JPS6335592B2 - - Google Patents
Info
- Publication number
- JPS6335592B2 JPS6335592B2 JP59048091A JP4809184A JPS6335592B2 JP S6335592 B2 JPS6335592 B2 JP S6335592B2 JP 59048091 A JP59048091 A JP 59048091A JP 4809184 A JP4809184 A JP 4809184A JP S6335592 B2 JPS6335592 B2 JP S6335592B2
- Authority
- JP
- Japan
- Prior art keywords
- aluminum nitride
- powder
- sintered body
- nitride powder
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000843 powder Substances 0.000 claims description 56
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 47
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 15
- 229910052582 BN Inorganic materials 0.000 claims description 14
- 238000005245 sintering Methods 0.000 claims description 14
- 239000011812 mixed powder Substances 0.000 claims description 13
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 7
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 7
- HOWFTCIROIVKLW-UHFFFAOYSA-L strontium;dinitrite Chemical compound [Sr+2].[O-]N=O.[O-]N=O HOWFTCIROIVKLW-UHFFFAOYSA-L 0.000 claims description 5
- GJTDJAPHKDIQIQ-UHFFFAOYSA-L barium(2+);dinitrite Chemical compound [Ba+2].[O-]N=O.[O-]N=O GJTDJAPHKDIQIQ-UHFFFAOYSA-L 0.000 claims description 3
- RAFRTSDUWORDLA-UHFFFAOYSA-N phenyl 3-chloropropanoate Chemical compound ClCCC(=O)OC1=CC=CC=C1 RAFRTSDUWORDLA-UHFFFAOYSA-N 0.000 claims description 3
- 239000002245 particle Substances 0.000 description 22
- 238000000034 method Methods 0.000 description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 11
- 238000002156 mixing Methods 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 239000011575 calcium Substances 0.000 description 7
- 239000002612 dispersion medium Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 239000002131 composite material Substances 0.000 description 6
- 239000012535 impurity Substances 0.000 description 6
- 239000007788 liquid Substances 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000004677 Nylon Substances 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 229910052791 calcium Inorganic materials 0.000 description 3
- 239000000292 calcium oxide Substances 0.000 description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 229920001778 nylon Polymers 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000001272 pressureless sintering Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 239000011164 primary particle Substances 0.000 description 2
- 229910000521 B alloy Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 238000002050 diffraction method Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000007580 dry-mixing Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 239000011872 intimate mixture Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 150000002826 nitrites Chemical class 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920002037 poly(vinyl butyral) polymer Polymers 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Description
本発明は高純度、高密度でかつ特に熱伝導性に
優れた窒化アルミニウム焼結体の製造方法に関す
る。
窒化アルミニウム焼結体は公知で、その耐熱
性、耐食性あるいは強度などの優れた物性の他に
高熱伝導性を有する絶縁体として最近特に注目さ
れている物質である。
しかしながら、従来、窒化アルミニウム焼結体
を製造するための原料として用いられる窒化アル
ミニウム粉末は、その製造方法に依拠して、種々
の不純物を不可避的に含有し、かつ粒子径や粒子
径分布が十分なものではなかつたため、高純度で
緻密な焼結体を与えることが難しく、多量の焼結
助剤を使用しても焼結性特に常圧焼結時の焼結性
が十分でなく熱伝導性など窒化アルミニウム本来
の優れた特性を十分発揮させることが困難であつ
た。
本発明者等は、窒化アルミニウム粉末及びその
焼結体について鋭意研究した結果、従来にない高
純度な均一微粉末でかつ焼結性に優れた新規な窒
化アルミニウム粉末を見出し既に提案した。更に
研究を続けた結果、窒化アルミニウム粉末の焼結
特性及び焼結体特性が使用する焼結助剤によつて
大きく影響されることを見出し、本発明を完成さ
せ、ここに提案するに至つた。
すなわち、本発明は窒化アルミニウム粉末また
は窒化アルミニウム粉末と窒化硼素及び／または
窒化珪素との混合粉末に焼結助剤を添加して窒化
アルミニウム焼結体を製造するに際し、該焼結助
剤として亜硝酸カルシウム、亜硝酸バリウム及び
亜硝酸ストロンチウムよりなる群から選ばれた少
くとも１種の化合物を使用することを特徴とする
窒化アルミニウム焼結体の製造方法である。
本発明で使用する窒化アルミニウム粉末は特に
限定されず公知の窒化アルミニウム粉末を用いう
る。特に有効な窒化アルミニウム粉末は、平均粒
子径2μｍ以下で3μｍ以下の粒子を70容量％以上
の割合で含有し、酸素含有量が３重量％以下、か
つ陽イオン不純物含有量が0.5重量％以下含まれ
ている粉末である。ここで言う平均粒子径とは、
粉末の走査型電子顕微鏡の写真などから計算され
る一次粒子の粒子径の平均値ではなく、沈降式の
粒度分布測定器によつて実測されるような二次凝
集粒子の大きさの平均値を言う。一次粒子がいく
ら細かくても、それが凝集し、特に2μｍ以上に
なると、焼結の際緻密化が十分進まず、その結果
として熱伝導性の高いものが得られない場合があ
る。また酸素含有量が３重量％以上、陽イオン不
純物量が0.5重量％以上含まれる窒化アルミニウ
ム粉末を原料として用いると、焼結体の粒界にこ
れらの不純物が第２相を形成し、熱伝導率を著し
く低下させる場合がある。本発明の実施に好適に
使用される前記窒化アルミニウム粉末の製造法の
代表的なものを例示すれば次ぎのとおりである。
(1) 純度99.0重量％好ましくは99.5重量％以上
で、平均粒子径が2μｍ以下で3μｍ以下の粒子
を70容量％以上の割合で含有する酸化アルミナ
微粉末と、灰分含量が最大0.2重量％で平均粒
子径が1μｍ以下のカーボン微粉末とを液体分
散媒体中で緊密に混合し、その際該酸化アルミ
ナ微粉末対該カーボン微粉末の重量比は１：
0.36〜１：１であり、
(2) 得られた緊密混合物を、適宜乾燥し、窒素ま
たはアンモニアの雰囲気下で1400〜1700℃の温
度で焼成し、
(3) 次いで得られた微粉末を酸素を含む雰囲気下
で600〜900℃の温度で加熱して未反応のカーボ
ンを加熱除去する
工程によつて得ることができる。
本発明において、前記窒化アルミニウム粉末と
混合して複合原料として使用しうる他の成分の１
つは窒化硼素粉末である。該窒化硼素粉末はよく
知られている層状結晶化合物である。本発明で使
用する該窒化硼素粉末は特に限定されず公知のも
のが使用できる。一般に好適に使用される窒化硼
素粉末は、窒化硼素の純度が97.0重量％以上好ま
しくは99.0重量％以上で、平均粒子径が5μｍ以下
のものである。また該窒化硼素粉末の製法も特に
限定されず公知の方法が採用できる。
例えば、
(1) 尿素の存在下にH3BO3またはNa2B4O7を
NH3雰囲気中で500〜950℃で加熱して製造す
る方法、
(2) BCI3とNH3とを反応させて製造する方法、
(3) Fe−Ｂ合金を500〜1400℃の温度で加熱し、
その後Feを例えば酸で溶解除去する方法、
等が採用できる。
また、本発明において、前記窒化アルミニウム
粉末と混合して複合原料として使用しうる他の成
分の１つは窒化珪素である。該窒化珪素粉末もま
たよく知られた化合物で、本発明においては特に
限定されずこれら公知のものを使用できる。一般
には純度95重量％以上好ましくは97重量％以上の
ものが好適である。
更にまた、前記原料として混合粉を使用する場
合は、一般に窒化アルミニウム粉末の混合比を50
％以上とするのがよく、より好ましくは60％以上
とするのが好適である。
本発明の最大の特徴は、焼結助剤としてカルシ
ウム、バリウムまたはストロンチウムの亜硝酸塩
を使用することである。これらの亜硝酸塩は高温
下例えば1000℃以上でも酸化カルシウムに変化し
ない安定な化合物である。該カルシウム、バリウ
ムまたはストロンチウムの亜硝酸塩が、前記窒化
アルミニウム粉末または該窒化アルミニウム粉末
を含む混合粉末の焼結に際し、どのような作用で
これらの焼結体の焼結性を向上させかつ焼結体に
付与される特性例えば高熱伝導性を著しく向上さ
せうるのかその作用は現在なお明確ではない。本
発明者等は、前記亜硝酸塩が高温下でも安定であ
り、しかも液状で存在しうるので、窒化アルミニ
ウム粉末または窒化アルミニウムを含む混合粉末
により均一に分散し、前記効果を発揮するものと
推定している。
本発明における上記焼結助剤の使用量は、焼結
体に要求される性状に応じて異なり一概に限定で
きないが、一般には窒化アルミニウム粉末または
窒化アルミニウム粉末を含む前記混合粉末中に
0.01〜５重量％の範囲から選べば好適である。
本発明における前記窒化アルミニウム粉末また
は窒化アルミニウム粉末を含む前記混合粉末と焼
結助剤との混合は特に限定されず、乾式混合であ
つても湿式混合であつてもよい。特に好適な実施
態様は湿式混合すなわち液体分散媒体を使用する
湿式状態での混合である。該液体分散媒体は特に
限定されず、一般に使用される水、アルコール
類、炭化水素類またはこれらの混合物が好適に使
用される。特に工業的に最も好適に採用されるの
は、メタノール、エタノール、ブタノールなどの
炭素原子数４以下の低級アルコール類である。
また、前記原料の混合に使用する湿式混合装置
としては、特に限定されず公知のものが使用され
るが、材質に基因する不純物成分を生じないもの
を選ぶのが好ましい。例えば、材質としては窒化
アルミニウム自身あるいはポリエチレン、ポリウ
レタン、ナイロンなどのプラスチツク材料あるい
はこれらで被覆された材質などを選定すればよ
い。
該液体分散媒体中で均一に混合した混合物は適
宜乾燥後、ホツトプレスあるいは常圧下に焼結し
て窒化アルミニウム焼結体または複合焼結体とす
ればよい。ホツトプレスの場合は公知の方法がそ
のまま採用でき、例えば該混合物を黒鉛などのモ
ールドに充填し、通常50〜300Kg／cm2の圧力を加
えながら窒素気流中1600℃〜2100℃に加熱し、焼
結体を製造するとよい。また上記常圧焼結の場合
には、該混合物をそのままかあるいはパラフイン
やポリビニルブチラールなどの公知のバインダー
を添加して所望の形状にラバープレスなどの方法
で成形した後焼成するのが一般的である。あるい
は該混合物に結合剤、可塑剤、解膠剤及び有機溶
媒を加えて泥漿とし、これをドクターブレード成
形機を用いてシート状成形物とした後焼成する方
法も好適に採用し得る。該常圧焼結の条件として
は、一般に窒素雰囲気下1600〜2000℃の温度で焼
成するとよい。
本発明の方法で得られる窒化アルミニウム焼結
体、窒化アルミニウムと窒化硼素及び／または窒
化珪素との複合焼結体は、耐熱性、耐食性に優れ
かつ低誘電損失、高熱伝導率など窒化アルミニウ
ムが本来有する優れた特性を発揮するセラミツク
スであり、各種基板材料、放熱材料、絶縁材料と
して工業的価値が極めて高いものである。
本発明における焼結助剤の添加は必らずしも窒
化アルミニウム粉末または窒化アルミニウム粉末
を含む混合粉末に添加する必要はなく、予めこれ
らの粉末の製造時に亜硝酸カルシウム、亜硝酸バ
リウム及び亜硝酸ストロンチウムからなる群から
選ばれた少くとも１種の化合物が含まれるように
該粉末の製造原料中に混合して得た窒化アルミニ
ウム粉末または前記混合粉末を使用してもよい。
本発明を更に具体的に説明するため以下実施例
を挙げて説明するが、本発明はこれらの実施例に
限定されるものではない。
実施例 １
純度99.99％（不純物分析値を表１に示す）で
平均粒子径が0.52μｍで3μｍ以下の粒子の割合が
95vol％のアルミナ100重量部と、灰分0.08wt％で
平均粒子径が0.45μｍのカーボンブラツク50重量
部とを、ナイロン製ポツトとナイロンコーテイン
グしたボールを用いエタノールを分散媒体として
均一にボールミル混合した。得られた混合物を乾
燥後、高純度黒鉛製平皿に入れ電気炉内に窒素ガ
スを３／minで連続的に供給しながら1600℃の
温度で６時間加熱した。得られた反応混合物を空
気中で750℃の温度で４時間加熱し、未反応のカ
ーボンを酸化除去した。得られた白色の粉末はＸ
線回折分析（Xray diffraction analysis）の結
果、単相（single phase）のAlNであり、Al2O3
の回折ピークは無かつた。また該粉末の平均粒子
径を粒度分布測定器（堀場製作所CAPA−500）
を用いて測定したところ1.31μｍであり、3μｍ以
下が90容量％を占めた。走査型電子顕微鏡による
観察ではこの粉末は平均0.7μｍ程度の均一な粒子
であつた。また比表面積の測定値は4.0m2／ｇで
あつた。この粉末の分析値を表２に示す。
表１ Al2O3粉末分析値
Al2O3含有量 99.99％
元素 含有量（PPM）
Mg ＜ 5
Cr ＜10
Si 30
Zn ＞ 5
Fe 22
Cu ＜ 5
Ca ＜20
Ni 15
Ti ＜ 5
表２ AlN粉末分析値
AlN含有量 97.8％
元素 含有量
Mg ＜ 5 （PPM）
Cr 21 （ 〃 ）
Si 125 （ 〃 ）
Zn 9 （ 〃 ）
Fe 20 （ 〃 ）
Cu ＜ 5 （ 〃 ）
Mn 5 （ 〃 ）
Ni 27 （ 〃 ）
Ti ＜ 5 （ 〃 ）
Co ＜ 5 （ 〃 ）
Al 64.8 （wt％）
Ｎ 33.4 （ 〃 ）
Ｏ 1.1 （ 〃 ）
Ｃ 0.11（ 〃 ）
このようにして得られた窒化アルミニウム粉末
に、予め硝酸カルシウム（Ca（NO3）2・4H2O）
を700℃で１時間加熱して得た亜硝酸カルシウム
（Ca（NO2）2・H2O）及び同様にして得た亜硝酸
ストロンチウムをそれぞれ0.5重量％となるよう
添加し、エタノールを分散媒として均一に混合し
た。混合後撹拌しながら徐々にエタノールを飛ば
して乾燥した。この混合粉末を0.6ｇを内径13mm
の金型で一軸プレスし、次いで2000Kg／cm2の圧力
でラバープレスして円板状の成形体とした。この
成形体を内壁をBN（窒化ホウ素）コーテイング
した黒鉛製るつぼに入れ、１気圧の窒素中で1800
℃、３時間焼成した。焼成後の焼結体は直径約10
mmの黄味を帯びた透光感のある焼結体で、密度は
3.24ｇ／cm2であつた。この焼結体を厚み２mmに研
摩したものについて理学電機製レーザー法熱定数
測定装置PS−７を用いて非接触法で熱伝導率を
測定したところ112W／ｍＫであつた。
比較例として、窒化アルミニウムにCaOを1.0
重量％加えたもの、CaCO3をCaOに換算して1.0
重量％加えたものについて、前記実施例と全く同
じ手順で焼結体を作成し熱伝導率及び焼結体中の
Ca含有量の測定を行つた。結果を前記実施例と
ともに表３No.３及び４に示す。
The present invention relates to a method for manufacturing an aluminum nitride sintered body having high purity, high density, and particularly excellent thermal conductivity. Sintered aluminum nitride is a well-known substance that has recently attracted particular attention as an insulator that has excellent physical properties such as heat resistance, corrosion resistance, and strength, as well as high thermal conductivity. However, the aluminum nitride powder conventionally used as a raw material for manufacturing aluminum nitride sintered bodies inevitably contains various impurities depending on the manufacturing method, and the particle size and particle size distribution are insufficient. Therefore, it is difficult to provide a highly pure and dense sintered body, and even if a large amount of sintering aid is used, the sinterability, especially during pressureless sintering, is insufficient and the heat conduction is poor. It has been difficult to fully demonstrate the excellent properties inherent to aluminum nitride, such as its properties. As a result of extensive research into aluminum nitride powder and its sintered body, the present inventors have discovered and already proposed a novel aluminum nitride powder that is a uniformly fine powder of unprecedented purity and has excellent sinterability. As a result of further research, it was discovered that the sintering characteristics of aluminum nitride powder and the characteristics of the sintered compact are greatly affected by the sintering aid used, and the present invention was completed and proposed here. . That is, the present invention provides for producing an aluminum nitride sintered body by adding a sintering aid to aluminum nitride powder or a mixed powder of aluminum nitride powder and boron nitride and/or silicon nitride. This is a method for producing an aluminum nitride sintered body, characterized in that at least one compound selected from the group consisting of calcium nitrate, barium nitrite, and strontium nitrite is used. The aluminum nitride powder used in the present invention is not particularly limited, and any known aluminum nitride powder can be used. Particularly effective aluminum nitride powder contains particles with an average particle size of 2 μm or less and 3 μm or less in a proportion of 70% or more by volume, an oxygen content of 3% by weight or less, and a cation impurity content of 0.5% by weight or less. It is a powder that is The average particle size referred to here is
Rather than the average particle size of primary particles calculated from scanning electron microscope photographs of powder, we use the average size of secondary agglomerated particles as measured by a sedimentation type particle size distribution analyzer. To tell. No matter how fine the primary particles are, if they agglomerate, especially if they become larger than 2 μm, densification will not proceed sufficiently during sintering, and as a result, a product with high thermal conductivity may not be obtained. Furthermore, if aluminum nitride powder containing 3% by weight or more of oxygen and 0.5% by weight or more of cationic impurities is used as a raw material, these impurities will form a second phase at the grain boundaries of the sintered body, improving thermal conductivity. may significantly reduce the rate. Typical methods for producing the aluminum nitride powder preferably used in the practice of the present invention are as follows. (1) Fine alumina powder with a purity of 99.0% by weight, preferably 99.5% by weight or more, containing particles with an average particle diameter of 2 μm or less and 3 μm or more in a proportion of 70% by volume or more, and an ash content of at most 0.2% by weight. Fine carbon powder having an average particle size of 1 μm or less is intimately mixed in a liquid dispersion medium, and the weight ratio of the fine alumina powder to the fine carbon powder is 1:
0.36 to 1:1; (2) the intimate mixture obtained is optionally dried and calcined at a temperature of 1400 to 1700°C under an atmosphere of nitrogen or ammonia; (3) the fine powder obtained is then heated with oxygen. It can be obtained by heating at a temperature of 600 to 900° C. in an atmosphere containing carbon to remove unreacted carbon. In the present invention, one of the other components that can be mixed with the aluminum nitride powder and used as a composite raw material.
One is boron nitride powder. The boron nitride powder is a well-known layered crystal compound. The boron nitride powder used in the present invention is not particularly limited, and any known powder can be used. Generally, the boron nitride powder preferably used has a boron nitride purity of 97.0% by weight or more, preferably 99.0% by weight or more, and an average particle size of 5 μm or less. Furthermore, the method for producing the boron nitride powder is not particularly limited, and any known method can be employed. For example, (1) H 3 BO 3 or Na 2 B 4 O 7 in the presence of urea.
A method of manufacturing by heating at 500 to 950℃ in an NH 3 atmosphere, (2) A method of manufacturing by reacting BCI 3 and NH 3 , (3) A method of heating Fe-B alloy at a temperature of 500 to 1400℃ death,
After that, a method of dissolving and removing Fe with, for example, an acid can be adopted. Furthermore, in the present invention, one of the other components that can be mixed with the aluminum nitride powder and used as a composite raw material is silicon nitride. The silicon nitride powder is also a well-known compound, and in the present invention, these known compounds can be used without particular limitation. Generally, purity of 95% by weight or more, preferably 97% by weight or more is suitable. Furthermore, when mixed powder is used as the raw material, the mixing ratio of aluminum nitride powder is generally 50%.
% or more, more preferably 60% or more. The most important feature of the present invention is the use of calcium, barium or strontium nitrite as a sintering aid. These nitrites are stable compounds that do not change to calcium oxide even at high temperatures, for example above 1000°C. When sintering the aluminum nitride powder or the mixed powder containing the aluminum nitride powder, what effect does the calcium, barium or strontium nitrite have on improving the sinterability of the sintered body and improving the sintered body? At present, it is still unclear whether the properties imparted to it, such as high thermal conductivity, can be significantly improved. The present inventors presume that since the nitrite is stable even at high temperatures and can exist in liquid form, it can be uniformly dispersed by aluminum nitride powder or a mixed powder containing aluminum nitride, thereby exerting the above effect. ing. The amount of the sintering aid used in the present invention varies depending on the properties required of the sintered body and cannot be absolutely limited, but it is generally added to the aluminum nitride powder or the mixed powder containing aluminum nitride powder.
It is preferable to select from the range of 0.01 to 5% by weight. The mixing of the aluminum nitride powder or the mixed powder containing the aluminum nitride powder and the sintering aid in the present invention is not particularly limited, and may be dry mixing or wet mixing. A particularly preferred embodiment is wet mixing, ie mixing in the wet state using a liquid dispersion medium. The liquid dispersion medium is not particularly limited, and commonly used water, alcohols, hydrocarbons, or mixtures thereof are preferably used. In particular, lower alcohols having 4 or less carbon atoms, such as methanol, ethanol, and butanol, are most preferably employed industrially. Further, the wet mixing device used for mixing the raw materials is not particularly limited and any known device may be used, but it is preferable to select one that does not generate impurity components due to the materials. For example, the material may be aluminum nitride itself, a plastic material such as polyethylene, polyurethane, nylon, or a material coated with these materials. The mixture uniformly mixed in the liquid dispersion medium may be suitably dried and then hot-pressed or sintered under normal pressure to form an aluminum nitride sintered body or a composite sintered body. In the case of hot pressing, a known method can be used as is; for example, the mixture is filled into a graphite mold, heated to 1600°C to 2100°C in a nitrogen stream while applying a pressure of usually 50 to 300 kg/cm 2 , and sintered. It is better to manufacture the body. In addition, in the case of the above-mentioned pressureless sintering, the mixture is generally fired as it is or after adding a known binder such as paraffin or polyvinyl butyral to the desired shape by a method such as a rubber press. be. Alternatively, a method may be suitably employed in which a binder, a plasticizer, a peptizer, and an organic solvent are added to the mixture to form a slurry, which is formed into a sheet-like product using a doctor blade molding machine, and then fired. As conditions for the pressureless sintering, it is generally preferable to sinter at a temperature of 1,600 to 2,000°C in a nitrogen atmosphere. The aluminum nitride sintered body obtained by the method of the present invention, the composite sintered body of aluminum nitride and boron nitride and/or silicon nitride, has excellent heat resistance, corrosion resistance, low dielectric loss, high thermal conductivity, etc. Ceramics exhibits excellent properties and has extremely high industrial value as various substrate materials, heat dissipation materials, and insulating materials. The sintering aid in the present invention does not necessarily need to be added to aluminum nitride powder or mixed powder containing aluminum nitride powder, but calcium nitrite, barium nitrite, and nitrous acid are added in advance during the production of these powders. An aluminum nitride powder obtained by mixing at least one compound selected from the group consisting of strontium into the raw material for producing the powder or the mixed powder described above may be used. EXAMPLES In order to explain the present invention more specifically, the present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Example 1 The purity is 99.99% (impurity analysis values are shown in Table 1), the average particle diameter is 0.52 μm, and the proportion of particles of 3 μm or less is
100 parts by weight of 95 vol% alumina and 50 parts by weight of carbon black having an ash content of 0.08 wt% and an average particle diameter of 0.45 μm were uniformly mixed in a ball mill using a nylon pot and a nylon-coated ball using ethanol as a dispersion medium. After drying the resulting mixture, it was placed in a flat plate made of high-purity graphite and heated at a temperature of 1600° C. for 6 hours while continuously supplying nitrogen gas at 3/min in an electric furnace. The resulting reaction mixture was heated in air at a temperature of 750° C. for 4 hours to oxidize and remove unreacted carbon. The white powder obtained is
As a result of Xray diffraction analysis, it is single phase AlN, Al 2 O 3
There was no diffraction peak. In addition, the average particle diameter of the powder was measured using a particle size distribution analyzer (Horiba, Ltd. CAPA-500).
As a result of measurement, it was 1.31 μm, and 90% by volume was 3 μm or less. When observed using a scanning electron microscope, this powder was found to be uniform particles with an average size of about 0.7 μm. Further, the measured value of the specific surface area was 4.0 m 2 /g. The analytical values of this powder are shown in Table 2. Table 1 Al 2 O 3 powder analysis values Al 2 O 3 content 99.99% Element Content (PPM) Mg < 5 Cr < 10 Si 30 Zn > 5 Fe 22 Cu < 5 Ca < 20 Ni 15 Ti < 5 Table 2 AlN Powder analysis AlN content 97.8% Element content Mg < 5 (PPM) Cr 21 (〃) Si 125 (〃) Zn 9 (〃) Fe 20 (〃) Cu < 5 (〃) Mn 5 (〃) Ni 27 ( 〃 ) Ti < 5 ( 〃 ) Co < 5 ( 〃 ) Al 64.8 (wt%) N 33.4 ( 〃 ) O 1.1 ( 〃 ) C 0.11 ( 〃 ) The aluminum nitride powder thus obtained was preliminarily soaked with nitric acid. Calcium (Ca(NO 3 ) 2・4H 2 O)
Calcium nitrite (Ca(NO 2 ) 2 H 2 O) obtained by heating at 700°C for 1 hour and strontium nitrite obtained in the same manner were added at a concentration of 0.5% each, and ethanol was used as a dispersion medium. Mixed evenly. After mixing, the mixture was dried by gradually removing ethanol while stirring. 0.6g of this mixed powder with an inner diameter of 13mm
The material was uniaxially pressed using a mold, and then rubber pressed at a pressure of 2000 kg/cm 2 to form a disc-shaped molded product. This molded body was placed in a graphite crucible whose inner wall was coated with BN (boron nitride), and heated at 1800 m in nitrogen at 1 atm.
C. for 3 hours. After firing, the sintered body has a diameter of approximately 10
mm yellowish translucent sintered body with a density of
It was 3.24 g/cm 2 . This sintered body was polished to a thickness of 2 mm, and its thermal conductivity was measured by a non-contact method using a laser method thermal constant measuring device PS-7 manufactured by Rigaku Denki, and it was found to be 112 W/mK. As a comparative example, 1.0% CaO was added to aluminum nitride.
Weight% added, CaCO 3 converted to CaO 1.0
A sintered body was prepared using the same procedure as in the above example, and the thermal conductivity and the content of the sintered body were
The Ca content was measured. The results are shown in Table 3 Nos. 3 and 4 together with the above examples.
【表】
実施例 ２
実施例１で用いたものと同じ窒化アルミニウム
粉末にBa（NO2）2・H2O0.5重量％添加して、エタ
ノールを分散媒として実施例１と同様の方法で混
合、乾燥した。この粉末も実施例１と同様の方法
で成形、Ｂ焼結して密度3.23ｇ／cm2の焼結体を得
た。この焼結体の熱伝導率を測定したところ
105W／ｍＫであつた。また、比較として窒化ア
ルミニウム粉末にBaCO3をBaO換算で0.5重量％
添加し、前記と全く同じ手順によつて常圧焼結し
た焼結体は、密度が3.22ｇ／cm2で熱伝導率は
73W／ｍＫであつた。
実施例 ３
実施例１で得た窒化アルミニウム粉末80重量部
と平均粒子径2.5μｍ、粒径5μｍ以下の粒子の割合
が95容量％で、かつ純度が99.5％の六方晶窒化硼
素粉末20重量部とを混合して混合粉末を用いた以
外は実施例１と同様に湿式混合を行い、助剤を含
む混合物を得た。上記混合粉末12ｇを内壁を窒化
ホウ素粉末でコーテイングした黒鉛製モールドに
入れ、200Kg／cm2の加圧下、１気圧の窒素中にお
いて2000℃で３時間加圧焼結を行つた。
得られた複合焼結体は、曲げ強度が34Kg／mm2で
熱伝導率は75W／ｍＫであつた。
実施例 ４
実施例３における窒化硼素粉末に代り、平均粒
子径2.2μｍ、純度99.2％の窒化珪素を用いた以外
は実施例３と同様に実施した。その結果、得られ
た複合焼結体は、曲げ強度30Kg／mm2、熱伝導率は
52W／ｍＫであつた。[Table] Example 2 0.5% by weight of Ba(NO 2 ) 2 H 2 O was added to the same aluminum nitride powder as used in Example 1, and the same method as in Example 1 was carried out using ethanol as a dispersion medium. Mixed and dried. This powder was also molded and B-sintered in the same manner as in Example 1 to obtain a sintered body with a density of 3.23 g/cm 2 . The thermal conductivity of this sintered body was measured.
It was 105W/mK. In addition, for comparison, 0.5% by weight of BaCO 3 (calculated as BaO) was added to aluminum nitride powder.
The sintered body, which was added and sintered under pressure using the same procedure as above, had a density of 3.22 g/cm 2 and a thermal conductivity of
It was 73W/mK. Example 3 80 parts by weight of the aluminum nitride powder obtained in Example 1 and 20 parts by weight of hexagonal boron nitride powder with an average particle size of 2.5 μm, a proportion of particles with a particle size of 5 μm or less at 95% by volume, and a purity of 99.5%. Wet mixing was carried out in the same manner as in Example 1, except that a mixed powder was used by mixing the following, and a mixture containing the auxiliary agent was obtained. 12 g of the above mixed powder was placed in a graphite mold whose inner wall was coated with boron nitride powder, and pressure sintering was performed at 2000° C. for 3 hours under a pressure of 200 kg/cm 2 in nitrogen at 1 atmosphere. The obtained composite sintered body had a bending strength of 34 Kg/mm 2 and a thermal conductivity of 75 W/mK. Example 4 The same procedure as in Example 3 was carried out except that silicon nitride having an average particle diameter of 2.2 μm and a purity of 99.2% was used instead of the boron nitride powder in Example 3. As a result, the obtained composite sintered body had a bending strength of 30Kg/mm 2 and a thermal conductivity of
It was 52W/mK.
Claims (1)
ム粉末と窒化硼素及び／または窒化珪素との混合
粉末に焼結助剤を添加して窒化アルミニウム焼結
体を製造するに際し、該焼結助剤として亜硝酸カ
ルシウム、亜硝酸バリウム及び亜硝酸ストロンチ
ウムよりなる群から選ばれた少くとも１種の化合
物を使用することを特徴とする窒化アルミニウム
焼結体の製造方法。 ２ 焼結助剤の添加量が窒化アルミニウム粉末ま
たは窒化アルミニウム粉末と窒化硼素及び／また
は窒化珪素との混合粉末に対して0.01〜５重量％
の範囲である特許請求の範囲１記載の窒化アルミ
ニウム焼結体の製造方法。[Claims] 1. When producing an aluminum nitride sintered body by adding a sintering aid to aluminum nitride powder or a mixed powder of aluminum nitride powder and boron nitride and/or silicon nitride, the sintering aid A method for producing an aluminum nitride sintered body, characterized in that at least one compound selected from the group consisting of calcium nitrite, barium nitrite, and strontium nitrite is used as the sintered body. 2. The amount of sintering aid added is 0.01 to 5% by weight based on aluminum nitride powder or mixed powder of aluminum nitride powder and boron nitride and/or silicon nitride.
A method for producing an aluminum nitride sintered body according to claim 1, which is within the range of.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59048091A JPS60195058A (en) | 1984-03-15 | 1984-03-15 | Manufacture of aluminum nitride sintered body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59048091A JPS60195058A (en) | 1984-03-15 | 1984-03-15 | Manufacture of aluminum nitride sintered body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60195058A JPS60195058A (en) | 1985-10-03 |
| JPS6335592B2 true JPS6335592B2 (en) | 1988-07-15 |
Family
ID=12793644
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59048091A Granted JPS60195058A (en) | 1984-03-15 | 1984-03-15 | Manufacture of aluminum nitride sintered body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60195058A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4719187A (en) * | 1985-10-10 | 1988-01-12 | Corning Glass Works | Dense sintered bodies of nitride materials |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5023411A (en) * | 1973-06-30 | 1975-03-13 | ||
| JPS5832073A (en) * | 1981-08-21 | 1983-02-24 | 株式会社日立製作所 | Sintered body |
-
1984
- 1984-03-15 JP JP59048091A patent/JPS60195058A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5023411A (en) * | 1973-06-30 | 1975-03-13 | ||
| JPS5832073A (en) * | 1981-08-21 | 1983-02-24 | 株式会社日立製作所 | Sintered body |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60195058A (en) | 1985-10-03 |
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