JP3779686B2 - Circuit board manufacturing method - Google Patents

Description

【００３０】
表１から明らかなように、基材４の材料内に対して色調を変化させる事でレーザ光の必要ピークパワーを小さくする事が可能となり、孔加工性を確保し、かつレーザ光の必要ピークパワーを抑えて加工精度を向上しながら、孔加工されない部分での副成分物質であるガラス繊維４ｂやアラミド繊維４ｃ等の存在によって基材の機械的、電気的な性能を確保する事ができる。
【００３１】
以上のように第１の実施例によれば、基材に対して色調を変化させる事でレーザ光の吸収率の差を小さくするとともに吸収効率を向上させる事が可能となり、より広範囲の加工条件を設定する事ができ、高品質な孔加工ができる。したがって、品質及び加工性、生産性、歩留りを向上させる事ができる。
以下本発明の第２の実施例について図面を参照しながら説明する。
【００３２】
図３は本発明の第２の実施例を示す回路基板の製造における基材処理装置の模式図である。
【００３３】
図３に示すようにオゾン室１０内にステージ５が置かれ、これに主成分となる樹脂材料を含浸させていない基材４が保持される。オゾン室１０の天井部各所にオゾン発生装置６から延びたオゾン供給ダクト７が接続されるとともに、オゾン室１０の側壁下部には真空ポンプ９を持った排気ダクト１１が接続されている。また、オゾン室１０の天井部のオゾン供給ダクト７の各接続部の間に紫外線照射部８が設けられている。
【００３４】
本実施例では回路基板を製造するのに、その前段階で以上のような処理装置を用いる。具体的には、まず樹脂分を含浸させていない基材４をステージ５上に配置する。この場合の基材４は主成分である樹脂が含浸されていない、したがって強化材である前記副成分からなるもので、レーザ光による加工では主成分として含浸させる樹脂よりも多くのエネルギーを必要とするものである。
【００３５】
つぎに真空ポンプ９によってオゾン室１０の空気を除去しつつ、オゾン発生装置６から供給されるオゾンをオゾン供給ダクト７を介しオゾン室１０内に供給して基材４に吹きかける。
【００３６】
基材４の種類によってはステージ５内部にセットした熱源から熱を加えて所定の時間保持する。また、オゾンの代わりに紫外線照射部８から紫外線を照射し所定の時間保持する事で処理を終了する。
【００３７】
表２に所定時間処理した後に孔加工を行った場合の真円度と断面形状及び孔壁面での繊維成分の占有率を示す。
【００３８】
【表２】

【００３９】
表２から明らかなように紫外線又はオゾンの効果が確認される。これは、基材４の副成分の機械的加工性が向上することによると見られる。基材４の材料に複合させる副成分であるアラミド繊維４ｃ等を紫外線照射処理またはオゾン処理した場合も同様の効果が確認された。しかし、一般的に用いられているガラス繊維の場合には効果は確認されなかった。
【００４０】
以上のように第２の実施例によれば、基材４を紫外線又はオゾン雰囲気中に暴露する事で基材の孔加工性を向上させ、高品質な孔加工が可能となり、品質及び加工性、生産性、歩留りを向上させる事ができる。
【００４１】
なお、本実施例では、紫外線の照射処理とオゾン処理のどちらかを採用するようにしたが、場合によっては双方の処理を行うようにすることもできる。
【００４２】
図４は本発明の第３の実施例を示すペースト充填工程の模式的図である。
【００４３】
図４に示すように、ステージ５に保持された基材４の孔加工された貫通孔４ｄに、充填ヘッド２１によってペースト２２を押圧して充填する。
【００４４】
充填ヘッド２１は上下方向及び矢印Ａで示す充填動作方向に移動が可能となっている。通常、充填ヘッド２１が基材４の上を移動する際に充填ヘッド２１と基材４との接触点近傍に存在するペースト２２は流動可能流域が小さい事と、周囲の圧力勾配が小さいために、粘度を単純に低くするだけでは極めて流動しにくい状態となっている。
【００４５】
ペースト２２自身の温度を上昇させる事で流動性は向上するが、特に熱硬化型などのペースト２２を使用すれば、ペースト２２の寿命は低下する。ペースト２２の充填に必要な流動性を確保する部分は、ペースト２２が基材４に設けられた貫通孔４ｄに近接する部分だけで十分であり、貫通孔４ｄにペースト２２が充填されるのに必要な圧力は充填ヘッド２１及びペースト２２自身の矢印Ｂで示すローリングにより発生する流体圧力（hydlaulic pressure）によって与えられる（例えばD.E.Riemer:"INk Hydrodynamics of Screen Printing".Proceedings ISHM Symposium1985）。ペースト２２のローリングは基材４の印刷面から充填ヘッド２１のペースト押圧面２１ａに沿って上方に上る事で形成されるため、充填ヘッド２２のペースト押圧面２１ａに対して所定の温度勾配を設ける事で、ペースト押圧面２１ａの印刷面に接する側で温度が高く、印刷面から離れる程温度が低くなるような温度勾配によって、ローリングするペースト２２の印刷面に接触する部分で粘性を低下させて流動性を向上させるとともに、ペースト押圧面２１ａにおける基材４の印刷面、および充填ヘッド２１から離れる側で低温となることによって流動性を抑えてペースト押圧面２１ａの印刷面との接触部分の流体圧力を高めるので、ペースト２２を所定量安定して充填することができるのに併せ、前記低温部にて揮発性成分の発散をも抑制してペースト２２全体を所定粘度に保ち易いので連続印刷性を向上させる事ができる。
【００４６】
表３に一般的な充填条件におけるペーストの充填深さと充填ヘッド２１内の温度差を示す。
【００４７】
【表３】

【００４８】
表３から明らかなように充填力の向上が得られている事が分かる。これを本実施例ではペースト２２の印刷面と接触する部分に対して加熱し、ペースト２２の印刷面および充填ヘッド２１が離れる部分が低温となるように、充填ヘッド２１に内蔵した上下２つのヒータ２３、２４によって温度勾配を設定する事で達成している。また、ペースト自身が揮発成分を含有している場合には温度の上昇によって揮発成分が失われ粘度が上昇する事は一般的に知られた事である。ペースト２２の印刷面および充填ヘッド２１から離れて外気にさらされる部分が低温となる事によりペースト２２の揮発成分の発散による硬化反応を抑制していることが明かであり、連続印刷性を向上させる事が可能となる。なお、本実施例においてはマスクを用いない直接印刷法について行ったが、基材４上にマスクが存在していても同様の事である。
【００４９】
なお、前記のような温度勾配は、ペースト２２を加熱する部分のヒータ２３だけを設けるようにしても達成されるし、ヒータ２３、２４間に適数のヒータを内蔵してもよい。ヒータの数が多いと温度勾配をより強制的に細かく設定することができる。また、ヒータ２３の位置からヒータ２４の位置まで容量を漸減しながら連続する１つのヒータを内蔵するようにしてもよい。
【００５０】
また本実施例では、ヒータ２３、２４の通電回路中にボリューム２３ａ、２４ａを設けて、ヒータ２３、２４の発熱量を調整し、前記のような温度勾配を種々に設定できるようにしてある。
【００５１】
これによって、ペースト２２およびこれの充填の広範囲な条件に対応して、各種条件の回路基板を高品質に製造することができる。
【００５２】
図５、図６は本発明の第４の実施例を示す回路基板の製造における充填工程に用いる装置の模式図である。
【００５３】
充填装置は図５に概略を示すように、ステージ５上の基材４にペースト２２を充填する充填ヘッド２１は、例えばガイド２５とこのガイド２５に案内される左右方向スライダ２６とによって充填方向に移動され、左右方向スライダ２６の上のガイド２７とこれに案内される上下方向スライダ２８とによって上下に移動される。また、充填ヘッド２１は基材４との接触側が自由端となるように上下方向スライダ２８上に軸２９によって回動できるように枢支され、基材４との接触角θが可変になっている。
【００５４】
充填ヘッド２１は軸２９に連結したアクチュエータＡ１によって軸２９のまわりに回動され、上下方向スライダ２８に連結したアクチュエータＡ２によって上下方向に移動され、左右方向スライダ２６に連結したアクチュエータＡ３によって左右方向に移動される。
【００５５】
従来の印刷方式の場合では、ペースト２２の供給量に関わらず一定の設定角度で充填が行われているがペースト２２の量が減少すればペースト２２中に発生する流体圧力も減少し充填力が低下する。この関係はD.E.Riemarによって以下のような相関になると報告されている（"INk Hydrodynamics of Screen Printing". Proceedings ISHM Symposium1985）。
【００５６】
【数１】

【００５７】
ここで、ｐはペースト中に発生する圧力、μはペーストの流動速度、ｖは充填ヘッドの移動速度、Ｖはペーストの体積、θは充填ヘッドと基材との接触角度、ｋは比例常数である。
【００５８】
この圧力差が基材４に設けられた貫通孔に対してペースト２２を充填するのに必要な圧力差となり、工学的によく知られたハーゲン・ポワズイユの式に代入する事で貫通孔に対するペースト２２の充填状態を知る事ができる。従って充填状態を一定にするためには印刷工程中常にｐを一定にしてやる事が重要となる。
【００５９】
一般には充填の作業が続いてもペースト体積の減少量が無視できるほど十分なペーストを投入する事で対応しているが、ペースト２２自身の粘度や組成の変化に対応する事はできていない。
【００６０】
しかしながら本実施例の方法では、１ストロークで減少するペースト２２の量を把握しておく事で、充填ヘッド２１の速度を
【００６１】
【数２】

【００６２】
に増加させる事でペースト量の変動に対応でき、一度のペースト２２の投入量を減少させる事が可能となった。表４は初期ペースト投入量による従来法と本実施例の方法による１００枚印刷した後の充填力の変動を充填深さの変動率の観点で確認したものである。
【００６３】
【表４】

【００６４】
表４から明らかなように速度制御の効果を確認する事ができる。以上の方法により工程歩留まりの向上が可能となり、連続生産性を向上させる事が可能となる。本実施例では速度の制御について行ったが、角度については、
【００６５】
【数３】

【００６６】
を満足するΔθを求め、Δθずつ角度を減少させていく操作を行えば同様の事である。
【００６７】
図６はこのような制御のための制御回路の一例を示している。前記各アクチュエータＡ１〜Ａ３はマイクロコンピュータ３１によって駆動制御するようにし、前記速度の変化条件を含む制御条件は操作パネル３２によって種々に入力できるようにしてある。
【００６８】
また、充填ヘッド２１の角度や速度、高さが設定通りであるように、それぞれを検出するセンサからの入力によってフィードバック制御するようにしてある。
【００６９】
本実施例では、充填ヘッド２１を軸２９のまわりに回動させて印刷面との接触角θも自動的に変えることができ、このθを小さくすることによっても充填率が向上するので、ペースト量の変化に対応することができる。もっとも、印刷面との接触側が自由端となる充填ヘッド２１の接触角θを変えると、自由端高さが変化するので、これを補正して所定の高さを維持するように制御する。図７に示す第５の実施例の印刷面との接触側で支持した充填ヘッド２１に適用した場合はそのような補正は不要となる。
【００７０】
なお、充填ヘッド２１の移動速度と接触角θとの双方を変化させてペースト量の変化に対応することもできる。
【００７１】
図７は本発明の第５の実施例を示す回路基板の製造における充填工程に用いる装置の模式図である。
【００７２】
本実施例の充填ヘッド２１は図７に示すように、ペースト押圧面２１ａでのステージ５の上の基材４の印刷面に接触する側Ｃをホルダー４１で支持し、印刷面から離れる側Ｄが自由端となるようにした点を特徴としている。さらに具体的には、本実施例は平スキージタイプにも適用できるが、このタイプを少し変形した横断面３角形のブレードタイプとしてあり、ペースト押圧面２１ａの印刷面との接触側Ｃから印刷面から離れる側Ｄに向けて厚みが漸減するようにしてある。
【００７３】
充填ヘッド２１を下動させて基材４との間でペースト充填のための印圧を加えたとき、従来の平スキージタイプの充填ヘッドの支持構造では、ペースト押圧面２１ａの印刷面から離れる側Ｄを支持しているので、ホダーによる印圧はこのＤ点近傍に与えられ、印刷面に接触する側Ｃは自由端となって難なく撓みやつぶれが生じて、これがペースト２２の押圧に大きな逃げとなり、基材４の貫通孔４ｄにペースト２２を充填するのに重要なＣ側での押圧が弱くなり、安定した充填は望めない。
【００７４】
しかも、接触角θが初期の設定より小さくなり、充填ヘッドの材質や印圧を加える部分の構造により接触角度と接触部分のつぶれている量が異なるために調整する必要があった。
【００７５】
また、充填ヘッド先端のつぶれ量は基材の印刷面の凹凸に追随する必要最低限に抑えておかなければ基材に設けられた貫通孔に充填したペーストをかき取る現象が発生する。
【００７６】
また、角スキージタイプにおいては、最初から４つの角は丸まっているために、表面の掻き取り性は極端に悪く、必要以上の印圧を加えて先端のつぶれ量を確保する必要があったため、充填したペーストを孔から掻き取る量が不安定となっていた。
【００７７】
これに対し本実施例では、基材４の孔加工された貫通孔４ｄにペースト２２を押圧して充填する充填ヘッド２１が、ペースト押圧面２１ａにおける基材４の印刷面との接触側Ｃでホルダー４１により支持されていて、印刷面から離れる側Ｄが自由端となって変形することによって必要な撓み性を確保しながら、印刷面と接触する側Ｃではペースト２２の押圧に対する逃げを抑制しながら基材４の印刷面の凹凸に対応する必要最小限の弾性を弾性材の選択と言う材料的に確保して、ペースト２２の経時的な粘度の上昇や消費による減量があっても、特別な制御の必要なくペーストを所定量安定して充填することができ、連続印刷性を向上することもできる。
【００７８】
このように本実施例では、印圧は充填ヘッド２１の基材４に接触するＣ点に直接かかる事になり充填ヘッド２１の撓みによる接触角度の減少をなくす事ができる。この状態を観察したところ、充填ヘッド２１と基材４との接触部分の撓みは存在していなかった。したがって、以上の装置を用いる事により、ペーストの充填機能を持つ部分の条件設定が製造中一定に保つ事が可能となり、一定の品質のものを生産する事が可能となり、製造歩留まりを向上させる事が可能となる。
【００７９】
図８は本発明の第６の実施例を示す回路基板製造におけるペーストの充填工程の前処理状態を示す充填装置の模式図である。
【００８０】
本実施例は図８に示すように、ステージ５の上の基材４の印刷面に対し、充填ヘッド２１によってペーストを押圧して充填する前に前処理材５１を塗布するようにしている。このために、充填ヘッド２１と前処理ヘッド５２とを備えており、基材４の孔加工された貫通孔４ｄに充填ヘッド２１によってペーストを充填する工程において、ペーストを充填する作業の前に、基材４の印刷面にペーストの含有物と同じ不揮発の有機成分を前処理材５１として前処理ヘッド５２によって塗布する。
【００８１】
前処理ヘッド５２が基材４の上を接触しながら移動して基材４の表面に前処理材５１を塗布する際、前処理材５１は前処理ヘッド５２によって基材４の印刷面から十分かき取られるが、基材４の表面に吸着する分が基材４上に残される。このときに発生する吸着機構は、ペーストの充填中も基材４上で同じく発生するため、ペーストの粘度上昇がおこる。事前にペースト中の不揮発の有機成分を前処理材５１として基材４上に塗布した場合としない場合のペーストの粘度上昇の結果を図９に示す。図９から明らかなようにペースト中の不揮発の有機成分の塗布の効果が見受けられる。
【００８２】
これは、基材４と前処理ヘッド５２とによる前処理材５１のかきとりが、ペーストのかきとりと同程度である事に起因すると考えて良い。かきとりの状態が甘ければ、基材４の表面に有機成分を残す事になり、ペースト自身の粘度を低下させる事もあるために注意が必要である。以上の結果からペーストの充填工程の前にペースト中の不揮発の有機成分を基材上に塗布する事でペーストの粘度上昇を抑制し、連続印刷性を向上させる事が可能となる。本実施例において塗布ヘッドはウレタンゴム製のスキージを用いたが基材上に蒸着などの操作によって有機成分を吸着させても効果は同様の事になる。
【００８３】
図１０は本発明の第７の実施例を示すペースト充填状態の説明図である。
【００８４】
本実施例は図１０に示すように、圧縮性を有する基材の孔加工された貫通孔にペーストを押圧して充填する工程において、ペースト２２の充填が最大で貫通孔の５〜２０％の未充填部分６１が残るように充填する。
【００８５】
これにより、基材が圧縮されるときのペースト２２を未充填部分６１に逃がせるようにして、行き場のないペースト２２の反発力によって起こる層間の導通部分の剥離を防ぐ事ができる。
【００８６】
さらに具体的には、基材４は貫通孔４ｄにペースト２２を充填した後、両面を銅箔ではさんで加熱、プレスする事で両面板を形成し、その後銅箔を所望のパターンにエッチングする事で回路基板を形成する。これら一連の工程の中で、基材４を銅箔にはさんで加熱、プレスする際に基材４の圧縮が貫通孔４ｄ中に充填されたペースト２２の許容量以上行われると、ペースト２２が硬化した後に銅箔を基材４から引き剥そうとする方向に力を発生させ、層間の導通の信頼性を著しく低下させる。これは、貫通孔４ｄ中に充填されたペースト２２が圧縮された場合、許容量以上となる部分の逃げ道がないために発生するものであり、基材４が多孔質なものの場合には基材４中に滲み出す事になる。基材４中にペースト２２が滲み出した場合には絶縁抵抗の低下など回路基板としての信頼性を低下させる事になり、回避しなければならない。
【００８７】
これを、基材４に形成された貫通孔４ｄ中にペースト２２の移動できる空間を前記未充填部分６１によって形成し、許容量以上に圧縮されたペーストを貫通孔４ｄ内に収めることでこれらの課題を解決する事ができる。表５に貫通孔４ｄの平均直径と平均直径に対する未充填部分６１によるくぼみ量を変化させた場合の導通抵抗の良、不良を示す。
【００８８】
【表５】

【００８９】
表５から明らかなように、平均孔径に対して５〜２０％の未充填部分を作る事で、導通抵抗の信頼性を得る事ができた。以上の結果から貫通孔の平均直径の５〜２０％の深さのくぼみ量となるようにペーストを押圧して充填する事により、圧縮された基材の反発力によって起こる層間の導通部分の剥離、信頼性の低下を防ぐ事ができる。
【００９０】
【発明の効果】
本発明の回路基板の製造方法によれば、レーザ光による孔加工性の劣る物質に対して紫外線照射又はオゾン中への暴露を行う事で、機械的な孔加工性を事後的に向上させ、孔加工後の孔品質、歩留り、生産性を向上する事ができる。
【図面の簡単な説明】
【図１】本発明の第１の実施例における孔加工装置の模式図である。
【図２】色調に対するレーザの波長と反射率の関係を示すグラフである。
【図３】本発明の第２の実施例における回路基板の製造装置の模式図である。
【図４】本発明の第３の実施例における回路基板の製造装置のペースト充填機能を持つ部分を示す模式図である。
【図５】本発明の第４の実施例における回路基板の製造装置の充填機能を持つ部分を示す模式図である。
【図６】図５の装置の充填部分に関する制御回路のブロック図である。
【図７】本発明の第５の実施例における回路基板の製造装置の充填機能を持つ部分を示す模式図である。
【図８】本発明の第６の実施例を示す回路基板の製造装置のペースト中の不揮発の有機成分を塗布する機能を持つ部分を示す模式図である。
【図９】本発明の第５の実施例におけるペースト中の不揮発の有機成分を基材上に塗布した場合としない場合のペーストの粘度上昇の結果を示すグラフである。
【図１０】本発明の第７の実施例を示す回路基板の製造方法によるペーストの充填後の充填状態を示す模式図である。
【図１１】従来の第１の印刷装置の模式図である。
【図１２】従来の第２の印刷装置の模式図である。
【符号の説明】
１ レーザ光源
４ 基材
４ａ 主成分
４ｂ ガラス繊維
４ｃ アラミド繊維
４ｄ 貫通孔
６ オゾン発生装置
７ オゾン供給ダクト
８ 紫外線照射部[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a circuit board used in a circuit of an electronic device.
[0002]
[Prior art]
In recent years, circuit boards have changed from single-sided boards that form circuits only on one side to double-sided boards that form circuits on both sides, and multilayer circuit boards that form circuits in multiple layers, in order to achieve small size and high performance. Currently, many substrates with advanced multi-layers are used.
[0003]
The via holes formed in the circuit board are usually formed one by one by a drill or a punching machine. In order to reduce costs, high-speed drilling is partly performed with a laser.
[0004]
In laser drilling, it is necessary to set conditions such as laser wavelength, output, and pulse width, but the main component is epoxy resin with good processability, which is called glass fiber or aramid fiber as a reinforcing material. In drilling a substrate made of so-called FRP or the like made of two or more substances combined with other subcomponents, the conditions of the conditions can be changed by changing the output, pulse width, etc. in order to correspond to the subcomponents on the processing surface. Adjustments are made to improve yield.
[0005]
Moreover, in the process of pressing and filling the paste with respect to the drilled via hole or through hole, the paste is manufactured by a printing method using a filling head called a squeegee. In the printing method, a very large number of conditions such as squeegee hardness, angle, printing pressure, and filling operation speed are required.Slight differences in the settings affect the quality. To improve the yield and quality in the paste filling process.
[0006]
In the paste filling process, squeegees have been devised, such as flat squeegees, sword squeegees, squeegees that have a curved contact surface with the printed surface, and squeegee shapes that are devised. Is heated to a certain temperature to reduce the viscosity of the paste and improve the filling power.
[0007]
As for the viscosity change of the paste, the viscosity of the paste increases in proportion to the operating time, so the paste viscosity is stabilized by replacing the paste at regular intervals or adding an organic solvent to adjust the viscosity. .
[0008]
Furthermore, in order to control the filling amount of the paste into the hole-processed via hole or through-hole, the filling amount is stabilized by filling the surface of the substrate with the amount of paste filling the hole.
[0009]
A specific example of the above-described conventional circuit board manufacturing method will be described below with reference to FIGS.
[0010]
FIGS. 11A and 11B illustrate two examples of circuit board manufacturing methods and apparatuses in a conventional hole drilling process.
[0011]
In FIG. 11A, a is a laser light source, b is a reflecting mirror, c is a condenser lens, d is a base material, and e is a releasable film. The release film e is bonded to both surfaces of the base material d. The direction of the laser light emitted from the laser light source a is changed by the reflection mirror b and is directed to the condensing lens c, where the diameter is narrowed and irradiated onto the substrate d on which the release film e is bonded. The light energy given from the laser light is absorbed by the base material d and converted into thermal energy to form through holes in the base material d and the release film e.
[0012]
In FIG. 11B, f is a drill. The drill f descends while rotating from above the base material d, and through holes are formed by sequentially drilling holes in the releasable film e and the base material d with a cutting edge at the tip of the drill f.
[0013]
FIGS. 12A and 12B illustrate two circuit board manufacturing methods and apparatuses in a conventional paste filling process.
[0014]
12 (a) and 12 (b), k is a mask and is placed on the substrate d.
[0015]
m and n are squeegees that move on the mask k while touching. p is a paste and q is a stage. The base material d is disposed in contact with the stage q. A mask k is disposed above the base material d with a slight space, and the paste p can be supplied onto the mask k. Squeegees m and n are arranged above the mask k, and the squeegees m and n can move in the vertical direction and the printing direction.
[0016]
First, the base material d is set at a predetermined position on the stage q. Next, the position of the through hole formed in the base material d and the position of the hole formed in the mask k are matched, and the mask k is set on the base material d. Next, the paste p is supplied onto the mask k, and the squeegees m and n are lowered and held in a state where a predetermined pressure is applied to the substrate d. Further, printing is performed by moving the squeegee m in the printing direction and moving the paste p on the base material d, and the paste p is pressed and filled into the through holes in which the hole is formed in the base material d.
[0017]
[Problems to be solved by the invention]
However, in the hole drilling process of the circuit board manufacturing method of the above-described prior art, extremely small hole drilling is difficult by the method using a drill, and the productivity is low and the cost is high. Even in the method using a laser, the hole shape becomes a distorted circular shape or the cross-sectional shape becomes a drum shape as shown in FIG. In the processing of base materials composed of two or more substances as described above, it is difficult to select the optimal processing conditions mainly due to differences in the processing conditions of the substances that are subcomponents. Therefore, it has a serious problem that both quality and productivity are poor and yield is poor.
[0018]
Further, in the paste filling step of the above conventional circuit board manufacturing method, the filling shape and amount of the paste greatly change even due to a mechanical error, and a filling defect represented by omission or fading occurs. When the flat squeegee n shown in (b) of 12 is used, it is difficult to set and maintain the contact angle with the mask or the substrate printing surface, and the variation in the amount of paste filled in the through hole becomes large. There is a serious problem that it is extremely difficult to control properly. In addition, when the angle squeegee m as shown in FIG. 12A is used, it is easy to set the contact angle with the mask or the substrate printing surface, but the sharpness of the tip portion in contact with the substrate printing surface. Since there is a shortage of remaining paste on the mask or base material, and the amount of paste used for filling is small, frequent paste replenishment is required, which has the problem of poor productivity. In addition, when the viscosity of the paste may increase due to the diffusion of volatile components, or when a paste with a high viscosity is used, a large shortage of the filling amount will occur under the filling conditions that were set to be in good condition. It has a problem that it takes a very long time to set the correct filling conditions again. The filling method with a built-in heater in the squeegee simply reduces the viscosity of the paste, has little effect on the rolling or filling of the paste, and has little effect, so it is necessary to set and adjust the conditions. The remaining problem remains that productivity is poor.
[0019]
In view of the above problems, an object of the present invention is to provide a circuit board manufacturing method capable of improving manufacturing yield, quality, and productivity.
[0020]
[Means for Solving the Problems]
In order to solve the above problems, the circuit board manufacturing method of the present invention is based on an organic substance having poor mechanical workability other than the main component constituting the base material subjected to ultraviolet irradiation or ozone exposure treatment. Laser drilling is performed on the material.
[0021]
[Action]
In the above configuration of the method for manufacturing a circuit board according to the present invention, the mechanical hole workability is improved afterwards by exposing the substance having poor hole workability by laser light to ultraviolet irradiation or ozone exposure. It is possible to improve hole quality, yield, and productivity after drilling.
[0022]
【Example】
Several embodiments of the circuit board manufacturing method and the related apparatus of the present invention will be described below with reference to the drawings.
[0023]
1 and 2 show a first embodiment of the present invention. FIG. 1A shows a schematic diagram of a hole processing apparatus used for manufacturing a circuit board. In FIG. 1A, 1 is a laser light source, 2 is a reflection mirror, 3 is a condensing lens, and laser light emitted from the laser light source 1 passes through the condensing lens 3 via the reflection mirror 2. Reference numeral 4 denotes a base material of a circuit board to be manufactured, which is irradiated with laser light having an increased energy density after passing through the condenser lens 3 and is subjected to hole processing by the thermal energy of the laser light. 5 is a stage for holding the base material 4 in contact and positioning for the hole processing.
[0024]
In this embodiment, the above laser is applied to the base material 4 that has been subjected to color tone change processing in the material in order to perform hole processing for manufacturing a circuit board using the hole processing apparatus shown in FIG. Drill holes.
[0025]
FIG. 2 is a graph showing the wavelength and reflectance of the laser with respect to color tone. As is clear from FIG. 2, the reflectance of the laser light clearly depends on the color tone. From this, it is apparent that the workability can be improved by selecting the color tone in the material of the base material 4 during the laser hole machining and changing it to a color tone satisfying this.
[0026]
Experimentally, in the method of dispersing the metal in the material of the base material 4, heat from the laser light is transmitted to the periphery of the metal powder, and the roundness is reduced. However, when the accuracy of the hole diameter is not required, the metal powder is used. Or addition of metal oxide powder is sufficient.
[0027]
On the other hand, when the color tone was changed by adding an organic component such as thymol red, an accuracy of ± 8% was obtained in the case of yellow using an ABS resin as the main component of the substrate 4. In particular, the added organic component is volatilized during the drilling process and removed from the through hole at the same time as the drilling process. In addition, the substrate 4 can be processed and designed, and the workability, quality, and productivity can be improved.
[0028]
Further, as schematically shown in FIG. 1B, the base material 4 is made of a main component material 4a such as an epoxy resin and a reinforcing material such as a glass fiber 4b and an aramid fiber 4c as subcomponents in terms of workability. In the case of a so-called FRP that is combined, when a blackening treatment such as surface carbonization or a change in color tone or a chemical treatment is applied to a portion such as an aramid fiber 4c that is an organic fiber among the subcomponents, the color tone It has been clarified that the peak power required for the laser beam used for drilling can be suppressed by maintaining the accuracy of roundness ± 10% when the change processing is not performed. The results are shown in Table 1.
[0029]
[Table 1]

[0030]
As is apparent from Table 1, the required peak power of the laser beam can be reduced by changing the color tone with respect to the material of the base material 4, ensuring the hole workability and the necessary peak of the laser beam. The mechanical and electrical performance of the base material can be ensured by the presence of the glass fiber 4b, the aramid fiber 4c, and the like, which are subcomponent materials in the portion that is not perforated, while suppressing the power and improving the processing accuracy.
[0031]
As described above, according to the first embodiment, by changing the color tone with respect to the base material, it is possible to reduce the difference in the absorption rate of the laser light and improve the absorption efficiency, and a wider range of processing conditions. Can be set, and high-quality drilling can be performed. Therefore, quality, workability, productivity, and yield can be improved.
A second embodiment of the present invention will be described below with reference to the drawings.
[0032]
FIG. 3 is a schematic view of a substrate processing apparatus in the production of a circuit board showing a second embodiment of the present invention.
[0033]
As shown in FIG. 3, a stage 5 is placed in an ozone chamber 10, and a substrate 4 that is not impregnated with a resin material as a main component is held therein. An ozone supply duct 7 extending from the ozone generator 6 is connected to various places on the ceiling of the ozone chamber 10, and an exhaust duct 11 having a vacuum pump 9 is connected to the lower portion of the side wall of the ozone chamber 10. Further, an ultraviolet irradiation unit 8 is provided between each connection part of the ozone supply duct 7 on the ceiling part of the ozone chamber 10.
[0034]
In this embodiment, the processing apparatus as described above is used in the previous stage to manufacture the circuit board. Specifically, the base material 4 not impregnated with the resin is first placed on the stage 5. In this case, the base material 4 is not impregnated with the resin as the main component, and is therefore composed of the subcomponent as a reinforcing material, and processing with laser light requires more energy than the resin impregnated as the main component. To do.
[0035]
Next, while the air in the ozone chamber 10 is removed by the vacuum pump 9, ozone supplied from the ozone generator 6 is supplied into the ozone chamber 10 through the ozone supply duct 7 and sprayed onto the substrate 4.
[0036]
Depending on the type of the substrate 4, heat is applied from a heat source set inside the stage 5 and held for a predetermined time. In addition, the process is terminated by irradiating ultraviolet rays from the ultraviolet irradiation unit 8 instead of ozone and holding for a predetermined time.
[0037]
Table 2 shows the roundness, the cross-sectional shape and the occupation ratio of the fiber component on the hole wall surface when hole processing is performed after processing for a predetermined time.
[0038]
[Table 2]

[0039]
As is clear from Table 2, the effect of ultraviolet rays or ozone is confirmed. This seems to be due to the improved mechanical processability of the subcomponents of the substrate 4. The same effect was confirmed when the aramid fibers 4c, which are subcomponents combined with the material of the base material 4, were subjected to ultraviolet irradiation treatment or ozone treatment. However, the effect was not confirmed in the case of the glass fiber generally used.
[0040]
As described above, according to the second embodiment, the base material 4 is exposed to an ultraviolet or ozone atmosphere to improve the base material's hole workability, enabling high-quality hole processing. Quality and workability , Productivity and yield can be improved.
[0041]
In this embodiment, either the ultraviolet irradiation process or the ozone process is employed, but both processes may be performed depending on circumstances.
[0042]
FIG. 4 is a schematic diagram of a paste filling process showing a third embodiment of the present invention.
[0043]
As shown in FIG. 4, the paste 22 is pressed and filled into the through-hole 4 d of the base material 4 held by the stage 5 by the filling head 21.
[0044]
The filling head 21 can move in the vertical direction and the filling operation direction indicated by the arrow A. Normally, when the filling head 21 moves on the base material 4, the paste 22 existing in the vicinity of the contact point between the filling head 21 and the base material 4 has a small flowable basin and a small pressure gradient around it. It is very difficult to flow by simply lowering the viscosity.
[0045]
Although the fluidity is improved by raising the temperature of the paste 22 itself, the life of the paste 22 is reduced especially when a paste 22 such as a thermosetting type is used. The portion that ensures the fluidity necessary for filling the paste 22 is sufficient for the paste 22 to be close to the through-hole 4d provided in the substrate 4, and the paste 22 is filled in the through-hole 4d. The required pressure is given by the fluid pressure generated by the rolling indicated by the arrow B of the filling head 21 and the paste 22 itself (eg Deriemer: “INk Hydrodynamics of Screen Printing”. Proceedings ISHM Symposium 1985). The rolling of the paste 22 is formed by rising upward from the printing surface of the base material 4 along the paste pressing surface 21a of the filling head 21, so that a predetermined temperature gradient is provided to the paste pressing surface 21a of the filling head 22. Thus, the temperature is high on the side of the paste pressing surface 21a in contact with the printing surface, and the temperature is lowered as the distance from the printing surface decreases. The fluid in the contact portion with the printing surface of the paste pressing surface 21a while improving the fluidity and suppressing the fluidity by lowering the temperature on the printing surface of the base material 4 on the paste pressing surface 21a and the side away from the filling head 21. Since the pressure is increased, the paste 22 can be stably filled with a predetermined amount and also suppresses the emission of volatile components at the low temperature portion. Since easy to maintain the entire paste 22 to a predetermined viscosity Te can be improved continuous printing property.
[0046]
Table 3 shows the paste filling depth and the temperature difference in the filling head 21 under general filling conditions.
[0047]
[Table 3]

[0048]
As is apparent from Table 3, it can be seen that an improvement in filling power is obtained. In this embodiment, the upper and lower two heaters built in the filling head 21 are heated so that the portion contacting the printing surface of the paste 22 is heated, and the portion where the printing surface of the paste 22 and the filling head 21 are separated from each other has a low temperature. This is achieved by setting a temperature gradient according to 23 and 24. In addition, it is generally known that when the paste itself contains a volatile component, the viscosity increases due to the loss of the volatile component due to an increase in temperature. It is clear that the printing surface of the paste 22 and the portion exposed to the outside air away from the filling head 21 are at a low temperature, thereby suppressing the curing reaction due to the diffusion of volatile components of the paste 22 and improving the continuous printability. Things will be possible. In the present embodiment, the direct printing method without using a mask was performed, but the same applies even if a mask is present on the substrate 4.
[0049]
The temperature gradient as described above can be achieved by providing only the heater 23 for heating the paste 22, or an appropriate number of heaters may be incorporated between the heaters 23 and 24. If the number of heaters is large, the temperature gradient can be more finely set forcibly. Also, one continuous heater may be built in while gradually reducing the capacity from the position of the heater 23 to the position of the heater 24.
[0050]
Further, in this embodiment, the volumes 23a and 24a are provided in the energization circuits of the heaters 23 and 24 so that the amount of heat generated by the heaters 23 and 24 can be adjusted to set various temperature gradients as described above.
[0051]
Thereby, the circuit board of various conditions can be manufactured with high quality corresponding to the wide range of conditions of the paste 22 and the filling thereof.
[0052]
FIG. 5 and FIG. 6 are schematic views of an apparatus used for a filling process in the manufacture of a circuit board according to a fourth embodiment of the present invention.
[0053]
As shown schematically in FIG. 5, the filling head 21 for filling the base material 4 on the stage 5 with the paste 22 is arranged in the filling direction by, for example, a guide 25 and a horizontal slider 26 guided by the guide 25. It is moved and moved up and down by a guide 27 on the left / right slider 26 and a vertical slider 28 guided by the guide 27. Further, the filling head 21 is pivotally supported on the vertical slider 28 by a shaft 29 so that the contact side with the substrate 4 becomes a free end, and the contact angle θ with the substrate 4 becomes variable. Yes.
[0054]
The filling head 21 is rotated around the shaft 29 by the actuator A1 connected to the shaft 29, moved in the vertical direction by the actuator A2 connected to the vertical slider 28, and moved in the horizontal direction by the actuator A3 connected to the horizontal slider 26. Moved.
[0055]
In the case of the conventional printing method, filling is performed at a fixed angle regardless of the supply amount of the paste 22, but if the amount of the paste 22 decreases, the fluid pressure generated in the paste 22 also decreases and the filling force increases. descend. This relationship has been reported by DEriemar as follows ("INk Hydrodynamics of Screen Printing". Proceedings ISHM Symposium 1985).
[0056]
[Expression 1]

[0057]
Here, p is the pressure generated in the paste, μ is the flow rate of the paste, v is the moving speed of the filling head, V is the volume of the paste, θ is the contact angle between the filling head and the substrate, and k is a proportional constant. is there.
[0058]
This pressure difference becomes the pressure difference necessary to fill the paste 22 with respect to the through-hole provided in the base material 4, and the paste for the through-hole is substituted into the Hagen-Poiseuille equation well known in engineering. 22 filling states can be known. Therefore, in order to make the filling state constant, it is important to keep p constant during the printing process.
[0059]
In general, even if the filling operation is continued, it is possible to cope with a change in the viscosity and composition of the paste 22 itself, although sufficient paste is introduced so that the reduction amount of the paste volume can be ignored.
[0060]
However, in the method of this embodiment, the speed of the filling head 21 can be reduced by grasping the amount of the paste 22 that decreases in one stroke.
[0061]
[Expression 2]

[0062]
It is possible to cope with fluctuations in the amount of paste by increasing the amount of the paste 22 and to reduce the amount of paste 22 charged once. Table 4 shows the variation in filling force after printing 100 sheets according to the conventional method and the method of this embodiment depending on the initial paste input amount in terms of the variation rate of the filling depth.
[0063]
[Table 4]

[0064]
As apparent from Table 4, the effect of speed control can be confirmed. With the above method, the process yield can be improved and the continuous productivity can be improved. In this example, the speed was controlled, but the angle was
[0065]
[Equation 3]

[0066]
If Δθ satisfying the above is obtained and the angle is decreased by Δθ, the same operation is performed.
[0067]
FIG. 6 shows an example of a control circuit for such control. The actuators A1 to A3 are driven and controlled by a microcomputer 31, and various control conditions including the speed change condition can be input by the operation panel 32.
[0068]
Further, feedback control is performed by an input from a sensor for detecting each of the filling head 21 so that the angle, speed, and height of the filling head 21 are as set.
[0069]
In this embodiment, the filling head 21 can be rotated around the axis 29 to automatically change the contact angle θ with the printing surface, and the filling rate can be improved by reducing this θ. Can respond to changes in quantity. However, if the contact angle θ of the filling head 21 in which the contact side with the printing surface is the free end is changed, the free end height changes, and this is corrected and controlled to maintain a predetermined height. When applied to the filling head 21 supported on the contact side with the printing surface of the fifth embodiment shown in FIG. 7, such correction is unnecessary.
[0070]
It is also possible to respond to the change in the paste amount by changing both the moving speed of the filling head 21 and the contact angle θ.
[0071]
FIG. 7 is a schematic view of an apparatus used for a filling process in manufacturing a circuit board according to a fifth embodiment of the present invention.
[0072]
As shown in FIG. 7, the filling head 21 of this embodiment supports a side C of the paste pressing surface 21a that contacts the printing surface of the substrate 4 on the stage 5 with a holder 41, and is a side D away from the printing surface. Is characterized by a free end. More specifically, the present embodiment can also be applied to a flat squeegee type. However, this type is a blade type with a triangular cross section obtained by slightly deforming this type, and the printing surface from the contact side C with the printing surface of the paste pressing surface 21a. The thickness is gradually reduced toward the side D away from the head.
[0073]
In the conventional flat squeegee type filling head support structure, when the printing head 21 is moved downward and printing pressure is applied between the base 4 and the base 4, the side away from the printing surface of the paste pressing surface 21 a Since D is supported, the printing pressure by the hodder is applied in the vicinity of this point D, and the side C in contact with the printing surface becomes a free end and is easily bent and crushed. Thus, the pressure on the C side, which is important for filling the paste 22 in the through hole 4d of the base material 4, is weakened, and stable filling cannot be expected.
[0074]
In addition, the contact angle θ is smaller than the initial setting, and the contact angle and the amount of collapse of the contact portion are different depending on the material of the filling head and the structure of the portion to which the printing pressure is applied.
[0075]
Further, if the crushing amount at the front end of the filling head is not kept to the minimum necessary to follow the unevenness of the printing surface of the base material, a phenomenon occurs in which the paste filled in the through holes provided in the base material is scraped off.
[0076]
Also, in the corner squeegee type, since the four corners are rounded from the beginning, the scraping property of the surface is extremely bad, and it is necessary to secure the amount of crushing of the tip by applying more printing pressure than necessary. The quantity of scraping the filled paste from the hole was unstable.
[0077]
On the other hand, in the present embodiment, the filling head 21 that presses and fills the paste 22 into the through-hole 4d in which the hole is formed in the substrate 4 is on the contact side C of the paste pressing surface 21a with the printing surface of the substrate 4. The side C, which is supported by the holder 41 and is deformed with the side D away from the printing surface as a free end, ensures the necessary flexibility, while the side C in contact with the printing surface suppresses escape against the pressing of the paste 22. However, the necessary minimum elasticity corresponding to the unevenness of the printing surface of the base material 4 is ensured as a material called selection of an elastic material, and even if the paste 22 increases in viscosity over time or is reduced due to consumption, it is special. The paste can be stably filled in a predetermined amount without the need for any control, and the continuous printability can be improved.
[0078]
As described above, in this embodiment, the printing pressure is directly applied to the point C that contacts the base material 4 of the filling head 21, and the decrease in the contact angle due to the bending of the filling head 21 can be eliminated. When this state was observed, there was no bending of the contact portion between the filling head 21 and the substrate 4. Therefore, by using the above equipment, it is possible to keep the condition setting of the part having the paste filling function constant during manufacturing, it is possible to produce a product of a certain quality, and improve the manufacturing yield. Is possible.
[0079]
FIG. 8 is a schematic view of a filling apparatus showing a pretreatment state of a paste filling step in manufacturing a circuit board according to a sixth embodiment of the present invention.
[0080]
In this embodiment, as shown in FIG. 8, the pretreatment material 51 is applied to the printing surface of the substrate 4 on the stage 5 before the paste is pressed and filled by the filling head 21. For this purpose, a filling head 21 and a pretreatment head 52 are provided, and in the step of filling the through hole 4d in the base material 4 with the paste by the filling head 21, before the operation of filling the paste, The same non-volatile organic component as that contained in the paste is applied to the printing surface of the substrate 4 as the pretreatment material 51 by the pretreatment head 52.
[0081]
When the pretreatment head 52 moves while contacting the substrate 4 to apply the pretreatment material 51 to the surface of the substrate 4, the pretreatment material 51 is sufficiently removed from the printing surface of the substrate 4 by the pretreatment head 52. Although scraped off, the amount adsorbed on the surface of the substrate 4 remains on the substrate 4. The adsorption mechanism generated at this time is also generated on the substrate 4 during the filling of the paste, so that the viscosity of the paste increases. FIG. 9 shows the result of the increase in the viscosity of the paste when the non-volatile organic component in the paste is applied as a pretreatment material 51 on the base material 4 in advance. As is clear from FIG. 9, the effect of application of the non-volatile organic component in the paste can be seen.
[0082]
This may be attributed to the fact that the scraping of the pretreatment material 51 by the substrate 4 and the pretreatment head 52 is similar to the scraping of the paste. If the scraper is in a poor state, an organic component is left on the surface of the base material 4, and the viscosity of the paste itself may be lowered, so care must be taken. From the above results, it is possible to suppress the increase in the viscosity of the paste and improve the continuous printability by applying the non-volatile organic component in the paste onto the substrate before the paste filling step. In this embodiment, a urethane rubber squeegee is used as the coating head. However, the same effect can be obtained even if an organic component is adsorbed on the substrate by an operation such as vapor deposition.
[0083]
FIG. 10 is an explanatory diagram of the paste filling state according to the seventh embodiment of the present invention.
[0084]
In this example, as shown in FIG. 10, in the process of pressing and filling the paste into the hole-processed through hole of the base material having compressibility, the paste 22 is filled up to 5 to 20% of the through hole. Fill so that the unfilled portion 61 remains.
[0085]
Thereby, the paste 22 when the base material is compressed can be allowed to escape to the unfilled portion 61, and peeling of the conductive portion between layers caused by the repulsive force of the paste 22 having nowhere to go can be prevented.
[0086]
More specifically, after the base material 4 fills the through holes 4d with the paste 22, a double-sided plate is formed by heating and pressing both sides of the copper foil, and then the copper foil is etched into a desired pattern. The circuit board is formed. In these series of steps, when the base material 4 is heated and pressed between the copper foils, the base material 4 is compressed more than the allowable amount of the paste 22 filled in the through holes 4d. After curing, a force is generated in a direction in which the copper foil is peeled off from the base material 4, and the reliability of conduction between layers is significantly reduced. This occurs when the paste 22 filled in the through-hole 4d is compressed, because there is no escape path in the portion exceeding the allowable amount, and when the substrate 4 is porous, the substrate 22 4 will ooze out. If the paste 22 oozes into the base material 4, the reliability of the circuit board is reduced, such as a decrease in insulation resistance, and must be avoided.
[0087]
By forming a space in which the paste 22 can move in the through-hole 4d formed in the base material 4 by the unfilled portion 61, and putting the paste compressed more than the allowable amount in the through-hole 4d The problem can be solved. Table 5 shows good and poor conduction resistance when the through hole 4d has an average diameter and the amount of depression by the unfilled portion 61 with respect to the average diameter is changed.
[0088]
[Table 5]

[0089]
As is clear from Table 5, the reliability of the conduction resistance could be obtained by making an unfilled portion of 5 to 20% with respect to the average pore diameter. From the above results, the conductive part is peeled off between layers caused by the repulsive force of the compressed base material by pressing and filling the paste so that the depth of the recess is 5 to 20% of the average diameter of the through holes. This can prevent a decrease in reliability.
[0090]
【The invention's effect】
According to the method for producing a circuit board of the present invention, mechanical hole workability is improved afterwards by performing ultraviolet irradiation or exposure to ozone on a substance having poor hole workability by laser light. Hole quality, yield, and productivity after drilling can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of a hole drilling apparatus in a first embodiment of the present invention.
FIG. 2 is a graph showing a relationship between laser wavelength and reflectance with respect to color tone;
FIG. 3 is a schematic view of a circuit board manufacturing apparatus according to a second embodiment of the present invention.
FIG. 4 is a schematic diagram showing a portion having a paste filling function of a circuit board manufacturing apparatus according to a third embodiment of the present invention.
FIG. 5 is a schematic diagram showing a portion having a filling function of a circuit board manufacturing apparatus according to a fourth embodiment of the present invention.
6 is a block diagram of a control circuit for the filling portion of the apparatus of FIG.
FIG. 7 is a schematic view showing a portion having a filling function of a circuit board manufacturing apparatus according to a fifth embodiment of the present invention.
FIG. 8 is a schematic view showing a portion having a function of applying a nonvolatile organic component in a paste of a circuit board manufacturing apparatus according to a sixth embodiment of the present invention.
FIG. 9 is a graph showing the result of the increase in viscosity of the paste when the nonvolatile organic component in the paste is applied on a substrate and when it is not applied in the fifth embodiment of the present invention.
FIG. 10 is a schematic diagram showing a filling state after filling a paste by a circuit board manufacturing method according to a seventh embodiment of the present invention.
FIG. 11 is a schematic diagram of a first conventional printing apparatus.
FIG. 12 is a schematic diagram of a conventional second printing apparatus.
[Explanation of symbols]
1 Laser light source
4 Base material
4a Main component
4b glass fiber
4c Aramid fiber
4d through hole
6 Ozone generator
7 Ozone supply duct
8 UV irradiation part

Claims (2)

  In a circuit board manufacturing method in which a hole is machined using a laser on a base material, an organic substance having poor mechanical workability other than the main component constituting the base material is subjected to ultraviolet irradiation or exposure to an ozone atmosphere. A method of manufacturing a circuit board, wherein a laser hole is machined on a material.   In the method of manufacturing a circuit board in which holes are drilled using a laser on a base material, organic substances with poor mechanical workability other than the main components forming the base material are irradiated with ultraviolet rays and exposed to an ozone atmosphere. A method of manufacturing a circuit board, wherein laser drilling is performed on a base material made.

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