JP2004082495A - Heat-resistant flexible copper-clad laminate with high visibility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant flexible copper-clad laminate with high visibility by solving the problem that the positioning of a semiconductor chip is impossible due to the inferior optical transparency of a film during mounting the chip, in manufacturing COF(chip on film) from a two-layer or a false two-layer FPC(flexible printed circuitboard) using an ILB(inner lead bonding) device. <P>SOLUTION: The copper-clad laminate is constituted of a heat-resistant bonded ply obtained by forming a thermoplastic polyimide layer on one side or both sides of a heat-resistant base film and a copper foil formed on one side or both sides of the bond ply. The copper foil of the copper-clad laminate has the mat surface roughness of 1.5 μm or less of Rz and 0.2 μm or less of Ra by a measurement method described in JIS B0601. In addition, the light transmission of the bonded ply with the formed copper foil removed by etching at a wavelength of 600 nm is not less than 30%. <P>COPYRIGHT: (C)2004,JPO

Description

（式中、ｎは１以上の整数である。Ａは４価の有機基、Ｘは２価の有機基を示す。）で表されるアミド酸の化学構造を有することを特徴とする前記の耐熱性フレキシブル銅張積層板に関する。
【００１０】
更に好ましい実施態様は、前記一般式（化２６）中のＡが下記式（化２７）：
【００１１】
【化２７】

（式中、Ｒは２価の有機基である。）
の構造を主成分として含む４価の有機基であることを特徴とする前記の耐熱性フレキシブル銅張積層板に関する。
【００１２】
更に好ましい実施態様は、前記式（化２７）中のＲが下記構造単位（化２８）〜（化３０）：
【００１３】
【化２８】

【００１４】
【化２９】

【００１５】
【化３０】

に示す群から選択される１種以上であることを特徴とする前記の耐熱性フレキシブル銅張積層板に関する。
【００１６】
更に好ましい実施態様は、前記一般式（化２６）中のＸが下記構造単位（化３１）〜（化５０）：
【００１７】
【化３１】

【００１８】
【化３２】

【００１９】
【化３３】

【００２０】
【化３４】

【００２１】
【化３５】

【００２２】
【化３６】

【００２３】
【化３７】

【００２４】
【化３８】

【００２５】
【化３９】

【００２６】
【化４０】

【００２７】
【化４１】

【００２８】
【化４２】

【００２９】
【化４３】

【００３０】
【化４４】

【００３１】
【化４５】

【００３２】
【化４６】

【００３３】
【化４７】

【００３４】
【化４８】

【００３５】
【化４９】

【００３６】
【化５０】

に示す２価の有機基の群から選択される１種以上であること特徴とする前記いずれかに記載の耐熱性フレキシブル銅張積層板に関する。
【００３７】
好ましい実施態様は、前記の耐熱性ボンドプライにおける耐熱性ベースフィルムが、非熱可塑性ポリイミドフィルムであることを特徴とする耐熱性フレキシブル銅張積層板に関する。
【００３８】
【発明の実施の形態】
まず、本発明における熱可塑性ポリイミド層を形成する際の原料であるポリアミド酸溶液の調製方法について説明する。
【００３９】
ポリアミド酸は、酸二無水物とジアミンとを有機溶媒中で反応させることにより得られる。まず、アルゴン、窒素などの不活性ガス雰囲気中において、一般式（化５１）：
【００４０】
【化５１】

（式中、Ｙは４価の有機基を示す。）で表される少なくとも１種の酸二無水物を有機溶媒中に溶解、又は拡散させ、この溶液中に一般式（化５２）：
【００４１】
【化５２】

（式中、Ｘは２価の有機基を示す。）で表される少なくとも１種のジアミンを、固体または有機溶媒溶液の状態で添加する。さらに、前記の一般式（化５１）で表される１種又は２種以上の酸二無水物の混合物を固体または有機溶媒溶液の状態で添加し、ポリイミドの前駆体であるポリアミド酸溶液を得る。また、この反応において、上記添加手順とは逆に、まずジアミンの溶液を調製し、この溶液中に固体または有機溶媒溶液の状態である酸二無水物を添加してもよい。このときの反応温度は、−１０℃〜０℃程度が好ましい（あまりにも反応温度が高いと解重合が始まる）。反応時間は概ね３０分間〜３時間程度が好ましい。かかる反応により熱可塑性ポリイミドの前駆体であるポリアミド酸溶液が調製される。
【００４２】
本発明における熱可塑性ポリイミドの前駆体であるポリアミド酸としては、耐熱性、加工性（易接着性）、低吸水性、電気特性等の観点から、前記（化２６）で示される構造のものが好ましく、更には（化２７）、（化２８）〜（化３０）、（化３１）〜（化５０）で示される構造のものがより好ましい。なお、（化２６）中のＡが（化２７）の構造を主成分として含む４価の有機基であることが好ましいが、ここで主成分とは、５０ｍｏｌ％以上を含有することを示す。
【００４３】
ポリアミド酸の合成反応に使用される有機溶媒としては、例えばジメチルスルホキシド、ジエチルスルホキシド等のスルホキシド系溶媒、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジエチルホルムアミド等のホルムアミド系溶媒、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジエチルアセトアミド等のアセトアミド系溶媒を挙げることができる。これらを１種類のみで用いることも、２種あるいは３種以上からなる混合溶媒を用いることもできる。また、これらの有機溶媒に加えて、ポリアミド酸が溶解しにくい溶媒である非溶媒とからなる混合溶媒も用いることもできる。前記のポリアミド酸に対する非溶媒としては、アセトン、メタノール、エタノール、イソプロパノール、ベンゼン、メチルセロソルブ等を挙げることができる。
【００４４】
係るポリアミド酸、及びこれから得られるポリイミドの分子量は特に制限されるものではないが、耐熱性接着剤としての強度を維持するためには、数平均分子量が５万以上、さらには８万以上、特には１０万以上であることが好ましい。接着層に用いられるポリイミドの前駆体であるポリアミド酸（溶液）の数平均分子量は、ＧＰＣ（ゲル浸透クロマトグラフィー）により測定が可能である。
【００４５】
次に、これらポリアミド酸からポリイミドを得る方法としては、熱的又は化学的に脱水閉環（イミド化）する方法を用いることができる。熱的に脱水閉環（イミド化）する方法としては、具体的には、ポリアミド酸溶液を、常圧で加熱乾燥もしくは減圧下で加熱乾燥する方法がある。
【００４６】
常圧で加熱乾燥を行う場合、まず有機溶媒を蒸発させるために１５０℃以下の温度で約５分間〜９０分間加熱を行うのが好ましい。続いてこれを加熱乾燥してイミド化するが、イミド化させる際の加熱温度は１５０℃〜４００℃の範囲であることが好ましい。特に最終の熱処理は３００℃以上、さらには３００〜４００℃で行うことが好ましい。
【００４７】
減圧下で加熱乾燥を行う場合は、溶媒除去とイミド化を同時に行うことができる。加熱温度としては、１５０℃〜２００℃の範囲であることが好ましい。この方法は減圧下で加熱するため、系内から水を除去しやすいという利点があり、そのため、常圧加熱に比べてイミド環の加水分解及びそれに伴う分子量低下が起こりにくいことが特徴である。
【００４８】
化学的に脱水閉環（イミド化）する方法については、上記ポリアミド酸溶液に化学量論以上の脱水剤及び触媒である第３級アミンとを加え、加熱処理することがあげられる。この場合、単に熱的に脱水する方法と同様の条件で処理すると、脱水剤及び触媒を用いた方が短時間で所望のポリイミドが得られる。また、触媒として使用される第３級アミンとしては、ピリジン、α−ピコリン、β−ピコリン、γ−ピコリン、トリメチルアミン、トリエチルアミン、イソキノリンなどが好ましく例示され得る。
【００４９】
得られたポリイミド樹脂を溶解させる有機溶媒としては、例えばジメチルスルホキシド、ジエチルスルホキシド等のスルホキシド系溶媒、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジエチルホルムアミド等のホルムアミド系溶媒、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジエチルアセトアミド等のアセトアミド系溶媒、Ｎ−メチル−２−ピロリドン等のピロリドン系溶媒、テトラヒドロフラン、１，４−ジオキサン、ジオキソラン等のエーテル系溶媒を挙げることができる。これらを１種類のみで用いることも、２種あるいは３種以上からなる混合溶媒も用いることもできる。
【００５０】
続いて耐熱性ベースフィルムについて説明する。本発明で使用されるベースフィルムは、部品実装時の半田リフロー温度が高いため耐熱性が必要であり、耐熱性があればどんなフィルムでもよく、一般にポリイミド系のフィルムが好適に用いられる。ただし、ポリイミド系フィルムのうち熱可塑性ポリイミドフィルムは、２００〜３００℃に明確なＴｇ（ガラス転移温度）を持ち、弾性率が１桁以上低下するため、高温加工時の寸法変化率が大きくなる問題があり、耐熱性ベースフィルムには不適切である。従って、このような、明確なＴｇがなくＴｇにおける急激な弾性率の低下が生じない非熱可塑性ポリイミドフィルムであることが好ましい。上記ポリイミドフィルムは、特に制限されるものではないが、供給面から、すでに上市されている鐘淵化学工業製のアピカルＡＨ、同ＮＰＩ、あるいは同ＨＰが好適に用いられる。その他、要求特性に応じて、種々の酸二無水物とジアミンの組み合わせから得られるポリイミドフィルムを用いることができる。
【００５１】
この耐熱性ベースフィルムに上述の熱可塑性ポリイミド溶液あるいはその前駆体として当業者には一般的に知られているポリアミド酸溶液を塗布し、所望の構成の耐熱性ボンドプライを得ることができる。なお、ボンドプライとは、接着層を有するフィルムのことを指し、接着剤層単体であっても、接着層を最外層に持つ多層材であっても構わない。これと薄層金属シートを積層することにより、耐熱性フレキシブル薄層金属シート積層体を得ることができるのである。ここで、薄層金属シートとは、例えば銅箔、アルミ箔、ＳＵＳ箔等があり、中でも銅箔が好ましい。
【００５２】
耐熱性ボンドプライと薄層金属シートを積層する方法は特に限定されず、当業者で有れば容易に技術的に構想することができるいかなる種類の方法により行うことができる。その中でも、連続的に処理できる加熱加圧ラミネート方式を選択して行うことが好ましい。
【００５３】
本発明に係る視認性に優れた耐熱性フレキシブル銅張積層板は、形成した銅箔をエッチング除去したボンドプライにおいて、波長６００ｎｍにおける光線透過率が３０％以上であることを言い、更に望ましくは４０％以上である。上記光線透過率は、ＩＬＢ装置でのフィルムを介しての半導体チップの位置決めの点から高い方が好ましく、上記光線透過率が３０％未満である場合はフィルムを介して半導体チップの位置を判別するのが困難であるため好ましくない。なお、上記の光線透過率は、分光光度計により測定することができる。
【００５４】
上記の光線透過率が上記の範囲内であるためには、プレス成形したボンドプライ側に積層する銅箔のマット面の粗面が出来るだけスムーズであることが重要であり、その銅箔のマット面の粗度は、ＪＩＳ　Ｂ０６０１に記載の測定法において、Ｒｚが１．５μｍ以下かつ、Ｒａが０．２μｍ以下であることにより達成され得る。更に好ましくは、Ｒｚは１．０μｍ以下であり、Ｒａは０．１５μｍ以下である。Ｒｚが１．５μｍ以上であり、Ｒａが０．２μｍ以上であるならば、粗い形状が転写するため、本発明でいうところの視認性が低下し、ＴＡＢのＩＬＢ工程にかけられない問題が発生するため好ましくない。ここで、マット面の粗度とは、銅箔の接着面側の表面粗さであり、またＪＩＳ　Ｂ０６０１記載の測定法におけるＲｚとは十点平均粗さを意味し、Ｒａとは中心線平均粗さを意味する。なお、ＲｚおよびＲａは、表面粗さ測定器により測定することができる。
【００５５】
以上、本発明の実施の形態について説明したが、本発明はこれによって限定されるものではなく、本発明はその趣旨を逸脱しない範囲で当業者の知識に基づき、種々なる改良、変更、修正を加えた様態で実施しうるものである。
【００５６】
【実施例】
実施例により本発明をより具体的に説明するが、本発明はこれらの実施例によって何ら限定されるものではない。
【００５７】
（実施例１）
系全体を氷水で冷やし、窒素置換をした４０００ｍｌの三口のセパラブルフラスコに、１００ｇの２，２’−ビス［４−（４−アミノフェノキシ）フェニル］プロパン（以下、ＢＡＰＰという）を７０８．４ｇのジメチルホルムアミド（以下、ＤＭＦという）を溶媒として用いて投入し、充分に溶解させた。１５分間の撹拌の後、１０８．２ｇのｐ−フェニレンビス（トリメリット酸モノエステル無水物）モノマー（以下、ＴＭＨＱという）を粉体で投入した。３０分間攪拌の後、さらに３．４ｇのＴＭＨＱを８．４ｇのＤＭＦでスラリーとし、フラスコ内の溶液の粘度に注意しながら徐々に投入した。その後１時間撹拌しながら放置し、固形分濃度２３％のポリアミド酸を得た。その後、１２９６ｇのＤＭＦを加え１時間撹拌し、粘度約５ポイズに調整した。このポリアミド酸溶液をポリイミドフィルム（アピカル１２．５ＨＰ；鐘淵化学工業（株）製）の両面に、熱可塑性ポリイミド層の最終片面厚みが２μｍとなるように塗布した後、１２０℃、３５０℃で各２分間加熱して溶媒を除去し、ボンドプライを得た。その両側に金属材料（古河電工（株）製の電解銅箔Ｆ０−ＷＳ：厚み１８μｍ、粗度Ｒｚ＝１．３μｍ　、Ｒａ＝０．２μｍ　）を配し、さらにその両側に保護材料（鐘淵化学工業（株）製のアピカル１２５ＮＰＩ）を配した状態で、図１に示す熱ロールラミネート装置で、ラミ温度３５０℃、ラミ圧力５０Ｎ／ｍｍ、ラミ速度３．５ｍ／ｍｉｎの条件でラミネートを行い、耐熱性フレキシブル銅張積層板を得た。得られた耐熱性フレキシブル銅張積層板から、形成した銅箔をエッチング除去したボンドプライの波長６００ｎｍにおける光線透過率をＪＡＳＣＯ　Ｕ−ｂｅｓｔ３０で測定した。その結果を表１に示す。
【００５８】
（実施例２）
使用する銅箔を、（株）ジャパンエナジー社製ＢＨＹ−２２Ｂ−Ｔ（厚み１８μｍ、粗度Ｒｚ＝１．４μｍ　、Ｒａ＝０．２μｍ　）に変えた以外は実施例１と同様に耐熱性フレキシブル銅張積層板を作製し、その光線透過率を測定した。結果を表１に示す。
【００５９】
（実施例３）
使用する銅箔を、（株）ジャパンエナジー社製ＡＭ−ＦＮ（厚み９μｍ、粗度Ｒｚ＝１．５μｍ　、Ｒａ＝０．２μｍ　）に変えた以外は実施例１と同様に耐熱性フレキシブル銅張積層板を作製し、その光線透過率を測定した。結果を表１に示す。
【００６０】
（実施例４）
使用する銅箔を、古河電工株式会社製の電解銅箔Ｂ−ＷＳ（厚み１８μｍ、粗度Ｒｚ＝１．４μｍ　、Ｒａ＝０．２μｍ　）に変えた以外は実施例１と同様に耐熱性フレキシブル銅張積層板を作製し、その光線透過率を測定した。結果を表１に示す。
【００６１】
（比較例１）
使用する銅箔を古河電工株式会社製の電解銅箔Ｆ１−ＷＳ（厚み１８μｍ、粗度Ｒｚ＝１．９μｍ　、Ｒａ＝０．４μｍ　）に変えた以外は実施例１と同様に耐熱性フレキシブル銅張積層板を作製し、その光線透過率を測定した。結果を表１に示す。
【００６２】
（比較例２）
使用する銅箔を古河電工株式会社製の電解銅箔Ｆ２−ＷＳ（厚み１８μｍ、粗度Ｒｚ＝２．１μｍ　、Ｒａ＝０．５μｍ　）に変えた以外は実施例１と同様に耐熱性フレキシブル銅張積層板を作製し、その光線透過率を測定した。結果を表１に示す。
【００６３】
【表１】

表１から明らかなように、　Ｒｚが１．５μｍ以下かつ、Ｒａが０．２μｍ以下である銅箔を使用することにより、銅箔エッチング後のボンドプライの光線透過率が３０％以上となり、ＩＬＢ装置での半導体チップの位置決めが容易に行えるようになる。
【００６４】
【発明の効果】
本発明に係る耐熱性フレキシブル銅張積層板は、波長６００ｎｍにおける光線透過率すなわち視認性に優れるため、ＩＬＢ装置を用いて２層或いは擬似２層ＦＰＣからＣＯＦを製造する場合において、半導体チップを搭載する際の位置決めが容易にできる利点を有する。ＣＯＦ等の今後の新規高密度実装材料用途に好適である。
【図面の簡単な説明】
【図１】２対のラミネートロールを有するの熱ロールラミネート装置
【符号の説明】
１　　金属材料
２　　接着フィルム
３　　保護フィルム
４　　熱ロールラミネート装置
５　　保護フィルム巻取装置
６　　製品巻取装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-resistant flexible copper-clad laminate in a bond ply having a thermoplastic polyimide layer on at least one side of a base film, and further having a copper foil laminated on at least one side thereof.
[0002]
[Prior art]
2. Description of the Related Art In recent years, high performance, high functionality, and miniaturization of electronic devices have been rapidly advanced, and accordingly, electronic components used have also been required to be reduced in size and weight. Therefore, there is a further demand for materials for electronic components to improve various physical properties such as heat resistance, mechanical strength, and electrical characteristics. High performance and high performance are required. In particular, the thickness, adhesive strength, dimensional stability, alkali etchability, chemical resistance, water absorption, and electrical properties of polyimide used as an insulating layer in flexible printed wiring boards (hereinafter, referred to as FPC) and HDD wireless suspensions. Various characteristics are required.
[0003]
Recently, the demand for heat resistance has increased, and a pseudo two-layer type using a polyimide resin as an adhesive (for example, JP-A-05-13902), and a two-layer type without using an adhesive layer (for example, JP-A-08-18402) Is also used.
[0004]
The above-mentioned FPC and HDD wireless suspension are manufactured through many processes. In particular, a COF (Chip on Flex) is manufactured using an inner lead bonding (hereinafter, referred to as ILB) apparatus used in a TAB (Tape Automated Bonding) method. )), The position of the semiconductor chip to be mounted is detected using a CCD camera through a two-layer or pseudo-two-layer FPC film, so that the transparency of the film, in other words, high light transmittance is required. Have been.
[0005]
[Problems to be solved by the invention]
The present invention solves the problem that when a COF is manufactured from a two-layer or pseudo-two-layer FPC using an ILB device, the chip cannot be positioned due to poor light transmittance of a film when a semiconductor chip is mounted. It is another object of the present invention to provide a heat-resistant flexible copper-clad laminate excellent in visibility.
[0006]
[Means for Solving the Problems]
The present inventors have solved the above-mentioned problems, have excellent light transmittance, and have conducted intensive studies for the purpose of providing a copper-clad laminate having both characteristics to be provided, and as a result, a heat-resistant base film In a heat-resistant bond ply in which a thermoplastic polyimide is formed on one or both surfaces, a heat-resistant flexible copper-clad laminate on which a copper foil having a specific surface roughness is formed on one or both surfaces to form a copper-clad substrate. The present invention was found to exhibit a light transmittance of a certain numerical value or more, which led to the present invention.
[0007]
That is, the present invention is a heat-resistant bond ply in which a thermoplastic polyimide layer is formed on one or both sides of a heat-resistant base film, and further a copper-clad laminate formed by forming a copper foil on one or both sides thereof. The roughness of the matte surface of the copper foil was determined by the measurement method described in JIS B0601, Rz was 1.5 μm or less, Ra was 0.2 μm or less, and the wavelength of the bond ply obtained by etching and removing the formed copper foil was 600 nm. A heat-resistant flexible copper-clad laminate characterized by having a light transmittance of 30% or more.
[0008]
In a preferred embodiment, the precursor of the thermoplastic polyimide used for the adhesive layer has a general formula (Formula 26):
[0009]
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(Wherein, n is an integer of 1 or more; A is a tetravalent organic group, and X is a divalent organic group). The present invention relates to a heat-resistant flexible copper-clad laminate.
[0010]
In a more preferred embodiment, A in the general formula (Chemical Formula 26) is represented by the following Formula (Chemical Formula 27):
[0011]
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(In the formula, R is a divalent organic group.)
The present invention relates to the above-mentioned heat-resistant flexible copper-clad laminate, which is a tetravalent organic group containing the above structure as a main component.
[0012]
In a further preferred embodiment, R in the above formula (Chemical formula 27) is the following structural unit (Chemical formula 28) to (Chemical formula 30):
[0013]
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[0014]
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[0015]
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Wherein the heat-resistant flexible copper-clad laminate is at least one selected from the group shown in (1).
[0016]
In a further preferred embodiment, X in the general formula (Chemical Formula 26) is the following structural unit (Chemical Formula 31) to (Chemical Formula 50):
[0017]
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[0018]
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[0019]
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[0020]
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[0021]
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[0022]
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[0023]
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[0024]
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[0025]
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[0026]
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[0027]
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[0028]
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[0029]
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[0030]
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[0031]
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[0032]
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[0033]
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[0034]
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[0035]
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[0036]
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The heat-resistant flexible copper-clad laminate according to any one of the above, wherein the heat-resistant flexible copper-clad laminate is at least one selected from the group of divalent organic groups shown in the following.
[0037]
A preferred embodiment relates to a heat-resistant flexible copper-clad laminate, wherein the heat-resistant base film in the heat-resistant bond ply is a non-thermoplastic polyimide film.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
First, a method for preparing a polyamic acid solution as a raw material for forming a thermoplastic polyimide layer in the present invention will be described.
[0039]
Polyamic acid is obtained by reacting an acid dianhydride with a diamine in an organic solvent. First, in an atmosphere of an inert gas such as argon or nitrogen, a general formula (Formula 51):
[0040]
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(Wherein, Y represents a tetravalent organic group.) At least one acid dianhydride represented by the following formula is dissolved or diffused in an organic solvent, and the solution is dispersed in the solution by the general formula (Formula 52):
[0041]
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(In the formula, X represents a divalent organic group.) At least one diamine represented by the following formula (1) is added in the form of a solid or an organic solvent solution. Further, a mixture of one or more acid dianhydrides represented by the above general formula (Formula 51) is added in the form of a solid or organic solvent solution to obtain a polyamic acid solution which is a polyimide precursor. . In this reaction, contrary to the above addition procedure, a diamine solution may be prepared first, and an acid dianhydride in the form of a solid or organic solvent solution may be added to the solution. The reaction temperature at this time is preferably about −10 ° C. to 0 ° C. (If the reaction temperature is too high, depolymerization starts). The reaction time is preferably about 30 minutes to 3 hours. By this reaction, a polyamic acid solution which is a precursor of the thermoplastic polyimide is prepared.
[0042]
The polyamic acid which is a precursor of the thermoplastic polyimide in the present invention has a structure represented by the above formula (Chemical Formula 26) from the viewpoint of heat resistance, processability (easy adhesion), low water absorption, electric characteristics and the like. More preferably, those having the structures represented by (Chem. 27), (Chem. 28) to (Chem. 30), and (Chem. 31) to (Chem. 50) are more preferable. It is preferable that A in (Chemical Formula 26) is a tetravalent organic group containing the structure of (Chemical Formula 27) as a main component, but the main component means that the content is 50 mol% or more.
[0043]
Examples of the organic solvent used in the polyamic acid synthesis reaction include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and N, N-dimethyl. Acetamide solvents such as acetamide and N, N-diethylacetamide can be mentioned. These can be used alone or in combination of two or more. Further, in addition to these organic solvents, a mixed solvent composed of a non-solvent which is a solvent in which the polyamic acid is hardly dissolved can also be used. Examples of the non-solvent for the polyamic acid include acetone, methanol, ethanol, isopropanol, benzene, and methyl cellosolve.
[0044]
The molecular weight of the polyamic acid and the polyimide obtained therefrom is not particularly limited, but in order to maintain the strength as a heat-resistant adhesive, the number average molecular weight is 50,000 or more, further 80,000 or more, particularly Is preferably 100,000 or more. The number average molecular weight of the polyamic acid (solution), which is a precursor of polyimide used for the adhesive layer, can be measured by GPC (gel permeation chromatography).
[0045]
Next, as a method for obtaining a polyimide from these polyamic acids, a method of thermally or chemically dehydrating a ring closure (imidization) can be used. As a method of thermally dehydrating ring closure (imidization), specifically, there is a method of heating and drying a polyamic acid solution at normal pressure or under reduced pressure.
[0046]
When heating and drying at normal pressure, it is preferable to first heat at a temperature of 150 ° C. or lower for about 5 minutes to 90 minutes in order to evaporate the organic solvent. Subsequently, this is heated and dried for imidization, and the heating temperature for imidization is preferably in the range of 150 ° C to 400 ° C. In particular, the final heat treatment is preferably performed at 300 ° C. or higher, more preferably at 300 to 400 ° C.
[0047]
When heat drying is performed under reduced pressure, solvent removal and imidization can be performed simultaneously. The heating temperature is preferably in the range of 150C to 200C. This method has the advantage that water is easily removed from the system because it is heated under reduced pressure, and therefore, it is characterized in that the hydrolysis of the imide ring and the accompanying decrease in molecular weight are less likely to occur as compared with normal pressure heating.
[0048]
As a method of chemically dehydrating and ring-closing (imidizing), it is possible to add a dehydrating agent having a stoichiometric amount or more and a tertiary amine which is a catalyst to the above polyamic acid solution, followed by heat treatment. In this case, if the treatment is carried out under the same conditions as in the method of simply thermally dehydrating, a desired polyimide can be obtained in a shorter time by using a dehydrating agent and a catalyst. Preferred examples of the tertiary amine used as a catalyst include pyridine, α-picoline, β-picoline, γ-picoline, trimethylamine, triethylamine, and isoquinoline.
[0049]
Examples of the organic solvent for dissolving the obtained polyimide resin include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and N, N-dimethylacetamide. And acetamide solvents such as N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone, and ether solvents such as tetrahydrofuran, 1,4-dioxane, and dioxolane. These may be used alone or in combination of two or more.
[0050]
Next, the heat-resistant base film will be described. The base film used in the present invention needs to have heat resistance due to a high solder reflow temperature at the time of component mounting. Any film having heat resistance may be used, and a polyimide-based film is generally suitably used. However, among the polyimide films, the thermoplastic polyimide film has a clear Tg (glass transition temperature) at 200 to 300 ° C., and the modulus of elasticity is reduced by one digit or more. And is unsuitable for heat-resistant base films. Therefore, it is preferable that the non-thermoplastic polyimide film does not have such a clear Tg and does not cause a sharp decrease in the elastic modulus at the Tg. The above-mentioned polyimide film is not particularly limited, but from the supply side, Apical AH, NPI or HP manufactured by Kaneka Chemical Industry, which is already on the market, is preferably used. In addition, polyimide films obtained from various combinations of acid dianhydrides and diamines can be used according to required characteristics.
[0051]
The above-mentioned thermoplastic polyimide solution or a polyamic acid solution generally known to those skilled in the art as a precursor thereof is applied to the heat-resistant base film to obtain a heat-resistant bond ply having a desired structure. The bond ply refers to a film having an adhesive layer, and may be a single adhesive layer or a multilayer material having an adhesive layer as an outermost layer. By laminating this and the thin metal sheet, a heat-resistant flexible thin metal sheet laminate can be obtained. Here, the thin metal sheet includes, for example, copper foil, aluminum foil, SUS foil and the like, and among them, copper foil is preferable.
[0052]
The method of laminating the heat-resistant bond ply and the thin metal sheet is not particularly limited, and can be performed by any kind of method that can be easily conceived by those skilled in the art. Among them, it is preferable to select a heating and pressure laminating method which can be continuously processed.
[0053]
The heat-resistant flexible copper-clad laminate having excellent visibility according to the present invention has a light transmittance at a wavelength of 600 nm of 30% or more, more preferably 40, in a bond ply obtained by etching and removing a formed copper foil. % Or more. The light transmittance is preferably higher from the viewpoint of positioning of the semiconductor chip via the film in the ILB device. If the light transmittance is less than 30%, the position of the semiconductor chip is determined via the film. It is not preferable because it is difficult. The above light transmittance can be measured by a spectrophotometer.
[0054]
In order for the above light transmittance to be within the above range, it is important that the rough surface of the matte surface of the copper foil to be laminated on the press-formed bond ply side is as smooth as possible. The surface roughness can be achieved by the measurement method described in JIS B0601 when Rz is 1.5 μm or less and Ra is 0.2 μm or less. More preferably, Rz is 1.0 μm or less, and Ra is 0.15 μm or less. If Rz is 1.5 μm or more and Ra is 0.2 μm or more, a coarse shape is transferred, so that the visibility as referred to in the present invention is reduced, and a problem that cannot be applied to the TAB ILB process occurs. Therefore, it is not preferable. Here, the roughness of the mat surface is the surface roughness of the bonding surface side of the copper foil, Rz in the measurement method described in JIS B0601 means ten-point average roughness, and Ra is the center line average. Means roughness. Note that Rz and Ra can be measured by a surface roughness measuring device.
[0055]
As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and the present invention can be variously modified, changed, and modified based on the knowledge of those skilled in the art without departing from the gist of the present invention. It can be implemented in an added manner.
[0056]
【Example】
The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[0057]
(Example 1)
The whole system was cooled with ice water, and 708.4 g of 100 g of 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as BAPP) was placed in a 4000 ml three-neck separable flask purged with nitrogen. Of dimethylformamide (hereinafter, referred to as DMF) as a solvent and sufficiently dissolved. After stirring for 15 minutes, 108.2 g of p-phenylenebis (trimellitic acid monoester anhydride) monomer (hereinafter referred to as TMHQ) was charged as a powder. After stirring for 30 minutes, 3.4 g of TMHQ was further slurried with 8.4 g of DMF, and gradually added while paying attention to the viscosity of the solution in the flask. Thereafter, the mixture was allowed to stand with stirring for 1 hour to obtain a polyamic acid having a solid content of 23%. Thereafter, 1296 g of DMF was added and stirred for 1 hour to adjust the viscosity to about 5 poise. This polyamic acid solution was applied to both sides of a polyimide film (Apical 12.5HP; manufactured by Kaneka Chemical Industry Co., Ltd.) so that the final one-sided thickness of the thermoplastic polyimide layer was 2 μm, and then heated at 120 ° C. and 350 ° C. The solvent was removed by heating for 2 minutes each to obtain a bond ply. A metal material (electrolytic copper foil F0-WS manufactured by Furukawa Electric Co., Ltd .: thickness 18 μm, roughness Rz = 1.3 μm, Ra = 0.2 μm) is disposed on both sides thereof, and a protective material (Kanebuchi) is disposed on both sides thereof. Laminating was performed with a hot roll laminating apparatus shown in FIG. 1 under the conditions of a laminating temperature of 350 ° C., a laminating pressure of 50 N / mm, and a laminating speed of 3.5 m / min in a state where Chemical Industry Co., Ltd. (Nippon Chemical Co., Ltd., 125 NPI) was arranged. Thus, a heat-resistant flexible copper-clad laminate was obtained. From the obtained heat-resistant flexible copper-clad laminate, the light transmittance at a wavelength of 600 nm of the bond ply obtained by etching away the formed copper foil was measured by JASCO U-best30. Table 1 shows the results.
[0058]
(Example 2)
Heat resistant flexible as in Example 1 except that the copper foil used was changed to BHY-22BT (thickness 18 μm, roughness Rz = 1.4 μm, Ra = 0.2 μm) manufactured by Japan Energy Co., Ltd. A copper-clad laminate was prepared and its light transmittance was measured. Table 1 shows the results.
[0059]
(Example 3)
Heat-resistant flexible copper-clad in the same manner as in Example 1 except that the used copper foil was changed to AM-FN (9 μm in thickness, roughness Rz = 1.5 μm, Ra = 0.2 μm) manufactured by Japan Energy Co., Ltd. A laminate was prepared and its light transmittance was measured. Table 1 shows the results.
[0060]
(Example 4)
Heat-resistant flexible as in Example 1 except that the copper foil used was changed to electrolytic copper foil B-WS (thickness 18 μm, roughness Rz = 1.4 μm, Ra = 0.2 μm) manufactured by Furukawa Electric Co., Ltd. A copper-clad laminate was prepared and its light transmittance was measured. Table 1 shows the results.
[0061]
(Comparative Example 1)
Heat-resistant flexible copper in the same manner as in Example 1 except that the used copper foil was changed to an electrolytic copper foil F1-WS (18 μm, roughness Rz = 1.9 μm, Ra = 0.4 μm) manufactured by Furukawa Electric Co., Ltd. A laminated laminate was prepared and its light transmittance was measured. Table 1 shows the results.
[0062]
(Comparative Example 2)
Heat-resistant flexible copper in the same manner as in Example 1 except that the used copper foil was changed to Furukawa Electric Co., Ltd. electrolytic copper foil F2-WS (thickness 18 μm, roughness Rz = 2.1 μm, Ra = 0.5 μm). A laminated laminate was prepared and its light transmittance was measured. Table 1 shows the results.
[0063]
[Table 1]

As is clear from Table 1, by using a copper foil having an Rz of 1.5 μm or less and an Ra of 0.2 μm or less, the light transmittance of the bond ply after the etching of the copper foil becomes 30% or more, and ILB The semiconductor chip can be easily positioned in the apparatus.
[0064]
【The invention's effect】
The heat-resistant flexible copper-clad laminate according to the present invention has excellent light transmittance, that is, visibility at a wavelength of 600 nm. Therefore, when a COF is manufactured from a two-layer or pseudo-two-layer FPC using an ILB device, a semiconductor chip is mounted. This has the advantage that positioning can be easily performed. It is suitable for future new high-density packaging materials such as COF.
[Brief description of the drawings]
FIG. 1 is a hot roll laminating apparatus having two pairs of laminating rolls.
DESCRIPTION OF SYMBOLS 1 Metal material 2 Adhesive film 3 Protective film 4 Heat roll laminating device 5 Protective film winding device 6 Product winding device

Claims (6)

In a heat-resistant bond ply in which a thermoplastic polyimide layer is formed on one or both sides of a heat-resistant base film, a copper-clad laminate formed by further forming a copper foil on one or both sides thereof, and a matte surface of the copper foil. The roughness is measured by the method described in JIS B0601, Rz is 1.5 μm or less, Ra is 0.2 μm or less, and the light transmittance at a wavelength of 600 nm of the bond ply obtained by etching off the formed copper foil is 30 μm. % Of the heat-resistant flexible copper-clad laminate. The precursor of the thermoplastic polyimide used for the adhesive layer is represented by the general formula (Formula 1):

Wherein n is an integer of 1 or more; A represents a tetravalent organic group; and X represents a divalent organic group. 2. The heat-resistant flexible copper-clad laminate according to 1. A in the general formula (Chemical formula 1) is represented by the following formula (Chemical formula 2):

(In the formula, R is a divalent organic group.)
The heat-resistant flexible copper-clad laminate according to claim 2, wherein the heat-resistant flexible copper-clad laminate is a tetravalent organic group containing the structure as a main component. R in the above formula (Formula 2) is a structural unit represented by the following formulas (Formula 3) to (Formula 5):

4. The heat-resistant flexible copper-clad laminate according to claim 3, wherein the laminate is at least one member selected from the group consisting of: X in the general formula (Chemical formula 1) is the following structural unit (Chemical formula 6) to (Chemical formula 25):

The heat-resistant flexible copper-clad laminate according to any one of claims 2 to 4, wherein the heat-resistant flexible copper-clad laminate is at least one selected from the group of divalent organic groups shown in the following. The heat-resistant flexible copper-clad laminate according to claim 1, wherein the heat-resistant base film in the heat-resistant bond ply is a non-thermoplastic polyimide film.

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