JP4136084B2 - Printed wiring board - Google Patents

Description

【００２９】
【化２】

【００３０】
なお、添加成分として挙げた上記熱硬化性樹脂としては、ビスフェノール型エポキシ樹脂を用いることができる。このビスフェノール型エポキシ樹脂には、ビスフェノールＡ型エポキシ樹脂とビスフェノールＦ型のエポキシ樹脂があり、耐塩基性を重視する場合には前者が、低粘度化が要求される場合（塗布性を重視する場合）には後者がよい。
【００３１】
また、添加成分として挙げた上記感光性モノマーとしては、多価アクリル系モノマーを用いることができる。多価アクリル系モノマーは、解像度を向上させることができるからである。例えば、下記化学式３および化学式４に示すような構造の多価アクリル系モノマーが望ましい。ここで、化学式３は日本化薬製のＤＰＥ−６Ａであり、化学式４は共栄社化学製のＲ−６０４である。
【００３２】
【化３】

【００３３】
【化４】

【００３４】
さらに、ソルダーレジスト組成物には、ベンゾフェノン（ＢＰ）やミヒラーケトン（ＭＫ）を添加してもよい。これらは、開始剤、反応促進剤として作用するからである。
このＢＰとＭＫは、30〜70℃に加熱したグリコールエーテル系溶媒に同時に溶解させて均一混合し、他の成分と混合することが望ましい。溶解残渣がなく、完全に溶解できるからである。
【００３５】
本発明のプリント配線板において、配線基板は、特には限定されないが、表面が粗化処理された樹脂絶縁材上にめっきレジストが形成され、そのめっきレジストの非形成部分にパッドを含む導体回路が形成された、いわゆるアディティブプリント配線板、ビルドアップ多層プリント配線板であることが望ましい。
このような配線基板にソルダーレジスト組成物を塗布する場合、ソルダーレジスト層の開口径は、導体パッド径よりも大きくすることができる。これにより、樹脂であるめっきレジストは、はんだ体とはなじまずに該はんだ体を弾くため、はんだ体のダムとして作用する。
【００３６】
本発明のプリント配線板において、ソルダーレジスト層の厚さは、５〜30μｍとすることが望ましい。薄すぎるとはんだ体のダムとしての効果が低下し、厚すぎると現像処理しにくいからである。
【００３７】
また、本発明のプリント配線板としてさらに好適な構成は、前記導体回路の表面に粗化層が形成されている構造である。
このような構造のプリント配線板では、パッド（ＩＣチップや電子部品を搭載する部分）を含む導体回路の表面に形成した粗化層がアンカーとして作用するので、導体回路とソルダーレジスト層が強固に密着している。また、パッド表面に供給保持されるはんだ体の密着性も改善される。
また、特に、ノボラック型エポキシ樹脂のアクリレートは、剛直骨格を持つため、耐熱性、耐塩基性には優れるが、フレキシビリティーに欠けるため、高温、多湿条件下での剥離が生じやすい。この点、導体回路の表面に粗化層を形成した上記構成によれば、このような剥離を防止することができる。
【００３８】
ここで、上記粗化層は、研磨処理、エッチング処理、酸化還元処理およびめっき処理のいずれかにより形成されることが望ましい。これらの処理のうち、酸化還元処理は、NaOH（20ｇ／ｌ）、NaCl0₂（50ｇ／ｌ）、Na₃PO₄（15.0ｇ／ｌ）の水溶液を酸化浴（黒化浴）、NaOH（ 2.7ｇ／ｌ）、NaBH₄ （ 1.0ｇ／ｌ）の水溶液を還元浴として用い、めっき処理は、硫酸銅８ｇ／ｌ、硫酸ニッケル 0.6ｇ／ｌ、クエン酸15ｇ／ｌ、次亜リン酸ナトリウム29ｇ／ｌ、ホウ酸31ｇ／ｌおよびアセチレン含有ポリオキシエチレン系の界面活性剤 0.1ｇ／ｌの水溶液からなるｐＨ＝９の銅−ニッケル−リンめっき用の無電解めっき浴を用いることが望ましい。
特に、銅−ニッケル−リンめっきによる合金層の粗化層は、針状構造でソルダーレジスト層内にくい込むので、そのアンカー効果によってソルダーレジスト層との密着性向上に寄与するからである。また、この粗化層は、電気導電性であるので、パッド表面にはんだ体を形成しても除去する必要がない。
【００３９】
前記粗化層を構成する合金層の組成は、銅、ニッケル、リンの割合で、それぞれ90〜96wt％、１〜５wt％、 0.5〜２wt％であることが望ましい。これらの組成割合のときに、針状の構造を有するからである。また、前記粗化層の厚さは、 0.5〜７μｍであることが望ましい。厚すぎても薄すぎてもソルダーレジスト層やはんだ体との密着性が低下するからである。
【００４０】
なお、パッド上にはんだ体を供給保持する場合には、そのパッド表面にニッケル−金めっきを施しておくとよい。ニッケル層は、銅との密着性を改善し、また金との密着性にも優れ、金層ははんだ体との馴染みがよいからである。
はんだ体は、層状であってもよく、ボール状のいわゆる「はんだバンプ」であってもよい。
【００４１】
次に、本発明のプリント配線板を製造する一方法について説明する。
(1) まず、コア基板の表面に内層銅パターンを形成した配線基板を作製する。
このコア基板への銅パターンは、銅張積層板をエッチングして行うか、あるいは、ガラスエポキシ基板やポリイミド基板、セラミック基板、金属基板などの基板に無電解めっき用接着剤層を形成し、この接着剤層表面を粗化して粗化面とし、ここに無電解めっきを施す方法、もしくはその粗化面全体に無電解めっきを施し、めっきレジストを形成し、めっきレジスト非形成部分に電解めっきを施した後、めっきレジストを除去し、エッチング処理して、電解めっき膜と無電解めっき膜からなる導体回路を形成する方法、により形成される。
【００４２】
さらに、上記配線基板の導体回路の表面に銅−ニッケル−リンからなる粗化層を形成することができる。
この粗化層は、無電解めっきにより形成される。この無電解めっき水溶液の液組成は、銅イオン濃度、ニッケルイオン濃度、次亜リン酸イオン濃度が、それぞれ 2.2×10^-2〜4.1 ×10^-2 mol／ｌ、 2.2×10^-3〜 4.1×10^-3 mol／ｌ、0.20〜0.25 mol／ｌであることが望ましい。
この範囲で析出する被膜の結晶構造は針状構造になるため、アンカー効果に優れるからである。この無電解めっき浴には上記化合物に加えて錯化剤や添加剤を加えてもよい。
粗化層の形成方法としては、この他に酸化−還元処理、銅表面を粒界に沿ってエッチングして粗化面を形成する方法などがある。
【００４３】
なお、コア基板には、スルーホールが形成され、このスルーホールを介して表面と裏面の配線層を電気的に接続することができる。
また、スルーホールおよびコア基板の導体回路間には樹脂が充填されて、平滑性を確保してもよい。
さらに、コア基板には、その内層に導体回路を有していてもよく、その内層導体回路は、コア基板を貫通するスルーホールによりコア基板表面の導体回路と接続される。
さらに、スルーホールに、金属粒子、無機粒子、樹脂粒子を含む樹脂組成物が充填されて、その充填樹脂を被覆する導体層が形成されていてもよい。この導体層にバイアホールを接続させることができる。
【００４４】
(2) 次に、前記(1) で作製した配線基板の上に、層間樹脂絶縁層を形成する。
本発明では、層間樹脂絶縁材として前述した無電解めっき用接着剤を用いることが望ましい。
【００４５】
(3) 前記(2) で形成した無電解めっき用接着剤層を乾燥した後、必要に応じてバイアホール形成用開口を設ける。
このとき、感光性樹脂の場合は、露光，現像してから熱硬化することにより、また、熱硬化性樹脂の場合は、熱硬化したのちレーザー加工することにより、前記接着剤層にバイアホール形成用の開口部を設ける。
【００４６】
(4) 次に、硬化した前記接着剤層の表面に存在するエポキシ樹脂粒子を酸あるいは酸化剤によって溶解または分解して除去し、接着剤層表面を粗化処理する。
ここで、上記酸としては、リン酸、塩酸、硫酸、あるいは蟻酸や酢酸などの有機酸があるが、特に有機酸を用いることが望ましい。粗化処理した場合に、バイアホールから露出する金属導体層を腐食させにくいからである。
一方、上記酸化剤としては、クロム酸、過マンガン酸塩（過マンガン酸カリウムなど）の水溶液を用いることが望ましい。
【００４７】
(5) 次に、接着剤層表面を粗化した配線基板に触媒核を付与する。
触媒核の付与には、貴金属イオンや貴金属コロイドなどを用いることが望ましく、一般的には、塩化パラジウムやパラジウムコロイドを使用する。なお、触媒核を固定するために加熱処理を行うことが望ましい。このような触媒核としてはパラジウムがよい。
【００４８】
(6) 次に、無電解めっき用接着剤層表面に無電解めっきを施し、粗化面全面に、その粗面に沿って凹凸を有する薄膜の無電解めっき膜を形成する。このとき、無電解めっき膜の厚みは、 0.1〜５μｍ、より望ましくは 0.5〜３μｍとする。
つぎに、無電解めっき膜上にめっきレジストを形成する。
めっきレジスト組成物としては、特にクレゾールノボラック型エポキシ樹脂やフェノールノボラック型エポキシ樹脂のアクリレートとイミダゾール硬化剤からなる組成物を用いることが望ましいが、他に市販品のドライフィルムを使用することもできる。
【００４９】
(7) 次に、基板を10〜35℃、望ましくは15〜30℃の水で水洗する。
この理由は、水洗温度が35℃を超えると水が揮発してしまい、無電解めっき膜の表面が乾燥して、酸化してしまい、電解めっき膜が析出しない。そのため、エッチング処理により、無電解めっき膜が溶解してしまい、導体が存在しない部分が生じてしまう。一方、10℃未満では水に対する汚染物質の溶解度が低下し、洗浄力が低下してしまうからである。特に、バイアホールのランドの径が 200μｍ以下になると、めっきレジストが水をはじくため、水が揮発しやすく、電解めっきの未析出という問題が発生しやすい。
なお、洗浄水の中には、各種の界面活性剤、酸、アルカリを添加しておいてもよい。また、洗浄後に硫酸などの酸で洗浄してもよい。
【００５０】
(8) 次に、めっきレジスト非形成部に電解めっきを施し、導体回路、ならびにバイアホールを形成する。
ここで、上記電解めっきとしては、銅めっきを用いることが望ましい。
【００５１】
(9) さらに、めっきレジストを除去した後、硫酸と過酸化水素の混合液や過硫酸ナトリウム、過硫酸アンモニウムなどの水溶液からなるエッチング液でめっきレジスト下の無電解めっき膜を溶解除去して、独立した導体回路とする。
【００５２】
(10)次に、導体回路の表面に粗化層を形成する。
粗化層の形成方法としては、エッチング処理、研磨処理、酸化還元処理、めっき処理がある。
これらの処理のうち酸化還元処理は、NaOH（20ｇ／ｌ）、NaClO₂（50ｇ／ｌ）、Na₃PO₄（15.0ｇ／ｌ）の水溶液を酸化浴（黒化浴）、NaOH（ 2.7ｇ／ｌ）、NaBH₄(1.0 ｇ／ｌ）の水溶液を還元浴とする。
また、銅−ニッケル−リン合金層からなる粗化層は、無電解めっき処理による析出により形成する。
この合金の無電解めっき液としては、硫酸銅１〜40ｇ／ｌ、硫酸ニッケル 0.1〜 6.0ｇ／ｌ、クエン酸10〜20ｇ／ｌ、次亜リン酸塩10〜100 ｇ／ｌ、ホウ酸10〜40ｇ／ｌ、アセチレン含有ポリオキシエチレン系の界面活性剤0.01〜10ｇ／ｌの水溶液からなる液組成のめっき浴を用いることが望ましい。
【００５３】
(11)次に、この基板上に層間樹脂絶縁層として、無電解めっき用接着剤層を形成する。
(12)さらに、 (3)〜(9) の工程を繰り返してさらに上層の導体回路を設け、はんだパッドとして機能する平板状導体パッドとバイアホールを形成し、多層配線基板を得る。
(13)ついで、導体パッドとバイアホール表面に粗化層を設ける。この粗化層の形成方法は、前記(10)で説明したものと同様である。
【００５４】
(14)ノボラック型エポキシ樹脂のアクリレート、熱可塑性樹脂、硬化剤、耐熱性樹脂粒子および必要に応じて開始剤、感光性モノマー等を溶剤と混合して攪拌し、下層用のソルダーレジスト組成物を得る。
【００５５】
(15)ノボラック型エポキシ樹脂のアクリレート、熱可塑性樹脂、硬化剤、および必要に応じて開始剤、感光性モノマー等を溶剤と混合して攪拌し、上層用のソルダーレジスト組成物を得る。
【００５６】
(16)次に、こうして得られた配線基板の両面に、前記(14)で得た下層用のソルダーレジスト組成物を塗布して60〜80℃で５〜60分間乾燥し、さらに前記(15)で得た上層用のソルダーレジスト組成物を塗布して60〜80℃で５〜60分間乾燥する。なお、ソルダーレジスト組成物を塗布する際に、前記配線基板は、垂直に立てた状態でロールコータの一対の塗布用ロールのロール間に挟み、下側から上側へ搬送させて基板の両面にソルダーレジスト組成物を同時に塗布することが望ましい。この理由は、現在のプリント配線板の基本仕様は両面であり、カーテンコート法（樹脂を滝のように上から下へ流し、この樹脂の”カーテン”に基板をくぐらせて塗布する方法）では、片面しか塗布できないからである。前述したソルダーレジスト組成物は、両面同時に塗布する上記方法のために使用できる。即ち、前述したソルダーレジスト組成物は、粘度が25℃で１〜10Pa・ｓであるため、基板を垂直に立てて塗布しても流れず、また転写も良好である。
【００５７】
(17)次に、ソルダーレジスト組成物の塗膜に、開口部を描画したフォトマスクフィルムを載置して露光、現像処理することにより、導体回路のうちパッド部分を露出させた開口部を形成する。このようにして開口部を形成した塗膜を、さらに80℃〜150 ℃で１〜10時間の熱処理により硬化させる。これにより、開口部を有するソルダーレジスト層は導体回路の表面に設けた粗化層と密着する。次いで、 100〜1000ｇ／ｌのクロム酸水溶液に５〜30分間浸漬してエッチング処理し、開口底部に残存している樹脂を除去する。
【００５８】
ここで、前記開口部の開口径は、パッドの径よりも大きくすることができ、パッドを完全に露出させてもよい。この場合、フォトマスクがずれてもパッドがソルダーレジストで被覆されることはなく、またソルダーレジストがはんだ体に接触せず、はんだ体にくびれが生じないため、クラックが発生しにくくなる。
逆に、前記開口部の開口径は、パッドの径よりも小さくすることができ、この場合、パッド表面の粗化層とソルダーレジストが密着する。また、いわゆるセミアディティブ法を採用する場合は、無電解めっき用接着剤の粗化層の深さが浅くなり（１〜３μｍ）、まためっきレジストがないのでパッドが剥離やすいが、ソルダーレジストの開口部の開口径を、パッドの径よりも小さくして、パッドの一部をソルダーレジスト層で被覆することにより、パッド剥離を抑制することができる。
【００５９】
(18)次に、前記開口部から露出した前記はんだパッド部上に「ニッケル−金」の金属層を形成する。
【００６０】
(19)前記開口部から露出した前記はんだパッド部上にはんだ体を供給する。
はんだ体の供給方法としては、はんだ転写法や印刷法を用いることができる。ここで、はんだ転写法は、プリプレグにはんだ箔を貼合し、このはんだ箔を開口部分に相当する箇所のみを残してエッチングすることによりはんだパターンを形成してはんだキャリアフィルムとし、このはんだキャリアフィルムを、基板のソルダーレジスト開口部分にフラックスを塗布した後、はんだパターンがパッドに接触するように積層し、これを加熱して転写する方法である。一方、印刷法は、パッドに相当する箇所に貫通孔を設けたメタルマスクを基板に載置し、はんだペーストを印刷して加熱処理する方法である。
【００６１】
【実施例】
（実施例１）
Ａ．上層の無電解めっき用接着剤の調製
▲１▼．クレゾールノボラック型エポキシ樹脂（日本化薬製、分子量2500）の25％アクリル化物を80wt％の濃度でＤＭＤＧに溶解させた樹脂液を35重量部、感光性モノマー（東亜合成製、アロニックスＭ315 ）3.15重量部、消泡剤（サンノプコ製、Ｓ−65） 0.5重量部、ＮＭＰを 3.6重量部を攪拌混合した。
▲２▼．ポリエーテルスルフォン（ＰＥＳ）12重量部、エポキシ樹脂粒子（三洋化成製、ポリマーポール）の平均粒径1.0 μｍのものを7.2 重量部、平均粒径 0.5μｍのものを3.09重量部を混合した後、さらにＮＭＰ30重量部を添加し、ビーズミルで攪拌混合した。
▲３▼．イミダゾール硬化剤（四国化成製、2E4MZ-CN）２重量部、光開始剤（チバガイギー製、イルガキュア Ｉ−907 ）２重量部、光増感剤（日本化薬製、DETX -S） 0.2重量部、ＮＭＰ 1.5重量部を攪拌混合した。
これらを混合して２層構造の層間樹脂絶縁層を構成する上層側の接着剤層として用いられる無電解めっき用接着剤組成物を調製した。
【００６２】
Ｂ．下層の層間樹脂絶縁剤の調製
▲１▼．クレゾールノボラック型エポキシ樹脂（日本化薬製、分子量2500）の25％アクリル化物を80wt％の濃度でＤＭＤＧに溶解させた樹脂液を35重量部、感光性モノマー（東亜合成製、アロニックスＭ315 ）４重量部、消泡剤（サンノプコ製、Ｓ−65）0.5 重量部、ＮＭＰを 3.6重量部を攪拌混合した。
▲２▼．ポリエーテルスルフォン（ＰＥＳ）12重量部、エポキシ樹脂粒子（三洋化成製、ポリマーポール）の平均粒径 0.5μｍのものを14.49 重量部、を混合した後、さらにＮＭＰ30重量部を添加し、ビーズミルで攪拌混合した。
▲３▼．イミダゾール硬化剤（四国化成製、2E4MZ-CN）２重量部、光開始剤（チバガイギー製、イルガキュア Ｉ−907 ）２重量部、光増感剤（日本化薬製、DETX-S）0.2 重量部、ＮＭＰ1.5 重量部を攪拌混合した。
これらを混合して、２層構造の層間樹脂絶縁層を構成する下層側の絶縁剤層として用いられる樹脂組成物を調製した。
【００６３】
Ｃ．樹脂充填剤の調製
▲１▼．ビスフェノールＦ型エポキシモノマー（油化シェル製、分子量310,YL983U） 100重量部、表面にシランカップリング剤がコーティングされた平均粒径 1.6μｍのSiＯ₂ 球状粒子（アドマテック製、CRS 1101−CE、ここで、最大粒子の大きさは後述する内層銅パターンの厚み（15μｍ）以下とする） 170重量部、レベリング剤（サンノプコ製、ペレノールＳ４）1.5 重量部を３本ロールにて混練して、その混合物の粘度を23±１℃で45,000〜49,000cps に調整した。
▲２▼．イミダゾール硬化剤（四国化成製、2E4MZ-CN）6.5 重量部。
これらを混合して樹脂充填剤を調製した。
【００６４】
Ｄ．上層用ソルダーレジスト組成物の調製
ＤＭＤＧに溶解させた80wt％のクレゾールノボラック型エポキシ樹脂（日本化薬製）のエポキシ基25％をアクリル化した感光性付与のオリゴマー（分子量4000）を35重量部、ポリエーテルスルフォン（ＰＥＳ）12重量部、イミダゾール硬化剤（四国化成製、2E4MZ-CN）2.0 重量部、感光性モノマーである多価アクリルモノマー（東亜合成製、M-325 ） 4.0重量部、消泡剤（サンノプコ社製、S-65） 0.5 重量部を混合し、さらに、これらの混合物に対して光開始剤としてのイルガキュアＩ-907（チバガイギー製）2.0 重量部、光増感剤としてのDETX-S（日本化薬製）0.2 重量部を加えて、ＮＭＰ36.8重量部を加え、粘度を25℃で 3.0±0.5 Pa・ｓに調整した上層用ソルダーレジスト組成物を得た。
なお、粘度測定は、Ｂ型粘度計（東京計器、 DVL-B型）で 60rpmの場合はローターNo.4、６rpm の場合はローターNo.3によった。
【００６５】
Ｅ．下層用ソルダーレジスト組成物の調製
ＤＭＤＧに溶解させた80wt％のクレゾールノボラック型エポキシ樹脂（日本化薬製）のエポキシ基25％をアクリル化した感光性付与のオリゴマー（分子量4000）を35重量部、ポリエーテルスルフォン（ＰＥＳ）12重量部、平均粒径0.5 μｍのエポキシ樹脂粒子（三洋化成製、ポリマーポール S-50 ）14.5重量部、イミダゾール硬化剤（四国化成製、2E4MZ-CN）2.0 重量部、感光性モノマーである多価アクリルモノマー（東亜合成製、M-325 ） 4.0重量部、消泡剤（サンノプコ社製、S-65 ）0.5 重量部を混合し、さらに、これらの混合物に対して光開始剤としてのイルガキュアＩ-907（チバガイギー製）2.0 重量部、光増感剤としてのDETX-S（日本化薬製）0.2 重量部を加えて、ＮＭＰ55.8重量部を加え、粘度を25℃で 3.0±0.5 Pa・ｓに調整した下層用ソルダーレジスト組成物を得た。
なお、粘度測定は、Ｂ型粘度計（東京計器、 DVL-B型）で 60rpmの場合はローターNo.4、６rpm の場合はローターNo.3によった。
【００６６】
Ｆ．プリント配線板の製造方法
(1) 厚さ１mmのガラスエポキシ樹脂またはＢＴ（ビスマレイミドトリアジン）樹脂からなる基板１の両面に18μｍの銅箔８がラミネートされている銅張積層板を出発材料とした（図１参照）。まず、この銅張積層板をドリル削孔し、めっきレジストを形成した後、無電解めっき処理してスルーホール９を形成し、さらに、銅箔８を常法に従いパターン状にエッチングすることにより、基板１の両面に内層銅パターン４を形成した。
【００６７】
(2) 内層銅パターン４およびスルーホール９を形成した基板を水洗いし、乾燥した後、酸化浴（黒化浴）として、NaOH（20ｇ／ｌ）、NaClO₂（50ｇ／ｌ）、Na₃PO₄（15.0ｇ／ｌ）の水溶液、還元浴として、NaOH（ 2.7ｇ／ｌ）、NaBH₄ （ 1.0ｇ／ｌ）の水溶液を用いた酸化−還元処理により、内層導パターン４およびスルーホール９の表面に粗化層11を設けた（図２参照）。
【００６８】
(3) 樹脂充填剤10を、基板の片面にロールコータを用いて塗布することにより、導体回路４間あるいはスルーホール９内に充填し、70℃, 20分間で乾燥させ、他方の面についても同様にして樹脂充填剤10を導体回路４間あるいはスルーホール９内に充填し、70℃, 20分間で加熱乾燥させた（図３参照）。
【００６９】
(4) 前記(3) の処理を終えた基板の片面を、＃600 のベルト研磨紙（三共理化学製）を用いたベルトサンダー研磨により、内層銅パターン４の表面やスルーホール９のランド表面に樹脂充填剤10が残らないように研磨し、次いで、前記ベルトサンダー研磨による傷を取り除くためのバフ研磨を行った。このような一連の研磨を基板の他方の面についても同様に行った。
次いで、 100℃で１時間、120 ℃で３時間、 150℃で１時間、 180℃で７時間の加熱処理を行って樹脂充填剤10を硬化した（図４参照）。
【００７０】
このようにして、スルーホール９等に充填された樹脂充填剤10の表層部および内層導体回路４上面の粗化層11を除去して基板両面を平滑化し、樹脂充填剤10と内層導体回路４の側面とが粗化層11を介して強固に密着し、またスルーホール９の内壁面と樹脂充填剤10とが粗化層11を介して強固に密着した配線基板を得た。即ち、この工程により、樹脂充填剤10の表面と内層銅パターン４の表面が同一平面となる。ここで、充填した硬化樹脂のＴｇ点は155.6 ℃、線熱膨張係数は44.5×10^-6／℃であった。
【００７１】
(5) 前記(4) の処理で露出した内層導体回路４およびスルーホール９のランド上面に、厚さ 2.5μｍのCu−Ni−Ｐ合金からなる粗化層（凹凸層）11を形成し、さらに、その粗化層11の表面に厚さ 0.3μｍのSn層を設けた（図５参照、但し、Sn層については図示しない）。
その形成方法は以下のようである。即ち、基板を酸性脱脂してソフトエッチングし、次いで、塩化パラジウムと有機酸からなる触媒溶液で処理して、Pd触媒を付与し、この触媒を活性化した後、硫酸銅８ｇ／ｌ、硫酸ニッケル 0.6ｇ／ｌ、クエン酸15ｇ／ｌ、次亜リン酸ナトリウム29ｇ／ｌ、ホウ酸31ｇ／ｌ、界面活性剤（日信化学工業製、サーフィノール465 ） 0.1ｇ／ｌの水溶液からなるｐＨ＝９の無電解めっき浴にてめっきを施し、銅導体回路４上面およびスルーホール９のランド上面にCu−Ni−Ｐ合金の粗化層11を形成した。次いで、ホウフッ化スズ0.1mol／ｌ、チオ尿素1.0mol／ｌの水溶液を用い、温度50℃、ｐＨ＝1.2 の条件でCu−Sn置換反応させ、粗化層11の表面に厚さ0.3 μｍのSn層を設けた（Sn層については図示しない）。
【００７２】
(6) 基板の両面に、Ｂの層間樹脂絶縁剤（粘度 1.5Pa・ｓ）をロールコータで塗布し、水平状態で20分間放置してから、60℃で30分の乾燥を行い、絶縁剤層2aを形成した。
さらにこの絶縁剤層2aの上にＡの無電解めっき用接着剤（粘度７Pa・ｓ）をロールコータを用いて塗布し、水平状態で20分間放置してから、60℃で30分の乾燥を行い、接着剤層2bを形成し、厚さ35μｍの層間樹脂絶縁層２を形成した（図６参照）。
【００７３】
(7) 前記(6) で層間樹脂絶縁層２を形成した基板の両面に、85μｍφの黒円が印刷されたフォトマスクフィルムを密着させ、超高圧水銀灯により 500mJ／cm² で露光した。これをＤＭＤＧ溶液でスプレー現像することにより、その層間樹脂絶縁層２に85μｍφのバイアホールとなる開口を形成した。さらに、当該基板を超高圧水銀灯により3000mJ／cm² で露光し、100 ℃で１時間、その後 150℃で５時間の加熱処理をすることにより、フォトマスクフィルムに相当する寸法精度に優れた開口（バイアホール形成用開口６）を有する厚さ35μｍの層間樹脂絶縁層２を形成した（図７参照）。なお、バイアホールとなる開口には、スズめっき層を部分的に露出させた。
【００７４】
(8) バイアホール形成用開口を形成した基板を、 800ｇ／ｌのクロム酸水溶液に70℃で19分間浸漬し、層間樹脂絶縁層２の接着剤層2bの表面に存在するエポキシ樹脂粒子を溶解除去することにより、当該層間樹脂絶縁層２の表面を粗面（深さ３μｍ）とし、その後、中和溶液（シプレイ社製）に浸漬してから水洗いした（図８参照）。
さらに、粗面化処理した該基板の表面に、パラジウム触媒（アトテック製）を付与することにより、層間樹脂絶縁層２の表面およびバイアホール用開口６の内壁面に触媒核を付けた。
【００７５】
(9) 以下の組成の無電解銅めっき水溶液中に基板を浸漬して、粗面全体に厚さ 0.6μｍの無電解銅めっき膜12を形成した（図９参照）。このとき、めっき膜が薄いために無電解めっき膜表面には凹凸が観察された。
〔無電解めっき水溶液〕
ＥＤＴＡ 150 ｇ／ｌ
硫酸銅 20 ｇ／ｌ
ＨＣＨＯ 30 ml／ｌ
ＮａＯＨ 40 ｇ／ｌ
α、α’−ビピリジル 80 mg／ｌ
ＰＥＧ 0.1 ｇ／ｌ
〔無電解めっき条件〕
70℃の液温度で30分
【００７６】
(10)前記(9) で形成した無電解めっき膜12上に市販の感光性ドライフィルムを張り付け、マスクを載置して、100 mJ／cm² で露光、0.8 ％炭酸ナトリウムで現像処理し、厚さ15μｍのめっきレジスト３を設けた（図10参照）。
【００７７】
(11)ついで、基板を50℃の水で洗浄して脱脂し、25℃の水で水洗後、さらに硫酸で洗浄してから、以下の条件で電解銅めっきを施し、厚さ15μｍの電解銅めっき膜13を形成した（図11参照）。

【００７８】
(12)めっきレジスト３を５％ＫＯＨ水溶液で剥離除去した後、そのめっきレジスト３下の無電解めっき膜12を硫酸と過酸化水素の混合液でエッチング処理して溶解除去し、無電解銅めっき膜12と電解銅めっき膜13からなる厚さ18μｍの導体回路（バイアホール７を含む）５を形成した。さらに、70℃で800g／l のクロム酸水溶液に３分間浸漬して、導体回路非形成部分に位置する導体回路間の無電解めっき用接着剤層の表面を１μｍエッチング処理し、その表面に残存するパラジウム触媒を除去した（図12参照）。
【００７９】
(13)導体回路５を形成した基板を、硫酸銅８ｇ／ｌ、硫酸ニッケル 0.6ｇ／ｌ、クエン酸15ｇ／ｌ、次亜リン酸ナトリウム29ｇ／ｌ、ホウ酸31ｇ／ｌ、界面活性剤（日信化学工業製、サーフィノール465 ） 0.1ｇ／ｌの水溶液からなるｐＨ＝９の無電解めっき液に浸漬し、該導体回路５の表面に厚さ３μｍの銅−ニッケル−リンからなる粗化層11を形成した（図13参照）。このとき、形成した粗化層11をＥＰＭＡ（蛍光Ｘ線分析装置）で分析したところ、Cu：98 mol％、Ni： 1.5 mol％、Ｐ： 0.5 mol％の組成比であった。
さらに、ホウフッ化スズ 0.1 mol／ｌ、チオ尿素 1.0 mol／ｌの水溶液を用い、温度50℃、ｐＨ＝1.2 の条件でCu−Sn置換反応を行い、前記粗化層11の表面に厚さ0.3 μｍののSn層を設けた（Sn層については図示しない）。
【００８０】
(14)前記 (6)〜(13)の工程を繰り返すことにより、さらに上層の導体回路を形成し、多層配線板を得た。但し、Sn置換は行わなかった（図14〜19参照）。
【００８１】
(15)次に、前記(14)で得られた多層配線基板の両面に、Ｄのソルダーレジスト組成物（粘度3.0 Pa・ｓ）をロールコータで塗布し、60℃で30分の乾燥を行い、下層のソルダーレジスト層（厚み16μｍ）を形成した。
さらにこの層の上にＥのソルダーレジスト組成物をロールコータを用いて塗布し、60℃で30分の乾燥を行い、上層のソルダーレジスト層（厚み８μｍ）を形成し、２層構造のソルダーレジスト層とした。
【００８２】
(16)次に、円パターン（マスクパターン）が描画された厚さ５mmのフォトマスクフィルムを密着させて載置し、1000mJ／cm² の紫外線で露光し、ＤＭＤＧ現像処理した。
そしてさらに、80℃で１時間、 100℃で１時間、 120℃で１時間、 150℃で３時間の条件で加熱処理し、引き続き800g/lのクロム酸水溶液に19分間浸漬してエッチング処理し、開口底部に残存している樹脂を除去し、はんだパッド部分が開口した（開口径 200μｍ）ソルダーレジスト層（厚み20μｍ）14を形成した。
【００８３】
(17)次に、ソルダーレジスト層14を形成した基板を、塩化ニッケル30ｇ／ｌ、次亜リン酸ナトリウム10ｇ／ｌ、クエン酸ナトリウム10ｇ／ｌの水溶液からなるｐＨ＝５の無電解ニッケルめっき液に20分間浸漬して、開口部に厚さ５μｍのニッケルめっき層15を形成した。さらに、その基板を、シアン化金カリウム２ｇ／ｌ、塩化アンモニウム75ｇ／ｌ、クエン酸ナトリウム50ｇ／ｌ、次亜リン酸ナトリウム10ｇ／ｌの水溶液からなる無電解金めっき液に93℃の条件で23秒間浸漬して、ニッケルめっき層15上に厚さ0.03μｍの金めっき層16を形成した。
【００８４】
(18)そして、ソルダーレジスト層14の開口部に、はんだペーストを印刷して 200℃でリフローすることによりはんだバンプ（はんだ体）17を形成し、はんだバンプ17を有するプリント配線板を製造した（図20参照）。
【００８５】
（比較例１）
下層のソルダーレジスト層のみを形成したこと以外は、実施例１と同様にしてはんだバンプを有するプリント配線板を製造した。
【００８６】
（比較例２）
ソルダーレジスト層として下記の組成物を使用したこと以外は、実施例１と同様にしてはんだバンプを有するプリント配線板を製造した。
ＤＭＤＧに溶解させた80wt％のクレゾールノボラック型エポキシ樹脂（日本化薬製）のエポキシ基25％をアクリル化した感光性付与のオリゴマー（分子量4000）を35重量部、イミダゾール硬化剤（四国化成製、2E4MZ-CN）2.0 重量部、感光性モノマーである多価アクリルモノマー（東亜合成製、M-325 ） 4.0重量部、消泡剤（サンノプコ社製、S-65）0.5 重量部を混合し、さらに、これらの混合物に対して、光開始剤としてのイルガキュアＩ-907（チバガイギー製）2.0 重量部、光増感剤としてのDETX-S（日本化薬製）0.2 重量部を加えて、ＮＭＰ36.8重量部を加え、粘度を25℃で 3.0±0.5 Pa・ｓに調整したソルダーレジスト組成物を得た。
なお、粘度測定は、Ｂ型粘度計（東京計器、 DVL-B型）で 60rpmの場合はローターNo.4、６rpm の場合はローターNo.3によった。
【００８７】
（比較例３）
上層のソルダーレジスト層のみを形成したこと以外は、実施例１と同様にしてはんだバンプを有するプリント配線板を製造した。
【００８８】
このようにしてプリント配線板を製造するにあたり、ソルダーレジスト層における開口底部の現像残りの有無および表面荒れの有無を調べた。
また、このようにして製造したプリント配線板について、−55〜125 ℃で1000回のヒートサイクル試験を実施し、光学顕微鏡によりソルダーレジスト層におけるクラック発生の有無を確認した。
これらの結果を表１に示す。
【００８９】
この表に示す結果から明らかなように、本実施例の構成では、開口部の現像残り（樹脂残り）がなく、また、ソルダーレジスト層表面も平滑で、ヒートサイクルに対する耐性も優れていた。
【００９０】
【表１】

【００９１】
【発明の効果】
以上説明したように本発明によれば、ソルダーレジスト層に開口を形成する際に現像不良が発生しても、そのソルダーレジスト層の表面荒れを招くことなく、開口底部の残存する樹脂を確実にエッチング除去することができる。
しかも、本発明のプリント配線板を構成するソルダーレジスト層は、ノボラック型エポキシ樹脂のアクリレートと熱可塑性樹脂との樹脂複合体を主成分としているので、このソルダーレジスト層の熱膨張率は低く、導体層との熱膨張率差に起因したクラックの発生を抑制でき、ヒートサイクル条件下での耐クラック性に優れるプリント配線板を提供することができる。
【図面の簡単な説明】
【図１】本発明にかかるプリント配線板の一製造工程を示す図である。
【図２】本発明にかかるプリント配線板の一製造工程を示す図である。
【図３】本発明にかかるプリント配線板の一製造工程を示す図である。
【図４】本発明にかかるプリント配線板の一製造工程を示す図である。
【図５】本発明にかかるプリント配線板の一製造工程を示す図である。
【図６】本発明にかかるプリント配線板の一製造工程を示す図である。
【図７】本発明にかかるプリント配線板の一製造工程を示す図である。
【図８】本発明にかかるプリント配線板の一製造工程を示す図である。
【図９】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１０】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１１】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１２】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１３】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１４】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１５】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１６】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１７】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１８】本発明にかかるプリント配線板の一製造工程を示す図である。
【図１９】本発明にかかるプリント配線板の一製造工程を示す図である。
【図２０】本発明にかかるプリント配線板の一製造工程を示す図である。
【符号の説明】
１ 基板
２ 樹脂絶縁層
2a 絶縁剤層
2b 接着剤層
３ めっきレジスト
４ 内層導体回路（内層銅パターン）
５ 外層導体回路（外層銅パターン）
６ バイアホール用開口
７ バイアホール
８ 銅箔
９ スルーホール
10 充填樹脂（樹脂充填剤）
11 粗化層
12 無電解めっき膜
13 電解めっき膜ニッケルめっき層
14 ソルダーレジスト層
15 ニッケルめっき層
16 金めっき層
17 はんだバンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printed wiring board, and in particular, proposes a printed wiring board having a solder resist layer excellent in thermal cycle characteristics.
[0002]
[Prior art]
Generally, in printed wiring boards, a solder resist layer is coated on the outermost layer for the purpose of protecting the conductor circuit exposed on the surface layer and preventing the leakage and bridging of the solder body supplied to the surface of the conductor pad on which the electronic component is mounted. The In this case, the solder resist layer protects other conductor circuits by providing openings that expose only the conductor pads on which the IC chip is mounted, while solder bumps supplied to mount the IC chip in this opening. It functions as a solder dam of a spherical or protruding solder body called.
[0003]
As such a solder resist layer, it is desirable to use a composition composed mainly of an acrylate of a novolac type epoxy resin in which Pb migration hardly occurs.
However, since this solder resist layer is mainly composed of a novolac type epoxy resin, there is a problem that cracks due to a difference in thermal expansion coefficient from the conductor layer are likely to occur during a heat cycle test.
[0004]
As a solder resist layer that can suppress the occurrence of such cracks, the inventors have found a new structure in which a composition composed mainly of a resin composite of an acrylate of a novolac type epoxy resin and a thermoplastic resin is used as a matrix. It was.
However, in this configuration, a resin composite of a novolac-type epoxy resin acrylate and a thermoplastic resin is excellent in chemical resistance, so that development failure occurs when an opening is formed in the solder resist layer during normal exposure development processing. However, there is a new problem that the resin remains at the bottom of the opening.
[0005]
On the other hand, the inventors further provide an acid such as chromic acid or the like in the matrix as a solder resist layer that can be reliably removed by etching even if a development residue occurs at the bottom of the opening after exposure and development. The inventors have found a composition composed of a composition obtained by dispersing heat-resistant resin particles soluble in an oxidizing agent.
However, in this solder resist layer, when the resin residue is removed by etching with an acid or an oxidant, the acid- or oxidant-soluble heat-resistant resin particles present on the surface of the layer other than the openings are also removed. A new problem arises that the surface becomes rough and the underfill formed here is peeled off.
[0006]
[Problems to be solved by the invention]
Therefore, the present invention has been made to solve the above-described problems of the prior art, and its main purpose is to remove the development residue at the bottom of the opening without causing surface roughness, and to achieve thermal cycle characteristics. It is providing the printed wiring board which formed the soldering resist layer which has the outstanding structure.
[0007]
[Means for Solving the Problems]
As a result of earnest research for the realization of the above object, the inventor has completed the present invention having the following contents.
(1) The printed wiring board of the present invention is a printed wiring board in which a conductive resist circuit is provided on a wiring board in which a conductive circuit is formed on the outermost resin insulation layer, and the solder resist layer is provided on the printed wiring board. The upper layer is composed of a composition composed mainly of a resin composite of a novolac epoxy resin acrylate and a thermoplastic resin, and the lower layer is a resin composite of a novolac epoxy resin acrylate and a thermoplastic resin. Consists of a composition in which heat-resistant resin particles soluble in an acid or oxidant are dispersed in a matrix that is hardly soluble in an acid or oxidant as a main component, and a composite layer obtained by curing these compositions It is characterized by forming .
[0008]
(2) Further, the printed wiring board of the present invention is provided on the solder resist layer while providing a solder resist layer covering the conductor circuit on the wiring board in which the conductor circuit is formed on the outermost resin insulating layer. A part of the conductor circuit exposed from the opened opening is formed as a pad, and the solder resist layer is formed on the pad, and the solder resist layer is formed on the pad, and the upper layer is an acrylate of a novolac epoxy resin. It is composed of a composition mainly composed of a resin complex with a thermoplastic resin, and the lower layer is hardly soluble in an acid or an oxidizer mainly composed of a resin complex of an acrylate of a novolac type epoxy resin and a thermoplastic resin. Consists of a composition in which heat-resistant resin particles soluble in an acid or an oxidizing agent are dispersed in a matrix, and a composite layer formed by curing these compositions It is characterized by forming .
[0009]
In the printed wiring board described in the above (1) or (2), the solder resist layer preferably has an upper layer / lower layer thickness ratio of 1/1 to 1/3 in the upper layer / lower layer. Further, the blending ratio of the thermoplastic resin is preferably 50 wt% or less, the thermoplastic resin is preferably polyether sulfone (PES), and the blending ratio of the heat-resistant resin particles is 5 to 40 wt%. Preferably there is. The solder resist layer preferably has a thermal expansion coefficient of 40 to 50 ppm / ° C. Furthermore, a roughened layer is preferably formed on the surface of the conductor circuit, and the roughened layer is preferably an alloy layer made of copper-nickel-phosphorus.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the printed wiring board of the present invention, the solder resist layer is composed of a composition mainly composed of a resin composite of an acrylate of a novolac type epoxy resin and a thermoplastic resin, and the lower layer is an acrylate of a novolac type epoxy resin. And a composition comprising a heat-resistant resin particle soluble in an acid or an oxidant dispersed in a matrix that is hardly soluble in an acid or an oxidant, the main component of which is a resin composite of a resin and a thermoplastic resin . It is characterized in that it is formed from a composite layer formed by curing the composition .
[0011]
Thus, if a composition in which resin particles dissolved in an acid or an oxidant are present in the matrix of the resin composite is used as the lower layer of the solder resist layer, poor development occurs when forming an opening in the solder resist layer. However, since the resin particles are dissolved in the etching process using an acid or an oxidant, and the resin matrix surrounding the resin particles is also dissolved or damaged, the resin remaining at the bottom of the opening can be reliably removed. . Moreover, in the etching process using an acid or an oxidant, since the composition containing only the resin composite as a main component is used as the upper layer of the solder resist layer, the surface of the solder resist layer excluding the opening may be roughened. Absent.
[0012]
Further, according to the configuration of the solder resist layer, since the composition mainly composed of a resin composite of an acrylate of a novolak type epoxy resin and a thermoplastic resin is used, the coefficient of thermal expansion is low and the thermoplastic resin is used. Since the rigidity is improved due to the above, the occurrence of cracks due to the difference in thermal expansion coefficient with the conductor layer can be suppressed, and a printed wiring board excellent in crack resistance under heat cycle conditions can be provided.
[0013]
In such a printed wiring board of the present invention, the film thickness of the upper layer and the lower layer of the solder resist layer is preferably 1/1 to 1/3 in the upper layer / lower layer. The reason for this is that when the thickness of the upper layer is less than 1/3 of the thickness of the lower layer, the upper layer is removed when the remaining resin is removed with an acid or an oxidizing agent. This is because the opening is not formed when the thickness is larger than the thickness.
[0014]
In the lower solder resist layer, the blending ratio of the heat-resistant resin particles soluble in the acid or the oxidizing agent is preferably 5 to 40 wt% with respect to the total solid content of the solder resist containing the heat-resistant resin particles. This is because if the amount of the heat-resistant resin particles is too small, the resin residue cannot be completely removed, and conversely if the amount is too large, the opening becomes too large. The average particle size of the heat resistant resin particles is preferably 0.1 to 1.0 μm. This is because the resin residue can be removed without making the opening too large.
As the heat-resistant resin particles, it is desirable to use epoxy resin particles and amino resin particles (melamine resin, gunaamine resin, urea resin) cured with an amine curing agent.
[0015]
Polyether sulfone (PES), polysulfone, polyphenylene sulfide, polyphenyl ether, polyether imide, or the like can be used as the thermoplastic resin of the resin composite constituting the solder resist layer. In particular, polyether sulfone (PES) is more preferable in terms of being easily dissolved in an organic solvent and having a low dielectric constant.
[0016]
The amount of the thermoplastic resin is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, based on the total solid content of the resin matrix of the solder resist composition excluding the heat-resistant resin particles. This is because the opening can be made without lowering the fracture toughness value.
[0017]
Moreover, as the acrylate of the novolac type epoxy resin constituting the resin composite, an epoxy resin obtained by reacting glycidyl ether of phenol novolac or cresol novolac with acrylic acid, methacrylic acid or the like can be used.
[0018]
Various curing agents can be used for the resin composite having such a configuration, but it is desirable to use an imidazole curing agent that is liquid at 25 ° C. This is because uniform kneading is difficult with powder, and liquid can be uniformly kneaded.
Such liquid imidazole curing agents include 1-benzyl-2-methylimidazole (product name: 1B2MZ), 1-cyanoethyl-2-ethyl-4-methylimidazole (product name: 2E4MZ-CN), 4-methyl-2- Ethyl imidazole (product name: 2E4MZ) or the like can be used.
The amount of the imidazole curing agent added is desirably 1 to 10% by weight based on the total solid content of the solder resist composition. This is because uniform mixing is easy if the amount added is within this range.
[0019]
In the present invention, the solder resist composition for forming the solder resist layer uses NMP (N-methylpyrrolidone) or a glycol ether solvent as a solvent, and has a viscosity of 1 to 10 Pa · s at 25 ° C., More preferably, it is preferably adjusted to 2 to 3 Pa · s.
Thus, according to the solder resist composition adjusted to a viscosity of 1 Pa · s or more at 25 ° C., the obtained solder resist layer has a small gap between resin molecular chains, and diffusion of Pb (lead lead) moving through this gap. As a result of less migration, short circuit defects in the printed wiring board are reduced. Further, when the viscosity of the solder resist composition is 1 Pa · s or more at 25 ° C., the composition does not sag even if the both surfaces are applied simultaneously with the substrate standing upright, and good application is possible. Become. However, when the viscosity of the solder resist composition exceeds 10 Pa · s at 25 ° C., the upper limit is set to 10 Pa · s because application by a roll coater is impossible.
Furthermore, when a glycol ether solvent is used as the solvent, the solder resist layer using such a composition does not generate free oxygen and does not oxidize the copper pad surface. In addition, it is less harmful to the human body.
As such a glycol ether solvent, at least one selected from the following structural formulas, particularly preferably diethylene glycol dimethyl ether (DMDG) and triethylene glycol dimethyl ether (DMTG) is used. This is because these solvents can completely dissolve benzophenone and Michler's ketone as reaction initiators by heating at about 30 to 50 ° C.
_{CH 3 O- (CH 2 CH 2} O) n -CH 3 (n = 1~5)
The glycol ether solvent is preferably 10 to 40 wt% with respect to the total weight of the solder resist composition.
[0020]
Such solder resist compositions include other antifoaming agents and leveling agents, thermosetting resins for improving heat resistance and base resistance and imparting flexibility, and photosensitive monomers for improving resolution. Etc. can be added.
Furthermore, you may add a pigment | dye and a pigment to a soldering resist composition. This is because the wiring pattern can be concealed. It is desirable to use phthalocyanine green as this dye.
[0021]
In particular, in the present invention, it is desirable to add an acrylic ester polymer having a molecular weight of about 500 to 5,000 to the solder resist composition. This is because this polymer is liquid at 25 ° C., is easily compatible with cresol novolac epoxy resin acrylate, and has a leveling action and a defoaming action. For this reason, the formed solder resist layer is excellent in surface smoothness, and does not have irregularities due to repelling or bubbles. Further, this polymer has compatibility with the photosensitive resin component, and is not dispersed in the resin component and does not lower the light transmission property. Therefore, a development residue is hardly generated.
[0022]
The acrylic ester polymer used in the present invention is preferably an ester polymer with an alcohol having 1 to 10 carbon atoms and acrylic acid, methacrylic acid or a derivative thereof. Examples of the alcohol having 1 to 10 carbon atoms, preferably 3 to 8 carbon atoms used in the present invention include propyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, pentyl alcohol, hexyl alcohol and octyl alcohol. Monohydric alcohols such as 2-ethylhexyl alcohol and amyl alcohol, and polyhydric alcohols such as 1,2-ethanediol.
[0023]
This acrylic ester polymer is excellent in compatibility with cresol novolac epoxy resin acrylate, and in particular, 2-ethylhexyl acrylate (2EHA), butyl acrylate (BA), ethyl acrylate (EA) and hydroxyethyl acrylate (HEA). The polymer of at least 1 sort (s) of acrylic acid ester chosen from these is desirable. Since 2-ethylhexyl acrylate is branched, it can impart a surface-active action and prevents the plating resist from being repelled by dust. Further, butyl acrylate is responsible for leveling and defoaming, and ethyl acrylate and hydroxyethyl acrylate are considered to improve compatibility. The four types of acrylates may be used alone or in combination of two or more, or two or more types of acrylates selected from the four types of acrylates may be used alone or in combination. May be used.
[0024]
For example, when all four acrylates are used, the weight composition ratio of 2-ethylhexyl acrylate / butyl acrylate is preferably 40/60 to 60/40, and a mixture of 2-ethylhexyl acrylate and butyl acrylate / ethyl acrylate. 90/10 to 97/3, and a mixture of 2-ethylhexyl acrylate and butyl acrylate / hydroxyethyl acrylate is preferably 95/5 to 99/1.
[0025]
The molecular weight of such an acrylic ester polymer is preferably about 500 to 5,000. In this range, it is liquid at 25 ° C., and is easily mixed with the photosensitive resin when preparing the solder resist. When the molecular weight exceeds 5000, the viscosity increases, and the leveling action and antifoaming action decrease. On the other hand, when the molecular weight is less than 500, no leveling action or antifoaming action is observed. Furthermore, the molecular weight of a particularly desirable acrylic ester polymer is 2000 to 3000. In this range, the viscosity is 250 to 550 cp (25 ° C.), and it becomes easier to prepare a solder resist.
[0026]
The added amount of the acrylic ester polymer is 0.1 to 5 parts by weight, preferably 0.2 to 1.0 part by weight, based on 100 parts by weight of the photosensitive resin component. If the amount is less than 0.1 parts by weight, the leveling action and defoaming action are reduced, and Pb migration and cracks are likely to occur due to bubbles. Conversely, if it exceeds 5 parts by weight, the glass transition point is lowered and the heat resistance is lowered. Because it does.
[0027]
In the present invention, it is desirable to add a compound having the structure of the following chemical formula 1 as an initiator and a compound having the structure of the following chemical formula 2 as a photosensitizer to the solder resist composition. This is because these compounds are easily available and highly safe for the human body.
[0028]
[Chemical 1]

[0029]
[Chemical 2]

[0030]
In addition, as the thermosetting resin mentioned as the additive component, a bisphenol type epoxy resin can be used. This bisphenol type epoxy resin includes a bisphenol A type epoxy resin and a bisphenol F type epoxy resin. When the basic resistance is important, the former is required when the viscosity is reduced (when the coating property is important). The latter is better for).
[0031]
Moreover, a polyvalent acrylic monomer can be used as the photosensitive monomer mentioned as the additive component. This is because the polyvalent acrylic monomer can improve the resolution. For example, a polyacrylic monomer having a structure as shown in Chemical Formula 3 and Chemical Formula 4 below is desirable. Here, chemical formula 3 is DPE-6A manufactured by Nippon Kayaku, and chemical formula 4 is R-604 manufactured by Kyoeisha Chemical.
[0032]
[Chemical 3]

[0033]
[Formula 4]

[0034]
Furthermore, you may add a benzophenone (BP) and Michler's ketone (MK) to a soldering resist composition. This is because they act as initiators and reaction accelerators.
It is desirable that BP and MK are simultaneously dissolved in a glycol ether solvent heated to 30 to 70 ° C., uniformly mixed, and mixed with other components. This is because there is no dissolution residue and it can be completely dissolved.
[0035]
In the printed wiring board of the present invention, the wiring board is not particularly limited, but a conductive circuit including a plating resist formed on a resin insulating material whose surface has been roughened and a pad included in a portion where the plating resist is not formed is provided. A so-called additive printed wiring board or build-up multilayer printed wiring board is desirable.
When a solder resist composition is applied to such a wiring board, the opening diameter of the solder resist layer can be made larger than the conductor pad diameter. As a result, the plating resist, which is a resin, acts as a dam of the solder body because it repels the solder body without conforming to the solder body.
[0036]
In the printed wiring board of the present invention, the thickness of the solder resist layer is desirably 5 to 30 μm. This is because if the thickness is too thin, the effect of the solder body as a dam is lowered, and if it is too thick, the development processing is difficult.
[0037]
Further, a more preferable configuration as the printed wiring board of the present invention is a structure in which a roughened layer is formed on the surface of the conductor circuit.
In the printed wiring board having such a structure, the roughened layer formed on the surface of the conductor circuit including the pad (portion on which the IC chip or electronic component is mounted) acts as an anchor, so that the conductor circuit and the solder resist layer are strengthened. It is in close contact. In addition, the adhesion of the solder body supplied and held on the pad surface is also improved.
In particular, acrylates of novolak type epoxy resins have a rigid skeleton and are excellent in heat resistance and base resistance, but lack flexibility, and thus are easily peeled off under high temperature and high humidity conditions. In this regard, according to the above configuration in which the roughened layer is formed on the surface of the conductor circuit, such peeling can be prevented.
[0038]
Here, the roughening layer is preferably formed by any one of polishing treatment, etching treatment, oxidation-reduction treatment, and plating treatment. Among these treatments, the oxidation-reduction treatment is performed by using an aqueous solution of NaOH (20 g / l), NaCl0 ₂ (50 g / l), Na ₃ PO ₄ (15.0 g / l) as an oxidation bath (blackening bath), NaOH (2.7 g / l), an aqueous solution of NaBH ₄ (1.0 g / l) was used as the reducing bath, and the plating treatment was copper sulfate 8 g / l, nickel sulfate 0.6 g / l, citric acid 15 g / l, sodium hypophosphite 29 g It is desirable to use an electroless plating bath for copper-nickel-phosphorus plating at pH = 9, comprising an aqueous solution of 0.1 g / l of a polyoxyethylene-based surfactant containing 0.1 g / l of boric acid and 31 g / l of boric acid.
In particular, the roughened layer of the alloy layer formed by copper-nickel-phosphorus plating has a needle-like structure and is difficult to enter into the solder resist layer, so that the anchor effect contributes to improving the adhesion with the solder resist layer. Further, since this roughened layer is electrically conductive, it does not need to be removed even if a solder body is formed on the pad surface.
[0039]
The composition of the alloy layer constituting the roughening layer is preferably 90 to 96 wt%, 1 to 5 wt%, and 0.5 to 2 wt% in terms of copper, nickel, and phosphorus, respectively. This is because the composition ratio has a needle-like structure. The roughened layer preferably has a thickness of 0.5 to 7 μm. This is because the adhesiveness to the solder resist layer and the solder body is lowered if it is too thick or too thin.
[0040]
In addition, when supplying and holding a solder body on a pad, it is good to give nickel-gold plating to the pad surface. This is because the nickel layer improves the adhesion with copper and is excellent in the adhesion with gold, and the gold layer is familiar with the solder body.
The solder body may be layered or may be a ball-shaped so-called “solder bump”.
[0041]
Next, one method for producing the printed wiring board of the present invention will be described.
(1) First, a wiring substrate having an inner layer copper pattern formed on the surface of the core substrate is manufactured.
The copper pattern on the core substrate is formed by etching a copper-clad laminate, or by forming an adhesive layer for electroless plating on a substrate such as a glass epoxy substrate, a polyimide substrate, a ceramic substrate, or a metal substrate. The surface of the adhesive layer is roughened to form a roughened surface, and electroless plating is applied to this surface, or the entire roughened surface is subjected to electroless plating, a plating resist is formed, and electrolytic plating is applied to a portion where the plating resist is not formed. After the application, the plating resist is removed and an etching process is performed to form a conductor circuit composed of an electrolytic plating film and an electroless plating film.
[0042]
Furthermore, the roughening layer which consists of copper-nickel-phosphorus can be formed in the surface of the conductor circuit of the said wiring board.
This roughening layer is formed by electroless plating. The composition of this electroless plating aqueous solution is such that the copper ion concentration, nickel ion concentration, and hypophosphite ion concentration are 2.2 × 10 ^{−2 to} 4.1 × 10 ⁻² mol / l and 2.2 × 10 ⁻³ to 4.1 ×, respectively. 10 ⁻³ mol / l, preferably 0.20 to 0.25 mol / l.
This is because the crystal structure of the coating deposited in this range becomes a needle-like structure, and thus the anchor effect is excellent. In addition to the above compounds, complexing agents and additives may be added to the electroless plating bath.
Other methods for forming the roughened layer include oxidation-reduction treatment and a method of forming a roughened surface by etching the copper surface along the grain boundary.
[0043]
A through hole is formed in the core substrate, and the wiring layers on the front surface and the back surface can be electrically connected through the through hole.
Further, resin may be filled between the through hole and the conductor circuit of the core substrate to ensure smoothness.
Further, the core substrate may have a conductor circuit in its inner layer, and the inner layer conductor circuit is connected to the conductor circuit on the surface of the core substrate by a through hole penetrating the core substrate.
Furthermore, the through hole may be filled with a resin composition containing metal particles, inorganic particles, and resin particles, and a conductor layer covering the filled resin may be formed. Via holes can be connected to this conductor layer.
[0044]
(2) Next, an interlayer resin insulating layer is formed on the wiring board produced in (1).
In the present invention, it is desirable to use the above-described adhesive for electroless plating as the interlayer resin insulating material.
[0045]
(3) After drying the electroless plating adhesive layer formed in (2), a via hole forming opening is provided as necessary.
At this time, in the case of a photosensitive resin, a via hole is formed in the adhesive layer by exposing and developing and then thermosetting, and in the case of a thermosetting resin, by thermosetting and then laser processing. An opening is provided.
[0046]
(4) Next, the epoxy resin particles present on the surface of the cured adhesive layer are removed by dissolution or decomposition with an acid or an oxidizing agent, and the surface of the adhesive layer is roughened.
Here, examples of the acid include phosphoric acid, hydrochloric acid, sulfuric acid, and organic acids such as formic acid and acetic acid. It is particularly preferable to use an organic acid. This is because when the roughening treatment is performed, the metal conductor layer exposed from the via hole is hardly corroded.
On the other hand, as the oxidizing agent, it is desirable to use an aqueous solution of chromic acid or permanganate (such as potassium permanganate).
[0047]
(5) Next, a catalyst nucleus is imparted to the wiring board whose surface of the adhesive layer is roughened.
For imparting the catalyst nucleus, it is desirable to use a noble metal ion or a noble metal colloid. Generally, palladium chloride or a palladium colloid is used. It is desirable to perform heat treatment to fix the catalyst core. Palladium is preferable as such a catalyst nucleus.
[0048]
(6) Next, electroless plating is performed on the surface of the adhesive layer for electroless plating, and a thin electroless plating film having irregularities along the rough surface is formed on the entire roughened surface. At this time, the thickness of the electroless plating film is 0.1 to 5 μm, more preferably 0.5 to 3 μm.
Next, a plating resist is formed on the electroless plating film.
As the plating resist composition, a composition comprising an acrylate of a cresol novolac type epoxy resin or a phenol novolac type epoxy resin and an imidazole curing agent is particularly preferable, but a commercially available dry film can also be used.
[0049]
(7) Next, the substrate is washed with water at 10 to 35 ° C., preferably 15 to 30 ° C.
This is because when the washing temperature exceeds 35 ° C., water volatilizes, the surface of the electroless plating film is dried and oxidized, and the electrolytic plating film is not deposited. Therefore, the electroless plating film is dissolved by the etching process, and a portion where no conductor exists is generated. On the other hand, if the temperature is lower than 10 ° C., the solubility of the pollutant in water decreases, and the cleaning power decreases. In particular, when the via hole land diameter is 200 μm or less, the plating resist repels water, so that the water tends to volatilize and the problem of non-deposition of electrolytic plating tends to occur.
In addition, various surfactants, acids, and alkalis may be added to the washing water. Moreover, you may wash | clean with acids, such as a sulfuric acid, after washing | cleaning.
[0050]
(8) Next, electrolytic plating is performed on the plating resist non-forming portion to form a conductor circuit and a via hole.
Here, it is desirable to use copper plating as the electrolytic plating.
[0051]
(9) Further, after removing the plating resist, the electroless plating film under the plating resist is dissolved and removed with an etching solution composed of a mixed solution of sulfuric acid and hydrogen peroxide or an aqueous solution such as sodium persulfate or ammonium persulfate. Conductor circuit.
[0052]
(10) Next, a roughening layer is formed on the surface of the conductor circuit.
As a method for forming the roughened layer, there are an etching process, a polishing process, an oxidation-reduction process, and a plating process.
Among these treatments, the oxidation-reduction treatment is performed by using an aqueous solution of NaOH (20 g / l), NaClO ₂ (50 g / l), Na ₃ PO ₄ (15.0 g / l) as an oxidation bath (blackening bath), NaOH (2.7 g). / L), an aqueous solution of NaBH ₄ (1.0 g / l) is used as the reducing bath.
Moreover, the roughening layer which consists of a copper-nickel-phosphorus alloy layer is formed by precipitation by an electroless-plating process.
The electroless plating solution for this alloy includes copper sulfate 1-40 g / l, nickel sulfate 0.1-6.0 g / l, citric acid 10-20 g / l, hypophosphite 10-100 g / l, boric acid 10 It is desirable to use a plating bath having a liquid composition comprising an aqueous solution of ˜40 g / l and an acetylene-containing polyoxyethylene-based surfactant of 0.01 to 10 g / l.
[0053]
(11) Next, an electroless plating adhesive layer is formed on this substrate as an interlayer resin insulation layer.
(12) Further, the steps (3) to (9) are repeated to provide a further upper conductor circuit, and flat conductor pads and via holes that function as solder pads are formed to obtain a multilayer wiring board.
(13) Next, a roughening layer is provided on the surface of the conductor pad and the via hole. The method for forming this roughened layer is the same as that described in (10) above.
[0054]
(14) A novolak epoxy resin acrylate, thermoplastic resin, curing agent, heat-resistant resin particles and, if necessary, an initiator, a photosensitive monomer, etc. are mixed with a solvent and stirred to obtain a solder resist composition for the lower layer. obtain.
[0055]
(15) An acrylate of a novolak type epoxy resin, a thermoplastic resin, a curing agent, and, if necessary, an initiator, a photosensitive monomer and the like are mixed with a solvent and stirred to obtain a solder resist composition for an upper layer.
[0056]
(16) Next, the lower layer solder resist composition obtained in (14) above was applied to both sides of the wiring board thus obtained and dried at 60 to 80 ° C. for 5 to 60 minutes. The solder resist composition for the upper layer obtained in step 1) is applied and dried at 60 to 80 ° C. for 5 to 60 minutes. When applying the solder resist composition, the wiring board is sandwiched between a pair of application rolls of a roll coater in a vertically standing state and conveyed from the lower side to the upper side to be soldered on both sides of the board. It is desirable to apply the resist composition simultaneously. The reason for this is that the basic specifications of the current printed wiring board are double-sided, and the curtain coating method (a method in which the resin flows from top to bottom like a waterfall and the substrate is applied to the resin “curtain”) is applied. This is because only one side can be applied. The above-described solder resist composition can be used for the above-mentioned method of applying both surfaces simultaneously. That is, since the above-described solder resist composition has a viscosity of 1 to 10 Pa · s at 25 ° C., it does not flow even when the substrate is applied vertically, and the transfer is also good.
[0057]
(17) Next, a photomask film on which the opening is drawn is placed on the coating film of the solder resist composition, and exposed and developed to form an opening that exposes the pad portion of the conductor circuit. To do. The coating film thus formed with the opening is further cured by heat treatment at 80 ° C. to 150 ° C. for 1 to 10 hours. Thereby, the soldering resist layer which has an opening part closely_contact | adheres with the roughening layer provided in the surface of the conductor circuit. Next, it is immersed in a 100 to 1000 g / l chromic acid aqueous solution for 5 to 30 minutes and etched to remove the resin remaining at the bottom of the opening.
[0058]
Here, the opening diameter of the opening may be larger than the diameter of the pad, and the pad may be completely exposed. In this case, even if the photomask is displaced, the pad is not covered with the solder resist, and since the solder resist does not contact the solder body and the solder body is not constricted, cracks are less likely to occur.
Conversely, the opening diameter of the opening can be made smaller than the diameter of the pad. In this case, the roughened layer on the pad surface and the solder resist are in close contact. In addition, when the so-called semi-additive method is adopted, the depth of the roughened layer of the electroless plating adhesive becomes shallow (1 to 3 μm), and since there is no plating resist, the pad is easy to peel off. By making the opening diameter of the part smaller than the diameter of the pad and covering a part of the pad with the solder resist layer, the pad peeling can be suppressed.
[0059]
(18) Next, a “nickel-gold” metal layer is formed on the solder pad exposed from the opening.
[0060]
(19) A solder body is supplied onto the solder pad portion exposed from the opening.
As a method for supplying the solder body, a solder transfer method or a printing method can be used. Here, the solder transfer method is to paste a solder foil on a prepreg, and to etch the solder foil by leaving only the portion corresponding to the opening portion, thereby forming a solder carrier film, and this solder carrier film. After the flux is applied to the solder resist opening of the substrate, the solder pattern is laminated so as to contact the pad, and this is transferred by heating. On the other hand, the printing method is a method in which a metal mask provided with a through hole at a position corresponding to a pad is placed on a substrate, a solder paste is printed, and heat treatment is performed.
[0061]
【Example】
(Example 1)
A. Preparation of upper layer electroless plating adhesive (1). 35 parts by weight of a resin solution prepared by dissolving 25% acrylate of cresol novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., molecular weight 2500) in DMDG at a concentration of 80 wt%, photosensitive monomer (Aronix M315, manufactured by Toagosei Co., Ltd.) 3.15 wt. Parts, 0.5 parts by weight of antifoaming agent (Sannopco, S-65) and 3.6 parts by weight of NMP were mixed with stirring.
(2). After mixing 12 parts by weight of polyethersulfone (PES), 7.2 parts by weight of epoxy resin particles (manufactured by Sanyo Kasei, polymer pole) with an average particle diameter of 1.0 μm, and 3.09 parts by weight with an average particle diameter of 0.5 μm, Further, 30 parts by weight of NMP was added and stirred and mixed with a bead mill.
(3). Imidazole curing agent (Shikoku Chemicals, 2E4MZ-CN) 2 parts by weight, Photoinitiator (Ciba Geigy, Irgacure I-907) 2 parts, Photosensitizer (Nippon Kayaku, DETX -S) 0.2 parts by weight, 1.5 parts by weight of NMP was mixed with stirring.
These were mixed to prepare an electroless plating adhesive composition used as an upper adhesive layer constituting an interlayer resin insulating layer having a two-layer structure.
[0062]
B. Preparation of lower interlayer resin insulation (1). 35 parts by weight of a resin solution prepared by dissolving 25% acrylate of cresol novolak type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., molecular weight 2500) in DMDG at a concentration of 80 wt%, photosensitive resin (Aronix M315, manufactured by Toagosei Co., Ltd.) Part, 0.5 part by weight of antifoaming agent (Sanopco, S-65) and 3.6 parts by weight of NMP were mixed with stirring.
(2). Mix 12 parts by weight of polyethersulfone (PES) and 14.49 parts by weight of epoxy resin particles (manufactured by Sanyo Kasei, polymer pole) with an average particle size of 0.5 μm, then add 30 parts by weight of NMP and stir in a bead mill. Mixed.
(3). Imidazole curing agent (Shikoku Chemicals, 2E4MZ-CN) 2 parts by weight, Photoinitiator (Ciba Geigy, Irgacure I-907) 2 parts, Photosensitizer (Nippon Kayaku, DETX-S) 0.2 parts by weight, 1.5 parts by weight of NMP was stirred and mixed.
These were mixed to prepare a resin composition to be used as an insulating layer on the lower layer side constituting an interlayer resin insulating layer having a two-layer structure.
[0063]
C. Preparation of resin filler (1). Bisphenol F type epoxy monomer (Oilized shell, molecular weight 310, YL983U) 100 parts by weight, SiO ₂ spherical particles with an average particle diameter of 1.6 μm coated with a silane coupling agent on the surface (manufactured by Admatech, CRS 1101-CE, here The maximum particle size is not more than the thickness (15 μm) of the inner layer copper pattern described later) 170 parts by weight and 1.5 parts by weight of a leveling agent (manufactured by San Nopco, Perenol S4) are kneaded with three rolls, and the mixture The viscosity of was adjusted to 45,000-49,000 cps at 23 ± 1 ° C.
(2). 6.5 parts by weight of imidazole curing agent (Shikoku Chemicals, 2E4MZ-CN).
These were mixed to prepare a resin filler.
[0064]
D. Preparation of Solder Resist Composition for Upper Layer 35 parts by weight of photosensitizing oligomer (molecular weight 4000) obtained by acrylated 25% of epoxy group of 80 wt% cresol novolac type epoxy resin (manufactured by Nippon Kayaku) dissolved in DMDG, 12 parts by weight of polyethersulfone (PES), 2.0 parts by weight of imidazole curing agent (Shikoku Kasei, 2E4MZ-CN), 4.0 parts by weight of polyvalent acrylic monomer (Made by Toagosei Co., Ltd., M-325), defoaming 0.5 parts by weight of an agent (Sannopco, S-65), and further 2.0 parts by weight of Irgacure I-907 (Ciba Geigy) as a photoinitiator and DETX- as a photosensitizer for these mixtures. 0.2 parts by weight of S (manufactured by Nippon Kayaku) was added, 36.8 parts by weight of NMP was added, and a solder resist composition for an upper layer having a viscosity adjusted to 3.0 ± 0.5 Pa · s at 25 ° C. was obtained.
Viscosity was measured with a B-type viscometer (Tokyo Keiki, DVL-B type) at 60 rpm with rotor No. 4 and at 6 rpm with rotor No. 3.
[0065]
E. Preparation of solder resist composition for lower layer 35 parts by weight of a photosensitizing oligomer (molecular weight 4000) obtained by acrylated 25% of an epoxy group of 80 wt% cresol novolac type epoxy resin (manufactured by Nippon Kayaku) dissolved in DMDG. 12 parts by weight of polyethersulfone (PES), 14.5 parts by weight of epoxy resin particles having an average particle size of 0.5 μm (manufactured by Sanyo Chemical Co., Ltd., Polymer Pole S-50), 2.0 parts by weight of imidazole curing agent (manufactured by Shikoku Chemicals, 2E4MZ-CN), A polyvalent acrylic monomer (manufactured by Toa Gosei Co., Ltd., M-325), which is a photosensitive monomer, is mixed with 4.0 parts by weight and an antifoaming agent (Sannopco, S-65) is mixed with 0.5 part by weight. Add 2.0 parts by weight of Irgacure I-907 (manufactured by Ciba Geigy) as an initiator, 0.2 parts by weight of DETX-S (manufactured by Nippon Kayaku) as a photosensitizer, add 55.8 parts by weight of NMP, and increase the viscosity to 25 ° C. Adjust to 3.0 ± 0.5 Pa · s An adjusted lower layer solder resist composition was obtained.
Viscosity was measured with a B-type viscometer (Tokyo Keiki, DVL-B type) at 60 rpm with rotor No. 4 and at 6 rpm with rotor No. 3.
[0066]
F. Method for manufacturing printed wiring board
(1) The starting material was a copper clad laminate in which 18 μm copper foil 8 was laminated on both sides of a substrate 1 made of glass epoxy resin or BT (bismaleimide triazine) resin having a thickness of 1 mm (see FIG. 1). First, after drilling the copper-clad laminate and forming a plating resist, electroless plating treatment is performed to form a through hole 9, and further, the copper foil 8 is etched into a pattern according to a conventional method, Inner layer copper patterns 4 were formed on both sides of the substrate 1.
[0067]
(2) The substrate on which the inner layer copper pattern 4 and the through hole 9 are formed is washed with water, dried, and then used as an oxidation bath (blackening bath), NaOH (20 g / l), NaClO ₂ (50 g / l), Na ₃ PO ₄ (15.0 g / l) aqueous solution, as a reducing bath, by oxidation-reduction treatment using NaOH (2.7 g / l), NaBH ₄ (1.0 g / l) aqueous solution, A roughened layer 11 was provided on the surface (see FIG. 2).
[0068]
(3) Resin filler 10 is applied to one side of the substrate using a roll coater, filled between conductor circuits 4 or through holes 9, and dried at 70 ° C. for 20 minutes. Similarly, the resin filler 10 was filled between the conductor circuits 4 or in the through holes 9 and dried by heating at 70 ° C. for 20 minutes (see FIG. 3).
[0069]
(4) One side of the substrate after the processing of (3) is applied to the surface of the inner layer copper pattern 4 or the land surface of the through hole 9 by belt sander polishing using # 600 belt polishing paper (manufactured by Sankyo Rikagaku). Polishing was performed so that the resin filler 10 did not remain, and then buffing was performed to remove scratches due to the belt sander polishing. Such a series of polishing was similarly performed on the other surface of the substrate.
Next, the resin filler 10 was cured by heat treatment at 100 ° C. for 1 hour, 120 ° C. for 3 hours, 150 ° C. for 1 hour, and 180 ° C. for 7 hours (see FIG. 4).
[0070]
In this way, the surface layer portion of the resin filler 10 filled in the through holes 9 and the like and the roughening layer 11 on the upper surface of the inner layer conductor circuit 4 are removed to smooth both surfaces of the substrate, and the resin filler 10 and the inner layer conductor circuit 4 are smoothed. A wiring substrate was obtained in which the side surface of the through hole 9 was firmly adhered via the roughened layer 11 and the inner wall surface of the through hole 9 and the resin filler 10 were firmly adhered via the roughened layer 11. That is, by this step, the surface of the resin filler 10 and the surface of the inner layer copper pattern 4 are flush. Here, the filled cured resin had a Tg point of 155.6 ° C. and a linear thermal expansion coefficient of 44.5 × 10 ⁻⁶ / ° C.
[0071]
(5) A roughened layer (concave / convex layer) 11 made of a Cu—Ni—P alloy with a thickness of 2.5 μm is formed on the land surface of the inner layer conductor circuit 4 and the through hole 9 exposed by the process of (4), Further, an Sn layer having a thickness of 0.3 μm was provided on the surface of the roughened layer 11 (see FIG. 5, but the Sn layer is not shown).
The formation method is as follows. That is, the substrate is acid degreased and soft etched, then treated with a catalyst solution comprising palladium chloride and an organic acid to give a Pd catalyst, and after activating this catalyst, copper sulfate 8 g / l, nickel sulfate PH consisting of an aqueous solution of 0.6 g / l, citric acid 15 g / l, sodium hypophosphite 29 g / l, boric acid 31 g / l, surfactant (Nisshin Chemical Industries, Surfinol 465) 0.1 g / l = 9 was plated in an electroless plating bath to form a roughened layer 11 of Cu—Ni—P alloy on the upper surface of the copper conductor circuit 4 and the land upper surface of the through hole 9. Next, a Cu-Sn substitution reaction was performed using an aqueous solution of tin borofluoride 0.1 mol / l and thiourea 1.0 mol / l under the conditions of a temperature of 50 ° C. and a pH = 1.2, and the surface of the roughened layer 11 had a thickness of 0.3 μm. An Sn layer was provided (the Sn layer is not shown).
[0072]
(6) Apply B interlayer resin insulation (viscosity 1.5Pa · s) on both sides of the board with a roll coater, leave it in a horizontal state for 20 minutes, and then dry at 60 ° C for 30 minutes. Layer 2a was formed.
Furthermore, apply the A electroless plating adhesive (viscosity 7 Pa · s) on this insulating layer 2a using a roll coater, leave it in a horizontal state for 20 minutes, and then dry at 60 ° C for 30 minutes. Then, an adhesive layer 2b was formed, and an interlayer resin insulation layer 2 having a thickness of 35 μm was formed (see FIG. 6).
[0073]
(7) A photomask film on which a 85 μmφ black circle was printed was adhered to both surfaces of the substrate on which the interlayer resin insulating layer 2 was formed in (6), and was exposed at 500 mJ / cm ² with an ultrahigh pressure mercury lamp. By spray-developing this with a DMDG solution, an opening serving as a via hole of 85 μmφ was formed in the interlayer resin insulating layer 2. Furthermore, the substrate was exposed to 3000 mJ / cm ² with an ultra-high pressure mercury lamp, and heat-treated at 100 ° C. for 1 hour and then at 150 ° C. for 5 hours. An interlayer resin insulation layer 2 having a thickness of 35 μm and having via-hole forming openings 6) was formed (see FIG. 7). Note that the tin plating layer was partially exposed in the opening serving as the via hole.
[0074]
(8) The substrate with the via hole opening is immersed in an 800 g / l chromic acid aqueous solution at 70 ° C. for 19 minutes to dissolve the epoxy resin particles present on the surface of the adhesive layer 2b of the interlayer resin insulation layer 2 By removing, the surface of the interlayer resin insulation layer 2 was roughened (depth: 3 μm), and then immersed in a neutralization solution (manufactured by Shipley Co., Ltd.) and washed with water (see FIG. 8).
Furthermore, a catalyst core was attached to the surface of the interlayer resin insulating layer 2 and the inner wall surface of the via hole opening 6 by applying a palladium catalyst (manufactured by Atotech) to the surface of the roughened substrate.
[0075]
(9) The substrate was immersed in an electroless copper plating aqueous solution having the following composition to form an electroless copper plating film 12 having a thickness of 0.6 μm over the entire rough surface (see FIG. 9). At this time, since the plating film was thin, unevenness was observed on the surface of the electroless plating film.
[Electroless plating aqueous solution]
EDTA 150 g / l
Copper sulfate 20 g / l
HCHO 30 ml / l
NaOH 40 g / l
α, α'-bipyridyl 80 mg / l
PEG 0.1 g / l
[Electroless plating conditions]
30 minutes at a liquid temperature of 70 ° C
(10) A commercially available photosensitive dry film is pasted on the electroless plating film 12 formed in (9) above, a mask is placed, exposed at 100 mJ / cm ² , developed with 0.8% sodium carbonate, A plating resist 3 having a thickness of 15 μm was provided (see FIG. 10).
[0077]
(11) Next, the substrate is washed with water at 50 ° C. and degreased, washed with water at 25 ° C. and further washed with sulfuric acid, and then subjected to electrolytic copper plating under the following conditions to obtain electrolytic copper having a thickness of 15 μm. A plating film 13 was formed (see FIG. 11).

[0078]
(12) After stripping and removing the plating resist 3 with a 5% KOH aqueous solution, the electroless plating film 12 under the plating resist 3 is etched and removed with a mixed solution of sulfuric acid and hydrogen peroxide, and electroless copper plating is performed. A conductor circuit (including the via hole 7) 5 having a thickness of 18 μm composed of the film 12 and the electrolytic copper plating film 13 was formed. Furthermore, the surface of the adhesive layer for electroless plating between the conductor circuits located in the conductor circuit non-formed part is etched by 1 μm for 3 minutes at 70 ° C. in 800 g / l chromic acid aqueous solution, and remains on the surface. The palladium catalyst to be removed was removed (see FIG. 12).
[0079]
(13) The substrate on which the conductor circuit 5 is formed is made of 8 g / l copper sulfate, 0.6 g / l nickel sulfate, 15 g / l citric acid, 29 g / l sodium hypophosphite, 31 g / l boric acid, a surfactant ( Made by Nissin Chemical Industry Co., Ltd., Surfynol 465) Roughened with copper-nickel-phosphorus having a thickness of 3 μm on the surface of the conductor circuit 5 by dipping in an electroless plating solution having a pH of 9 consisting of an aqueous solution of 0.1 g / l. Layer 11 was formed (see FIG. 13). At this time, when the formed roughened layer 11 was analyzed by EPMA (fluorescence X-ray analyzer), the composition ratio was Cu: 98 mol%, Ni: 1.5 mol%, P: 0.5 mol%.
Further, a Cu—Sn substitution reaction was performed using an aqueous solution of tin borofluoride 0.1 mol / l and thiourea 1.0 mol / l under the conditions of a temperature of 50 ° C. and a pH = 1.2, and the surface of the roughened layer 11 had a thickness of 0.3 A μm Sn layer was provided (the Sn layer is not shown).
[0080]
(14) By repeating the steps (6) to (13), an upper conductor circuit was formed to obtain a multilayer wiring board. However, Sn substitution was not performed (see FIGS. 14 to 19).
[0081]
(15) Next, apply the D solder resist composition (viscosity: 3.0 Pa · s) to both sides of the multilayer wiring board obtained in (14) above with a roll coater, and dry at 60 ° C. for 30 minutes. A lower solder resist layer (thickness: 16 μm) was formed.
Furthermore, a solder resist composition of E is applied onto this layer using a roll coater, dried at 60 ° C. for 30 minutes to form an upper solder resist layer (thickness 8 μm), and a two-layer solder resist Layered.
[0082]
(16) Next, a photomask film having a thickness of 5 mm on which a circular pattern (mask pattern) was drawn was placed in close contact, exposed to 1000 mJ / cm ² of ultraviolet light, and DMDG developed.
Further, heat treatment was performed at 80 ° C. for 1 hour, 100 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 3 hours, followed by etching by immersion in 800 g / l chromic acid aqueous solution for 19 minutes. Then, the resin remaining at the bottom of the opening was removed, and a solder resist layer (thickness 20 μm) 14 in which the solder pad portion was opened (opening diameter 200 μm) was formed.
[0083]
(17) Next, the substrate on which the solder resist layer 14 is formed is an electroless nickel plating solution having a pH of 5 comprising an aqueous solution of nickel chloride 30 g / l, sodium hypophosphite 10 g / l and sodium citrate 10 g / l. And a nickel plating layer 15 having a thickness of 5 μm was formed in the opening. Further, the substrate was applied to an electroless gold plating solution composed of an aqueous solution of potassium gold cyanide 2 g / l, ammonium chloride 75 g / l, sodium citrate 50 g / l and sodium hypophosphite 10 g / l at 93 ° C. A gold plating layer 16 having a thickness of 0.03 μm was formed on the nickel plating layer 15 by dipping for 23 seconds.
[0084]
(18) And, solder bumps (solder bodies) 17 were formed by printing solder paste in the openings of the solder resist layer 14 and reflowing at 200 ° C., and a printed wiring board having the solder bumps 17 was manufactured ( (See Figure 20).
[0085]
(Comparative Example 1)
A printed wiring board having solder bumps was produced in the same manner as in Example 1 except that only the lower solder resist layer was formed.
[0086]
(Comparative Example 2)
A printed wiring board having solder bumps was produced in the same manner as in Example 1 except that the following composition was used as the solder resist layer.
35 parts by weight of a photosensitizing oligomer (molecular weight 4000) obtained by acrylating 25% of an epoxy group of 80 wt% of a cresol novolac type epoxy resin (manufactured by Nippon Kayaku) dissolved in DMDG, an imidazole curing agent (manufactured by Shikoku Chemicals, 2E4MZ-CN) 2.0 parts by weight, polyacrylic monomer that is a photosensitive monomer (manufactured by Toagosei Co., Ltd., M-325), 4.0 parts by weight, antifoaming agent (Sannopco, S-65) 0.5 part by weight, and NMP 36.8 was added to these mixtures by adding 2.0 parts by weight of Irgacure I-907 (manufactured by Ciba Geigy) as a photoinitiator and 0.2 parts by weight of DETX-S (manufactured by Nippon Kayaku) as a photosensitizer. A solder resist composition having a viscosity adjusted to 3.0 ± 0.5 Pa · s at 25 ° C. was obtained by adding parts by weight.
Viscosity was measured with a B-type viscometer (Tokyo Keiki, DVL-B type) at 60 rpm with rotor No. 4 and at 6 rpm with rotor No. 3.
[0087]
(Comparative Example 3)
A printed wiring board having solder bumps was produced in the same manner as in Example 1 except that only the upper solder resist layer was formed.
[0088]
Thus, when manufacturing a printed wiring board, the presence or absence of the development remaining of the opening bottom part in a soldering resist layer and the presence or absence of surface roughness were investigated.
Moreover, about the printed wiring board manufactured in this way, the heat cycle test was implemented 1000 times at -55-125 degreeC, and the presence or absence of the crack generation in a soldering resist layer was confirmed with the optical microscope.
These results are shown in Table 1.
[0089]
As is apparent from the results shown in this table, in the configuration of this example, there was no development residue (resin residue) in the opening, the surface of the solder resist layer was smooth, and the resistance to heat cycle was excellent.
[0090]
[Table 1]

[0091]
【The invention's effect】
As described above, according to the present invention, even if a development failure occurs when forming an opening in the solder resist layer, the resin remaining at the bottom of the opening is reliably ensured without causing surface roughness of the solder resist layer. Etching can be removed.
Moreover, since the solder resist layer constituting the printed wiring board of the present invention is mainly composed of a resin composite of an acrylate of a novolac type epoxy resin and a thermoplastic resin, the coefficient of thermal expansion of the solder resist layer is low, and the conductor The generation of cracks due to the difference in thermal expansion coefficient with the layer can be suppressed, and a printed wiring board excellent in crack resistance under heat cycle conditions can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a manufacturing process of a printed wiring board according to the present invention.
FIG. 2 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 3 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 4 is a view showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 5 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 6 is a view showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 7 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 8 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 9 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 10 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 11 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 12 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 13 is a view showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 14 is a view showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 15 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 16 is a view showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 17 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 18 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 19 is a view showing one manufacturing process of the printed wiring board according to the present invention.
FIG. 20 is a diagram showing a manufacturing process of the printed wiring board according to the present invention.
[Explanation of symbols]
1 Substrate 2 Resin insulation layer
2a Insulation layer
2b Adhesive layer 3 Plating resist 4 Inner layer conductor circuit (Inner layer copper pattern)
5 Outer layer conductor circuit (outer layer copper pattern)
6 Via hole opening 7 Via hole 8 Copper foil 9 Through hole
10 Filling resin (resin filler)
11 Roughening layer
12 Electroless plating film
13 Electrolytic plating film Nickel plating layer
14 Solder resist layer
15 Nickel plating layer
16 Gold plating layer
17 Solder bump

Claims (9)

For the printed circuit board on which the conductor circuit is formed on the outermost resin insulation layer, the solder circuit layer is provided by covering the conductor circuit ,
The solder resist layer is composed of a composition mainly composed of a resin composite of a novolac type epoxy resin acrylate and a thermoplastic resin, and the lower layer is a resin composed of a novolac type epoxy resin acrylate and a thermoplastic resin. Consists of a composition in which heat-resistant resin particles soluble in an acid or an oxidant are dispersed in a matrix that is hardly soluble in an acid or an oxidant, the main component of which is a composite, and these compositions are cured. A printed wiring board formed from a composite layer . A wiring board having a conductor circuit formed on the outermost resin insulation layer is provided with a solder resist layer covering the conductor circuit and a part of the conductor circuit exposed from the opening provided in the solder resist layer is provided. In a printed wiring board formed as a pad and supplying and holding a solder body on the pad,
The solder resist layer is composed of a composition mainly composed of a resin composite of a novolac type epoxy resin acrylate and a thermoplastic resin, and the lower layer is a resin composed of a novolac type epoxy resin acrylate and a thermoplastic resin. Consists of a composition in which heat-resistant resin particles soluble in an acid or an oxidant are dispersed in a matrix that is hardly soluble in an acid or an oxidant, the main component of which is a composite , and these compositions are cured. A printed wiring board formed from a composite layer .   The printed wiring board according to claim 1, wherein the solder resist layer has an upper layer / lower layer thickness ratio of 1/1 to 1/3 in an upper layer / lower layer.   The printed wiring board according to claim 1, wherein a blending ratio of the thermoplastic resin is 50 wt% or less.   The printed wiring board according to claim 1, wherein the thermoplastic resin is polyether sulfone (PES).   The printed wiring board according to any one of claims 1 to 5, wherein a blending ratio of the heat-resistant resin particles is 5 to 40 wt%.   The printed wiring board according to any one of claims 1 to 6, wherein a thermal expansion coefficient of the lower solder resist layer is 40 to 50 ppm / ° C.   The printed wiring board according to claim 1, wherein a roughened layer is formed on a surface of the conductor circuit.   The printed wiring board according to claim 8, wherein the roughened layer is an alloy layer made of copper-nickel-phosphorus.

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