JP3842981B2

JP3842981B2 - Substrate manufacturing method, electronic component manufacturing method, and electronic component mounting method

Info

Publication number: JP3842981B2
Application number: JP2001075685A
Authority: JP
Inventors: 守光若林
Original assignee: 守光若林; 株式会社斉藤製作所
Priority date: 2001-03-16
Filing date: 2001-03-16
Publication date: 2006-11-08
Anticipated expiration: 2021-03-16
Also published as: JP2002280715A

Description

【０００１】
【発明の属する技術分野】
この発明は電子回路基板に電子部品等を電気的に接続するとともに機械的にも固定する実装技術に関するものであり、とくに有害物質である鉛を含有する合金であるはんだなどの材料を用いることなく実装を行うこと、および部品自体に鉛を含まなくする、いわゆる鉛フリー実装技術に関するものである。
【０００２】
【従来の技術】
電子部品の実装には、はんだ付けを行うのが従来の常識であり他の方法はほとんど実用に供されなかったが、近年はんだや部品自体に含まれる鉛が有害な環境汚染物質であることからこの使用が禁止される方向にあり、さらに有機錫が環境ホルモンとして有害であるとする実験結果もあり、鉛入りはんだに代わる材料もしくは、はんだ付けに代わる方法が探索されている。
しかしながら従来のはんだ付けの特性レベルを実現するための鉛フリーはんだ合金は従来の温度よりも約３０度はんだ付け温度を上げなければならず、低融点のはんだ合金をつくるには、ビスマスなどの材料をまぜればよいもののはんだ付け特性や機械的強度に問題があり、従来のはんだにくらべて明らかに信頼性が劣る問題があった、またいずれの場合も錫はベースとなる金属であり、錫が否定された場合は、錫を含まないはんだ付け合金はほとんど不可能であることなどの問題がある。
またはんだ温度の上昇は２５０℃の熱歪みを基板および部品に発生させることとなり、一部のLSIなどの部品においては致命的な問題ともなるほか、液晶や電解コンデンサなど、もともと熱に弱い電子部品は実装できない問題があった。
他の方法としては導電性接着材料を用いて接着により実装する方法も知られているが、接着材料を厚く付着しなければ部品電極面での凹凸の吸収ができず接着力が不十分であり、厚くつけると部品をつけた際に接着材料が横方向にはみ出して隣の回路と短絡を生じやすい問題があった。
また組み立てられる電子部品についてもはんだ付け性確保のために電極部にはんだめっきをほどこし、本体にもはんだの温度に耐えるようなものとするため、鉛を含むガラスをベースとしたメタルグレーズなどの材料が使われていたが、この鉛についても問題となっていた。
別の方法としては異方性導電フィルムなどの材料により接続する方法も知られているが、この方法は完全な平面同士の接着で均等に圧力をかけられるようなものでなければ使いにくい問題があり一般の電子部品の接続には向かない問題があった。
さらに米国特許４１７０６７７号（１９７９年１０月９日出願）には本発明でも用いている感磁性フィラーを含有する接着材料を塗布した後磁界をかけることによりその感磁性フィラーが磁力線の方向に配列され導電路を形成することで電気的接続を行うことが開示されているが、発明者の経験によればこの導電路はごく細いものが限られた少数しか形成されず、しかも接触部への接触圧力も小さく酸化などによりおかされて信頼性が取れない問題があった。
発明者は先に特願２００１−６１９０９において導電性接着材料を接着ベースとした接続方法を発明し出願しているが、導電性接着材料は導電性を実現するために銀などの粉末を６０パーセント程度含有する必要があるため接着強度が劣る問題があり、特に発明の主眼である感磁性粉末を電極面に立てる形で付着するような場合に粉末が接着材料に突っ込んだ形での接着が実現しにくい問題があった。
【０００３】
【発明が解決しようとする課題】
本発明が解決しようとする課題の第一は電子回路の実装および電子部品自体において鉛を使わないこと、第二は高温を用いないこと、第三は従来の導電性接着材料のみの接着方法で問題であった横方向へのはみ出しによる短絡を防ぐに有効な方法を提供すること、さらに導電性を有しない通常の接着材料を用いても導電性が確保できる接続方法を実現することにある。
さらに導電性接着材料は貴金属である銀を大量に含むので高価であるがこれをなくするかまたは少なくすることでコストダウンを図ることにある。
【０００４】
【課題を解決するための手段】
本発明においては電子部品実装にはんだ付け法を用いないことにより、鉛を使わないことおよび高温を用いないことの二点は実現し、さらに高温を用いないことにより電子部品の構成材料から鉛を取り除くことを可能ならしめたものである。
また導電性接着材料のみによる接着方法における導電性接着材料のはみ出しを防ぐ方法を実現するものであり、その構造を形成するのに導電性接着材料を用いなくても接着性に優れた通常の接着材料で導電接続を可能ならしめる方法を含むものである。
【０００５】
従来の導電性接着材料のみによる電子部品の接着には接着材料の厚さを確保することにより、部品と接着材料との接触面を確保し接着力を確保することが行われていた、またこの厚さには部品の接続面の平坦性やICなどのように多数のリード線を持つ部品の足の並びの平坦性のばらつきを吸収してすべての接続を確保する意味もあった。
しかしながらこの厚さは部品を実装した際に導電性接着材料を横方向にはみ出させる効果をもち、実装部品の位置決めのばらつきとあいまって隣のパターンとの短絡を生じやすく、実用上はリードピッチで０．７ミリ以下のものには適用しがたく、近年すくなくとも０．３３ミリピッチが要求される実装には合わない問題があった。
さらに高価な銀を含む材料を厚く付けることはコストが高くなる問題があり、このコストダウンも常に求められるところであった。
【０００６】
また発明者による先願の特願２００１−６１９０９では導電性接着材料を用いて感磁性導電粉末などを付着する方法を用いていたが、導電性接着材料はもともと銀などの成分が６０パーセントほど入っており、接着性を犠牲にせざるを得ない問題があり、当然コストも問題であった。
【０００７】
本発明では接続すべき電極面に通常の接着材料もしくは感磁性導電粉を銀に比べて少量で接着力の低下が少ない２０パーセント程度含んだ接着材料を塗布した後、導電性粒子もしくは感磁性導電体を電極面に立てる形で圧力もしくは磁気による吸着力を印加して接着し導電性粒子もしくは感磁性導電体による凹凸または針状突起が多数出ているような形状をつくり、実装においては基板側と部品側の突起部分がかみ合った形で導電接続がなされその状態で接着固定されるものである、このため導電性接着材料を使わなくても接続は可能であるが、より確実性を求めて導電性接着材料を使った場合においても横方向への広がりは少なく、凹凸もしくは針山の谷に押し付けられるような方法で吸収するものであり隣接する導体パターン間で短絡する可能性はきわめて少なくなくなるものである。
感磁性導電粉をフィラーとして用いた接着材料は本発明では主たる導電材料である感磁性導電体の接触を補強する働きとして、絶縁性接着材料に代えてもちいており、米国特許４１７０６７７号とはその構成が全く異なり、主たる導電体は接着材料中には含まれておらず新たに外部から感磁性導電体を大量に付着させて多数の導電路を形成しているのが本発明の特徴であり、この感磁性導電粉のフィラーによっても導電路が補強されることでより高い導電性と信頼性が得られている。
機械的強度の確保のため電気的接続の後にさらに絶縁性接着材料をディスペンスなどの方法で付着することで補強することができる。
このような形で接続リードピッチ０．３３ミリの高密度実装にも対応可能である。
【０００８】
本発明によれば従来のような導電性接着材料の横方向への広がりがすくなく高密度の実装にも応用可能である、また導電性はほとんどが感磁性導電体や導電性粒子により担われることから、レジンと金属粉の混成体である従来の導電接着材料よりも導電性に優れており少ない接触面積であっても従来よりは導電性に優れ信頼性もマイグレーションの可能性が低いことなどから優れている、さらに機械的な強度は絶縁性接着材料により全面的な接着を行うので問題はない。
またはんだ付けの高温にさらされないので、組み立てるべき電子部品においてはんだ付け性を確保するためのはんだめっきが不要であり、部品自体の耐熱性も不要であることから鉛を含むガラスなどの高温耐熱性材料を用いないで部品を構成することが出来る。
【０００９】
【実施例】
本発明による低温度鉛レス実装方法の実施例を述べるに際し、まず主要材料について述べる。
【００１０】
１接着材料
本発明においてはおおむね５種類の接着材料を試している。
第一には基板および部品の電極面に印刷により接着する絶縁性接着剤であり、印刷性、および金属粒子の付着性に優れたものである、出来れば一液性が望ましいがライフが一日以上確保できるならば二液性のものでもよい。
第二に同じく印刷に用いられるものとして感磁性導電粉をフィラーとして含んでいる接着材料がある。
このフィラーは印刷性を最適にするのに役立つ程度の量である２０パーセント程度を含むものであり、一般には接着材料としては導電性をもっていないものである。
この２０パーセントという含有量は一例であって印刷性と導電接続性の兼ね合いから決まるものである、実験的には５パーセントから５０パーセントの広い範囲で実用可能であった。
フィラーの材質としてはニッケルフレーク粉末で４００メッシュパス程度の粒度のものであったが、ニッケル粉の表面に銀をメッキしたものも導電性向上の目的で用いている。
これらの粉末は磁界の存在で磁力線の方向に並行して立ち上がった形で磁石にひきつけられ、その結果磁石の反対側の面ではフィラーの密度が低くなり、外部から感磁性導電体を付着する際に感磁性導電体がフィラーに邪魔されずに接着材料に入って行きやすく接着しやすくなる利点があり、磁石側である電極面側は導電性フィラーが電極面に高い密度で引き付けられ導電性接続がより確実になる利点がある。
第三の接着材料は絶縁性であり全面に薄く塗布した後実装して接着を完了した後実装に寄与しなかった部分は洗い流すことが出来るものである。
これを用いる際には硬化剤もしくは硬化促進効果をもつ材料を部品側の接着面に塗布するかもしくは導電性粒子の表面に薄くコーティングしておくなどの方法により、部品実装部分のみ硬化するかもしくは硬化を早めるかする方法に用いている。
第四の接着材料は実装の機械的補強に用いるもので実装完了後ディスペンサーなどを用いて接着部分に塗布し、補強するものである。
第五の接着材料は一般の導電性接着剤であり接着面の一方に印刷もしくはディスペンスなどの方法によって塗布し、双方の接続面を電気的につなぐことで接着するものである。
この特性は印刷性と、凹凸面でも流れ落ちない程度の固さをもっていることである。
【００１１】
２感磁性導電体
主としてニッケルフレークで50メッシュパス、２00メッシュストップ程度のかなり粗い分布を持つものを用いたが分布としてはこれに限るものではなく一般に導電性接着材料などに使われている金属粉よりは粗い分布のものが好ましい結果を得ている。
高密度の実装間隔が求められる場合はこの粒度分布はより細かな方を選択することになる。
他にフレーク状や粒状のニッケルさらにはフレーク状または粒状のニッケルに銀メッキを１ミクロン以上の厚さに施したものさらにはフェライトなどの磁性体の針状結晶体に銀メッキを施したものも試しているが磁気に感応して吸着されるような材料でありかつ導電性を有するものであればよい。
ここでは接着材料にはじめからフィラーとして入れる場合の感磁性導電粉もしくは後の工程で感磁性導電体に磁力で付着させる用途の感磁性導電粉とは区別して用い、導電粉とは400メッシュパス程度の細かなものであり、導電体とは前記の粗いものと定義してのべている。
これらはいずれも従来の導電接着材料のように貴金属である銀を多く含まず、コスト的なメリットもあるものである。
【００１２】
３導電体粒子
これは磁性を利用しない場合のものであり、ここでは銅粉で５０ないし１５０メッシュのものを用いた、これは接着剤に付着した際に押し付けても接着材料中に埋まってしまわない程度の粗さとして選んでいる、この粒度分布も前記同様にこれに限るものではない。
【００１３】
次に作業についてのべる。
１まず基板の電極面に第一の接着材料のペーストをスクリーン印刷法により指定のパターンで付着する、この際スクリーンのメッシュは１２５メッシュで印刷厚さは２０−３０ミクロン、乾燥硬化後は１０−２０ミクロンになるようなものであったがこれは細かな粒度の導電体を用いる場合には薄くすることになる。
【００１４】
２この印刷直後の基板を平面型のフェライト磁石の表面にシートを敷いた状態で磁石の中心付近に置き、上から篩いを用いて感磁性導電体を全面にくまなく行き渡るように振りかけた。
フェライト磁石の磁力は表面で５００ガウス以上あれば十分であり他の磁石でもかまわない。
【００１５】
３この後全面にシートをかけてゴムなどを介して軽く圧力を全面に行き渡るように印加し第一の接着材料に感磁性導電体を食い込ませるようにした。
なお感磁性導電体は磁力線の方向に整列する性質がありそのことから基板面に垂直に立った状態に保たれており、この方向性をそこなわないように圧力印加をおこなっている。
この押さえ工程は強力な磁石を用いて感磁性導電体を確実に電極と導電接続できる場合などには省略することも可能である。
【００１６】
４この後磁石からほぼ垂直な方向に基板を引き上げて取り出した後、接着されなかった感磁性導電体を振り落とし、必要な場合にはガラスなどを用いて再度全面をおさえて平面性を確保する試みも行ったが通常この押さえの必要はない。
【００１７】
５この後１２０℃５分の加熱硬化工程に通した、この際感磁性導電体の垂直方向性を保持するため磁石の上に置いた状態で加熱すればより完璧である、その後表面側からサマリウムコバルト磁石のような強力な磁石をもちいて残留の接着しなかった感磁性導電体を取り除いた。
この温度に関しては用いる材料によりその最適条件を選べばよいが、通常はエポキシなどでは１５０℃以下，シリコン系などでは１８０℃以下である。
磁石の耐熱劣化などの観点からも低い温度がのぞましい。
【００１８】
６この基板に第一の接着材料をほぼ同じパターンで印刷するかもしくはディスペンスすることにより感磁性導電体の付着した部分に付着した。
この際の材料は先の印刷材料よりは幾分固いものであり、厚さは３０ミクロン以上を確保するようにマスクもしくはディスペンサーを選定している。
この硬さは感磁性導電体の表面で接着材料が流失してしまわない程度のものであり、この後の工程で部品側の導電体との接着が可能な程度のものである。
【００１９】
７この状態で基板を磁石の上に置き電子部品を正確な位置に配置し実装した、この際圧力を印加して部品の電極部の導電体が基板の感磁性導電体の先端部と噛み合わさる程度にまで押しこむとともに磁力でその状態を保つようにした。
この際部品の電極表面にも同様の方法で感磁性導電体もしくは導電体粒子を施したものを用いている。
双方の材料が感磁性でない導電体粒子の場合は機械的圧力のみで押さえることになり磁石は用いなくても良い。
この部品への感磁性導電体もしくは導電体粒子の接着方法については後に詳述する。
【００２０】
８この後再度加熱硬化した、条件は同じく１２０℃５分であった。
９この状態で回路機能テスト等に供し接続不良などがないかを検査し問題があれば速乾性の銀塗料を細い筆で塗布する方法などにより修正した。
【００２１】
１０この後第四の接着材料である透明エポキシ接着剤を接着部の上から塗布し硬化して部品の機械的接着強度を確保した。
１１原則として銀を含む導電性塗料などは使わないかもしくは少なくしていることは本発明の主眼の一つであるが、このことは銀が水分と電界の存在下でマイグレーションと称される移行現象を発生して短絡を生ぜしめる可能性をなくするかまたは少なくし、信頼性を高めることにつながっているほかコストダウンにもつながっている。
【００２２】
ここでこの方法に用いる部品の特徴および部品の電極に感磁性導電体もしくは導電性粒子を接着する方法についてのべる。
ここに用いる部品としては代表的なものとしてチップ抵抗器とリード端子をもっているLSIなどの表面実装部品について説明する。
【００２３】
チップ抵抗器の工程においては一般に平面状のセラミック基板に印刷等によりガラスを含むメタルグレーズ系材料をもちいてスクリーン印刷法により所定形状に形成した後おおむね８５０℃で焼成して抵抗体や電極を形成し、レーザーによるトリミングを行い、絶縁保護および表示印刷などを行った基板をチョコレート形状に一次分割し、分割側面に導電性材料を塗布し硬化させた後個別に分割し、めっき工程において電極部分にニッケルとはんだのめっきをかさねてはんだ付け性を確保することをおこなっている。
【００２４】
本発明においてはまずめっきの工程をなくすることにより工程短縮と鉛を用いないことを可能にしている。
さらに抵抗器や電極などの材料は、はんだの熱にさらされないことからはんだ耐熱性への配慮が不要であり、鉛を含むガラスをベースとした従来の材料から鉛を含まないレジンをベースとした材料に変更することができる。
一般にこれらレジン系材料は高温系材料のようにパラジウムやルテニウムなどの高価な材料を含まずコストにおいても大きなメリットがある。
一例をあげれば抵抗材料としては１５０℃程度で硬化するフェノール、エポキシなどのレジンにカーボンブラックなどの導電粉末を混ぜたものや、さらには
２５０℃以上の温度で硬化するドリルレジン（ポリイミド系）をベースにカーボンブラックなどを混ぜたものなどである。
【００２５】
ドリルレジンによる抵抗や電極はその後の工程で用いられるエポキシなどの材料の乾燥硬化温度よりもはるかに高い温度で硬化処理されることから、工程変化が少ない利点がある。
電極材料としては前記の抵抗材料の中で低抵抗値の材料を用いることも可能であるが銀粉末などを前記レジン材料に混ぜたものがよい。
【００２６】
この工程においてはレジン系材料を用いて一般の工程と同様にセラミック基板表面に抵抗体を印刷し、さらに表と裏の面に電極を印刷しそれぞれ所定の乾燥硬化をおこない、レーザーなどにより抵抗値のトリミングを行い、表側に絶縁性保護材料をほどこす。
この段階で裏面の電極で分割線から０．１ミリほど離れた位置に接着材料を印刷し、先に基板について行ったと同様に磁界をかけた状態で感磁性導電体を振り掛け、押さえることにより接続面を形成する。
この場合の接着材料は導電性を有する第五のタイプが良い。
後に他の実施例として基板について詳述するが感磁性を有しない導電体粒子を付着する場合については磁界をかけないことをのぞいては同様に行っている。
この後チョコレート状に分割し、側面に主として銀塗料などを塗布して表裏を導通させる。
【００２７】
これらの乾燥硬化温度は一般例に述べたガラス系材料の場合の８５０℃と異なり、よく用いられるエポキシ系材料では１５０℃以下、もっとも高いドリル系材料でも３００℃以下であり、はるかに低いものである。
これをさらに個別に分割することによりチップ抵抗器が完成される。
【００２８】
別の作り方として特に小型のチップ抵抗器の場合、側面電極形成部にスリットを形成してスパッターなどの方法によりスリットの側面に薄膜を形成して表裏を導通することも行われているが、この場合は側面電極形成後に接着材料を印刷することで同様に感磁性導電体もしくは導電体粒子を接着し形成すればよい、この際はスリット部から離れたパターンなどは不要であり裏面の電極全面に印刷してよい。
【００２９】
LSIなどの場合、リード線は平面に並ぶように作られており、この平面性を損なわないように治具などを作りそこにはめ込んで印刷法により、リード部表面に接着材料を付着し、先の方法と同様に感磁性導電体や導電体粒子をつける方法やマスクした状態で接着材料をスプレーにより付着した後感磁性導電体や導電体粒子を付着する方法がある。
できるならばリードフレームを切断する以前にこれをやったほうがリードの平面性を損ないにくく有利である。
このリード部についてもはんだ付け性は不要であり、鉛を含むはんだなどの材料のめっきは不要である。
以上のように本発明によれば接続のみならず、部品レベルでも鉛を含まない工程が実現できるものである
【００３０】
「その他の実施例」
１感磁性導電体を用いない方法としては基板面に３０ミクロン程度に第一の接着材料を所定パターンに塗布したのち、５０メッシュパス、１５０メッシュストップ程度の導電体粒子を基板の接着面にふりかけた後、圧力をかけて接着部分に導電体粒子を接着する方法も試みた。
この後付着しなかった導電体粒子は振り落として取り除いた。
他の工程については先に述べたと同様におこなった。
【００３１】
２基板に部品を実装する場合において、まず基板に全面に第三の接着材料であるエポキシ接着剤の硬化の遅いタイプを薄く塗布した後、部品の実装側の面に硬化剤もしくは硬化促進剤を薄く塗布し基板を磁石の上に置いた状態で部品実装を行い部品の電極部および他の接触面で接着し硬化した後、接続部以外の硬化の遅いかまたは硬化しないエポキシ接着剤を洗い流す方法も試みた。
この方法によれば接着材料の位置決めによる塗布の面倒がなく、部品実装の位置決めの精度のみで実装の位置決め精度が決定する点で有利である、また接着材料の印刷性を考慮する必要がないので流動性の高い接着材料を薄く付着して、導電体同士の接着に邪魔にならないように出来る点でも有利である。
部品側の感磁性導電体もしくは粒状導電体に導電性を損なわない程度に硬化剤もしくは硬化促進剤をコーティングしておくことで接続面および部品表面近傍のみ硬化を早める方法も有効であった、また硬化促進性のある金属イオンを発生させる材料を用いそれに反応しやすい接着材料を選択することも一つの方法である。
いずれの場合も磁石で引き付けておくことで部品の接続が強固になり動きにくい効果があった。
【００３２】
3 感磁性導電体に強磁性体であるニッケルやフェライト粉に銀メッキしたものなどを選択しそれぞれ基板側および部品側に付着した後も磁石作用が残っているようにし、実装の前に遊離した感磁性導電粉をその磁化された感磁性導電体に吸着させて実装し、磁力により電気的接続を確保した状態で接着剤で固めることも行なった。
これによれば遊離感磁性導電体がクッション作用をして部品やICの足の平坦性のばらつきを吸収して確実な接続がえられた。
【００３３】
４部品を基板に実装するに際し感磁性導電粉をフィラーとして含む接着材料を基板側接続面に塗布し磁界をかけた状態で部品を実装し硬化させることもおこなった。
この方法の利点は接着材料中の感磁性導電粉が接続面に垂直に立つ方向で配向されるので電気的接続を強化できることにある。
とくに感磁性導電粉は基板電極表面に押し付けられる方向に磁力が働くので接触する確率が高く、また反対側は接着成分の比率が高く、外部から付着する感磁性導電体がフィラーに邪魔されずに接着材料に入り込み、さらに接着成分が多いことから接着しやすい利点がある。
また感磁性導電粉は総体として感磁性導電体を包むような形で接触し、これがない場合の平面との点接触に比較して接続の確実性が高まる効果がある。
この際接着材料が所定位置よりはみ出すことがあっても感磁性導電粉は垂直方向に配向され水平方向には絶縁されるので問題はないことから接着材料の塗布の位置決めはラフなものでも良い利点がある、さらには部品本体部分もこの接着材料で同時に固定することが出来るので機械的強度も向上する。
【００３４】
５これまで述べたいずれの場合においても基板側はN極を上に向けた磁石に載せ、部品側はS極を上に向けた磁石の上に載せる事で統一した、この方向は逆でもかまわないのだが統一基準としてこのようにした。
これにより基板側の感磁性体表面はN極、部品側はS極に磁化され実装の際にお互いに引き合うことから位置決めに対してセルフアラインメント効果が生じ好都合であった。これが反対であったならば反発力で位置をずらす効果をもつことになり、この点は重要である。
感磁性導電体同士が引き合うことで導電接続が完全になり、外部の磁石にも引き付けられることから強固に接続され、接着材料で固める際にも位置ずれが発生しにくい効果もあった。
【００３５】
６先に特願２００１−６１９０９に出願したごとく基板側を本発明による感磁性導電体などが表面に露出した構造とし、部品側に導電性接着材料を塗布して接着することも有効であった。
この際は部品側の導電接着材料は５０ミクロン程度に比較的厚く付着し、部品電極面の平坦性のばらつきを吸収するようにしたが、接着材料は感磁性導電体の間に垂直に押さえつけられて吸収され、横方向へのはみ出しは少なく、０．３３ミリメートルピッチの高密度実装に耐えられる方法であることが確認されている。
これについては部品側と基板側の構成を逆にして基板側に導電性接着材料を塗布する方法も同様に有効であった。
【００３６】
７（００３５項）に述べた方法において接着材料を絶縁性のものにして部品を押し付ける形で電気的接続を図ることも試みたが、感磁性導電体などの表面は微視的には平坦ではなく、接触点が少なくなることから採用しなかった。
【００３７】
８（００３５項）に述べた方法において接着材料に感磁性導電粉をフィラーとして含む接着材料を部品電極側に付着して磁界の存在下でフィラーを磁石で部品電極側に引き付けつつ部品をおさえつけて接着硬化する方法も試みて有効であることを確認した。
この際の感磁性導電粉の含有比率は基板側の場合よりも高く２５ないし５０パーセント程度とし、ステンレスマスクなどで印刷するかもしくはディスペンサーを用いて５０ミクロン程度の厚さに付着した、厚く付けることの必要性と、導電路を増やす目的からもフィラー分が多いほうが固めの接着材料に出来るので有利であり、さらに基板側の感磁性導電体の平坦性のばらつきは感磁性導電粉のフィラーで吸収されて導電路が確保され、しかも感磁性導電体は接着材料成分比率の高い部分で接着固定されるので機械的強度の点でも有利である。
これについては部品側と基板側の構成を逆にして、基板側に感磁性導電粉を含む接着材料を塗布する方法も同様に有効であった。
【００３８】
【発明の効果】
本発明によれば高温で処理する必要のあるはんだ付けをなくすることが出来るので鉛を用いない実装および部品自体に鉛を用いないことが可能となりまた従来のように導電性接着剤のみで接続する場合に比較して高密度に実装することも可能になった。
また接着性の良い材料を使うことから確実な接続も可能となった。
さらに低い温度で処理することから従来はんだ付けでは実装出来なかった電解コンデンサーや液晶などの電子部品も同時に実装出来るようになった、従来液晶などは基板に直接実装することは出来ずゼブラゴムやフレキシブルケーブルを使っていたがこれらの部品をなくすることも出来るようになった。
【００３９】
「参考文献」特願２００１−６１９０９
米国特許第４１７０６７７号
【図面の簡単な説明】
【図１】図１は基板もしくは部品の導体電極に接着材料を付着した後磁界を印加して感磁性導電体を電極面にほぼ垂直に立てるとともに電極と接触することで電気的に導通するようにしさらに加熱硬化して固めたものの模式断面図である。
ここで磁界の方向を矢印で示しているが、部品の場合は磁界の方向はS極となるものである。
【図２】図２は基板もしくは部品の導体電極に接着材料を付着した後導電性粒子を付着し押し付けることにより電極と接触することで電気的に導通するようにしさらに加熱硬化して固めたものの模式断面図である。
【図３】図３はフィラーとして感磁性導電粉を含む接着材料を基板もしくは部品の導体電極に付着した後磁界を印加してこのフィラーを電極面にひきつけて電気的接触を図るとともに感磁性導電体を付着してそれを電極面にほぼ垂直になる形で立てて電極面方向に引き付けて、電極と直接接触するかもしくは導電性を有するフィラーを介して電極と電気的に導通するようにした後加熱硬化して固めたものの模式断面図である。
ここにおいて磁界の方向は基板の場合はN極、部品の場合はS極とするが図では矢印でN極を示している。
【図４】図４は基板側を下、部品側を上として図１に示す形の電極部を対向させて接続し、接着材料で固定した形の接続方法の模式断面図である。
ここでは双方に感磁性導電体を用いた場合を示しているが、導電性粒子を一方または双方に用いた場合も磁界を印加するかしないかの違いを除いてはほぼ同様である。
【図５】図５は基板側を下、部品側を上として図１に示す形の電極部を対向させて双方の間に感磁性導電フィラーを含む接着剤を介在させ、フィラーにより導電性を向上させた形で接続する方法の模式断面図である。
ここでは感磁性導電体を用いた場合の例を示しているが、一方もしくは双方に導電体粒子を用いた場合についても同様の形状で導電性の向上が期待できる。
銀などを含む導電性接着材料を用いた場合の形状も感磁性導電フィラーが磁気により配向されることを除けばほぼ同様の形状に仕上がる。
【図６】図６は基板を下、部品を上として感磁性導電体に感磁性導電粉を付着させて感磁性導電粉を介して上下の電気的接続を図るとともに接着材料により固めた形の接続方法を示す模式断面図である。
【図７】図７は基板を下、部品を上として基板側は感磁性導電体を付着した接続部を有し、部品側には導電接着材料を付着して所定の位置に実装して押さえつけて硬化せしめることにより導電接続した場合の模式断面図である。
【図８】図８は基板を下、部品を上として基板側は感磁性導電体を付着した接続部を有し、部品側には感磁性導電粉をフィラーとして含む接着材料を付着して所定の位置に実装して押さえて磁界の存在下で硬化せしめることにより導電接続した場合の模式断面図である。
【符号の説明】
１基板本体
２基板側電極
３基板側接着材料
４感磁性導電体
５導電性粒子
６感磁性導電粉を含む接着材料
７感磁性導電粉によるフィラー
８接着材料
９部品側感磁性導電体
１０部品側電極
１１部品本体
１２部品側接着材料
１３感磁性導電粉末
１４導電性接着材料
１５部品電極側の感磁性導電粉末を含む接着材料[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mounting technique for electrically connecting an electronic component to an electronic circuit board and mechanically fixing the electronic circuit board, and particularly without using a material such as solder which is an alloy containing lead which is a harmful substance. The present invention relates to a so-called lead-free mounting technique that performs mounting and eliminates lead in the component itself.
[0002]
[Prior art]
For mounting electronic parts, soldering has been common sense and other methods have hardly been put to practical use, but in recent years lead contained in solder and parts itself is a harmful environmental pollutant. There is an experimental result that this use is prohibited and organic tin is harmful as an environmental hormone, and a material replacing lead-containing solder or a method replacing soldering is being searched.
However, the lead-free solder alloy for realizing the level of soldering characteristics of conventional soldering has to raise the soldering temperature by about 30 degrees from the conventional temperature. In order to produce a solder alloy with a low melting point, a material such as bismuth is used. However, there is a problem in soldering characteristics and mechanical strength, and there is a problem that the reliability is clearly inferior to conventional solder. In each case, tin is a base metal. If denied, there is a problem that a soldering alloy containing no tin is almost impossible.
In addition, a rise in solder temperature will cause a thermal strain of 250 ° C to be generated on the board and components, which will be a fatal problem for some LSI components, as well as electronic components that are inherently vulnerable to heat, such as liquid crystals and electrolytic capacitors. Had a problem that could not be implemented.
As another method, a method of mounting by bonding using a conductive adhesive material is also known, but unless the adhesive material is attached thickly, the unevenness on the part electrode surface cannot be absorbed and the adhesive force is insufficient. When the parts are attached thickly, the adhesive material protrudes in the lateral direction, and there is a problem that a short circuit with the adjacent circuit is likely to occur.
In addition, in order to ensure solderability of the electronic parts to be assembled, solder plating is applied to the electrode part, and the body is also resistant to the temperature of the solder. Therefore, materials such as metal glaze based on glass containing lead are used. Was used, but this lead was also a problem.
As another method, a method of connecting with a material such as an anisotropic conductive film is also known, but this method has a problem that it is difficult to use unless pressure can be applied evenly by adhesion between perfect planes. There was a problem that was not suitable for connecting general electronic components.
Further, in U.S. Pat. No. 4,170,677 (filed on Oct. 9, 1979), the magnetic sensitive filler is arranged in the direction of the magnetic field lines by applying a magnetic field after applying the adhesive material containing the magnetic sensitive filler used in the present invention. Although it is disclosed that electrical connection is made by forming a conductive path, according to the inventor's experience, only a very small number of these conductive paths are formed, and the contact to the contact portion is also made. There was a problem that the pressure was low and the reliability was not obtained due to oxidation.
The inventor has previously invented and applied for a connection method based on a conductive adhesive material in Japanese Patent Application No. 2001-61909, but the conductive adhesive material is made of 60% of a powder such as silver in order to achieve conductivity. There is a problem that the adhesive strength is inferior because it needs to be contained to a certain extent, especially when the magnetically sensitive powder that is the main focus of the invention is attached in the form of standing on the electrode surface, the adhesion in the form that the powder thrusts into the adhesive material There was a problem that was difficult to do.
[0003]
[Problems to be solved by the invention]
The first problem to be solved by the present invention is that lead is not used in the mounting of the electronic circuit and the electronic component itself, the second is that no high temperature is used, and the third is a conventional bonding method using only a conductive adhesive material. The object is to provide an effective method for preventing a short circuit due to a lateral protrusion which has been a problem, and to realize a connection method capable of ensuring conductivity even when a normal adhesive material having no conductivity is used.
Furthermore, since the conductive adhesive material contains a large amount of silver which is a noble metal, it is expensive. However, the cost is reduced by eliminating or reducing the conductive adhesive material.
[0004]
[Means for Solving the Problems]
In the present invention, by not using a soldering method for electronic component mounting, two points of not using lead and not using high temperature are realized, and furthermore, lead from component materials of electronic components is not used by not using high temperature. It is possible to remove it.
In addition, it realizes a method to prevent the protrusion of the conductive adhesive material in the adhesive method using only the conductive adhesive material, and normal adhesion excellent in adhesiveness without using the conductive adhesive material to form the structure. It includes a method for enabling a conductive connection with a material.
[0005]
Conventionally, the adhesion of electronic parts using only conductive adhesive materials has been achieved by ensuring the thickness of the adhesive material, thereby ensuring the contact surface between the component and the adhesive material, and ensuring the adhesive force. Thickness also meant to ensure all connections by absorbing the flatness of the connecting surfaces of the components and the flatness of the alignment of the legs of components with many lead wires, such as ICs.
However, this thickness has the effect of causing the conductive adhesive material to protrude laterally when the component is mounted, and is likely to cause a short circuit with the adjacent pattern due to variations in the positioning of the mounted component. It has been difficult to apply to those of 0.7 mm or less, and there has been a problem that in recent years it is not suitable for mounting requiring a pitch of 0.33 mm.
Furthermore, there is a problem that it is expensive to apply a thick material containing expensive silver, and this cost reduction has always been required.
[0006]
In addition, in the prior application Japanese Patent Application No. 2001-61909 by the inventor, a method of adhering magnetosensitive conductive powder using a conductive adhesive material was used, but the conductive adhesive material originally contained about 60% of components such as silver. However, there is a problem that the adhesiveness must be sacrificed, and the cost is also a problem.
[0007]
In the present invention, after applying an adhesive material containing about 20 percent of a normal adhesive material or a magnetically sensitive conductive powder in a small amount and having a small decrease in adhesive strength compared to silver to the electrode surface to be connected, the conductive particles or the magnetically sensitive conductive material is applied. Adhesive force applied by pressure or magnetism is applied with the body standing on the electrode surface to create a shape with many irregularities or needle-like protrusions due to conductive particles or magnetically sensitive conductor. Conductive connection is made with the protruding part on the component side engaged, and it is bonded and fixed in that state, so connection is possible without using conductive adhesive material, but more certainty is required Even when a conductive adhesive material is used, there is little spread in the lateral direction, and it is absorbed by a method that is pressed against unevenness or the valley of a needle mountain, and short-circuits between adjacent conductor patterns. Possibility is something that would very little.
In the present invention, the adhesive material using the magnetically conductive powder as a filler can be replaced with an insulating adhesive material as a function to reinforce the contact of the magnetically conductive material which is the main conductive material. US Pat. No. 4,170,677 The feature of the present invention is that the configuration is completely different, and the main conductor is not included in the adhesive material, and a large number of magnetically sensitive conductors are newly attached from the outside to form a large number of conductive paths. Also, higher conductivity and reliability are obtained by reinforcing the conductive path by the filler of the magnetically conductive powder.
In order to ensure the mechanical strength, after the electrical connection, the insulating adhesive material can be further reinforced by attaching it by a method such as dispensing.
In this manner, high-density mounting with a connection lead pitch of 0.33 mm can be supported.
[0008]
According to the present invention, the conventional conductive adhesive material does not spread in the horizontal direction and can be applied to high-density mounting, and the conductivity is mostly borne by the magnetically-sensitive conductor and conductive particles. Therefore, it is more conductive than the conventional conductive adhesive material that is a composite of resin and metal powder, and even with a small contact area, it has better conductivity and reliability and is less likely to migrate. There is no problem because the mechanical strength is excellent because the entire surface is bonded by an insulating adhesive material.
In addition, because it is not exposed to the high temperature of soldering, it does not require solder plating to ensure solderability in the electronic parts to be assembled, and the heat resistance of the parts themselves is also not required. Parts can be constructed without using materials.
[0009]
【Example】
In describing an embodiment of the low-temperature lead-less mounting method according to the present invention, first, main materials will be described.
[0010]
1 Adhesive material
In the present invention, approximately five types of adhesive materials are tried.
The first is an insulating adhesive that adheres to the electrode surfaces of substrates and components by printing, and is excellent in printability and adhesion of metal particles. If the above can be secured, a two-component type may be used.
Secondly, there is an adhesive material containing magnetically-sensitive conductive powder as a filler, which is also used for printing.
This filler contains about 20 percent, which is an amount useful for optimizing the printability, and is generally not conductive as an adhesive material.
This 20% content is an example, and is determined by the balance between printability and conductive connectivity, and was experimentally usable in a wide range of 5% to 50%.
The filler material was nickel flake powder having a particle size of about 400 mesh pass, but the surface of nickel powder plated with silver is also used for the purpose of improving conductivity.
These powders are attracted to the magnet in the form of rising in parallel with the direction of the lines of magnetic force in the presence of a magnetic field, and as a result, the density of the filler is reduced on the opposite surface of the magnet, and the magnetically conductive conductor is attached from the outside. In addition, there is an advantage that the magnetically sensitive conductor is easy to enter the adhesive material without being obstructed by the filler, and it is easy to adhere, and the conductive filler is attracted to the electrode surface with high density on the electrode side, which is the magnet side. There is an advantage that becomes more certain.
The third adhesive material is insulative, and the portion that did not contribute to the mounting after the thin film was applied to the entire surface and mounted to complete the bonding can be washed away.
When using this, either the component mounting part is cured by a method such as applying a curing agent or a material having a curing accelerating effect to the adhesive surface on the component side or thinly coating the surface of the conductive particles, or It is used as a method to accelerate curing.
The fourth adhesive material is used for mechanical reinforcement of mounting, and is applied and reinforced by using a dispenser after completion of mounting.
The fifth adhesive material is a general conductive adhesive, which is applied to one of the adhesion surfaces by a method such as printing or dispensing, and is bonded by electrically connecting the two connection surfaces.
This characteristic is that it has a printability and a hardness that does not flow down even on an uneven surface.
[0011]
2 Magnetic sensitive conductor
Nickel flakes with 50 mesh pass and a fairly coarse distribution of about 200 mesh stop were used. However, the distribution is not limited to this, and it is generally coarser than the metal powder used for conductive adhesive materials. Have obtained favorable results.
When a high-density mounting interval is required, the finer particle size distribution is selected.
In addition, flaky or granular nickel, flaky or granular nickel with a silver plating thickness of 1 micron or more, or a magnetic acicular crystal such as ferrite with silver plating Any material can be used as long as it is a material that can be adsorbed in response to magnetism.
Here, it is used separately from the magnetically-sensitive conductive powder when it is first added to the adhesive material as a filler or the magnetically-sensitive conductive powder that is applied to the magnetically sensitive conductor by a magnetic force in the subsequent process. The conductor is defined as the rough one described above.
These do not contain much silver, which is a noble metal like conventional conductive adhesive materials, and have a cost advantage.
[0012]
3 Conductor particles
This is a case where magnetism is not used. Here, copper powder of 50 to 150 mesh is used, which is rough enough not to be buried in the adhesive material even if pressed against the adhesive. The particle size distribution selected here is not limited to this as described above.
[0013]
Next, I will talk about the work.
1 First, paste of the first adhesive material is attached to the electrode surface of the substrate in a specified pattern by screen printing. At this time, the screen mesh is 125 mesh, the printing thickness is 20-30 microns, and after drying and curing, 10- Although it was 20 microns, this would be reduced when a fine particle size conductor is used.
[0014]
2 The substrate immediately after printing was placed near the center of a flat ferrite magnet with a sheet laid on it, and the magnetically conductive material was sprinkled all over the entire surface using a sieve from above.
It is sufficient that the magnetic force of the ferrite magnet is 500 gauss or more on the surface, and other magnets may be used.
[0015]
3. After this, a sheet was applied to the entire surface, and light pressure was applied across the entire surface through rubber or the like to cause the magnetically sensitive conductor to bite into the first adhesive material.
The magnetic sensitive conductor has the property of being aligned in the direction of the lines of magnetic force, so that it is kept in a state of being perpendicular to the substrate surface, and pressure is applied so as not to impair this directionality.
This pressing step can be omitted when the magnetosensitive conductor can be reliably conductively connected to the electrode using a strong magnet.
[0016]
4 After this, the substrate is lifted and taken out from the magnet in a substantially vertical direction, and then the magnetic sensitive conductor that has not been bonded is shaken off, and if necessary, the entire surface is held again using glass or the like to ensure flatness. Attempts have been made, but there is usually no need for this hold down.
[0017]
5 After that, it was passed through a heating and curing step at 120 ° C. for 5 minutes. At this time, it was more perfect if it was heated on the magnet in order to maintain the perpendicularity of the magnetically sensitive conductor. Using a strong magnet such as a cobalt magnet, the remaining non-bonded magnetic sensitive conductor was removed.
The optimum condition for this temperature may be selected depending on the material used, but is usually 150 ° C. or lower for epoxy or the like, and 180 ° C. or lower for silicon or the like.
A low temperature is also desirable from the viewpoint of heat resistance degradation of the magnet.
[0018]
6 The first adhesive material was printed on the substrate in approximately the same pattern, or dispensed to adhere to the portion where the magnetic sensitive conductor was adhered.
The material at this time is somewhat harder than the previous printing material, and the mask or dispenser is selected so as to ensure a thickness of 30 microns or more.
This hardness is such that the adhesive material will not be washed away on the surface of the magnetic sensitive conductor, and is such that it can be adhered to the component-side conductor in the subsequent steps.
[0019]
7 In this state, the substrate is placed on the magnet and the electronic component is placed and mounted at the correct position. At this time, the pressure is applied so that the conductor of the electrode portion of the component meshes with the tip of the magnetically conductive conductor of the substrate. I pushed it to the extent and kept it in a magnetic force.
At this time, the surface of the electrode of the component is applied with a magnetic sensitive conductor or conductor particles by the same method.
In the case where both materials are non-magnetic conductor particles, they are pressed only by mechanical pressure, and a magnet may not be used.
The method of adhering the magnetically sensitive conductor or conductor particles to this part will be described in detail later.
[0020]
8 After this, it was again heated and cured. The condition was also 120 ° C. for 5 minutes.
9 In this state, it was used for circuit function tests, etc. to check for poor connections, and if there was a problem, it was corrected by applying a quick-drying silver paint with a thin brush.
[0021]
10 Thereafter, a transparent epoxy adhesive, which is a fourth adhesive material, was applied from above the adhesive portion and cured to ensure the mechanical adhesive strength of the component.
11 In principle, one of the main points of the present invention is not to use or reduce the conductive paint containing silver, which means that silver is referred to as migration in the presence of moisture and electric field. This eliminates or reduces the possibility of causing a short circuit by causing a phenomenon, leading to increased reliability and cost reduction.
[0022]
Here, the characteristics of the parts used in this method and the method of adhering a magnetic sensitive conductor or conductive particles to the electrodes of the parts will be described.
As a typical component used here, a surface mount component such as an LSI having a chip resistor and a lead terminal will be described.
[0023]
In the chip resistor process, generally, a metal glaze material containing glass is formed on a flat ceramic substrate by printing or the like and formed into a predetermined shape by a screen printing method, and then fired at about 850 ° C. to form a resistor and an electrode. Then, trimming with laser, insulation protection and display printing, etc., are divided into chocolate shapes, and then divided into individual parts after applying and curing a conductive material on the divided side surfaces, and in the plating process The soldering performance is ensured by plating nickel and solder.
[0024]
In the present invention, it is possible to shorten the process and not to use lead by eliminating the plating process.
In addition, since resistors and electrodes are not exposed to the heat of solder, there is no need to consider soldering heat resistance. Based on lead-free glass-based conventional materials based on lead-based resin Can be changed to material.
In general, these resin-based materials do not include expensive materials such as palladium and ruthenium unlike high-temperature-based materials, and have a great merit in terms of cost.
For example, as a resistance material, a resin such as phenol or epoxy that cures at about 150 ° C. mixed with conductive powder such as carbon black,
For example, carbon black or the like mixed with a drill resin (polyimide) that cures at a temperature of 250 ° C. or higher.
[0025]
Since the resistance and the electrode by the drill resin are cured at a temperature much higher than the drying and curing temperature of the material such as epoxy used in the subsequent process, there is an advantage that the process change is small.
As the electrode material, it is possible to use a material having a low resistance value among the above-mentioned resistance materials, but it is preferable to mix silver powder into the resin material.
[0026]
In this process, a resin material is used to print a resistor on the surface of the ceramic substrate in the same way as in the general process, electrodes are printed on the front and back surfaces, and each is dried and cured. Trimming is performed and an insulating protective material is applied to the front side.
At this stage, the adhesive material is printed at a position about 0.1 mm away from the dividing line with the electrode on the back side, and the connection is made by sprinkling and pressing the magnetically sensitive conductor in a state where a magnetic field is applied in the same manner as previously performed on the substrate. Form a surface.
In this case, the adhesive material is preferably the fifth type having conductivity.
Although the substrate will be described in detail later as another embodiment, the same applies to the case where conductive particles having no magnetic sensitivity are attached except that no magnetic field is applied.
After that, it is divided into chocolates, and silver paint or the like is mainly applied to the side surfaces to make the front and back conductive.
[0027]
These drying and curing temperatures differ from 850 ° C. in the case of glass-based materials described in the general examples, and are 150 ° C. or less for commonly used epoxy-based materials and 300 ° C. or less for the highest drill-based materials, which is much lower. is there.
This is further divided individually to complete the chip resistor.
[0028]
Another method of making a chip resistor, in particular, is to form a slit in the side electrode formation part and form a thin film on the side of the slit by a method such as sputtering. In this case, the adhesive material is printed after the side electrode is formed, and the magnetically sensitive conductor or the conductive particles may be adhered in the same manner. In this case, a pattern away from the slit portion is unnecessary, and the entire surface of the back electrode is not required. May be printed.
[0029]
In the case of LSIs, etc., the lead wires are made to be arranged in a plane. A jig is made so as not to impair this flatness, and a bonding method is applied to the surface of the lead part by a printing method. In the same manner as in the above method, there are a method of attaching a magnetic sensitive conductor and conductive particles, and a method of attaching a magnetic sensitive conductor and conductive particles after adhering an adhesive material in a masked state by spraying.
If possible, it is advantageous to do this before cutting the lead frame because the flatness of the lead is not impaired.
This lead portion also does not require solderability and does not require plating of a material such as solder containing lead.
As described above, according to the present invention, not only connection but also a process not containing lead can be realized even at the component level.
[0030]
"Other examples"
1 As a method that does not use a magnetically sensitive conductor, first coat the first adhesive material to a predetermined pattern of about 30 microns on the substrate surface, then sprinkle the conductive particles of about 50 mesh pass and 150 mesh stop on the adhesion surface of the substrate. After that, a method of applying pressure to adhere the conductive particles to the adhesion portion was also attempted.
Thereafter, the conductor particles that did not adhere were shaken off and removed.
Other steps were performed as described above.
[0031]
2. When mounting a component on a board, first apply a slow-curing type of epoxy adhesive, which is a third adhesive material, to the entire surface of the board, and then apply a curing agent or accelerator to the surface on the mounting side of the part. After thinly applying and mounting the component with the substrate placed on the magnet, bonding and curing at the electrode part and other contact surface of the component, washing away the slow-curing or non-curing epoxy adhesive other than the connection part Also tried.
According to this method, there is no troublesome application due to the positioning of the adhesive material, which is advantageous in that the positioning accuracy of the mounting is determined only by the positioning accuracy of the component mounting, and it is not necessary to consider the printability of the adhesive material. It is also advantageous in that an adhesive material having high fluidity can be thinly attached so as not to obstruct the adhesion between the conductors.
It was also effective to accelerate the curing only on the connection surface and the vicinity of the component surface by coating the magnetic sensitive conductor or granular conductor on the component side with a curing agent or curing accelerator to such an extent that the conductivity is not impaired. One method is to use a material that generates a metal ion that promotes hardening, and to select an adhesive material that easily reacts to the material.
In either case, there was an effect that the connection of parts became strong and hard to move by attracting with a magnet.
[0032]
3 Select a magnetically-sensitive conductor such as nickel or ferrite powdered with silver as a ferromagnetic material, so that the magnet action remains after adhering to the substrate side and the component side, and released before mounting. The magnetically-sensitive conductive powder was mounted on the magnetized magnetically-sensitive conductor, and was hardened with an adhesive in a state where electrical connection was ensured by a magnetic force.
According to this, the free magnetic conductor acts as a cushion and absorbs the variation in the flatness of the parts and the IC feet, thereby providing a reliable connection.
[0033]
4 When mounting a component on a substrate, an adhesive material containing magnetically-sensitive conductive powder as a filler was applied to the substrate-side connection surface, and the component was mounted and cured in a state where a magnetic field was applied.
The advantage of this method is that the electrical connection can be strengthened because the magnetically-sensitive conductive powder in the adhesive material is oriented in a direction perpendicular to the connection surface.
In particular, the magnetically conductive powder has a high probability of contact because the magnetic force acts in the direction pressed against the surface of the substrate electrode, and the opposite side has a high ratio of adhesive components, so that the magnetically conductive conductor adhering from the outside is not obstructed by the filler. There is an advantage that the adhesive material is easy to bond because it enters the adhesive material and has many adhesive components.
In addition, the magnetically-sensitive conductive powder contacts as a whole so as to enclose the magnetically-sensitive conductor, and has an effect of increasing the reliability of connection as compared with point contact with a flat surface in the absence of this.
At this time, even if the adhesive material protrudes from a predetermined position, the magnetically sensitive conductive powder is oriented in the vertical direction and insulated in the horizontal direction, so there is no problem, so the positioning of the adhesive material application may be rough. Furthermore, since the component main body portion can be fixed simultaneously with this adhesive material, the mechanical strength is also improved.
[0034]
5 In any of the cases described so far, the board side is placed on the magnet with the N pole facing up, and the component side is placed on the magnet with the S pole facing up. This direction may be reversed. I did this as a unified standard.
As a result, the surface of the magnetic material on the substrate side is magnetized to the N pole and the component side is magnetized to the S pole and attracts each other at the time of mounting. If this is the opposite, it will have the effect of shifting the position by the repulsive force, which is important.
When the magnetically sensitive conductors are attracted to each other, the conductive connection becomes complete, and since the magnetic connection is also attracted to an external magnet, it is firmly connected, and there is also an effect that misalignment hardly occurs even when it is hardened with an adhesive material.
[0035]
6 It was also effective to have the substrate side exposed to the surface of the magnetic sensitive conductor according to the present invention as described in Japanese Patent Application No. 2001-61909 and apply a conductive adhesive material to the component side for adhesion. .
In this case, the conductive adhesive material on the component side adheres relatively thickly to about 50 microns to absorb the variation in flatness of the component electrode surface, but the adhesive material is pressed vertically between the magnetic sensitive conductors. It is confirmed that this method can withstand high density mounting with a pitch of 0.33 millimeters with little protrusion in the lateral direction.
For this, a method of applying a conductive adhesive material to the substrate side by reversing the configuration of the component side and the substrate side was also effective.
[0036]
7 In the method described in (0035), an attempt was made to make the electrical connection by pressing the parts with an insulating adhesive material, but the surface of the magnetically sensitive conductor is not microscopically flat. Not used because there are fewer contact points.
[0037]
8 In the method described in (0035), an adhesive material containing magnetically-sensitive conductive powder as a filler is adhered to the component electrode side in the adhesive material, and the component is held down while attracting the filler to the component electrode side with a magnet in the presence of a magnetic field. The method of adhesive curing was also tried and confirmed to be effective.
At this time, the content ratio of the magnetically conductive powder is about 25 to 50% higher than that on the substrate side, and it is printed with a stainless mask or attached to a thickness of about 50 microns using a dispenser. For the purpose of increasing the number of conductive paths and the purpose of increasing the conductive path, it is advantageous because a harder adhesive material can be used, and the variation in flatness of the magnetic sensitive conductor on the substrate side is absorbed by the filler of the magnetic sensitive conductive powder. Thus, a conductive path is ensured, and the magnetically sensitive conductor is bonded and fixed at a portion having a high adhesive material component ratio, which is advantageous in terms of mechanical strength.
For this, a method of applying an adhesive material containing magnetically-sensitive conductive powder to the substrate side by reversing the configuration of the component side and the substrate side was also effective.
[0038]
【The invention's effect】
According to the present invention, it is possible to eliminate the soldering that needs to be processed at a high temperature, so that it is possible to mount without using lead and to use no lead in the component itself, and to connect only with a conductive adhesive as in the past. Compared to the case, it can be mounted at a higher density.
In addition, since a material with good adhesiveness is used, reliable connection is possible.
Since it is processed at a lower temperature, it has become possible to mount electronic capacitors such as electrolytic capacitors and liquid crystals that could not be mounted by conventional soldering at the same time. Conventional liquid crystals cannot be mounted directly on the board. Zebra rubber and flexible cables However, these parts can be eliminated.
[0039]
"References" Japanese Patent Application 2001-61909
U.S. Pat. No. 4,170,677
[Brief description of the drawings]
FIG. 1 shows that a conductive material is applied to a conductor electrode of a substrate or a component, and then a magnetic field is applied so that the magnetically sensitive conductor is substantially perpendicular to the electrode surface and electrically conductive by contacting the electrode. FIG. 3 is a schematic cross-sectional view of a material further cured by heat curing.
Here, the direction of the magnetic field is indicated by an arrow, but in the case of a component, the direction of the magnetic field is the S pole.
[Fig. 2] Fig. 2 shows an example in which an adhesive material is attached to a conductive electrode of a substrate or a component, and then conductive particles are attached and pressed to make contact with the electrode so as to be electrically connected and further heat-cured and hardened. It is a schematic cross section.
FIG. 3 shows an adhesive material containing a magnetically-sensitive conductive powder as a filler applied to a conductor electrode of a substrate or a component, and a magnetic field is applied to attract the filler to the electrode surface for electrical contact and magnetically conductive The body was attached and it was raised almost vertically to the electrode surface and attracted in the direction of the electrode surface so that it was in direct contact with the electrode or electrically connected to the electrode through a conductive filler. It is a schematic cross section of what was hardened by post-heating curing.
Here, the direction of the magnetic field is N pole in the case of a substrate and S pole in the case of a component, but the N pole is indicated by an arrow in the figure.
FIG. 4 is a schematic cross-sectional view of a connection method in which electrode portions of the shape shown in FIG. 1 are connected to each other with the substrate side facing down and the component side facing up, and fixed with an adhesive material.
Here, the case where a magnetically sensitive conductor is used for both is shown, but the case where the conductive particles are used for one or both is substantially the same except that a magnetic field is applied or not.
FIG. 5 is a diagram showing the electrode part of the shape shown in FIG. 1 with the substrate side facing down and the component side facing up, and an adhesive containing a magnetosensitive conductive filler interposed between the two, and the filler is used to make the conductivity conductive. It is a schematic cross section of the method of connecting in the improved form.
Here, an example in which a magnetically sensitive conductor is used is shown, but the improvement in conductivity can be expected with the same shape when one or both of the conductor particles are used.
The shape in the case of using a conductive adhesive material containing silver or the like is also finished in substantially the same shape except that the magnetosensitive conductive filler is magnetically oriented.
FIG. 6 is a diagram in which a magnetically sensitive conductive powder is attached to a magnetically sensitive conductor with the substrate facing down and the components facing upward to make an upper and lower electrical connection through the magnetically sensitive conductive powder and solidified by an adhesive material. It is a schematic cross section which shows a connection method.
FIG. 7 shows a connection part with a magnetic sensitive conductor attached on the board side with the board facing down and the component facing up, and a conductive adhesive material is attached to the component side and mounted in place and pressed down. It is a schematic cross section at the time of conducting conductive connection by hardening.
FIG. 8 shows a connection part to which a magnetically sensitive conductor is attached on the substrate side with the substrate facing down and the component facing up, and an adhesive material containing a magnetically sensitive conductive powder as a filler is adhered to the component side. It is a schematic cross section at the time of carrying out conductive connection by mounting in this position, pressing down and hardening in the presence of a magnetic field.
[Explanation of symbols]
1 Board body
2 Substrate side electrode
3 Substrate side adhesive material
4 Magnetic sensitive conductor
5 conductive particles
6 Adhesive material containing magnetically sensitive conductive powder
7 Filler with magnetic sensitive conductive powder
8 Adhesive materials
9 Magnetic sensing conductor on the component side
10 Component side electrode
11 Parts body
12 Component side adhesive material
13 Magnetosensitive conductive powder
14 Conductive adhesive material
15 Adhesive material containing magnetically conductive powder on the component electrode side

Claims

Print the adhesive material on the electrodes on the board,
The magnetically sensitive conductor in the form of needles or flakes attached to the adhesive material immediately after printing is sprinkled with the magnetic field applied to the entire surface of the substrate to stand the magnetically sensitive conductor on the adhesive material. Attached in a state,
Pressurizing the entire surface of the substrate so as not to impair the standing direction of the magnetic sensitive conductor,
Shake off the magnetic sensitive conductor that was not adhered from the substrate,
Heat-curing the adhesive material,
A method for manufacturing a substrate, which includes a step of removing a magnetically-sensitive conductor that has not been bonded.

An adhesive material containing 5 to 50 percent of a magnetically conductive powder as a filler is printed on a substrate electrode,
By sprinkling a needle-like or flake-like magnetic sensitive conductor adhering to the first adhesive material on a substrate immediately after printing in a state where a magnetic field is applied to the entire surface of the substrate, the magnetic sensitive conductor is attached to the adhesive material. Attached in a standing state,
Shake off the magnetic sensitive conductor that was not adhered from the substrate,
Heat-curing the adhesive material,
A method for manufacturing a substrate, which includes a step of removing a magnetically-sensitive conductor that has not been bonded.

Print the first adhesive material on the electrode of the part,
By sprinkling the part immediately after printing with a needle-like or flake-like magnetic sensitive conductor adhering to the first adhesive material in a state where a magnetic field is applied to the entire surface of the part, the magnetic sensitive conductor is attached to the adhesive material. Attached in a standing state,
Pressurize the entire surface so as not to impair the standing direction of the magnetically sensitive conductor over the component,
Shake off the magnetic sensitive conductor that was not adhered from the part,
Heat-curing the adhesive material,
A method for manufacturing an electronic component, which includes a step of removing a magnetic sensitive conductor that has not been bonded.

Print an adhesive material containing 5 to 50 percent of the magnetically conductive powder as a filler on the electrode of the component,
By sprinkling the part immediately after printing with a needle-like or flake-like magnetic sensitive conductor adhering to the first adhesive material in a state where a magnetic field is applied to the entire surface of the part, the magnetic sensitive conductor is attached to the adhesive material. Attached in a standing state,
Shake off the magnetic sensitive conductor that was not adhered from the part,
Heat-curing the adhesive material,
A method for manufacturing an electronic component, which includes a step of removing a magnetic sensitive conductor that has not been bonded.

The adhesive material is attached to a portion of the substrate obtained by the manufacturing method according to claim 1 or 2 to which the magnetically sensitive conductor is attached,
The magnetic sensitive conductor attached to the electrode portion of the component obtained by the manufacturing method according to claim 3 or claim 4 is pushed to such an extent that the magnetic sensitive conductor is engaged with the tip of the magnetic sensitive conductor of the substrate,
An electronic component mounting method that includes a step of heat-curing the adhesive material.

Applying an adhesive material to the entire surface of the substrate obtained by the manufacturing method according to claim 1 or 2,
Applying a curing agent or a curing accelerating material to the electrode part of the component obtained by the manufacturing method according to claim 3 or claim 4,
Push the magnetically sensitive conductor attached to the electrode part of the part to the extent that it engages with the tip of the magnetically conductive conductor of the substrate,
An electronic component mounting method including a step of washing and removing an uncured adhesive material while an adhesive applied to an electrode portion of the component is cured and another portion is uncured.

The magnetic adhesive powder is included in the adhesive material, and a magnetic field is applied so that the magnetic sensitive conductor powder is oriented across the connection surface between the substrate and the component. A method for mounting electronic components that undergo a process.

The part to which the magnetic sensitive conductor of the board obtained by the manufacturing method according to claim 1 or 2 is attached by a magnet, and the electronic component obtained by the manufacturing method according to claim 3 or 4 A method for mounting an electronic component, wherein the magnetic parts of different magnetic poles are given to the electrode portions, and the process according to any one of claims 5 to 7 is performed.