JP3817645B2

JP3817645B2 - Electroless copper plating method and apparatus, copper replenishment apparatus, and electroless copper plating replenisher preparation method and apparatus

Info

Publication number: JP3817645B2
Application number: JP2002138359A
Authority: JP
Inventors: 峰雄川本; 武之板橋; 晴夫赤星; 正飯田; 智行宮崎
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2002-05-14
Filing date: 2002-05-14
Publication date: 2006-09-06
Anticipated expiration: 2022-05-14
Also published as: JP2003328142A

Description

【０００１】
【発明の属する技術分野】
本発明は、プリント配線板や各種プラスチックに無電解銅めっきを行う新規な無電解銅めっき方法とその装置及びその銅補給装置並びにその無電解銅めっき補給液の作成方法とその装置に関する。
【０００２】
【従来の技術】
従来、プリント配線板や各種プラスチックのめっきに使用する無電解銅めっき液には、一般に銅成分として硫酸銅５水和物、還元剤にホルムアルデヒドを用いている。しかし、不足する銅イオンやホルムアルデヒドを補給して無電解銅めっき液を繰り返し使用して行くと、反応生成物として硫酸イオン；SO_４ ^２−やギ酸イオン；HCOO⁻などが蓄積し、めっき液比重の増加と共に溶存酸素濃度が低下してめっき液が不安定になったり、めっき膜表面に銅微粒子が付着しやすくなる。このため、ある時点でめっき液を更新するという問題があり、無電解銅めっき液の長寿命化が課題となる。
【０００３】
この課題に対して、特開平8-67987号公報では低温槽内でめっき液を霧状に吹き付けて反応生成物を再結晶化させて除去する方法を提案している。更に、特開平7-286279号公報では硫酸イオンに水酸化バリウムを添加して硫酸バリウムで除去する方法が提案されている。また、ギ酸イオンについては、特開昭56-136967号公報のような電気透析法か、逆浸透膜法で除去する方法が行われている。
【０００４】
一方、硫酸イオンの蓄積防止については、特公昭59-32542号公報に硫酸銅５水和物の変わりに水酸化銅、酸化銅、オキシ酸銅、又、銅の塩基性炭酸塩、塩基性塩化物、塩基性硫酸塩を使用することが提案されている。また、これら銅成分を溶解してめっき槽へ移送する装置については、特開平5-306471号公報、特開平6-25863号公報、特開平9-137298号公報に提案されている。
【０００５】
更に、特開平6-192844号公報には、無電解めっき液に被めっき物の温度を所定に保つために所定の温度の空気、不活性ガスを吹込むこと、又めっき液の溶存酸素濃度を所定に保つために酸素、空気をめっき液の補給槽に吹込むことが示されている。
【０００６】
【発明が解決しようとする課題】
従来の硫酸銅５水和物の変わりに上記した水酸化第二銅(Cu(OH)_２)、酸化第二銅（CuO）などを使用する方法に関しては、特開平5-306471号公報、特開平6-25863号公報、特開平9-137298号公報などに提案されているような装置を利用するが、前記した銅成分を溶解する銅溶解槽内や、作成した銅補給液を貯蔵する貯液槽内でめっき液が不安定となり、酸化第一銅が生成する問題がある。このため、目的としたCu濃度の補給液が得られない他、沈降した酸化第一銅(Cu₂O)の微粒子が原因で移送経路に設置した濾過器内フィルタ−が目詰まりを起こす。この酸化第一銅の生成速度は、銅溶解槽や貯液槽内の補給液の温度に強く依存し、温度が高くなるに伴って速くなる。
【０００７】
又、特開平6-192844号公報には、無電解銅めっき液への銅補給については示されていない。
【０００８】
本発明の目的は、銅溶解槽や貯液槽内の銅補給液の安定性を高めて酸化第一銅の生成を防止し、所定の銅濃度の銅補給液をめっき槽へ供給することができる無電解銅めっき方法とその装置及びその銅補給装置並びにその無電解銅めっき補給液の作成方法とその装置を提供することにある。
【０００９】
【課題を解決するための手段】
本発明は、めっき槽中の無電解銅めっき液の一部を抜き取り、該抜き取った無電解銅めっき液を銅溶解槽に貯蔵し、その底部に設けられた複数の噴出口より酸素含有ガスを吹き込み、該酸素含有ガスを吹き込んだ無電解銅めっき液により水酸化第二銅及び酸化第二銅の少なくとも１種を溶解した無電解銅めっき補給液を貯液槽に貯蔵し、その底部に設けられた複数の噴出口より前記酸素含有ガスを吹き込み、該酸素含有ガスが吹き込まれた前記無電解銅めっき補給液を前記めっき槽に補給しながら銅めっきを行うことを特徴とする無電解銅めっき方法にある。水酸化第二銅及び酸化第二銅の他に、塩化第一銅、塩化第二銅及び炭酸銅の少なくとも１種の銅化合物が好ましいが、作業性の点で水酸化第二銅及び酸化第二銅が特に好ましい。
【００１０】
具体的には、無電解銅めっき液に空気と酸素ガスとの混合ガス、窒素ガスと酸素ガスとの混合ガス及び酸素ガスのいずれか１種を吹き込み、該酸素含有ガスを吹き込んだ無電解銅めっき液により水酸化第二銅及び酸化第二銅の少なくとも１種を溶解し、該酸化銅を溶解した無電解銅めっき液を前記めっき槽に補給しながら銅めっきを行うものである。
【００１１】
本発明は、めっき槽と、該めっき槽から移送ポンプによって移送された前記無電解銅めっき液によって水酸化第二銅及び酸化第二銅の少なくとも１種を溶解して銅補給液を生成する銅溶解槽と、該銅溶解槽内底部に設けられた複数の噴出口より酸素含有ガスを吹き込む酸素含有ガス噴出手段と、前記銅溶解槽内の前記無電解銅めっき補給液を移送ポンプによって移送し貯蔵する貯液槽と、該貯液槽内底部に設けられた複数の噴出口より酸素含有ガスを吹き込む酸素含有ガス噴出し手段と、前記銅溶解槽内の前記銅補給液を前記めっき槽に供給する経路とを具備したことを特徴とする無電解銅めっき装置にある。
【００１３】
本発明は、めっき中の無電解銅めっき液の一部を抜き取った前記無電解銅めっき液を銅溶解槽に貯蔵しその底部に設けられた複数の噴出口より酸素含有ガスを吹き込み、該酸素含有ガスが吹き込まれた無電解銅めっき液により水酸化第二銅及び酸化第二銅の少なくとも１種を溶解した無電解銅めっき補給液を貯液槽に貯蔵しその底部に設けられた複数の噴出口より前記酸素含有ガスを吹き込むことを特徴とする無電解銅めっき液の銅補給液の作成方法にある。
【００１４】
具体的には、無電解銅めっき液に、空気と酸素ガスとの混合ガス、窒素ガスと酸素ガスとの混合ガス及び酸素ガスのいずれか１種を吹き込み、該ガスが吹き込まれた無電解銅めっき液により銅化合物を溶解することを特徴とする。
【００１５】
更に、本発明は、めっき槽より移送ポンプによって無電解銅めっき液が移送される経路と、めっき槽より無電解銅めっき液の一部を抜き取った前記無電解銅めっき液に水酸化第二銅及び酸化第二銅の少なくとも１種を前記無電解銅めっき液によって溶解して無電解銅めっき補給液を生成する銅溶解槽と、該銅溶解槽中の前記無電解銅めっき補給液を別途貯蔵する貯液槽と、前記銅溶解槽中の前記無電解銅めっき補給液を前記貯液槽に移送する移送ポンプと、前記貯液槽中の前記無電解銅めっき補給液を前記めっき槽に移送する移送ポンプと、前記銅溶解槽内底部と貯液槽内底部とに設けられた複数の噴出口より酸素含有ガス噴出手段とを具備したことを特徴とする無電解銅めっき用銅補給装置にある。
【００１６】
前記銅溶解槽中の前記無電解銅めっき補給液を前記貯液槽に濾過器を介して移送することが好ましい。
【００１７】
又、本発明は、前記貯液槽の無電解銅めっき補給液を移送ポンプによってめっき槽に移送する経路と、前記無電解銅めっき補給液を前記濾過器に接続された切り替えバルブを介して前記めっき槽に移送する経路とを有することが好ましい。
【００１９】
銅溶解槽及び貯液槽での銅補給液の温度が高く、且つ攪拌器だけの攪拌の場合、銅補給液の溶存酸素濃度が低下してEDTAと錯体化した銅が一部解離して、酸化第一銅が浮遊し始め、これが核となって酸化第一銅の沈降が加速する。しかし、これに酸素含有ガスを吹き込むことで銅補給液の溶存酸素濃度が高まり、酸化第一銅生成の防止ができて銅補給液の安定性が図られる。
【００２０】
めっき槽内の無電解銅めっき液の成分は、銅源、錯化剤、還元剤、ｐＨ調整剤、添加剤からなる。銅源として、めっき液を作成する場合は硫酸銅５水和物を用いても良く、水酸化第二銅、酸化第二銅の内１種以上を用いても良い。塩化第一銅又は塩化第二銅を用いても良いが、めっき液中に塩素イオンが増加するのでその除去が必要である。また、炭酸銅はCuCO_３とCu(OH)_２との混合物であり、両者の比率がロット毎で異なる時があり、安定した銅濃度管理がややできにくい。
【００２１】
錯化剤にはEDTAを使用する。銅とEDTAとの濃度範囲は、無電解銅めっき液の用途によって異なるが、一般に銅濃度は約0.02mol/L〜0.08mol/L、EDTA濃度は約0.08mol〜0.167mol/Lの範囲で使用する。還元剤は一般には37%ホルマリン溶液、またはパラホルムアルデヒド、もしくはグリオキシル酸などが使用できる。また、ｐＨ調整剤には水酸化ナトリウム、水酸化カリウムを用いる。添加剤は各種界面活性剤の他、公知のジビリジルに代表される複素環化合物、ケイ素化合物、ゲルマニウム化合物、炭酸塩などが用いられる。この無電解銅めっき液は、一般的にはめっき槽底部に設けられた空気噴出しパイプから噴出す空気よって溶存酸素濃度を高めて安定化を図り、温度15℃〜80℃で使用する。
【００２２】
銅溶解槽及び貯液槽での銅補給液の銅mol濃度を、無電解銅めっき液の銅mol濃度の少なくとも1.5倍、好ましくは1.5〜5倍、より好ましくは2〜3倍とすることで、無電解銅めっき液の不足銅分量を補うために必用な銅補給液の供給量が少なくて済む。
【００２３】
又、銅補給液に含まれる銅濃度と錯化剤であるエチレンジアミン四酢酸（EDTA）とのmol濃度比を、銅を1とした場合、EDTAを1.2〜4.0倍にすることにより、銅−EDTAの錯体化の進行が速まると共に解離しにくい錯体となり、結果的に銅補給液の安定性向上に寄与する。
【００２４】
即ち、銅溶解槽で作成する銅補給液中の銅mol濃度は、上記した無電解銅めっき液中の少なくとも1.5倍以上、好ましくは2〜3倍としておく。これは、めっき反応で無電解銅めっき液の銅が消費されるのを補うためである。また、銅補給液中のEDTA濃度は、無電銅めっき液中のEDTA濃度と同量としておく。これによって、作成した銅補給液をめっき槽へ移送ポンプで送った場合、無電解銅めっき液中のEDTA濃度が変化しない。この条件下での銅補給液中の銅とEDTAとのmol濃度比は、銅を１とした場合、EDTAは1.2〜4.0の範囲とする。銅とEDTAとのmol濃度比を、銅１に対してEDTAを１にすると銅とEDTAとの錯体化が十分に進行せず、銅が完全に溶解しない問題が発生する。銅１に対してEDTAは1.2以上とすることで安定化が達成できる。
【００２５】
本発明において、めっき液槽に空気をめっき液に吹込むのは、めっき液中の溶存酸素を高めてめっき液の不安定化(分解防止)を防ぐためである。空気を吹込むと、めっき液中の溶存酸素濃度は０．５〜２．５ｐｐｍであり、又酸素を吹込むとめっき液中の溶存酸素濃度が３．Ｏｐｐｍ以上に高まり、被めっき材に析出した銅が酸化されてめっき反応が停止し、銅が溶解してくる問題がある。しかし、ＣｕＯやＣｕ（ＯＨ）_２を溶解する銅溶解槽や貯液槽への酸素含有ガスの吹込みは、めっき液中の溶存酸素濃度を高めて、これら銅化合物の溶解作用を高めるのと、溶解したＣｕ２^＋とＥＤＴＡとの錯体化物の安定化を図る、言いかえれば酸化第一銅Ｃｕ_２Ｏの生成防止を図ることができる。従って、銅溶解槽や貯液槽へ吹込む酸素含有ガスは、空気以外に、酸素と窒素、又は酸素そのものを使用することができ、溶存酸素濃度の幅が広く、Ｏ．３〜３．５ｐｐｍ（めっき液中の飽和溶存酸素濃度に近い値、水の飽和溶存酸素濃度３．８ｐｐｍ）の範囲で実施することができる。
【００２６】
【発明の実施の形態】
（実施例１）
図１は、本発明の無電解銅めっき装置の構成図である。銅溶解槽１に無電解銅めっき液の銅補給源として水酸化第二銅Ｃｕ（ＯＨ）_２、酸化第二銅ＣｕＯの１種以上の酸化第二銅微粉末、水酸化第二銅微粉末が別途設けられた供給装置によって供給され、攪拌プロペラ２で攪拌溶解して銅補給液３を作成し、この銅補給液３を移送ポンプ４によって濾過器５を介して貯液槽６に貯蔵し、その後、移送ポンプ７によってめっき槽８の無電解銅めっき液９へ送る経路、又銅溶解槽１から移送ポンプ４によって濾過器５を介してめっき槽８の無電解銅めっき液９へ直接送る経路とを有し、銅溶解槽１と貯液槽６とに酸素含有ガス噴出し装置から供給される酸素含有ガスを供給する酸素含有ガス噴出しパイプ１０が設けられている。このパイプ１０から酸素含有ガスを銅補給液中に吹込むことによって銅溶解槽での酸化第二銅、水酸化第二銅の溶解均一性を高め、且つ銅溶解槽内と貯液槽内での酸化第一銅（Ｃｕ２Ｏ）の生成を防止し、溶解したＣｕ２^＋とＥＤＴＡとの錯体化物の安定化が促進される。
【００２７】
又、銅溶解槽１と貯液槽６とに設けた酸素含有ガス噴出しパイプ１０から酸素含有ガスを吹き込むことによって銅補給液３を安定化させることができる。銅溶解槽１と貯液槽６の銅補給液３の銅ｍｏｌ濃度を、無電解銅めっき液９の銅ｍｏｌ濃度の少なくとも１．５倍とし、且つ銅補給液３に含まれる銅と錯化剤であるＥＤＴＡとのｍｏｌ濃度比を、銅を１とした場合、ＥＤＴＡを４．０倍として、銅溶解槽１と貯液槽６とに酸素含有ガスを吹き込むことによって銅補給液３の安定化が図られる。
【００２８】
本発明では、この銅溶解槽１内で酸素含有ガス噴出しパイプ１０から酸素含有ガスを吹き込む点にある。これは、無電解銅めっき液９が例えば４０℃以上で使用していた場合、この温度より低い銅補給液３を補給すると、無電解銅めっき液９の温度を一定に保つことが難しくなるため、銅溶解槽１内の銅補給液３の温度を無電解銅めっき液９と同温度にしておく必要があるが、銅補給液３の温度を４０℃以上にすると、溶存酸素が低下して時間経過と共に酸化第一銅の沈降を起こす問題があるためである。この問題を解決するため、酸素含有ガス噴出しパイプ１０から酸素含有ガスを吹き込み、溶存酸素濃度を高めて酸化第一銅の沈降を防止する。酸素含有ガスを吹き込む方法は、めっき槽８の底に設けた空気吹き出しパイプ１１と同じものを設置して、外部から空気、酸素ガス、または窒素と酸素との混合ガスを供給して行うことができる。
【００２９】
銅溶解槽１で作成した銅補給液３は移送ポンプ４で濾過器５を介して、貯液槽６に送って貯蔵後に移送ポンプ７でめっき槽８へ送るか、あるいは、銅溶解槽１から移送ポンプ４で濾過器５を介して切り替えバルブ１２を操作してめっき槽８へ直接送る。銅補給液３を貯液槽６に送った場合、貯液槽６内でも銅補給液３の温度を無電解銅めっき液９と同じ温度にしておく。この場合でも銅補給液３の酸化第一銅生成防止のため、銅溶解槽１と同様に酸素含有ガス噴出しパイプ１０を設置して酸素含有ガスを吹き込むことが重要である。
【００３０】
また、銅溶解槽１や貯液槽６の銅補給液３が減少した場合、めっき槽８の無電解銅めっき液９を移送ポンプ１３によって銅溶解槽1へ送り、新たに水酸化第二銅または酸化第二銅を溶解して銅補給液３を作成する。この一連の経路を循環して、無電解銅めっき液９の銅補給を効率良く実施できる。
【００３１】
本実施例では、前述の装置を用いて無電解銅めっきを行った。めっき槽１に表１に示す組成の無電解銅めっき液Ａを作成して空気攪拌下、30℃に加温した。このめっき液の比重は20℃で1.024であった。銅溶解槽１では酸素ガスによる攪拌を行いながら攪拌器２を稼動させ、銅含有率62.6%の水酸化第二銅を溶解して銅濃度0.030mol/Lの表２に示す組成の銅補給液Ａを作成した。この銅補給液Ａの銅濃度は、無電解銅めっき液２の銅濃度の1.5倍であり、銅濃度とEDTA濃度とのmol比は、銅を１とした場合、EDTAは約2.77である。この銅補給液Ａを加温器で30℃に保ち、移送ポンプ４で濾過器５を介して貯液槽６に送った。貯液槽６では空気攪拌を行いながら加温器で30℃に保った。
【００３２】
【表１】

【００３３】
【表２】

【００３４】
その後、めっき槽８の無電解銅めっき液Ａに浴負荷1.5dm^２/Lの条件でめっき触媒を付与した銅貼り積層板を浸漬して60分めっきした。無電解銅めっき液Ａの銅濃度は0.018mol/Lに低下していた。次に、移送ポンプ４、移送ポンプ７を稼動して、銅溶解槽１→貯液槽６→めっき槽８の経路で銅補給液Ａの移送を始め、且つめっき槽８内の無電解銅めっき液Ａの消費される37%ホルマリンとpH調整剤のNaOHを30分毎に補給しながらめっきを10ｈ行い、約10.2μm厚のめっき膜を得た。銅溶解槽１内と貯液槽６内とには酸化第一銅の沈降は認められず、濾過器５のフィルタ−の目詰まりも起こらなかった。
【００３５】
以上の操作で10ｈめっきを１回として、繰り返しめっきを行った結果、ギ酸イオンの蓄積によって35回でめっき液比重が20℃で約1.102となったが、無電解銅めっき液Ａは安定であり、めっき膜表面も銅色を呈して銅微粒子の付着も認められなかった。また、銅溶解槽１内と貯液槽６内とに酸化第一銅の沈降は認められず、濾過器５のフィルタ−に目詰まりは起こらなかった。
【００３６】
（比較例１）
実施例１において、銅溶解槽１内の酸素ガスでの攪拌と、貯液槽６内の空気攪拌を行わずに、攪拌器２のみの攪拌とした以外は同様に行った結果、両槽内の銅補給液Ａは約４時間経過時点から酸化第一銅の沈降が認められ始め、約8ｈ経過後では両槽内の銅濃度が初期濃度の約73％に低下していた。一方、濾過器５のフィルタ−には酸化第一銅の目詰まりが発生していた。
【００３７】
（比較例２）
実施例１において、銅補給液Ａの銅成分のみを従来の硫酸銅５水和物7.50g/L(銅濃度0.03mol/L)とした銅補給液Ｂを作成して、酸素ガスによる攪拌を行いながら実施例１と同様に行った。その結果、めっき槽８内の無電解銅めっき液Ａは、ギ酸イオンの他、補給液Ｂの硫酸銅５水和物に起因する硫酸イオンの蓄積によって、繰り返しめっき16回でめっき液比重が20℃で1.106となり、めっき槽８の一部内壁に銅析出が認められ、めっき膜表面に銅微粒子が付着していた。
【００３８】
（実施例２）
実施例１において、無電解銅めっき液Ａの銅成分のみを銅含有率73.48%の酸化第二銅1.74g/L(銅濃度0.020mol/L)とした無電解銅めっき液Ｂを銅溶解槽１で作成した。この無電解銅めっき液Ｂを移送ポンプ４で濾過器５を介してめっき槽８へ送った。そして、銅溶解槽１内を洗浄した後、新たに銅補給液Ａを作成して、その他の方法を実施例１と同じ条件で10ｈめっきを１回として繰り返しめっきを行った。その結果、実施例１と同様の結果が得られた。
【００３９】
（実施例３）
めっき槽８に銅含有率73.48%の酸化第二銅を用いて表３の組成の無電解銅めっき液Ｃを作成し、空気攪拌下、72℃に加温した。このめっき液の比重は20℃で1.032であった。銅溶解槽１内では同様に空気攪拌を行いながら攪拌器２を稼動させて酸化第二銅を溶解して銅濃度0.080mol/Lの表４に示す銅補給液Ｃを作成して加温器で72℃に保った。この銅補給液Ｃの銅濃度は、無電解銅めっき液Ｃの銅濃度の2.0倍であり、また、銅濃度とEDTA濃度とのmol比は、銅を１とした場合、EDTAは約1.46である。この銅補給液Ｃを移送ポンプ４で濾過器５を介して貯液槽６に送った。貯液槽６内でも空気攪拌を行いながら加温器で72℃に保った。
【００４０】
【表３】

【００４１】
【表４】

【００４２】
その後、めっき槽８に浴負荷1.5dm^２/Lの条件でめっき触媒を付与した銅貼り積層板を浸漬すると同時に、移送ポンプ４と移送ポンプ7を稼動して、銅溶解槽４→貯液槽８→めっき槽１の経路で銅補給液Ｃの移送を始め、且つめっき槽１内の無電解銅めっき液Ｃの消費される37%ホルマリンとｐＨ調整剤のNaOHを15５分毎に補給しながらめっきを10ｈ行った。めっき膜厚は25μmであった。その結果、銅溶解槽１内と貯液槽６内とには酸化第一銅の沈降は認められず、濾過器5のフィルタ−にも目詰まりが認められなかった。
【００４３】
以上の条件で10ｈめっきを1回として、15回の繰り返しめっきを行った結果、ギ酸イオンの蓄積によってめっき液比重が20℃で約1.112となったが、無電解銅めっき液Ｃは安定であり、めっき膜表面も銅色を呈して銅微粒子の付着も認められなかった。また、銅溶解槽1内と貯液槽6内とにも酸化第一銅の沈降がなく、濾過器５のフィルタ−の目詰まりも起こらなかった。
【００４４】
（比較例３）
実施例３において、銅溶解槽1内と、貯液槽6内の空気攪拌を行わず、攪拌器２のみの攪拌を行った。それ以外は、同様に行った結果、両槽内の銅補給液は約２時間経過時点から酸化第一銅の沈降が認められ始め、約4ｈ経過後では両槽内の銅濃度が初期濃度の約54%に低下していた。また、濾過器5のフィルタ−にも酸化第一銅の目詰まりが発生していた。
【００４５】
（比較例４）
実施例３において、銅補給液Ｃの銅成分のみを従来の硫酸銅５水和物20.0g/L(銅濃度0.080mol/L)とした銅補給液Ｄを作成し、空気攪拌を行いながら同様に行った。その結果、ギ酸イオンの他、補給液Ｄからの硫酸イオンの蓄積によって繰り返しめっき８回でめっき液比重が20℃で1.116となり、めっき槽８の一部内壁に銅析出が認められ、めっき膜表面にも銅微粒子が付着した。
【００４６】
（実施例４）
実施例３において、無電解銅めっき液Ｃの銅成分のみを銅含有率62.6%の水酸化第二銅4.06g/L(銅濃度0.040mol/L)とした無電解銅めっき液Ｄを銅溶解槽１で作成した。この無電解銅めっき液Ｄを移送ポンプ４で濾過器５を介してめっき槽８へ送った。そして、銅補給液Ｃも含めてその他の方法を実施例３と同じ条件で10ｈめっきを１回として繰り返しめっきを行った。その結果、実施例３と同様の結果が得られた。
【００４７】
（実施例５）
めっき槽８に銅含有率62.6%の水酸化第二銅を用いて表５の組成の無電解銅めっき液Ｅを作成し、空気攪拌下、50℃に加温した。このめっき液の比重は20℃で1.039であった。銅溶解槽１内では同様に空気攪拌を行いながら攪拌器２を稼動させて水酸化第二銅を溶解して銅濃度0.060mol/Lの表６の銅補給液Ｅを作成して加温器で50℃に保った。この銅補給液Ｅの銅濃度は、無電解銅めっき液Ｅの銅濃度の3.0倍である。またこの銅補給液Ｅの組成では、水酸化第二銅以外の成分及び濃度を、無電解銅めっき液組成Ｅと同じくした。銅補給液Ｅ中の銅濃度とEDTA濃度とのmol比は、銅を１とした場合、EDTAは4.0倍である。この銅補給液Ｅを移送ポンプ４で濾過器５を介して貯液槽６に送った。貯液槽６内でも空気攪拌を行いながら加温器で50℃に保った。
【００４８】
【表５】

【００４９】
【表６】

【００５０】
その後、めっき槽８に浴負荷1.5dm^２/Lの条件でめっき触媒を付与した銅貼り積層板を浸漬すると同時に、移送ポンプ４と移送ポンプ７を稼動して、銅溶解槽１→貯液槽６→めっき槽８の経路で銅補給液Ｅの移送を始め、且つめっき槽１内の無電解銅めっき液Ｃの消費される37%ホルマリンとpH調整剤のNaOHを20分毎に補給しながらめっきを10ｈ行った。めっき膜厚は30μmであった。その結果、銅溶解槽１内と貯液槽６内とには酸化第一銅の沈降は認められず、濾過器５のフィルタ−に目詰まりは起こらなかった。
【００５１】
以上の条件で10ｈめっきを1回として、11回の繰り返しめっきを行った結果、ギ酸イオンの蓄積によってめっき液比重が20℃で約1.109となったが、無電解銅めっき液Ｅは安定であり、めっき膜表面も銅色を呈して銅微粒子の付着も認められなかった。また、銅溶解槽１内と貯液槽６内とにも酸化第一銅の沈降がなく、濾過器５のフィルタ−の目詰まりも起こらなかった。
【００５２】
（比較例５）
実施例５において、銅溶解槽１内と、貯液槽６内の空気攪拌を行わず、攪拌器２による攪拌を行いながら同様に行った結果、両槽内の銅補給液は約3時間経過時点から酸化第一銅の沈降が認められ始め、約７ｈ経過後では両槽内の銅濃度が初期濃度の約61%に低下しており、濾過器５のフィルタ−にも一部、酸化第一銅の目詰まりが発生していた。
【００５３】
（実施例６）
めっき槽８に銅含有率73.48%の酸化第二銅を用いて表７の組成の無電解銅めっき液Ｆを作成し、空気攪拌下、70℃に加温した。このめっき液の比重は20℃で1.036であった。銅溶解槽１内では同様にO_２攪拌を行いながら攪拌器２を稼動させて酸化第二銅を溶解して銅濃度0.075mol/Lの表８の銅補給液Ｆを作成して加温器で70℃に保った。この銅補給液Ｆの銅濃度は、無電解銅めっき液Ｆの銅濃度の2.5倍とし、銅濃度とEDTA濃度とのmol比は、銅を１とした場合、EDTAは1.2倍である。この銅補給液Ｆを移送ポンプ４で濾過器５を介して貯液槽６に送った。貯液槽６内でも空気攪拌を行いながら加温器で70℃に保った。
【００５４】
【表７】

【００５５】
【表８】

【００５６】
その後、めっき槽８に浴負荷1.2dm^２/Lの条件でめっき触媒を付与した銅貼り積層板を浸漬すると同時に、移送ポンプ４と移送ポンプ７を稼動して、銅溶解槽１→貯液槽６→めっき槽８の経路で銅補給液Ｆの移送を始め、且つめっき槽１内の無電解銅めっき液Ｆの消費される37%ホルマリンとpH調整剤のNaOHを20分毎に補給しながらめっきを6ｈ行った。めっき膜厚は約25μmであった。その結果、銅溶解槽１内と貯液槽６内とには酸化第一銅の沈降は認められず、濾過器５のフィルタ−にも目詰まりが認められなかった。
【００５７】
以上の条件で6ｈめっきを1回として、10回の繰り返しめっきを行った結果、ギ酸イオンの蓄積によってめっき液比重が20℃で約1.114となったが、無電解銅めっき液Ｆは安定であり、めっき膜表面も銅色を呈して銅微粒子の付着も認められなかった。また、銅溶解槽１内と貯液槽６内とにも酸化第一銅の沈降がなく、濾過器５のフィルタ−の目詰まりも起こらなかった。
【００５８】
（比較例６）
実施例６において、銅補給液Ｆの銅成分のみを従来の硫酸銅５水和物18.73g/L(銅濃度0.075mol/L)とした銅補給液Ｇを作成して、空気攪拌を行いながら実施例１と同様に行った。その結果、めっき槽８内の無電解銅めっき液Ｆは、ギ酸イオンの他、補給液Ｇの硫酸銅５水和物に起因する硫酸イオンの蓄積によって、繰り返しめっき６回でめっき液比重が20℃で1.113となり、めっき槽８の一部内壁に銅析出が認められ、めっき膜表面が暗銅色になり銅微粒子の付着が発生していた。
【００５９】
【発明の効果】
以上のように、本発明によれば、銅溶解槽と貯液槽との銅補給液に酸素含有ガスを吹き込むことにより、銅補給液の安定性が向上することが明らかである。これによって、銅補給液を長期間に渡って使用できる。更に、銅溶解槽、貯液槽、移送ポンプ４、移送ポンプ７、濾過器５内のフィルタ−に酸化第一銅の沈降や目詰まりが起こらないため、過硫酸アンモニウム水溶液などに代表される銅エッチング液での洗浄回数を削減できるので、これらの廃液処理量を低減することができる。また、繰り返しめっきを行ってもめっき膜表面に銅微粒子の付着が起こらないため、めっき液を長期間に渡って使用することができる。
【００６０】
又、本発明は、40℃以下で使用する薄付け無電解銅めっき液や、40℃〜80℃で使用する厚付け無電解銅めっき液にも有効である。
【図面の簡単な説明】
【図１】本発明の銅溶解槽と貯液槽を具備した無電解銅めっき装置の構成図。
【符号の説明】
１…銅溶解槽、２…攪拌プロペラ、３…銅補給液、４…移送ポンプ、５…濾過器、６…貯液槽、７…移送ポンプ、８…めっき槽、９…無電解銅めっき液、１０…酸素含有ガス噴出しパイプ、１１…空気噴出しパイプ、１２…切り替えバルブ、１３…移送ポンプ。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a novel electroless copper plating method for electroless copper plating on printed wiring boards and various plastics, its apparatus, its copper replenishing apparatus, and itsElectrolesscopperPlatingOf replenisherHow to makeLawAnd its equipmentAbout.
[0002]
[Prior art]
Conventionally, electroless copper plating solutions used for plating printed circuit boards and various plastics generally use copper sulfate pentahydrate as a copper component and formaldehyde as a reducing agent. However, replenishing deficient copper ions and formaldehyde and repeatedly using electroless copper plating solution will result in sulfate ions as reaction products; SO₄ ^2-And formate ion; HCOO⁻As the plating solution specific gravity increases, the dissolved oxygen concentration decreases and the plating solution becomes unstable, or the copper fine particles easily adhere to the surface of the plating film. For this reason, there exists a problem of renewing a plating solution at a certain time, and the lifetime improvement of an electroless copper plating solution becomes a subject.
[0003]
In response to this problem, Japanese Patent Application Laid-Open No. 8-67987 proposes a method in which a reaction solution is recrystallized and removed by spraying a plating solution in a mist form in a low temperature bath. Further, JP-A-7-286279 proposes a method of adding barium hydroxide to sulfate ions and removing it with barium sulfate. Further, formate ions are removed by electrodialysis as disclosed in JP-A-56-136967 or by reverse osmosis membrane method.
[0004]
On the other hand, regarding the prevention of sulfate ion accumulation, Japanese Patent Publication No. 59-32542 discloses copper hydroxide, copper oxide, copper oxyacid, copper basic carbonate, basic chloride instead of copper sulfate pentahydrate. It has been proposed to use a basic sulfate. Further, apparatuses for dissolving these copper components and transferring them to the plating tank have been proposed in JP-A-5-306471, JP-A-6-255863, and JP-A-9-137298.
[0005]
Further, JP-A-6-192844 discloses that air at a predetermined temperature and inert gas are blown into the electroless plating solution to keep the temperature of the object to be plated at a predetermined value, and the dissolved oxygen concentration of the plating solution is set. It is shown that oxygen and air are blown into a plating solution supply tank in order to maintain a predetermined level.
[0006]
[Problems to be solved by the invention]
The above cupric hydroxide (Cu (OH)) instead of the conventional copper sulfate pentahydrate₂), A method using cupric oxide (CuO), etc., as disclosed in JP-A-5-306471, JP-A-6-255863, JP-A-9-137298, etc. Although used, there is a problem that the plating solution becomes unstable in the copper dissolution tank for dissolving the copper component described above or in the liquid storage tank for storing the prepared copper replenisher, and cuprous oxide is generated. For this reason, the replenisher with the desired Cu concentration cannot be obtained, and the precipitated cuprous oxide (Cu₂The filter in the filter installed in the transfer path is clogged due to the fine particles of O). The production rate of cuprous oxide strongly depends on the temperature of the replenisher in the copper dissolution tank and the liquid storage tank, and increases as the temperature increases.
[0007]
Japanese Laid-Open Patent Publication No. 6-192844 does not disclose replenishment of copper to the electroless copper plating solution.
[0008]
  The object of the present invention is to increase the stability of the copper replenisher in the copper dissolution tank and the storage tank to prevent the formation of cuprous oxide, and to supply a copper replenisher with a predetermined copper concentration to the plating tank. Electroless copper plating method and apparatus, copper replenishment apparatus and the sameElectrolesscopperPlatingOf replenisherHow to makeLawAnd its equipmentIs to provide.
[0009]
[Means for Solving the Problems]
  The present invention is to extract a part of the electroless copper plating solution in the plating tank and to remove the electroless copper plating solutionCopper dissolution tankInStore and from multiple spouts at the bottomOxygen-containing gas is blown, and at least one of cupric hydroxide and cupric oxide is dissolved by the electroless copper plating solution into which the oxygen-containing gas is blown.UnravelElectroless copper platingSupplyLiquidThe electroless copper plating replenisher in which the oxygen-containing gas is blown from a plurality of jets provided at the bottom of the storage tank and the oxygen-containing gas is blown.The electroless copper plating method is characterized in that copper plating is performed while replenishing in the plating tank. In addition to cupric hydroxide and cupric oxide, at least one copper compound of cuprous chloride, cupric chloride and copper carbonate is preferred, but cupric hydroxide and oxidized copper are preferred in terms of workability. Dicopper is particularly preferred.
[0010]
Specifically, the electroless copper plating solution is blown with any one of a mixed gas of air and oxygen gas, a mixed gas of nitrogen gas and oxygen gas, and oxygen gas, and the oxygen-containing gas is blown into the electroless copper plating solution. At least one of cupric hydroxide and cupric oxide is dissolved by a plating solution, and copper plating is performed while supplying an electroless copper plating solution in which the copper oxide is dissolved to the plating tank.
[0011]
  The present invention provides a copper replenisher by dissolving at least one of cupric hydroxide and cupric oxide with a plating tank and the electroless copper plating solution transferred from the plating tank by a transfer pump. Dissolution tank and the copper dissolution tankFrom multiple spouts provided at the bottomOxygen-containing gas jet for blowing oxygen-containing gasStartStep andA storage tank that transfers and stores the electroless copper plating replenisher in the copper dissolution tank by a transfer pump, and an oxygen-containing gas jet that blows oxygen-containing gas from a plurality of outlets provided in the bottom of the storage tank And meansThe electroless copper plating apparatus includes a path for supplying the copper replenisher in the copper dissolution tank to the plating tank.
[0013]
  The present inventionPart of the electroless copper plating solution during plating was extractedElectroless copper plating solutionCopper dissolution tankInFrom multiple spouts stored and provided at the bottomBlowing oxygen-containing gas,Oxygen contentDissolve at least one of cupric hydroxide and cupric oxide in the electroless copper plating solution into which gas has been blownThe electroless copper plating replenisher is stored in a storage tank and the oxygen-containing gas is blown from a plurality of jets provided at the bottom thereof.The present invention provides a method for preparing a copper replenisher for an electroless copper plating solution.
[0014]
Specifically, any one of a mixed gas of air and oxygen gas, a mixed gas of nitrogen gas and oxygen gas, and oxygen gas is blown into the electroless copper plating solution, and the electroless copper into which the gas is blown A copper compound is dissolved by a plating solution.
[0015]
  Furthermore, the present invention provides a path through which an electroless copper plating solution is transferred from a plating tank by a transfer pump;To the electroless copper plating solution, which is a part of the electroless copper plating solution extracted from the plating tankDissolving at least one of cupric hydroxide and cupric oxide with the electroless copper plating solution;ElectrolesscopperPlatingCopper dissolution tank for producing a replenisher, and the copper dissolutionA storage tank for separately storing the electroless copper plating replenisher in the tank, a transfer pump for transferring the electroless copper plating replenisher in the copper dissolution tank to the storage tank, and From a transfer pump for transferring the electroless copper plating replenisher to the plating tank, and a plurality of spouts provided in the bottom part of the copper dissolution tank and the bottom part of the liquid storage tankOxygen-containing gas ejectionmeansAnd a copper replenishing device for electroless copper plating.
[0016]
  in frontIn the copper dissolution tankElectrolesscopperPlatingThe replenisher is transferred to the storage tank through a filter.Is preferable.
[0017]
  The present invention also provides,in frontRecordElectroless storage tankcopperPlatingA path for transferring the replenisher to the plating tank by a transfer pump;ElectrolesscopperPlatingA path for transferring replenisher to the plating tank via a switching valve connected to the filterIt is preferable to have.
[0019]
When the temperature of the copper replenishment liquid in the copper dissolution tank and the storage tank is high, and stirring only with the stirrer, the dissolved oxygen concentration of the copper replenishment liquid decreases, and the copper complexed with EDTA partially dissociates, Cuprous oxide begins to float, and this serves as a nucleus to accelerate the precipitation of cuprous oxide. However, by blowing oxygen-containing gas into this, the dissolved oxygen concentration of the copper replenisher increases, so that cuprous oxide formation can be prevented and the stability of the copper replenisher is achieved.
[0020]
The components of the electroless copper plating solution in the plating tank include a copper source, a complexing agent, a reducing agent, a pH adjusting agent, and an additive. When preparing a plating solution as a copper source, copper sulfate pentahydrate may be used, or one or more of cupric hydroxide and cupric oxide may be used. Although cuprous chloride or cupric chloride may be used, since chloride ions increase in the plating solution, it is necessary to remove them. Copper carbonate is CuCO₃And Cu (OH)₂The ratio of the two may differ from lot to lot, and stable copper concentration control is somewhat difficult.
[0021]
EDTA is used as the complexing agent. The concentration range of copper and EDTA varies depending on the application of the electroless copper plating solution. Generally, the copper concentration is about 0.02 mol / L to 0.08 mol / L, and the EDTA concentration is about 0.08 mol to 0.167 mol / L. To do. As the reducing agent, a 37% formalin solution, paraformaldehyde, glyoxylic acid or the like can be generally used. Moreover, sodium hydroxide and potassium hydroxide are used for the pH adjuster. In addition to various surfactants, known additives include heterocyclic compounds typified by dibilidyl, silicon compounds, germanium compounds, and carbonates. This electroless copper plating solution is generally used at a temperature of 15 ° C. to 80 ° C. by stabilizing the dissolved oxygen concentration by increasing the concentration of dissolved oxygen with air jetted from an air jet pipe provided at the bottom of the plating tank.
[0022]
By making the copper mol concentration of the copper replenisher in the copper dissolution tank and the storage tank at least 1.5 times, preferably 1.5-5 times, more preferably 2-3 times the copper mol concentration of the electroless copper plating solution The supply amount of the copper replenisher necessary for supplementing the insufficient copper content of the electroless copper plating solution can be reduced.
[0023]
In addition, when the molar concentration ratio of the copper concentration contained in the copper replenisher and the ethylenediaminetetraacetic acid (EDTA), which is a complexing agent, is 1, the copper EDTA is increased by 1.2 to 4.0 times when the EDTA is 1.2 to 4.0 times. As a result, the complexation of the copper accelerates and becomes a complex that is difficult to dissociate.
[0024]
That is, the copper mol concentration in the copper replenisher prepared in the copper dissolution tank is at least 1.5 times or more, preferably 2 to 3 times that in the above-described electroless copper plating solution. This is to compensate for the consumption of copper in the electroless copper plating solution in the plating reaction. Further, the EDTA concentration in the copper replenishing solution is set to the same amount as the EDTA concentration in the electroless copper plating solution. Thereby, when the prepared copper replenisher is sent to the plating tank by a transfer pump, the EDTA concentration in the electroless copper plating solution does not change. The molar concentration ratio of copper and EDTA in the copper replenisher under these conditions is such that EDTA is in the range of 1.2 to 4.0 when copper is 1. If the molar concentration ratio of copper and EDTA is set to 1 with respect to copper 1, complexation between copper and EDTA does not proceed sufficiently, and a problem that copper does not completely dissolve occurs. Stabilization can be achieved by setting the EDTA to 1.2 or more with respect to copper 1.
[0025]
  In the present invention, air is blown into the plating solution bath to increase the dissolved oxygen in the plating solution andBadThis is to prevent stabilization (decomposition prevention). When air is blown, the dissolved oxygen concentration in the plating solution is 0.5 to 2.5 ppm, and when oxygen is blown, the dissolved oxygen concentration in the plating solution is 3. There is a problem in that the copper is increased to Oppm or more, and the copper deposited on the material to be plated is oxidized to stop the plating reaction and the copper is dissolved. However, CuO and Cu (OH)₂Injecting oxygen-containing gas into a copper dissolution tank or a storage tank that dissolves copper increases the dissolved oxygen concentration in the plating solution to enhance the dissolution action of these copper compounds, and dissolves Cu2⁺To stabilize the complex of EDTA and EDTA, in other words, cuprous oxide Cu₂O generation can be prevented. Therefore, the oxygen-containing gas blown into the copper dissolution tank or the storage tank can use oxygen and nitrogen or oxygen itself in addition to air, and has a wide range of dissolved oxygen concentration. It can be carried out in the range of 3 to 3.5 ppm (value close to the saturated dissolved oxygen concentration in the plating solution, saturated dissolved oxygen concentration of water 3.8 ppm).
[0026]
DETAILED DESCRIPTION OF THE INVENTION
  (Example 1)
  FIG. 1 is a configuration diagram of an electroless copper plating apparatus of the present invention. Cupric hydroxide Cu (OH) as a copper supply source for the electroless copper plating solution in the copper dissolution tank 1₂Then, one or more cupric oxide fine powders of cupric oxide CuO and cupric hydroxide fine powder are supplied by a supply device provided separately, and stirred and dissolved with a stirring propeller 2 to prepare a copper replenisher 3 The copper replenisher 3 is stored in the liquid storage tank 6 through the filter 5 by the transfer pump 4 and then sent to the electroless copper plating solution 9 in the plating tank 8 by the transfer pump 7, or the copper dissolution tank 1 to the electrolysis copper plating solution 9 of the plating tank 8 via the filter 5 by the transfer pump 4 and supplied from the oxygen-containing gas ejection device to the copper dissolution tank 1 and the storage tank 6 An oxygen-containing gas ejection pipe 10 for supplying the oxygen-containing gas to be used is provided. Oxygen-containing gas from this pipe 10 in the copper replenisherTo blowOf cupric oxide and cupric hydroxide in the copper dissolution tankAverageCu2 dissolved by preventing the production of cuprous oxide (Cu2O) in the copper dissolution tank and the storage tank.⁺Stabilization of the complex of EDTA with EDTA is promoted.
[0027]
  Also, an oxygen-containing gas jet provided in the copper dissolution tank 1 and the liquid storage tank 6pipeBy blowing oxygen-containing gas from 10, the copper replenisher 3 can be stabilized. The copper mol concentration of the copper replenisher 3 in the copper dissolution tank 1 and the storage tank 6 is at least 1.5 times the copper mol concentration of the electroless copper plating solution 9 and is complexed with copper contained in the copper replenisher 3 When the molar concentration ratio with the EDTA, which is the agent, is 1, the copper replenishment liquid 3 is stabilized by blowing the oxygen-containing gas into the copper dissolution tank 1 and the liquid storage tank 6 with 4.0 times the EDTA. Is achieved.
[0028]
  In the present invention, the oxygen-containing gas is blown from the oxygen-containing gas jet pipe 10 in the copper dissolution tank 1. This is because, when the electroless copper plating solution 9 is used at, for example, 40 ° C. or more, it is difficult to keep the temperature of the electroless copper plating solution 9 constant if the copper replenishing solution 3 lower than this temperature is replenished. The temperature of the copper replenisher 3 in the copper dissolution tank 1 must be the same as that of the electroless copper plating solution 9.EssentialHowever, if the temperature of the copper replenisher 3 is set to 40 ° C. or higher, the dissolved oxygen is lowered, and there is a problem of causing precipitation of cuprous oxide over time. In order to solve this problem, an oxygen-containing gas is blown from the oxygen-containing gas ejection pipe 10 and the dissolved oxygen concentration isTheIncrease to prevent cuprous oxide settling. The oxygen-containing gas is blown by installing the same air blowing pipe 11 provided at the bottom of the plating tank 8 and supplying air, oxygen gas, or a mixed gas of nitrogen and oxygen from the outside. it can.
[0029]
The copper replenisher 3 prepared in the copper dissolution tank 1 is sent to the liquid storage tank 6 via the filter 5 by the transfer pump 4 and sent to the plating tank 8 by the transfer pump 7 after storage or from the copper dissolution tank 1. The switching valve 12 is operated via the filter 5 by the transfer pump 4 and sent directly to the plating tank 8. When the copper replenishment liquid 3 is sent to the liquid storage tank 6, the temperature of the copper replenishment liquid 3 is set to the same temperature as the electroless copper plating liquid 9 in the liquid storage tank 6. Even in this case, it is important to install the oxygen-containing gas ejection pipe 10 and blow in the oxygen-containing gas in the same manner as the copper dissolution tank 1 in order to prevent the formation of cuprous oxide in the copper replenisher 3.
[0030]
When the copper replenisher 3 in the copper dissolution tank 1 and the storage tank 6 decreases, the electroless copper plating solution 9 in the plating tank 8 is sent to the copper dissolution tank 1 by the transfer pump 13 and newly cupric hydroxide is added. Alternatively, the copper replenisher 3 is prepared by dissolving cupric oxide. By circulating through this series of paths, the copper replenishment of the electroless copper plating solution 9 can be carried out efficiently.
[0031]
In this example, electroless copper plating was performed using the above-described apparatus. An electroless copper plating solution A having the composition shown in Table 1 was prepared in the plating tank 1 and heated to 30 ° C. with air stirring. The specific gravity of this plating solution was 1.024 at 20 ° C. In the copper dissolution tank 1, the stirrer 2 is operated while stirring with oxygen gas to dissolve cupric hydroxide having a copper content of 62.6%, and a copper replenisher having the composition shown in Table 2 having a copper concentration of 0.030 mol / L. A was created. The copper concentration of the copper replenishing solution A is 1.5 times the copper concentration of the electroless copper plating solution 2, and the molar ratio of the copper concentration to the EDTA concentration is about 2.77 when copper is 1. This copper replenisher A was kept at 30 ° C. with a heater, and sent to the liquid storage tank 6 through the filter 5 with the transfer pump 4. The liquid storage tank 6 was kept at 30 ° C. with a heater while stirring air.
[0032]
[Table 1]

[0033]
[Table 2]

[0034]
Thereafter, bath load 1.5 dm in electroless copper plating solution A in plating tank 8²The copper-clad laminate provided with a plating catalyst under the conditions of / L was immersed and plated for 60 minutes. The copper concentration of the electroless copper plating solution A was lowered to 0.018 mol / L. Next, the transfer pump 4 and the transfer pump 7 are operated to start the transfer of the copper replenisher A through the route of the copper dissolution tank 1 → the liquid storage tank 6 → the plating tank 8 and the electroless copper plating in the plating tank 8. Plating was performed for 10 hours while replenishing 37% formalin, which consumes liquid A, and NaOH, a pH adjusting agent every 30 minutes, to obtain a plating film having a thickness of about 10.2 μm. No settling of cuprous oxide was observed in the copper dissolution tank 1 and the liquid storage tank 6, and the filter of the filter 5 was not clogged.
[0035]
As a result of repeated plating with 10 hours of plating performed once as a result of the above operation, the specific gravity of the plating solution became about 1.102 at 20 ° C after 35 times due to accumulation of formate ions, but the electroless copper plating solution A is stable. The surface of the plating film also showed a copper color, and no adhesion of copper fine particles was observed. Further, no precipitation of cuprous oxide was observed in the copper dissolution tank 1 and the liquid storage tank 6, and the filter of the filter 5 was not clogged.
[0036]
(Comparative Example 1)
In Example 1, the same results were obtained except that the stirring with the oxygen gas in the copper dissolution tank 1 and the air stirring in the liquid storage tank 6 were not performed, but only the stirrer 2 was stirred. In the copper replenisher A, the precipitation of cuprous oxide began to be observed after about 4 hours, and after about 8 hours, the copper concentration in both tanks had dropped to about 73% of the initial concentration. On the other hand, the filter of the filter 5 was clogged with cuprous oxide.
[0037]
(Comparative Example 2)
In Example 1, a copper replenisher B with only the copper component of the copper replenisher A as a conventional copper sulfate pentahydrate 7.50 g / L (copper concentration 0.03 mol / L) was prepared and stirred with oxygen gas. The same procedure as in Example 1 was performed. As a result, the electroless copper plating solution A in the plating tank 8 has a plating solution specific gravity of 20 times after repeated plating 16 times due to accumulation of sulfate ions caused by copper sulfate pentahydrate in the replenishing solution B in addition to formate ions. It became 1.106 at ° C., copper deposition was observed on a part of the inner wall of the plating tank 8, and copper fine particles were adhered to the surface of the plating film.
[0038]
(Example 2)
In Example 1, an electroless copper plating solution B in which only the copper component of the electroless copper plating solution A was 1.74 g / L of cupric oxide having a copper content of 73.48% (copper concentration 0.020 mol / L) 1 was created. This electroless copper plating solution B was sent to the plating tank 8 through the filter 5 by the transfer pump 4. And after wash | cleaning the inside of the copper dissolution tank 1, the copper replenishing liquid A was newly created, and it plated by repeating 10h plating once on the other conditions on the same conditions as Example 1. FIG. As a result, the same result as in Example 1 was obtained.
[0039]
(Example 3)
An electroless copper plating solution C having the composition shown in Table 3 was prepared in the plating tank 8 using cupric oxide having a copper content of 73.48%, and heated to 72 ° C. with air stirring. The specific gravity of this plating solution was 1.032 at 20 ° C. In the copper dissolving tank 1, the stirrer 2 is operated while stirring air in the same manner to dissolve the cupric oxide to produce a copper replenisher C shown in Table 4 having a copper concentration of 0.080 mol / L and a heater. At 72 ° C. The copper concentration of the copper replenisher C is 2.0 times the copper concentration of the electroless copper plating solution C, and the molar ratio of the copper concentration to the EDTA concentration is about 1.46 when the copper is 1. is there. This copper replenisher C was sent to the storage tank 6 through the filter 5 by the transfer pump 4. The liquid storage tank 6 was kept at 72 ° C. with a heater while stirring air.
[0040]
[Table 3]

[0041]
[Table 4]

[0042]
Then, bath load 1.5dm in plating tank 8²At the same time as dipping the copper-clad laminate with plating catalyst applied under the conditions of / L, the transfer pump 4 and the transfer pump 7 are operated, and the copper replenisher is routed through the route of the copper dissolution tank 4 → the storage tank 8 → the plating tank 1. The plating was carried out for 10 hours while the transfer of C was started and 37% formalin consumed by the electroless copper plating solution C in the plating tank 1 and the pH adjusting agent NaOH were replenished every 155 minutes. The plating film thickness was 25 μm. As a result, no precipitation of cuprous oxide was observed in the copper dissolution tank 1 and the liquid storage tank 6, and no clogging was observed in the filter of the filter 5.
[0043]
As a result of repeated plating 15 times with 10 h plating performed under the above conditions, the specific gravity of the plating solution became about 1.112 at 20 ° C due to accumulation of formate ions, but the electroless copper plating solution C is stable. The surface of the plating film also showed a copper color, and no adhesion of copper fine particles was observed. Moreover, there was no sedimentation of cuprous oxide in the copper dissolution tank 1 and the liquid storage tank 6, and the filter of the filter 5 was not clogged.
[0044]
(Comparative Example 3)
In Example 3, the air in the copper dissolution tank 1 and the liquid storage tank 6 was not stirred, and only the stirrer 2 was stirred. Otherwise, as a result of the same operation, the copper replenisher in both tanks began to see the precipitation of cuprous oxide after about 2 hours, and after about 4 hours, the copper concentration in both tanks reached the initial concentration. It decreased to about 54%. Also, the filter of the filter 5 was clogged with cuprous oxide.
[0045]
(Comparative Example 4)
In Example 3, a copper replenisher D was prepared in which only the copper component of the copper replenisher C was a conventional copper sulfate pentahydrate of 20.0 g / L (copper concentration 0.080 mol / L), and the same was performed while stirring air. Went to. As a result, due to the accumulation of sulfate ions from the replenisher D in addition to the formate ions, the specific gravity of the plating solution became 1.116 at 20 ° C after repeated plating 8 times, and copper deposition was observed on a part of the inner wall of the plating tank 8, and the plating film surface Also, copper fine particles adhered.
[0046]
(Example 4)
In Example 3, the electroless copper plating solution D was prepared by dissolving only the copper component of the electroless copper plating solution C into cupric hydroxide 4.06 g / L (copper concentration 0.040 mol / L) having a copper content of 62.6%. Created in tank 1. The electroless copper plating solution D was sent to the plating tank 8 through the filter 5 by the transfer pump 4. Then, other methods including the copper replenisher C were repeated under the same conditions as in Example 3 for 10 h plating once. As a result, the same result as in Example 3 was obtained.
[0047]
(Example 5)
An electroless copper plating solution E having the composition shown in Table 5 was prepared in the plating tank 8 using cupric hydroxide having a copper content of 62.6% and heated to 50 ° C. with air stirring. The specific gravity of this plating solution was 1.039 at 20 ° C. In the copper dissolution tank 1, the stirrer 2 is operated in the same manner while stirring the air to dissolve the cupric hydroxide to prepare the copper replenisher E shown in Table 6 having a copper concentration of 0.060 mol / L, and the heater. At 50 ° C. The copper concentration of the copper replenishing solution E is 3.0 times the copper concentration of the electroless copper plating solution E. In the composition of the copper replenisher E, components and concentrations other than cupric hydroxide were the same as those of the electroless copper plating solution composition E. The molar ratio of the copper concentration and the EDTA concentration in the copper replenisher E is 4.0 times when copper is 1. This copper replenisher E was sent to the storage tank 6 via the filter 5 by the transfer pump 4. The liquid storage tank 6 was kept at 50 ° C. with a heater while stirring air.
[0048]
[Table 5]

[0049]
[Table 6]

[0050]
Then, bath load 1.5dm in plating tank 8²At the same time as immersing the copper-clad laminate to which the plating catalyst has been applied under the conditions of / L, the transfer pump 4 and the transfer pump 7 are operated, and the copper replenisher is routed through the route of the copper dissolution tank 1 → the storage tank 6 → the plating tank 8. The plating was carried out for 10 hours while the transfer of E was started and 37% formalin consumed by the electroless copper plating solution C in the plating tank 1 and NaOH of pH adjusting agent were replenished every 20 minutes. The plating film thickness was 30 μm. As a result, no precipitation of cuprous oxide was observed in the copper dissolution tank 1 and the liquid storage tank 6, and the filter of the filter 5 was not clogged.
[0051]
Under the above conditions, 10 hours of plating was performed once, and as a result of repeated plating 11 times, the specific gravity of the plating solution was approximately 1.109 at 20 ° C due to the accumulation of formate ions, but the electroless copper plating solution E is stable. The surface of the plating film also showed a copper color, and no adhesion of copper fine particles was observed. Moreover, there was no sedimentation of cuprous oxide in the copper dissolution tank 1 and the liquid storage tank 6, and the filter of the filter 5 was not clogged.
[0052]
(Comparative Example 5)
In Example 5, the copper replenishment liquid in both tanks passed about 3 hours as a result of performing similarly in the copper dissolution tank 1 and in the liquid storage tank 6 without performing the air agitation with the agitator 2. From the time point, the precipitation of cuprous oxide began to be observed, and after about 7 hours, the copper concentration in both tanks had dropped to about 61% of the initial concentration. There was a clogging of a cup of copper.
[0053]
(Example 6)
An electroless copper plating solution F having the composition shown in Table 7 was prepared in the plating tank 8 using cupric oxide having a copper content of 73.48%, and heated to 70 ° C. with air stirring. The specific gravity of this plating solution was 1.036 at 20 ° C. Similarly in the copper dissolution tank 1 O₂While stirring, the stirrer 2 was operated to dissolve cupric oxide to prepare a copper replenisher F shown in Table 8 having a copper concentration of 0.075 mol / L, and kept at 70 ° C. with a heater. The copper concentration of the copper replenishing solution F is 2.5 times the copper concentration of the electroless copper plating solution F, and the molar ratio of the copper concentration to the EDTA concentration is 1.2 when EDTA is 1. This copper replenisher F was sent to the storage tank 6 through the filter 5 by the transfer pump 4. The liquid storage tank 6 was kept at 70 ° C. with a heater while stirring air.
[0054]
[Table 7]

[0055]
[Table 8]

[0056]
Then, bath load 1.2dm in plating tank 8²At the same time as immersing the copper-clad laminate to which the plating catalyst has been applied under the conditions of / L, the transfer pump 4 and the transfer pump 7 are operated, and the copper replenisher is routed through the route of the copper dissolution tank 1 → the storage tank 6 → the plating tank 8. The plating was carried out for 6 hours while the transfer of F was started and 37% formalin consumed by the electroless copper plating solution F in the plating tank 1 and NaOH of pH adjusting agent were replenished every 20 minutes. The plating film thickness was about 25 μm. As a result, no precipitation of cuprous oxide was observed in the copper dissolution tank 1 and the liquid storage tank 6, and no clogging was observed in the filter of the filter 5.
[0057]
Under the above conditions, 6h plating was performed once, and as a result of repeated plating 10 times, the specific gravity of the plating solution was about 1.114 at 20 ° C due to the accumulation of formate ions, but the electroless copper plating solution F is stable. The surface of the plating film also showed a copper color, and no adhesion of copper fine particles was observed. Moreover, there was no sedimentation of cuprous oxide in the copper dissolution tank 1 and the liquid storage tank 6, and the filter of the filter 5 was not clogged.
[0058]
(Comparative Example 6)
In Example 6, a copper replenisher G, in which only the copper component of the copper replenisher F was 18.73 g / L of conventional copper sulfate pentahydrate (copper concentration 0.075 mol / L), was prepared, and air stirring was performed. The same operation as in Example 1 was performed. As a result, the electroless copper plating solution F in the plating tank 8 has a plating solution specific gravity of 20 in six repetitions of plating due to accumulation of sulfate ions caused by copper sulfate pentahydrate in the replenishing solution G in addition to formate ions. The temperature was 1.113 at 0 ° C., and copper deposition was observed on a part of the inner wall of the plating tank 8, and the surface of the plating film became dark copper color, and copper fine particles adhered.
[0059]
【The invention's effect】
As described above, according to the present invention, it is apparent that the stability of the copper replenishing liquid is improved by blowing the oxygen-containing gas into the copper replenishing liquid in the copper dissolution tank and the liquid storage tank. As a result, the copper replenisher can be used over a long period of time. Furthermore, since copper precipitation and clogging do not occur in the copper dissolution tank, the liquid storage tank, the transfer pump 4, the transfer pump 7, and the filter in the filter 5, copper etching represented by an ammonium persulfate aqueous solution or the like. Since the number of times of washing with the liquid can be reduced, the amount of waste liquid treated can be reduced. Moreover, since the copper fine particles do not adhere to the plating film surface even if the plating is repeated, the plating solution can be used for a long period of time.
[0060]
The present invention is also effective for a thin electroless copper plating solution used at 40 ° C. or less and a thick electroless copper plating solution used at 40 ° C. to 80 ° C.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an electroless copper plating apparatus including a copper dissolution tank and a liquid storage tank according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Copper dissolution tank, 2 ... Stirring propeller, 3 ... Copper replenisher, 4 ... Transfer pump, 5 ... Filter, 6 ... Storage tank, 7 ... Transfer pump, 8 ... Plating tank, 9 ... Electroless copper plating solution DESCRIPTION OF SYMBOLS 10 ... Oxygen-containing gas ejection pipe, 11 ... Air ejection pipe, 12 ... Switching valve, 13 ... Transfer pump.

Claims

Part of the electroless copper plating solution in the plating tank is extracted, the extracted electroless copper plating solution is stored in a copper dissolution tank, and oxygen-containing gas is blown from a plurality of jets provided at the bottom of the electroless copper plating solution. by containing gas blown write Mareta the electroless copper plating solution was stored electroless copper plating replenishing solution loosened dissolved at least one cupric and cupric oxide hydroxide in the liquid storage tank, at the bottom thereof Electroless copper, wherein the oxygen-containing gas is blown from a plurality of provided outlets , and copper plating is performed while the electroless copper plating replenisher into which the oxygen-containing gas has been blown is replenished to the plating tank. Plating method.

According to claim 1, wherein the oxygen-containing gas, an electroless copper plating method characterized in that either of the mixed gas and oxygen gas with the mixed gas, nitrogen gas and oxygen gas of the air and oxygen gas.

3. The electroless copper plating replenisher according to claim 1 or 2, wherein the copper concentration of the electroless copper plating replenisher in the copper dissolution tank and the storage tank is 1.5 times or more the copper concentration of the electroless copper plating liquid. The electroless copper plating method is characterized in that the molar concentration of ethylenediaminetetraacetic acid (EDTA), which is a complexing agent, is 1.2 to 4.0 times the molar concentration of copper contained in the copper.

A plating tank having an electroless copper plating solution, dissolved in the electroless copper plating at least one cupric and cupric oxide hydroxide by the transported the electroless copper plating solution by transfer pump from the plating tank A copper dissolution tank for generating a replenisher, oxygen-containing gas blowing means for blowing oxygen-containing gas from a plurality of jets provided at the bottom of the copper dissolution tank, and the electroless copper plating replenishment in the copper dissolution tank a reservoir for savings built to transport the liquid by the transfer pump, and an oxygen-containing gas injection means blowing an oxygen-containing gas from a plurality of ejection ports provided in said liquid storage tank bottom, the said liquid storage tank An electroless copper plating apparatus comprising: a path for supplying an electroless copper plating replenisher to the plating tank.

Oite to claim 4, wherein the copper dissolution tank and reservoir of the electroless copper plating replenishing solution copper concentration more than 1.5 times the copper concentration of the electroless copper plating solution of the electroless copper plating replenishers The electroless copper plating apparatus is characterized in that the molar concentration of ethylenediaminetetraacetic acid (EDTA), which is a complexing agent, is 1.2 to 4.0 times the molar concentration of copper contained in.

Blowing oxygen-containing gas from a plurality of ejection ports for the electroless copper plating solution was withdrawn part of the electroless copper plating solution is provided at the bottom thereof and stored in the copper dissolution tank in the plating, the oxygen-containing gas is blown stores the electroless copper plating replenisher prepared by dissolving at least one cupric and cupric oxide hydroxide in the liquid storage tank by the electroless copper plating solution with which a plurality of ejection ports provided at the bottom thereof electroless copper plating come method creates auxiliary liquid supply, characterized in that blowing the oxygen-containing gas.

According to claim 7, wherein the oxygen-containing gas, mixed gas, electroless copper plating-out auxiliary supply, wherein either a mixed gas and oxygen gas of nitrogen gas and oxygen gas of the air and oxygen gas How to make a liquid.

9. The copper concentration in the electroless copper plating replenisher according to claim 7 or 8, wherein the copper concentration in the electroless copper plating replenisher is 1.5 times or more the copper concentration in the electroless copper plating replenisher. A method for producing an electroless copper plating replenisher, characterized in that the molar concentration of ethylenediaminetetraacetic acid (EDTA), which is a complexing agent, is 1.2 to 4.0 times.

Dissolving at least one of cupric hydroxide and cupric oxide in the electroless copper plating solution obtained by extracting a part of the electroless copper plating solution from the plating tank, and forming a replenishing solution for electroless copper plating a tank, a storage tank for separately storing the electroless copper plating replenishers the copper dissolver, a transfer pump for feeding transfer the electroless copper plating replenishers of the copper dissolution tank to said storage tank the a transfer pump to the electroless copper plating replenishing solution transferred to the plating tank, a plurality of oxygen-containing gas from the ejection port provided in said copper dissolution tank bottom and the liquid storage tank bottom of the liquid storage tank replenishing apparatus of the electroless copper plating replenishing solution, characterized in that a injection detemir stage.

According to claim 9, replenishing device of an electroless copper plating replenishing solution, characterized in that the transfer by the transfer pump the electroless copper plating replenishing liquid through the filter to the reservoir.

According to claim 9 or 10, wherein the electroless copper plating solution supply device of the electroless copper plating-out auxiliary liquid supply, wherein said a copper concentration of the electroless copper plating replenishing solution go higher than the copper concentration.

12. The path according to claim 10 or 11, wherein a path for transferring the electroless copper plating replenisher in the storage tank to the plating tank by a transfer pump, and a switching valve connected to the filter for the electroless copper plating replenisher. A copper replenishing device for electroless copper plating, characterized in that a path for transfer to the plating tank is provided.