JP3989974B2

JP3989974B2 - Multilayer printed wiring board and manufacturing method thereof

Info

Publication number: JP3989974B2
Application number: JP365295A
Authority: JP
Inventors: 一安田中; 洋大平
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1995-01-13
Filing date: 1995-01-13
Publication date: 2007-10-10
Anticipated expiration: 2022-10-10
Also published as: JPH08195561A

Description

【０００１】
【産業上の利用分野】
本発明は、多層印刷配線板及びその製造方法に関する。
【０００２】
【従来の技術】
周知の通り、電子機器には多くの半導体装置や電子部品等が印刷配線板に搭載・固定されて組み込まれている。こうした印刷配線板は、電子機器の小形化や高機能化などの点から高集積・高機能化した半導体装置を高密度で実装するために多層化した構成のものが用いられている。
【０００３】
以下、多層化した構成の印刷配線板、すなわち多層印刷配線板の従来の技術を図１１乃至図１５を参照して説明する。図１１乃至図１５は各製造工程における断面図であり、製造工程に従って順に説明する。
【０００４】
先ず、図１１に示す第１の工程において、第１の銅箔１上に合成樹脂と銀粉とからなる導電ペーストによって略円錐形の導電性バンプ２を所定位置に形成する。そして導電性バンプ２上に配線板の基体となるガラス織布等で強化した第１の合成樹脂シート３と第２の銅箔４を重ね合わせる。
【０００５】
次に図１２に示す第２の工程において、前工程で重ね合わせたものを加熱加圧して一体化し、第１の銅箔１と第１の合成樹脂シート３、第２の銅箔４とを積層し三層構造の基板５を形成する。この時の加熱加圧によって導電性バンプ２が第１の合成樹脂シート３を貫通して第２の銅箔４に固着し、第１の銅箔１と第２の銅箔４とを接続する。
【０００６】
続いて図１３に示す第３の工程において、三層構造の基板５の第１の銅箔１と第２の銅箔４とを所定のパターン形状となるようにエッチングする。
【０００７】
次に図１４に示す第４の工程において、第３の銅箔６及び第４の銅箔７のそれぞれの所定位置に合成樹脂と銀粉とからなる導電ペーストによって略円錐形の導電性バンプ８，９を形成する。そして各導電性バンプ８，９が、基板５のエッチングされた第１の銅箔１及び第２の銅箔４の所定の部位と、同じく配線板の基体となるガラス織布等で強化した第２の合成樹脂シート１０及び第３の合成樹脂シート１１を間に介在させながら対向するように配置し、第３の銅箔６と基板５及び第４の銅箔７を重ね合わせる。
【０００８】
次に図１５に示す第５の工程において、前工程で重ね合わせたものを加熱加圧して第３の銅箔６と第２の合成樹脂シート１０及び三層構造の基板５、さらに第３の合成樹脂シート１１、第４の銅箔７とを一体化する。この時の加熱加圧によって導電性バンプ８，９が第２の合成樹脂シート１０及び第３の合成樹脂シート１１をそれぞれ貫通して第１の銅箔１と第２の銅箔４に固着し、第１の銅箔１と第３の銅箔６、また第２の銅箔４と第４の銅箔７とを接続する。
【０００９】
続いて表裏両面の第３の銅箔６と第４の銅箔７とを所定のパターン形状となるようにエッチングし、両外表面にそれぞれパッド１２，１３を備えるようにする。これにより第１の銅箔１と第２の銅箔４を内層導体とし、これらと表層のパッド１２，１３とを導電性バンプ２，８，９で固着し接続した多層印刷配線板１４が形成される。
【００１０】
しかしながら、上記の各工程を経て製造された多層印刷配線板１４に、そのパッド１２，１３に電子部品等を半田付けによって実装した場合、パッド１２，１３の固着強度が弱く、パッド１２，１３が剥がれて電子部品等が脱落してしまう虞があった。このため、パッド１２，１３の固着強度を強くし電子部品等の脱落を防止するようパッド１２，１３の寸法を大きくする必要があった。また逆にパッド１２，１３の寸法を大きくすることでパッド１２，１３間の距離や配線間の距離も広がってしまい、実装密度を上げることが困難な状況にあった。
【００１１】
【発明が解決しようとする課題】
上記のように多層印刷配線板の表面に設けられたパッドの固着強度が弱く、実装した電子部品等がパッドと共に脱落してしまう虞があり、またこれを防止しようとパッド寸法を大きくすると配線間の距離等が小さくならず、実装密度を高くすることができない。このような状況に鑑みて本発明はなされたもので、その目的とするところは実装した電子部品等の脱落を防止することができると共に実装密度を高くすることができるようにした多層印刷配線板及びその製造方法を提供することにある。
【００１２】
【課題を解決するための手段】
本発明の多層印刷配線板及びその製造方法は、合成樹脂製の錐台状の導電性バンプを貫通するように備えた複数の基体を積層し、内設した内層金属箔間及び内層金属箔と表層に設けたパッドとを前記導電性バンプでそれぞれ接続してなる多層印刷配線板において、前記内層金属箔と表層のパッドを接続する導電性バンプが、小面積側の底面を前記パッドに固着し、大面積側の底面を前記内層金属箔に固着しており、かつ積層した前記基体の最上部及び最下部の基体が、それぞれ該基体の上下面上に前記内層金属箔と表層のパッドとを設けていることを特徴とするものであり、
さらに、基体の主部がエポキシ樹脂等の合成樹脂でなると共に、導電性バンプが銀粉末とエポキシ樹脂等の合成樹脂とからなるものであることを特徴とするものであり、
さらに、導電性バンプが円錐台状に形成されていることを特徴とするものであり、
また、第１の銅箔面の片方面に導電性ペーストによる印刷によって略円錐形の第１の導電性バンプを形成する第１の工程と、前記第１の銅箔の前記第１の導電性バンプ側に第１の合成樹脂シートと第２の銅箔を重ね合わせた後に加熱加圧して一体化し、前記第１の導電性バンプを前記第１の合成樹脂シートを貫通させ、該第１の導電性バンプの先端部を前記第２の銅箔面に固着する第２の工程と、前記第１及び第２の銅箔の少なくとも内設される前記第１の銅箔を所定パターンとなるようエッチングして第１の基板を形成する第３の工程と、前記第１の基板の所定パターンとした前記第１の銅箔の他方面に導電性ペーストによる印刷によって略円錐形の第２の導電性バンプを形成する第４の工程と、第３の銅箔面の片方面に導電性ペーストによる印刷によって略円錐形の第３の導電性バンプを形成する第５の工程と、前記第３の銅箔の前記第３の導電性バンプ側に第２の合成樹脂シートと第４の銅箔を重ね合わせた後に加熱加圧して一体化し、前記第３の導電性バンプを前記第２の合成樹脂シートを貫通させ該第３の導電性バンプの先端部を前記第４の銅箔面に固着する第６の工程と、前記第３及び第４の銅箔の少なくとも内設される前記第３の銅箔を所定パターンとなるようエッチングして第２の基板を形成する第７の工程と、前記第１の基板の第２の導電性バンプ側に第３の合成樹脂シートと前記第２の基板を重ね合わせた後に加熱加圧して一体化し、前記第２の導電性バンプを前記第３の合成樹脂シートを貫通させ該第２の導電性バンプの先端部を前記第２の基板の第３の銅箔面に固着する第８の工程とを備えて多層化することを特徴とする製造方法であり、
また、第１表面に部分的に第１の金属箔が配置され、第２表面に第２の金属箔が配置された第１の基体と、前記第１の基体を貫通して前記第１の金属箔と前記第２の金属箔とを小面積面を該第２の金属箔側として接続する錐台状の第１の導電性バンプと、第１表面に部分的に第３の金属箔が配置され、第２表面に第４の金属箔が配置された第２の基体と、前記第２の基体を貫通して前記第３の金属箔と前記第４の金属箔とを小面積面を該第４の金属箔側として接続する錐台状の第２の導電性バンプと、前記第１の基体と前記第２の基体の間に、前記第１の金属箔と前記第３の金属箔とを第１、第２表面にそれぞれ埋め込むようにして密着して設けられた第３の基体と、前記第３の基体を貫通して前記第１の金属箔と前記第３の金属箔とを接続する第３の導電性バンプとを備えていることを特徴とするものである。
【００１３】
【作用】
上記のように構成された多層印刷配線板及びその製造方法は、合成樹脂製の錐台状の導電性バンプの小面積側の底面を表層のパッドに固着し、大面積側の底面を複数の基体を積層し内設した内層導体に固着するようしたので、表層のパッドは固着力の弱い導電性バンプとの固着面積を少なくし、固着力の強い基体との固着面積を多くすることができ、これによってパッド全体の固着強度が増加する。その結果、パッドに半田付けによって実装した電子部品等の脱落が防止でき、さらにパッド間あるいは配線間距離を小さくできて電子部品等の実装密度を高くすることができる。
【００１４】
【実施例】
以下、本発明の実施例を図１乃至図１０を参照して説明する。図１乃至図８は第１の実施例の各製造工程における断面図であり、図９及び図１０は第２の実施例の製造工程における断面図である。
【００１５】
先ず、第１の実施例を製造工程に従って順に説明する。
図１に示す第１の工程において、厚さ３５μｍの表裏両面を粗化した第１の銅箔２１の片方面に、エポキシ樹脂と銀粉末とからなる導電ペーストを用いて所定の第１のパターンのスクリーン印刷を行い、これを乾燥させた後、再び導電ペーストを用い同一のパターンのスクリーン印刷・乾燥を５回繰り返す。その後、１８０℃のオーブンで導電ペーストを加熱硬化させ、第１の銅箔２１の片方面の所定位置に高さ０．３ｍｍ、底面径０．３５ｍｍの略円錐形の導電性バンプ２２を形成する。
【００１６】
そして導電性バンプ２２に、未硬化のエポキシ樹脂と強化用のガラス織布あるいはガラス不織布等でなり配線板の基体となる第１の合成樹脂シート２３と厚さ３５μｍの第２の銅箔２４を重ね合わせる。
【００１７】
次に図２に示す第２の工程において、前工程で重ね合わせたものを１００℃に加熱し、合成樹脂シート２３が軟化した状態でプレスを用いて２ＭＰａで重ね合わせ方向に加圧する。さらに、この圧力を保持したままの状態で１７０℃まで昇温し、１時間保持した後に冷却し、第１の銅箔２１と第１の合成樹脂シート２３、第２の銅箔２４とを積層し三層構造の第１の基板２５を形成する。この時の加熱加圧によって導電性バンプ２２が第１の合成樹脂シート２３を貫通し、さらに導電性バンプ２２の先端部が変形して第２の銅箔２４の粗化した片方面に固着し、第１の銅箔２１と第２の銅箔２４とを接続する。
【００１８】
続いて図３に示す第３の工程において、三層構造の第１の基板２５の第１の銅箔２１と第２の銅箔２４の表面にそれぞれエッチングレジスト膜を形成し、さらにこれを所定のパターンとなるようにする。その後、塩化第二鉄溶液を用いて第１の銅箔２１と第２の銅箔２４を所定のパターン形状となるようにエッチングする。
【００１９】
また同様に、図４に示す第４の工程において、厚さ３５μｍの表裏両面を粗化した第３の銅箔２６の片方面に、エポキシ樹脂と銀粉末とからなる導電ペーストを用いて例えば第１の工程における第１のパターンと裏返しの関係となる所定の第２のパターンのスクリーン印刷を行い、これを乾燥させた後、再び導電ペーストを用い同一のパターンのスクリーン印刷・乾燥を５回繰り返す。その後、１８０℃のオーブンで導電ペーストを加熱硬化させ、第３の銅箔２６の片方面の所定位置に高さ０．３ｍｍ、底面径０．３５ｍｍの略円錐形の導電性バンプ２７を形成する。
【００２０】
そして導電性バンプ２７の先端側に未硬化のエポキシ樹脂と強化用のガラス織布あるいはガラス不織布等でなり同じく配線板の基体となる第２の合成樹脂シート２８と厚さ３５μｍの第４の銅箔２９を重ね合わせる。
【００２１】
次に図５に示す第５の工程において、前工程で重ね合わせたものを１００℃に加熱し、第２の合成樹脂シート２８が軟化した状態でプレスを用いて２ＭＰａで重ね合わせ方向に加圧する。さらに、この圧力を保持したままの状態で１７０℃まで昇温し、１時間保持した後に冷却し、第３の銅箔２６と第２の合成樹脂シート２８、第４の銅箔２９とを積層し三層構造の第２の基板３０を形成する。この時の加熱加圧によって導電性バンプ２７が第２の合成樹脂シート２８を貫通し、さらに導電性バンプ２７の先端部が変形して第４の銅箔２９の粗化した片方面に固着し、第３の銅箔２６と第４の銅箔２９とを接続する。
【００２２】
続いて図６に示す第６の工程において、三層構造の第２の基板３０の第３の銅箔２６と第４の銅箔２９の表面にそれぞれエッチングレジスト膜を形成し、さらにこれを所定のパターンとなるようにする。その後、塩化第二鉄溶液を用いて第３の銅箔２６と第４の銅箔２９を所定のパターン形状となるようにエッチングする。
【００２３】
次に図７に示す第７の工程において、第２の基板３０に形成されている第３の銅箔２６の他方面に、エポキシ樹脂と銀粉末とからなる導電ペーストを用いて例えば第１の工程におけるのと同様の第１のパターンのスクリーン印刷を行い、これを乾燥させた後、再び導電ペーストを用い同一のパターンのスクリーン印刷・乾燥を５回繰り返す。その後、１８０℃のオーブンで導電ペーストを加熱硬化させ、第３の銅箔２６の他方面の所定位置に高さ０．３ｍｍ、底面径０．３５ｍｍの略円錐形の導電性バンプ３１を形成する。
【００２４】
そして導電性バンプ３１の先端側に、未硬化のエポキシ樹脂と強化用のガラス織布あるいはガラス不織布等でなり同じく配線板の基体となる第３の合成樹脂シート３２を間に介在させ、第１の銅箔２１の他方面が対向するように第１の基板２５を配置して重ね合わせる。
【００２５】
次に図８に示す第８の工程において、前工程で重ね合わせたものを１００℃に加熱し、第３の合成樹脂シート３２が軟化した状態でプレスを用いて２ＭＰａで重ね合わせ方向に加圧する。さらに、この圧力を保持したままの状態で１７０℃まで昇温し、１時間保持した後に冷却し、第１の基板２５と第３の合成樹脂シート３２、第２の基板３０とを積層して多層印刷配線板３３とする。この時の加熱加圧によって導電性バンプ３１が第３の合成樹脂シート３２を貫通し、さらに導電性バンプ３１の先端部が変形して第１の銅箔２１の粗化した他方面に固着し、第１の銅箔２１と第３の銅箔２６とを接続する。
【００２６】
こうして形成された多層印刷配線板３３では、外表面に露出した第２の銅箔２４と第４の銅箔２９がそれぞれ半導体装置や電子部品を実装するためのパッドＰを構成する。そして表層のパッドＰと内層導体となっている第１の銅箔２１及び第３の銅箔２６とは、それぞれに固着した導電性バンプ２２，２７，３１を介して接続される。
【００２７】
また、第２の銅箔２４と第４の銅箔２９の構成するパッドＰは、円錐台状となった導電性バンプ２２，２７の小面積側の底面に固着していると共に、パッドＰの残りの面は第１の合成樹脂シート２３及び第２の合成樹脂シート２８に固着した状態になっている。
【００２８】
次に、上記のように構成された多層印刷配線板３３のパッドＰの固着強度を測定し、従来のものと比較した。比較は、表層のパッドを１ｍｍ角に形成し、これに直径０．８ｍｍの錫めっき銅線を半田付けし、この銅線をパッドＰに対し垂直方向に引き剥がすように引っ張りパッドが剥がれる力を測定した。
【００２９】
この結果、本実施例の多層印刷配線板３３のパッドＰは、１ｋｇ／ｍｍ²までの力では剥がれず、１ｋｇ／ｍｍ²以上の固着強度を示した。これに対し、従来技術による多層印刷配線板のパッドでは固着強度が、０．５ｋｇ／ｍｍ²であった。
【００３０】
これは、本実施例の多層印刷配線板３３ではパッドＰとの固着力の弱い導電性バンプ２２，２７に対しては固着面積が小さい小面積側の底面での固着とし、パッドＰとの固着力の強い第１の合成樹脂シート２３及び第２の合成樹脂シート２８に対しては固着面積が大きくなるようにし、パッドＰ全体での固着力が増すように構成したことに基づいているからである。なお、従来技術による多層印刷配線板では導電性バンプのパッドに対する関係が逆となっている。
【００３１】
さらに、多層印刷配線板３３に対して熱サイクル試験や吸水試験等を行ったがそれぞれ十分な耐性を示し、実用的に何等問題ないことが確認された。
【００３２】
そして、多層印刷配線板３３にそのパッドＰに電子部品等を半田付けし実装しても、パッドＰの固着強度が強いためにパッドＰが剥がれ電子部品等が脱落してしまう虞も少なくなり、パッドＰを大きくする必要もない。また、パッドＰの固着強度が同じであればその大きさを小さくすることができ、パッドＰ間の距離や配線間の距離も狭くすることができて実装密度を高くすることが可能となる。
【００３３】
尚、上記の第１の実施例では２層の内層導体が内設されているが、１層もしくは３層以上内設されていてもよい。
【００３４】
例えば、１層の内層導体を備えた多層印刷配線板については第２の実施例として図９及び図１０に示すように、先ず図９に示す第１の工程で、上記第１の実施例の第４の工程乃至第６の工程を経て得た第２の基板２８の第３の銅箔２６の表面に、エポキシ樹脂と銀粉末とからなる導電ペーストを用いて所定パターンのスクリーン印刷を行い、これを乾燥させた後、再び導電ペーストを用い同一のパターンのスクリーン印刷・乾燥を５回繰り返す。その後、１８０℃のオーブンで導電ペーストを加熱硬化させ、第３の銅箔２６の面に高さ０．３ｍｍ、底面径０．３５ｍｍの略円錐形の導電性バンプ４１を形成する。
【００３５】
そして導電性バンプ４１の先端側に、未硬化のエポキシ樹脂と強化用のガラス織布あるいはガラス不織布等でなり配線板の基体となる合成樹脂シート４２と厚さ３５μｍの銅箔４３を重ね合わせる。
【００３６】
次に図１０に示す第２の工程において、前工程で重ね合わせたものを１００℃に加熱し、合成樹脂シート４２が軟化した状態でプレスを用いて２ＭＰａで重ね合わせ方向に加圧する。さらに、この圧力を保持したままの状態で１７０℃まで昇温し、１時間保持した後に冷却し、第２の基板２８と合成樹脂シート４２、銅箔４３とを積層して一体化する。この時の加熱加圧によって導電性バンプ４１が合成樹脂シート４２を貫通し、さらに導電性バンプ４１の先端部が変形して銅箔４３の面に固着し、第３の銅箔２６と銅箔４３とを接続する。
【００３７】
そして銅箔４３を所定のパターン形状となるようにエッチングすることで多層印刷配線板４４を得る。なお、外表面に露出した第４の銅箔２９と銅箔４３がそれぞれ半導体装置や電子部品を実装するためのパッドＰを構成し、表層のパッドＰと内層導体となっている第３の銅箔２６とは、それぞれに固着した導電性バンプ２７，４１を介して接続される。
【００３８】
また、第４の銅箔２９と銅箔４３の構成するパッドＰは、円錐台状となった導電性バンプ２７，４１の小面積側の底面に固着していると共に、パッドＰの残りの面は第２の合成樹脂シート２８及び合成樹脂シート４２に固着した状態になっている。
【００３９】
このため、上記のように構成した本実施例の多層印刷配線板４４においても第１の実施例と同様の効果が得られる。
【００４０】
さらに、３層以上の内層導体を備えた多層印刷配線板については、上記第１及び第２の実施例の各工程を適宜組み合わせ実施することによって得ることができる。
【００４１】
また、上記の各実施例の多層印刷配線板３３，４４は両面実装の配線板であるが片面実装の配線板であってもよく、また配線板の基体としての合成樹脂シートについてもガラス織布あるいはガラス不織布等で強化したエポキシ樹脂に限るものではなく、ポリイミド樹脂やフェノール樹脂であってもよい。
【００４２】
【発明の効果】
以上の説明から明らかなように本発明は、錐台状の導電性バンプの小面積側の底面を表層のパッドに固着し、大面積側の底面を複数の基体を積層し内設した内層導体に固着するよう構成したことにより、パッドの固着強度が増加し実装した電子部品等の脱落を防止することができ、さらに電子部品等の実装密度を高くすることができる等の効果を奏する。
【図面の簡単な説明】
【図１】本発明の第１の実施例における第１の工程の断面図である。
【図２】本発明の第１の実施例における第２の工程の断面図である。
【図３】本発明の第１の実施例における第３の工程の断面図である。
【図４】本発明の第１の実施例における第４の工程の断面図である。
【図５】本発明の第１の実施例における第５の工程の断面図である。
【図６】本発明の第１の実施例における第６の工程の断面図である。
【図７】本発明の第１の実施例における第７の工程の断面図である。
【図８】本発明の第１の実施例における第８の工程の断面図である。
【図９】本発明の第２の実施例における第１の工程の断面図である。
【図１０】本発明の第２の実施例における第２の工程の断面図である。
【図１１】従来例における第１の工程の断面図である。
【図１２】従来例における第２の工程の断面図である。
【図１３】従来例における第３の工程の断面図である。
【図１４】従来例における第４の工程の断面図である。
【図１５】従来例における第５の工程の断面図である。
【符号の説明】
２１，２６…銅箔（内層導体）
２２，２７，３１…導電性バンプ
２３，２８，３２…合成樹脂シート（基体）
２４，２９…銅箔
３３…多層印刷配線板
Ｐ…パッド[0001]
[Industrial application fields]
The present invention relates to a multilayer printed wiring board and a method for manufacturing the same.
[0002]
[Prior art]
As is well known, many semiconductor devices, electronic components, and the like are mounted and fixed on a printed wiring board in an electronic device. As such a printed wiring board, a multilayered structure is used in order to mount a highly integrated and highly functional semiconductor device at a high density in terms of downsizing and high functionality of electronic equipment.
[0003]
Hereinafter, a conventional technique of a printed wiring board having a multilayered structure, that is, a multilayer printed wiring board will be described with reference to FIGS. 11 to 15 are cross-sectional views in each manufacturing process, which will be described in order according to the manufacturing process.
[0004]
First, in a first step shown in FIG. 11, a substantially conical conductive bump 2 is formed at a predetermined position on the first copper foil 1 with a conductive paste made of synthetic resin and silver powder. Then, the first synthetic resin sheet 3 reinforced with a glass woven cloth or the like serving as a substrate of the wiring board and the second copper foil 4 are superposed on the conductive bumps 2.
[0005]
Next, in the 2nd process shown in FIG. 12, what was piled up in the previous process is integrated by heating and pressing, and the first copper foil 1, the first synthetic resin sheet 3, and the second copper foil 4 are combined. A substrate 5 having a three-layer structure is formed by stacking. At this time, the conductive bump 2 penetrates the first synthetic resin sheet 3 and is fixed to the second copper foil 4 by heating and pressing at this time, and the first copper foil 1 and the second copper foil 4 are connected. .
[0006]
Subsequently, in the third step shown in FIG. 13, the first copper foil 1 and the second copper foil 4 of the substrate 5 having a three-layer structure are etched so as to have a predetermined pattern shape.
[0007]
Next, in a fourth step shown in FIG. 14, substantially conical conductive bumps 8 are formed at predetermined positions of the third copper foil 6 and the fourth copper foil 7 by a conductive paste made of synthetic resin and silver powder, 9 is formed. The conductive bumps 8 and 9 are reinforced with a predetermined portion of the etched first copper foil 1 and the second copper foil 4 of the substrate 5 and a glass woven cloth or the like that also serves as a substrate of the wiring board. The second synthetic resin sheet 10 and the third synthetic resin sheet 11 are arranged so as to face each other while being interposed therebetween, and the third copper foil 6, the substrate 5, and the fourth copper foil 7 are overlapped.
[0008]
Next, in the fifth step shown in FIG. 15, the superposed one in the previous step is heated and pressed to form the third copper foil 6, the second synthetic resin sheet 10, the three-layer substrate 5, and the third The synthetic resin sheet 11 and the fourth copper foil 7 are integrated. At this time, the conductive bumps 8 and 9 pass through the second synthetic resin sheet 10 and the third synthetic resin sheet 11 and are fixed to the first copper foil 1 and the second copper foil 4 by heating and pressing at this time. The first copper foil 1 and the third copper foil 6, and the second copper foil 4 and the fourth copper foil 7 are connected.
[0009]
Subsequently, the third copper foil 6 and the fourth copper foil 7 on both the front and back surfaces are etched so as to have a predetermined pattern shape, and pads 12 and 13 are provided on both outer surfaces, respectively. As a result, a multilayer printed wiring board 14 is formed in which the first copper foil 1 and the second copper foil 4 are used as inner layer conductors, and the pads 12 and 13 on the surface layer are fixedly connected by the conductive bumps 2, 8 and 9. Is done.
[0010]
However, when an electronic component or the like is mounted on the pads 12 and 13 by soldering on the multilayer printed wiring board 14 manufactured through the above steps, the bonding strength of the pads 12 and 13 is weak, and the pads 12 and 13 There is a risk that the electronic parts and the like may fall off due to peeling. For this reason, it is necessary to increase the dimensions of the pads 12 and 13 so as to increase the fixing strength of the pads 12 and 13 and prevent the electronic components from falling off. Conversely, increasing the dimensions of the pads 12 and 13 increases the distance between the pads 12 and 13 and the distance between the wirings, making it difficult to increase the mounting density.
[0011]
[Problems to be solved by the invention]
As mentioned above, the adhesive strength of the pads provided on the surface of the multilayer printed wiring board is weak, and there is a risk that the mounted electronic components may fall off with the pads. Therefore, the mounting density cannot be increased. SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and the object of the present invention is to provide a multilayer printed wiring board that can prevent the mounted electronic components from falling off and can increase the mounting density. And a manufacturing method thereof.
[0012]
[Means for Solving the Problems]
The multilayer printed wiring board and the manufacturing method thereof according to the present invention are formed by laminating a plurality of bases provided so as to penetrate through a synthetic resin frustum-like conductive bump, and between inner metal foils and inner metal foils provided therein. in the multilayer printed wiring board formed by connecting each pad provided on a surface layer with said conductive bumps, conductive bumps which connect the inner metal foil and the surface layer of the pad, and secured to the bottom surface of the small area side on the pad , and fixing a bottom surface of the large-area side to the inner metal foil and the top and bottom of the substrate laminated with said substrate, said inner metal foil on the upper and lower surfaces of the respective base body and a surface layer pad It is characterized by providing,
Furthermore, the main part of the substrate is made of a synthetic resin such as an epoxy resin, and the conductive bumps are made of silver powder and a synthetic resin such as an epoxy resin,
Further, the conductive bump is formed in a truncated cone shape,
In addition, a first step of forming a first conductive bump having a substantially conical shape by printing with a conductive paste on one surface of the first copper foil surface, and the first conductivity of the first copper foil The first synthetic resin sheet and the second copper foil are overlapped on the bump side and then integrated by heating and pressing, and the first conductive bump is penetrated through the first synthetic resin sheet. A second step of fixing the front end of the conductive bump to the second copper foil surface, and the first copper foil provided at least in the first and second copper foils to have a predetermined pattern A third step of etching to form a first substrate; and a second conductive having a substantially conical shape by printing with a conductive paste on the other surface of the first copper foil having a predetermined pattern on the first substrate. A conductive paste on one side of the third copper foil surface and the fourth step of forming the conductive bump A fifth step of forming a substantially conical third conductive bump by printing, a second synthetic resin sheet and a fourth copper foil on the third conductive bump side of the third copper foil Are stacked together by heating and pressurizing, and the third conductive bump is made to penetrate the second synthetic resin sheet, and the tip of the third conductive bump is fixed to the fourth copper foil surface. And a seventh step of forming a second substrate by etching at least the third copper foil provided in the third and fourth copper foils into a predetermined pattern, The third synthetic resin sheet and the second substrate are overlapped on the second conductive bump side of the first substrate and then integrated by heating and pressing, and the second conductive bump is integrated with the third conductive bump. A second end of the second conductive bump is inserted through the synthetic resin sheet and the third copper of the second substrate is inserted. A manufacturing method characterized by a multilayer structure and a eighth step of fixing the surface,
In addition, the first metal foil is partially disposed on the first surface and the second metal foil is disposed on the second surface, and the first substrate penetrates the first substrate. A frustum-shaped first conductive bump connecting the metal foil and the second metal foil with the small area surface as the second metal foil side, and a third metal foil partially on the first surface A second base having a fourth metal foil disposed on the second surface, and passing through the second base, the third metal foil and the fourth metal foil having a small area surface. A frustum-like second conductive bump connected as the fourth metal foil side, and the first metal foil and the third metal foil between the first base and the second base. Are embedded in close contact with the first and second surfaces, respectively, and the first metal foil and the third metal foil are inserted through the third base. Connection And it is characterized in that it comprises a third conductive bumps that.
[0013]
[Action]
In the multilayer printed wiring board configured as described above and the manufacturing method thereof, the bottom surface on the small area side of the frustum-shaped conductive bump made of synthetic resin is fixed to the surface pad, and the bottom surface on the large area side is attached to a plurality of bottom surfaces. Since the base is laminated and fixed to the inner conductor, the surface pad can reduce the fixing area with the conductive bump with weak fixing force and increase the fixing area with the strong fixing base. This increases the adhesion strength of the entire pad. As a result, the electronic components mounted on the pads by soldering can be prevented from falling off, and the distance between the pads or the wiring can be reduced to increase the mounting density of the electronic components.
[0014]
【Example】
Embodiments of the present invention will be described below with reference to FIGS. 1 to 8 are cross-sectional views in each manufacturing process of the first embodiment, and FIGS. 9 and 10 are cross-sectional views in the manufacturing process of the second embodiment.
[0015]
First, the first embodiment will be described in order according to the manufacturing process.
In the first step shown in FIG. 1, a predetermined first pattern is formed by using a conductive paste made of epoxy resin and silver powder on one side of the first copper foil 21 whose front and back surfaces are roughened with a thickness of 35 μm. After the screen printing is performed and dried, the same pattern screen printing and drying are repeated 5 times using the conductive paste again. Thereafter, the conductive paste is heated and cured in an oven at 180 ° C. to form a substantially conical conductive bump 22 having a height of 0.3 mm and a bottom surface diameter of 0.35 mm at a predetermined position on one side of the first copper foil 21. .
[0016]
Then, the conductive bump 22 is made of an uncured epoxy resin, a reinforcing glass woven fabric or a glass nonwoven fabric, and the like, and a first synthetic resin sheet 23 serving as a substrate of a wiring board and a second copper foil 24 having a thickness of 35 μm. Overlapping.
[0017]
Next, in the second step shown in FIG. 2, the superposed one in the previous step is heated to 100 ° C., and the synthetic resin sheet 23 is softened and pressed in the superposing direction at 2 MPa using a press. Further, while maintaining this pressure, the temperature was raised to 170 ° C., held for 1 hour, then cooled, and the first copper foil 21, the first synthetic resin sheet 23, and the second copper foil 24 were laminated. A first substrate 25 having a three-layer structure is formed. At this time, the conductive bump 22 penetrates the first synthetic resin sheet 23 by heating and pressing, and the tip of the conductive bump 22 is further deformed and fixed to the roughened one side of the second copper foil 24. The first copper foil 21 and the second copper foil 24 are connected.
[0018]
Subsequently, in a third step shown in FIG. 3, an etching resist film is formed on the surface of each of the first copper foil 21 and the second copper foil 24 of the first substrate 25 having the three-layer structure, and this is further formed in a predetermined manner To be the pattern. Then, the 1st copper foil 21 and the 2nd copper foil 24 are etched so that it may become a predetermined pattern shape using a ferric chloride solution.
[0019]
Similarly, in the fourth step shown in FIG. 4, for example, a conductive paste made of epoxy resin and silver powder is used on one side of the third copper foil 26 having a 35 μm thick roughened front and back surfaces. Screen printing of a predetermined second pattern that is reversed with respect to the first pattern in step 1 is performed, dried, and then screen printing and drying of the same pattern is repeated five times using the conductive paste again. . Thereafter, the conductive paste is heated and cured in an oven at 180 ° C. to form a substantially conical conductive bump 27 having a height of 0.3 mm and a bottom surface diameter of 0.35 mm at a predetermined position on one side of the third copper foil 26. .
[0020]
Then, a second synthetic resin sheet 28 which is made of uncured epoxy resin and reinforcing glass woven fabric or glass nonwoven fabric on the front end side of the conductive bump 27 and which is also the base of the wiring board, and a fourth copper having a thickness of 35 μm. The foil 29 is overlapped.
[0021]
Next, in the fifth step shown in FIG. 5, the superposed one in the previous step is heated to 100 ° C., and the second synthetic resin sheet 28 is softened and pressed in the superposing direction at 2 MPa using a press. . Further, while maintaining this pressure, the temperature was raised to 170 ° C., held for 1 hour, then cooled, and the third copper foil 26, the second synthetic resin sheet 28, and the fourth copper foil 29 were laminated. Then, the second substrate 30 having a three-layer structure is formed. At this time, the conductive bump 27 penetrates the second synthetic resin sheet 28 by heating and pressing, and the tip of the conductive bump 27 is further deformed and fixed to the roughened one side of the fourth copper foil 29. The third copper foil 26 and the fourth copper foil 29 are connected.
[0022]
Subsequently, in a sixth step shown in FIG. 6, an etching resist film is formed on the surface of each of the third copper foil 26 and the fourth copper foil 29 of the second substrate 30 having the three-layer structure, and this is further formed in a predetermined manner. To be the pattern. Then, the 3rd copper foil 26 and the 4th copper foil 29 are etched so that it may become a predetermined pattern shape using a ferric chloride solution.
[0023]
Next, in the seventh step shown in FIG. 7, for example, a first paste is formed on the other surface of the third copper foil 26 formed on the second substrate 30 using a conductive paste made of epoxy resin and silver powder. Screen printing of the same first pattern as in the process is performed, and after this is dried, screen printing and drying of the same pattern are repeated 5 times using the conductive paste again. Thereafter, the conductive paste is heated and cured in an oven at 180 ° C., and a substantially conical conductive bump 31 having a height of 0.3 mm and a bottom surface diameter of 0.35 mm is formed at a predetermined position on the other surface of the third copper foil 26. .
[0024]
Then, a third synthetic resin sheet 32 made of an uncured epoxy resin and a reinforcing glass woven fabric or glass nonwoven fabric, which is also the base of the wiring board, is interposed between the first bumps of the conductive bumps 31, The first substrate 25 is placed and overlapped so that the other surface of the copper foil 21 faces the other.
[0025]
Next, in the eighth step shown in FIG. 8, the superposed one in the previous step is heated to 100 ° C., and the third synthetic resin sheet 32 is softened and pressed in the superposing direction at 2 MPa using a press. . Further, while maintaining this pressure, the temperature is raised to 170 ° C., held for 1 hour, then cooled, and the first substrate 25, the third synthetic resin sheet 32, and the second substrate 30 are laminated. The multilayer printed wiring board 33 is used. The conductive bump 31 penetrates the third synthetic resin sheet 32 by heating and pressing at this time, and the tip of the conductive bump 31 is further deformed and fixed to the roughened other surface of the first copper foil 21. The first copper foil 21 and the third copper foil 26 are connected.
[0026]
In the multilayer printed wiring board 33 formed in this way, the second copper foil 24 and the fourth copper foil 29 exposed on the outer surface constitute pads P for mounting semiconductor devices and electronic components, respectively. Then, the surface layer pad P and the first copper foil 21 and the third copper foil 26 serving as the inner layer conductor are connected to each other through conductive bumps 22, 27, and 31 fixed thereto.
[0027]
Further, the pad P constituted by the second copper foil 24 and the fourth copper foil 29 is fixed to the bottom surface on the small area side of the conductive bumps 22 and 27 having a truncated cone shape. The remaining surface is fixed to the first synthetic resin sheet 23 and the second synthetic resin sheet 28.
[0028]
Next, the adhesion strength of the pad P of the multilayer printed wiring board 33 configured as described above was measured and compared with the conventional one. For comparison, a surface layer pad is formed into a 1 mm square, a tin-plated copper wire having a diameter of 0.8 mm is soldered thereto, and the pulling force of the pulling pad is peeled off so that the copper wire is peeled in a direction perpendicular to the pad P. It was measured.
[0029]
As a result, the pad P of the multilayer printed wiring board 33 of this embodiment is not peeling with a force of up to 1 kg / mm ^2, it showed 1 kg / mm ² or more bonding strength. On the other hand, the fixing strength of the pad of the multilayer printed wiring board according to the prior art was 0.5 kg / mm ² .
[0030]
This is because the multi-layer printed wiring board 33 of this embodiment is fixed to the bottom surface on the small area side where the fixing area is small with respect to the conductive bumps 22 and 27 having a low fixing force with the pad P, and is fixed to the pad P. This is because the first synthetic resin sheet 23 and the second synthetic resin sheet 28 having strong adhesion force are configured to have a large fixing area so that the fixing force of the entire pad P is increased. is there. In the conventional multilayer printed wiring board, the relationship between the conductive bumps and the pads is reversed.
[0031]
Further, a heat cycle test and a water absorption test were performed on the multilayer printed wiring board 33, and each of them exhibited sufficient resistance, and it was confirmed that there was no practical problem.
[0032]
And even if an electronic component or the like is soldered and mounted on the pad P on the multilayer printed wiring board 33, the pad P is strong and the possibility that the electronic component or the like falls off due to the strong bonding strength of the pad P is reduced. There is no need to increase the pad P. Further, if the fixing strength of the pads P is the same, the size can be reduced, the distance between the pads P and the distance between the wirings can be reduced, and the mounting density can be increased.
[0033]
In the first embodiment described above, two layers of inner conductors are provided. However, one or more layers may be provided.
[0034]
For example, as shown in FIG. 9 and FIG. 10 as a second embodiment for a multilayer printed wiring board provided with one inner layer conductor, first, in the first step shown in FIG. Screen printing of a predetermined pattern is performed on the surface of the third copper foil 26 of the second substrate 28 obtained through the fourth to sixth steps using a conductive paste made of epoxy resin and silver powder, After drying this, screen printing / drying of the same pattern is repeated 5 times using the conductive paste again. Thereafter, the conductive paste is heated and cured in an oven at 180 ° C., and a substantially conical conductive bump 41 having a height of 0.3 mm and a bottom surface diameter of 0.35 mm is formed on the surface of the third copper foil 26.
[0035]
Then, a synthetic resin sheet 42 made of an uncured epoxy resin and a reinforcing glass woven fabric or glass nonwoven fabric and serving as a substrate of the wiring board and a copper foil 43 having a thickness of 35 μm are superimposed on the front end side of the conductive bump 41.
[0036]
Next, in the second step shown in FIG. 10, the superposed one in the previous step is heated to 100 ° C., and the synthetic resin sheet 42 is softened and pressed in the superposing direction at 2 MPa using a press. Further, while maintaining this pressure, the temperature is raised to 170 ° C., held for 1 hour, cooled, and the second substrate 28, the synthetic resin sheet 42, and the copper foil 43 are laminated and integrated. At this time, the conductive bump 41 penetrates the synthetic resin sheet 42 by heating and pressurization, and the tip of the conductive bump 41 is deformed and fixed to the surface of the copper foil 43, and the third copper foil 26 and the copper foil 43 is connected.
[0037]
Then, the multilayer printed wiring board 44 is obtained by etching the copper foil 43 so as to have a predetermined pattern shape. The fourth copper foil 29 and the copper foil 43 exposed on the outer surface constitute a pad P for mounting a semiconductor device or an electronic component, respectively, and a third copper serving as a surface layer pad P and an inner layer conductor. The foil 26 is connected via conductive bumps 27 and 41 fixed to the foil 26, respectively.
[0038]
Further, the pad P constituted by the fourth copper foil 29 and the copper foil 43 is fixed to the bottom surface of the conductive bumps 27 and 41 having a truncated cone shape on the small area side, and the remaining surface of the pad P Is fixed to the second synthetic resin sheet 28 and the synthetic resin sheet 42.
[0039]
For this reason, the multilayer printed wiring board 44 of the present embodiment configured as described above can achieve the same effects as those of the first embodiment.
[0040]
Furthermore, a multilayer printed wiring board having three or more inner layer conductors can be obtained by appropriately combining the steps of the first and second embodiments.
[0041]
In addition, the multilayer printed wiring boards 33 and 44 of the above embodiments are both-side mounted wiring boards, but they may be single-sided mounting boards. Also, a synthetic resin sheet as a substrate of the wiring board is also a glass woven fabric. Or it is not restricted to the epoxy resin reinforced with a glass nonwoven fabric etc., A polyimide resin and a phenol resin may be sufficient.
[0042]
【The invention's effect】
As is apparent from the above description, the present invention provides an inner-layer conductor in which the bottom surface on the small area side of the frustum-like conductive bump is fixed to the surface layer pad, and the bottom surface on the large area side is formed by laminating a plurality of substrates. By being configured so as to be fixed to the pad, it is possible to increase the fixing strength of the pad, prevent the mounted electronic component from falling off, and further increase the mounting density of the electronic component.
[Brief description of the drawings]
FIG. 1 is a sectional view of a first step in a first embodiment of the present invention.
FIG. 2 is a sectional view of a second step in the first embodiment of the present invention.
FIG. 3 is a sectional view of a third step in the first embodiment of the present invention.
FIG. 4 is a sectional view of a fourth step in the first embodiment of the present invention.
FIG. 5 is a sectional view of a fifth step in the first embodiment of the present invention.
FIG. 6 is a sectional view of a sixth step in the first embodiment of the present invention.
FIG. 7 is a sectional view of a seventh step in the first embodiment of the present invention.
FIG. 8 is a sectional view of an eighth step in the first embodiment of the present invention.
FIG. 9 is a sectional view of a first step in a second embodiment of the present invention.
FIG. 10 is a sectional view of a second step in the second embodiment of the present invention.
FIG. 11 is a sectional view of a first step in a conventional example.
FIG. 12 is a sectional view of a second step in the conventional example.
FIG. 13 is a sectional view of a third step in the conventional example.
FIG. 14 is a sectional view of a fourth step in the conventional example.
FIG. 15 is a sectional view of a fifth step in the conventional example.
[Explanation of symbols]
21, 26 ... Copper foil (inner layer conductor)
22, 27, 31 ... conductive bumps 23, 28, 32 ... synthetic resin sheet (substrate)
24, 29 ... copper foil 33 ... multilayer printed wiring board P ... pad

Claims

A plurality of bases provided so as to penetrate through the frustum-shaped conductive bumps made of synthetic resin are laminated, and the inner bumps provided between the inner metal foils and the inner metal foil and the pads provided on the surface layer are respectively provided by the conductive bumps. In the multilayer printed wiring board formed by connection, the conductive bumps connecting the inner layer metal foil and the surface layer pad have the bottom surface on the small area side fixed to the pad and the bottom surface on the large area side fixed to the inner layer metal foil. A multilayer printed wiring board characterized in that the uppermost and lowermost substrates of the laminated substrates are each provided with the inner layer metal foil and a surface layer pad on the upper and lower surfaces of the substrate .

2. The multilayer printed wiring board according to claim 1, wherein the main part of the substrate is made of a synthetic resin such as an epoxy resin, and the conductive bumps are made of silver powder and a synthetic resin such as an epoxy resin.

The multilayer printed wiring board according to claim 1 or 2, wherein the conductive bumps are formed in a truncated cone shape.

A first step of forming a substantially conical first conductive bump on one side of the first copper foil surface by printing with a conductive paste;
After the first synthetic resin sheet and the second copper foil are superposed on the first conductive bump side of the first copper foil, they are integrated by heating and pressing, and the first conductive bump is attached to the first copper bump. A second step of penetrating the synthetic resin sheet of 1 and fixing the tip of the first conductive bump to the second copper foil surface;
A third step of forming a first substrate by etching the first copper foil provided at least in the first and second copper foils into a predetermined pattern;
A fourth step of forming a substantially conical second conductive bump on the other surface of the first copper foil having a predetermined pattern on the first substrate by printing with a conductive paste;
A fifth step of forming a substantially conical third conductive bump by printing with a conductive paste on one side of the third copper foil surface;
The second synthetic resin sheet and the fourth copper foil are superposed on the third conductive bump side of the third copper foil, and then integrated by heating and pressing, and the third conductive bump is attached to the third copper bump. A sixth step of penetrating through the synthetic resin sheet of 2 and fixing the tip of the third conductive bump to the fourth copper foil surface;
A seventh step of forming a second substrate by etching the third copper foil provided at least in the third and fourth copper foils into a predetermined pattern;
The third synthetic resin sheet and the second substrate are overlapped on the second conductive bump side of the first substrate and then integrated by heating and pressing, and the second conductive bump is integrated with the third conductive bump. An eighth step of passing through the synthetic resin sheet and fixing the tip of the second conductive bump to the third copper foil surface of the second substrate;
A multilayer printed wiring board manufacturing method characterized by comprising a multilayer.

A first substrate in which a first metal foil is partially disposed on a first surface and a second metal foil is disposed on a second surface;
A frustum-shaped first conductive bump penetrating the first base and connecting the first metal foil and the second metal foil with a small area surface as the second metal foil side;
A second substrate in which a third metal foil is partially disposed on the first surface and a fourth metal foil is disposed on the second surface;
A frustum-shaped second conductive bump that penetrates the second base and connects the third metal foil and the fourth metal foil with the small area surface as the fourth metal foil side;
A third layer provided between the first base and the second base in close contact with the first metal foil and the third metal foil so as to be embedded in the first and second surfaces, respectively. A base of
A third conductive bump penetrating the third base and connecting the first metal foil and the third metal foil;
A multilayer printed wiring board comprising: