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JP4587576B2 - Multilayer wiring board - Google Patents

Multilayer wiring board Download PDF

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Publication number
JP4587576B2
JP4587576B2 JP2001022250A JP2001022250A JP4587576B2 JP 4587576 B2 JP4587576 B2 JP 4587576B2 JP 2001022250 A JP2001022250 A JP 2001022250A JP 2001022250 A JP2001022250 A JP 2001022250A JP 4587576 B2 JP4587576 B2 JP 4587576B2
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JP
Japan
Prior art keywords
circuit layer
layer
insulating layer
wiring board
woven fabric
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JP2001022250A
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Japanese (ja)
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JP2002232152A (en
Inventor
昭哉 藤崎
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Kyocera Corp
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Kyocera Corp
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Description

【0001】
【発明の属する技術分野】
本発明は、配線基板を作製するための配線基板用絶縁シートと、それを用いた半導体素子収納用パッケージなどに適した多層配線基板に関するものである。
【0002】
【従来技術】
近年、電子機器は小型化が進んでいるが、近年携帯情報端末の発達や、コンピューターを持ち運んで操作するいわゆるモバイルコンピューティングの普及によってさらに小型、薄型且つ高精細の多層配線基板が求められる傾向にある。
【0003】
また、通信機器に代表されるように、高速動作が求められる電子機器が広く使用されるようになってきた。高速動作が求められるということは、高い周波数の信号に対し、正確なスイッチングが可能であるなど多種な要求を含んでいる。そのような電子機器に対応するため、高速な動作に適した多層プリント配線板が求められている。
【0004】
高速な動作を行うためには、配線の長さを短くし、電気信号の伝播に要する時間を短縮することが必要である。配線の長さを短縮するために、配線の幅を細くし、配線の間隙を小さくするという、小型、薄型且つ高精細の多層配線基板が求められる傾向にある。このような微細高密度配線回路を有する配線基板は、従来法のプリント基板では、コア基板に対し、コア基板を貫通するビアホールを形成し、その内部にメッキ等を施して層間の接続を行う場合が多く、ビアホールによって回路設計が制限され高密度配線が難しかった。
【0005】
また、所定の基板表面に絶縁層と導体回路層を交互にコーティング及びメッキ等、あるいはビアホール形成等を施して多層化する所謂ビルドアップ法も開発されているが、ビルドアップ法もビアホールの配置上の制約があり、高密度配線化が難しかった。しかも、ビルドアップ法による多層化においては、導体回路層をエッチング法で形成したり、さらにはビアホール内面にメッキ等の手法によって導体を被着させる等の工程を繰り返し行った場合、絶縁層がエッチング液やメッキ液等に浸漬されるが、配線の高密度化に伴い、積層数が増加すると、絶縁層がこれらの薬品に浸漬される回数が多くなる結果、絶縁層自体が吸湿し変質してしまうという問題があった。また、全体に工程が複雑なので高価な配線基板とならざるを得ず、一般的な配線板には使用されていなかった。
【0006】
一般的に、配線板のコア基板として用いられる絶縁材料には、有機樹脂に対してガラスクロスを使用したプリプレグが主に使用されており、配線板の機械的特性及び熱的特性を向上させている。
【0007】
そのような高密度配線の要求に対応するため、セラミック多層配線基板の製造工程と同様な工程、即ち、ビアホール導体および導体回路層が形成された複数の絶縁シートを積層する多層プリント配線板が特開平10−27959号などによって提案されている。
【0008】
この方法では、具体的には、絶縁シートにビアホールを加工し金属粉末を充填してビアホール導体を形成した後、予め表面に金属箔からなる導体回路層が形成された転写シートから、前記導体回路層を転写して導体回路層を形成して1層の配線シートを作成し、同様にして作成した複数の配線シートを積層して一体化して多層化するものである。
【0009】
【発明が解決しようとする課題】
上記の特開平10−27959号によって提案される転写法では、絶縁シートをエッチング液やメッキ液などの薬品に浸漬しないドライプロセスで作製することができるために、絶縁シートの劣化が無く、また熱と圧力により導体回路層を絶縁シート表面に埋設させるため平坦性に優れるなどの長所を有する。
【0010】
しかしながら、ガラス織布と有機樹脂からなる絶縁シートに、緻密質な金属箔導体回路層を転写、埋設させようとする場合、絶縁シート中の未硬化の樹脂が流れやすく、配線パターンが変形し、微細配線を形成する場合には、隣接する配線層と接触して回路がショートしてしまう問題があった。
【0011】
また、ビア形成部に導体回路層を転写、硬化した際、ガラス織布上下の樹脂層が流れによってビアホール導体が変形しやすく、時には破断しオープン不良につながる場合もある。
【0012】
従って、本発明は、ガラス織布と有機樹脂からなるプリプレグの表面に金属箔などの緻密な導体層を転写させる場合に、上記のような未硬化の樹脂の流れによる回路の不良の発生を防止して、信頼性の高い多層配線基板を提供することを目的とする。
【0013】
【課題を解決するための手段】
本発明者は、上記目的に対して検討を重ねた結果、耐熱性織布上の熱硬化性樹脂層の厚みを適正に調整することによって、導体回路層の凹凸部と耐熱性織布とを接触、係合させることによって、耐熱性織布中に導体回路層を固定し、導体回路層の流れやビアホール導体の変形を防止できることを見いだし、本発明に至った。
【0014】
即ち、本発明の多層配線基板、耐熱性織布と熱硬化性樹脂との複合材料からなる絶縁層と、該絶縁層表面及び該絶縁層間に形成された複数層の導体回路層と、上下の前記導体回路層を接続するために、前記絶縁層に形成されたビアホール内に金属粉末を充填してなる複数のビアホール導体を具備する多層配線基板において、前記導体回路層前記絶縁層の表面に埋設されているとともに、前記導体回路層の前記絶縁層への埋設側の表面粗さ(Rz)が1.5〜8μmであり、前記導体回路層の厚みが、前記絶縁層の前記耐熱性織布から前記絶縁層表面に至る熱硬化性樹脂層の厚みよりも大きく、且つ前記導体回路層の埋設側表面の凹凸部と前記耐熱性織布の繊維体とが互いに係合していることを特徴とするものである。
【0015】
上記多層配線基板では、前記耐熱性織布を構成する繊維体の平均直径をa(μm)としたとき、前記導体回路層の埋設側表面粗さRzが、a/4<Rz<3aの関係を満足することが望ましく、これによって、導体回路層の埋設側表面の凹凸部と前記耐熱性織布との係合を強めることができる。
【0016】
【発明の実施の形態】
以下、本発明の多層配線基板を図面に基づき詳細に説明する。
【0017】
図1は、本発明の多層配線基板の一例を示す概略断面図、図2は、絶縁層と導体回路層との要部拡大断面図である。図1の多層配線基板Aによれば、絶縁基板1は、熱硬化性樹脂1aと耐熱性織布1bの織布または不織布との複合体からなる絶縁層2を多層に積層してなるものである。そして、この絶縁基板1には、絶縁層に形成されたビアホール内に少なくとも金属粉末を充填してなるビアホール導体4が形成されており、さらに、そのビアホール導体4の端部には、金属箔からなる導体回路層5が各絶縁層2の表面に埋設された構造からなる。
【0018】
本発明の多層配線基板における絶縁層2を構成する熱硬化性樹脂1aとしては例えば、PPE(ポリフェニレンエーテル)、BTレジン(ビスマレイミドトリアジン)、エポキシ樹脂、ポリイミド樹脂、フッ素樹脂、フェノール樹脂が挙げられ、さらにそれらの樹脂の硬化剤を含み、さらには無機質フィラーを含んでもよい。用いられる無機質フィラーとしては、SiO、Al、AlN、SiCの群から選ばれる少なくとも1種が使用でき、熱硬化性樹脂:無機質フィラーの体積比率で15:85〜90:10の比率で複合化されるのが適当である。
【0019】
一方、耐熱性織布1bは、繊維を数百本束ねて糸状に形成したものを編んだものからなり、繊維(フィラメント)としては1〜10μmの径が適当であり、これを束ねた糸は円換算で25〜100μm程度の直径を有するものが望ましい。耐熱性織布としては、一般に無機繊維が好んで用いられているが、無機繊維としては、例えば、Eガラス、ホウケイ酸ガラス、シリカガラスの群から選ばれる少なくとも1種のガラス繊維が好適に用いられ、特に繊維強度、コスト等のバランスの観点からEガラス繊維が最も望ましい。また、この無機繊維はその線径が4〜8μmであることが強度と加工性の点で望ましい。更に、アラミド織布などの高強度、高耐熱の有機繊維でも良い。また、ガラス織布及び無機質フィラーの表面は樹脂との塗れを良くするために、カップリング処理されていても良い。
【0020】
また、本発明によれば、導体回路層5の埋設側表面の凹凸部と絶縁層2中の前記耐熱性織布1bとが互いに係合していることが重要であって、かかる構造によって、導体回路層5を未硬化状態の絶縁層2表面に埋設形成する場合に、未硬化樹脂の流れによって導体回路層5のずれを防止することができるとともに、絶縁層2表面に導体回路層5とともに形成されたビアホール導体4の変形をも防止することができる。つまり、導体回路層5の埋設された部分が、耐熱性織布1bに楔を打ち、結果として導体回路層5やビアホール導体4の変形を防止し電気的ショート等を回避できることになる。
【0021】
また、本発明によれば、このような構造を形成するために、上記絶縁層2の表面に埋設された導体回路層5の厚みを熱硬化性樹脂層3の厚みLより大きくすることによって、導体回路層5と耐熱性織布1bとの係合を確実に行うことができる。例えば、通常、高密度配線基板として用いられる線間/線幅は200μm/200μm以下であるので、導体回路層5を形成する銅箔などの金属箔の厚みは35μm以下となる。絶縁層2における熱硬化性樹脂層3の厚みLは35μm以下の樹脂厚みを設定することになる。
【0022】
上記の条件は、熱硬化性樹脂層3の厚みLが導体回路層5よりも厚いと、導体回路層5の埋設側の凹凸部が、耐熱性織布1bまで届かず、結果として転写や硬化の熱履歴の際に、樹脂が流れるに伴って導体回路層5も移動し、結果として配線パターンの変形や電気的ショートを招いてしまうためである。この絶縁層2における熱硬化性樹脂層3の厚みは、通常の耐熱性織布1bを熱硬化性樹脂中に浸漬し、引き上げる引き上げ法や、ドクターブレード法などに耐熱性織布に熱硬化性樹脂を含浸させて絶縁層2を形成する場合において、その熱硬化性樹脂の粘度や被覆回数などによって任意に調整することができる。
【0023】
また、本発明によれば、上記絶縁層2の表面に埋設形成されている導体回路層5が絶縁層2への埋設側の表面粗さ(Rz)が1.5〜8μmであることも重要である。これは表面粗さRzが1.5μmよりも小さく平滑である場合、耐熱性織布の繊維(フィラメント)との係合できず、Rzが8μmよりも粗いと、繊維と係合しても導体回路層5のずれを有効に防止することができないためである。
【0024】
本発明の多層配線基板における導体回路層5は、一般に銅箔からなり、通常配線基板に用いる場合、片面が凹凸のついたマット面、もう片面が平坦なシャイニー面から構成されるが、絶縁層2に埋設される側は、通常、マット面によって形成されれるが、シャイニー面を荒らして表面粗さが上記の範囲であれば、シャイニー面でもよく、また絶縁層2との密着強度を高めるために防錆処理やカップリング処理が施されていてもよい。
【0025】
さらに、本発明によれば、耐熱性織布1bを構成する繊維体(フィラメント)の平均直径をa(μm)とした時、導体回路層5の埋設側表面粗さRzが、a/4<Rz<3aの関係を満足することが望ましい。これは、表面粗さRzがa/4径よりも小さいと、導体回路層5の凸部が、織布1b 内に楔を打ち込んだとしても、織布のフィラメントに固定されず、結果として転写硬化時に起こる樹脂流れに応じて、導体回路も移動し回路パターンの変形やひどいときには伝記的ショートに至ってしまう。また、3aよりも大きいと導体回路層5を転写により形成する際に、織布1bのフィラメントを押し広げる作用が大きく、転写後の寸法変化が大きくなってしまうのである。さらに、ひどいときには基板の亀裂を招いてしまう場合も有る。
【0026】
次に、本発明の多層配線基板の製造工程を図3をもとに説明する。まず、絶縁材料11に対して、未硬化の状態(Bステージ状態)でパンチング、レーザー等により所望のビアホール12を形成し(b)、そのビアホール12内に導体ペーストを充填してビアホール導体13を形成する(c)。
【0027】
導体ペーストは、銅、アルミニウム、金、銀の群から選ばれる少なくとも1種、または2種以上の合金を主体とする金属粉末、溶剤、熱硬化性樹脂及び硬化剤より構成される。溶剤はα−テルピネオール、2−オクタノールや室温で液状の熱硬化性樹脂などが用いられる。熱硬化性樹脂及び硬化剤は絶縁シートの硬化を妨げない同組成の樹脂もしくは同じ温度で硬化する樹脂が選択される。これは導電性組成物同士の硬化後の保形性を保つために用いられる。
【0028】
次に、転写シート14表面に金属箔を接着した後、エッチング等の処理により導体回路層15を形成したものを作製する(d)。転写シート14は、導体回路層15形成時のエッチングなどの工程に耐える機械的特性や寸法安定性を有するものが用いられ、ポリエチレン系のものが好適に使用される。また、金属箔を接着するための接着剤としては、酸、アルカリに強いアクリル酸エステル等が好適に用いられる。
【0029】
その後、ビアホール導体3が形成された絶縁シート11に上記導体回路層15が形成された転写シート14を位置合わせして積層し、Bステージ状態の絶縁シートを70〜200℃に加熱しながら導体回路層15が絶縁シート11表面に埋設できる程度の圧力を印加し、その後、転写シート14を引き剥がすことにより、導体回路層15を絶縁シート14の表面に転写して1層の配線シートaを作製する(e)。導体回路層15を埋設するための圧力としては、10kg/cm2以上、特に20〜70kg/cm2の範囲が望ましい。
【0030】
かかる転写工程において、絶縁層11に形成された導体回路層15とは、その厚み方向に対する絶縁層11が有する収縮性または圧縮性から絶縁層表面と導体回路層5表面とが同一平面となるように平坦化することができる。ビアホール導体13は、導体回路層15の埋設によって厚み方向に圧縮されることから充填性がアップし低抵抗化が実現できる。
【0031】
その後、上記と同様な工程によって、片面のみ及び両面に導体回路層を転写した絶縁シートb,cを作製し、これらを位置合わせして積層した後(f)、絶縁材料1中の熱硬化性樹脂が完全硬化する温度に加熱することにより図1に示したような多層配線基板を作製することができる。
【0032】
【実施例】
平均厚さ100μmのEガラスで織られたガラス織布に、ポリフェニレンエーテル(PPE)樹脂を含浸させ、図2に示す熱硬化性樹脂層の厚さがX(μm)の絶縁材料からなる半硬化状態の絶縁シートを形成した。次に、この絶縁シートを用いて、炭酸ガスレーザ加工法によって、所定の位置に直径が0.1mmのビアホールを形成し、このビアホールに、平均粒径が4μmの表面に銀を被覆した銅粉100重量部、セルロース0.2重量部、2−オクタノール10重量部とを混合した金属ペーストを充填してビアホール導体を形成し、50℃で60分加熱して乾燥させた。
【0033】
一方、厚さ25μmのポチエチレンテレフタレート樹脂(PET)製の樹脂フィルムに厚さYμmの銅箔を貼りつけ(転写シート)、これを公知のフォトレジスト法等によって鏡像の導体回路層を形成した。そして、ビアホール導体を形成した絶縁基板の表面側および裏面側に転写シートを位置合わせして重ね合わせ、少なくともビアホール導体形成位置に5kg/cm2の圧力を印加して、ビアホール導体の両端部側から導体回路層を絶縁層内に埋め込み処理し、コア用配線シートを作製した。
【0034】
同様にして、ビアホール導体を形成した絶縁シートの片面のみに導体回路層を形成した配線シートを4枚作製し、前記コア用配線シートの上下面に2枚の配線シートを位置合わせして積層した後、温度200℃、圧力20kg/cm2で硬化して、導体回路層6層の多層配線基板を作製した。
【0035】
作製した多層配線基板の初期導通、及び絶縁抵抗を測定し、試験後の導通不良(オープン)、絶縁不良(ショート)や外観(目視)導体回路層のふくれや回路の抵抗変化が生じたものを不良として、各試料につき50サンプル作製したうちの良品率を表1に示した。
【0036】
【表1】

Figure 0004587576
【0037】
表1の結果から明らかなように、熱硬化性樹脂層の厚みが銅箔よりも厚い場合(試料No.1、3、9、15)、導体回路層と耐熱性織布における繊維体との係合がうまくできず、導体回路層の転写時に樹脂の流れによるショートが発生した。また、導体回路層の表面粗さが1.5〜8μmから逸脱するもの、導体回路層の埋設側表面粗さRzが、a/4<Rz<3a(a:繊維体の平均径)の関係から逸脱するものは、いずれも係合できず、ショート不良やオープン不良が発生した。これに対して、導体回路層と耐熱性織布の繊維体とが係合した試料No.2、5〜7、11〜13、17〜19は、いずれもショート不良やオープン不良を抑制することができた。
【0038】
【発明の効果】
以上詳述したとおり、本発明の多層配線基板によれば、銅箔で形成した微細な導体回路層を形成した場合においても、導体回路層の変形や断線などの発生のない、かつ金属粉末を充填してなるビアホール導体の変形や断線の無い良好な多層配線基板を作製することができる。
【図面の簡単な説明】
【図1】本発明の多層配線基板の概略断面図である。
【図2】本発明の多層配線基板における絶縁層と導体回路層との要部拡大断面図である。
【図3】本発明の多層配線基板の製造工程を説明するための図である。
【符号の説明】
1 絶縁基板
2 絶縁層
3 熱硬化性樹脂層
4 ビアホール導体
5 導体回路層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiring board insulating sheet for producing a wiring board, and a multilayer wiring board suitable for a semiconductor element storage package using the same.
[0002]
[Prior art]
In recent years, electronic devices have been reduced in size, but in recent years, with the development of portable information terminals and the spread of so-called mobile computing that carries and operates computers, there is a tendency for more compact, thin and high-definition multilayer wiring boards to be required. is there.
[0003]
Moreover, as represented by communication devices, electronic devices that require high-speed operation have been widely used. The demand for high-speed operation includes various requirements such as accurate switching for high-frequency signals. In order to cope with such an electronic device, a multilayer printed wiring board suitable for high-speed operation is required.
[0004]
In order to perform high-speed operation, it is necessary to shorten the length of the wiring and shorten the time required for propagation of the electric signal. In order to reduce the length of the wiring, there is a tendency to require a small, thin and high-definition multilayer wiring board in which the width of the wiring is reduced and the gap between the wirings is reduced. In a conventional printed circuit board, a wiring board having such a fine high-density wiring circuit is formed when a via hole penetrating the core board is formed on the core board and plating is performed on the inside thereof to connect the layers. In many cases, circuit design was limited by via holes, making high-density wiring difficult.
[0005]
In addition, a so-called build-up method has been developed in which an insulating layer and a conductor circuit layer are alternately coated and plated on a predetermined substrate surface, or via holes are formed, so-called build-up methods have been developed. It was difficult to make high-density wiring. In addition, in multi-layering by the build-up method, the insulating layer is etched when the conductive circuit layer is formed by an etching method or when the conductor is repeatedly applied to the inner surface of the via hole by a technique such as plating. As the number of layers increases with increasing wiring density, the number of times the insulating layer is immersed in these chemicals increases, resulting in moisture absorption and alteration. There was a problem that. Moreover, since the process is complicated as a whole, it has to be an expensive wiring board and has not been used for a general wiring board.
[0006]
In general, prepregs that use glass cloth against organic resin are mainly used as insulating materials used as the core substrate of wiring boards, which improves the mechanical and thermal characteristics of wiring boards. Yes.
[0007]
In order to meet the demand for such high-density wiring, a process similar to the manufacturing process of a ceramic multilayer wiring board, that is, a multilayer printed wiring board in which a plurality of insulating sheets on which via-hole conductors and conductor circuit layers are formed is laminated. Proposed by Kaihei 10-27959.
[0008]
In this method, specifically, after forming a via hole conductor by processing a via hole in an insulating sheet and filling a metal powder, the conductor circuit is formed from a transfer sheet in which a conductor circuit layer made of a metal foil is previously formed on the surface. The layer is transferred to form a conductor circuit layer to prepare a single-layer wiring sheet, and a plurality of wiring sheets prepared in the same manner are stacked and integrated to form a multilayer.
[0009]
[Problems to be solved by the invention]
In the transfer method proposed by the above Japanese Patent Application Laid-Open No. 10-27959, the insulating sheet can be produced by a dry process that does not immerse in chemicals such as an etching solution and a plating solution. In addition, since the conductor circuit layer is embedded in the surface of the insulating sheet by pressure, it has advantages such as excellent flatness.
[0010]
However, when transferring and embedding a dense metal foil conductor circuit layer on an insulating sheet made of glass woven fabric and organic resin, uncured resin in the insulating sheet tends to flow, and the wiring pattern is deformed. In the case of forming fine wiring, there is a problem that the circuit is short-circuited due to contact with an adjacent wiring layer.
[0011]
Further, when the conductor circuit layer is transferred and cured to the via forming portion, the via hole conductor is easily deformed by the flow of the resin layer above and below the glass woven fabric, and sometimes breaks and leads to an open defect.
[0012]
Therefore, the present invention prevents the occurrence of circuit defects due to the flow of uncured resin as described above when transferring a dense conductor layer such as metal foil onto the surface of a prepreg made of glass woven fabric and organic resin. An object of the present invention is to provide a highly reliable multilayer wiring board.
[0013]
[Means for Solving the Problems]
As a result of repeated studies on the above-mentioned purpose, the present inventor appropriately adjusted the thickness of the thermosetting resin layer on the heat-resistant woven fabric, thereby providing the uneven portion of the conductor circuit layer and the heat-resistant woven fabric. As a result of contact and engagement, the inventors have found that the conductor circuit layer can be fixed in the heat-resistant woven fabric, and that the flow of the conductor circuit layer and the deformation of the via-hole conductor can be prevented, leading to the present invention.
[0014]
That is, the multilayer wiring board of the present invention comprises an insulating layer made of a composite material of a heat-resistant woven fabric and a thermosetting resin, a plurality of conductor circuit layers formed between the surface of the insulating layer and the insulating layer , in order to connect the conductive circuit layer under the above, in the multilayer wiring board comprising a plurality of via hole conductors formed by filling the metal powder in the via hole formed in the insulating layer, the conductive circuit layer is the insulation Rutotomoni is embedded in the surface of the layer, the surface roughness of the buried side to the insulating layer of the conductor circuit layer (Rz) is 1.5~8Myuemu, the thickness of the conductive circuit layer, the insulating layer wherein greater than the thickness of the thermosetting resin layer of a heat resistant woven fabric leading to the surface of the insulating layer, and the fibrous body and is engaged with each other of the heat-resistant fabric with uneven portions of the buried side of the surface of the conductive circuit layer and it is characterized in that it is if.
[0015]
In the multilayer wiring board, wherein when the mean diameter of the fibers constituting the heat-resistant woven fabric was a ([mu] m), surface roughness Rz of the embedded side of the conductor circuit layer, a / 4 <Rz <3a of It is desirable to satisfy the relationship, and this can strengthen the engagement between the concavo-convex portion on the buried surface of the conductor circuit layer and the heat resistant woven fabric.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the multilayer wiring board of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a schematic cross-sectional view showing an example of the multilayer wiring board of the present invention, and FIG. 2 is an enlarged cross-sectional view of a main part of an insulating layer and a conductor circuit layer. According to the multilayer wiring board A of FIG. 1, the insulating substrate 1 is formed by laminating an insulating layer 2 made of a composite of a thermosetting resin 1a and a woven or non-woven fabric of a heat-resistant woven fabric 1b in multiple layers. is there. The insulating substrate 1 has a via hole conductor 4 formed by filling at least a metal powder in a via hole formed in the insulating layer. Further, the end of the via hole conductor 4 is made of a metal foil. The conductor circuit layer 5 is composed of a structure in which the surface of each insulating layer 2 is embedded.
[0018]
The thermosetting resin 1a constituting the insulating layer 2 in the multi-layer wiring board of the present invention for example, PPE (polyphenylene ether), BT resin (bismaleimide triazine), include epoxy resins, polyimide resins, fluorocarbon resins, phenol resins Further, a curing agent for those resins may be included, and further an inorganic filler may be included. As an inorganic filler to be used, at least one selected from the group of SiO 2 , Al 2 O 2 , AlN, and SiC can be used, and the ratio of thermosetting resin: inorganic filler is 15:85 to 90:10. It is suitable to be combined with.
[0019]
On the other hand, the heat-resistant woven fabric 1b is formed by knitting a bundle of hundreds of fibers formed into a thread shape, and a fiber (filament) having a diameter of 1 to 10 μm is appropriate. What has a diameter of about 25-100 micrometers in conversion of a circle is desirable. In general, inorganic fibers are preferably used as the heat-resistant woven fabric. As the inorganic fibers, for example, at least one glass fiber selected from the group of E glass, borosilicate glass, and silica glass is preferably used. In particular, E glass fiber is most desirable from the viewpoint of balance of fiber strength, cost, and the like. Further, it is desirable that the inorganic fiber has a wire diameter of 4 to 8 μm from the viewpoint of strength and workability. Furthermore, organic fibers having high strength and high heat resistance such as aramid woven fabric may be used. Further, the surface of the glass woven fabric and the inorganic filler may be subjected to a coupling treatment in order to improve the coating with the resin.
[0020]
In addition, according to the present invention, it is important that the concavo-convex portion on the buried side surface of the conductor circuit layer 5 and the heat-resistant woven fabric 1b in the insulating layer 2 are engaged with each other. When the conductor circuit layer 5 is embedded in the surface of the uncured insulating layer 2, the conductor circuit layer 5 can be prevented from shifting due to the flow of the uncured resin, and the conductor circuit layer 5 is disposed on the surface of the insulating layer 2. Deformation of the formed via-hole conductor 4 can also be prevented. That is, the embedded portion of the conductor circuit layer 5 hits the heat-resistant woven fabric 1b, and as a result, the conductor circuit layer 5 and the via-hole conductor 4 can be prevented from being deformed and an electrical short circuit can be avoided.
[0021]
Moreover, according to the present invention, in order to form such a structure, by making the thickness of the conductor circuit layer 5 embedded in the surface of the insulating layer 2 larger than the thickness L of the thermosetting resin layer 3, The conductor circuit layer 5 and the heat-resistant woven fabric 1b can be reliably engaged. For example, since the line spacing / line width used as a high-density wiring board is usually 200 μm / 200 μm or less, the thickness of a metal foil such as a copper foil forming the conductor circuit layer 5 is 35 μm or less. The thickness L of the thermosetting resin layer 3 in the insulating layer 2 is set to a resin thickness of 35 μm or less.
[0022]
When the thickness L of the thermosetting resin layer 3 is thicker than that of the conductor circuit layer 5, the concavo-convex portion on the embedded side of the conductor circuit layer 5 does not reach the heat-resistant woven fabric 1b, resulting in transfer or curing. This is because the conductor circuit layer 5 also moves as the resin flows during the heat history, resulting in deformation of the wiring pattern and electrical short. The thickness of the thermosetting resin layer 3 in the insulating layer 2 is such that the ordinary heat resistant woven fabric 1b is dipped in the thermosetting resin and then pulled up, the doctor blade method or the like is applied to the heat resistant woven fabric. When the insulating layer 2 is formed by impregnating the resin, it can be arbitrarily adjusted depending on the viscosity of the thermosetting resin, the number of times of coating, and the like.
[0023]
Further, according to the present invention, it is also important that the conductor circuit layer 5 embedded in the surface of the insulating layer 2 has a surface roughness (Rz) on the side embedded in the insulating layer 2 of 1.5 to 8 μm. It is. This means that when the surface roughness Rz is smaller than 1.5 μm and is smooth, it cannot be engaged with the fibers (filaments) of the heat-resistant woven fabric. This is because the displacement of the circuit layer 5 cannot be effectively prevented.
[0024]
The conductor circuit layer 5 in the multilayer wiring board of the present invention is generally made of a copper foil, and when used for a normal wiring board, it is composed of a matte surface with an uneven surface and a shiny surface with a flat surface on the other side. The side embedded in 2 is usually formed by a matte surface. However, if the surface roughness is within the above range by roughening the shiny surface, it may be a shiny surface, and in order to increase the adhesion strength with the insulating layer 2. Rust prevention treatment and coupling treatment may be given to.
[0025]
Furthermore, according to the present invention, when the average diameter of the fibrous body (filament) constituting the heat-resistant woven fabric 1b is a (μm), the embedded-side surface roughness Rz of the conductor circuit layer 5 is a / 4 < It is desirable to satisfy the relationship of Rz <3a. This is because when the surface roughness Rz is smaller than the diameter of a / 4, the convex portion of the conductor circuit layer 5 is not fixed to the filament of the woven fabric even if the wedge is driven into the woven fabric 1b, resulting in transfer. Depending on the resin flow that occurs during curing, the conductor circuit also moves, leading to a bilateral short when the circuit pattern is deformed or severe. On the other hand, if it is larger than 3a, when the conductor circuit layer 5 is formed by transfer, the action of pushing the filament of the woven fabric 1b is large, and the dimensional change after transfer becomes large. Furthermore, in severe cases, the substrate may be cracked.
[0026]
Next, the manufacturing process of the multilayer wiring board of the present invention will be described with reference to FIG. First, a desired via hole 12 is formed by punching, laser, or the like in an uncured state (B stage state) with respect to the insulating material 11 (b), and the via hole 12 is filled with a conductive paste to form the via hole conductor 13. Form (c).
[0027]
The conductor paste is composed of a metal powder mainly composed of at least one selected from the group of copper, aluminum, gold, and silver, or two or more alloys, a solvent, a thermosetting resin, and a curing agent. As the solvent, α-terpineol, 2-octanol or a thermosetting resin which is liquid at room temperature is used. As the thermosetting resin and the curing agent, a resin having the same composition that does not hinder the curing of the insulating sheet or a resin that cures at the same temperature is selected. This is used in order to maintain the shape retention after curing of the conductive compositions.
[0028]
Next, a metal foil is bonded to the surface of the transfer sheet 14, and then a conductor circuit layer 15 is formed by a process such as etching (d). As the transfer sheet 14, a sheet having mechanical properties and dimensional stability that can withstand a process such as etching when the conductor circuit layer 15 is formed is used, and a polyethylene sheet is preferably used. In addition, as an adhesive for bonding the metal foil, an acrylic acid ester resistant to acid or alkali is preferably used.
[0029]
Thereafter, the transfer sheet 14 on which the conductor circuit layer 15 is formed is aligned and laminated on the insulating sheet 11 on which the via-hole conductor 3 is formed, and the B-stage insulating sheet is heated to 70 to 200 ° C. A pressure sufficient to embed the layer 15 on the surface of the insulating sheet 11 is applied, and then the transfer sheet 14 is peeled off, whereby the conductor circuit layer 15 is transferred to the surface of the insulating sheet 14 to produce a single wiring sheet a. (E). The pressure for embedding the conductor circuit layer 15 is preferably 10 kg / cm 2 or more, particularly in the range of 20 to 70 kg / cm 2 .
[0030]
In the transfer step, the surface of the insulating layer and the surface of the conductor circuit layer 5 are flush with the conductor circuit layer 15 formed on the insulating layer 11 because of the contractibility or compressibility of the insulating layer 11 in the thickness direction. Can be flattened. Since the via-hole conductor 13 is compressed in the thickness direction by embedding the conductor circuit layer 15, the filling property is improved and a reduction in resistance can be realized.
[0031]
Thereafter, by the same process as described above, insulating sheets b and c having a conductor circuit layer transferred to only one side and both sides are prepared, and after aligning and laminating them (f), the thermosetting in the insulating material 1 is performed. The multilayer wiring board as shown in FIG. 1 can be produced by heating to a temperature at which the resin is completely cured.
[0032]
【Example】
Semi-cured made of an insulating material in which a glass woven fabric woven with E glass having an average thickness of 100 μm is impregnated with polyphenylene ether (PPE) resin and the thermosetting resin layer shown in FIG. 2 has a thickness of X (μm) An insulating sheet in a state was formed. Next, by using this insulating sheet, a copper powder 100 in which a via hole having a diameter of 0.1 mm is formed at a predetermined position by a carbon dioxide laser processing method, and silver is coated on the surface having an average particle diameter of 4 μm in this via hole. A via-hole conductor was formed by filling a metal paste mixed with parts by weight, 0.2 part by weight of cellulose, and 10 parts by weight of 2-octanol, and dried by heating at 50 ° C. for 60 minutes.
[0033]
On the other hand, a copper foil having a thickness of Y μm was attached to a resin film made of polyethylene terephthalate resin (PET) having a thickness of 25 μm (transfer sheet), and a mirror image conductor circuit layer was formed by a known photoresist method or the like. Then, the transfer sheet is aligned and overlapped on the front surface side and the back surface side of the insulating substrate on which the via hole conductor is formed, and a pressure of 5 kg / cm 2 is applied at least to the via hole conductor forming position, from both end sides of the via hole conductor. The conductor circuit layer was embedded in the insulating layer to produce a core wiring sheet.
[0034]
Similarly, four wiring sheets in which a conductor circuit layer is formed on only one side of an insulating sheet in which via-hole conductors are formed are produced, and the two wiring sheets are aligned and stacked on the upper and lower surfaces of the core wiring sheet. Thereafter, it was cured at a temperature of 200 ° C. and a pressure of 20 kg / cm 2 to produce a multilayer wiring board having 6 conductor circuit layers.
[0035]
Measure the initial continuity and insulation resistance of the produced multilayer wiring board, and the continuity failure after test (open), insulation failure (short), appearance (visually) conductor circuit layer bulge or circuit resistance change occurred Table 1 shows the percentage of non-defective products out of 50 samples prepared for each sample.
[0036]
[Table 1]
Figure 0004587576
[0037]
As is clear from the results of Table 1, when the thermosetting resin layer is thicker than the copper foil (sample Nos. 1, 3, 9, and 15), the conductor circuit layer and the fibrous body in the heat-resistant woven fabric Engagement was not successful, and a short circuit occurred due to the flow of resin during transfer of the conductor circuit layer. The conductor circuit layer has a surface roughness that deviates from 1.5 to 8 μm, and the conductor circuit layer has a buried surface roughness Rz of a / 4 <Rz <3a (a: average diameter of the fibrous body). Anything deviating from the above could not be engaged, resulting in short-circuit failure or open failure. On the other hand, Sample No. in which the conductor circuit layer and the fiber body of the heat resistant woven fabric were engaged. 2, 5-7, 11-13, and 17-19 were all able to suppress short-circuit failure and open failure.
[0038]
【The invention's effect】
As described above, according to the multilayer wiring board of the present invention, it can have contact in the case of forming a fine conductor circuit layer formed by copper foil, without the occurrence of deformation or disconnection of the conductor circuit layer, and A good multilayer wiring board free from deformation or disconnection of via-hole conductors filled with metal powder can be produced.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a multilayer wiring board according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a main part of an insulating layer and a conductor circuit layer in the multilayer wiring board of the present invention.
FIG. 3 is a drawing for explaining the manufacturing process of the multilayer wiring board of the present invention.
[Explanation of symbols]
1 Insulating substrate 2 Insulating layer 3 Thermosetting resin layer 4 Via-hole conductor 5 Conductor circuit layer

Claims (2)

耐熱性織布と熱硬化性樹脂との複合材料からなる絶縁層と、該絶縁層表面及び該絶縁層間に形成された複数層の導体回路層と、上下の前記導体回路層を接続するために、前記絶縁層に形成されたビアホール内に金属粉末を充填してなる複数のビアホール導体を具備する多層配線基板において、前記導体回路層が前記絶縁層の表面に埋設されているとともに、前記導体回路層の前記絶縁層への埋設側の表面粗さ(Rz)が1.5〜8μmであり、前記導体回路層の厚みが、前記絶縁層の前記耐熱性織布から前記絶縁層表面に至る熱硬化性樹脂層の厚みよりも大きく、且つ前記導体回路層の埋設側表面の凹凸部と前記耐熱性織布とが互いに係合していることを特徴とする多層配線基板。Connecting the insulating layer made of a composite material of a heat resistant woven fabric and a thermosetting resin, and a plurality of layers conductive circuit layer formed on the surface and the insulating layers of the insulating layer, the conductive circuit layer above under Therefore, in the multilayer wiring board having a plurality of via-hole conductors formed by filling the metal powder into the via holes formed in the insulating layer, with the conductive circuit layer is embedded in the surface of the insulating layer, wherein the embedded side of the surface roughness of the insulating layer of the conductor circuit layer (Rz) is 1.5~8Myuemu, the thickness of the conductive circuit layer from the heat-resistant woven fabric of said insulating layer of said insulating layer greater than the thickness of the thermosetting resin layer to reach the surface, and a multilayer wiring board and the uneven portion of the buried side of the surface of the conductive circuit layer and the heat-resistant woven fabric characterized in that it engaged with each other. 前記耐熱性織布を構成する繊維体の平均直径をa(μm)としたとき、前記導体回路層の埋設側表面粗さRzが、a/4<Rz<3aの関係を満足することを特徴とする請求項1記載の多層配線基板。 When the average diameter of the fibers constituting the heat-resistant woven fabric was a ([mu] m), that the surface roughness Rz of the embedded side of the conductive circuit layer satisfies a relationship of a / 4 <Rz <3a multilayer wiring board according to claim 1 Symbol mounting features.
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JP5295596B2 (en) * 2008-03-19 2013-09-18 新光電気工業株式会社 Multilayer wiring board and manufacturing method thereof
JP4738430B2 (en) * 2008-03-24 2011-08-03 京セラ株式会社 Wiring board manufacturing method
JP5473413B2 (en) 2008-06-20 2014-04-16 株式会社半導体エネルギー研究所 Wiring substrate manufacturing method, antenna manufacturing method, and semiconductor device manufacturing method
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US11979982B2 (en) * 2019-10-30 2024-05-07 Tanazawa Hakkosha Co., Ltd. Printed wiring board and method for manufacturing printed wiring board

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