WO2017170856A1 - Method for manufacturing spherical aluminum nitride particles, and device for manufacturing spherical aluminum nitride particles - Google Patents

Method for manufacturing spherical aluminum nitride particles, and device for manufacturing spherical aluminum nitride particles Download PDF

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WO2017170856A1
WO2017170856A1 PCT/JP2017/013218 JP2017013218W WO2017170856A1 WO 2017170856 A1 WO2017170856 A1 WO 2017170856A1 JP 2017013218 W JP2017013218 W JP 2017013218W WO 2017170856 A1 WO2017170856 A1 WO 2017170856A1
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aluminum nitride
gas concentration
carbon monoxide
microwave
spherical aluminum
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PCT/JP2017/013218
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French (fr)
Japanese (ja)
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杉橋　敦史
佐藤　裕
澤野　清志
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新日鉄住金マテリアルズ株式会社
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Publication of WO2017170856A1 publication Critical patent/WO2017170856A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/072—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with aluminium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating

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  • the present invention relates to a method for producing spherical aluminum nitride particles and an apparatus for producing spherical aluminum nitride particles.
  • Spherical alumina (Al 2 O 3 ) particles are widely used in electronic devices such as semiconductor substrates as members such as fillers or heat dissipation sheets having excellent thermal conductivity.
  • a method is known in which alumina particles are provided with an aluminum nitride modified layer by nitriding by heating the alumina particles in a nitrogen atmosphere (Patent Document 1). .
  • the powdered kneaded product of alumina particles to which carbon is adhered is heated for 5 minutes or more in a state of being heated to 1400 ° C. or higher and 1700 ° C. or lower by microwave heating.
  • Patent Document 1 since the temperature of the powdery kneaded material is monitored by inserting a sheath type thermocouple into the powdery kneaded material, only the local temperature by the thermocouple is known. Even if the degree of nitridation is managed based on such local information, the degree of nitridation varies, and it is difficult to obtain spherical aluminum nitride particles having a desired degree of nitridation. Furthermore, since the thermocouple itself is also made of metal, when the thermocouple is inserted into the heating furnace, the firing reaction of the powdered kneaded product may be affected.
  • the temperature of the surface of the powdered kneaded material is not necessarily uniform, and is maintained in a heating furnace at a constant temperature for a certain period of time. Therefore, it is difficult to use the conventional firing management method, so that there is a problem that it is difficult to obtain spherical aluminum nitride particles having a desired degree of nitridation.
  • the present invention has been made in view of the above problems, and provides a spherical aluminum nitride particle production method and a spherical aluminum nitride particle production apparatus capable of obtaining spherical aluminum nitride particles having a desired degree of nitriding.
  • the purpose is to do.
  • a mixture containing spherical alumina particles and a carbon-based material powder is irradiated with microwaves in a nitrogen atmosphere in an applicator, so that at least a part of the spherical alumina particles is obtained.
  • the carbon monoxide gas concentration (% by volume) in the exhaust gas from the applicator is monitored, and the maximum value of the carbon monoxide gas concentration is determined.
  • the microwave irradiation is ended at an end timing determined from the maximum value.
  • the spherical aluminum nitride particle production apparatus of the present invention includes a spherical alumina particle irradiated with microwaves in a nitrogen atmosphere in an applicator equipped with a microwave oscillator, and the spherical alumina particle is irradiated with the microwave.
  • a spherical aluminum nitride particle production apparatus for producing spherical aluminum nitride particles by nitriding at least a part of particles, and measuring carbon monoxide gas concentration (% by volume) in exhaust gas from the applicator Based on the gas analyzer and the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer, the maximum value of the carbon monoxide gas concentration was detected, and the maximum value was determined based on the maximum value. And a control unit that terminates microwave irradiation by the microwave oscillator at an end timing.
  • the microwave irradiation can be terminated at an end timing determined based on the concentration of carbon monoxide gas generated according to the degree of nitridation of the entire spherical alumina particles to be processed in the applicator (heating furnace), there are variations in locality.
  • variation in the degree of nitriding can be suppressed, and spherical aluminum nitride particles having a desired degree of nitriding can be obtained.
  • sample temperature which is an example of a graph showing the incident power and reflected power of the microwave, and a CO concentration and the CO 2 concentration in the exhaust gas. It is an example of the fluorescent X-ray spectrum of what collected a part of spherical aluminum nitride particle
  • AlN aluminum nitride
  • the spherical aluminum nitride particles are mainly modified by nitriding the vicinity of the surface of the spherical alumina particles in order to ensure the performance as a filler or a heat radiation sheet, and the surface of the spherical alumina particles is aluminum nitride.
  • the nitriding reaction proceeds, and the spherical alumina particles as a whole are converted into spherical aluminum nitride.
  • the spherical alumina particles used for obtaining the spherical aluminum nitride particles may be spherical or substantially spherical.
  • the spherical alumina particles are preferably 5 to 150 ⁇ m in terms of 50 mass% average particle diameter (D50) determined on a mass basis using, for example, a laser particle size distribution analyzer (CILAS-920 manufactured by CILAS). This is because the produced spherical aluminum nitride particles are mixed with a resin to obtain a heat conduction characteristic required when the filler is used as a filler.
  • the spherical alumina particles those obtained by granulating alumina powder into a spherical shape can be used.
  • the spherical alumina powder can be obtained, for example, by an alkoxide method, a Bayer method, an ammonium alum pyrolysis method, or an ammonium dosonite pyrolysis method.
  • the granulation method include a wet stirring granulation method and a spray drying method.
  • particles granulated by the spray drying method are used.
  • the spray drying method may be any method such as a nozzle method or a disk method.
  • the carbon-based material powder examples include graphite, carbon black, acetylene black, amorphous carbon and the like, which may be naturally derived or industrially produced.
  • the metal content is 1% by mass or less, and preferably the metal content is 0.1% by mass or less so as not to affect the insulation performance of the aluminum nitride after production.
  • the carbon-based powder is desirably present so as to cover the spherical alumina particles that are the mixed raw material, and more preferably has an average particle diameter equal to or smaller than the average diameter of the spherical alumina particles.
  • the mixture containing the spherical alumina particles and the carbon-based material powder can be prepared by mixing the spherical alumina particles and the carbon-based material powder in a dry manner with a ball mill or the like.
  • a liquid dispersion medium such as water or alcohol may be added.
  • the mixing ratio is desirably about 0.5 times or less of the Al 2 O 3 / 3C stoichiometric ratio based on the following reaction formula.
  • FIG. 1 is a schematic cross-sectional view of one embodiment of the spherical aluminum nitride particle production apparatus of the present invention.
  • the spherical aluminum nitride particle production apparatus 1 includes an applicator (heating furnace) 2, a microwave oscillator 3, a carbon monoxide gas analyzer 13, and a control unit 14.
  • the applicator 2 is provided with a stirrer 5 for making the electromagnetic field distribution in the applicator 2 uniform and a mounting table 7 on which the heat insulating materials 8a and 8b are placed.
  • a quartz window 9 is provided in the opening formed at the position.
  • the heat insulating materials 8a and 8b are made of a plate or fiber having a predetermined thickness, and are laminated so as to surround the entire mortar 8c.
  • the mounting table 7 is made of a material mainly composed of, for example, microwave permeable alumina, silica, mullite, tridymite, magnesium oxide, sialon, aluminum nitride, and the heat insulating materials 8a and 8b are microwave permeable. It consists of fibrous alumina, silica, mullite and the like.
  • the mortar 8c is made of, for example, microwave-permeable high-purity alumina, silica, tridymite, magnesium oxide, sialon, aluminum nitride, and the like, and contains therein a mixture 6 containing spherical alumina particles and carbonaceous material powder. ing.
  • the mixture 6 surrounded by the heat insulating materials 8a and 8b and accommodated in the mortar 8c passes through the quartz window 9 provided in the applicator 2, the heat insulating materials 8a and 8b, and the openings formed in the mortar 8c.
  • the surface temperature can be monitored by the infrared camera 10.
  • the applicator 2 is provided with a waveguide 4 that guides the microwave from the microwave oscillator 3 into the applicator 2 at a predetermined position on the side wall.
  • a microwave irradiation output meter (not shown) for measuring the microwave irradiation output of the microwave actually irradiated from the microwave oscillator 3
  • a microwave reflection output meter (not shown) for measuring the microwave reflected from the light source.
  • the microwave irradiation output meter and the microwave reflection output meter send the measurement results obtained when the microwave is irradiated from the microwave oscillator 3 into the applicator 2 to the control unit 14 described later.
  • the applicator 2 is provided with a nitrogen gas supply pipe 11 and an exhaust gas pipe 12.
  • the nitrogen gas supply pipe 11 is connected to a nitrogen gas storage unit such as a cylinder (not shown), and supplies the nitrogen gas in the nitrogen gas storage unit into the applicator 2.
  • the exhaust gas pipe 12 discharges the exhaust gas from the applicator 2 to the outside of the applicator 2 via a carbon monoxide gas analyzer 13 capable of online analysis.
  • nitrogen gas is supplied from the upper side of the mixture 6 and exhaust gas is exhausted from the lower side of the mixture 6.
  • the present invention is not limited to such a positional relationship, and the reverse It may be a positional relationship.
  • the carbon monoxide gas analysis method performed by the carbon monoxide gas analyzer 13 includes a mass spectrometry method, an infrared absorption method, a constant potential electrolysis method, and the like, and any method may be used.
  • the carbon monoxide gas analyzer 13 capable of online analysis is used.
  • the present invention is not limited to this, and a gas trap is provided in the exhaust gas pipe 12 and manually by a sampler each time. Batch analysis may be performed.
  • the carbon monoxide gas analyzer 13 measures the concentration of carbon monoxide gas in the exhaust gas sent from the applicator 2 by irradiating the microwave from the microwave oscillator 3 into the applicator 2, for example. The result is sent to the control unit 14 as carbon monoxide gas concentration data.
  • the control unit 14 sends the control unit 14 as carbon monoxide gas concentration data.
  • the carbon-based material powder absorbs the microwave, whereby the temperature of the mixture 6 rises, and carbon monoxide (hereinafter referred to as “CO”) according to the above reaction formula. May occur).
  • the control unit 14 monitors the concentration value of the carbon monoxide gas in the applicator 2 based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13, and detects the maximum value of the carbon monoxide gas concentration. Can do. In addition to this, the control unit 14 generates a microwave irradiation end signal at a predetermined end timing based on the maximum value of the carbon monoxide gas concentration, and sends it to the microwave oscillator 3. The end timing determined by the control unit 14 is determined in advance by the control unit 14 based on the end timing at which spherical aluminum nitride particles having a desired degree of nitridation can be produced from the spherical alumina particles. Is.
  • the microwave oscillator 3 that has received the microwave irradiation end signal ends the irradiation of the microwave that was output to produce the spherical aluminum nitride particles.
  • the microscopic timing is determined at a predetermined end timing based on the carbon monoxide gas concentration generated according to the nitridation degree of the entire spherical aluminum nitride particles processed and generated in the applicator 2. Since the irradiation of the wave can be terminated, the nitridation degree of the spherical aluminum nitride particles can be controlled without depending on the heating temperature of the mixture 6 that can detect only local values. Spherical aluminum nitride particles can be obtained.
  • the microwave irradiation by the microwave oscillator 3 can be completed at the end timing at which spherical aluminum nitride particles having a desired nitriding degree are obtained, useless heating by the microwave oscillator 3 is prevented. Can do.
  • the degree of nitridation of the spherical aluminum nitride particles is controlled by monitoring the CO concentration.
  • the carbon monoxide gas is not simply detected by the fact that the carbon monoxide gas is not emitted.
  • the microwave irradiation is terminated at an end timing determined with reference to the maximum value of the carbon monoxide gas concentration in a state where the generation of is still continued. More specifically, after the maximum value of the carbon monoxide gas concentration (% by volume) is passed and before the carbon monoxide gas is no longer detected, the maximum value of the carbon oxide gas concentration is determined as a reference.
  • the microwave irradiation ends at the end timing.
  • FIG. 2 is an example of a graph of the concentration of carbon monoxide gas (hereinafter also referred to as CO) in the exhaust gas.
  • CO carbon monoxide gas
  • the CO concentration reaches a maximum value just before about 4 hours from the start of microwave irradiation, and then gradually decreases.
  • the CO concentration decreases to a low level and decreases. The degree of is also getting smaller. Therefore, in this example, the microwave irradiation was stopped after 7 hours.
  • CO 2 carbon dioxide gas
  • control unit 14 terminates the microwave irradiation by the microwave oscillator 3 at any point in time from about 4 hours to about 7 hours from the start of the microwave irradiation.
  • the maximum value of the CO concentration does not need to appear as the peak of the mountain-shaped peak as in this example, but may be the upper bottom of the trapezoidal peak where the same value continues for a certain period.
  • the control unit 14 determines the maximum value of the carbon monoxide gas concentration, for example, the control unit 14 monitors the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13, for example, When the combustion of the residual oxygen in the applicator 2 is completed, the temperature of the mixture 6 is limited to a temperature range where the temperature is 600 ° C. or higher, and the highest value of the carbon monoxide gas concentration is sequentially detected. When the carbon monoxide gas concentration decreases by a predetermined value or more, the highest value of the detected carbon monoxide gas concentration may be determined as the maximum value of the carbon monoxide gas concentration.
  • FIG. 2 shows a microwave output (microwave irradiation output P (t) measured by a microwave irradiation output meter (not shown in FIG. 1), and “incident (kW)” in FIG. And a microwave output measured by a microwave reflection output meter (microwave reflection output Pr (t), expressed as “reflection (kW)” in FIG. 2), which will be described later. It is used when calculating the converted CO gas concentration ⁇ (t) (t indicates time).
  • the output of the microwave fluctuates by about ⁇ 1 kw.
  • the reflected power from the stirrer 5 for making the electromagnetic field uniform in the spherical aluminum nitride particle production apparatus 1 of FIG. This is because it affects the oscillation of the microwave.
  • the rotation of the stirrer 5 is on the order of several tens of rpm for firing aluminum nitride, which takes a long time of several hours. Therefore, the microwave output duration ( ⁇ t) is about several seconds to one minute. It is also possible to use the average value at ⁇ , that is, the time average value (W) from time t ⁇ t to time t, as the irradiation microwave power P (t) and the reflected microwave power Pr (t).
  • FIG. 3 shows an example of a fluorescent X-ray spectrum of a sample obtained by sampling a part of the spherical aluminum nitride particles after completing the microwave irradiation at a predetermined time t. Since the analysis depth of the fluorescent X-ray spectrum is several ⁇ m at the maximum, Al 2 O 3 does not remain at a depth within several ⁇ m from the alumina particle surface, and AlN and AlON, which is an intermediate, from the spectrum. Can be confirmed.
  • AlN production rate (%) can be defined using the main peak height intensity of each material of these fluorescent X-rays.
  • FIG. 3 is an X-ray diffraction pattern of spherical aluminum nitride particles measured by a Rigaku X-ray diffractometer “RINT-2500TTR”.
  • the content ratio of AlN is calculated by calculating the maximum peak intensity of AlN (PDF card No. 25-1133), Al 2 O 3 (PDF card No. 10-0173), and AlON (PDF card No. 48-0686). Measurements were made, and the AlN content was calculated as a percentage from the intensity ratio by the following formula.
  • AlN production rate (%) peak height of AlN / (peak height of Al 2 O 3 , AlN, and AlON)
  • the AlN generation rate (t) at a predetermined time t has a good negative correlation with the ratio of the CO gas concentration at the time t after the start of microwave irradiation to the maximum CO gas concentration. It was found that the thermal conductivity (W / mK) showed a good positive correlation. From here, if the CO gas concentration ratio is monitored, spherical aluminum nitride particles having a desired thermal conductivity (W / mK) can be produced.
  • FIG. 4 is a graph showing a negative correlation between the AlN production rate (%) and the converted CO gas concentration ratio ⁇ (t) (described later).
  • the horizontal axis represents the converted CO gas concentration ratio ⁇ (t) at a predetermined time t.
  • the microwave output in the microwave oscillator 3 is changed, and there is also a loss due to the reflection of the microwave in the applicator 2, so the converted CO gas that compensates for these effects
  • a concentration ratio ⁇ (t) is used.
  • the converted CO gas concentration ⁇ (t) and the converted CO gas concentration ratio ⁇ (t) used when obtaining the converted CO gas concentration ratio ⁇ (t) will be described in detail.
  • the unit of concentration is volume% unless otherwise specified, and the unit of output is W.
  • ⁇ (t) which is a measured value of the CO gas concentration in the exhaust gas at a predetermined time t
  • ⁇ (t) ⁇ (t) / ⁇ P (t)
  • ⁇ P is a net microwave output obtained by the following equation (2).
  • ⁇ P (t) P (t) ⁇ Pr (t) (2)
  • P (t) is a microwave irradiation output at a predetermined time t
  • Pr (t) is a microwave reflection output at a predetermined time t.
  • P (t) and Pr (t) can be measured with a microwave irradiation output meter and a microwave reflection output meter.
  • the CO gas concentration that compensates for the fluctuation of the microwave output during firing is obtained. That is, when the microwave is output from the microwave oscillator 3, the microwave output from the microwave oscillator 3 may be lowered or increased depending on various circumstances. Accordingly, the reaction rate in the mixture 6 changes, and the CO gas concentration changes accordingly. Therefore, by dividing ⁇ (t) by ⁇ P (t), the CO gas concentration that compensates for fluctuations in the output of the microwave can be obtained.
  • the microwave output is reduced from the viewpoint of preventing damage to the device and safety
  • the reaction for converting alumina to aluminum nitride is an endothermic reaction, and the energy required for the reaction is supplied by microwave power. Therefore, when the output of the microwave to be irradiated is reduced, the rate at which the raw material alumina is converted to aluminum nitride is reduced, and the amount of CO gas generated as the raw material alumina is converted to aluminum nitride is reduced. The measured CO gas concentration decreases.
  • the microwave output during firing more precisely the microwave reflected back from the irradiated microwave output, is returned. It is necessary to correct the generated CO gas concentration using the net irradiated microwave output minus the reflected output.
  • the control unit 14 uses the microwave irradiation output meter and the microwave reflection output meter to receive the microwave irradiation output P (t) and the microwave reflection output Pr (t).
  • the converted CO gas concentration ⁇ (t) can be obtained from the measured CO gas concentration value ⁇ (t) obtained based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13.
  • the concentration value of carbon monoxide gas in the applicator 2 is monitored based on the converted CO gas concentration ⁇ (t) thus obtained by the control unit 14, and carbon monoxide.
  • the maximum value of the gas concentration may be specified.
  • the control unit 14 predetermines the end conversion CO gas concentration ⁇ end based on the maximum value of the carbon monoxide gas concentration as the end timing of the microwave irradiation at which spherical aluminum nitride particles having a desired nitriding degree can be obtained. Keep it.
  • the control unit 14 monitors the converted CO gas concentration ⁇ (t) obtained based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13, and the converted CO gas concentration ⁇ (t) is The microwave irradiation can be terminated when the end conversion CO gas concentration ⁇ end is reached.
  • the converted CO gas concentration ratio ⁇ (t) can be obtained from the ratio of the converted CO gas concentration ⁇ (t) at a predetermined time t to ⁇ max as shown in the following equation (3).
  • Equivalent CO gas concentration ratio ⁇ (t) ⁇ (t) / ⁇ max (3)
  • control unit 14 can convert the microwave stop conversion CO based on the maximum value of the carbon monoxide gas concentration as the microwave irradiation end timing at which spherical aluminum nitride particles having a desired nitriding degree can be obtained.
  • a gas concentration ratio ⁇ 0 is determined in advance, and the converted CO gas concentration ⁇ (t) and the converted CO gas concentration maximum value ⁇ max obtained based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13 are monitored. and Yuki, the terms CO gas concentration ratio gamma (t) is also possible to terminate the irradiation of the microwaves when reduced to gamma 0 a predetermined.
  • FIG. 5 is a graph showing a positive correlation between the AlN production rate (%) and the thermal conductivity (W / mK).
  • the thermal conductivity is obtained by mixing spherical aluminum nitride particles with a resin (general-purpose epoxy Bis-A type) at a volume ratio of 80:20, molding on a flat plate, and drying treatment. It was measured. The thermal conductivity was measured using a steady method.
  • the thermal conductivity for filler use is preferably 15 W / mK or more, and the AlN production rate (%) is preferably 45% or more from FIG.
  • the converted CO gas concentration ratio ⁇ (t) is confirmed in FIG. 4 based on the result of FIG.
  • the converted CO gas concentration ratio ⁇ (t) is 1.0 or less, preferably 0.8 or less.
  • the microwave irradiation may be terminated after the CO gas concentration reaches the maximum value.
  • the converted gas concentration ratio ⁇ (t) is 0. It was found that it is preferable to finish the firing at 1 or more. Accordingly, ⁇ 0 is preferably 1.0 to 0.1, and more preferably 0.9 to 0.1.
  • FIG. 6 is a scanning electron microscope (SEM) photograph of spherical aluminum nitride particles obtained in Examples described later. From FIG. 6, it can be seen that the spherical aluminum nitride particles are almost spherical and are suitable for the filler.
  • FIG. 7 is a mapping image of the particles of FIG. 6 by electron probe microanalysis (EPMA). As can be seen from FIG. 7, the degree of nitriding is about several ⁇ m to several tens ⁇ m from the surface of the spherical aluminum nitride particles, and it can be seen that the central portion of the spherical aluminum nitride particles is not nitrided.
  • SEM scanning electron microscope
  • the carbon-based powder is prepared so as to contain a large amount of carbon C in the above reaction formula in comparison with the molar equivalent of prepared Al 2 O 3 .
  • the cause of the reduction in generation is not carbon C deficiency in the material.
  • some of the spherical aluminum nitride particles are not completely nitrided at the center, the reduction of the CO gas concentration accompanying the progress of nitriding is reduced by the aluminum nitride layer generated in the spherical alumina. It is thought that it is influenced by the fact that N 2 gas is difficult to reach the inside of the aluminum nitride particles.
  • the present invention does not simply follow the amount of production on the right side in the above reaction formula, but comprehensively determines the production state of the spherical aluminum nitride including the surface and internal state of the spherical aluminum nitride.
  • the converted CO gas concentration ratio ⁇ (t) was determined based on the maximum value of the carbon monoxide gas concentration before the CO gas concentration ratio ⁇ (t) became 0 (that is, before the time when the CO gas concentration was below the detection limit). It is desirable to prevent the nitriding of the spherical aluminum nitride particles from proceeding excessively by terminating the microwave irradiation at a predetermined end timing.
  • spherical alumina particles Spherical alumina powder AX35-125 manufactured by Micron
  • 51 g of carbon-based material powder activated carbon for electrode material manufactured by Kuraray Chemical Co., Ltd.
  • 220 g of the raw material mixture is put in a high-purity alumina mortar and carbon monoxide gas in an applicator 2 of the spherical aluminum nitride particle production apparatus 1 having the configuration shown in FIG. 1 under a nitrogen gas stream of 50 L / min.
  • FIG. 6 shows a scanning electron micrograph of the spherical aluminum nitride particles obtained. As described above, it can be seen from FIG.
  • FIG. 7 shows an EPMA mapping image of spherical aluminum nitride particles.
  • the spherical aluminum nitride particles having a particle size of about 50 ⁇ m are nitrided from the surface by about 5 ⁇ m
  • the spherical aluminum nitride particles having a particle size of 30 ⁇ m or less are nitrided by about 10 ⁇ m. It was.
  • the calcined spherical aluminum nitride particles were mixed with a resin (general-purpose epoxy resin) at a volume ratio of 80:20, and the thermal conductivity of a sample molded and dried into a plate shape was about 21 w / mk measured by a steady method.
  • a resin general-purpose epoxy resin

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Abstract

Provided are a method for manufacturing spherical aluminum nitride particles and a device for manufacturing spherical aluminum nitride particles, whereby spherical aluminum nitride particles having the desired degree of nitridation can be obtained. In a device (1) for manufacturing spherical aluminum nitride particles, microwave irradiation can be terminated at a termination timing set in advance on the basis of the concentration of carbon monoxide gas generated in accordance with the degree of nitridation of spherical alumina particles processed in an applicator (2), and the degree of nitridation of the spherical alumina particles can therefore be controlled irrespective of the heating temperature, variations in the degree of nitridation can be suppressed, and spherical aluminum nitride particles having the desired degree of nitridation can be obtained.

Description

球状窒化アルミニウム粒子の製造方法及び球状窒化アルミニウム粒子製造装置Spherical aluminum nitride particle manufacturing method and spherical aluminum nitride particle manufacturing apparatus
　本発明は、球状窒化アルミニウム粒子の製造方法及び球状窒化アルミニウム粒子製造装置に関する。 The present invention relates to a method for producing spherical aluminum nitride particles and an apparatus for producing spherical aluminum nitride particles.
　球状アルミナ（Al2O3)粒子は、熱伝導性に優れたフィラー又は放熱シート等の部材として、半導体基板等の電子デバイスに広く使用されている。熱伝導性をさらに高めるために、アルミナ粒子を窒素雰囲気中でマイクロ波加熱して窒化することによって、窒化アルミニウム改質層を備えたアルミナ粒子を製造する方法が知られている（特許文献１）。同方法では、カーボンを付着させたアルミナ粒子の粉状混練物をマイクロ波加熱により１４００℃以上１７００℃以下の温度にした状態で５分間以上保持して熱処理を行う。 Spherical alumina (Al 2 O 3 ) particles are widely used in electronic devices such as semiconductor substrates as members such as fillers or heat dissipation sheets having excellent thermal conductivity. In order to further enhance the thermal conductivity, a method is known in which alumina particles are provided with an aluminum nitride modified layer by nitriding by heating the alumina particles in a nitrogen atmosphere (Patent Document 1). . In this method, the powdered kneaded product of alumina particles to which carbon is adhered is heated for 5 minutes or more in a state of being heated to 1400 ° C. or higher and 1700 ° C. or lower by microwave heating.
特開2011-219309号公報JP 2011-219309 JP
　しかしながら、特許文献１では、粉状混練物中にシース型熱電対を挿入して当該粉状混練物の温度を監視しているため、熱電対による局所的な温度しか分からない。このような局所的な情報に基づいて窒化の度合いを管理しても、窒化の程度にばらつきを生じ、所望の窒化度合いの球状窒化アルミニウム粒子を得ることが難しい。さらに、熱電対自体も金属製であるため、加熱炉内に熱電対を挿入した場合、粉状混練物の焼成反応に影響を与えてしまう恐れもある。 However, in Patent Document 1, since the temperature of the powdery kneaded material is monitored by inserting a sheath type thermocouple into the powdery kneaded material, only the local temperature by the thermocouple is known. Even if the degree of nitridation is managed based on such local information, the degree of nitridation varies, and it is difficult to obtain spherical aluminum nitride particles having a desired degree of nitridation. Furthermore, since the thermocouple itself is also made of metal, when the thermocouple is inserted into the heating furnace, the firing reaction of the powdered kneaded product may be affected.
　また、マイクロ波による直接加熱では、一般的に行われている電気炉加熱と異なり、粉状混練物の表面等の温度が必ずしも均一とは成らず、一定温度の加熱炉内で一定時間保持する、という従来の焼成管理方法を利用することも困難であるため、その点からも所望する窒化度合いの球状窒化アルミニウム粒子を得ることが難しいという問題があった。 Also, in direct heating by microwave, unlike the electric furnace heating that is generally performed, the temperature of the surface of the powdered kneaded material is not necessarily uniform, and is maintained in a heating furnace at a constant temperature for a certain period of time. Therefore, it is difficult to use the conventional firing management method, so that there is a problem that it is difficult to obtain spherical aluminum nitride particles having a desired degree of nitridation.
　本発明は、上記のような問題に鑑みてなされたものであり、所望の窒化度合いの球状窒化アルミニウム粒子を得ることがきる、球状窒化アルミニウム粒子の製造方法、及び球状窒化アルミニウム粒子製造装置を提供することを目的とする。 The present invention has been made in view of the above problems, and provides a spherical aluminum nitride particle production method and a spherical aluminum nitride particle production apparatus capable of obtaining spherical aluminum nitride particles having a desired degree of nitriding. The purpose is to do.
　本発明の球状窒化アルミニウム粒子の製造方法は、アプリケーター内で、球状アルミナ粒子と炭素系材料粉末とを含む混合物に、窒素雰囲気中でマイクロ波を照射して、該球状アルミナ粒子の少なくとも一部を窒化して球状窒化アルミニウム粒子を製造する、球状窒化アルミニウム粒子の製造方法において、前記アプリケーターからの排ガス中の一酸化炭素ガス濃度（体積％）を監視し、該一酸化炭素ガス濃度の最大値を基準として、該最大値から定めた終了タイミングでマイクロ波の照射を終了することを特徴とする。 In the method for producing spherical aluminum nitride particles of the present invention, a mixture containing spherical alumina particles and a carbon-based material powder is irradiated with microwaves in a nitrogen atmosphere in an applicator, so that at least a part of the spherical alumina particles is obtained. In the method for producing spherical aluminum nitride particles by nitriding to produce spherical aluminum nitride particles, the carbon monoxide gas concentration (% by volume) in the exhaust gas from the applicator is monitored, and the maximum value of the carbon monoxide gas concentration is determined. As a reference, the microwave irradiation is ended at an end timing determined from the maximum value.
　また、本発明の球状窒化アルミニウム粒子製造装置は、マイクロ波発振器を備えるアプリケーター内で、球状アルミナ粒子と炭素系材料粉末とを含む混合物に、窒素雰囲気中でマイクロ波を照射して、該球状アルミナ粒子の少なくとも一部を窒化して球状窒化アルミニウム粒子を製造する、球状窒化アルミニウム粒子製造装置であって、前記アプリケーターからの排ガス中の一酸化炭素ガスの濃度（体積％）を測定する一酸化炭素ガス分析器と、該一酸化炭素ガス分析器から受け取った一酸化炭素ガス濃度データを基に、一酸化炭素ガス濃度の最大値を検出し、該最大値を基準として、該最大値から定めた終了タイミングで、前記マイクロ波発振器によるマイクロ波の照射を終了させる制御部と、を備えることを特徴とする。 In addition, the spherical aluminum nitride particle production apparatus of the present invention includes a spherical alumina particle irradiated with microwaves in a nitrogen atmosphere in an applicator equipped with a microwave oscillator, and the spherical alumina particle is irradiated with the microwave. A spherical aluminum nitride particle production apparatus for producing spherical aluminum nitride particles by nitriding at least a part of particles, and measuring carbon monoxide gas concentration (% by volume) in exhaust gas from the applicator Based on the gas analyzer and the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer, the maximum value of the carbon monoxide gas concentration was detected, and the maximum value was determined based on the maximum value. And a control unit that terminates microwave irradiation by the microwave oscillator at an end timing.
　本発明は、アプリケーター（加熱炉）内で処理する球状アルミナ粒子全体の窒化度に応じて発生する一酸化炭素ガス濃度に基づき定めた終了タイミングでマイクロ波の照射を終了できるので、ばらつきのある局所的な温度監視値に基づいて窒化アルミニウムの焼成の進捗を管理する方法と比較して、窒化度のばらつきが抑えられ、所望の窒化度合いの球状窒化アルミニウム粒子を得ることができる。 In the present invention, since the microwave irradiation can be terminated at an end timing determined based on the concentration of carbon monoxide gas generated according to the degree of nitridation of the entire spherical alumina particles to be processed in the applicator (heating furnace), there are variations in locality. As compared with a method of managing the progress of the firing of aluminum nitride based on a typical temperature monitoring value, variation in the degree of nitriding can be suppressed, and spherical aluminum nitride particles having a desired degree of nitriding can be obtained.
本発明の球状窒化アルミニウム粒子製造装置の一態様の断面模式図である。It is a cross-sectional schematic diagram of one aspect | mode of the spherical aluminum nitride particle manufacturing apparatus of this invention. 試料温度と、マイクロ波の入射出力及び反射出力と、排気ガス中のＣＯ濃度及びＣＯ２濃度とを示すグラフの一例である。And sample temperature, which is an example of a graph showing the incident power and reflected power of the microwave, and a CO concentration and the CO 2 concentration in the exhaust gas. 所定の時間ｔでマイクロ波の照射を停止して、球状窒化アルミニウム粒子の一部を採取したものの蛍光X線スペクトルの一例である。It is an example of the fluorescent X-ray spectrum of what collected a part of spherical aluminum nitride particle | grains by stopping microwave irradiation at predetermined time t. 窒化アルミニウム（ＡｌＮ）生成率（％）と換算ＣＯ（ガス）濃度のピーク比との負の相関を示すグラフである。It is a graph which shows the negative correlation with aluminum nitride (AlN) production rate (%) and the peak ratio of conversion CO (gas) density | concentration. ＡｌＮ生成率（％）と熱伝導率（Ｗ／ｍＫ）との正の相関を示すグラフである。It is a graph which shows the positive correlation with AlN production | generation rate (%) and thermal conductivity (W / mK). 実施例で得られた球状窒化アルミニウム粒子の走査型電子顕微鏡（ＳＥＭ）写真である。It is a scanning electron microscope (SEM) photograph of the spherical aluminum nitride particles obtained in the examples. 実施例で得られた球状窒化アルミニウム粒子の電子プローブマイクロ分析（ＥＰＭＡ：Electron Probe Micro Analyzer）によるマッピング画像である。It is a mapping image by the electron probe microanalysis (EPMA: Electron | Probe | Micro | Analyzer) of the spherical aluminum nitride particle | grains obtained in the Example.
　本発明において、球状窒化アルミニウム粒子とは、主に、フィラー又は放熱用シートとしての性能を確保するために球状アルミナ粒子の表面近傍を窒化することで改質し、球状アルミナ粒子の表面を窒化アルミニウムとなしたものをいうが、それ以外にも、窒化反応が進み、球状アルミナ粒子全体が、球状窒化アルミニウムと化したものも含んでいる。 In the present invention, the spherical aluminum nitride particles are mainly modified by nitriding the vicinity of the surface of the spherical alumina particles in order to ensure the performance as a filler or a heat radiation sheet, and the surface of the spherical alumina particles is aluminum nitride. In addition, the nitriding reaction proceeds, and the spherical alumina particles as a whole are converted into spherical aluminum nitride.
　本発明において、球状窒化アルミニウム粒子を得るために用いる球状アルミナ粒子は真球状又は略真球状であればよい。球状アルミナ粒子は、例えば、レーザ粒度分布測定機（CILAS製CILAS-920）を用いて質量基準で求めた５０質量％平均粒子径（Ｄ５０）で５～１５０μｍであることが望ましい。これは、製造した球状窒化アルミニウム粒子を樹脂と混合し、フィラーとした場合に必要な熱伝導特性を得やすい粒子径であることによる。 In the present invention, the spherical alumina particles used for obtaining the spherical aluminum nitride particles may be spherical or substantially spherical. The spherical alumina particles are preferably 5 to 150 μm in terms of 50 mass% average particle diameter (D50) determined on a mass basis using, for example, a laser particle size distribution analyzer (CILAS-920 manufactured by CILAS). This is because the produced spherical aluminum nitride particles are mixed with a resin to obtain a heat conduction characteristic required when the filler is used as a filler.
　球状アルミナ粒子は、アルミナ粉末を球状に造粒することにより得られたものを使うことができる。球状アルミナ粉末は、例えばアルコキシド法、バイヤー法、アンモニウム明ばん熱分解法、又はアンモニウムドーソナイト熱分解法等によって得ることができる。造粒法としては、湿式撹拌造粒法、スプレードライ法等があるが、好ましくはスプレードライ法により造粒した粒子が使用される。スプレードライ法としては、ノズル法、ディスク法等の何れの方式であってもよい。 As the spherical alumina particles, those obtained by granulating alumina powder into a spherical shape can be used. The spherical alumina powder can be obtained, for example, by an alkoxide method, a Bayer method, an ammonium alum pyrolysis method, or an ammonium dosonite pyrolysis method. Examples of the granulation method include a wet stirring granulation method and a spray drying method. Preferably, particles granulated by the spray drying method are used. The spray drying method may be any method such as a nozzle method or a disk method.
　炭素系材料粉末としては、例えば黒鉛、カーボンブラック、アセチレンブラック、無定形炭素等の粉末が挙げられ、天然由来であっても工業的に製造されたものであってもよい。好ましくは製造後の窒化アルミニウムの絶縁性能に影響を与えないために、金属含有率が１質量％以下、好ましくは金属含有率が０．１質量％以下であるものが望ましい。炭素系粉末は混合原料である球状アルミナ粒子を被覆するように存在することが望ましく、球状アルミナ粒子の上記平均径以下の平均粒径を有することがより望ましい。 Examples of the carbon-based material powder include graphite, carbon black, acetylene black, amorphous carbon and the like, which may be naturally derived or industrially produced. Preferably, the metal content is 1% by mass or less, and preferably the metal content is 0.1% by mass or less so as not to affect the insulation performance of the aluminum nitride after production. The carbon-based powder is desirably present so as to cover the spherical alumina particles that are the mixed raw material, and more preferably has an average particle diameter equal to or smaller than the average diameter of the spherical alumina particles.
　球状アルミナ粒子と炭素系材料粉体とを含む混合物は、球状アルミナ粒子と炭素系材料粉体を乾式でボールミル等により混合することで調製することができる。混合の際に、例えば水、アルコール等の液状分散媒を加えてもよいが、乾燥する手間がかかるので、好ましくは乾式で混合する。混合比は、下記反応式に基づくＡｌ２Ｏ３／３Ｃ化学量論比の０．５倍以下程度が望ましい。
　Ａｌ２Ｏ３　＋　３Ｃ　＋Ｎ２　→　２ＡｌＮ　＋３ＣＯ The mixture containing the spherical alumina particles and the carbon-based material powder can be prepared by mixing the spherical alumina particles and the carbon-based material powder in a dry manner with a ball mill or the like. In mixing, for example, a liquid dispersion medium such as water or alcohol may be added. However, since it takes time to dry, it is preferably mixed dry. The mixing ratio is desirably about 0.5 times or less of the Al 2 O 3 / 3C stoichiometric ratio based on the following reaction formula.
Al 2 O 3 + 3C + N 2 → 2AlN + 3CO
　また、本発明では、必ずしも混合する球状アルミナ粒子全体を窒化アルミニウムに変換させる必要はなく、後述のように球状アルミナ粒子の表層近傍を窒化アルミニウムに転換するだけでもよい。従って、上記反応式において、原料として用意されたＡｌ２Ｏ３のモル等量に対応する量のカーボンを含む炭素原料を用意する必要はない。一方、表面から目的とする深さまで窒化するために必要な理論値よりもＣを多くしておく。そうしておくことで、上記反応式の反応が進んだ際に、炭素Ｃ不足による一酸化炭素発生量の低減は生じないようにしてある。 Further, in the present invention, it is not always necessary to convert the entire spherical alumina particles to be mixed into aluminum nitride, and only the surface layer vicinity of the spherical alumina particles may be converted into aluminum nitride as described later. Therefore, in the above reaction formula, it is not necessary to prepare a carbon raw material containing an amount of carbon corresponding to the molar equivalent of Al 2 O 3 prepared as a raw material. On the other hand, C is made larger than the theoretical value necessary for nitriding from the surface to the target depth. By doing so, when the reaction of the above reaction formula proceeds, a reduction in the amount of carbon monoxide generated due to carbon C deficiency does not occur.
　なお、Ａｌ２Ｏ３／３Ｃ化学量論比の０．５倍を超えた場合は、Ａｌ２Ｏ３の還元される量が少なくなり、これに伴って窒化により窒化アルミニウムＡｌＮとなる割合が少なくなり、目的とする窒化アルミニウム含有量の粒子を得ることができない。 When the Al 2 O 3 / 3C stoichiometric ratio exceeds 0.5 times, the amount of Al 2 O 3 to be reduced is reduced, and accordingly, the proportion of aluminum nitride AlN due to nitriding is reduced. Thus, particles having the desired aluminum nitride content cannot be obtained.
　図１は、本発明の球状窒化アルミニウム粒子製造装置の一態様の断面模式図である。球状窒化アルミニウム粒子製造装置１は、アプリケーター（加熱炉）２と、マイクロ波発振器３と、一酸化炭素ガス分析器１３と、制御部１４とを備える。アプリケーター２には、アプリケーター２内の電磁界分布を均一化するためのスターラー５と、断熱材８ａ，８ｂが載置される載置台７とが内部に設けられており、アプリケーター２の天板所定位置に形成された開口部に石英窓９が設けられている。 FIG. 1 is a schematic cross-sectional view of one embodiment of the spherical aluminum nitride particle production apparatus of the present invention. The spherical aluminum nitride particle production apparatus 1 includes an applicator (heating furnace) 2, a microwave oscillator 3, a carbon monoxide gas analyzer 13, and a control unit 14. The applicator 2 is provided with a stirrer 5 for making the electromagnetic field distribution in the applicator 2 uniform and a mounting table 7 on which the heat insulating materials 8a and 8b are placed. A quartz window 9 is provided in the opening formed at the position.
　断熱材８ａ，８ｂは、所定の厚みを有した板状又はファイバー状のものからなり、こう鉢８ｃ全体を取り囲むように積層されている。なお、載置台７は、例えばマイクロ波透過性のアルミナ、シリカ、ムライト、トリジマイト、酸化マグネシウム、サイアロン、窒化アルミニウム等を主成分とした素材からなり、断熱材８ａ，８ｂは、マイクロ波透過性の繊維状のアルミナ、シリカ、ムライト等からなる。こう鉢８ｃは、例えばマイクロ波透過性の高純度アルミナ、シリカ、トリジマイト、酸化マグネシウム、サイアロン、窒化アルミニウム等からなり、球状アルミナ粒子と炭素系材料粉体とを含む混合物６を、内部に収容している。なお、断熱材８ａ，８ｂに取り囲まれ、かつこう鉢８ｃ内に収容された混合物６は、アプリケーター２に設けた石英窓９、断熱材８ａ，８ｂ及びこう鉢８ｃに形成された開口部を通して、例えば赤外線カメラ１０により表面温度を監視し得る。 The heat insulating materials 8a and 8b are made of a plate or fiber having a predetermined thickness, and are laminated so as to surround the entire mortar 8c. The mounting table 7 is made of a material mainly composed of, for example, microwave permeable alumina, silica, mullite, tridymite, magnesium oxide, sialon, aluminum nitride, and the heat insulating materials 8a and 8b are microwave permeable. It consists of fibrous alumina, silica, mullite and the like. The mortar 8c is made of, for example, microwave-permeable high-purity alumina, silica, tridymite, magnesium oxide, sialon, aluminum nitride, and the like, and contains therein a mixture 6 containing spherical alumina particles and carbonaceous material powder. ing. The mixture 6 surrounded by the heat insulating materials 8a and 8b and accommodated in the mortar 8c passes through the quartz window 9 provided in the applicator 2, the heat insulating materials 8a and 8b, and the openings formed in the mortar 8c. For example, the surface temperature can be monitored by the infrared camera 10.
　アプリケーター２には、マイクロ波発振器３からのマイクロ波を当該アプリケーター２内へと導く導波路４が側壁の所定位置に設けられている。この実施の形態の場合、導波路４の途中には、マイクロ波発振器３から実際に照射されたマイクロ波のマイクロ波照射出力を計測するマイクロ波照射出力計（図示せず）と、アプリケーター２内から反射してきたマイクロ波を計測するマイクロ波反射出力計（図示せず）とが設けられている。 The applicator 2 is provided with a waveguide 4 that guides the microwave from the microwave oscillator 3 into the applicator 2 at a predetermined position on the side wall. In the case of this embodiment, in the middle of the waveguide 4, a microwave irradiation output meter (not shown) for measuring the microwave irradiation output of the microwave actually irradiated from the microwave oscillator 3, and in the applicator 2 And a microwave reflection output meter (not shown) for measuring the microwave reflected from the light source.
　マイクロ波照射出力計及びマイクロ波反射出力計は、マイクロ波発振器３からアプリケーター２内へマイクロ波が照射される際に得られた計測結果を、それぞれ後述する制御部１４に送出する。 The microwave irradiation output meter and the microwave reflection output meter send the measurement results obtained when the microwave is irradiated from the microwave oscillator 3 into the applicator 2 to the control unit 14 described later.
　アプリケーター２には、窒素ガス供給管１１と排気ガス管１２とが設けられている。窒素ガス供給管１１は、図示しないボンベ等の窒素ガス貯留部と接続されており、当該窒素ガス貯留部内の窒素ガスをアプリケーター２内に供給する。排気ガス管１２は、アプリケーター２内からの排ガスがオンライン分析可能な一酸化炭素ガス分析器１３を経由させてアプリケーター２外に排出する。なお、図１では、窒素ガスが混合物６の上側から供給され、排気ガスが混合物６の下側から排気される構成としたが、本発明は、このような位置関係に限定されず、逆の位置関係であってもよい。 The applicator 2 is provided with a nitrogen gas supply pipe 11 and an exhaust gas pipe 12. The nitrogen gas supply pipe 11 is connected to a nitrogen gas storage unit such as a cylinder (not shown), and supplies the nitrogen gas in the nitrogen gas storage unit into the applicator 2. The exhaust gas pipe 12 discharges the exhaust gas from the applicator 2 to the outside of the applicator 2 via a carbon monoxide gas analyzer 13 capable of online analysis. In FIG. 1, nitrogen gas is supplied from the upper side of the mixture 6 and exhaust gas is exhausted from the lower side of the mixture 6. However, the present invention is not limited to such a positional relationship, and the reverse It may be a positional relationship.
　一酸化炭素ガス分析器１３によって行われる一酸化炭素ガス分析法としては、質量分析法、赤外線吸収法、定電位電解法等があり、いずれの方法を利用してもよい。 The carbon monoxide gas analysis method performed by the carbon monoxide gas analyzer 13 includes a mass spectrometry method, an infrared absorption method, a constant potential electrolysis method, and the like, and any method may be used.
　また、図１の構成では、オンライン分析可能な一酸化炭素ガス分析器１３を用いたが、本発明はこれに限らず、排気ガス管１２にガストラップを設け、サンプラーにより手動にて、その都度バッチ分析を行ってよい。 In the configuration of FIG. 1, the carbon monoxide gas analyzer 13 capable of online analysis is used. However, the present invention is not limited to this, and a gas trap is provided in the exhaust gas pipe 12 and manually by a sampler each time. Batch analysis may be performed.
　一酸化炭素ガス分析器１３は、例えばマイクロ波発振器３からアプリケーター２内へマイクロ波が照射されることでアプリケーター２内から送られてくる排気ガス中の一酸化炭素ガス濃度を計測し、その測定結果を一酸化炭素ガス濃度データとして制御部１４に送出する。アプリケーター２内では、マイクロ波の照射が開始されると、炭素系材料粉末がマイクロ波を吸収することで、混合物６の温度が上昇し、上記反応式に従い一酸化炭素（以下「ＣＯ」とする場合がある）が発生する。 The carbon monoxide gas analyzer 13 measures the concentration of carbon monoxide gas in the exhaust gas sent from the applicator 2 by irradiating the microwave from the microwave oscillator 3 into the applicator 2, for example. The result is sent to the control unit 14 as carbon monoxide gas concentration data. In the applicator 2, when the microwave irradiation is started, the carbon-based material powder absorbs the microwave, whereby the temperature of the mixture 6 rises, and carbon monoxide (hereinafter referred to as “CO”) according to the above reaction formula. May occur).
　制御部１４は、一酸化炭素ガス分析器１３から受け取った一酸化炭素ガス濃度データを基に、アプリケーター２内の一酸化炭素ガスの濃度値を監視し、一酸化炭素ガス濃度の最大値を検知し得る。これに加えて制御部１４は、一酸化炭素ガス濃度の最大値を基準に予め定めた終了タイミングでマイクロ波照射終了信号を生成し、これをマイクロ波発振器３に送出する。なお、制御部１４で定められた終了タイミングは、球状アルミナ粒子から所望の窒化度合いとなった球状窒化アルミニウム粒子を製造できる終了タイミングを予め調べおき、これに基づいて制御部１４に予め定められたものである。 The control unit 14 monitors the concentration value of the carbon monoxide gas in the applicator 2 based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13, and detects the maximum value of the carbon monoxide gas concentration. Can do. In addition to this, the control unit 14 generates a microwave irradiation end signal at a predetermined end timing based on the maximum value of the carbon monoxide gas concentration, and sends it to the microwave oscillator 3. The end timing determined by the control unit 14 is determined in advance by the control unit 14 based on the end timing at which spherical aluminum nitride particles having a desired degree of nitridation can be produced from the spherical alumina particles. Is.
　マイクロ波照射終了信号を受け取ったマイクロ波発振器３は、球状窒化アルミニウム粒子を製造するために出力していたマイクロ波の照射を終了する。これにより、球状窒化アルミニウム粒子製造装置１では、アプリケーター２内で処理されて生成される球状窒化アルミニウム粒子全体の窒化度に応じて発生する一酸化炭素ガス濃度に基づき予め定められた終了タイミングでマイクロ波の照射を終了できるので、局所的な値しか検知できない混合物６の加熱温度に依存せずに球状窒化アルミニウム粒子の窒化度を制御でき、かくして窒化度のばらつきが抑えられ、所望の窒化度合いの球状窒化アルミニウム粒子を得ることができる。 The microwave oscillator 3 that has received the microwave irradiation end signal ends the irradiation of the microwave that was output to produce the spherical aluminum nitride particles. Thereby, in the spherical aluminum nitride particle manufacturing apparatus 1, the microscopic timing is determined at a predetermined end timing based on the carbon monoxide gas concentration generated according to the nitridation degree of the entire spherical aluminum nitride particles processed and generated in the applicator 2. Since the irradiation of the wave can be terminated, the nitridation degree of the spherical aluminum nitride particles can be controlled without depending on the heating temperature of the mixture 6 that can detect only local values. Spherical aluminum nitride particles can be obtained.
　また、球状窒化アルミニウム粒子製造装置１では、所望の窒化度合いの球状窒化アルミニウム粒子が得られる終了タイミングでマイクロ波発振器３によるマイクロ波の照射を終了できるので、マイクロ波発振器３による無駄な加熱を防止し得る。 Moreover, in the spherical aluminum nitride particle manufacturing apparatus 1, since the microwave irradiation by the microwave oscillator 3 can be completed at the end timing at which spherical aluminum nitride particles having a desired nitriding degree are obtained, useless heating by the microwave oscillator 3 is prevented. Can do.
　なお、所望の窒化度合いの達成後もマイクロ波の照射を継続した場合、球状窒化アルミニウム粒子の表面での窒化アルミニウムの成長が継続し、球状の窒化アルミニウムの粒子の表面に不均一な凹凸が発生する。表面の凹凸が大きな球状の窒化アルミニウムの粒子をフィラー材として用いると、樹脂中への球状窒化アルミニウム粒子の混合比率が低下し、フィラーとしての熱伝導性能が得られないという問題が発生する。 If microwave irradiation is continued even after the desired degree of nitridation is achieved, aluminum nitride continues to grow on the surface of the spherical aluminum nitride particles, resulting in uneven unevenness on the surface of the spherical aluminum nitride particles. To do. When spherical aluminum nitride particles having large surface irregularities are used as the filler material, the mixing ratio of the spherical aluminum nitride particles into the resin is lowered, and there is a problem that the heat conduction performance as a filler cannot be obtained.
　本発明では、このＣＯ濃度を監視することによって、球状窒化アルミニウム粒子の窒化度合いを制御するが、単に一酸化炭素ガスが出なくなったことで反応の完結を検知するのではなく、一酸化炭素ガスの生成が未だ続いている状態で、一酸化炭素ガス濃度の最大値を基準に定めた終了タイミングでマイクロ波照射を終了することを特徴とする。より詳細には、一酸化炭素ガス濃度（体積％）の最大値を過ぎた後で、一酸化炭素ガスが検出されなくなる前までの間であって、酸化炭素ガス濃度の最大値を基準に定めた終了タイミングでマイクロ波照射を終了する。 In the present invention, the degree of nitridation of the spherical aluminum nitride particles is controlled by monitoring the CO concentration. However, the carbon monoxide gas is not simply detected by the fact that the carbon monoxide gas is not emitted. The microwave irradiation is terminated at an end timing determined with reference to the maximum value of the carbon monoxide gas concentration in a state where the generation of is still continued. More specifically, after the maximum value of the carbon monoxide gas concentration (% by volume) is passed and before the carbon monoxide gas is no longer detected, the maximum value of the carbon oxide gas concentration is determined as a reference. The microwave irradiation ends at the end timing.
　次に、一酸化炭素ガス濃度の最大値を基準に予め定めた終了タイミングについて詳細に説明する。ここで、図２は、排気ガス中の一酸化炭素ガス（以下、ＣＯとも呼ぶ）濃度のグラフの一例である。この例では、ＣＯ濃度はマイクロ波の照射開始から約４時間直前辺りで最大値に達した後、徐々に低下してゆき、約７時間が経過する頃には、低レベルに低減して低減の程度も小さくなっている。そこで、本例では７時間経過を見てマイクロ波の照射を停止した。 Next, the end timing predetermined based on the maximum value of the carbon monoxide gas concentration will be described in detail. Here, FIG. 2 is an example of a graph of the concentration of carbon monoxide gas (hereinafter also referred to as CO) in the exhaust gas. In this example, the CO concentration reaches a maximum value just before about 4 hours from the start of microwave irradiation, and then gradually decreases. When about 7 hours pass, the CO concentration decreases to a low level and decreases. The degree of is also getting smaller. Therefore, in this example, the microwave irradiation was stopped after 7 hours.
　なお、マイクロ波の照射開始後約０．５時間に見られるＣＯ濃度の小さいピークは、並行して二酸化炭素ガス（ＣＯ２）も発生していることから分かるように、アプリケーター２内に残留している酸素により混合物中の炭素系材料が燃焼されて発生したものであり、本発明における窒化反応とは関係ない。 In addition, as can be seen from the fact that carbon dioxide gas (CO 2 ) is also generated in parallel, a small peak of CO concentration seen about 0.5 hour after the start of microwave irradiation remains in the applicator 2. It is generated by burning the carbon-based material in the mixture with the oxygen being present, and is not related to the nitriding reaction in the present invention.
　従って、この例の場合、制御部１４は、マイクロ波の照射開始から約４時間経過～約７時間のいずれかの時点で、マイクロ波発振器３によるマイクロ波の照射を終了させることが考えられる。なお、ＣＯ濃度の最大値は、本例のように山型形状のピークの頂点として現れる必要はなく、一定期間ほぼ同じ値が続く、台形状のピークの上底部であってもよい。 Therefore, in this example, it is conceivable that the control unit 14 terminates the microwave irradiation by the microwave oscillator 3 at any point in time from about 4 hours to about 7 hours from the start of the microwave irradiation. Note that the maximum value of the CO concentration does not need to appear as the peak of the mountain-shaped peak as in this example, but may be the upper bottom of the trapezoidal peak where the same value continues for a certain period.
　因みに、制御部１４において一酸化炭素ガス濃度の最大値を決定する場合には、例えば、一酸化炭素ガス分析器１３から受け取った一酸化炭素ガス濃度データを制御部１４で監視してゆき、例えばアプリケーター２中の残存酸素の燃焼が終了する時点として、混合物６の温度が６００℃以上になる温度範囲に限定して、一酸化炭素ガス濃度の最も高い値を順次検出してゆき、その値から所定値以上、一酸化炭素ガス濃度が下がったときに、検知した一酸化炭素ガス濃度の最も高い値を一酸化炭素ガス濃度の最大値として決定してもよい。 Incidentally, when the control unit 14 determines the maximum value of the carbon monoxide gas concentration, for example, the control unit 14 monitors the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13, for example, When the combustion of the residual oxygen in the applicator 2 is completed, the temperature of the mixture 6 is limited to a temperature range where the temperature is 600 ° C. or higher, and the highest value of the carbon monoxide gas concentration is sequentially detected. When the carbon monoxide gas concentration decreases by a predetermined value or more, the highest value of the detected carbon monoxide gas concentration may be determined as the maximum value of the carbon monoxide gas concentration.
　なお、図２には、マイクロ波照射出力計（図１にて図示せず）によって計測したマイクロ波の出力（マイクロ波照射出力P(t)であり、図２中「入射（ｋＷ）」と表記）と、マイクロ波反射出力計によって計測したマイクロ波の出力（マイクロ波反射出力Pr（t）であり、図２中「反射（ｋＷ）」と表記）も示されており、これは後述する換算ＣＯガス濃度β（ｔ）を計算する際に使用される（ｔは時間を示す）。 2 shows a microwave output (microwave irradiation output P (t) measured by a microwave irradiation output meter (not shown in FIG. 1), and “incident (kW)” in FIG. And a microwave output measured by a microwave reflection output meter (microwave reflection output Pr (t), expressed as “reflection (kW)” in FIG. 2), which will be described later. It is used when calculating the converted CO gas concentration β (t) (t indicates time).
　図２では、マイクロ波の出力が±１ｋｗ程度変動している様に見えるが、これは図１の球状窒化アルミニウム粒子製造装置１において、電磁界を均一化するためのスターラー５からの反射電力がマイクロ波の発振に影響しているためである。数時間という長い時間を要する窒化アルミニウムの焼成に対して、スターラー５の回転は数十ｒｐｍのオーダーであるので、マイクロ波の出力としては、数秒～１分程度のマイクロ波測定継続時間（Δｔ）での平均した値、即ち、時間ｔ－Δｔから時間ｔまでの時間平均値（Ｗ）を用いて、照射マイクロ波電力P(t)、反射マイクロ波電力Pr（t）としてもよい。 In FIG. 2, it appears that the output of the microwave fluctuates by about ± 1 kw. This is because the reflected power from the stirrer 5 for making the electromagnetic field uniform in the spherical aluminum nitride particle production apparatus 1 of FIG. This is because it affects the oscillation of the microwave. The rotation of the stirrer 5 is on the order of several tens of rpm for firing aluminum nitride, which takes a long time of several hours. Therefore, the microwave output duration (Δt) is about several seconds to one minute. It is also possible to use the average value at λ, that is, the time average value (W) from time t−Δt to time t, as the irradiation microwave power P (t) and the reflected microwave power Pr (t).
　図３は、所定の時間ｔでマイクロ波の照射を終了して、球状窒化アルミニウム粒子の一部を採取したものの蛍光X線スペクトルの一例である。蛍光X線スペクトルの分析深さは最大でも数μｍであるから、同スペクトルから、アルミナ粒子表面から数μｍ以内の深さにはＡｌ２Ｏ３が残っておらず、ＡｌＮと中間体であるＡｌＯＮが存在することが確認できる。 FIG. 3 shows an example of a fluorescent X-ray spectrum of a sample obtained by sampling a part of the spherical aluminum nitride particles after completing the microwave irradiation at a predetermined time t. Since the analysis depth of the fluorescent X-ray spectrum is several μm at the maximum, Al 2 O 3 does not remain at a depth within several μm from the alumina particle surface, and AlN and AlON, which is an intermediate, from the spectrum. Can be confirmed.
　これらの蛍光X線のそれぞれの材料のメインピーク高さ強度を用いて下記ＡｌＮ生成率（％）を定義することができる。例えば、図３は、リガク製Ｘ線回折装置「ＲＩＮＴ－２５００ＴＴＲ」により測定した球状窒化アルミニウム粒子のX線回折パターンである。ＡｌＮの含有比率の計算は、ＡｌＮ（ＰＤＦカードＮｏ．２５－１１３３）、Ａｌ２Ｏ３（ＰＤＦカードＮｏ．１０－０１７３）、及びＡｌＯＮ（ＰＤＦカードＮｏ．４８－０６８６）の最大ピークの強度を測定し、それらの強度比から、次式によりＡｌＮ含有量を百分率計算した。
　ＡｌＮ生成率（％）＝ＡｌＮのピーク高さ／（Ａｌ２Ｏ３、ＡｌＮ、及びＡｌＯＮのピーク高さの合計） The following AlN production rate (%) can be defined using the main peak height intensity of each material of these fluorescent X-rays. For example, FIG. 3 is an X-ray diffraction pattern of spherical aluminum nitride particles measured by a Rigaku X-ray diffractometer “RINT-2500TTR”. The content ratio of AlN is calculated by calculating the maximum peak intensity of AlN (PDF card No. 25-1133), Al 2 O 3 (PDF card No. 10-0173), and AlON (PDF card No. 48-0686). Measurements were made, and the AlN content was calculated as a percentage from the intensity ratio by the following formula.
AlN production rate (%) = peak height of AlN / (peak height of Al 2 O 3 , AlN, and AlON)
　本発明者らが種々検討したところ、所定時間ｔにおけるＡｌＮ生成率（ｔ）は、マイクロ波照射開始後の時間ｔにおけるＣＯガス濃度の、ＣＯガス濃度最大値に対する比と良好な負の相関を示すと共に、熱伝導率（Ｗ／ｍＫ）と良好な正の相関を示すことを見出した。ここから、ＣＯガス濃度比を監視すれば、所望の熱伝導率（Ｗ／ｍＫ）を有する球状窒化アルミニウム粒子を作れる。 As a result of various studies by the present inventors, the AlN generation rate (t) at a predetermined time t has a good negative correlation with the ratio of the CO gas concentration at the time t after the start of microwave irradiation to the maximum CO gas concentration. It was found that the thermal conductivity (W / mK) showed a good positive correlation. From here, if the CO gas concentration ratio is monitored, spherical aluminum nitride particles having a desired thermal conductivity (W / mK) can be produced.
　図４は、ＡｌＮ生成率（％）と換算ＣＯガス濃度比γ（ｔ）（後述する）との負の相関を示すグラフである。同グラフにおいて、横軸は所定時間ｔにおける換算ＣＯガス濃度比γ（ｔ）である。図４では、球状窒化アルミニウム粒子の製造時、マイクロ波発振器３におけるマイクロ波の出力を変更する場合、またアプリケーター２内におけるマイクロ波の反射による損失もあるため、これらの影響を補償した換算ＣＯガス濃度比γ（ｔ）が使用されている。以下、換算ＣＯガス濃度比γ（ｔ）を求める際に用いる換算ＣＯガス濃度β（ｔ）と、換算ＣＯガス濃度比γ（ｔ）とについて詳細に説明する。なお、以下において、濃度の単位は特に断りの無い限り体積％とし、出力の単位はＷとする。 FIG. 4 is a graph showing a negative correlation between the AlN production rate (%) and the converted CO gas concentration ratio γ (t) (described later). In the graph, the horizontal axis represents the converted CO gas concentration ratio γ (t) at a predetermined time t. In FIG. 4, when the spherical aluminum nitride particles are manufactured, the microwave output in the microwave oscillator 3 is changed, and there is also a loss due to the reflection of the microwave in the applicator 2, so the converted CO gas that compensates for these effects A concentration ratio γ (t) is used. Hereinafter, the converted CO gas concentration β (t) and the converted CO gas concentration ratio γ (t) used when obtaining the converted CO gas concentration ratio γ (t) will be described in detail. In the following description, the unit of concentration is volume% unless otherwise specified, and the unit of output is W.
　ここでは、所定時間ｔにおける排気ガス中のＣＯガス濃度実測値であるα(t)を、下記式（１）により換算し、所定時間ｔにおける換算ＣＯガス濃度β（ｔ）を求める。
　β（ｔ）＝α(t)／ΔP(t)　　　　　　　　　　　　　（１）
　ΔPは下記式（２）で求められる正味マイクロ波出力である。
　ΔP(t)＝P(t)－Pr(t)　　　　　　　　　　　　　　　（２）
　P(t)は所定時間ｔのマイクロ波照射出力であり、Pr(t)は所定時間ｔのマイクロ波反射出力である。図１及び図２に示すように、スターラー５等の影響によりマイクロ波の照射及び反射出力の時間変動が大きい場合は、前述のように、それぞれ所定のマイクロ波測定継続時間（Δｔ）での平均したマイクロ波の照射出力P(t)、反射出力Pr(t)を用いる。 Here, α (t), which is a measured value of the CO gas concentration in the exhaust gas at a predetermined time t, is converted by the following equation (1) to obtain a converted CO gas concentration β (t) at the predetermined time t.
β (t) = α (t) / ΔP (t) (1)
ΔP is a net microwave output obtained by the following equation (2).
ΔP (t) = P (t) −Pr (t) (2)
P (t) is a microwave irradiation output at a predetermined time t, and Pr (t) is a microwave reflection output at a predetermined time t. As shown in FIG. 1 and FIG. 2, when the time variation of the microwave irradiation and the reflected output is large due to the influence of the stirrer 5 or the like, as described above, the average over the predetermined microwave measurement duration (Δt), respectively. The microwave irradiation output P (t) and reflection output Pr (t) are used.
　なお、上述した球状窒化アルミニウム粒子製造装置１では、P(t)及びPr(t)について、マイクロ波照射出力計及びマイクロ波反射出力計により測定できる。 In addition, in the spherical aluminum nitride particle production apparatus 1 described above, P (t) and Pr (t) can be measured with a microwave irradiation output meter and a microwave reflection output meter.
　α(t)を正味マイクロ波出力ΔP(t)で除することで、焼成途中のマイクロ波出力の変動を補償したＣＯガス濃度が求められる。すなわち、マイクロ波発振器３でマイクロ波を出力する際には、種々の事情によってマイクロ波発振器３におけるマイクロ波の出力を下げ、或いは上げることが行われることもあり、その場合、マイクロ波の出力に応じて混合物６における反応速度が変わり、これに応じてＣＯガス濃度が変化してしまう。そこで、α(t)をΔP(t)で除することで、マイクロ波の出力の変動を補償したＣＯガス濃度を求めることができる。 ＣＯ By dividing α (t) by the net microwave output ΔP (t), the CO gas concentration that compensates for the fluctuation of the microwave output during firing is obtained. That is, when the microwave is output from the microwave oscillator 3, the microwave output from the microwave oscillator 3 may be lowered or increased depending on various circumstances. Accordingly, the reaction rate in the mixture 6 changes, and the CO gas concentration changes accordingly. Therefore, by dividing α (t) by ΔP (t), the CO gas concentration that compensates for fluctuations in the output of the microwave can be obtained.
　例えば、局所加熱の進行により放射温度計での温度計測値が焼成容器や断熱材の使用温度範囲を超えて上昇した場合などにおいて、装置の損傷防止および安全上の観点からマイクロ波出力を低下させる必要が生じる場合がある。アルミナを窒化アルミニウムに転換する反応は吸熱反応であり、反応に必要なエネルギーはマイクロ波の電力により供給される。従って、照射するマイクロ波の出力を低下させると、原料アルミナが窒化アルミニウムに転換される速度が低下し、原料アルミナが窒化アルミニウムに転換されることに伴って発生するＣＯガスの発生量が低下し、計測しているＣＯガス濃度が低下する。この様な場合においても、原料アルミナから窒化アルミニウムへの転換の進行を誤差なく監視するためには、焼成中のマイクロ波出力、正確には、照射マイクロ波出力から反射して戻ってくるマイクロ波反射出力を差し引いた、正味の照射マイクロ波出力を用いて、発生しているＣＯガス濃度を補正することが必要である。 For example, in the case where the measured temperature value of the radiation thermometer rises beyond the operating temperature range of the baking container or heat insulating material due to the progress of local heating, the microwave output is reduced from the viewpoint of preventing damage to the device and safety There may be a need. The reaction for converting alumina to aluminum nitride is an endothermic reaction, and the energy required for the reaction is supplied by microwave power. Therefore, when the output of the microwave to be irradiated is reduced, the rate at which the raw material alumina is converted to aluminum nitride is reduced, and the amount of CO gas generated as the raw material alumina is converted to aluminum nitride is reduced. The measured CO gas concentration decreases. Even in such a case, in order to monitor the progress of the conversion from raw material alumina to aluminum nitride without error, the microwave output during firing, more precisely the microwave reflected back from the irradiated microwave output, is returned. It is necessary to correct the generated CO gas concentration using the net irradiated microwave output minus the reflected output.
　ここで例えば、球状窒化アルミニウム粒子製造装置１においては、制御部１４によって、マイクロ波照射出力計及びマイクロ波反射出力計から受け取ったマイクロ波照射出力P(t)及びマイクロ波反射出力Pr(t)と、一酸化炭素ガス分析器１３から受け取った一酸化炭素ガス濃度データを基に得たＣＯガス濃度実測値α(t)により、換算ＣＯガス濃度β（ｔ）を求めることができる。 Here, for example, in the spherical aluminum nitride particle producing apparatus 1, the control unit 14 uses the microwave irradiation output meter and the microwave reflection output meter to receive the microwave irradiation output P (t) and the microwave reflection output Pr (t). The converted CO gas concentration β (t) can be obtained from the measured CO gas concentration value α (t) obtained based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13.
　球状窒化アルミニウム粒子製造装置１では、このようにして制御部１４にて求めた換算ＣＯガス濃度β（ｔ）を基に、アプリケーター２内の一酸化炭素ガスの濃度値を監視し、一酸化炭素ガス濃度の最大値を特定してもよい。この場合、制御部１４は、所望の窒化度合いの球状窒化アルミニウム粒子を得ることがきるマイクロ波照射の終了タイミングとして、一酸化炭素ガス濃度の最大値を基準に終了換算ＣＯガス濃度βendを予め定めておく。制御部１４は、一酸化炭素ガス分析器１３から受け取った一酸化炭素ガス濃度データを基に求めた換算ＣＯガス濃度β（ｔ）を監視してゆき、当該換算ＣＯガス濃度β（ｔ）が終了換算ＣＯガス濃度βendとなったときにマイクロ波の照射を終了させることもできる。 In the spherical aluminum nitride particle production apparatus 1, the concentration value of carbon monoxide gas in the applicator 2 is monitored based on the converted CO gas concentration β (t) thus obtained by the control unit 14, and carbon monoxide. The maximum value of the gas concentration may be specified. In this case, the control unit 14 predetermines the end conversion CO gas concentration βend based on the maximum value of the carbon monoxide gas concentration as the end timing of the microwave irradiation at which spherical aluminum nitride particles having a desired nitriding degree can be obtained. Keep it. The control unit 14 monitors the converted CO gas concentration β (t) obtained based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13, and the converted CO gas concentration β (t) is The microwave irradiation can be terminated when the end conversion CO gas concentration βend is reached.
　次に、上述した換算ＣＯガス濃度比γ（ｔ）について説明する。上記と同様の方法で、ＣＯガス濃度が最大となったときの濃度を式（１）及び（２）により換算して、アプリケーター２から送られてくる排気ガス中の換算ＣＯガス濃度最大値βmaxを求める。換算ＣＯガス濃度比γ（ｔ）は、下記式（３）に示すように、所定時間ｔにおける換算ＣＯガス濃度β（ｔ）の、βmaxに対する比により求めることができる。
　換算ＣＯガス濃度比γ（ｔ）＝β（ｔ）／βmax　　　　　（３） Next, the above-described converted CO gas concentration ratio γ (t) will be described. In the same manner as described above, the concentration when the CO gas concentration becomes maximum is converted by the equations (1) and (2), and the converted CO gas concentration maximum value βmax in the exhaust gas sent from the applicator 2 Ask for. The converted CO gas concentration ratio γ (t) can be obtained from the ratio of the converted CO gas concentration β (t) at a predetermined time t to βmax as shown in the following equation (3).
Equivalent CO gas concentration ratio γ (t) = β (t) / βmax (3)
　この場合、例えば制御部１４は、所望の窒化度合いの球状窒化アルミニウム粒子を得ることができるマイクロ波照射の終了タイミングとして、一酸化炭素ガス濃度の最大値を基準にした、マイクロ波停止の換算ＣＯガス濃度比γ０を予め定めておき、一酸化炭素ガス分析器１３から受け取った一酸化炭素ガス濃度データを基に求めた換算ＣＯガス濃度β（ｔ）や換算ＣＯガス濃度最大値βmaxを監視してゆき、換算ＣＯガス濃度比γ（ｔ）が、予め定めたγ０まで低下したときにマイクロ波の照射を終了させることもできる。 In this case, for example, the control unit 14 can convert the microwave stop conversion CO based on the maximum value of the carbon monoxide gas concentration as the microwave irradiation end timing at which spherical aluminum nitride particles having a desired nitriding degree can be obtained. A gas concentration ratio γ 0 is determined in advance, and the converted CO gas concentration β (t) and the converted CO gas concentration maximum value βmax obtained based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer 13 are monitored. and Yuki, the terms CO gas concentration ratio gamma (t) is also possible to terminate the irradiation of the microwaves when reduced to gamma 0 a predetermined.
　図５は、ＡｌＮ生成率（％）と熱伝導率（Ｗ／ｍＫ）との正の相関を示すグラフである。熱伝導率は、球状窒化アルミニウム粒子を樹脂（汎用エポキシＢｉｓ－Ａ型）と体積比８０：２０で混合し、平板上に成型して乾燥処理した板状成型体に対しての熱伝導率を測定した。熱伝導率の測定は定常法を用いて計測した。フィラー用途向けの熱伝導率としては、１５Ｗ／ｍＫ以上であることが好ましく、図５からＡｌＮ生成率（％）が４５％以上であることが好ましい。図５の結果を基に図４において、換算ＣＯガス濃度比γ（ｔ）を確認した場合、換算ＣＯガス濃度比γ（ｔ）が１．０以下、好ましくは０．８以下であること望ましいことが確認できた。即ち、換算ＣＯガス濃度比γ（ｔ）が１．０以下ということは、ＣＯガス濃度が最大値になった後にマイクロ波の照射を終了すればよいことが分かる。また窒化が進み過ぎた場合、球状窒化アルミニウム粒子の表面の凹凸発生により球状窒化アルミニウム粒子（フィラー）の樹脂への混合可能量が低下することを考慮すると、換算ガス濃度比γ（ｔ）が０．１以上で焼成を終了することが好ましいことが分かった。従って、γ０は１．０～０．１が好ましく、０．９～０．１がより好ましい。 FIG. 5 is a graph showing a positive correlation between the AlN production rate (%) and the thermal conductivity (W / mK). The thermal conductivity is obtained by mixing spherical aluminum nitride particles with a resin (general-purpose epoxy Bis-A type) at a volume ratio of 80:20, molding on a flat plate, and drying treatment. It was measured. The thermal conductivity was measured using a steady method. The thermal conductivity for filler use is preferably 15 W / mK or more, and the AlN production rate (%) is preferably 45% or more from FIG. When the converted CO gas concentration ratio γ (t) is confirmed in FIG. 4 based on the result of FIG. 5, the converted CO gas concentration ratio γ (t) is 1.0 or less, preferably 0.8 or less. I was able to confirm. That is, when the converted CO gas concentration ratio γ (t) is 1.0 or less, it is understood that the microwave irradiation may be terminated after the CO gas concentration reaches the maximum value. When the nitridation has progressed too much, considering that the amount of spherical aluminum nitride particles (filler) that can be mixed into the resin decreases due to the occurrence of irregularities on the surface of the spherical aluminum nitride particles, the converted gas concentration ratio γ (t) is 0. It was found that it is preferable to finish the firing at 1 or more. Accordingly, γ 0 is preferably 1.0 to 0.1, and more preferably 0.9 to 0.1.
　図６は、後述する実施例で得られた球状窒化アルミニウム粒子の走査型電子顕微鏡（ＳＥＭ：Scanning Electron Microscope）写真である。図６から、球状窒化アルミニウム粒子がほぼ真球状でありフィラーに好適であることが分かる。図７は図６の粒子の電子プローブマイクロ分析（ＥＰＭＡ：Electron Probe Micro Analyzer）によるマッピング画像である。図７から分かるように、窒化の度合いは球状窒化アルミニウム粒子表面から数μｍ～数十μｍ程度であり、球状窒化アルミニウム粒子中央部は窒化されていないことが分かる。 FIG. 6 is a scanning electron microscope (SEM) photograph of spherical aluminum nitride particles obtained in Examples described later. From FIG. 6, it can be seen that the spherical aluminum nitride particles are almost spherical and are suitable for the filler. FIG. 7 is a mapping image of the particles of FIG. 6 by electron probe microanalysis (EPMA). As can be seen from FIG. 7, the degree of nitriding is about several μm to several tens μm from the surface of the spherical aluminum nitride particles, and it can be seen that the central portion of the spherical aluminum nitride particles is not nitrided.
　また、上述のように、本発明では、上記反応式において、用意されたＡｌ２Ｏ３のモル当量に比べ、炭素Ｃを多量に含むように炭素系粉末を調製してあるため、ＣＯガスの発生の低減の原因は、材料中の炭素Ｃ不足ではない。一方で、球状窒化アルミニウム粒子の中には、中央部が完全に窒化されていないものがあることから、窒化の進捗に伴うＣＯガス濃度の低減は、球状アルミナに生じた窒化アルミニウム層によって、球状窒化アルミニウム粒子の内部までＮ２ガスが届きにくくなっていることの影響を受けているものと考えられる。即ち、本発明は、上記反応式における右辺の生成量を単に追っているわけではなく、球状窒化アルミニウムの表面及び内部の状態を含め、包括的に球状窒化アルミニウムの生成状態を判断するものである。 Further, as described above, in the present invention, since the carbon-based powder is prepared so as to contain a large amount of carbon C in the above reaction formula in comparison with the molar equivalent of prepared Al 2 O 3 , The cause of the reduction in generation is not carbon C deficiency in the material. On the other hand, since some of the spherical aluminum nitride particles are not completely nitrided at the center, the reduction of the CO gas concentration accompanying the progress of nitriding is reduced by the aluminum nitride layer generated in the spherical alumina. It is thought that it is influenced by the fact that N 2 gas is difficult to reach the inside of the aluminum nitride particles. That is, the present invention does not simply follow the amount of production on the right side in the above reaction formula, but comprehensively determines the production state of the spherical aluminum nitride including the surface and internal state of the spherical aluminum nitride.
　以上の結果から、換算ＣＯガス濃度比γ（ｔ）が０となる前（即ちＣＯガス濃度が検出限界以下となる時点より前）において、一酸化炭素ガス濃度の最大値を基準に決められた所定の終了タイミングでマイクロ波の照射を終了させることで、球状窒化アルミニウム粒子の窒化が進み過ぎないようにすることが望ましい。 From the above results, the converted CO gas concentration ratio γ (t) was determined based on the maximum value of the carbon monoxide gas concentration before the CO gas concentration ratio γ (t) became 0 (that is, before the time when the CO gas concentration was below the detection limit). It is desirable to prevent the nitriding of the spherical aluminum nitride particles from proceeding excessively by terminating the microwave irradiation at a predetermined end timing.
　以下、実施例により、より具体的に本発明効果を説明する。球状アルミナ粒子（マイクロン社製球状アルミナ粉末ＡＸ３５－１２５）１６９ｇと、炭素系材料粉末（クラレケミカル社製電極材料用活性炭）５１ｇとを、ボールミルで１時間混合し、原料混合物を調製した。該原料混合物２２０ｇを、高純度アルミナ製のこう鉢に入れて、図１に示す構成の球状窒化アルミニウム粒子製造装置１のアプリケーター２内で、５０Ｌ／分の窒素ガス気流下で、一酸化炭素ガス分析器１３として設けた堀場製作所製ポータブルガス分析計ＰＧ－２４０で排気ガス中のＣＯ濃度をオンライン分析しながら、マイクロ波により加熱処理した。マイクロ波照射を開始してから４．５時間後、換算ＣＯガス濃度比γが約０．７となった時点で、マイクロ波の照射を手動にて停止した。得られた反応混合物を取り出した後に、余剰の活性炭を７００℃の大気雰囲気加熱炉にて燃焼除去して、アルミナ粒子の少なくとも一部が窒化アルミニウムである球状窒化アルミニウム粒子を得た。図６に得られた球状窒化アルミニウム粒子の走査型電子顕微鏡写真を示す。上述したように、図６から、マイクロ波により加熱処理されて得られた球状窒化アルミニウム粒子はほぼ真球であり、フィラーとして好適であることが分かる。また、図７に球状窒化アルミニウム粒子のEPMAマッピング画像を示す。図７右上の窒素のマッピング画像から分かるように、粒径が約５０μｍの球状窒化アルミニウム粒子では表面から約５μｍが窒化されており、粒径が３０μｍ以下の球状窒化アルミニウム粒子では約１０μｍ程度窒化されていた。焼成した球状窒化アルミニウム粒子を樹脂（汎用エポキシ樹脂）と体積比８０：２０で混合し、板状に成型乾燥した試料の熱伝導率を定常法により測定した約２１ｗ／ｍｋであった。 Hereinafter, the effects of the present invention will be described more specifically with reference to examples. 169 g of spherical alumina particles (Spherical alumina powder AX35-125 manufactured by Micron) and 51 g of carbon-based material powder (activated carbon for electrode material manufactured by Kuraray Chemical Co., Ltd.) were mixed for 1 hour by a ball mill to prepare a raw material mixture. 220 g of the raw material mixture is put in a high-purity alumina mortar and carbon monoxide gas in an applicator 2 of the spherical aluminum nitride particle production apparatus 1 having the configuration shown in FIG. 1 under a nitrogen gas stream of 50 L / min. While analyzing the CO concentration in the exhaust gas on-line with a portable gas analyzer PG-240 manufactured by HORIBA, Ltd. provided as the analyzer 13, heat treatment was performed using microwaves. After 4.5 hours from the start of microwave irradiation, microwave irradiation was manually stopped when the converted CO gas concentration ratio γ reached approximately 0.7. After taking out the obtained reaction mixture, excess activated carbon was burned and removed in an air atmosphere heating furnace at 700 ° C. to obtain spherical aluminum nitride particles in which at least part of the alumina particles was aluminum nitride. FIG. 6 shows a scanning electron micrograph of the spherical aluminum nitride particles obtained. As described above, it can be seen from FIG. 6 that the spherical aluminum nitride particles obtained by heat treatment with microwaves are almost true spheres and are suitable as fillers. FIG. 7 shows an EPMA mapping image of spherical aluminum nitride particles. As can be seen from the nitrogen mapping image in the upper right of FIG. 7, the spherical aluminum nitride particles having a particle size of about 50 μm are nitrided from the surface by about 5 μm, and the spherical aluminum nitride particles having a particle size of 30 μm or less are nitrided by about 10 μm. It was. The calcined spherical aluminum nitride particles were mixed with a resin (general-purpose epoxy resin) at a volume ratio of 80:20, and the thermal conductivity of a sample molded and dried into a plate shape was about 21 w / mk measured by a steady method.
　１　球状窒化アルミニウム粒子製造装置
　２　アプリケーター（加熱炉）
　３　マイクロ波発振器
　４　導波路
　５　スターラー
　６　球状アルミナ粒子と炭素系材料粉体とを含む混合物
　７　載置台
　８ａ，８ｂ　断熱材
　９　石英窓
１０　赤外線カメラ
１１　窒素ガス供給管
１２　排気ガス管
１３　一酸化炭素ガス分析器
１４　制御部 1 Spherical aluminum nitride particle production equipment 2 Applicator (heating furnace)
DESCRIPTION OF SYMBOLS 3 Microwave oscillator 4 Waveguide 5 Stirrer 6 Mixture containing spherical alumina particle and carbonaceous material powder 7 Mounting table 8a, 8b Heat insulating material 9 Quartz window 10 Infrared camera 11 Nitrogen gas supply pipe 12 Exhaust gas pipe 13 Carbon monoxide Gas analyzer 14 controller

Claims (6)

  1. 　アプリケーター内で、球状アルミナ粒子と炭素系材料粉末とを含む混合物に、窒素雰囲気中でマイクロ波を照射して、該球状アルミナ粒子の少なくとも一部を窒化して球状窒化アルミニウム粒子を製造する、球状窒化アルミニウム粒子の製造方法において、
    　前記アプリケーターからの排ガス中の一酸化炭素ガス濃度（体積％）を監視し、該一酸化炭素ガス濃度の最大値を基準として、該最大値から定めた終了タイミングでマイクロ波の照射を終了することを特徴とする、球状窒化アルミニウム粒子の製造方法。     In the applicator, the mixture containing the spherical alumina particles and the carbonaceous material powder is irradiated with microwaves in a nitrogen atmosphere to nitride at least a part of the spherical alumina particles to produce spherical aluminum nitride particles. In the method for producing aluminum nitride particles,
    The carbon monoxide gas concentration (volume%) in the exhaust gas from the applicator is monitored, and the microwave irradiation is terminated at an end timing determined from the maximum value with reference to the maximum value of the carbon monoxide gas concentration. A method for producing spherical aluminum nitride particles, characterized in that
  2. 　前記一酸化炭素ガス濃度が、下記式（１）により求められる換算ＣＯガス濃度β（ｔ）であることを特徴とする請求項１記載の球状窒化アルミニウム粒子の製造方法。
    　β（ｔ）＝α(t) /ΔP(t)　　　　　　　　　　　　　（１）
    　α(t)：マイクロ波照射開始後の時間ｔにおける、排気ガス中の一酸化炭素ガス濃度（体積％）の実測値。
    　ΔP(t)：下記式（２）で求められる正味マイクロ波出力（Ｗ）。
    　ΔP(t)＝P(t)－Pr(t)　　　　　　　　　　　　　　　　　（２）
    　P(t)：マイクロ波照射開始後の時間ｔにおけるマイクロ波照射出力、又は、時間ｔ－Δｔから時間ｔにおけるマイクロ波照射出力の時間平均値（Ｗ）。
    　Pr(t)：マイクロ波照射開始後の時間ｔにおけるマイクロ波反射出力、又は、時間ｔ－Δｔから時間ｔにおけるマイクロ波反射出力の時間平均値（Ｗ）。
    　Δｔ：所定のマイクロ波測定継続時間。     The method for producing spherical aluminum nitride particles according to claim 1, wherein the carbon monoxide gas concentration is a converted CO gas concentration β (t) obtained by the following formula (1).
    β (t) = α (t) / ΔP (t) (1)
    α (t): Actual measurement value of carbon monoxide gas concentration (% by volume) in exhaust gas at time t after the start of microwave irradiation.
    ΔP (t): Net microwave output (W) obtained by the following equation (2).
    ΔP (t) = P (t) −Pr (t) (2)
    P (t): microwave irradiation output at time t after the start of microwave irradiation, or time average value (W) of microwave irradiation output from time t-Δt to time t.
    Pr (t): microwave reflected output at time t after the start of microwave irradiation, or time average value (W) of microwave reflected output from time t-Δt to time t.
    Δt: predetermined microwave measurement duration.
  3. 　前記最大値に対する一酸化炭素ガス濃度の比が所定の値となった時点でマイクロ波の照射を終了することを特徴とする請求項１又は２に記載の球状窒化アルミニウム粒子の製造方法。 3. The method for producing spherical aluminum nitride particles according to claim 1, wherein the microwave irradiation is terminated when the ratio of the carbon monoxide gas concentration to the maximum value reaches a predetermined value.
  4. 　前記比が、下記式（３）により求められる換算ＣＯガス濃度比γ（ｔ）であることを特徴とする請求項３記載の球状窒化アルミニウム粒子の製造方法。
    　換算ＣＯガス濃度比γ（ｔ）＝β（ｔ）／βmax　　　　　（３）
    　βmax：一酸化炭素ガス濃度が最大となったときの上記式（１）に基づき換算された換算ＣＯガス濃度最大値。     The method for producing spherical aluminum nitride particles according to claim 3, wherein the ratio is a converted CO gas concentration ratio γ (t) obtained by the following formula (3).
    Equivalent CO gas concentration ratio γ (t) = β (t) / βmax (3)
    βmax: The maximum converted CO gas concentration value converted based on the above formula (1) when the carbon monoxide gas concentration becomes maximum.
  5. 　前記最大値が、前記混合物の表面温度が６００℃以上で検出されることを特徴とする請求項１～４のいずれか１項記載の球状窒化アルミニウム粒子の製造方法。 5. The method for producing spherical aluminum nitride particles according to claim 1, wherein the maximum value is detected when the surface temperature of the mixture is 600 ° C. or higher.
  6. 　マイクロ波発振器を備えるアプリケーター内で、球状アルミナ粒子と炭素系材料粉末とを含む混合物に、窒素雰囲気中でマイクロ波を照射して、該球状アルミナ粒子の少なくとも一部を窒化して球状窒化アルミニウム粒子を製造する、球状窒化アルミニウム粒子製造装置であって、
    　前記アプリケーターからの排ガス中の一酸化炭素ガスの濃度（体積％）を測定する一酸化炭素ガス分析器と、
    　該一酸化炭素ガス分析器から受け取った一酸化炭素ガス濃度データを基に、一酸化炭素ガス濃度の最大値を検出し、該最大値を基準として、該最大値から定めた終了タイミングで、前記マイクロ波発振器によるマイクロ波の照射を終了させる制御部と、
    　を備えることを特徴とする、球状窒化アルミニウム粒子製造装置。     In an applicator equipped with a microwave oscillator, a mixture containing spherical alumina particles and carbon-based material powder is irradiated with microwaves in a nitrogen atmosphere, and at least a part of the spherical alumina particles is nitrided to form spherical aluminum nitride particles A spherical aluminum nitride particle production apparatus for producing
    A carbon monoxide gas analyzer for measuring the concentration (% by volume) of carbon monoxide gas in the exhaust gas from the applicator;
    Based on the carbon monoxide gas concentration data received from the carbon monoxide gas analyzer, the maximum value of the carbon monoxide gas concentration is detected, and at the end timing determined from the maximum value based on the maximum value, A control unit for terminating microwave irradiation by the microwave oscillator;
    An apparatus for producing spherical aluminum nitride particles, comprising:
PCT/JP2017/013218 2016-03-30 2017-03-30 Method for manufacturing spherical aluminum nitride particles, and device for manufacturing spherical aluminum nitride particles WO2017170856A1 (en)

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