JP2004025288A - Flux and solder paste for soldering circuit board, and circuit board used therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve wettability of a fused solder particularly for the pattern of a circuit board, in relation to a flux and solder paste used for soldering electronic parts on the circuit board and to a circuit board having a residual film of the flux and the solder paste before or after the soldering of the electronic parts. <P>SOLUTION: The flux in which pyrazole as an activator is combinedly used with rosin is obtained, as are the solder paste in which this flux is used and the circuit board which has the residual film of the flux and the solder paste and which is before or after the mounting of the electronic parts. <P>COPYRIGHT: (C)2004,JPO

Description

（式中、Ｒ_１は水素、炭素数１〜５の直鎖若しくは分岐を持つアルキル基、フェニル基、ハロゲン化フェニル基、メトキシフェニル基、アミノ基、ヒドロキシ基、ハロゲン原子（Ｃｌ、Ｂｒ、Ｉ等）、カルボキシル基、メトキシ基又はベンジル基を表わし、ｎは０〜３の整数を表わし、ｎが２以上のときは（Ｒ_１）ｎのＲ_１は同一又は異なっていてもよく、Ｒ_２は水素、炭素数１〜５の直鎖若しくは分岐を持つアルキル基、フェニル基、ハロゲン化フェニル基、メトキシフェニル基、アミノ基、ヒドロキシ基、ハロゲン原子（Ｃｌ、Ｂｒ、Ｉ等）、カルボキシル基、メトキシ基又はベンジル基を表わす。）
【００１３】
ピラゾール誘導体及びその塩の具体例としては、５−アミノ−１，３−ジメチルピラゾール塩酸塩、３−アミノ−５−ヒドロキシピラゾール、３−アミノピラゾール、３−（４−クロロフェニル）ピラゾール、ピラゾール−３，５−ジカルボン酸ジエチル、３，５−ジメチルピラゾール、３−（４−メトキシフェニル）ピラゾール、３−メチル−１−フェニル−１Ｈ−ピラゾール、３−メチルピラゾール、３−フェニルピラゾール、３，５−ピラゾールジカルボン酸一水和物、３−（４−トリル）ピラゾール、３−アミノピラゾール−４−カルボン酸、３，４−ジアミノ−５−ヒドロキシピラゾール硫酸塩、４−メチルピラゾール、５−クロロ−１，３−ジメチルピラゾール、１−フェニルピラゾール、３，５−ジフェニルピラゾール、３，５−ジメチル−１−フェニルピラゾール、４−ブロモ−３−メチルピラゾール、１，３，５−トリメチルピラゾールが挙げられる。
【００１４】
ピラゾール、その誘導体及びこれらの塩の少なくとも１種は、フラックス中０．０１〜１０．０％（重量％、以下同様）、好ましくは０．１〜３．０％であり、添加量が少な過ぎる場合にはその添加による効果（上述した特開平５−３９２号公報に記載されている、そこから引用した上記文言に示されているような効果）が得られず、逆に添加量が多過ぎるとフラックス中において溶解し難くなる。
【００１５】
本発明のフラックスには、「非解離性のハロゲン化化合物からなる非解離型活性剤」を含有させてもよく、非解離性のハロゲン化化合物としてはハロゲン原子が共有結合により結合した非塩系の有機化合物が挙げられる。このようにハロゲン原子が非解離性であると、回路基板の金属を腐食したり、フラックスに残留してもその電気絶縁性を害することも少なくできる。このような非解離性のハロゲン化化合物ははんだ付時に溶融はんだの２００℃以上になる高温に曝されると、その一部が分解しハロゲンあるいはその簡単な化合物を生じ、これにより活性を示すことができ、その際その分解物が揮発性であればイオン性物質をフラックス膜に残留させないようにすることができる。
ハロゲン化化合物としては、塩素化物、臭素化物、フッ化物のように塩素、臭素、フッ素の各単独元素の共有結合による化合物でもよいが、その３者の任意の２つ又は全部のそれぞれの共有結合を有する化合物でもよい。これらの化合物は、水性溶媒に対する溶解性を向上させるために、例えばハロゲン化アルコールのように水酸基等の極性基を有することが好ましい。ハロゲン化アルコールとしては、例えば２，３−ジブロモプロパノール、２，３ジブロモブタンジオール、１，４−ジブロモ−２−ブタノール、トリブロモネオペンチルアルコール等の臭素化アルコール、１，３−ジクロロ−２−プロパノール、１，４−ジクロロ−２−ブタノール等の塩素化アルコール、３−フルオロカテコール等のフッ素化アルコール、その他のこれらに類する化合物が挙げられる。
他の活性剤を併用することもでき、これにはアミン類、アミン塩類（エチレンジアミン等のポリアミン、シクロヘキシルアミン、ジエチルアミン等のアミンの有機酸塩や無機酸塩（塩酸、硫酸等の鉱酸塩））、有機酸類、アミノ酸類、アミド系化合物等が挙げられる。具体的にはジフェニルグアニジン臭化水素酸塩、シクロヘキシルアミン臭化水素酸塩、ジエチルアミン塩酸塩、コハク酸、アジピン酸、セバシン酸、トリエタノールアミン、モノエタノールアミン等が挙げられる。活性剤は上記ピラゾール等を含めてフラックス中に０．１〜１０％加えられることが好ましい。非解離型活性剤は上記ピラゾール等を含めてフラックス中０．１〜１０％加えることが好ましい。これより少ないと、ブリッジ、つららなどのはんだ付不良を発生し易くなり、これより多いと溶解性の低下によるフラックスの液組成の安定性の低下を起こす場合がある。
【００１６】
本発明において、「ロジン系樹脂を含有する樹脂成分」とは、ロジン系樹脂は必ず使用するが、その他の樹脂を併用してもよいことを示す。「ロジン系樹脂」としては、例えばガムロジン、ウッドロジン、トール油ロジン、不均化ロジン、重合ロジン、水素添加ロジン及びこれらの誘導体等のロジン類が挙げられるが、これらの変性物であるロジン系変性樹脂も挙げられ、そのロジン系変性樹脂としては、ディールス・アルダー反応の反応成分となり得る上記のロジン類の不飽和有機酸変性樹脂（（メタ）アクリル酸等の脂肪族の不飽和一塩基酸、フマル酸、マレイン酸等のα，β−不飽和カルボン酸等の脂肪族不飽和二塩基酸、桂皮酸等の芳香族環を有する不飽和カルボン酸等の変性樹脂）及びこれらの変性物等のアビエチン酸やその変性物を主成分とするものが挙げられ、これらは単独あるいは２種以上混合して用いられる。これらの内、酸価が１００より小さくなく、好ましくは酸価が１８０より小さくないロジン系変性樹脂は、アンモニアその他の揮発性アミン化合物（残渣に残留し難いように沸点が２００℃より高くなく（ピラゾ−ル、その誘導体、これらの塩も含まれる場合がある）、フラックス中、０．１〜２０重量％含有させ、フラックスのｐＨ１０以下、好ましくは７〜８にする。）とともに用いると水溶化（フラックス中、水が５０％より少なくない）することができ、フラックスやこのフラックスを用いたソルダーペースト中の有機溶剤を無くすか、少なくすることができ、これらの製造や使用において有機溶剤の揮散による大気汚染の問題を回避することができる。これによれば、大気中に有機溶剤を排出する量を減らすことができ、その排出をほどんどないようにすることができる回路基板はんだ付用フラックス及びソルダーペーストを提供することができる。
「ロジン系樹脂」がフラックスやソルダーペーストの膜の樹脂成分としての性能を有するには、噴流はんだ付方法、リフローはんだ付方法のいずれの場合でも、そのはんだ付性を損なわないために、その軟化点（ＪＩＳに定める環球法）は、噴流はんだ付方法の場合には６０〜１５０℃が好ましく、リフローはんだ付する場合にははんだ付時の温度が高いので７０〜１５０℃が好ましい。低過ぎるとフラックス膜に粘着性が生じ、高過ぎると溶融はんだに押し退けられる性質が損なわれ、溶融はんだのはんだ付ランドに対するぬれを害することがある。
【００１７】
上記のロジン系樹脂は、フラックス中に０．１〜３０％含有されてもよいが、ピラゾール等を併用する場合にはフラックス中に０．１〜１５％にも減らすことができ、それだけフラックスの残渣膜の洗浄をないようにできる点で好ましいがが、少な過ぎると、フラックスとしての機能を有することができず、多すぎるとコスト高になるのみならず、フラックスの粘度が大きくなり、プリント回路基板に均一に塗布することができず、また、フラックス膜が厚くなりすぎ、溶融はんだのはんだ付ランドに対する濡れを害することがある。ソルダーペーストに使用するフラックスについても同様のことが言える。
ソルダーペーストに使用するフラックス中のロジン系樹脂は、０．１〜７０％含有されてもよいが、ピラゾール等を併用する場合には、フラックス中に０．１〜６０％に減らすことができる。
【００１８】
ロジン系樹脂と併用することができるその他樹脂としては、アクリル系樹脂が挙げられる。アクリル系樹脂としては、アルコール等の極性溶媒に溶解できるものが従来のロジン類を用いたフラックスやソルダーペーストと同様に製造し、使用し易い点から好ましい。アクリル系樹脂としては、（メタ）アクリル系モノマー、例えば（メタ）アクリル酸、（メタ）アクリル酸エステルを主成分としたホモポリマーやコポリマーが挙げられる。また、スチレン−水溶性不飽和二塩基酸系共重合体樹脂（スチレン系モノマーとマレイン酸、フマル酸、イタコン酸等の共重合体）もロジン系樹脂や、さらにアクリル系樹脂と併用できる。ロジン系樹脂と併用するこれらの樹脂は、フラックス中、２〜３０％が挙げられる。
ロジン系樹脂とこれらのその他の樹脂を含有するフラックス膜、このフラックスを用いて得られるソルダーペーストの残渣膜のガラス転移温度は、寒暖の差の激しい雰囲気下（−３０℃と、＋８０℃に繰り返し曝す温度サイクル試験）におかれることによる衝撃である、いわゆる冷熱衝撃にも耐えるためにも重要であり、７０℃（ＤＳＣ（示差熱量計）による測定）より高くないことが好ましく、そのためには高沸点溶剤の併用も好ましい。
その高沸点溶剤としては、沸点が１５０℃より低くない、いわゆる可塑剤とすることができる、（メタ）アクリル酸エステル、フタル酸エステル、脂肪族二塩基酸エステルが挙げられる。この高沸点溶剤は、フラックス中、０．１〜１５％が好ましい。
【００１９】
フラックス及びソルダーペーストの成分として用いられる溶剤としては、アルコール系溶媒、セロソルブ類等が挙げられ、その内でもイソプロピルアルコールが好ましく、これら有機溶媒は単独あるいは複数混合して用いられるが、水性溶剤を用いてもよく、水性溶剤としては水及びこれと水に溶解性のある有機溶剤の混合溶剤が用いられる。
本発明のフラックス及びソルダーペーストに使用するフラックスには、つや消し剤、発泡剤、消泡剤を０．１〜１０％、カオリン、エアロジール（日本エエロジール社製）、有機ベントナイト、硬化ひまし油等のチクソ剤を１〜１０％加えてもよく、その他の添加剤を加えてもよい。
【００２０】
本発明のフラックスを製造するには、ロジン系樹脂、これと併用するその他の樹脂、ピラゾール等、必要に応じて他の活性剤、その他の添加剤を有機溶剤に溶解すればよいが、上記のディールス・アルダー反応によるロジン系樹脂の不飽和有機酸変性樹脂のような酸価が１００より小さくないロジン系変性樹脂を使用する場合には、この樹脂を水と上記のアンモニア等の塩基性剤の混合物に徐々に加え、撹拌しながら溶解させ、さらに活性剤や、必要に応じて他の樹脂や可塑剤を助剤として加えて完成する。この際、上記変性樹脂を有機溶剤に溶解させておき、これを水と塩基性剤の混合溶媒に溶解させ、ついで必要に応じて他の成分を加え、完成するようにしてもよい。その際、有機溶剤をフラックスに含有させる場合にはその有機溶剤を上記変性樹脂の溶剤に使用し、その不足分はさらにその溶液に加えてから以下同様に操作すれば良い。このようにすると上記変性樹脂の水と塩基性剤の混合溶媒に対する溶解の作業性を向上させることかできる。また、フラックスに有機溶剤をほとんど含ませたくない場合は、上記変性樹脂を水と塩基性剤の混合溶媒に溶解させるときの撹拌の際にその有機溶剤を揮発させるようにしても良く、その場合には有機溶剤としては揮発性の有機溶剤を用いることが好ましい。
【００２１】
本発明のソルダーペーストを製造するには、本発明のフラックスとはんだ粉末を撹拌混合するのが好ましいが、使用するフラックスには、上述したようにロジン系樹脂のほかにアクリル系樹脂等の他の樹脂成分、グリコールエーテル系、アルコール系、芳香族系、エステル系等の溶剤、その他の溶剤の中から選択した溶剤を用い、その他活性剤、チクソ剤、必要に応じてその他添加剤を撹拌混合して製造してもよい。
そのはんだ粉末としては、有鉛のはんだ粉末の他に無鉛のはんだ粉末も使用する事ができる。この場合には、はんだ粉末とフラックスの合計に占めるそのフラックスの割合が９〜６０％である事が好ましい。
また、無鉛のはんだ粉末としては、Ｓｎ／Ａｇ、Ｓｎ／Ａｇ／Ｃｕ、Ｓｎ／Ａｇ／Ｃｕ／Ｂｉ、Ｓｎ／Ｓｂ等が挙げられる。
【００２２】
本発明のフラックスをプリント回路基板に塗布する塗布方法としては、ロールコーティング、浸漬法、スプレー法や、例えばフラックスに空気を吹き込む等によりバブリングさせて発泡させ、その泡をプリント回路基板に付着させるような塗布方法等、従来のフラックス塗布方法を同じようにして用いることができる。
このようにして塗布され、乾燥された本発明のフラックス膜は、有機溶剤や、水及び塩基性剤が揮発除去され、上記ロジン系樹脂とピラゾール等を含有する活性剤とからなるフラックス膜が形成される。そして噴流はんだ付方法、リフローはんだ付方法のいずれによってはんだ付を行っても、このロジン系樹脂は基本的にはロジンの性質を示すから、フラックス膜は溶融はんだが接触するまでははんだ付ランドに対する空気中の酸素を遮断してその表面の銅の酸化を防止し、溶融はんだが接触したときはその熱により溶融し、溶融はんだに押し退けられて塗布面のはんだ付ランドを露出させ、その際ピラゾール等の活性剤もはんだ付ランドのフラックス塗布前あるいははんだ付時に生じることのある銅酸化物を還元し、溶融はんだを金属銅のはんだ付ランドに良く濡らすことができる。
そして、そのはんだ付後は、揮発性塩基性剤を使用しているときは、この変性樹脂は塩基性剤が除去されているから水には溶解せず、したがって親水性の樹脂が疎水性の樹脂に変わり、電子部品を搭載した後の回路基板表面の絶縁性を害することがなく、回路をショートさせる等のことなくその信頼性を発揮することができる。
【００２３】
本発明のフラックスは、このようにプリント回路基板に塗布され、はんだ付が行われた後も洗浄することなく、電子部品を搭載した回路基板に被覆されたままにされ、本発明はこのようなフラックス膜付の電子部品搭載後の回路基板を提供する。また、本発明のソルダーペーストについてもその残渣膜は洗浄することなく、電子部品を搭載した回路基板に被覆されたままにされ、本発明はこのようなソルダーペーストの残渣膜付の電子部品搭載後の回路基板を提供する。
また、本発明のフラックスは、銅張り積層板をエッチング処理して回路配線パターンを形成した後、あるいはさらにそのパターン表面の銅酸化物を除くソフトエッチング処理を行った後、そのパターンを形成したプリント回路基板に塗布し、そのパターンをはんだ付作業まで酸化から保護する保護膜としても用いることができ、このような保護膜付プリント回路基板も本発明は提供する。
【００２４】
本発明のソルダーペーストの印刷膜は、溶融はんだの温度により押し退けられ、溶融はんだを金属面に接触させる事ができる。
この様にして電子部品がはんだ付されたプリント回路基板が得られるが、本発明に係わる本来の樹脂成分又はフラックスの残さ膜を洗浄しない場合でも、アクリル系樹脂が併用されておればロジン類のみの場合に比べてその膜は強靭であり、その強靭さの程度も分子量を変えて設計する事ができ、その選択幅を大きくできるので、寒暖の差が大きい場合でもマイクロクラックの発生を防止できる。
本発明においては、リフローはんだ付後のはんだ付樹脂成分の膜又ははんだ付けフラックスの残さ膜（はんだ接合部及びはんだ付後のフラックスの残さ膜）を有するプリント回路基板も提供する。
【００２５】
【実施例】
次に本発明の実施例を説明する。
本発明のフラックス、ソルダーペーストは、通常のフラックス、ソルダーペーストのようにして使用され、プリント回路基板にフラックス膜、ソルダーペースト膜が形成される。以下にそのフラックス、ソルダーペースト及びフラックス膜、ソルダーペーストの残渣膜を形成した回路基板の実施例を示す。
【００２６】
実施例１（フラックスの例）
以下の組成のフラックスを調製した。
ロジン　　　　　　　　　　　　　　１０．０ｇ
ピラゾール　　　　　　　　　　　　　０．５ｇ
イソプロピルアルコール　　　　　　８９．５ｇ
合計　　　　　　　　　　　　　　１００．０ｇ
上記各成分を攪拌混合することによってフラックスを得た。このフラックスの粘度をレッドウッド粘度計で測定したところ３．５ｍＰａ・ｓ（測定温度３０℃）であった。
【００２７】
実施例２〜５（フラックス）
実施例１において、表１に示す配合に変えたこと以外は同様にして実施例２〜５のフラックスを調製した。実施例１と同様に粘度を測定したところ、いずれもその粘度はほぼ同程度であった。
【００２８】
比較例１〜３（フラックス）
実施例１において、表１に示す配合に変えたこと以外は同様にして比較例１〜３のフラックスを調製した。実施例１と同様に粘度を測定したところ、いずれもその粘度はほぼ同程度であった。
【００２９】
上記実施例、比較例で得られたそれぞれのフラックスを用いて以下の試験を行った。
（ａ）ウエッティングバランス法によるぬれ上がり性（ぬれ作用力）の試験
１５ｍｍ×７ｍｍ×０．２ｍｍの銅板を１１％硫酸、３．８％過酸化水素を含む水溶液中に２０±１℃で６０秒間浸漬してソフトエッチングを行った後取り出し、３０秒間イオン交換水で洗浄する。この後、イソプロピルアルコール、酢酸エチルで順次洗浄し、表面を十分脱水した後、自然乾燥した。
この銅板の表裏両面の全面に上記実施例１〜５、比較例の１〜３のそれぞれのフラックスを浸漬法により塗布した試験片を約２５０℃の溶融はんだ（Ｓｎ／Ｐｂ＝６３／３７（質量比））の水平面に一端側から垂直に侵入させると、それとともに溶融はんだは断面略Ｖ字状に引き込まれるが、その侵入を停止すると、時間の経過とともに引き込まれた溶融はんだは徐々に上昇し、水平面に復帰したところで試験片がこの水平面に垂直になり、さらに溶融はんだは試験片の表面に沿って断面逆略Ｖ字状に上昇し、上昇し切る。この試験片の侵入から溶融はんだが水平面に復帰するまでの時間を「ぬれ時間（秒」として測定し、その時点では試験片には溶融はんだからは上下方向には何らの力も加わっていないが、溶融はんだが上記のように上昇するにつれて試験片は下側に引っ張られ、その上昇し切ったところでその引っ張り力は最大になるので、この最大の引っ張り力を「ぬれ作用力（ｍＮ）」として測定する。
ぬれ時間が短いほど、また、ぬれ作用力が大きいほど、試験片に対するぬれ性がよく、フラックス膜の銅板の銅酸化物等に対する還元作用や、銅板を空気による酸化から防止する機能が高く、フラックスの性能がよいことを示す。
【００３０】
（ｂ）スルーホール上がり率の試験
上記（ａ）項で用いたと同様のフラックスを、直径０．１〜１．０ｍｍのスルーホール（内壁にメッキ膜を施した貫通孔）を１８０個形成した試験片（図１に示すものと同様のもの）にスプレー法により塗布した後、噴流はんだ付装置（（株）タムラ・エフ・エーシステム製ＨＣ３３−３６ＳＮＸ）により約２５０℃の噴流はんだを形成し、その溶融はんだに試験片の一方の主面側を水平に４秒接触させ、大気中に取り出す。そして、上記スルーホールに対して溶融はんだがどこまで上昇して固化したかを観察し、図１（イ）に示すいずれのものも「合格」、図１（ロ）に示すいずれかのものを「不合格」として判定し、「スルーホール上がり率（％）」として、全数のスルーホールの内「合格」の数を百分率（％）で表す。
（ｃ）銅板腐食試験
上記のフラックス膜を形成した銅板の試験片について、ＪＩＳ−Ｚ−３１９７（１９９９）により試験を行った。「銅板腐食」のないものを「合格」、あるものを「不合格」として判定する。
上記（ａ）〜（ｃ）の試験の結果を上記各実施例、各比較例のフラックスの組成とともに表１に示す。
なお、上記実施例のフラックス膜の絶縁抵抗は１０^１３Ω以上であり、電圧印加後の抵抗も１０^１３以上であり、電圧印加後の銅板の腐食も認められなかった。
【００３１】
実施例６（ソルダーペースト）
以下の組成のソルダーペーストを調製した。
（フラックスの組成）
ロジン　　　　　　　　　　　　　　　　　　５．０ｇ
ピラゾール　　　　　　　　　　　　　　　　０．１ｇ
硬化ひまし油　　　　　　　　　　　　　　　０．７ｇ
ブチルカルビトール　　　　　　　　　　　　４．２ｇ
合計　　　　　　　　　　　　　　　　　　１０．０ｇ
（ソルダーペーストの組成）
上記フラックス　　　　　　　　　　　　　　１０．０ｇ
はんだ粉末（Ｓｎ／Ｐｂ＝６３／３７）　　　９０．０ｇ
（アトマイズ法により製造）
合計　　　　　　　　　　　　　　　　　　１００．０ｇ
上記フラックスは上記配合物を攪拌混合して調製したが、その粘度を実施例１と同様に測定したところ、４０Ｐａ・ｓであった。
また、上記ソルダーペーストは上記フラックスとはんだ粉末（アトマイズ法により製造したはんだ粉末）の配合物を１時間混練して調整したが、その粘度を実施例１と同様に測定したところ、１９０Ｐａ・ｓであった。
【００３２】
実施例７〜１０（ソルダーペースト）
実施例６において、表１に示す配合に変えたこと以外は同様にして実施例７〜９のソルダーペーストを調製した。実施例６と同様に粘度を測定したところ、いずれもその粘度はほぼ同程度であった。
【００３３】
比較例４〜６（ソルダーペースト）
実施例６において、表１に示す配合に変えたこと以外は同様にして比較例４〜６のソルダーペーストを調製した。実施例１と同様に粘度を測定したところ、いずれもその粘度はほぼ同程度であった。
【００３４】
上記実施例６〜１０、比較例４〜６で得られたそれぞれのフラックスを用いて上記（ａ）の試験を行ない（フラックスの相違によりソルダーペーストのこれら試験の結果が左右されるので、その結果はフラックスの試験結果をみればわかる）、さらに上記実施例６〜１０、比較例４〜６で得られたそれぞれのソルダーペーストを用いて以下の試験を行なった。
（ｄ）はんだ付性試験
３０ｍｍ×３０ｍｍ×０．２ｍｍの銅板を１１％硫酸、３．８％過酸化水素を含む水溶液中に２０±１℃で６０秒間浸漬してソフトエッチングを行った後取り出し、３０秒間イオン交換水で洗浄する。この後、イソプロピルアルコール、酢酸エチルで順次洗浄し、表面を十分脱水した後、自然乾燥した。
この銅板に上記のそれぞれのソルダーペーストを厚さ２００μｍのメタルマスクを用いたスクリーン印刷法により塗布した。
このソルダーペースト膜を形成した銅板の試験片について、２３５℃、３０秒間加熱し、溶融はんだのぬれ度合を「ぬれ性」として測定し、不ぬれ、ディウェットのないものを「良好」、不ぬれ、ディウェットのあるものを「不良」として判定した。
（ｅ）銅板腐食試験　ＪＩＳ　Ｚ　３２８４（１９８４）により試験を行なった。「銅板腐食」のないものを「合格」、あるものを「不合格」として判定した。
上記（ａ）、（ｄ）、（ｅ）の試験の結果を上記各実施例、各比較例のソルダーペーストの組成とともに表２に示す。
【００３５】
実施例１１（電子部品搭載前の回路基板の例）
上記（ａ）、（ｂ）の試験において、フラックス膜で被覆した銅板は、銅表面の保護機能からすれば、はんだ付ランドにフラックスの残渣膜の保護膜を形成した電子部品搭載前のプリント回路基板と見なすことができ、本発明の電子部品搭載前の回路基板の実施例と見なすことができる。
【００３６】
実施例１２（電子部品搭載後の回路基板の例（フラックス膜の場合）
上記（ａ）、（ｂ）の試験において、フラックス膜を形成した銅板についてそれぞれの試験を行った後のものは、通常のはんだ付を行った後のものに相当し、はんだ付ランドにフラックスの残渣膜の絶縁膜を形成した電子部品搭載後のプリント回路基板と見なすことができ、本発明の電子部品搭載後の回路基板の実施例と見なすことができる。
なお、清浄化されたスルーホール基板（５０×５０×１．６ｍｍ　３６０穴／枚）にスプレーフラクサーで上記実施例のフラックスを塗布した後、自動はんだ付装置によりはんだ付を行ったが、良好であった。
【００３７】
実施例１３（電子部品搭載後の回路基板の例）（ソルダーペースト膜の場合）
上記（ｄ）の試験において、ソルダーペースト膜を形成した銅板についてその試験を行った後のものは、通常のはんだ付を行った後のものに相当し、はんだ付ランドにソルダーペーストの残渣膜の絶縁膜を形成した電子部品搭載後のプリント回路基板と見なすことができ、本発明の電子部品搭載後の回路基板の実施例と見なすことができる。
【００３８】
【表１】

【００３９】
【表２】

【００４０】
以上の結果から、本発明の実施例のフラックス膜は、ロジン系物質と、活性剤としてピラゾールやジメチルピラゾールの使用により、この両者との関係では、同じロジン系物質と、その他の系統の活性剤を使用した比較例１、２に比べ、「銅板腐食」がいずれも合格であることを除くいずれの性能も顕著に優れ、また、樹脂成分を使用せずピラゾールのみを使用した比較例３に比べ、同様に「銅板腐食」を除くいずれの性能も更に顕著に優れることがわかり、上記の両者の使用による相乗効果が顕れている。
また、本発明の実施例のソルダーペースト膜は、ロジン系物質と、活性剤としてピラゾールやジメチルピラゾールの使用により、この両者との関係では、同じロジン系物質と、その他の系統の活性剤を使用した比較例４、５に比べ、また、ピラゾールの代わりにメチル−１Ｈ−ベンゾトリアゾールを使用した比較例６に比べ、「ぬれ作用力」は２倍以上、「ぬれ時間」は４倍以上優れ、上記の両者の使用による相乗効果が顕れている。特に、メチル−１Ｈ−ベンゾトリアゾールに比べてピラゾールが特に優れることは、同じアゾール類に属していても選択性があることを示しているといえる。
なお、単に「％」とあるは質量％を示す。
【００４１】
【発明の効果】
本発明によれば、ロジン系樹脂とピラゾール等を併用したので、回路基板の金属面の酸化物等の還元作用に優れ、溶融はんだのぬれ性が良く、特に複数回のリフローはんだ付工程を行う場合やその後に噴流はんだ付を行う場合において、後に行うリフローはんだ付や噴流はんだ付でも、有鉛はんだのみならず無鉛はんだについても、溶融はんだのぬれ性やぬれ上がり性が良く、塗布性を損なわず、均一な塗布膜を形成でき、しかもピラゾールを併用した分ロジン系樹脂の使用量を減らして低残渣膜を可能にしながら、はんだ付性を害さず、はんだ付ランドの腐食性が少なく、電気絶縁性の良い信頼性の高い回路基板はんだ付用フラックス及びソルダーペーストを提供することができる。
そして、このような回路基板はんだ付用フラックスやソルダーペーストを塗布してはんだ付ランドを保護した電子部品搭載前の回路基板及び電子部品搭載後の回路基板を提供することができる。
【図面の簡単な説明】
【図１】プリント回路基板のスルーホールに対する溶融はんだのぬれ上がり状態を示す説明図であり、（イ）は合格、（ロ）は不合格の場合を示す。[0001]
[Industrial applications]
The present invention relates to a flux used when soldering an electronic component to a circuit board, a solder paste, and a circuit board before or after soldering an electronic component having these residual films, and particularly, the wettability of molten solder to a pattern of the circuit board. With respect to what was improved.
[0002]
[Prior art]
2. Description of the Related Art In an electronic device, a circuit board on which electronic components are mounted is used as a component constituting a circuit having one function. As the circuit board, for example, a printed circuit board is one in which a circuit wiring pattern is formed on a copper-clad laminate, for example, and electronic components are mounted thereon so that one circuit unit can be formed. However, in order to mount a capacitor, a resistor, or the like as the electronic component, these components are soldered and connected and fixed to a copper foil land of the circuit wiring pattern, that is, a soldering land.
In order to solder electronic components to a printed circuit board in this way, for example, a chip-shaped electronic component having electrodes at both ends is arranged at a predetermined location on the printed circuit board such that the electrodes at both ends are located on soldered lands. Then, the temporary fixing is performed, and then the temporarily fixed electronic component is soldered by being brought into contact with the molten solder to be jetted, that is, a so-called jet-type soldering method, or a solder paste is applied to a soldering land. Similarly, the so-called reflow soldering method is used in which the electrodes of electronic components are positioned and heated, and the solder powder of the solder paste is melted and soldered. It is increasing because of the advantage of miniaturization. As for miniaturization, recently, surface mounting on printed circuit boards is in the direction of so-called high density, in which electronic components are miniaturized and their mounting density is increased. .5 mm).
[0003]
Regardless of the reflow soldering method or the jet soldering method, the electronic components are automatically supplied to the printed circuit board that is continuously transported, and the electrodes or leads are soldered to lands or through holes. Although automatic soldering is performed, flux is usually applied to the soldering lands or through holes in the previous process, and then the molten solder is contacted, or solder paste is applied. This prevents the copper foil of the land to be soldered from being oxidized by heat or the like at the time of soldering, thereby preventing poor soldering. This is because the soldering lands of the printed circuit board are heated to 200 ° C. to 300 ° C. during soldering, so that not only when the surface is exposed but also when a protective film is formed on the surface, This is because, when a flux is applied during soldering, the film blocks oxygen to prevent oxidation of the copper foil, reduces existing oxides, and wets the molten solder well.
As such a flux, a rosin-based flux is often used, and its composition is mainly composed of a rosin-based resin, and an amine halide, an activator such as an organic acid, and further according to other purposes, such as a solder. It is common to add a matting agent that gives a matting effect to the attached land and various additives such as a foaming agent that improves foaming properties, etc., and dissolve it in a solvent mainly containing alcohol such as ethyl alcohol and isopropyl alcohol. It is used for When this flux is used in an automatic soldering apparatus, it is accommodated in a fuser provided in the apparatus and applied by a foaming, jet or spray coating means.
In general, rosin or rosin-modified resin, which is a rosin-modified resin, has excellent electrical insulation and moisture resistance, prevents oxidation of the soldering lands even when soldering at high temperatures, and melts on the copper foil surface by the heat of the molten solder. It has good so-called soldering performance that enables molten solder to come into contact with it, and has been used as a soldering flux since ancient times.
[0004]
As the solder paste, a paste-like composition containing a solder powder and a flux is used. The flux is based on rosin or a rosin-modified resin, and a small amount of amine halide such as amine hydrochloride is added thereto. An activator such as a salt or an organic acid, a thixotropic agent such as hardened castor oil, and other materials in which various materials are dissolved in a solvent depending on the purpose are generally used. This is because, as described above, the rosin-based resin has excellent soldering performance and the like, and a solder paste is generally produced by mixing a solder powder and a flux using the rosin-based resin.
[0005]
However, recently, with the progress of surface mounting, the demand for high-density mounting of electronic components has increased, and circuit patterns have been formed on both sides of the printed circuit board, and reflow soldering using solder paste on the front side. Then, reflow soldering is performed in the same way on the back side, and through holes for connecting the circuit patterns on both sides (electroless plating is applied to the inner surface of the through hole of the printed circuit board, and the circuit pattern on both sides is Also, the soldering of the electronic component is performed by inserting the lead of the electronic component into a conductor which enables conductor connection.
In any such soldering, after the flux is applied, reflow soldering or jet soldering is performed, but each time the conductor of the soldering land and through hole is repeatedly heated, it is easy to oxidize, As the soldering is performed later, the wettability of the molten solder to the soldering lands and through holes after the flux application becomes worse. In particular, in the last step of jet soldering for through holes, after reflow soldering electronic components on both sides of the printed circuit board, insert the leads of the electronic components into the through holes from the front side, then apply flux to the back side, The jet solder (sprayed molten solder) is brought into contact with the back surface side. At that time, the molten solder rises by being wetted by the plated film of the through-hole. The product is acceptable as shown in (a), but if the wet-up is insufficient, the product is unacceptable as shown in FIG. In FIG. 1, "PTH" is a through hole with a plated film in which a plated film is formed on the inner wall of the through hole provided on the printed circuit board (reticulated line portion) and the surrounding surface and back surface. Part) shows a state in which the molten solder has solidified after wetting or about to get wet. If the "solder" is applied to the inside of the through hole and the subsequent plating film on the front and back surfaces without leakage, the passing product in the same figure (a) will also cover the entire plating film on the front and back surfaces. Even if it is best to be piled up, it is not necessary up to that point (the one on the right from the left end in the figure), but for the rejected products in the figure (b), the "solder" is almost completely filled in the through holes However, if there is a leak on the surface and the back surface that follows this, there is a large leak, and further, the filling of the inside of the through hole is gradually reduced. Even those that can no longer be served (ones from the left end in the figure to the right in order).
[0006]
[Problems to be solved by the invention]
In the case where the reflow soldering is performed a plurality of times and the last jet soldering is performed as described above, regardless of the case of the first reflow soldering, in other cases, particularly, in the case of the last jet soldering, It is not possible to avoid the danger of producing rejected products as shown in FIG. 1 (b) only by using the conventional flux or solder paste. Also, in reflow soldering, wettability of molten solder due to melting of a solder paste coating film on a soldering land and wettability of electrodes at both ends of a chip component to be soldered are required, and this is insufficient. In some cases, the soldering strength is insufficient and the chip components are liable to fall off and other soldering defects are likely to occur. In particular, when a lead-free solder is used, the molten solder has lower wettability to the metal than the molten solder of the lead-based solder, so the above-mentioned problem is further increased, and the merits of the improvement are increased.
As other conventional fluxes, for example, a flux containing a monocyclic or polycyclic azole such as imidazole and pyrazole as an activator as described in JP-A-5-392. If a cream solder (solder paste) containing this flux is used, the activity is not exhibited when not heated, and the oxides, sulfides, hydroxides, and chlorides present on the metal surface when heated. , Sulfates and carbonates, and purify the metal.The heterocyclic compound containing at least one nitrogen atom hardly remains as a residue even if it remains as a residue.・ In addition, if a thickener (eg, ethylcellulose) is used in the cream solder that results in an ultra-low residue after soldering, soldering No post-washing is necessary after the printed circuit board. "(However, an example using pyrazole is not shown), and a flux containing a large amount of conventional natural resin such as rosin or synthetic resin, etc. Cream solder has the drawback that a large amount of residue adheres to the printed circuit board, and it is necessary to clean it using a solvent such as chlorofluorocarbon, but after saying that the use of chlorofluorocarbon will be completely prohibited in the near future. It is said that it can be improved. And, while a flux using imidazole and methyl-1H-benzotriazole together with a solvent as the azoles is shown, a comparative example of a flux using 20% by weight of rosin as a resin component without using the azoles is shown. Further, while an example of a cream solder using 0.3% by weight of ethyl cellulose as a resin component together with methyl-1H-benzotriazole as the azole is shown, the azole is not used. Comparative examples of cream solder using 5% by weight of hydrogenated rosin are shown, and these problems are caused by using 20% by weight or 5% by weight of rosin in flux and solder paste. It is shown that.
[0007]
However, in particular, since the solder paste is applied to the pattern forming surface of the printed circuit board by, for example, screen printing, appropriate viscosity is required from the viewpoint of printability to form a uniform continuous film. It can be said that those described in the above publication also contain ethylcellulose, but ethylcellulose rapidly increases in viscosity with a small content compared to rosins, and it is not only difficult to adjust the viscosity, but even if only a small amount is used. Even when a thixotropic agent such as hardened castor oil is used, the residue adhering to the soldering land has poor uniform melting property with respect to molten solder (about 260 ° C.) as compared with the residue of rosin (ethyl cellulose). The melting temperature is high.) As a result, the residual film is pushed away by the molten solder generated by heating the solder paste coating film. When the molten solder is hardly in direct contact with the metal of the land with solder, so-called poor wetting occurs, and when the molten solder solidifies on the residual film, the residual film is non-conductive. Therefore, there is a problem that not only the direct contact of the solder on the metal surface of the soldering land tends to be insufficient, but also the bonding strength of the solder to the soldering land tends to decrease.
In the case of the flux, even if any of the above-mentioned fluxers is used, it is preferable that the flux has a certain degree of viscosity, and it is preferable to include a resin component for that purpose. However, if ethyl cellulose is contained in a small amount, the same problem as in the case of the solder paste described above occurs. Further, the wettability of the molten solder is lower than that of the flux film containing no rosin.
[0008]
In addition to the above publications, JP-A-6-15483 discloses a flux and a solder paste containing a benzimidazole compound, and JP-A-5-237688 discloses a flux containing a benzimidazole compound having an alkyl group at the 2-position. JP-A-3-238196 and JP-A-3247752 disclose a flux containing benzotriazole and the like, and JP-B-5-23880 discloses a flux containing imidazolyl succinic acid. No mention is made of a solder paste using a pyrazole-based compound as an activator or a flux.
[0009]
A first object of the present invention is to provide a circuit board soldering flux and a solder paste which are excellent in reducing oxides and the like on the metal surface of a circuit board and have good wettability of molten solder.
A second object of the present invention is to perform wet reflow soldering or multiple subsequent reflow soldering steps, and to perform wet reflow soldering or reflow soldering later, and to perform wet reflow soldering or wet reflow soldering. It is an object of the present invention to provide a flux and a solder paste for soldering a circuit board.
A third object of the present invention is to provide a flux for soldering a circuit board and a solder paste which can form a uniform coating film without impairing coatability, and which does not impair solderability with a low residue film.
A fourth object of the present invention is to provide a highly reliable circuit board soldering flux and solder paste having low corrosiveness of soldering lands and good electrical insulation.
A fifth object of the present invention is to provide a circuit board before mounting electronic components, in which a soldering land is protected by applying a circuit board soldering flux to achieve the above object.
A sixth object of the present invention is to provide a circuit board after mounting electronic components, which does not impair the reliability of the circuit function, has good productivity, and can be obtained at low cost.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides (1) a pyrazole-based compound in a resin component containing a rosin-based resin and a flux used when soldering an electronic component to a circuit board containing at least a solvent component. And a flux for soldering a circuit board, comprising:
The present invention also provides (2) the flux for soldering a circuit board according to the above (1), wherein the pyrazole-based compound is at least one selected from the group consisting of pyrazole, derivatives thereof, and salts thereof; (4) a solder paste for soldering a circuit board containing a pyrazole-based compound, wherein the solder paste contains at least a solder powder and a resin component and is used when soldering an electronic component to a circuit board. In a solder paste containing at least a solder powder and a flux for a solder paste, the flux is a flux for soldering a circuit board according to the above (1); An electrode coated with a soldering land using the circuit board soldering flux of (1) or (2). A circuit board before or after soldering a component; (6) a circuit board after mounting an electronic component having a residue film after soldering using the solder paste for soldering a circuit board according to the above (3) or (4) Is provided.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the "pyrazole compound" includes, for example, "at least one selected from the group consisting of pyrazole, derivatives thereof, and salts thereof" (hereinafter, sometimes referred to as "pyrazole or the like"), and an activator. Used as “Pyrazole” is a 1,2-diazole, a substance having a boiling point of 184 ° C. to 185 ° C. (719 mmHg), which is easily soluble in water, ethanol, ether, and benzene. It is a substituent substitution product of pyrazole having a substituent, and “these salts” are salts of the above-mentioned pyrazoles or pyrazole derivatives with organic or inorganic acids. Salts can increase water solubility.
Examples of these acids include mineral acids such as hydrochloric acid and sulfuric acid, phosphoric acid and other inorganic acids, and organic acids such as carboxylic acid, organic phosphoric acid and organic sulfuric acid. Good, but a plurality of them may be used in combination.
Examples of the pyrazole and its derivative include a compound represented by the following general formula [Formula 1].
[0012]
Embedded image

(Where R ₁ Is hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, a phenyl group, a halogenated phenyl group, a methoxyphenyl group, an amino group, a hydroxy group, a halogen atom (such as Cl, Br, I), a carboxyl group, Represents a methoxy group or a benzyl group, n represents an integer of 0 to 3, and when n is 2 or more, (R ₁ ) N R ₁ May be the same or different; ₂ Is hydrogen, a linear or branched alkyl group having 1 to 5 carbon atoms, a phenyl group, a halogenated phenyl group, a methoxyphenyl group, an amino group, a hydroxy group, a halogen atom (such as Cl, Br, I), a carboxyl group, Represents a methoxy group or a benzyl group. )
[0013]
Specific examples of pyrazole derivatives and salts thereof include 5-amino-1,3-dimethylpyrazole hydrochloride, 3-amino-5-hydroxypyrazole, 3-aminopyrazole, 3- (4-chlorophenyl) pyrazole, and pyrazole-3. Diethyl, 5-dicarboxylate, 3,5-dimethylpyrazole, 3- (4-methoxyphenyl) pyrazole, 3-methyl-1-phenyl-1H-pyrazole, 3-methylpyrazole, 3-phenylpyrazole, 3,5- Pyrazole dicarboxylic acid monohydrate, 3- (4-tolyl) pyrazole, 3-aminopyrazole-4-carboxylic acid, 3,4-diamino-5-hydroxypyrazole sulfate, 4-methylpyrazole, 5-chloro-1 , 3-dimethylpyrazole, 1-phenylpyrazole, 3,5-diphenylpyrazole, 3, - dimethyl-1-phenylpyrazole, 4-bromo-3-methylpyrazole, 1,3,5-trimethyl pyrazole and the like.
[0014]
At least one of pyrazole, a derivative thereof and a salt thereof is 0.01 to 10.0% (% by weight, hereinafter the same), preferably 0.1 to 3.0% in the flux, and the addition amount is too small. In such a case, the effect of the addition (the effect as described in the above-mentioned Japanese Patent Application Laid-Open No. 5-392 as described in the above-mentioned wording) cannot be obtained, and the amount of addition is too large. And it becomes difficult to dissolve in the flux.
[0015]
The flux of the present invention may contain a “non-dissociable activator composed of a non-dissociable halogenated compound”. As the non-dissociable halogenated compound, a non-salt-based compound in which a halogen atom is bonded by a covalent bond may be used. Organic compounds of the formula When the halogen atom is non-dissociative, the metal of the circuit board is not corroded, and even if the halogen atom remains in the flux, the electrical insulation property is not impaired. When these non-dissociative halogenated compounds are exposed to high temperatures of 200 ° C or more of the molten solder during soldering, some of them are decomposed to produce halogens or simple compounds thereof, thereby exhibiting activity. In this case, if the decomposition product is volatile, the ionic substance can be prevented from remaining on the flux membrane.
The halogenated compound may be a compound formed by a covalent bond of each single element of chlorine, bromine, and fluorine, such as a chlorinated compound, a brominated compound, and a fluoride compound. May be a compound having These compounds preferably have a polar group such as a hydroxyl group such as a halogenated alcohol in order to improve solubility in an aqueous solvent. Examples of the halogenated alcohol include brominated alcohols such as 2,3-dibromopropanol, 2,3 dibromobutanediol, 1,4-dibromo-2-butanol and tribromoneopentyl alcohol, and 1,3-dichloro-2- Examples include chlorinated alcohols such as propanol and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and other similar compounds.
Other activators can be used in combination, such as amines, amine salts (organic acid salts and inorganic acid salts of amines such as polyamines such as ethylenediamine, cyclohexylamine and diethylamine (mineral salts such as hydrochloric acid and sulfuric acid)). ), Organic acids, amino acids, amide compounds and the like. Specific examples include diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine hydrochloride, succinic acid, adipic acid, sebacic acid, triethanolamine, monoethanolamine and the like. The activator is preferably added to the flux in an amount of 0.1 to 10% including the above-mentioned pyrazole and the like. The non-dissociative activator is preferably added in an amount of 0.1 to 10% in the flux, including the above-mentioned pyrazole. If the amount is less than this, soldering defects such as bridges and icicles tend to occur, and if it is more than this, the stability of the flux liquid composition may decrease due to the decrease in solubility.
[0016]
In the present invention, the “resin component containing a rosin-based resin” indicates that a rosin-based resin is always used, but other resins may be used in combination. Examples of the “rosin-based resin” include rosins such as gum rosin, wood rosin, tall oil rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. The rosin-based modified resin includes, as the rosin-based unsaturated organic acid-modified resin ((meth) acrylic acid or the like) which can be a reaction component of the Diels-Alder reaction, Modified resins such as aliphatic unsaturated dibasic acids such as α, β-unsaturated carboxylic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid) and modified products thereof. Examples include those containing abietic acid or a modified product thereof as a main component, and these may be used alone or in combination of two or more. Among these, rosin-based modified resins whose acid value is not less than 100, and preferably whose acid value is not less than 180, are ammonia and other volatile amine compounds (boiling point is not higher than 200 ° C. so as to hardly remain in the residue ( Pyrazole, a derivative thereof, or a salt thereof) may be contained in the flux, and 0.1 to 20% by weight is contained in the flux to make the flux pH 10 or less, preferably 7 to 8). (Less than 50% of water in the flux), eliminating or reducing the flux and the organic solvent in the solder paste using the flux, and evaporating the organic solvent in the production and use of these. Can avoid the problem of air pollution. According to this, it is possible to provide a flux for soldering a circuit board and a solder paste, which can reduce the amount of the organic solvent discharged into the atmosphere and can suppress the discharge of the organic solvent.
In order for rosin resin to have the performance as a resin component of flux and solder paste films, it must be softened in both the jet soldering method and the reflow soldering method in order not to impair the solderability. The point (the ring and ball method defined in JIS) is preferably from 60 to 150 ° C in the case of the jet soldering method, and is preferably from 70 to 150 ° C in the case of reflow soldering because the temperature during soldering is high. If the temperature is too low, the flux film becomes sticky, and if the temperature is too high, the property of being displaced by the molten solder is impaired, which may impair wettability of the molten solder to the soldering land.
[0017]
The above-mentioned rosin-based resin may be contained in the flux in an amount of 0.1 to 30%. However, when pyrazole or the like is used in combination, the rosin resin can be reduced to 0.1 to 15% in the flux. Although it is preferable in that the residual film can be prevented from being washed, if the amount is too small, it cannot have a function as a flux.If the amount is too large, not only does the cost increase, but also the viscosity of the flux increases, and the printed circuit becomes large. It cannot be applied uniformly to the substrate, and the flux film becomes too thick, which may impair wettability of the molten solder to the soldering land. The same can be said for the flux used for the solder paste.
The rosin-based resin in the flux used for the solder paste may be contained in an amount of 0.1 to 70%, but when pyrazole or the like is used in combination, the rosin resin can be reduced to 0.1 to 60% in the flux.
[0018]
Other resins that can be used in combination with the rosin resin include acrylic resins. As the acrylic resin, those which can be dissolved in a polar solvent such as alcohol are preferable because they can be manufactured and used similarly to fluxes and solder pastes using conventional rosins. Examples of the acrylic resin include homopolymers and copolymers containing (meth) acrylic monomers such as (meth) acrylic acid and (meth) acrylic acid ester as main components. In addition, a styrene-water-soluble unsaturated dibasic acid-based copolymer resin (a copolymer of a styrene-based monomer and maleic acid, fumaric acid, itaconic acid, etc.) can also be used in combination with a rosin-based resin or an acrylic resin. These resins used in combination with the rosin-based resin may be 2 to 30% in the flux.
The glass transition temperature of the flux film containing the rosin-based resin and these other resins, and the residual film of the solder paste obtained by using this flux, is measured in an atmosphere having a drastic temperature difference (-30 ° C and + 80 ° C repeatedly). It is important to withstand so-called thermal shock, which is the impact of exposure to a temperature cycle test, and is preferably not higher than 70 ° C. (measured by a DSC (differential calorimeter)). It is also preferable to use a boiling point solvent in combination.
Examples of the high-boiling solvent include (meth) acrylic acid esters, phthalic acid esters, and aliphatic dibasic acid esters, which can be so-called plasticizers having a boiling point not lower than 150 ° C. The content of the high boiling point solvent in the flux is preferably 0.1 to 15%.
[0019]
Examples of the solvent used as a component of the flux and the solder paste include alcohol solvents, cellosolves, and the like. Among them, isopropyl alcohol is preferable.These organic solvents are used alone or in combination of two or more. Water may be used as the aqueous solvent, and a mixed solvent of water and an organic solvent soluble in water may be used.
The flux used in the flux and the solder paste of the present invention includes a matting agent, a foaming agent, 0.1 to 10% of a defoaming agent, kaolin, aerial (manufactured by Nippon Egille Co., Ltd.), organic bentonite, and hardened castor oil. The agent may be added at 1 to 10%, and other additives may be added.
[0020]
In order to produce the flux of the present invention, a rosin-based resin, another resin used in combination therewith, pyrazole, etc., if necessary, other activators and other additives may be dissolved in an organic solvent. When using a rosin-based modified resin having an acid value not less than 100, such as an unsaturated organic acid-modified resin of a rosin-based resin obtained by the Diels-Alder reaction, the resin is treated with water and a basic agent such as ammonia. The mixture is gradually added to the mixture, dissolved with stirring, and further completed by adding an activator and, if necessary, another resin or a plasticizer as an auxiliary agent. At this time, the modified resin may be dissolved in an organic solvent, and then dissolved in a mixed solvent of water and a basic agent. Then, if necessary, other components may be added to complete the modification. At that time, when an organic solvent is contained in the flux, the organic solvent is used as the solvent for the modified resin, and the shortage may be further added to the solution, and then the same operation may be performed. By doing so, the workability of dissolving the modified resin in a mixed solvent of water and a basic agent can be improved. Also, when it is desired that the organic solvent is hardly contained in the flux, the organic solvent may be volatilized at the time of stirring when dissolving the modified resin in a mixed solvent of water and a basic agent. It is preferable to use a volatile organic solvent as the organic solvent.
[0021]
In order to produce the solder paste of the present invention, it is preferable to stir and mix the flux of the present invention and the solder powder.However, the flux to be used includes, in addition to the rosin-based resin as described above, another resin such as an acrylic-based resin. Using a solvent selected from resin components, glycol ethers, alcohols, aromatics, esters, and other solvents, and other solvents, stir and mix other activators, thixotropic agents, and other additives as necessary. May be manufactured.
As the solder powder, lead-free solder powder can be used in addition to leaded solder powder. In this case, the ratio of the flux to the total of the solder powder and the flux is preferably 9 to 60%.
Examples of the lead-free solder powder include Sn / Ag, Sn / Ag / Cu, Sn / Ag / Cu / Bi, and Sn / Sb.
[0022]
The coating method for applying the flux of the present invention to a printed circuit board includes roll coating, dipping, spraying, and bubbling by, for example, blowing air into the flux to foam the foam, and attaching the foam to the printed circuit board. A conventional flux coating method such as a simple coating method can be used in the same manner.
The flux film of the present invention coated and dried in this manner forms a flux film comprising the rosin-based resin and an activator containing pyrazole or the like, from which an organic solvent, water and a basic agent are volatilized and removed. Is done. Regardless of whether the soldering is performed by the jet soldering method or the reflow soldering method, the rosin-based resin basically shows the properties of rosin, so the flux film is applied to the soldering land until the molten solder contacts. It blocks oxygen in the air to prevent oxidation of copper on the surface, and when molten solder comes in contact, it melts due to the heat and is pushed away by the molten solder, exposing the soldering land on the application surface, The activator also reduces the copper oxide which may be generated before the soldering land is coated with the flux or at the time of soldering, so that the molten solder can be well wetted on the metal copper soldering land.
After soldering, when using a volatile basic agent, this modified resin does not dissolve in water because the basic agent has been removed, and therefore the hydrophilic resin becomes hydrophobic. Instead of resin, the reliability can be exhibited without impairing the insulation of the surface of the circuit board after mounting the electronic components and without shorting the circuit.
[0023]
The flux of the present invention is thus applied to the printed circuit board, and is not covered with the washing after soldering, but is left covered on the circuit board on which the electronic components are mounted. Provided is a circuit board after mounting an electronic component with a flux film. Also, the residual film of the solder paste of the present invention is not cleaned, and is left covered on the circuit board on which the electronic component is mounted. A circuit board is provided.
In addition, the flux of the present invention may be formed by etching a copper-clad laminate to form a circuit wiring pattern, or after performing a soft etching treatment to remove copper oxide on the pattern surface, and then forming a printed pattern. The present invention also provides a printed circuit board with such a protective film, which can be applied to a circuit board and used as a protective film for protecting the pattern from oxidation until soldering.
[0024]
The printed film of the solder paste of the present invention is pushed away by the temperature of the molten solder, and the molten solder can be brought into contact with the metal surface.
In this way, a printed circuit board to which the electronic components are soldered can be obtained, but even if the original resin component or the residual film of the flux according to the present invention is not washed, if the acrylic resin is used in combination, only rosins are used. The film is tougher than in the case of, and the degree of toughness can be designed by changing the molecular weight, and the selection range can be increased, so that the occurrence of microcracks can be prevented even when the difference in temperature is large .
In the present invention, there is also provided a printed circuit board having a film of a resin component for soldering after reflow soldering or a residual film of soldering flux (residual film of solder joint and flux after soldering).
[0025]
【Example】
Next, examples of the present invention will be described.
The flux and solder paste of the present invention are used like ordinary flux and solder paste, and a flux film and a solder paste film are formed on a printed circuit board. Hereinafter, examples of the circuit board on which the flux, the solder paste, the flux film, and the residual film of the solder paste are formed will be described.
[0026]
Example 1 (Example of flux)
A flux having the following composition was prepared.
Rosin 10.0g
0.5 g of pyrazole
89.5 g of isopropyl alcohol
100.0g in total
A flux was obtained by stirring and mixing the above components. When the viscosity of this flux was measured with a redwood viscometer, it was 3.5 mPa · s (measuring temperature 30 ° C.).
[0027]
Examples 2 to 5 (flux)
Fluxes of Examples 2 to 5 were prepared in the same manner as in Example 1, except that the formulations shown in Table 1 were changed. When the viscosity was measured in the same manner as in Example 1, the viscosities were almost the same.
[0028]
Comparative Examples 1-3 (flux)
Fluxes of Comparative Examples 1 to 3 were prepared in the same manner as in Example 1 except that the formulations shown in Table 1 were changed. When the viscosity was measured in the same manner as in Example 1, the viscosities were almost the same.
[0029]
The following tests were performed using the respective fluxes obtained in the above Examples and Comparative Examples.
(A) Wetting balance (wetting force) test by the wetting balance method
A 15 mm × 7 mm × 0.2 mm copper plate is immersed in an aqueous solution containing 11% sulfuric acid and 3.8% hydrogen peroxide at 20 ± 1 ° C. for 60 seconds, soft-etched, taken out, and then taken out with ion-exchanged water for 30 seconds. Wash. Thereafter, the resultant was sequentially washed with isopropyl alcohol and ethyl acetate, the surface was sufficiently dehydrated, and then naturally dried.
A test piece in which the flux of each of Examples 1 to 5 and Comparative Examples 1 to 3 was applied to the entire surface on both the front and back surfaces of the copper plate by a dipping method was melted at approximately 250 ° C. (Sn / Pb = 63/37 (mass) When the molten solder is drawn into the horizontal plane vertically from one end from the one side, the molten solder is drawn in with a substantially V-shaped cross section. When the penetration is stopped, the drawn solder gradually rises with the passage of time. When the test piece returns to the horizontal plane, the test piece becomes perpendicular to the horizontal plane, and the molten solder rises along the surface of the test piece in a substantially V-shaped inverted cross section, and rises completely. The time from the intrusion of the test piece to the return of the molten solder to the horizontal surface was measured as "wetting time (seconds). At that time, no force was applied to the test piece from the molten solder in the vertical direction, As the molten solder rises as described above, the test piece is pulled downward, and when the test piece is completely lifted, the maximum tensile force is obtained. I do.
The shorter the wetting time and the greater the wetting action force, the better the wettability of the test piece, the higher the effect of the flux film on reducing copper oxide on the copper plate and the function of preventing the copper plate from being oxidized by air. It shows that the performance is good.
[0030]
(B) Through-hole rise rate test
The same flux as that used in the above item (a) was used for a test piece (same as that shown in FIG. 1) in which 180 through-holes (through-holes provided with a plating film on the inner wall) having a diameter of 0.1 to 1.0 mm were formed. Of the test piece was sprayed at a temperature of about 250 ° C. using a jet soldering device (HC33-36SNX manufactured by Tamura FA System Co., Ltd.), and one of the test pieces was applied to the molten solder. The main surface is contacted horizontally for 4 seconds and taken out into the atmosphere. Then, the extent to which the molten solder rose and solidified with respect to the through holes was observed, and any of the ones shown in FIG. The number of “pass” out of all through holes is expressed as a percentage (%) as “through-hole rise rate (%)”.
(C) Copper plate corrosion test
The test piece of the copper plate on which the flux film was formed was tested according to JIS-Z-3197 (1999). Those without "copper plate corrosion" are judged as "pass", and those with "copper plate corrosion" are judged as "fail".
The results of the tests (a) to (c) are shown in Table 1 together with the composition of the flux in each of the above Examples and Comparative Examples.
The insulation resistance of the flux film of the above embodiment was 10 ¹³ Ω or more, and the resistance after voltage application is 10 ¹³ As described above, no corrosion of the copper plate after voltage application was observed.
[0031]
Example 6 (solder paste)
A solder paste having the following composition was prepared.
(Flux composition)
Rosin 5.0g
0.1 g of pyrazole
Hardened castor oil 0.7g
4.2 g of butyl carbitol
Total 10.0g
(Composition of solder paste)
The above flux 10.0g
Solder powder (Sn / Pb = 63/37) 90.0g
(Manufactured by the atomizing method)
100.0g in total
The above-mentioned flux was prepared by stirring and mixing the above-mentioned components. When the viscosity was measured in the same manner as in Example 1, it was 40 Pa · s.
The above-mentioned solder paste was adjusted by kneading a mixture of the above-mentioned flux and solder powder (solder powder produced by an atomizing method) for 1 hour. When the viscosity was measured in the same manner as in Example 1, the viscosity was 190 Pa · s. there were.
[0032]
Examples 7 to 10 (Solder paste)
The solder pastes of Examples 7 to 9 were prepared in the same manner as in Example 6, except that the formulations shown in Table 1 were changed. When the viscosity was measured in the same manner as in Example 6, the viscosities were almost the same in all cases.
[0033]
Comparative Examples 4 to 6 (Solder paste)
In Example 6, solder pastes of Comparative Examples 4 to 6 were prepared in the same manner except that the composition was changed to the composition shown in Table 1. When the viscosity was measured in the same manner as in Example 1, the viscosities were almost the same.
[0034]
The test (a) was performed using the fluxes obtained in Examples 6 to 10 and Comparative Examples 4 to 6 (the results of these tests on the solder paste are affected by differences in the flux. Can be seen from the test results of the flux). Further, the following tests were performed using the respective solder pastes obtained in Examples 6 to 10 and Comparative Examples 4 to 6.
(D) Solderability test
A 30 mm × 30 mm × 0.2 mm copper plate is immersed in an aqueous solution containing 11% sulfuric acid and 3.8% hydrogen peroxide at 20 ± 1 ° C. for 60 seconds to perform soft etching, taken out, and then taken out with ion-exchanged water for 30 seconds. Wash. Thereafter, the resultant was sequentially washed with isopropyl alcohol and ethyl acetate, the surface was sufficiently dehydrated, and then naturally dried.
Each of the above solder pastes was applied to this copper plate by a screen printing method using a metal mask having a thickness of 200 μm.
The test piece of the copper plate on which the solder paste film was formed was heated at 235 ° C. for 30 seconds, and the wettability of the molten solder was measured as “wetability”. , And those with dewetting were judged as "poor".
(E) Copper plate corrosion test A test was performed according to JIS Z 3284 (1984). Those without "copper plate corrosion" were judged as "pass" and those with "copper corrosion" were judged as "fail".
The results of the tests (a), (d) and (e) are shown in Table 2 together with the composition of the solder paste of each of the above Examples and Comparative Examples.
[0035]
Example 11 (Example of circuit board before mounting electronic components)
In the above tests (a) and (b), the copper plate coated with the flux film is printed on a printed circuit before mounting electronic components, where the protection film of the flux residue film is formed on the soldering land in view of the function of protecting the copper surface. It can be regarded as a substrate, and can be regarded as an embodiment of the circuit board before mounting electronic components of the present invention.
[0036]
Example 12 (Example of circuit board after mounting electronic components (in the case of flux film)
In the above tests (a) and (b), those after the respective tests were performed on the copper plate on which the flux film was formed correspond to those after the normal soldering, and the flux of the flux was applied to the soldered lands. It can be regarded as a printed circuit board after mounting an electronic component on which an insulating film of a residual film is formed, and can be regarded as an embodiment of a circuit board after mounting an electronic component of the present invention.
The flux of the above example was applied to a cleaned through-hole substrate (50 × 50 × 1.6 mm, 360 holes / sheet) using a spray fluxer, and soldering was performed by an automatic soldering apparatus. Met.
[0037]
Example 13 (Example of circuit board after mounting electronic components) (In case of solder paste film)
In the above test (d), the copper plate on which the solder paste film was formed was subjected to the test, and was equivalent to that after normal soldering. It can be regarded as a printed circuit board after mounting an electronic component on which an insulating film is formed, and can be regarded as an embodiment of a circuit board after mounting an electronic component of the present invention.
[0038]
[Table 1]

[0039]
[Table 2]

[0040]
From the above results, the flux membrane of the embodiment of the present invention, the rosin-based material, the use of pyrazole or dimethylpyrazole as an activator, in the relationship between the two, the same rosin-based material, other activators In comparison with Comparative Examples 1 and 2, all of the performances except that "copper plate corrosion" passed were remarkably excellent, and as compared with Comparative Example 3 using only pyrazole without using a resin component. Similarly, all of the performances except for “copper plate corrosion” were found to be more remarkably excellent, and the synergistic effect of using both of them was apparent.
In addition, the solder paste film according to the embodiment of the present invention uses a rosin-based material and pyrazole or dimethylpyrazole as an activator, and in the relationship between the two, the same rosin-based material and other activators are used. Compared to Comparative Examples 4 and 5, and Comparative Example 6 using methyl-1H-benzotriazole instead of pyrazole, the "wetting action force" was twice or more, and the "wetting time" was four times or more, The synergistic effect of using both of them is apparent. In particular, the fact that pyrazole is particularly superior to methyl-1H-benzotriazole indicates that it has selectivity even if it belongs to the same azoles.
In addition, “%” simply indicates mass%.
[0041]
【The invention's effect】
According to the present invention, since a rosin-based resin and pyrazole are used in combination, they are excellent in the action of reducing oxides and the like on the metal surface of a circuit board, have good wettability of molten solder, and particularly perform a plurality of reflow soldering steps. In the case of or in the case of performing jet soldering afterwards, even in reflow soldering or jet soldering performed later, not only leaded solder but also lead-free solder has good wettability and wet upability of molten solder, impairing coatability. A low-residue film by reducing the amount of rosin-based resin used in combination with pyrazole, without impairing solderability, and reducing the corrosiveness of soldered lands, It is possible to provide a circuit board soldering flux and a solder paste having good insulation properties and high reliability.
Further, it is possible to provide a circuit board before mounting electronic components and a circuit board after mounting electronic components, in which the soldering flux or the solder paste is applied to protect the soldering lands.
[Brief description of the drawings]
FIGS. 1A and 1B are explanatory diagrams showing a state in which molten solder wets up a through hole of a printed circuit board; FIG.

Claims (6)

A flux for soldering a circuit board containing a pyrazole compound, wherein the flux is used for soldering an electronic component to a circuit board containing at least a resin component containing a rosin resin and a solvent component. The flux for soldering a circuit board according to claim 1, wherein the pyrazole-based compound is at least one selected from the group consisting of pyrazole, derivatives thereof, and salts thereof. A solder paste for soldering a circuit board, containing a pyrazole compound, in a solder paste containing at least a solder powder and a resin component, which is used when soldering an electronic component to a circuit board. A solder paste containing at least a solder powder and a solder paste flux used when soldering an electronic component to a circuit board, wherein the flux is the flux for circuit board soldering according to claim 1. Solder paste. A circuit board before or after soldering an electronic component coated with a soldering land using the circuit board soldering flux according to claim 1 or 2. A circuit board after mounting electronic components, the circuit board having a residual film after soldering using the solder paste for circuit board soldering according to claim 3.

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