JP4001493B2 - Mounting board manufacturing method - Google Patents

Description

【００８９】
比較例１のポリウレタン組成物の場合、ブリードは見られないが、フラックス面に対する接着力は５０ｇ／ｍｍ²であった。このときの破壊状態は、界面破壊であり、接着性は良くない。
【００９０】
フラックス面に対する接着力を上げるため、比較例２に示したように、オルガノポリシロキサン化合物を配合した場合であっても、その接着力は８０ｇ／ｍｍ²で、改善されていない。しかも、この場合には、オルガノポリシロキサン化合物が相溶せずにブリード現象が起こり、また、破壊状態も界面破壊であり、接着性の改善は見られない。
【００９１】
オルガノポリシロキサン化合物のブリード防止のため、比較例３に示したように、ブリード防止剤を配合した場合には、接着力が２００ｇ／ｍｍ²に改善され、オルガノポリシロキサン化合物のブリードも見られない。しかし、その破壊状態は界面破壊である。
【００９２】
この比較例３の組成に、実施例に示したように、シランカップリング剤を配合することにより、接着力は向上する。さらに、その破壊状態は凝集破壊に至る良好な接着性を示し、オルガノポリシロキサン化合物のブリードも観察されない。
【００９３】
（比較例４）
比較例４の熱硬化性ポリウレタン組成物は、実施例のポリウレタン組成物に含まれる成分のうち、エポキシ樹脂のみ配合しなかった場合の熱硬化性ポリウレタン組成物である。この比較例４に示した熱硬化性ポリウレタン組成物を、以下では、「比較例４のポリウレタン組成物」という。
【００９４】
（比較例５）
比較例５の熱硬化性ポリウレタン組成物は、実施例のポリウレタン組成物に含まれる成分のうち、ＰＢ系ウレタンプレポリマーを、ＰＰＧ系ウレタンプレポリマーに代えた場合の熱硬化性ポリウレタン組成物である。この比較例５に示した熱硬化性ポリウレタン組成物を、以下では、「比較例５のポリウレタン組成物」という。
【００９５】
（比較例６）
比較例６では、熱硬化性エポキシ樹脂組成物（サンスター技研株式会社製ペンギンセメント１０９０）を用いる。この比較例６に示した熱硬化性エポキシ樹脂組成物を、以下では、「比較例６のエポキシ樹脂組成物」という。
【００９６】
比較例４ないし６に示した各組成物についても、実施例のポリウレタン組成物と同様、２０℃における粘度、誘電率、誘電正接および体積抵抗率を測定する。実施例、および比較例４ないし６の測定結果を表２に示す。
【００９７】
【表２】

【００９８】
比較例４に示すように、組成にエポキシ樹脂を含有しない場合には、体積抵抗率に大きな変化はないが、粘度が増加する。また、比較例５に示すように、その組成にＰＢ系ウレタンプレポリマーを含有しない場合には、その粘度は低下するが、充分な体積抵抗率を得ることができなくなる。
【００９９】
次に、実施例、および比較例４ないし６に示した熱硬化性ポリウレタン組成物、熱硬化性エポキシ樹脂組成物をアンダーフィル材として用いた実装基板について比較検討した結果について説明する。
【０１００】
図１はアンダーフィル材が用いられている実装基板の断面概略図である。実装基板１０は、エポキシ樹脂母体のＦＲ−５相当の電子回路基板１１に、ＣＳＰ（０．５ｍｍピッチ共晶系はんだボール、ボール数２４０個、パッケージサイズ１０ｍｍ）１２がはんだボール１３を介して接合されている。そして、電子回路基板１１とＣＳＰ１２との間隙に、アンダーフィル材１４が充填・硬化されている。
【０１０１】
上記構成の実装基板１０の製造は、まず、電子回路基板１１表面に、Ｓｎ／３７Ｐｂ共晶系はんだペースト材（日本アルファメタルズ社製ＲＭＡ９０８６）を、約１５０μｍの厚みでスクリーン印刷する。次いで、ＣＳＰ１２を搭載し、ピーク温度２３０℃で、リフローはんだ付けを行う。
【０１０２】
そして、このはんだのフラックス残渣が存在している無洗浄の状態で、電子回路基板１１とＣＳＰ１２との間隙に、アンダーフィル材１４を充填する。アンダーフィル材１４を充填する際には、ＣＳＰ１２下部にアンダーフィル材１４が浸透するように、ＣＳＰ１２の脇からディスペンサを用いて塗布・滴下する。そして、１０分間静置後、８０℃で５分間キュアを行い、アンダーフィル材１４の充填を終了する。
【０１０３】
アンダーフィル材１４の浸透効果を確認するため、実装基板１０をＣＳＰ１２の位置で切断し、はんだボール１３近傍での、アンダーフィル材１４の充填状態を検査した。
【０１０４】
図３は比較例４のポリウレタン組成物を用いた場合の実装基板の断面概略図、図４は実施例のポリウレタン組成物を用いた場合の実装基板の断面概略図である。
【０１０５】
図３に示すように、アンダーフィル材１４ａに、エポキシ樹脂を含有していない比較例４のポリウレタン組成物を用いた場合には、実装基板１０ａにおいて、ＣＳＰ１２ａの下面には充分に浸透して充填されているが、電子回路基板１１ａには、その全面に充填されていない。これは、電子回路基板１１ａ表面に存在するフラックス残渣１５ａにより、アンダーフィル材１４ａの浸透が阻害されてしまったためである。
【０１０６】
一方、図４に示すように、実施例のポリウレタン組成物を用いた場合には、実装基板１０ｂにおいて、ＣＳＰ１２ｂの下面および電子回路基板１１ｂ表面に、アンダーフィル材１４ｂが、フラックス残渣を取り込んだ状態で、ほぼ全面に充填されている。したがって、電子回路基板１１ｂとＣＳＰ１２ｂとの接合面積を確保することができ、接着力の向上が期待される。
【０１０７】
ここで、図３に示した実装基板１０ａと、図４に示した実装基板１０ｂについて、ＣＳＰ１２ａ，１２ｂの接着力を、落下試験により比較する。
図５は落下試験方法の説明図である。落下試験は、実装基板１０ａ，１０ｂを、その実装面を下向きにした状態で、１ｍの高さからタイル床５０に対して繰り返し自由落下させる。そして、ＣＳＰ１２ａ，１２ｂのはんだボールでなるディジーチェーンのループ接続抵抗値が、初期値（約０．５Ω）よりも１０％増大した落下回数を不良とする。なお、この落下試験では、落下５０回ごとに、ループ接続抵抗値の測定を行うものとする。落下試験の結果を表３に示す。
【０１０８】
【表３】

【０１０９】
アンダーフィル材に比較例４のポリウレタン組成物を用いた場合には、落下回数が平均約２００回で、ループ接続抵抗値が増大して不良となってしまう。一方、実施例のポリウレタン組成物を用いた場合には、落下回数が平均約３００回以上であっても、ループ接続抵抗値の増大がない。これにより、実施例のポリウレタン組成物は、その組成にエポキシ樹脂を含有することで、フラックス残渣が存在していても、接着面積を確保し、接着力を高く維持することができる。したがって、この熱硬化性ポリウレタン組成物は、例えば携帯電話のような、高い耐落下衝撃信頼性を必要とする機器などにも、充分適用することが可能である。
【０１１０】
さらに、アンダーフィル材を充填する前に、フラックス洗浄が不要になるので、その薬液処理に伴う電子部品の性能信頼性低下を招くことがない。また、洗浄工程および乾燥工程が不要となるので、作業効率が向上する。そして、このフラックス洗浄のための洗浄設備の費用、洗浄に係る廃液処理費用などを削減することができ、実装工程の低コスト化が図られるようになる。
【０１１１】
次に、アンダーフィル材で電子回路基板に接着されている電子部品のリペア性について説明する。
熱硬化性ポリウレタン組成物を、電子部品と電子回路基板との間隙に充填し、一旦硬化した後、電子部品をリペアする場合には、硬化した熱硬化性ポリウレタン組成物を、再び加熱して軟化し、その接着力を低下させる必要がある。
【０１１２】
硬化した熱硬化性ポリウレタン組成物の加熱による接着力変化を測定するため、図２に示した方法により、アンダーフィル材２１を電子回路基板２３に硬化する。そして、硬化後、この電子回路基板２３をホットプレート２４に配置し、室温から２５０℃までの所定温度で加熱し、各所定温度到達後２分でのＴ字型釘２２の接着力を測定する。
【０１１３】
図６はアンダーフィル材にかける温度と接着力の関係を示す図である。ここでは、比較例６のエポキシ樹脂組成物、実施例のポリウレタン組成物を用いた場合について、図２に示した方法により、それぞれ接着力を測定する。なお、図６では、比較例６のエポキシ樹脂組成物を用いた場合の温度と接着力の関係を破線で、実施例のポリウレタン組成物を用いた場合の温度と接着力の関係を実線で、それぞれ示している。
【０１１４】
比較例６のエポキシ樹脂組成物を用いた場合には、加熱温度が１５０℃から２００℃の範囲で緩やかに接着力が低下している。一方、実施例のポリウレタン組成物を用いた場合には、加熱温度が１４０℃を超えると、急激に接着力が低下し、温度１６０℃では、１０ｇｆ／ｍｍ²（０．１Ｎ／ｍｍ²）以下となる。
【０１１５】
電子部品をリペアする場合には、はんだの融点（１８３℃）以上に加熱する必要がある。当然、電子部品を取り外すタイミングとしては、はんだの融点以上かつ低温度域、そして短時間で行うことが望ましい。実施例のポリウレタン組成物を用いた場合には、図６に示したように、加熱温度が約１４０℃でその接着力が急激に小さくなるので、電子部品を低温で取り外すことができる。すなわち、はんだを取り外せる温度では、実施例のポリウレタン組成物は充分軟化しており、電子部品の取り外しを、熱的・機械的ダメージを抑えて、容易に行うことが可能になる。
【０１１６】
一方、比較例６のエポキシ樹脂組成物では、実施例のポリウレタン組成物が示すような傾向は認められず、加熱温度が約５０℃以上では、実施例のポリウレタン組成物よりも高い接着力を示すようになる。すなわち、比較例６のエポキシ樹脂組成物では、実施例のポリウレタン組成物に比べ、取り外す際に、より高い温度まで加熱することを要するとともに、より大きな力が必要になる。また、一般に、従来広く用いられている熱硬化性エポキシ樹脂組成物は、その軟化温度が２００℃以上で、さらに、電子回路基板への残渣の付着も強く、リペア作業には困難を要してしまう。この点で、実施例のポリウレタン組成物は、リペア性に非常に優れているといえ、この熱硬化性ポリウレタン組成物は、各種用途に用いられる実装基板に広く適用することが可能である。
【０１１７】
なお、実際に、実装基板から、アンダーフィル材が充填された電子部品をリペアする場合には、取り外す電子部品に、１Ｎから３Ｎのおもりを吊るし、加熱によるはんだの溶融の際、アンダーフィル材の軟化開始時に自然落下させることで、その電子部品を取り外すことができる。このような原理を用いることにより、最適なタイミングで電子部品を取り外すことが可能になる。
【０１１８】
また、電子部品をリペアする場合に、加熱によるはんだの溶融、アンダーフィル材の軟化開始時を目視で検出するためのサーモセンサラベルを、電子部品の近傍に配置して行うこともできる。このほか、取り外す電子部品のはんだよりも、１０℃から５０℃高い温度のはんだ融点材を、電子部品の近傍に配置してもよい。
【０１１９】
一般に、電子回路基板上には、複数の電子部品が密集して配置されており、電子部品をリペアする場合には、この電子部品に近接する他の電子部品も加熱されることになる場合が多い。すなわち、リペアすべき不良電子部品と共に、良品電子部品もリペア熱の影響で高温にさらされる。そのため、このリペア熱で良品電子部品の接着力が喪失されないことが必要である。
【０１２０】
図７は接着力の回復性を示す図である。接着力回復性は、比較例６のエポキシ樹脂組成物、実施例のポリウレタン組成物を用い、まず、図２に示したのと同様の方法を用いて、一旦加熱して５分間保持したアンダーフィル材を、ここでは、そのまま室温まで冷却し、接着力を測定することにより評価する。なお、図７では、比較例６のエポキシ樹脂組成物を用いた場合の温度と接着力の関係を破線で、実施例のポリウレタン組成物を用いた場合の温度と接着力の関係を実線で、それぞれ示している。
【０１２１】
実施例のポリウレタン組成物の接着力は、図７に示したように、比較例６のエポキシ樹脂組成物と同様、はんだの溶融温度程度の加熱であれば、その冷却後に、加熱する前のレベルまで充分回復することがわかる。したがって、実施例のポリウレタン組成物によれば、電子部品のリペアのための加熱を行っても、それに近接する他の電子部品の接着信頼性を維持することが可能である。このように、アンダーフィル材に、本発明に係る熱硬化性ポリウレタン組成物を用いることにより、電子部品のリペア専用設備についてのコスト低減を図ることが可能になる。
【０１２２】
次に、アンダーフィル材の電気絶縁性について説明する。
電子部品と電子回路基板との間隙に充填されて使用されるアンダーフィル材の電気絶縁性を検討するため、比較例６のエポキシ樹脂組成物、実施例のポリウレタン組成物を用い、絶縁抵抗試験を実施した。ここでの絶縁抵抗試験は、ＩＰＣ−ＴＭ−６５０の２−６−３−３項に準じ、以下の手順で行う。
【０１２３】
（１）まず、ＩＰＣ−Ｂ−２５規格に準じた、くし歯型パターンが形成された銅箔パターン（間隙０．３１８ｍｍ、導体幅０．３１８ｍｍ）上に、アンダーフィル材を約０．５ｍｍの厚みに塗布し、硬化する。硬化条件は、実施例のポリウレタン組成物では８０℃で５分、比較例６のエポキシ樹脂組成物では１５０℃で１０分とした。なお、比較のため、アンダーフィル材を塗布しない銅箔パターンも準備する。
【０１２４】
（２）温度２３℃、湿度５０％に管理した恒温槽にサンプルを２４時間放置して調湿し、その後、サンプルの初期絶縁抵抗値を測定した。この初期絶縁抵抗値の測定は、測定電圧１００Ｖで、１分印加後に行う。
【０１２５】
（３）サンプルを温度３５±２℃、湿度８５％の恒温槽に入れ、１時間後に、（２）と同様に絶縁抵抗値を測定する。なお、このときの絶縁抵抗値を、以下「１時間後絶縁抵抗値」という。
【０１２６】
（４）印加電圧ＤＣ５０Ｖをかけ、４日間（９６時間）、温度３５±２℃、湿度８５％の恒温槽に入れて印加試験を行う。ここで、印加時は、（２）の場合と印加極性を逆転させる。
【０１２７】
（５）４日間経過後、温度３５±２℃、湿度８５％の恒温槽にて、くし歯パターンの絶縁抵抗値を測定する。ここで、測定時は、（３）の場合と極性を逆転させる。なお、このときの絶縁抵抗値を、以下「９６時間後絶縁抵抗値」という。
【０１２８】
（６）参考値として、（４）のサンプルを、温度２３℃、湿度５０％の雰囲気下に約３時間放置し、乾燥後の絶縁抵抗値を測定した。なお、このときの絶縁抵抗値を、以下「乾燥後絶縁抵抗値」という。
【０１２９】
ここで、ＩＰＣ−６５０の絶縁抵抗試験規格値は、くし歯間隔が１．２７ｍｍでＩＲ値が１×１０¹¹Ω、くし歯間隔が０．３１８ｍｍでＩＲ値が２×１０¹⁰Ωである。
【０１３０】
図８は絶縁抵抗の測定結果を示す図である。図８では、実施例のポリウレタン組成物を用いた場合を実線で、比較例６のエポキシ樹脂組成物を用いた場合を破線で、アンダーフィル材を塗布しない場合を一点鎖線で示している。
【０１３１】
図８に示したように、初期絶縁抵抗値は、３種とも規格値２×１０¹⁰Ω以上の値を示している。しかし、比較例６のエポキシ樹脂組成物を用いた場合には、１時間後絶縁抵抗値の測定時点で、すでに規格値を外れ、９６時間後絶縁抵抗値および乾燥後絶縁抵抗値とも規格値を外れたままである。
【０１３２】
一方、実施例のポリウレタン組成物を用いた場合には、１時間後絶縁抵抗値、９６時間後絶縁抵抗値とも、恒温槽内での測定において終始規格値を上回り、乾燥後絶縁抵抗値も、規格値を下回ることがない。したがって、実施例のポリウレタン組成物は、高い電気絶縁信頼性を実現することができる。
【０１３３】
このような高い電気絶縁信頼性は、本発明の熱硬化性ポリウレタン組成物が、炭化水素系ポリオールから得られる末端イソシアネート基含有ウレタンプレポリマーを、その組成に含有していることによる寄与が大きい。また、熱硬化性ポリウレタン組成物の高い電気絶縁信頼性により、微細電極ピッチのはんだ接合間の電気絶縁性を確保することが可能になる。
【０１３４】
以上説明したように、本発明に係る熱硬化性ポリウレタン組成物をアンダーフィル材に用いることにより、フラックス洗浄を行うことなく、アンダーフィル材を電子回路基板と電子部品との間隙に充填することができる。その結果、実装基板における接着性および電気絶縁性を維持しつつ、電子部品実装工程を簡略化することができ、実装基板の生産性を向上することができる。
【０１３５】
また、アンダーフィル材を用いた実装基板製造においては、実装される電子部品に対向する位置に細孔を設けた電子回路基板を使用してもよい。
図９は細孔を有する電子回路基板を用いた実装基板の断面図、図１０は図９の実装基板を実装面と反対の面の側から見た図である。
【０１３６】
実装基板３０の電子回路基板３１には、これに実装されるＣＳＰ３２に対向する位置に、直径が０．１ｍｍから１．０ｍｍの細孔３３が形成されている。この電子回路基板３１に、ＣＳＰ３２がはんだボール３４を介して実装され、その間隙にアンダーフィル材３５が充填される。
【０１３７】
ここで、電子回路基板３１とＣＳＰ３２との間隙にアンダーフィル材３５を充填する際には、空気が巻き込まれる場合がある。しかし、このような細孔３３を有する電子回路基板３１では、充填時に巻き込まれた空気を、細孔３３から逃がすことができる。したがって、アンダーフィル材３５を円滑かつ確実に、間隙に充填することができるとともに、従来、アンダーフィル材３５の硬化時に発生する可能性の高かったポップコーン現象を回避することができる。これにより、ＣＳＰ３２と電子回路基板３１との接着信頼性を向上させることができる。
【０１３８】
また、電子回路基板には、塗布したアンダーフィル材の流出を回避するためのダムを形成しておくようにしてもよい。
図１１はダム構造を有する電子回路基板を用いた実装基板の平面図、図１２はダム構造を有する電子回路基板を用いた実装基板の断面図である。
【０１３９】
実装基板４０の電子回路基板４１上には、電子回路基板４１との間隙にアンダーフィル材４２が充填されるＣＳＰ４３と、充填されない表面実装型の半導体素子４４とが隣接して実装されている。
【０１４０】
ここで、ＣＳＰ４３に対してアンダーフィル材４２を充填しようとすると、特にこのアンダーフィル材４２の粘度が低い場合には、塗布したアンダーフィル材４２が、半導体素子４４側へと流出する可能性がある。一般に、空気の誘電率は約１程度であるが、アンダーフィル材４２の誘電率は約４程度である。例えば、この実装基板４０が、ギガヘルツ帯の高周波信号処理が行われる用途に用いられる場合には、アンダーフィル材４２の有無が、その高周波特性（いわゆる寄生容量現象）に大きく影響する。すなわち、アンダーフィル材４２が充填されない半導体素子４４の側に、アンダーフィル材４２が充填されてしまうことを回避する必要がある。そのため、電子回路基板４１の実装面側には、あらかじめ、ＣＳＰ４３と半導体素子４４のリード４４ａとの間に、ダム４５を形成する。
【０１４１】
このダム４５は、温度１５０℃で１分間の条件で硬化する速硬性シリコーン樹脂（東レダウンコーニング社製ＤＡ６５２３）で形成する。その形成の際には、この速硬性シリコーン樹脂をディスペンサにより塗布した後、これを、ピーク温度２３０℃で行うリフローはんだ付けのときに硬化させる。したがって、アンダーフィル材４２を塗布する前に、速硬性シリコーン樹脂を硬化させてダム４５を形成しておくことができる。また、このような速硬性シリコーン樹脂は、剥離性、柔軟性があるため、ダム４５の材質として好適である。
【０１４２】
このように電子回路基板４１にダム４５を形成することにより、アンダーフィル材４２が充填されるＣＳＰ４３の側と充填されない半導体素子４４の側との作り分けが可能となる。したがって、高周波帯での使用環境下にあっても、寄生容量現象などを回避して高周波特性に与える影響をなくし、良好な周波数特性の実装基板４０を形成することができる。
【０１４３】
なお、ここで用いる速硬性シリコーン樹脂は、１２０℃から１８０℃の加熱温度範囲で、１０分以内の短時間で硬化するように設計されたものである。主成分は、分子中に、ケイ素原子に結合した少なくとも２個のアルケニル基を有するジメチルポリシロキサンである。このほか、架橋剤として、分子中に、ケイ素原子結合した少なくとも２個の水素原子を有する有機水素化ポリシロキサンを、ヒドロシリル化反応触媒の存在下で加熱硬化させたものが用いられる。さらに、必要に応じて、シリカなどの充填剤、その他の添加剤を用いてもよい。ダム材として用いる速硬性シリコーン樹脂には、ヒドロシリル化反応用金属触媒を熱可塑性樹脂でマイクロカプセル化した熱活性触媒を処方したものを用いるのが好ましい。
【０１４４】
また、上記のダム４５が形成されている電子回路基板４１のＣＳＰ４３に対向する位置に、図９および図１０に示したものと同様の細孔を形成しもよい。これにより、アンダーフィル材４２の流出が防止されるとともに、塗布時に巻き込まれた空気の逃げ道が確保されるようになる。
【０１４５】
（付記１） 熱硬化性ポリウレタン組成物において、
炭化水素系ポリオールから得られる末端イソシアネート基含有ウレタンプレポリマーと、ポリエーテルポリオールから得られる末端イソシアネート基含有ウレタンプレポリマーとの重量比９：１から２：８の混合物と、
エポキシ樹脂と、
オルガノポリシロキサン化合物と、
前記オルガノポリシロキサン化合物のブリードを防止するブリード防止剤と、
シランカップリング剤と、を有し、体積抵抗率が１．０×１０⁹Ω・ｃｍ以上であることを特徴とする熱硬化性ポリウレタン組成物。
【０１４６】
（付記２） ５重量％から３０重量％の前記エポキシ樹脂と、０．５重量％から５重量％の前記オルガノポリシロキサン化合物と、０．０１重量％から１．０重量％の前記ブリード防止剤と、０．５重量％から５重量％の前記シランカップリング剤と、を有していることを特徴とする付記１記載の熱硬化性ポリウレタン組成物。
【０１４７】
（付記３） 表面の活性基を微粉体により被覆した微粉粒子被覆硬化剤を有することを特徴とする付記１記載の熱硬化性ポリウレタン組成物。
（付記４） 温度１６０℃以上で加熱された場合の接着力が０．１Ｎ／ｍｍ²以下であることを特徴とする付記１記載の熱硬化性ポリウレタン組成物。
【０１４８】
（付記５） 突起状電極を有する電子部品と、電子部品が実装される電子回路基板との間隙にアンダーフィル材が充填された実装基板において、
炭化水素系ポリオールから得られる末端イソシアネート基含有ウレタンプレポリマーと、ポリエーテルポリオールから得られる末端イソシアネート基含有ウレタンプレポリマーとの重量比９：１から２：８の混合物と、
エポキシ樹脂と、
オルガノポリシロキサン化合物と、
前記オルガノポリシロキサン化合物のブリードを防止するブリード防止剤と、
シランカップリング剤と、を有する体積抵抗率１．０×１０⁹Ω・ｃｍ以上の熱硬化性ポリウレタン組成物を含むアンダーフィル材を有することを特徴とする実装基板。
【０１４９】
（付記６） 前記熱硬化性ポリウレタン組成物は、５重量％から３０重量％の前記エポキシ樹脂と、０．５重量％から５重量％の前記オルガノポリシロキサン化合物と、０．０１重量％から１．０重量％の前記ブリード防止剤と、０．５重量％から５重量％の前記シランカップリング剤と、を有していることを特徴とする付記５記載の実装基板。
【０１５０】
（付記７） 前記熱硬化性ポリウレタン組成物は、表面の活性基を微粉体により被覆した微粉粒子被覆硬化剤を有することを特徴とする付記５記載の実装基板。
【０１５１】
（付記８） 前記熱硬化性ポリウレタン組成物は、温度１６０℃以上で加熱された場合の接着力が０．１Ｎ／ｍｍ²以下であることを特徴とする付記５記載の実装基板。
【０１５２】
（付記９） 突起状電極を有する電子部品と、電子部品が実装される電子回路基板との間隙にアンダーフィル材が充填された実装基板の製造方法において、
電子回路基板の実装面をフラックス塗布処理またはフラックスを含むはんだペーストを印刷し、
前記実装面に電子部品の突起状電極をはんだ接合し、
フラックス洗浄することなく前記電子部品と前記電子回路基板との間隙にアンダーフィル材を充填することを特徴とする実装基板の製造方法。
【０１５３】
（付記１０） 突起状電極を有する電子部品と、電子部品が実装される電子回路基板との間隙にアンダーフィル材が充填された実装基板の電子部品のリペア方法において、
電子回路基板に実装されている電子部品におもりを吊るし、
前記電子部品の突起状電極のはんだを加熱により溶融し、
前記はんだの溶融の際に、アンダーフィル材を軟化させて前記電子部品を自由落下させることを特徴とするリペア方法。
【０１５４】
（付記１１） 前記はんだの溶融と前記アンダーフィル材の軟化とを検出するため、前記電子部品の近傍に、サーモセンサラベルを配置することを特徴とする付記１０記載のリペア方法。
【０１５５】
（付記１２） 前記はんだの溶融と前記アンダーフィル材の軟化とを検出するため、前記電子部品の近傍に、前記はんだよりも高い融点のはんだ材料を配置することを特徴とする付記１０記載のリペア方法。
【０１５６】
（付記１３） 突起状電極を有する電子部品が実装される電子回路基板において、
実装される電子部品に対向する位置に、アンダーフィル材の充填時に巻き込まれる空気が抜ける、直径０．１ｍｍから１．０ｍｍの細孔を有することを特徴とする電子回路基板。
【０１５７】
（付記１４） 突起状電極を有する電子部品が実装される電子回路基板において、
電子部品が実装される領域の外側に、塗布されたアンダーフィル材が流出するのを防止するためのダムが形成されていることを特徴とする電子回路基板。
【０１５８】
（付記１５） 前記ダムは、前記電子部品のはんだ付け温度以下の温度で硬化するシリコーン樹脂からなることを特徴とする付記１４記載の電子回路基板。
（付記１６） 前記電子部品に対向する位置に、アンダーフィル材の充填時に巻き込まれる空気が抜ける、直径０．１ｍｍから１．０ｍｍの細孔を有することを特徴とする付記１４記載の電子回路基板。
【０１５９】
【発明の効果】
以上説明したように本発明では、熱硬化性ポリウレタン組成物が、その組成に、末端イソシアネート基含有ウレタンプレポリマーおよびエポキシ樹脂のほか、オルガノポリシロキサン化合物、ブリード防止剤およびシランカップリング剤を有する構成にした。このため、熱硬化性ポリウレタン組成物をアンダーフィル材に用いる場合には、フラックス洗浄をすることなく、その充填が可能になるとともに、電子部品と電子回路基板とを充分な強度で接着することができる。
【０１６０】
また、電子回路基板に細孔を設けることで、アンダーフィル材の充填の際、空気ボイドの発生を防止し、接着不良の発生を防止できる。
さらに、電子回路基板にダムを形成することで、アンダーフィル材の充填時の流出を防止して接着信頼性を向上できるとともに、良好な周波数特性の実装基板を形成することができる。
【図面の簡単な説明】
【図１】アンダーフィル材が用いられている実装基板の断面概略図である。
【図２】接着性評価方法の説明図である。
【図３】比較例４のポリウレタン組成物を用いた場合の実装基板の断面概略図である。
【図４】実施例のポリウレタン組成物を用いた場合の実装基板の断面概略図である。
【図５】落下試験方法の説明図である。
【図６】アンダーフィル材にかける温度と接着力の関係を示す図である。
【図７】接着力の回復性を示す図である。
【図８】絶縁抵抗の測定結果を示す図である。
【図９】細孔を有する電子回路基板を用いた実装基板の断面図である。
【図１０】図９の実装基板を実装面と反対の面の側から見た図である。
【図１１】ダム構造を有する電子回路基板を用いた実装基板の平面図である。
【図１２】ダム構造を有する電子回路基板を用いた実装基板の断面図である。
【符号の説明】
１０，１０ａ，１０ｂ，３０，４０ 実装基板
１１，１１ａ，１１ｂ，２３，３１，４１ 電子回路基板
１２，３２，４３ ＣＳＰ
１３，３４ はんだボール
１４，１４ａ，１４ｂ，２１，３５，４２ アンダーフィル材
１５ａ フラックス残渣
２２ Ｔ字型釘
２４ ホットプレート
３３ 細孔
４４ 半導体素子
４４ａ リード
４５ ダム
５０ タイル床[0001]
BACKGROUND OF THE INVENTION
  The present inventionMounting board manufacturing methodIn particular, in the gap between the electronic component having a protruding electrode such as a solder ball and the electronic circuit board on which the electronic component is mounted.Underfill materialFillMounting board manufacturing methodAbout.
[0002]
[Prior art]
In recent years, from the viewpoint of miniaturization and improvement in mounting density, an electronic component has been formed in a protruding shape, and is mounted on an electronic circuit board via the protruding electrode. Electronic components having protruding electrodes include BGA (Ball-Grid-Array), CSP (Chip-Size-Package), FC (Flip-Chip), LGA (Land-Grid-Array package), SON (Small -Outline-Non lead package), QFN (Quad-Flatpack-Non lead package), BCC (Bump-Chip-Carrier package) and the like.
[0003]
Since such an electronic component has a small connection area when mounted on an electronic circuit board, there is a risk of causing a connection failure due to a drop impact, external force to the electronic circuit board, or deformation due to heat. For this reason, an underfill material is filled in the gap between the electronic component and the electronic circuit board on which the electronic component is mounted and cured, thereby bonding the electronic component to the electronic circuit board and improving the connection reliability.
[0004]
Conventionally, as such an underfill material, Japanese Patent Application Laid-Open No. 10-204259 proposes a thermosetting epoxy composition mainly composed of an epoxy resin. Recently, a thermosetting type comprising a terminal isocyanate group-containing urethane prepolymer, which is a urethane prepolymer containing an isocyanate (NCO) group at the molecular terminal, and a fine particle-coated hardener coated with fine powder particles on the surface of the hardener particle. Urethane-based compositions have been proposed. However, some problems still remain when using an epoxy-based composition or a urethane-based composition as the underfill material.
[0005]
For example, when an epoxy-based composition is used for an underfill material, firstly, since the curing temperature is high and the curing time is long, the thermal damage to the electronic circuit board and the mounted parts is large, and the work efficiency is lowered. Was invited. In this case, there is still a problem with respect to the amount of energy consumed by processing at a high temperature for a long time. Epoxy compositions generally require heat curing for 60 minutes at a temperature of 80 ° C. to 10 minutes at a temperature of 150 ° C. When this is cured at a temperature as low as 80 ° C. under short heating conditions, a curing reaction will occur even at room temperature. Therefore, when the epoxy composition is stored, it is necessary to store it at a temperature around 5 ° C. or lower, and there is a problem in the storage stability.
[0006]
And the 2nd problem in the case of using an epoxy-type composition is the point that softening does not advance unless the hardened epoxy resin is heated to the high temperature of 250 degreeC or more. For this reason, when the electronic component once mounted is repaired, the electronic circuit board and the electronic component are exposed to a high temperature, and thermal damage increases. Furthermore, after removal of the electronic component, an epoxy resin residue adheres to the surface of the electronic circuit board, and it is necessary to remove it. Further, during the repairing operation, other adjacent electronic components are also exposed to a high temperature by heating the cured epoxy resin. Therefore, during repair work of the target electronic component, with heating, the adhesive force between other electronic components and the electronic circuit board may be reduced, leading to poor connection or reduced impact resistance. is there.
[0007]
In contrast to the epoxy-based composition having such problems, the urethane-based composition can be cured at a low temperature of 60 ° C. or higher, and is sufficiently sufficient at 80 ° C. for 10 minutes or less in heat curing conditions. It can be cured. Furthermore, this urethane-based composition can be stored at room temperature and has good storage stability. Moreover, the softening temperature is lower than that of the epoxy composition, and the mounted electronic component can be easily removed by local heating in a temperature range of 180 ° C. to 250 ° C.
[0008]
By the way, when an electronic component is mounted on an electronic circuit board via a protruding electrode such as a solder ball, first, flux processing is performed on the mounting surface side, and then solder bonding to the electronic circuit board is performed. Is called. And the method of filling and hardening the underfill material which consists of the above-mentioned epoxy-type composition and urethane type composition in the gap | interval of the joined electronic component and an electronic circuit board is taken.
[0009]
[Problems to be solved by the invention]
However, when a urethane-based composition is used for the underfill material, there is a flux residue on the surface of the electronic circuit board when the underfill material is filled in the gap between the bonded electronic component and the electronic circuit board and cured. In this case, penetration of the underfill material into the surface of the electronic circuit board is hindered, and as a result, sufficient adhesive force between the electronic component and the electronic circuit board due to the underfill material cannot be secured. Therefore, after soldering, before the underfill material is filled, flux cleaning using a chemical solution is performed to remove the flux residue on the surface of the electronic circuit board.
[0010]
In this flux cleaning, along with the treatment with the chemical solution, there is a possibility that the performance reliability of the mounted electronic component may be reduced, and also a flux residue cleaning step and a substrate drying step after cleaning are necessary. The work efficiency was reduced. In addition to the need for cleaning equipment for flux cleaning, management costs for reducing environmental burdens, such as treatment of waste liquid related to the cleaning, are also required.
[0011]
In addition, when filling the gap between the electronic component and the electronic circuit board with the underfill material, since the gap is several tens μm to several hundred μm, the gap may be filled unless the viscosity is, for example, 5000 mPa · s. Can not. And even if it is such a low-viscosity underfill material, air may be involved at the time of filling. When the underfill material is cured in this state, a so-called popcorn phenomenon occurs in which air voids that have lost their escape path burst. As a result, a bonding failure between the electronic component and the electronic circuit board may occur, or a decrease in adhesion may be caused.
[0012]
Furthermore, with the recent increase in the density of the mounting substrate, the electrode gap of the electronic component and the conductor gap of the electronic circuit board are narrowed, and the underfill material used is required to have high electrical insulation reliability.
[0013]
In addition, in the case of a mounting substrate that performs high-frequency signal processing in the gigahertz band, such as a mobile phone, the presence or absence of the underfill material depends on the difference in dielectric constant ε between air and the underfill material, and the high-frequency characteristics of the mounting substrate. It has a big impact. Therefore, it is necessary to avoid filling the electronic component that does not require adhesion with the underfill material, and to make a filled portion and an unfilled portion separately.
[0014]
  The present invention has been made in view of such points, and has high electrical insulation properties and bonds desired electronic components and electronic circuit boards with sufficient strength without performing flux cleaning. CanMounting board manufacturing methodThe purpose is to provide.
[0016]
[Means for Solving the Problems]
  In the present invention, in order to solve the above problems,In a mounting substrate manufacturing method in which an underfill material is filled in a gap between an electronic component having a protruding electrode and an electronic circuit substrate on which the electronic component is mounted, the mounting surface of the electronic circuit substrate includes a flux coating process or a flux. Solder paste is printed, the protruding electrode of the electronic component is soldered to the mounting surface, the underfill material is filled in the gap between the electronic component and the electronic circuit board without cleaning the flux, and the underfill material is A mixture of a terminal isocyanate group-containing urethane prepolymer obtained from a hydrocarbon-based polyol and a terminal isocyanate group-containing urethane prepolymer obtained from a polyether polyol in a weight ratio of 9: 1 to 2: 8, an epoxy resin, and an organo Bleed of the polysiloxane compound and the organopolysiloxane compound The volume resistivity of 1.0 × 10 having a bleed inhibitor to stop, a silane coupling agent, a ⁹ A method for producing a mounting board comprising a thermosetting polyurethane composition having a resistance of Ω · cm or moreIs provided.
[0017]
As shown in FIG. 1, the thermosetting polyurethane composition having the above configuration is filled in a gap between the electronic component CSP 12 and the electronic circuit board 11 on which the electronic component CSP 12 is mounted, as shown in FIG. The circuit board 11 is bonded. The thermosetting polyurethane composition used for the underfill material 14 has, in addition to the terminal isocyanate group-containing urethane prepolymer and epoxy resin, an organopolysiloxane compound, a bleed inhibitor and a silane coupling agent. . Thereby, permeation of the underfill material 14 to the surface of the electronic circuit board 11 is not hindered by the flux.
[0018]
Furthermore, the thermosetting polyurethane composition having the above-described structure exhibits high adhesive strength, cures at a relatively low temperature, and recovers adhesive strength even after being softened by heating. Therefore, in the mounting substrate 10 in which this thermosetting polyurethane composition is used for the underfill material 14, the electronic circuit substrate 11 and the CSP 12 are bonded with sufficient strength, and the CSP 12 is easily repaired.
[0019]
  Manufacturing method of mounting substrate of the present inventionTo the lawAccording to this, efficiency can be improved by omitting the flux cleaning process., ExpensesThe work burden is also reduced.
[0020]
  Also, RealElectronic circuit board having pores through which excess air and excess air can be removed at the position facing the electronic component to be mountedIf you useThe generation of air voids when filling the underfill material is prevented, and the underfill material is sufficiently adequately filled in the lower part of the component, thereby avoiding poor bonding between the electronic component and the electronic circuit board and a decrease in the adhesive force. .
[0021]
  further, ElectricAn electronic circuit board in which a dam for preventing the applied underfill material from flowing out is formed outside the region where the child component is mounted.If you useThe underfill material can be prevented from flowing out to an electronic component that does not require bonding with the underfill material, and a filled portion and an unfilled portion can be separately formed on the mounting substrate.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
In the mounting substrate, an underfill material is filled in the gap between the electronic component on which the protruding electrodes such as solder balls are formed and the electronic circuit substrate on which the electronic component is mounted, and the electronic component and the electronic circuit substrate Is glued. A thermosetting polyurethane composition containing a terminal isocyanate group-containing urethane prepolymer, an epoxy resin, a polyorganosiloxane compound, a bleed inhibitor and a silane coupling agent is used for the underfill material. Furthermore, a curing agent, a plasticizer, an adhesion promoter, an antiaging agent, a dehydrating agent and the like are blended with the thermosetting polyurethane composition as necessary.
[0023]
The main component of such a thermosetting polyurethane composition is a terminal isocyanate group-containing urethane prepolymer. This terminal isocyanate group-containing urethane prepolymer can be obtained by reacting a polyol with an excess of a polyisocyanate compound.
[0024]
As the polyol used for the production of the terminal isocyanate group-containing urethane prepolymer, a hydrocarbon-based polyol having a main chain composed of C—C bonds such as an acrylic polyol, a polybutadiene-based polyol, and a polyolefin-based polyol is used as an essential component.
[0025]
In addition to these hydrocarbon-based polyols, polyether polyols such as polyoxyalkylene polyols, modified polyether polyols, and polytetramethylene ether glycol can be used in combination with the hydrocarbon-based polyols. Alternatively, polyester polyols such as condensed polyester polyols, cocoton polyester polyols, and polycarbonate diols can be used in combination with hydrocarbon polyols.
[0026]
On the other hand, examples of the polyisocyanate compound to be reacted with the above polyol include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, isopropylidenebis (4- Cyclohexyl isocyanate) and hydrogenated xylene diisocyanate can be used.
[0027]
Usually, the polyol and the polyisocyanate compound are reacted under the condition that the NCO / OH equivalent ratio is 1.5 to 2.5, preferably 1.9 to 2.2. Thereby, the terminal isocyanate group containing urethane prepolymer whose molecular terminal is a urethane prepolymer having an isocyanate group is generated. The molecular weight of the terminal isocyanate group-containing urethane prepolymer produced by this reaction is adjusted to a range of 800 to 50000, preferably 1000 to 10,000.
[0028]
Here, among the terminal isocyanate group-containing urethane prepolymers, in particular, the hydrocarbon polyol urethane prepolymer (PB prepolymer) obtained by using a polybutadiene polyol gives the material electrical insulation and its volume resistance. 1.0 × 10 rate⁹A high value of Ω · cm or more can be obtained. However, this PB-based prepolymer has a relatively high viscosity, and by itself, it is difficult to fill a narrow gap between the electronic component and the electronic circuit board. Therefore, it is preferable to use a polyether polyol-based urethane prepolymer (PPG-based prepolymer) using a polyether polyol having a relatively low viscosity to reduce the viscosity. At this time, the mixing ratio of the PB prepolymer and the PPG prepolymer is usually 9: 1 to 2: 8, preferably 9: 1 to 5: 5.
[0029]
Further, instead of using a mixture of PB-based prepolymer and PPG-based prepolymer, a mixture in which a polybutadiene-based polyol and a polyether polyol are mixed at a predetermined ratio is used, and this is reacted with an excess amount of a polyisocyanate compound to obtain terminal isocyanate It is also possible to obtain a group-containing urethane prepolymer.
[0030]
The epoxy resin contained in the thermosetting polyurethane composition tends to toughen the cured product of this composition. Furthermore, the wettability and adhesion reliability of the electronic circuit board with respect to the flux-treated surface are improved without reducing the volume resistivity.
[0031]
As the epoxy resin used for the thermosetting polyurethane composition, bisphenol A type, F type, AD type, or phenol type, cresol type, cycloaliphatic type, glycidyl ester type, glycidylamine type, etc. can be used. It is preferable to use a liquid at room temperature.
[0032]
The epoxy resin is used by blending in the range of 5 to 30% by weight, preferably 7 to 20% by weight of the thermosetting polyurethane composition. When the blending amount is less than 5% by weight, the physical properties of the cured product are not improved. On the other hand, when it exceeds 15% by weight, the viscosity increases, so that workability is lowered, and further, the permeability to the gap between the electronic component and the electronic circuit board tends to be lowered.
[0033]
Moreover, an epoxy resin is used so that it may become the range of 1 weight part to 15 weight part with respect to 100 weight part of terminal isocyanate group containing urethane prepolymers. If it is less than 1 part by weight, improvement in physical properties due to the epoxy resin cannot be expected, and improvement in adhesion to the flux-treated surface cannot be obtained. Moreover, when it exceeds 15 weight part, a viscosity will become high, workability | operativity will fall, and also the permeability to the gap | interval of an electronic component and an electronic circuit board will be impaired.
[0034]
The organopolysiloxane compound used in the thermosetting polyurethane composition is used for the purpose of improving the wettability of the electronic circuit board with respect to the flux-treated surface and improving the adhesion. Furthermore, this organopolysiloxane compound contributes to the improvement of the permeability of the thermosetting polyurethane composition.
[0035]
As such an organopolysiloxane compound, HOSi-group, HSi-group, H_ThreeIt contains CSi-groups, and dimethylpolysiloxane compounds, diethylpolysiloxane compounds, diphenylpolysiloxane compounds, dimethyl-diphenylpolysiloxane compounds, diethyl-diphenylpolysiloxane compounds, etc. can be used and are selected from these. Use at least one kind.
[0036]
The molecular weight of the organopolysiloxane compound is usually in the range of about 800 to 30000, preferably about 900 to 20000. The organopolysiloxane compound is contained in the range of 0.5% to 5.0% by weight of the thermosetting polyurethane composition. If the content is less than 0.5% by weight, no effect can be obtained in improving adhesion promoting property, wettability, and permeability into the gap between the electronic component and the electronic circuit board of the thermosetting polyurethane composition. Moreover, when content exceeds 5.0 weight%, the tendency for a viscosity to rise with progress of days will be seen, and the storage stability of a thermosetting polyurethane composition will be impaired.
[0037]
The anti-bleeding agent improves the compatibility between the epoxy resin and the organopolysiloxane compound, and suppresses separation of the organopolysiloxane compound from the thermosetting polyurethane composition.
[0038]
  As an anti-bleeding agent used in the thermosetting polyurethane composition, unlike the above-described organopolysiloxane compound, as a functional group at both terminals or part of the side chainAPolysiloxane compounds containing mino groups, imino groups, carboxyl groups, mercapto groups, glycidyl groups, and modified products thereof are used.In addition, a modified product of a polysiloxane compound containing a hydroxyl group as a functional group at both ends or part of a side chain is used.
[0039]
Examples of the modified body include those obtained by inactivating reactive functional groups contained in the original polysiloxane compound. Inactivation methods include addition reaction of polyhydric active hydrides via diisocyanate compounds, graft polymerization reaction with (meth) acrylic acid esters as side chains, or inclusion in thermosetting polyurethane compositions. There is a method in which a glycidyl group-containing compound having compatibility with an epoxy resin to be added is reacted. Specific examples are shown below.
[0040]
As a first method for inactivating reactive functional groups, for example, (a) a terminal hydroxyl group-containing polysiloxane compound is used as a polysiloxane compound containing the predetermined functional group at both ends or side chains, Further, (b) a polyvalent active hydride, (c) a diisocyanate compound, and (d) a both-end active hydrogen chain extender are used as raw materials. The reaction conditions are (a) component 1 mol, (b) component 2 to 5 mol, (d) component 2 to 6 mol, and the components (a), (b) and (d) The component (c) is made to react with the total mole of (1).
[0041]
In this case, polyoxyalkylene ether diol, propylene glycol, polyethylene glycol, polypropylene ethylene glycol, bisphenol A type propylene and / or ethylene adduct, polyester polyol, etc. are used as the polyvalent active hydride as component (b). be able to.
[0042]
The diisocyanate compound as component (c) includes aromatic diisocyanates such as 2,4- or 2,6-tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), xylylene diisocyanate, and hexamethylene diisocyanate. Aliphatic diisocyanates such as lysine diisocyanate, isophorone diisocyanate, hydrogenated MDI, and hydrogenated TDI can be used.
[0043]
And, as the both-end active hydrogen chain extender as component (d), ethylene glycol, propylene glycol, butanediol, dimethylolcyclohexane, methyliminodiethanol, dimethylolpropionic acid, ethylenediamine, hexamethylenediamine, etc. can be used. it can.
[0044]
As a first reaction example using this first method, first, a terminal hydroxyl group-containing polysiloxane compound as component (a) and a diisocyanate compound as component (c) are used in an appropriate solvent if necessary. The reaction is carried out in the temperature range of 20 ° C. to 120 ° C. for 2 hours to 120 hours to form a monoadduct. Furthermore, the polyoxyalkylene ether diol as the component (b) and the diisocyanate compound as the component (c) are reacted under the same conditions to form a monoadduct. Examples of the solvent that can be used here include ethyl acetate, butyl acetate, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, chloroform, and tetrahydrofuran.
[0045]
Next, each mono-adduct formed is subjected to a block addition reaction in the presence of both terminal active hydrogen chain extenders as component (d) at a temperature range of 20 ° C. to 120 ° C. for 3 hours to 24 hours. Thus, a modified product of the terminal hydroxyl group-containing polysiloxane compound is obtained.
[0046]
In addition, as a second reaction example using this first method, the components (a), (b), (c) and (d) may be used in a one-batch system in the above-mentioned solvent if necessary. This is a block addition reaction. In addition to the first reaction example, a modified product of the terminal hydroxyl group-containing polysiloxane compound can be obtained by the second reaction example.
[0047]
In addition, as said (a) component, it can replace with the terminal hydroxyl group containing polysiloxane compound, and can also use the polysiloxane compound containing an amino group or an imino group at the terminal.
[0048]
As a second method for inactivating the reactive functional group, for example, (a) a mercapto group-containing polysiloxane compound is used as the polysiloxane compound having the predetermined functional group at both ends or side chains. (B) Graft polymerization of (meth) acrylic acid ester.
[0049]
This graft polymerization reaction may be carried out by heating in the presence of a polymerization initiator in a suitable organic solvent (dichloromethane, tetrahydrofuran, dimethylformamide, etc.) or by a photopolymerization reaction in the presence of a photopolymerization initiator. Let Thereby, the modified body by the graft polymerization reaction of a mercapto group containing polysiloxane compound can be obtained.
[0050]
As the (a) component mercapto group-containing polysiloxane compound used here, a commercially available product having a mercapto group equivalent of about 3300 to 33000 is used.
In addition, as the (meth) acrylic acid ester used as the component (b), for example, methyl (meth) acrylate, ethyl (meth) acrylate, benzyl (meth) acrylate, butyl (meth) acrylate, or glycidyl (meth) acrylate is used. be able to.
[0051]
In this second method, 10 parts by weight to 20 parts by weight, preferably 15 parts by weight of (meth) acrylic acid ester as component (b) with respect to 100 parts by weight of the mercapto group-containing polysiloxane compound as component (a). The graft polymerization reaction is carried out in the range of from 20 to 20 parts by weight.
[0052]
The third method of inactivating the reactive functional group is as follows: (a) a polysiloxane compound containing an amino group, a carboxyl group or a mercapto group at both ends or side chains; and (b) a compound containing a glycidyl group. Is an addition reaction. As the amino group-containing polysiloxane compound, carboxyl group-containing polysiloxane compound and mercapto group-containing polysiloxane compound used as the component (a), commercially available products can be used. Moreover, said epoxy resin can be used as a glycidyl group containing compound which is (b) component.
[0053]
The addition reaction in this third method is necessary under heating at room temperature to 40 ° C. to 130 ° C. so that the glycidyl group of component (b) becomes excessive with respect to the reactive functional group of component (a). Depending on the reaction, the reaction is carried out by adding a catalyst in an appropriate solvent (tetrahydrofuran, toluene, xylene, n-hexane, cyclohexane, chloroform, ethanol, methanol, etc.). The modified product is colorless and transparent or light yellow or white after removal of the solvent.
[0054]
The bleed inhibitor described above uses 0.01% by weight to 1.0% by weight of the thermosetting polyurethane composition. If it is less than 0.01% by weight, bleeding of the organopolysiloxane compound contained in the thermosetting polyurethane composition cannot be suppressed, and if it exceeds 1.0% by weight, the thermosetting polyurethane composition Tend to increase with the passage of days.
[0055]
The silane coupling agent used in the thermosetting polyurethane composition improves the wettability, adhesiveness, and permeability to the flux-treated surface, like the above organopolysiloxane compound.
[0056]
The silane coupling agent is used in the range of 0.5% to 5.0% by weight of the thermosetting polyurethane composition. If it is less than 0.5% by weight, the effect of improving the adhesion promoting property, wettability, and permeability to the gap between the electronic component and the electronic circuit board of the thermosetting polyurethane composition cannot be obtained. Moreover, when it exceeds 5.0 weight%, the tendency for a viscosity to rise with the progress of days will be seen, and the storage stability of a thermosetting polyurethane composition will be impaired.
[0057]
Examples of the silane coupling agent include aminosilane compounds (for example, γ-aminopropyltriethoxysilane, β-aminoethyltrimethoxysilane, γ-aminopropyldiethoxysilane, γ-allylaminopropyltriethoxysilane, β- (β- Aminoethylthioethyl) diethoxymethylsilane, β- (β-aminoethylthioethyl) triethoxysilane, β-phenylaminopropyltrimethoxysilane, γ-cyclohexylaminopropyltrimethoxysilane, β-benzylaminopropyltrimethoxysilane , Γ- (vinylbenzylaminopropyl) triethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, β-aminoethylaminomethylmethoxysilane, γ- [β- (β-aminoethylamino Ethyla ) Propyl] triethoxysilane, N- (3-triethoxysilylpropyl) urea, etc.); mercaptosilane compounds (for example, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, mercaptomethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane and the like; epoxy silane (for example, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, [2- (3,4-epoxy-4-methylcyclohexyl) propyl) methyldiethoxy Silane, (3-glycidylpropyl) methyldiethoxysilane, 3-glycidylpropyl-trimethoxysilane, etc.); isocyanate silane compounds (for example, γ-isocyanatopropyltriethoxysilane, γ-isocyanate silane) Pills trimethoxysilane), or the like can be used.
[0058]
In addition, when using what has an active hydrogen group which reacts with the isocyanate group of terminal isocyanate group containing urethane prepolymer among silane coupling agents, it is made to react with another silane coupling agent beforehand, and an active hydrogen group is made into It is desirable to inactivate the functional group it has.
[0059]
In addition to the above composition, the thermosetting polyurethane composition may contain a curing agent, a plasticizer, an adhesion promoter, an antiaging agent, a dehydrating agent, and the like.
As the curing agent used in the thermosetting polyurethane composition, a fine particle-coated curing agent obtained by coating the surface of a solid curing agent having a specific melting point with fine powder particles and inactivating the surface active groups of the curing agent particles is preferable. Used for.
[0060]
Inactivation of the surface active group is carried out by grinding the curing agent into curing agent particles having a central particle diameter of 20 μm or less, mixing fine powder particles having a central particle diameter of 2 μm or less, and coating the surface of the curing agent particles. Done. The curing agent and the fine particle powder are mixed so that the weight ratio of the fine particle powder to the curing agent is in the range of 0.001 to 0.7, preferably 0.01 to 0.5. For this mixing, a shear friction mixing method in which fine particles are fixed to the surface of the curing agent, a high-speed impact mixing stirrer such as a jet mill, or a compression shear stirrer can be used.
[0061]
Examples of the curing agent used for such a fine particle coating curing agent include an active hydrogen group-containing polyamine compound that reacts with an isocyanate group, such as an imidazole compound (imidazole, 2-methylimidazole, 2-ethylimidazole, 2- Ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 2-dodecylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and their acetic acid, lactic acid, salicylic acid, benzoic acid, adipic acid, phthalate Carboxylic acid salts such as acid, citric acid, tartaric acid, maleic acid, trimellitic acid, etc.); imidazoline compounds (2-methylimidazoline, 2-phenylimidazoline, 2-undecylimidazoline, 2-heptadecylimidazoline, 1- ( -Hydroxy-3-phenoxypropyl) -2-phenylimidazoline, 1- (2-hydroxy-3-butoxypropyl) -2-methylimidazoline, etc.); amino compounds (4,4'-diaminodiphenylmethane, 2,4'- Diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 2,2′-diaminobiphenyl, 2,4′-diaminodiphenyl, 3,3′-diaminobiphenyl, 2,4-diaminophenol, 2,5-diaminophenol, o-phenylenediamine, m-phenylenediamine, 2,3-tolylenediamine, 2,4-tolylenediamine, 2,5-tolylenediamine, 2,6-tolylenediamine, 3 Aromatic amine compounds such as 1,4-tolylenediamine, 1,12-dodeca Aliphatic amine compounds such as diamine, 1,10-decanediamine, 1,8-octanediamine, 1,14-tetradecanediamine, and 1,16-hexadecanediamine); Guanazine compounds (such as dicyandiamine); Other acid anhydrides (Phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylated hexahydrophthalic anhydride, trimellitic anhydride, etc.), dibasic acid hydrazides (such as adipic acid dihydrazide, sebacic acid dihydrazide), guanamines (benzoguanamine) Etc.), melamine, and amine adduct systems (such as 2-ethyl-4-methylimidazole and bisphenol A epoxy resin adducts) can be used, and one or more of these can be selected and used.
[0062]
The fine particles used in the fine particle coating curing agent include titanium oxide, calcium carbonate, clay, silica, zirconia, carbon, alumina, talc, etc. for inorganic systems, and polyvinyl chloride and polyacrylic resins for organic systems. Polystyrene, polyethylene, polypropylene and the like can be used.
[0063]
In such a mixing treatment of the hardener and fine powder, the fine powder adheres to the surface of the hardener particles by the action of static electricity, melts and adheres due to heat generated by friction, impact or compression shear, The active groups on the surface of the hardener particles are coated with fine powder particles by being embedded and fixed, or chemically activated and fixed.
[0064]
The fine particle-coated hardener is activated when heated to the melting point of the hardener and softened and melted. That is, when the fine particle-coated hardener is softened and melted, the amino group which is the active group of the hardener reacts with the isocyanate group of the terminal isocyanate group-containing urethane prepolymer, and the terminal isocyanate group-containing urethane prepolymer is cured. The fine particle particle coating curing agent is used by blending it in a range where the equivalent ratio of the amino group to the isocyanate group of the terminal isocyanate group-containing urethane prepolymer is approximately 1.
[0065]
Furthermore, the fine particle coating curing agent is softened and melted to react with the terminal isocyanate group-containing urethane prepolymer and also react with the epoxy resin. Thereby, the toughness of the hardening body of a thermosetting polyurethane composition comes to improve.
[0066]
Plasticizers used in thermosetting polyurethane compositions include phthalic acid esters, isophthalic acid esters, adipic acid esters, azelaic acid esters, sebacic acid esters, maleic acid esters, fumaric acid esters, trimellitic acid esters, pyromellitic esters. Acid esters, phosphate esters, sulfonate esters, and the like can be used.
[0067]
As the adhesion promoter, titanate coupling agents, aluminum coupling agents, epoxy resins, phenol resins, and the like can be used.
As the anti-aging agent, hindered phenols, monophenols, bis-tris polyphenols, thiobisphenols, and the like can be used.
[0068]
A dehydrating agent contributes to the improvement of the storage stability of a thermosetting polyurethane composition. As the dehydrating agent, 1 to 10% by weight, preferably 2 to 5% by weight of the thermosetting polyurethane composition is usually used. As the dehydrating agent, calcium oxide, zeolite, silica gel, ethyl silicate, ethyl orthophosphate, ethyl formate, ethyl orthoacetate and the like can be used.
[0069]
In addition, the thermosetting polyurethane composition may contain a usual additive as required. Such additives include fillers, reinforcing agents (fibers such as glass fibers, cellulose, polyethylene powder, polypropylene powder, quartz powder, silica, mica, clay, aluminum, calcium carbonate, aluminum oxide, aluminum hydroxide, Gypsum, antimony oxide, bentonite, erodiol, lithopone, barite, titanium oxide, etc.), pigment, organic solvent (toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, etc.), reactive diluent (butyl glycidyl ether, N, NI-diglycidyl-o-toluidine, phenylglycidyl ether, styrene oxide, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, etc.) Reactive groups diluent (dioctyl phthalate, dibutyl phthalate, dioctyl adipate, and petroleum solvent), modified epoxy resins (urethane-modified epoxy resins, such as alkyd-modified epoxy resin) and the like.
[0070]
As shown above, the thermosetting polyurethane composition of the present invention has a terminal isocyanate group-containing urethane prepolymer, epoxy resin, organopolysiloxane compound, bleed inhibitor and silane coupling agent in its composition. . The thermosetting polyurethane composition having such a composition is 1.0 × 10⁹It is possible to realize a high volume resistivity of Ω · cm or more. And when using this thermosetting polyurethane composition for an underfill material, the viscosity is usually adjusted to 500 mPa · s to 50000 mPa · s, preferably 1000 mPa · s to 20000 mPa · s.
[0071]
This thermosetting polyurethane composition contains an organopolysiloxane compound and an anti-bleeding agent in its composition, so that it does not contain these and adheres to the flux-treated surface compared to conventional thermosetting epoxy resin compositions. Good sex. Furthermore, the adhesiveness is further improved by including a silane coupling agent in the composition. Therefore, flux cleaning which has been conventionally performed before filling with the underfill material becomes unnecessary.
[0072]
In addition, if a fine particle coating curing agent is blended with this thermosetting polyurethane composition, the room temperature solid curing agent is softened, melted and reactivated by heating to about the melting point of the curing agent. The thermosetting polyurethane composition can be quickly cured at a low temperature. When filling the thermosetting polyurethane composition with a liquid underfill material by capillarity, if the temperature is about the melting point of the curing agent or lower than that, the filling is heated. It can also be done. Thereby, the viscosity of an underfill material can be reduced, moderate fluidity can be imparted, and capillary action can be promoted.
[0073]
Moreover, the thermosetting polyurethane composition has a tendency that the urethane bond of the cured product is depolymerized at a temperature of 180 ° C. or higher and 350 ° C. or lower, but when it is cooled to about room temperature again, the urethane bond is regenerated, It has the property of returning to almost the original cured state. Therefore, when this thermosetting polyurethane composition is used as an underfill material, even if a defect occurs in an electronic component, the electronic component can be easily repaired, and at the same time to other electronic components exposed to high temperatures. Can prevent damage due to heat. Furthermore, since the removal from the electronic circuit board is easy, the electronic circuit board can be effectively regenerated.
[0074]
Hereinafter, the present invention will be described more specifically with reference to examples.
(Example)
(1) Terminal isocyanate group-containing prepolymer
(A) PPG urethane prepolymer
(A-1) Terminal isocyanate group-containing urethane prepolymer
100 g of polypropylene ether diol (molecular weight 3000) is weighed and put into a reaction vessel substituted with nitrogen gas. Next, 11.6 g of tolylene diisocyanate (TDI) is weighed and charged. After the addition, the temperature is raised to 80 ° C. with stirring, and a synthesis reaction is performed at about 80 ° C. for 2 hours. The NCO group content of the obtained urethane prepolymer (A1) was 2.5% by weight.
[0075]
(A-2) Terminal isocyanate group-containing urethane prepolymer
100 g of polypropylene ether triol (molecular weight 1000) and 52 g of tolylene diisocyanate (TDI) are subjected to a synthesis reaction at about 80 ° C. for 2 hours. The NCO group content of the obtained urethane prepolymer (A2) was 8.5% by weight.
[0076]
(A-3) PPG urethane prepolymer
The urethane prepolymers (A-1) and (A-2) produced by the above method are mixed, and a PPG urethane prepolymer having an NCO group content of 3.2% by weight and a viscosity at 20 ° C. of 20000 mPa · s is obtained. Obtained.
[0077]
(B) PB urethane prepolymer
100 g of polybutadiene diol (molecular weight 1200) and 32 g of tolylene diisocyanate (TDI) are put into a reaction vessel substituted with nitrogen gas, and a synthetic reaction is carried out with stirring at about 80 ° C. for 2 hours. The obtained PB urethane prepolymer had an NCO group content of 5.8% by weight and a viscosity at 20 ° C. of 50000 mPa · s.
[0078]
(2) Fine particle coating curing agent
1,10-decanediamine (melting point: 60 ° C.) used as a curing agent and titanium oxide having a center particle size of 0.27 μm are mixed at a ratio of 1: 0.3, and stirred and pulverized by a jet mill. A fine particle-coated hardener having a diameter of about 10 μm is obtained.
[0079]
(3) Preparation of thermosetting polyurethane composition
To 12 g of the PPG urethane prepolymer prepared in the above (A-3) and 28 g of the PB urethane prepolymer of (B), 15 g of the fine particle particle coating curing agent of (2) is mixed.
[0080]
Furthermore, 5 g of tri (2-ethylhexyl) trimellitate, which is a trimellitic acid ester plasticizer, and 20 g of dioctyl adipate, which is an adipate ester plasticizer, are blended as plasticizers. Furthermore, 20 g of epoxy resin (bisphenol A type), 2.5 g of polyether-modified dimethylsiloxane as organopolysiloxane, 2.0 g of silane coupling agent, 0.03 g of bleed inhibitor, and hindered phenol anti-aging agent as viscosity stabilizer 0.1 g and 3 g of zeolite dehydrating agent are blended and mixed uniformly to obtain a thermosetting polyurethane composition. The viscosity of the obtained thermosetting polyurethane composition at 20 ° C. was 4200 mPa · s.
[0081]
The thermosetting polyurethane composition prepared as shown in this Example is hereinafter referred to as “Example Polyurethane Composition”.
Here, the viscosity of the polyurethane composition of the example is measured using a BH type rotational viscometer under the condition of a rotational speed of 20 rpm. Further, the polyurethane composition of this example is cured under heating conditions at a temperature of 80 ° C. for 10 minutes, and the dielectric constant, dielectric loss tangent (tan δ), and volume resistivity are measured as electrical characteristics. The dielectric constant, dielectric loss tangent (tan δ) and volume resistivity are measured according to JIS K-6911. At that time, the dielectric constant and the dielectric loss tangent (tan δ) are measured under the condition of 1 MHz, and the volume resistivity is measured under the applied condition of 500V.
[0082]
(Comparative Example 1)
Comparative Example 1 is a case where the composition does not contain the organopolysiloxane, the silane coupling agent, and the bleed inhibitor used in the polyurethane composition of the example. Hereinafter, the thermosetting polyurethane composition shown in Comparative Example 1 is referred to as “polyurethane composition of Comparative Example 1”.
[0083]
(Comparative Example 2)
The comparative example 2 is a case where the composition does not include the silane coupling agent and the bleed inhibitor used in the polyurethane composition of the example. Hereinafter, the thermosetting polyurethane composition shown in Comparative Example 2 is referred to as “polyurethane composition of Comparative Example 2”.
[0084]
(Comparative Example 3)
Comparative Example 3 is a case where the silane coupling agent used in the polyurethane composition of the example is not included in the composition. Hereinafter, the thermosetting polyurethane composition shown in Comparative Example 3 is referred to as “polyurethane composition of Comparative Example 3”.
[0085]
After curing each composition shown in Comparative Examples 1 to 3 at a temperature of 80 ° C. under curing conditions for 10 minutes, the adhesiveness of the cured body to the flux surface and the non-flux surface, the fracture state to the flux surface, and the presence or absence of bleeding To evaluate.
[0086]
Here, the adhesive evaluation method will be described.
FIG. 2 is an explanatory diagram of an adhesive evaluation method. The influence which the difference in a composition of a thermosetting polyurethane composition has on the adhesive force is examined using the method shown in FIG. First, the underfill material 21 was formed into a T-shaped nail (plated Sn-10Pb, φ5 (19.63 mm²)) Apply to 22. Then, the applied underfill material 21 is cured on the flux surface of the FR-4 electronic circuit board 23 of the epoxy resin base that has been subjected to the flux treatment. The flux used here is NO. 001-01 is applied to the electronic circuit board 23, and the thickness of the dried flux layer is 10 μm. After the underfill material 21 is cured on the electronic circuit board 23, a tensile strength test is performed on the T-shaped nail 22. Furthermore, in this adhesive evaluation, the case where the underfill material 21 is cured on the non-flux surface of the electronic circuit board 23 not subjected to the flux treatment is also evaluated.
[0087]
The adhesive evaluation results for the compositions shown in Comparative Examples 1 to 3 are shown in Table 1 together with the evaluation results for the polyurethane compositions of the examples.
[0088]
[Table 1]

[0089]
In the case of the polyurethane composition of Comparative Example 1, no bleed is observed, but the adhesive force to the flux surface is 50 g / mm.²Met. The fracture state at this time is interface fracture, and the adhesiveness is not good.
[0090]
In order to increase the adhesive strength to the flux surface, as shown in Comparative Example 2, even when an organopolysiloxane compound is blended, the adhesive strength is 80 g / mm.²And it has not improved. In addition, in this case, the bleed phenomenon occurs because the organopolysiloxane compound is not compatible with each other, and the fracture state is also interface fracture, and no improvement in adhesion is observed.
[0091]
In order to prevent bleeding of the organopolysiloxane compound, as shown in Comparative Example 3, when an anti-bleeding agent is blended, the adhesive strength is 200 g / mm.²And no bleeding of the organopolysiloxane compound is observed. However, the fracture state is interface fracture.
[0092]
As shown in the Examples, the adhesive strength is improved by blending the composition of Comparative Example 3 with a silane coupling agent. Further, the broken state shows good adhesiveness leading to cohesive failure, and bleeding of the organopolysiloxane compound is not observed.
[0093]
(Comparative Example 4)
The thermosetting polyurethane composition of Comparative Example 4 is a thermosetting polyurethane composition when only the epoxy resin is not blended among the components contained in the polyurethane composition of the example. Hereinafter, the thermosetting polyurethane composition shown in Comparative Example 4 is referred to as “polyurethane composition of Comparative Example 4”.
[0094]
(Comparative Example 5)
The thermosetting polyurethane composition of Comparative Example 5 is a thermosetting polyurethane composition when the PB urethane prepolymer is replaced with the PPG urethane prepolymer among the components contained in the polyurethane composition of the example. . Hereinafter, the thermosetting polyurethane composition shown in Comparative Example 5 is referred to as “polyurethane composition of Comparative Example 5”.
[0095]
(Comparative Example 6)
In Comparative Example 6, a thermosetting epoxy resin composition (Penguin cement 1090 manufactured by Sunstar Giken Co., Ltd.) is used. Hereinafter, the thermosetting epoxy resin composition shown in Comparative Example 6 is referred to as “an epoxy resin composition of Comparative Example 6”.
[0096]
For each of the compositions shown in Comparative Examples 4 to 6, the viscosity, dielectric constant, dielectric loss tangent and volume resistivity at 20 ° C. are measured in the same manner as the polyurethane composition of the example. The measurement results of Examples and Comparative Examples 4 to 6 are shown in Table 2.
[0097]
[Table 2]

[0098]
As shown in Comparative Example 4, when the composition does not contain an epoxy resin, the volume resistivity does not change greatly, but the viscosity increases. Further, as shown in Comparative Example 5, when the composition does not contain a PB urethane prepolymer, the viscosity decreases, but a sufficient volume resistivity cannot be obtained.
[0099]
Next, a description will be given of the results of a comparative study of mounting substrates using the thermosetting polyurethane composition and the thermosetting epoxy resin composition shown in Examples and Comparative Examples 4 to 6 as underfill materials.
[0100]
FIG. 1 is a schematic cross-sectional view of a mounting substrate in which an underfill material is used. The mounting board 10 is bonded to an electronic circuit board 11 corresponding to an epoxy resin base FR-5 and a CSP (0.5 mm pitch eutectic solder balls, 240 balls, package size 10 mm) 12 via solder balls 13. Has been. The underfill material 14 is filled and cured in the gap between the electronic circuit board 11 and the CSP 12.
[0101]
In manufacturing the mounting substrate 10 having the above-described configuration, first, Sn / 37Pb eutectic solder paste material (RMA9086 manufactured by Nippon Alpha Metals Co., Ltd.) is screen-printed on the surface of the electronic circuit board 11 with a thickness of about 150 μm. Next, the CSP 12 is mounted and reflow soldering is performed at a peak temperature of 230 ° C.
[0102]
Then, the underfill material 14 is filled in the gap between the electronic circuit board 11 and the CSP 12 in a non-cleaning state where the solder flux residue is present. When the underfill material 14 is filled, it is applied and dropped from the side of the CSP 12 using a dispenser so that the underfill material 14 penetrates into the lower part of the CSP 12. Then, after standing for 10 minutes, curing is performed at 80 ° C. for 5 minutes, and the filling of the underfill material 14 is completed.
[0103]
In order to confirm the penetration effect of the underfill material 14, the mounting substrate 10 was cut at the position of the CSP 12 and the filling state of the underfill material 14 in the vicinity of the solder balls 13 was inspected.
[0104]
FIG. 3 is a schematic cross-sectional view of the mounting substrate when the polyurethane composition of Comparative Example 4 is used, and FIG. 4 is a schematic cross-sectional view of the mounting substrate when the polyurethane composition of the example is used.
[0105]
As shown in FIG. 3, when the polyurethane composition of Comparative Example 4 that does not contain an epoxy resin is used for the underfill material 14a, the lower surface of the CSP 12a is sufficiently penetrated and filled in the mounting substrate 10a. However, the entire surface of the electronic circuit board 11a is not filled. This is because the penetration of the underfill material 14a is hindered by the flux residue 15a existing on the surface of the electronic circuit board 11a.
[0106]
On the other hand, as shown in FIG. 4, when the polyurethane composition of the example is used, the underfill material 14b takes in the flux residue on the lower surface of the CSP 12b and the surface of the electronic circuit board 11b in the mounting substrate 10b. And almost the entire surface is filled. Therefore, it is possible to secure a bonding area between the electronic circuit board 11b and the CSP 12b, and an improvement in adhesive strength is expected.
[0107]
Here, regarding the mounting substrate 10a shown in FIG. 3 and the mounting substrate 10b shown in FIG. 4, the adhesive strengths of the CSPs 12a and 12b are compared by a drop test.
FIG. 5 is an explanatory diagram of a drop test method. In the drop test, the mounting boards 10a and 10b are repeatedly and freely dropped from the height of 1 m onto the tile floor 50 with the mounting surfaces thereof facing downward. The number of drops in which the daisy chain loop connection resistance value of the solder balls of the CSPs 12a and 12b is increased by 10% from the initial value (about 0.5Ω) is regarded as defective. In this drop test, the loop connection resistance value is measured every 50 drops. The results of the drop test are shown in Table 3.
[0108]
[Table 3]

[0109]
When the polyurethane composition of Comparative Example 4 is used for the underfill material, the average number of drops is about 200, and the loop connection resistance value increases, resulting in a failure. On the other hand, when the polyurethane composition of the example is used, the loop connection resistance value does not increase even if the average number of drops is about 300 times or more. Thereby, the polyurethane composition of an Example contains an epoxy resin in the composition, and even if a flux residue exists, an adhesive area can be ensured and adhesive force can be maintained high. Therefore, this thermosetting polyurethane composition can be sufficiently applied to devices such as mobile phones that require high drop impact resistance reliability.
[0110]
Furthermore, since flux cleaning is not required before filling the underfill material, the performance reliability of the electronic component is not reduced due to the chemical treatment. Moreover, since the washing process and the drying process are not necessary, the working efficiency is improved. Further, it is possible to reduce the cost of the cleaning equipment for the flux cleaning, the waste liquid processing cost related to the cleaning, and the like, and the cost of the mounting process can be reduced.
[0111]
Next, the repairability of the electronic component bonded to the electronic circuit board with the underfill material will be described.
When the thermosetting polyurethane composition is filled in the gap between the electronic component and the electronic circuit board, and once cured, the electronic component is repaired. The cured thermosetting polyurethane composition is softened by heating again. However, it is necessary to reduce the adhesive strength.
[0112]
In order to measure the adhesive force change due to heating of the cured thermosetting polyurethane composition, the underfill material 21 is cured on the electronic circuit board 23 by the method shown in FIG. After curing, this electronic circuit board 23 is placed on a hot plate 24, heated at a predetermined temperature from room temperature to 250 ° C., and the adhesive force of the T-shaped nail 22 is measured 2 minutes after reaching each predetermined temperature. .
[0113]
FIG. 6 is a diagram showing the relationship between the temperature applied to the underfill material and the adhesive force. Here, for the case where the epoxy resin composition of Comparative Example 6 and the polyurethane composition of Examples are used, the adhesive strength is measured by the method shown in FIG. In FIG. 6, the relationship between the temperature and the adhesive force when the epoxy resin composition of Comparative Example 6 is used is a broken line, and the relationship between the temperature and the adhesive force when the polyurethane composition of the example is used is a solid line. Each is shown.
[0114]
When the epoxy resin composition of Comparative Example 6 was used, the adhesive force gradually decreased when the heating temperature ranged from 150 ° C to 200 ° C. On the other hand, in the case where the polyurethane composition of the example was used, when the heating temperature exceeded 140 ° C., the adhesive strength rapidly decreased, and at a temperature of 160 ° C., 10 gf / mm.²(0.1 N / mm²)
[0115]
When repairing an electronic component, it is necessary to heat it above the melting point of solder (183 ° C.). Of course, it is desirable to remove the electronic component in a short time above the melting point of the solder and in a low temperature range. When the polyurethane composition of the example is used, as shown in FIG. 6, the adhesive force decreases rapidly at a heating temperature of about 140 ° C., so that the electronic component can be removed at a low temperature. That is, at the temperature at which the solder can be removed, the polyurethane compositions of the examples are sufficiently softened, and the electronic components can be easily removed while suppressing thermal and mechanical damage.
[0116]
On the other hand, in the epoxy resin composition of Comparative Example 6, the tendency as shown in the polyurethane composition of the example is not recognized, and when the heating temperature is about 50 ° C. or higher, the adhesive strength is higher than that of the polyurethane composition of the example. It becomes like this. That is, the epoxy resin composition of Comparative Example 6 requires heating to a higher temperature and a greater force when removing the epoxy resin composition of Comparative Example 6 than the polyurethane composition of Examples. In general, thermosetting epoxy resin compositions that have been widely used in the past have a softening temperature of 200 ° C. or higher, and the adhesion of residues to the electronic circuit board is also strong, making repair work difficult. End up. In this respect, it can be said that the polyurethane compositions of the examples are very excellent in repairability, and this thermosetting polyurethane composition can be widely applied to mounting substrates used in various applications.
[0117]
When actually repairing an electronic component filled with an underfill material from a mounting board, a weight of 1N to 3N is hung on the electronic component to be removed, and when the solder is melted by heating, The electronic component can be removed by allowing it to fall naturally at the start of softening. By using such a principle, it becomes possible to remove the electronic component at an optimal timing.
[0118]
Further, when repairing an electronic component, a thermosensor label for visually detecting the melting of solder by heating and the start of softening of the underfill material can be arranged in the vicinity of the electronic component. In addition, a solder melting point material having a temperature 10 to 50 ° C. higher than the solder of the electronic component to be removed may be disposed in the vicinity of the electronic component.
[0119]
Generally, a plurality of electronic components are densely arranged on an electronic circuit board. When repairing an electronic component, other electronic components in the vicinity of the electronic component may be heated. Many. That is, non-defective electronic components as well as defective electronic components to be repaired are exposed to high temperatures due to the influence of repair heat. For this reason, it is necessary that the adhesive force of the non-defective electronic component is not lost by the repair heat.
[0120]
FIG. 7 is a view showing the recoverability of the adhesive force. Adhesive strength recovery was performed by using the epoxy resin composition of Comparative Example 6 and the polyurethane composition of Examples, and using the same method as shown in FIG. The material is evaluated here by cooling it to room temperature and measuring the adhesion. In FIG. 7, the relationship between the temperature and the adhesive force when the epoxy resin composition of Comparative Example 6 is used is a broken line, and the relationship between the temperature and the adhesive force when the polyurethane composition of the example is used is a solid line. Each is shown.
[0121]
As shown in FIG. 7, the adhesive strength of the polyurethane composition of the example is the same level as that of the epoxy resin composition of Comparative Example 6 as long as the solder is heated to about the melting temperature of the solder. It turns out that it fully recovers. Therefore, according to the polyurethane composition of the example, even when heating for repairing the electronic component is performed, it is possible to maintain the adhesion reliability of other electronic components in the vicinity thereof. Thus, by using the thermosetting polyurethane composition according to the present invention for the underfill material, it is possible to reduce the cost of the dedicated repair equipment for electronic components.
[0122]
Next, the electrical insulation of the underfill material will be described.
In order to study the electrical insulation of the underfill material used by filling the gap between the electronic component and the electronic circuit board, an insulation resistance test was conducted using the epoxy resin composition of Comparative Example 6 and the polyurethane composition of the Example. Carried out. The insulation resistance test here is performed according to the following procedure according to the section 2-6-3-3 of IPC-TM-650.
[0123]
(1) First, an underfill material of about 0.5 mm is formed on a copper foil pattern (gap 0.318 mm, conductor width 0.318 mm) in which a comb-tooth pattern is formed in accordance with the IPC-B-25 standard. Apply to thickness and cure. Curing conditions were 80 ° C. for 5 minutes for the polyurethane composition of the example and 10 minutes at 150 ° C. for the epoxy resin composition of Comparative Example 6. For comparison, a copper foil pattern not coated with an underfill material is also prepared.
[0124]
(2) The sample was allowed to stand for 24 hours in a thermostat controlled at a temperature of 23 ° C. and a humidity of 50% to adjust the humidity, and then the initial insulation resistance value of the sample was measured. The initial insulation resistance value is measured after applying for 1 minute at a measurement voltage of 100V.
[0125]
(3) The sample is placed in a thermostatic chamber having a temperature of 35 ± 2 ° C. and a humidity of 85%, and after 1 hour, the insulation resistance value is measured in the same manner as in (2). The insulation resistance value at this time is hereinafter referred to as “insulation resistance value after 1 hour”.
[0126]
(4) Apply an applied voltage of DC 50 V and perform an application test in a constant temperature bath at a temperature of 35 ± 2 ° C. and a humidity of 85% for 4 days (96 hours). Here, at the time of application, the application polarity is reversed from the case of (2).
[0127]
(5) After 4 days, the insulation resistance value of the comb pattern is measured in a constant temperature bath at a temperature of 35 ± 2 ° C. and a humidity of 85%. Here, at the time of measurement, the polarity is reversed from the case of (3). The insulation resistance value at this time is hereinafter referred to as “insulation resistance value after 96 hours”.
[0128]
(6) As a reference value, the sample of (4) was left in an atmosphere at a temperature of 23 ° C. and a humidity of 50% for about 3 hours, and the insulation resistance value after drying was measured. The insulation resistance value at this time is hereinafter referred to as “insulation resistance value after drying”.
[0129]
Here, the standard value of the insulation resistance test of IPC-650 is that the intertooth spacing is 1.27 mm and the IR value is 1 × 10.¹¹Ω, comb tooth spacing is 0.318 mm and IR value is 2 × 10^TenΩ.
[0130]
FIG. 8 is a diagram showing the measurement results of the insulation resistance. In FIG. 8, the case where the polyurethane composition of the Example is used is indicated by a solid line, the case where the epoxy resin composition of Comparative Example 6 is used is indicated by a broken line, and the case where the underfill material is not applied is indicated by an alternate long and short dash line.
[0131]
As shown in FIG. 8, the initial insulation resistance values are standard values of 2 × 10 for all three types.^TenA value of Ω or more is shown. However, when the epoxy resin composition of Comparative Example 6 was used, it was already out of the standard value at the time of measuring the insulation resistance value after 1 hour, and the insulation resistance value after 96 hours and the insulation resistance value after drying were both standard values. It remains off.
[0132]
On the other hand, when using the polyurethane composition of the example, both the insulation resistance value after 1 hour and the insulation resistance value after 96 hours exceeded the standard value throughout the measurement in the thermostat, and the insulation resistance value after drying was also Never fall below the standard value. Therefore, the polyurethane composition of an Example can implement | achieve high electrical insulation reliability.
[0133]
Such high electrical insulation reliability greatly contributes to the fact that the thermosetting polyurethane composition of the present invention contains a terminal isocyanate group-containing urethane prepolymer obtained from a hydrocarbon-based polyol in its composition. Further, the high electrical insulation reliability of the thermosetting polyurethane composition makes it possible to ensure electrical insulation between the solder joints of the fine electrode pitch.
[0134]
As described above, by using the thermosetting polyurethane composition according to the present invention for the underfill material, the underfill material can be filled in the gap between the electronic circuit board and the electronic component without performing flux cleaning. it can. As a result, the electronic component mounting process can be simplified while maintaining the adhesiveness and electrical insulation of the mounting substrate, and the productivity of the mounting substrate can be improved.
[0135]
Further, in manufacturing a mounting board using an underfill material, an electronic circuit board provided with pores at positions facing electronic components to be mounted may be used.
9 is a cross-sectional view of a mounting board using an electronic circuit board having pores, and FIG. 10 is a view of the mounting board of FIG. 9 as viewed from the side opposite to the mounting surface.
[0136]
The electronic circuit board 31 of the mounting board 30 is formed with pores 33 having a diameter of 0.1 mm to 1.0 mm at positions facing the CSP 32 mounted thereon. A CSP 32 is mounted on the electronic circuit board 31 via solder balls 34, and an underfill material 35 is filled in the gap.
[0137]
Here, when the underfill material 35 is filled in the gap between the electronic circuit board 31 and the CSP 32, air may be involved. However, in the electronic circuit board 31 having such pores 33, the air entrained during filling can escape from the pores 33. Therefore, the underfill material 35 can be filled in the gap smoothly and reliably, and the popcorn phenomenon that has been highly likely to occur when the underfill material 35 is cured can be avoided. Thereby, the adhesive reliability of CSP32 and the electronic circuit board 31 can be improved.
[0138]
Moreover, you may make it form the dam for avoiding the outflow of the applied underfill material in the electronic circuit board.
FIG. 11 is a plan view of a mounting board using an electronic circuit board having a dam structure, and FIG. 12 is a cross-sectional view of the mounting board using an electronic circuit board having a dam structure.
[0139]
On the electronic circuit board 41 of the mounting board 40, a CSP 43 in which a gap with the electronic circuit board 41 is filled with an underfill material 42 and a non-filled surface mount type semiconductor element 44 are mounted adjacently.
[0140]
Here, when trying to fill the CSP 43 with the underfill material 42, especially when the viscosity of the underfill material 42 is low, there is a possibility that the applied underfill material 42 flows out to the semiconductor element 44 side. is there. In general, the dielectric constant of air is about 1, but the dielectric constant of the underfill material 42 is about 4. For example, when the mounting substrate 40 is used for applications where high frequency signal processing in the gigahertz band is performed, the presence or absence of the underfill material 42 greatly affects the high frequency characteristics (so-called parasitic capacitance phenomenon). That is, it is necessary to avoid filling the underfill material 42 on the side of the semiconductor element 44 that is not filled with the underfill material 42. Therefore, a dam 45 is formed in advance between the CSP 43 and the lead 44 a of the semiconductor element 44 on the mounting surface side of the electronic circuit board 41.
[0141]
The dam 45 is formed of a fast-curing silicone resin (DA6523 manufactured by Toray Down Corning) that cures at a temperature of 150 ° C. for 1 minute. In the formation, this fast-curing silicone resin is applied by a dispenser and then cured at the time of reflow soldering performed at a peak temperature of 230 ° C. Accordingly, the dam 45 can be formed by curing the fast-curing silicone resin before applying the underfill material 42. Further, such a fast-curing silicone resin is suitable as a material for the dam 45 because it has peelability and flexibility.
[0142]
By forming the dam 45 on the electronic circuit board 41 in this way, it is possible to make the CSP 43 side filled with the underfill material 42 and the semiconductor element 44 side not filled. Therefore, even under the use environment in the high frequency band, it is possible to avoid the parasitic capacitance phenomenon and the like to eliminate the influence on the high frequency characteristics, and to form the mounting substrate 40 with good frequency characteristics.
[0143]
The fast-curing silicone resin used here is designed to be cured within a short time of 10 minutes within a heating temperature range of 120 ° C. to 180 ° C. The main component is dimethylpolysiloxane having at least two alkenyl groups bonded to silicon atoms in the molecule. In addition, as the crosslinking agent, an organic hydrogenated polysiloxane having at least two hydrogen atoms bonded to silicon atoms in the molecule is heated and cured in the presence of a hydrosilylation reaction catalyst. Furthermore, you may use fillers, such as a silica, and another additive as needed. As the fast-curing silicone resin used as the dam material, it is preferable to use a resin formulated with a thermally active catalyst obtained by microencapsulating a metal catalyst for hydrosilylation reaction with a thermoplastic resin.
[0144]
Moreover, you may form the same pore as what was shown in FIG. 9 and FIG. 10 in the position facing CSP43 of the electronic circuit board 41 in which said dam 45 is formed. As a result, the underfill material 42 is prevented from flowing out, and an escape route for the air entrained during application is secured.
[0145]
(Appendix 1) In the thermosetting polyurethane composition,
A mixture of a terminal isocyanate group-containing urethane prepolymer obtained from a hydrocarbon-based polyol and a terminal isocyanate group-containing urethane prepolymer obtained from a polyether polyol in a weight ratio of 9: 1 to 2: 8;
Epoxy resin,
An organopolysiloxane compound;
An anti-bleeding agent for preventing bleeding of the organopolysiloxane compound;
A silane coupling agent, and a volume resistivity of 1.0 × 10⁹A thermosetting polyurethane composition characterized by being at least Ω · cm.
[0146]
(Supplementary Note 2) 5% to 30% by weight of the epoxy resin, 0.5% to 5% by weight of the organopolysiloxane compound, and 0.01% to 1.0% by weight of the bleed inhibitor. The thermosetting polyurethane composition according to appendix 1, wherein 0.5 to 5% by weight of the silane coupling agent is included.
[0147]
(Additional remark 3) The thermosetting polyurethane composition of Additional remark 1 characterized by having the fine particle particle | grain coating hardening agent which coat | covered the active group of the surface with fine powder.
(Appendix 4) Adhesive strength when heated at a temperature of 160 ° C. or higher is 0.1 N / mm²The thermosetting polyurethane composition according to supplementary note 1, which is:
[0148]
(Additional remark 5) In the mounting board | substrate with which the underfill material was filled in the clearance gap between the electronic component which has a protruding electrode, and the electronic circuit board in which an electronic component is mounted,
A mixture of a terminal isocyanate group-containing urethane prepolymer obtained from a hydrocarbon-based polyol and a terminal isocyanate group-containing urethane prepolymer obtained from a polyether polyol in a weight ratio of 9: 1 to 2: 8;
Epoxy resin,
An organopolysiloxane compound;
An anti-bleeding agent for preventing bleeding of the organopolysiloxane compound;
And volume resistivity 1.0 × 10 having a silane coupling agent⁹A mounting substrate comprising an underfill material containing a thermosetting polyurethane composition of Ω · cm or more.
[0149]
(Appendix 6) The thermosetting polyurethane composition comprises 5 wt% to 30 wt% of the epoxy resin, 0.5 wt% to 5 wt% of the organopolysiloxane compound, and 0.01 wt% to 1 wt%. The mounting board according to appendix 5, wherein 0.0% by weight of the bleed inhibitor and 0.5% to 5% by weight of the silane coupling agent are included.
[0150]
(Additional remark 7) The said thermosetting polyurethane composition has the fine particle particle | grain coating hardening agent which coat | covered the active group of the surface with fine powder, The mounting board | substrate of Additional remark 5 characterized by the above-mentioned.
[0151]
(Appendix 8) The thermosetting polyurethane composition has an adhesive strength of 0.1 N / mm when heated at a temperature of 160 ° C or higher.²The mounting board according to appendix 5, wherein:
[0152]
(Additional remark 9) In the manufacturing method of the mounting board | substrate with which the underfill material was filled in the clearance gap between the electronic component which has a protruding electrode, and the electronic circuit board in which an electronic component is mounted,
Print the soldering paste containing flux coating or flux on the mounting surface of the electronic circuit board,
Soldering the protruding electrode of the electronic component to the mounting surface,
A mounting substrate manufacturing method comprising filling an underfill material in a gap between the electronic component and the electronic circuit board without performing flux cleaning.
[0153]
(Additional remark 10) In the repair method of the electronic component of the mounting board | substrate with which the underfill material was filled in the clearance gap between the electronic component which has a protruding electrode, and the electronic circuit board in which an electronic component is mounted,
Hanging weights on electronic components mounted on electronic circuit boards,
Melting the solder of the protruding electrode of the electronic component by heating,
A repair method comprising softening an underfill material and free-falling the electronic component when the solder is melted.
[0154]
(Additional remark 11) The repair method of Additional remark 10 characterized by arrange | positioning a thermosensor label in the vicinity of the said electronic component, in order to detect melting of the said solder and softening of the said underfill material.
[0155]
(Supplementary note 12) The repair according to Supplementary note 10, wherein a solder material having a melting point higher than that of the solder is disposed in the vicinity of the electronic component in order to detect melting of the solder and softening of the underfill material. Method.
[0156]
(Additional remark 13) In the electronic circuit board by which the electronic component which has a protruding electrode is mounted,
An electronic circuit board having pores having a diameter of 0.1 mm to 1.0 mm through which air entrained during filling with an underfill material is removed at a position facing an electronic component to be mounted.
[0157]
(Additional remark 14) In the electronic circuit board by which the electronic component which has a protruding electrode is mounted,
An electronic circuit board, wherein a dam for preventing the applied underfill material from flowing out is formed outside an area where electronic parts are mounted.
[0158]
(Additional remark 15) The said dam consists of a silicone resin hardened | cured at the temperature below the soldering temperature of the said electronic component, The electronic circuit board of Additional remark 14 characterized by the above-mentioned.
(Supplementary note 16) The electronic circuit board according to supplementary note 14, having a pore having a diameter of 0.1 mm to 1.0 mm through which air entrained during filling with an underfill material is removed at a position facing the electronic component. .
[0159]
【The invention's effect】
As described above, in the present invention, the thermosetting polyurethane composition has, in addition to the terminal isocyanate group-containing urethane prepolymer and epoxy resin, an organopolysiloxane compound, a bleed inhibitor and a silane coupling agent. I made it. For this reason, when the thermosetting polyurethane composition is used for the underfill material, it can be filled without flux cleaning, and the electronic component and the electronic circuit board can be bonded with sufficient strength. it can.
[0160]
In addition, by providing pores in the electronic circuit board, it is possible to prevent the occurrence of air voids when filling the underfill material and to prevent the occurrence of poor adhesion.
Furthermore, by forming a dam on the electronic circuit board, it is possible to prevent the outflow when the underfill material is filled to improve the adhesion reliability, and it is possible to form a mounting board with good frequency characteristics.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a mounting substrate in which an underfill material is used.
FIG. 2 is an explanatory diagram of an adhesion evaluation method.
FIG. 3 is a schematic cross-sectional view of a mounting board when the polyurethane composition of Comparative Example 4 is used.
FIG. 4 is a schematic cross-sectional view of a mounting substrate when the polyurethane composition of the example is used.
FIG. 5 is an explanatory diagram of a drop test method.
FIG. 6 is a diagram showing the relationship between the temperature applied to the underfill material and the adhesive force.
FIG. 7 is a diagram showing adhesiveness recoverability.
FIG. 8 is a diagram showing measurement results of insulation resistance.
FIG. 9 is a cross-sectional view of a mounting board using an electronic circuit board having pores.
10 is a view of the mounting substrate of FIG. 9 as viewed from the side opposite to the mounting surface.
FIG. 11 is a plan view of a mounting board using an electronic circuit board having a dam structure.
FIG. 12 is a cross-sectional view of a mounting board using an electronic circuit board having a dam structure.
[Explanation of symbols]
10, 10a, 10b, 30, 40 Mounting board
11, 11a, 11b, 23, 31, 41 Electronic circuit board
12, 32, 43 CSP
13, 34 Solder balls
14, 14a, 14b, 21, 35, 42 Underfill material
15a Flux residue
22 T-shaped nails
24 Hot plate
33 pores
44 Semiconductor elements
44a lead
45 Dam
50 tile floor

Claims (3)

In the manufacturing method of the mounting substrate in which the underfill material is filled in the gap between the electronic component having the protruding electrode and the electronic circuit substrate on which the electronic component is mounted,
  Print the soldering paste containing flux coating or flux on the mounting surface of the electronic circuit board,
  Soldering the protruding electrode of the electronic component to the mounting surface,
  Filling the gap between the electronic component and the electronic circuit board without flux cleaning with an underfill material,
  The underfill material is
  A mixture of a terminal isocyanate group-containing urethane prepolymer obtained from a hydrocarbon-based polyol and a terminal isocyanate group-containing urethane prepolymer obtained from a polyether polyol in a weight ratio of 9: 1 to 2: 8;
  Epoxy resin,
  An organopolysiloxane compound;
  An anti-bleeding agent for preventing bleeding of the organopolysiloxane compound;
  And volume resistivity 1.0 × 10 having a silane coupling agent ⁹ A method for producing a mounting substrate, comprising a thermosetting polyurethane composition having an Ω · cm or more. The electronic circuit board has pores having a diameter of 0.1 mm to 1.0 mm through which air entrained when the underfill material is filled escapes at a position facing the electronic component to be mounted. Item 2. A method for manufacturing a mounting board according to Item 1. 2. The electronic circuit board according to claim 1, wherein a dam for preventing the filled underfill material from flowing out is formed outside a region where the electronic component is mounted. Manufacturing method of mounting substrate.

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