JPH045705B2

JPH045705B2 -

Info

Publication number: JPH045705B2
Application number: JP58013657A
Authority: JP
Inventors: Teru Okunoyama
Original assignee: Toshiba Chemical Products Co Ltd
Current assignee: Toshiba Chemical Products Co Ltd
Priority date: 1983-02-01
Filing date: 1983-02-01
Publication date: 1992-02-03
Also published as: JPS59140279A

Abstract

PURPOSE:To provide the titled adhesive which exhibits excellent thermal strength even when cured after being left to stand for a long time, by mixing a resin mainly composed of a bismaleimide and a triazine resin monomer, an epoxy resin which is liquid at room temp. and an electrically conductive powder. CONSTITUTION:A component (A) composed of a bismaleimide of formula I (wherein Ar1 is a bivalent arom. group) and a triazine resin contg. a diisocyanate unit of formula II (wherein Ar2 is a bivalent arom. group) and triazine rings of formula III formed by the cyclopolymerization of at least three molecules of said diisocyanate in the molecular structure and having isocyanate groups at its terminal, an epoxy resin (B) which is liquid at room temp. such as bisphenol A epoxy resin, and an electrically conductive powder (C) such as silver powder are mixed together in such a proportion as to give a weight ratio of component A to component B of 10:90-90:10, thus obtaining the desired solventless electrically conductive adhesive. This adhesive is suitable for use in bonding IC chip to an insulated substrate, etc.

Description

[Detailed description of the invention]

［発明の技術分野］本発明は、絶縁基板や電極にICチツプを接着
するのに好適な無溶剤型導電性接着剤に関する。［発明の技術的背景とその問題点］金属薄板（リードフレーム）や絶縁基板上の所
定部分にIC，LSIおよびLED等の半導体チツプを
接続する工程は、素子の長期信頼性に影響を与え
る重要な工程のひとつである。従来からこの方法のひとつとして、チツプ裏面
のSiをリードフレーム上のAuメツキ面に加熱圧
着し、Au−Siの共晶法が主流であつた。しかし、
近年の貴金属、特にAuの高騰を契機として、樹
脂モールド型半導体素子ではAu−Si共晶法から
ハンダを使用する方法、導電性接着剤を使用する
方法等に急速に移行しつつある。しかし、ハンダを使用する方法は、一部実用化
されているがハンダやハンダボールが飛散して電
極等に付着し、腐食・断線の原因となる可能性が
指摘されている。一方導電性接着剤を使用する方
法では、通常銀粉末を配合したエポキシ樹脂が10
年程度から一部実用化されてきたが信頼性の面で
Au−Siの共晶法に比較して満足すべきものがな
かつた。導電性接着剤を使用した場合は、樹脂やその硬
化剤が半導体素子接着用として作られたものでな
いためAl電極の腐食を促進し断線不良の原因と
なる場合が多い。また従来、熱時強度向上のため
固形のエポキシ樹脂を溶剤で希釈したタイプの系
を使用しているためにスクリユー印刷やデイスペ
ンサー等により所定部分上に接着剤を塗布した後
のタツクフリータイムが短かく、その結果、長時
間放置後に硬化させた場合の強度が極端に低下す
るという欠点があつた。［発明の目的］本発明は、上記の欠点を除去するためになされ
たもので、不純物物が少なく、熱的強度が強く、
しかも長時間放置後の硬化においても強度の低下
が少ない半導体チツプマウント用の無溶剤型導電
性接着剤を提供することを目的としている。［発明の概要］本発明は、上記の目的を達成すべく鋭意研究を
重ねた結果、後述する結合剤を使用すれば不純物
が少なく、熱時強度が強く、しかも長時間放置後
の硬化においても強度低下の少ない半導体チツプ
マウント用の導電性接着剤が得られることを見い
出したものである。即ち、本発明は、(a)ビスマレイミドとトリアジ
ン樹脂モノマーとを主成分としてなる樹脂と、(b)
常温で液状のエポキシ樹脂と、(c)導電性粉体とを
ベヒクル（Vehicle）とすることを特徴とする半
導体チツプマウント用の無溶剤型導電性接着剤で
ある。本発明に使用する(a)ビスマレイミドとトリアジ
ン樹脂モノマーとを主成分としてなる樹脂は、一般式で表されるビスマレイミド、並びに一般式Ｎ≡Ｃ−Ｏ−Ar₂−Ｏ−Ｃ≡Ｎで表されるジシアネート、及びこのジシアネート
が３分子以上環化重合したトリアジン環を分子中に有し、かつ分子未端にシアネート基
（Ｎ≡Ｃ−Ｏ−）を有するトリアジン樹脂とから
成つている。このような樹脂としては、例えば三菱ガス化学
社製“BTレンジ”（商品名）がある。このよう
なBTレンジとしては、例えばBT2170，
BT2470，BT2300，BT2400，BT3103等のよう
な銘柄が市販されており、そのいずれも本発明に
使用することができる。本発明に使用される(b)常温で液状のエポキシ樹
脂としては、現在工業生産されているものとして
次のようなものがある。例えばシエル化学社製エ
ピコート（Epikote）827，828等のビスフエノー
ルＡ型エポキシ樹脂、ダイセル化学工業社製セロ
キサイド2021，ユニオンカーバイド社製ERL−
4221，4299，4234，4206等のシクロ系エポキシ樹
脂およびその他ビスフエノールＦ型エポキシ樹脂
等が挙げられる。これらのエポキシ樹脂はそれぞ
れ単独で、または２種以上混合して使用される。 (a)ビスマレイミドとトリアジン樹脂モノマーと
を主成分として成る樹脂と、(b)常温で液状のエポ
キシ樹脂との配合割合は10：90〜90：10（重量比）
の範囲にあることが望ましく、なかんずく30：70
〜70：30（重量比）の範囲にあることが望ましい。
(a)の割合が10重量部未満では、得られるベヒクル
の耐熱性が劣り、熱時の強度が低下し、逆に(b)の
成分の配合割合が10重量部未満では、ベヒクルの
粘度が高くなり作業性が悪くなる。従つて上記範
囲が好ましい。また本発明に用いる(c)導電性粉体としては、フ
レーク状、球状、あるいは樹脂コートされた平均
粒径10μ以下の銀、銅等の金属粉を使用するのが
好ましい。(c)導電性粉体とベヒクル（(a)＋(b)）と
の配合割合は60：40〜90：10（重量比）が適して
いる。導電性粉体が60重量部未満では満足な導電
性が得られないし、また90重量部を超える場合は
作業性や半導体チツプとのなじみが悪くなる。従
つて上記範囲が好ましい。本発明においては、以
上の成分の他に粘度を調整する目的でモノエポキ
シ化合物や有機溶剤を導電性接着剤100重量部に
対して10重量％の範囲内で必要に応じて使用する
こともできる。本発明の無溶剤型導電性接着剤は、以上に述べ
た各成分を３本ロール等により混練して製造す
る。そして接着剤を所定の場所にデイスペンサ
ー、スクリーン印刷およびピン転写法等によつて
塗布した後、数秒から数十時間後、各種半導体チ
ツプを載せ加熱硬化させて使用する。本発明の無
溶剤型導電性接着剤は種々の硬化条件で硬化でき
るが、150℃で２時間のオーブン硬化もしくは250
℃以上で数分のヒータブロツク硬化が好ましい。［発明の実施例］次に本発明の実施例について説明する。実施例１〜３、比較例第１表に示す各成分を３本ロールにより３回混
練して一液型導電性接着剤を製造した。得られた
導電性接着剤の導電性、硬化後のチツプなじみ
性、発泡性および各種条件下での熱時強度は第１
表に示す通りであつた。第１表中の比較例は従来
のクレゾールノボラツク型エポキシ樹脂−フエノ
ール樹脂硬化系ベヒクルをブチルセロソルブで希
釈した後、第１表に示した銀粉を混練して導電性
接着剤とし、実施例と同様にして特性を第１表に
示した。 [Technical Field of the Invention] The present invention relates to a solvent-free conductive adhesive suitable for bonding IC chips to insulating substrates and electrodes. [Technical background of the invention and its problems] The process of connecting semiconductor chips such as ICs, LSIs, and LEDs to predetermined parts on thin metal plates (lead frames) and insulating substrates is an important process that affects the long-term reliability of devices. This is one of the most important processes. Conventionally, one method for this has been the Au-Si eutectic method, in which Si on the backside of the chip is heat-pressed onto the Au-plated surface of the lead frame. but,
Due to the recent rise in the price of precious metals, particularly Au, resin-molded semiconductor devices are rapidly transitioning from the Au-Si eutectic method to methods using solder, conductive adhesives, etc. However, although some methods using solder have been put into practical use, it has been pointed out that the solder and solder balls may scatter and adhere to electrodes, etc., causing corrosion and disconnection. On the other hand, in the method using conductive adhesive, epoxy resin containing silver powder is usually used to
It has been partially put into practical use since about 2000, but
There was nothing satisfactory compared to the Au-Si eutectic method. When a conductive adhesive is used, the resin and its curing agent are not made for bonding semiconductor elements, which often accelerates corrosion of the Al electrode and causes disconnection. In addition, conventional systems have used solid epoxy resin diluted with solvent to improve strength when heated, so there is less tack-free time after applying the adhesive to a designated area using screw printing or a dispenser. As a result, there was a drawback that the strength was extremely reduced when cured after being left for a long time. [Object of the invention] The present invention was made to eliminate the above-mentioned drawbacks, and has few impurities, high thermal strength,
Moreover, it is an object of the present invention to provide a solvent-free conductive adhesive for semiconductor chip mounts that exhibits less strength loss even when cured after being left for a long time. [Summary of the Invention] As a result of intensive research to achieve the above object, the present invention has been developed to achieve low impurities, high strength when heated, and even hardening after being left for a long time by using the binder described below. It has been discovered that a conductive adhesive for semiconductor chip mounts can be obtained with little reduction in strength. That is, the present invention provides (a) a resin mainly composed of bismaleimide and triazine resin monomer, and (b)
This is a solvent-free conductive adhesive for semiconductor chip mounts, characterized by using an epoxy resin that is liquid at room temperature and (c) conductive powder as a vehicle. (a) The resin mainly composed of bismaleimide and triazine resin monomer used in the present invention has the general formula bismaleimide represented by, dicyanate represented by the general formula N≡C-O-Ar ₂ -O-C≡N, and a triazine ring obtained by cyclopolymerizing three or more molecules of this dicyanate. in its molecule, and a triazine resin having a cyanate group (N≡C-O-) at the end of the molecule. An example of such a resin is "BT Range" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd., for example. Examples of such BT ranges include BT2170,
Brands such as BT2470, BT2300, BT2400, BT3103, etc. are commercially available, and any of them can be used in the present invention. As the (b) epoxy resin that is liquid at room temperature used in the present invention, there are the following ones currently being industrially produced. For example, bisphenol A type epoxy resins such as Epikote 827 and 828 manufactured by Ciel Chemical Co., Ltd., Celoxide 2021 manufactured by Daicel Chemical Industries, Ltd., and ERL- manufactured by Union Carbide Co., Ltd.
Examples include cyclo-based epoxy resins such as 4221, 4299, 4234, and 4206, and other bisphenol F-type epoxy resins. These epoxy resins may be used alone or in combination of two or more. The blending ratio of (a) resin mainly composed of bismaleimide and triazine resin monomer and (b) epoxy resin that is liquid at room temperature is 10:90 to 90:10 (weight ratio)
It is desirable that it be within the range of 30:70, especially 30:70.
It is desirable that the ratio be in the range of ~70:30 (weight ratio).
If the proportion of (a) is less than 10 parts by weight, the heat resistance of the resulting vehicle will be poor, and the strength when heated will decrease. Conversely, if the proportion of component (b) is less than 10 parts by weight, the viscosity of the vehicle will be reduced. It becomes expensive and the workability deteriorates. Therefore, the above range is preferable. Further, as the conductive powder (c) used in the present invention, it is preferable to use flake-like, spherical, or resin-coated metal powder such as silver or copper having an average particle size of 10 μm or less. (c) A suitable blending ratio of the conductive powder and vehicle ((a)+(b)) is 60:40 to 90:10 (weight ratio). If the amount of conductive powder is less than 60 parts by weight, satisfactory conductivity cannot be obtained, and if it exceeds 90 parts by weight, workability and compatibility with semiconductor chips will deteriorate. Therefore, the above range is preferable. In the present invention, in addition to the above-mentioned components, a monoepoxy compound or an organic solvent may be used as necessary within a range of 10% by weight based on 100 parts by weight of the conductive adhesive for the purpose of adjusting the viscosity. . The solvent-free conductive adhesive of the present invention is produced by kneading the above-mentioned components using a three-roll roll or the like. After applying the adhesive to a predetermined location using a dispenser, screen printing, pin transfer method, etc., various semiconductor chips are placed on the adhesive after several seconds to several tens of hours, and the adhesive is heated and cured for use. The solvent-free conductive adhesive of the present invention can be cured under various curing conditions, including oven curing at 150°C for 2 hours or
Heater block curing for several minutes at temperatures above 0.degree. C. is preferred. [Embodiments of the Invention] Next, embodiments of the present invention will be described. Examples 1 to 3, Comparative Example Each component shown in Table 1 was kneaded three times using three rolls to produce a one-component conductive adhesive. The electrical conductivity, chip compatibility after curing, foamability, and heat strength under various conditions of the obtained electrically conductive adhesive were the highest.
It was as shown in the table. In the comparative example in Table 1, a conventional cresol novolac type epoxy resin-phenol resin curing vehicle was diluted with butyl cellosolve, and then the silver powder shown in Table 1 was kneaded to make a conductive adhesive. The characteristics are shown in Table 1.

【表】［発明の効果］以上の説明から明らかなように本発明の無溶剤
型導電性接着剤は、接着剤を長時間放置した後に
おいてもチツプとのなじみ性および熱時強度が強
く、しかも高速硬化においても発泡せず、従来の
導電性接着剤に比較して多くの利点を有してい
る。[Table] [Effects of the Invention] As is clear from the above description, the solvent-free conductive adhesive of the present invention has strong compatibility with chips and strong strength when heated, even after the adhesive is left for a long time. Moreover, it does not foam even when cured at high speed, and has many advantages over conventional conductive adhesives.

Claims

[Claims] 1. A vehicle comprising (a) a resin mainly composed of bismaleimide and triazine resin monomers, (b) an epoxy resin that is liquid at room temperature, and (c) a conductive powder. A solvent-free conductive adhesive for semiconductor chip mounts. 2. A patent in which the blending ratio of (a) a resin whose main components are bismaleimide and triazine resin monomer and (b) an epoxy resin that is liquid at room temperature is in the range of 10:90 to 90:10 (weight ratio). A solvent-free conductive adhesive for semiconductor chip mount according to claim 1. 3 (a) The resin mainly composed of bismaleimide and triazine resin monomer has the general formula bismaleimide represented by, dicyanate represented by the general formula N≡C-O-Ar ₂ -O-C≡N, and a triazine ring obtained by cyclopolymerizing three or more molecules of the dicyanate. in the molecule and a cyanate group (N
≡C-O-) The semiconductor chip according to claim 1 or 2, comprising a triazine resin (wherein Ar ₁ and Ar ₂ represent the same or different divalent aromatic groups) Solvent-free conductive adhesive for mounting.