JP3813766B2

JP3813766B2 - Printed circuit board connection structure

Info

Publication number: JP3813766B2
Application number: JP19450699A
Authority: JP
Inventors: 晶英佐藤
Original assignee: 秋田日本電気株式会社
Priority date: 1999-07-08
Filing date: 1999-07-08
Publication date: 2006-08-23
Anticipated expiration: 2019-07-08
Also published as: JP2001024300A

Description

【０００１】
【発明の属する技術分野】
本発明は、プリント配線基板の接続構造に関し、特にフレキシブルプリント配線基板とリジッドプリント配線基板の接続構造に関する。
【０００２】
【従来の技術】
近年ポリイミドフィルムのような可撓性を有するフレキシブルプリント配線基板（以下、フレキシブル基板）は、空間を有効利用できるために基板同士を接続する手段、特にフレキシブル基板とは呼べないようなリジッドなプリント配線基板（以下、リジッド基板）間の接続や、半導体装置を搭載してリジッド基板に接続するためのＴＡＢ式基板として各種電子装置に広く使用されている。
【０００３】
従来、フレキシブル基板をリジッド基板に接続する方法としては、これらの二つの基板の端子間を半田や導電性ペーストで接続する方法があるが、これらの方法は最近の狭小化された端子を有する基板間の接続には端子間が半田や導電ペーストでショートを起こしやすいためにこれらの方法に代わって異方性導電接着剤を使用した接続方法が開発され使用されるようになった。
【０００４】
図７は、特開平５―７４８５０号公報（第1の従来例）に開示されている異方性導電接着剤を使用して半導体装置を搭載したフレキシブル基板をガラス基板（リジッド基板）に接続する例である。図６に示すように、電極パターン１５を設けたガラス基板１４と、対向するフレキシブル基板１６にリード１７とリードよりも厚い凸部（絶縁層）１８を設け、フレキシブル基板１６の凹んだリード１７に電極パターン１５をかみ合わせ、異方性導電接着剤（表示していない）を用いて接続をはかる構成である。
【０００５】
図８は特開平５―２２６８０１号公報（第２の従来例）で開示されているリジッド基板同士を接続する方法で、フレキシブル基板とリジッド基板の接続にも応用できる方法であり、液晶表示パネル１９のガラス基板２０（リジッド基板）の接続端子２１に、これにガラス基板２３製の回路基板２２（リジッド基板）の接続端子２５（絶縁膜２４上にめっき等で形成）を異方性導電接着剤２８（絶縁性接着剤２７に導電性微粒子２６を分散させたもの）で接続した例である。
【０００６】
また、図９は特開平７―９２９２０号公報（第３の従来例）に開示されている液晶表示パネル２９のガラス基板３０（リジッド基板）の接続端子３１にＴＣＰ(テーブキャリアパッケージ)３２（フレキシブル基板）の接続端子３３を異方性導電接着剤で接続する例である。異方性導電接着剤としては合成樹脂膜３４中に導電粒子３５と導電粒子３５よりも粒径の小さい絶縁粒子３６を混入したものが使用されている。
【０００７】
【発明が解決しようとする課題】
上記の第１の従来例では、フレキシブル基板１６のリード間に凸部（絶縁層）１８を設け、ガラス基板１４の電極パターン１５との位置合わせを容易化しているが、異方性導電接着剤を挟み込む時に混入した導電性異物により、電極パターン（リード）間に電気的なショートが発生する可能性がある。本技術においては、フレキシブル基板１６のリード１７とガラス基板１４の電極パターン１５間の距離は凸部（絶縁層）１８の高さで規制されることになり、異方性導電接着剤の塗布量のバラツキにより電極パターン１５とリード１７間の接続抵抗にバラツキが生じやすい問題があり、また両基板間の異方性導電性接着剤の量が少ないために両基板の機械的な接続強度が低下する問題があった。
【０００８】
上記の第２の従来例では、異方性導電接着剤２８を挟み込む時に混入した導電性異物により接続端子間に電気的なショートが発生する問題や両基板間の合わせずれが大きくなる問題があった。
【０００９】
また、上記の第３の従来例では、異方性導電接着剤の合成樹脂膜３４中に導電粒子３５よりも小さな絶縁粒子３６の添加により、導電粒子３５同士が隣接端子間で接触しあいリーク(短絡による電気的な漏れ)が発生することを防止しているが、ＴＣＰ３２と液晶パネル２９の合わせずれの問題や上記の二つの公報の技術と同様に、異方性導電接着剤を液晶表示パネルとＴＣＰの間に挟み込む時に混入する導電性異物により隣接した接続端子間の電気的なショートが発生する可能性があった。
【００１０】
また、上記の技術にはその他次のような共通的な問題点があった。
（１）フレキシブル基板の基材により接続端子が見えないために、各々の接続端子を目合わせする時に個別にアライメントマークを設ける必要があった。また、目視による出来映え確認が難しかった。
（２）リジッド基板とフレキシブル基板の熱膨張率が大きく、熱圧着時に各々が熱伸縮し、接続端子の位置ずれが生じる。このときにずれを規制するものが無いためにずれた状態で異方性導電接着剤が熱硬化し、電気的なオープン・ショートの原因となっていた。
【００１１】
本発明の目的は、上記のような異方性導電接着剤を使用する基板接続技術の問題点を解決したフレキシブル基板とリジット基板の接続構造を提供することである。
【００１２】
【課題を解決するための手段】
本発明は、フレキシブル基板の接続端子とリジッド基板の接続端子を対向させて異方性導電接着剤で電気的に接続したプリント配線基板の接続構造において、前記リジッド基板の前記接続端子間に設けられた凸状絶縁体が、対向する前記フレキシブル基板の前記接続端子間に前記フレキシブル基板を貫通して設けられた貫通孔に挿入し、前記異方性導電接着剤で前記フレキシブル基板の前記接続端子とそれに対向する前記リジッド基板の前記接続端子が電気的に接続されていることを特徴として構成される。
【００１３】
前記凸状絶縁体の厚さは、前記リジッド基板の前記接続端子の厚さと前記フレキシブル基板の前記接続端子の厚みよりも厚く、前記リジッド基板の前記接続端子の厚さと前記フレキシブル基板の厚みよりも薄くする構成とすることにより異方性導電接着剤と基板との接触面積を増加させて両基板間の機械的接続強度を向上し、また異方性導電接着剤表面等に付着した導電性異物を前記両基板の前記接続端子表面から隔離でき導電性異物による前記接続端子間のショートを防止することができる。
【００１４】
前記凸状絶縁体を前記リジッド基板の前記接続端子間に設け、これを前記フレキシブル基板の前記接続端子間に設けた貫通孔に挿入して前記異方性導電接着剤で両基板を接続するようにすることにより両基板の対応する端子同士の合わせずれを低減できることができる。
【００１５】
【発明の実施の形態】
本発明の第１の実施の形態のフレキシブル基板とリジッド基板の接続構造（以下、基板接続構造という）について図面を参照して説明する。
【００１６】
図１は本発明の第１の実施の形態の基板接続構造を示す拡大断面図である。図中符号１はリジッド基板、２はリジッド基板の基材である。また、符号３はリジッド基板の表面に形成された接続端子であり、符号４はリジッド基板１の接続端子間に形成された凸状絶縁体である。
【００１７】
図中符号５はフレキシブル基板、６はその基材、７はフレキシブル基板５をリジッド基板１に接続するための接続端子である。また、符号８は両基板の端子間を電気的に接続するための異方性導電接着剤であり、符号１０はフレキシブル基板５の貫通孔であり、フレキシブル基板５の接続端子７間に基材６を貫通して設けられる。
【００１８】
図１のように本発明の第１の実施の形態では、リジッド基板１の接続端子３間に設けられた凸状絶縁体４がフレキシブル基板５の接続端子７側から貫通孔１０に挿入され、異方性導電接着剤８をフレキシブル基板５の接続端子７と反対面から貫通孔１０に熱溶融浸入させて両基板の接続端子３，７間に挟み込み熱圧着させて両基板の端子間を異方性導電接着剤８を介して電気的に接続した構造を特徴とするものである。
【００１９】
図２は図１のリジッド基板１の構造を示す概略図であり、（ａ）は平面図、（ｂ）は（ａ）のＡ―Ａ‘線に沿った断面図である。リジット基板１の基材には、ガラス繊維で強化されたエポキシ樹脂やポリイミド樹脂や透明ガラス基板等を使用でき、接続端子３は、銅箔をエッチングでパターニングし、その表面にニッケルめっきと金めっき等を施したものが使用される。
【００２０】
リジッド基板１の接続端子３間に設けた凸状絶縁体４は感光性レジストのフォトリソグラフィによるパターニングや熱硬化性レジストのレーザ光による微細加工により形成され、フレキシブル基板５の貫通孔１０に挿入できるサイズで矩形体または四角錘台の形状をしている。このときの凸状絶縁体４の厚さは、リジッド基板１の接続端子３の厚みにフレキシブル基板５（図３参照）の接続端子７の厚みを加えたものよりも厚く、リジッド基板１の接続端子３の厚みとフレキシブル基板５の厚み(端子+基材)を加えたものよりも薄くする必要がある。凸状絶縁体４の厚さがリジッド基板の接続端子の厚みにフレキシブル基板の接続端子の厚みを加えたものよりも厚くリジッド基板の接続端子の厚みにフレキシブル基板の接続端子の厚みを加えたものよりも薄くなると凸状絶縁体表面に押しやられる導電性異物により端子間のショートは発生しやすくなる。また凸状絶縁体４の厚さが、リジッド基板の接続端子の厚みとフレキシブル基板の厚み(端子+基材)を加えたものよりも厚くなると両基板間で異方性導電接着剤の導電粒子を潰す為に必要な加圧力が不足するので好ましくない。
【００２１】
なお、凸状絶縁体４形成用の感光性レジストや熱硬化性レジストとしてはエポキシ樹脂系レジストを使用することができる。
【００２２】
接続端子３の両側には接続端子３に接続する配線等を保護するためにレジスト９が被覆されるが、レジスト９には、凸状絶縁体４形成用の感光性レジストや熱硬化性レジストを使用することができる。
【００２３】
図３は図１のフレキシブル基板５の構造を示す概略図であり、（ａ）は平面図、（ｂ）は（ａ）のＡ―Ａ‘線に沿った断面図である。フレキシブル基板５の基材には、可撓性のすぐれたポリイミド樹脂等が使用される。接続端子７は、銅箔をエッチングでパターニングし、その表面にニッケルめっきと金めっき等を施したものが使用される。貫通孔１０はパンチング加工等で接続端子７間に図２のリジッド基板１の凸状絶縁体４が挿入できるサイズに加工される。なお、フレキシブル基板５側を櫛歯状にすると、そのフレキシブル性のため接続部が変形する懸念があるので、基材に貫通孔を設けただけの構成としている。
【００２４】
図４は、図１の本発明の第１の実施の形態の基板接続構造を形成する方法を説明するための概略断面図である。
【００２５】
図４を参照して第１の実施の形態の基板接続構造形成方法について詳細に説明する。まず、図２に示した構造のリジッド基板１に厚さ３０〜５０μｍのフィルム状の異方性導電性接着剤８をセットする。
【００２６】
次いで、異方性導電接着剤８上に図３の構造のフレキシブル基板とクッション材１２を順次セットした後、ヒートツール１１でクッション材１２表面から異方性導電性接着剤８が再溶融して硬化する温度で所定の時間加圧加熱し、異方性導電接着剤８で両基板の端子間を電気的に接続する。この方法により図１の基板接続構造を得ることができる。なお、異方性導電接着剤８のバインダ樹脂には熱硬化性のエポキシ樹脂やウレタン樹脂が使用でき、また異方性導電接着剤８の導電粒子には、ニッケル等の金属粒子またはアクリル系樹脂球にニッケルや金めっきを施したものやさらにこれらに絶縁コートした直径４〜８μｍの粒子が使用される。
【００２７】
図５は従来の基板接続構造と本発明の基板接続構造を比較した基板要部の拡大断面図である。図５からわかるように、本発明（図５（ｂ）参照）では、従来の基板接続構造（図５（ａ）参照）と比較して次のような優れた効果を得ることができる。
（１）リジッド基板の凸状絶縁体とフレキシブル基板の貫通孔を位置ずれの規制に使用することが可能となり、ずれによる電気的なオープン・ショートが無くなる。
（２）隣接する接続端子間の導電性異物１３を凸状絶縁体４で端子間から押しのけることにより電気的なショートを防ぐことが可能となる。
（３）異方性導電接着剤８のフレキシブル基板５及びリジッド基板１と接触する面積が従来構成と比較すると大幅に増えることで機械的な接続強度を保たせることが可能となる。
（４）フレキシブル基板５の貫通孔１０によりフレキシブル基板とリジッド基板１の接続端子７間の目合わせによる位置決め及び出来映え確認が容易となる。
【００２８】
次に本発明の第２の実施の形態の基板接続構造について図６を参照して説明する。本発明の実施の形態では、上記の第１の実施の形態においてリジッド基板１の接続端子３間に設けた凸状絶縁体４の形状をその断面形状が階段形状になるように形成した場合であり、接続構造は第１の実施の形態と同様な工程で形成される。
【００２９】
リジッド基板１の接続端子３間に設けた凸状絶縁体４はエポキシ樹脂系の感光性レジストのフォトリソグラフィによるパターニングや熱硬化性エポキシ樹脂の硬化樹脂膜のレーザ加工による微細加工により形成され、フレキシブル基板５の貫通孔１０に挿入できるサイズで矩形体または四角錘台の形状をしている。このときの凸状絶縁体４の全体の厚さは、上記の第１の実施の形態と同様にリジッド基板１の接続端子３の厚みにフレキシブル基板５（図５参照）の接続端子７の厚みを加えたものよりも厚く、リジッド基板１の接続端子３の厚みとフレキシブル基板５の厚み(端子+基材)を加えたものよりも薄くする必要がある。凸状絶縁体４の厚さがリジッド基板の接続端子の厚みにフレキシブル基板の接続端子の厚みを加えたものよりも厚くリジッド基板の接続端子の厚みにフレキシブル基板の接続端子の厚みを加えたものよりも薄くなると凸状絶縁体表面に押しやられる導電性異物により端子間のショートは発生しやすくなる。また凸状絶縁体４の厚さが、リジッド基板の接続端子の厚みとフレキシブル基板の厚み(端子+基材)を加えたものよりも厚くなると両基板間で異方性導電接着剤の導電粒子を潰すために必要な加圧力が不足するので好ましくない。
【００３０】
本実施の形態では、凸状絶縁体４の形状をその断面形状が階段形状になるように形成することにより上記第１の実施の形態と比較して、異方性導電接着剤との接触面積をさらに増加させることができ、機械的接続強度を向上できる効果がある。
【００３１】
【発明の効果】
以上説明したように本発明では次のような効果を得ることができる。
（１）フレキシブル基板に貫通孔を設けたために、熱圧着前の目合わせによる位置決め及び熱圧着後の出来映え確認が容易となる。
（２）フレキシブル基板の貫通孔にプリント基板の凸状絶縁体を熱圧着時に挿入することで、熱圧着時の熱伸縮等による各々の基板の端子ずれが規制され、端子ずれによる電気的なオープン・ショートの発生を防止できる。
（３）フレキシブル基板の貫通孔にプリント基板の凸状絶縁体を熱圧着時に挿入することで、異方性導電接着剤を挟み込むときに混入した導電異物を隣接する端子間から押しのけることができ、電気的なショートの発生を防止できる。
（４）熱圧着時に異方性導電接着剤がフレキシブル基板の貫通孔の側面とプリント基板の凸状絶縁体の周囲に付着するために異方性導電接着剤の基板との接着する面積が増え、両基板と異方性導電接着剤機械的な接続強度を向上することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の基板接続構造を示す断面拡大図である。
【図２】本発明の第１の実施の形態の基板接続構造に使用されるリジッド基板の構造断面図である。
【図３】本発明の第１の実施の形態の基板接続構造に使用されるフレキシブル基板の構造断面図である。
【図４】本発明の第１の実施の形態の基板接続構造の形成方法を説明するための概略断面図である。
【図５】従来の基板接続構造と本発明の基板接続構造を比較した基板要部の拡大断面図である。
【図６】本発明の第２の実施の形態の基板接続構造を示す断面拡大図である。
【図７】従来の第1の基板接続構造例を示す断面拡大図である。
【図８】従来の第２の基板接続構造例を示す断面拡大図である。
【図９】従来の第３の基板接続構造例を示す断面拡大図である。
【符号の説明】
１リジッド基板
２，６基材
３，７，２１，２５，３１，３３接続端子
４凸状絶縁体
５，１６フレキシブル基板
８，２８異方性導電接着剤
９レジスト
１０貫通孔
１１ヒートツール
１２クッション
１３導電性異物
１４，２０，２３，３０ガラス基板
１５電極パターン
１７リード
１８凸部（絶縁層）
１９，２９液晶表示パネル
２２回路基板
２４絶縁膜
２６導電性微粒子
２７絶縁性接着剤
３２ＴＣＰ
３４合成樹脂膜
３５導電粒子
３６絶縁粒子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a connection structure for a printed wiring board, and more particularly to a connection structure for a flexible printed wiring board and a rigid printed wiring board.
[0002]
[Prior art]
In recent years, flexible printed wiring boards having flexibility such as polyimide films (hereinafter referred to as flexible boards) are means for connecting the boards to each other because space can be used effectively, especially rigid printed wiring that cannot be called flexible boards. It is widely used in various electronic devices as a TAB type substrate for connecting between substrates (hereinafter referred to as rigid substrates) or mounting a semiconductor device to connect to a rigid substrate.
[0003]
Conventionally, as a method of connecting a flexible substrate to a rigid substrate, there is a method of connecting the terminals of these two substrates with solder or conductive paste, but these methods are recent substrates having narrowed terminals. In connection with each other, a connection method using an anisotropic conductive adhesive has been developed and used instead of these methods because terminals are easily short-circuited with solder or conductive paste.
[0004]
FIG. 7 shows a method of connecting a flexible substrate mounted with a semiconductor device to a glass substrate (rigid substrate) using an anisotropic conductive adhesive disclosed in Japanese Patent Laid-Open No. 5-74850 (first conventional example). It is an example. As shown in FIG. 6, the glass substrate 14 provided with the electrode pattern 15, the lead 17 and the convex portion (insulating layer) 18 thicker than the lead are provided on the opposing flexible substrate 16, and the concave lead 17 of the flexible substrate 16 is provided. The electrode pattern 15 is engaged, and an anisotropic conductive adhesive (not shown) is used for connection.
[0005]
FIG. 8 shows a method of connecting rigid substrates disclosed in Japanese Patent Application Laid-Open No. 5-226801 (second conventional example), which is applicable to the connection between a flexible substrate and a rigid substrate. The connection terminal 21 of the circuit board 22 (rigid substrate) made of the glass substrate 23 (formed on the insulating film 24 by plating or the like) is connected to the connection terminal 21 of the glass substrate 20 (rigid substrate) of the anisotropic conductive adhesive. This is an example in which the connection is made with 28 (in which conductive fine particles 26 are dispersed in an insulating adhesive 27).
[0006]
FIG. 9 shows a TCP (Table Carrier Package) 32 (flexible) connected to the connection terminal 31 of the glass substrate 30 (rigid substrate) of the liquid crystal display panel 29 disclosed in Japanese Patent Application Laid-Open No. 7-92920 (third conventional example). This is an example in which the connection terminal 33 of the substrate is connected with an anisotropic conductive adhesive. As the anisotropic conductive adhesive, a synthetic resin film 34 in which conductive particles 35 and insulating particles 36 having a smaller particle diameter than the conductive particles 35 are mixed is used.
[0007]
[Problems to be solved by the invention]
In the first conventional example, the convex portion (insulating layer) 18 is provided between the leads of the flexible substrate 16 to facilitate the alignment with the electrode pattern 15 of the glass substrate 14, but the anisotropic conductive adhesive There is a possibility that an electrical short circuit may occur between the electrode patterns (leads) due to the conductive foreign matter mixed when sandwiching the electrode. In the present technology, the distance between the lead 17 of the flexible substrate 16 and the electrode pattern 15 of the glass substrate 14 is regulated by the height of the convex portion (insulating layer) 18, and the amount of the anisotropic conductive adhesive applied There is a problem in that the connection resistance between the electrode pattern 15 and the lead 17 is likely to vary due to variations in the resistance, and the mechanical connection strength between the two substrates is reduced due to the small amount of anisotropic conductive adhesive between the two substrates. There was a problem to do.
[0008]
In the second conventional example, there is a problem that an electrical short circuit occurs between the connection terminals due to the conductive foreign matter mixed when the anisotropic conductive adhesive 28 is sandwiched, and a problem that the misalignment between the two substrates becomes large. It was.
[0009]
In the third conventional example, addition of insulating particles 36 smaller than the conductive particles 35 in the synthetic resin film 34 of the anisotropic conductive adhesive causes the conductive particles 35 to contact each other between adjacent terminals and leak ( In the same way as the problem of misalignment between the TCP 32 and the liquid crystal panel 29 and the techniques of the above two publications, an anisotropic conductive adhesive is applied to the liquid crystal display panel. There is a possibility that an electrical short-circuit between adjacent connection terminals may occur due to conductive foreign matter mixed when sandwiched between TCP and TCP.
[0010]
In addition, the above technique has the following common problems.
(1) Since the connection terminals cannot be seen due to the base material of the flexible substrate, it is necessary to provide alignment marks individually when aligning the connection terminals. Also, it was difficult to confirm the workmanship by visual inspection.
(2) The thermal expansion coefficient of the rigid substrate and the flexible substrate is large, and each of them is thermally expanded and contracted at the time of thermocompression bonding, resulting in displacement of the connection terminals. At this time, since there is nothing that regulates the deviation, the anisotropic conductive adhesive is thermally cured in the displaced state, causing an electrical open / short circuit.
[0011]
The objective of this invention is providing the connection structure of the flexible board | substrate and rigid board | substrate which solved the problem of the board | substrate connection technique using the above anisotropic conductive adhesives.
[0012]
[Means for Solving the Problems]
The present invention provides a printed wiring board connection structure in which a connection terminal of a flexible board and a connection terminal of a rigid board are opposed to each other and electrically connected with an anisotropic conductive adhesive, and is provided between the connection terminals of the rigid board. convex insulator is inserted into the through hole provided through the flexible substrate between the connecting terminals of the flexible substrate facing the said connecting terminals of the flexible substrate with the anisotropic conductive adhesive The connection terminal of the rigid board facing the electrical connection is electrically connected.
[0013]
The thickness of the convex insulator is larger than the thickness of the connection terminal of the rigid board and the thickness of the connection terminal of the flexible board, and more than the thickness of the connection terminal of the rigid board and the thickness of the flexible board. By making it thin, the contact area between the anisotropic conductive adhesive and the substrate is increased to improve the mechanical connection strength between the two substrates, and the conductive foreign matter adhered to the surface of the anisotropic conductive adhesive, etc. Can be isolated from the surfaces of the connection terminals of the two substrates, and a short circuit between the connection terminals due to conductive foreign matter can be prevented.
[0014]
The convex insulator is provided between the connection terminals of the rigid substrate, and is inserted into a through hole provided between the connection terminals of the flexible substrate so that the two substrates are connected with the anisotropic conductive adhesive. Thus, the misalignment between the corresponding terminals of both substrates can be reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A connection structure between a flexible substrate and a rigid substrate (hereinafter referred to as a substrate connection structure) according to a first embodiment of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is an enlarged sectional view showing a substrate connection structure according to a first embodiment of the present invention. In the figure, reference numeral 1 is a rigid substrate, and 2 is a base material of the rigid substrate. Reference numeral 3 denotes a connection terminal formed on the surface of the rigid substrate, and reference numeral 4 denotes a convex insulator formed between the connection terminals of the rigid substrate 1.
[0017]
In the figure, reference numeral 5 is a flexible substrate, 6 is its base material, and 7 is a connection terminal for connecting the flexible substrate 5 to the rigid substrate 1. Reference numeral 8 is an anisotropic conductive adhesive for electrically connecting the terminals of both substrates, reference numeral 10 is a through hole of the flexible substrate 5, and a base material is provided between the connection terminals 7 of the flexible substrate 5. 6 is provided.
[0018]
In the first embodiment of the present invention as shown in FIG. 1, the convex insulator 4 provided between the connection terminals 3 of the rigid substrate 1 is inserted into the through hole 10 from the connection terminal 7 side of the flexible substrate 5, The anisotropic conductive adhesive 8 is hot-melted into the through-hole 10 from the opposite side of the connection terminal 7 of the flexible substrate 5 and is sandwiched between the connection terminals 3 and 7 of both substrates to be thermocompression-bonded so that the terminals of both substrates are different. It is characterized by a structure in which it is electrically connected via an isotropic conductive adhesive 8.
[0019]
2A and 2B are schematic views showing the structure of the rigid substrate 1 of FIG. 1, wherein FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along the line AA ′ of FIG. The base material of the rigid substrate 1 can be an epoxy resin reinforced with glass fiber, a polyimide resin, a transparent glass substrate, or the like, and the connection terminal 3 is patterned by etching a copper foil, and nickel plating and gold plating on the surface thereof Etc. are used.
[0020]
The convex insulator 4 provided between the connection terminals 3 of the rigid substrate 1 is formed by photolithography patterning of a photosensitive resist or fine processing by laser light of a thermosetting resist, and can be inserted into the through hole 10 of the flexible substrate 5. It is rectangular or square frustum in size. The thickness of the convex insulator 4 at this time is larger than the thickness of the connection terminal 3 of the rigid substrate 1 plus the thickness of the connection terminal 7 of the flexible substrate 5 (see FIG. 3). It is necessary to make it thinner than the sum of the thickness of the terminal 3 and the thickness of the flexible substrate 5 (terminal + base material). Thickness of the convex insulator 4 is thicker than the thickness of the connection terminal of the rigid board added to the thickness of the connection terminal of the rigid board, and the thickness of the connection terminal of the rigid board is added to the thickness of the connection terminal of the rigid board If the thickness is smaller than that, a short circuit between the terminals is likely to occur due to the conductive foreign material pushed to the surface of the convex insulator. Further, when the thickness of the convex insulator 4 becomes thicker than the sum of the thickness of the connection terminal of the rigid substrate and the thickness of the flexible substrate (terminal + base material), the conductive particles of the anisotropic conductive adhesive between the two substrates This is not preferable because the pressure required for crushing is insufficient.
[0021]
An epoxy resin resist can be used as the photosensitive resist or thermosetting resist for forming the convex insulator 4.
[0022]
A resist 9 is coated on both sides of the connection terminal 3 to protect the wiring and the like connected to the connection terminal 3. The resist 9 is coated with a photosensitive resist or a thermosetting resist for forming the convex insulator 4. Can be used.
[0023]
3A and 3B are schematic views showing the structure of the flexible substrate 5 in FIG. 1, wherein FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view taken along the line AA ′ in FIG. For the base material of the flexible substrate 5, a polyimide resin or the like having excellent flexibility is used. As the connection terminal 7, a copper foil is patterned by etching, and the surface thereof is subjected to nickel plating, gold plating, or the like. The through hole 10 is processed to a size that allows the convex insulator 4 of the rigid substrate 1 of FIG. 2 to be inserted between the connection terminals 7 by punching or the like. In addition, when the flexible substrate 5 side is made into a comb-tooth shape, there exists a possibility that a connection part may deform | transform for the flexibility, Therefore It is set as the structure which provided the through-hole only in the base material.
[0024]
FIG. 4 is a schematic cross-sectional view for explaining a method of forming the substrate connection structure according to the first embodiment of the present invention shown in FIG.
[0025]
The substrate connection structure forming method of the first embodiment will be described in detail with reference to FIG. First, a film-like anisotropic conductive adhesive 8 having a thickness of 30 to 50 μm is set on the rigid substrate 1 having the structure shown in FIG.
[0026]
Next, after the flexible substrate having the structure shown in FIG. 3 and the cushion material 12 are sequentially set on the anisotropic conductive adhesive 8, the anisotropic conductive adhesive 8 is remelted from the surface of the cushion material 12 with the heat tool 11. Pressurize and heat at a curing temperature for a predetermined time, and the anisotropic conductive adhesive 8 electrically connects the terminals of both substrates. By this method, the substrate connection structure of FIG. 1 can be obtained. The binder resin of the anisotropic conductive adhesive 8 can be a thermosetting epoxy resin or urethane resin. The conductive particles of the anisotropic conductive adhesive 8 can be metal particles such as nickel or an acrylic resin. Particles having a diameter of 4 to 8 μm, which are obtained by applying nickel or gold plating to spheres and further insulatingly coating them, are used.
[0027]
FIG. 5 is an enlarged cross-sectional view of the main part of the substrate comparing the conventional substrate connection structure and the substrate connection structure of the present invention. As can be seen from FIG. 5, in the present invention (see FIG. 5B), the following excellent effects can be obtained as compared with the conventional substrate connection structure (see FIG. 5A).
(1) The convex insulator of the rigid substrate and the through hole of the flexible substrate can be used for positional displacement control, and electrical open / short due to the displacement is eliminated.
(2) An electrical short circuit can be prevented by pushing the conductive foreign material 13 between adjacent connection terminals from between the terminals by the convex insulator 4.
(3) Since the area of the anisotropic conductive adhesive 8 in contact with the flexible substrate 5 and the rigid substrate 1 is significantly increased as compared with the conventional configuration, the mechanical connection strength can be maintained.
(4) The through hole 10 of the flexible board 5 facilitates positioning and confirmation of workmanship between the flexible board and the connection terminal 7 of the rigid board 1.
[0028]
Next, a substrate connection structure according to a second embodiment of the present invention will be described with reference to FIG. In the embodiment of the present invention, the shape of the convex insulator 4 provided between the connection terminals 3 of the rigid substrate 1 in the first embodiment is formed so that the cross-sectional shape thereof is a stepped shape. Yes, the connection structure is formed in the same process as in the first embodiment.
[0029]
The convex insulator 4 provided between the connection terminals 3 of the rigid substrate 1 is formed by photolithography patterning of an epoxy resin-based photosensitive resist or fine processing by laser processing of a cured resin film of a thermosetting epoxy resin. A rectangular body or a square frustum is formed in a size that can be inserted into the through hole 10 of the substrate 5. The total thickness of the convex insulator 4 at this time is the same as the thickness of the connection terminal 3 of the rigid substrate 1 as in the first embodiment, but the thickness of the connection terminal 7 of the flexible substrate 5 (see FIG. 5). The thickness of the connection terminal 3 of the rigid substrate 1 and the thickness of the flexible substrate 5 (terminal + base material) are required to be thinner than those obtained by adding the thickness of the rigid substrate 1. Thickness of the convex insulator 4 is thicker than the thickness of the connection terminal of the rigid board added to the thickness of the connection terminal of the rigid board, and the thickness of the connection terminal of the rigid board is added to the thickness of the connection terminal of the rigid board If the thickness is smaller than that, a short circuit between the terminals is likely to occur due to the conductive foreign material pushed to the surface of the convex insulator. Further, when the thickness of the convex insulator 4 becomes thicker than the sum of the thickness of the connection terminal of the rigid substrate and the thickness of the flexible substrate (terminal + base material), the conductive particles of the anisotropic conductive adhesive between the two substrates This is not preferable because the pressurizing force necessary for crushing is insufficient.
[0030]
In the present embodiment, the contact area with the anisotropic conductive adhesive is formed in comparison with the first embodiment by forming the shape of the convex insulator 4 so that the cross-sectional shape thereof is a stepped shape. Can be further increased, and the mechanical connection strength can be improved.
[0031]
【The invention's effect】
As described above, the present invention can provide the following effects.
(1) Since the through hole is provided in the flexible substrate, positioning by alignment before thermocompression bonding and confirmation of workmanship after thermocompression bonding are facilitated.
(2) Inserting the convex insulator of the printed circuit board into the through hole of the flexible circuit board during thermocompression restricts terminal displacement of each substrate due to thermal expansion and contraction during thermocompression bonding.・ Short can be prevented.
(3) By inserting the convex insulator of the printed circuit board into the through hole of the flexible circuit board at the time of thermocompression bonding, the conductive foreign matter mixed in when sandwiching the anisotropic conductive adhesive can be pushed away between adjacent terminals, The occurrence of electrical shorts can be prevented.
(4) Since the anisotropic conductive adhesive adheres to the side surface of the through hole of the flexible substrate and the periphery of the convex insulator of the printed circuit board at the time of thermocompression bonding, the area where the anisotropic conductive adhesive adheres to the substrate increases. The mechanical connection strength between the two substrates and the anisotropic conductive adhesive can be improved.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing a substrate connection structure according to a first embodiment of the present invention.
FIG. 2 is a structural cross-sectional view of a rigid substrate used in the substrate connection structure according to the first embodiment of the present invention.
FIG. 3 is a structural sectional view of a flexible substrate used in the substrate connection structure according to the first embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view for explaining the method for forming the substrate connection structure according to the first embodiment of the present invention.
FIG. 5 is an enlarged cross-sectional view of the main part of the substrate comparing the conventional substrate connection structure and the substrate connection structure of the present invention.
FIG. 6 is an enlarged cross-sectional view showing a substrate connection structure according to a second embodiment of the present invention.
FIG. 7 is an enlarged cross-sectional view showing an example of a conventional first substrate connection structure.
FIG. 8 is an enlarged cross-sectional view showing a second conventional substrate connection structure example.
FIG. 9 is an enlarged cross-sectional view showing a third conventional substrate connection structure example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rigid board | substrate 2,6 Base material 3,7,21,25,31,33 Connection terminal 4 Convex insulator 5,16 Flexible board | substrate 8,28 Anisotropic conductive adhesive 9 Resist 10 Through-hole 11 Heat tool 12 Cushion 13 Conductive foreign matter 14, 20, 23, 30 Glass substrate 15 Electrode pattern 17 Lead 18 Convex part (insulating layer)
19, 29 Liquid crystal display panel 22 Circuit board 24 Insulating film 26 Conductive fine particles 27 Insulating adhesive 32 TCP
34 Synthetic resin film 35 Conductive particles 36 Insulating particles

Claims

In a printed wiring board connection structure in which a connection terminal of a flexible board and a connection terminal of a rigid board are opposed to each other and electrically connected with an anisotropic conductive adhesive, between the connection terminals on the flat rigid board , the rigid The connection of the flexible substrate facing the convex insulator, which is provided thicker than the sum of the thickness of the connection terminal of the substrate and the thickness of the connection terminal of the flexible substrate, and is formed of a material different from the rigid substrate Inserted in a through hole provided through the flexible substrate between the terminals, and the anisotropic conductive adhesive electrically connects the connection terminal of the flexible substrate and the connection terminal of the rigid substrate opposed thereto A printed wiring board connection structure characterized by the above.

The thickness of the convex insulator before SL and the thickness of the connection terminals of the rigid substrate, the printed wiring board of the thin claim 1, wherein than the sum of the connection thickness as the thickness of the flexible substrate terminals of the flexible substrate Connection structure.

The printed wiring board connection structure according to claim 1, wherein a shape of the convex insulator is a rectangular body, a square frustum, or a stepped shape thereof.

The printed wiring board connection structure according to claim 1, wherein the convex insulator is formed by photolithography patterning of a photosensitive resist or laser processing of a thermosetting resist.

The printed wiring board connection structure according to claim 4, wherein an epoxy resin resist is used as the photosensitive resist.

The printed wiring board connection structure according to claim 4, wherein an epoxy resin resist is used as the thermosetting resist.

The printed wiring board connection structure according to claim 1, wherein the connection terminals of the rigid board and the flexible board have a structure in which nickel plating and gold plating are sequentially coated on a copper foil.

The length of the through hole of the flexible substrate is the same as the length of the connection terminal of the flexible substrate, and the width of the through hole is larger than the width of the convex insulator of the rigid substrate. Printed wiring board connection structure.

The anisotropic conductive adhesive includes a surface of the convex insulator, between the connection terminal of the flexible board and the connection terminal of the rigid board opposed thereto, the through-hole wall, the side of the connection terminal of the flexible board, and The printed wiring board connection structure according to claim 1, wherein a side surface of the connection terminal of the rigid board is covered.

The printed wiring board connection structure according to claim 1, wherein a thermosetting epoxy resin or urethane resin is used as the binder resin of the anisotropic conductive adhesive.