JP2004269955A

JP2004269955A - Copper sulfate plating device, and plating method

Info

Publication number: JP2004269955A
Application number: JP2003061621A
Authority: JP
Inventors: Masayuki Yokoi; 昌幸横井; Tsutomu Morikawa; 務森河; Takao Nakade; 卓男中出; Shinichi Sato; 眞市左藤; Susumu Yuya; 進湯屋; Hirokatsu Shimizu; 宏勝清水
Original assignee: UINGU KK; Daiso Co Ltd; Osaka Prefecture
Current assignee: UINGU KK; Osaka Prefecture; Osaka Soda Co Ltd
Priority date: 2003-03-07
Filing date: 2003-03-07
Publication date: 2004-09-30
Anticipated expiration: 2023-03-07
Also published as: JP3903120B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper sulfate plating device and a plating method where various points at issue in the case when a metal anode and an insoluble anode are used are solved. <P>SOLUTION: The plating device is provided a copper plating tank (A) where an insoluble anode is installed in the inside of an anode chamber separated from a plating liquid with a cation exchange membrane and a circulation type dissolution tank (B) for dissolving copper oxide. When plating is performed using the device, copper oxide in an amount equivalent to the loss of copper ions in the plating liquid having a chlorine ion concentration of 35 to 1,100 ppm is charged/dissolved into the dissolution tank, and the copper ion concentration in the circulating plating liquid is controlled. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は印刷用ロールの銅めっき、プリント配線基盤のスルホール銅めっき、電解銅箔等の硫酸銅めっき浴からの銅めっき技術に関するものである。
【０００２】
【従来の技術および発明が解決しようとする課題】
従来の酸性硫酸銅めっきにおいて、電気銅や無酸素銅を陽極として溶解すると、溶解過程で多量の一価のＣｕ^＋イオンが形成され、これが不均化反応を起こすなどして、めっき液中に多量の銅の微粒子や亜酸化銅の微粒子を形成する。これがめっき液中に浮遊してめっき皮膜中に取りこまれ、皮膜に重大な損傷をあたえるため不都合があった。
【０００３】
これに対して含リン銅陽極は銅の溶解性の点では優れていたが、やはりＣｕ^＋イオンの形成は避けられず、めっき時にはめっき液を強く空気攪拌してＣｕ^＋イオンを酸化除去しなければならず、この空気攪拌により、含りん銅陽極の溶解効率は１００％を超え、長期の連続めっきを行うとめっき液濃度が増加し、最適品質の銅めっき皮膜を得られなかった。
また、含リン銅は溶解時に銅陽極表面にリン化銅を主成分とする黒いヘドロ状の付着膜を形成し、この中に金属スライムも形成される。これら陽極上の付着物は容易に脱落して溶液内に浮遊分散するため、通常、耐酸性の布袋（アノードバッグ）に銅陽極を装入しているが、この布袋がヘドロ状のスライムにより目詰まりを起こし、手間をかけて定期的に洗浄する必要があった。この場合、陽極上の付着物のめっき液内への脱落、浮遊分散は、アノードバッグで完全に除去できず頻繁にめっき皮膜にピットやザラツキなどの損傷を与えるなどの問題がある。また、含リン銅のコストそのものが高いという問題もあった。
【０００４】
更に、以上の問題点とは別に、一般に金属陽極を用いる場合、めっき操業の過程で陽極自体の大きさ、陽極面積、被めっき面に対する配置が変化し、めっき厚さの分布が変化することも大きな問題であった。
【０００５】
また、金属陽極を用いた場合、電極の不働態化を防ぐために必須の添加剤として加えられている塩化物イオンは、約４０〜１００ｐｐｍの間で管理する必要がある。ところが、めっき液の調製に水道水を使用した場合に、夏場など水道水の塩化物濃度が高いときなど、塩化物イオン濃度が増加し、銅陽極上で溶解度の低い塩化銅を沈殿形成してアノードを不動態化する不都合がある。このため、めっき液中の塩化物イオン濃度を約１００ｐｐｍ以下に管理しなければならないなどの問題があった。
【０００６】
このような問題を解決するため、金属陽極の代替として不溶性陽極を導入し、更に、めっき処理によるめっき液中の銅イオンの消耗を補填するために、めっき槽と金属銅溶解槽を併設する方法が開示されている（特開平０４−２８８９５、特開平０４−３２００８９）。しかし、これらは銅イオンの補給に金属銅を用いているため、めっき液への金属銅の溶解性が悪く、めっき処理で消耗する銅イオンを十分補給することができなかった。また、不溶性陽極を直接めっき液中に設置しているため、不溶性陽極表面で、めっき液中に含まれる添加剤が分解消耗したり、塩素イオンが酸化されて塩素ガスが発生する問題があった。
従って、本発明の目的は、金属陽極を用いた場合の上記問題点を解決することであり、直接的には、その解決法として不溶性陽極を導入した場合の上記問題点を解決することである。
【０００７】
【課題を解決するための手段】
本発明者らは、上記課題について鋭意検討した結果、新規なめっき装置を見出し、本発明を完成するに至った。
【０００８】
すなわち、本発明は、カチオン交換膜でめっき液から隔てた陽極室内に不溶性陽極を設置した銅めっき槽（Ａ）と、酸化銅を溶解するための循環式溶解槽（Ｂ）を備えためっき装置である。
【０００９】
また、本発明による装置を用いてめっきを行う際、３５〜１，１００ｐｐｍの塩素イオン濃度を有するめっき液に含まれる銅イオンのめっきによる損失量相当の酸化銅を溶解槽に投入・溶解し、循環しているめっき液の銅イオン濃度を制御することを特徴とするめっき方法を開示するものである。
【００１０】
銅めっき槽（Ａ）は、めっきを実際行う陰極室とそれに対してカチオン交換膜で隔てられた陽極室から構成される。陽極室には不溶性陽極が装填されている。
【００１１】
本発明で使用できるカチオン交換膜は、炭化水素系のカチオン交換膜やパーフルオロカーボンのカチオン交換膜が好ましい。炭化水素系のカチオン交換膜としては旭硝子製のセレミオンやトクヤマ製のネオセプタなどがあり、パーフルオロカーボンのカチオン交換膜としてはデュポン社製のナフィオンなどが使用できる。
【００１２】
本発明に使用できる不溶性陽極は、チタン基体に酸化イリジウムを主成分として被覆した陽極が好ましい。皮膜の密着性の点からは酸化イリジウムに酸化タンタル、酸化チタン、酸化スズなどを混合した混合酸化物の被膜が好適である。特に酸化タンタルと混合した酸化イリジウムが長時間の使用が可能である点で最も望ましい。
ここで、陽極反応は酸素発生反応が主であるため水素イオンが発生し、酸性度が増大してチタン基体の腐食が生じやすい。そのため、チタン基体と混合酸化物被膜の間に酸性電解液に耐食性の強いタンタル金属薄膜の中間層をスパッタリング等の方法で導入し、チタン基体の腐食を防止してもよい。
【００１３】
本発明で使用できるめっき液は、通常の銅めっきに使用される硫酸銅水溶液であれば特に限定されない。硫酸銅水溶液の好ましい濃度範囲はＣｕＳＯ_４・５Ｈ_２Ｏとして１５０〜３００ｇ／Ｌであり、Ｈ_２ＳＯ_４としては４０〜７０ｇ／Ｌである。
【００１４】
本発明に使用できる陽極室は、カチオン交換膜によりめっき液から隔てられ、内部に不溶性陽極が装填されて酸性電解液で満たされた形態をとっている。ここで酸性電解液は陽極上で酸素発生をする電解液であれば硫酸水溶液やりん酸水溶液等、特に限定されないが、めっき液の酸性成分と合致させるのがよく、硫酸水溶液が好ましい。好ましい酸性電解液の濃度範囲は４０〜１５０ｇ／Ｌである。
【００１５】
酸化銅を溶解するための循環式溶解槽（Ｂ）は、めっき処理による銅イオンの消耗量を補填する機能を有するものであればいかなる構造であってよいが、より効率よく酸化銅を溶解し、不純物のない良質の銅イオンをめっき液に補充するためには、循環式溶解槽（Ｂ）の内部に隔壁を設けて酸化銅溶解室と緩衝室に二分するのが好ましい。この場合、両室間には不溶性の粒子その他の不純物を取り除くためにフィルタを設置してよい。
【００１６】
酸化銅の形態は特に限定されないが、溶解性を考慮すると粉体を使用するのが好ましい。
【００１７】
【発明の実施の形態】
本発明の硫酸銅めっき装置は陽極室とめっき室をカチオン交換膜で分離し、陽極室に酸性電解液を入れ、めっき室に銅めっき液を入れ、陽極に不溶性陽極を使用し、かつ銅イオンの補給は酸化銅を溶解槽で溶解して補給可能にした装置である。
【００１８】
本発明の好ましい装置の模式図を図１に示す。カチオン交換膜（１０）でめっき液から隔てた陽極室内（１１）に不溶性陽極（９）を設置した銅めっき槽（６）、酸化銅の溶解槽（７）、ろ過器（２）、循環ポンプ（３）、酸化銅供給装置（８）およびめっき電源（１）から構成される。本装置で被めっき物（４）がめっきされる。めっき液の攪拌は空気（５）を吹き込み気泡（１２）による攪拌を行う。但し、攪拌は機械攪拌でもよい。めっき液はめっき槽からポンプあるいはオーバーフローにより溶解槽に循環され、溶解槽で酸化銅を溶解したのち、ろ過器をへて循環ポンプでめっき液槽に再循環される。
【００１９】
次に、好ましい溶解槽の構造を図２に示す。溶解槽（７）は複数の隔壁板（１８）およびフィルター（１５）で仕切られた構造とし、酸化銅溶解室（１３）と緩衝室（１６）および隔壁とフィルターで仕切られた少なくとも１つの隔壁室（１４）からなる。銅めっき槽（６）からポンプあるいはオーバーフロー（１７）により導入されためっき液は、緩衝室（１６）および溶解室（１３）へ分流して供給される。この場合、溶解槽（７）に導入されるめっき液量が銅めっき槽容量と比較して十分小さい場合などでは、めっき液を分流せず、そのまま溶解室（１３）に導入してもよい。
【００２０】
溶解室に入っためっき液には酸化銅粉末を投入して攪拌により溶解し、これは第一番目の隔壁板をオーバーフローし、フィルターを通って第１の隔壁室にいたる。ここで用いられる酸化銅粉末の平均粒径は３０〜６０μｍのものが速く溶解できる点で好ましい。フィルターはこの酸化銅粉末が溶解室で十分に解けきらないで隔壁室に移行するのを大部分防止するためのものであり、金属銅陽極に使われるアノードバックの布等を使用することができる。第２の隔壁板は下部に通液できるように隙間が設けられ緩衝室と連結しており、緩衝室に分流されためっき液と合流する。ここでは隔壁を２枚としたが３枚以上にして複数以上の隔壁室を設けてもよい。但し，液の流れは、隔壁板をオーバーフローするものおよび隔壁板の下部を通液するものであればよい。
【００２１】
陽極室のカチオン交換膜の膜電流密度は、３Ａ／ｄｍ^２〜４０Ａ／ｄｍ^２に維持するのが適当である。４０Ａ／ｄｍ^２以上になるとめっき液中の塩素イオンが陽極室に漏洩し、それが無視できなくなり、かつ不溶性陽極上での塩素ガス発生をもたらす一方、３Ａ／ｄｍ^２以下では陽極室に銅イオンが浸出し、陽極室の液抵抗が大きくなるため好ましくない。
【００２２】
本発明の硫酸銅めっき装置を用いてめっきを行う際、めっき液中の銅イオン損失量相当の酸化銅を溶解槽に投入・溶解することで、循環しているめっき液の銅イオン濃度を制御することができる。具体的には電流量から計算した酸化銅の必要量を人為的に溶解槽に投入してもよく、あるいは酸化銅の投入をコンピュータ制御により自動化することもできる。
【００２３】
本発明の硫酸銅めっき装置には、めっき液中の塩素イオン濃度の制御を目的として、めっき液が銀と接触する部分（Ｃ）および生成する塩化銀を除去する部分（Ｄ）を装備することができる。めっき液が循環途中で銀と接触することでめっき液中の塩素イオンが銀と反応し塩化銀が生成可能であって、その生成した塩化銀が何らかの手段により捕捉除去可能であればよい。
【００２４】
また、本発明の装置を用いてめっきを行う際、めっきによる銅イオン損失量相当の酸化銅を溶解槽に投入・溶解し、循環しているめっき液に含まれる銅イオン濃度を制御すること、および、めっき液を銀と適宜接触させることで塩化銀を生成させ、めっき液中の塩素イオン濃度を３５〜１，１００ｐｐｍに制御することを特徴とするめっき方法が開示される。
【００２５】
めっき液が銀と接触する部分（Ｃ）または生成する塩化銀を除去する部分（Ｄ）は、溶解槽（Ｂ）の内部または循環路に設けられているのが好ましく、さらに望ましくは両部分が溶解槽の内部に設けるのが好ましい。具体的には、図２の溶解槽では、生成する塩化銀を既設のフィルターで除去できるため、隔壁室内部で銀とめっき液を接触させるのが効率の面で望ましい。
【００２６】
使用できる銀の形態は銀板、銀粒子その他の形態であってよい。銀粒子等とめっき液との接触面積や接触時間等を制御することで塩素イオンの除去量を調整することができる。具体的にはサンプリングしためっき液中の塩素イオン濃度を分析し、適当量の銀を適当な時間、人為的に溶解槽の隔壁室に投入してもよく、または塩素イオン濃度の計測から銀の投入までをコンピュータ制御により自動化することもできる。
【００２７】
【実施例】
（実施例１）
容量８リットルの矩形槽の内部を塩ビ制板で４室に仕切り、それぞれめっき室５リットル、溶解室１リットル、隔壁室１リットルおよび緩衝槽室２リットルとした。めっき室にはアクリル板およびカチオン交換膜（旭硝子製セレミオン）を用いて作製した液量５００ｍＬの陽極室を設けてある。カチオン交換膜面積は１ｄｍ^２、陽極室液には５％硫酸を用いた。不溶性陽極にはチタン基体上に酸化イリジウム７０モル％と酸化タンタル３０モル％組成の被覆を３０ｇ／ｍ^２した電極を用いた。めっき液には光沢硫酸銅めっき液を用い、総液量は６リットルとした。液組成を表１に示す。光沢剤（ウイング製）をそれぞれ４時間ごとに０．２ｍｌ補給し、１０時間ごとに純水で液面調整を行った。
【００２８】
【表１】

【００２９】
各室にあらかじめ硫酸銅めっき液を満たしたのちマイクロポンプで緩衝室のめっき液をめっき室に導入して、めっき液を循環するようにした。この実験では分流していない。この状態でめっき室（めっき液量約４リットル）において真鍮板（１０×６ｃｍ^２）上に銅めっきを電流密度：１０Ａ／ｄｍ^２（めっき槽電流６Ａ），液温：４０℃で４０時間行った。４時間毎に真鍮板を取り替えめっき外観を観察した。この間、４時間間隔で、酸化銅３５．６ｇ（４時間６Ａの通電により析出した銅に相当する量）を溶解室に投入し攪拌溶解させた。Ｃｌ⁻イオン濃度は徐々に増加したが、銅濃度と硫酸濃度は安定しており、良好なめっき外観を長期間維持した。
めっき液の分析は、銅濃度はＥＤＴＡ滴定で、水素イオンは中和滴定で、Ｃｌ⁻イオンは銀―塩化銀滴定で行った。
【００３０】
【表２】

１）Ｃｕ^２＋濃度はＣｕＳＯ_４・５Ｈ_２Ｏ（ｇ／Ｌ）を表す。以下全て同様である。
２）Ｈ^＋濃度はＨ_２ＳＯ_４（ｇ／Ｌ）を表す。以下全て同様である。
【００３１】
（実施例２〜７および比較例１〜４）
容量８リットルの矩形槽の内部を塩ビ制板で４室に仕切り、それぞれめっき室５リットル、溶解室１リットル、隔壁室１リットルおよび緩衝槽室２リットルとした。その模式図を図２示す。めっき室にはアクリル板およびカチオン交換膜（旭硝子製セレミオン）を用いて作製した液量５００ｍＬの陽極室をもうけてある。カチオン交換膜面積は１ｄｍ^２、陽極室液には５％硫酸を用いた。不溶性陽極にはチタン基体上に酸化イリジウム７０モル％と酸化タンタル３０モル％組成の被覆を３０ｇ／ｍ^２した電極を用いた。めっき液には光沢硫酸銅めっき液を用い、総液量は６リットルとした。塩素イオンを除く液組成を表３に示す。
【００３２】
【表３】

【００３３】
各室にあらかじめ硫酸銅めっき液を満たしたのちマイクロポンプで緩衝室のめっき液をめっき室に導入して、めっき液を循環するようにした。この実験では分流していない。この状態でめっき室（めっき液量約４リットル）において真鍮板（１０×６ｃｍ^２）上に銅めっきを１０Ａ／ｄｍ^２（めっき槽電流６Ａ）で２０分間行った。この場合、２０分間毎に真鍮板を取り替え、塩素イオン濃度をＮａＣｌを添加することにより１０ｐｐｍから２０００ｐｐｍまで変化させた。得られためっき外観を観察するとともにめっき硬さを測定した。３０ｐｐｍまでは光沢はあるものの表面に瘤状突起が現れ、３５ｐｐｍを超えると平滑で光沢のあるめっきが得られた。さらに塩化物濃度を上昇させたところ、１１００ｐｐｍまでは平滑で光沢のある銅めっきが得られ、硬さもＨｖ２００程度であった。１２００ｐｐｍを超えると光沢が失われ、めっき硬さも低下した。表４にその結果を示す。
【００３４】
【表４】

【００３５】
（比較例５）
めっき室（５リットル）に実施例１の陽極室の代わりにチタンケースに含りん銅を充填してアノードバッグで覆った従来型の可溶性陽極を用いて真鍮板（１０×６ｃｍ^２）上に銅めっきを電流密度：１０Ａ／ｄｍ^２（めっき槽電流６Ａ），液温：４０℃で４０時間行った。その結果を表５に示す。時間の経過とともにＣｕ^２＋濃度は上昇し、めっきの外観にもザラツキが見られた。
【表５】

【００３６】
【発明の効果】
めっき処理により失われるめっき液中の銅イオン相当量の酸化銅粉末を溶解室に投入することで、めっき液中の硫酸銅濃度を一定に保つことができ、良好なめっき被膜を安定に得ることができる。また、金属銅陽極を用いないので、銅陽極に由来するめっきのザラツキ、ピットを著しく抑制でき、金属銅陽極使用に伴うヘドロ除去等の作業時の危険性を効果的に回避することができる。
また、めっき液中の塩素イオン濃度の許容範囲が３５〜１，１００ｐｐｍと、可溶性の含りん銅陽極を使う場合に比べ大幅に広がり、めっき浴管理が簡単になる。
更に、めっき液中の塩素イオン濃度を制御することにより、光沢のある安定した銅めっき被膜を得ることが可能である。
【図面の簡単な説明】
【図１】硫酸銅めっき装置の実施の形態を示す図である。
【図２】溶解槽を示す図である。
【符号の説明】
１めっき電源
２ろ過器
３循環ポンプ
４被めっき物
５空気
６銅めっき槽
７酸化銅溶解槽
８酸化銅供給装置
９不溶性陽極
１０カチオン交換膜
１１陽極室
１２気泡
１３溶解室
１４隔壁室
１５フィルター
１６緩衝室
１７オーバーフローめっき液
１８隔壁板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique of copper plating from a copper sulfate plating bath such as copper plating of a printing roll, through-hole copper plating of a printed wiring board, and electrolytic copper foil.
[0002]
2. Description of the Related Art
In conventional acidic copper sulfate plating, when electrolytic copper or oxygen-free copper is dissolved as an anode, a large amount of monovalent Cu ⁺ ions are formed in the dissolving process, which causes a disproportionation reaction and the like, and the plating solution contains A large amount of copper fine particles and cuprous oxide fine particles are formed. This floats in the plating solution and is taken into the plating film, causing serious damage to the film, which is inconvenient.
[0003]
On the other hand, the phosphorus-containing copper anode was excellent in terms of the solubility of copper, but the formation of Cu ⁺ ions was still unavoidable, and the plating solution had to be vigorously agitated during plating to remove the Cu ⁺ ions by oxidation. This air agitation caused the dissolution efficiency of the phosphorous-containing copper anode to exceed 100%, and when long-term continuous plating was performed, the concentration of the plating solution increased, and a copper plating film of optimal quality could not be obtained.
In addition, the phosphorus-containing copper forms a black sludge-like adhered film mainly composed of copper phosphide on the surface of the copper anode when dissolved, and metal slime is also formed therein. These deposits on the anode easily fall off and float and disperse in the solution. Therefore, a copper anode is usually placed in an acid-resistant cloth bag (anode bag). It had to be clogged and required time-consuming and regular cleaning. In this case, there is a problem that the deposits on the anode fall into the plating solution and are suspended and dispersed, which cannot be completely removed by the anode bag and frequently damage the plating film such as pits and roughness. There is also a problem that the cost of phosphorous-containing copper itself is high.
[0004]
Furthermore, apart from the above problems, when a metal anode is generally used, the size of the anode itself, the area of the anode, the arrangement with respect to the surface to be plated change in the course of the plating operation, and the distribution of the plating thickness may change. It was a big problem.
[0005]
When a metal anode is used, chloride ions added as an essential additive in order to prevent passivation of the electrode need to be controlled at about 40 to 100 ppm. However, when tap water is used to prepare the plating solution, when the chloride concentration of tap water is high, such as in summer, the chloride ion concentration increases, and copper chloride with low solubility precipitates on the copper anode. There is the disadvantage of passivating the anode. For this reason, there has been a problem that the chloride ion concentration in the plating solution must be controlled to about 100 ppm or less.
[0006]
In order to solve such a problem, a method in which an insoluble anode is introduced as a substitute for a metal anode, and a plating tank and a metal copper dissolving tank are provided in parallel to compensate for the consumption of copper ions in the plating solution due to the plating process. Are disclosed (JP-A-04-28895 and JP-A-04-320089). However, since metal copper is used for replenishing the copper ions, the solubility of the metal copper in the plating solution is poor, and the copper ions consumed in the plating process cannot be sufficiently replenished. In addition, since the insoluble anode is directly installed in the plating solution, there is a problem that additives contained in the plating solution are decomposed and consumed on the surface of the insoluble anode, and chlorine gas is generated by oxidation of chlorine ions. .
Therefore, an object of the present invention is to solve the above problems when using a metal anode, and directly to solve the above problems when introducing an insoluble anode as a solution. .
[0007]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have found a new plating apparatus, and have completed the present invention.
[0008]
That is, the present invention provides a plating apparatus including a copper plating tank (A) in which an insoluble anode is installed in an anode chamber separated from a plating solution by a cation exchange membrane, and a circulation type melting tank (B) for dissolving copper oxide. It is.
[0009]
Further, when plating using the apparatus according to the present invention, copper oxide equivalent to the amount of loss due to plating of copper ions contained in the plating solution having a chloride ion concentration of 35 to 1,100 ppm is charged and dissolved in a dissolving tank, It discloses a plating method characterized by controlling the copper ion concentration of a circulating plating solution.
[0010]
The copper plating tank (A) comprises a cathode chamber where plating is actually performed and an anode chamber separated therefrom by a cation exchange membrane. The anode compartment is loaded with an insoluble anode.
[0011]
The cation exchange membrane usable in the present invention is preferably a hydrocarbon cation exchange membrane or a perfluorocarbon cation exchange membrane. Examples of the hydrocarbon-based cation exchange membrane include Selemion manufactured by Asahi Glass and Neosepta manufactured by Tokuyama. As the cation exchange membrane of perfluorocarbon, Nafion manufactured by DuPont can be used.
[0012]
The insoluble anode that can be used in the present invention is preferably an anode obtained by coating a titanium substrate with iridium oxide as a main component. From the viewpoint of the adhesion of the film, a mixed oxide film obtained by mixing iridium oxide with tantalum oxide, titanium oxide, tin oxide, or the like is preferable. In particular, iridium oxide mixed with tantalum oxide is most desirable in that it can be used for a long time.
Here, since the anodic reaction is mainly an oxygen generating reaction, hydrogen ions are generated, the acidity is increased, and the titanium substrate is likely to be corroded. Therefore, an intermediate layer of a highly corrosion-resistant tantalum metal thin film may be introduced into the acidic electrolyte between the titanium substrate and the mixed oxide film by a method such as sputtering to prevent corrosion of the titanium substrate.
[0013]
The plating solution that can be used in the present invention is not particularly limited as long as it is a copper sulfate aqueous solution used for ordinary copper plating. A preferred concentration range of copper sulfate aqueous solution is 150 to 300 g / L as CuSO ₄ · 5H ₂ _O, as the H 2 SO ₄ is 40~70g / L.
[0014]
The anode chamber that can be used in the present invention is separated from the plating solution by a cation exchange membrane, has an insoluble anode loaded therein, and is filled with an acidic electrolyte. Here, the acidic electrolyte is not particularly limited, such as an aqueous solution of sulfuric acid or an aqueous solution of phosphoric acid, as long as it is an electrolyte that generates oxygen on the anode. The preferred concentration range of the acidic electrolyte is 40 to 150 g / L.
[0015]
The circulating dissolution tank (B) for dissolving copper oxide may have any structure as long as it has a function of compensating for the consumption of copper ions due to the plating treatment. In order to replenish high-quality copper ions free of impurities to the plating solution, it is preferable to provide a partition in the circulation type dissolving tank (B) and divide it into a copper oxide dissolving chamber and a buffer chamber. In this case, a filter may be provided between the two chambers to remove insoluble particles and other impurities.
[0016]
The form of the copper oxide is not particularly limited, but it is preferable to use a powder in consideration of solubility.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
In the copper sulfate plating apparatus of the present invention, the anode chamber and the plating chamber are separated by a cation exchange membrane, an acidic electrolyte is put in the anode chamber, a copper plating solution is put in the plating chamber, an insoluble anode is used as the anode, and copper ions are used. The replenishment is an apparatus in which copper oxide can be supplied by dissolving copper oxide in a dissolving tank.
[0018]
A schematic diagram of a preferred device of the present invention is shown in FIG. Copper plating tank (6) with insoluble anode (9) installed in anode chamber (11) separated from plating solution by cation exchange membrane (10), copper oxide dissolving tank (7), filter (2), circulation pump (3) It comprises a copper oxide supply device (8) and a plating power supply (1). An object to be plated (4) is plated by the present apparatus. The stirring of the plating solution is performed by blowing air (5) and stirring by bubbles (12). However, the stirring may be mechanical stirring. The plating solution is circulated from the plating tank to the dissolving tank by a pump or overflow, and after dissolving the copper oxide in the dissolving tank, is recirculated to the plating solution tank by a circulation pump through a filter.
[0019]
Next, a preferred structure of the dissolving tank is shown in FIG. The dissolution tank (7) has a structure partitioned by a plurality of partition plates (18) and a filter (15), and at least one partition partitioned by a copper oxide dissolution chamber (13) and a buffer chamber (16) and a partition and a filter. It consists of a room (14). The plating solution introduced from the copper plating tank (6) by the pump or the overflow (17) is divided and supplied to the buffer chamber (16) and the dissolution chamber (13). In this case, for example, when the amount of the plating solution introduced into the dissolution tank (7) is sufficiently smaller than the capacity of the copper plating tank, the plating solution may be directly introduced into the dissolution chamber (13) without being divided.
[0020]
A copper oxide powder is charged into the plating solution in the melting chamber and dissolved by stirring. The molten copper powder overflows the first partition plate, passes through the filter, and reaches the first partition chamber. The average particle diameter of the copper oxide powder used here is preferably 30 to 60 μm because it can be dissolved quickly. The filter is for preventing most of the copper oxide powder from being transferred to the partition chamber without being sufficiently melted in the melting chamber, and an anode back cloth used for a metal copper anode can be used. . The second partition plate is provided with a gap so as to allow the liquid to pass therethrough and is connected to the buffer chamber, and merges with the plating solution diverted to the buffer chamber. Here, the number of partitions is two, but three or more partitions may be provided to provide a plurality of partitions. However, the flow of the liquid may be any as long as it overflows the partition plate and passes through the lower part of the partition plate.
[0021]
It is appropriate to maintain the membrane current density of the cation exchange membrane in the anode compartment at 3 A / dm ^{2 to} 40 A / dm ² . 40A / dm ² or more the chlorine ions in the plating solution leaks to the anode chamber, it can not be ignored, and while providing chlorine gas generated on the insoluble anode, copper ions to the anode chamber at 3A / dm ² or less Is leached and the liquid resistance of the anode chamber is increased, which is not preferable.
[0022]
When performing plating using the copper sulfate plating apparatus of the present invention, the copper ion concentration in the circulating plating solution is controlled by charging and dissolving copper oxide equivalent to the amount of copper ions in the plating solution into the dissolving tank. can do. Specifically, the required amount of copper oxide calculated from the amount of current may be artificially charged into the dissolving tank, or the charging of copper oxide may be automated by computer control.
[0023]
The copper sulfate plating apparatus of the present invention is provided with a portion (C) where the plating solution comes into contact with silver and a portion (D) for removing generated silver chloride for the purpose of controlling the chloride ion concentration in the plating solution. Can be. As long as the plating solution comes into contact with silver during the circulation, chloride ions in the plating solution can react with silver to generate silver chloride, and the generated silver chloride can be captured and removed by some means.
[0024]
Further, when plating using the apparatus of the present invention, copper oxide equivalent to the amount of copper ion loss due to plating is charged and dissolved in a dissolving tank, and the concentration of copper ions contained in the circulating plating solution is controlled, In addition, a plating method is disclosed in which silver chloride is generated by appropriately bringing a plating solution into contact with silver, and a chloride ion concentration in the plating solution is controlled to 35 to 1,100 ppm.
[0025]
The part (C) where the plating solution comes into contact with silver or the part (D) from which the generated silver chloride is removed is preferably provided inside the dissolution tank (B) or in a circulation path, and more preferably both parts are provided. It is preferably provided inside the dissolution tank. Specifically, in the dissolving tank of FIG. 2, the generated silver chloride can be removed by an existing filter, and therefore, it is desirable from the viewpoint of efficiency that silver and the plating solution are brought into contact inside the partition wall chamber.
[0026]
The form of silver that can be used may be a silver plate, silver particles, or other forms. By controlling the contact area and contact time between the silver particles and the like and the plating solution, the amount of chlorine ions removed can be adjusted. Specifically, the chloride ion concentration in the sampled plating solution is analyzed, and an appropriate amount of silver may be artificially added to the partition chamber of the dissolution tank for an appropriate time, or the silver ion may be measured from the chloride ion concentration measurement. It is also possible to automate up to the input by computer control.
[0027]
【Example】
(Example 1)
The inside of a rectangular tank having a capacity of 8 liters was partitioned into four chambers by a PVC plate, and each had a plating chamber of 5 liters, a dissolution chamber of 1 liter, a partition wall chamber of 1 liter, and a buffer tank chamber of 2 liters. The plating chamber is provided with an anode chamber having a liquid volume of 500 mL prepared using an acrylic plate and a cation exchange membrane (Selemion manufactured by Asahi Glass). The area of the cation exchange membrane was 1 dm ² , and 5% sulfuric acid was used for the anode compartment liquid. As the insoluble anode, an electrode obtained by coating a titanium substrate with a coating composed of 70 mol% of iridium oxide and 30 mol% of tantalum oxide at 30 g / m ² was used. A bright copper sulfate plating solution was used as the plating solution, and the total amount was 6 liters. Table 1 shows the liquid composition. A brightener (manufactured by Wing) was replenished at 0.2 ml every 4 hours, and the liquid level was adjusted with pure water every 10 hours.
[0028]
[Table 1]

[0029]
After each chamber was previously filled with a copper sulfate plating solution, the plating solution in the buffer chamber was introduced into the plating chamber by a micropump to circulate the plating solution. No shunting was performed in this experiment. In this state, copper plating was performed on a brass plate (10 × 6 cm ² ) at a current density of 10 A / dm ² (plating bath current of 6 A) and a solution temperature of 40 ° C. for 40 hours in a plating chamber (plating solution amount: about 4 liters). Was. The brass plate was replaced every 4 hours and the plating appearance was observed. During this period, 35.6 g of copper oxide (an amount corresponding to copper precipitated by applying a current of 6 A for 4 hours) was charged into the melting chamber at an interval of 4 hours to be stirred and dissolved. Although the Cl ^- ion concentration gradually increased, the copper concentration and the sulfuric acid concentration were stable, and a good plating appearance was maintained for a long time.
The analysis of the plating solution was performed by copper concentration by EDTA titration, hydrogen ion by neutralization titration, and Cl ⁻ ion by silver-silver chloride titration.
[0030]
[Table 2]

1) ^{Cu 2+} concentration represents _{_{CuSO 4 · 5H 2 O (g}} / L). Hereinafter, the same applies to all cases.
2) H ⁺ concentration represents H ₂ SO ₄ (g / L). Hereinafter, the same applies to all cases.
[0031]
(Examples 2 to 7 and Comparative Examples 1 to 4)
The inside of a rectangular tank having a capacity of 8 liters was partitioned into four chambers by a PVC plate, and each had a plating chamber of 5 liters, a dissolution chamber of 1 liter, a partition wall chamber of 1 liter, and a buffer tank chamber of 2 liters. The schematic diagram is shown in FIG. The plating chamber is provided with an anode chamber having a liquid volume of 500 mL prepared using an acrylic plate and a cation exchange membrane (Selemion manufactured by Asahi Glass). The area of the cation exchange membrane was 1 dm ² , and 5% sulfuric acid was used for the anode compartment liquid. As the insoluble anode, an electrode obtained by coating a titanium substrate with a coating composed of 70 mol% of iridium oxide and 30 mol% of tantalum oxide at 30 g / m ² was used. A bright copper sulfate plating solution was used as the plating solution, and the total amount was 6 liters. Table 3 shows the composition of the solution excluding chloride ions.
[0032]
[Table 3]

[0033]
After each chamber was previously filled with a copper sulfate plating solution, the plating solution in the buffer chamber was introduced into the plating chamber by a micropump to circulate the plating solution. No shunting was performed in this experiment. In this state, copper plating was performed on a brass plate (10 × 6 cm ² ) at 10 A / dm ² (plating bath current: 6 A) for 20 minutes in a plating chamber (plating solution amount: about 4 liters). In this case, the brass plate was replaced every 20 minutes, and the chloride ion concentration was changed from 10 ppm to 2000 ppm by adding NaCl. Observation of the resulting plating appearance and plating hardness were measured. Up to 30 ppm, although glossy, knob-like projections appeared on the surface, and when over 35 ppm, smooth and glossy plating was obtained. When the chloride concentration was further raised, smooth and glossy copper plating was obtained up to 1100 ppm, and the hardness was about Hv200. If it exceeds 1200 ppm, the luster was lost and the plating hardness was lowered. Table 4 shows the results.
[0034]
[Table 4]

[0035]
(Comparative Example 5)
In place of the anode chamber of Example 1 in the plating chamber (5 liters), a titanium case was filled with phosphorous copper and covered with an anode bag, and a conventional soluble anode was used to cover copper on a brass plate (10 × 6 cm ² ). The plating was performed at a current density of 10 A / dm ² (plating bath current of 6 A) and a solution temperature of 40 ° C. for 40 hours. Table 5 shows the results. As time passed, the concentration of Cu ²⁺ increased, and roughness of the plating was observed.
[Table 5]

[0036]
【The invention's effect】
By introducing into the melting chamber copper oxide powder equivalent to the copper ions in the plating solution that is lost by the plating process, the concentration of copper sulfate in the plating solution can be kept constant, and a good plating film can be obtained stably. Can be. In addition, since a metal copper anode is not used, roughness and pits of plating derived from the copper anode can be significantly suppressed, and dangers at the time of work such as sludge removal associated with the use of the metal copper anode can be effectively avoided.
In addition, the allowable range of the chloride ion concentration in the plating solution is 35 to 1,100 ppm, which is much wider than the case where a soluble phosphorus-containing copper anode is used, and the plating bath management is simplified.
Further, by controlling the chloride ion concentration in the plating solution, it is possible to obtain a glossy and stable copper plating film.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a copper sulfate plating apparatus.
FIG. 2 is a view showing a dissolving tank.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plating power supply 2 Filter 3 Circulation pump 4 Plated object 5 Air 6 Copper plating tank 7 Copper oxide dissolving tank 8 Copper oxide supply device 9 Insoluble anode 10 Cation exchange membrane 11 Anode chamber 12 Bubbles 13 Dissolution chamber 14 Partition chamber 15 Filter 16 Buffer room 17 Overflow plating solution 18 Partition plate

Claims

A plating apparatus comprising a copper plating tank (A) in which an insoluble anode is installed in an anode chamber separated from a plating solution by a cation exchange membrane, and a circulation type dissolving tank (B) for dissolving copper oxide.

2. The plating apparatus according to claim 1, wherein the insoluble anode is an anode obtained by coating a titanium substrate with iridium oxide as a main component.

The plating apparatus according to claim 1, further comprising a partition plate, a filter, and a stirrer inside the circulation type melting tank (B).

4. The plating apparatus according to claim 1, further comprising a portion (C) in which the plating solution comes into contact with silver and a portion (D) for removing generated silver chloride.

5. The plating according to claim 4, wherein a portion (C) where the plating solution comes into contact with silver or a portion (D) for removing generated silver chloride is provided inside the dissolution tank (B) or in a circulation path. apparatus.

When performing plating using the apparatus according to claim 1, copper oxide equivalent to a loss amount due to plating of copper ions contained in a plating solution having a chloride ion concentration of 35 to 1,100 ppm is charged and dissolved in a dissolving tank, A plating method comprising controlling the copper ion concentration of a circulating plating solution.

When performing plating using the apparatus according to claim 4, copper oxide equivalent to the amount of copper ion loss due to plating is charged and dissolved in a dissolving tank, and the concentration of copper ions contained in the circulating plating solution is controlled. Also, a plating method characterized in that silver chloride is generated by appropriately bringing a plating solution into contact with silver, and a chloride ion concentration in the plating solution is controlled to 35 to 1,100 ppm.