JP2005040696A

JP2005040696A - Liquid application method

Info

Publication number: JP2005040696A
Application number: JP2003202247A
Authority: JP
Inventors: Yoshihiro Nakada; 佳宏中田; Kohei Hasegawa; 晃平長谷川
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2003-07-28
Filing date: 2003-07-28
Publication date: 2005-02-17
Anticipated expiration: 2023-07-28
Also published as: JP4292903B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid application method by which a liquid is accurately transferred to an objective material from a transfer pin without leaving the liquid. <P>SOLUTION: The transfer pin 1 on the tip 1a of which a fixed quantity of the liquid L is stuck is moved downward to the objective material 7 and is stopped at a position where the liquid is brought into contact with the objective material. Ultrasonic vibration U is applied to the transfer pin 1 as it is stopped and the contact angle θ of the bottom surface or the side surface of the tip part 1a of the transfer pin 1 with the liquid L is controlled to ≥90°. When the transfer pin 1 is drawn up at ≥90° contact angle θ, the liquid L is easily separated from the surface of the transfer pine 1 to transfer the liquid to the objective material without leaving the liquid l on the transfer pin 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は導電ペースト、接着剤、シリコーンオイルなどの粘性のある液体を対象物に対して微少量ずつ塗布するのに適した液体塗布方法に関するものである。
【０００２】
【従来の技術】
【特許文献１】特開平８−２５７４８４号公報
【特許文献２】特開平８−３１８２１０号公報
【特許文献３】特開平１１−１５６２５９号公報
従来、電子部品などの表面に、液状樹脂や接着剤などの液体を所定量正確に塗布する方式として、ピン転写方式と呼ばれる液体塗布方法が知られている。
ピン転写方式とは、転写ピンの先端部に液体を付着させ、これを対象物に転着させる方式であるが、粘性を有する液体の場合には、対象物に転着させる際に液体が転写ピンに残留するという問題がある。
特に、電子部品に１０μｇ〜数１０μｇ程度の微少量の液体を塗布する場合、転写ピンに液体が一部でも残留すると、対象物への塗布量が大きくばらつくことになる。
【０００３】
このような課題を解消するため、特許文献１では、先端部に液体が付着した転写ピンを対象物の表面に当てた後、転写ピンを僅かの高さだけ上昇させ、そこで転写ピンを一旦停止させた後、上昇させたり、あるいは一旦停止後、小さなストロークで細かく上下動させた後、上昇させる方法が提案されている。
しかし、この方法では、途中で一旦転写ピンを停止させるだけであり、転写ピンから液体を積極的に分離するための操作を行わないので、転写ピンへの液体の残留を確実に防止できないという欠点がある。
【０００４】
特許文献２には、先端に液体を付着させた転写ピンを対象物に接近または接触させ、転写ピンに超音波振動を印加しながら引き上げることにより、転写ピンへの液体の残留を防止した塗布方法が提案されている。
特許文献３も、特許文献２と同様に、スタンプピンを接着剤を蓄えた容器の上部へ移動させ、スタンプ面に接着剤を付着させた後、スタンプピンを上昇させ、スタンプピンを基板の位置まで移動させ、そこで再びスタンプピンを下降させ、スタンプ面に付着した接着剤を基板に転写する方法が提案されている。スタンプピンに付着した接着剤の糸引き現象を防止するため、スタンプピンの表面にシリコン薄膜などの撥水性を持つ薄膜を形成したり、バイブレータや超音波発生装置などの振動を与える方法が提案されている。
【０００５】
【発明が解決しようとする課題】
特許文献２および３に記載の塗布方法では、共に転写ピンに超音波振動を印加することで、転写ピンからの液体の分離性を高めることが可能である。
しかしながら、特許文献２のように先端がテーパ状に尖った塗布ツールを使用した場合、液体を塗布ツールから対象物に転着させる際、塗布ツールの先端が対象物に当たり、対象物を傷つける可能性が高い。また、液体を送り出す際に塗布ツールの側面に液体が残ることがある。
また、特許文献３では、転写ピン（スタンプピン）の底面に液体を付着させるので、対象物を傷つける恐れは少ないが、単に超音波振動を印加しながら転写ピンを上昇させるだけでは、必ずしも転写ピンへの液体の残留を防止しえない。
すなわち、液体と転写ピンとの間には物性的な特有の条件があり、その条件を満足しないと、転写ピンへの液体の残留を確実に防止することができない。
【０００６】
そこで、本発明の目的は、液体と転写ピンとの間で物性的な特有の条件を満足させることにより、転写ピンから対象物へ液体の残留なく精度よく転写することができる液体塗布方法を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するため、請求項１に記載の発明は、転写ピンの先端部に液体を付着させ、これを対象物に転着させる液体塗布方法において、上記先端部に一定量の液体を付着させた転写ピンを対象物に対して降下させ、上記液体が対象物に接触する位置で転写ピンを停止させる工程と、上記停止状態で転写ピンに超音波振動を印加し、転写ピンの先端部底面または先端部側面と液体との接触角θを９０°以上とする工程と、上記接触角θを９０°以上とした状態で転写ピンを上昇させる工程と、を有する液体塗布方法を提供する。
【０００８】
一般に、接着剤、導電ペースト、シリコーンオイルなどの粘性を持つ液体ではその表面張力γが数十（ｍＮ／ｍ）であるのに対し、転写ピン（表面処理済みの金属材料の場合）の単位面積当たりの表面自由エネルギーＥは数百（ｍＮ／ｍ）程度であるから、Ｅ＞γであり、液体が転写ピンの表面に対して濡れる。つまり、転写ピンの表面と液体との接触角θが９０°より小さい。そのため、転写ピンを対象物に近づけた状態から引き上げると、転写ピンに液体の一部が残留してしまい、塗布量が安定しない。
ところが、転写ピンを対象物に近づけた状態で停止させ、この停止状態で転写ピンに超音波振動を印加すると、転写ピンの先端部底面または先端部側面と液体との接触角θが９０°以上となる。この状態で転写ピンを上昇させると、液体が転写ピンの表面から簡単に分離し、転写ピンに液体を残留させずに対象物へ転写することができる。
転写ピンに液体が残留しないので、対象物への塗布量が安定するとともに、転写ピンに残留した液体を除去する作業も不要となる。
なお、超音波振動の方向は、縦方向（転写ピンの軸方向）でもよいし、横方向（転写ピンの軸線と直交方向）、さらには斜め方向でもよい。
【０００９】
請求項２のように、超音波振動の印加により、転写ピンの先端部底面または先端部側面と液体との接触角θを９０°以上とした後、所定の待機時間を設けた後に転写ピンを上昇させるようにしてもよい。
つまり、転写ピンの先端部と液体との接触角θが９０°以上となった時、即座に転写ピンを上昇させてもよいが、所定の待機時間を設ければ、より確実に転写ピンから液体を分離でき、液体を対象物に完全に転写できる。
上記の待機時間としては、例えば０．１秒程度でよい。
【００１０】
請求項３のように、次の関係式が成立する超音波振動を印加するのがよい。
２Ｍ（πｆＡ）^２＞γ_ＬＳ・・・（１）
但し、Ｍ：転写ピンの先端部底面への液体付着量（ｋｇ）、ｆ：超音波の周波数（Ｈｚ）、Ａ：超音波の振幅（ｍ）、γ_Ｌ：液体の表面自由エネルギー（Ｊ／ｍ^２）、Ｓ：液体の表面積（ｍ^２）である。
上記不等式の左辺は超音波エネルギーを表し、右辺は液体の全表面エネルギーを表す。超音波振動の周波数および振幅を大きくすれば、それだけ転写ピンと液体との分離性は向上するが、大きなエネルギーを必要とするとともに、転写ピンの支持装置にも影響を与える。
上記式を満足する超音波振動を与えることで、比較的小さなエネルギーで、転写ピンの表面と液体との接触角θを９０°以上とする時間を短縮できる。
【００１１】
請求項４は、転写ピンの先端部に液体を付着させるために、均一に均された液面に上記転写ピンの先端部を接触させ、転写ピンの先端部側面と液面との接触角αが９０°以上となる位置に転写ピンを制御する工程と、上記転写ピンを上昇させることにより、転写ピンの先端部底面のみに液体を付着させる工程と、を有することを特徴とする。
転写ピンの先端部に液体を付着させる場合、例えば液中に転写ピンの先端部を浸漬させる方法もあるが、これでは転写ピンの先端部底面だけでなく、先端部の周囲にも付着することになる。先端部の周囲に付着した液体の量は毎回変動するので、塗布量にばらつきが発生しやすい。
そこで、請求項４では、均一に均された液面に転写ピンを接触させ、先端部側面と液面との接触角αが９０°以上となる位置に転写ピンを制御し、その後で転写ピンを上昇させる。転写ピンを液体中に挿入すると、転写ピンの側面と液体との接触角αは挿入深さに伴って大きくなり、やがて接触角αは９０°以上になる。さらに転写ピンを深く挿入すると、接触角αは９０°より小さくなり、液体が転写ピンの側面に濡れ広がる。
そこで、接触角αが９０°以上になった深さで転写ピンを停止させ、その位置から転写ピンを引き上げることで、転写ピンの先端部底面のみに液体を付着させることができる。先端部底面に付着した液体の量Ｍは、次式のように底面積によって決まるので、安定した塗布量に制御できる。
【数１】

但し、ρ：液体密度、β：転写ピン先端部底面と液体との接触角、Ｄ：転写ピンの先端部底面の直径、Ｍ：転写ピンの先端部底面に付着する液体の量。
請求項４にかかる方法は、降伏応力を有しない液体に適用するのが望ましい。降伏応力を有しない液体とは、液体流動させるのに必要な応力が０の液体のことであり、例えばアンダーフィル剤やシリコーンオイルなどがある。
【００１２】
請求項５のように、転写ピンの先端部に液体を付着させるために、均一に均された液面に上記転写ピンの先端部を接触させ、転写ピンの先端部側面と液面との接触角αが９０°以上となるように超音波振動を印加する工程と、上記転写ピンを上昇させることにより、転写ピンの先端部底面のみに液体を付着させる工程と、を有するものでもよい。
請求項４では、転写ピンの位置を制御することで、転写ピンの先端部側面と液面との接触角αが９０°以上となるようにしたが、請求項５では超音波振動を印加することで、転写ピンの先端部側面と液面との接触角αを９０°以上としたものである。つまり、転写ピンを液体に挿入した時には接触角αが９０°より小さくても、超音波振動を印加することで液体が転写ピンの側面に対して弾かれ、接触角αが９０°以上となる。この時に転写ピンを引き上げると、先端部底面のみに液体を付着させることができる。超音波振動の方向は縦方向でもよいし、横方向あるいは斜め方向でもよい。
この場合も、（２）式と同様に、液量を転写ピンの先端部底面の直径Ｄによって一定に定量できる。
請求項５にかかる方法は、降伏応力を有する液体に適用するのが望ましい。降伏応力を有する液体とは、液体流動させるのに必要な応力が０ではない液体のことであり、例えば接着剤、導電性ペースト、封止用樹脂、クリームはんだ、セラミックスラリー、ワックスなどがある。
【００１３】
【発明の実施の形態】
図１は本発明にかかる液体塗布装置の一例を示す。
図において、１は転写ピンであり、その下端部には軸部１ａが一体に形成されている。転写ピン１はＳＵＳなどの金属材料よりなり、軸部１ａは例えば直径が０．４ｍｍ程度の細径な円柱形に形成されている。軸部１ａの表面には、表面自由エネルギーをできるだけ低くするため、フッ素コーティング処理が施されている。
【００１４】
転写ピン１は、駆動装置２に連結されており、上下方向に駆動されるとともに、高さ位置が高精度に制御される。駆動装置２としては、例えばボイスコイルモータや、電動モータとボールネジ機構との組み合わせなどを用いることができる。転写ピン１の上部には、所定の縦振動Ｕ（例えば６０ｋＨｚ、５μｍ_０−Ｐ）を転写ピン１に印加する超音波振動子３が取り付けられている。
【００１５】
転写ピン１の下方には、水平方向に移動可能なテーブル４，５が設けられ、一方のテーブル４上には液体Ｌを貯留した容器６が載置され、他方のテーブル５上には液体Ｌを塗布する対象物７が載置されている。この実施例の液体Ｌは、例えば粘度：５０Ｐａ・ｓ、密度：０．９７６ｍｇ／ｍｍ^３のシリコーンオイルである。容器６には、貯留された液体Ｌの液面を均すための液面均し手段（図示せず）が設けられ、１回の転写毎に液面を均す操作を実施する。
【００１６】
図２は転写ピンの先端部に液体を付着させる動作を示す原理図である。
図２の（ａ）は、容器６を転写ピン１の直下になる位置へテーブル４を水平移動させ、駆動装置２によって転写ピン１を降下させ、転写ピン１の軸部１ａの底面を容器６の液体Ｌの均一に均された液面に接触させた状態を示す。この状態では、軸部１ａの側面と液面との接触角αが９０°より小さい。
図２の（ｂ）は、駆動装置２によって転写ピン１をさらに降下させ、軸部１ａを液体Ｌの液面より僅かに浸漬させ、軸部１ａの側面と液面との接触角αが９０°以上となる位置（例えば浸漬深さ４０μｍ以下程度）に制御した状態を示す。
図２の（ｃ）は、軸部１ａを液体Ｌの液面から引き上げた状態を示す。上記のように軸部１ａの側面と液面との接触角αが９０°以上の状態から軸部１ａを引き上げると、軸部１ａの底面のみに液体を付着させることができる。この時、軸部１ａには一定量の液体Ｌが付着する。
【００１７】
図２の（ｂ）では、軸部１ａの側面と液面との接触角αが９０°以上となる位置に転写ピン１を制御したが、上記の方法以外にも、接触角αを９０°以上とすることが可能である。
すなわち、軸部１ａの側面と液面との接触角αが９０°より小さい位置へ浸漬した状態で、転写ピン１に縦方向の超音波振動Ｕ（図２の（ｂ）に破線矢印で示す）を印加すると、やがて接触角αが９０°以上になるので、この時点で転写ピン１を引き上げれば、図２と同様に、軸部１ａの底面のみに液体Ｌを付着させることができる。
【００１８】
軸部１ａの底面に付着した液体の量Ｍは、液体密度をρ（ｍｇ／ｍｍ^３）、軸部１ａの底面と液体との接触角をβ（°）、軸部１ａの底面の直径をＤ（ｍｍ）とすると、次式によって求めることができる。
【数２】

例えば、ρ＝０．９７６ｍｇ／ｍｍ^３、β＝７０°、Ｄ＝φ０．４ｍｍとすると、約１０μｇの液体Ｌが軸部１ａの底面に付着する。
【００１９】
図３は転写ピンの先端部に付着した液体を対象物に転着させる動作を示す。
図３の（ａ）は、転写ピン１の軸部１ａを対象物７に近づけ、液体Ｌを対象物７に接触させた状態を示す。この状態では、軸部１ａの側面と液面との接触角θは９０°より小さい。
図３の（ｂ）は、転写ピン１に縦方向の超音波振動Ｕを印加した状態を示す。超音波振動Ｕの印加により、液体Ｌのみかけ上の表面張力が大きくなり、軸部１ａの側面と液体Ｌとの接触角θが９０°以上となる。接触角θが９０°以上となった後、僅かな待機時間（例えば０．１ｓ）を設けた後に転写ピン１を引き上げる。
超音波振動の印加条件は、次の式が成立するように設定する。すなわち、転写ピンの先端部底面への液体付着量Ｍ（ｋｇ）、超音波の振幅Ａ（ｍ）、超音波の周波数ｆ（Ｈｚ）、液体の表面自由エネルギーγ_Ｌ（Ｊ／ｍ^２）、液体の表面積Ｓ（ｍ^２）とすると、
２Ｍ（πｆＡ）^２＞γ_ＬＳ・・・（１）
である。
例えば、Ｍ＝１０μｇ、γ_Ｌ＝２１．３×１０^−３Ｊ／ｍ^２、Ｓ＝０．１９×１０^−６ｍ^２の場合、ｆ＝６０ｋＨｚ、Ａ＝５μｍ_０−Ｐとすれば、接触角θを９０°以上とすることができる。
図３の（ｃ）は転写ピン１を引き上げる状態を示す。引上げる途中も、超音波振動Ｕを転写ピン１に印加するのがよい。これにより、液体Ｌは完全に対象物７に転着され、軸部１ａには液体Ｌが残留しない。すなわち、（２）式で求めた液体Ｌの量Ｍが全て対象物７に乗り移るので、高精度な塗布を実現できる。
【００２０】
図４は、転写ピンの先端部に付着した液体を対象物に転着させる動作の他の例を示す。
図３の（ｂ）では、軸部１ａの側面に液体Ｌが付着しない状態で超音波振動Ｕを印加することにより、軸部１ａの側面と液体Ｌとの接触角θを９０°以上としたが、図４に示すように、軸部１ａの側面に液体Ｌが付着した状態で超音波振動Ｕを印加しても、軸部１ａの側面と液体Ｌとの接触角θを９０°以上とすることが可能である。
この場合も、転写ピン１を引き上げると、軸部１ａには液体Ｌが残留しない。
【００２１】
図５は、転写ピンの先端部に付着した液体を対象物に転着させる動作のさらに他の例を示す。
図３，図４では、転写ピン１に超音波振動Ｕを印加することにより、軸部１ａの側面と液体Ｌとの接触角θを９０°以上とした例を示したが、図５では軸部１ａの底面と液体Ｌとの接触角θを９０°以上としたものである。
図５の（ａ）は、底面に液体Ｌが付着した軸部１ａを示す。
図５の（ｂ）は、軸部１ａを対象物７に近づけ、液体Ｌを対象物７に接触させた状態を示す。この時の軸部１ａは、図３の（ｂ）に比べて対象物７から離れた位置にあり、液体Ｌは軸部１ａの底面から外側へはみ出していない。
図５の（ｃ）は縦方向の超音波振動Ｕを印加した状態を示す。超音波振動Ｕの印加により、軸部１ａの底面と液体Ｌとの接触角θが９０°以上となる。
図５の（ｄ）は、軸部１ａを引き上げた状態を示し、対象物７に全ての液体Ｌが転写され、軸部１ａには液体Ｌが残留しない。
【００２２】
上記実施例では、転写ピン１の先端部（軸部１ａ）の底面のみに液体Ｌを付着させる例を示したが、底面だけでなく側面にも液体を付着させてもよい。但し、側面に液体が付着すると、液体が転写ピンに残留しやすくなるとともに、液体の塗布量のばらつきが発生しやすくなる。これに対し、転写ピンの先端部底面のみに液体を付着させれば、上記の問題を解消できるので、望ましい。
【００２３】
図１に示す液体塗布装置では、転写ピン１の下方に可動テーブル４，５を設け、このテーブル４，５上に液体容器６および対象物７をそれぞれ配置し、転写ピン１は上下方向にのみ駆動され、容器６と対象物７が水平方向に駆動される例を示したが、これに限るものではない。例えば転写ピン１および駆動装置２をロボットのアームなどに取り付け、転写ピン１を水平方向に移動させることにより、液体容器６から液体Ｌを受け取り、対象物７へ転写するようにしてもよい。その他、転写ピン１、容器６、対象物７の駆動機構は任意に設定できる。
【００２４】
【発明の効果】
以上の説明で明らかなように、請求項１に係る発明によれば、液体を付着させた転写ピンを液体が対象物に接触する位置で停止させた状態で転写ピンに超音波振動を印加することにより、転写ピンの先端部底面または先端部側面と液体との接触角θを９０°以上とし、その後で転写ピンを引き上げるようにしたので、液体が転写ピンの表面から簡単に分離し、転写ピンに液体を残留させずに対象物へ転写することができる。
そのため、対象物への高い塗布精度を維持できるとともに、転写ピンに残留した液体を除去する作業も不要となるという効果を有する。
【図面の簡単な説明】
【図１】液体塗布装置の一例の概略図である。
【図２】転写ピンの先端部に液体を付着させる動作を示す原理図である。
【図３】転写ピンの先端部に付着した液体を対象物に転着させる動作の原理図である。
【図４】転写ピンの先端部に付着した液体を対象物に転着させる動作の他の実施例の原理図である。
【図５】転写ピンの先端部に付着した液体を対象物に転着させる動作のさらに他の例の原理図である。
【符号の説明】
１転写ピン
１ａ軸部
２上下駆動装置
３超音波振動子
４，５テーブル
６容器
７対象物
Ｌ液体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid application method suitable for applying a viscous liquid, such as a conductive paste, an adhesive, or silicone oil, to an object minutely.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 8-257484 [Patent Document 2] Japanese Patent Application Laid-Open No. 8-318210 [Patent Document 3] Japanese Patent Application Laid-Open No. 11-156259 Conventionally, a liquid resin or an adhesive is applied to the surface of an electronic component or the like. As a method for accurately applying a predetermined amount of liquid such as the above, a liquid application method called a pin transfer method is known.
The pin transfer method is a method in which a liquid is attached to the tip of a transfer pin and transferred to an object. In the case of a viscous liquid, the liquid is transferred when transferred to the object. There is a problem of remaining on the pin.
In particular, when a very small amount of liquid of about 10 μg to several tens of μg is applied to an electronic component, if even a part of the liquid remains on the transfer pin, the amount of application to the object greatly varies.
[0003]
In order to solve such a problem, in Patent Document 1, after a transfer pin having liquid attached to the tip is applied to the surface of the object, the transfer pin is raised by a slight height, and the transfer pin is temporarily stopped there. A method has been proposed in which the robot is lifted or lifted, or once stopped and then moved up and down with a small stroke and then lifted.
However, this method only stops the transfer pin once in the middle, and does not perform an operation for positively separating the liquid from the transfer pin, so that the liquid cannot be reliably prevented from remaining on the transfer pin. There is.
[0004]
Patent Document 2 discloses a coating method that prevents a liquid from remaining on a transfer pin by bringing a transfer pin having a liquid attached to its tip close to or in contact with an object and pulling it up while applying ultrasonic vibration to the transfer pin. Has been proposed.
In Patent Document 3, as in Patent Document 2, the stamp pin is moved to the upper part of the container storing the adhesive, and after the adhesive is attached to the stamp surface, the stamp pin is raised, and the stamp pin is moved to the position of the substrate. A method is proposed in which the stamp pin is lowered again and the adhesive adhered to the stamp surface is transferred to the substrate. In order to prevent the stringing phenomenon of the adhesive adhering to the stamp pin, a method has been proposed in which a thin film having water repellency such as a silicon thin film is formed on the surface of the stamp pin, or a vibration is applied to a vibrator or an ultrasonic generator. ing.
[0005]
[Problems to be solved by the invention]
In the coating methods described in

Patent Documents

2 and 3, it is possible to improve the separability of the liquid from the transfer pin by applying ultrasonic vibration to the transfer pin.
However, when a coating tool with a tapered tip is used as in Patent Document 2, when the liquid is transferred from the coating tool to the target, the tip of the coating tool may hit the target and damage the target. Is expensive. Further, when the liquid is sent out, the liquid may remain on the side surface of the application tool.
Further, in Patent Document 3, since the liquid is attached to the bottom surface of the transfer pin (stamp pin), there is little risk of damaging the object. However, the transfer pin is not necessarily raised simply by raising the transfer pin while applying ultrasonic vibration. It is impossible to prevent liquid from remaining on the surface.
That is, there is a condition specific to physical properties between the liquid and the transfer pin, and if the condition is not satisfied, the liquid cannot be reliably prevented from remaining on the transfer pin.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid application method capable of accurately transferring a liquid from a transfer pin to an object without remaining liquid by satisfying specific conditions of physical properties between the liquid and the transfer pin. There is.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided a liquid application method in which a liquid is attached to the tip of a transfer pin and transferred to an object, and a certain amount of liquid is attached to the tip. Lowering the transferred transfer pin with respect to the object, stopping the transfer pin at a position where the liquid contacts the object, and applying ultrasonic vibration to the transfer pin in the stopped state, Provided is a liquid application method comprising a step of setting a contact angle θ between a bottom surface or a side surface of a tip portion and a liquid to 90 ° or more and a step of raising a transfer pin in a state where the contact angle θ is set to 90 ° or more.
[0008]
Generally, liquids with viscosity such as adhesives, conductive pastes, and silicone oils have a surface tension γ of several tens (mN / m), whereas the unit area of a transfer pin (in the case of a surface-treated metal material) Since the hit surface free energy E is about several hundreds (mN / m), E> γ, and the liquid wets the surface of the transfer pin. That is, the contact angle θ between the surface of the transfer pin and the liquid is smaller than 90 °. For this reason, when the transfer pin is pulled up from a state close to the object, a part of the liquid remains on the transfer pin, and the coating amount is not stable.
However, when the transfer pin is stopped in a state close to the object and ultrasonic vibration is applied to the transfer pin in this stopped state, the contact angle θ between the bottom surface of the transfer pin or the side surface of the transfer pin and the liquid is 90 ° or more. It becomes. When the transfer pin is raised in this state, the liquid is easily separated from the surface of the transfer pin, and can be transferred to the object without leaving the liquid on the transfer pin.
Since no liquid remains on the transfer pin, the amount of application to the object is stabilized, and the operation of removing the liquid remaining on the transfer pin is not required.
The direction of ultrasonic vibration may be the vertical direction (axial direction of the transfer pin), the horizontal direction (perpendicular to the axis of the transfer pin), or an oblique direction.
[0009]
According to claim 2, by applying ultrasonic vibration, the contact angle θ between the tip bottom surface or tip side surface of the transfer pin and the liquid is set to 90 ° or more, and then the transfer pin is mounted after a predetermined waiting time is provided. You may make it raise.
That is, when the contact angle θ between the tip of the transfer pin and the liquid becomes 90 ° or more, the transfer pin may be immediately raised, but if a predetermined waiting time is provided, the transfer pin can be more reliably removed. The liquid can be separated and the liquid can be completely transferred to the object.
The waiting time may be about 0.1 seconds, for example.
[0010]
As in claim 3, it is preferable to apply ultrasonic vibration that satisfies the following relational expression.
2M (πfA) ² > γ _L S (1)
Where M: amount of liquid adhering to the bottom surface of the tip of the transfer pin (kg), f: frequency of ultrasonic waves (Hz), A: amplitude of ultrasonic waves (m), γ _L : surface free energy of liquid (J / m ² ), S: surface area (m ² ) of the liquid.
The left side of the above inequality represents ultrasonic energy, and the right side represents the total surface energy of the liquid. Increasing the frequency and amplitude of the ultrasonic vibration improves the separability between the transfer pin and the liquid, but requires a large amount of energy and affects the transfer pin support device.
By applying ultrasonic vibration that satisfies the above formula, it is possible to shorten the time for which the contact angle θ between the surface of the transfer pin and the liquid is 90 ° or more with relatively small energy.
[0011]
According to a fourth aspect of the present invention, the tip of the transfer pin is brought into contact with the uniformly leveled liquid surface in order to allow the liquid to adhere to the tip of the transfer pin, and the contact angle α between the side of the tip of the transfer pin and the liquid surface And a step of controlling the transfer pin to a position where the angle is 90 ° or more and a step of causing the liquid to adhere only to the bottom surface of the tip of the transfer pin by raising the transfer pin.
When attaching the liquid to the tip of the transfer pin, for example, there is a method of immersing the tip of the transfer pin in the liquid, but this also adheres not only to the bottom of the tip of the transfer pin but also to the periphery of the tip. become. Since the amount of liquid adhering to the periphery of the tip varies every time, the application amount tends to vary.
Therefore, in claim 4, the transfer pin is brought into contact with the uniformly leveled liquid surface, the transfer pin is controlled to a position where the contact angle α between the side surface of the tip and the liquid surface is 90 ° or more, and then the transfer pin To raise. When the transfer pin is inserted into the liquid, the contact angle α between the side surface of the transfer pin and the liquid increases with the insertion depth, and the contact angle α eventually becomes 90 ° or more. When the transfer pin is further inserted deeply, the contact angle α becomes smaller than 90 °, and the liquid spreads wet on the side surface of the transfer pin.
Therefore, the transfer pin is stopped at a depth at which the contact angle α is 90 ° or more, and the transfer pin is pulled up from that position, so that the liquid can be attached only to the bottom surface of the transfer pin. Since the amount M of the liquid adhering to the bottom surface of the tip is determined by the bottom area as in the following equation, it can be controlled to a stable coating amount.
[Expression 1]

Where ρ: liquid density, β: contact angle between bottom surface of transfer pin tip and liquid, D: diameter of bottom surface of tip of transfer pin, M: amount of liquid adhering to bottom surface of tip of transfer pin.
The method according to claim 4 is preferably applied to a liquid having no yield stress. The liquid having no yield stress is a liquid having no stress necessary for liquid flow, such as an underfill agent or silicone oil.
[0012]
In order to make the liquid adhere to the tip of the transfer pin as in claim 5, the tip of the transfer pin is brought into contact with the uniformly leveled liquid surface, and the contact between the tip of the transfer pin and the liquid surface. There may be included a step of applying ultrasonic vibration so that the angle α is 90 ° or more and a step of attaching the liquid only to the bottom surface of the tip of the transfer pin by raising the transfer pin.
In claim 4, by controlling the position of the transfer pin, the contact angle α between the tip side surface of the transfer pin and the liquid surface is 90 ° or more, but in claim 5, ultrasonic vibration is applied. As a result, the contact angle α between the side surface of the tip of the transfer pin and the liquid surface is set to 90 ° or more. That is, when the transfer pin is inserted into the liquid, even if the contact angle α is smaller than 90 °, the liquid is repelled against the side surface of the transfer pin by applying ultrasonic vibration, and the contact angle α becomes 90 ° or more. . When the transfer pin is pulled up at this time, the liquid can be attached only to the bottom surface of the tip. The direction of ultrasonic vibration may be the vertical direction, the horizontal direction, or the oblique direction.
Also in this case, the amount of liquid can be quantified with the diameter D of the bottom surface of the tip of the transfer pin, similarly to the equation (2).
The method according to claim 5 is preferably applied to a liquid having a yield stress. A liquid having a yield stress is a liquid whose stress necessary for flowing the liquid is not zero, and examples thereof include an adhesive, a conductive paste, a sealing resin, a cream solder, a ceramic slurry, and a wax.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a liquid coating apparatus according to the present invention.
In the figure, reference numeral 1 denotes a transfer pin, and a shaft portion 1a is integrally formed at a lower end portion thereof. The transfer pin 1 is made of a metal material such as SUS, and the shaft portion 1a is formed in a thin cylindrical shape having a diameter of about 0.4 mm, for example. The surface of the shaft portion 1a is subjected to a fluorine coating process in order to make the surface free energy as low as possible.
[0014]
The transfer pin 1 is connected to the driving device 2 and is driven in the vertical direction, and the height position is controlled with high accuracy. As the driving device 2, for example, a voice coil motor or a combination of an electric motor and a ball screw mechanism can be used. An ultrasonic vibrator 3 that applies a predetermined longitudinal vibration U (for example, 60 kHz, 5 μm _0-P ) to the transfer pin 1 is attached to the top of the transfer pin 1.
[0015]
Below the transfer pin 1, horizontally movable tables 4 and 5 are provided. On one table 4, a container 6 storing the liquid L is placed, and on the other table 5 the liquid L is placed. An object 7 to be applied is placed. The liquid L in this embodiment is, for example, a silicone oil having a viscosity of 50 Pa · s and a density of 0.976 mg / mm ³ . The container 6 is provided with a liquid leveling means (not shown) for leveling the liquid level of the stored liquid L, and performs an operation of leveling the liquid level for each transfer.
[0016]
FIG. 2 is a principle view showing the operation of attaching the liquid to the tip of the transfer pin.
In FIG. 2A, the table 4 is moved horizontally to a position immediately below the transfer pin 1, the transfer pin 1 is lowered by the driving device 2, and the bottom surface of the shaft portion 1a of the transfer pin 1 is placed on the bottom of the container 6. A state in which the liquid L is brought into contact with the uniformly leveled liquid surface is shown. In this state, the contact angle α between the side surface of the shaft portion 1a and the liquid surface is smaller than 90 °.
In FIG. 2B, the transfer pin 1 is further lowered by the driving device 2, the shaft portion 1a is slightly immersed from the liquid surface of the liquid L, and the contact angle α between the side surface of the shaft portion 1a and the liquid surface is 90. A state in which the position is controlled to a position where the angle is greater than or equal to (for example, an immersion depth of about 40 μm or less) is shown.
FIG. 2C shows a state in which the shaft portion 1a is pulled up from the liquid level of the liquid L. As described above, when the shaft portion 1a is lifted from a state where the contact angle α between the side surface of the shaft portion 1a and the liquid surface is 90 ° or more, the liquid can be attached only to the bottom surface of the shaft portion 1a. At this time, a certain amount of liquid L adheres to the shaft portion 1a.
[0017]
In FIG. 2B, the transfer pin 1 is controlled at a position where the contact angle α between the side surface of the shaft portion 1a and the liquid surface is 90 ° or more. However, in addition to the above method, the contact angle α is set to 90 °. This can be done.
That is, in a state where the contact angle α between the side surface of the shaft portion 1a and the liquid surface is immersed in a position smaller than 90 °, the ultrasonic vibration U in the vertical direction is indicated on the transfer pin 1 (indicated by a broken line arrow in FIG. 2B). ) Is eventually applied, the contact angle α becomes 90 ° or more. If the transfer pin 1 is pulled up at this point, the liquid L can be attached only to the bottom surface of the shaft portion 1a as in FIG.
[0018]
The amount M of the liquid adhering to the bottom surface of the shaft portion 1a is defined as ρ (mg / mm ³ ) of the liquid density, β (°) as the contact angle between the bottom surface of the shaft portion 1a and the liquid, and the diameter of the bottom surface of the shaft portion 1a. If it is D (mm), it can obtain | require by following Formula.
[Expression 2]

For example, when ρ = 0.976 mg / mm ³ , β = 70 °, and D = φ0.4 mm, about 10 μg of liquid L adheres to the bottom surface of the shaft portion 1a.
[0019]
FIG. 3 shows the operation of transferring the liquid adhering to the tip of the transfer pin to the object.
FIG. 3A shows a state in which the shaft portion 1 a of the transfer pin 1 is brought close to the object 7 and the liquid L is brought into contact with the object 7. In this state, the contact angle θ between the side surface of the shaft portion 1a and the liquid surface is smaller than 90 °.
FIG. 3B shows a state in which ultrasonic vibration U in the vertical direction is applied to the transfer pin 1. By applying the ultrasonic vibration U, the apparent surface tension of the liquid L increases, and the contact angle θ between the side surface of the shaft portion 1a and the liquid L becomes 90 ° or more. After the contact angle θ reaches 90 ° or more, the transfer pin 1 is pulled up after a short waiting time (for example, 0.1 s).
The application condition of the ultrasonic vibration is set so that the following formula is established. That is, the liquid adhesion amount M (kg) to the bottom surface of the tip of the transfer pin, the amplitude A (m) of the ultrasonic wave, the frequency f (Hz) of the ultrasonic wave, the surface free energy γ _L (J / m ² ) of the liquid, Given the surface area S (m ² ) of the liquid,
2M (πfA) ² > γ _L S (1)
It is.
For example, when M = 10 μg, γ _L = 21.3 × 10 ⁻³ J / m ² , and S = 0.19 × 10 ⁻⁶ m ² , contact is made when f = 60 kHz and A = 5 μm _0-P. The angle θ can be 90 ° or more.
FIG. 3C shows a state where the transfer pin 1 is pulled up. It is preferable to apply the ultrasonic vibration U to the transfer pin 1 even during the pulling. Thereby, the liquid L is completely transferred to the object 7, and the liquid L does not remain in the shaft portion 1a. That is, since all the amount M of the liquid L obtained by the equation (2) is transferred to the object 7, high-precision coating can be realized.
[0020]
FIG. 4 shows another example of the operation for transferring the liquid adhering to the tip of the transfer pin to the object.
In FIG. 3B, the contact angle θ between the side surface of the shaft portion 1a and the liquid L is set to 90 ° or more by applying ultrasonic vibration U in a state where the liquid L does not adhere to the side surface of the shaft portion 1a. However, as shown in FIG. 4, even if the ultrasonic vibration U is applied with the liquid L attached to the side surface of the shaft portion 1a, the contact angle θ between the side surface of the shaft portion 1a and the liquid L is 90 ° or more. Is possible.
Also in this case, when the transfer pin 1 is pulled up, the liquid L does not remain on the shaft portion 1a.
[0021]
FIG. 5 shows still another example of the operation of transferring the liquid adhering to the tip of the transfer pin to the object.
3 and 4 show examples in which the contact angle θ between the side surface of the shaft portion 1a and the liquid L is set to 90 ° or more by applying ultrasonic vibration U to the transfer pin 1, but FIG. The contact angle θ between the bottom surface of the part 1a and the liquid L is 90 ° or more.
(A) of FIG. 5 shows the axial part 1a which the liquid L adhered to the bottom face.
FIG. 5B shows a state in which the shaft portion 1 a is brought close to the object 7 and the liquid L is brought into contact with the object 7. The shaft portion 1a at this time is located farther from the object 7 than FIG. 3B, and the liquid L does not protrude outward from the bottom surface of the shaft portion 1a.
FIG. 5C shows a state where the longitudinal ultrasonic vibration U is applied. By applying the ultrasonic vibration U, the contact angle θ between the bottom surface of the shaft portion 1a and the liquid L becomes 90 ° or more.
(D) of FIG. 5 shows the state which pulled up the axial part 1a, all the liquid L is transcribe | transferred to the target object 7, and the liquid L does not remain in the axial part 1a.
[0022]
In the above embodiment, the liquid L is attached only to the bottom surface of the tip portion (shaft portion 1a) of the transfer pin 1, but the liquid may be attached not only to the bottom surface but also to the side surface. However, if the liquid adheres to the side surface, the liquid tends to remain on the transfer pin and variations in the amount of liquid applied tend to occur. On the other hand, it is desirable to apply the liquid only to the bottom surface of the tip of the transfer pin because the above problem can be solved.
[0023]
In the liquid coating apparatus shown in FIG. 1, movable tables 4 and 5 are provided below the transfer pin 1, and a liquid container 6 and an object 7 are arranged on the tables 4 and 5, respectively. The transfer pin 1 is only in the vertical direction. Although the example which drives and the container 6 and the target object 7 are driven to the horizontal direction was shown, it does not restrict to this. For example, the transfer pin 1 and the driving device 2 may be attached to a robot arm or the like, and the transfer pin 1 may be moved in the horizontal direction to receive the liquid L from the liquid container 6 and transfer it to the object 7. In addition, the drive mechanism of the transfer pin 1, the container 6, and the object 7 can be arbitrarily set.
[0024]
【The invention's effect】
As is apparent from the above description, according to the first aspect of the invention, the ultrasonic vibration is applied to the transfer pin while the transfer pin to which the liquid is attached is stopped at the position where the liquid contacts the object. As a result, the contact angle θ between the tip bottom surface or the tip side surface of the transfer pin and the liquid is set to 90 ° or more, and then the transfer pin is pulled up, so that the liquid is easily separated from the surface of the transfer pin and transferred. The liquid can be transferred to the object without leaving the liquid on the pin.
Therefore, it is possible to maintain high application accuracy to the object and to eliminate the need to remove the liquid remaining on the transfer pin.
[Brief description of the drawings]
FIG. 1 is a schematic view of an example of a liquid application apparatus.
FIG. 2 is a principle diagram showing an operation of attaching a liquid to the tip of a transfer pin.
FIG. 3 is a principle diagram of an operation for transferring a liquid adhering to a tip portion of a transfer pin to an object.
FIG. 4 is a principle diagram of another embodiment of the operation of transferring the liquid adhering to the tip of the transfer pin to the object.
FIG. 5 is a principle diagram of still another example of the operation for transferring the liquid adhering to the tip of the transfer pin to the object.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transfer pin 1a Shaft part 2 Vertical drive apparatus 3 Ultrasonic vibrators 4, 5 Table 6 Container 7 Object L Liquid

Claims

In a liquid application method in which a liquid is attached to the tip of a transfer pin and transferred to an object,
A step of lowering a transfer pin with a fixed amount of liquid attached to the tip portion with respect to the object, and stopping the transfer pin at a position where the liquid contacts the object;
Applying ultrasonic vibration to the transfer pin in the stopped state, and setting the contact angle θ between the tip bottom surface or the tip side surface of the transfer pin and the liquid to 90 ° or more;
And a step of raising the transfer pin in a state where the contact angle θ is 90 ° or more.

By applying the ultrasonic vibration, the transfer pin is raised after a predetermined waiting time is set after the contact angle θ between the bottom surface of the transfer pin or the side surface of the transfer pin and the liquid is 90 ° or more. The liquid application method according to claim 1.

The liquid application method according to claim 1, wherein ultrasonic vibration that satisfies the following relational expression is applied.
2M (πfA) ² > γ _L S (1)
Where M: amount of liquid adhering to the bottom surface of the tip of the transfer pin (kg), f: frequency of ultrasonic waves (Hz), A: amplitude of ultrasonic waves (m), γ _L : surface free energy of liquid (J / m ² , S: surface area (m ² ) of the liquid.

In order to attach liquid to the tip of the transfer pin,
A step of bringing the tip of the transfer pin into contact with the uniformly leveled liquid surface, and controlling the transfer pin at a position where the contact angle α between the side surface of the tip of the transfer pin and the liquid surface is 90 ° or more;
The liquid application method according to claim 1, further comprising a step of causing the liquid to adhere only to the bottom surface of the tip of the transfer pin by raising the transfer pin.

In order to attach liquid to the tip of the transfer pin,
Applying the ultrasonic vibration so that the tip of the transfer pin is brought into contact with the uniformly leveled liquid surface, and the contact angle α between the side of the tip of the transfer pin and the liquid surface is 90 ° or more;
The liquid application method according to claim 1, further comprising a step of causing the liquid to adhere only to the bottom surface of the tip of the transfer pin by raising the transfer pin.