JP2004006613A - Copper foil for printed wiring board and its producing method, and copper clad laminate employing copper foil for printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper foil for making a hole directly by carbon dioxide gas laser under a state where an auxiliary metal layer of nickel and a coating of an organic material for enhancing absorption of laser light are not present on the surface of the outer layer copper foil of a copper clad laminate. <P>SOLUTION: In the copper foil for producing a printed wiring board having a roughened surface on one side of a bulk copper layer, the bulk copper layer is composed of a high carbon content copper containing carbon by 0.03-0.40 wt.%. <P>COPYRIGHT: (C)2004,JPO

Description

【００２３】
この表１から分かるように、試料番号１に相当する純銅層の炭素含有量は０．００３ｗｔ％と測定されており、炭素含有量が０．０１５ｗｔ％〜０．４０ｗｔ％の高炭素含有銅とが掲載されている。これらのレーザー穴明け加工性を対比すると、高炭素含有銅中の炭素含有量が０．０３ｗｔ％を越えたところから、レーザー穴明け加工性が著しく改善していると考えられるのである。即ち、４００穴中の殆どが良好に穴明け加工されているのである。従って、高炭素含有銅中の炭素含有量が０．０３ｗｔ％を下限値としているのである。そして、ここで上限値を０．４０ｗｔ％としているのは、以下の製造方法の中で説明するが、この炭素含有量を越えて炭素を含有させることは非常に困難となるのである。
【００２４】
一方で、以上の述べてきたバルク銅層の全てを高炭素含有銅で構成した銅箔の場合には、熱伝導性が純銅に比べて低くなると同時に、電気的抵抗値が上昇することが考えられるための、欠点が想定できる。即ち、回路設計によっては、使用可能な場面が限定されてくる可能性がある。特に、現段階に置いて問題がないとしても、コンピュータのクロック周波数がＧＨｚレベルで高速化するようになっており、高周波用途での発熱問題、信号伝達の遅延等を引き起こす事も考えられる。
【００２５】
そこで、他の請求項に記載した「バルク銅層の片面側に粗化処理面を設け、他面側に光沢面を備えるプリント配線板製造用の銅箔であって、バルク銅層は、粗化処理面の反対面側に炭素含有量が０．０８ｗｔ％〜０．４０ｗｔ％である０．１μｍ〜５μｍの厚さの高炭素含有銅層を備え、当該高炭素含有銅層の下に純銅層を備えることを特徴とするプリント配線板用銅箔。」を用いることで上述の問題を解決することが可能となる。この銅箔を模式的に示したのが、図２である。
【００２６】
即ち、このプリント配線板用銅箔は、バルク銅層の粗化処理面の反対面側の０．１μｍ〜５μｍの厚さ分のみを高炭素含有銅層として、バルク銅層のその他部分を純銅層としたものである。このような層構成を採用することで、銅張積層板の状態でのレーザー穴明け加工が終了する迄、高炭素含有銅層を残し、その後のメッキ処理を行う前の、銅張積層板の表面の整面処理の段階で、高炭素含有銅層のみを除去するのである。即ち、化学的エッチング処理又はバフ研磨処理等の物理処理若しくはこれらの処理を組みあわせて用いることで、高炭素含有銅層のみを容易に除去することが出来るのである。この高炭素含有銅層を除去することが出来れば、純銅の層のみが銅張積層板に残ることになり、最終的に形成する導電回路の電気抵抗の阻害要因となるものは存在しないことになるのである。
【００２７】
ここで、銅箔表面に所定厚の高炭素含有銅層を設けた場合のレーザー加工理論を考える。　ここで銅とニッケルとの熱伝導性能は、純銅の熱伝導率が７００℃において３５４Ｗ・ｍ^−１・Ｋ^−１、高炭素含有銅は７００℃において１００〜１８０Ｗ・ｍ^−１・Ｋ^−１であり、高炭素含有銅は純銅の熱伝導率の約１／３〜１／２であり、純銅と比べ熱の伝導性が極めて遅いものであった。従って、レーザー光が銅張積層板の銅箔の上に形成した高炭素含有銅層の表面に照射されると、高炭素含有銅層の照射部位のみに熱エネルギーが集中し、熱の拡散速度に比べ、レーザー光による熱エネルギーの供給速度の方が速く、レーザーの照射部位が容易に高炭素含有銅の融点に達するものと考えられる。
【００２８】
その結果、高炭素含有銅は純銅に比べ、レーザー光照射による温度上昇が素早く起こり、容易に溶解し、蒸発することになるものと考えられる。そして、レーザー光の照射により、高炭素含有銅層が一旦溶解を始め沸点に達すると、高炭素含有銅の沸点温度の熱量が熱の良導体である純銅層に伝達され、その純銅層に伝達された熱エネルギーは、銅箔表面が熱伝導性の低い高炭素含有銅で被覆されていることもあり散逸しにくく、連続したレーザー光照射による熱エネルギーの供給と併せて容易に純銅の溶解温度を越えた温度上昇が連続的に起こり、レーザー光による銅箔層の除去が容易に行えるものとなると考えられるのである。
【００２９】
表２には、上述してきたバルク銅層が高炭素含有銅層（約３μｍ）と純銅層（約９μｍ）とからなるプリント配線板用銅箔であって、公称厚さ１２μｍ厚さのものを、厚さ５０μｍのＦＲ−４プリプレグの両面にプレス加工することにより張り付け、両面銅張積層板を製造し、これを用いてサイクル法でのレーザー穴明け加工試験を行った結果を示している。なお、レーザー穴明け加工試験は、表１で用いた試験条件と同様である。
【００３０】
【表２】

【００３１】
この表２から分かるように、試料番号１が炭素含有量０．００３ｗｔ％の純銅層のみでバルク銅層を形成した銅箔を用いた銅張積層板であり、その他が炭素含有量が０．０１７ｗｔ％〜０．４０ｗｔ％の高炭素含有銅層を備えたバルク銅層であって、高炭素含有銅層（約３μｍ）と純銅層（約９μｍ）とからなる銅箔を用いた銅張積層板とが対比して掲載されている。これらのレーザー穴明け加工性を対比すると、高炭素含有銅層中の炭素含有量が０．０８ｗｔ％を越えたところから、レーザー穴明け加工性が著しく改善していると考えられるのである。即ち、４００穴中の全てが良好に穴明け加工されているのである。従って、高炭素含有銅中の炭素含有量が０．０８ｗｔ％を下限値としているのである。そして、ここで上限値を０．４０ｗｔ％としているのは、以下の製造方法の中で説明するが、この炭素含有量を越えて炭素を含有させることは非常に困難となるのである。
【００３２】
そして、ここで用いる高炭素含有層の厚さは０．１〜５μｍとすることが好ましい。この範囲を定めた意味合いは、レーザー加工後の高炭素含有銅層の除去が容易で、以下に述べる高炭素含有銅層のレーザー穴明け加工性能を改善する役割が十分に発揮できる範囲として定めたものである。上限値である５μｍを越える厚さの高炭素含有銅層を形成しても、レーザー穴明け加工性がそれ以上に増加するものでもなく、レーザー加工後の除去作業が困難となるだけで、経済性を損なうものとなるからである。
【００３３】
また、下限値である０．１μｍを下回る厚さの場合は、レーザー穴明け加工性能にバラツキを生じるのである。例えば、０．０３μｍの厚さの場合でも、高炭素含有銅層を全く備えていない銅張積層板を用いた場合と比較して、レーザー穴明け加工性能が向上しないわけではない。遙かに優れたレーザー穴明け加工性能が得られるが、ロット間によるバラツキが大きくなるのである。なお、ここで形成する高炭素含有銅層の表面は、光沢を有する平滑な金属面であっても、艶消し状の面であっても全く支障はない。この点が、光沢を有する銅箔表面を直接穴明けする場合と根本的に異なるのである。
【００３４】
そして、以上に述べてきた２種類のプリント配線板用銅箔を用いれば、レーザー光の吸収効率等を高めるためのニッケル補助金属層のような異種金属層又は有機材層等を設けることなく、銅張積層板の銅箔層の直接レーザー穴明け加工が容易に可能となるのである。しかしながら、この高炭素含有銅層の表面に更にニッケル補助金属層を設ければ、よりレーザー穴明け加工性が向上するものとなる。即ち、図４（ａ）及び図４（ｂ）に示す層構成を採用するのである。
【００３５】
以上に述べた「高炭素含有銅層をバルク銅層として用いる場合」、「高炭素含有銅層をバルク銅層の表層部分にのみ用いる場合」のいずれのプリント配線板用銅箔であっても、非常に優れたレーザー穴明け加工性能を示すことを説明してきた。ところが、更に研究を続けると、同じ炭素量を含んだ高炭素含有銅層であっても、その結晶組織の違いによって、レーザー穴明け性能が異なってくることが判明したのである。
【００３６】
電解で製造した場合の高炭素含有銅層の結晶組織は、次の２種類に分類することができる。即ち、タイプ▲１▼は「図５に示すような、析出開始位置ＤＳから析出終了位置ＤＦまで、ほぼ連続的に成長した針状組織であり且つ微細な結晶組織であるもの。」、タイプ▲２▼は「図６に示すように、極めて微細な結晶組織であると思われるが、析出開始位置ＤＳから析出終了位置ＤＦまで、不連続に成長した結晶組織であるもの。」、このどちらの組織であっても、高濃度に炭素を含有しない場合と比べれば、レーザー穴明け性能を改善することは可能であるが、これらの結晶組織の内でも特に、タイプ▲１▼の連続的に成長した針状組織であり且つ微細な結晶組織である場合に、最も優れたレーザー穴明け性能を示すのである。
【００３７】
タイプ▲１▼とタイプ▲２▼とのレーザー穴明け性能を端的に表すためには、低エネルギーでのレーザー穴明け結果を見れば明らかとなる。この低エネルギーレーザー穴明け加工試験は、１ショット目が８．３ｍＪで２ショット目が１．７ｍＪ（トータル加工エネルギー１０ｍＪ）のパルスエネルギーを用いて行った。その他、レーザー照射条件は、周波数２０００Ｈｚ、マスク径７．０ｍｍ、１ショット目が２１μｓｅｃ．で２ショット目が２μｓｅｃ．のパルス幅、オフセット０．０、レーザー光径１４０μｍとし、銅張積層板に１００μｍの加工径の穴を４００穴形成することを予定して行ったものである。この結果、タイプ▲１▼の結晶組織を有する公称厚さ９μｍ銅箔の場合には４００穴／４００穴で１００％の開口率であるが、タイプ▲２▼の結晶組織を有する公称厚さ９μｍ銅箔の場合には０穴／４００穴で０％の開口率となるのである。
【００３８】
タイプ▲１▼の針状組織の微細というレベルがどの程度のものであるかは、図５の純銅層６側の電解銅箔の結晶組織と対比すれば明瞭に把握できると考える。この純銅層６も電解法により作られた通常の電解銅箔組織である。この純銅層６の結晶組織と比べて、タイプ▲１▼の針状組織の結晶粒の幅が非常に小さなものとなっていることが理解できると考える。このような形状の結晶組織が、レーザー穴明け加工において、非常に有用となるのである。本件発明者等が思うに、結晶粒レベルで考えた場合、熱伝導は結晶粒界よりも結晶粒内における方が速いものと考えられる。従って、結晶粒の形状が連続的に成長した針状結晶組織は、不連続に成長した針状結晶組織に比べて、熱伝導が結晶粒の形状に沿って縦方向に伝導しやすくなり、銅箔の厚さ方向への穴明け加工が容易になるものと考えられるのである。
【００３９】
続いて、上述してきたプリント配線板銅箔の製造方法に関して説明する。まず、請求項には、「バルク銅層は、膠、ゼラチン、コラーゲンペプチドのいずれか一種又は二種以上を３０ｐｐｍ〜１０００ｐｐｍ含有する硫酸銅溶液を電解することで製造し、その片面側に粗化処理を施し、更に必要な表面処理を施すことを特徴とするプリント配線板用銅箔の製造方法。」としている。この製造方法は、バルク銅層の全てが高炭素含有銅で構成されているプリント配線板用銅箔に関するものである。
【００４０】
通常の電解銅箔のバルク銅層も、同じく硫酸銅溶液であって、電解銅箔の伸び率の改善のためなどに膠を添加する手法が採用されている。しかしながら、このときの膠等の添加量は、２０ｐｐｍ以下である。これに対して、本件発明に係る製造方法では、３０ｐｐｍ以上の膠等の濃度範囲を採用するのである。３０ｐｐｍの濃度とすることで、高炭素含有銅中の炭素含有濃度を０．０４ｗｔ％とすることが出来るのである。
【００４１】
硫酸銅溶液中の膠濃度と、その硫酸銅溶液を電解することにより得られた高炭素含有銅中の炭素量との関係を調べた結果を図３に示している。この図３から分かるように、縦軸に高炭素含有銅中の炭素含有量、横軸に製造に用いた硫酸銅溶液中の膠濃度と採ると、対数関数的関係と成っていることが分かる。即ち、硫酸銅液中の膠濃度が１０００ｐｐｍ付近で、ほぼ飽和して、それ以上に高炭素含有銅中の炭素量は増加しないようになるのである。そして、レーザー穴明け加工試験の実証結果から、硫酸銅液中の膠濃度が３０ｐｐｍを越えるあたりから、レーザー穴明け加工性が飛躍的に上昇し出すのである。この傾向は、ゼラチン、コラーゲンペプチドを用いた場合も同様である。
【００４２】
他の請求項には、「硫酸銅溶液を電解することで純銅箔を製造し、膠、ゼラチン、コラーゲンペプチドのいずれか一種又は二種以上を１００ｐｐｍ〜１０００ｐｐｍ含有する硫酸銅溶液を用いて、この純銅箔の片面側に０．１μｍ〜５μｍの厚さの高炭素含有銅層を電解法で形成し、他面側に粗化処理を施し、更に必要な表面処理を施すことを特徴とするプリント配線板銅箔の製造方法。」としている。この製造方法は、バルク銅層の片面側の０．１μｍ〜５μｍの厚さのみが高炭素含有銅層であり、その他純銅層であり、他面側に粗化処理等の施されているプリント配線板用銅箔に関するものである。
【００４３】
このプリント配線板用銅箔の製造は、まず通常の電解銅箔の製造に用いる硫酸銅溶液を電解することで、バルク銅層を形成する純銅層を純銅箔とし製造する。このときに用いる硫酸銅溶液とは、完全に純粋な硫酸銅溶液を意味するものではなく、従来の銅箔を製造する際に用いる常識的な範囲での添加剤を用いることを想定している。従って、２０ｐｐｍ以下の膠を添加すること、その他セルロース等の添加剤を用いることも当然に可能なものとして記載している。
【００４４】
そして、この純銅箔の片面に、高炭素含有銅層を形成するのである。この高炭素含有銅層を、膠、ゼラチン、コラーゲンペプチドのいずれか一種又は二種以上を１００ｐｐｍ〜１０００ｐｐｍ含有する硫酸銅溶液を用いて、この純銅箔の片面側に０．１μｍ〜５μｍの厚さの高炭素含有銅層を電解法で形成するのである。
【００４５】
この製造方法では、１００ｐｐｍ以上の膠等の濃度範囲を採用するのである。１００ｐｐｍの濃度とすることで、高炭素含有銅中の炭素含有濃度を０．０８ｗｔ％とすることが出来るのである。そして、上限濃度に関しては、前述したと同様の理由で定まったのである。
【００４６】
更に、電解で製造する高炭素含有銅層の結晶組織は、電流密度を制御することにより、上述したタイプ▲１▼、タイプ▲２▼の結晶組織の造り分けが可能となるのである。厳密に言えば、電解液中の膠等の濃度との関係もあるため、明確な電流値として記載することは困難であるが、例えば、タイプ▲１▼の結晶組織を得ようとすると１０Ａ／ｄｍ^２以下の低電流密度を採用し、タイプ▲２▼の結晶組織を得ようとすると２０Ａ／ｄｍ^２以上の高電流密度を採用する等である。従って、このタイプ別結晶組織の造り分けを行おうとすると、生産ラインの特質、電解液の構成成分の濃度等を考慮し、工程毎に電流密度を決定すべきである。
【００４７】
以上のようにして、本件発明に係るプリント配線板用銅箔が得られる。そして、このプリント配線板用銅箔を用いて得られる銅張積層板は、ニッケル補助金属層又は有機材層を備えることなく、直接銅箔層のレーザー穴明け加工が可能となる。
【００４８】
ところが、ニッケル補助金属層又は有機材層を更に設ければ、従来にない程、良好なレーザー穴明け加工性に優れたものとなるのである。即ち、ニッケル補助金属層又は有機材層を設けることで加工穴の真円度が向上するのである。このことは、以下の実施形態でニッケル補助金属層を設けた場合の真円度を対比して示すこととする。
【００４９】
ニッケル補助金属層又は有機材層設けた場合のプリント配線板銅箔の層構成は、図４（ａ）及び（ｂ）に示すようになる。そして、これらのプリント配線板用銅箔の製造方法は、図４（ａ）として示す銅箔の場合は、「バルク銅層は、膠、ゼラチン、コラーゲンペプチドのいずれか一種又は二種以上を３０ｐｐｍ〜１０００ｐｐｍ含有する硫酸銅溶液を電解することで製造し、その片面側にニッケル補助金属層又は有機材層を形成し、他面側に粗化処理を施し、更に必要な表面処理を施すことを特徴とするプリント配線板銅箔の製造方法。」を採用する。
【００５０】
そして、図４（ｂ）として示す銅箔の場合は、「硫酸銅溶液を電解することで純銅箔を製造し、膠、ゼラチン、コラーゲンペプチドのいずれか一種又は二種以上を１００ｐｐｍ〜１０００ｐｐｍ含有する硫酸銅溶液を用いて、この純銅箔の片面側に０．１μｍ〜５μｍの厚さの高炭素含有銅層を電解法で形成し、この高炭素含有銅層の上にニッケル補助金属層又は有機材層を形成し、他面側に粗化処理を施し、更に必要な表面処理を施すことを特徴とするプリント配線板銅箔の製造方法。」を採用するのである。
【００５１】
ここで言うニッケル補助金属層は、ニッケル又はニッケル合金を用いて形成するものである。例えば、ニッケル層を形成する場合は、ニッケルメッキ液として用いられる溶液を広く使用することが可能である。例えば、▲１▼硫酸ニッケルを用いニッケル濃度が５〜８０ｇ／ｌ、液温２０〜５０℃、ｐＨ２〜６、電流密度０．３〜１０Ａ／ｄｍ^２の条件、▲２▼硫酸ニッケルを用いニッケル濃度が５〜３０ｇ／ｌ、ピロリン酸カリウム５０〜５００ｇ／ｌ、液温２０〜５０℃、ｐＨ８〜１１、電流密度０．３〜１０Ａ／ｄｍ^２の条件、▲３▼硫酸ニッケルを用いニッケル濃度が１０〜７０ｇ／ｌ、ホウ酸２０〜６０ｇ／ｌ、液温２０〜５０℃、ｐＨ２〜６、電流密度１〜５０Ａ／ｄｍ^２の条件、その他一般のワット浴の条件とする等である。
【００５２】
ニッケル−亜鉛合金層を形成する場合は、例えば、硫酸ニッケルを用いニッケル濃度が１〜３０ｇ／ｌ、ピロリン酸亜鉛を用いて亜鉛濃度が１〜３０ｇ／ｌ、ピロリン酸カリウム５０〜５００ｇ／ｌ、液温２０〜５０℃、ｐＨ８〜１１、電流密度０．３〜１０Ａ／ｄｍ^２の条件等である。
【００５３】
ニッケル−コバルト合金層を形成する場合は、例えば、硫酸コバルト８０〜１８０ｇ／ｌ、硫酸ニッケル８０〜１２０ｇ／ｌ、ホウ酸２０〜４０ｇ／ｌ、塩化カリウム１０〜１５ｇ／ｌ、リン酸２水素ナトリウム０．１〜１５ｇ／ｌ、液温３０〜５０℃、ｐＨ３．５〜４．５、電流密度１〜１０Ａ／ｄｍ^２の条件等である。
【００５４】
また、リン酸系溶液を用いることで、ニッケル−リン合金メッキとすることも可能である。この場合、硫酸ニッケル１２０〜１８０ｇ／ｌ、塩化ニッケル３５〜５５ｇ／ｌ、Ｈ_３ＰＯ_４３０〜５０ｇ／ｌ、Ｈ_３ＰＯ_３２０〜４０ｇ／ｌ、液温７０〜９５℃、ｐＨ１〜２、電流密度５〜５０Ａ／ｄｍ^２の条件等である。
【００５５】
次に、有機材層を構成するレーザーの吸収効率を高めるための樹脂材としては、レーザービームの波長が含まれる赤外領域での吸収が良好なポリエチレンテレフタレート（ＰＥＴ）、ポリエチレン等の熱可塑性樹脂を用いることが好ましい。これらの樹脂層は、該当の樹脂溶液を塗布して乾燥させるか、フィルム状に加工してラミネートする等により有機材層とするのである。
【００５６】
【発明の実施の形態】
以下に、上述してきたプリント配線板用銅箔を用いて銅張積層板を製造し、その銅張積層板を用いてレーザー穴明け加工を行った結果を示すこととする。
【００５７】
第１実施形態：　　この実施形態では、図１に示したバルク銅層２の全てを高炭素含有銅で構成したプリント配線板用銅箔１を製造した。最初に、バルク銅層２を電解銅箔の電解装置のチタン製ドラム表面に電解析出することにより製造した。このときの電解液に、硫酸銅溶液であって、銅濃度６０ｇ／ｌ、フリー硫酸濃度１５０ｇ／ｌ、膠濃度８００ｐｐｍ、液温４８℃の溶液を用いて、電流密度５Ａ／ｄｍ^２で電解し、高炭素含有銅を箔状にしてバルク銅層２が得られた。このバルク銅層２の片面は、チタン製ドラムの表面形状の転写した光沢面であり、他面は、一定の凹凸を持つ粗面となる。なお、この高炭素含有銅からなるバルク銅層２の炭素含有量は、０．３５ｗｔ％であり、タイプ▲１▼の結晶組織を持つものであった。
【００５８】
そして、表面処理として、このバルク銅層２の粗面に、微細銅粒３を析出付着させて、粗化処理面４を形成した。この粗化処理面４の形成に先立ち、まず当該析離箔の表面を酸洗処理して、バルク銅層２に付いた油脂成分を完全に除去し、余分な表面酸化被膜除去を行った。この酸洗処理には、濃度１００ｇ／ｌ、液温３０℃の希硫酸溶液を用い、浸漬時間３０秒とした。
【００５９】
そして、酸洗処理が終了すると、次にはバルク銅層２の粗面に微細銅粒３を形成する工程として、粗面上に微細銅粒３を析出付着させる工程と、この微細銅粒３の脱落を防止するための被せメッキ工程とが施される。前者の微細銅粒３を析出付着させる工程では、硫酸銅系溶液であって、濃度が銅７ｇ／ｌ、硫酸１００ｇ／ｌ、液温２５℃、電流密度１０Ａ／ｄｍ^２の条件で、１０秒間電解した。
【００６０】
以上のようにして、一旦バルク銅層２の粗面に微細銅粒３を付着形成すると、微細銅粒３の脱落を防止するための被せメッキ工程では、平滑メッキ条件で微細銅粒３を被覆するように銅を均一析出させた。ここでは平滑メッキ条件として、硫酸銅溶液であって、濃度が銅６０ｇ／ｌ、硫酸１５０ｇ／ｌ、液温４５℃、電流密度１５Ａ／ｄｍ^２の条件とし、２０秒間電解した。
【００６１】
上述した粗化処理が終了すると、次には当該銅箔の両面に防錆処理を施した、防錆処理は、プリント配線板用銅箔１の表面が酸化腐食することを防止するためのものであり、防錆処理には、ベンゾトリアゾール、イミダゾール等を用いる有機防錆、若しくは亜鉛、クロメート、亜鉛合金等を用いる無機防錆のいずれを採用しても問題はないが、ここでは以下に述べる条件の無機防錆を採用した。硫酸亜鉛浴を用い、硫酸濃度７０ｇ／ｌ、亜鉛濃度２０ｇ／ｌとし、液温４０℃、電流密度１５Ａ／ｄｍ^２とし、亜鉛防錆処理を施した。なお、図面中では、防錆処理層の記載は省略している。
【００６２】
防錆処理が終了すると、最終的にプリント配線板用銅箔１は、電熱器により雰囲気温度１１０℃に加熱された炉内で４０秒かけて乾燥し、完成した公称厚さ１２μｍのプリント配線板用銅箔１とした。
【００６３】
このプリント配線板用銅箔１と、内層回路を形成した内層コア材とを用いて、内層回路入りの銅張積層板を製造した。当該内層コア材の両面に、それぞれ１００μｍ厚のＦＲ−４のプリプレグ１枚とを介して、当該プリント配線板用銅箔を熱間プレス加工して張り合わせ、内層回路付銅張積層板を製造した。そして、この両面からブラインドビアホールとなる穴部を炭酸ガスレーザーを用いて形成した。このときの炭酸ガスレーザーによる穴明け加工条件は、上述した表１の説明で示した条件（トータル加工エネルギー２０ｍＪ）をそのまま採用している。その結果、穴明け加工した４００穴中、全ての穴が良好に穴明け加工でき、加工された穴の真円度が平均で０．９５であった。また、上述したトータル加工エネルギー１０ｍＪの条件で４００穴の穴明け加工を行った。その結果、加工された穴の真円度は０．８４であるが、４００穴全ての穴に穴明け加工が可能であった。
【００６４】
第２実施形態：　　この実施形態では、図２に示したバルク銅層２が高炭素含有銅層５と純銅層６とで構成したプリント配線板銅箔１’を製造した。最初に、９μｍ厚さの純銅層６を電解銅箔の電解装置のチタン製ドラム表面に電解析出することにより製造した。このときの電解液に、硫酸銅溶液であって、銅濃度６０ｇ／ｌ、フリー硫酸濃度１５０ｇ／ｌ、膠１０ｐｐｍ、液温４８℃の溶液を用いて、電流密度６０Ａ／ｄｍ^２で電解し、純銅層６を箔状にして連続的に巻き取った。この純銅箔６の片面は、チタン製ドラムの表面形状の転写した光沢面であり、他面は、一定の凹凸を持つ粗面となる。
【００６５】
そして、この純銅箔６の光沢面に、３μｍ厚の高炭素含有銅層５を形成した。この高炭素含有銅層５の形成には、電解液として硫酸銅溶液であって、銅濃度６０ｇ／ｌ、フリー硫酸濃度１５０ｇ／ｌ、膠濃度１０００ｐｐｍ、液温４８℃の溶液を用いて、電流密度５Ａ／ｄｍ^２で電解することに行った。このようにして、高炭素含有銅層５と純銅層６とが積層された状態で構成した箔状のバルク銅層２を製造した。なお、このときの高炭素含有銅層５の炭素含有量は０．４０ｗｔ％であり、タイプ▲１▼の結晶組織を持つものであった。
【００６６】
以下、第１実施形態で述べたと同様の方法で、バルク銅層２の純銅層６の表面に粗化処理を施し、防錆処理を施すことにより、プリント配線板用銅箔１’の製造を行った。従って、粗化処理及び防錆処理の条件は、第１実施形態と同様であり、重複した記載を避けるため、ここでの説明は省略する。
【００６７】
このプリント配線板用銅箔１’と、内層回路を形成した内層コア材とを用いて、第１実施形態と同様の方法で内層回路付銅張積層板を製造した。この内層回路付銅張積層板の両面からブラインドビアホールとなる穴部を炭酸ガスレーザーを用いて形成した。このときの炭酸ガスレーザーによる穴明け加工条件は、上述した表１の説明で示した条件（トータル加工エネルギー２０ｍＪ）をそのまま採用している。その結果、穴明け加工した４００穴中、全ての穴が良好に穴明け加工でき、加工された穴の真円度が平均で０．９４であった。また、上述したトータル加工エネルギー１０ｍＪの条件で４００穴の穴明け加工を行った。その結果、加工された穴の真円度は０．８６であるが、４００穴全ての穴に穴明け加工が可能であった。
【００６８】
第３実施形態：　　この実施形態では、図４（ａ）に示したバルク銅層２の全てを高炭素含有銅で構成し、粗化処理面の反対面側にニッケル補助金属層Ｐを形成したプリント配線板用銅箔１ａを製造した。最初に、バルク銅層２を電解銅箔の電解装置のチタン製ドラム表面に電解析出することにより製造した。このときの電解液に、硫酸銅溶液であって、銅濃度６０ｇ／ｌ、フリー硫酸濃度１５０ｇ／ｌ、膠濃度８００ｐｐｍ、液温４８℃の溶液を用いて、電流密度６Ａ／ｄｍ^２で電解し、高炭素含有銅を９μｍ厚の箔状にして連続的に巻き取り、バルク銅層２を得た。このバルク銅層２の片面は、チタン製ドラムの表面形状の転写した光沢面であり、他面は、一定の凹凸を持つ粗面となる。なお、この高炭素含有銅からなるバルク銅層２の炭素含有量は、０．３５ｗｔ％であり、タイプ▲１▼の結晶組織を持つものであった。
【００６９】
そして、当該バルク銅層２の光沢面側の表面にニッケル補助金属層Ｐとして、０．５μｍ厚さのニッケル層を形成した。ニッケル層の形成は、ニッケルメッキ液として用いられる溶液を広く使用することが可能であるが、ここでは硫酸ニッケルを用い、ニッケル濃度が６０ｇ／ｌ、ホウ酸が３０ｇ／ｌ、液温３０℃、ｐＨ３、電流密度５Ａ／ｄｍ^２の条件を採用した。
【００７０】
以下、当該バルク銅層の粗面側に第１実施形態と同様にして、粗化処理を行い粗化処理面４を形成し、防錆処理を施した。但し、第１実施形態は、両面共に防錆処理を行ったが、本実施形態の場合は片面がニッケル層であるため、防錆処理を必要とせず、粗化処理面４のみに防錆処理を施した。従って、粗化処理と防錆処理に関しての重複した説明を避けるため、ここでの説明を省略する。
【００７１】
このプリント配線板用銅箔１ａと、内層回路を形成した内層コア材とを用いて、第１実施形態と同様の方法で内層回路付銅張積層板を製造した。この内層回路付銅張積層板の両面からブラインドビアホールとなる穴部を炭酸ガスレーザーを用いて形成した。このときの炭酸ガスレーザーによる穴明け加工条件は、上述した表１の説明で示した条件（トータル加工エネルギー２０ｍＪ）をそのまま採用している。
【００７２】
レーザー穴明け加工が終了すると、光沢面側に存在するニッケル補助金属層をエッチング除去した。このニッケルの選択エッチングには、６００ｍｌ／ｌ濃度の硫酸溶液を用いて、この溶液中で銅張積層板をアノード分極し電解でニッケル層を剥離した。そして、その後、穴明け加工した４００穴中の全てを観察した。この結果、全ての穴が良好に穴明け加工できており、加工された穴の真円度が平均で０．９８であり、第１実施形態と対比しても良好な穴形状が得られている。
【００７３】
また、レーザー加工条件を、上述したレーザー加工のトータル加工エネルギー１０ｍＪの条件に代えて、４００穴の穴明け加工を行った。その結果、加工された穴の真円度は０．８７であるが、４００穴全ての穴に穴明け加工が可能であった。
【００７４】
第４実施形態：　　この実施形態では、図４（ｂ）に示したバルク銅層２が高炭素含有銅層５と純銅層６とで構成され、粗化処理面４の反対面側の最表層にニッケル補助金属層Ｐを備えたプリント配線板用銅箔１ｂを製造した。最初に、９μｍ厚さの純銅層６を上述した電解銅箔の製造装置で製造し、この純銅層６の光沢面に、約３μｍ厚の高炭素含有銅層５を形成する所までは、第２実施形態と同様である。従って、重複記載を避けるため、ここでの説明は省略する。
【００７５】
純銅層６の光沢面側に高炭素含有銅層５の形成が終了すると、続いて高炭素含有銅層５の表面にニッケル補助金属層Ｐを形成したのである。このときのニッケル補助金属層Ｐは、第３実施形態と同様の方法により０．５μｍ厚さのニッケル層とした。従って、この製造条件等に関しても第３実施形態と同様であるため、重複した記載を避けるため、ここでの記載を省略する。
【００７６】
更に、粗化処理と防錆処理に関しても第３実施形態と同様に、ニッケル補助金属層Ｐを形成した箔の粗面側に第１実施形態と同様にして、粗化処理を行い粗化処理面４を形成し、防錆処理を施した。但し、第１実施形態は、両面に防錆処理を行ったが、本実施形態の場合は片面がニッケル層であるため、防錆処理を必要とせず、粗化処理面４のみに防錆処理を施した。従って、粗化処理と防錆処理に関しての重複した説明を避けるため、ここでの説明を省略する。
【００７７】
このプリント配線板用銅箔１ｂと、内層回路を形成した内層コア材とを用いて、第１実施形態と同様の方法で内層回路付銅張積層板を製造した。この内層回路付銅張積層板の両面からブラインドビアホールとなる穴部を炭酸ガスレーザーを用いて形成した。このときの炭酸ガスレーザーによる穴明け加工条件は、上述した表１の説明で示した条件（トータル加工エネルギー２０ｍＪ）をそのまま採用している。
【００７８】
レーザー穴明け加工が終了すると、光沢面側に存在するニッケル補助金属層をエッチング除去した。このニッケルの選択エッチングには、６００ｍｌ／ｌ濃度の硫酸溶液を用いて、この溶液中で銅張積層板をアノード分極し電解でニッケル層を剥離した。そして、その後、穴明け加工した４００穴中の全てを観察した。この結果、全ての穴が良好に穴明け加工できており、加工された穴の真円度が平均で０．９８であり、第１実施形態と対比しても良好な穴形状が得られている。
【００７９】
また、レーザー加工条件を、上述したレーザー加工のトータル加工エネルギー１０ｍＪの条件に代えて、４００穴の穴明け加工を行った。その結果、加工された穴の真円度は０．８８であるが、４００穴全ての穴に穴明け加工が可能であった。
【００８０】
比較例：　　この実施形態では、バルク銅層の全てを純銅で構成した銅箔を製造した。最初に、バルク銅層を電解銅箔の電解装置のチタン製ドラム表面に電解析出することにより製造した。このときの電解液に、硫酸銅溶液であって、銅濃度６０ｇ／ｌ、フリー硫酸濃度１５０ｇ／ｌ、膠濃度１０ｐｐｍ、液温４８℃の溶液を用いて、電流密度６０Ａ／ｄｍ^２で電解し、析出銅を箔状にして連続的に巻き取った。このバルク銅層の片面は、チタン製ドラムの表面形状の転写した光沢面であり、他面は、一定の凹凸を持つ粗面となる。なお、この純銅からなるバルク銅層の炭素含有量は、０．０１ｗｔ％であり、結晶組織は針状組織であるが、タイプ▲１▼の結晶粒ほど微細なものではないものであった。
【００８１】
そして、以下表面処理として行った、粗化処理及び防錆処理等は第１実施形態と同様であるため、ここでは重複した記載を避けるため記載を省略する。このようにして、バルク銅層の全てが純銅から成るプリント配線板用銅箔を製造した。
【００８２】
このプリント配線板用銅箔と、内層回路を形成した内層コア材とを用いて、第１実施形態と同様の方法で内層回路付銅張積層板を製造した。この内層回路付銅張積層板の両面からブラインドビアホールとなる穴部を炭酸ガスレーザーを用いて形成した。このときの炭酸ガスレーザーによる穴明け加工条件（トータル加工エネルギー２０ｍＪ）は、上述した表１の説明で示した条件をそのまま採用している。
【００８３】
レーザー穴明け加工が終了すると、その後、穴明け加工した４００穴中の全てを観察した。この結果、４００穴中の４穴のみが良好に穴明け加工できていると判断できるものであり、良好に加工できたと判断できる穴の真円度が平均で０．９０であった。この結果を、上述の実施形態と対比することで明らかとなるように、本件発明の持つ効果としてレーザー穴明け加工性能が著しく向上すると言えるのである。
【００８４】
また、レーザー加工条件を、上述したレーザー加工のトータル加工エネルギー１０ｍＪの条件に代えて、４００穴の穴明け加工を行った。その結果、４００穴の全てで穴明け加工することができず、上記した実施形態に比べ、レザー穴明け性能が全く異なることが明らかとなるのである。
【００８５】
【発明の効果】
以上のように本件発明にかかるプリント配線板用銅箔を用いることで、炭酸ガスレーザーを用いた銅張積層板の銅箔層の直接穴明け加工が可能となる。即ち、従来の銅箔の直接穴明け加工で、銅箔の表面に必ず必要とされたレーザー光吸収効率を高めるためのニッケル補助金属層又は有機材層を不要とし、異種金属元素等を含まないため、ニッケル補助金属層等の剥離工程を不要とし、しかも、廃水処理の負担を著しく軽減することでトータル製造コストの著しい削減が可能となるのである。また一方で、本件発明に係るニッケル補助金属層等を設けたプリント配線板用銅箔とすることで、レーザー穴明け加工の加工精度をより大幅に向上させることが可能となる。
【図面の簡単な説明】
【図１】プリント配線板用銅箔の断面模式図。
【図２】プリント配線板用銅箔の断面模式図。
【図３】硫酸銅溶液中の膠濃度とその硫酸銅溶液を電解することにより得られた高炭素含有銅中の炭素量との関係を表す図。
【図４】プリント配線板用銅箔の断面模式図。
【図５】高炭素含有銅層の断面結晶組織観察像。
【図６】高炭素含有銅層の断面結晶組織観察像。
【図７】レーザー加工手順を表す模式図。
【符号の説明】
１　　プリント配線板用銅箔
２　　バルク銅層
３　　微細銅粒
４　　粗化処理面
５　　高炭素含有銅層
６　　純銅層
Ｐ　　補助金属層（又は有機材層）[0001]
[Industrial applications]
The present invention relates to a copper foil for a printed wiring board. In particular, the present invention relates to a copper foil that is useful when drilling such as via hole processing using a carbon dioxide laser.
[0002]
[Prior art]
In recent years, due to the demand for lighter, thinner and smaller electronic and electrical equipment, downsizing of the printed wiring boards mounted therein has also been performed at the same time, and there is a remarkable amount of wiring circuit density, mounting density, and high multilayering of printed wiring boards. . The term “multilayered printed wiring board” refers to a state in which a plurality of layers on which a conductor circuit is formed are multilayered via an insulating resin layer. It is common to provide a conducting means.
[0003]
Of the interlayer conduction means, through holes are formed by mechanically drilling a printed wiring board to form through holes, and copper plating is applied to the inner wall surfaces of the through holes to ensure interlayer conduction. On the other hand, what is called a via hole is a through hole like a through hole, a blind via hole which is not a through hole but simply a recessed state, and is a state buried in an interlayer of a printed wiring board. There is an interstitial via hole or the like, which has a common feature that the hole diameter is very small as compared with the through hole and mechanical drilling is difficult.
[0004]
Therefore, in forming the shape of the via hole, a laser drilling method has been adopted in view of the advantages that fine drilling is possible, the processing position accuracy is excellent, and the processing speed is high. Various laser oscillation sources are used for laser drilling, and the most widely used is a so-called carbon dioxide laser.
[0005]
However, when the copper foil layer and the insulating resin layer of the printed wiring board were simultaneously drilled using a carbon dioxide gas laser, the phenomenon that good drilling was difficult due to the presence of the copper foil layer occurred. . In order to solve this problem, the use of a copper foil provided with a nickel layer or a nickel alloy layer on its surface as an auxiliary metal layer (hereinafter, simply referred to as “nickel auxiliary metal layer”) reduces the absorption efficiency of laser light. Techniques have been used to improve the drilling workability by the enhanced carbon dioxide laser. On the other hand, a method of forming an organic material film capable of increasing the absorption efficiency of laser light on the surface of a copper foil has also been widely used.
[0006]
In such a case, laser drilling is performed in a procedure as shown in FIG. That is, in FIG. 7, a four-layer copper in which a copper foil C provided with a nickel auxiliary metal layer or an organic material film P on the surface is disposed as an outer layer via an insulating layer on both sides of an inner layer core material IB having an inner layer circuit IC. The laminated laminate PWB is taken as an example. In this case, after the drilling is completed as shown in FIG. 7A, the nickel auxiliary metal layer or the organic material film P is removed as shown in FIG. Thus, a plated copper layer for obtaining interlayer conduction is formed on the inner wall surface of the via hole, and circuit formation etching is performed.
[0007]
[Patent Document 1]
Japanese Patent No. 3258308
[Patent Document 2]
JP 2001-347599 A
[0008]
[Problems to be solved by the invention]
However, in the case described above, the following problem has occurred. When a nickel auxiliary metal layer is provided, it is necessary to remove the nickel auxiliary metal layer by etching after laser drilling, so nickel components are eluted in the etching waste liquid or cleaning water, and the waste liquid treatment is complicated. And increased the production running cost of the printed wiring board. On the other hand, even when an organic material film is provided, since it is required to remove the organic material film after laser drilling, the organic material film component will be contained in the etching waste liquid or cleaning water, and similarly, The waste liquid treatment becomes complicated, which causes a rise in the running cost of manufacturing a printed wiring board.
[0009]
Further, when the nickel auxiliary metal layer is to be removed by etching, a nickel selective etching solution is preferably used in a state where nickel or a nickel alloy and copper coexist to preferentially dissolve only nickel and not dissolve the copper component. Except for the etching solution that is usually used to remove nickel, the dissolution rate of nickel is slow, and even the copper components that constitute the circuit are eroded, causing pinholes in the circuit and dissolving the circuit. Had become. Even if the above-described nickel selective etching solution is used, the production cost is increased because of the special etching solution.
[0010]
Considering the above, ideally, a copper foil that can be drilled by a carbon dioxide gas laser without a nickel auxiliary metal layer and an organic material coating is required.
[0011]
[Means for Solving the Problems]
Therefore, the present inventors have conducted intensive research and found that, as shown below, it is possible to directly drill by a carbon dioxide gas laser without providing a different metal and organic material coating such as a nickel auxiliary metal layer that enhances the laser absorption efficiency. I came up with copper foil.
[0012]
Claims are provided for a copper foil for manufacturing a printed wiring board having a roughened surface on one side of a bulk copper layer and a glossy surface on the other side, wherein the bulk copper layer has a carbon content of 0.1%. The copper foil for a printed wiring board is characterized by being composed of high carbon content copper of from 0.3 wt% to 0.40 wt%. FIG. 1 shows a schematic sectional view of this copper foil.
[0013]
At this stage, a clear theory has not yet been established as to why a high carbon content copper layer is used as the bulk copper layer to easily improve laser drilling performance. However, while continuing the research, the present inventors have obtained a feeling that the laser drilling performance is improved by the following principle.
[0014]
The copper constituting the bulk copper layer of the conventional copper foil is so-called pure copper having a purity of 99.99 wt% or more, and the amount of carbon contained therein is about 0.005 wt%. On the other hand, the bulk copper layer of the copper foil in the present invention is composed of high carbon content copper having a carbon content of 0.03 wt% to 0.40 wt% by containing an organic substance. By thus increasing the carbon content in copper, the thermal conductivity of copper is reduced. The thermal conductivity of pure copper is 354 W · m at 700 ° C. ^-1 ・ K ^-1 Is a good conductor of heat, the high carbon-containing copper having a carbon content of 0.03 to 0.40 wt% by containing the organic matter according to the present invention has a thermal conductivity of 100 to 180 W · m. ^-1 ・ K ^-1 And the thermal conductivity decreases.
[0015]
The present inventors considered the reason why it is difficult to perform drilling with a laser beam when using a normal copper foil as follows. Here, assuming that the laser output energy is P and the surface reflection and heat conduction loss are η, the energy contributing to the temperature rise of the workpiece is P (1−η). Therefore, P (1−η) = m · C · ΔT holds. Here, m is π (d / 2), where d is the diameter of the hole processed by the laser beam, H is the processed thickness, and ρ is the specific gravity of copper. ² H · ρ, P (1−η) = π (d / 2) ² H · ρ · C · ΔT Therefore, ΔT = 4P (1−η) / (π · d ² H · ρ · C). Using this equation, consider the conditions under which copper dissolves. Here, a pulse width of 18 μsec. The pulse energy was 16.0 mJ, the laser beam diameter was 160 μm, and holes having a processing diameter of 125 μm were formed in copper foils of various thicknesses, ρ = 8.94 g / cm. ³ , C = 0.39 J / K · g, ΔT = 4P (1−η) / (10.95 · d ² Using H), consider this as a theoretical equation.
[0016]
In order to enable the copper foil to be drilled by laser light, the laser light must be capable of dissolving copper and guiding the temperature to a temperature higher than the boiling point. Using the reflectance on the copper foil surface as the value of η based on the above theoretical formula and simulating the rise temperature, a difference of more than 1000 ° C. occurs in the rise temperature only by a 1% change in the reflectance. In order to enable continuous dissolution of the copper foil layer, it is understood that the condition that the reflectance is less than 98% must be satisfied.
[0017]
The initial surface of the copper foil to be subjected to laser drilling is a glossy surface, but has a certain degree of roughness and cannot be said to be a smooth mirror surface. However, when the irradiation of the laser beam is started, the copper foil surface having a predetermined roughness begins to melt, and when the copper component on the initial irradiation surface dissolves and evaporates, a smooth mirror surface copper surface is formed thereunder. It will be. The reflectance of the mirror-finished copper foil surface is usually a surface having a reflectance of 98% or more. As a result, laser processing beyond a certain depth becomes difficult.
[0018]
When a hole is to be formed in copper by laser processing, a process in which copper is continuously evaporated by a predetermined thickness of copper foil must be reproducible. That is, during the laser irradiation, at least the irradiation site must be higher than the boiling point temperature of copper.
[0019]
However, here, the heat conduction performance of pure copper and high carbon content copper will be compared. Pure copper has a thermal conductivity of 354 W · m at 700 ° C. ^-1 ・ K ^-1 It is a good conductor of heat. In contrast, high-carbon copper is 100-180 W · m at 700 ° C. ^-1 ・ K ^-1 Which is about ３ to の of the thermal conductivity of pure copper, indicating that heat conductivity is extremely slow as compared with pure copper. Considering this, when irradiating laser light on the copper foil surface with a bulk copper layer composed of pure copper of the copper clad laminate, part of the laser light is reflected from the mirror surface copper foil surface and the remaining laser Light is applied as heat energy at a predetermined position to form a through hole or hole such as IVH or BVH. At this time, as the surface of the copper foil melts and transforms into a mirror-like state, the reflectance of the laser light increases and the rate of conversion to thermal energy decreases. Looking at the area of the entire copper-clad laminate, the area of the part where laser processing is performed is very small, and even if that part becomes instantaneously hot, copper, which is a good conductor of heat, is It is thought that it becomes difficult to immediately diffuse the amount of heat given by, and to stop the concentrated amount of heat in a part. That is, compared to the supply rate of the thermal energy given by the laser beam, the rate at which the amount of heat given to the copper foil layer is diffused and dispersed is greater, making it difficult to reach the boiling point of copper. Conceivable.
[0020]
In contrast, high carbon content copper transfers heat only at about one-half to one-third of the thermal conductivity of pure copper. Therefore, when the laser light is irradiated on the surface of the copper foil having the bulk copper layer composed of the high carbon content copper of the copper-clad laminate, the supply speed of the thermal energy by the laser light is faster than the heat diffusion speed. It is thought that heat energy is quickly concentrated on the irradiated portion, and the laser irradiated portion easily reaches the boiling point of copper. Then, the thermal energy transmitted to the copper foil having the bulk copper layer composed of the high carbon content copper is difficult to be dissipated due to the low thermal conductivity of the bulk copper layer, and the thermal energy of the continuous laser beam irradiation is reduced. It is considered that the temperature rise exceeding the melting temperature of copper occurs easily and continuously in conjunction with the supply, and the copper foil layer can be easily removed by laser light.
[0021]
Table 1 shows that the above-described copper foil for a printed wiring board, having a nominal thickness of 10 μm, was attached to both sides of a FR-4 prepreg having a thickness of 100 μm by pressing, and a double-sided copper-clad laminate was applied. The figure shows the results of manufacturing a plate and using it to perform a laser drilling test by the cycle method. The laser drilling test was performed using pulse energy of 18.3 mJ for the first shot and 1.7 mJ for the second shot (total processing energy of 20 mJ). Other laser irradiation conditions are a frequency of 2000 Hz, a mask diameter of 7.0 mm, and a first shot of 21 μsec. And the second shot is 2 μsec. And a laser beam diameter of 140 μm, and 400 holes with a processing diameter of 100 μm were formed in the copper-clad laminate. Therefore, the inventors of the present invention determined that the machining was performed satisfactorily in the range where the hole diameter after the machining was 90 to 110 μm as a criterion.
[0022]
[Table 1]

[0023]
As can be seen from Table 1, the carbon content of the pure copper layer corresponding to sample No. 1 was measured to be 0.003 wt%, and the carbon content was 0.015 wt% to 0.40 wt%. Is published. Comparing these laser drilling properties, it is considered that the laser drilling property has been remarkably improved since the carbon content in the high carbon content copper exceeded 0.03 wt%. That is, most of the 400 holes are well drilled. Therefore, the lower limit of the carbon content of the high-carbon copper is 0.03 wt%. The reason why the upper limit value is set to 0.40 wt% will be described in the following manufacturing method. However, it becomes very difficult to contain carbon exceeding this carbon content.
[0024]
On the other hand, in the case of a copper foil in which all of the bulk copper layers described above are made of high-carbon copper, the thermal conductivity is considered to be lower than that of pure copper, and at the same time, the electrical resistance value is thought to increase. Disadvantages can be assumed. That is, depending on the circuit design, usable scenes may be limited. In particular, even if there is no problem at the present stage, the clock frequency of the computer is being increased at the GHz level, which may cause a heat generation problem in a high frequency application, a delay in signal transmission, and the like.
[0025]
Accordingly, a copper foil for manufacturing a printed wiring board having a roughened surface on one side of a bulk copper layer and a glossy surface on the other side, wherein the bulk copper layer is A high-carbon-containing copper layer having a carbon content of 0.08 wt% to 0.40 wt% and a thickness of 0.1 μm to 5 μm on the opposite side of the chemically treated surface, and pure copper below the high-carbon copper layer. The above-mentioned problem can be solved by using a copper foil for printed wiring boards characterized by comprising a layer. " FIG. 2 schematically shows this copper foil.
[0026]
That is, the copper foil for a printed wiring board has a high carbon content copper layer only in a thickness of 0.1 μm to 5 μm on the side opposite to the roughened surface of the bulk copper layer, and other portions of the bulk copper layer are pure copper. It is a layer. By adopting such a layer configuration, until the laser drilling process in the state of the copper-clad laminate is completed, the high-carbon-containing copper layer is left, and the copper-clad laminate before plating is performed. At the stage of the surface smoothing treatment, only the high carbon content copper layer is removed. That is, by using a physical treatment such as a chemical etching treatment or a buff polishing treatment or a combination of these treatments, only the high carbon content copper layer can be easily removed. If this high carbon content copper layer can be removed, only the pure copper layer will remain on the copper-clad laminate, and there is no obstacle to the electrical resistance of the finally formed conductive circuit. It becomes.
[0027]
Here, a laser processing theory in the case where a high carbon content copper layer having a predetermined thickness is provided on the copper foil surface is considered. Here, the thermal conductivity of copper and nickel is such that the thermal conductivity of pure copper is 354 W · m at 700 ° C. ^-1 ・ K ^-1 , High carbon content copper is 100 ~ 180W ・ m at 700 ℃ ^-1 ・ K ^-1 The high carbon content copper was about ３ to の of the thermal conductivity of pure copper, and the heat conductivity was extremely slow as compared with pure copper. Therefore, when the laser beam is irradiated on the surface of the high carbon content copper layer formed on the copper foil of the copper clad laminate, heat energy is concentrated only on the irradiated portion of the high carbon content copper layer, and the heat diffusion rate It is considered that the rate of supply of thermal energy by the laser beam is higher than that of the laser beam, and the laser irradiation site easily reaches the melting point of the high carbon content copper.
[0028]
As a result, it is considered that the high-carbon-containing copper rapidly rises in temperature due to laser beam irradiation, and is easily dissolved and evaporated as compared with pure copper. When the high-carbon-containing copper layer once starts melting and reaches the boiling point by laser light irradiation, the calorie at the boiling point of the high-carbon-containing copper is transmitted to the pure copper layer, which is a good conductor of heat, and transmitted to the pure copper layer. The heat energy is difficult to dissipate because the copper foil surface is coated with high carbon content copper with low thermal conductivity, and it can easily adjust the melting temperature of pure copper in conjunction with the supply of heat energy by continuous laser light irradiation. It is considered that the excessive temperature rise occurs continuously, and the copper foil layer can be easily removed by the laser beam.
[0029]
Table 2 shows that the above-described bulk copper layer is a copper foil for a printed wiring board having a high carbon content copper layer (about 3 μm) and a pure copper layer (about 9 μm) and having a nominal thickness of 12 μm. The results are shown in which a double-sided copper-clad laminate was manufactured by pressing on both sides of a FR-4 prepreg having a thickness of 50 μm by press working, and a laser drilling test was performed by a cycle method using the laminate. Note that the laser drilling test is the same as the test conditions used in Table 1.
[0030]
[Table 2]

[0031]
As can be seen from Table 2, Sample No. 1 was a copper-clad laminate using a copper foil having a bulk copper layer formed only of a pure copper layer having a carbon content of 0.003 wt%, and the other had a carbon content of 0.1%. A copper-clad laminate using a copper foil comprising a high carbon content copper layer (about 3 μm) and a pure copper layer (about 9 μm), comprising a high carbon content copper layer of 017 wt% to 0.40 wt%. It is posted in contrast to the board. Comparing these laser drilling properties, it is considered that the laser drilling property has been remarkably improved when the carbon content in the high carbon content copper layer exceeds 0.08 wt%. That is, all of the 400 holes are well drilled. Therefore, the lower limit of the carbon content of the high-carbon copper is 0.08 wt%. The reason why the upper limit value is set to 0.40 wt% will be described in the following manufacturing method. However, it becomes very difficult to contain carbon exceeding this carbon content.
[0032]
The thickness of the high carbon content layer used here is preferably from 0.1 to 5 μm. The meaning of defining this range is defined as a range where removal of the high carbon content copper layer after the laser processing is easy and the role of improving the laser drilling performance of the high carbon content copper layer described below can be sufficiently exhibited. Things. Even if a high carbon content copper layer having a thickness exceeding the upper limit of 5 μm is formed, the laser drilling processability does not increase any more, and the removal work after the laser processing becomes difficult, and the economy is reduced. This is because the property is impaired.
[0033]
On the other hand, if the thickness is less than the lower limit of 0.1 μm, the laser drilling performance varies. For example, even when the thickness is 0.03 μm, the laser drilling performance is not improved as compared with the case where a copper-clad laminate having no high carbon content copper layer is used. Although much superior laser drilling performance can be obtained, variation between lots increases. It should be noted that the surface of the high carbon content copper layer formed here does not matter at all whether it is a smooth metal surface having gloss or a matte surface. This point is fundamentally different from the case where a glossy copper foil surface is directly drilled.
[0034]
Then, using the two types of copper foil for a printed wiring board described above, without providing a dissimilar metal layer or an organic material layer such as a nickel auxiliary metal layer for enhancing the absorption efficiency of laser light, etc. Direct laser drilling of the copper foil layer of the copper-clad laminate becomes easy. However, when a nickel auxiliary metal layer is further provided on the surface of the high carbon content copper layer, the laser drilling processability is further improved. That is, the layer configuration shown in FIGS. 4A and 4B is adopted.
[0035]
Regarding the copper foil for any printed wiring board of the above-mentioned `` when the high-carbon content copper layer is used as the bulk copper layer '' and `` when the high-carbon content copper layer is used only for the surface layer portion of the bulk copper layer '' Has demonstrated very good laser drilling performance. However, as a result of further study, it has been found that even in a high carbon content copper layer containing the same amount of carbon, the laser drilling performance is different depending on the crystal structure.
[0036]
The crystal structure of the high carbon content copper layer when manufactured by electrolysis can be classified into the following two types. That is, type (1) is “a needle-like structure and a fine crystal structure that have grown almost continuously from the precipitation start position DS to the precipitation end position DF as shown in FIG. 5”, and the type (1). 2) “A crystal structure that seems to have an extremely fine crystal structure as shown in FIG. 6, but that has grown discontinuously from the precipitation start position DS to the precipitation end position DF”. Although it is possible to improve the laser drilling performance as compared with the case where the carbon is not contained at a high concentration even in the case of the structure, the type (1) of the continuous growth is particularly preferable in these crystal structures. In the case of a needle-like structure and a fine crystal structure, the most excellent laser drilling performance is exhibited.
[0037]
In order to clearly express the laser drilling performance of the type (1) and the type (2), it becomes clear from the result of laser drilling with low energy. This low energy laser drilling test was performed using pulse energy of 8.3 mJ for the first shot and 1.7 mJ for the second shot (total processing energy of 10 mJ). Other laser irradiation conditions are a frequency of 2000 Hz, a mask diameter of 7.0 mm, and a first shot of 21 μsec. And the second shot is 2 μsec. The pulse width, the offset was 0.0, the laser beam diameter was 140 μm, and 400 holes having a processing diameter of 100 μm were formed in the copper clad laminate. As a result, in the case of a copper foil having a nominal thickness of 9 μm having a crystal structure of type (1), the opening ratio is 100% at 400 holes / 400 holes, but a nominal thickness of 9 μm having a crystal structure of type (2). In the case of copper foil, the opening ratio is 0% at 0 holes / 400 holes.
[0038]
It is considered that the degree of fineness of the needle-shaped structure of type (1) can be clearly understood by comparing with the crystal structure of the electrolytic copper foil on the pure copper layer 6 side in FIG. The pure copper layer 6 also has a normal electrolytic copper foil structure produced by an electrolytic method. It is considered that the width of the crystal grains of the needle-shaped structure of type (1) is very small as compared with the crystal structure of the pure copper layer 6. Such a crystal structure is very useful in laser drilling. The present inventors think that, when considered at the crystal grain level, heat conduction is faster in a crystal grain than in a grain boundary. Therefore, the needle-shaped crystal structure in which the shape of the crystal grains is continuously grown becomes easier to conduct heat conduction in the longitudinal direction along the shape of the crystal grains, compared to the needle-shaped crystal structure in which the shape of the crystal grains is discontinuously grown. It is considered that drilling in the thickness direction of the foil is facilitated.
[0039]
Subsequently, a method of manufacturing the above-described printed wiring board copper foil will be described. First, in the claims, "The bulk copper layer is manufactured by electrolyzing a copper sulfate solution containing 30 ppm to 1000 ppm of one or more of glue, gelatin, and collagen peptide, and roughened on one side thereof. A method for producing a copper foil for a printed wiring board, comprising performing a treatment and further performing a necessary surface treatment. " This manufacturing method relates to a copper foil for a printed wiring board in which all of the bulk copper layers are made of high carbon content copper.
[0040]
The bulk copper layer of a normal electrolytic copper foil is also a copper sulfate solution, and a method of adding glue to improve the elongation of the electrolytic copper foil is employed. However, the amount of glue or the like added at this time is 20 ppm or less. On the other hand, in the production method according to the present invention, a concentration range of glue or the like of 30 ppm or more is adopted. By setting the concentration to 30 ppm, the carbon content in the high-carbon copper can be reduced to 0.04 wt%.
[0041]
FIG. 3 shows the result of examining the relationship between the glue concentration in the copper sulfate solution and the amount of carbon in the high-carbon copper obtained by electrolyzing the copper sulfate solution. As can be seen from FIG. 3, when the ordinate indicates the carbon content in the high-carbon copper, and the abscissa indicates the concentration of the glue in the copper sulfate solution used for the production, a logarithmic relationship is obtained. . That is, when the concentration of glue in the copper sulfate solution is around 1000 ppm, it is almost saturated, and the carbon content in the high carbon content copper does not increase any more. And, from the verification results of the laser drilling test, the laser drilling workability dramatically increases when the glue concentration in the copper sulfate solution exceeds 30 ppm. This tendency is the same when gelatin or collagen peptide is used.
[0042]
In another claim, `` a pure copper foil is manufactured by electrolyzing a copper sulfate solution, and glue, gelatin, and a copper peptide solution containing 100 ppm to 1000 ppm of any one or more of collagen peptides, A print characterized in that a high-carbon-containing copper layer having a thickness of 0.1 μm to 5 μm is formed on one side of a pure copper foil by an electrolytic method, a roughening treatment is performed on the other surface, and a necessary surface treatment is further performed. Manufacturing method of copper foil for wiring board. " In this manufacturing method, only the thickness of 0.1 μm to 5 μm on one side of the bulk copper layer is a high carbon content copper layer, the other is a pure copper layer, and the other side has a roughened surface. The present invention relates to a copper foil for a wiring board.
[0043]
In manufacturing the copper foil for a printed wiring board, first, a pure copper layer forming a bulk copper layer is manufactured as a pure copper foil by electrolyzing a copper sulfate solution used for manufacturing a normal electrolytic copper foil. The copper sulfate solution used at this time does not mean a completely pure copper sulfate solution, and it is assumed that an additive within a range of common sense used when manufacturing a conventional copper foil is assumed. . Accordingly, it is described that it is naturally possible to add 20 ppm or less of glue and to use other additives such as cellulose.
[0044]
Then, a high carbon content copper layer is formed on one side of the pure copper foil. Using a copper sulfate solution containing 100 ppm to 1000 ppm of one or more of glue, gelatin, and collagen peptide, the high carbon content copper layer has a thickness of 0.1 μm to 5 μm on one side of the pure copper foil. Is formed by an electrolytic method.
[0045]
In this manufacturing method, a concentration range of glue or the like of 100 ppm or more is adopted. By setting the concentration to 100 ppm, the carbon content in the high-carbon copper can be reduced to 0.08 wt%. The upper limit concentration is determined for the same reason as described above.
[0046]
Further, by controlling the current density, the crystal structure of the high carbon content copper layer produced by electrolysis can be classified into the above-mentioned type (1) and type (2) crystal structures. Strictly speaking, it is difficult to describe as a clear current value because there is a relationship with the concentration of glue or the like in the electrolytic solution. dm ² When the following low current density is adopted and a crystal structure of type (2) is to be obtained, 20 A / dm ² For example, the above high current density is adopted. Therefore, in order to separate the crystal structures by type, the current density should be determined for each process in consideration of the characteristics of the production line, the concentration of the constituents of the electrolytic solution, and the like.
[0047]
As described above, the copper foil for a printed wiring board according to the present invention is obtained. Then, the copper-clad laminate obtained by using the copper foil for a printed wiring board can directly perform laser drilling of the copper foil layer without including the nickel auxiliary metal layer or the organic material layer.
[0048]
However, if a nickel auxiliary metal layer or an organic material layer is further provided, the laser drilling workability becomes better than ever before. That is, by providing the nickel auxiliary metal layer or the organic material layer, the roundness of the processed hole is improved. This will be shown in comparison with the roundness when the nickel auxiliary metal layer is provided in the following embodiments.
[0049]
The layer structure of the printed wiring board copper foil when the nickel auxiliary metal layer or the organic material layer is provided is as shown in FIGS. Then, in the case of the copper foil shown in FIG. 4 (a), the method of manufacturing these copper foils for printed wiring boards is as follows: "The bulk copper layer contains 30 ppm of one or more of glue, gelatin, and collagen peptide. It is manufactured by electrolyzing a copper sulfate solution containing up to 1000 ppm, forming a nickel auxiliary metal layer or an organic material layer on one side thereof, performing a roughening treatment on the other surface side, and further performing a necessary surface treatment. Characteristic method of manufacturing printed wiring board copper foil. "
[0050]
Then, in the case of the copper foil shown in FIG. 4 (b), "a pure copper foil is produced by electrolyzing a copper sulfate solution and contains 100 ppm to 1000 ppm of one or more of glue, gelatin, and collagen peptide. Using a copper sulfate solution, a high carbon-containing copper layer having a thickness of 0.1 μm to 5 μm is formed on one side of the pure copper foil by an electrolytic method, and a nickel auxiliary metal layer or a nickel-containing metal layer is formed on the high carbon-containing copper layer. A method for producing a printed wiring board copper foil, comprising forming an equipment layer, performing a roughening treatment on the other surface side, and further performing a necessary surface treatment. "
[0051]
The nickel auxiliary metal layer mentioned here is formed using nickel or a nickel alloy. For example, when forming a nickel layer, a solution used as a nickel plating solution can be widely used. For example, {circle around (1)} nickel sulfate has a nickel concentration of 5 to 80 g / l, a liquid temperature of 20 to 50 ° C., a pH of 2 to 6, and a current density of 0.3 to 10 A / dm. ² (2) Using nickel sulfate, nickel concentration 5 to 30 g / l, potassium pyrophosphate 50 to 500 g / l, liquid temperature 20 to 50 ° C., pH 8 to 11, current density 0.3 to 10 A / dm ² (3) Using nickel sulfate, nickel concentration is 10 to 70 g / l, boric acid is 20 to 60 g / l, liquid temperature is 20 to 50 ° C., pH is 2 to 6, and current density is 1 to 50 A / dm. ² And other general watt bath conditions.
[0052]
When a nickel-zinc alloy layer is formed, for example, nickel concentration is 1 to 30 g / l using nickel sulfate, zinc concentration is 1 to 30 g / l using zinc pyrophosphate, potassium pyrophosphate is 50 to 500 g / l, Liquid temperature 20-50 ° C, pH 8-11, current density 0.3-10A / dm ² And the like.
[0053]
When forming a nickel-cobalt alloy layer, for example, cobalt sulfate 80 to 180 g / l, nickel sulfate 80 to 120 g / l, boric acid 20 to 40 g / l, potassium chloride 10 to 15 g / l, sodium dihydrogen phosphate 0.1-15 g / l, liquid temperature 30-50 ° C., pH 3.5-4.5, current density 1-10 A / dm ² And the like.
[0054]
In addition, nickel-phosphorus alloy plating can be performed by using a phosphoric acid-based solution. In this case, nickel sulfate 120 to 180 g / l, nickel chloride 35 to 55 g / l, H ₃ PO ₄ 30-50 g / l, H ₃ PO ₃ 20-40 g / l, liquid temperature 70-95 ° C, pH 1-2, current density 5-50 A / dm ² And the like.
[0055]
Next, as a resin material for improving the absorption efficiency of the laser constituting the organic material layer, thermoplastic resins such as polyethylene terephthalate (PET) and polyethylene, which have good absorption in the infrared region including the wavelength of the laser beam, are used. It is preferable to use These resin layers are formed into an organic material layer by applying a corresponding resin solution and drying, or by processing into a film and laminating.
[0056]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a result of manufacturing a copper-clad laminate using the above-described copper foil for a printed wiring board and performing laser drilling using the copper-clad laminate will be described.
[0057]
First embodiment: In this embodiment, a copper foil 1 for a printed wiring board in which all of the bulk copper layer 2 shown in FIG. First, a bulk copper layer 2 was produced by electrolytic deposition on the surface of a titanium drum of an electrolytic copper foil electrolysis apparatus. A current density of 5 A / dm was used as the electrolytic solution at this time using a copper sulfate solution having a copper concentration of 60 g / l, a free sulfuric acid concentration of 150 g / l, a glue concentration of 800 ppm, and a liquid temperature of 48 ° C. ² , And the high carbon content copper was made into a foil to obtain a bulk copper layer 2. One surface of the bulk copper layer 2 is a glossy surface to which the surface shape of the titanium drum has been transferred, and the other surface is a rough surface having certain irregularities. The carbon content of the bulk copper layer 2 composed of the high-carbon-containing copper was 0.35 wt%, and had a type (1) crystal structure.
[0058]
Then, as a surface treatment, fine copper particles 3 were deposited and adhered on the rough surface of the bulk copper layer 2 to form a roughened surface 4. Prior to the formation of the roughened surface 4, first, the surface of the separated foil was subjected to an acid washing treatment to completely remove the fat component attached to the bulk copper layer 2, and an excess surface oxide film was removed. In this pickling treatment, a dilute sulfuric acid solution having a concentration of 100 g / l and a liquid temperature of 30 ° C. was used, and the immersion time was 30 seconds.
[0059]
Then, when the pickling treatment is completed, next, as a step of forming fine copper grains 3 on the rough surface of bulk copper layer 2, a step of depositing and attaching fine copper grains 3 on the rough surface; And a covering plating step for preventing falling off. In the former step of depositing and adhering the fine copper particles 3, it is a copper sulfate solution having a concentration of copper of 7 g / l, sulfuric acid of 100 g / l, a liquid temperature of 25 ° C., and a current density of 10 A / dm. ² Electrolysis was performed for 10 seconds.
[0060]
As described above, once the fine copper grains 3 are formed on the rough surface of the bulk copper layer 2 by adhesion, the fine copper grains 3 are coated under a smooth plating condition in the cover plating step for preventing the fine copper grains 3 from falling off. To uniformly deposit copper. Here, the copper plating solution is a copper sulfate solution having a concentration of 60 g / l of copper, 150 g / l of sulfuric acid, a liquid temperature of 45 ° C., and a current density of 15 A / dm. ² And electrolyzed for 20 seconds.
[0061]
When the above-described roughening treatment is completed, the copper foil is then subjected to rust prevention treatment on both surfaces. The rust prevention treatment is for preventing the surface of the copper foil 1 for printed wiring boards from being oxidized and corroded. In the rust prevention treatment, there is no problem in adopting any of organic rust prevention using benzotriazole, imidazole or the like, or inorganic rust prevention using zinc, chromate, zinc alloy or the like, but is described here below. The condition of inorganic rust prevention was adopted. Using a zinc sulfate bath, sulfuric acid concentration 70 g / l, zinc concentration 20 g / l, liquid temperature 40 ° C, current density 15 A / dm ² And subjected to zinc rust prevention treatment. In the drawings, the description of the rustproofing layer is omitted.
[0062]
When the rust prevention treatment is completed, the copper foil 1 for a printed wiring board is finally dried for 40 seconds in a furnace heated to an atmospheric temperature of 110 ° C. by an electric heater, and the completed printed wiring board having a nominal thickness of 12 μm is completed. Copper foil 1 for use.
[0063]
Using this copper foil 1 for printed wiring boards and an inner layer core material on which an inner layer circuit was formed, a copper-clad laminate containing an inner layer circuit was manufactured. The copper foil for a printed wiring board was hot-pressed and bonded to both surfaces of the inner core material via one FR-4 prepreg having a thickness of 100 μm to produce a copper-clad laminate with an inner circuit. . Then, from both surfaces, holes serving as blind via holes were formed using a carbon dioxide laser. At this time, the conditions for drilling by the carbon dioxide gas laser employ the same conditions (total processing energy of 20 mJ) described in the description of Table 1 above. As a result, all of the 400 drilled holes were successfully drilled, and the roundness of the drilled holes was 0.95 on average. In addition, 400 holes were drilled under the condition of the total processing energy of 10 mJ described above. As a result, the roundness of the machined hole was 0.84, but all 400 holes could be machined.
[0064]
Second embodiment: In this embodiment, a printed wiring board copper foil 1 ′ in which the bulk copper layer 2 shown in FIG. 2 was composed of the high carbon content copper layer 5 and the pure copper layer 6 was manufactured. First, a 9 μm thick pure copper layer 6 was produced by electrolytic deposition on the surface of a titanium drum of an electrolytic copper foil electrolysis apparatus. As the electrolytic solution at this time, a copper sulfate solution having a copper concentration of 60 g / l, a free sulfuric acid concentration of 150 g / l, a glue of 10 ppm, and a liquid temperature of 48 ° C. was used, and the current density was 60 A / dm. ² And the pure copper layer 6 was made into a foil shape and continuously wound up. One surface of the pure copper foil 6 is a glossy surface on which the surface shape of the titanium drum has been transferred, and the other surface is a rough surface having certain irregularities.
[0065]
Then, a high carbon content copper layer 5 having a thickness of 3 μm was formed on the glossy surface of the pure copper foil 6. The formation of the high carbon content copper layer 5 is performed by using a copper sulfate solution as an electrolytic solution having a copper concentration of 60 g / l, a free sulfuric acid concentration of 150 g / l, a glue concentration of 1000 ppm, and a liquid temperature of 48 ° C. Density 5A / dm ² And electrolysis. Thus, the bulk copper layer 2 in the form of a foil, in which the high carbon content copper layer 5 and the pure copper layer 6 were laminated, was manufactured. At this time, the carbon content of the high carbon content copper layer 5 was 0.40 wt%, and had a type (1) crystal structure.
[0066]
Hereinafter, in the same manner as described in the first embodiment, the surface of the pure copper layer 6 of the bulk copper layer 2 is subjected to a roughening treatment and a rust-preventive treatment to produce a copper foil 1 ′ for a printed wiring board. went. Therefore, the conditions of the roughening treatment and the rust prevention treatment are the same as those of the first embodiment, and the description is omitted here to avoid duplicating descriptions.
[0067]
Using the copper foil for printed wiring board 1 'and the inner layer core material on which the inner layer circuit was formed, a copper-clad laminate with an inner layer circuit was manufactured in the same manner as in the first embodiment. Holes serving as blind via holes were formed from both sides of the copper-clad laminate with the inner layer circuit using a carbon dioxide laser. At this time, the conditions for drilling by the carbon dioxide gas laser employ the same conditions (total processing energy of 20 mJ) described in the description of Table 1 above. As a result, of the 400 holes that were drilled, all the holes were successfully drilled, and the roundness of the drilled holes was 0.94 on average. In addition, 400 holes were drilled under the condition of the total processing energy of 10 mJ described above. As a result, the roundness of the machined hole was 0.86, but all 400 holes could be machined.
[0068]
Third embodiment: In this embodiment, all of the bulk copper layer 2 shown in FIG. 4A is made of high carbon content copper, and a copper auxiliary metal layer P is formed on the opposite side of the roughened surface. A foil 1a was manufactured. First, a bulk copper layer 2 was produced by electrolytic deposition on the surface of a titanium drum of an electrolytic copper foil electrolysis apparatus. A current density of 6 A / dm was used as the electrolytic solution at this time using a copper sulfate solution having a copper concentration of 60 g / l, a free sulfuric acid concentration of 150 g / l, a glue concentration of 800 ppm, and a liquid temperature of 48 ° C. ² , And the high-carbon-containing copper was formed into a foil having a thickness of 9 μm and continuously wound to obtain a bulk copper layer 2. One surface of the bulk copper layer 2 is a glossy surface to which the surface shape of the titanium drum has been transferred, and the other surface is a rough surface having certain irregularities. The carbon content of the bulk copper layer 2 composed of the high-carbon-containing copper was 0.35 wt%, and had a type (1) crystal structure.
[0069]
Then, a nickel layer having a thickness of 0.5 μm was formed as a nickel auxiliary metal layer P on the surface on the glossy side of the bulk copper layer 2. For the formation of the nickel layer, a solution used as a nickel plating solution can be widely used. Here, nickel sulfate is used, the nickel concentration is 60 g / l, boric acid is 30 g / l, the solution temperature is 30 ° C., pH 3, current density 5A / dm ² The conditions were adopted.
[0070]
Hereinafter, roughening treatment was performed on the roughened surface side of the bulk copper layer in the same manner as in the first embodiment to form a roughened surface 4 and rust prevention treatment was performed. However, in the first embodiment, rust prevention treatment was performed on both surfaces. However, in the case of this embodiment, since one side is a nickel layer, rust prevention treatment is not required, and only the roughened surface 4 is subjected to rust prevention treatment. Was given. Therefore, in order to avoid redundant description of the roughening process and the rust prevention process, the description is omitted here.
[0071]
Using the copper foil 1a for a printed wiring board and the inner core material on which the inner layer circuit was formed, a copper-clad laminate with an inner layer circuit was manufactured in the same manner as in the first embodiment. Holes serving as blind via holes were formed from both sides of the copper-clad laminate with the inner layer circuit using a carbon dioxide laser. At this time, the conditions for drilling by the carbon dioxide gas laser employ the same conditions (total processing energy of 20 mJ) described in the description of Table 1 above.
[0072]
When the laser drilling was completed, the nickel auxiliary metal layer existing on the glossy side was removed by etching. For the selective etching of nickel, a copper-clad laminate was anodic-polarized in this solution using a sulfuric acid solution having a concentration of 600 ml / l, and the nickel layer was peeled off by electrolysis. After that, all of the 400 holes drilled were observed. As a result, all the holes were successfully drilled, the roundness of the processed holes was 0.98 on average, and a good hole shape was obtained as compared with the first embodiment. I have.
[0073]
The laser processing conditions were changed to the above-mentioned laser processing conditions of a total processing energy of 10 mJ, and 400 holes were drilled. As a result, the roundness of the machined hole was 0.87, but all 400 holes could be machined.
[0074]
Fourth embodiment: In this embodiment, the bulk copper layer 2 shown in FIG. 4B is composed of the high carbon content copper layer 5 and the pure copper layer 6, and the outermost layer on the opposite side of the roughened surface 4 has a nickel auxiliary metal layer. The copper foil 1b for printed wiring boards provided with P was manufactured. First, the pure copper layer 6 having a thickness of 9 μm is manufactured by the above-described apparatus for manufacturing an electrolytic copper foil, and the high carbon content copper layer 5 having a thickness of about 3 μm is formed on the glossy surface of the pure copper layer 6. This is the same as the second embodiment. Therefore, the description here is omitted to avoid redundant description.
[0075]
After the formation of the high carbon content copper layer 5 on the glossy side of the pure copper layer 6, the nickel auxiliary metal layer P was subsequently formed on the surface of the high carbon content copper layer 5. At this time, the nickel auxiliary metal layer P was a nickel layer having a thickness of 0.5 μm in the same manner as in the third embodiment. Therefore, the manufacturing conditions and the like are the same as those in the third embodiment, and the description is omitted here to avoid redundant description.
[0076]
Further, in the same manner as in the third embodiment, the roughening treatment and the rust prevention treatment are performed on the rough surface side of the foil on which the nickel auxiliary metal layer P is formed in the same manner as in the first embodiment. Surface 4 was formed and subjected to rust prevention treatment. However, in the first embodiment, rust prevention treatment was performed on both surfaces. However, in the case of this embodiment, since one surface is a nickel layer, rust prevention treatment is not required, and only the roughened surface 4 is subjected to rust prevention treatment. Was given. Therefore, in order to avoid redundant description of the roughening process and the rust prevention process, the description is omitted here.
[0077]
Using the copper foil 1b for a printed wiring board and the inner core material on which the inner layer circuit was formed, a copper-clad laminate with an inner layer circuit was manufactured in the same manner as in the first embodiment. Holes serving as blind via holes were formed from both sides of the copper-clad laminate with the inner layer circuit using a carbon dioxide laser. At this time, the conditions for drilling by the carbon dioxide gas laser employ the same conditions (total processing energy of 20 mJ) described in the description of Table 1 above.
[0078]
When the laser drilling was completed, the nickel auxiliary metal layer existing on the glossy side was removed by etching. For the selective etching of nickel, a copper-clad laminate was anodic-polarized in this solution using a sulfuric acid solution having a concentration of 600 ml / l, and the nickel layer was peeled off by electrolysis. After that, all of the 400 holes drilled were observed. As a result, all the holes were successfully drilled, the roundness of the processed holes was 0.98 on average, and a good hole shape was obtained as compared with the first embodiment. I have.
[0079]
The laser processing conditions were changed to the above-mentioned laser processing conditions of a total processing energy of 10 mJ, and 400 holes were drilled. As a result, the roundness of the machined hole was 0.88, but all 400 holes could be machined.
[0080]
Comparative example: In this embodiment, a copper foil in which the entire bulk copper layer is made of pure copper was manufactured. First, a bulk copper layer was produced by electrolytic deposition on the surface of a titanium drum of an electrolytic apparatus for electrolytic copper foil. As the electrolytic solution at this time, a copper sulfate solution having a copper concentration of 60 g / l, a free sulfuric acid concentration of 150 g / l, a glue concentration of 10 ppm, and a liquid temperature of 48 ° C. was used, and the current density was 60 A / dm. ² , And the deposited copper was formed into a foil and continuously wound. One surface of the bulk copper layer is a glossy surface on which the surface shape of the titanium drum has been transferred, and the other surface is a rough surface having certain irregularities. The carbon content of the bulk copper layer made of pure copper was 0.01 wt%, and the crystal structure was a needle-like structure, but was not as fine as the type (1) crystal grains.
[0081]
Since the roughening treatment and the rust-prevention treatment and the like performed as the surface treatment are the same as those in the first embodiment, the description is omitted here to avoid duplicating description. In this way, a copper foil for a printed wiring board in which all of the bulk copper layers were made of pure copper was manufactured.
[0082]
Using this copper foil for a printed wiring board and the inner layer core material on which the inner layer circuit was formed, a copper-clad laminate with an inner layer circuit was manufactured in the same manner as in the first embodiment. Holes serving as blind via holes were formed from both sides of the copper-clad laminate with the inner layer circuit using a carbon dioxide laser. At this time, the conditions for drilling by the carbon dioxide laser (total processing energy: 20 mJ) are the same as those described in Table 1 described above.
[0083]
When the laser drilling was completed, all of the 400 holes drilled were then observed. As a result, it was determined that only four of the 400 holes were successfully drilled, and the roundness of the hole that was determined to be successfully drilled was 0.90 on average. As will be apparent from a comparison of this result with the above-described embodiment, it can be said that the laser drilling performance is significantly improved as an effect of the present invention.
[0084]
The laser processing conditions were changed to the above-mentioned laser processing conditions of a total processing energy of 10 mJ, and 400 holes were drilled. As a result, drilling cannot be performed at all of the 400 holes, and it becomes clear that the laser drilling performance is completely different from the above-described embodiment.
[0085]
【The invention's effect】
As described above, by using the copper foil for a printed wiring board according to the present invention, it is possible to directly drill a copper foil layer of a copper-clad laminate using a carbon dioxide laser. That is, the conventional direct drilling of copper foil eliminates the need for a nickel auxiliary metal layer or an organic material layer to increase the required laser light absorption efficiency on the surface of the copper foil, and does not include a dissimilar metal element or the like. Therefore, a step of removing the nickel auxiliary metal layer or the like is not required, and the burden on the wastewater treatment is significantly reduced, so that the total manufacturing cost can be significantly reduced. On the other hand, by using the copper foil for a printed wiring board provided with the nickel auxiliary metal layer and the like according to the present invention, the processing accuracy of laser drilling can be significantly improved.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a copper foil for a printed wiring board.
FIG. 2 is a schematic cross-sectional view of a copper foil for a printed wiring board.
FIG. 3 is a graph showing the relationship between the concentration of glue in a copper sulfate solution and the amount of carbon in copper with a high carbon content obtained by electrolyzing the copper sulfate solution.
FIG. 4 is a schematic cross-sectional view of a copper foil for a printed wiring board.
FIG. 5 is a cross-sectional crystal structure observation image of a high carbon content copper layer.
FIG. 6 is a cross-sectional crystal structure observation image of a high carbon content copper layer.
FIG. 7 is a schematic view showing a laser processing procedure.
[Explanation of symbols]
1 Copper foil for printed wiring boards
2 Bulk copper layer
3 Fine copper grains
4 Roughened surface
5 High carbon content copper layer
6 Pure copper layer
P auxiliary metal layer (or organic material layer)

Claims (13)

A copper foil for manufacturing a printed wiring board having a roughened surface on one side of a bulk copper layer,
The copper foil for a printed wiring board, wherein the bulk copper layer is made of high carbon content copper having a carbon content of 0.03 wt% to 0.40 wt%. The copper foil for a printed wiring board according to claim 1, wherein the cross-sectional observation crystal structure of the bulk copper layer is a fine and continuous needle-like crystal. The copper foil for a printed wiring board according to claim 1, wherein a nickel auxiliary metal layer having a thickness of 0.1 μm to 2.0 μm is provided on a surface of the bulk copper layer. The copper foil for a printed wiring board according to any one of claims 1 to 3, wherein an organic material layer for improving laser absorption efficiency is provided on a surface of the bulk copper layer. A copper foil for manufacturing a printed wiring board having a roughened surface on one side of a bulk copper layer,
The bulk copper layer includes a high carbon content copper layer having a carbon content of 0.08 wt% to 0.40 wt% and a thickness of 0.1 μm to 5 μm on the opposite side of the roughened surface, and the high carbon content. A copper foil for a printed wiring board, comprising a pure copper layer below the copper layer. The copper foil for a printed wiring board according to claim 5, wherein the cross-sectional observation crystal structure of the high carbon content copper layer is a fine and continuous needle-like crystal. The copper foil for a printed wiring board according to claim 5, wherein a nickel auxiliary metal layer having a thickness of 0.1 μm to 2.0 μm is provided on a surface of the bulk copper layer. The copper foil for a printed wiring board according to any one of claims 5 to 7, wherein an organic material layer for improving laser absorption efficiency is provided on a surface of the bulk copper layer. It is a manufacturing method of the copper foil for printed wiring boards of Claim 1 or Claim 2, Comprising:
The bulk copper layer is manufactured by electrolyzing a copper sulfate solution containing 30 ppm to 1000 ppm of one or more of glue, gelatin, and collagen peptide, and one side thereof is subjected to a roughening treatment, and further necessary surface is formed. A method for producing a copper foil for a printed wiring board, which comprises performing a treatment. It is a manufacturing method of the copper foil for printed wiring boards of Claim 3 or Claim 4, Comprising:
The bulk copper layer is manufactured by electrolyzing a copper sulfate solution containing 30 ppm to 1000 ppm of one or more of glue, gelatin, and collagen peptide, and forming a nickel auxiliary metal layer or an organic material layer on one side thereof. And performing a roughening treatment on the other surface side and further performing a necessary surface treatment. It is a manufacturing method of the copper foil for printed wiring boards of Claim 5 or Claim 6, Comprising:
A pure copper foil is manufactured by electrolyzing a copper sulfate solution, and glue, gelatin, and a copper sulfate solution containing 100 ppm to 1000 ppm of any one or more of collagen peptides are used. A method for producing a copper foil for a printed wiring board, comprising forming a high carbon content copper layer having a thickness of 5 μm by an electrolytic method, performing a roughening treatment on the other surface side, and further performing a necessary surface treatment. It is a manufacturing method of the copper foil for printed wiring boards of Claim 7 or Claim 8, Comprising:
A pure copper foil is manufactured by electrolyzing a copper sulfate solution, and glue, gelatin, and a copper sulfate solution containing 100 ppm to 1000 ppm of any one or more of collagen peptides are used. A high carbon content copper layer having a thickness of 5 μm is formed by an electrolytic method, a nickel auxiliary metal layer or an organic material layer is formed on the high carbon content copper layer, and a roughening treatment is performed on the other surface side. A method for producing a copper foil for a printed wiring board, characterized by applying a special surface treatment. A copper-clad laminate obtained by using the copper foil for a printed wiring board according to any one of claims 1 to 8.

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