JP2004174992A

JP2004174992A - Laminated substrate for high-frequency and its manufacturing method

Info

Publication number: JP2004174992A
Application number: JP2002345531A
Authority: JP
Inventors: Toshiaki Kuwabara; 原利明桑; Seiichiro Iwai; 誠一郎祝
Original assignee: Nippon Valqua Industries Ltd; Nihon Valqua Kogyo KK
Current assignee: Nippon Valqua Industries Ltd; Nihon Valqua Kogyo KK
Priority date: 2002-11-28
Filing date: 2002-11-28
Publication date: 2004-06-24

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for high-frequency which is excellent in bending strength and bending elasticity by using PMP, is excellent in surface smoothness, and can be easily manufactured at a low cost. <P>SOLUTION: This laminated substrate for high frequency is constituted by bonding a first insulating layer 20, a second insulating layer 30 which is provided at least on one surface of the first insulating layer 20, and a conductive layer 40 which is provided on the surface of the second insulating layer 30. The first insulating layer 20 and the second insulating layer 30 respectively comprise a prepreg which is formed in such a manner that a poly-4-methyl-1-pentene (PMP) film and a fiber base material containing a fiber selected from among a glass fiber, an aramid fiber, a polyester fiber and a carbon fiber are laminated, and pressurized while being heated, and the fiber base material is impregnated with PMP. Also, the fiber base material for the first insulating layer 20 is a woven fabric or a felt-like nonwoven fabric, and the fiber base material for the second insulating layer 30 is a combed nonwoven fabric. A PMP film (layer) 50 is preferably inserted between respective layers. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の技術分野】
本発明は、高周波用の電気回路やフラットアンテナ等に使用される高周波用積層基板およびその製造方法に関する。
基板は、半導体などの電子部品を載せる台としての役割を有し、通常、電子部品同士を電気的に繋ぐ配線が配設される。
【０００２】
【発明の技術的背景】
近年、情報通信の急拡大に伴い、これに対応すべく、多量の情報を瞬時に送受信し処理可能なマイクロ波、ミリ波などの高周波領域における高速通信及び処理が行われるようになっている。これに伴い、高周波領域での使用が可能で、より品質の安定した回路基板（電子基板、基板などともいう。）が求められている。
【０００３】
電子基板は、誘電体材料でもあるため、マイクロ波、ミリ波などの高周波領域で電磁波の伝送損失が低減されるように、低誘電率及び低誘電正接化が必要であり、これらを満足する誘電体材料の中で、最もポピュラーに使われているのがフッ素樹脂である。
このフッ素樹脂単体だけで基板を作れば、最も誘電特性が優れた基板ができるが、フッ素樹脂単体の基板では、銅などの配線回路材に比して線熱膨張係数のオーダーの違いから、配線回路を形成する金属箔（例えば銅箔）との密着性が確保されないなど、様々な問題点がある。
【０００４】
そこで、これらの問題点を解決するために、フッ素樹脂に充填材を配合・充填し、あるいはフッ素樹脂板に他の基材を積層したものなどが提案されているが、最もよく用いられているのは、ガラスクロスを基材としたフッ素樹脂系の基板（以下、ガラスフッ素基板という。）である。
このガラスフッ素基板の作り方としては、一例を挙げると、フッ素樹脂をディスパージョンの状態でガラスクロスなどの基材に含浸させ乾燥し、このようにフッ素樹脂が含浸されたガラスクロスを所定の厚さになるまで積層し、加熱・加圧する。次いで、得られた積層板の表裏両面に金属箔（例えば銅箔）を載せて、再度加熱・加圧すると、金属箔層が表裏面に形成されたガラスフッ素基板が得られる。
【０００５】
このようなガラスフッ素基板は、基材として使用されるクロス（織布）が、繊維を束ねて編組してできているため、どうしてもその網目が（極薄の）金属箔に転写されてしまい、その結果、基板表面に凹凸が出来て平滑性のない基板になってしまうという問題があった。特に、高周波領域で基板を使用する場合は、周波数が高くなると基板表面に形成される線路パターンの幅寸法がより小さくなり、また、他の線路との間隔も狭くなる。そのため、基板表面に凹凸があると、線路パターンの寸法精度が悪くなるので、このような状態で高周波領域にて基板を使用すると伝搬する電磁波の損失が著しく大きくなるため、高周波用途では使用できなくなる。
【０００６】
このような基板の平滑性の問題に対して、特開平６−３２６４７４号公報（特許文献１）には、銅箔下の表面絶縁層として、ガラス不織布に熱硬化性樹脂を含浸させたプリプレグを用いることにより、基板の平滑性を達成した多層プリント配線板が開示されている。
しかしながら、フッ素樹脂基板にこの技術を応用した場合、平滑性は改善されたが、さらに下記のような問題点が解決されずにいた。
（イ）柔らかいため、ワイヤーボンディングやバンプ溶接がしにくい。
（ロ）加工性（特にドリル加工性）が悪い。
（ハ）銅箔との密着性に乏しい。
（ニ）フッ素樹脂の価格が高価なため、基板としての価格も高価になる。
（ホ）フッ素樹脂の繊維基材に対する含浸性が悪く、均一に含浸させることが困難で、作業性が悪い。
【０００７】
【特許文献１】
特開平６−３２６４７４号公報
【０００８】
【発明の目的】
本発明は、上記のような従来技術に鑑みてなされたものであって、高周波特性に優れ、繊維基材に対する含浸性および接着性が良好で、積層板の製造および導体層の接合が容易であり、かつ曲げ強度および曲げ弾性率に優れ、表面平滑性に優れた高周波用積層基板およびその製造方法を提供することを目的としている。
【０００９】
【発明の概要】
本発明に係る高周波用積層基板（単に、基板等とも言う。）は、第一絶縁層と、少なくともその一方面に設けられた第二絶縁層と、第二絶縁層の表面に設けられた導体層とが接合されてなり、
第一絶縁層と第二絶縁層とが、それぞれ、ポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムと、ガラス繊維、アラミド繊維、ポリエステル繊維、炭素繊維のうちから選択される繊維を含有する繊維基材とを積層し、加熱下に加圧し、ＰＭＰを上記繊維基材に含浸させて成るプリプレグよりなり、かつ、
上記第一絶縁層用の繊維基材が、織布またはフェルト状不織布であり、第二絶縁層用の繊維基材が、抄造された不織布であることを特徴としている。
【００１０】
本発明の基板においては、上記第一絶縁層用および第二絶縁層用の何れの繊維基材も、ガラス繊維製基材であることが好ましい。
また、本発明の基板においては、上記第二絶縁層が、第一絶縁層の両面に設けられ、２枚の第二絶縁層の表面にはそれぞれ導体層が設けられていることが好ましい。
【００１１】
本発明の基板においては、第一絶縁層と第二絶縁層との間、および第二絶縁層と導体層との間には、さらに、ポリ−４−メチル−１−ペンテン（ＰＭＰ）層が設けられていてもよい。
本発明に係る高周波用積層基板の製造方法は、
（ａ）ポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムと、ガラス繊維、アラミド繊維、ポリエステル繊維、炭素繊維のうちから選択される繊維を含有する織布またはフェルト状不織布の繊維基材とを積層し、加熱下に加圧し、ＰＭＰを該織布またはフェルト状不織布の繊維基材に含浸させて成る第一絶縁層用プリプレグと、
（ｂ）ポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムと、ガラス繊維、アラミド繊維、ポリエステル繊維、炭素繊維のうちから選択される繊維を含有する抄造された不織布の繊維基材とを積層し、加熱下に加圧し、ＰＭＰを該抄造された不織布の繊維基材に含浸させて成る第二絶縁層用プリプレグとを準備し、
第一絶縁層用プリプレグ（ａ）の少なくとも一方面に第二絶縁層用プリプレグ（ｂ）を載置し、さらにその第二絶縁層用プリプレグ（ｂ）の表面に導体箔（ｃ）を載置した状態で、
加熱下に加圧して、これら絶縁層用プリプレグ（ａ）、（ｂ）および導体箔（ｃ）を接合一体化することを特徴としている。
【００１２】
本発明の上記製法においては、上記織布またはフェルト状不織布の繊維基材および、抄造された不織布の繊維基材が何れもガラス繊維製であることが好ましい。
本発明の上記製法においては、第二絶縁層用プリプレグが、第一絶縁層用プリプレグの両面に載置され、２枚の第二絶縁層用プリプレグの表面にはそれぞれ導体箔が載置されることが好ましい。
【００１３】
本発明の上記製法においては、第一絶縁層用プリプレグと第二絶縁層用プリプレグとの間、および第二絶縁層用プリプレグと導体箔との間には、さらに、ポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムが介装されてもよい。
本発明によれば、ＰＭＰを用いて曲げ強度および曲げ弾性率に優れ、表面平滑性に優れた高周波用基板を簡単に製造でき、安価に提供することができる。
【００１４】
【発明の具体的説明】
以下、本発明に係る高周波用積層基板およびその製造方法について、添付図面を参照しつつ具体的に説明する。なお、図中、同一部材には同一符号が付されている。
＜高周波用積層基板＞
図１および図２は、それぞれ、本発明に係る高周波用積層基板（単に、基板等とも言う。）の好適な一態様を示す模式断面図である。
【００１５】
図１には、３層構成の本発明に係る高周波用積層基板が示され、図２には、５層構成の本発明に係る高周波用積層基板が示されている。
図１に示す高周波用積層基板１０は、第一絶縁層２０と、その一方面２２に設けられた第二絶縁層３０と、第二絶縁層３０の表面３２に設けられた導体層４０とが接合されてなっている。
【００１６】
図２に示す高周波用積層基板１０Ａは、図１に示す第一絶縁層２０の表裏面に、第二絶縁層３０と、導体層４０とが順次接合されてなっている。
＜第一絶縁層、第二絶縁層＞
この第一絶縁層２０と第二絶縁層３０とは、それぞれ、図示せぬポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムと、図示せぬガラス基材とを積層し、加熱下に加圧し、ＰＭＰをガラス基材に含浸させて成るプリプレグよりなっている。
【００１７】
このＰＭＰは、従来用いられていたフッ素樹脂に比べて硬く、比重も小さいため、本発明の高周波用積層基板は、ガラスフッ素基板に比べて硬く、軽量となる。従って、本発明の基板を用いると、ワイヤーボンディングやバンプ溶接も可能であり、該基板が用いられる機器類全体の軽量化に貢献できる。
上記ＰＭＰフィルムとしては、４−メチル−１−ペンテンの単独重合体であるポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムの他、４−メチル−１−ペンテンに少量の他の共重合モノマーを共重合させてなる４−メチル−１−ペンテン系共重合体からなるフィルムであってもよい。
【００１８】
ＰＭＰフィルムは公知の方法により成形され、例えば、市販の「オピュラン（商品名）」（三井化学（株）製、厚み５０μｍ）等を使用できる。
このようなＰＭＰフィルムは、１枚〜複数枚積層して用いてもよい。
さらに、本発明では、上記第一絶縁層２０用のガラス基材としては、ガラスクロスまたはガラスフェルトが用いられ、高周波用積層基板の強度向上に貢献する。
【００１９】
本発明では、この上記第一絶縁層２０用のガラス基材としては、特にガラスクロスが好ましく、ガラスクロスは、直径５〜１５μｍφ程度のガラス糸（フィラメント）を数十〜数百本程度撚り合わせた撚糸（ヤーン）を縦糸、横糸として織り込んだものであり、ガラスクロスの厚みは、３０μｍ〜１９０μｍ程度のものが好ましい。
【００２０】
このようなガラスクロスとしては、例えば、「Ｅ１５Ａ０４（商品名）」（ユニチカ（株）製、厚さ１２０μｍ）、「ＷＥＡ１８Ｔ」（日東紡（株）製、厚さ１９０μｍ）などを用いることができる。このようなガラスクロスは、１枚〜複数枚積層して用いてもよい。
また、第二絶縁層３０用のガラス基材としては、抄造されたガラス製不織布が使用され、好適には、ガラスペーパーまたはガラスマットが用いられる。
【００２１】
本発明では、第二絶縁層３０用のガラス基材としては、特にガラスペーパーが好ましく、ガラスペーパーは、太さ０．０２〜５０μｍで繊維長６〜３８ｍｍのガラス（短）繊維を水中に分散し、湿式で抄造（抄紙）したシート状物である。なお、ガラスペーパーには、ガラス繊維、の他に、バインダー、ガラス繊維とバインダーとの接着性を向上させる表面処理剤、合成繊維等が含まれていてもよい。
【００２２】
このようなガラスペーパーとしては、例えば、「グラベスト（商品名）」（オリベスト（株）製、繊維径６〜２０μｍ、繊維長６〜３８ｍｍ）、「サーフェースマット（商品名）」（日東紡製）などを用いることができる。このようなガラスペーパーは、１枚〜複数枚積層して用いてもよい。
本発明では、このように第一絶縁層と導体層との間に、基材がガラスペーパーまたはガラスマットからなる平滑性の良好な第二絶縁層を介装しているので、第一絶縁層の表面の凹凸が直接、導体層の表面の凹凸となって現れることがなく、極めて平滑な導体層が得られる。
【００２３】
上記説明においては、第一絶縁層用、第二絶縁層用の繊維基材として、ガラス基材を用いる態様について説明したが、本発明は、上記態様に限定されず、基材としては、耐熱性、難燃性、誘電特性（低比誘電率、低誘電正接）に優れ、線熱膨張係数が小さく金属と同じかそれ以下であれば、ガラス基材に代えて用いることができ、アラミド繊維基材、ポリエステル繊維基材、炭素繊維基材などを用いても良好な効果を奏する。
【００２４】
また、本発明においては、図３の高周波用積層基板１０Ｂあるいは図４の高周波用積層基板１０Ｃに示すように、第一絶縁層２０と第二絶縁層３０との間、および第二絶縁層３０と導体層４０との間には、得られる高周波用積層基板中のガラス含有率を調整し、強度、誘電特性、接着強度を向上させるために、ＰＭＰフィルムからなるＰＭＰ層５０が介装されていてもよい。このようなＰＭＰ層５０の厚みは、特に限定されないが、ＰＭＰフィルムの厚み２５〜１００μｍ（厚）に比して、加熱・加圧され若干薄層化されるものの、このＰＭＰフィルム（厚）とほぼ同様であって、通常２０〜１００μｍ程度である。これら図３、図４に示す高周波用積層基板１０Ｂ、１０Ｃでは、図１〜２に示す高周波用積層基板１０、１０Ａに比して、特にプリプレグ間の接着強度の向上という効果を奏する。
【００２５】
また、本発明においては、求められる高周波用積層基板の強度、寸法、電気特性等に応じて、上記第一絶縁層、第二絶縁層などは、それぞれ独立に、１〜複数枚のシートから構成されていてもよい。
この時、得られた高周波用積層基板中の繊維基材比率を１０〜３０ｗｔ％に調整することが好ましい。高周波用積層基板中の繊維基材比率が１０ｗｔ％未満であると、充分な強度の基板が得られなくなる傾向があり、また３０ｗｔ％を超えると、満足のいく誘電特性の基板が得られなくなる傾向がある。
＜導体層＞
導体層４０は、銅箔（例：電解銅箔や圧延銅箔）、金箔などの良導電性の金属箔から構成されている。
【００２６】
金属箔の厚みは、特に限定されないが、通常、５〜７０μｍ、好ましくは９〜３５μｍ程度である。このような金属箔は、１枚〜複数枚積層して用いてもよい。
以上詳述したことから明らかなように、本発明では、誘電特性が高周波領域で良いとされているフッ素樹脂と同等でかつ、フッ素樹脂に比べて安価な熱溶融性樹脂であるＰＭＰを用いている。そのため、ガラスフッ素基板よりもはるかに安価に基板を製造することが可能となっている。
【００２７】
また、本発明では、このように樹脂としてＰＭＰを用いているが、この場合においても、さらに得られる基材の耐熱性を向上させるためにはガラスクロスなどの基材を用いる必要があるが、本発明では、上記したように、ＰＭＰをガラスクロスなどと積層し、ＰＭＰの溶融温度以上の温度にまで加熱しつつ、同時にガラスクロスなどの基材にＰＭＰが含浸するように（染み込んでいくように）加圧しているので、基材へのＰＭＰの含浸と、積層体である高周波用積層基板の成形とをＰＭＰの融点以上の温度での加熱加圧により行うことができ、一回の工程で成形を済ませることが可能となっている。
【００２８】
換言すれば、本発明では、従来例に存在したような、ガラスフッ素基板のようにフッ素樹脂ディスパージョンをガラスクロスに含浸させるためだけの特別の工程が無い。そのために、より安価に高周波用積層基板が作製可能となっている。ところで、高周波領域で高周波用積層基板（基板）を使用する場合には、周波数が高くなると、基板表面に形成される線路パターン幅がより狭くなり、また他の線路との間隔も狭くなる。よって、基板表面にもし凹凸があると線路パターンの寸法精度が悪くなり、高周波領域で該基材を使用すると、伝搬する電磁波の損失が著しく大きくなる。
【００２９】
そこで、本発明では、上記記載に明らかなように、例えば、銅箔と、ＰＭＰ含浸ガラスクロスとの間に、耐熱性のある、抄紙法により製造（抄造）された不織布、例えば、ガラスペーパーを挟み込んで、基板を製造している。
抄紙された不織布であるガラスペーパー等は、ガラスクロスやガラスフェルトに比べて、はるかに目が細かいので、ＰＭＰ含浸ガラスペーパー表面にはその凹凸が見られず、その表面に銅箔などを接合すると、著しく平滑な導体面が形成される。
【００３０】
要するに、本発明によれば、フッ素樹脂に比してより安価でありフッ素樹脂と同等の電気的特性等を有するＰＭＰを用いて、曲げ強度および曲げ弾性率が優れ、表面平滑性に優れた高周波用基板を、フッ素樹脂を用いるよりも安全で、より少ない工程で簡単に製造でき、安価に提供することができる。
次に、このような高周波用積層基板の製造方法について特に詳説する。
【００３１】
＜高周波用積層基板の製造＞
本発明に係る高周波用積層基板の製造方法では、例えば、図１に示す高周波用積層基板１０は、図５に示すように、離型フィルム６０が配置された下側に位置する基台側加熱加圧用プレス７０Ａの表面に、上記第一絶縁層２０となる第一絶縁層用プリプレグ（ａ）２０を載せ、さらにその表面（紙面に向かって上面）２２に、上記第二絶縁層３０となる第二絶縁層用プリプレグ（ｂ）３０を載置し、さらにその第二絶縁層用プリプレグ３０の表面３２に導体箔（例えば、０．０１８ｍｍ（厚）の銅箔）４０を載置した状態で、離型フィルム６０を介して、この積層された加熱加圧前のシート１０Ｗの上方に配置された移動可能な加熱加圧金型７０Ｂを、
ＰＭＰの融点２４０℃以上の温度、好ましくは２４０℃〜２６０℃の加熱下に、図中矢印で示すプリプレグの厚み方向下方に圧力８〜１５ｋｇ／ｃｍ^２で２〜１０分間程度加圧して、これら絶縁層用プリプレグ２０、３０および導体箔４０を接合一体化すれば、所望の高周波用積層基板１０を製造することができる。
【００３２】
なお、加熱加圧前の上記積層されたシート１０Ｗは、上記層構成となる限り任意の順序で積層、配列することができる。
また、例えば、図２に示す高周波用積層基板１０Ａは、図６に示すように、離型フィルム６０が配置された下側に位置する基台側加熱加圧用プレス７０Ａの表面に、下から上に向かって、導体箔４０、第二絶縁層用プリプレグ３０、第一絶縁層用プリプレグ２０、第二絶縁層用プリプレグ３０、導体箔４０の順序でシートまたは箔を載置した状態で、この積層された加熱加圧前のシート１０Ｘの上方に離型フィルム６０を介して配置された可動可能な加熱加圧金型７０Ｂを、同上の条件下に加熱・加圧して、これらを接合一体化して、高周波用積層基板１０Ｘを製造すればよい。
【００３３】
また、例えば、図３、図４に示す高周波用積層基板１０Ｂ、１０Ｃも、上記と同様にして製造でき、例えば、図３、図４に示すような順序で各層用のシートまたは箔を載置した状態で、上記と同様なプレスを用いて、同上の条件下に加熱・加圧して、これらを接合一体化して、高周波用積層基板１０Ｂ、１０Ｃをそれぞれ製造すればよい。
【００３４】
なお、これらの高周波用積層基板製造の際に、第一絶縁層用プリプレグ２０、第二絶縁層用プリプレグ３０あるいはＰＭＰフィルムの枚数は限定されず、特に第一絶縁層用プリプレグの枚数は、求められる高周波用積層基板の厚さに応じて、適宜変更可能である。
この時、得られた高周波用積層基板中の繊維基材比率を１０〜３０ｗｔ％に調整することが好ましい。１０ｗｔ％未満であると、充分な基板の強度が得られなくなる傾向があり、３０ｗｔ％より多いと、銅箔との接着強度が得られなくなる傾向がある。
【００３５】
上記高周波用積層基板を製造する際に用いられる、上記第一絶縁層用プリプレグ（ａ）自体は、図示せぬポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムと、図示せぬガラス繊維、アラミド繊維、ポリエステル繊維、炭素繊維などの繊維を含有する織布またはフェルト状不織布の繊維基材とを積層し、ＰＭＰの融点２４０℃以上の温度、好ましくは２４０〜２６０℃の温度での加熱下に、圧力８〜１５ｋｇ／ｃｍ^２で２〜１０分間程度加圧し、ＰＭＰを該織布またはフェルト状不織布の繊維基材に含浸させて得られたプリプレグである。
【００３６】
また、第二絶縁層用プリプレグ（ｂ）は、ポリ−４−メチル−１−ペンテン（ＰＭＰ）フィルムと、ガラス繊維、アラミド繊維、ポリエステル繊維、炭素繊維などの繊維を抄造した不織布である繊維基材とを積層し、上記と同様の温度での加熱下に上記と同様の圧力で、第一絶縁用プリプレグ形成の場合に比して肉薄故に、より短時間である０．５〜５分間程度加圧し、ＰＭＰを繊維基材に含浸させて得られる。
【００３７】
このような加熱加圧の際には、平板プレスなどを用いることができる。
すなわち、第一絶縁層用プリプレグ（ａ）と第二絶縁層用プリプレグ（ｂ）との主な相違点は、第一絶縁層用プリプレグ形成用の繊維基材が、織布またはフェルト状不織布であるのに対して、第二絶縁層用プリプレグ形成用の繊維基材は、平滑性により優れた抄造された不織布である点にあり、本発明ではこのような第二絶縁層用プリプレグを第一絶縁層用プリプレグと導体箔の間に介装しているので、得られる高周波用積層基板は、表面平滑性に優れ、電磁波の伝搬特性に優れる傾向がある。
【００３８】
本発明においては、第二絶縁層用プリプレグが、第一絶縁層用プリプレグの両面に載置され、２枚の第二絶縁層用プリプレグの表面にはそれぞれ導体箔が載置されることが好ましい。
このように、本発明によれば、ＰＭＰを用いて曲げ強度および曲げ弾性率が優れ、表面平滑性に優れた高周波用基板を、溶剤を使用せず、従って取り扱い上より安全に、しかも少ない工程で簡単に製造でき、安価に提供することができる。
【００３９】
＜用途＞
本発明に係る高周波用積層基板は、回路基板として用いられるだけでなく、平面アンテナなどとして用いられる。
【００４０】
【発明の効果】
本発明に係る高周波用積層基板は、従来の高周波用積層基板に存在していた凹凸が解消でき、表面平滑性に優れていることから、高い寸法精度で線路パターンが形成できる。故に高周波領域でも電磁波の伝搬損失が損なわれない。
また、本発明に係る高周波用積層基板は、硬いため、電子部品の実装時に押圧されても屈曲・変形しにくく、実装作業性に優れ、ワイヤーボンディング等の半導体に代表される電子部品の実装も容易に行える。さらに、本発明の高周波用積層基板は、前記したような従来の基板に比して重量が軽いため、基板が組み込まれる装置（完成品）の軽量化も実現可能である。
【００４１】
また、本発明の高周波用積層基板には、電子基板などの基板用絶縁材料として用いられ、フッ素樹脂と同等の低誘電率で低誘電正接の誘電体としての機能も有するポリ−４−メチル−１−ペンテン（ＰＭＰ）が用いられているが、このＰＭＰフィルムは、フッ素樹脂に比べて安価であり、しかも、基板を作製する過程において、フッ素樹脂を用いる場合のような、樹脂を基材に含浸させる独立した１工程が省けるので、コストダウンに貢献でき、安価に基板が提供できる。
【００４２】
よって、本発明によれば、高周波領域で使用可能な優れた基板を、より工程の少ない簡単な工程で、安価に提供できる。
【００４３】
【実施例】
以下、本発明に係る高周波積層板およびその製造方法について、実施例に基づいてさらに具体的に説明するが、本発明は係る実施例により何ら限定されるものではない。
【００４４】
【実施例１】
図４に示すような高周波用積層基板を、以下の方法で作製した。
第一絶縁層用プリプレグ（Ｃ層）：
ガラスクロス（商品名：Ｅ１５Ａ０４、ユニチカ（株）製、面積×厚み＝１０ｃｍ×１０ｃｍ×１３０μｍ（厚）、重さ：１．６５ｇ）の両面にＰＭＰフィルム（商品名：オピュラン、三井化学（株）製、面積×厚さ：１０ｃｍ×１０ｃｍ×１００μｍ（厚）、重さ：０．８３ｇ）をそれぞれ１枚ずつ積層し、２４０℃で１０ｋｇ／ｃｍ^２の条件で５分間、平板プレスを行い、ガラスクロスにＰＭＰが含浸されたプリプレグを得た。
【００４５】
第二絶縁層用プリプレグ（Ｂ層）：
ガラスペーパー（商品名：グラベスト、オリベスト（株）製、面積×厚み＝１０ｃｍ×１０ｃｍ×４２０μｍ（厚）、重さ：０．５３ｇ）の両面にＰＭＰフィルム（商品名：オピュラン、三井化学（株）製、面積×厚さ：１０ｃｍ×１０ｃｍ×５０μｍ（厚）、重さ：０．４１ｇ）をそれぞれ１枚ずつ積層し、２４０℃で成形圧１０ｋｇ／ｃｍ^２の条件で１分間、平板プレスを行い、ガラスペーパーにＰＭＰが含浸されたプリプレグを得た。
導体層・箔（Ａ層）
厚みが０．０１８ｍｍの銅箔を使用した。
ＰＭＰフィルム
ＰＭＰフィルム（商品名：オピュラン、三井化学（株）製、面積×厚さ：１０ｃｍ×１０ｃｍ×５０μｍ（厚）、重さ：０．４１ｇ）
高周波用積層基板（基板）の製造
図５あるいは図６と同様のプレスを用い、離型フィルム６０がセットされた基台側加熱加圧用プレス７０Ａの表面に、図４に示すように、一番下から順に銅箔（Ａ層）４０、ＰＭＰフィルム５０、第二絶縁層（Ｂ層）３０用プリプレグ、ＰＭＰフィルム５０、第一絶縁層（Ｃ層、設定厚さにより枚数を変更。）２０用プリプレグ、ＰＭＰフィルム５０、Ｂ層３０用プリプレグ、ＰＭＰフィルム５０、銅箔（Ａ層）４０の順に積層した。
【００４６】
次いで、２４０℃で成形圧１０ｋｇ／ｃｍ^２の条件で５分間、平板プレスを行い上記積層物を一体化した。
なお、プレス時に、移動可能な加熱加圧金型（上板）７０Ｂと基台側加熱加圧用プレス（下板）７０Ａの“ずれ”あるいは“傾き”を防止する治具（図示せず）を用い、プリプレグの横流れを最小限に抑制した。
【００４７】
得られた高周波用積層基板の厚みは、１．２５ｍｍであった。
また、得られた積層基板中のガラス基材比率は、２０ｗｔ％であった。
【００４８】
【比較例１】
中興化成（株）製のガラスフッ素基板（型名：ＣＱＦ−５０２）を用いた。
【００４９】
【比較例２】
実施例１で用いた第一絶縁層用プリプレグを２枚重ね合わせ、その両面に、実施例１と同様の銅箔を積層して、２４０℃で成形圧１０ｋｇ／ｃｍ^２の条件で５分間、平板プレスを行い上記積層物を一体化した。
得られた基板の厚みは、１．２５ｍｍで、得られた積層基板中のガラス基材比率は、２０ｗｔ％であった。
【００５０】
【評価・結果】
実施例１及び比較例１〜２で得られた積層基板について、表１に示す諸特性を測定した。
結果を表１にまとめて示す。
なお、測定法は以下のとおり。
＜比誘電率及び誘電正接＞
比誘電率及び誘電正接は、ＪＩＳ規格Ｃ６４８１に従い１２ＧＨｚで測定した。
＜平滑性＞
平滑性については、表面粗さ計（ｓｕｒｆｃｏｍ４８０Ａ）を用い、ＪＩＳ規格Ｂ０９０１に従い測定した。
＜路線パターンの寸法精度＞
線路パターンの寸法精度は、線路パターン（幅寸法２ｍｍ）をエッチングにより形成し、その線路形状を目視により評価した。
【００５１】
◎はパターン線路の幅方向の仕上がりが優、○は良、△は可、×は不可を示す。
＜コスト＞
◎：コストが著しく低い
○：コストがやや低い
△：コストがやや高い
×：コストが著しく高い
【００５２】
【表１】

【００５３】
＜考察＞
上記実施例と比較例とを対比すれば明らかなように、本発明の実施例に係る高周波用積層基板は、何れも比誘電率が２．５以下であり、比誘電率が小さく、高周波領域では電気信号の伝搬速度が速い。現在までに上市されている基板の中で、一番比誘電率が小さいものはガラスフッ素基板（比較例１）であり、これと同等の比誘電率を有している。
【００５４】
また、本発明の実施例に係る高周波用積層基板は、誘電正接が１０^−３オーダー以下であり、誘電正接が小さく、伝わる電気信号の損失が小さい。高周波領域でこれまで使用されてきた低誘電率基板は、比較例１に示すようなガラスフッ素基板であるが、そのガラスフッ素基板と同等の誘電正接を有していることが分かる。
【００５５】
また、本発明に係る高周波用積層基板は、ガラスフッ素基板よりも凹凸が無く、平滑性に優れている。
その結果、本発明の高周波用積層基板は、線路パターンの寸法精度が良く、高周波領域で使用すると、伝搬する電磁波の損失が著しく小さくなる。また、本発明の高周波用積層基板は、半田耐熱性が２６０℃×３０ｓｅｃ．で銅箔の膨れ、剥がれが無い。
【００５６】
また、本発明の高周波用積層基板は、難燃性を有し、ＵＬ（アメリカの試験機関）が設定した難燃性（耐燃性）を評価するための試験方法（ｓｕｂｊｅｃｔ９４）によれば、難燃性の度合いは、「ＵＬ９４−ＶＯ」であり、サンプルが着火または引火したとしても該サンプルが３０秒以上燃え続けない（燃え広がらない）ことを示している。
【００５７】
また、本発明の高周波用積層基板は、ガラスフッ素基板よりも軽く、また、ガラスフッ素基板よりも安価である。
【図面の簡単な説明】
【図１】図１は、本発明の一実施例に係る高周波用積層基板の好適な一態様を示す模式断面図である。図１には、３層構成の本発明に係る高周波用積層基板が示されている。
【図２】図２は、本発明の他の実施例に係る高周波用積層基板の好適な一態様を示す模式断面図である。図２には、５層構成の本発明に係る高周波用積層基板が示されている。
【図３】図３は、図１に示す３層構成の高周波用積層基板の各層間にＰＭＰフィルム（層）が介装された態様を示す、高周波用積層基板の模式断面図である。
【図４】図４は、図２に示す５層構成の高周波用積層基板の各層間にＰＭＰフィルム（層）が介装された態様を示す、高周波用積層基板の模式断面図である。
【図５】図５は、図１に示す本発明の一実施例に係る高周波用積層基板の製法を説明する模式説明図である。
【図６】図６は、図２に示す本発明の他の実施例に係る高周波用積層基板の製法を説明する模式説明図である。
【符号の説明】
１０、１０Ａ、１０Ｂ、１０Ｃ、・・・・・・高周波用積層基板（基板）
２０・・・・・・第一絶縁層、第一絶縁シート
２２・・・・・・第一絶縁層の一方面
２４・・・・・・第一絶縁層の他方面（裏面）
３０・・・・・・第二絶縁層、第二絶縁シート
３２・・・・・・第二絶縁層の表面
３４・・・・・・第二絶縁層の下面
４０・・・・・・導体層、導体箔
５０・・・・・・ＰＭＰ層、ＰＭＰシート
６０・・・・・・離型フィルム
７０Ａ・・・・・・基台側加熱加圧用プレス
７０Ｂ・・・・・・可動可能な加熱加圧金型[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-frequency laminated substrate used for a high-frequency electric circuit, a flat antenna, and the like, and a method for manufacturing the same.
The substrate has a role as a base on which electronic components such as semiconductors are mounted, and wirings for electrically connecting the electronic components are usually provided.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
In recent years, with the rapid expansion of information communication, high-speed communication and processing in high-frequency regions such as microwaves and millimeter waves capable of instantaneously transmitting and receiving a large amount of information have been performed to cope with this. Along with this, a circuit board (also referred to as an electronic board, a board, or the like) that can be used in a high frequency region and has more stable quality is demanded.
[0003]
Since the electronic substrate is also a dielectric material, it must have a low dielectric constant and a low dielectric loss tangent so as to reduce transmission loss of electromagnetic waves in high frequency regions such as microwaves and millimeter waves. Among the body materials, the most popular one is fluororesin.
If a substrate is made of only this fluororesin alone, a substrate with the most excellent dielectric properties can be obtained.However, with a substrate made of only fluororesin, the difference in the linear thermal expansion coefficient compared to the wiring circuit material such as copper causes There are various problems, for example, the adhesion to a metal foil (for example, a copper foil) forming a circuit is not ensured.
[0004]
Therefore, in order to solve these problems, a composition in which a filler is compounded and filled in a fluororesin, or a material in which another base material is laminated on a fluororesin plate has been proposed, but is most often used. Is a fluororesin-based substrate having a glass cloth as a base material (hereinafter, referred to as a glass-fluorine substrate).
As an example of how to make this glass fluorine substrate, as an example, a fluororesin is impregnated into a base material such as a glass cloth in a dispersion state and dried, and the glass cloth impregnated with the fluororesin in a predetermined thickness is thus obtained. And heat and press. Next, a metal foil (eg, copper foil) is placed on both the front and back surfaces of the obtained laminate, and heated and pressed again to obtain a glass-fluorine substrate having a metal foil layer formed on the front and back surfaces.
[0005]
In such a glass-fluorine substrate, a cloth (woven cloth) used as a base material is made by bundling and braiding fibers, so that the mesh is inevitably transferred to a (ultra-thin) metal foil, As a result, there is a problem that unevenness is formed on the substrate surface, resulting in a substrate having no smoothness. In particular, when the substrate is used in a high frequency region, as the frequency increases, the width dimension of the line pattern formed on the substrate surface becomes smaller, and the interval between the line and the other line becomes narrower. Therefore, if the surface of the substrate has irregularities, the dimensional accuracy of the line pattern deteriorates. If the substrate is used in a high-frequency region in such a state, the loss of the transmitted electromagnetic wave becomes extremely large, and the device cannot be used in high-frequency applications. .
[0006]
To deal with such a problem of substrate smoothness, Japanese Patent Application Laid-Open No. 6-326474 (Patent Document 1) discloses a prepreg obtained by impregnating a glass nonwoven fabric with a thermosetting resin as a surface insulating layer below a copper foil. A multilayer printed wiring board which achieves smoothness of a substrate by using the same has been disclosed.
However, when this technology is applied to a fluororesin substrate, the smoothness is improved, but the following problems have not been solved.
(A) Since it is soft, it is difficult to perform wire bonding or bump welding.
(B) Poor workability (especially drill workability).
(C) Poor adhesion to copper foil.
(D) Since the price of the fluororesin is high, the price as the substrate is also high.
(E) The impregnating property of the fluororesin with respect to the fiber base material is poor, it is difficult to impregnate uniformly, and the workability is poor.
[0007]
[Patent Document 1]
JP-A-6-326474
[0008]
[Object of the invention]
The present invention has been made in view of the prior art as described above, and has excellent high-frequency characteristics, good impregnation and adhesion to a fiber base material, and facilitates production of a laminate and bonding of a conductor layer. It is an object of the present invention to provide a laminated substrate for high frequency, which is excellent in bending strength and flexural modulus and excellent in surface smoothness, and a method for manufacturing the same.
[0009]
Summary of the Invention
A high-frequency laminated substrate (hereinafter, simply referred to as a substrate or the like) according to the present invention includes a first insulating layer, a second insulating layer provided on at least one surface thereof, and a conductor provided on a surface of the second insulating layer. Layers are joined together,
The first insulating layer and the second insulating layer each contain a poly-4-methyl-1-pentene (PMP) film and a fiber selected from glass fiber, aramid fiber, polyester fiber, and carbon fiber. It is made of a prepreg obtained by laminating a fiber base material, applying pressure under heating, and impregnating the fiber base material with PMP, and
The fibrous base material for the first insulating layer is a woven fabric or a felt-like nonwoven fabric, and the fibrous base material for the second insulating layer is a nonwoven fabric formed.
[0010]
In the substrate of the present invention, it is preferable that the fiber base material for both the first insulating layer and the second insulating layer is a glass fiber base material.
Further, in the substrate of the present invention, it is preferable that the second insulating layer is provided on both surfaces of the first insulating layer, and a conductor layer is provided on each of the surfaces of the two second insulating layers.
[0011]
In the substrate of the present invention, a poly-4-methyl-1-pentene (PMP) layer is further provided between the first insulating layer and the second insulating layer and between the second insulating layer and the conductor layer. It may be provided.
The method for manufacturing a high-frequency laminated substrate according to the present invention includes:
(A) a poly-4-methyl-1-pentene (PMP) film and a fiber substrate of a woven or felt-like nonwoven fabric containing a fiber selected from glass fiber, aramid fiber, polyester fiber, and carbon fiber; A prepreg for a first insulating layer formed by impregnating the fiber base material of the woven fabric or the felt-like nonwoven fabric with PMP by applying pressure under heating, and
(B) Laminating a poly-4-methyl-1-pentene (PMP) film and a fiber substrate of a nonwoven fabric made of a fiber containing a fiber selected from glass fiber, aramid fiber, polyester fiber and carbon fiber. And pressurizing under heating to prepare a second insulating layer prepreg obtained by impregnating the fiber base material of the nonwoven fabric with PMP,
A second insulating layer prepreg (b) is placed on at least one surface of the first insulating layer prepreg (a), and a conductor foil (c) is placed on the surface of the second insulating layer prepreg (b). In the state
It is characterized in that these insulating prepregs (a) and (b) and the conductor foil (c) are joined and integrated by pressing under heating.
[0012]
In the production method of the present invention, it is preferable that the fiber base of the woven fabric or the felt-like nonwoven fabric and the fiber base of the formed nonwoven fabric are both made of glass fiber.
In the above method of the present invention, the prepreg for the second insulating layer is placed on both sides of the prepreg for the first insulating layer, and the conductor foil is placed on the surface of the two prepregs for the second insulating layer. Is preferred.
[0013]
In the above-mentioned production method of the present invention, between the prepreg for the first insulating layer and the prepreg for the second insulating layer, and between the prepreg for the second insulating layer and the conductor foil, furthermore, poly-4-methyl-1 -Penten (PMP) film may be interposed.
ADVANTAGE OF THE INVENTION According to this invention, it is easy to manufacture the board | substrate for high frequency which was excellent in bending strength and bending elastic modulus, and was excellent in surface smoothness using PMP, and can provide it inexpensively.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a high-frequency laminated substrate and a method of manufacturing the same according to the present invention will be specifically described with reference to the accompanying drawings. In the drawings, the same members are denoted by the same reference numerals.
<Laminated substrate for high frequency>
1 and 2 are schematic cross-sectional views each showing a preferred embodiment of a high-frequency laminated substrate (hereinafter, simply referred to as a substrate or the like) according to the present invention.
[0015]
FIG. 1 shows a high-frequency laminated substrate according to the present invention having a three-layer structure, and FIG. 2 shows a high-frequency laminated substrate according to the present invention having a five-layer structure.
1 includes a first insulating layer 20, a second insulating layer 30 provided on one surface 22 thereof, and a conductor layer 40 provided on a surface 32 of the second insulating layer 30. It has been joined.
[0016]
In the high-frequency laminated substrate 10A shown in FIG. 2, the second insulating layer 30 and the conductor layer 40 are sequentially bonded to the front and back surfaces of the first insulating layer 20 shown in FIG.
<First insulating layer, second insulating layer>
Each of the first insulating layer 20 and the second insulating layer 30 is formed by laminating a poly-4-methyl-1-pentene (PMP) film (not shown) and a glass substrate (not shown), and It consists of a prepreg formed by pressing and impregnating a glass substrate with PMP.
[0017]
Since the PMP is harder and has a lower specific gravity than conventionally used fluororesin, the high-frequency laminated substrate of the present invention is harder and lighter than a glass fluorine substrate. Therefore, when the substrate of the present invention is used, wire bonding and bump welding can be performed, and it is possible to contribute to weight reduction of the whole equipment using the substrate.
Examples of the PMP film include a poly-4-methyl-1-pentene (PMP) film, which is a homopolymer of 4-methyl-1-pentene, and a small amount of other copolymerized monomer in 4-methyl-1-pentene. May be a film composed of a 4-methyl-1-pentene copolymer obtained by copolymerizing
[0018]
The PMP film is formed by a known method, and for example, commercially available “OPULAN (trade name)” (manufactured by Mitsui Chemicals, Inc., thickness 50 μm) or the like can be used.
One to a plurality of such PMP films may be laminated and used.
Further, in the present invention, a glass cloth or a glass felt is used as the glass base material for the first insulating layer 20, which contributes to the improvement of the strength of the high frequency laminated substrate.
[0019]
In the present invention, as the glass substrate for the first insulating layer 20, a glass cloth is particularly preferable, and the glass cloth is formed by twisting several tens to several hundreds of glass threads (filaments) having a diameter of about 5 to 15 μmφ. The twisted yarn (yarn) is woven as warp and weft, and the thickness of the glass cloth is preferably about 30 μm to 190 μm.
[0020]
As such a glass cloth, for example, “E15A04 (trade name)” (manufactured by Unitika Ltd., thickness: 120 μm), “WEA18T” (manufactured by Nittobo Co., Ltd., thickness: 190 μm) or the like can be used. it can. Such a glass cloth may be used by laminating one or more sheets.
Further, as a glass substrate for the second insulating layer 30, a nonwoven fabric made of glass is used, and glass paper or a glass mat is preferably used.
[0021]
In the present invention, the glass substrate for the second insulating layer 30 is particularly preferably glass paper, and the glass paper has glass (short) fibers having a thickness of 0.02 to 50 μm and a fiber length of 6 to 38 mm dispersed in water. It is a sheet-like material that is wet-formed (paper-made). The glass paper may contain, in addition to the glass fiber, a binder, a surface treatment agent for improving the adhesiveness between the glass fiber and the binder, a synthetic fiber, and the like.
[0022]
Examples of such glass paper include “Gravest (trade name)” (manufactured by Olivet Co., Ltd., fiber diameter 6 to 20 μm, fiber length 6 to 38 mm), “Surface mat (trade name)” (manufactured by Nitto Boshoku) ) Can be used. One to a plurality of such glass papers may be laminated and used.
In the present invention, since the base material has the smooth insulating second insulating layer made of glass paper or glass mat interposed between the first insulating layer and the conductor layer, the first insulating layer Of the surface of the conductor layer does not directly appear as irregularities on the surface of the conductor layer, and an extremely smooth conductor layer can be obtained.
[0023]
In the above description, the embodiment in which a glass substrate is used as the fiber base material for the first insulating layer and the second insulating layer has been described. However, the present invention is not limited to the above embodiment. Excellent in heat resistance, flame retardancy, dielectric properties (low relative permittivity, low dielectric loss tangent), low linear thermal expansion coefficient equal to or less than metal, can be used in place of glass substrate, aramid fiber Good effects can also be obtained by using a substrate, a polyester fiber substrate, a carbon fiber substrate, or the like.
[0024]
Further, in the present invention, as shown in the high-frequency laminated substrate 10B of FIG. 3 or the high-frequency laminated substrate 10C of FIG. 4, between the first insulating layer 20 and the second insulating layer 30, A PMP layer 50 made of a PMP film is interposed between the PMP layer and the conductor layer 40 in order to adjust the glass content in the obtained high-frequency laminated substrate and to improve the strength, dielectric properties, and adhesive strength. You may. Although the thickness of the PMP layer 50 is not particularly limited, the PMP film (thickness) is slightly reduced by heating and pressing compared to the thickness of the PMP film of 25 to 100 μm (thickness). It is almost the same, and is usually about 20 to 100 μm. The high frequency laminated substrates 10B and 10C shown in FIGS. 3 and 4 have an effect of improving the adhesive strength between prepregs, in particular, as compared with the high frequency

laminated substrates

10 and 10A shown in FIGS.
[0025]
In the present invention, the first insulating layer, the second insulating layer, and the like are each independently formed of one to a plurality of sheets, depending on the strength, dimensions, electrical characteristics, and the like of the high-frequency laminated substrate required. It may be.
At this time, it is preferable to adjust the fiber base ratio in the obtained high frequency laminated substrate to 10 to 30 wt%. When the ratio of the fiber base material in the high frequency laminated substrate is less than 10 wt%, a substrate having a sufficient strength tends to be unable to be obtained, and when it exceeds 30 wt%, a substrate having satisfactory dielectric properties tends not to be obtained. There is.
<Conductor layer>
The conductor layer 40 is made of a highly conductive metal foil such as a copper foil (eg, an electrolytic copper foil or a rolled copper foil) or a gold foil.
[0026]
The thickness of the metal foil is not particularly limited, but is usually about 5 to 70 μm, preferably about 9 to 35 μm. One to a plurality of such metal foils may be laminated and used.
As is apparent from the above detailed description, the present invention uses PMP, which is a heat-meltable resin that is equivalent to a fluororesin whose dielectric properties are good in a high-frequency region and is inexpensive compared to a fluororesin. I have. Therefore, it is possible to manufacture the substrate at a much lower cost than the glass fluorine substrate.
[0027]
Further, in the present invention, PMP is used as the resin as described above, but in this case, it is necessary to use a substrate such as glass cloth in order to further improve the heat resistance of the obtained substrate. In the present invention, as described above, PMP is laminated with a glass cloth or the like, and while the PMP is heated to a temperature equal to or higher than the melting temperature of the PMP, the substrate such as the glass cloth is impregnated with the PMP (so that the PMP is impregnated). 2) Since the pressure is applied, the impregnation of the base material with PMP and the molding of the high-frequency laminated substrate, which is a laminate, can be performed by heating and pressing at a temperature equal to or higher than the melting point of PMP. It is possible to complete the molding.
[0028]
In other words, in the present invention, there is no special process for impregnating a glass cloth with a fluororesin dispersion like a glass-fluorine substrate as in the conventional example. Therefore, a high-frequency laminated substrate can be manufactured at lower cost. By the way, when a high-frequency laminated substrate (substrate) is used in a high-frequency region, as the frequency increases, the width of a line pattern formed on the substrate surface becomes narrower, and the interval between the line and other lines also becomes narrow. Therefore, if the substrate surface has irregularities, the dimensional accuracy of the line pattern deteriorates, and if the substrate is used in a high-frequency region, the loss of propagating electromagnetic waves increases significantly.
[0029]
Therefore, in the present invention, as is apparent from the above description, for example, a non-woven fabric, such as glass paper, which is heat-resistant and produced (paper-formed) by a paper-making method between a copper foil and a PMP-impregnated glass cloth is used. The substrate is being sandwiched.
Glass paper, which is a non-woven paper made, is much finer than glass cloth or glass felt, so no irregularities are seen on the surface of PMP impregnated glass paper. A remarkably smooth conductor surface is formed.
[0030]
In short, according to the present invention, using a PMP that is cheaper than a fluororesin and has the same electrical characteristics and the like as a fluororesin, the bending strength and the flexural modulus are excellent, and the high frequency having excellent surface smoothness is used. The substrate for use is safer than using a fluororesin, can be easily manufactured with fewer steps, and can be provided at low cost.
Next, a method for manufacturing such a high-frequency laminated substrate will be specifically described in detail.
[0031]
<Manufacture of high frequency laminated substrate>
In the method for manufacturing a high-frequency laminated substrate according to the present invention, for example, the high-frequency laminated substrate 10 shown in FIG. 1 has a base-side heating located on the lower side where the release film 60 is disposed as shown in FIG. The first insulating layer prepreg (a) 20 to be the first insulating layer 20 is placed on the surface of the press 70A, and the second insulating layer 30 is formed on the surface (upper surface toward the paper surface) 22 thereof. The second insulating layer prepreg (b) 30 is placed, and the conductor foil (for example, 0.018 mm (thickness) copper foil) 40 is placed on the surface 32 of the second insulating layer prepreg 30. The movable heating and pressing mold 70B, which is disposed above the laminated sheet 10W before heating and pressing, via the release film 60,
Under heating at a melting point of PMP of 240 ° C. or higher, preferably 240 ° C. to 260 ° C., a pressure of 8 to 15 kg / cm below the prepreg in the thickness direction indicated by an arrow in the drawing.²Then, the insulating

prepregs

20 and 30 and the conductive foil 40 are joined and integrated by pressurizing for about 2 to 10 minutes, whereby a desired high-frequency laminated substrate 10 can be manufactured.
[0032]
The stacked sheets 10W before heating and pressing can be stacked and arranged in any order as long as the above-described layer configuration is obtained.
Further, for example, as shown in FIG. 6, the high-frequency laminated substrate 10A shown in FIG. 2 is provided on the surface of the base-side heating / pressing press 70A located on the lower side where the release film 60 is disposed, from below to above. In the state where a sheet or foil is placed in the order of the conductor foil 40, the prepreg 30 for the second insulation layer, the prepreg 20 for the first insulation layer, the prepreg 30 for the second insulation layer, and the conductor foil 40, the lamination is performed. The movable heating / pressing mold 70B disposed above the sheet 10X before heating and pressing via the release film 60 is heated and pressed under the same conditions as above, and these are joined and integrated. What is necessary is just to manufacture the high frequency laminated substrate 10X.
[0033]
In addition, for example, the high-frequency laminated substrates 10B and 10C shown in FIGS. 3 and 4 can be manufactured in the same manner as described above. For example, the sheets or foils for the respective layers are placed in the order shown in FIGS. In this state, using a press similar to that described above, heating and pressing are performed under the same conditions as above, and these are joined and integrated to produce the high frequency laminated substrates 10B and 10C, respectively.
[0034]
The number of the first insulating layer prepreg 20, the second insulating layer prepreg 30 or the number of the PMP film is not limited in the production of the high frequency laminated substrate, and in particular, the number of the first insulating layer prepreg is determined. It can be appropriately changed according to the thickness of the high frequency laminated substrate to be obtained.
At this time, it is preferable to adjust the fiber base ratio in the obtained high frequency laminated substrate to 10 to 30 wt%. If it is less than 10 wt%, sufficient strength of the substrate tends not to be obtained, and if it is more than 30 wt%, the adhesive strength to the copper foil tends not to be obtained.
[0035]
The prepreg (a) itself for the first insulating layer used when manufacturing the high-frequency laminated substrate is a poly-4-methyl-1-pentene (PMP) film (not shown) and a glass fiber (not shown). Laminated with a woven or felt-like nonwoven fiber base material containing fibers such as aramid fiber, polyester fiber and carbon fiber, and heated at a temperature of PMP melting point of 240 ° C or higher, preferably 240 to 260 ° C. , Pressure 8-15kg / cm²Is a prepreg obtained by impregnating the fibrous base material of the woven fabric or felt-like nonwoven fabric with PMP for about 2 to 10 minutes.
[0036]
The prepreg (b) for the second insulating layer is a non-woven fabric made of a paper made of a poly-4-methyl-1-pentene (PMP) film and fibers such as glass fiber, aramid fiber, polyester fiber, and carbon fiber. The material is laminated and heated under the same temperature and at the same pressure at the same pressure as above, because it is thinner than in the case of forming the first insulating prepreg, which is a shorter time of about 0.5 to 5 minutes. It is obtained by applying pressure and impregnating the fiber base material with PMP.
[0037]
At the time of such heating and pressing, a flat plate press or the like can be used.
That is, the main difference between the prepreg for the first insulating layer (a) and the prepreg for the second insulating layer (b) is that the fiber base material for forming the prepreg for the first insulating layer is a woven fabric or a felt-like nonwoven fabric. On the other hand, the fibrous base material for forming the prepreg for the second insulating layer is in the point that it is a nonwoven fabric which is excellent in smoothness and is formed, and in the present invention, such a prepreg for the second insulating layer is firstly used. Since it is interposed between the insulating layer prepreg and the conductive foil, the obtained high frequency laminated substrate tends to have excellent surface smoothness and excellent electromagnetic wave propagation characteristics.
[0038]
In the present invention, it is preferable that the prepreg for the second insulating layer is placed on both surfaces of the prepreg for the first insulating layer, and the conductor foil is placed on the surface of each of the two prepregs for the second insulating layer. .
As described above, according to the present invention, a high-frequency substrate having excellent flexural strength and flexural modulus and excellent surface smoothness using PMP can be prepared without using a solvent, and therefore, can be processed safely and with fewer steps. , And can be provided at low cost.
[0039]
<Application>
The high-frequency laminated substrate according to the present invention is used not only as a circuit board but also as a planar antenna or the like.
[0040]
【The invention's effect】
The high-frequency laminated substrate according to the present invention can eliminate the unevenness existing in the conventional high-frequency laminated substrate and has excellent surface smoothness, so that a line pattern can be formed with high dimensional accuracy. Therefore, the propagation loss of the electromagnetic wave is not impaired even in a high frequency region.
Further, since the high-frequency laminated substrate according to the present invention is hard, it is difficult to bend or deform even when pressed during mounting of electronic components, has excellent mounting workability, and can mount electronic components typified by semiconductors such as wire bonding. Easy to do. Furthermore, since the high-frequency laminated substrate of the present invention is lighter in weight than the conventional substrate as described above, it is possible to reduce the weight of an apparatus (finished product) in which the substrate is incorporated.
[0041]
Further, the laminated substrate for high frequency of the present invention is used as an insulating material for a substrate such as an electronic substrate, and has a low dielectric constant equivalent to that of a fluororesin and also has a function as a dielectric having a low dielectric loss tangent. Although 1-pentene (PMP) is used, this PMP film is inexpensive as compared with fluororesin, and in the process of manufacturing a substrate, a resin is used as a base material as in the case of using fluororesin. Since one independent step of impregnation can be omitted, cost can be reduced and a substrate can be provided at low cost.
[0042]
Therefore, according to the present invention, an excellent substrate that can be used in a high-frequency region can be provided at a low cost with a simple process with fewer processes.
[0043]
【Example】
Hereinafter, the high-frequency laminate according to the present invention and the method of manufacturing the same will be described more specifically with reference to examples, but the present invention is not limited to the examples.
[0044]
Embodiment 1
A high-frequency laminated substrate as shown in FIG. 4 was produced by the following method.
Prepreg for first insulating layer (C layer):
PMP films (trade names: Opulan, Mitsui Chemicals, Inc.) on both sides of a glass cloth (trade name: E15A04, manufactured by Unitika Ltd., area × thickness = 10 cm × 10 cm × 130 μm (thickness), weight: 1.65 g) ), Area × thickness: 10 cm × 10 cm × 100 μm (thickness), weight: 0.83 g) are laminated one by one, and 10 kg / cm at 240 ° C.²The plate was pressed for 5 minutes under the conditions described above to obtain a prepreg in which a glass cloth was impregnated with PMP.
[0045]
Prepreg for second insulating layer (layer B):
PMP film (trade name: Opulan, Mitsui Chemicals, Inc.) on both sides of glass paper (trade name: Gravest, manufactured by Olivet Co., Ltd., area × thickness = 10 cm × 10 cm × 420 μm (thickness), weight: 0.53 g) , Area × thickness: 10 cm × 10 cm × 50 μm (thickness), weight: 0.41 g), and laminated at 240 ° C. at a molding pressure of 10 kg / cm.²The plate was pressed for 1 minute under the conditions described above to obtain a prepreg in which glass paper was impregnated with PMP.
Conductor layer / foil (layer A)
A copper foil having a thickness of 0.018 mm was used.
PMP film
PMP film (trade name: Opulan, manufactured by Mitsui Chemicals, Inc., area × thickness: 10 cm × 10 cm × 50 μm (thickness), weight: 0.41 g)
Manufacture of laminated substrates (substrates) for high frequency
Using the same press as in FIG. 5 or FIG. 6, on the surface of the base-side pressurizing press 70A on which the release film 60 is set, as shown in FIG. 40, PMP film 50, prepreg for the second insulating layer (B layer) 30, PMP film 50, prepreg for the first insulating layer (C layer, the number of which is changed according to the set thickness) 20, PMP film 50, B layer 30 Prepreg, PMP film 50, and copper foil (layer A) 40 in this order.
[0046]
Then, at 240 ° C., a molding pressure of 10 kg / cm²The plate was pressed for 5 minutes under the conditions described above to integrate the laminate.
At the time of pressing, a jig (not shown) for preventing the movable heating / pressing die (upper plate) 70B and the base side heating / pressing press (lower plate) 70A from "shifting" or "tilting" is provided. Used to minimize cross flow of the prepreg.
[0047]
The thickness of the obtained high frequency laminated substrate was 1.25 mm.
Further, the glass substrate ratio in the obtained laminated substrate was 20% by weight.
[0048]
[Comparative Example 1]
A glass fluorine substrate (model name: CQF-502) manufactured by Chuko Kasei Co., Ltd. was used.
[0049]
[Comparative Example 2]
Two prepregs for the first insulating layer used in Example 1 were laminated, and the same copper foil as in Example 1 was laminated on both surfaces thereof, and a molding pressure of 10 kg / cm was applied at 240 ° C.²The plate was pressed for 5 minutes under the conditions described above to integrate the laminate.
The thickness of the obtained substrate was 1.25 mm, and the glass substrate ratio in the obtained laminated substrate was 20 wt%.
[0050]
【Evaluation results】
Various characteristics shown in Table 1 were measured for the laminated substrates obtained in Example 1 and Comparative Examples 1 and 2.
The results are summarized in Table 1.
In addition, the measuring method is as follows.
<Relative permittivity and dielectric loss tangent>
The relative permittivity and the dielectric loss tangent were measured at 12 GHz according to JIS C6481.
<Smoothness>
The smoothness was measured using a surface roughness meter (surfcom 480A) in accordance with JIS B0901.
<Dimension accuracy of route pattern>
The dimensional accuracy of the line pattern was evaluated by forming a line pattern (width 2 mm) by etching and visually checking the line shape.
[0051]
◎ indicates that the finish in the width direction of the pattern line is excellent, は indicates good, Δ indicates acceptable, and × indicates unacceptable.
<Cost>
◎: Cost is extremely low
○: Cost is slightly lower
△: Cost is slightly higher
×: remarkably high cost
[0052]
[Table 1]

[0053]
<Discussion>
As is clear from the comparison between the above example and the comparative example, the high frequency laminated substrates according to the examples of the present invention each have a relative dielectric constant of 2.5 or less, a low relative dielectric constant, and a high frequency range. Then, the propagation speed of the electric signal is high. Among the substrates marketed so far, the one having the smallest relative dielectric constant is a glass fluorine substrate (Comparative Example 1), which has a dielectric constant equivalent to this.
[0054]
Further, the high frequency laminated substrate according to the embodiment of the present invention has a dielectric loss tangent of 10^-3It is less than the order, the dielectric loss tangent is small, and the loss of the transmitted electric signal is small. The low dielectric constant substrate that has been used so far in the high frequency region is a glass fluorine substrate as shown in Comparative Example 1. It can be seen that the substrate has a dielectric loss tangent equivalent to that of the glass fluorine substrate.
[0055]
Further, the high-frequency laminated substrate according to the present invention has no irregularities and is excellent in smoothness as compared with the glass fluorine substrate.
As a result, the high-frequency laminated substrate of the present invention has a high dimensional accuracy of the line pattern, and when used in a high-frequency region, the loss of the transmitted electromagnetic wave is significantly reduced. Further, the high frequency laminated substrate of the present invention has a solder heat resistance of 260 ° C. × 30 sec. No swelling and peeling of copper foil.
[0056]
Further, the high-frequency laminated substrate of the present invention has flame retardancy, and according to the test method (subject 94) for evaluating flame retardancy (flame resistance) set by UL (a testing institute in the United States). The degree of flammability is "UL94-VO", indicating that the sample does not continue to burn (does not spread) for more than 30 seconds even if the sample ignites or ignites.
[0057]
Further, the high-frequency laminated substrate of the present invention is lighter than a glass-fluorine substrate and is less expensive than a glass-fluorine substrate.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a high-frequency laminated substrate according to one embodiment of the present invention. FIG. 1 shows a high-frequency laminated substrate according to the present invention having a three-layer structure.
FIG. 2 is a schematic cross-sectional view showing a preferred embodiment of a high-frequency laminated substrate according to another embodiment of the present invention. FIG. 2 shows a five-layer laminated high-frequency substrate according to the present invention.
FIG. 3 is a schematic cross-sectional view of the high-frequency laminated substrate, showing a mode in which a PMP film (layer) is interposed between layers of the three-layer laminated high-frequency substrate shown in FIG. 1;
4 is a schematic cross-sectional view of the high-frequency laminated substrate, showing a mode in which a PMP film (layer) is interposed between layers of the five-layer laminated high-frequency substrate shown in FIG. 2;
FIG. 5 is a schematic explanatory view for explaining a method for manufacturing the high-frequency laminated substrate according to the embodiment of the present invention shown in FIG. 1;
FIG. 6 is a schematic explanatory view for explaining a method for manufacturing a high-frequency laminated substrate according to another embodiment of the present invention shown in FIG. 2;
[Explanation of symbols]
10, 10A, 10B, 10C,..., High frequency laminated substrate (substrate)
20: First insulating layer, first insulating sheet
22 One side of the first insulating layer
24: The other surface (back surface) of the first insulating layer
30... Second insulating layer, second insulating sheet
32: Surface of second insulating layer
34 lower surface of second insulating layer
40 ... conductor layer, conductor foil
50: PMP layer, PMP sheet
60 Release film
70A ... Press for heating and pressurizing on base side
70B ... Movable heating and pressing mold

Claims

The first insulating layer, the second insulating layer provided on at least one surface thereof, the conductor layer provided on the surface of the second insulating layer is joined,
The first insulating layer and the second insulating layer each contain a poly-4-methyl-1-pentene (PMP) film and a fiber selected from glass fiber, aramid fiber, polyester fiber, and carbon fiber. It is made of a prepreg obtained by laminating a fiber base material, applying pressure under heating, and impregnating the fiber base material with PMP, and
A high-frequency laminated substrate, wherein the fiber base material for the first insulating layer is a woven fabric or a felt-like nonwoven fabric, and the fiber base material for the second insulating layer is a nonwoven fabric formed.

The high-frequency laminated substrate according to claim 1, wherein the fiber substrate for the first insulating layer and the fiber substrate for the second insulating layer are both reinforced substrates containing glass fibers.

3. The high-frequency device according to claim 1, wherein the second insulating layer is provided on both surfaces of the first insulating layer, and a conductor layer is provided on each of the surfaces of the two second insulating layers. 4. Laminated substrate.

A poly-4-methyl-1-pentene (PMP) layer is further provided between the first insulating layer and the second insulating layer and between the second insulating layer and the conductor layer. The high-frequency laminated substrate according to any one of claims 1 to 3, wherein:

(A) a poly-4-methyl-1-pentene (PMP) film and a fiber substrate of a woven or felt-like nonwoven fabric containing a fiber selected from glass fiber, aramid fiber, polyester fiber, and carbon fiber; A prepreg for a first insulating layer formed by impregnating the fiber base material of the woven fabric or the felt-like nonwoven fabric with PMP by applying pressure under heating, and
(B) laminating a poly-4-methyl-1-pentene (PMP) film and a nonwoven fabric base made of fibers selected from glass fiber, aramid fiber, polyester fiber, and carbon fiber, and heating. And pressurized below to prepare a prepreg for a second insulating layer obtained by impregnating the fiber base of the nonwoven fabric with PMP.
A second insulating layer prepreg (b) is placed on at least one surface of the first insulating layer prepreg (a), and a conductive foil (c) is placed on the surface of the second insulating layer prepreg (b). With that,
A method for producing a high-frequency laminated substrate, characterized in that these insulating prepregs (a) and (b) and a conductor foil (c) are joined and integrated by applying pressure under heating.

The method for producing a high-frequency laminated substrate according to claim 5, wherein the fiber base material of the woven or felt-like nonwoven fabric and the fiber base material of the formed nonwoven fabric are both made of glass fiber.

The second insulating layer prepreg (b) is placed on both sides of the first insulating layer prepreg (a), and the surfaces of the two second insulating layer prepregs (b) are each provided with a conductor foil (c). The method for manufacturing a high-frequency laminated substrate according to claim 5, wherein

A poly-polypropylene is further provided between the first insulating layer prepreg (a) and the second insulating layer prepreg (b) and between the second insulating layer prepreg (b) and the conductor foil (c). The method for producing a high-frequency laminated substrate according to any one of claims 5 to 7, wherein a 4-methyl-1-pentene (PMP) film is interposed.