present invention is a wet method, but can effectively suppress the aggregation of inorganic metal oxide powder. As described above, in the case of a method for removing magnetized foreign matter by a wet method, aggregation of powder occurs during the treatment, making it difficult to obtain an inorganic metal oxide powder having the same particle size distribution and BET as before the treatment. In the method for removing magnetized foreign matter according to the present invention, the BET of the inorganic metal oxide powder after the treatment, i.e., after the magnetized foreign matter is removed, is approximately the same as the BET of the inorganic metal oxide powder before the treatment. In other words, the change rate of the BET of the inorganic metal oxide powder after the treatment relative to the BET of the inorganic metal oxide powder before the treatment (BET after treatment / BET before treatment) is preferably 20% or less, more preferably 10% or less, and even more preferably 1.0% to 5%.

[0030] The method for removing magnetized foreign matter according to the present invention can halve the amount of magnetized foreign matter in inorganic oxide powder by spray drying a slurry containing inorganic metal oxide powder and a specific alcohol. In other words, the removal rate of magnetized foreign matter after spray drying, calculated by the following formula (3), is preferably 50% or more. (Magnetic foreign matter removal rate) (XY) / X × 100(%) (3) X: Total number of magnetized foreign particles in 100 g of inorganic metal oxide powder before treatment (average value) Y: Total number of magnetized foreign particles in 100 g of inorganic metal oxide powder after spray drying (average value)

[0031] Furthermore, the method for removing magnetized foreign matter according to the present invention can remove fine magnetized foreign matter adhering to the surface of inorganic metal oxide powder. For example, in the case of inorganic metal oxide powder with a D50 particle size of 1 μm or less, ultrafine powder with an average particle size of about 50 to 200 nm tends to adhere to the powder surface, but this ultrafine powder can be effectively removed. The removal rate of ultrafine powder from inorganic metal oxide powder with a D50 particle size of 1 μm or less is preferably 50% or more, and more preferably 60 to 95%. The removal rate of magnetized foreign matter having an average particle size of 45 μm or more from an inorganic metal oxide powder having a D50 particle size of more than 1 μm and not more than 100 μm is preferably 50% or more, and more preferably 55 to 98%. The removal rate of ultrafine powder and the removal rate of magnetized foreign matter having an average particle size of 45 μm or more are values ​​calculated using the removal rate of magnetized foreign matter of the above formula (3).

[0032] [Method of manufacturing inorganic metal oxide powder] The inorganic metal oxide powder according to the present invention can be produced, for example, by obtaining an inorganic metal oxide powder by a conventionally known dry method or wet method, and then carrying out a foreign matter removal step using the above-mentioned method for removing magnetized foreign matter. An example of a dry method for obtaining inorganic metal oxide powder is a method in which commercially available ores are crushed and classified, if necessary, and then fed into a high-temperature flame to form fine spherical powders. As an example of the wet method, a slurry containing a raw material powder is sprayed into a flame to remove the solvent, thereby obtaining an inorganic metal oxide powder.

[0033] The method for producing an inorganic metal oxide powder according to the present invention may include, for example, the following steps. (i) optionally, crushing and classifying the ore to obtain a raw powder; (ii) feeding the raw powder into a high-temperature flame in a reaction vessel to produce a fine spherical powder (molten powder); (iii) optionally classifying and collecting the fine spherical powder to obtain an inorganic metal oxide powder having a predetermined D50 particle size; and (iv) A step of spray drying a slurry containing the inorganic metal oxide powder obtained in (iii) and a dispersion medium containing a monohydric alcohol having a linear or branched alkyl group having 1 to 3 carbon atoms.

[0034] <Process (i)> The ore used in step (i) is preferably high purity (for example, 95% or more). Examples of the ore include silica, titanium, magnesium, and calcium ores. These may be used alone or in combination of two or more. Of these, it is more preferable to use silica. The ore is pulverized using a pulverizer such as a vibration mill or a ball mill, so that an ore powder having a desired average particle size can be appropriately selected. In the case of preparing the inorganic metal oxide powder of the first embodiment, the D50 particle size of the raw material powder prepared in step (i) is preferably 0.1 to 5 μm, more preferably 0.2 to 1 μm. In the case of preparing the metal-free oxide powder of the second embodiment, the D50 particle size of the raw material powder prepared in step (i) is preferably 0.5 to 90 μm, more preferably 1 to 70 μm. In addition, the raw material powder may be a mixture of multiple types of raw material powders having different particle sizes.

[0035] <Process (ii)> In step (ii), the raw material powder obtained in step (i) is injected into a high-temperature flame formed by a combustible gas and a combustion supporting gas using a burner, melted and spheroidized at a temperature above the melting point of the raw material powder (for example, a temperature of 2,000°C or higher in the case of silica (quartz stone)), and classified and collected while cooling to obtain a spheroidized powder (fine spherical powder). As the combustible gas, hydrocarbon gases such as acetylene, ethylene, propane, butane, etc.; gaseous fuels such as LPG and LNG; and liquid fuels such as kerosene and heavy oil; can be used. As the combustion supporting gas, oxygen, oxygen-rich cooling gas, and air can be used.

[0036] In step (ii), the D50 particle size of the fine spherical powder may be adjusted by adjusting the discharge speed when collecting the powder (eg, with an air classifier, etc.).

[0037] <Step (iii)> In step (iii), the fine spherical powder obtained in step (ii) is further classified and collected, if necessary, by sieving or the like, to obtain an inorganic metal oxide powder having a predetermined D50 particle size.

[0038] <Process (iv)> Step (iv) is a step of removing magnetized foreign matter from the inorganic metal oxide powder by the above-mentioned method for removing magnetized foreign matter. That is, a slurry containing the inorganic metal oxide powder obtained in step (iii) and a dispersion medium containing a monohydric alcohol having a linear or branched alkyl group having 1 to 3 carbon atoms is spray-dried. A preferred embodiment of step (iv) is the same as the above-mentioned method for removing magnetized foreign matter. Furthermore, the above-mentioned deironization step, i.e., a step of removing magnetized foreign matter using a magnet, may be included in a step before or after step (iv). In one embodiment, it is preferable to include a deironization step in a step before step (iv). Moreover, it is more preferable that the deironization step is wet deironization. As the "wet deironization", it is preferable to use a method of filtering the inorganic metal oxide powder obtained in step (iii) to remove large-sized magnetized foreign matter using a magnet.

[0039] After the step (iv), the inorganic metal oxide powder is collected, thereby obtaining an inorganic metal oxide powder having the desired physical properties and D50 particle size.

[0040] [Application] The inorganic metal oxide powder according to the present invention can be used for the production of semiconductor encapsulation materials, etc. In particular, since the aggregation of powder particles is suppressed and the BET is the same as that before the magnetized foreign matter is removed, the resin composition containing the inorganic metal oxide powder according to the present invention is less likely to deteriorate in various physical properties such as flowability, burrs, and moldability while suppressing defects caused by the magnetized foreign matter. Therefore, it can be preferably used for the production of semiconductor encapsulation materials for electronic devices.

[0041] <Resin composition> The resin composition according to the present invention contains the inorganic metal oxide powder described above. The content of the inorganic metal oxide powder in the resin composition is not particularly limited and can be appropriately adjusted depending on the purpose. For example, in the case of a resin composition containing the inorganic metal oxide powder of the first embodiment, the ratio of the inorganic metal oxide powder of the first embodiment in the resin composition is preferably 5 to 50 mass %, more preferably 10 to 40 mass %, based on the total mass of the resin composition. In addition, in the case of a resin composition containing the inorganic metal oxide powder of the second embodiment, the proportion of the inorganic metal oxide powder of the second embodiment in the resin composition is preferably 40 to 95 mass %, more preferably 70 to 93 mass %, relative to the total mass of the resin composition.

[0042] (resin) The resin is not particularly limited as long as it is one that is normally used in the field of semiconductor encapsulation materials. For example, epoxy resin; silicone resin; phenol resin; melamine resin; urea resin; unsaturated polyester; fluororesin; polyimide, polyamideimide, polyetherimide, and other polyimides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide; wholly 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, and the like. These may be used alone or in combination of two or more. Of these, it is more preferable to include epoxy resin.

[0043] The epoxy resin is not particularly limited, and examples thereof include phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, epoxidized novolac resin of phenols and aldehydes, glycidyl ethers of bisphenol A, bisphenol F, and bisphenol S, glycidyl ester acid epoxy resins obtained by reacting polybasic acids such as phthalic acid and dimer acid with epochlorohydrin, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified polyfunctional epoxy resins, β-naphthol novolac type epoxy resins, 1,6-dihydroxynaphthalene type epoxy resins, 2,7-dihydroxynaphthalene type epoxy resins, bishydroxybiphenyl type epoxy resins, and epoxy resins into which halogens such as bromine have been introduced to impart flame retardancy. These may be used alone or in combination of two or more. Of these, it is more preferable to include at least one epoxy resin selected from bisphenol type epoxy resins such as bisphenol A type epoxy resins and bisphenol F type epoxy resins and alicyclic epoxy resins.

[0044] (hardening agent) When the resin contains an epoxy resin, the resin composition preferably further contains a curing agent. Examples of the curing agent include a novolac type resin obtained by reacting one or more mixtures selected from the group consisting of phenol, cresol, xylenol, resorcinol, chlorophenol, t-butylphenol, nonylphenol, isopropylphenol, octylphenol, etc. with formaldehyde, paraformaldehyde, or paraxylene under an oxidation catalyst, a polyparahydroxystyrene resin, a bisphenol compound such as bisphenol A or bisphenol S, a trifunctional phenol such as pyrogallol or phloroglucinol, an acid anhydride such as maleic anhydride, phthalic anhydride, or pyromellitic anhydride, and an aromatic amine such as metaphenylenediamine, diaminodiphenylmethane, or diaminodiphenylsulfone.

[0045] The content of the curing agent is preferably such that the active hydrogen equivalent (or acid anhydride equivalent) of the curing agent is 0.01 to 1.25 per 1 epoxy equivalent of the epoxy resin.

[0046] (Other additives) The resin composition may contain a curing accelerator, a release agent, a coupling agent, a colorant, etc., within the range not impairing the effects of the present invention. The curing accelerator is not particularly limited, and examples of the curing accelerator include 1,8-diazabicyclo(5,4,0)undecene-7, triphenylphosphine, benzyldimethylamine, and 2-methylimidazole. Examples of the release agent include natural waxes, synthetic waxes, metal salts of straight-chain fatty acids, acid amides, esters, and paraffin. The coupling agent may be a silane coupling agent, such as epoxy silanes (gamma-glycidoxypropyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, amino silanes (aminopropyltriethoxysilane, ureidopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, etc.), hydrophobic silane compounds (phenyltrimethoxysilane, methyltrimethoxysilane, octadecyltrimethoxysilane, etc.), and mercaptosilanes.

[0047] <Method of producing resin composition> The method for producing the resin composition is not particularly limited, and the resin composition can be produced by stirring, dissolving, mixing, and dispersing a predetermined amount of each material. The apparatus for mixing, stirring, dispersing, etc. of the mixture is not particularly limited, but a mortar and pestle machine equipped with a stirring and heating device, a three-roll mill, a ball mill, a planetary mixer, etc. can be used. These apparatuses may also be used in appropriate combination. EXAMPLES

[0048] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

[0049] [Example 1] A spherical amorphous silica powder (manufactured by Denka Co., Ltd., product name: FB-950FD) manufactured by a dry method (flame fusion method) was prepared, and the total number (average value) of magnetized foreign matter before processing was measured using the following method, which was 3,683 pieces / 100 g. The silica powder was then dispersed in isopropyl alcohol to prepare a slurry (slurry concentration: 20% by mass). This slurry was subjected to wet iron removal to remove magnetized foreign matter contained in the silica powder, and then placed in a spray dryer (manufactured by Yamato Scientific Co., Ltd., product name: GB-210+GAS410 type), spray dried at a spray inlet temperature of 220°C (maximum temperature) and a mixed solvent evaporation rate of 1300mL / hr (maximum value) to obtain a silica powder. After the magnetized foreign matter removal process, the silica powder was collected, and the content ratio of aggregates, the total number of magnetized foreign matter (average value), D50 particle size, and specific surface area were measured by the following methods. The results are shown in Table 1.

[0050] (Agglomerate content) 300 g of ion-exchanged water was added to 100 g of silica powder and treated with an ultrasonic device (manufactured by AS ONE Corporation, product name: ASU CLEANER, model: AUS-20M) at an output of 500 W for 5 minutes. Thereafter, in accordance with JIS Z 8815-1994, the mixture was sieved through a sieve with 150 μm openings. The silica powder remaining on the sieve was dried at 60° C. for 4 hours, and then its mass: W (g) was measured. The content ratio of aggregates was also calculated according to the following formula (1). Aggregate content (ppm) = (W(g) / 100(g)) x 10 6 (1)

[0051] (Total number of magnetized foreign objects (average value)) A: 10 g of silica powder and 40 mL of ion-exchanged water were placed in a centrifuge tube. Next, the centrifuge tube was placed in a φ150 mm container filled with water so that the water level in the centrifuge tube was the same as that of the container, and the tube was dispersed for 2 minutes using a homogenizer (manufactured by SONICS Co., Ltd., product name: VC-505) at an output of 500 W. The slurry after the dispersion process was placed in a resin tray with a thickness of 0.2 mm, and magnetized foreign matter was collected using a magnet with a magnetic force of 12,000 gauss. B: The procedure of A was repeated 10 times to collect magnetized foreign matter contained in 100 g of silica powder. The collected slurry containing magnetized foreign matter was suction filtered using a membrane filter (filter diameter: 1 μm, Millipore, model: JAWP04700) to collect the magnetized foreign matter on the filter. After that, the entire area on the filter was observed under an optical microscope (magnification: 100 times) and the total number of magnetized foreign matter was counted. C: A and B were repeated five times, and the average value was taken as the "total number of magnetized foreign matter (average value)."

[0052] (D50 particle size measurement) Using a laser diffraction / scattering particle size distribution analyzer (manufactured by Beckman Coulter, product name: LS-230), the silica powder was dispersed using water (refractive index: 1.33) as the solvent for 2 minutes as pretreatment at an output of 200 W using an ultrasonic generator UD-200 (with ultra-micro tip TP-040 attached) manufactured by Tommy Seiko Co., Ltd., and then the volume-based cumulative diameter of the silica powder was measured.

[0053] (Measurement of specific surface area) The specific surface area of ​​the silica powder was measured by the BET method using a fully automatic specific surface area measuring device (manufactured by Mountec Co., Ltd., product name: Macsorb HM model-1208).

[0054] [Example 2] Except for changing the slurry concentration to 50% by mass, the magnetized foreign matter was removed from the silica powder (FB-950FD) in the same manner as in Example 1. In addition, the content ratio of agglomerates after the magnetized matter treatment, the total number (average value) of magnetized foreign matter, the D50 particle size, and the specific surface area were measured. The results are shown in Table 1.

[0055] [Example 3] The magnetic particles were removed from the silica powder (FB-950FD) in the same manner as in Example 2, except that the dispersion medium was a mixed solvent of isopropyl alcohol and water (ratio of isopropyl alcohol: 50% by mass). In addition, the content ratio of aggregates after the magnetic treatment, the total number (average value) of magnetic particles, D50 particle size, and specific surface area were measured. The results are shown in Table 1.

[0056] [Comparative Example 1] Except for changing the dispersion medium to water, the magnetized foreign matter was removed from the silica powder (FB-950FD) in the same manner as in Example 2. In addition, the content ratio of agglomerates after the magnetized matter treatment, the total number (average value) of magnetized foreign matter, the D50 particle size, and the specific surface area were measured. The results are shown in Table 1.

[0057] [Table 1]

[0058] As shown in Table 1, the silica powders of Examples 1 to 3 obtained by the manufacturing method according to the present invention, which includes a step of removing magnetized foreign matter, had an aggregate ratio of 30 ppm or less, and the total number (average value) of magnetized foreign matter was 2,000 or less per 100 g. On the other hand, the silica powder of Comparative Example 1, in which magnetized foreign matter was removed using only water as the dispersion medium, had an aggregate ratio higher than 30 ppm, and the total number (average value) of magnetized foreign matter was also high. From these results, it was found that the present invention can provide an inorganic metal oxide powder with fewer aggregates and a smaller total number of magnetized foreign matter, and a manufacturing method thereof. When the amounts of ionic impurities in Examples 1 to 3 were measured, the amounts of Fe ions were 50 ppm or less, Na ions were 10 ppm or less, and chloride ions were 2 ppm or less.

Claims

1. An inorganic oxide powder comprising: The inorganic oxide powder includes silica powder, An inorganic metal oxide powder having an aggregate content of 30 ppm (mass basis) or less, a total number (average value) of magnetized foreign matter of 2,000 or less per 100 g, and a volume-based cumulative diameter (D50) of more than 1 μm and 100 μm or less, as determined by the following measurement method. (Measurement method) 300 g of ion-exchanged water is added to 100 g of inorganic metal oxide powder and treated with an ultrasonic device for 5 minutes. After that, the powder is sieved through a sieve with 150 μm openings in accordance with JIS Z 8815-1994. The inorganic metal oxide powder remaining on the sieve is dried at 60° C. for 4 hours, and then the mass of the aggregates: W (g) is measured. The value calculated by the following formula (1) is taken as the content ratio of the aggregates. Aggregate content (ppm)=(W(g) / 100(g))×10 ６ ...(1)

2. 2. The method for producing the inorganic metal oxide powder according to claim 1, comprising spray drying a slurry containing an inorganic metal oxide powder and a dispersion medium containing a monohydric alcohol having a linear or branched alkyl group having 1 to 3 carbon atoms.

3. 3. The method for producing an inorganic metal oxide powder according to claim 2, wherein the dispersion medium contains the monohydric alcohol and water, and the proportion of the monohydric alcohol relative to the total amount (100 mass%) of the monohydric alcohol and the water is 50 mass% or more.

4. The method for producing an inorganic metal oxide powder according to claim 2 or 3, wherein the monohydric alcohol includes isopropyl alcohol.

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