JP3815765B2 - Manufacturing method of multilayer printed wiring board - Google Patents

Description

【００１９】
このアルカリ難溶性金属層２の厚さは、０．００５〜３．０μｍの範囲が好ましい。このアルカリ難溶性金属層２の厚さが０．００５μｍより薄いと該アルカリ難溶性金属層と熱硬化性樹脂層との密着強度が弱く、このため該アルカリ難溶性金属層上に形成される外層銅層７と熱硬化性樹脂層３との充分な密着強度が得られず、３．０μｍより厚すぎると炭酸ガスレーザによる穴開けが困難となる。
【００２０】
また、本発明ではアルカリ難溶性金属層２の外側にクロメート処理、さらにその外側にシランカップリング剤処理を行うと、熱硬化性樹脂３とアルカリ難溶性金属２を介した外層銅層７との接着強度をさらに高めることができる。さらに、銅箔１のアルカリ難溶性金属層２が設けられていない面（たとえばシャイン面）上に亜鉛、錫、ニッケル、クロメートやイミダゾール、アミノトリアゾール、ベンゾトリアゾールなどの防錆処理を施すことができる。
【００２１】
次に、このように銅箔の表面に電着されたアルカリ難溶性金属層２の表面に熱硬化性樹脂ワニスを塗布して熱硬化性樹脂３を形成した後、該熱硬化性樹脂を１４０〜１５０℃で５〜２０分間加熱し、半硬化状態にして、複合銅箔を得る。この熱硬化性樹脂ワニスのベース樹脂としては、エポキシ樹脂（油化シェル（株）製エピコート１００１）などを用いることができる。この熱硬化性樹脂３を形成するための熱硬化性樹脂ワニスとしては、エポキシ樹脂に、硬化剤としてジシアンジアミド、硬化促進剤として２Ｅ４ＭＺ（四国化成（株）製）、溶剤としてメチルエチルケトンを用いてこれらを適宜混合して得たエポキシ樹脂組成物を用いることができる。この熱硬化性樹脂層としては、熱硬化性樹脂をガラスクロス、アラミドペーパーなどの繊維基材に含浸半硬化させたプリプレグまたは熱硬化性樹脂フィルムを使用してもよい。この半硬化状態の熱硬化性樹脂３の厚さとしては、２０〜２００μｍの範囲が好ましい。この熱硬化性樹脂３の厚さが２０μｍより薄いと層間絶縁性および充分な密着強度が得られず、また、２００μｍより厚すぎると小径のバイアホールが形成しにくくなり好ましくない。
【００２２】
このように熱硬化樹脂層３を半硬化状態にした樹脂付き複合銅箔を、樹脂側を接着面として、内層回路を有する内層樹脂基板の片面または両面に配置した後、１５０〜２００℃で加熱成型して積層して、内層回路入り多層板を得る（図１（ａ））。
【００２３】
次に、このように積層された内層回路入り多層板をアルカリエッチングによりアルカリ難溶性金属層を選択的に残して表面の銅箔を除去する（図１（ｂ））。このようなアルカリエッチング液としては、例えば、ＮＨ₄ＯＨ２００〜２５０ｇ／Ｌ、ＮＨ₄Ｃ１１３０〜１６０ｇ／Ｌ、Ｃｕ１５０〜１６０ｇ／Ｌを含む溶液を用いて、温度４０〜５０℃で行う。アルカリ難溶性金属２の表面形状は、アルカリ難溶性金属が電着される銅箔面により異なるが、銅箔面としては、銅箔粗化面の使用が好ましい。このような銅箔粗化面にアルカリ難溶性金属を電着すると、アルカリ難溶性金属２の表面は銅箔粗化面の転写となるためレーザビームが吸収されやすい凹凸に富んだ表面となり、レーザ穴開けが容易となる。
【００２４】
次いで、表面の銅箔層が除去された図１（ｂ）に示された内層回路入り多層板にレーザビームを照射してアルカリ難溶性金属層２と樹脂層３を同時に穴開けしてバイアホール６を形成して穴開き多層板（ａ）を製造する（図１（ｃ））。本発明に用いられるレーザの種類は、炭酸ガスレーザである。レーザビームを照射し、穴開け後、必要に応じてデスミア処理を行っても良い。
【００２５】
このようにバイアホールが形成された内層回路入り多層板（ａ）の表面上に、ピロリン酸銅メッキ溶液（奥野製薬（株）製ＯＰＣ−７５０無電解銅メッキ溶液）を用いて液温２０〜２５℃で１５〜２０分間の無電解メッキを行い、約０．１ミクロンのメッキ層を形成する。このメッキ層はバイアホールの絶縁樹脂層表面にも形成される。さらに、この無電解銅メッキ表面に銅３０〜１００ｇ／Ｌ、硫酸５０〜２００ｇ／Ｌを含む溶液を用いて、温度３０〜８０℃、陰極電流密度１０〜１００Ａ／ｄｍ²で電解メッキを行い、５〜３５μｍの銅メッキ層７を形成する（図１（ｄ））。この銅メッキ層７はバイアホールの絶縁樹脂層表面にも形成される。絶縁樹脂と強固な接着力を有するアルカリ難溶性金属２上に銅メッキ層７を形成させると、この外層銅層７とアルカリ難溶性金属層２には結合力があるため、外層銅層７を樹脂層３に直接メッキする場合と比べ、絶縁樹脂層と外層銅層との間に高い接着強度が得られる。
【００２６】
このようにして形成された外層銅層７の表面に、定法に従い、フォトレジストとしてマイクロポジット２４００（シプレー（株）製）を約７μｍ塗布して乾燥後、このフォトレジスト面に露光機により、所定の回路を形成したマスクを用いて露光部と非露光部を形成する。露光後、ＫＯＨ１０％溶液により現像してレジストパターン９を形成する（図１（ｅ））。次いで、塩化第二銅（ＣｕＣｌ₂）１００ｇ／Ｌ、遊離塩酸濃度１００ｇ／Ｌを含む溶液を用いて、温度５０℃で酸エッチングを行い、アルカリ難溶性金属層２と外層銅層７の一部を溶解して、内層回路４上のパッド１０と接続された外層回路８を形成する。
【００２７】
最後に、ＮａＯＨ３％溶液を用いて温度５０℃で銅箔面に塗布したフォトレジストを溶解除去し、多層プリント配線板を作成する（図１（ｆ））。
【００２８】
本発明の場合、アルカリ難溶性金属層２の厚さは外層銅層７の厚さに比べ非常に薄く、金属箔の合計厚さが通常のサブトラクト法と比べ、通常使用する銅箔の厚さ（通常は１８μｍ）とアルカリ難溶性金属の厚さ（最大３μｍ）の差の分（１５μｍ以上）薄くなるため、エッチング性が著しく改善されファイン回路の形成が容易となる。
【００２９】
またもう一つの方法としては、図２に示すパターンメッキ法がある。図２（ａ）〜（ｃ）は、上記図１（ａ）〜（ｃ）と同様なものであって、バイアホール６が形成された内層回路入り多層板（ａ）の表面にフォトレジストをラミネートまたは塗布後、露光、現像してレジストパターン９を形成し、回路およびパッド１０とする部分のみアルカリ難溶性金属を露出させる（図２（ｄ））。次いで、前記方法と同様にして無電解メッキ、電解メッキを行い回路と同じ配置を有する銅層７を形成する（図２（ｅ））。メッキ終了後、フォトレジストをＮａＯＨ３％溶液を用いる通常の方法で溶解除去すると、外層回路８が形成されるとともに銅回路の間にアルカリ難溶性金属が残る（図２（ｆ））。
【００３０】
このアルカリ難溶性金属層は、外層回路８の銅の厚さと比べ極めて薄いため、塩化第二銅や塩化第二鉄などの通常の酸エッチング液で短時間処理して溶解させることができ、外層回路８を錫メッキで保護することなく、外層銅回路間のアルカリ難溶性金属層を除去することができる（図２（ｇ））。このようにして本発明では、アンダーカットを発生させずにファインパターンを精度よく形成することができる。
【００３１】
本発明は３層以上の多層の内層樹脂基板に対しても適用できる。また、積層、レーザ穴開け、メッキ、パターニングの工程を繰り返すことにより、レーザバイアを持つ層の多層化も可能であり、任意の層数の多層プリント配線板の製造に適用できる。
【００３２】
【実施例】
以下、実施例及び比較例に基づき本発明をさらに具体的に説明する。
実施例１
光沢面粗度（Ｒｚ）１．９μｍ、粗面粗度（Ｒｚ）５μｍを有する公称厚さ１８μｍの電解銅箔の光沢面に、銅１０ｇ／Ｌ、硫酸１００ｇ／Ｌ、温度４０℃の硫酸銅溶液中で、前記銅箔を陰極として３０Ａ／ｄｍ²の電流密度で５秒間、銅を片面に電着して粗化処理した。このように粗化処理した表面の粗度（Ｒｚ）は２．９μｍであった。
【００３３】
このように粗化処理した電解銅箔を陰極として、次に示す浴中で温度２０℃で電解処理を行い、錫メッキ（アルカリ難溶性金属）を施して錫層を形成した。処理面上の錫の量は、１．２ｇ／ｍ²（約０．２μｍ）であった。
【００３４】
【表２】

【００３５】
水洗後、錫メッキを施した表面に、さらに無水クロム酸２ｇ／Ｌ、ｐＨ１１．０の電解溶液を用いて、電流密度０．５Ａ／ｄｍ²で５秒間、電解クロメート処理を行い粗化処理された銅箔を得た。
【００３６】
この銅箔の粗化表面に、エポキシ樹脂（油化シェル（株）製エピコート１００１）１００部、硬化剤としてジシアンジアミド２．５部、促進剤として２Ｅ４ＭＺ（四国化成（株）製）０．２部をメチルエチルケトンの溶剤中で混合して得たエポキシ樹脂ワニスを７５μｍの厚みで塗布し、１３０℃で１０分間加熱して半硬化状態とした樹脂付きの複合銅箔を作成した。
【００３７】
両面に内層回路が形成され、黒化処理が施された０．５ｍｍ厚さのＦＲ−４基材（松下電工（株）製Ｒ−１７６６）をコアとして、この両面に前記樹脂付きの複合銅箔を樹脂面が内層回路側になるように積み重ね、１８０℃で６０分間、圧力２０ｋｇ／ｃｍ²で真空プレスを用いて成型し、図１（ａ）に示すような内層回路入り多層板を得た。
【００３８】
このように成形された内層回路入り多層板の銅箔面に、ＮＨ₄ＯＨ２００ｇ／Ｌ、ＮＨ₄Ｃｌ１３０ｇ／Ｌ、Ｃｕ１５０ｇ／Ｌを含む溶液を用いて、温度５０℃にてアルカリエッチングを行い、銅箔を除去して錫層（アルカリ難溶性金属層）を露出させた。
【００３９】
次に、このようにエッチング除去され、錫層が露出した面に炭酸ガスレーザ（レーザ出力６０Ｗ）により、レーザ径１００μｍで前記内層回路部分まで１００μｍφの穴開けを行い、バイアホールを形成して、図１（ｃ）に示すような穴開き多層板（ａ）を得た。
【００４０】
このようにバイアホールが形成された開口部を含む錫層の上にＯＰＣ−７５０無電解銅メッキ溶液（奥野製薬（株）製）を用いて液温２３℃で１８分間の無電解メッキを行い、約０．１ミクロンのメッキ厚とした。さらに、この無電解銅メッキ表面に銅１００ｇ／Ｌ、硫酸１５０ｇ／Ｌを含む溶液を用いて、温度２５℃で陰極電流密度５Ａ／ｄｍ²で電解メッキを行い、２０μｍメッキ厚の外層銅層を形成した。
【００４１】
このように形成された外層銅層の表面に、定法に従い、フォトレジストとしてマイクロポジット２４００（シプレー（株）製）を約７μｍ塗布して乾燥後、このフォトレジスト面に露光機により、所定の回路を形成したマスクを用いて露光部と非露光部を形成してレジストパターンを設けた。露光後、ＫＯＨ１０％溶液により現像し、塩化第二銅（ＣｕＣｌ₂）１００ｇ／Ｌ、遊離塩酸濃度１００ｇ／Ｌを含む溶液を用いて、温度５０℃で酸エッチングを行い外層回路を形成した。最後に、ＮａＯＨ５％溶液を用いて温度３０℃で外層回路上に残留したフォトレジストを除去し、多層プリント配線板を作成した。
【００４２】
このようにして得られた２０μｍ厚さの外層銅回路の多層プリント配線板からの引き剥がし強さ（ｋｇｆ／ｃｍ）をＪＩＳ−Ｃ６４８１法により測定した。得られた結果を表３に示す。
比較例１
銅箔１として通常の１８μｍ銅箔（三井金属鉱業製３ＥＣ−III）を使用し、アルカリ難溶性金属（錫）を電着させない以外は、実施例１と同様にしてエポキシ樹脂ワニスを粗面上に塗布し、１３０℃で１０分間加熱して半硬化状態とした樹脂付きの複合銅箔を作成した。
【００４３】
この樹脂付き銅箔を、両面に内層回路を形成し、黒化処理を施した０．５ｍｍ厚さのＦＲ−４内層回路基板をコアとして、この両面に前記樹脂付き銅箔を樹脂面が内層回路側になるように積み重ね、実施例１と同じ条件で成型し、内層回路入り多層板を得た。以後実施例１と同じ工程で多層プリント配線板を作成した。
【００４４】
このようにして得られた２０μｍ厚さの外層銅層の多層プリント配線板からの引き剥がし強さ（ｋｇｆ／ｃｍ）をＪＩＳ−Ｃ６４８１法により測定した。得られた結果を表３に示す。
比較例２
比較例１と同様の樹脂付きの銅箔を使用し、同様に成型して内層回路入り多層板を作成した。次に、レーザ加工前に穴開けする部分の銅箔に同じ直径の穴をエッチングにより形成し、以後、実施例１と同じ条件で加工して多層プリント配線板を作成した。ただし外層銅層は除去しなかった。
【００４５】
このようにして得られたトータル銅層の厚み３８μｍを有する外層回路の引き剥がし強さ（ｋｇｆ／ｃｍ）をＪＩＳ−Ｃ６４８１法により測定した。得られた結果を表３に示す。
【００４６】
【表３】

【００４７】
表３に示すように、実施例１では比較例１と比べて内層樹脂と外層回路の接着強度を高めることができ、かつ比較例２よりもファインな外層回路をエッチング加工することができる。
【００４８】
【発明の効果】
本発明の多層プリント配線板の製造方法によれば、従来の方法に比べて多層プリント配線板のレーザによるバイアホール形成を容易に行うことができ、かつ外層回路と絶縁樹脂との密着性が改善される。
【図面の簡単な説明】
【図１】 本発明の多層プリント配線板の製造工程を示す図である。
【図２】 本発明の多層プリント配線板の製造工程を示す図である。
【符号の説明】
１：銅箔
２：アルカリ難溶性金属
３：熱硬化性樹脂層
４：内層回路
５：内層樹脂層
６：バイアホール
７：外層銅層
８：外層回路
９：レジストパターン
10：パッド[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a multilayer printed wiring board, and in particular, an outer layer circuit that facilitates formation of a via hole by a laser at the time of manufacturing the multilayer printed wiring board and is formed from plated copper (copper layer), and the outer layer circuit The present invention relates to a method for manufacturing a multilayer printed wiring board having improved adhesion with an insulating resin (thermosetting insulating resin) existing between inner layer circuits.
[0002]
[Prior art]
In order to meet the demands for smaller, lighter, and higher performance electronic devices, multilayer printed wiring boards are required to have a reduced circuit width and smaller via holes. Drilling holes with a diameter of 200 μm or less is difficult by mechanical drilling, and recently lasers have been widely used.
[0003]
Among various types of lasers, carbon dioxide lasers can drill holes in organic materials such as epoxy resins and polyimide resins at high speed, and are most frequently used industrially for printed wiring. Due to reflection, it is difficult to perforate thick copper foil. Therefore, as disclosed in Japanese Patent Laid-Open No. 4-3676, the copper foil is removed by etching only in the hole portion having the same size as the via hole diameter, and then the laser beam is irradiated to the same position. It is necessary to make a hole. The diameter of the laser beam used at this time is larger than the diameter of the via hole.
[0004]
[Problems to be solved by the invention]
In the method of performing window opening etching on a multilayer board in which normal copper foil with resin is bonded to both surfaces of the inner resin board and then irradiating with a laser beam, plating must be applied on the thickness of the copper foil. Therefore, the thickness of the outer copper layer is the sum of the thickness of the original copper foil and the thickness of the plated copper, and it is not easy to obtain a fine circuit by etching for circuit formation. In addition, in order to etch the hole portion of the outer layer circuit in accordance with the position of the inner layer circuit, special high accuracy is required for the alignment, and it is not easy.
[0005]
On the other hand, there is also a method in which an insulating resin is coated on both surfaces of an inner layer insulating resin substrate on which an inner layer circuit is formed, and after drilling with a laser, copper plating is directly applied to the resin surface to form an outer layer copper layer. In this case, only the copper layer is applied. In such a case, in order to obtain adhesion strength between the copper layer and the insulating resin formed by coating the insulating resin, the surface of the insulating resin must be roughened, and the surface of the insulating resin is further roughened. However, the adhesion strength with the insulating resin is often insufficient.
[0006]
The present invention solves these problems of the prior art, facilitates the formation of a via hole by a laser at the time of manufacturing a multilayer printed wiring board, and improves the adhesion between the outer layer circuit and the insulating resin. It is to provide a manufacturing method.
[0007]
[Means for Solving the Problems]
As a result of intensive research on the problems of the above prior art, the present inventors have electrodeposited a hardly alkaline metal that dissolves in a normal acidic etching solution but does not dissolve in an alkaline etching solution on the surface of the copper foil. By solving this problem of the prior art, it was found that a multilayer printed wiring board that facilitates via hole formation by a laser of the multilayer printed wiring board and improved adhesion between the outer circuit and the insulating resin can be obtained, The present invention has been completed.
[0008]
That is, in the method for producing a multilayer printed wiring board according to the present invention, a surface of a copper foil is electrodeposited with a hardly alkali-soluble metal that is soluble in an acid etching solution, and then a thermosetting resin is applied to the surface. The thermosetting resin is heated to a semi-cured state to form a composite copper foil, and the resin side of the composite copper foil is used as an adhesive surface and disposed on one or both sides of an inner layer resin substrate having an inner layer circuit on one or both sides. post-heated molded by laminating, the alkali-soluble metal layer selectively left by removing the copper foil surface by alkali etching, and then the thermosetting and the alkali-soluble metal layer by irradiating a carbon dioxide gas laser beam And forming a copper layer by electroplating after electroless plating or by electroless plating after forming a hole in the conductive resin layer at the same time, thereby forming an outer layer circuit connected to the inner layer circuit. It is intended.
[0009]
As the copper foil surface on which the alkali-soluble metal is electrodeposited, 1) a glossy surface, 2) a matte surface, 3) a roughened glossy surface, or 4) a roughened matte surface is used.
[0010]
According to such a method, via holes can be easily formed in a multilayer printed wiring board by a laser beam, an outer layer circuit formed of a copper layer, and an insulating resin existing between the outer layer circuit and the inner layer circuit The adhesive force between the two can be improved.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the manufacturing method of the multilayer printed wiring board of this invention is demonstrated in more detail using FIGS.
[0012]
As the copper foil, either an electrolytic copper foil or a rolled copper foil can be used, but the case where an electrolytic copper foil is used will be described below.
[0013]
FIG. 1 is a diagram showing a manufacturing process of a multilayer printed wiring board by a panel plating method in the present invention. FIG. 2 is a diagram showing a manufacturing process of a multilayer printed wiring board by a pattern plating method in the present invention. 1 and 2, 1 is a copper foil, 2 is a hardly alkali-soluble metal, 3 is a thermosetting insulating resin, 4 is an inner layer circuit, 5 is an inner layer resin layer, 6 is a via hole, 7 is an outer layer copper layer, Reference numeral 8 denotes an outer layer circuit, 9 denotes a resist pattern, and 10 denotes a pad.
[0014]
In the production of the multilayer printed wiring board of the present invention, first, the alkali poorly soluble metal 2 is applied on the surface of the copper foil 1 (glossy surface, mat surface, roughened glossy surface or roughened matte surface). Electrodeposit. The roughness (Rz) of the copper foil surface on which the hardly alkali-soluble metal 2 is electrodeposited is 0.5 to 15 μm, preferably 2.5 to 15 μm. If the roughness of the copper foil surface is less than 0.5 μm, it is not preferable in that the adhesion strength between the alkali-insoluble metal and the thermosetting resin is insufficient. This is not preferable in that it easily causes a cutting phenomenon.
[0015]
The roughening treatment of the copper foil is performed, for example, on the glossy surface or matte surface of the copper foil 1 in a copper sulfate solution of copper 10 to 20 g / L, sulfuric acid 30 to 100 g / L, and temperature 20 to 40 ° C. It can be performed by electrodepositing copper on one side for 5 to 20 seconds at a current density of 30 to 50 A / dm ² using the foil as a cathode.
[0016]
The thickness of the copper foil 1 to be used is preferably in the range of 5 to 100 μm. If the copper foil is thicker than 100 μm, it takes time to etch, causing a problem in productivity. On the other hand, when the copper foil is too thin than 5 μm, production as a copper foil is difficult.
[0017]
Next, in the present invention, an alkali poorly soluble metal 2 that is dissolved in a normal acidic etching solution but not dissolved in an alkaline etching solution is electrodeposited on the surface of the copper foil 1. In the present invention, various alkali-insoluble and acid-soluble metals can be used. Examples of the alkali-insoluble metal 2 include tin, nickel and cobalt, tin-zinc alloy, zinc-nickel alloy and tin-copper. An alloy such as an alloy is exemplified, and among these, one selected from the group consisting of tin, zinc-tin alloy, zinc-nickel alloy and tin-copper alloy is preferable, and tin and tin-zinc alloy are resistant to alkali etching. And most preferred. As a method for forming the alkali poorly soluble metal layer 2, electrolytic treatment is performed in a bath shown below as a tin plating bath composition using a copper foil as a cathode.
[0018]
[Table 1]

[0019]
The thickness of the alkali hardly soluble metal layer 2 is preferably in the range of 0.005 to 3.0 μm. If the thickness of the hardly alkali-soluble metal layer 2 is less than 0.005 μm, the adhesion strength between the hardly alkali-soluble metal layer and the thermosetting resin layer is weak, and therefore the outer layer formed on the hardly alkali-soluble metal layer. Sufficient adhesion strength between the copper layer 7 and the thermosetting resin layer 3 cannot be obtained, and if it is thicker than 3.0 μm, it is difficult to make a hole with a carbon dioxide laser.
[0020]
Further, in the present invention, when the chromate treatment is performed on the outer side of the alkali poorly soluble metal layer 2 and further the silane coupling agent treatment is performed on the outer side, the outer layer copper layer 7 via the thermosetting resin 3 and the alkali poorly soluble metal 2 is formed. The adhesive strength can be further increased. Further, the surface of the copper foil 1 on which the hardly alkali-soluble metal layer 2 is not provided (for example, the shine surface) can be subjected to rust prevention treatment such as zinc, tin, nickel, chromate, imidazole, aminotriazole, and benzotriazole. .
[0021]
Next, a thermosetting resin varnish is applied to the surface of the alkali poorly soluble metal layer 2 electrodeposited on the surface of the copper foil in this manner to form the thermosetting resin 3, and then the thermosetting resin 140 is added. It heats at -150 degreeC for 5 to 20 minutes, makes it a semi-hardened state, and obtains composite copper foil. An epoxy resin (Epicoat 1001 manufactured by Yuka Shell Co., Ltd.) or the like can be used as the base resin of the thermosetting resin varnish. As the thermosetting resin varnish for forming this thermosetting resin 3, dicyandiamide is used as an epoxy resin, 2E4MZ (manufactured by Shikoku Kasei Co., Ltd.) as a curing agent, and methyl ethyl ketone as a solvent. An epoxy resin composition obtained by appropriately mixing can be used. As this thermosetting resin layer, a prepreg or thermosetting resin film obtained by impregnating and semi-curing a fiber base material such as glass cloth or aramid paper with a thermosetting resin may be used. The thickness of the semi-cured thermosetting resin 3 is preferably in the range of 20 to 200 μm. When the thickness of the thermosetting resin 3 is less than 20 μm, interlayer insulation and sufficient adhesion strength cannot be obtained, and when the thickness is more than 200 μm, it is difficult to form a small diameter via hole.
[0022]
After placing the resin-coated composite copper foil in which the thermosetting resin layer 3 is in a semi-cured state in this way on one side or both sides of the inner layer resin substrate having the inner layer circuit with the resin side as an adhesive surface, heat at 150 to 200 ° C. Molding and lamination are performed to obtain a multilayer board with an inner circuit (FIG. 1A).
[0023]
Next, the copper foil on the surface is removed by selectively leaving the hardly alkali-soluble metal layer by alkali etching of the multilayer board with the inner layer circuit thus laminated (FIG. 1B). Examples of such an alkali etching solution, for example, by using _{NH 4 OH200~250g / L, NH 4} C1130~160g / L, a solution containing Cu150~160g / L, carried out at a temperature 40 to 50 ° C.. Although the surface shape of the alkali poorly soluble metal 2 varies depending on the copper foil surface on which the alkali hardly soluble metal is electrodeposited, it is preferable to use a roughened copper foil surface as the copper foil surface. When electrodepositing a hardly alkali-soluble metal on such a roughened copper foil surface, the surface of the hardly alkali-soluble metal 2 becomes a transfer of the roughened copper foil surface, so that a laser beam is easily absorbed and the surface is rich in irregularities. Drilling is easy.
[0024]
Next, the multilayer board with an inner layer circuit shown in FIG. 1B from which the copper foil layer on the surface has been removed is irradiated with a laser beam to simultaneously drill the alkali-insoluble metal layer 2 and the resin layer 3 to form a via hole. 6 is formed to produce a perforated multilayer board (a) (FIG. 1C). The type of laser used in the present invention is a carbon dioxide laser . After irradiating with a laser beam and making a hole, desmear treatment may be performed as necessary.
[0025]
On the surface of the multilayer board (a) with inner layer circuits in which via holes are formed in this way, using a pyrophosphoric acid copper plating solution (OPC-750 electroless copper plating solution manufactured by Okuno Pharmaceutical Co., Ltd.), a liquid temperature of 20 to Electroless plating is performed at 25 ° C. for 15 to 20 minutes to form a plating layer of about 0.1 microns. This plated layer is also formed on the surface of the insulating resin layer in the via hole. Furthermore, electrolytic plating is performed at a temperature of 30 to 80 ° C. and a cathode current density of 10 to 100 A / dm ² using a solution containing copper 30 to 100 g / L and sulfuric acid 50 to 200 g / L on the electroless copper plating surface. A copper plating layer 7 having a thickness of 5 to 35 μm is formed (FIG. 1D). The copper plating layer 7 is also formed on the surface of the insulating resin layer in the via hole. When the copper plating layer 7 is formed on the insulating resin and the alkali poorly soluble metal 2 having a strong adhesive force, the outer copper layer 7 and the alkali hardly soluble metal layer 2 have a bonding force. Compared to the case where the resin layer 3 is directly plated, a higher adhesive strength can be obtained between the insulating resin layer and the outer copper layer.
[0026]
According to a conventional method, about 7 μm of microposit 2400 (manufactured by Shipley Co., Ltd.) is applied as a photoresist on the surface of the outer copper layer 7 formed in this way and dried. An exposed portion and a non-exposed portion are formed using a mask on which the circuit is formed. After the exposure, the resist pattern 9 is formed by developing with a 10% KOH solution (FIG. 1 (e)). Next, acid etching is performed at a temperature of 50 ° C. using a solution containing cupric chloride (CuCl ₂ ) 100 g / L and free hydrochloric acid concentration 100 g / L, and a part of the alkali poorly soluble metal layer 2 and a part of the outer copper layer 7 The outer layer circuit 8 connected to the pad 10 on the inner layer circuit 4 is formed.
[0027]
Finally, the photoresist applied to the copper foil surface is dissolved and removed using a NaOH 3% solution at a temperature of 50 ° C. to produce a multilayer printed wiring board (FIG. 1F).
[0028]
In the case of the present invention, the thickness of the hardly alkali-soluble metal layer 2 is very thin compared to the thickness of the outer copper layer 7, and the total thickness of the metal foil is the thickness of the copper foil that is normally used compared to the normal subtract method. (Normally 18 μm) and the thickness (15 μm or more) of the difference between the thickness of alkali-insoluble metal (maximum 3 μm) and the thickness become thinner (15 μm or more).
[0029]
As another method, there is a pattern plating method shown in FIG. 2 (a) to 2 (c) are the same as FIGS. 1 (a) to 1 (c), and a photoresist is applied to the surface of the multilayer board (a) with an inner layer circuit in which the via holes 6 are formed. After laminating or coating, the resist pattern 9 is formed by exposure and development, and the alkali-insoluble metal is exposed only in the circuit and the pad 10 (FIG. 2D). Next, electroless plating and electrolytic plating are performed in the same manner as described above to form a copper layer 7 having the same arrangement as the circuit (FIG. 2 (e)). When the photoresist is dissolved and removed by an ordinary method using a NaOH 3% solution after the plating is finished, an outer layer circuit 8 is formed and an alkali hardly soluble metal remains between copper circuits (FIG. 2 (f)).
[0030]
Since this hardly alkali-soluble metal layer is extremely thin compared to the copper thickness of the outer layer circuit 8, it can be dissolved by treating with a normal acid etching solution such as cupric chloride or ferric chloride for a short time. Without protecting the circuit 8 with tin plating, the alkali-insoluble metal layer between the outer layer copper circuits can be removed (FIG. 2G). Thus, in the present invention, a fine pattern can be formed with high accuracy without causing undercut.
[0031]
The present invention can also be applied to a multi-layer inner resin substrate having three or more layers. Further, by repeating the steps of laminating, laser drilling, plating, and patterning, the layers having laser vias can be multi-layered and can be applied to the production of a multilayer printed wiring board having an arbitrary number of layers.
[0032]
【Example】
Hereinafter, the present invention will be described more specifically based on examples and comparative examples.
Example 1
On the glossy surface of an electrolytic copper foil having a glossy surface roughness (Rz) of 1.9 μm and a roughness surface roughness (Rz) of 5 μm, copper 10 g / L, sulfuric acid 100 g / L, and copper sulfate at a temperature of 40 ° C. In the solution, the copper foil was used as a cathode, and copper was electrodeposited on one side at a current density of 30 A / dm ² for 5 seconds for roughening treatment. The roughness (Rz) of the surface thus roughened was 2.9 μm.
[0033]
Using the electrolytic copper foil thus roughened as a cathode, electrolytic treatment was performed at a temperature of 20 ° C. in the following bath, and tin plating (alkali hardly soluble metal) was applied to form a tin layer. The amount of tin on the treated surface was 1.2 g / m ² (about 0.2 μm).
[0034]
[Table 2]

[0035]
After washing with water, the surface subjected to tin plating is further subjected to roughening treatment by electrolytic chromate treatment for 5 seconds at a current density of 0.5 A / dm ² using an electrolytic solution of chromic anhydride 2 g / L and pH 11.0. A copper foil was obtained.
[0036]
On the roughened surface of the copper foil, 100 parts of epoxy resin (Epicoat 1001 manufactured by Yuka Shell Co., Ltd.), 2.5 parts of dicyandiamide as a curing agent, and 0.2 part of 2E4MZ (manufactured by Shikoku Chemicals Co., Ltd.) An epoxy resin varnish obtained by mixing in a solvent of methyl ethyl ketone was applied in a thickness of 75 μm, and heated at 130 ° C. for 10 minutes to produce a semi-cured composite copper foil with a resin.
[0037]
A composite copper with resin on both sides, with a 0.5 mm thick FR-4 base material (R-1766 manufactured by Matsushita Electric Works Co., Ltd.) with inner layer circuits formed on both sides and blackened. The foil is stacked so that the resin surface is on the inner layer circuit side, and molded at 180 ° C. for 60 minutes using a vacuum press at a pressure of 20 kg / cm ² to obtain a multilayer board with an inner layer circuit as shown in FIG. It was.
[0038]
Copper foil surface of the thus molded inner layer circuit containing the multilayer board, with _{NH 4 OH200g / L, NH 4} Cl130g / L, a solution containing Cu150g / L, Alkali etching at temperature 50 ° C., copper The foil was removed to expose the tin layer (alkali poorly soluble metal layer).
[0039]
Next, a hole having a diameter of 100 μm is drilled to the inner layer circuit portion with a carbon dioxide laser (laser output 60 W) on the surface where the tin layer is exposed by etching in this way, thereby forming a via hole. A perforated multilayer board (a) as shown in 1 (c) was obtained.
[0040]
Electroless plating is performed for 18 minutes at a liquid temperature of 23 ° C. using an OPC-750 electroless copper plating solution (Okuno Pharmaceutical Co., Ltd.) on the tin layer including the opening in which the via hole is formed. The plating thickness was about 0.1 microns. Further, using an electroless copper plating surface with a solution containing 100 g / L of copper and 150 g / L of sulfuric acid, electrolytic plating is performed at a temperature of 25 ° C. and a cathode current density of 5 A / dm ² to form an outer copper layer having a thickness of 20 μm. Formed.
[0041]
According to a conventional method, about 7 μm of microposit 2400 (manufactured by Shipley Co., Ltd.) is applied to the surface of the outer copper layer formed in this way and dried, and then a predetermined circuit is formed on the photoresist surface by an exposure machine. An exposed portion and a non-exposed portion were formed using a mask formed with a resist pattern. After the exposure, development was performed with a 10% KOH solution, and acid etching was performed at a temperature of 50 ° C. using a solution containing cupric chloride (CuCl ₂ ) 100 g / L and free hydrochloric acid concentration 100 g / L to form an outer layer circuit. Finally, the photoresist remaining on the outer layer circuit was removed using a NaOH 5% solution at a temperature of 30 ° C. to produce a multilayer printed wiring board.
[0042]
The peel strength (kgf / cm) of the 20 μm-thick outer layer copper circuit thus obtained from the multilayer printed wiring board was measured by the JIS-C6481 method. The obtained results are shown in Table 3.
Comparative Example 1
A normal 18 μm copper foil (3EC-III made by Mitsui Mining & Mining) was used as the copper foil 1 and the epoxy resin varnish was coated on the rough surface in the same manner as in Example 1 except that an alkali poorly soluble metal (tin) was not electrodeposited. A composite copper foil with a resin that was heated to 130 ° C. for 10 minutes to be in a semi-cured state was prepared.
[0043]
With this resin-coated copper foil, an inner layer circuit is formed on both sides, and a blackened FR-4 inner layer circuit board with a thickness of 0.5 mm is used as a core. They were stacked so as to be on the circuit side and molded under the same conditions as in Example 1 to obtain a multilayer board with an inner layer circuit. Thereafter, a multilayer printed wiring board was prepared by the same process as in Example 1.
[0044]
The peel strength (kgf / cm) of the 20 μm-thick outer layer copper layer thus obtained from the multilayer printed wiring board was measured by the JIS-C6481 method. The obtained results are shown in Table 3.
Comparative Example 2
The same resin-coated copper foil as in Comparative Example 1 was used and molded in the same manner to prepare a multilayer board with an inner layer circuit. Next, a hole having the same diameter was formed by etching in the copper foil in the portion to be drilled before laser processing, and thereafter processed under the same conditions as in Example 1 to produce a multilayer printed wiring board. However, the outer copper layer was not removed.
[0045]
The peel strength (kgf / cm) of the outer layer circuit having a total copper layer thickness of 38 μm thus obtained was measured by the JIS-C6481 method. The obtained results are shown in Table 3.
[0046]
[Table 3]

[0047]
As shown in Table 3, in Example 1, the adhesive strength between the inner layer resin and the outer layer circuit can be increased as compared with Comparative Example 1, and the outer layer circuit finer than Comparative Example 2 can be etched.
[0048]
【The invention's effect】
According to the method for producing a multilayer printed wiring board of the present invention, via holes can be easily formed by a laser on the multilayer printed wiring board and the adhesion between the outer layer circuit and the insulating resin is improved as compared with the conventional method. Is done.
[Brief description of the drawings]
FIG. 1 is a diagram showing a manufacturing process of a multilayer printed wiring board according to the present invention.
FIG. 2 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.
[Explanation of symbols]
1: Copper foil 2: Alkali poorly soluble metal 3: Thermosetting resin layer 4: Inner layer circuit 5: Inner layer resin layer 6: Via hole 7: Outer layer copper layer 8: Outer layer circuit 9: Resist pattern
10: Pad

Claims (10)

After electrodepositing a hardly alkali-soluble metal that is soluble in an acid etching solution but hardly soluble in an alkali etching solution on the surface of the copper foil, a thermosetting resin is applied to the surface, and the thermosetting resin is applied. The composite copper foil is formed in a semi-cured state by heating, the resin side of the composite copper foil is used as the adhesive surface, and the resin layer is placed on one or both sides of the inner layer resin substrate having the inner layer circuit on one side or both sides, and then heat molded. stacked, the alkali-soluble metal layer selectively left by removing the copper foil surface by alkali etching, and then the thermosetting resin layer and the alkali-soluble metal layer by irradiating a carbon dioxide laser beams simultaneously Manufacturing a multilayer printed wiring board characterized by forming a perforated multilayer board (a) by forming a hole and then forming a copper layer on the multilayer board to form an outer layer circuit connected to the inner layer circuit Method. A copper layer is formed on the perforated multilayer board (a), and then a resist is applied and then a resist pattern is formed, and then acid etching is performed to remove a part of the outer layer copper layer and the alkali poorly soluble metal. The method for producing a multilayer printed wiring board according to claim 1, wherein a circuit is formed. After applying a resist on the perforated outer layer plate (a), a resist pattern is formed, and a copper layer is formed between the resist patterns and on the perforated resin surface. The method for producing a multilayer printed wiring board according to claim 1, wherein the outer layer circuit connected to the inner layer circuit is formed by removing the soluble metal layer. 2. The method according to claim 1, wherein a roughness Rz of the surface of the copper foil on which the alkali-soluble metal is electrodeposited is 0.5 to 15 μm. 5. The method according to claim 1, wherein the copper foil has a thickness of 5 to 100 μm, and the alkali hardly soluble metal layer has a thickness of 0.005 to 3.0 μm. 6. The method according to claim 1, wherein the hardly alkali-soluble metal is one selected from the group consisting of tin, zinc-tin alloy, zinc-nickel alloy and tin-copper alloy. The method according to claim 1, wherein the copper foil is an electrolytic copper foil or a rolled copper foil. The method according to claim 1, further comprising a chromate layer provided on the alkali-insoluble metal layer of the composite copper foil. The method according to any one of claims 1 to 6, wherein a prepreg or a thermosetting resin film in which a fiber base material is impregnated with a thermosetting resin is used instead of the thermosetting resin layer. A multilayer printed wiring board manufactured by the method according to claim 1.

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