JP2004228349A

JP2004228349A - Manufacturing method of multilayer printed wiring board

Info

Publication number: JP2004228349A
Application number: JP2003014552A
Authority: JP
Inventors: Michihiro Miyauchi; 美智博宮内
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-01-23
Filing date: 2003-01-23
Publication date: 2004-08-12

Abstract

【課題】貫通穴加工の生産性を向上させ、低コストで穴加工を行える高放熱性を有する多層プリント配線板を提供する。
【解決手段】無機フィラーを含む熱硬化性樹脂からなる両面基板１０７に、樹脂が半硬化状態で貫通穴１０８をあける位置に予め貫通穴１０５をあけておき、両面基板１０７の両側に樹脂シート１０１、銅箔１０４を積層し樹脂が硬化する温度より低い温度でプレスして多層化した後、樹脂が半硬化状態で貫通穴１０８をあけた後、樹脂を本硬化させ、銅めっき、パターン形成を行い多層プリント配線板を得る。
【選択図】図１An object of the present invention is to provide a multi-layer printed wiring board having high heat dissipation, which can improve the productivity of through hole processing and can perform hole processing at low cost.
A double-sided board made of a thermosetting resin containing an inorganic filler is provided with through-holes in advance at positions where through-holes are made in a semi-cured state of the resin, and resin sheets are provided on both sides of the double-sided board. After laminating the copper foil 104 and pressing at a temperature lower than the temperature at which the resin cures to form a multilayer, the resin is semi-cured, the through-hole 108 is opened, the resin is fully cured, and copper plating and pattern formation are performed. Then, a multilayer printed wiring board is obtained.
[Selection diagram] Fig. 1

Description

【０００１】
【発明の属する技術分野】
本発明は多層プリント配線板の製造方法に関するものである。
【０００２】
【従来の技術】
近年、電子機器の小型化、高性能化に伴い、半導体の高密度、高機能化が望まれている。そのため、これを実装する回路基板も小型高密度のものが要望されている。この結果、部品、回路基板の放熱が大きな課題となってきている。放熱性の良い回路基板として、銅やアルミニウムなどの金属板を使用し、この金属板の片面に電気絶縁層を介して回路パターンを形成する金属ベース基板が知られている。しかし、比較的厚い金属板を用いるために重たくなり、小型軽量化が困難である。また、電気絶縁層の熱伝導が悪いため絶縁層を薄くしなければならないため、絶縁耐圧の問題が生じる場合もある。さらに、両面実装できる多層の金属コア基板は、金属板の両側にガラス−エポキシの両面板あるいは多層板を貼り付けるため熱伝導が悪くなり放熱性が低下してしまう。
【０００３】
この課題を解決する方法として、絶縁材料として熱硬化性樹脂の中に無機フィラーを高濃度に充填した樹脂を用いた高熱伝導の多層プリント配線板の製造方法が開示されている。この多層基板の製造方法を図５に示す。図５（Ａ）に示すように、離型性フィルム５０１上に、無機質フィラーと熱硬化性樹脂を含む熱伝導シート状物５０２を作製し、図５（Ｂ）に示すように、離型性フィルム５０１側から熱伝導シート状物５０２に貫通穴５０３を形成する。次に図５（Ｃ）に示すように、貫通穴５０３に導電性樹脂組成物５０４を充填する。このような導電性樹脂組成物５０４を充填した熱伝導シート状物５０２を複数枚用意し、離型性フィルム５０１を剥離し、そのうちの１枚（図５の（Ｄ））を除いて、図５（Ｅ）、（Ｆ）、（Ｇ）に示すように、熱伝導シート状物５０２の離型性フィルム５０１を剥離した面に導電性樹脂組成物５０４を用いて配線パターン５０５ａ〜５０５ｄを形成する。次に、熱伝導シート状物を図５（Ｈ）のように重ねさらにその両面に金属箔５０６を重ねる。これを加熱加圧し各々の熱伝導シート状物を硬化接着させ（図５（Ｉ））、最後に最外層の配線パターン５０７を形成する（図５（Ｊ））。
【０００４】
なお、この出願の発明に関連する先行技術文献情報としては、例えば、特許文献１が知られている。
【０００５】
【特許文献１】
特開平１０−１７３０９７号公報
【０００６】
【発明が解決しようとする課題】
この発明では、貫通スルーホールの作製については記述されていない。挿入部品を実装したり、基板を機器に取りつけたりするためには、貫通スルーホールが必要である。一般的に、貫通スルーホールを作製するためには、図５（Ｉ）の多層構造基板に穴加工を行い貫通穴を形成後、銅めっきを行い貫通スルーホールを形成する。しかしながら、無機フィラーが樹脂中に高濃度に充填されているため（７０〜９５重量部）、例えば、ドリルによる穴加工では無機フィラーによりドリルが激しく磨耗するため、１００穴ぐらいでバリが発生し穴径が小さくなり高品質な穴を得ることができない。このように、一般のガラス−エポキシ基板に比べてドリルの寿命が短く、穴加工コストが増大し、また高品質の穴を得ることができないという課題を有している。また、パンチングによる穴加工では、熱硬化性樹脂が完全硬化しているため、パンチングが基板に挿入できないあるいは基板が割れる等で穴加工自体ができないという課題を有している。
【０００７】
また、穴加工を加熱加圧し各々の熱伝導シート状物を硬化させる前の図５（Ｈ）の積層した段階で行う方法が考えられる。しかしながら、熱伝導シート状物の樹脂が未硬化の状態で穴加工を行い、その後加熱加圧を行った場合、加熱により樹脂が軟化しその状態で加圧されるため、穴が変形してしまい、貫通スルーホールを形成できないという課題を有している。
【０００８】
本発明は、上記の課題を解決するためになされたものであり、貫通穴の加工を容易にし生産性良く低コストで高放熱の多層プリント配線板を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するために、本発明は以下の構成を有するものである。
【００１０】
本発明の請求項１に記載の発明は、特に、無機フィラーを含む軟体の熱硬化性樹脂組成物をシート状にした樹脂シートの片面又は両面に金属箔を接着し、その後プレスしながら加熱し半硬化させる第１の半硬化工程と、前記半硬化させた基板の所望位置に少なくとも第１の貫通穴を形成し、その後この基板を熱硬化性樹脂の硬化温度まで加熱し本硬化させる第１の本硬化工程と、前記本硬化させた基板に所望の回路パターン形成を行うパターン形成工程と、前記パターン形成された基板の両面をそれぞれ新たな無機フィラーを含む軟体の熱硬化性樹脂組成物をシート化した樹脂シートおよびその外側に金属箔で挟みこみプレスしながら加熱し半硬化させる第２の半硬化工程と、前記半硬化させた基板の前記所望位置に形成された第１の貫通穴内に第２の貫通穴を形成し、その後この基板を熱硬化性樹脂の硬化温度まで加熱し本硬化させる第２の本硬化工程とを有する多層プリント配線板の製造方法であり、第２の貫通穴を形成する位置に事前に第１の貫通穴を形成することにより、半硬化状態で第２の貫通穴を形成することができるようになり、穴加工治具の磨耗を抑制し穴加工を容易にできるという作用効果が得られる。
【００１１】
本発明の請求項２に記載の発明は、特に、第１の本硬化工程とパターン形成工程の間に、前記本硬化させた基板をめっきする請求項１記載の多層プリント配線板の製造方法であり、第１の貫通穴を通して両側の金属箔を電気的に接続することができるようになり、より高密度な基板が作製できるという作用効果が得られる。
【００１２】
本発明の請求項３に記載の発明は、特に、熱硬化性樹脂組成物は、液状の熱硬化性樹脂と熱可塑性樹脂パウダーとを成分として含み、かつ前記熱可塑性樹脂パウダーが液状の前記熱硬化性樹脂の液状成分を吸収して膨潤することにより固形状になるものを用いる請求項１または２記載の多層プリント配線板の製造方法であり、このような樹脂を用いることにより、熱硬化性樹脂が硬化しない温度で基板を半硬化状態にすることができ、穴加工治具の磨耗を抑制し穴加工を容易にできるという作用効果が得られる。
【００１３】
本発明の請求項４に記載の発明は、特に、第１の貫通穴および第２の貫通穴をパンチングにより形成することを特徴とする請求項１または２記載の多層プリント配線板の製造方法であり、半硬化の状態でパンチングにより第１、第２の貫通穴の加工を行うので、パンチング治具と無機フィラーの接触距離が樹脂厚程度と非常に短いため、パンチング治具の磨耗が少なく高寿命で穴加工ができ、より高品質で低コストな穴加工ができるという作用効果が得られる。
【００１４】
本発明の請求項５に記載の発明は、特に、パターン形成時に第１の貫通穴をスルーホールとして形成することを特徴とする請求項２記載の多層プリント配線板の製造方法であり、第１の貫通穴を通して両側の金属箔を電気的に接続することができるようになり、より高密度な基板が作製できるという作用効果が得られる。
【００１５】
本発明の請求項６に記載の発明は、特に、第１の半硬化工程と第１の本硬化工程の間に、第１の貫通穴以外の貫通穴を形成するとともに、パターン形成時に前記貫通穴をスルーホールとして形成することを特徴とする請求項２記載の多層プリント配線板の製造方法であり、第１の貫通穴以外の貫通穴を通して両側の金属箔を電気的に接続することができるようになり、より高密度な基板が作製できるという作用効果が得られる。
【００１６】
本発明の請求項７に記載の発明は、特に、熱硬化性樹脂として、エポキシ樹脂、フェノール樹脂あるいはシアネート樹脂の少なくともひとつを含む構成であり、これらの樹脂により耐熱性や電気絶縁性に優れた多層プリント配線板を作製できるという作用効果が得られる。
【００１７】
本発明の請求項８に記載の発明は、特に、無機フィラーとして、Ａｌ_２Ｏ_３、ＭｇＯ、ＳｉＯ_２、ＢＮあるいはＡｌＮから選ばれた少なくとも一種の無機フィラーを用いることにより、放熱性に優れた電気絶縁性基板が得られるという作用効果が得られる。また、これら無機フィラーの組み合わせ、量をコントロールすることにより、所望の熱膨張係数をもつ多層プリント配線板を作製できるという作用効果も得られる。
【００１８】
本発明の請求項９に記載の発明は、特に、無機フィラーが、７０〜９５重量％含むことにより、高熱伝導の無機フィラーが高濃度に充填されているため放熱性に優れた基板が得られるという作用効果が得られる。
【００１９】
本発明の請求項１０に記載の発明は、特に、無機フィラーの粒径が、０．１〜１００μｍである構成にしたものであり、樹脂絶縁層の厚さが０．１〜２ｍｍであるため、粒径が大きくなり過ぎると均一に充填できなくなり、また、粒径が小さくなり過ぎると高価であり、また無機フィラーの取り扱いが難しくなる。この範囲の粒径の無機フィラーを使用することにより無機フィラーを樹脂中に均一に高充填することができ、熱伝導率の高い基板が得られるという作用効果が得られる。
【００２０】
本発明の請求項１１に記載の発明は、金属箔として少なくとも片面粗面化された面を有する１２〜２００μｍ厚みの銅箔を用いることにより、樹脂と金属箔との密着力を高めることができ、貫通穴作製時に樹脂と金属箔の剥離を抑え容易に穴加工ができるようになる。また銅を用いているため熱伝導率が高く、導電率も良いため微細なパターン形成が可能である。また、箔厚を厚くすると大電流を流すことができる。
【００２１】
本発明の請求項１２に記載の発明は、第１の半硬化工程での加熱処理を１００〜１４０℃ですることにより、熱硬化性樹脂の硬化が起こらずしかも熱硬化性樹脂組成物中の熱可塑性樹脂パウダーが液状の熱硬化性樹脂の液状成分を吸収して膨潤し固形状になり、樹脂が半硬化状態の基板を作製することができ、第１の貫通穴作製時の穴加工治具の磨耗を抑制し、穴加工を容易に行うことができるようになる。
【００２２】
本発明の請求項１３に記載の発明は、第１の本硬化工程での硬化温度を１５０〜２３０℃にすることにより、熱硬化性樹脂を硬化させることができ、次工程のめっき形成やパターン形成時に酸やアルカリ等の薬品に影響されない電気絶縁性の優れた樹脂を得ることができる。
【００２３】
本発明の請求項１４に記載の発明は、第２の半硬化工程での加熱処理を１００〜１４０℃ですることにより、熱硬化性樹脂の硬化が起こらずしかも熱硬化性樹脂組成物中の熱可塑性樹脂パウダーが液状の熱硬化性樹脂の液状成分を吸収して膨潤し固形状になり、樹脂が半硬化状態の基板を作製することができ、第２の貫通穴作製時の穴加工治具の磨耗を抑制し、穴加工を容易に行うことができるようになる。
【００２４】
本発明の請求項１５に記載の発明は、第２の本硬化工程での硬化温度を１５０〜２３０℃にすることにより、熱硬化性樹脂を硬化させることができ、熱的、耐薬品性、電気絶縁性に優れた樹脂を得ることができる。
【００２５】
本発明の請求項１６に記載の発明は、第１の貫通穴の径が第２の貫通穴の径よりも大きくすることにより、基板の収縮や貫通穴の位置ずれが起きても第２の貫通穴を加工するとき、加工治具が第１の貫通穴内の半硬化樹脂中を通過させることができ、穴加工治具の磨耗を抑制し、穴加工を容易に行うことができるようになる。
【００２６】
本発明の請求項１７に記載の発明は、特に、第１の貫通穴の直径を第２の貫通穴の直径よりも０．１〜１．０ｍｍ大きくするのが望ましい。０．１ｍｍより小さくなると第２の貫通穴加工時に位置ずれ等により硬化した樹脂部を加工する可能性があり、加工治具の磨耗、破損、基板にクラックの発生等が起こってしまう。さらに、第１の貫通穴をめっきしスルーホールを形成している場合は第１、第２のスルーホールの絶縁性が得られない場合がある。逆に第１の貫通穴の径を大きくし過ぎると、配線の自由度が下がり、高密度化の妨げとなるため、できれば第１の貫通穴の直径を第２の貫通穴の直径よりも１．０ｍｍ以内に抑えるのが良い。
【００２７】
本発明の請求項１８に記載の発明は、特に、パターン形成された基板を少なくとも２枚以上用いて、それぞれの基板を位置合わせしながら新たな無機フィラーを含む軟体の熱硬化性樹脂組成物をシート状にした樹脂シートで挟みこんで積層するとともに、両最外層に金属箔を積層し、その後プレスしながら加熱して半硬化させる第３の半硬化工程と、前記半硬化させた基板の前記所望位置に形成された第１の貫通穴内に第２の貫通穴を形成し、その後この基板を熱硬化性樹脂の硬化温度まで加熱し本硬化させる第３の本硬化工程とを有する多層プリント配線板の製造方法であり、所望の位置に同一個所に貫通穴を形成した複数のパターン形成された基板を位置合わせしながら積層することにより、６層板以上の多層プリント基板を容易に作製できるという作用効果が得られる。
【００２８】
本発明の請求項１９に記載の発明は、特に、複数のパターン形成された基板の内少なくとも一枚の基板が、第１の本硬化工程とパターン形成工程の間に、前記本硬化させた基板をめっきする請求項１８記載の多層プリント配線板の製造方法であり、第１の貫通穴を通して両側の金属箔を電気的に接続することができるようになり、より高密度な基板が作製できるという作用効果が得られる。
【００２９】
本発明の請求項２０に記載の発明は、特に、パターン形成時に第１の貫通穴をスルーホールとして形成することを特徴とする請求項１９記載の多層プリント配線板の製造方法であり、第１の貫通穴を通して両側の金属箔を電気的に接続することができるようになり、より高密度な基板が作製できるという作用効果が得られる。
【００３０】
本発明の請求項２１に記載の発明は、特に、第１の半硬化工程と第１の本硬化工程の間に、第１の貫通穴以外の貫通穴を形成するとともに、パターン形成時に前記貫通穴をスルーホールとして形成することを特徴とする請求項１９記載の多層プリント配線板の製造方法であり、第１の貫通穴以外の貫通穴を通して両側の金属箔を電気的に接続することができるようになり、より高密度な基板が作製できるという作用効果が得られる。
【００３１】
本発明の請求項２２に記載の発明は、第３の半硬化工程での加熱処理を１００〜１４０℃ですることにより、熱硬化性樹脂の硬化が起こらずしかも熱硬化性樹脂組成物中の熱可塑性樹脂パウダーが液状の熱硬化性樹脂の液状成分を吸収して膨潤し固形状になり、樹脂が半硬化状態の基板を作製することができ、第３の貫通穴作製時の穴加工治具の磨耗を抑制し、穴加工を容易に行うことができるようになる。
【００３２】
本発明の請求項２３に記載の発明は、第３の本硬化工程での硬化温度を１５０〜２３０℃にすることにより、熱硬化性樹脂を硬化させることができ、熱的、耐薬品性、電気絶縁性に優れた樹脂を得ることができる。
【００３３】
本発明の請求項２４に記載の発明は、特に、第２の半硬化工程に代えて、パターン形成された基板の所望位置に設けられた第１の貫通穴内に樹脂を充填する工程と、その基板の両面をそれぞれ樹脂フィルムおよびその外側を金属箔で挟みこみプレス又はラミネートする工程を有する請求項１または２記載の多層プリント配線板の製造方法であり、第１の貫通穴を樹脂で充填しているためその基板の両側を挟みこむ絶縁樹脂が、フィルムや流動性の少ない樹脂を使用することが可能となり安価に容易に放熱性の良い多層プリント基板が作製可能という作用効果が得られる。
【００３４】
本発明の請求項２５に記載の発明は、第１の貫通穴内に充填する樹脂として、無機フィラーを含む軟体の熱硬化性樹脂組成物を用いることにより、穴加工がしやすく安価で放熱性の良い多層プリント配線板を得ることができるようになる。
【００３５】
本発明の請求項２６に記載の発明は、樹脂フィルムとして、低温低荷重で熱圧着が可能な熱硬化性樹脂を用いることにより、ラミネートにより安価で生産性の良い方法で多層プリント配線板を作製できるようになる。
【００３６】
本発明の請求項２７に記載の発明は、樹脂フィルムの中に無機フィラーとしてＡｌ_２Ｏ_３、ＭｇＯ、ＳｉＯ_２、ＢＮあるいはＡｌＮの少なくとも一種の無機フィラーを含むことにより、より放熱性の優れた多層プリント配線板が得られるようになる。また、これら無機フィラーの組み合わせ、量をコントロールすることにより、樹脂フィルムの熱膨張係数を両面基板の樹脂の熱膨張係数に近づけることができるため、歪、反り等の少ない信頼性の高い多層プリント配線板を作製できるという作用効果も得られる。
【００３７】
本発明の請求項２８に記載の発明は、特に、樹脂フィルムおよびその外側を金属箔に代えて、樹脂付き銅箔で基板の両面を挟みこむことを特徴とする請求項２４記載の多層プリント配線板の製造方法であり、樹脂付き銅箔を用いることにより、より簡便に安価に生産性良く多層プリント配線板を作製できるという作用効果も得られる。
【００３８】
本発明の請求項２９に記載の発明は、樹脂フィルムの厚さが２０μｍ以上２００μｍ以下であることが望ましい。２０μｍより薄くなると絶縁信頼性に問題が生じてくる。また、２００μｍより厚くなると放熱性が低下する問題が生じるようになる。
【００３９】
【発明の実施の形態】
（実施の形態１）
以下、実施の形態１を用いて、本発明の特に請求項１に記載の発明について説明する。
【００４０】
図１は、本発明の実施の形態１における多層プリント配線板の製造工程を示す断面図である。
【００４１】
図において、１０１は無機フィラーを含む軟体の熱硬化性樹脂シートであり、７０〜９５重量部の無機材料からなる熱伝導性フィラーと熱硬化性樹脂組成物である。熱伝導性の無機フィラーとしては、Ａｌ_２Ｏ_３、ＭｇＯ、ＳｉＯ_２、ＢＮあるいはＡｌＮから選ばれた少なくとも一種の無機フィラーであり、この実施の形態ではＡｌ_２Ｏ_３を使用している。無機フィラーの粒径は０．１〜１００μｍが望ましく、この実施の形態では、平均粒径が３μｍと１２μｍの２種類の混合を用いている。大小２種類の粒径の無機フィラーを用いることによって、大きな粒径の無機フィラーの隙間に小さな粒径の無機フィラーが充填されるため、高密度に無機フィラーを充填することができた。無機フィラーの充填量は、８７重量％である。熱硬化性樹脂組成物は、液状の熱硬化性樹脂と熱可塑性樹脂パウダーとを成分として含み、この熱可塑性樹脂パウダーが液状の前記熱硬化性樹脂の液状成分を吸収して膨潤することにより固形状になるという特徴がある。熱硬化性樹脂としてはエポキシ樹脂、フェノール樹脂あるいはシアネート樹脂の少なくともひとつを含むものであり、この実施の形態ではビスフェノールＡ型液状エポキシ樹脂を用いている。さらに、硬化剤、硬化促進剤および難燃剤として臭素化エポキシ樹脂を添加している。液状エポキシ樹脂、硬化剤、硬化促進剤および臭素化エポキシ樹脂は約１１重量％である。また、エポキシ樹脂の硬化温度以下でシートが半硬化状態で可撓性を持たせるために熱可塑性樹脂パウダーを約２％含有している。この樹脂を押出し成形法によりシート状に形成する。他にもシート状の形成にドクターブレード法、コーター法あるいは圧延法を用いて行うこともある。
【００４２】
樹脂シート１０１の両側に、図１（Ａ）に示すように銅箔１０４を貼り付ける。樹脂シート１０１の樹脂表面は粘着性があるため、樹脂と銅箔の界面に空気が噛み込まないように、シートの端面からローラーをかけながら銅箔１０４を貼り付ける。銅箔１０４は樹脂シート１０１と接する面を５μｍ前後粗化しており、厚さは３５μｍである。尚、細線パターンが必要なときは１２，１８μｍの薄い銅箔を、大電流が流れるような製品では７０〜２００μｍの銅箔を用いると良い。
【００４３】
次に、図１（Ｂ）に示すように、プレスしながら加熱加圧して樹脂シート１０１を半硬化させる（第１の半硬化工程）。この時の最高温度は、エポキシ樹脂の硬化反応が起こらず、しかも熱可塑性樹脂パウダーが液状エポキシ樹脂の液状成分を吸収して膨潤し固形状になる温度にする必要がある。この第１の半硬化工程での加熱温度は１００〜１４０℃とするのが望ましく、この実施の形態では生産性とプロセスの安定性を考えて、１３０℃で３０分間プレスを行っている。一般のガラス−エポキシ基板では、１８０℃前後までの昇温時間およびエポキシ樹脂を完全に硬化させる必要があるため、２〜３時間プレスする必要がある。このため、ガラス−エポキシ基板に比べて短時間での成形が可能であり生産性が良い。
【００４４】
次に、図１（Ｃ）に示すように貫通スルーホールを形成したい所望の位置に穴加工を行い、第１の貫通穴１０５を形成する。貫通穴の形成方法としては、一般のガラス−エポキシ基板で用いられているドリル加工やパンチングマシンによる打ち抜き加工法や金型による打ち抜き加工法などがあり、特に、穴あけ治具の磨耗や生産性、コストを考えた場合パンチングマシンによる穴あけが望ましい。
【００４５】
穴あけした基板を恒温槽内でエポキシ樹脂が硬化する温度で加熱し樹脂１０３を硬化させる（第１の本硬化工程、図１（Ｄ））。この本硬化工程では、特に基板への加圧が必要でないため、安価な装置で大量に処理できるため低コストで基板作製が容易に行える。第１の本硬化工程での硬化温度は１５０〜２３０℃が望ましく、この実施の形態では１７０℃で２時間行っている。
【００４６】
次に、銅箔表面にドライフィルムレジストを貼り付け、回路パターンを露光、現像、エッチング、ドライフィルムレジスト剥離を行い、図１（Ｅ）に示すようなパターン形成された配線パターン１０６を有する両面基板１０７を形成する。
【００４７】
４層基板を作製するために、パターン形成された両面基板１０７の両側に無機フィラーを含む軟体の熱硬化性樹脂シート１０１とさらにその外側に銅箔１０４を積層する（図１（Ｆ））。次に、プレスしながら加熱加圧して樹脂シート１０１をパターン間や第１の貫通穴１０５内に充填するとともに銅箔１０４および両面基板１０７と接着させた後、半硬化させる（第２の半硬化工程、図１（Ｇ））。この第２の半硬化工程での加熱温度は１００〜１４０℃とするのが望ましく、この実施の形態では生産性とプロセスの安定性を考えて、１３０℃でプレスを行っている。
【００４８】
次に、内層にある銅パターンでできた認識マークをＸ線認識装置で認識し穴加工の位置合わせを行い、第１の貫通穴１０５内に第２の貫通穴１０８を形成する（図１（Ｈ））。形成方法は、第１の貫通穴と同じで良い。第１の貫通穴１０５内に第２の貫通穴１０８を形成するため、第１の貫通穴１０５の径は第２の貫通穴１０８よりも大きくする必要がある。穴加工時の認識装置での位置合わせ精度、穴加工位置精度、また基材の寸法収縮のばらつき等を考慮すると、第１の貫通穴１０５の直径は第２の貫通穴１０８の直径よりも０．１ｍｍ以上大きくするのが望ましい。しかしながら、第１の貫通穴１０５の穴径を大きくし過ぎると、高密度配線ができなくなったり、積層しプレスして多層化したときに、第１の貫通穴１０５内に樹脂が不足する場合があるため、第１の貫通穴１０５の直径は第２の貫通穴１０８の直径よりも１．０ｍｍ以上大きくしないほうが望ましい。次に、恒温槽内でエポキシ樹脂が硬化する温度で加熱し樹脂を硬化させる（第２の本硬化工程、図１（Ｉ））。この本硬化工程では、特に基板への加圧が必要でない。第２の本硬化工程での硬化温度は１５０〜２３０℃が望ましく、この実施の形態では１７０℃で行っている。
【００４９】
最外層１０４とその下の内層パターン１０６とを電気的に接続する場合は、スルーホールを形成したい所望の位置にエッチングにより外層の銅箔１０４の銅を除去した後、レーザー加工法により銅を除去した所にある樹脂１０３を除去し内層パターン１０６の表面を露出させる。その後は、銅めっき、パターン形成、ソルダーレジスト形成等を行い多層プリント配線板を形成した。
【００５０】
（実施の形態２）
以下、実施の形態２を用いて、本発明の特に請求項２、５、６に記載の発明について説明する。
【００５１】
図２は、本発明の実施の形態２における多層プリント配線板の製造工程を示す断面図である。
【００５２】
実施の形態１と同じように第１の半硬化工程まで実施する（図２（Ａ）、（Ｂ））。第１の貫通穴２０１を形成する穴加工工程において、図２（Ｃ）に示すように、第１の貫通穴２０１以外に貫通穴２０２を形成する。貫通穴２０２は上下の銅パターンの接続用であり、この貫通穴２０２内には後で述べる第２の貫通穴を形成しないため、その径は第１の貫通穴２０１より小さくすることができる。
【００５３】
次に実施の形態１と同じように第１の本硬化を行う（図２（Ｄ））。次に上下の銅箔１０４を電気的に接続するために銅めっき２０３を行う（図２（Ｅ））。銅めっき２０３の厚さは約２０μｍである。次に、銅箔１０４表面にドライフィルムレジストを貼り付け、回路パターンを露光、現像、エッチング、ドライフィルムレジスト剥離を行い、図２（Ｆ）に示すようなパターン形成された配線パターン２０４を有する両面基板２０６を形成する。この時、第１の貫通スルーホール２０５ａは、この図ではスルーホール内に銅めっき２０３があり、上下の配線パターン２０４が電気的に接続しているが、設計パターンによっては、パターン形成において穴内の銅めっき２０３を除去して、上下の配線パターン２０４を電気的に接続しない場合もある。
【００５４】
この後は、実施の形態１の４層基板作製のための積層工程以降と同一の工程を用いて多層プリント配線板を形成する（図２（Ｇ）〜（Ｊ））。
【００５５】
（実施の形態３）
以下、実施の形態３を用いて、本発明の特に請求項１８、１９、２０、２１に記載の発明について説明する。
【００５６】
図３は、本発明の実施の形態３における多層プリント配線板の製造工程を示す断面図である。
【００５７】
実施の形態１あるいは２を用いてパターン形成された両面基板３０１を複数枚形成する。３０１ａは銅めっきされた両面基板であり、３０１ｂは銅めっきされていない基板である。銅めっきの有無は設計パターンによる。各両面基板３０１にある第１の貫通穴３０２はすべて同じ位置に形成されている。
【００５８】
図３（Ａ）に示すように、複数のパターン形成された両面基板３０１を位置合わせしながら無機フィラーを含む軟体の熱硬化性樹脂シート１０１を交互に挟みこみながら積層し、両最外層に銅箔１０４を積層する。
【００５９】
次に、実施の形態１と同じようにプレスしながら加熱加圧して半硬化させる（第３の半硬化工程、図３（Ｂ））。この第３の半硬化工程での加熱温度は１００〜１４０℃とするのが望ましい。この実施の形態では生産性とプロセスの安定性を考えて、１３０℃でプレスを行っている。次に、同じように内層にある認識マークを用いて穴加工の位置合わせを行い、第１の貫通穴３０２内に第２の貫通穴３０３を形成する（図３（Ｃ））。次に、恒温槽内でエポキシ樹脂が硬化する温度で加熱し樹脂を本硬化３０４させる（第３の本硬化工程、図３（Ｄ））。この本硬化工程では、特に基板への加圧が必要でない。第３の本硬化工程での硬化温度は１５０〜２３０℃が望ましく、この実施の形態では１７０℃で行っている。
【００６０】
その後は、実施の形態１と同じように、スルーホール加工、銅めっき、パターン形成、ソルダーレジスト形成等を行い多層プリント配線板を形成した。このような方法により、６層以上の多層プリント配線板を容易に得ることができるようになった。
【００６１】
（実施の形態４）
以下、実施の形態４を用いて、本発明の特に請求項２４に記載の発明について説明する。
【００６２】
図４は、本発明の実施の形態４における多層プリント配線板の製造工程を示す断面図である。
【００６３】
パターン形成された両面基板４０３は実施の形態１あるいは２と同じ方法で形成する（図４（Ａ））。この図では貫通穴４０２に銅めっきは施されていないが、銅めっきを行い上下の銅パターンの導通を取ったものでも良い。この両面基板４０３に形成された貫通穴４０２内に樹脂４０４を充填する（図４（Ｂ））。充填する樹脂として、無機フィラーを含む軟体の熱硬化性樹脂組成物で成分は樹脂シート１０１と同じである。ただし粘度は樹脂を充填しやすいように調整している。
【００６４】
この両面基板４０３の両側に樹脂フィルム４０６とさらにその外側に銅箔４０５を積層する（図４（Ｃ））。樹脂フィルム４０６として、低温低荷重で熱圧着が可能な熱硬化性樹脂（例えば、日立化成工業株式会社製低弾性接着フィルムＧＦ３６００）を用いると良い。この樹脂フィルム４０６の厚さは、２０〜２００μｍであり、これを用いることにより薄い多層基板を作製できるようになる。これを、プレスあるいはラミネートにより一体化する（図４（Ｄ））。この時の温度は、１００〜１３０℃で行うのが望ましく、この実施の形態では１２０℃で行っている。樹脂フィルム４０６の中に熱伝導率を上げるために無機フィラーを添加したものを用いるとさらに良い。無機フィラーとしてはＡｌ_２Ｏ_３、ＭｇＯ、ＳｉＯ_２、ＢＮあるいはＡｌＮの少なくとも１種類含むものを用いると良い。また、樹脂フィルム４０６と銅箔４０５の代わりに、樹脂付き銅箔（例えば、日立化成工業株式会社製ＭＣＦ−６０００Ｅ）を用いて積層しても良い。
【００６５】
次に、第１の貫通穴４０２の位置に穴加工を行い貫通穴４０７を形成する（図４（Ｅ））。最後に恒温槽内で加熱し、樹脂４０４と樹脂フィルム４０６を硬化させる（図４（Ｆ））。この時の硬化温度は１５０〜２３０℃が望ましく、この実施の形態では１７０℃で行っている。
【００６６】
このような方法で、絶縁層の薄い多層プリント配線板を簡便な方法で生産性良く得ることができるようになった。
【００６７】
【発明の効果】
以上のように、本発明によれば、無機フィラーを含む軟体の熱硬化性樹脂組成物をシート状にした樹脂シートの片面又は両面に金属箔を接着し、その後プレスしながら加熱し半硬化させる第１の半硬化工程と、前記半硬化させた基板の所望位置に少なくとも第１の貫通穴を形成し、その後この基板を熱硬化性樹脂の硬化温度まで加熱し本硬化させる第１の本硬化工程と、前記本硬化させた基板に所望の回路パターン形成を行うパターン形成工程と、前記パターン形成された基板の両面をそれぞれ新たな無機フィラーを含む軟体の熱硬化性樹脂組成物をシート化した樹脂シートおよびその外側に金属箔で挟みこみプレスしながら加熱し半硬化させる第２の半硬化工程と、前記半硬化させた基板の前記所望位置に形成された第１の貫通穴内に第２の貫通穴を形成し、その後この基板を熱硬化性樹脂の硬化温度まで加熱し本硬化させる第２の本硬化工程と有することにより、第２の貫通穴を形成する位置に事前に第１の貫通穴を形成しその中を半硬化状態の樹脂が充填されているため、半硬化状態で第２の貫通穴を形成することができるようになり、穴加工治具の磨耗を抑制し高寿命化ができるため、高熱伝導の多層プリント配線板の穴加工を安価に行うことができるという効果を奏するものである。
【図面の簡単な説明】
【図１】本発明の実施形態１における多層プリント配線板の製造工程を示す断面図
【図２】本発明の実施形態２における多層プリント配線板の製造工程を示す断面図
【図３】本発明の実施形態３における多層プリント配線板の製造工程を示す断面図
【図４】本発明の実施形態４における多層プリント配線板の製造工程を示す断面図
【図５】従来の高熱伝導の多層プリント配線板の製造方法を説明する製造工程の断面図
【符号の説明】
１０１無機フィラーを含む軟体の熱硬化性樹脂シート
１０２半硬化した樹脂
１０３本硬化した樹脂
１０４銅箔
１０５第１の貫通穴
１０６配線パターン
１０７パターン形成された両面基板
１０８第２の貫通穴
２０１第１の貫通穴
２０２第１の貫通穴以外の貫通穴
２０３銅めっき
２０４配線パターン
２０５ａスルーホール
２０５ｂスルーホール
２０６パターン形成された両面基板
２０７第２の貫通穴
３０１ａ、３０１ｂパターン形成された両面基板
３０２第１の貫通穴
３０３第２の貫通穴
３０４本硬化した樹脂
４０１配線パターン
４０２第１の貫通穴
４０３パターン形成された両面基板
４０４樹脂
４０５銅箔
４０６樹脂フィルム
４０７第２の貫通穴
５０１離型性フィルム
５０２熱伝導シート状物
５０３貫通穴
５０４導電性樹脂組成物
５０５ａ〜５０５ｄ配線パターン
５０６金属箔
５０７配線パターン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a multilayer printed wiring board.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the miniaturization and high performance of electronic devices, higher density and higher functionality of semiconductors have been desired. Therefore, a small and high-density circuit board for mounting the same is demanded. As a result, heat dissipation of components and circuit boards has become a major issue. 2. Description of the Related Art As a circuit board having good heat dissipation, a metal base board is known which uses a metal plate such as copper or aluminum and forms a circuit pattern on one surface of the metal plate via an electric insulating layer. However, the use of a relatively thick metal plate increases the weight, making it difficult to reduce the size and weight. In addition, the insulating layer has to be thinned due to poor heat conduction of the electric insulating layer, which may cause a problem of withstand voltage. Further, in a multilayer metal core substrate that can be mounted on both sides, since a glass-epoxy double-sided board or a multilayer board is attached to both sides of the metal plate, heat conduction is deteriorated and heat dissipation is reduced.
[0003]
As a method for solving this problem, a method for manufacturing a multilayer printed wiring board having high thermal conductivity using a resin obtained by filling a high concentration of an inorganic filler in a thermosetting resin as an insulating material is disclosed. FIG. 5 shows a method for manufacturing this multilayer substrate. As shown in FIG. 5A, a heat conductive sheet 502 containing an inorganic filler and a thermosetting resin is formed on a release film 501, and as shown in FIG. A through hole 503 is formed in the heat conductive sheet 502 from the film 501 side. Next, as shown in FIG. 5C, the conductive resin composition 504 is filled in the through holes 503. A plurality of heat conductive sheet materials 502 filled with such a conductive resin composition 504 are prepared, the release film 501 is peeled off, and only one of them (FIG. 5D) is removed. 5 (E), (F), and (G), wiring patterns 505a to 505d are formed on the surface of the thermally conductive sheet material 502 from which the release film 501 has been peeled using the conductive resin composition 504. I do. Next, the heat conductive sheet materials are stacked as shown in FIG. 5 (H), and the metal foil 506 is further stacked on both surfaces thereof. This is heated and pressed to cure and bond the respective heat conductive sheet materials (FIG. 5 (I)), and finally, an outermost wiring pattern 507 is formed (FIG. 5 (J)).
[0004]
As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
[0005]
[Patent Document 1]
JP-A-10-173097
[0006]
[Problems to be solved by the invention]
In the present invention, the production of the through-hole is not described. In order to mount an insertion part or attach a board to a device, a through-hole is required. Generally, in order to form a through-hole, a through-hole is formed in the multilayer structure substrate of FIG. 5I to form a through-hole, and then plated with copper to form a through-hole. However, since the inorganic filler is filled in the resin at a high concentration (70 to 95 parts by weight), for example, in drilling with a drill, the drill is severely worn by the inorganic filler. The diameter is so small that high quality holes cannot be obtained. As described above, there are problems that the life of the drill is shorter than that of a general glass-epoxy substrate, the cost of drilling increases, and a high-quality hole cannot be obtained. Further, in the hole processing by punching, since the thermosetting resin is completely cured, there is a problem that the hole processing itself cannot be performed because the punching cannot be inserted into the substrate or the substrate is cracked.
[0007]
Further, a method is conceivable in which the hole processing is performed at the stage of lamination shown in FIG. 5 (H) before heating and pressing to harden each heat conductive sheet. However, if a hole is formed in a state where the resin of the heat conductive sheet is uncured and then heated and pressed, the resin is softened by heating and pressed in that state, so the hole is deformed. However, there is a problem that a through-hole cannot be formed.
[0008]
The present invention has been made to solve the above-described problems, and has as its object to provide a low-cost, high-heat-dissipation multilayer printed wiring board that facilitates processing of a through hole and has good productivity.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
[0010]
The invention according to claim 1 of the present invention particularly adheres a metal foil to one or both sides of a resin sheet formed of a soft thermosetting resin composition containing an inorganic filler, and then heats while pressing. A first semi-curing step of semi-curing, forming at least a first through hole at a desired position of the semi-cured substrate, and then heating the substrate to a curing temperature of a thermosetting resin to perform a first curing. Main curing step, a pattern forming step of forming a desired circuit pattern on the fully cured substrate, a soft thermosetting resin composition containing a new inorganic filler on both sides of the pattern-formed substrate, respectively. A second semi-curing step of heating and semi-curing while sandwiching the resin sheet into a sheet and a metal foil on the outside thereof while pressing, and a first through-hole formed at the desired position of the semi-cured substrate Forming a second through-hole in the substrate, and then heating the substrate to the curing temperature of the thermosetting resin and performing a full-curing step. By forming the first through-hole in advance at the position where the hole is to be formed, the second through-hole can be formed in a semi-cured state. The effect of being easy to obtain is obtained.
[0011]
The invention according to claim 2 of the present invention is a method for manufacturing a multilayer printed wiring board according to claim 1, wherein the board that has been hardened is plated between the first hardening step and the pattern forming step. In addition, the metal foils on both sides can be electrically connected to each other through the first through holes, and the operation and effect that a higher-density substrate can be manufactured can be obtained.
[0012]
The invention according to claim 3 of the present invention is characterized in that the thermosetting resin composition contains a liquid thermosetting resin and a thermoplastic resin powder as components, and the thermoplastic resin powder is a liquid thermosetting resin. 3. The method for producing a multilayer printed wiring board according to claim 1, wherein a liquid component of the curable resin absorbs and swells to form a solid state. The substrate can be in a semi-cured state at a temperature at which the resin is not cured, and the effect of suppressing abrasion of the drilling jig and facilitating drilling can be obtained.
[0013]
The invention according to claim 4 of the present invention is a method for manufacturing a multilayer printed wiring board according to claim 1 or 2, wherein the first through hole and the second through hole are formed by punching. Yes, since the first and second through holes are processed by punching in a semi-cured state, the contact distance between the punching jig and the inorganic filler is very short, approximately the same as the resin thickness. The working effect that a hole can be formed with a long service life and a higher quality and lower cost hole can be formed can be obtained.
[0014]
The invention according to claim 5 of the present invention is the method for manufacturing a multilayer printed wiring board according to claim 2, wherein the first through hole is formed as a through hole during pattern formation. The metal foils on both sides can be electrically connected to each other through the through-holes, and the effect that a higher-density substrate can be manufactured can be obtained.
[0015]
The invention according to claim 6 of the present invention particularly forms a through-hole other than the first through-hole between the first semi-curing step and the first main-curing step, and further includes forming the through-hole at the time of pattern formation. 3. The method for manufacturing a multilayer printed wiring board according to claim 2, wherein the holes are formed as through holes, and the metal foils on both sides can be electrically connected through through holes other than the first through holes. As a result, the effect of being able to manufacture a higher-density substrate can be obtained.
[0016]
The invention according to claim 7 of the present invention has a configuration in which at least one of an epoxy resin, a phenol resin and a cyanate resin is contained as the thermosetting resin, and these resins are excellent in heat resistance and electrical insulation. The effect of being able to produce a multilayer printed wiring board is obtained.
[0017]
The invention according to claim 8 of the present invention particularly provides an inorganic filler containing Al ₂ O ₃ , MgO, SiO ₂ By using at least one inorganic filler selected from the group consisting of BN, AlN, and BN, the effect of obtaining an electrically insulating substrate excellent in heat dissipation can be obtained. In addition, by controlling the combination and amount of these inorganic fillers, it is possible to obtain a functional effect that a multilayer printed wiring board having a desired coefficient of thermal expansion can be produced.
[0018]
According to the ninth aspect of the present invention, in particular, when the inorganic filler is contained in an amount of 70 to 95% by weight, the inorganic filler having high thermal conductivity is filled in a high concentration, so that a substrate excellent in heat dissipation can be obtained. The operation and effect are obtained.
[0019]
The invention according to claim 10 of the present invention is particularly configured such that the particle diameter of the inorganic filler is 0.1 to 100 μm, and the thickness of the resin insulating layer is 0.1 to 2 mm. If the particle size is too large, uniform filling cannot be achieved. If the particle size is too small, it is expensive and the handling of the inorganic filler becomes difficult. By using an inorganic filler having a particle diameter in this range, the inorganic filler can be uniformly and highly filled in the resin, and the effect of obtaining a substrate having high thermal conductivity can be obtained.
[0020]
The invention according to claim 11 of the present invention can increase the adhesion between the resin and the metal foil by using a copper foil having a thickness of 12 to 200 μm having at least one surface roughened surface as the metal foil. In addition, when a through-hole is formed, peeling of the resin and the metal foil is suppressed, and a hole can be easily formed. Further, since copper is used, the thermal conductivity is high and the conductivity is good, so that a fine pattern can be formed. When the foil thickness is increased, a large current can flow.
[0021]
In the invention according to claim 12 of the present invention, the heat treatment in the first semi-curing step is performed at 100 to 140 ° C., so that the thermosetting resin does not cure and the thermosetting resin composition contains The thermoplastic resin powder absorbs the liquid component of the liquid thermosetting resin and swells to a solid state, thereby making it possible to produce a substrate in which the resin is in a semi-cured state. The wear of the tool is suppressed, and the drilling can be easily performed.
[0022]
According to the invention of claim 13 of the present invention, the thermosetting resin can be cured by setting the curing temperature in the first full curing step to 150 to 230 ° C. It is possible to obtain a resin having excellent electrical insulation properties that is not affected by chemicals such as acids and alkalis during formation.
[0023]
The invention according to claim 14 of the present invention is characterized in that the heat treatment in the second semi-curing step is performed at 100 to 140 ° C., so that the thermosetting resin does not harden and the thermosetting resin composition The thermoplastic resin powder absorbs the liquid component of the liquid thermosetting resin and swells to a solid state, whereby a substrate in which the resin is in a semi-cured state can be manufactured. The wear of the tool is suppressed, and the drilling can be easily performed.
[0024]
The invention according to claim 15 of the present invention is capable of curing a thermosetting resin by setting the curing temperature in the second main curing step to 150 to 230 ° C., so that thermal, chemical resistance, A resin having excellent electrical insulation properties can be obtained.
[0025]
In the invention according to claim 16 of the present invention, the diameter of the first through-hole is made larger than the diameter of the second through-hole, so that the second through-hole can be contracted even if the shrinkage of the substrate or the displacement of the through-hole occurs. When processing the through-hole, the processing jig can pass through the semi-cured resin in the first through-hole, thereby suppressing the abrasion of the hole processing jig and making the hole processing easier. .
[0026]
In the invention according to claim 17 of the present invention, it is particularly desirable that the diameter of the first through hole is larger than the diameter of the second through hole by 0.1 to 1.0 mm. If the diameter is smaller than 0.1 mm, the cured resin portion may be processed due to displacement or the like during the processing of the second through-hole, and a processing jig may be worn, damaged, cracked on the substrate, or the like. Further, when the first through-hole is plated to form the through-hole, the insulating properties of the first and second through-holes may not be obtained. Conversely, if the diameter of the first through-hole is too large, the degree of freedom of wiring is reduced and the density is hindered, so if possible, the diameter of the first through-hole should be one more than the diameter of the second through-hole. It is better to keep it within 0.0 mm.
[0027]
The invention according to claim 18 of the present invention particularly provides a soft thermosetting resin composition containing a new inorganic filler while using at least two or more patterned substrates and aligning each substrate. A third semi-curing step of sandwiching and laminating the sheet-shaped resin sheets, laminating a metal foil on both outermost layers, and then heating and semi-curing while pressing, and Forming a second through-hole in the first through-hole formed at a desired position, and then heating the substrate up to the curing temperature of the thermosetting resin and performing a full-curing step. This is a method of manufacturing a board. A multilayer printed board of six or more layers can be easily manufactured by stacking a plurality of patterned boards each having a through hole at a desired position at the same position while aligning the boards. Effect that wear can be obtained.
[0028]
The invention according to claim 19 of the present invention is characterized in that at least one substrate among a plurality of patterned substrates is the substrate which has been fully cured between a first full curing step and a pattern forming step. 19. The method for manufacturing a multilayer printed wiring board according to claim 18, wherein the metal foils on both sides can be electrically connected to each other through the first through hole, and a higher-density substrate can be manufactured. An effect can be obtained.
[0029]
The invention according to claim 20 of the present invention is the method for manufacturing a multilayer printed wiring board according to claim 19, wherein the first through hole is formed as a through hole during pattern formation. The metal foils on both sides can be electrically connected to each other through the through-holes, and the effect that a higher-density substrate can be manufactured can be obtained.
[0030]
The invention according to claim 21 of the present invention is characterized in that a through-hole other than the first through-hole is formed between the first semi-curing step and the first main curing step, and the through-hole is formed during pattern formation. 20. The method for manufacturing a multilayer printed wiring board according to claim 19, wherein the holes are formed as through holes, and the metal foils on both sides can be electrically connected through through holes other than the first through holes. As a result, the effect of being able to manufacture a higher-density substrate can be obtained.
[0031]
In the invention according to claim 22 of the present invention, the heat treatment in the third semi-curing step is performed at 100 to 140 ° C., so that the thermosetting resin does not cure and the thermosetting resin composition contains The thermoplastic resin powder absorbs the liquid component of the liquid thermosetting resin and swells to a solid state, so that a substrate in which the resin is in a semi-cured state can be manufactured. The wear of the tool is suppressed, and the drilling can be easily performed.
[0032]
The invention according to claim 23 of the present invention is capable of curing a thermosetting resin by setting the curing temperature in the third main curing step to 150 to 230 ° C., so that thermal, chemical resistance, A resin having excellent electrical insulation properties can be obtained.
[0033]
In the invention according to claim 24 of the present invention, in particular, a step of filling a resin into a first through hole provided at a desired position of a pattern-formed substrate instead of the second semi-curing step, 3. The method for producing a multilayer printed wiring board according to claim 1 or 2, further comprising a step of sandwiching both sides of the substrate with a resin film and the outside thereof with a metal foil and pressing or laminating, wherein the first through hole is filled with a resin. Therefore, a film or a resin having low fluidity can be used as the insulating resin sandwiching the both sides of the substrate, and an operation effect that a multi-layer printed circuit board having good heat dissipation can be easily manufactured at low cost can be obtained.
[0034]
The invention according to claim 25 of the present invention uses a soft thermosetting resin composition containing an inorganic filler as a resin to be filled in the first through-hole, so that the hole can be easily formed and is inexpensive and has a heat radiation property. A good multilayer printed wiring board can be obtained.
[0035]
The invention according to claim 26 of the present invention uses a thermosetting resin that can be thermocompression-bonded at a low temperature and a low load as a resin film to produce a multilayer printed wiring board by lamination at a low cost and with good productivity. become able to.
[0036]
The invention according to claim 27 of the present invention is characterized in that Al is used as an inorganic filler in a resin film. ₂ O ₃ , MgO, SiO ₂ , Or BN or AlN, it is possible to obtain a multilayer printed wiring board having more excellent heat dissipation. In addition, by controlling the combination and amount of these inorganic fillers, the coefficient of thermal expansion of the resin film can be made closer to the coefficient of thermal expansion of the resin on the double-sided substrate, so that highly reliable multilayer printed wiring with little distortion, warpage, etc. The effect of being able to produce a plate is also obtained.
[0037]
The invention according to claim 28 of the present invention is characterized in that both sides of the substrate are sandwiched between resin-coated copper foils instead of the resin film and the metal foil on the outside thereof. This is a method for manufacturing a board, and the use of a copper foil with a resin also has the effect of producing a multilayer printed wiring board more simply, inexpensively, and with good productivity.
[0038]
In the invention described in claim 29 of the present invention, it is desirable that the thickness of the resin film is not less than 20 μm and not more than 200 μm. If the thickness is less than 20 μm, a problem occurs in insulation reliability. On the other hand, when the thickness is more than 200 μm, a problem that heat radiation property is deteriorated occurs.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Hereinafter, the first embodiment of the present invention will be described with reference to the first embodiment.
[0040]
FIG. 1 is a cross-sectional view showing a step of manufacturing the multilayer printed wiring board according to Embodiment 1 of the present invention.
[0041]
In the figure, 101 is a soft thermosetting resin sheet containing an inorganic filler, which is a thermoconductive filler and a thermosetting resin composition composed of 70 to 95 parts by weight of an inorganic material. As the thermally conductive inorganic filler, Al ₂ O ₃ , MgO, SiO ₂ , BN or AlN is at least one kind of inorganic filler. ₂ O ₃ You are using The particle size of the inorganic filler is desirably 0.1 to 100 μm. In this embodiment, two types of mixtures having an average particle size of 3 μm and 12 μm are used. By using inorganic fillers having two types of particle sizes, large and small, the gaps between the inorganic fillers having a large particle size are filled with the inorganic filler having a small particle size. The filling amount of the inorganic filler is 87% by weight. The thermosetting resin composition contains a liquid thermosetting resin and a thermoplastic resin powder as components. It has the characteristic of being shaped. The thermosetting resin contains at least one of an epoxy resin, a phenol resin and a cyanate resin. In this embodiment, a bisphenol A type liquid epoxy resin is used. Further, a brominated epoxy resin is added as a curing agent, a curing accelerator and a flame retardant. The liquid epoxy resin, curing agent, curing accelerator and brominated epoxy resin are about 11% by weight. Further, the sheet contains about 2% of a thermoplastic resin powder so as to have flexibility in a semi-cured state below the curing temperature of the epoxy resin. This resin is formed into a sheet by an extrusion molding method. Alternatively, the sheet may be formed using a doctor blade method, a coater method or a rolling method.
[0042]
Copper foils 104 are attached to both sides of the resin sheet 101 as shown in FIG. Since the resin surface of the resin sheet 101 has adhesiveness, the copper foil 104 is attached while applying a roller from the end face of the sheet so that air does not bite into the interface between the resin and the copper foil. The copper foil 104 has a surface in contact with the resin sheet 101 roughened by about 5 μm, and has a thickness of 35 μm. When a fine line pattern is required, a thin copper foil of 12, 18 μm is preferably used, and a copper foil of 70 to 200 μm is preferably used for a product in which a large current flows.
[0043]
Next, as shown in FIG. 1 (B), the resin sheet 101 is semi-cured by pressing while heating (first semi-curing step). The maximum temperature at this time needs to be a temperature at which the curing reaction of the epoxy resin does not occur, and the thermoplastic resin powder absorbs the liquid component of the liquid epoxy resin and swells to be solid. The heating temperature in the first semi-curing step is desirably 100 to 140 ° C. In this embodiment, the pressing is performed at 130 ° C. for 30 minutes in consideration of productivity and process stability. In a general glass-epoxy substrate, it is necessary to press for about 2 to 3 hours because it is necessary to raise the temperature up to about 180 ° C. and completely cure the epoxy resin. For this reason, molding can be performed in a shorter time as compared with a glass-epoxy substrate, and the productivity is good.
[0044]
Next, as shown in FIG. 1C, a hole is formed at a desired position where a through hole is to be formed, and a first through hole 105 is formed. As a method of forming the through hole, there are a drilling method used in a general glass-epoxy substrate, a punching method using a punching machine, a punching method using a mold, and the like. Considering the cost, it is desirable to use a punching machine.
[0045]
The perforated substrate is heated in a thermostat at a temperature at which the epoxy resin is cured to cure the resin 103 (first full curing step, FIG. 1D). In the main curing step, the substrate is not particularly required to be pressurized, and can be processed in a large amount with an inexpensive apparatus, so that the substrate can be easily manufactured at low cost. The curing temperature in the first main curing step is desirably 150 to 230 ° C., and in this embodiment, the curing is performed at 170 ° C. for 2 hours.
[0046]
Next, a dry film resist is attached to the surface of the copper foil, the circuit pattern is exposed, developed, etched, and the dry film resist is stripped, and a double-sided substrate having a patterned wiring pattern 106 as shown in FIG. 107 is formed.
[0047]
In order to manufacture a four-layer substrate, a soft thermosetting resin sheet 101 containing an inorganic filler is laminated on both sides of a patterned double-sided substrate 107, and a copper foil 104 is further laminated on the outside thereof (FIG. 1F). Next, the resin sheet 101 is heated and pressurized while being pressed to fill the space between the patterns and the first through-holes 105 and is adhered to the copper foil 104 and the double-sided substrate 107 and then semi-cured (second semi-cured Step, FIG. 1 (G)). The heating temperature in the second semi-curing step is desirably 100 to 140 ° C. In this embodiment, the pressing is performed at 130 ° C. in consideration of productivity and process stability.
[0048]
Next, a recognition mark made of a copper pattern in the inner layer is recognized by an X-ray recognition apparatus, and the position of the hole processing is adjusted to form a second through hole 108 in the first through hole 105 (FIG. 1 ( H)). The formation method may be the same as that of the first through hole. In order to form the second through-hole 108 in the first through-hole 105, the diameter of the first through-hole 105 needs to be larger than that of the second through-hole 108. In consideration of the positioning accuracy of the recognition device at the time of drilling, the drilling position accuracy, and the variation in dimensional shrinkage of the base material, the diameter of the first through hole 105 is smaller than the diameter of the second through hole 108 by 0. It is desirable to increase the size by at least 1 mm. However, if the diameter of the first through-hole 105 is too large, high-density wiring may not be performed, or resin may be insufficient in the first through-hole 105 when laminated and pressed to form a multilayer. Therefore, it is preferable that the diameter of the first through hole 105 is not larger than the diameter of the second through hole 108 by 1.0 mm or more. Next, the resin is cured by heating at a temperature at which the epoxy resin cures in a thermostat (second full curing step, FIG. 1 (I)). In this main curing step, pressure is not particularly required on the substrate. The curing temperature in the second main curing step is desirably 150 to 230C, and in this embodiment, the curing is performed at 170C.
[0049]
When the outermost layer 104 is electrically connected to the inner layer pattern 106 thereunder, after removing the copper of the outer layer copper foil 104 by etching at a desired position where a through hole is to be formed, the copper is removed by a laser processing method. The resin 103 in the place where it has been removed is removed, and the surface of the inner layer pattern 106 is exposed. Thereafter, copper plating, pattern formation, solder resist formation, and the like were performed to form a multilayer printed wiring board.
[0050]
(Embodiment 2)
Hereinafter, the second embodiment of the present invention will be described with reference to the second embodiment.
[0051]
FIG. 2 is a cross-sectional view illustrating a manufacturing process of the multilayer printed wiring board according to Embodiment 2 of the present invention.
[0052]
The steps up to the first semi-curing step are performed as in the first embodiment (FIGS. 2A and 2B). In the hole forming step for forming the first through hole 201, as shown in FIG. 2C, a through hole 202 other than the first through hole 201 is formed. The through-hole 202 is for connecting the upper and lower copper patterns, and since a second through-hole described later is not formed in the through-hole 202, the diameter thereof can be made smaller than that of the first through-hole 201.
[0053]
Next, first main curing is performed in the same manner as in Embodiment 1 (FIG. 2D). Next, copper plating 203 is performed to electrically connect the upper and lower copper foils 104 (FIG. 2E). The thickness of the copper plating 203 is about 20 μm. Next, a dry film resist is attached to the surface of the copper foil 104, the circuit pattern is exposed, developed, etched, and the dry film resist is peeled off, thereby forming a double-sided surface having a patterned wiring pattern 204 as shown in FIG. A substrate 206 is formed. At this time, the first through-hole 205a has a copper plating 203 in the through-hole in this figure and the upper and lower wiring patterns 204 are electrically connected. In some cases, the copper plating 203 is removed and the upper and lower wiring patterns 204 are not electrically connected.
[0054]
Thereafter, a multilayer printed wiring board is formed by using the same steps as those after the laminating step for manufacturing the four-layer board of the first embodiment (FIGS. 2G to 2J).
[0055]
(Embodiment 3)
Hereinafter, the third embodiment of the present invention will be described with reference to the third embodiment.
[0056]
FIG. 3 is a cross-sectional view showing a step of manufacturing the multilayer printed wiring board according to Embodiment 3 of the present invention.
[0057]
A plurality of double-sided substrates 301 having a pattern formed using Embodiment Mode 1 or 2 are formed. 301a is a copper-plated double-sided board, and 301b is a non-copper-plated board. The presence or absence of copper plating depends on the design pattern. The first through holes 302 in each double-sided substrate 301 are all formed at the same position.
[0058]
As shown in FIG. 3A, a plurality of patterned double-sided substrates 301 are aligned and laminated while alternately sandwiching a soft thermosetting resin sheet 101 containing an inorganic filler, and copper is formed on both outermost layers. The foil 104 is laminated.
[0059]
Next, it is heated and pressurized and semi-cured while being pressed in the same manner as in Embodiment 1 (third semi-curing step, FIG. 3B). The heating temperature in the third semi-curing step is desirably 100 to 140 ° C. In this embodiment, the pressing is performed at 130 ° C. in consideration of productivity and process stability. Next, similarly, the position of the hole processing is adjusted using the recognition mark in the inner layer, and the second through hole 303 is formed in the first through hole 302 (FIG. 3C). Next, the epoxy resin is heated in a thermostat at a temperature at which the epoxy resin is cured, and the resin is fully cured 304 (third full curing step, FIG. 3D). In this main curing step, pressure is not particularly required on the substrate. The curing temperature in the third main curing step is desirably 150 to 230 ° C., and in this embodiment, the curing is performed at 170 ° C.
[0060]
Thereafter, as in the first embodiment, through-hole processing, copper plating, pattern formation, solder resist formation, and the like were performed to form a multilayer printed wiring board. According to such a method, a multilayer printed wiring board having six or more layers can be easily obtained.
[0061]
(Embodiment 4)
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
[0062]
FIG. 4 is a cross-sectional view showing a manufacturing process of the multilayer printed wiring board according to Embodiment 4 of the present invention.
[0063]
The patterned double-sided substrate 403 is formed by the same method as in Embodiment 1 or 2 (FIG. 4A). In this figure, the through-hole 402 is not plated with copper, but may be plated with copper to establish conduction between the upper and lower copper patterns. The resin 404 is filled in the through holes 402 formed in the double-sided substrate 403 (FIG. 4B). As a resin to be filled, a soft thermosetting resin composition containing an inorganic filler has the same components as the resin sheet 101. However, the viscosity is adjusted so that the resin can be easily filled.
[0064]
A resin film 406 is laminated on both sides of the double-sided substrate 403, and a copper foil 405 is further laminated on the outside thereof (FIG. 4C). As the resin film 406, a thermosetting resin (for example, a low elastic adhesive film GF3600 manufactured by Hitachi Chemical Co., Ltd.) that can be thermocompression-bonded at a low temperature and a low load is preferably used. The thickness of the resin film 406 is 20 to 200 μm, and by using this, a thin multilayer substrate can be manufactured. This is integrated by pressing or laminating (FIG. 4D). The temperature at this time is desirably 100 to 130 ° C., and in this embodiment, the temperature is 120 ° C. It is more preferable to use a resin film 406 to which an inorganic filler is added to increase the thermal conductivity. Al as inorganic filler ₂ O ₃ , MgO, SiO ₂ , BN or AlN may be used. Further, instead of the resin film 406 and the copper foil 405, a copper foil with a resin (for example, MCF-6000E manufactured by Hitachi Chemical Co., Ltd.) may be used for lamination.
[0065]
Next, a hole is formed at the position of the first through hole 402 to form a through hole 407 (FIG. 4E). Lastly, the resin 404 and the resin film 406 are cured by heating in a thermostat (FIG. 4F). The curing temperature at this time is desirably 150 to 230 ° C, and in this embodiment, the curing temperature is 170 ° C.
[0066]
With such a method, a multilayer printed wiring board having a thin insulating layer can be obtained with a simple method with high productivity.
[0067]
【The invention's effect】
As described above, according to the present invention, a soft thermosetting resin composition containing an inorganic filler is bonded to a metal sheet on one or both surfaces of a resin sheet formed into a sheet, and then heated and semi-cured while being pressed. A first semi-curing step, and a first full-curing in which at least a first through hole is formed at a desired position of the semi-cured substrate, and thereafter, the substrate is heated to a curing temperature of a thermosetting resin and fully cured. Step, a pattern forming step of forming a desired circuit pattern on the fully cured substrate, and both sides of the patterned substrate were sheeted with a soft thermosetting resin composition containing a new inorganic filler, respectively. A second semi-curing step of heating and semi-curing while pressing the resin sheet and its outside with a metal foil, and a second semi-curing step in a first through hole formed at the desired position of the semi-cured substrate. Forming a through-hole, and then heating the substrate to the curing temperature of the thermosetting resin and performing a full-curing step, whereby the first through-hole is formed in advance at the position where the second through-hole is to be formed. Since the hole is formed and the resin in the semi-cured state is filled therein, the second through-hole can be formed in the semi-cured state, thereby suppressing the abrasion of the hole processing jig and extending the life. Therefore, there is an effect that it is possible to inexpensively drill holes in a multilayer printed wiring board having high thermal conductivity.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a manufacturing process of a multilayer printed wiring board according to Embodiment 1 of the present invention.
FIG. 2 is a cross-sectional view illustrating a manufacturing process of the multilayer printed wiring board according to Embodiment 2 of the present invention.
FIG. 3 is a sectional view showing a manufacturing process of the multilayer printed wiring board according to Embodiment 3 of the present invention.
FIG. 4 is a sectional view showing a manufacturing process of the multilayer printed wiring board according to Embodiment 4 of the present invention.
FIG. 5 is a cross-sectional view of a manufacturing process for explaining a conventional method for manufacturing a high-heat-conductivity multilayer printed wiring board.
[Explanation of symbols]
101 Soft thermosetting resin sheet containing inorganic filler
102 Semi-cured resin
103 hardened resin
104 Copper foil
105 1st through hole
106 Wiring pattern
107 Double-sided board with pattern formation
108 second through hole
201 First through hole
202 Through-holes other than the first through-hole
203 Copper plating
204 Wiring pattern
205a Through hole
205b Through hole
206 Patterned double-sided board
207 Second through hole
301a, 301b Double-sided substrate with pattern formation
302 first through hole
303 second through hole
304 hardened resin
401 Wiring pattern
402 First Through Hole
403 Patterned double-sided board
404 resin
405 copper foil
406 resin film
407 Second through hole
501 Release film
502 Heat conductive sheet
503 Through hole
504 conductive resin composition
505a-505d Wiring pattern
506 metal foil
507 Wiring pattern

Claims

A first semi-curing step in which a metal foil is adhered to one or both surfaces of a resin sheet formed from a soft thermosetting resin composition containing an inorganic filler and then pressed and then heated and semi-cured while pressing; Forming at least a first through-hole at a desired position of the cured substrate, and thereafter heating the substrate to a curing temperature of a thermosetting resin to perform a full curing; A pattern forming step of forming a circuit pattern, and sandwiching both sides of the patterned substrate with a resin sheet made of a soft thermosetting resin composition containing a new inorganic filler and a metal foil on the outside thereof. A second semi-curing step of heating and semi-curing while pressing; forming a second through-hole in the first through-hole formed at the desired position of the semi-cured substrate; The method for manufacturing a multilayer printed wiring board and a second curing step of heating and curing to the curing temperature of the thermosetting resin.

The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the substrate that has been hardened is plated between a first hardening step and a pattern forming step.

The thermosetting resin composition contains a liquid thermosetting resin and a powdery thermoplastic resin as components, and the powdery thermoplastic resin absorbs a liquid component of the liquid thermosetting resin. The method for producing a multilayer printed wiring board according to claim 1 or 2, wherein a material which becomes a solid by swelling is used.

3. The method according to claim 1, wherein the first through hole and the second through hole are formed by punching.

3. The method according to claim 2, wherein the first through hole is formed as a through hole during pattern formation.

A through hole other than the first through hole is formed between the first semi-curing step and the first main curing step, and the through hole is formed as a through hole during pattern formation. 3. The method for producing a multilayer printed wiring board according to 2.

3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the thermosetting resin is at least one of an epoxy resin, a phenol resin, and a cyanate resin.

As the inorganic _{_{filler, Al 2 O 3, MgO,}} SiO 2, BN or at least one of a method for manufacturing a multilayer printed wiring board according to claim 1 or 2, wherein the inorganic filler of AlN.

3. The method for producing a multilayer printed wiring board according to claim 1, wherein the inorganic filler is contained in an amount of 70 to 95% by weight.

3. The method for producing a multilayer printed wiring board according to claim 1, wherein the particle size of the inorganic filler is 0.1 to 100 [mu] m.

3. The method for producing a multilayer printed wiring board according to claim 1, wherein the metal foil is a copper foil having a thickness of 12 to 200 [mu] m having at least one roughened surface.

The method for producing a multilayer printed wiring board according to claim 1 or 2, wherein the heating temperature in the first semi-curing step is 100 to 140 ° C.

The method for producing a multilayer printed wiring board according to claim 1, wherein the curing temperature in the first main curing step is 150 to 230 ° C. 4.

The method according to claim 1, wherein the heating temperature in the second semi-curing step is 100 to 140 ° C. 4.

The method for producing a multilayer printed wiring board according to claim 1, wherein the curing temperature in the second main curing step is 150 to 230 ° C. 4.

6. The method according to claim 1, wherein the diameter of the first through hole is larger than the diameter of the second through hole.

17. The method according to claim 16, wherein the diameter of the first through hole is 0.1 to 1.0 mm larger than the diameter of the second through hole.

Using at least two or more patterned substrates, sandwiching and laminating a soft thermosetting resin composition containing a new inorganic filler with a sheet-shaped resin sheet while aligning the respective substrates, A third semi-curing step of laminating metal foils on both outermost layers and then heating and semi-curing while pressing, and a second semi-curing step in a first through hole formed at the desired position of the semi-cured substrate. Forming a through hole, and thereafter heating the substrate to the curing temperature of the thermosetting resin and performing a final curing step.

19. The method for manufacturing a multilayer printed wiring board according to claim 18, wherein at least one of the plurality of pattern-formed substrates is plated with the main-cured substrate between the first main-curing step and the pattern-forming step. Method.

20. The method according to claim 19, wherein the first through hole is formed as a through hole during pattern formation.

A through hole other than the first through hole is formed between the first semi-curing step and the first main curing step, and the through hole is formed as a through hole during pattern formation. 20. The method for manufacturing a multilayer printed wiring board according to claim 19.

20. The method for manufacturing a multilayer printed wiring board according to claim 18, wherein the heating temperature in the third semi-curing step is 100 to 140C.

The method for producing a multilayer printed wiring board according to claim 18 or 19, wherein the curing temperature in the third main curing step is 150 to 230 ° C.

Instead of the second semi-curing step, a step of filling a resin into a first through-hole provided at a desired position on a patterned substrate, and a resin film on both sides of the substrate and a metal foil on the outside thereof, respectively. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, further comprising a step of sandwiching press or laminating.

25. The method for manufacturing a multilayer printed wiring board according to claim 24, wherein the resin filled in the first through hole is a soft thermosetting resin composition containing an inorganic filler.

25. The method for manufacturing a multilayer printed wiring board according to claim 24, wherein a thermosetting resin capable of thermocompression bonding at a low temperature and a low load is used as the resin film.

Method for manufacturing a multilayer printed wiring board according to claim 26 further including _Al 2 _O 3, MgO as the inorganic filler, at least one inorganic filler _SiO 2, BN or AlN in the resin film.

25. The method for manufacturing a multilayer printed wiring board according to claim 24, wherein both sides of the substrate are sandwiched between resin-coated copper foils instead of the resin film and the outside thereof with the metal foil.

25. The method for manufacturing a multilayer printed wiring board according to claim 24, wherein the thickness of the resin film is 20 μm or more and 200 μm or less.