Powder containing aluminum nitride particles, method for producing the same, and resin composition

Abstract

This disclosure provides a powder containing aluminum nitride particles that can achieve high diffuse reflectance and low dielectric loss tangent, a method for producing the same, and a resin composition containing the powder. [Solution] A powder containing aluminum nitride particles, wherein the average crystallite diameter of the aluminum nitride particles is 50 nm or more and less than 130 nm, and the oxygen content of the powder is 0.75% by mass or less. Preferably, the average particle size (D50) of the powder is 1 to 50 μm. Preferably, the diffuse reflectance of the powder at a wavelength of 500 nm is 80% or more.

Description

[Technical Field]

[0001] This disclosure relates to a powder containing aluminum nitride particles, a method for producing the same, and a resin composition. [Background technology]

[0002] In recent years, with the increase in the volume of information and communication in the telecommunications field, the use of high-frequency signals in electronic devices and communication equipment has been expanding. On the other hand, applying high-frequency signals to these devices has also led to the problem of increased transmission loss of circuit signals. Therefore, materials with low dielectric loss tangents are required for use in high-frequency devices.

[0003] Incidentally, aluminum nitride has a high thermal conductivity close to that of metals, and is therefore used as a high thermal conductivity material. Sintered aluminum nitride bodies are put into practical use as substrates for semiconductors, and aluminum nitride powder is used as a heat dissipation filler. For example, Patent Document 1 proposes aluminum nitride powder that has high thermal conductivity and good fluidity when filled into a resin composition. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7506278 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] As mentioned above, aluminum nitride powder is primarily used as a heat dissipation filler, and no aluminum nitride powder with a low dielectric loss tangent that can be applied to high-speed communication equipment is known.

[0006] When aluminum nitride powder is applied as a ceramic filler for next-generation high-speed communication equipment, it is presumed that high purity, small particle size, good compatibility with resin components, and low dielectric loss tangent are required. Generally, it is thought that the presence of impurities or crystal defects in powder reduces diffuse reflectance. In other words, in aluminum nitride powder, if there are few impurities or crystal defects (i.e., high purity), the diffuse reflectance will be high. Typical aluminum nitride powder has low diffuse reflectance, i.e., low purity. When the inventors of this invention investigated higher-purity aluminum nitride powder, they found that simply increasing the diffuse reflectance of aluminum nitride powder significantly increases the dielectric loss tangent.

[0007] The object of this disclosure is to provide a powder containing aluminum nitride particles that can achieve high diffuse reflectance and low dielectric loss tangent, a method for producing the same, and a resin composition containing the powder. [Means for solving the problem]

[0008] This disclosure includes the following aspects: A powder containing aluminum nitride particles, The average crystallite diameter of the aluminum nitride particles is 50 nm or more and less than 130 nm. A powder having an oxygen content of 0.75% by mass or less. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a powder containing aluminum nitride particles that can achieve high diffuse reflectance and low dielectric loss tangent, a method for producing the same, and a resin composition containing the powder. [Modes for carrying out the invention]

[0010] One embodiment of the present disclosure will be described in detail below, but the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each embodiment disclosed herein can be combined with any other features disclosed herein. If multiple upper and lower limits are given for a particular parameter, any combination of these upper and lower limits can be used to create a suitable numerical range. The lower and / or upper limits of the numerical ranges described herein may be replaced with numerical values ​​within that range, as shown in the examples. The expression "X~Y" indicating a numerical range means "X or greater and Y or less". If a particular description given for one embodiment also applies to other embodiments, that description may be omitted in the other embodiments.

[0011] [Powder containing aluminum nitride particles] The powder containing aluminum nitride particles according to this embodiment is a powder in which the average crystallite diameter of the aluminum nitride particles is 50 nm or more and less than 130 nm, and the oxygen content of the powder is 0.75% by mass or less. According to the powder containing aluminum nitride particles of this embodiment, high purity and low dielectric loss tangent can be achieved.

[0012] In this specification, "powder containing aluminum nitride particles according to this embodiment" may also be simply referred to as "aluminum nitride-based powder." From the viewpoint of achieving high purity and low dielectric loss tangent, the content of aluminum nitride particles in the aluminum nitride powder of this embodiment is preferably 98% by mass or more, more preferably 99.0% by mass or more, even more preferably 99.5% by mass or more, and particularly preferably 99.9% by mass or more, relative to the total mass of the aluminum nitride powder. The upper limit of the content of aluminum nitride particles in the aluminum nitride powder of this embodiment may be 100% by mass.

[0013] <Average crystallite size of aluminum nitride particles> In the aluminum nitride-based powder according to this embodiment, the average crystallite diameter of the aluminum nitride particles is 50 nm or more and less than 130 nm. By containing aluminum nitride particles with an average crystallite diameter of 50 nm or more and less than 130 nm, and by having an oxygen content of 0.75% by mass or less in the powder, an aluminum nitride-based powder with high diffuse reflectance and low dielectric loss tangent is obtained. The average crystallite diameter of the aluminum nitride particles in the powder can be measured under the following conditions.

[0014] (Measurement of average crystallite size) The average crystallite size can be calculated by molding aluminum nitride particles into a resin holder and performing X-ray diffraction measurements using an X-ray diffractometer (e.g., Bruker Corporation, product name "D8 ADVENCE"). The measurement can be performed using the continuous scan method, scanning speed 0.017° / 0.5sec, tube voltage: 40kV, tube current: 40mA, X-ray source: CuKα (λ=1.5406Å), slit width: divergent slit: 0.5°, solar slit: 4°, measurement range: 2θ=10°~140°. The crystalline phase can be identified in the obtained X-ray diffraction pattern, and the average crystallite size can be determined by qualitative analysis and Scherrer method using peak diffraction (e.g., the software "TOPAS"). The crystallite size obtained by the Scherrer method is a value calculated in an X-ray diffractometer based on Scherrer's formula: crystallite size D = K × λ / (β × cosθ) (where K is Scherrer's constant, λ is the wavelength of the X-rays used, β is the broadening of the diffraction line width, and θ is the Bragg angle).

[0015] In one embodiment, the average crystallite diameter of the aluminum nitride particles may be 80 nm or more and less than 130 nm, or 90 to 120 nm.

[0016] <Oxygen content of powder containing aluminum nitride particles> The oxygen content of the powder comprising aluminum nitride particles according to the present embodiment is 0.75% by mass or less. To adjust the oxygen content to 0.75% by mass or less, for example, it is preferable to remove oxygen by firing an aluminum nitride-based powder at a high temperature in an inert gas atmosphere. Note that for the aluminum nitride-based powder according to the present embodiment, it is also necessary to control the average crystallite diameter of the aluminum nitride particles within a specific range. The aluminum nitride-based powder according to the present embodiment (that is, a powder comprising aluminum nitride particles having an average crystallite diameter of 50 nm or more and less than 130 nm and having an oxygen content of 0.75% by mass or less) is preferably prepared by the production method described later.

[0017] In one embodiment, from the viewpoint of easily achieving a lower dielectric loss tangent, the oxygen content of the powder is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.35% by mass or less. Note that the oxygen content of the aluminum nitride-based powder can be measured by the following method.

[0018] (Measurement of Oxygen Content) The oxygen content can be measured using an oxygen-nitrogen analyzer. For example, it can be measured by heating the aluminum nitride-based powder from 20°C to 2210°C in an argon atmosphere. As the temperature increases, oxygen is detected first, and nitrogen is detected thereafter.

[0019] The oxygen content can be easily reduced by increasing the heat treatment temperature to 1700°C or higher during the production process of the aluminum nitride-based powder.

[0020] In the field of thermally conductive fillers, it is known that device performance can be maintained by increasing the diffuse reflectance of aluminum nitride-based powder and thereby increasing its purity. It is also known that the thermal conductivity changes when the contact area between crystallites changes. On the other hand, no studies have been conducted on the parameters that affect the dielectric properties of aluminum nitride-based powder. According to the inventors' studies, it was found that in high-purity aluminum nitride-based powder, the dielectric loss tangent increases significantly compared to aluminum nitride-based powder before purification. As a result of further investigation, the inventors found that the average crystallite diameter of the aluminum nitride particles affects the dielectric loss tangent of the aluminum nitride-based powder. Furthermore, they found that if the aluminum nitride-based powder contains aluminum nitride particles whose average crystallite diameter is controlled within a specific range, and the oxygen content of the entire powder is below a certain value, then high purity and low dielectric loss tangent can be achieved. Although the exact reason is unclear, it is presumed that the voids in the grain boundaries increase as the crystallite diameter decreases, thus reducing the dielectric loss tangent. Therefore, from the viewpoint of the dielectric loss tangent of the aluminum nitride-based powder according to this embodiment, a smaller crystallite diameter is considered preferable. Traditionally, a larger crystallite size has been considered preferable from the standpoint of thermal conductivity, so this result differs from conventional technical understanding.

[0021] In one embodiment, from the viewpoint of easily achieving a lower dielectric loss tangent, it is preferable that the aluminum nitride-based powder contains trace amounts of oxygen and impurities. From this viewpoint, the lower limit of the oxygen content in the aluminum nitride-based powder may be 0.1% by mass or more. That is, the oxygen content in the aluminum nitride-based powder may be 0.1 to 0.75% by mass, 0.2 to 0.7% by mass, or 0.3 to 0.7% by mass. In one embodiment, from the viewpoint of obtaining an aluminum nitride-based powder with higher purity and lower dielectric constant, the oxygen content may be 0.01 to 0.2% by mass, 0.01 to 0.15% by mass, or 0.01 to 0.1% by mass.

[0022] <Impurity content of aluminum nitride-based powder> Aluminum nitride powder may contain trace amounts of impurities. Here, "impurities" refers to components other than aluminum nitride and oxygen, specifically including B, Ca, Cu, Cr, Fe, Na, Ni, Si, Sn, and compounds thereof. When aluminum nitride powder contains impurities, the content is preferably 0.30% by mass or less, more preferably 0.20% by mass or less, and even more preferably 0.10% by mass or less, relative to the total mass of the aluminum nitride powder. The lower limit is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.08% by mass or more. In one embodiment, the aluminum nitride powder may contain one or more impurities selected from silicon and silicon compounds. When one or more impurities selected from silicon and silicon compounds are present, the content of silicon and silicon compounds in the aluminum nitride powder is preferably 0.001 to 0.25% by mass, more preferably 0.002 to 0.15% by mass, and even more preferably 0.002 to 0.1% by mass, based on the total mass of the aluminum nitride powder. In one embodiment, the aluminum nitride powder may contain one or more impurities selected from iron and iron compounds. When one or more impurities selected from iron and iron compounds are present, the content of iron and iron compounds in the aluminum nitride powder is preferably 0 to 0.01% by mass, more preferably 0.0004 to 0.005% by mass, and even more preferably 0.0005 to 0.0025% by mass, based on the total mass of the aluminum nitride powder. In one embodiment, the aluminum nitride powder may contain one or more impurities selected from carbon and carbon compounds. When one or more impurities selected from carbon and carbon compounds are present, the content of carbon and carbon compounds in the aluminum nitride powder is preferably 0.01 to 0.1% by mass, more preferably 0.02 to 0.08% by mass, and even more preferably 0.03 to 0.06% by mass, based on the total mass of the aluminum nitride powder. Furthermore, in one embodiment, the impurity content in the aluminum nitride powder may be zero. Here, "zero impurity content" means that when the amount of impurities in the aluminum nitride powder is measured by the following method, no impurities are detected, or the amount of impurities is below the limit of quantification, in which case the impurity content is zero.

[0023] (Measurement of impurity levels) The impurity content in aluminum nitride powder can be measured by the following procedure. The aluminum nitride powder is dissolved by pressurized acid decomposition to prepare a sample solution. The resulting sample solution is then subjected to quantitative elemental analysis using, for example, an ICP emission spectrometer (e.g., Shimadzu, product name: ICPE-9820). The carbon content is measured using, for example, a LECO CS844.

[0024] <Average particle size (D50) of aluminum nitride-based powder> The average particle size (D50) of aluminum nitride-based powder is preferably 1 to 50 μm. If the aluminum nitride-based powder contains relatively large aluminum nitride particles with an average crystallite diameter of 50 nm or more and less than 130 nm, and has a relatively small average particle size (D50), it is easier to achieve a low dielectric loss tangent. From the viewpoint of obtaining a powder with an even lower dielectric loss tangent, an average particle size (D50) of 3 to 30 μm is more preferable, 3 to 15 μm is even more preferable, and 3 to 10 μm is particularly preferable.

[0025] (Measurement of average particle size (D50)) In this specification, the average particle diameter refers to the 50% cumulative diameter (median diameter) in the volume-based cumulative particle size distribution. More specifically, it refers to the particle diameter (D50) when the cumulative value in the volume-based cumulative particle size distribution obtained by laser diffraction scattering for powder reaches 50%. A laser diffraction scattering particle size distribution analyzer can be used for measurement. For example, a Microtrac MT3300EXII (Microtrac-Bell Co., Ltd.) can be used as a laser diffraction scattering particle size distribution analyzer. The specific measurement procedure involves, for example, adding aluminum nitride powder to an aqueous solution of deionized water mixed with 20 wt% sodium hexametaphosphate. Next, mixing and dispersion are performed using an ultrasonic homogenizer (e.g., Nippon Seiki Seisakusho Co., Ltd., product name: US-150E) to obtain a sample for measurement, and the particle size is measured using a laser diffraction scattering particle size distribution analyzer. From the obtained particle size distribution of the aluminum nitride powder, the particle sizes (μm) of D10 (10% of the volume accumulated from the smallest particle size side), D50 (50% of the volume accumulated), and D90 (90% of the volume accumulated from the smallest particle size side) can be determined.

[0026] In one embodiment, the average particle size (D90) of the aluminum nitride-based powder may be 6 to 60 μm, and preferably 8 to 50 μm. In one embodiment, the average particle size (D10) of the aluminum nitride-based powder may be 1.5 to 14 μm, and preferably 2 to 13 μm. The span value ((D90-D10) / D50) in the particle size distribution of the aluminum nitride powder may be 0.45 to 1.15, and preferably 0.5 to 1.10.

[0027] <Diffuse reflectance of aluminum nitride-based powder> In the powder containing aluminum nitride particles according to this embodiment, the diffuse reflectance (500 nm) may be 80% or more, preferably 85% or more, and more preferably 88% or more. If the diffuse reflectance (500 nm) is 80% or more, it becomes easier to obtain aluminum nitride-based powder with high purity and low dielectric loss tangent. In this specification, diffuse reflectance refers to the content of impurities and crystal defects in aluminum nitride-based powder. Generally, it is believed that the presence of impurities or crystal defects in a powder reduces its diffuse reflectance. In other words, in powders containing aluminum nitride particles, the diffuse reflectance tends to be higher when there are fewer impurities and crystal defects. The diffuse reflectance (500 nm) of aluminum nitride-based powder can be measured under the following conditions.

[0028] (Measurement of diffuse reflectance (500 nm)) Diffuse reflectance can be measured, for example, using a device consisting of a UV-Vis spectrophotometer (V-650) manufactured by JASCO Corporation with an integrating sphere device (ISV-722) attached. Baseline correction is performed using a standard reflector (Spectralon), and a solid sample holder filled with aluminum nitride powder (a quartz cell filled with aluminum nitride powder and tapped 20 times) is set up. Diffuse reflectance is then measured at a wavelength of 500 nm. The parameter settings for the measurement conditions are: response medium, bandwidth 2.0 nm, scanning speed 200 nm / min, data acquisition interval 0.5 nm, scanning mode continuous, control-related correction set to baseline, switching wavelength 340 nm, light source set to "automatic", and filter switching set to "stop scanning".

[0029] <Crystal plane of aluminum nitride particles> In one embodiment, it is preferable that the ratio of the (002) plane to the (100) plane in the crystal plane of the aluminum nitride particles is 0.60 or less. Generally, when aluminum nitride raw material powder is fired at high temperature, the C plane (the crystal plane of the hexagonal base) of the crystal in the aluminum nitride particles grows, and the crystallite diameter of the aluminum nitride particles tends to increase. According to the inventors' studies, it has been found that when the crystallite diameter becomes too large (i.e., when the average crystallite diameter is 130 nm or more), the dielectric loss tangent tends to increase. If the ratio of the (002) plane to the (100) plane in the crystal plane of the aluminum nitride particles is 0.60 or less, it becomes easier to achieve a low dielectric loss tangent. In one embodiment, the ratio of the (002) plane to the (100) plane may be 0.58 or less, or 0.56 or less. The ratio of the (002) plane to the (100) plane can be measured by the following method.

[0030] (Method for measuring crystal planes) X-ray diffraction measurements of aluminum nitride powder are performed using an X-ray diffractometer (for example, Bruker Corporation, product name "D8 ADVENCE"). From the obtained X-ray diffraction spectrum, peak intensities corresponding to the (002) plane and the (100) plane are obtained, and the ratio of the (002) plane to the (100) plane is calculated from these peak intensities.

[0031] <Dielectric loss tangent> As described above, the aluminum nitride-based powder according to this embodiment can achieve a low dielectric loss tangent. In one embodiment, the dielectric loss tangent (Df:tanδ) of the aluminum nitride-based powder at 1 GHz is 3.2 × 10⁻¹⁰. -2 Preferably less than 3.1 × 10 -2 The following is more preferable: 3.0 × 10 -2 The following is even more preferable: 1.0 × 10 -2 The following conditions are particularly preferable. Note that the dielectric loss tangent tanδ of the aluminum nitride powder refers to the value at 1 GHz measured by the cavity resonator contact method in accordance with JIS C2565. Furthermore, other detailed measurement conditions shall follow those described in the examples below.

[0032] [Method for producing powder containing aluminum nitride particles] The aluminum nitride-based powder according to this embodiment can be prepared by a manufacturing method comprising: preparing aluminum nitride raw material powder (step (1)); heating the aluminum nitride raw material powder in an inert gas atmosphere at 1700 to 2100°C to obtain a calcined product (step (2)); and pulverizing the calcined product (step (3)). The manufacturing method according to this embodiment will be described below.

[0033] <Process (1)> Step (1) is to prepare aluminum nitride raw material powder (hereinafter referred to as "raw material powder"). Here, "raw material powder" refers to aluminum nitride-based powder with an oxygen content of more than 0.75% by mass, or powder containing aluminum nitride particles with an average crystallite diameter of less than 50 nm or 130 nm or more. Commercially available raw material powder may be used.

[0034] While there are no particular limitations on the average particle size (D50) of the raw material powder, particles of 0.5 to 10 μm may be used from the viewpoint of easily adjusting the D50 of the final aluminum nitride-based powder to 1 to 50 μm. Furthermore, while there are no particular limitations on the diffuse reflectance (500 nm) or impurity content of the raw material powder, from the viewpoint of preventing particle sintering from progressing easily, a diffuse reflectance (500 nm) of 60% or more and an impurity content of 0.3 mass% or less are preferred.

[0035] In one embodiment, preparing the raw material powder may include adding one or more additives selected from silicon and silicon-containing compounds to the raw material powder. After adding one or more additives selected from silicon and silicon-containing compounds to the raw material powder, heating the raw material powder containing the additives at a predetermined temperature makes it easier to obtain powder with a low oxygen content while preventing an increase in the average crystallite size. Although the exact reason why adding one or more additives selected from silicon and silicon-containing compounds to the raw material powder yields the above effect is unclear, it is thought that when the raw material powder containing the additives is heated in an inert gas atmosphere, oxygen inside the aluminum nitride particles diffuses within the particles, and external oxygen combines with silicon, causing the oxygen atoms to react with silicon to form silicon monoxide, which then vaporizes. In the chemical composition of oxygen and silicon and / or silicon compounds in aluminum nitride powder, it is known that oxygen concentration and silicon concentration are inversely correlated (Defects and lumniness control of AlN ceramic by Si-doping Scripta Materialia 110 (2016) 109-112). Therefore, it is conceivable that silicon and / or silicon compounds contribute to oxygen desorption from aluminum nitride-based powders.

[0036] The silicon compound is not particularly limited as long as it contains silicon, and examples include silicon carbide and silicon nitride. These may be used individually or in combination of two or more. Of these, silicon nitride is preferable from the viewpoint of reducing oxygen content and improving diffuse reflectance.

[0037] In one embodiment, from the viewpoint of efficiently reducing the oxygen content while keeping the amount of impurities in the final powder low, the proportion of the additive added to the raw material powder is preferably 0 to 3.0% by mass, more preferably 0 to 1.5% by mass, and even more preferably 0 to 1.0% by mass, relative to the total mass of the raw material powder.

[0038] <Process (2)> Step (2) involves heating the raw material powder at 1700-2100°C under an inert gas atmosphere to obtain a calcined product. By heating the raw material powder at the above temperature, a powder can be obtained that contains aluminum nitride particles with an average crystallite diameter of 50 nm or more and less than 130 nm, and has an oxygen content of 0.75% by mass or less. Furthermore, impurities and defects inside the particles are more easily reduced, and the diffuse reflectance (500 nm) is more easily improved. Examples of inert gases include argon and nitrogen. From the viewpoint of suppressing crystal growth and achieving the desired average crystallite diameter, as well as the rate of mass change, the heating temperature is preferably 1700 to 1900°C, and more preferably 1700 to 1800°C. The heating time is not particularly limited, but from the viewpoint of the rate of mass change, it is preferably 1 to 15 hours, and more preferably 3 to 5 hours.

[0039] (Mass change rate) In one embodiment, the mass change rate before and after step (2) is preferably 4% by mass or less, and more preferably 3.5% by mass or less. If the mass change rate is 4% by mass or less, it is easier to obtain high-purity (high diffuse reflectance) aluminum nitride-based powder while suppressing an increase in dielectric loss tangent. Note that if step (1) includes the addition of one or more additives selected from silicon and silicon-containing compounds, the mass change rate tends to be small. The rate of change in mass of aluminum nitride powder before and after heating is calculated using the following formula (1), where W1 (g) is the mass of the aluminum nitride raw material powder before heating and W2 (g) is the mass of the aluminum nitride powder after heating. Mass change rate (mass%) = (W1-W2) / W1×100 (1)

[0040] <Process (3)> Step (3) is to grind the aluminum nitride-based powder obtained after step (2). Grinding can be done using a grinding machine such as a bead mill, ball mill, vibratory mill, or pot mill. Furthermore, the process may include classifying the resulting aluminum nitride-based powder after pulverization. Examples of classification methods include sieving, liquid cyclone classification, and wind classification. In one embodiment, the aluminum nitride-based powder may also be surface-treated with a surface treatment agent or washed.

[0041] [Application] The aluminum nitride-based powders of this disclosure have high diffuse reflectance and low dielectric loss tangent. Such aluminum nitride-based powders can be suitably used as ceramic fillers for high-frequency band (e.g., GHz band) equipment.

[0042] [Resin composition] The resin composition according to this embodiment comprises the aforementioned aluminum nitride-based powder and one or more resins selected from thermosetting resins and thermoplastic resins. The content of aluminum nitride-based powder in the resin composition is not particularly limited and can be adjusted as appropriate depending on the purpose. For example, when used as a substrate material for high frequency bands or as an insulating material, it may be blended in an amount of 1 to 95% by mass relative to the total mass of the resin composition, and more preferably in an amount of 10 to 80% by mass.

[0043] <Resin> The resin composition according to this embodiment comprises one or more resins selected from thermosetting resins and thermoplastic resins. More specifically, examples include polyethylene resin; polypropylene resin; epoxy resin; silicone resin; phenolic resin; melamine resin; urea resin; unsaturated polyester resin; fluororesin; polyamide resins such as polyimide resin, polyamideimide resin, and polyetherimide resin; polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin; polyphenylene sulfide resin; fully aromatic polyester resin; polysulfone resin; liquid crystal polymer resin; polyethersulfone resin; polycarbonate resin; maleimide-modified resin; ABS resin; AAS (acrylonitrile-acrylic rubber-styrene) resin; AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin; hydrocarbon elastomer resin; polyphenylene ether resin; aromatic polyene resin; olefin-aromatic vinyl compound-aromatic polyene copolymer resin (resin containing ethylene-styrene-divinylbenzene), etc. These may be used individually or in combination of two or more.

[0044] When the resin composition according to this embodiment is used as a substrate material or insulating material for high-frequency band applications, known low-dielectric resins used for this purpose can be employed. Specifically, as the low-dielectric resin, at least one resin selected from hydrocarbon elastomer resins, polyphenylene ether resins, aromatic polyene resins, and olefin-aromatic vinyl compound-aromatic polyene copolymer resins (preferably resins containing ethylene-styrene-divinylbenzene) can be used. Of these, hydrocarbon elastomer resins or polyphenylene ether resins are preferred.

[0045] The resin composition according to this embodiment may contain curing agents, curing accelerators, mold release agents, coupling agents, colorants, flame retardants, ion capture agents, etc., to the extent that they do not impede the effects of the present invention.

[0046] <Method for producing resin compositions> The method for producing the resin composition according to this embodiment is not particularly limited and can be produced by stirring, dissolving, mixing, and dispersing predetermined amounts of each material. The apparatus for mixing, stirring, and dispersing these mixtures is not particularly limited, but a stirring 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 combinations.

[0047] As described above, the resin composition containing the aluminum nitride-based powder according to the present invention can achieve a low dielectric loss tangent.

[0048] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of this disclosure are disclosed below. [1] A powder containing aluminum nitride particles, The average crystallite diameter of the aluminum nitride particles is 50 nm or more and less than 130 nm. A powder having an oxygen content of 0.75% by mass or less. [2] The powder according to [1], wherein the average particle size (D50) of the powder is 1 to 50 μm. [3] The powder according to [1] or [2], wherein the diffuse reflectance of the powder at a wavelength of 500 nm is 80% or more. [4] The powder according to [2] or [3], wherein the average particle size (D50) is 3 to 30 μm. [5] The powder according to any one of [1] to [4], wherein the oxygen content is 0.35% by mass or less. [6] The powder according to any one of [1] to [5], wherein the ratio of (002) planes to (100) planes in the crystal plane of the aluminum nitride particles is 0.60 or less. [7] The dielectric loss tangent (Df:tanδ) of the powder at 1 GHz is 3.2 × 10 -2 A powder described in any of [1] to [6], which is less than [1]. A method for producing powder according to any one of [8] [1] to [7], Prepare aluminum nitride raw material powder. The aluminum nitride raw material powder is heated at 1700-2100°C under an inert gas atmosphere to obtain a calcined product, and A method for producing powder, comprising grinding the aforementioned calcined product. [9] The method for producing the powder according to [8], further comprising preparing the aluminum nitride raw material powder by adding one or more additives selected from silicon and silicon-containing compounds to the aluminum nitride raw material powder.

[10] A method for producing the powder according to [8] or [9], wherein the rate of change in mass before and after obtaining the calcined product is 4% by mass or less. A resin composition comprising the powder described in any of [1] to [7] and one or more resins selected from thermosetting resins and thermoplastic resins. Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments. [Examples]

[0049] The present disclosure will be further illustrated by the following examples, but these examples will not limit the interpretation of the present disclosure.

[0050] (Examples 1, 4, Comparative Example 2) Aluminum nitride raw material powder with an average particle size of 3 μm (manufactured by Denka Co., Ltd., SAN SR7; 100% by mass) was placed in an atmospheric pressure firing furnace (manufactured by Fuji Denpa Co., Ltd., model number: HM10000). Under an argon gas atmosphere, the aluminum nitride raw material powder was fired at 0.025 MPaG under the firing conditions shown in Table 1 to obtain aluminum nitride-based powder. The oxygen content, average particle size (D50), particle size (D10), particle size (D90), impurity amount, diffuse reflectance (500 nm), (002) plane / (100) plane ratio, dielectric loss tangent, and mass change rate (mass%) of the obtained aluminum nitride-based powder were measured. In addition, the average crystallite diameter (nm) of the aluminum nitride particles contained in the obtained aluminum nitride-based powder was measured. Regarding the purity of the obtained aluminum nitride-based powder, those with a diffuse reflectance (at 500 nm) of 80% or higher were evaluated as acceptable, and those with a diffuse reflectance (at 500 nm) of less than 80% were evaluated as unacceptable. In addition, the dielectric loss tangent was evaluated in accordance with the following evaluation criteria, using the dielectric loss tangent of Comparative Example 2 as a reference value. (Evaluation of Dielectric Loss Tangent) Good: the value of the dielectric loss tangent is 1.0×10 -2 It was less than . Fair: the value of the dielectric loss tangent is 1.0×10 -2 or more and 3.29×10 -2 It was less than . Unacceptable: the value of the dielectric loss tangent is 3.29×10 -2 It was greater than or equal to .

[0051] (Examples 2 to 3, 5 to 8) The additives shown in Table 1 were added to aluminum nitride raw material powder having an average particle diameter of 3 µm (manufactured by Denka Company Limited, SAN SR7; 99 mass%), and the mixture was charged into an atmospheric pressure firing furnace (manufactured by Fuji Denpa Co., Ltd., model number: HM10000). Under a nitrogen gas atmosphere at 0.025 MPaG, the mixture of the aluminum nitride raw material powder and the additive was fired under the firing conditions shown in Table 1 to obtain an aluminum nitride-based powder. The oxygen content, average particle diameter (D50), particle diameter (D10), particle diameter (D90), impurity content, diffuse reflectance (at 500 nm), the ratio of (002) plane to (100) plane, dielectric loss tangent, and mass change rate (mass%) of the obtained aluminum nitride-based powder were measured. In addition, the average crystallite diameter (nm) of the aluminum nitride particles contained in the obtained aluminum nitride-based powder was measured. The purity criteria and overall evaluation of the obtained aluminum nitride-based powder were evaluated as described in Example 1. The results are shown in Table 1.

[0052] (Comparative Example 1) The oxygen content, average particle size (D50), particle size (D10), particle size (D90), impurity content, diffuse reflectance (500 nm), (002) plane / (100) plane ratio, dielectric loss tangent, and mass change rate (mass%) of aluminum nitride raw material powder with an average particle size of 3 μm (manufactured by Denka Co., Ltd., SAN SR7; 100% by mass) were measured. The average crystallite size (nm) of the aluminum nitride particles contained in the aluminum nitride raw material powder was also measured. The purity standards and overall evaluation of the aluminum nitride raw material powder were evaluated as described in Example 1. The results are shown in Table 1.

[0053] [Table 1]

[0054] (Method for measuring oxygen content) The oxygen content was measured using an oxygen and nitrogen analyzer (manufactured by Horiba, Ltd., product name: EMGA-920) under the following conditions. The measurement was performed by heating 0.03 g of aluminum nitride powder in an argon atmosphere from 20°C to 2210°C.

[0055] (Method for measuring diffuse reflectance) The diffuse reflectance was measured using a device consisting of a JASCO UV-Vis spectrophotometer (V-650) with an integrating sphere device (ISV-722) attached. Baseline correction was performed using a standard reflector (Spectralon), and a solid sample holder filled with aluminum nitride powder (a quartz cell filled with aluminum nitride powder and tapped 20 times) was set up. Diffuse reflectance was measured at a wavelength of 500 nm. The parameter settings for the measurement conditions were: response medium, bandwidth 2.0 nm, scanning speed 200 nm / min, data acquisition interval 0.5 nm, scanning mode continuous, baseline specified for control-related correction, switching wavelength 340 nm, light source set to "automatic", and filter switching set to "stop scanning". Table 1 shows the measured diffuse reflectance (%) at 500 nm.

[0056] (Method for measuring average crystallite size) The average crystallite size was determined by X-ray diffraction measurement using an X-ray diffractometer (Bruker Corporation, product name "D8 ADVENCE") after molding aluminum nitride particles into a resin holder. The measurement was performed using the continuous scan method, with a scanning speed of 0.017° / 0.5sec, tube voltage of 40kV, tube current of 40mA, X-ray source: CuKα (λ=1.5406Å), slit width: divergent slit: 0.5°, solar slit: 4°, and measurement range: 2θ=10°~140°. The crystalline phase was identified in the obtained X-ray diffraction pattern. The crystallite size was determined by qualitative analysis and Scherrer method using peak diffraction (software "TOPAS"). The crystallite size obtained by the Scherrer method was calculated using Scherrer's formula in an X-ray diffractometer: crystallite size D = K × λ / (β × cosθ) (where K is Scherrer's constant, λ is the wavelength of the X-rays used, β is the broadening of the diffraction linewidth, and θ is the Bragg angle).

[0057] (Method for measuring average particle size) The particle size at which the cumulative particle size distribution (D50), at which the cumulative value reached 50%, at which the cumulative value reached 10%, and at which the cumulative value reached 90% (D90) in the volume-based cumulative particle size distribution obtained by laser diffraction scattering for aluminum nitride-based powder was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT3300EXII (Microtrac-Bell Co., Ltd.)). First, 0.225 g of the aluminum nitride powder to be measured was added to 62 ml of an aqueous solution of deionized water mixed with 2 ml of 20 wt% sodium hexametaphosphate. Next, the sample was mixed and dispersed for 3 minutes using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, product name: US-150E) to obtain a sample for measurement, and the particle size was measured using a laser diffraction / scattering particle size distribution analyzer. From the particle size distribution of the obtained aluminum nitride powder, the particle sizes (μm) of D10 (10% of the volume cumulative from the smallest particle size), D50 (50% of the volume cumulative), and D90 (90% of the volume cumulative from the smallest particle size) were determined.

[0058] (Method for measuring the crystal plane of aluminum nitride particles) X-ray diffraction measurements of aluminum nitride powder were performed using an X-ray diffractometer (manufactured by Bruker Corporation, product name "D8 ADVENCE"). From the obtained X-ray diffraction spectra, peak intensities corresponding to the (002) plane and the (100) plane were acquired, and the ratio of the (002) plane to the (100) plane was calculated from these peak intensities.

[0059] (Method for measuring impurities) The impurity content in aluminum nitride powder was measured using the following procedure. A sample solution was prepared by dissolving the aluminum nitride powder using a pressurized acid decomposition method. The resulting sample solution was then subjected to quantitative elemental analysis using an ICP emission spectrometer (Shimadzu Corporation, product name: ICPE-9820). The carbon content was measured using a LECO CS844.

[0060] (Method for measuring dielectric loss tangent) The obtained aluminum nitride-based powder was filled into a Teflon® tube, and the dielectric loss tangent of the aluminum nitride-based powder was measured. The dielectric loss tangent tanδ (1 GHz) was measured under the following conditions. Measurement method: Cylindrical cavity resonator method Measurement environment: Temperature 23°C, relative humidity 50% Measurement conditions: Sample size: Outer diameter 8mm, inner diameter 7mm, cylindrical shape Cavity1GHz Measuring instrument: Keycom Corporation, Model number: DPS18

[0061] (Method for measuring the rate of change in mass) The mass (wt%) of the aluminum nitride raw material powder and the aluminum nitride-based powder after calcination was measured using an electronic balance. The mass of the aluminum nitride raw material powder before heating was denoted as W1, and the mass of the aluminum nitride-based powder after heating was denoted as W2. The calculation was performed using the following formula. Mass change rate = (W1 - W2) / W1 × 100

[0062] As shown in Table 1, the aluminum nitride-based powder satisfying the configuration of this embodiment had a high diffuse reflectance at 500 nm, was a high-purity aluminum nitride-based powder, and achieved a low dielectric loss tangent. [Industrial applicability]

[0063] The powder containing aluminum nitride particles in this embodiment is a high-purity aluminum nitride-based powder with a low dielectric loss tangent. Such powder has industrial applicability as a ceramic filler for high-frequency band (e.g., GHz band) equipment.

Claims

1. A powder containing aluminum nitride particles, The average crystallite size of the aluminum nitride particles is 50 nm or more and less than 130 nm. A powder having an oxygen content of 0.75% by mass or less.

2. The powder according to claim 1, wherein the average particle size (D50) of the powder is 1 to 50 μm.

3. The powder according to claim 1 or 2, wherein the diffuse reflectance of the powder at a wavelength of 500 nm is 80% or more.

4. The powder according to claim 2, wherein the average particle size (D50) is 3 to 30 μm.

5. The powder according to claim 1 or 2, wherein the oxygen content is 0.35% by mass or less.

6. The powder according to claim 1 or 2, wherein the ratio of (002) planes to (100) planes in the crystal plane of the aluminum nitride particles is 0.60 or less.

7. The dielectric loss tangent (Df: tanδ) of the aforementioned powder at 1 GHz is 3.2 × 10⁻¹⁰. －２ The powder according to claim 1 or 2, which is less than [amount missing].

8. A method for producing the powder according to claim 1 or 2, Prepare aluminum nitride raw material powder. The aluminum nitride raw material powder is heated at 1700 to 2100°C under an inert gas atmosphere to obtain a calcined product, and A method for producing powder, comprising grinding the aforementioned calcined product.

9. Furthermore, the method for producing the powder according to claim 8, wherein preparing the aluminum nitride raw material powder includes adding one or more additives selected from silicon and silicon-containing compounds to the aluminum nitride raw material powder.

10. The method for producing the powder according to claim 9, wherein the rate of mass change before and after obtaining the calcined product is 4% by mass or less.

11. A resin composition comprising the powder described in claim 1 or 2 and one or more resins selected from thermosetting resins and thermoplastic resins.

Images