JP2004130482A - Micro component and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic micro component that has a complex three-dimensional shape, for example, and can be easily and simply manufactured even in about 100 μm or shorter, and its manufacturing method. <P>SOLUTION: Solution or paste containing composite metal nano particles that has an organic compound shell structure composed of a metal nucleus that is composed of one or more kinds of metals and has a size of 0.5-100 nm and organic compound directly coupled to the metal nucleus is held on a matrix and is dried and molded. The molded precursor body is burned to be molded in an arbitrary solid. <P>COPYRIGHT: (C)2004,JPO

Description

【００１０】
表１に示すように、例えば直径２０ｎｍの銀粒子を用いれば、焼結は、６０〜８０℃と常温に極めて近い温度で起きる（低温焼結）。これが本発明によるマイクロ部品製作の原理・機構の本質をなしている。つまり、複合型金属ナノ粒子を低温焼成させると、複合型金属ナノ粒子の保護層（有機化合物）が離脱し、同時に金属核同士が融着・焼結して、バルクの金属が形成され、これによって、金属製で、例えば複雑な立体形状を有し、しかも１００μｍ程度以下であっても、立体形状のマイクロ部品の製作が可能となる。つまり、光造形法では光硬化性樹脂のマイクロ部品の製作に限定されるが、本発明では金属製のマイクロ部品の加工が可能になる。
【００１１】
本発明による複合型金属ナノ粒子は、小さな金属核の周囲を、有機化合物によって結合・被覆した構造を有しており、これをマイクロ部品の原料として利用する。このような複合型金属ナノ粒子は、例えば金属塩と有機化合物を加熱還元することによって容易かつ安価に製造することができる。このように、金属核の周囲を有機化合物で結合・被覆した状態の複合型金属ナノ粒子は、単なる金属粒子同士の場合と異なり、これを一定量集合しておいても、相互に凝集・粗大化してしまうという不具合を回避することができるという大きな利点を持っている。
【００１２】
前述のように、粒子は、その大きさが小さいほど容易に焼結を起こすことができるので、相互に凝集を生じることなく、均一な分散状態を保持することが極めて重要かつ不可欠な特性となる。金属核の周囲を有機化合物で結合・被覆した状態の複合型金属ナノ粒子ならば、これを、適当な溶媒等に溶解した場合でも凝集・粗大化を起こすことなく、マイクロ部品の材料として有効に使用できるという優れた機能を持っている。
【００１３】
本発明にあっては、常温に近い極めて低い温度の加熱による焼成でマイクロ部品を作製することができ、しかも一旦作製されたマイクロ部品を再溶融するためには、その金属のバルク状態の融点まで昇温・加熱することが必要となる。例えば、銀粒子を用いてマイクロ部品を作製した場合、マイクロ部品は、少なくとも９６０℃以上に加熱しないと溶融しない。これによって、耐熱性に優れたマイクロ部品となすことができる。
【００１４】
請求項２に記載の発明は、前記任意の立体形状は、中空または末広がり構造を持つことを特徴とする請求項１記載のマイクロ部品である。これらの部品は、例えば各種マイクロマシン（マイクロアクチュエータ、マクロポンプ、マイクロセンサー等）用の部品として有用である。
前記複合型金属ナノ粒子は、金属塩とアルコール系有機化合物とを混合して加熱合成した後、これに還元剤を加えて加熱還元することによって生成することができる。
【００１５】
請求項３に記載の発明は、前記複合型金属ナノ粒子の殻構造を形成する有機化合物が脂肪酸及び／または高級アルコールであることを特徴とする請求項１または２記載のマイクロ部品である。
請求項４に記載の発明は、前記複合型金属ナノ粒子の金属成分が、Ａｕ，Ａｇ，Ｐｔ，Ｐｄ，Ｃｕのうち１以上であることを特徴とする請求項１または２記載のマイクロ部品である。
請求項５に記載の発明は、前記複合型金属ナノ粒子を含む溶液もしくはペーストに、０．１ミクロン以上の大きさを持つ金属粉末、有機化合物粉末、またはセラミック粉末からなる骨材を単独もしくは組合せて添加することにより、複合型金属ナノ粒子由来の金属中に均一に骨材が分散された構造を持つことを特徴とする請求項１または２記載のマイクロ部品である。
【００１６】
請求項６に記載の発明は、１種類以上の金属から構成された金属核と該金属核に直接結合された有機化合物からなる有機化合物殻構造を持ち、金属核部分の大きさが０．５〜１００ｎｍである複合型金属ナノ粒子を含む溶液もしくはペーストを母型に保持し乾燥し成形された前駆成形体を焼成して任意の立体に成形したことを特徴とするマイクロ部品製造方法である。
【００１７】
溶液化またはペースト化に用いる溶剤としては、例えばトルエン、ターピネオール、テレビン油などが用いられる。始めに、母型を用いて前駆成形体を作成する。そののち、複合型金属ナノ粒子の保護層（有機化合物）が分解・脱離する温度、例えば２００〜５００℃で、電気炉などで数分〜最長数時間、複合型金属ナノ粒子を含む前駆成形体を焼成し、同時に金属核同士を融着・焼結することで、バルクの金属が形成されるため、金属製の立体部品の製作が可能となる。この後、公知の方法で母型を剥離すれば、立体形状のマイクロ部品が完成する。製作する立体部品（マイクロ部品）が大きい場合は、例えば金属粉を添加したペーストを使用して立体部品を製作することで、有機化合物の分解による体積収縮を小さくすることができる。
【００１８】
複合型金属ナノ粒子を含む溶液またはペーストを母型に保持成形させる方法としては、予め公知の方法で製作した母型に溶液またはペーストを塗布したり、充填したりする方法、更には、複合型金属ナノ粒子を含む溶液またはペースト中に母型を浸漬させる方法が挙げられる。溶液またはペーストを母型に塗布する場合は、母型の内周面への塗布、あるいは外周面への塗布の両方が可能であり、目的形状によってどちらかを選択すれば良い。この方法を用いることで、従来の切削法では作製が困難であると考えられる１００μｍ以下の大きさの立体形状マイクロ部品の製作が可能となる。更に、電鋳法、無電解めっき法、スパッタ成膜法では製作が困難な末広がり形状の部品、著しい不連続部を持つ複雑な形状の部品を容易に製作することができる。また、溶液またはペーストの粘度を変えたり、溶液またはペーストの塗布・焼成の回数を変えたりすることで、マイクロ部品の肉厚を変化させることができる。更に、母型に溶液またはペーストを直接塗布した後に焼成することでマイクロ部品が形成できるため、電鋳法で必要不可欠な伝導性付与工程や、無電解めっき法で必要不可欠な触媒や還元剤が不要となる。
【００１９】
請求項７に記載の発明は、前記母型が光造形法によって作成されたプラスチック製マイクロ部品であることを特徴とする請求項６記載のマイクロ部品製造方法である。
請求項８に記載の発明は、前記マイクロ部品を母型とし、他のマイクロ部品を製造することを特徴とする請求項６記載のマイクロ部品製造方法である。この方法で一旦作製されたマイクロ部品が再溶融するためには、材料金属のバルク状態の融点まで昇温・加熱することが必要となる。このため、低温焼結で作製できるマイクロ部品の母型として使用できる。
請求項９に記載の発明は、熱分解性の母型を用い、前記複合型金属ナノ粒子を含む溶液もしくはペーストを母型に保持し乾燥し成形された前駆成形体を焼成しマイクロ部品を作成した後、母型を加熱分解することを特徴とする請求項６乃至８のいずれかに記載のマイクロ部品製造方法である。
【００２０】
例えば、複合型金属ナノ粒子を含む溶液またはペーストの焼成温度より高温で気化あるいは溶融する材料で母型を形成しておき、前駆成形体の焼成（すなわちマイクロ部品形成）後、母型を気化、あるいは溶融温度まで温度を上げることで、母型を気化・焼失させて消失させるようにすることができる。この方法によって、今まで母型の剥離が困難であった中空形状の部品や、中空球状の部品を容易に製作することができる。なお、母型の消失は、化学的薬剤や溶媒による分解、溶解によって行うようにしても良い。この母型の材質としては、例えば、樹脂やワックス等が挙げられる。
【００２１】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参照して説明する。
先ず、図２に示すように、実質的に金属成分からなる金属核３０と、Ｃ，Ｈ及び／またはＯを主成分とする有機化合物からなる結合・被覆層（有機化合物層）３２とからなる構造を持つ複合型金属ナノ粒子３４を作製する。このような複合型金属ナノ粒子３４は、金属核３０が有機化合物からなる結合・被覆層３２により覆われているので安定であり、しかも溶媒中において凝集する傾向が小さい。
【００２２】
この複合型金属ナノ粒子３４は、有機化合物と出発物質である金属塩、例えば炭酸塩、蟻酸塩または酢酸塩由来の金属成分から構成されており、その中心部が金属成分からなり、その周りを結合性有機化合物が取り囲んでいる。この時、有機化合物と金属成分とは、その一部または全部が化学的に結合した状態で一体化して存在しており、界面活性剤によりコーティングされることにより安定化された従来のナノ粒子と異なり、安定性が高いとともに、より高い金属濃度においても安定である。
【００２３】
複合型金属ナノ粒子３４の金属核３０の平均直径ｄは、１００ｎｍ程度以下、好ましくは２０ｎｍ以下、更に好ましくは５ｎｍ以下とする。また、結合・被覆層３２の高さｈは、例えば１．５ｎｍ程度である。この金属核３０の平均直径ｄの最小値は、可能な限り特に限定されないが、一般的には０．５ｎｍ程度、または１．０ｎｍ程度である。このように構成することにより、金属核３０を構成する金属粒子は前述の低温焼結を起こすことが可能となる。
【００２４】
この複合型金属ナノ粒子３４は、例えば非水系溶媒中でかつ結合性有機化合物の存在下で金属塩、例えば炭酸塩、蟻酸塩または酢酸塩をその分解還元温度以上でかつ結合性有機化合物の分解温度以下で加熱することによって製造することができる。金属成分としては、例えばＣｕ，Ａｇ，Ａｕ，Ｉｎ，Ｓｉ，Ｔｉ，Ｇｅ，Ｓｎ，Ｆｅ，Ｃｏ，ＮＩ，Ｒｕ，Ｒｈ，Ｐｄ，Ｏｓ，Ｉｒ，Ｐｔ，Ｖ，Ｃｒ及びＢｉの少なくとも１種が用いられる。結合性の有機化合物としては、例えば炭素数８以上の直鎖アルコール、または炭素数８以上の直鎖脂肪酸が用いられる。
【００２５】
加熱温度は、金属塩、例えば炭酸塩、蟻酸塩または酢酸塩の分解還元温度以上でかつ結合性有機化合物の分解温度以下である、例えば酢酸銀の場合、分解開始温度が２００℃であるので、２００℃以上かつ上記の結合性有機化合物が分解しない温度に保持すればよい。この場合、結合性有機化合物が分解しにくいようにするために、加熱雰囲気は、不活性ガス雰囲気であることが好ましいが、非水溶剤の選択により、大気下においても加熱可能である。
【００２６】
加熱が終了した後、公知の精製法により精製を行う。精製法は例えば遠心分離、膜精製、溶媒抽出等により行えば良い。
【００２７】
そして、複合型金属ナノ粒子３４をトルエン、タービネオール、テレビン油等の所定の有機溶媒に分散させた溶液またはペースト状の原料を用意する。金属核３０の表面を有機化合物からなる結合・被覆層（有機化合物層）３２で結合・被覆した構造を持つ複合型金属ナノ粒子３４は、この有機化合物層３２に金属核３０を保護する保護皮膜としての役割を果たさせることで、溶媒中に安定して分散し、しかも粒子としての高い性状安定性を有する。従って、低温で焼結・溶融結合可能な結合素材（複合型金属ナノ粒子３４）を均一に分散させた原料を得ることができる。このように、複合型金属ナノ粒子が均一に分散された原料を、下記のように、母型の幅数μｍの凹部内にも均一に供給することで、１００μｍ以下の立体形状マイクロ部品の製造が可能になる。
【００２８】
ここで、複合型金属ナノ粒子３４を、金属部分の全液体に対する重量比率が好ましくは１％以上、８５％以下となるように有機溶媒に分散させ、これに分散剤やゲル化剤を適宜添加して液状化することで、低温で焼結・溶融結合可能な接合素材（複合型金属ナノ粒子３４）を均一に分散させた所望の加熱時の流動性を有する液状の原料を得ることができる。複合型金属ナノ粒子３４の金属部分の全液体に対する重量比率が８５％を超えると、液状の原料としての流動性が著しく低下するので、母型の凹部等に充填するに際し、充填の不完全な部分を生じやすくなる。
【００２９】
更に、複合型金属ナノ粒子３４の金属部分の全液体に対する重量比率が１％以下では、原料に含まれる有機成分が多過ぎる結果、焼成時の脱ガスが不十分となって、焼結部品（マイクロ部品）に欠陥を生じやすい。
【００３０】
複合型金属ナノ粒子３４を、金属部分の全流動体に対する重量比率が好ましくは１５〜９０％となるように有機溶媒に分散させ、これに分散剤やゲル化剤を適宜添加して液状化し、ペースト状に調整することで、低温で焼結・溶融結合可能な接合素材（複合型金属ナノ粒子３４）を均一に分散させた、所望の流動性を有するペースト状の原料を得ることができる。
【００３１】
この時、必要に応じて、０．１μｍ程度の大きさの、例えば金属粉末、プラスチック粉末、金属・プラスチック以外の無機物粉末等のうち単独で、もしくはこれらを組合せた骨材を添加して、原料中に均一に分散させてもよい。このように、骨材を添加することで、複合型金属ナノ粒子単独の場合と異なり、各種の特性を加えることができる。
【００３２】
この骨材としては、例えばＡｌ，Ｃｕ，Ｍｇ，Ｆｅ，Ｎｉ，Ａｕ，ＡｇまたはＰｄからなる金属粉末を使用することができる。このように、金属粉末を骨材として添加することで、例えばマイクロ部品が大きい場合に、有機化合物の分解による体積収縮を小さくすることもできる。
【００３３】
次に、前述の複合型金属ナノ粒子３４を所定の有機溶媒に分散させた溶液またはペースト状の原料を使用して、立体形状のマイクロ部品を作製する例を説明する。
【００３４】
このマイクロ部品の製作は、予め公知の方法で製作した母型に、複合型金属ナノ粒子を含む液体またはペーストからなる原料を保持し、乾燥成形させる第１工程と、この原料を保持させた母型を、複合型金属ナノ粒子３４の結合・被覆層（有機化合物層）３２が分解・脱離する温度、例えば２００〜５００℃で、電気炉などで数分〜最長数時間加熱して原料を焼成する第２工程と、公知の方法で母型を剥離除去するか、または消失させる第３工程で実施される。
【００３５】
複合型金属ナノ粒子を含む溶液またはペーストを母型に保持させる方法としては、予め公知の方法で製作した母型に溶液またはペーストを塗布したり、充填したりする方法、更には、複合型金属ナノ粒子を含む溶液またはペースト中に母型を浸漬させる方法が挙げられる。
【００３６】
図３は、マイクロ部品の製作の一例を示す。先ず、図３（ａ）に示すように、所定の形状のキャビティ４０を有する一対の母型４２，４２を閉じる。そして、図３（ｂ）に示すように、この母型４２，４２で区画形成されたキャビティ４０の内部に、複合型金属ナノ粒子を含む液体またはペーストからなる原料４４を充填して保持させ、その後乾燥させて、前駆成形体を形成させる（第１工程）。
【００３７】
この状態で、原料４４を保持した母型４２，４２全体を、原料４４に含まれる複合型金属ナノ粒子３４の結合・被覆層（有機化合物層）３２が分解・脱離する温度、例えば２００〜５００℃で、電気炉などで数分〜最長数時間加熱して原料４４を焼成する（第２工程）。つまり、原料４４に含まれるトルエン等の溶媒を蒸発させ、更に原料４４の主成分である複合型金属ナノ粒子３４を、この結合・被覆層（有機化合物層）３２を金属核（銀超微粒子）３０から離脱させる温度への加熱、或いは結合・被覆層３２自体の分解温度以上への加熱によって、金属核３０から結合・被覆層３２を離脱させるか、或いは結合・被覆層３２を分解して蒸散させる。これにより、金属核３０同士を直接接触させ焼結させて、バルクの金属からなる金属層を形成する。
【００３８】
次に、図３（ｃ）に示すように、公知の方法で母型４２，４２を剥離、除去することで、母型４２，４２のキャビティ４０に沿った所望の形状、例えば末広がり形状を有し、バルクの金属からなる中実のマイクロ部品４６を作製する。
なお、第２工程で原料を焼成する場合は、有機化合物が離脱しやすいよう、若干の酸素雰囲気で行うことが望ましい。
【００３９】
図４は、マイクロ部品の製作の他の例を示す。この例は、一対の母型４２ａ，４２ａの内周面に、複合型金属ナノ粒子を含む液体またはペーストからなる原料４４ａを塗布して保持させ、この原料４４ａを乾燥させ、前駆成形体を形成した後に焼成し、これによって、中空で末広がり形状の、バルクの金属からなるマイクロ部品４６ａを作製するようにしたものである。
この場合、原料４４ａとなる液体またはペーストの粘度を変えたり、塗布・焼成の回数を変えたりすることで、マイクロ部品４６ａの肉厚を変化させることができる。
【００４０】
上記の各例によれば、従来の切削法では作製が困難であると考えられる１００μｍ以下の大きさの立体形状マイクロ部品の製作が可能となる。更に、電鋳法、無電解めっき法、スパッタ成膜法では製作が困難な末広がり形状の中実または中空部品、著しい不連続部を持つ複雑な形状の中実または中空部品を容易に製作することができる。更に、母型に溶液またはペーストを直接塗布した後に焼成することでマイクロ部品が形成できるため、電鋳法で必要不可欠な伝導性付与工程や、無電解めっき法で必要不可欠な触媒や還元剤が不要となる。
【００４１】
図５は、マイクロ部品の製作の更に他の例を示す。この例は、例えば樹脂やワックスからなり、焼成温度よりも高く、かつ焼成後のバルクの金属の溶融温度よりも低い温度で気化または溶融する材料で、例えば球形の母型４２ｂを作製する。そして、この母型４２ｂの外周面に、複合型金属ナノ粒子を含む液体またはペーストからなる原料４４ｂを塗布して保持させ、この原料４４ｂを乾燥させ、前駆成形体を形成した後に焼成する。この焼成後、この焼成温度よりも高く、かつ焼成後のバルクの金属の溶融温度より低い、母型４２ｂの気化または溶融温度まで温度を上げることで、母型４２ｂを気化または溶融させ、この気化した気体または溶融した液体をマイクロ部品４６ｂに設けた貫通孔４８から外部に排出して、母型４２ｂを消失させ、これによって、中空球状の、バルクの金属からなるマイクロ部品４６ｂを作製するようにしたものである。
この例によれば、今まで母型の剥離が困難であった中空形状の部品や、中空球状の部品を容易に製作することができる。なお、母型の消失は、化学的薬剤や溶媒による分解、溶解によって行うようにしても良い。
【００４２】
（実施例１）
ラウリルアルコール保護型の銀ナノ粒子を含む溶液またはペーストからなる原料を用いて、図３に示す立体形状マイクロ部品を作製した。すなわち、ＬＩＧＡプロセス等の公知の技術で作製した母型４２，４２に、テレビン油を溶剤として作製した複合型ナノ粒子を含む溶液またはペースト（１０ｇ／１００ｍｌ）からなる原料４４を充填し、８０℃で３時間乾燥した後、２４０℃で２時間焼成した。そして、焼成後、公知の方法で母型４２，４２を剥離除去し、立体形状マイクロ部品４６を作製した。この部品４６は、マイクロマシン用の金属部品として有用である。
【００４３】
（実施例２）
ステアリルアルコール保護型の銅ナノ粒子を含み、０．１μｍのＡｌ粉末を添加した原料を用いて、図４に示す立体形状マイクロ部品を作製した。すなわち、公知の技術で作製した母型４２ａ，４２ａの内周面に、ターピネオールを溶剤として作製した複合型ナノ粒子を含む溶液またはペースト（２０ｇ／１００ｍｌ）からなる原料４４ａを塗布し、８０℃で３時間乾燥した後、２６０℃で１．５時間焼成した。そして、焼成後、公知の方法で母型４２ａ，４２ａを剥離除去し、末広がり形の立体形状マイクロ部品４６ａを作製した。この部品４６ａは、マイクロマシン用の金属部品として有用である。
【００４４】
（実施例３）
ステアリル酸保護型の銀ナノ粒子ペーストを含み、骨材を添加した溶液またはペーストからなる原料を用いて、図５に示す立体形状マイクロ部品を作製した。
すなわち、高温溶融・除去タイプの母型４２ｂの外周面に、ターピネオールを溶剤として作製した複合型ナノ粒子を含む溶液またはペースト（２０ｇ／１００ｍｌ）からなる原料４４ｂを塗布し、８０℃で３時間乾燥した後、２６０℃で２時間焼成した。さらに、３５０℃で２時間焼成し、母型４２ｂを消失させ、中空の立体形状マイクロ部品４６ｂを作製した。この部品４６ｂは、マイクロマシン用の金属部品として有用である。
【００４５】
【発明の効果】
以上説明したように、本発明によれば、複合型金属ナノ粒子を用い、１００μｍ以下の金属製の立体形状マイクロ部品を提供することができる。しかも、従来の方法では困難な、中空、あるいは末広がり形の立体形状マイクロ部品も提供することが可能であり、さらに、製造工程で触媒を使用しないので化学物質の使用量を低減でき、環境負荷も小さい。
【図面の簡単な説明】
【図１】焼結による小粒子の結合の状態を示す図である。
【図２】本発明に使用される複合型金属ナノ粒子の外観図である。
【図３】本発明の実施の形態のマイクロ部品の製作工程を工程順に示す断面図である。
【図４】本発明の他の実施の形態のマイクロ部品の製作工程を工程順に示す断面図である。
【図５】本発明の更に他の実施の形態のマイクロ部品の製作工程を工程順に示す断面図である。
【符号の説明】
３０　金属核
３２　有機化合物層
３４　複合型金属ナノ粒子
４０　キャビティ
４２，４２ａ，４２ｂ　母型
４４，４４ａ，４４ｂ　原料
４６，４６ａ，４６ｂ　マイクロ部品[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a micropart having a complicated three-dimensional shape and used for various micromachines (microactuators, micropumps, microsensors, etc.) and molds, and a method of manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in order to realize high-performance micromachines, development of manufacturing technology for ultra-fine mechanisms and components has attracted attention. In addition, demands for small-quantity multi-product production and complicated processing shapes are increasing. For this reason, attention is paid to an optical molding method that directly uses three-dimensional CAD data generated on a computer to create a three-dimensional shape, and creates an arbitrary complex three-dimensional shape by scanning with a photocurable resin and a laser beam. Have been.
[0003]
[Problems to be solved by the invention]
However, in the conventional stereolithography method, since a component is manufactured using a photocurable resin, a micro component made of metal cannot be manufactured. In addition, as a method of processing a small metal part, a cutting method, an electroforming method, an electroless plating method, a sputtering film forming method, and the like are widely known. However, in the cutting method, since there is a mechanical limit in a tool or the like to be used, it is generally difficult to manufacture a small part of 100 μm or less, a divergent part, or a hollow part. In addition, in the electroforming method, electroless plating method and sputter film forming method, parts are manufactured by anisotropic metal growth along the matrix, so that divergent type and complex shapes with extremely discontinuous parts are formed. It is generally difficult to make a part or a part that is nearly hollow. Furthermore, in the electroforming method, it is indispensable to perform a conductive treatment on the matrix, and in the electroless plating method, since a catalyst and a reducing agent are used, there is a problem that the process is complicated and a load on the environment is large. .
[0004]
The present invention has been made in view of the above circumstances, and is made of metal, for example, has a complicated three-dimensional shape, and can be easily and easily manufactured even if it is about 100 μm or less, and a method of manufacturing the same. The purpose is to provide.
[0005]
[Means for Solving the Problems]
The invention according to claim 1 has an organic compound shell structure composed of a metal nucleus composed of one or more metals and an organic compound directly bonded to the metal nucleus, and the size of the metal nucleus portion is 0.5. A micropart, characterized in that a solution or paste containing composite type metal nanoparticles having a thickness of １００100 nm is held in a matrix, dried, and a molded precursor is fired to be formed into an arbitrary three-dimensional structure.
[0006]
Generally, it is known that, when particles having small diameters are brought into contact with each other and heated to a certain temperature or higher, the particles are strengthened to bond with each other, and finally a sintering phenomenon in which the whole is integrated is caused (for example, See Seita Sakui, "Metallurgy of One Million People" (1989.9 Agne), pp.272-277). Such a sintering phenomenon has a property that the smaller the diameter of the particles that come into contact with each other, the more the number of contact points in the unit volume system, and the lower the sintering start temperature, the smaller the particle diameter. Sintering is likely to occur.
[0007]
FIG. 1A illustrates a process in which sintering occurs between the small particles 20a and 20b, and FIG. 1B illustrates a process in which sintering occurs between the small particles 20 and the large object 22. The process is schematically shown (for example, see Seita Sakui, “Metallurgy of One Million People” (1989.9 Agne), pages 272 to 277). That is, in FIGS. 1 (a) and 1 (b), the imaginary line indicates the form before sintering, and the solid line indicates the form after sintering. Research on the sintering phenomena has demonstrated that atoms constituting the surface and inside of small particles diffuse and move due to thermal activation, and this gradually moves to the contact part, thereby promoting bonding.
[0008]
The driving force that causes this diffusion of atoms is the surface tension of the material, which acts particularly strongly on the concave surface around the point where the two objects are in contact in a small area, pulling the atoms to the point of contact The tendency becomes stronger. The surface tension is generated by the surface energy. This surface energy is stored on the surface of the granular material, and the total surface energy in the system is proportional to the total surface area of the particles. The smaller the value is, the larger the surface energy becomes, and sintering is likely to occur (see, for example, Seitai Sakui, “Metalology for One Million People” (1989.9 Agne), pages 272 to 277).
[0009]
The average diameter of the metal nuclei of the composite metal nanoparticles according to the present invention is 0.5 to 100 nm, preferably 1 to 20 nm, more preferably 1 to 5 nm. The minimum value of the average diameter of the metal nuclei is not particularly limited as long as production is possible, but is generally about 0.5 nm or about 1.0 nm. Table 1 shows the temperature at which metal ultrafine particles (Fe, Ag, Ni, Cu) having a diameter of about 50 nm or less start sintering (for example, Noboru Ichinose, Yoshiharu Ozaki, Seiichiro Kashu, "Introduction to Ultrafine Particle Technology" ( (1988.8 Ohm) see pages 26-29).
[Table 1]

[0010]
As shown in Table 1, when silver particles having a diameter of, for example, 20 nm are used, sintering occurs at a temperature very close to room temperature of 60 to 80 ° C. (low-temperature sintering). This constitutes the essence of the principle and mechanism of the production of micro parts according to the present invention. In other words, when the composite metal nanoparticles are fired at a low temperature, the protective layer (organic compound) of the composite metal nanoparticles is detached, and at the same time, the metal cores are fused and sintered to form a bulk metal. Accordingly, it is possible to manufacture a three-dimensional micro component even if it is made of metal and has, for example, a complicated three-dimensional shape and is about 100 μm or less. That is, the stereolithography is limited to the production of microparts made of a photocurable resin, but the present invention enables the processing of microparts made of metal.
[0011]
The composite metal nanoparticles according to the present invention have a structure in which the periphery of a small metal nucleus is bonded and covered with an organic compound, and is used as a raw material for a micro component. Such composite metal nanoparticles can be easily and inexpensively produced by, for example, heating and reducing a metal salt and an organic compound. In this way, composite metal nanoparticles in a state in which the periphery of the metal nucleus is bonded and covered with an organic compound are different from mere metal particles. There is a great advantage that the problem of being converted can be avoided.
[0012]
As mentioned above, the smaller the size of a particle, the easier it is to cause sintering. Therefore, it is extremely important and indispensable to maintain a uniform dispersion state without causing mutual aggregation. . If the composite metal nanoparticles are in the state of being bound and covered with an organic compound around the metal nucleus, they can be effectively used as a material for micro components without agglomeration and coarsening even when dissolved in an appropriate solvent. It has an excellent function that can be used.
[0013]
In the present invention, it is possible to produce a micro component by baking by heating at an extremely low temperature close to room temperature, and in order to re-melt the micro component once produced, the melting point of the bulk state of the metal It is necessary to raise the temperature and heat. For example, when a micro component is manufactured using silver particles, the micro component does not melt unless heated to at least 960 ° C. or higher. Thereby, a micro component having excellent heat resistance can be obtained.
[0014]
The invention according to claim 2 is the micro component according to claim 1, wherein the arbitrary three-dimensional shape has a hollow or divergent structure. These components are useful, for example, as components for various micromachines (microactuator, macropump, microsensor, etc.).
The composite metal nanoparticles can be produced by mixing and heating a metal salt and an alcohol-based organic compound, and then adding a reducing agent thereto and reducing by heating.
[0015]
The invention according to claim 3 is the micro component according to claim 1 or 2, wherein the organic compound forming the shell structure of the composite metal nanoparticle is a fatty acid and / or a higher alcohol.
The invention according to claim 4 is the micro component according to claim 1 or 2, wherein the metal component of the composite metal nanoparticle is at least one of Au, Ag, Pt, Pd, and Cu. is there.
The invention according to claim 5 is that the aggregate or the metal powder, the organic compound powder, or the ceramic powder having a size of 0.1 μm or more is used alone or in combination with the solution or paste containing the composite metal nanoparticles. The micro component according to claim 1 or 2, wherein the micro component has a structure in which the aggregate is uniformly dispersed in the metal derived from the composite metal nanoparticles by adding the metal component.
[0016]
The invention according to claim 6 has an organic compound shell structure composed of a metal nucleus composed of one or more kinds of metals and an organic compound directly bonded to the metal nucleus, and the size of the metal nucleus portion is 0.5. A micropart manufacturing method, characterized in that a solution or paste containing composite-type metal nanoparticles having a thickness of about 100 nm is held in a matrix, dried, and the formed precursor molded body is baked to form an arbitrary three-dimensional body.
[0017]
As a solvent used for solution or paste formation, for example, toluene, terpineol, turpentine oil and the like are used. First, a precursor molded body is prepared using a matrix. Thereafter, at a temperature at which the protective layer (organic compound) of the composite metal nanoparticles is decomposed and desorbed, for example, 200 to 500 ° C., for several minutes to a maximum of several hours in an electric furnace or the like, the precursor molding including the composite metal nanoparticles is performed. By firing the body and simultaneously fusing and sintering the metal nuclei, a bulk metal is formed, so that a metal three-dimensional component can be manufactured. Thereafter, if the matrix is peeled off by a known method, a three-dimensional micro component is completed. When the three-dimensional component (micro component) to be manufactured is large, the volume shrinkage due to the decomposition of the organic compound can be reduced by manufacturing the three-dimensional component using, for example, a paste to which metal powder is added.
[0018]
As a method of holding and molding a solution or paste containing composite type metal nanoparticles in a matrix, a method of applying or filling a solution or paste to a matrix prepared in advance by a known method, and a method of further filling the composite mold A method of immersing the matrix in a solution or paste containing metal nanoparticles can be used. When the solution or paste is applied to the matrix, both application to the inner peripheral surface and application to the outer peripheral surface of the matrix are possible, and either one may be selected according to the target shape. By using this method, it is possible to manufacture a three-dimensionally shaped micro part having a size of 100 μm or less, which is considered to be difficult to manufacture by a conventional cutting method. Further, it is possible to easily manufacture a divergent component having a difficult shape by electroforming, electroless plating, or sputtering film forming, or a component having a complicated shape having a significant discontinuity. In addition, the thickness of the micro component can be changed by changing the viscosity of the solution or the paste or changing the number of times of applying and firing the solution or the paste. Furthermore, since microparts can be formed by directly applying a solution or paste to the matrix and then baking, a conductive imparting step indispensable in electroforming and a catalyst and reducing agent indispensable in electroless plating are required. It becomes unnecessary.
[0019]
The invention according to claim 7 is the method for manufacturing a micro component according to claim 6, wherein the matrix is a plastic micro component created by stereolithography.
The invention according to claim 8 is the method for manufacturing a micro component according to claim 6, wherein the micro component is used as a matrix and another micro component is manufactured. In order to re-melt the micro component once manufactured by this method, it is necessary to raise the temperature to the melting point of the bulk state of the material metal and to heat it. For this reason, it can be used as a master of a micro component that can be manufactured by low-temperature sintering.
According to a ninth aspect of the present invention, a micropart is prepared by using a thermally decomposable matrix, holding the solution or paste containing the composite type metal nanoparticles in the matrix, drying and firing the formed precursor molded body. The method according to any one of claims 6 to 8, wherein the mother die is thermally decomposed after performing the step.
[0020]
For example, a matrix is formed from a material that vaporizes or melts at a temperature higher than the firing temperature of the solution or paste containing the composite type metal nanoparticles, and after firing the precursor molded body (that is, forming a micropart), the matrix is vaporized. Alternatively, by raising the temperature to the melting temperature, the matrix can be vaporized and burned out and disappear. By this method, it is possible to easily manufacture a hollow component or a hollow spherical component, which has been difficult to separate the mother die. The disappearance of the matrix may be performed by decomposition or dissolution with a chemical agent or a solvent. Examples of the material of the matrix include a resin and wax.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, as shown in FIG. 2, a metal core 30 substantially composed of a metal component and a bonding / coating layer (organic compound layer) 32 composed of an organic compound mainly containing C, H and / or O are formed. The composite metal nanoparticles 34 having a structure are produced. Such composite metal nanoparticles 34 are stable because the metal nuclei 30 are covered with the bonding / coating layer 32 made of an organic compound, and have a small tendency to aggregate in a solvent.
[0022]
The composite metal nanoparticles 34 are composed of an organic compound and a metal component derived from a metal salt as a starting material, for example, carbonate, formate or acetate. A binding organic compound surrounds. At this time, the organic compound and the metal component are present in a state in which a part or all of them are integrated in a state of being chemically bonded, and the conventional nanoparticles stabilized by being coated with a surfactant. Differently, it is more stable and stable at higher metal concentrations.
[0023]
The average diameter d of the metal nuclei 30 of the composite metal nanoparticles 34 is about 100 nm or less, preferably 20 nm or less, more preferably 5 nm or less. The height h of the bonding / coating layer 32 is, for example, about 1.5 nm. Although the minimum value of the average diameter d of the metal core 30 is not particularly limited as much as possible, it is generally about 0.5 nm or about 1.0 nm. With such a configuration, the metal particles forming the metal core 30 can be subjected to the low-temperature sintering described above.
[0024]
The composite metal nanoparticles 34 can be used to decompose a metal salt, for example, a carbonate, formate or acetate, at a temperature not lower than its decomposition reduction temperature in a non-aqueous solvent and in the presence of a binding organic compound, and to decompose the binding organic compound. It can be produced by heating below the temperature. Examples of the metal component include at least one of Cu, Ag, Au, In, Si, Ti, Ge, Sn, Fe, Co, NI, Ru, Rh, Pd, Os, Ir, Pt, V, Cr, and Bi. Used. As the binding organic compound, for example, a linear alcohol having 8 or more carbon atoms or a linear fatty acid having 8 or more carbon atoms is used.
[0025]
The heating temperature is equal to or higher than the decomposition reduction temperature of a metal salt, such as a carbonate, formate or acetate, and equal to or lower than the decomposition temperature of a binding organic compound. For example, in the case of silver acetate, the decomposition start temperature is 200 ° C. What is necessary is just to hold at 200 degreeC or more and the temperature which does not decompose the said binding organic compound. In this case, the heating atmosphere is preferably an inert gas atmosphere in order to make the binding organic compound difficult to decompose. However, heating can be performed in the atmosphere by selecting a non-aqueous solvent.
[0026]
After the heating is completed, purification is performed by a known purification method. The purification may be performed by, for example, centrifugation, membrane purification, solvent extraction, or the like.
[0027]
Then, a solution or paste-like raw material in which the composite metal nanoparticles 34 are dispersed in a predetermined organic solvent such as toluene, turbineol, or turpentine oil is prepared. The composite metal nanoparticles 34 having a structure in which the surface of the metal nucleus 30 is bonded and covered with a bonding / coating layer (organic compound layer) 32 made of an organic compound are used as the protective film for protecting the metal nucleus 30 on the organic compound layer 32. As a result, the particles are stably dispersed in a solvent and have high property stability as particles. Therefore, it is possible to obtain a raw material in which a bonding material (composite metal nanoparticles 34) that can be sintered and melt-bonded at a low temperature is uniformly dispersed. As described below, the raw material in which the composite metal nanoparticles are uniformly dispersed is uniformly supplied into the concave portion having a width of several μm of the matrix, as described below, thereby manufacturing a three-dimensional micropart having a size of 100 μm or less. Becomes possible.
[0028]
Here, the composite metal nanoparticles 34 are dispersed in an organic solvent so that the weight ratio of the metal portion to the total liquid is preferably 1% or more and 85% or less, and a dispersant or a gelling agent is appropriately added thereto. By liquefaction, it is possible to obtain a liquid material having desired fluidity at the time of heating in which a bonding material (composite metal nanoparticles 34) capable of being sintered and melt-bonded at a low temperature is uniformly dispersed. . If the weight ratio of the metal portion of the composite metal nanoparticles 34 to the total liquid exceeds 85%, the fluidity as a liquid raw material is significantly reduced. Parts are more likely to occur.
[0029]
Further, when the weight ratio of the metal portion of the composite metal nanoparticles 34 to the total liquid is 1% or less, the amount of the organic component contained in the raw material is too large, so that the degassing at the time of firing becomes insufficient and the sintered component ( Micro-parts).
[0030]
The composite metal nanoparticles 34 are dispersed in an organic solvent so that the weight ratio of the metal portion to the total fluid is preferably 15 to 90%, and a dispersant or a gelling agent is appropriately added thereto to liquefy, By adjusting to a paste state, it is possible to obtain a paste-like raw material having desired fluidity in which a bonding material (composite metal nanoparticles 34) that can be sintered and melt-bonded at a low temperature is uniformly dispersed.
[0031]
At this time, if necessary, for example, a metal powder, a plastic powder, an inorganic powder other than metal and plastic, etc. having a size of about 0.1 μm alone or by adding an aggregate obtained by combining these materials, It may be uniformly dispersed therein. Thus, by adding the aggregate, various characteristics can be added unlike the case of the composite metal nanoparticles alone.
[0032]
As the aggregate, for example, a metal powder made of Al, Cu, Mg, Fe, Ni, Au, Ag or Pd can be used. As described above, by adding the metal powder as an aggregate, for example, when the micro component is large, the volume shrinkage due to the decomposition of the organic compound can be reduced.
[0033]
Next, an example of manufacturing a three-dimensional micro component using a solution or paste-like raw material in which the above-described composite metal nanoparticles 34 are dispersed in a predetermined organic solvent will be described.
[0034]
This micropart is manufactured by holding a raw material composed of a liquid or paste containing composite type metal nanoparticles in a mother die manufactured in advance by a known method, and drying and forming the first step, and a mother step of holding the raw material. The mold is heated at a temperature at which the bonding / coating layer (organic compound layer) 32 of the composite metal nanoparticles 34 decomposes and desorbs, for example, 200 to 500 ° C. in an electric furnace or the like for several minutes to a maximum of several hours, and the raw material is heated. It is carried out in a second step of firing and a third step of removing or removing the matrix by a known method.
[0035]
As a method of holding the solution or paste containing the composite metal nanoparticles in the matrix, a method of applying or filling the solution or paste to the matrix prepared by a known method in advance, and further, a method of holding the composite metal A method of immersing the matrix in a solution or paste containing nanoparticles is exemplified.
[0036]
FIG. 3 shows an example of manufacturing a micro component. First, as shown in FIG. 3A, a pair of mother dies 42 having a cavity 40 having a predetermined shape are closed. Then, as shown in FIG. 3B, a raw material 44 made of a liquid or a paste containing composite metal nanoparticles is filled and held inside the cavity 40 defined by the matrixes 42, 42, Thereafter, the precursor is dried to form a precursor molded body (first step).
[0037]
In this state, the entire matrix 42 holding the raw material 44 is heated to a temperature at which the bonding / coating layer (organic compound layer) 32 of the composite metal nanoparticles 34 contained in the raw material 44 decomposes and desorbs, for example, 200 to 200 ° C. The raw material 44 is fired by heating at 500 ° C. for several minutes to a maximum of several hours in an electric furnace or the like (second step). That is, the solvent such as toluene contained in the raw material 44 is evaporated, and the composite metal nanoparticles 34 which are the main components of the raw material 44 are further combined with the bonding / coating layer (organic compound layer) 32 by the metal nucleus (ultrafine silver particles). Heating to a temperature at which the bonding / coating layer 32 is released from the metal core 30 or heating to a temperature higher than the decomposition temperature of the bonding / coating layer 32 itself, or decomposing and evaporating the bonding / coating layer 32 from the metal core 30. Let it. As a result, the metal cores 30 are brought into direct contact with each other and sintered to form a metal layer made of bulk metal.
[0038]
Next, as shown in FIG. 3C, by removing and removing the mother dies 42, 42 by a known method, a desired shape along the cavity 40 of the mother dies 42, 42, for example, a divergent shape is obtained. Then, a solid micro component 46 made of bulk metal is manufactured.
Note that when firing the raw material in the second step, it is preferable to perform the firing in a slight oxygen atmosphere so that the organic compound is easily released.
[0039]
FIG. 4 shows another example of manufacturing a micro component. In this example, a raw material 44a made of a liquid or a paste containing composite metal nanoparticles is applied to the inner peripheral surfaces of a pair of mother dies 42a, 42a and held, and the raw material 44a is dried to form a precursor molded body. After that, firing is performed to produce a hollow micro-part 46a made of a bulk metal having a divergent shape.
In this case, the thickness of the micro component 46a can be changed by changing the viscosity of the liquid or paste serving as the raw material 44a or changing the number of times of application and firing.
[0040]
According to each of the above examples, it is possible to manufacture a three-dimensionally shaped micro part having a size of 100 μm or less, which is considered to be difficult to manufacture by a conventional cutting method. Furthermore, it is easy to manufacture solid or hollow parts with divergent shapes that are difficult to manufacture by electroforming, electroless plating, or sputtering film formation, or solid or hollow parts with complicated shapes that have significant discontinuities. Can be. Furthermore, since microparts can be formed by directly applying a solution or paste to the matrix and then baking, a conductive imparting step indispensable in electroforming and a catalyst and reducing agent indispensable in electroless plating are required. It becomes unnecessary.
[0041]
FIG. 5 shows still another example of fabrication of a micro component. In this example, for example, a spherical matrix 42b is made of a material made of, for example, resin or wax and vaporized or melted at a temperature higher than the firing temperature and lower than the melting temperature of the bulk metal after firing. Then, a raw material 44b made of a liquid or a paste containing the composite metal nanoparticles is applied to and held on the outer peripheral surface of the matrix 42b, and the raw material 44b is dried to form a precursor molded body and then fired. After the firing, the temperature of the matrix 42b is raised or raised to a temperature higher than the firing temperature and lower than the melting temperature of the bulk metal after firing, thereby evaporating or melting the matrix 42b. The gas or the melted liquid is discharged to the outside through the through hole 48 provided in the micro component 46b to dissipate the matrix 42b, thereby forming a hollow spherical micro component 46b made of bulk metal. It was done.
According to this example, it is possible to easily manufacture a hollow-shaped component or a hollow-spherical component, which has been difficult to remove the master block until now. The disappearance of the matrix may be performed by decomposition or dissolution with a chemical agent or a solvent.
[0042]
(Example 1)
Using a raw material composed of a solution or paste containing silver nanoparticles protected by lauryl alcohol, a three-dimensionally shaped micropart shown in FIG. 3 was produced. That is, a matrix 44 prepared by a known technique such as the LIGA process is filled with a raw material 44 composed of a solution or paste (10 g / 100 ml) containing composite nanoparticles prepared using turpentine as a solvent. After drying for 3 hours, it was baked at 240 ° C. for 2 hours. Then, after firing, the mother dies 42, 42 were peeled and removed by a known method, thereby producing a three-dimensionally shaped micro component 46. This component 46 is useful as a metal component for a micromachine.
[0043]
(Example 2)
Using a raw material containing stearyl alcohol-protected copper nanoparticles and adding 0.1 μm of Al powder, a three-dimensional micropart shown in FIG. 4 was produced. That is, a raw material 44a made of a solution or paste (20 g / 100 ml) containing composite nanoparticles prepared using terpineol as a solvent is applied to the inner peripheral surfaces of the matrixes 42a, 42a prepared by a known technique, and heated at 80 ° C. After drying for 3 hours, it was baked at 260 ° C. for 1.5 hours. Then, after firing, the mother dies 42a, 42a were peeled and removed by a known method to produce a divergent three-dimensional micropart 46a. This part 46a is useful as a metal part for a micromachine.
[0044]
(Example 3)
A three-dimensional micropart shown in FIG. 5 was produced using a raw material comprising a solution or paste containing a stearyl acid-protected silver nanoparticle paste and an aggregate added thereto.
That is, a raw material 44b composed of a solution or paste (20 g / 100 ml) containing composite nanoparticles prepared using terpineol as a solvent is applied to the outer peripheral surface of the high-temperature melting / removing type mold 42b, and dried at 80 ° C. for 3 hours. After that, firing was performed at 260 ° C. for 2 hours. Further, it was baked at 350 ° C. for 2 hours to eliminate the matrix 42b, thereby producing a hollow three-dimensional micro component 46b. This part 46b is useful as a metal part for a micromachine.
[0045]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a three-dimensional metal micropart having a size of 100 μm or less using composite metal nanoparticles. In addition, it is possible to provide hollow or divergent three-dimensional microparts that are difficult with conventional methods, and because no catalyst is used in the manufacturing process, the amount of chemical substances used can be reduced and the environmental burden can be reduced. small.
[Brief description of the drawings]
FIG. 1 is a view showing a state of bonding of small particles by sintering.
FIG. 2 is an external view of a composite metal nanoparticle used in the present invention.
FIG. 3 is a cross-sectional view showing the steps of manufacturing the micro component according to the embodiment of the present invention in the order of steps.
FIG. 4 is a cross-sectional view showing a process of manufacturing a micro component according to another embodiment of the present invention in the order of steps.
FIG. 5 is a cross-sectional view showing a step of manufacturing a micro component according to still another embodiment of the present invention in the order of steps.
[Explanation of symbols]
Reference Signs List 30 metal nucleus 32 organic compound layer 34 composite type metal nanoparticle 40 cavity 42, 42a, 42b matrix 44, 44a, 44b raw material 46, 46a, 46b micro component

Claims (9)

Composite metal nanoparticles having an organic compound shell structure composed of a metal nucleus composed of at least one metal and an organic compound directly bonded to the metal nucleus, wherein the size of the metal nucleus portion is 0.5 to 100 nm A micropart, characterized in that a solution or paste containing is dried in a matrix, dried and molded into a three-dimensional body. The micro component according to claim 1, wherein the arbitrary three-dimensional shape has a hollow or divergent structure. 3. The micro component according to claim 1, wherein the organic compound forming the shell structure of the composite metal nanoparticles is a fatty acid and / or a higher alcohol. The micro component according to claim 1, wherein a metal component of the composite metal nanoparticle is at least one of Au, Ag, Pt, Pd, and Cu. A solution or paste containing the composite metal nanoparticles is added with a metal powder having a size of 0.1 μm or more, an organic compound powder, or an aggregate composed of ceramic powder alone or in combination to obtain a composite metal. 3. The micropart according to claim 1, wherein the micropart has a structure in which the aggregate is uniformly dispersed in the metal derived from the nanoparticles. Composite metal nanoparticles having an organic compound shell structure composed of a metal nucleus composed of at least one metal and an organic compound directly bonded to the metal nucleus, wherein the size of the metal nucleus portion is 0.5 to 100 nm A method for producing a micropart, comprising: holding a solution or paste containing the above in a matrix; drying and molding the formed precursor molded body to form an arbitrary three-dimensional body; 7. The micro component manufacturing method according to claim 6, wherein the matrix is a plastic micro component created by an optical molding method. 7. The method of manufacturing a micro component according to claim 6, wherein the micro component is used as a matrix to manufacture another micro component. Using a thermally decomposable matrix, hold the solution or paste containing the composite type metal nanoparticles in the matrix, dry and mold the formed precursor molded body to produce microparts, and then thermally decompose the matrix. 9. The method for manufacturing a micro component according to claim 6, wherein:

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