JP3900800B2 - Bonding structure of circuit board and flexible printed circuit board - Google Patents

Bonding structure of circuit board and flexible printed circuit board Download PDF

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JP3900800B2
JP3900800B2 JP2000210519A JP2000210519A JP3900800B2 JP 3900800 B2 JP3900800 B2 JP 3900800B2 JP 2000210519 A JP2000210519 A JP 2000210519A JP 2000210519 A JP2000210519 A JP 2000210519A JP 3900800 B2 JP3900800 B2 JP 3900800B2
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circuit board
flexible printed
printed circuit
conductor pattern
conductor
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JP2002026480A (en
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周平 鶸田
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Brother Industries Ltd
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Brother Industries Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は、フレキシブルプリント回路基板の複数の導体パターンと回路基板の複数の導体パターンとを半田付けにより接合する接合構造に関する。
【０００２】
【従来の技術】
従来、インクジェットプリンタ等の印字ヘッドが移動して印字を行うシリアルプリンタでは、印字ヘッドと、印字ヘッドを駆動する駆動ＩＣを搭載した駆動回路基板との間を、フレキシブルプリント回路基板（ＦＰＣ）を用いて接続していた。この場合に、駆動回路基板とフレキシブルプリント回路基板との接続は、フレキシブルプリント回路基板上に設けた複数の導体パターンと駆動回路基板に設けた複数の導体パターンとを半田付けで接合していた。
【０００３】
【発明が解決しようとする課題】
しかしながら、上記のように、印字ヘッドを駆動する駆動ＩＣを搭載した駆動回路基板とフレキシブルプリント回路基板とを半田付で接合する場合には、セ氏１８０度程度の温度を加えるために、加熱時にフレキシブルプリント回路基板が略０．１％程度伸びてしまい、フレキシブルプリント回路基板に設けた複数の導体パターンの間隔が狭ピッチになると、当該フレキシブルプリント回路基板に設けた複数の導体パターンと駆動回路基板に設けた複数の導体パターンとが端部でずれてしまうという問題点があった。
【０００４】
また、フレキシブルプリント回路基板上に設けた複数の導体パターンと駆動回路基板に設けた複数の導体パターンとの接続に用いた半田の量が多い場合には、半田により隣接する導体パターン同士を短絡させてしまうという問題点もあった。
【０００５】
本発明は、上記問題点を解決するためになされたものであり、回路基板の複数の導体パターンとフレキシブルプリント回路基板の複数の導体パターンとを半田付けにより正確に接続することができる回路基板とフレキシブルプリント回路基板との接合構造を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上述の目的を達成するために、請求項１に記載の発明では、フレキシブルプリント回路基板の複数の導体パターンと回路基板の複数の導体パターンとを半田付けにより接合する接合構造であって、前記回路基板の前記各導体パターンは、第１の所定幅を有し、第１の所定間隔で複数平行に配列され、前記第１の所定幅は、前記第１の所定間隔よりも大きく、前記回路基板の前記各導体パターンと対向する前記フレキシブルプリント回路基板の前記各導体パターンは、第２の所定幅を有し、第２の所定間隔で複数平行に配列され、前記第２の所定幅は、前記第２の所定間隔よりも小さく、前記回路基板の前記各導体パターンの長さは、前記フレキシブルプリント回路基板の前記各導体パターンの長さよりも長く形成され、前記フレキシブルプリント回路基板の前記複数の導体パターンを前記回路基板の複数の導体パターンに対向して半田付けしたときに、前記回路基板の前記複数の導体パターンの各々には、前記回路基板の導体パターンに対向しない露出部分が形成されていることを特徴とする。
【０００７】
この構成の接合構造では、前記回路基板の各導体パターンが、第１の所定幅を有し、第１の所定間隔で複数平行に配列され、第１の所定幅は、第１の所定間隔よりも大きく、フレキシブルプリント回路基板の各導体パターンが、第２の所定幅を有し、第２の所定間隔で複数平行に配列され、第２の所定幅は、第２の所定間隔よりも小さく構成されているので、回路基板にフレキシブルプリント回路基板を半田付けにより接合する場合に、フレキシブルプリント回路基板の各導体パターンを回路基板の各導体パターンに正確に接合することができる。また、半田付けの際の熱による膨張があってもパターンのずれを少なくできる。
【０００８】
【０００９】
また、この構成の接合構造では、回路基板の各導体パターンの長さは、前記フレキシブルプリント回路基板の各導体パターンの長さよりも長いので、回路基板の複数の導体パターンの各々には、露出部分が形成され、余分な半田が当該露出部分に保持され、回路基板の各導体パターンから溢れてしまうことがない。
【００１０】
また、請求項２に記載の接合構造は、請求項１に記載の発明の構成に加えて、前記回路基板の各導体パターンの長さと前記フレキシブルプリント回路基板の各導体パターンの長さの比は、略２対１であることを特徴とする。
【００１１】
この構成では、請求項１に記載の発明の作用に加えて、前記回路基板の各導体パターンの長さと前記フレキシブルプリント回路基板の各導体パターンの長さの比を、略２対１としているので、前記回路基板の各導体パターンがフレキシブルプリント回路基板の各導体パターンの長さの比べて十分に長く、半田付け時に融解した半田が露出部分に保持され、回路基板の各導体パターンから溢れてしまうことがない。
【００１２】
また、請求項３に記載の接合構造は、請求項１又は２に記載の発明の構成に加えて、前 記フレキシブルプリント回路基板の導体パターンの前記第２の所定幅は、前記回路基板の導体パターンの前記第１の所定幅よりも小さく、前記第２の所定間隔は、前記第１の所定間隔よりも大きいことを特徴とする。
【００１３】
この構成では、請求項１又は２に記載の発明の作用に加えて、回路基板にフレキシブルプリント回路基板を半田付けにより接合する場合に、フレキシブルプリント回路基板の各導体パターンを回路基板の各導体パターンに正確に接合することができる。
【００１４】
また、請求項４に記載の接合構造は、請求項１乃至３のいずれかに記載の発明の構成に加えて、前記フレキシブルプリント回路基板の各導体パターンの表面の半田付けされる部分以外の部分に、カバー層が形成され、当該カバー層が、前記回路基板の導体パターンに重なる部分の長さは、前記回路基板の厚み以上であることを特徴とする。
【００１５】
この構成では、請求項１乃至３のいずれかに記載の発明の作用に加えて、半田付けの後に、フレキシブルプリント回路基板を回路基板の近傍で折り曲げた場合にも、折り曲げ箇所の折り曲げ半径が大きくなり、回路基板の側端部のエッジで生じるストレスが緩和され、フレキシブルプリント回路基板の導体層の切断が防止できる。
【００１６】
【００１７】
【００１８】
【発明の実施の形態】
次に、本発明の第１の実施形態について図面を参照して説明する。図１は、本発明の一実施の形態のインクジェットプリンタの印字ヘッド用の駆動回路基板１の平面図である。図２は、駆動回路基板１に接合される前記フレキシブルプリント回路基板２の平面図である。
【００１９】
図１に示すように、駆動回路基板１は、略長方形に形成されたエポキシ樹脂製の回路基板基材３の表面に図示外の銅箔パターンが形成され、当該銅箔パターンには、図示外の樹脂膜による絶縁層が後述する駆動ＩＣ４の半田付け部分（図示外）及び後述する導体パターン５以外の部分に形成されている。また、駆動回路基板１には、図示外のインクジェットヘッドの圧電アクチュエータを駆動する駆動ＩＣ４が設けられている。さらに、駆動回路基板１の側端部１ａには、銅箔により略長方形に形成された導体パターン５が、後述する間隔及びサイズで複数平行に配列されている。なお、図１では、導体パターン５の長さをＬａとして表示している。
【００２０】
次に、図２を参照して、駆動回路基板１に接合されるフレキシブルプリント回路基板２について説明する。フレキシブルプリント回路基板２は、駆動回路基板１と図示外のインクジェットプリンタの印字ヘッドの圧電アクチュエータとを接続するものである。
【００２１】
図２に示すように、フレキシブルプリント回路基板２は、厚さ略２５μｍのポリイミド樹脂の基材により構成された可撓性を有する薄板の帯状のものである。そして、フレキシブルプリント回路基板２の駆動回路基板１に接合される側の側端部２ａは、幅が広く形成され、当該側端部２ａには、駆動回路基板１に接合される略長方形に形成された銅箔の導体パターン６が、後述する間隔及びサイズで複数平行に配列されている。なお、図２では、導体パターン６の長さをＬｂとして表示している。
【００２２】
次に、図３を参照して、駆動回路基板１の構造の詳細について説明する。図３は、駆動回路基板１の側端部１ａの拡大図である。
【００２３】
図３に示すように、駆動回路基板１の側端部１ａには、銅箔により構成された略長方形の導体パターン５が平行に複数配列されている。ここで、導体パターン５の長さをＬａ、幅をＷａ、導体パターン５の配列の間隔はＳａ、前記フレキシブルプリント回路基板２の導体パターン６の長さをＬｂとすると、Ｌａ、Ｌｂ、Ｗａ、Ｓａの関係は、以下のように定められている。
・Ｌａ：Ｌｂ＝２：１
・Ｗａ＞Ｓａ
【００２４】
上記の具体例をあげると、導体パターン５のサイズ長さＬａは、３ｍｍである。フレキシブルプリント回路基板２の導体パターン６の長さをＬｂが１．５ｍｍとなっているからである。また、導体パターン５の幅Ｗａは、約１１０μｍであり、導体パターン５の配列の間隔はＳａは、約６０μｍである。
【００２５】
次に、図４を参照して、フレキシブルプリント回路基板２の構造の詳細について説明する。図４は、フレキシブルプリント回路基板２の拡大図である。図４に示すように、フレキシブルプリント回路基板２の側端部２ａには、厚さ１８μｍの銅箔により構成された略長方形の導体パターン６が平行に複数配列されている。ここで、導体パターン６の長さをＬｂ、幅をＷｂ、導体パターン６の配列の間隔はＳｂとすると、Ｌｂ、Ｗｂ、Ｓｂの一例としては、導体パターン６の長さＬｂは、１．５ｍｍであり、導体パターン６の幅Ｗｂは、約５５μｍであり、導体パターン６の配列の間隔はＳｂは、約１１５μｍである。
【００２６】
次に、図５及び図６を参照して、駆動回路基板１及びフレキシブルプリント回路基板２の断面の構造について説明する。図５は、駆動回路基板１の図３におけるＡ−Ａ’線における矢視方向の断面図であり、図６は、フレキシブルプリント回路基板２の図４におけるＢ−Ｂ’線における矢視方向の断面図である。
【００２７】
図５に示すように、駆動回路基板１は、エポキシ樹脂製の回路基板基材３の表面に銅箔製の導体パターン５が設けられている。この導体パターン５は、フォトエッチング法により、回路基板基材３の表面に構成されたものである。
【００２８】
また、図６に示すように、フレキシブルプリント回路基板２は、厚さ２５のポリイミド樹脂の基材７上に、厚さ１８μｍの銅箔の導体層６’が形成され、当該導体層６’の上には、導体層６’の先端部の導体パターン６を避けて、厚さ２５のポリイミドのポリイミド樹脂のカバー層８が設けられている。従って、導体パターン６は、フレキシブルプリント回路基板２の側端部２ａ側に長さＬｂだけ露出していることになる。
【００２９】
なお、フレキシブルプリント回路基板２のサイズ及び導体パターン６の配置の間隔（ピッチ）等は、半田付け時に半田が硬化する寸前の温度である摂氏１８０度を基準にポリイミドの熱膨張を考慮して決定されている。
【００３０】
次に、図７乃至図９を参照して、駆動回路基板１とフレキシブルプリント回路基板２との半田付けについて説明する。図７は、駆動回路基板１にフレキシブルプリント回路基板２を重ねた状態を示す平面図であり、図８は、駆動回路基板１にフレキシブルプリント回路基板２を半田付けする状態を示した断面図であり、図９は、駆動回路基板１に半田付けしたフレキシブルプリント回路基板２を折り曲げた状態を示す断面図である。
【００３１】
まず、半田付け作業の前には、事前の処理として、駆動回路基板１の導体パターン５に金メッキを行っておく、導体パターン５の表面の電気伝導度の向上と、半田の付きを良くするためである。次に、フレキシブルプリント回路基板２の導体パターン６の表面に半田メッキを行っておく、この半田メッキを再度加熱して融解することにより駆動回路基板１の導体パターン５との接合を行うことになる。
【００３２】
次に、図７に示すように、駆動回路基板１の導体パターン５が上の面になるようにし、その上に、フレキシブルプリント回路基板２の導体パターン６が下になるように伏せて重ねる。このときに、フレキシブルプリント回路基板２は、厚さ２５μｍのポリミドの樹脂材で構成されているので、裏面から自身の導体パターン６及び駆動回路基板１の導体パターン５が透けて見えるので、駆動回路基板１の導体パターン５とフレキシブルプリント回路基板２の導体パターン６との位置合わせを行う。
【００３３】
このときに、図７に示すように、導体パターン５の基部を所定量露出して露出部５ａを形成する。これは、半田付け時に融解した余剰半田をその露出部５ａに逃がすためである。
【００３４】
また、駆動回路基板１の導体パターン５に、フレキシブルプリント回路基板２の導体パターン６を重ねる場合には、図８に示すように、カバー層８の一部が、駆動回路基板１の導体パターン５に重なるようにする（以下、「カバー層の重複部分」という）。具体的には、図８に示すように、カバー層の重複部分の長さをＬｏとし、駆動回路基板１全体の厚みをＴａとし、フレキシブルプリント回路基板２全体の厚みをＴｂとすると、ＬｏをＴａ以上の長さにし、また、ＬｏをＴｂ以上の長さにする。
【００３５】
次いで、図８に示すように、半田融解用のヒータバー１０により、フレキシブルプリント回路基板２の導体パターン６の裏面から摂氏１８０度以上に加熱する。すると、フレキシブルプリント回路基板２の導体パターン６に半田メッキした半田が融解する。次いで、ヒータバー１０をフレキシブルプリント回路基板２の導体パターン６の裏面から離すと、半田の温度が摂氏１８０度よりも下がって、半田が固化して駆動回路基板１の導体パターン５とフレキシブルプリント回路基板２の導体パターン６とが接合される。
【００３６】
このときに、導体パターン５の長さＬａは、導体パターン６の長さＬｂよりも長く構成されているので、前記図７に示すように、駆動回路基板１の導体パターン５の基部には、露出部５ａが形成されて、半田付け時に余剰な半田が表面張力により当該露出部５ａに保持されるために、隣り合う導体パターン５同士や導体パターン６同士が、半田でブリッジされてしまうことがない。
【００３７】
また、駆動回路基板１の導体パターン５の幅が、当該導体パターン５の間隔よりも広く、また、フレキシブルプリント回路基板２の導体パターン６の幅は、導体パターン６の間隔よりも短く構成されているので、駆動回路基板１の導体パターン５とフレキシブルプリント回路基板２の導体パターン６との位置合わせが容易になるという効果を生じる。また、半田付け時の熱による膨張があってもパターンがずれることが少ない。
【００３８】
さらに、図８に示すように、カバー層の重複部分の長さをＬｏを駆動回路基板１全体の厚みＴａ以上の長さにし、また、カバー層の重複部分の長さをＬｏをフレキシブルプリント回路基板２全体の厚みＴｂ以上の長さにしていることにより、図９に示すように、半田付けの後に、フレキシブルプリント回路基板２を駆動回路基板１の近傍で折り曲げた場合にも、折り曲げ箇所の折り曲げ半径が大きくなり、駆動回路基板１の側端部１ａのエッジで生じるストレスが緩和され、フレキシブルプリント回路基板２の導体層６’の切断が防止できる。
【００３９】
なお、本発明は上記の実施の形態に限られず、各種の変更が可能なことは言うまでもない、例えば、上記の実施の形態では、駆動回路基板１とフレキシブルプリント回路基板２との接合を例に説明したが、本発明は、フレキシブルプリント回路基板を半田付けにより接合するものであれば、印字ヘッドのアクチュエータの回路基板やその他の各種回路基板との接合に適用できることは言うまでもない。また、本発明は、インクジェットプリンタに限られず、各種の装置の回路基板に適用できることは言うまでもない。
【００４０】
【発明の効果】
以上説明したように、請求項１に係る発明では、回路基板の各導体パターンが、第１の所定幅を有し、第１の所定間隔で複数平行に配列され、第１の所定幅は、第１の所定間隔よりも大きく、フレキシブルプリント回路基板の各導体パターンは、第２の所定幅を有し、第２の所定間隔で複数平行に配列され、第２の所定幅は、第２の所定間隔よりも小さく構成されているので、回路基板にフレキシブルプリント回路基板を半田付けにより接合する場合に、フレキシブルプリント回路基板の各導体パターンを回路基板の各導体パターンに正確に接合することができる。
【００４１】
さらに、回路基板の各導体パターンの長さは、前記フレキシブルプリント回路基板の各導体パターンの長さより長いので、回路基板の複数の導体パターンの各々には、露出部分が形成され、余分な半田が当該露出部分に保持され、回路基板の各導体パターンから溢れてしまうことがない。
【００４２】
また、請求項２に記載の接合構造は、請求項１に記載の発明の効果に加えて、前記回路基板の各導体パターンの長さと前記フレキシブルプリント回路基板の各導体パターンの長さの比を、略２対１としているので、前記回路基板の各導体パターンがフレキシブルプリント回路基板の各導体パターンの長さの比べて十分に長く、半田付け時に融解した半田が露出部分に保持され、回路基板の各導体パターンから溢れてしまうことがない。
【００４３】
また、請求項３に記載の接合構造は、請求項１又は２に記載の発明の効果に加えて、前記フレキシブルプリント回路基板の導体パターンの前記第２の所定幅は、前記回路基板の導体パターンの前記第１の所定幅よりも小さく、前記第２の所定間隔は、前記第１の所定間隔よりも大きいことで、回路基板にフレキシブルプリント回路基板を半田付けにより接合する場合に、フレキシブルプリント回路基板の各導体パターンを回路基板の各導体パターンに正確に接合することができる。
【００４４】
また、請求項４に記載の接合構造は、請求項１乃至３のいずれかに記載の発明の効果に加えて、半田付けの後に、フレキシブルプリント回路基板を回路基板の近傍で折り曲げた場合にも、折り曲げ箇所の折り曲げ半径が大きくなり、回路基板の側端部のエッジで生じるストレスが緩和され、フレキシブルプリント回路基板の導体層の切断が防止できる。
【図面の簡単な説明】
【図１】 図１は、本発明の一実施の形態のインクジェットプリンタの印字ヘッド用の駆動回路基板１の平面図である。
【図２】 図２は、駆動回路基板１に接合される前記フレキシブルプリント回路基板２の平面図である。
【図３】 図３は、駆動回路基板１の側端部１ａの拡大図である。
【図４】図４は、フレキシブルプリント回路基板２の拡大図である。
【図５】 図５は、駆動回路基板１の図３におけるＡ−Ａ’線における矢視方向の断面図である。
【図６】 図６は、フレキシブルプリント回路基板２の図４におけるＢ−Ｂ’線における矢視方向の断面図である。
【図７】 図７は、駆動回路基板１にフレキシブルプリント回路基板２を重ねた状態を示す平面図である。
【図８】 図８は、駆動回路基板１にフレキシブルプリント回路基板２を半田付けする状態を示した断面図である。
【図９】 図９は、駆動回路基板１に半田付けしたフレキシブルプリント回路基板２を折り曲げた状態を示す断面図である。
【符号の説明】
１ 駆動回路基板
１ａ 側端部
２ フレキシブルプリント回路基板
２ａ 側端部
３ 回路基板基材
４ 駆動ＩＣ
５ 導体パターン
Ｌａ 長
Ｗａ 幅
Ｓａ 間隔
６ 導体パターン
Ｌｂ 長さ
Ｗｂ 幅
Ｓｂ 間隔
６’ 導体層
７ 基材
８ カバー層
１０ ヒータバー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joining structure for joining a plurality of conductor patterns of a flexible printed circuit board and a plurality of conductor patterns of a circuit board by soldering.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a serial printer that performs printing by moving a print head such as an ink jet printer uses a flexible printed circuit board (FPC) between the print head and a drive circuit board on which a drive IC that drives the print head is mounted. Connected. In this case, the drive circuit board and the flexible printed circuit board are connected by soldering a plurality of conductor patterns provided on the flexible printed circuit board and a plurality of conductor patterns provided on the drive circuit board.
[0003]
[Problems to be solved by the invention]
However, as described above, when the drive circuit board on which the drive IC for driving the print head is mounted and the flexible printed circuit board are joined by soldering, a temperature of about 180 degrees Celsius is applied. When the printed circuit board extends by about 0.1% and the interval between the plurality of conductor patterns provided on the flexible printed circuit board becomes a narrow pitch, the plurality of conductor patterns provided on the flexible printed circuit board and the drive circuit board There was a problem that a plurality of provided conductor patterns shifted from each other at the end.
[0004]
In addition, when the amount of solder used to connect the plurality of conductor patterns provided on the flexible printed circuit board and the plurality of conductor patterns provided on the drive circuit board is large, the adjacent conductor patterns are short-circuited by the solder. There was also a problem that it ended up.
[0005]
The present invention has been made to solve the above problems, a circuit board can be accurately connected and a plurality of conductor patterns of a plurality of conductive patterns of the circuit board and the flexible printed circuit board by soldering It is an object to provide a joint structure with a flexible printed circuit board .
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided a joining structure in which a plurality of conductor patterns of a flexible printed circuit board and a plurality of conductor patterns of a circuit board are joined by soldering, Each of the conductor patterns of the substrate has a first predetermined width and is arranged in parallel at a first predetermined interval, and the first predetermined width is larger than the first predetermined interval, and the circuit board Each of the conductor patterns of the flexible printed circuit board facing each of the conductor patterns has a second predetermined width and is arranged in parallel at a second predetermined interval, and the second predetermined width is The length of each conductor pattern of the circuit board is smaller than a second predetermined interval, and is longer than the length of each conductor pattern of the flexible printed circuit board. When the plurality of conductor patterns on the circuit board are soldered to face the plurality of conductor patterns on the circuit board, each of the plurality of conductor patterns on the circuit board faces the conductor pattern on the circuit board. An exposed portion that is not formed is formed .
[0007]
In the joining structure having this configuration, each conductor pattern of the circuit board has a first predetermined width and is arranged in parallel at a first predetermined interval, and the first predetermined width is greater than the first predetermined interval. Each of the conductor patterns of the flexible printed circuit board has a second predetermined width and is arranged in parallel at a second predetermined interval, and the second predetermined width is smaller than the second predetermined interval. Therefore, when the flexible printed circuit board is joined to the circuit board by soldering, each conductor pattern of the flexible printed circuit board can be accurately joined to each conductor pattern of the circuit board. Further, even if there is expansion due to heat during soldering, pattern deviation can be reduced.
[0008]
[0009]
Further, in the joining structure of this configuration, since the length of each conductor pattern of the circuit board is longer than the length of each conductor pattern of the flexible printed circuit board, each of the plurality of conductor patterns of the circuit board has an exposed portion. Is formed, and excess solder is held in the exposed portion, and does not overflow from each conductor pattern of the circuit board.
[0010]
The joining structure according to claim 2, in addition to the configuration of the invention according to claim 1, ratio of the length of the conductor patterns of the length of the conductor patterns of the circuit board and the flexible printed circuit board , Approximately 2 to 1.
[0011]
In this configuration, in addition to the operation of the invention according to claim 1 , the ratio of the length of each conductor pattern of the circuit board to the length of each conductor pattern of the flexible printed circuit board is approximately 2 to 1. Each conductor pattern of the circuit board is sufficiently longer than the length of each conductor pattern of the flexible printed circuit board, and the solder melted during soldering is held in the exposed portion and overflows from each conductor pattern of the circuit board. There is nothing.
[0012]
The joining structure according to claim 3, in addition to the configuration of the invention according to claim 1 or 2, wherein the second predetermined width of the conductor pattern before Symbol flexible printed circuit board, the conductor of the circuit board The second predetermined interval is smaller than the first predetermined width of the pattern, and the second predetermined interval is larger than the first predetermined interval.
[0013]
In this configuration, in addition to the operation of the invention described in claim 1 or 2 , when the flexible printed circuit board is joined to the circuit board by soldering, each conductor pattern of the flexible printed circuit board is replaced with each conductor pattern of the circuit board. Can be accurately joined.
[0014]
According to a fourth aspect of the present invention, in addition to the configuration of the invention according to any one of the first to third aspects, a portion other than a portion to be soldered on the surface of each conductor pattern of the flexible printed circuit board. In addition, a cover layer is formed, and a length of a portion where the cover layer overlaps a conductor pattern of the circuit board is equal to or greater than a thickness of the circuit board.
[0015]
In this configuration, in addition to the operation of the invention according to any one of claims 1 to 3, even when the flexible printed circuit board is bent in the vicinity of the circuit board after soldering, the bending radius of the bent portion is large. Thus, the stress generated at the edge of the side edge of the circuit board is relieved, and the conductor layer of the flexible printed circuit board can be prevented from being cut.
[0016]
[0017]
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a drive circuit board 1 for a print head of an ink jet printer according to an embodiment of the present invention. FIG. 2 is a plan view of the flexible printed circuit board 2 bonded to the drive circuit board 1.
[0019]
As shown in FIG. 1, the drive circuit board 1 has a copper foil pattern (not shown) formed on the surface of a circuit board base 3 made of an epoxy resin formed in a substantially rectangular shape. An insulating layer made of the resin film is formed on a portion other than a soldered portion (not shown) of the drive IC 4 described later and a conductor pattern 5 described later. The drive circuit board 1 is provided with a drive IC 4 for driving a piezoelectric actuator of an inkjet head (not shown). Furthermore, a plurality of conductor patterns 5 formed in a substantially rectangular shape with a copper foil are arranged in parallel on the side end portion 1a of the drive circuit board 1 at intervals and sizes described later. In FIG. 1, the length of the conductor pattern 5 is indicated as La.
[0020]
Next, the flexible printed circuit board 2 bonded to the drive circuit board 1 will be described with reference to FIG. The flexible printed circuit board 2 connects the drive circuit board 1 and a piezoelectric actuator of a print head of an ink jet printer (not shown).
[0021]
As shown in FIG. 2, the flexible printed circuit board 2 is a thin strip having flexibility and made of a polyimide resin base material having a thickness of about 25 μm. And the side edge part 2a by the side of the flexible printed circuit board 2 joined to the drive circuit board 1 is formed wide, and the side edge part 2a is formed in a substantially rectangular shape to be joined to the drive circuit board 1. A plurality of copper foil conductor patterns 6 are arranged in parallel at intervals and sizes described later. In FIG. 2, the length of the conductor pattern 6 is indicated as Lb.
[0022]
Next, details of the structure of the drive circuit board 1 will be described with reference to FIG. FIG. 3 is an enlarged view of the side end portion 1 a of the drive circuit board 1.
[0023]
As shown in FIG. 3, a plurality of substantially rectangular conductor patterns 5 made of copper foil are arranged in parallel on the side end portion 1 a of the drive circuit board 1. Here, when the length of the conductor pattern 5 is La, the width is Wa, the interval of the arrangement of the conductor patterns 5 is Sa, and the length of the conductor pattern 6 of the flexible printed circuit board 2 is Lb, La, Lb, Wa, The relationship of Sa is determined as follows.
・ La: Lb = 2: 1
・ Wa> Sa
[0024]
Taking the above specific example, the size length La of the conductor pattern 5 is 3 mm. This is because the length Lb of the conductive pattern 6 of the flexible printed circuit board 2 is 1.5 mm. The width Wa of the conductor pattern 5 is about 110 μm, and the spacing between the arrangements of the conductor patterns 5 is about 60 μm.
[0025]
Next, the details of the structure of the flexible printed circuit board 2 will be described with reference to FIG. FIG. 4 is an enlarged view of the flexible printed circuit board 2. As shown in FIG. 4, a plurality of substantially rectangular conductor patterns 6 made of copper foil having a thickness of 18 μm are arranged in parallel on the side end portion 2 a of the flexible printed circuit board 2. Here, assuming that the length of the conductor pattern 6 is Lb, the width is Wb, and the spacing of the arrangement of the conductor patterns 6 is Sb, as an example of Lb, Wb, and Sb, the length Lb of the conductor pattern 6 is 1.5 mm. The width Wb of the conductor pattern 6 is about 55 μm, and the spacing between the arrangement of the conductor patterns 6 is about 115 μm.
[0026]
Next, the cross-sectional structures of the drive circuit board 1 and the flexible printed circuit board 2 will be described with reference to FIGS. 5 is a cross-sectional view of the drive circuit board 1 taken along the line AA ′ in FIG. 3. FIG. 6 is a cross-sectional view of the flexible printed circuit board 2 taken along the line BB ′ in FIG. It is sectional drawing.
[0027]
As shown in FIG. 5, the drive circuit board 1 is provided with a conductive pattern 5 made of copper foil on the surface of a circuit board base 3 made of epoxy resin. The conductor pattern 5 is formed on the surface of the circuit board substrate 3 by a photoetching method.
[0028]
Further, as shown in FIG. 6, the flexible printed circuit board 2 has a copper foil conductor layer 6 ′ having a thickness of 18 μm formed on a polyimide resin base material 7 having a thickness of 25. On the top, a polyimide polyimide cover layer 8 having a thickness of 25 is provided, avoiding the conductor pattern 6 at the tip of the conductor layer 6 ′. Accordingly, the conductor pattern 6 is exposed on the side end portion 2a side of the flexible printed circuit board 2 by the length Lb.
[0029]
The size of the flexible printed circuit board 2 and the interval (pitch) between the conductor patterns 6 are determined in consideration of the thermal expansion of polyimide based on 180 degrees Celsius, which is a temperature just before the solder is cured during soldering. Has been.
[0030]
Next, soldering between the drive circuit board 1 and the flexible printed circuit board 2 will be described with reference to FIGS. FIG. 7 is a plan view showing a state in which the flexible printed circuit board 2 is overlaid on the drive circuit board 1, and FIG. 8 is a cross-sectional view showing a state in which the flexible printed circuit board 2 is soldered to the drive circuit board 1. There, FIG. 9 is a sectional view showing a state in which bending of the flexible printed circuit board 2 which is soldered to the drive circuit board 1.
[0031]
First, before the soldering operation, as a preliminary process, the conductor pattern 5 of the drive circuit board 1 is plated with gold so as to improve the electrical conductivity of the surface of the conductor pattern 5 and improve the soldering. It is. Next, solder plating is performed on the surface of the conductor pattern 6 of the flexible printed circuit board 2, and the solder plating is heated and melted again to join the conductor pattern 5 of the drive circuit board 1. .
[0032]
Next, as shown in FIG. 7, the conductor pattern 5 of the drive circuit board 1 is placed on the upper surface, and the conductor pattern 6 of the flexible printed circuit board 2 is faced down and overlaid thereon. At this time, since the flexible printed circuit board 2 is made of a polyimide resin material having a thickness of 25 μm, the conductor pattern 6 and the conductor pattern 5 of the drive circuit board 1 can be seen through from the back side. The conductor pattern 5 on the substrate 1 and the conductor pattern 6 on the flexible printed circuit board 2 are aligned.
[0033]
At this time, as shown in FIG. 7, a predetermined amount of the base portion of the conductor pattern 5 is exposed to form an exposed portion 5a. This is because excess solder melted at the time of soldering escapes to the exposed portion 5a.
[0034]
Further, when the conductor pattern 6 of the flexible printed circuit board 2 is overlaid on the conductor pattern 5 of the drive circuit board 1, a part of the cover layer 8 is part of the conductor pattern 5 of the drive circuit board 1 as shown in FIG. 8. (Hereinafter referred to as “overlapping portion of the cover layer”). Specifically, as shown in FIG. 8, when the length of the overlapping portion of the cover layer is Lo, the thickness of the entire drive circuit board 1 is Ta, and the total thickness of the flexible printed circuit board 2 is Tb, Lo is The length is not less than Ta, and Lo is not less than Tb.
[0035]
Next, as shown in FIG. 8, the heater bar 10 for melting the solder is heated from the back surface of the conductor pattern 6 of the flexible printed circuit board 2 to 180 degrees Celsius or more. Then, the solder plated on the conductor pattern 6 of the flexible printed circuit board 2 is melted. Next, when the heater bar 10 is separated from the back surface of the conductor pattern 6 of the flexible printed circuit board 2, the solder temperature is lowered below 180 degrees Celsius, and the solder is solidified so that the conductor pattern 5 of the drive circuit board 1 and the flexible printed circuit board 2 conductor patterns 6 are joined.
[0036]
At this time, since the length La of the conductor pattern 5 is longer than the length Lb of the conductor pattern 6, as shown in FIG. 7, the base portion of the conductor pattern 5 of the drive circuit board 1 has Since the exposed portion 5a is formed and excess solder is held by the exposed portion 5a due to surface tension during soldering, the adjacent conductor patterns 5 and the conductor patterns 6 may be bridged by the solder. Absent.
[0037]
The width of the conductor pattern 5 of the drive circuit board 1 is wider than the interval of the conductor pattern 5, and the width of the conductor pattern 6 of the flexible printed circuit board 2 is shorter than the interval of the conductor pattern 6. As a result, the conductor pattern 5 on the drive circuit board 1 and the conductor pattern 6 on the flexible printed circuit board 2 can be easily aligned. Further, even if there is expansion due to heat during soldering, the pattern is less likely to shift.
[0038]
Further, as shown in FIG. 8, the length of the overlapping portion of the cover layer is set to Lo equal to or greater than the thickness Ta of the entire drive circuit board 1, and the length of the overlapping portion of the cover layer is set to Lo. Since the length of the entire substrate 2 is equal to or greater than the thickness Tb, even when the flexible printed circuit board 2 is folded in the vicinity of the drive circuit board 1 after soldering, as shown in FIG. The bending radius is increased, the stress generated at the edge of the side end portion 1a of the drive circuit board 1 is relieved, and the conductor layer 6 ′ of the flexible printed circuit board 2 can be prevented from being cut.
[0039]
The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible. For example, in the above-described embodiment, the drive circuit board 1 and the flexible printed circuit board 2 are joined. As described above, it goes without saying that the present invention can be applied to the connection of the circuit board of the actuator of the print head and other various circuit boards as long as the flexible printed circuit board is joined by soldering. Needless to say, the present invention is not limited to an ink jet printer and can be applied to circuit boards of various devices.
[0040]
【The invention's effect】
As described above, in the invention according to claim 1, each conductor pattern of the circuit board has a first predetermined width and is arranged in parallel at a first predetermined interval, and the first predetermined width is: Each conductor pattern of the flexible printed circuit board is larger than the first predetermined interval, has a second predetermined width, and is arranged in parallel at the second predetermined interval, and the second predetermined width is equal to the second predetermined width. Since it is configured to be smaller than the predetermined interval , when the flexible printed circuit board is joined to the circuit board by soldering, each conductor pattern of the flexible printed circuit board can be accurately joined to each conductor pattern of the circuit board. .
[0041]
Furthermore , since the length of each conductor pattern of the circuit board is longer than the length of each conductor pattern of the flexible printed circuit board , an exposed portion is formed in each of the plurality of conductor patterns of the circuit board, and excess solder is formed. It is held by the exposed portion and does not overflow from each conductor pattern of the circuit board.
[0042]
The joining structure according to claim 2, in addition to the effect of the invention according to claim 1, the ratio of the length of the conductor patterns of the length of the conductor patterns of the circuit board and the flexible printed circuit board The conductor pattern of the circuit board is sufficiently long compared to the length of each conductor pattern of the flexible printed circuit board, and the solder melted during soldering is held in the exposed portion. There is no overflow from each conductor pattern.
[0043]
According to a third aspect of the present invention, in addition to the effect of the first or second aspect, the second predetermined width of the conductor pattern of the flexible printed circuit board is the conductor pattern of the circuit board. When the flexible printed circuit board is joined to the circuit board by soldering, the flexible printed circuit is smaller than the first predetermined width and the second predetermined interval is larger than the first predetermined interval. Each conductor pattern on the board can be accurately bonded to each conductor pattern on the circuit board.
[0044]
The joining structure according to claim 4, in addition to the effect of the invention according to either the claims 1 to 3, after the soldering, when bending the flexible printed circuit board in the vicinity of the circuit board In addition, the bending radius of the bent portion is increased, the stress generated at the edge of the side end portion of the circuit board is relieved, and the conductor layer of the flexible printed circuit board can be prevented from being cut.
[Brief description of the drawings]
FIG. 1 is a plan view of a drive circuit board 1 for a print head of an ink jet printer according to an embodiment of the present invention.
FIG. 2 is a plan view of the flexible printed circuit board 2 bonded to the drive circuit board 1;
FIG. 3 is an enlarged view of a side end 1a of the drive circuit board 1. FIG.
FIG. 4 is an enlarged view of the flexible printed circuit board 2;
FIG. 5 is a cross-sectional view of the drive circuit board 1 in the direction of the arrows along the line AA ′ in FIG. 3;
6 is a cross-sectional view of the flexible printed circuit board 2 in the direction of the arrows along the line BB ′ in FIG. 4;
FIG. 7 is a plan view showing a state in which a flexible printed circuit board 2 is overlaid on a drive circuit board 1;
FIG. 8 is a cross-sectional view showing a state in which a flexible printed circuit board 2 is soldered to a drive circuit board 1;
FIG. 9 is a cross-sectional view showing a state where the flexible printed circuit board 2 soldered to the drive circuit board 1 is bent.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Drive circuit board 1a Side edge part 2 Flexible printed circuit board 2a Side edge part 3 Circuit board base material 4 Drive IC
5 Conductor Pattern La Length Wa Width Sa Interval 6 Conductor Pattern Lb Length Wb Width Sb Interval 6 ′ Conductor Layer 7 Base Material 8 Cover Layer 10 Heater Bar

Claims (4)

フレキシブルプリント回路基板の複数の導体パターンと回路基板の複数の導体パターンとを半田付けにより接合する接合構造であって、
前記回路基板の前記各導体パターンは、第１の所定幅を有し、第１の所定間隔で複数平行に配列され、前記第１の所定幅は、前記第１の所定間隔よりも大きく、
前記回路基板の前記各導体パターンと対向する前記フレキシブルプリント回路基板の前記各導体パターンは、第２の所定幅を有し、第２の所定間隔で複数平行に配列され、前記第２の所定幅は、前記第２の所定間隔よりも小さく、
前記回路基板の前記各導体パターンの長さは、前記フレキシブルプリント回路基板の前記各導体パターンの長さよりも長く形成され、
前記フレキシブルプリント回路基板の前記複数の導体パターンを前記回路基板の複数の導体パターンに対向して半田付けしたときに、前記回路基板の前記複数の導体パターンの各々には、前記フレキシブルプリント回路基板の導体パターンに対向しない露出部分が形成されていることを特徴とする接合構造。A joining structure for joining a plurality of conductor patterns of a flexible printed circuit board and a plurality of conductor patterns of a circuit board by soldering,
Each of the conductor patterns of the circuit board has a first predetermined width and is arranged in parallel at a first predetermined interval, and the first predetermined width is larger than the first predetermined interval,
Each of the conductor patterns of the flexible printed circuit board facing the conductor patterns of the circuit board has a second predetermined width, and is arranged in parallel at a second predetermined interval, and the second predetermined width. Is smaller than the second predetermined interval,
The length of each conductor pattern of the circuit board is formed longer than the length of each conductor pattern of the flexible printed circuit board,
When the plurality of conductor patterns of the flexible printed circuit board are soldered opposite to the plurality of conductor patterns of the circuit board, each of the plurality of conductor patterns of the circuit board includes the flexible printed circuit board A bonding structure characterized in that an exposed portion that does not face the conductor pattern is formed . 前記回路基板の各導体パターンの長さと前記フレキシブルプリント回路基板の各導体パターンの長さの比は、略２対１であることを特徴とする請求項１に記載の接合構造。 Junction structure of claim 1, wherein the ratio of the length of the conductor patterns of the length and the flexible printed circuit board of the conductor pattern is about 2: 1 of the circuit board. 前記フレキシブルプリント回路基板の導体パターンの前記第２の所定幅は、前記回路基板の導体パターンの前記第１の所定幅よりも小さく、前記第２の所定間隔は、前記第１の所定間隔よりも大きいことを特徴とする請求項１又は２に記載の接合構造。The second predetermined width of the conductor pattern of the flexible printed circuit board is smaller than the first predetermined width of the conductor pattern of the circuit board, and the second predetermined interval is larger than the first predetermined interval. The joining structure according to claim 1, wherein the joining structure is large. 前記フレキシブルプリント回路基板の各導体パターンの表面の半田付けされる部分以外の部分に、カバー層が形成され、A cover layer is formed on a portion other than the portion to be soldered on the surface of each conductor pattern of the flexible printed circuit board,
当該カバー層が、前記回路基板の導体パターンに重なる部分の長さは、前記回路基板の厚み以上であることを特徴とする請求項１乃至３のいずれかに記載の接合構造。  The joining structure according to any one of claims 1 to 3, wherein a length of a portion where the cover layer overlaps a conductor pattern of the circuit board is equal to or greater than a thickness of the circuit board.
JP2000210519A 2000-07-11 2000-07-11 Bonding structure of circuit board and flexible printed circuit board Expired - Fee Related JP3900800B2 (en)

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