JP2017178751A - Spherical ain particles and manufacturing method therefor - Google Patents
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- 239000002245 particle Substances 0.000 title claims abstract description 198
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 23
- 239000000843 powder Substances 0.000 claims description 99
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 98
- 238000000034 method Methods 0.000 claims description 43
- 150000001875 compounds Chemical class 0.000 claims description 37
- 238000010438 heat treatment Methods 0.000 claims description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 35
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 29
- 238000002156 mixing Methods 0.000 claims description 14
- 229910052710 silicon Inorganic materials 0.000 claims description 13
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 7
- 238000001694 spray drying Methods 0.000 claims description 6
- 238000011049 filling Methods 0.000 abstract description 8
- 239000000945 filler Substances 0.000 abstract description 3
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 182
- 238000005121 nitriding Methods 0.000 description 45
- 238000006243 chemical reaction Methods 0.000 description 40
- 238000005245 sintering Methods 0.000 description 32
- 239000002994 raw material Substances 0.000 description 27
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 17
- 239000011347 resin Substances 0.000 description 17
- 229920005989 resin Polymers 0.000 description 17
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 12
- 229910052799 carbon Inorganic materials 0.000 description 12
- 239000012798 spherical particle Substances 0.000 description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 11
- 230000000694 effects Effects 0.000 description 11
- 239000012298 atmosphere Substances 0.000 description 10
- 239000000523 sample Substances 0.000 description 10
- 229910017109 AlON Inorganic materials 0.000 description 9
- 239000007789 gas Substances 0.000 description 9
- 229910052727 yttrium Inorganic materials 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 8
- 239000000047 product Substances 0.000 description 8
- 238000006722 reduction reaction Methods 0.000 description 8
- 238000007751 thermal spraying Methods 0.000 description 8
- 238000005469 granulation Methods 0.000 description 7
- 230000003179 granulation Effects 0.000 description 7
- 239000007791 liquid phase Substances 0.000 description 7
- 238000009826 distribution Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 5
- 230000005496 eutectics Effects 0.000 description 5
- 230000017525 heat dissipation Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 230000001737 promoting effect Effects 0.000 description 5
- 230000002829 reductive effect Effects 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- 239000008187 granular material Substances 0.000 description 4
- 238000013507 mapping Methods 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 239000010453 quartz Substances 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 239000004519 grease Substances 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 238000007561 laser diffraction method Methods 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- -1 yttrium alkoxide Chemical class 0.000 description 2
- OBOSXEWFRARQPU-UHFFFAOYSA-N 2-n,2-n-dimethylpyridine-2,5-diamine Chemical compound CN(C)C1=CC=C(N)C=N1 OBOSXEWFRARQPU-UHFFFAOYSA-N 0.000 description 1
- NGDQQLAVJWUYSF-UHFFFAOYSA-N 4-methyl-2-phenyl-1,3-thiazole-5-sulfonyl chloride Chemical compound S1C(S(Cl)(=O)=O)=C(C)N=C1C1=CC=CC=C1 NGDQQLAVJWUYSF-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000001479 atomic absorption spectroscopy Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 239000007806 chemical reaction intermediate Substances 0.000 description 1
- 239000008119 colloidal silica Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000011549 displacement method Methods 0.000 description 1
- 238000007580 dry-mixing Methods 0.000 description 1
- KEQVPIDOPAGWCP-UHFFFAOYSA-N ethanolate;yttrium(3+) Chemical compound [Y+3].CC[O-].CC[O-].CC[O-] KEQVPIDOPAGWCP-UHFFFAOYSA-N 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- IBSDADOZMZEYKD-UHFFFAOYSA-H oxalate;yttrium(3+) Chemical compound [Y+3].[Y+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O IBSDADOZMZEYKD-UHFFFAOYSA-H 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000003566 sealing material Substances 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 description 1
- QVOIJBIQBYRBCF-UHFFFAOYSA-H yttrium(3+);tricarbonate Chemical compound [Y+3].[Y+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O QVOIJBIQBYRBCF-UHFFFAOYSA-H 0.000 description 1
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- Ceramic Products (AREA)
Abstract
Description
本発明は、球状ＡｌＮ粒子およびその製造方法に関係する。 The present invention relates to spherical AlN particles and a method for producing the same.
ＡｌＮ（窒化アルミニウム）は、セラミックスの中でも高熱伝導性を有する材料であり、半導体用の基板としてＡｌＮの焼結体が実用化されている。ＡｌＮは、難焼結性の材料であることから、ＡｌＮ単体では焼結することが困難であり、一般にＣａ化合物、Ｙ化合物などが焼結助剤として用いられている。また、ＡｌＮは、高温で酸化されてしまうため、焼結の際は酸素を含まない不活性ガス雰囲気中、たとえば、窒素ガス雰囲気中で焼成するのが一般的である。 AlN (aluminum nitride) is a material having high thermal conductivity among ceramics, and an AlN sintered body has been put to practical use as a substrate for semiconductors. Since AlN is a hardly sinterable material, it is difficult to sinter with AlN alone, and Ca compounds, Y compounds, and the like are generally used as sintering aids. In addition, since AlN is oxidized at a high temperature, firing is generally performed in an inert gas atmosphere that does not contain oxygen, for example, in a nitrogen gas atmosphere.
一方、セラミックスの球状粒子は、半導体の封止材料や絶縁性樹脂基板、放熱シート等に用いられている。これらの用途には、ＳｉＯ2（シリカ）やＡｌ2Ｏ3（アルミナ）などの酸化物の球状粒子を樹脂と混合して使用されており、これらの球状粒子としては、溶射法により製造されたものが広く使われている。 On the other hand, ceramic spherical particles are used for semiconductor sealing materials, insulating resin substrates, heat dissipation sheets, and the like. In these applications, spherical particles of oxides such as SiO 2 (silica) and Al 2 O 3 (alumina) are mixed with a resin, and these spherical particles were produced by a thermal spraying method. Things are widely used.
特に、高熱伝導が求められる樹脂基板や放熱シート、放熱グリースなどには、シリカより熱伝導率の高いアルミナの球状粒子も用いられる。しかしながら、アルミナの熱伝導率は、焼結体で３０Ｗ／ｍＫ程度であり必ずしも高くなく、樹脂に高充填した材料の熱伝導率も１０数Ｗ／ｍＫのものしか得られない。 In particular, spherical particles of alumina having a higher thermal conductivity than silica are also used for resin substrates, heat radiating sheets, heat radiating grease, and the like that require high thermal conductivity. However, the thermal conductivity of alumina is about 30 W / mK in the sintered body, which is not necessarily high, and the thermal conductivity of the material highly filled in the resin can only be 10 tens W / mK.
今後、パワーデバイス等のより放熱性が求められる部品に適用する場合、更に高熱伝導率化が必要となる。これらの用途では、高熱伝導性とともに絶縁性が求められるため、ＡｌＮが有力な材料である。しかしながら、ＡｌＮは高温で酸化あるいは分解してしまうため、一般的な球状粒子の量産法である溶射法を適用して球状粒子を製造することが困難である。 In the future, when applied to parts that require more heat dissipation, such as power devices, higher thermal conductivity will be required. In these applications, insulation is required as well as high thermal conductivity, so AlN is a promising material. However, since AlN is oxidized or decomposed at a high temperature, it is difficult to produce spherical particles by applying a thermal spraying method, which is a general method for mass production of spherical particles.
溶射法は、搬送ガスを用いるなどして原料の粉末を高温の火炎中に供給し、原料を溶融させることで、表面張力により溶融した原料を球状化し、そのまま冷却することで球状粒子を得る方法である。溶射法では、火炎を形成するために燃料ガスと酸素とが必要であることから、酸化雰囲気で原料を溶融するため、非酸化物を溶射する場合、原料の少なくとも一部が酸化した球状粒子しか得ることができない。 The thermal spraying method is a method in which a raw material powder is supplied into a high-temperature flame by using a carrier gas, etc., and the raw material is melted to spheroidize the molten raw material by surface tension, and then cool as it is to obtain spherical particles It is. In the thermal spraying method, fuel gas and oxygen are required to form a flame. Therefore, in order to melt a raw material in an oxidizing atmosphere, when spraying a non-oxide, only spherical particles in which at least a part of the raw material is oxidized are used. Can't get.
特許文献１には、球状ＡｌＮ粒子を溶射により製造する方法として、ＡｌＮ粉末を可燃性ガスと搬送窒素と燃焼酸素と希釈空気により燃焼させた酸化性雰囲気下の火炎中に通して製造する方法が開示されている。 In Patent Document 1, as a method for producing spherical AlN particles by thermal spraying, there is a method for producing AlN powder by passing it through a flame in an oxidizing atmosphere in which an AlN powder is combusted by combustible gas, carrier nitrogen, combustion oxygen, and diluted air. It is disclosed.
また、球状ＡｌＮ粒子を得る方法として、特許文献２には球状のアルミナ粒子を窒化する方法が開示されている。この技術では、カーボン粒子とＡｌ2Ｏ3粒子とを混合したものを、窒素雰囲気下においてマイクロ波を照射して加熱することで、Ａｌ2Ｏ3及び酸窒化アルミニウムの少なくとも一方からなるコアと、コアの表面に形成されたＡｌＮ表面層と、を具えるＡｌＮ粒子が製造できる。 As a method for obtaining spherical AlN particles, Patent Document 2 discloses a method for nitriding spherical alumina particles. In this technique, a mixture of carbon particles and Al 2 O 3 particles is heated by irradiating microwaves in a nitrogen atmosphere, whereby a core made of at least one of Al 2 O 3 and aluminum oxynitride, AlN particles comprising an AlN surface layer formed on the surface of the core can be produced.
また、緻密なアルミナ粒子以外を原料として用いる方法として、特許文献３にはアルミナ粉末又はアルミナ水和物粉末の球状造粒物を出発原料として使用し、還元窒化を行うことにより球状窒化アルミニウム粉末を製造する方法が開示されている。 In addition, as a method of using a material other than dense alumina particles as a raw material, Patent Document 3 uses a spherical granulated product of alumina powder or alumina hydrate powder as a starting material, and a spherical aluminum nitride powder is obtained by performing reductive nitriding. A method of manufacturing is disclosed.
パワーデバイス等の高温環境下での使用あるいは高発熱化に伴い、放熱部材にはより高熱伝導化が求められており、特に樹脂基板や放熱シート、放熱グリースなど用いられるフィラー粒子として、樹脂に高充填でき高熱伝導性が得られる球状で緻密なＡｌＮ粒子は非常に有用である。 With use in high-temperature environments such as power devices or higher heat generation, heat dissipation members are required to have higher thermal conductivity, especially as filler particles used for resin substrates, heat dissipation sheets, heat dissipation grease, etc. Spherical and dense AlN particles that can be filled and have high thermal conductivity are very useful.
なお、特許文献１は、溶射によりＡｌＮ原料を球状化する技術を提案している。しかしながら、溶射による方法では、火炎を形成するために燃料ガスと酸素ガスもしくは酸素含有ガスを使用する必要があるため、原料のＡｌＮが酸化するのを防ぐことができない。 Patent Document 1 proposes a technique for spheroidizing the AlN raw material by thermal spraying. However, in the method by thermal spraying, it is necessary to use a fuel gas and an oxygen gas or an oxygen-containing gas to form a flame, so that the raw material AlN cannot be prevented from being oxidized.
さらに、特許文献１では、実施例に示されるようにＡｌＮ残量は最大で６０％であり、溶射過程でＡｌＮの４０％以上が酸化されてＡｌ2Ｏ3に変化してしまう。このため、熱伝導に重要な役割を果たす表面を、ＡｌＮより熱伝導率の低いＡｌ2Ｏ3が覆う構造になる。したがって、このような粒子を樹脂に混合した場合、高い熱伝導率を得ることができない。 Further, in Patent Document 1, as shown in Examples, the remaining amount of AlN is 60% at the maximum, and 40% or more of AlN is oxidized and changed to Al 2 O 3 during the thermal spraying process. For this reason, the surface that plays an important role in heat conduction is covered with Al 2 O 3 having a lower thermal conductivity than AlN. Therefore, when such particles are mixed with a resin, high thermal conductivity cannot be obtained.
また、特許文献２では、緻密なＡｌ2Ｏ3球状粒子を原料として用いて、窒化させる方法が提案されている。しかしながら、緻密なＡｌ2Ｏ3粒子を原料として用いた場合、窒化反応は表面から起こるため、表層にＡｌＮが形成されるが、内部は熱伝導率が低いＡｌ2Ｏ3、ＡｌＯＮ（酸窒化アルミニウム）として残ってしまう。 Patent Document 2 proposes a method of nitriding using dense Al 2 O 3 spherical particles as a raw material. However, when dense Al 2 O 3 particles are used as a raw material, the nitriding reaction takes place from the surface, so AlN is formed on the surface layer, but the inside has Al 2 O 3 , AlON (aluminum oxynitride) with low thermal conductivity ) Will remain.
このように表面層のみをＡｌＮ化した場合、内部までＡｌＮである粒子に比べて、樹脂と混合した際の熱伝導率は低くなってしまう。また、緻密なＡｌ2Ｏ3粒子を窒化した場合、窒化されて表面に形成されたＡｌＮ層と内部のコア（Ａｌ2Ｏ3）の間には、窒化反応の際に空隙が発生するため、樹脂と混合した際、ＡｌＮ層が剥がれてしまう。あるいは、当該空隙により熱伝導が低下してしまう。 Thus, when only the surface layer is made of AlN, the thermal conductivity when mixed with the resin is lower than that of the particles that are AlN to the inside. Also, when dense Al 2 O 3 particles are nitrided, voids are generated during the nitriding reaction between the nitrided AlN layer formed on the surface and the inner core (Al 2 O 3 ). When mixed with resin, the AlN layer is peeled off. Or heat conduction will fall by the said space | gap.
また、特許文献３には、アルミナ粉末又はアルミナ水和物粉末の球状造粒物を還元窒化する技術が開示されている。しかしながら、この方法を用いる場合、球状のＡｌＮ粒子を得ることができるが、球状ＡｌＮ粒子の原料として比表面積が３０〜５００ｍ2／ｇの球状造粒物を用いることが望ましいとしている。 Patent Document 3 discloses a technique for reducing and nitriding a spherical granulated product of alumina powder or alumina hydrate powder. However, when this method is used, spherical AlN particles can be obtained. However, it is desirable to use a spherical granulated product having a specific surface area of 30 to 500 m 2 / g as a raw material for the spherical AlN particles.
これは、造粒物の比表面積が小さ過ぎると、還元窒化工程での昇温過程或いは熱処理工程で粒子間の空隙が閉塞してしまい、球状造粒物の内部までの還元窒化が十分に行われなくなってしまう問題が生じるためである。 This is because if the specific surface area of the granulated product is too small, voids between the particles will be blocked in the temperature raising process or heat treatment process in the reduction nitriding process, and the reduction nitriding to the inside of the spherical granulated product will be performed sufficiently. This is because there is a problem that it will not be broken.
しかしながら、造粒粉の原料に比表面積が大きい、すなわち粒径が小さいものを用いた場合、造粒粉の内部での原料粉の充填密度が低くなり、高温での還元窒化過程でも空隙が多く残ったままＡｌＮへの反応が起こるため、最終的に得られる球状ＡｌＮ粒子の表面あるいは内部に空隙が多く残存してしまう問題がある。 However, if the raw material of the granulated powder has a large specific surface area, that is, a small particle size, the packing density of the raw material powder inside the granulated powder will be low, and there will be many voids even during the reductive nitriding process at high temperature. Since the reaction to AlN occurs while remaining, there is a problem that many voids remain on the surface or inside of the finally obtained spherical AlN particles.
例えば、特許文献３の球状ＡｌＮ粉末の比表面積が全般に高いが、これは、微細な気孔が多く残存していることを示しており、このため、特許文献３の球状ＡｌＮ粉末は、十分高い熱伝導度が得られない可能性がある。 For example, although the specific surface area of the spherical AlN powder of Patent Document 3 is generally high, this indicates that many fine pores remain, and thus the spherical AlN powder of Patent Document 3 is sufficiently high. Thermal conductivity may not be obtained.
また、特許文献３では、球状造粒物を、熱処理工程を経た後に還元窒化工程に供給することもできるとしており、この際、熱処理物は、ある程度以上の比表面積（例えば２ｍ2／ｇ以上）を有すべきとしている。具体的には、水酸化アルミニウムあるいはベーマイトの球状造粒物を、約６００℃で一定時間熱処理することにより得られたγ−アルミナの球状造粒物あるいは１１００℃以上の温度で一定時間熱処理することにより得られたα−アルミナの球状造粒物を、還元窒化工程に供給することができると述べられている。 Further, in Patent Document 3, the spherical granulated product can be supplied to the reduction nitriding step after the heat treatment step. At this time, the heat treated product has a specific surface area of a certain level (for example, 2 m 2 / g or more). Should have. Specifically, γ-alumina spherical granule obtained by heat treating aluminum hydroxide or boehmite spherical granule at a temperature of about 600 ° C. for a certain time, or heat treating at a temperature of 1100 ° C. or more for a certain time. It is stated that the spherical granules of α-alumina obtained by the above can be supplied to the reduction nitriding step.
しかしながら、還元窒化工程の前処理として熱処理を行う場合、熱処理を２回行うことになるため、製造コストが高くなる欠点がある。 However, when heat treatment is performed as a pretreatment for the reduction nitriding step, the heat treatment is performed twice, and thus there is a disadvantage that the manufacturing cost is increased.
本発明は、以上のような従来技術の問題点を鑑み、従来よりも生産性が高く、製造コストが低く、且つ高充填性、高熱伝導性を有し、半導体分野にも適用可能な球状ＡｌＮ粒子およびその製造方法を提供することを目的とする。 In view of the problems of the prior art as described above, the present invention is a spherical AlN that has higher productivity, lower manufacturing cost, high fillability, high thermal conductivity, and can be applied to the semiconductor field. An object is to provide particles and a method for producing the same.
本発明により、以下の態様が提供される。
［１］粒子全体の重量比１００ｗｔ％に対して、Ｙ2Ｏ3換算で０．０１〜０．５ｗｔ％のＹと、ＳｉＯ2換算で０．０１〜０．５ｗｔ％のＳｉと、ＡｌＮを含有し、前記ＡｌＮを６０ｗｔ％以上の割合で含有し、理論密度の９０％以上の相対密度を有し、円形度が０．８５〜１．００であることを特徴とする、球状ＡｌＮ粒子。
［２］平均粒径（Ｄ５０）が５〜１５０μｍであることを特徴とする、項目［１］に記載の球状ＡｌＮ粒子。
［３］平均粒径（Ｄ５０）が０．０５〜４μｍのＡｌ2Ｏ3粉末１００ｗｔ％に外割で、Ｙ2Ｏ3換算で０．００８〜０．５６５ｗｔ％のＹ化合物およびＳｉＯ2換算で０．００８〜０．５６５ｗｔ％のＳｉ化合物と、を混合し、球状に造粒した粉末を、炭素粉末と混合して、窒素雰囲気中で熱処理温度１６００〜１８００℃で熱処理することを特徴とする、項目［１］または［２］に記載の球状ＡｌＮ粒子の製造方法。
［４］平均粒径（Ｄ５０）が０．０５〜４μｍのＡｌ2Ｏ3粉末１００ｗｔ％に外割で、Ｙ2Ｏ3換算で０．００８〜０．５６５ｗｔ％のＹ化合物およびＳｉＯ2換算で０．００８〜０．５６５ｗｔ％のＳｉ化合物を、炭素粉末と混合し、球状に造粒した粉末を、マイクロ波により窒素雰囲気中で熱処理温度１４００〜１８００℃で窒化することを特徴とする、項目［１］または［２］に記載の球状ＡｌＮ粒子の製造方法。
［５］スプレードライ法により造粒した粉末を用いることを特徴とする、項目［３］または［４］に記載の球状ＡｌＮ粒子の製造方法。
The following aspects are provided by the present invention.
[1] For a weight ratio of 100 wt% of the entire particle, 0.01 to 0.5 wt% Y in terms of Y 2 O 3 , 0.01 to 0.5 wt% Si in terms of SiO 2 , and AlN Spherical AlN particles containing the AlN at a ratio of 60 wt% or more, having a relative density of 90% or more of the theoretical density, and a circularity of 0.85 to 1.00.
[2] The spherical AlN particles according to item [1], wherein the average particle diameter (D50) is 5 to 150 μm.
[3] an average particle diameter (D50) in outer percentage to the Al 2 O 3 powder 100 wt% of 0.05～4Myuemu, in 0.008～0.565Wt% of Y compound and in terms of SiO 2 in terms of Y 2 O 3 0.008 to 0.565 wt% Si compound is mixed and spherically granulated powder is mixed with carbon powder and heat treated at a heat treatment temperature of 1600 to 1800 ° C. in a nitrogen atmosphere. The method for producing spherical AlN particles according to item [1] or [2].
[4] an average particle diameter (D50) in outer percentage to the Al 2 O 3 powder 100 wt% of 0.05～4Myuemu, in 0.008～0.565Wt% of Y compound and in terms of SiO 2 in terms of Y 2 O 3 0.008 to 0.565 wt% Si compound is mixed with carbon powder and spherically granulated powder is nitrided at a heat treatment temperature of 1400 to 1800 ° C. in a nitrogen atmosphere by microwaves, The method for producing spherical AlN particles according to [1] or [2].
[5] The method for producing spherical AlN particles according to item [3] or [4], wherein a powder granulated by a spray drying method is used.
本発明によれば、従来よりも生産性が高く、製造コストが低く、且つ高充填性、高熱伝導性を有し、半導体分野にも適用可能な球状ＡｌＮ粒子およびその製造方法を提供することができる。 According to the present invention, it is possible to provide spherical AlN particles having higher productivity, lower manufacturing cost, higher filling property, higher thermal conductivity, and applicable to the semiconductor field, and a method for manufacturing the same. it can.
発明者は、上記課題を解決するために鋭意検討を重ねた結果、「Ｙ2Ｏ3換算で０．０１〜０．５ｗｔ％のＹとＳｉＯ2換算で０．０１〜０．５ｗｔ％のＳｉを含有し、ＡｌＮの含有比率が６０ｗｔ％以上であり、理論密度の９０％以上の相対密度を有し、円形度が０．８５〜１．００であることを特徴とする、球状ＡｌＮ粒子」が、下記に示す方法により製造できることを見出し、従来よりも生産性が高く、製造コストが低く、且つ高充填性、高熱伝導性を有し、半導体分野にも適用可能な球状ＡｌＮ粒子を実現できることを見出した。 As a result of intensive studies to solve the above problems, the inventor has found that "Y 2 O 3 converted to 0.01 to 0.5 wt% Y and SiO 2 converted to 0.01 to 0.5 wt% Si. Spherical AlN particles characterized in that the content ratio of AlN is 60 wt% or more, the relative density is 90% or more of the theoretical density, and the circularity is 0.85 to 1.00. However, it has been found that it can be produced by the method shown below, and it is possible to realize spherical AlN particles having higher productivity, lower production cost, high filling property, high thermal conductivity and applicable to the semiconductor field. I found.
（１．球状ＡｌＮ粒子の製造方法）
本発明による球状ＡｌＮ粒子は、Ａｌ2Ｏ3粉末と、Ａｌ2Ｏ3粉末１００ｗｔ％に外割で、Ｙ2Ｏ3換算で０．００８〜０．５ｗｔ％のＹ化合物およびＳｉＯ2換算で０．００８〜０．５ｗｔ％のＳｉ化合物と、を混合し、造粒・乾燥した造粒粉を、高温で熱処理する方法により製造することができる。以下、本発明の球状ＡｌＮ粒子の製造方法について工程順に詳細に説明する。
(1. Method for producing spherical AlN particles)
Spherical AlN particles according to the invention, Al 2 O 3 powder and, Al 2 O 3 powder 100 wt% to the outside split, Y 2 O 3 0 in 0.008～0.5Wt% of Y compound and in terms of SiO 2 in terms of It is possible to produce a granulated powder obtained by mixing 0.008 to 0.5 wt% of a Si compound and granulating and drying it at a high temperature. Hereinafter, the manufacturing method of the spherical AlN particle | grains of this invention is demonstrated in detail in order of a process.
＜原料＞
まず、本発明の球状ＡｌＮ粒子の製造方法において用いる原料について説明する。
<Raw material>
First, raw materials used in the method for producing spherical AlN particles of the present invention will be described.
（Ａｌ2Ｏ3粉末）
Ａｌ2Ｏ3の原料としては、本実施形態では、平均粒径（Ｄ５０）が０．０５〜４μｍのＡｌ2Ｏ3粉末を用いる。平均粒径（Ｄ５０）が０．０５μｍより小さいＡｌ2Ｏ3粉末を用いる場合、後述する造粒工程において、造粒・乾燥して得られる造粒粉中のＡｌ2Ｏ3粉末の充填率が低くなりやすいため、最終的に得られる球状ＡｌＮ粒子に空孔が残りやすくなる。また、平均粒径（Ｄ５０）が４μｍより大きいＡｌ2Ｏ3粉末を用いる場合、造粒粉の強度が低く、球状に造粒した造粒粉が壊れやすくなり、得られるＡｌＮ粒子の円形度が低下する。また、Ａｌ2Ｏ3粉末が窒化されてＡｌＮになる際、表面の凹凸が大きくなり、円形度が低下する。円形度が低下すると、樹脂と混合する際の充填率を上げることが難しくなることがある。
(Al 2 O 3 powder)
As a raw material of Al 2 O 3, in the present embodiment, an average particle diameter (D50) using the Al 2 O 3 powder 0.05～4Myuemu. When using an Al 2 O 3 powder having an average particle size (D50) smaller than 0.05 μm, the filling rate of the Al 2 O 3 powder in the granulated powder obtained by granulation and drying in the granulation step described later is Since it tends to be low, voids are likely to remain in the finally obtained spherical AlN particles. Further, when Al 2 O 3 powder having an average particle size (D50) larger than 4 μm is used, the strength of the granulated powder is low, and the granulated powder granulated in a spherical shape is easily broken, and the circularity of the obtained AlN particles is high. descend. Further, when the Al 2 O 3 powder is nitrided to become AlN, the surface unevenness increases and the circularity decreases. When the circularity is lowered, it may be difficult to increase the filling rate when mixing with the resin.
Ａｌ2Ｏ3粉末の平均粒径は、例えばレーザー回折法による粒度分布測定やＳＥＭにより観察した粒子のサイズの測定により、メディアン径（Ｄ５０）として算出される。 The average particle diameter of the Al 2 O 3 powder is calculated as the median diameter (D50), for example, by measuring the particle size distribution by a laser diffraction method or measuring the particle size observed by SEM.
また、原料に用いるＡｌ2Ｏ3粉末の比表面積は、２〜３０ｍ2／ｇの粉末であることが望ましい。比表面積が２ｍ2／ｇより小さいＡｌ2Ｏ3粉末を用いた場合、後述する熱処理工程における加熱過程でＡｌ2Ｏ3での焼結が起こりにくいため、造粒粉が球状であっても、Ａｌ2Ｏ3が窒化される過程あるいはＡｌＮが焼結する過程でいびつな形状になりやすく、高い円形度のＡｌＮ粒子を得ることが出来ないことがある。 The specific surface area of the Al 2 O 3 powder used for the raw material is preferably 2-30 m 2 / g. When Al 2 O 3 powder having a specific surface area of less than 2 m 2 / g is used, since sintering with Al 2 O 3 hardly occurs in the heating process in the heat treatment step described later, even if the granulated powder is spherical, In the process of nitriding Al 2 O 3 or the process of sintering AlN, the shape tends to become distorted, and it may be impossible to obtain AlN particles with high circularity.
また、比表面積が３０ｍ2／ｇより大きいＡｌ2Ｏ3粉末を用いた場合、熱処理工程における昇温過程あるいは窒化が起こる温度より低温での焼結が進行し易くなるため、Ａｌ2Ｏ3造粒粉の表面の気孔が閉塞してしまい、内部の窒化に必要な窒素が供給されずにＡｌＮ転換率の低い粒子になるため望ましくない。なお、比表面積は、ＪＩＳ−Ｚ８８３０に規定されるＢＥＴ比表面積測定法により測定することができる。 Also, if the specific surface area was used 30 m 2 / g greater than Al 2 O 3 powder, since the sintering at a lower temperature than the temperature at which the heating process or nitride in the heat treatment step take place is likely to proceed, Al 2 O 3 Concrete Since the pores on the surface of the granule are blocked, the nitrogen necessary for internal nitriding is not supplied and the particles have a low AlN conversion rate, which is not desirable. In addition, a specific surface area can be measured by the BET specific surface area measuring method prescribed | regulated to JIS-Z8830.
このように、原料に微細なＡｌ2Ｏ3粉末を用いることにより、窒化する前のＡｌ2Ｏ3の焼結も起こるが、窒化した後のＡｌＮ粒子も微細なためＡｌＮ粒子の焼結が進みやすく、理論密度の９０％以上の相対密度を有する緻密な球状ＡｌＮ粒子を得ることができる。 Thus, by using fine Al 2 O 3 powder as a raw material, sintering of Al 2 O 3 before nitriding also occurs, but since the AlN particles after nitriding are also fine, the sintering of AlN particles proceeds. It is easy to obtain dense spherical AlN particles having a relative density of 90% or more of the theoretical density.
（Ｙ化合物）
原料に用いるＹ化合物は、酸化イットリウム（Ｙ2Ｏ3）、炭酸イットリウム、蓚酸イットリウム、塩化イットリウム、硝酸イットリウム、トリエトキシイットリウム等のイットリウムアルコキシド等を用いることができる。
(Y compound)
As the Y compound used as a raw material, yttrium alkoxide such as yttrium oxide (Y 2 O 3 ), yttrium carbonate, yttrium oxalate, yttrium chloride, yttrium nitrate, and triethoxy yttrium can be used.
本実施形態では、Ｙ化合物は粉末状であることが好ましく、特に安価で安定なＹ2Ｏ3の粉末を用いることができる。特に、１μｍ以下の微細なＹ2Ｏ3粉末を用いることで造粒粉の焼結やＡｌＮ化した後の焼結が均一に起こるため、円形度が高く、ＡｌＮ転換率の高い球状ＡｌＮ粒子を得ることができる。 In the present embodiment, the Y compound is preferably in the form of a powder, and a particularly inexpensive and stable Y 2 O 3 powder can be used. In particular, by using fine Y 2 O 3 powder of 1 μm or less, granulated powder and sintering after AlN conversion occur uniformly, so spherical AlN particles with high circularity and high AlN conversion rate are obtained. Can be obtained.
（Ｓｉ化合物）
原料に用いるＳｉ化合物は、酸化ケイ素（ＳｉＯ2）、テトラメトキシシラン等のシリコンアルコキシド、コロイダルシリカ等を用いることができる。本実施形態では、Ｓｉ化合物は粉末状であることが好ましい。Ｓｉ化合物として、ＳｉＯ2を用いる場合、非晶質、石英、クリストバライト、等その構造は問わないが、１μｍ以下の微細なＳｉＯ2粉末を用いることで造粒粉中のＡｌ2Ｏ3の焼結が均一に起こるため、円形度が高く、ＡｌＮ転換率の高い球状ＡｌＮ粒子を得ることができる。
(Si compound)
As the Si compound used as a raw material, silicon alkoxide such as silicon oxide (SiO 2 ) and tetramethoxysilane, colloidal silica, and the like can be used. In the present embodiment, the Si compound is preferably in a powder form. When SiO 2 is used as the Si compound, amorphous, quartz, cristobalite, etc., the structure thereof does not matter, but by using a fine SiO 2 powder of 1 μm or less, sintering of Al 2 O 3 in the granulated powder Since this occurs uniformly, spherical AlN particles having a high degree of circularity and a high AlN conversion rate can be obtained.
Ｙ化合物およびＳｉ化合物は、原料として用いるＡｌ2Ｏ3粉末が窒化する前段階での焼結および窒化した後のＡｌＮ粒子の焼結を促進する焼結助剤として働くことで、緻密な球状粒子を得るために有効である。 Y compound and Si compound, that acts as a sintering aid to accelerate sintering of AlN particles after Al 2 O 3 powder used as raw material is sintered and nitrided in the previous stage of nitriding, dense spherical particles It is effective to obtain.
＜混合＞
上記のＡｌ2Ｏ3粉末と、Ｙ化合物およびＳｉ化合物と、を混合する方法は、均一に混合可能な混合方法であればどのような方法を用いても良い。たとえば、乾式混合、もしくは、水、アルコール、アセトン等の溶媒を用いた湿式混合で混合することができる。
<Mixed>
As a method of mixing the Al 2 O 3 powder, the Y compound, and the Si compound, any method may be used as long as it is a mixing method that allows uniform mixing. For example, it can be mixed by dry mixing or wet mixing using a solvent such as water, alcohol, and acetone.
混合時におけるＹ化合物およびＳｉ化合物の添加量は、Ａｌ2Ｏ3粉末１００ｗｔ％に対して外割で、Ｙ化合物の添加量が、Ｙ2Ｏ3換算で０．００８〜０．５６５ｗｔ％であり、Ｓｉ化合物の添加量が、ＳｉＯ2換算で０．００８〜０．５６５ｗｔ％である。 The amount of Y compound and Si compound added at the time of mixing is an extra percentage with respect to 100 wt% of Al 2 O 3 powder, and the amount of Y compound added is 0.008 to 0.565 wt% in terms of Y 2 O 3 . The amount of Si compound added is 0.008 to 0.565 wt% in terms of SiO 2 .
Ｙ2Ｏ3換算でのＹの量が０．００８ｗｔ％より少ない場合、ＡｌＮの焼結を促進する効果が得られず、緻密な球状ＡｌＮ粒子を得ることができない。また、０．５ｗｔ％より多くＹを含む場合、ＡｌＮの焼結が急激に進み、収縮が不均一になって粒子の形状がいびつになるため、十分に高い円形度の球状ＡｌＮ粒子を得ることが出来ない。 When the amount of Y in terms of Y 2 O 3 is less than 0.008 wt%, the effect of promoting the sintering of AlN cannot be obtained, and dense spherical AlN particles cannot be obtained. Further, when Y is contained in an amount of more than 0.5 wt%, the sintering of AlN proceeds rapidly, the shrinkage becomes non-uniform, and the shape of the particles becomes distorted, so that spherical AlN particles with sufficiently high circularity can be obtained. I can not.
ＳｉＯ2換算でのＳｉの量が０．００８ｗｔ％より少ない場合、窒化前のＡｌ2Ｏ3の焼結が進まず、Ａｌ2Ｏ3の窒化前にＡｌ2Ｏ3の骨格が形成されない。その結果、Ａｌ2Ｏ3の窒化あるいはＡｌＮが焼結する過程で粒子がいびつな形状になりやすく、高い円形度のＡｌＮ粒子を得ることが出来ない。０．５ｗｔ％より多くＳｉを含む場合、窒化前のＡｌ2Ｏ3の焼結が過度に進み、造粒粉の表面の気孔が閉塞してしまい、造粒粉内部の窒化が進まず、ＡｌＮの転換率が低い粒子となってしまうため、熱伝導率の高いＡｌＮ粒子を得ることが出来ない。 When the amount of Si in terms of SiO 2 is less than 0.008 wt%, sintering of Al 2 O 3 before nitriding does not proceed, and an Al 2 O 3 skeleton is not formed before nitriding of Al 2 O 3 . As a result, the particles tend to become distorted in the process of nitriding Al 2 O 3 or sintering AlN, and AlN particles with high circularity cannot be obtained. When more than 0.5 wt% Si is contained, sintering of Al 2 O 3 before nitriding proceeds excessively, pores on the surface of the granulated powder are blocked, and nitriding inside the granulated powder does not proceed, and AlN Therefore, AlN particles having high thermal conductivity cannot be obtained.
＜造粒＞
混合した粉末を球状に造粒する方法としては、スプレードライ、転動造粒、撹拌造粒、流動造粒などの方法を用いることができる。
<Granulation>
As a method of granulating the mixed powder into a spherical shape, methods such as spray drying, rolling granulation, stirring granulation, and fluid granulation can be used.
特にスプレードライ法を用いた場合、大量の原料粉を効率良く球状に造粒することができる。スプレードライによる造粒を行う場合、水等の溶媒に分散剤やバインダー等の添加材を用いることにより、原料が均一に分散し、強度の高い造粒粉を得ることができる。 In particular, when the spray drying method is used, a large amount of raw material powder can be efficiently granulated into a spherical shape. When performing granulation by spray drying, by using an additive such as a dispersant or a binder in a solvent such as water, the raw material is uniformly dispersed, and a granulated powder having high strength can be obtained.
また、窒化により得られる球状ＡｌＮ粒子は、造粒粉の粒径とほぼ同一であるため、造粒粉の粒径を制御することにより、所望の粒径の球状ＡｌＮ粒子を得ることができる。 Further, since the spherical AlN particles obtained by nitriding are almost the same as the particle size of the granulated powder, it is possible to obtain spherical AlN particles having a desired particle size by controlling the particle size of the granulated powder.
ここで、造粒粉は、過度に緻密ではなく、空隙を内包することで、後述する熱処理工程における窒化反応が球状粒子の表面だけでなく、造粒粉内部でも反応が起こることによりＡｌＮ転換率が６０％以上の球状ＡｌＮ粒子を得ることができる。緻密な１個のＡｌ2Ｏ3球状粒子を用いて、ＡｌＮ転換率の高い球状ＡｌＮ粒子を得ようとする場合、表面のＡｌＮが成長して、表面の凹凸が大きくなり、円形度を低下させてしまう。これに対し、本発明のＡｌＮ粒子は、造粒粉に含まれる個々のＡｌ2Ｏ3粒子が窒化されたものであるため、ＡｌＮ転換率が６０％以上になっても表面の凹凸が大きくなることない。その結果、０．８５〜１．００の高い円形度の球状ＡｌＮ粒子を得ることができる。 Here, the granulated powder is not excessively dense and contains voids, so that the nitriding reaction in the heat treatment process described later occurs not only on the surface of the spherical particles but also inside the granulated powder, so that the AlN conversion rate Can obtain spherical AlN particles of 60% or more. When trying to obtain spherical AlN particles with a high AlN conversion rate using a single fine Al 2 O 3 spherical particle, the surface AlN grows, the surface irregularities increase, and the circularity decreases. End up. On the other hand, since the AlN particles of the present invention are obtained by nitriding individual Al 2 O 3 particles contained in the granulated powder, surface irregularities increase even when the AlN conversion rate is 60% or more. There is nothing. As a result, spherical AlN particles having a high circularity of 0.85 to 1.00 can be obtained.
＜熱処理＞
球状の造粒粉を窒素含有雰囲気中で１６００〜１８００℃の温度で熱処理を行うことにより、球状のＡｌＮ粒子を得ることができる。
<Heat treatment>
Spherical AlN particles can be obtained by heat-treating the spherical granulated powder at a temperature of 1600 to 1800 ° C. in a nitrogen-containing atmosphere.
１６００℃より低い温度では、Ａｌ2Ｏ3の窒化が起こりにくく、ＡｌＮの転換率が低い粒子となるため望ましくない。１８００℃より高い温度で熱処理した場合、窒化してできた球状ＡｌＮ粒子同士が焼結をし始め、粒子が結合してしまったり、ＡｌＮ粒子の分解が起こり始めるため、望ましくない。 When the temperature is lower than 1600 ° C., nitriding of Al 2 O 3 hardly occurs and the conversion rate of AlN becomes low, which is not desirable. When heat treatment is performed at a temperature higher than 1800 ° C., spherical AlN particles formed by nitriding begin to sinter and the particles start to bond or the AlN particles start to decompose, which is not desirable.
Ａｌ2Ｏ3を直接窒化する場合、ＮＨ3ガスやＨ2ガスを用いることもできるが、安価かつ安全なＮ2ガスを窒素源とした場合、窒化反応が起こりにくく、還元窒化させることにより効率的にＡｌ2Ｏ3をＡｌＮに転換させることができる。 When directly nitriding Al 2 O 3 , NH 3 gas or H 2 gas can be used, but when cheap and safe N 2 gas is used as a nitrogen source, the nitriding reaction hardly occurs and the efficiency is improved by reduction nitriding. In particular, Al 2 O 3 can be converted to AlN.
この熱処理工程では、Ａｌ2Ｏ3が窒化される前に、Ａｌ2Ｏ3が焼結することにより、Ａｌ2Ｏ3粒子同士がネック形成により結合し、造粒粉の球形の形状を保ったまま、Ａｌ2Ｏ3の強固な骨格が形成される。その結果、窒化されてＡｌＮが生成する際も粒子が球形を保ったままで窒化反応が進み、円形度の高い球状ＡｌＮ粒子を得ることができる。 In this heat treatment step, before Al 2 O 3 is nitrided, Al 2 O 3 is sintered, whereby Al 2 O 3 particles are bonded to each other by neck formation, and the spherical shape of the granulated powder is maintained. As it is, a strong skeleton of Al 2 O 3 is formed. As a result, even when nitriding to produce AlN, the nitriding reaction proceeds while the particles remain spherical, and spherical AlN particles having a high degree of circularity can be obtained.
但し、窒化が進む前に過度にＡｌ2Ｏ3の焼結が進行してしまうと、造粒粉の空隙が閉塞してしまい、造粒粉内部の反応に必要な窒素が供給されなくなるため、ＡｌＮ転換率の高い球状ＡｌＮ粒子を得ることができなくなってしまう。 However, if the sintering of Al 2 O 3 proceeds excessively before nitriding proceeds, the gaps in the granulated powder will be blocked, and nitrogen necessary for the reaction inside the granulated powder will not be supplied. It becomes impossible to obtain spherical AlN particles having a high AlN conversion rate.
そこで、本発明者らは、Ａｌ2Ｏ3の焼結が適度に進行するための条件について、下記の知見に基づき検討を行った。 Therefore, the present inventors have examined the conditions for appropriately sintering Al 2 O 3 based on the following knowledge.
ＹをＹ2Ｏ3として添加した場合、Ｙ2Ｏ3とＡｌ2Ｏ3が共融する温度は、１８００℃以上であり、一旦Ｙ2Ｏ3とＡｌ2Ｏ3を均一に融かした場合でも共融温度は１７００℃以上と非常に高温であることが報告されている（Ｊｏｕｒｎａｌ ｏｆ Ｍａｔｅｒｉａｌｓ Ｓｃｉｅｎｃｅ １７０９−１７１８（１９８０））。 If the Y was added as Y 2 O 3, the temperature of Y 2 O 3 and Al 2 O 3 is eutectic is at 1800 ° C. or more, once Y 2 O 3 and Al 2 O 3 when the uniformly melted However, it has been reported that the eutectic temperature is as high as 1700 ° C. or higher (Journal of Materials Science 1709-1718 (1980)).
このため、Ｙ2Ｏ3を単独でＡｌ2Ｏ3に添加しても、Ａｌ2Ｏ3が焼結する１３００〜１６００℃といった温度域では、Ａｌ2Ｏ3の焼結にはほとんど寄与せず、Ａｌ2Ｏ3の焼結が進む前にＡｌ2Ｏ3の窒化が起こってしまい、造粒粉の形状を保つことができず、円形度が低いＡｌＮ粒子となってしまう。 Therefore, even if Y 2 O 3 is added alone to Al 2 O 3 , it hardly contributes to the sintering of Al 2 O 3 in the temperature range of 1300 to 1600 ° C. where Al 2 O 3 is sintered. , will happening nitriding of Al 2 O 3 before the sintering of Al 2 O 3 is proceeds, can not be maintained the shape of the granulated powder becomes circularity is lower AlN particles.
ＳｉＯ2とＡｌ2Ｏ3の共融点も１６００℃程度と高温であり（Ｊｏｕｒｎａｌ ｏｆ Ｔｈｅ Ａｍｅｒｉｃａｎ Ｃｅｒａｍｉｃ Ｓｏｃｉｅｔｙ ４５［５］２２９−２４２（１９６２））、共融点より低い温度で高融点化合物であるムライト（３Ａｌ2Ｏ3・２ＳｉＯ2）等を生成しやすいため、Ａｌ2Ｏ3の焼結を促進する効果は得られない。 The eutectic point of SiO 2 and Al 2 O 3 is as high as about 1600 ° C. (Journal of The American Ceramic Society 45 [5] 229-242 (1962)), and is a high melting point compound mullite at a temperature lower than the eutectic point ( 3Al 2 O 3 .2SiO 2 ) and the like are easily generated, and the effect of promoting the sintering of Al 2 O 3 cannot be obtained.
一方、Ｙ2Ｏ3とＳｉＯ2とＡｌ2Ｏ3の３者が共存する場合、共融点は１４００℃以下まで下げることが可能であり（日本セラミックス協会学術論文誌 ９９ ［３］ ２１５−２２１（１９９１）など）、液相生成によるＡｌ2Ｏ3に焼結促進の効果を得ることができる。 On the other hand, when the three of Y 2 O 3 , SiO 2, and Al 2 O 3 coexist, the eutectic point can be lowered to 1400 ° C. or less (Academic Journal of the Ceramic Society of Japan 99 [3] 215-221 ( 1991), etc.), the effect of promoting the sintering can be obtained in Al 2 O 3 by liquid phase generation.
そして、本発明者らは、熱処理工程において、Ｙ2Ｏ3とＳｉＯ2を同時に存在させて、Ａｌ2Ｏ3の窒化を行うことで、窒化前のＡｌ2Ｏ3の焼結が促進され、得られる球状ＡｌＮ粒子のＡｌＮ転換率を高める効果が得られることを見出した。これは、Ｙ2Ｏ3、ＳｉＯ2、Ａｌ2Ｏ3により低温で生成する液相中に窒素が溶け込み、ＡｌＮが析出する反応が起こり、ＡｌＮの生成を促進するためと考えられる。 Then, the present inventors have found that in the heat treatment step, simultaneously in the presence of Y 2 O 3 and SiO 2, by performing the nitriding of Al 2 O 3, sintering of Al 2 O 3 prior to nitriding is accelerated, It has been found that the effect of increasing the AlN conversion rate of the obtained spherical AlN particles can be obtained. This is considered to be because nitrogen is dissolved in a liquid phase generated at a low temperature by Y 2 O 3 , SiO 2 , and Al 2 O 3 and a reaction in which AlN precipitates occurs to promote the generation of AlN.
本発明者は、さらに、ＡｌＮ転換率が高く、かつ円形度の高いＡｌＮ粒子を得るために、ＹとＳｉの添加量の最適化を検討した。その結果、上述したように、Ａｌ2Ｏ3粉末１００ｗｔ％に対して外割で、ＹをＹ2Ｏ3換算で０．００８〜０．５６５ｗｔ％およびＳｉをＳｉＯ2換算で０．００８〜０．５６５ｗｔ％を添加することにより、熱処理工程において、昇温過程もしくは還元窒化のための高温での温度保持過程で、還元窒化前のＡｌ2Ｏ3の焼結が適度に進行することを見出し、本発明に至った。この効果は、Ａｌ2Ｏ3を窒化する際に、ＹとＳｉとが酸化物の状態で共存することにより、高温で液相を生成することにより得られる効果である。すなわち、雰囲気中の窒素がＡｌ2Ｏ3粒子内部へ侵入して窒化を妨げない程度にＡｌ2Ｏ3同士が結合し、その後の窒化の際に造粒粉の形状を保ったまま緻密化することで、より緻密な球状ＡｌＮ粒子を得ることが可能となる。 The inventor further studied optimization of the addition amounts of Y and Si in order to obtain AlN particles having a high AlN conversion rate and a high degree of circularity. As a result, as described above, Y is 0.008 to 0.565 wt% in terms of Y 2 O 3 and Si is in the range of 0.008 to 0 in terms of SiO 2 with respect to 100 wt% of Al 2 O 3 powder. It is found that by adding 565 wt%, sintering of Al 2 O 3 before reductive nitriding proceeds appropriately in the heat treatment step in the temperature raising step or the temperature holding step at a high temperature for reductive nitridation, The present invention has been reached. This effect is an effect obtained by generating a liquid phase at a high temperature when Y 2 and Si coexist in an oxide state when nitriding Al 2 O 3 . That is, Al 2 O 3 is bonded to such an extent that nitrogen in the atmosphere penetrates into the Al 2 O 3 particles and does not prevent nitriding, and densification is performed while maintaining the shape of the granulated powder during subsequent nitriding. This makes it possible to obtain finer spherical AlN particles.
ＡｌＮの焼結は、Ｙ2Ｏ3、ＳｉＯ2およびＡｌ2Ｏ3により生成する液相による液相焼結で進行するが、特にＹ2Ｏ3を含む液相が生成することによりＡｌＮの焼結を促進する効果が得られる。 AlN sintering proceeds by liquid phase sintering using a liquid phase generated by Y 2 O 3 , SiO 2, and Al 2 O 3. In particular, when a liquid phase containing Y 2 O 3 is generated, AlN is sintered. The effect of promoting ligation is obtained.
更にＡｌ2Ｏ3の焼結が均一に起こらないと、造粒粉がいびつな形に収縮を起こしていまい、高い円形度のＡｌＮ粒子を得ることができない。Ａｌ2Ｏ3の焼結を均一にするためには、局所的に急激な焼結が起こらないように、ＳｉＯ2とＹ2Ｏ3とを適切な添加量、すなわち、それぞれ０．００８〜０．５６５ｗｔ％の範囲で添加し、これらの添加成分をＡｌ2Ｏ3粉末と均一に分散、混合することが重要である。 Furthermore, if the sintering of Al 2 O 3 does not occur uniformly, the granulated powder shrinks in an irregular shape, and AlN particles with high circularity cannot be obtained. In order to make the sintering of Al 2 O 3 uniform, appropriate addition amounts of SiO 2 and Y 2 O 3 , that is, 0.008 to 0 respectively so that local rapid sintering does not occur. It is important to add in the range of .565 wt%, and to uniformly disperse and mix these additive components with the Al 2 O 3 powder.
なお、原料として用いるＡｌ2Ｏ3粉末に不純物として含まれるＳｉＯ2は、ほとんどがＡｌ2Ｏ3に固溶する等の形で内部に閉じこめられた状態で存在するため、焼結の進行を促進する効果が少ない。ＳｉＯ2は、Ａｌ2Ｏ3の焼結過程で粒界に存在し、粒界で液相を生成することで焼結を促進する効果が得られるので、ＳｉＯ2粉末などの形態でＡｌ2Ｏ3粉末原料に添加することにより、高い効果が得られる。 In addition, since the SiO 2 contained as an impurity in the Al 2 O 3 powder used as a raw material is mostly confined in a form such as being dissolved in Al 2 O 3 , the progress of sintering is promoted. There is little effect to do. Since SiO 2 exists at the grain boundary during the sintering process of Al 2 O 3 , and an effect of promoting sintering is obtained by generating a liquid phase at the grain boundary, Al 2 O in the form of SiO 2 powder or the like. High effect can be obtained by adding to 3 powder raw materials.
＜炭素粉末の使用＞
また、熱処理工程において、球状に造粒した粉末と炭素粉末とを混合して高温で熱処理することにより、よりＡｌＮ転換率が高い球状ＡｌＮ粒子を得ることができる。炭素粉末としては、活性炭、グラファイト、アモルファスカーボン等、いずれの形態の炭素粉末を用いることができる。
<Use of carbon powder>
In the heat treatment step, spherical AlN particles having a higher AlN conversion rate can be obtained by mixing spherically granulated powder and carbon powder and heat-treating them at a high temperature. As the carbon powder, any form of carbon powder such as activated carbon, graphite, and amorphous carbon can be used.
炭素粉末を、造粒した粉末と混合して熱処理することにより、炭素粉末が造粒粉の間に存在することで、造粒粉同士の焼結や融着等による結合を抑制することができる。その結果、円形度の高い球状ＡｌＮ粒子を得ることができ、樹脂と混合した際に高充填が可能となる。また、炭素を添加することにより、Ａｌ2Ｏ3の還元窒化を促進し、ＡｌＮ転換率の高い球状ＡｌＮ粒子を得ることができる。 By mixing and heat treating the carbon powder with the granulated powder, the carbon powder is present between the granulated powders, thereby suppressing the bonding between the granulated powders due to sintering or fusion. . As a result, spherical AlN particles having a high degree of circularity can be obtained, and high filling is possible when mixed with resin. Further, by adding carbon, reduction nitriding of Al 2 O 3 can be promoted, and spherical AlN particles having a high AlN conversion rate can be obtained.
さらに、炭素は、Ａｌ2Ｏ3と接触して還元し、Ｎ2ガスによる窒化を促す効果があるが、本発明による球状ＡｌＮ粒子は粒子内部でも窒化が進んでいるから、炭素がＡｌ2Ｏ3と接触還元してＣＯガスが生成し、ＣＯガスもＡｌ2Ｏ3の還元に寄与して窒化反応を促進していると考えられる。 Furthermore, although carbon is in contact with Al 2 O 3 and is reduced to promote nitridation by N 2 gas, since the spherical AlN particles according to the present invention are also nitrided inside the carbon, the carbon is Al 2 O. It is considered that CO gas is generated by catalytic reduction with 3, and CO gas contributes to the reduction of Al 2 O 3 and promotes the nitriding reaction.
＜マイクロ波による熱処理＞
また、造粒した粉末を熱処理する際に、マイクロ波により加熱する方法を用いてもよい。マイクロ波により加熱することにより、ルツボ等の容器にいれた粉末を内部まで均一に加熱でき、通常の外部加熱による熱処理よりも低温、且つ短時間で球状ＡｌＮ粒子を得ることができる。
<Heat treatment by microwave>
Further, when the granulated powder is heat-treated, a method of heating with a microwave may be used. By heating with microwaves, the powder contained in a container such as a crucible can be heated uniformly to the inside, and spherical AlN particles can be obtained at a lower temperature and in a shorter time than the heat treatment by normal external heating.
マイクロ波により加熱して球状ＡｌＮ粒子を得る場合、球状に造粒した粉末と炭素粉末を混合してマイクロ波照射することにより、マイクロ波の吸収効率の良い炭素が発熱源として作用するため、効率良く球状ＡｌＮ粒子を得ることが可能となる。マイクロ波により加熱する場合、熱処理工程における熱処理温度は、１４００〜１８００℃である。 When spherical AlN particles are obtained by heating with microwaves, carbon with a good absorption efficiency of microwaves acts as a heat source by mixing spherically granulated powder and carbon powder and irradiating with microwaves. It becomes possible to obtain spherical AlN particles well. When heating by a microwave, the heat treatment temperature in the heat treatment step is 1400 to 1800 ° C.
＜炭素除去処理＞
炭素粉末を添加して球状ＡｌＮ粒子を作製した場合、炭素を除去するために、大気等の酸化性雰囲気中４００〜１０００℃の温度で加熱して炭素を酸化除去することができる。この際、酸化雰囲気中で熱処理することにより、球状ＡｌＮ粒子の表面が酸化して酸化層が形成されることで、水分等とＡｌＮが直接反応することを防ぐ効果を得ることができる。
<Carbon removal treatment>
When carbon powder is added to produce spherical AlN particles, the carbon can be oxidized and removed by heating at a temperature of 400 to 1000 ° C. in an oxidizing atmosphere such as the atmosphere in order to remove the carbon. At this time, by performing a heat treatment in an oxidizing atmosphere, the surface of the spherical AlN particles is oxidized to form an oxide layer, thereby obtaining an effect of preventing moisture and the like from directly reacting with AlN.
（２．球状ＡｌＮ粒子）
上述した製造方法により得られる球状ＡｌＮ粒子は、粒子全体の重量比１００ｗｔ％に対して、Ｙ2Ｏ3換算で０．０１〜０．５ｗｔ％のＹと、ＳｉＯ2換算で０．０１〜０．５ｗｔ％のＳｉと、を含有し、ＡｌＮ転換率が６０ｗｔ％以上であり、理論密度の９０％以上の相対密度を有し、円形度が０．８５〜１．００であることを特徴とする、球状ＡｌＮ粒子である。
また、この方法により得られる球状ＡｌＮ粒子の比表面積は、粒子の粒度分布により変化するが、粒子を完全な球状のＡｌＮと仮定して平均粒径（Ｄ５０）から計算される比表面積の２０倍以内の値であることが望ましい。例えば、３０μｍの球状のＡｌＮ粒子の比表面積の理論値は０．０６ｍ2／ｇであり、本発明による球状ＡｌＮ粒子が平均粒径３０μｍの場合、比表面積は１．２ｍ2／ｇ以下であることが望ましい。比表面積がこれより大きい場合、粒子に空隙が多く含有されていることになり、熱伝導を低下させる原因となる。また、樹脂等と混合して使用する場合、粒子の空隙に樹脂成分が吸収されてしまうために樹脂混合物の粘度が高くなり、混合することが困難となる。
(2. Spherical AlN particles)
The spherical AlN particles obtained by the above-described production method have 0.01 to 0.5 wt% Y in terms of Y 2 O 3 and 0.01 to 0 in terms of SiO 2 with respect to 100 wt% of the total particle weight. 5 wt% Si, the AlN conversion is 60 wt% or more, the relative density is 90% or more of the theoretical density, and the circularity is 0.85 to 1.00, Spherical AlN particles.
The specific surface area of the spherical AlN particles obtained by this method varies depending on the particle size distribution of the particles, but is 20 times the specific surface area calculated from the average particle diameter (D50) assuming that the particles are perfectly spherical AlN. A value within the range is desirable. For example, the theoretical value of the specific surface area of 30 μm spherical AlN particles is 0.06 m 2 / g, and when the spherical AlN particles according to the present invention have an average particle size of 30 μm, the specific surface area is 1.2 m 2 / g or less. It is desirable. When the specific surface area is larger than this, a large amount of voids are contained in the particles, which causes a decrease in heat conduction. Moreover, when mixing and using with resin etc., since the resin component will be absorbed by the space | gap of particle | grains, the viscosity of a resin mixture will become high and it will become difficult to mix.
球状ＡｌＮ粒子に含まれるＹおよびＳｉの含有量は、例えば原子吸光法、ＩＣＰ質量分析（ＩＣＰ−ＭＳ）により測定することができる。 The contents of Y and Si contained in the spherical AlN particles can be measured, for example, by atomic absorption spectrometry or ICP mass spectrometry (ICP-MS).
球状ＡｌＮ粒子のＡｌＮ転換率は６０％以上であるため、樹脂等と混合した際に高い熱伝導率を得ることができる。ＡｌＮ転換率が６０％より少ない場合、未反応のＡｌ2Ｏ3あるいは反応中間生成物であるＡｌＯＮなどの熱伝導率の低い成分が多く含まれることから、樹脂と混合した際の熱伝導率が低くなってしまう。 Since the AlN conversion rate of the spherical AlN particles is 60% or more, a high thermal conductivity can be obtained when mixed with a resin or the like. When the AlN conversion rate is less than 60%, there are many components with low thermal conductivity such as unreacted Al 2 O 3 or reaction intermediate products such as AlON, so that the thermal conductivity when mixed with the resin is high. It will be lower.
球状ＡｌＮ粒子のＡｌＮ転換率は、Ｘ線回折等の分析により測定することができる。Ｘ線回折で測定する場合は、ＡｌＮおよびＡｌ2Ｏ3、ＡｌＯＮの最強ピークの強度比を計算することでＡｌＮ転換率を算出することが出来る。具体的には、ＡｌＮ、Ａｌ2Ｏ3およびＡｌＯＮが示す各Ｘ線回折ピークのうち、最も強度が大きいピークをそれぞれ選択し、これらのピークが示す強度の合計を１００％とした時に、ＡｌＮのピークの強度が占める比率を、ＡｌＮ転換率とする。 The AlN conversion rate of the spherical AlN particles can be measured by analysis such as X-ray diffraction. When measuring by X-ray diffraction, the AlN conversion can be calculated by calculating the intensity ratio of the strongest peaks of AlN, Al 2 O 3 , and AlON. Specifically, among the X-ray diffraction peaks indicated by AlN, Al 2 O 3 and AlON, the highest intensity peak is selected, and when the total intensity indicated by these peaks is 100%, the AlN The ratio occupied by the intensity of the peak is defined as the AlN conversion rate.
球状ＡｌＮ粒子の相対密度は、球状ＡｌＮ粒子の密度／球状ＡｌＮ粒子の理論密度、から求められ、本実施形態では、相対密度は理論密度の９０％以上である。したがって、ＡｌＮ粒子の内部に空隙が少なく、高い熱伝導率の粒子を得ることができる。 The relative density of the spherical AlN particles is obtained from the density of the spherical AlN particles / the theoretical density of the spherical AlN particles. In this embodiment, the relative density is 90% or more of the theoretical density. Therefore, there are few voids inside the AlN particles, and particles with high thermal conductivity can be obtained.
ここで言う理論密度は、以下のようにして求められる。すなわち、上記のＡｌＮ転換率を算出する方法と同様に、最も強度が大きいピークをそれぞれ選択し、これらのピークが示す強度の合計を１００％とした時に、ＡｌＮ、Ａｌ2Ｏ3およびＡｌＯＮの各ピークの強度が占める比率を、ＡｌＮ、Ａｌ2Ｏ3およびＡｌＯＮの含有比率とする。そして、これら含有比率に、ＡｌＮおよびＡｌ2Ｏ3、ＡｌＯＮの理論密度をそれぞれ乗じて、それらの合計値を理論密度とする。 The theoretical density said here is calculated | required as follows. That is, in the same manner as the above-described method for calculating the AlN conversion rate, when the peak having the highest intensity is selected and the total of the intensity indicated by these peaks is 100%, each of AlN, Al 2 O 3 and AlON The ratio occupied by the peak intensity is the content ratio of AlN, Al 2 O 3 and AlON. Then, these content ratios are multiplied by the theoretical densities of AlN, Al 2 O 3 , and AlON, respectively, and the total value thereof is taken as the theoretical density.
本発明の球状ＡｌＮ粒子は、上記のＡｌ化合物以外にＹとＳｉからなる化合物を含有している。しかしながら、Ｙ化合物、Ｓｉ化合物については、Ｙ量およびＳｉ量としては測定できるものの、その存在形態（酸化物、窒化物等）が判らない場合がある。この場合、ＹおよびＳｉの化合物を考慮した理論密度を算出することが困難であるため、ここでは、Ａｌ化合物に対して含有量が少ないＹ化合物およびＳｉ化合物を考慮せず、粒子がＡｌＮおよびＡｌ2Ｏ3、ＡｌＯＮから構成されるものとして理論密度を計算する。 The spherical AlN particles of the present invention contain a compound composed of Y and Si in addition to the above Al compound. However, for Y compounds and Si compounds, although the Y amount and the Si amount can be measured, the existence form (oxide, nitride, etc.) may not be known. In this case, since it is difficult to calculate the theoretical density in consideration of the Y and Si compounds, the Y compound and the Si compound having a small content with respect to the Al compound are not considered here, and the particles are made of AlN and Al. The theoretical density is calculated as being composed of 2 O 3 and AlON.
球状ＡｌＮ粒子の相対密度が、９０％未満の場合、粒子内部に１０％以上の空隙を有することになり、球状ＡｌＮ粒子の熱伝導率を低下させてしまう。 When the relative density of the spherical AlN particles is less than 90%, the particles have voids of 10% or more inside the particles, which reduces the thermal conductivity of the spherical AlN particles.
また、球状ＡｌＮ粒子が実質的に空隙を含まない場合、相対密度は１００％になるが、前述した様に、ＹおよびＳｉ化合物を考慮せず理論密度を計算し、それに対する相対密度を計算するため、計算上の理論密度が１００％を超えることもあり得る。 In addition, when the spherical AlN particles substantially do not contain voids, the relative density becomes 100%. As described above, the theoretical density is calculated without considering the Y and Si compounds, and the relative density is calculated. Thus, the theoretical theoretical density can exceed 100%.
球状ＡｌＮ粒子の密度は、ＪＩＳ−Ｒ１６２０「ファインセラミックス粉末の粒子密度測定方法」に準拠したピクノメータ法、懸ちょう法、気体置換法のいずれかの測定方法で測定することができる。 The density of the spherical AlN particles can be measured by any one of the pycnometer method, the suspension method, and the gas displacement method in accordance with JIS-R1620 “Method for measuring particle density of fine ceramic powder”.
球状ＡｌＮ粒子の円形度は、０．８５〜１．００の範囲とすることで、高い流動性が得られ、充填性の良いフィラーとして使用することができる。円形度が０．８５より低い場合は、いびつな形状の粒子が多く含まれることから、樹脂と混合した際の充填率を高くすることが困難となるため望ましくない。 When the circularity of the spherical AlN particles is in the range of 0.85 to 1.00, high fluidity can be obtained, and the spherical AlN particles can be used as a filler with good filling properties. When the circularity is lower than 0.85, since many irregular particles are contained, it is difficult to increase the filling rate when mixed with the resin, which is not desirable.
円形度は、市販のフロー式粒子像分析装置により測定することができる。また、走査型電子顕微鏡（ＳＥＭ）等の顕微鏡写真から画像解析処理ソフトウェアを用いて次のように求めることができる。ＡｌＮ粒子のサンプルの写真を撮影し、ＡｌＮ粒子（二次元投影図）の面積、周囲長さを計測する。ＡｌＮ粒子が真円であると仮定し、計測された面積を有する真円の円周を計算する。円形度＝円周/周囲長さの式により、円形度を求める。円形度＝１のときが、真円である。つまり、円形度が１に近いほど、真円に近いとされる。 The circularity can be measured by a commercially available flow type particle image analyzer. Moreover, it can obtain | require as follows using image analysis processing software from micrographs, such as a scanning electron microscope (SEM). A photograph of a sample of AlN particles is taken, and the area and perimeter of the AlN particles (two-dimensional projection view) are measured. Assuming that the AlN particle is a perfect circle, the circumference of the perfect circle having the measured area is calculated. The degree of circularity is obtained by the formula of circularity = circumference / perimeter length. When the circularity = 1, it is a perfect circle. That is, the closer the circularity is to 1, the closer to a perfect circle.
球状ＡｌＮ粒子は、平均粒径（Ｄ５０）が５〜１５０μｍであることが望ましい。平均粒径が１５０μｍを超えると、造粒粉の平均粒径もその程度であるため、熱処理時に、Ａｌ2Ｏ3粒子の内部までＡｌ2Ｏ3を窒化するのに必要な窒素が侵入しにくくなることがあり、粒子の中心にＡｌ2Ｏ3等が残った粒子になることがある。また、５μｍより小さい粒子の場合、熱処理時に、Ａｌ2Ｏ3が窒化されＡｌＮになる過程で他の粒子と焼結して凝集してしまい、円形度が低いＡｌＮ粒子が得られてしまう。 The spherical AlN particles preferably have an average particle diameter (D50) of 5 to 150 μm. When the average particle size exceeds 150 μm, the average particle size of the granulated powder is also about that level, so that it is difficult for nitrogen necessary for nitriding Al 2 O 3 to penetrate into the Al 2 O 3 particles during heat treatment. In some cases, Al 2 O 3 or the like remains in the center of the particle. In the case of particles smaller than 5 μm, during heat treatment, Al 2 O 3 is nitrided and becomes AlN, so that it sinters and aggregates with other particles, and AlN particles with low circularity are obtained.
なお、ここでの平均粒径は、例えばレーザー回折法による粒度分布測定等により求めることができる。また、ここで言う平均粒径は、メディアン径と呼ばれるもので、レーザー回折法等の方法で粒径分布を測定して、粒径の頻度の累積が５０％となる粒径を平均粒径（Ｄ５０）とする。 Here, the average particle diameter can be determined by, for example, particle size distribution measurement by a laser diffraction method. The average particle diameter referred to here is called the median diameter. The particle diameter distribution is measured by a method such as laser diffraction, and the particle diameter at which the cumulative frequency of the particle diameter is 50% is determined as the average particle diameter ( D50).
以下、実施例及び比較例を示し、本発明をより具体的に説明する。ただし、本発明は下記の実施例に限定して解釈されるものではない。
［実施例１］
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not construed as being limited to the following examples.
[Example 1]
表１に示す平均粒径および比表面積を有するＡｌ2Ｏ3粉１００ｗｔ％と、表１に示す添加量のＳｉＯ2粉（平均粒径１．０μｍ、石英粉）およびＹ2Ｏ3粉（平均粒径１．０μｍ）とに、ＰＶＡ系バインダー、ポリカルボン酸系分散剤および水を添加し、ボールミルで混合したものをスプレードライにより造粒した。得られた造粒粉と活性炭（平均粒径５μｍ）とを２：１の重量比で混合したものをカーボンルツボに入れ、窒素雰囲気中１７５０℃で加熱処理した。これを、さらに大気中６００℃で熱処理し、炭素（活性炭）を酸化・除去することにより、球状ＡｌＮ粒子を得た。 100 wt% Al 2 O 3 powder having the average particle size and specific surface area shown in Table 1, and the addition amounts of SiO 2 powder (average particle size 1.0 μm, quartz powder) and Y 2 O 3 powder (average) shown in Table 1 A PVA binder, a polycarboxylic acid dispersant, and water were added to a particle size of 1.0 μm and mixed with a ball mill, and granulated by spray drying. A mixture of the obtained granulated powder and activated carbon (average particle size 5 μm) at a weight ratio of 2: 1 was placed in a carbon crucible and heat-treated at 1750 ° C. in a nitrogen atmosphere. This was further heat-treated in the atmosphere at 600 ° C. to oxidize and remove carbon (activated carbon) to obtain spherical AlN particles.
得られた球状ＡｌＮ粒子の平均粒径（Ｄ５０）は、シーラス社製レーザー回折散乱式粒度分布測定装置「ＣＩＬＡＳ ９２０」により測定した。円形度は、Ｓｙｓｍｅｘ社製フロー式粒子像解析装置「ＦＰＩＡ−２１００」を用いて測定した。 The average particle size (D50) of the obtained spherical AlN particles was measured by a laser diffraction scattering type particle size distribution measuring device “CILAS 920” manufactured by Cirrus. The circularity was measured using a flow type particle image analyzer “FPIA-2100” manufactured by Sysmex.
ＡｌＮ転換率は、リガク製Ｘ線回折装置「ＲＩＮＴ−２５００ ＴＴＲ」によりＸ線回折パターンを測定した。ＡｌＮ転換率の計算は、ＡｌＮ（ＰＤＦカードＮｏ．２５−１１３３）Ａｌ2Ｏ3（ＰＤＦカードＮｏ．１０−０１７３）およびＡｌＯＮ（ＰＤＦカードＮｏ．４８−０６８６）の最大ピークの強度を測定し、その強度比からＡｌＮ転換率を百分率計算した。得られた球状ＡｌＮ粒子の特性を表２に示す。本発明による球状ＡｌＮ粒子（試料Ｎｏ．１〜８）は、０．９０〜０．９８と高い円形度を示し、ＡｌＮ転換率が７１〜９９％と高く、理論密度の計算値に対する相対密度も９０％以上と高かった。 The AlN conversion rate was determined by measuring an X-ray diffraction pattern using a Rigaku X-ray diffraction apparatus “RINT-2500 TTR”. The calculation of the AlN conversion rate is to measure the intensity of the maximum peak of AlN (PDF card No. 25-1133) Al 2 O 3 (PDF card No. 10-0173) and AlON (PDF card No. 48-0686), The AlN conversion was calculated as a percentage from the strength ratio. Table 2 shows the characteristics of the obtained spherical AlN particles. The spherical AlN particles according to the present invention (sample Nos. 1 to 8) have a high degree of circularity of 0.90 to 0.98, an AlN conversion rate as high as 71 to 99%, and a relative density with respect to the calculated value of the theoretical density. It was as high as 90% or more.
これに対し、Ｙ2Ｏ3およびＳｉＯ2の添加量が本発明の範囲外である試料（Ｎｏ．１０および１１）は円形度が０．８３〜０．８４と低かった。また、原料に平均粒径０．０１４μｍ、比表面積１２０ｍ2／ｇのＡｌ2Ｏ3粉末を用いた試料（Ｎｏ．１２）は、ＡｌＮ転換率が５９％と低いものしか得られなかった。原料が平均粒径４．７μｍと大きいＡｌ2Ｏ3粉末を用いた試料（Ｎｏ．９）は、相対密度が８６％と低いものしか得られなかった。 On the other hand, the samples (No. 10 and 11) in which the amounts of Y 2 O 3 and SiO 2 added were outside the range of the present invention had a low circularity of 0.83 to 0.84. In addition, a sample (No. 12) using an Al 2 O 3 powder having an average particle size of 0.014 μm and a specific surface area of 120 m 2 / g as a raw material had only a low AlN conversion rate of 59%. The sample (No. 9) using Al 2 O 3 powder having a large average particle size of 4.7 μm as the raw material had only a low relative density of 86%.
また、窒化の状態を確認するために、得られた球状ＡｌＮ粒子を樹脂に埋め込んで研磨し、粒子断面の元素分布を日本電子製電子プローブマイクロアナライザ (ＥＰＭＡ)「ＪＸＡ−８２３０」を用いて元素マッピングを測定した。 Moreover, in order to confirm the state of nitriding, the obtained spherical AlN particles were embedded in a resin and polished, and the element distribution of the particle cross section was measured using an electron probe microanalyzer (EPMA) “JXA-8230” manufactured by JEOL. Mapping was measured.
その結果、図１に示すように本発明によるものを粒子の内部でＯ（酸素）がほとんど見られず、粒子全体にＮ（窒素）が分布しており、粒子全体がほとんどＡｌＮになっていることが確認された。 As a result, as shown in FIG. 1, in the present invention, almost no O (oxygen) is observed inside the particles, N (nitrogen) is distributed throughout the particles, and the entire particles are almost AlN. It was confirmed.
これに対して、平均粒径３０μｍの緻密な球状Ａｌ2Ｏ3粒子を造粒粉の代わりに活性炭と混合して、実施例１と同様に作製した球状ＡｌＮ粒子では、ＡｌＮ転換率は４９％となり、本発明によるものより低いＡｌＮ転換率であった。また、ＥＰＭＡにより元素マッピングを測定した結果、図２に示すように粒子の外周にのみＮが分布しており、粒子の内部はほとんどＯが残っており、窒化が表面でしか起こっていないことが確認された。
［実施例２］
On the other hand, in the spherical AlN particles produced in the same manner as in Example 1 by mixing dense spherical Al 2 O 3 particles having an average particle size of 30 μm with activated carbon instead of the granulated powder, the AlN conversion is 49%. The conversion rate of AlN was lower than that according to the present invention. In addition, as a result of measuring element mapping by EPMA, as shown in FIG. 2, N is distributed only on the outer periphery of the particle, O remains in the inside of the particle, and nitriding occurs only on the surface. confirmed.
[Example 2]
平均粒径０．４μm、比表面積６．５ｍ2／ｇのＡｌ2Ｏ3粉と、ＳｉＯ2粉（平均粒径１．０μｍ、石英粉）０．０５ｗｔ％およびＹ2Ｏ3粉（平均粒径１．０μｍ）０．０５ｗｔ％と、を用いて、熱処理の温度を１６００〜１８５０℃とした以外は、実施例１と同様の方法で球状ＡｌＮ粒子を得た。得られた球状ＡｌＮ粒子は実施例１と同様の方法で評価した。 Al 2 O 3 powder having an average particle diameter of 0.4 μm and a specific surface area of 6.5 m 2 / g, SiO 2 powder (average particle diameter of 1.0 μm, quartz powder) 0.05 wt% and Y 2 O 3 powder (average particle) Spherical AlN particles were obtained in the same manner as in Example 1 except that the heat treatment temperature was changed to 1600 to 1850 ° C. using 0.05 wt% of diameter 1.0 μm). The obtained spherical AlN particles were evaluated in the same manner as in Example 1.
その結果、表３に示すように熱処理温度が１６００〜１８００℃（試料Ｎｏ．１４〜１７）では、円形度０．８５〜０．９５、ＡｌＮ転換率が６６〜９１％、相対密度が９１％以上の球状ＡｌＮ粒子が得られた。これに対し１５５０℃で熱処理した試料（Ｎｏ．１３）はＡｌＮ転換率が５１％と低く、相対密度も８６％と低いものしか得られなかった。また、１８５０℃で熱処理した試料（Ｎｏ．１８）は炭素がほとんど消失してしまい、粒子同士の凝集が激しく円形度が０．８３と低いものしか得られなかった。 As a result, as shown in Table 3, when the heat treatment temperature is 1600 to 1800 ° C. (Sample Nos. 14 to 17), the circularity is 0.85 to 0.95, the AlN conversion is 66 to 91%, and the relative density is 91%. The above spherical AlN particles were obtained. In contrast, the sample heat-treated at 1550 ° C. (No. 13) had only a low AlN conversion rate of 51% and a low relative density of 86%. Further, in the sample (No. 18) heat-treated at 1850 ° C., carbon almost disappeared, and the particles were agglomerated and only a low circularity of 0.83 was obtained.
実施例２と同じ平均粒径および比表面積を有するＡｌ2Ｏ3粉と、ＳｉＯ2粉（平均粒径１．０μｍ、石英粉）およびＹ2Ｏ3粉（平均粒径１．０μｍ）と、を用いて、実施例１と同様の方法で造粒粉を作成した。得られた造粒粉と活性炭（平均粒径５μｍ）とを２：１の重量比で混合したものをアルミナルツボに入れ、マイクロ波照射装置を用いて窒素雰囲気中でマイクロ波出力を徐々に出力を上げながら加熱し、最大３．５ｋＷの出力で１３５０〜１６５０℃に加熱し、球状ＡｌＮ粒子を得た。得られた球状ＡｌＮ粒子は実施例１と同様の方法で評価した。 And Al 2 O 3 powder having the same average particle size and specific surface area as in Example 2, and SiO 2 powder (mean particle size 1.0 .mu.m, quartz powder) and Y 2 O 3 powder (average particle size 1.0 .mu.m), A granulated powder was prepared in the same manner as in Example 1. A mixture of the obtained granulated powder and activated carbon (average particle size 5 μm) at a weight ratio of 2: 1 is placed in an alumina crucible, and microwave output is gradually output in a nitrogen atmosphere using a microwave irradiation device. And heated to 1350 to 1650 ° C. with a maximum output of 3.5 kW to obtain spherical AlN particles. The obtained spherical AlN particles were evaluated in the same manner as in Example 1.
その結果、表４に示すように熱処理温度１４００〜１６５０℃（試料Ｎｏ．２０〜２３）では、円形度０．９２〜０．９５、ＡｌＮ転換率が６３％以上、相対密度９０％以上の球状ＡｌＮ粒子が得られた。しかしながら、熱処理温度１３５０℃とした試料（Ｎｏ．１９）は、ＡｌＮ転換率が４８％、相対密度が８３％と低いものしか得られなかった。 As a result, as shown in Table 4, at a heat treatment temperature of 1400 to 1650 ° C. (sample Nos. 20 to 23), a spherical shape having a circularity of 0.92 to 0.95, an AlN conversion of 63% or more, and a relative density of 90% or more. AlN particles were obtained. However, the sample with a heat treatment temperature of 1350 ° C. (No. 19) was only obtained with a low AlN conversion of 48% and a relative density of 83%.
Claims (5)
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| WO2019017451A1 (en) * | 2017-07-21 | 2019-01-24 | 東洋アルミニウム株式会社 | Aluminum nitride powder and production method therefor |
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| KR20190129554A (en) * | 2018-05-11 | 2019-11-20 | 주식회사 엘지화학 | Manufacturing method of spherical aluminum nitride |
| WO2020145304A1 (en) * | 2019-01-09 | 2020-07-16 | 株式会社燃焼合成 | Spherical aln particle production method and spherical aln particles |
| JP2021172535A (en) * | 2020-04-21 | 2021-11-01 | 信越化学工業株式会社 | Method for producing spherical aluminum nitride powder and spherical aluminum nitride powder |
| WO2022039200A1 (en) * | 2020-08-20 | 2022-02-24 | 日鉄ケミカル＆マテリアル株式会社 | Spherical aln particles, production method therefor, and composite material containing same |
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