JP2004200230A6

JP2004200230A6 - Implementation method

Info

Publication number: JP2004200230A6
Application number: JP2002363962A
Authority: JP
Inventors: 和也佐藤; 源太郎関; 正己湯佐
Original assignee: Hitachi Chemical Co Ltd; Showa Denko Materials Co Ltd; Resonac Corp
Current assignee: Resonac Corp
Filing date: 2002-12-16
Publication date: 2005-09-02
Anticipated expiration: 2022-12-16

Abstract

【課題】熱硬化型接着剤の反応性にかかわりなく、接続信頼性を損なうことなく、基板の反りを防止する実装方法を提供する。
【解決手段】相対向する電極を有する、基板と実装部品を熱硬化型接着剤を介在させ、相対向する基板と実装部品をステージとヘッドとの間で、加熱加圧して加圧方向の電極間を電気的に接続する回路の実装方法であって、実装部品の熱圧着開始より遅れて基板を加熱する実装方法。
【選択図】図３Provided is a mounting method for preventing warping of a substrate without impairing connection reliability irrespective of the reactivity of a thermosetting adhesive.
A substrate and a mounting component having electrodes facing each other, a thermosetting adhesive interposed therebetween, and the substrate and the mounting component facing each other are heated and pressed between a stage and a head in a pressing direction. A method of mounting a circuit that electrically connects the components, wherein the substrate is heated after the start of thermocompression bonding of the mounted component.
[Selection] Figure 3

Description

【０００１】
【発明の属する技術分野】
本発明は、基板と実装部品とを熱硬化型接着剤を介して熱圧着する実装方法に関する。
【０００２】
【従来の技術】
相対する多数の電極を有する被接続部材を接続するための接続材料として、異方導電性フィルム（ＡＣＦ）、異方導電性ペースト（ＡＣＰ）、非導電性フィルム（ＮＣＦ）等の熱硬化型接着剤を介して基板と実装部品とを熱圧着する方法が知られている。これらは、プリント配線基板、ＬＣＤ用ガラス基板、フレキシブルプリント基板等の基板や、ＩＣ、ＬＳＩ等の半導体素子やパッケージなどの実装部品を接続する際、相対する電極同士の導通状態を保ち、隣接する電極同士の絶縁を保つように電気的接続と機械的固着を行う。このような熱硬化型接着剤の多くは熱硬化性樹脂を含有する接着剤成分と、必要により配合される導電性粒子とを含みフィルム状に形成されており、ＰＥＴ（ポリエチレンテレフタレート）等の支持体に積層した状態で製品化されている。そして使用に際しては、熱硬化型接着剤を被接続部材に設け、熱硬化性樹脂を硬化させて部材間の機械的固着を得るとともに、対向する電極間を直接または導電性粒子を介して接触させて電気的接続を得ている。例えば、ＬＣＤ用ガラス基板にＩＣチップを実装するＣＯＧ（Chip On Glass）では、図１に示したように、ＬＣＤ用ガラス基板１上に熱硬化型接着剤２を介在させ、相対向する基板と実装部品３をステージ４とヘッド５との間で、加熱加圧して加圧方向の電極間を電気的に接続する。一般的にヘッド５の温度は、１５０〜３００℃とし、ステージ４は、加熱せず室温付近か、ヘッドから伝熱され伝熱量と放散量がつりあった温度とする場合や、媒体による温度調整をすることが多い。これは、基板と実装部品の電極の位置あわせの際に、熱硬化型接着剤２の熱硬化反応が始まるのを抑制するためであり、さらに、実装工程において熱圧着毎に接続温度がばらつくことを防止するため、熱硬化反応の開始温度以下となる６０℃以下に加温している。
液晶表示用ガラスパネルへの液晶駆動用ＩＣの実装は、液晶駆動用ＩＣの実装されたフレキシブルテープとガラスパネルとを回路接続部材で接合するＯＬＢ実装方法や、液晶駆動用ＩＣを直接ガラスパネル上に回路接続部材で接合するＣＯＧ実装方法が用いられている。ＣＯＧ実装の場合、ＣＯＧに用いるガラス基板として、製品の軽量化や高密度実装を目的として、薄型で線膨張係数の低いものが使用されるようになり、例えば、従来の１．１ｍｍ厚の基板から０．７ｍｍ厚の基板が使用され、線膨張係数も従来の４．８×１０^- ^６／℃程度のものから３．１×１０^-6／℃程度のものが使用されるようになってきている。このように基板の薄型、低熱膨張になると、図２に示したように熱硬化型接着剤の熱分布歪みや内部応力により基板に反り変形が生じ表示にムラが出たり、接続抵抗の上昇を招くといった問題がある。
【０００３】
これに対し、熱硬化型接着剤を低弾性率化して基板の内部応力を低減させることが行われている。しかし、低弾性率の熱硬化型接着剤を使用した場合、基板の反りは抑制できても、接続信頼性が低下するという問題が生じる。
基板のそりを抑制する方法として、ステージとヘッドとの間で、基板と実装部品とを熱硬化型接着剤を介して熱圧着する実装方法において、熱圧着時のステージ温度を、硬化後の接着剤の温度と弾性率の関係における弾性率の変曲点の温度以上とする方法がある（例えば、特許文献１参照）。
【０００４】
【特許文献１】
特開２０００-３１２０６９号公報（第２−３頁、第１図）
【０００５】
【発明が解決しようとする課題】
しかしながら、特開２０００-３１２０６９号公報の方法ではあらかじめステージを加熱しているため、特に最近の低温反応型の熱硬化型接着剤を用いる場合、ステージを加熱しすぎると実装材料を熱圧着する前に熱硬化型接着剤が反応して接着できなくなり、一方でステージの加熱を弱めると接着はされるものの、本来の目的である、そりを抑制できない問題があった。
【０００６】
本発明は以上のような従来技術の問題点を抜本的に解決するものであり、相対向する電極を有する、基板と実装部品を熱硬化型接着剤を介在させ、相対向する基板と実装部品をステージとヘッドとの間で、加熱加圧して加圧方向の電極間を電気的に接続する回路の実装方法であって、熱硬化型接着剤の反応性にかかわりなく、接続信頼性を損なうことなく、基板の反りを防止することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の請求項１記載の発明は、相対向する電極を有する基板と実装部品を熱硬化型接着剤を介在させ、相対向する基板と実装部品をステージとヘッドとの間で、加熱加圧して加圧方向の電極間を電気的に接続する回路の実装方法であって、実装部品の熱圧着開始より遅れて基板を加熱することを特徴とする実装方法を提供するものである。
請求項２記載の発明は請求項１記載の発明に加えて、実装部品の熱圧着開始より遅れて基板を加熱した際の、基板の到達温度（Ｔ１：℃）と、硬化後の熱硬化性接着剤のガラス転移温度（Ｔ２：℃）との間に、
-３０≦Ｔ１―Ｔ２≦１００（℃）
が成立する実装方法を提供するものである。
請求項３記載の発明は請求項１、２記載の発明に加えて実装部品の熱圧着開始から、基板の加熱開始までの間（ｔｉ）が
０．０１s≦ｔｉ≦１０００ｈ
である実装方法を提供するものである。
請求項４記載の発明は請求項1〜３のいずれかに記載の発明に加えて基板の加熱について、実装部品の熱圧着終了後、別途基板を加熱して行う実装方法を提供するものである。
請求項５記載の発明は請求項１〜３のいずれかに記載の発明に加えて基板の加熱について、熱圧着開始より遅れてステージを加熱して行う実装方法を提供するものである。
請求項６記載の発明は請求項１〜５のいずれかに記載の発明に加えて硬化後の熱硬化型接着剤のガラス転移温度が８０〜２５０℃である実装方法を提供するものである。
【０００８】
【発明の実施の形態】
本発明は、図１に示したように、基板１上に熱硬化型接着剤２を介して実装部品３を配したものを、ステージ４とヘッド５の間で熱圧着することにより実装する場合において、ステージとヘッドとの間で、基板と実装部品とを熱硬化型接着剤を介して加熱加圧して加圧方向の電極間を電気的に接続する実装方法において、実装部品の熱圧着開始より遅れて基板を加熱する実装方法である。
本発明の基板１は、実装材料を所定の位置に配置して、電気的回路としてなるものであればよく、具体的にはガラス基板、ガラス強化エポキシ基板、紙フェノール基板、セラミック基板、積層板などが挙げられる。
本発明の熱硬化型接着剤２は、種々の異方導電性フィルム（ＡＣＦ）、異方導電性ペースト（ＡＣＰ）、非導電性フィルム（ＮＣＦ）等を使用することができる。
接続信頼性、導通抵抗の点から、硬化後の熱硬化型接着剤のガラス転移温度（Ｔｇ）が８０〜２５０℃のものを使用することが好ましく、１００〜２４０℃のものがより好ましく、１２０〜２３０℃がもっとも好ましい。
硬化後の熱硬化型接着剤のガラス転移温度（Ｔｇ）が８０℃未満の場合、そりが低減できるものの接続信頼性が低くなる傾向があり、一方硬化後の熱硬化型接着剤のガラス転移温度（Ｔｇ）が２５０℃を超える場合、基板の加熱により反りが低減されるに伴い、接続信頼性が低下する傾向がある。
ガラス転移温度（Ｔｇ）は例えば硬化後の熱硬化型接着剤のＴＭＡ測定やＤＭＡ測定によるｔａｎδピーク温度から算出できる。
熱硬化型接着剤中の熱硬化性樹脂成分は、例えば、（メタ）アクリル化合物、アクリル樹脂、ウレタン化合物、ウレタン樹脂、不飽和ポリエステル樹脂、エポキシ化合物、エポキシ樹脂、フェノール樹脂等からなるものを使用することができる。さらに熱硬化性樹脂の硬化反応の形態も二重結合のラジカル重合や、エポキシ樹脂のイオン重合、重付加など、いずれの重合形態を利用してよい。さらにそれ自身では熱硬化しないフィルム形成ポリマーを含んでいても良い。また、その他の添加物としてラジカル重合開始剤、エポキシ硬化剤、シランカップリング剤を含んでいても良い。
これらの熱硬化性樹脂成分やフィルム形成ポリマーやその他添加物の種類や量を調整することにより、熱硬化型接着剤２のガラス転移温度（Ｔｇ）を制御することができる。
【０００９】
本発明の実装部品としては、ＩＣチップ、ＬＳＩチップ、抵抗、コンデンサなど、基板上に直接実装するものであればいかなるものも用いることができる。
これらの中でＩＣチップ、ＬＳＩチップなど部品サイズが大きく、接続端子数が多い実装材料を用いた場合に本発明の効果が顕著に表れる。
【００１０】
本発明の実装部品の熱圧着開始より遅れて基板を加熱する方法としては、実装部品の熱圧着を開始した後に、熱圧着しながらステージを加熱する方法、実装部品の熱圧着を開始、圧力開放された後にステージを加熱する方法、実装部品の熱圧着を開始、終了した後に別途基板を加熱する方法等、いずれの方法を用いても良い。
【００１１】
ステージを加熱する方法としては、ステージ４に、セラミックヒーター、抵抗式のヒーターを内蔵したパルスヒーター等を用いることが好ましい。熱に対する寸法安定性や温度制御性が良好であるセラミックヒーターを用いると、ステージ４の温度制御が良好であり好ましい。
【００１２】
加熱ヘッド５は、金属製のブロックに加熱ヒーターを内蔵したもの等を使用することができる。熱圧着時に、熱硬化型接着剤２を介在して構成される基板１と実装部品とを、加熱ヘッド５によって、１端子当たり圧力５０〜２０００ｋｇ／ｃｍ²で加圧し、熱硬化型接着剤の硬化を行うに十分な熱を加えることが好ましい。
【００１３】
実装部品の熱圧着を開始、終了した後に別途基板を加熱する方法は、熱板上に基板を配置し、一定時間放置する方法、熱板上に基板を配置し基板を熱板に押し付ける方法、加熱炉の中に実装部品を実装した基板を投入する方法、基板に温風を吹き付ける方法、超音波やその他外部からのエネルギーを基板に与えて基板を加熱する方法など、いずれの方法を用いても良い。このとき、実装部品の熱圧着開始より遅れて基板を加熱した際の、基板の到達温度（Ｔ１：℃）と、硬化後の熱硬化性接着剤のガラス転移温度（Ｔ２：℃）との間に、−３０≦Ｔ１―Ｔ２≦１００（℃）が成立することが望ましく、−２５≦Ｔ１―Ｔ２≦９０（℃）が成立することがより望ましく、−２０≦Ｔ１―Ｔ２≦８０（℃）が成立することがさらに望ましく、−１５≦Ｔ１―Ｔ２≦７０（℃）が成立することが最も望ましく、−１０≦Ｔ１―Ｔ２≦６０（℃）が成立することが極めて望ましい。Ｔ１―Ｔ２>１００（℃）の場合には接続抵抗の上昇や、基板と実装部品との剥離が生じる傾向があり、一方Ｔ１―Ｔ２＜−３０(℃)の場合には、反り低減効果が減少する傾向がある。
また、本発明における実装部品の熱圧着開始から、基板の加熱開始までの間（ｔｉ）は０．０１ｓ≦ｔｉ≦１０００ｈの範囲であることが望ましく、０．０２ｓ≦ｔｉ≦１００ｈの範囲であることがより望ましく、０．０３ｓ≦ｔｉ≦１０ｈの範囲であることがさらに望ましく、０．０４ｓ≦ｔｉ≦１ｈの範囲であることが最も望ましい。
実装部品の熱圧着開始から、基板の加熱開始までの間（ｔｉ）が、０．０１ｓ未満の場合、接続抵抗の上昇や基板と実装部品との剥離が生じる傾向があり、一方、１０００ｈを超える場合には量産性に乏しくなる傾向がある。
【００１４】
本発明は、上記で説明した他に、ステージと加熱ヘッドとの間で、基板と実装部品とを熱硬化型接着剤を介在して熱圧着する実装方法において、基板１とＩＣチップ３のような実装部品の位置関係を逆にし、基板１側から加熱ヘッド５で加熱加圧しても良い。この場合、熱圧着に遅れて加熱するのは実装部品となる。
【００１５】
【実施例】
以下、本発明を実施例に基づいて具体的に説明する。
【００１６】
（実施例１〜１２、比較例１〜６）
基板として、ガラス基板（コーニング＃7059、外形３８ｍｍ×２８ｍｍ、厚さ０．７ｍｍ、表面にＩＴＯ（酸化インジウム錫）配線パターン（パターン幅５０μｍ、ピッチ５０μｍ）を有するもの）、実装部品として、ＩＣチップ（外形１．７ｍｍ×１７．２ｍｍ、厚さ０．５５ｍｍ、バンプの大きさ５０μｍ×５０μｍ、バンプのピッチ５０μｍ）を１００ＭＰａ(バンプ面積換算)の荷重をかけて加熱加圧して実装した。熱硬化型接着剤としては、表１に示した（ｉ）、（ｉｉ）又は（ｉｉｉ）の異方導電性フィルム（ＡＣＦ）を使用し、基板と実装部品に介在させ、セラミックヒーターからなるステージとセラミックヒーターからなるヘッド（５ｍｍ×３０ｍｍ）を用いて表２に示す条件で実装した。
なお、表２には、実装部品の熱圧着開始より遅れて基板を加熱した際の、基板の到達温度（Ｔ1：℃）と、硬化後の熱硬化性接着剤のガラス転移温度（Ｔ２：℃）の差Ｔ１―Ｔ２と、実装部品の熱圧着開始から、基板の加熱開始までの間（ti）もあわせて示した。
【００１７】
【表１】

【００１８】
（熱硬化型接着剤の硬化後のＴｇ測定）
異方導電性フィルムを幅５ｍｍ、長さ４０ｍｍの長方形型に切断した。このフィルムを、熱風乾燥機を用いて１７０℃で２時間加熱して、硬化した異方導電フィルムを作製した。これをＤＡＭ測定装置（Rheometrics 製 RSA II）で粘弾性スペクトルを測定し、ｔａｎδピークの値をＴｇとした。
【００１９】
（基板の反り）
図３に示したように、基板とＩＣチップの実装後のＩＣチップ側を平坦な台の上に置き、基板の上面の凸面から１２．５ｍｍ離れた箇所の高さＬを測定し、この値を反りの指標とした。
（接続信頼性測定方法）
接続信頼性測定用サンプルの接続直後の接続抵抗と、耐湿試験（８５℃、８５％ＲＨ）に５００時間放置後の接続抵抗を四端子法で測定した。１０サンプルの平均値を接続抵抗（Ω）とし、次の４段階の基準で接続抵抗を評価した。
○：１Ω未満
□：１Ω以上、５Ω未満
×：５Ω以上
ＯＰＥＮ：導通がなく、接続抵抗が測定できない
これらの結果を表１に示した。
【００２０】
【表２】

【００２１】
表１中、Ｔｇは、硬化後の熱硬化性接着剤のガラス転移温度（T２：℃）。基板加熱条件中の温度は、実装部品の熱圧着開始より遅れて基板を加熱した際の、基板の到達温度（Ｔ１：℃）。
ｔｉは、実装部品の熱圧着開始から、基板の加熱開始までの時間（ti）
表１の結果から、基板を加熱せず実装材料を熱圧着した比較例１〜３と比較して、実装材料を熱圧着し、その後に基板を加熱した実施例１〜１２では基板の反りが著しく抑制され、かつ接続信頼性も優れていることがわかる。一方、実装材料を熱圧着する前に基板を加熱した比較例４〜６では、ＯＰＥＮ不良が発生した。
【００２２】
【発明の効果】
本発明の実装方法によれば、ＩＣチップ等の実装部品を基板に熱硬化型接着剤を介在させ熱圧着により実装する場合に、熱硬化性接着剤の反応性にかかわりなく、接続信頼性を損なうことなく、基板の反りを防止することができる。
【図面の簡単な説明】
【図１】実装方法を説明する断面模式図。
【図２】基板のそりを説明する断面図。
【図３】実装部品実装後の基板の反りの測定方法を説明する断面図。
【符号の説明】
１．基板
２．熱硬化型接着剤
３．ＩＣチップ(実装部品)
４．ステージ
５．加熱ヘッド[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mounting method in which a substrate and a mounting component are thermocompression bonded via a thermosetting adhesive.
[0002]
[Prior art]
Thermosetting adhesion such as anisotropic conductive film (ACF), anisotropic conductive paste (ACP), non-conductive film (NCF), etc., as connecting material for connecting to-be-connected members having many opposing electrodes A method of thermocompression bonding a substrate and a mounted component via an agent is known. These are adjacent to each other while maintaining the conductive state between the opposing electrodes when connecting printed circuit boards, LCD glass substrates, flexible printed circuit boards, and other mounting parts such as semiconductor elements such as ICs and LSIs and packages. Electrical connection and mechanical fixation are performed so as to maintain insulation between the electrodes. Many of such thermosetting adhesives are formed into a film shape including an adhesive component containing a thermosetting resin and conductive particles blended if necessary, and support such as PET (polyethylene terephthalate) It is commercialized in a state of being laminated on the body. In use, a thermosetting adhesive is provided on the connected member, the thermosetting resin is cured to obtain mechanical fixation between the members, and the opposing electrodes are brought into contact directly or through conductive particles. To get an electrical connection. For example, in COG (Chip On Glass) in which an IC chip is mounted on a glass substrate for LCD, as shown in FIG. 1, a thermosetting adhesive 2 is interposed on the glass substrate 1 for LCD, The mounting component 3 is heated and pressed between the stage 4 and the head 5 to electrically connect the electrodes in the pressing direction. In general, the temperature of the head 5 is set to 150 to 300 ° C., and the stage 4 is not heated and is near room temperature or a temperature in which the heat transfer amount and the heat dissipation amount are balanced from the head, or temperature adjustment by a medium is performed. Often to do. This is to prevent the thermosetting reaction of the thermosetting adhesive 2 from starting when the electrodes of the substrate and the mounting component are aligned, and the connection temperature varies for each thermocompression bonding in the mounting process. In order to prevent this, it is heated to 60 ° C. or lower, which is lower than the start temperature of the thermosetting reaction.
The liquid crystal driving IC is mounted on the liquid crystal display glass panel by using an OLB mounting method in which the flexible tape on which the liquid crystal driving IC is mounted and the glass panel are joined by a circuit connecting member, or the liquid crystal driving IC is directly mounted on the glass panel. A COG mounting method is used in which a circuit connecting member is used for bonding. In the case of COG mounting, a thin glass substrate with a low coefficient of linear expansion is used as a glass substrate used for COG for the purpose of reducing the weight of the product and high-density mounting. For example, a conventional 1.1 mm thick substrate from is used a substrate of 0.7mm thickness, the linear expansion coefficient conventional 4.8 × 10 - come to ⁶ ^/ from ° C. of about things of about 3.1 × 10 ^-6 / ° C. is used ing. As shown in FIG. 2, when the substrate becomes thin and has a low thermal expansion, the substrate is warped and deformed due to thermal distribution distortion and internal stress of the thermosetting adhesive, resulting in uneven display and increased connection resistance. There is a problem of inviting.
[0003]
On the other hand, it is practiced to reduce the internal stress of the substrate by reducing the elastic modulus of the thermosetting adhesive. However, when a thermosetting adhesive having a low elastic modulus is used, there arises a problem that the connection reliability is lowered even if the warpage of the substrate can be suppressed.
As a method to suppress warping of the board, in the mounting method in which the board and the mounting component are thermocompression bonded between the stage and the head via a thermosetting adhesive, the stage temperature at the time of thermocompression is bonded after curing. There is a method in which the temperature is equal to or higher than the temperature of the inflection point of the elastic modulus in the relationship between the temperature of the agent and the elastic modulus (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP 2000-312069 (page 2-3, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, since the stage is heated in advance in the method disclosed in Japanese Patent Laid-Open No. 2000-312069, particularly when using a recent low-temperature reaction type thermosetting adhesive, if the stage is heated too much, the mounting material is not thermally bonded. However, there is a problem that warpage cannot be suppressed, which is the original purpose, although it is bonded when the heating of the stage is weakened.
[0006]
The present invention fundamentally solves the problems of the prior art as described above, and has a substrate and a mounting component having opposing electrodes and a thermosetting adhesive interposed between the substrate and the mounting component. Is a circuit mounting method in which the electrodes in the pressing direction are electrically connected between the stage and the head by heating and pressing, and the connection reliability is impaired regardless of the reactivity of the thermosetting adhesive. It aims at preventing the curvature of a board | substrate, without.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, a substrate having mounting electrodes and a mounting component are interposed with a thermosetting adhesive, and the facing substrate and mounting component are heated and pressurized between a stage and a head. A circuit mounting method for electrically connecting electrodes in a pressurizing direction is provided, wherein the substrate is heated after the start of thermocompression bonding of the mounted component.
In addition to the invention of claim 1, the invention described in claim 2 is the temperature reached by the substrate (T1: ° C.) and the thermosetting property after curing when the substrate is heated later than the start of thermocompression bonding of the mounted component. Between the glass transition temperature of the adhesive (T2: ° C.)
-30 ≦ T1-T2 ≦ 100 (℃)
It provides an implementation method that holds
In addition to the inventions of claims 1 and 2, the invention described in claim 3 has a period (ti) from the start of thermocompression bonding of the mounted component to the start of heating of the substrate of 0.01 s ti ≤ 1000 h.
It is intended to provide an implementation method.
In addition to the invention of any one of claims 1 to 3, the invention described in claim 4 provides a mounting method in which the substrate is heated by separately heating the substrate after completion of the thermocompression bonding of the mounted component. .
The invention according to claim 5 provides a mounting method in which, in addition to the invention according to any one of claims 1 to 3, the substrate is heated by heating the stage after the start of thermocompression bonding.
The invention according to claim 6 provides a mounting method in which the glass transition temperature of the cured thermosetting adhesive is 80 to 250 ° C. in addition to the invention according to any one of claims 1 to 5.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as shown in FIG. 1, when a mounting component 3 is arranged on a substrate 1 via a thermosetting adhesive 2 and is mounted by thermocompression bonding between a stage 4 and a head 5. In the mounting method in which the substrate and the mounting component are heated and pressurized via a thermosetting adhesive between the stage and the head to electrically connect the electrodes in the pressing direction, thermocompression bonding of the mounting component is started. This is a mounting method in which the substrate is heated later.
The substrate 1 of the present invention only needs to be an electrical circuit in which mounting materials are arranged at predetermined positions. Specifically, the substrate 1 is a glass substrate, a glass reinforced epoxy substrate, a paper phenol substrate, a ceramic substrate, a laminated plate. Etc.
As the thermosetting adhesive 2 of the present invention, various anisotropic conductive films (ACF), anisotropic conductive pastes (ACP), non-conductive films (NCF) and the like can be used.
From the viewpoint of connection reliability and conduction resistance, it is preferable to use a thermosetting adhesive having a glass transition temperature (Tg) of 80 to 250 ° C. after curing, more preferably 100 to 240 ° C., 120 ˜230 ° C. is most preferred.
When the glass transition temperature (Tg) of the thermosetting adhesive after curing is less than 80 ° C., the warpage can be reduced, but the connection reliability tends to be low, whereas the glass transition temperature of the thermosetting adhesive after curing is low. When (Tg) exceeds 250 ° C., the connection reliability tends to decrease as the warpage is reduced by heating the substrate.
The glass transition temperature (Tg) can be calculated from, for example, the tan δ peak temperature obtained by TMA measurement or DMA measurement of the cured thermosetting adhesive.
The thermosetting resin component in the thermosetting adhesive is, for example, one made of (meth) acrylic compound, acrylic resin, urethane compound, urethane resin, unsaturated polyester resin, epoxy compound, epoxy resin, phenol resin, etc. can do. Furthermore, the form of the curing reaction of the thermosetting resin may be any polymerization form such as radical polymerization of double bonds, ionic polymerization of epoxy resin, or polyaddition. Furthermore, it may contain a film-forming polymer that is not thermally cured by itself. Further, as other additives, a radical polymerization initiator, an epoxy curing agent, and a silane coupling agent may be included.
The glass transition temperature (Tg) of the thermosetting adhesive 2 can be controlled by adjusting the types and amounts of these thermosetting resin components, film-forming polymers, and other additives.
[0009]
As the mounting component of the present invention, any IC chip, LSI chip, resistor, capacitor, or the like that can be directly mounted on the substrate can be used.
Among these, the effects of the present invention are remarkably exhibited when a mounting material having a large component size such as an IC chip or an LSI chip and a large number of connection terminals is used.
[0010]
As a method of heating the substrate after the start of thermocompression bonding of the mounting component of the present invention, after starting thermocompression bonding of the mounting component, heating the stage while thermocompression bonding, starting thermocompression bonding of the mounting component, releasing pressure Any method may be used, such as a method of heating the stage after being heated, a method of heating the substrate separately after starting and ending the thermocompression bonding of the mounted components.
[0011]
As a method for heating the stage, it is preferable to use a ceramic heater, a pulse heater incorporating a resistance heater, or the like for the stage 4. It is preferable to use a ceramic heater having good dimensional stability against heat and temperature controllability because the temperature control of the stage 4 is good.
[0012]
As the heating head 5, a metal block having a built-in heater can be used. At the time of thermocompression bonding, the substrate 1 configured with the thermosetting adhesive 2 and the mounting component are pressed by the heating head 5 at a pressure of 50 to 2000 kg / cm ² per terminal, and the thermosetting adhesive It is preferable to apply sufficient heat to effect curing.
[0013]
The method of heating the substrate separately after starting and finishing the thermocompression bonding of the mounted components is to place the substrate on the hot plate and leave it for a certain time, to place the substrate on the hot plate and press the substrate against the hot plate, Use any method such as putting a board with mounted components in a heating furnace, blowing warm air to the board, or heating the board by applying ultrasonic waves or other external energy to the board. Also good. At this time, between the temperature reached by the substrate (T1: ° C.) and the glass transition temperature (T2: ° C.) of the cured thermosetting adhesive when the substrate is heated later than the thermocompression bonding of the mounted component. In addition, it is desirable that −30 ≦ T1−T2 ≦ 100 (° C.) is satisfied, more desirably −25 ≦ T1−T2 ≦ 90 (° C.), and −20 ≦ T1−T2 ≦ 80 (° C.). Is more preferable, −15 ≦ T1−T2 ≦ 70 (° C.) is most preferable, and −10 ≦ T1−T2 ≦ 60 (° C.) is very preferable. When T1−T2> 100 (° C.), there is a tendency that the connection resistance increases and the substrate and the mounting component are separated. On the other hand, when T1−T2 <−30 (° C.), there is a warp reduction effect. There is a tendency to decrease.
Moreover, it is desirable that the period (ti) from the start of thermocompression bonding of the mounted component to the start of heating of the substrate in the present invention is in the range of 0.01 s ti ≤ 1000 h, and in the range of 0.02 s ti ≤ 100 h. More preferably, the range is 0.03s ≦ ti ≦ 10h, and the most preferable range is 0.04s ≦ ti ≦ 1h.
When the time (ti) from the start of thermocompression bonding of the mounting component to the start of heating of the substrate is less than 0.01 s, there is a tendency that the connection resistance increases and the substrate and the mounting component are peeled off, but exceeds 1000 h. In some cases, the mass productivity tends to be poor.
[0014]
In addition to the above description, the present invention provides a mounting method in which a substrate and a mounting component are thermocompression bonded between a stage and a heating head with a thermosetting adhesive interposed between the substrate 1 and the IC chip 3. It is also possible to reverse the positional relationship of the mounted components and heat and press with the heating head 5 from the substrate 1 side. In this case, it is the mounted component that heats after the thermocompression bonding.
[0015]
【Example】
Hereinafter, the present invention will be specifically described based on examples.
[0016]
(Examples 1-12, Comparative Examples 1-6)
As a substrate, a glass substrate (Corning # 7059, outer shape 38 mm × 28 mm, thickness 0.7 mm, with an ITO (indium tin oxide) wiring pattern on the surface (pattern width 50 μm, pitch 50 μm)), as a mounting component, an IC chip (External dimensions 1.7 mm × 17.2 mm, thickness 0.55 mm, bump size 50 μm × 50 μm, bump pitch 50 μm) were mounted by heating and pressing with a load of 100 MPa (in terms of bump area). As the thermosetting adhesive, an anisotropic conductive film (ACF) of (i), (ii) or (iii) shown in Table 1 is used. And a head (5 mm × 30 mm) made of a ceramic heater and mounted under the conditions shown in Table 2.
Table 2 shows the temperature reached by the substrate (T1: ° C.) and the glass transition temperature (T2: ° C.) of the thermosetting adhesive after curing when the substrate was heated after the thermocompression bonding of the mounted component. ) Difference T1-T2 and (ti) from the start of thermocompression bonding of the mounted component to the start of heating of the substrate are also shown.
[0017]
[Table 1]

[0018]
(Tg measurement after curing of thermosetting adhesive)
The anisotropic conductive film was cut into a rectangular shape having a width of 5 mm and a length of 40 mm. This film was heated at 170 ° C. for 2 hours using a hot air drier to produce a cured anisotropic conductive film. This was measured with a DAM measuring device (RSA II manufactured by Rheometrics), and the value of the tan δ peak was defined as Tg.
[0019]
(Board warpage)
As shown in FIG. 3, the IC chip side after mounting the substrate and the IC chip is placed on a flat table, and the height L of the portion 12.5 mm away from the convex surface on the upper surface of the substrate is measured. Was used as an index of warpage.
(Connection reliability measurement method)
The connection resistance immediately after connection of the sample for connection reliability measurement and the connection resistance after being left in a moisture resistance test (85 ° C., 85% RH) for 500 hours were measured by the four-terminal method. The average value of 10 samples was defined as the connection resistance (Ω), and the connection resistance was evaluated according to the following four-stage criteria.
○: Less than 1Ω □: 1Ω or more, less than 5Ω ×: 5Ω or more OPEN: There is no continuity, and connection resistance cannot be measured.
[0020]
[Table 2]

[0021]
In Table 1, Tg is the glass transition temperature (T2: ° C.) of the thermosetting adhesive after curing. The temperature in the substrate heating condition is the temperature reached by the substrate when the substrate is heated after the start of thermocompression bonding of the mounted component (T1: ° C.).
ti is the time from the start of thermocompression bonding of the mounted component to the start of substrate heating (ti)
From the results of Table 1, compared to Comparative Examples 1 to 3 in which the mounting material was thermocompression bonded without heating the substrate, the substrates were warped in Examples 1 to 12 in which the mounting material was thermocompression bonded and then the substrate was heated. It can be seen that it is remarkably suppressed and the connection reliability is excellent. On the other hand, in Comparative Examples 4 to 6 where the substrate was heated before the mounting material was thermocompression bonded, an OPEN defect occurred.
[0022]
【The invention's effect】
According to the mounting method of the present invention, when mounting components such as IC chips are mounted on a substrate by thermocompression adhesive and thermocompression bonding, the connection reliability is improved regardless of the reactivity of the thermosetting adhesive. The warpage of the substrate can be prevented without loss.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating a mounting method.
FIG. 2 is a cross-sectional view illustrating warpage of a substrate.
FIG. 3 is a cross-sectional view illustrating a method for measuring the warpage of a board after mounting components are mounted.
[Explanation of symbols]
1. Substrate 2. 2. Thermosetting adhesive IC chip (mounting parts)
4). Stage 5. Heating head

Claims

A substrate having mounting electrodes and mounting components are interposed between thermosetting adhesives, and the substrate and mounting components facing each other are heated and pressed between the stage and the head to electrically connect the electrodes in the pressing direction. A method of mounting a circuit to be connected, wherein the substrate is heated after the start of thermocompression bonding of a mounted component.

Between the temperature reached by the substrate (T1: ° C.) and the glass transition temperature (T2: ° C.) of the thermosetting adhesive after curing when the substrate is heated after the start of thermocompression bonding of the mounted component,
-30 ≦ T1-T2 ≦ 100 (℃)
The mounting method according to claim 1, wherein:

The time from the start of thermocompression bonding of the mounted component to the start of heating of the substrate (ti) is 0.01 s ≦ ti ≦ 1000 h.
The mounting method according to claim 1, wherein:

The mounting method according to claim 1, wherein the substrate is heated by separately heating the substrate after completion of the thermocompression bonding of the mounted component.

The mounting method according to claim 1, wherein the substrate is heated by heating the stage after the start of thermocompression bonding.

The mounting method according to any one of claims 1 to 5, wherein the glass transition temperature of the cured thermosetting adhesive is 80 to 250 ° C.