JP2005023374A - Method for electroplating tin-based alloy - Google Patents

Method for electroplating tin-based alloy Download PDF

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JP2005023374A
JP2005023374A JP2003190530A JP2003190530A JP2005023374A JP 2005023374 A JP2005023374 A JP 2005023374A JP 2003190530 A JP2003190530 A JP 2003190530A JP 2003190530 A JP2003190530 A JP 2003190530A JP 2005023374 A JP2005023374 A JP 2005023374A
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tin
plating
liquid
based alloy
ions
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JP4219224B2 (en
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Hiromi Sonoda
宏美 園田
Katsuji Nakamura
勝司 中村
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SHINRIYOU DENSHI KK
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SHINRIYOU DENSHI KK
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for electroplating a tin-based alloy, which continuously plates many articles while giving them a consistent quality, without deterioration of the properties of a plating liquid caused by the formation of a solid matter during plating. <P>SOLUTION: The method for electroplating the tin-based alloy on an article 12 to be plated of a cathode with the use of a soluble anode 11 containing 90% or more tin comprises separating a liquid A16 around the soluble anode 11 from a liquid B13 around the cathode, with a diaphragm 17 made of a nonionic finely porous membrane made of a synthetic resin having superior transparency for tin but inferior transparency for silver; and adding a higher concentration of a surfactant into the liquid A16 than that added into the liquid B13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、鉛フリーはんだめっきに使用される錫系合金の電解めっき方法に関する。
【０００２】
【従来の技術】
従来、はんだ付けを必要とする部品、例えばチップ部品、水晶発振子、バンプ、コネクターピン、リードフレーム、各種フープ材、パッケージのリードピン、プリント基板の回路等の電子機器を構成する部品に対しては、錫めっきや錫鉛合金めっきを施すことが行われてきた。純粋な錫めっきでは、はんだ付け性の劣化や被膜にヒゲ状結晶ウィスカーが発生するなどの問題があった。また、近年、環境保護の観点から鉛の使用が控えられるようになり、鉛フリーのめっきが望まれるようになった。
【０００３】
鉛を含まないめっきとして例えば、錫−銀合金、錫−ビスマス合金、錫−銅合金などが検討されているが、従来知られている鉛フリーめっき被膜は、錫−鉛めっき被膜よりも２０度程度融点が高いので、接合時のエネルギーコストの低減と、他の部品への加熱量の低減を図るために融点の低い鉛フリーめっき被膜が望まれていた。
また、めっき被膜と接合される基板側のはんだ材料についても鉛フリー化が望まれており、例えば、共晶点に近い組成を有する錫−銀−銅合金がはんだ材料として用いられるようになってきた。ところが、この錫−銀−銅合金に類似の組成を有するめっき被膜は、めっき液の安定性の困難さから未だ得られておらず、錫−銀−銅合金を用いたはんだ材料との接合性の良好なめっき被膜が望まれていた。錫−銅合金めっきとしては、特定の有機化合物成分を含有するめっき浴及びそのめっき方法、更に、錫−銀−銅合金めっき浴及びそのめっき方法が開示されている（例えば、特許文献１参照）。
【０００４】
【特許文献１】
特開２００１−１６４３９６号公報（第３、４、７、８、２５〜２７頁）
【０００５】
【発明が解決しようとする課題】
ところが、特許文献１に具体的に開示されているめっき浴の組成では、各金属濃度が低く、工業的なめっきに用いるには生産性の点で問題があった。また、錫−銀−銅合金めっき浴は錫−銅合金めっき浴より更にはんだ濡れ性、液安定性、強度の点で優れているが、３種の金属イオン及び金属イオンの錯体を含有するために、調液が困難であり、特に工業化スケールでは取り扱うめっき薬液量が大量になり、長時間に渡って使用するために、めっき加工途中で固形物が生じたり、液質が変わることがあり、ひいてはめっきの品質が安定しない等の問題があった。また、特に金属イオンの濃度の高いめっき液を使用する際に、例えば、錫を９０％以上含有する溶解性陽極を用いた場合には銀イオンが銀化合物又は金属銀となって析出し易く、液の安定性を悪くし、不溶性陽極を用いた場合には、Ｓｎ２＋がＳｎ４＋になって不溶性沈澱を作り、液質を悪くするという問題があった。
【０００６】
本発明は、大量のめっき加工を連続的に行っても、加工途中で固形物が生じたり、液質が変わるといった品質の低下が起こらず、品質の安定しためっき加工を行うことが出来る錫系合金の電解めっき方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
前記目的に沿う第１の発明に係る錫系合金の電解めっき方法は、錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にした錫系合金の電解めっき方法において、前記溶解性陽極の周囲の液Ａと前記陰極の周囲の液Ｂを、１Ｃ（クーロン）の電気量を通電させたときに、錫イオンを陽極側から陰極側へ５×１０−５〜５×１０−４ｇ通す隔膜で仕切っている。
従って、溶解性陽極からの錫イオンは隔膜を通過して陰極液（めっき液）である液Ｂ中に入る事ができ、めっき液中の錫イオンを溶解性陽極で補給することができる。
１Ｃ（クーロン）の電気量を通電させたときに、陽極側から陰極側へ流れる錫イオンが５×１０−５ｇ（錫イオンの溶解量に対して約８．４％）より少ないと、めっき液中の錫イオンが減り過ぎて、めっき液の錫濃度を一定に保つのが困難になるし、錫イオンを５×１０−４ｇ（錫イオンの溶解量に対して約８４％）より多く通す隔膜だと銀イオンの透過性も増してしまうので、不適である。
【０００８】
第２の発明に係る錫系合金の電解めっき方法は、錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にした錫系合金の電解めっき方法において、前記溶解性陽極の周囲の液Ａと前記陰極の周囲の液Ｂを、他のめっき金属のイオンあるいは錯体より錫イオンを透過し易い隔膜で仕切っている。
従って、めっき液中の錫イオンを溶解性陽極で補給することができると共に、めっき液である液Ｂ中の錫イオンよりイオン化傾向の小さい他のめっき金属のイオンあるいは錯体、例えば銀イオンや銅イオンの錯体が液Ａ中に入って錫イオンと置換して金属化合物となって、析出するのを防ぐことができる。
【０００９】
第３の発明に係る錫系合金の電解めっき方法は、錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にした錫系合金の電解めっき方法において、前記溶解性陽極の周囲の液Ａと前記陰極の周囲の液Ｂを、孔径０．０１〜０．０５μｍで膜厚５〜１００μｍの微多孔膜からなる隔膜で仕切っている。
従って、径の小さい錫イオンは液Ａから液Ｂに移動できるが、液Ｂ中の他のめっき金属特に、その錯体、例えば銀イオンや銅イオンの錯体が隔膜を通過して、液Ａ中に侵入するのを防ぐことができる。
孔径及び膜厚が上記範囲外であると、錫イオンの透過性が非常に悪くなったり、錫イオン以外のめっき金属である銀イオンや銅イオン及びその錯体の透過性が増して不都合である。
【００１０】
第４の発明に係る錫系合金の電解めっき方法は、第１〜第３の発明に係る錫系合金の電解めっき方法において、前記液Ａに界面活性剤、特に好ましくは水溶性で非イオン性の界面活性剤を添加している。
従って、錫イオンの液Ａから液Ｂへの透過性がよくなっている。
第５の発明に係る錫系合金の電解めっき方法は、第４の発明に係る錫系合金の電解めっき方法において、前記液Ａに前記液Ｂ中の界面活性剤より高濃度になるように界面活性剤を添加している。
従って、液Ａから液Ｂへの錫イオンの透過性が、更に高まっている。
【００１１】
第６の発明に係る錫系合金の電解めっき方法は、第１〜第５の発明に係る錫系合金の電解めっき方法において、更に不溶性陽極を設け、前記不溶性陽極の周囲の液Ｃと前記液Ｂを他の隔膜で仕切っている。
溶解性陽極の他に不溶性陽極を設け、溶解性陽極への電流量を調整することによって、溶解性陽極からの錫イオンの過溶出による液Ｂ中の錫イオン濃度の過上昇を防止することができる。また、不溶性陽極の周囲の液Ｃと液Ｂを別の隔膜で仕切っているので、液Ｂ中の陽イオン、例えば銀イオンがこの不溶性陽極に触れるのを防止している。
ここで、液Ａと液Ｂを仕切る隔膜には錫イオンの透過性はよく、錫イオン以外の他のめっき金属イオン及びその錯体、例えば銀イオン及びその錯体の透過性の悪い膜が必要である。液Ｂと液Ｃを仕切る隔膜は、他のめっき金属イオン及びその錯体の透過性が悪ければ、錫イオンの透過性は良くても悪くても構わないので、液Ａと液Ｂを仕切る隔膜と同じ隔膜を使用してもよいし、異なる隔膜を使用してもよい。
【００１２】
第７の発明に係る錫系合金の電解めっき方法は、第６の発明に係る錫系合金の電解めっき方法において、前記めっき対象物にめっき金属をめっきさせるのに必要な電流を前記溶解性陽極と前記不溶性陽極の両方から流している。
一般に、錫系合金の電解めっき方法において、めっき対象物にめっき金属をめっきさせるのに必要な電流を錫を９０％以上含有する溶解性陽極に流している。
この時、錫を９０％以上含有する溶解性陽極は、流した電流量分だけ錫が溶解するが、錫を９０％以上含有する溶解性陽極は酸を含む陽極の周囲の液によって化学溶解もする。従って、めっき金属をめっきするのに必要な電流を溶解性陽極だけに流すと、溶解性陽極が化学溶解する分及び、錫以外のめっき金属を陰極に析出させる電流量で錫が溶解する分だけ錫が溶け過ぎてＳｎ２＋濃度が上昇し過ぎ、液のイオンバランスが崩れる。さらには、不溶性陽極だけに電流を流すとＳｎ２＋が酸化されてＳｎ４＋となり、Ｓｎ４＋は酸化錫となって沈澱析出して、液質を悪化させるという問題が発生する。
従って、溶解性陽極には、めっきに必要分から化学溶解分を除いた錫を溶解するのに必要な電流量のみを流し、不溶性陽極に残りの電流量を流し、溶解性陽極と不溶性陽極の両方から、めっき金属をめっきさせるのに必要な電流を流すことによって、前記問題を解決することができる。
【００１３】
第８の発明に係る錫系合金の電解めっき方法は、第１〜第７の発明に係る錫系合金の電解めっき方法において、前記液Ｂに孔径０．１〜０．３μｍの濾過膜を備えた循環回路を設け、前記液Ｂに低圧力をかけて前記濾過膜を通過させ、不純物を除去している。
液質の劣化の原因となる不純物、特に酸化第二錫や酸化銅、酸化銀を、液Ｂに低圧力をかけて孔径０．１〜０．３μｍの濾過膜を通過させることにより除去することができる。
【００１４】
第９の発明に係る錫系合金の電解めっき方法は、第１〜第８の発明に係る錫系合金の電解めっき方法において、前記液Ａは０．５〜１．５ｍｏｌ濃度のスルホン酸類を有している。
液Ａのスルホン酸類の濃度が０．５〜１．５ｍｏｌであるので、付加電流によって錫の溶解性を保つが、化学溶解するのを防ぐことができ、錫の過剰溶解を防ぐことができる。
【００１５】
第１０の発明に係る錫系合金の電解めっき方法は、第１〜第９の発明に係る錫系合金の電解めっき方法において、前記液Ｂは、水を主体とする媒体に、スルホン酸類、錫イオン、銅イオン及び銀イオンを含むめっき液であって、Ｓｎ２＋濃度が０．２１〜２ｍｏｌ／Ｌ、銀イオン濃度が０．０１〜０．１ｍｏｌ／Ｌ、銅イオン濃度が０．００２〜０．０２ｍｏｌ／Ｌに調整されている。
めっき液中の錫イオンはＳｎ２＋とＳｎ４＋とからなるが、Ｓｎ４＋は更に酸化されてＳｎＯ２ となり沈澱するため、めっきに関与するのはＳｎ２＋であると推定される。従って、Ｓｎ２＋の濃度を規制する。
これによって、融点が低い錫−銀−銅合金めっきが生産性高くでき、更に、好ましくはＳｎ２＋濃度を０．３〜１ｍｏｌ／Ｌ、銀イオン濃度を０．０２〜０．０５ｍｏｌ／Ｌ、銅イオン濃度を０．００３〜０．０１ｍｏｌ／Ｌとすることにより、錫−銀−銅の共晶点に近く、より融点が低い錫−銀−銅合金めっきが生産性高くできる。
【００１６】
【発明の実施の形態】
続いて、添付した図面を参照しつつ、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。
図１は本発明の第１の実施の形態に係る錫系合金の電解めっき方法の説明図、図２は本発明の第２の実施の形態に係る錫系合金の電解めっき方法の説明図、図３は本発明の第３の実施の形態に係る錫系合金の電解めっき方法の説明図である。
【００１７】
図１に示すように、本発明の第１の実施の形態に係る錫系合金の電解めっき方法に用いるめっき装置１０は、錫を９０％以上含有する２個の溶解性陽極１１と、陰極となるめっき対象物１２と、めっき金属成分をスルホン酸類に溶かして含有するめっき液１３（陰極の周囲の液Ｂの一例）と、めっき液１３を入れるめっき槽１４と、めっき液１３を必要に応じてかき混ぜる撹拌子１８を有している。
さらに、各溶解性陽極１１の周囲には、溶解性陽極１１を覆い不純物（特に酸化錫）を取り除く目の荒い市販の袋であるアノードバッグ１５と、陽極の周囲のアノード液１６（液Ａの一例）をめっき液１３と仕切る隔膜１７が設けられ、アノード液１６には、錫イオンのイオン状態を保つためにスルホン酸類の液が入れられている。このスルホン酸類の液の濃度は電流によってイオン化した錫が溶けてイオン状態を保つが、化学溶解はしにくい濃度である０．５〜１．５ｍｏｌ／Ｌとなっている。
さらに、アノード液１６には、アノード液１６からめっき液１３への錫イオンの透過性を高めるために、めっき液１３中の界面活性剤より、高い濃度で非イオン性で親水性の界面活性剤が添加されている。
【００１８】
本発明の第１の実施の形態に係る錫系合金のめっき方法は、まず、めっき槽１４内をめっき液１３で満たし、めっき液１３をかき混ぜる撹拌子１８を入れ、溶解性陽極１１をアノードバッグ１５で包み、隔膜１７で覆い、めっき槽１４内に入れる。隔膜１７は、錫イオンの透過性は良いが他のめっき金属イオンやその錯体、例えば、銀の錯体の透過性は悪い合成樹脂製で非イオン性の微多孔膜からなっている。次に、溶解性陽極１１の端子１９と陰極の端子２０をつなぎ、アノードバッグ１５内にアノード液１６を入れ、電流を流して、溶解性陽極の錫、及びめっき液１３中のめっき金属をめっき対象物１２（陰極）にめっきする。
ここで、めっき対象物１２である陰極１個に対して２個の溶解性陽極１１を対称的に設けるのは、陰極の両側に陽極を設けることによって、めっき対象物１２の両面にめっきをするためである。
【００１９】
めっき液１３は例えば、水を主体とする媒体に、スルホン酸類及び金属成分として錫、銀及び銅を必須成分として含有している。
金属成分はめっき液１３中で金属イオンとして存在しており、主として水とスルホン酸類からなるめっき母液と金属化合物を混合することによりめっき液１３が得られ、金属イオンの安定性のために、好ましくは有機錯化剤を添加して、金属イオン及び金属イオンの錯体として存在させるのが好ましい。
【００２０】
錫化合物の具体例としては、メタンスルホン酸、エタンスルホン酸、２−プロパノールスルホン酸、ｐ−フェノールスルホン酸などの有機スルホン酸の錫塩、硫酸錫、酸化錫、硝酸錫、塩化錫、臭化錫、ヨウ化錫、リン酸錫、ピロリン酸錫、酢酸錫、ギ酸錫、クエン酸錫、グルコン酸錫、酒石酸錫、乳酸錫、コハク酸錫、スルファミン酸錫、ホウフッ化錫、ケイフッ化錫などの第一錫化合物が挙げられる。これらの錫化合物は、一種単独又は二種以上混合して用いることができる。
【００２１】
銅化合物としては、上記スルホン酸の銅塩、硫酸銅、酸化銅、硫酸銅、塩化銅、臭化銅、ヨウ化銅、リン酸銅、ピロリン酸銅、酢酸銅、ギ酸銅、クエン酸銅、グルコン酸銅、酒石酸銅、乳酸銅、コハク酸銅、スルファミン酸銅、ホウフッ化銅、ケイフッ化銅などが挙げられる。これらの銅化合物は、一種単独又は二種以上混合して用いることができる。
【００２２】
銀化合物としては、上記スルホン酸の銀、硫酸銀、酸化銀、硝酸銀、塩化銀、臭化銀、ヨウ化銀、リン酸銀、ピロリン酸銀、酢酸銀、ギ酸銀、クエン酸銀、グルコン酸銀、酒石酸銀、乳酸銀、コハク酸銀、スルファミン酸銀、ホウフッ化銀、ケイフッ化銀などが挙げられる。これらの銀化合物は、一種単独又は二種以上混合して用いることができる。
【００２３】
スルホン酸類は、上記の金属成分を溶解可能とするものである限り、いずれも用いることができ、例えばメタンスルホン酸、エタンスルホン酸等の脂肪族スルホン酸、ベンゼンスルホン酸、トルエンスルホン酸等が挙げられる。これらの内、金属塩の溶解性、排水処理の容易性などの点で脂肪族スルホン酸が好ましく、メタンスルホン酸が特に好ましい。
これらスルホン酸類はめっき液１３中、好ましくは５０〜５００ｇ／Ｌ、更に好ましくは１００〜３００ｇ／Ｌ含まれる。
【００２４】
めっき液１３中、金属成分は強酸イオンの一例である例えば、スルホン酸イオンをカウンターアニオンとして金属イオン及び金属イオンの錯体の形で水を主体とする媒体に溶解しているが、錫イオンはＳｎ２＋及びＳｎ４＋、銅イオンはＣｕ＋ 又はＣｕ２＋、また銀イオンはＡｇ＋ として存在している。めっき液１３中の各金属の配合量は、Ｓｎ２＋として０．２１〜２ｍｏｌ／Ｌ、好ましくは０．２５〜１ｍｏｌ／Ｌ、銀として０．０１〜０．１ｍｏｌ／Ｌ、好ましくは０．０２〜０．０５ｍｏｌ／Ｌ、銅として０．００２〜０．０２ｍｏｌ／Ｌ、好ましくは０．００３〜０．０１ｍｏｌ／Ｌである。ここで、錫イオンはめっきに関与するのはＳｎ２＋であるため、Ｓｎ２＋の量を規制する。
また、錫、銀、銅の配合量によって、製造される錫−銀−銅の三元系のめっき液の組成を規制すると、めっき液を使用して作られるめっき被膜の組成も規制されるため、製造されるめっき被膜の融点ができるだけ低くなるように、錫、銀、銅の配合を決める。さらに、膜の融点を低くする効果を損なわない範囲で微量の金属元素を含有しても良い。微量金属としては、ニッケル、コバルト、金、ビスマス、鉛、パラジウム、アンチモン、亜鉛、鉄、ゲルマニウム、インジウム等があげられ、含有量としては、銅の含有量よりも少ないことが好ましい。
【００２５】
また、めっき液１３の性能の低下を妨げない範囲で、スルホン酸類と併用してめっき母液に可溶なスルホン酸塩や、有機酸及びその塩、無機酸及びその塩を配合することができる。無機酸としては例えば、硫酸、リン酸、縮合リン酸、硝酸、フッ化水素酸、ホウフッ化水素酸等が挙げられ、有機酸としては例えば、スルファミン酸、カルボン酸、ホスホン酸が挙げられる。上記した各酸の塩としては、可溶性塩であれば良く、例えば、Ｎａ塩、Ｋ塩等のアルカリ金属塩、Ｃａ塩等のアルカリ土類金属塩、ジエチルアミン塩等のアルキルアミン塩、アンモニウム塩等を使用できる。
【００２６】
めっき液１３は、添加剤として特定の有機錯化剤を含有することが好ましい。
好ましい有機錯化剤は、チオール化合物（分子内にＳＨ基を有する化合物）、チオ尿素化合物及び芳香族アミノ化合物である。
また、チオ尿素化合物はチオ尿素骨格を有する化合物であればいずれも用いることができる。また、芳香族アミノ化合物は芳香族環に直接アミノ基を有する化合物であればいずれも用いることができる。これら有機錯化剤はめっき母液に対する溶解度がある程度高いほうが、安定なめっき液を作成する観点から好ましく、溶解度としては好ましくは３ｇ／Ｌ以上、更に好ましくは５ｇ／Ｌ以上、特に好ましくは１０ｇ／Ｌ以上である。また、錯化剤分子があまり大きいと錯化能力が低下する傾向にあるので、分子量としては好ましくは２０００以下、更に好ましくは１０００以下、特に好ましくは８０〜５００である。
【００２７】
チオール化合物としては具体的には例えば、ブタンチオール、ペンタンチオール等の脂肪族チオール化合物、チオフェノール、トルエンチオール、ｏ−アミノチオフェノール等の芳香族チオール化合物、メルカプト酢酸、メルカプトコハク酸、メルカプト乳酸等のメルカプト基含有カルボン酸、システイン等のメルカプト基含有アミノ酸、アセチルシステイン等のメルカプト基含有アミノ酸誘導体が挙げられる。これらの内、水に対する溶解性、錯化剤としての性能、臭いが少ない等の観点から、メルカプト基含有カルボン酸又はメルカプト基含有アミノ酸及びその誘導体が好ましく、特にアセチルシステインが好ましい。なお、ジスルフィド結合を有する化合物を用い、めっき浴中で還元されてチオール化合物を生成させてもよい。
【００２８】
チオ尿素化合物としては具体的には例えば、チオ尿素、ジメチルチオ尿素、トリメチルチオ尿素、Ｎ，Ｎ’ −ジイソプロピルチオ尿素、アセチルチオ尿素、アリルチオ尿素、１，３−ジフェニルチオ尿素、チオセミカルバジド等が挙げられる。
【００２９】
芳香族アミノ化合物としては具体的には例えば、アニリン、メチルアニリン、メトキシアニリン等のアニリン化合物や、２，２’ −ジチオジアニリン等の分子内に２個のアニリン環を有する化合物が挙げられる。特に２，２’ −ジチオジアニリンが好ましい。
有機錯化剤のめっき液１３中の配合量は、好ましくは１〜１００ｇ／Ｌ、更に好ましくは１〜３０ｇ／Ｌ、更に好ましくは２〜２０ｇ／Ｌである。これら有機錯化剤は併用して用いてもよく、好ましくはメルカプタン化合物と芳香族アミノ化合物を併用するものであり、特にはアセチルシステインと２，２’ −ジチオジアニリンを併用するものである。
【００３０】
めっき液１３には、上記成分以外に界面活性剤を配合することができる。
界面活性剤は、めっき被膜の外観、緻密性、平滑性、密着性、均一電着性などの改善のために用いられる。なお、本実施の形態においては、界面活性剤はアノード液１６にメタンスルホン酸に追加して用いられ、アノード液１６中のＳｎ２＋イオンのめっき液１３への透過性を高める働きをする。ここで、アノード液１６に添加される界面活性剤の量はめっき液１３の界面活性剤の濃度より高くなるように添加される。なお、アノード液１６に添加される界面活性剤はめっき液１３中の界面活性剤と同じものを使用するのが好ましい。
界面活性剤としてはノニオン系で親水性の界面活性剤で、具体的には例えば、Ｃ１〜Ｃ２０アルカノール、フェノール、ナフトール、ビスフェノール類、Ｃ１〜Ｃ２５アルキルフェノール、アリールアルキルフェノール、Ｃ１〜Ｃ２５アルキルナフトール、Ｃ１〜Ｃ２５アルコキシル化リン酸（塩）、ソルビタンエステル、スチレン化フェノール、ポリアルキレングリコール、Ｃ１〜Ｃ３０脂肪族アミン、Ｃ１〜Ｃ２２脂肪族アミド等に、エチレンオキシド（ＥＯ）及びプロピレンオキシド（ＰＯ）から選ばれた少なくとも一種のアルキレンオキシドを２〜３００ｍｏｌ付加縮合したアルキレンオキシド系化合物が挙げられる。
【００３１】
なかでも、アルキレンオキシド系化合物が好ましく、具体的には例えば、ポリオキシエチレンα−ナフトールエーテル、ポリオキシエチレンβ−ナフトールエーテル、エチレンオキシドプロピレンオキシドブロックコポリマー、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンフェニルエーテル、ポリオキシエチレンアルキルアミノエーテル、ポリオキシエチレン脂肪酸エステル、ポリオキシエチレン多価アルコールエーテル、ポリエチレングリコール、ポリプロピレングリコール等が挙げられる。
めっき液１３に用いられる界面活性剤の配合量としては、好ましくは０．１〜５０ｇ／Ｌであり、更に好ましくは２〜１０ｇ／Ｌであり、アノード液１６に用いられる界面活性剤の配合量としては、めっき液１３に用いられるより高濃度であって、３〜１５ｇ／Ｌ、好ましくは５〜１２ｇ／Ｌとする。
【００３２】
めっき液１３には、めっき被膜表面の光沢剤としてアルデヒド化合物を配合することができる。
アルデヒド化合物としては、具体的には例えば１−ナフトアルデヒド、２−ナフトアルデヒド、ｏ−クロロベンズアルデヒド、ｍ−クロロベンズアルデヒド、ｐ−クロロベンズアルデヒド、２，４−ジクロロベンズアルデヒド、アセトアルデヒド、プロピオンアルデヒド、サリチルアルデヒド、２−チオフェンアルデヒド、３−チオフェンアルデヒド、ｏ−アニスアルデヒド、ｍ−アニスアルデヒド、ｐ−アニスアルデヒド、サリチルアルデヒドアリルエーテル、２−オキシ−３−メトキシベンズアルデヒド等が挙げられる。
アルデヒド化合物を用いる場合の配合量としては、好ましくは０．００１〜１０ｇ／Ｌ、更に好ましくは０．０５〜０．５ｇ／Ｌである。
めっき液１３には上記成分以外に、目的に応じて、公知の酸化防止剤、ｐＨ調整剤、緩衝剤などの各種添加剤を配合できる。
【００３３】
次に、めっき液１３の製造方法の一例について説明する。めっき液１３の製造に際して、上記の各成分を水及びスルホン酸類の混合物に溶解する必要があるが、溶解の順序を特定することによりめっき液１３が安定することが判明した。従来の２元系めっき液の製造においては、各金属成分と添加剤を水に溶解する順序として特に制約は無かったが、錫−銀−銅の３元系めっき液の製造においては、水に溶解する順序が重要となる。
錫−銀−銅の３元系めっき液は金属濃度が高いため、特に工業スケールで大量のめっき液を調整する場合には、調整むらが出やすい。
また、めっき液中の各成分のうち金属成分は水に対する溶解度はあまり高くないので、金属成分はある程度のスルホン酸の存在下に混合する必要がある。
従って、最初に、めっき液１３に含まれる水の３０重量％以上の水と、めっき液１３に含まれるスルホン酸類の５０重量％以上のスルホン酸類により敷水を作成し、該敷水に金属成分を混合することが好ましい。
【００３４】
本実施の形態に用いられる錫−銀−銅を含有するめっき液１３は、鉛を含まないめっき液であって、これを電解めっきすることによって形成されるめっき被膜は、従来の錫−鉛合金被膜に匹敵するはんだ接合強度を有するものとなる。従って、このめっき液１３は電子部品をめっき対象物１２とした場合に、はんだ付け性に優れためっき被膜を形成できる。
めっき対象物１２として用いられる電子部品には特に制限はないが、チップ部品、端子部品、プレス部品、水晶発振子、バンプ、コネクター、コネクターピン、リードフレーム、各種フープ材、パッケージのリードピン、ピングリッドアレイ、ボールグリッドアレイ、プリント基板の回路、スイッチ、抵抗、可変抵抗、コンデンサ、フィルタ、インダクタ、サーミスタ、水晶振動子等を挙げることが出来る。めっき被膜の厚さについては特に制限はないが、１〜２０μｍが好ましい。
【００３５】
本発明の第１の実施の形態に係る錫系合金の電解めっき方法は、常法を採用することができ、例えば、高速めっき法、ラック法、バレル法等のいずれのめっき方法も制限なく採用することができる。電解めっきの電流密度は、これらのめっき法によって０．０１〜１００Ａ／ｄｍ２ とすることができる。
本実施の形態では、特に０．０１〜５０Ａ／ｄｍ２ の範囲で適宜選定されるが、高速めっき法の場合は通常３〜５０Ａ／ｄｍ２ 、特に５〜４０Ａ／ｄｍ２ 、ラック法の場合は通常０．５〜５Ａ／ｄｍ２ 、特に１〜４Ａ／ｄｍ２ であり、バレル法の場合は通常０．０１〜１Ａ／ｄｍ２ 、特に０．０５〜０．５Ａ／ｄｍ２ である。めっき温度は１０〜５０℃、特に１５〜４０℃とすることができ、無撹拌でもよいし、カソードロッキング、スターラーによる撹拌、ポンプによる液流動などの撹拌を行うことも出来る。
また、めっきの外観は光沢、半光沢、無光沢があり、光沢めっきを得る場合は通常めっき液に光沢剤を添加して用いる。また、光沢めっきを得る場合は電流波形としてチョッパー電源波形を用いることが好ましく、また、半光沢めっきを得る場合は通常直流波形が好ましく用いられる。
【００３６】
溶解性陽極１１は、錫を９０％以上含有する可溶性の陽極であって、ニッケル、コバルト、金、ビスマス、鉛、パラジウム、アンチモン、亜鉛、鉄、インジウムから選ばれる１種又は２種以上の金属を含んでもよい。この溶解性陽極１１を用いることにより、この溶解性陽極１１を構成する金属からそれに相応する金属イオンをめっき金属イオンとしてめっき液に補給することができる。なお、陰極電流効率は、通常８０〜９９％である。
【００３７】
また、めっき液１３中の錫イオン濃度、銀イオン濃度及び銅イオン濃度は、適切な範囲に容易に管理することができる。この場合、目的とする良好なめっき被膜組成比率及び被膜物性を安定して得ることができるようにするために、めっき浴中の錫、銅、銀の各イオン濃度を、容量分析、光分析、電気分析、熱分析、Ｘ線分析、比色分析、重量分析等の分析法から選んだ１種又は２種以上の分析方法を併用してめっき浴を分析し、目的の数値の濃度となるようにめっき浴中に補給することが好ましい。
【００３８】
これらめっき浴中の主要金属イオンである錫イオン、銅イオン、銀イオンは、目的とするめっき被膜合金組成比率や被膜物性を与えるよう予め適切な濃度に配合されているが、めっき処理量が多くなるにつれ消費されて、めっき浴中の金属イオン濃度が変動する。これに伴い、消費された金属イオンを陽極からの溶解及び／又はめっき浴の外部から金属塩の濃厚溶液等の補給により、予め設定された濃度に維持することができる。
【００３９】
容量分析では、酸化還元滴定法、キレート滴定法、沈澱滴定法等がある。光分析では、比色分析、原子吸光分析法、誘導結合プラズマ発光分析法等がある。電気分析では、ポーラログラフィー、電量分析法、電位差測定法等がある。熱分析では、示差熱分析法、示差走査熱量分析法等がある。Ｘ線分析では、Ｘ線回折測定法、蛍光Ｘ線分析法等がある。
【００４０】
主要金属イオンである錫イオン、銀イオン、銅イオンをめっき液１３に補給する前に、めっき液１３中の当該金属イオン濃度を上述の分析法の内から選ばれる１種又は２種以上の分析方法を併用して分析し、測定して、その過不足分を算出し、当該金属イオンを陽極から溶出させる、あるいは／更に外部から金属塩の濃厚溶液、粉末、ペースト、固体の内から選ばれる１種又は２種以上で補給することができる。
【００４１】
特に、めっき液１３中に不純物を持ち込まないようにするには併用することが好ましい。この場合、金属塩の濃厚溶液、粉末、ペースト、固体は各金属イオンを供給する金属を単体で又は混合して補給してもよい。なお、金属塩の粉末、ペースト、固体での補給は、十分な撹拌が必要であり、濃厚溶液での補給が特に好ましい。
【００４２】
本実施の形態に係る錫系合金の電解めっき方法で得られためっき被膜は、銀の含有量が２．６〜３．４重量％、銅の含有量が０．４〜０．７重量％、残部が錫であり、合金の共晶点に近く融点の低いめっき被膜となる。中でも錫−銀−銅合金を用いたはんだペーストとの接合性が良好であり、組成が類似しているため接合強度（はんだ付け強度）が高く、且つ融点が低いために、はんだ付けに必要な熱量が低減できる。
【００４３】
次に、本発明の第２の実施の形態に係る錫系合金の電解めっき方法について、図２に示すめっき装置１０ａを参照して以下に説明する。
本実施の形態は、図２に示すように、前記した第１の実施の形態の２個の溶解性陽極１１のうち、１個を周囲に隔膜２３を設けた不溶性陽極２１とし、めっき液１３からの銀イオンがこの不溶性陽極２１に触れるのを防止した点と、溶解性陽極１１に流す電流量をめっき対象物１２にめっきされる錫の等価電流に実質的に一致させた点以外は第１の実施の形態と実質的に同じであり、めっき方法の手順も同様であるため、その詳細な説明は省略する。ここで、不溶性陽極２１を覆う隔膜２３は、銀イオンがこの不溶性陽極２１に触れるのを防止し、電流を流すものであれば、溶解性陽極１１を覆う隔膜１７と同じものを使用してもいいし、異なる隔膜を使用してもよい。
不溶性陽極２１としては通常使用される白金、白金めっきチタン、炭素等の不溶性陽極が用いられ、不溶性陽極２１の周りの液Ｃ２２はメタンスルホン酸のみとした。
また、第２の実施の形態において、アノード液１６にメタンスルホン酸と共に非イオン性の親水性界面活性剤を加えてもよい。
【００４４】
溶解性陽極１１を隔膜１７で覆い、めっき対象物１２からの銀イオンの侵入を抑えたところで、必要量の電流を流すと、めっき液１３中のＳｎ２＋濃度は例えば、６０００個のリードフレーム（めっき対象物）のめっき（６０００Ｆｒという）で、めっき液１３中のＳｎ２＋濃度がＩＣＰ測定法で計算して３３．７ｇ／Ｌに、１５０００Ｆｒで３９．７ｇ／Ｌに上昇していた。そしてめっき液１３には、酸化錫と思われる濁りが発生していた。
更に、溶解性陽極１１に１．５３Ｆの電気量の電流を流してめっきすると、溶解性陽極１１側の錫は８５．８ｇ溶解して減ったのに対し、めっき被膜中の錫は８０．２２ｇであった。
つまり溶解した錫のうち５．５８ｇはめっきに使用されず、余剰のＳｎ２＋となってめっき液１３中に溶けたと推察される。これは、１．５３Ｆの電流を流すと、流した電流分だけ錫が溶解するが、化学溶解によっても錫が溶解し、更に、錫以外のめっき金属をめっきするための電流量分だけ錫が過剰に溶解するため、溶解した錫のうち５．５８ｇは余剰の錫となったと考えられる。
従って、溶解性陽極１１側に流す電流量を、めっきされる量から化学溶解分を除いた錫を溶解するのに必要な電流量である１．４７８Ｆとし、残りの０．０５２Ｆの電流を隔膜２３で覆った不溶性陽極２１に流す、つまり、溶解性陽極と不溶性陽極の両方からめっきに必要な電流を流すことによって余剰のＳｎ２＋の発生を抑えることができた。
【００４５】
さらに、本発明の第３の実施の形態に係る錫系合金の電解めっき方法について、図３に示すめっき装置１０ｂを参照して以下に説明する。
図３に示すように、本実施の形態に用いるめっき装置１０ｂは、第１の実施の形態で用いためっき装置１０のめっき液１３に孔径０．１〜０．３μｍのポリエチレン製の不織布をセルロースコーティングした濾過膜２４を備えた循環回路２６を設け、めっき液１３に、ポンプ２５で水頭圧１０．０〜１２．０ｍの低圧力をかけて濾過膜２４を通過させている。これによって、めっき液１３中の固形分である不純物、例えば、酸化第二錫、酸化銅、酸化銀を濾過して取ることができ、液質の劣化を防止することができるようになる。この濾過膜２４の効果を見るために、４６０００Ｆｒのめっきによって、液が白濁し、Ｓｎ４＋が５１．９ｇ／Ｌとなった未処理のめっき液を、０．２μｍのポリエチレン製の不織布をセルロースコーティングしたアドバンテック社（ＡＤＶＡＮＴＥＣ）製の濾過膜２４を使用し、水頭圧１０．０〜１２．０ｍの低圧力で濾過膜２４を通過させる実験を行った。
圧力調製にはポンプを回転するモータをインバータモータとし、炉液が出る最小周波数に調整した。最小周波数は、水頭圧１１．６ｍ、流量１３０Ｌ／ｍｉｎ、３７Ｈｚであった。
【００４６】
液が白濁し、Ｓｎ４＋が５１．９ｇ／Ｌとなった未処理のめっき液１３が、濾過膜２４を１２時間通過することによって、Ｓｎ４＋が２．１ｇ／Ｌとなり、透明となった。
さらに、比較例として、同じく４６０００Ｆｒのめっきによって、白濁しためっき液を活性炭処理した。活性炭処理では液は白濁したままで、更に、活性炭により黒く濁った。次に市販の鉛フリーめっき用の凝集剤（フロック）処理を行ったが液の濁りはとれなかった。
【００４７】
次に４６０００Ｆｒのめっきによって、液が白濁し、Ｓｎ４＋が５１．９ｇ／Ｌとなった未処理のめっき液を同じ、０．２μｍのポリエチレン製の不織布をセルロースコーティングした濾過膜を使用し、３７Ｈｚの周波数、流量８３３ｍＬ／ｍｉｎで１２時間流したが液の濁りは取れなかった。同じ濾過膜を使用し、４０Ｈｚの周波数、流量６００ｍＬ／ｍｉｎで１２時間流した結果はＳｎ４＋が２５ｇ／Ｌであった。さらに、同じ濾過膜で５０Ｈｚの周波数、流量５ｍＬ／ｍｉｎで流した結果は液が透明に澄んでいた。
また、めっきの最初から循環回路２６を使用した場合にはめっき液１３は濁ることなく常に透明であった。
【００４８】
以上の結果から、０．１〜０．３μｍのポリエチレン製の不織布をセルロースコーティングした濾過膜２４を使用して、めっき液１３を低圧力で濾過することによって、不純物が発生しためっき液１３の再生に効果があると共に、この濾過膜２４をめっきの際に使用することによって、液の劣化を防ぐことがわかった。
なお、本実施の形態では第１の実施の形態で説明しためっき装置１０に循環回路２６を設けた場合について説明したが、循環回路２６を第２の実施の形態で説明しためっき装置１０ａに設けてもよい。
【００４９】
【実施例】
続いて、本発明の錫系合金の電解めっき方法において、隔膜効果をみるための実験、及びアノード浴に界面活性剤を加えることによるＳｎ２＋のめっき液への溶出効果をみるための実験について以下に説明する。
まずめっき装置１０を使用し、めっき槽１４に投入するめっき液１３を次のように調整した。
撹拌容器にめっき液調整に必要な水の１／３を入れ、さらに、５４重量％のメタンスルホン酸水溶液の全容を入れ敷水とした。
次に、撹拌しながら所要量の酸化銀の全容を入れ完全に黒沈がなく透明になったことを確認後、速やかに、水酸化第二銅の全容をいれ完全に溶解してから、錯化剤としてメルカプタン化合物の一例であるアセチルシステインを入れ溶解確認後他の錯化剤として芳香族アミノ化合物の一例である２，２’ −ジチオジアニリンを入れた。
薄水色のゲル状の液体になったら速やかにメタンスルホン酸第一錫を入れ、黄色透明になった。次にめっき液１３に必要な水の２／３を加え、最後に界面活性剤の一例であるα−ナフトールポリエトキシレート（ＥＯ１０モル）３ｇ／Ｌを入れ、めっき液１３の調整は終了した。めっき液１３中のメタンスルホン酸の濃度は２．６４ｍｏｌ／Ｌであり、Ｓｎ２＋濃度を０．２５〜２ｍｏｌ／Ｌ、銀イオン濃度を０．０１〜０．１ｍｏｌ／Ｌ、銅イオン濃度を０．００２〜０．０２ｍｏｌ／Ｌに調整した。
【００５０】
〔実施例１〕
まず、本発明の錫系合金の電解めっき方法において、隔膜効果をみるための実験について説明する。この実験においては、アノード浴には界面活性剤は入れずに実験を行った。
前記しためっき装置１０において、錫を９０％以上含有する溶解性陽極１１として純Ｓｎのアノード板（直方体インゴット）を２個用意し、陰極であるめっき対象物１２として０．３ｄｍ３ の銅製テストピースを用意した。めっき槽１４には５００ｍＬビーカーを使用し、上記で調整しためっき液１３で満たし、めっき液１３を撹拌するための撹拌子１８を入れる。
２枚の溶解性陽極１１をそれぞれアノードバッグ１５で包み、さらに隔膜１７で覆い、めっき槽１４に入れる。整流器＋側より２本配線を出しそれぞれの溶解性陽極１１の端子１９にクリップでしっかり固定した。一方、整流器−側より１本配線を出しめっき対象物１２の端子２０に同様に固定した。アノードバッグ１５内に５４重量％のメタンスルホン酸の８０ｍｌ（１．０５ｍｏｌ／Ｌ）を入れてアノード液１６とし、電流密度を５．８Ａ／ｄｍ２ 、電流波形を直流波形とし、１．５Ａの電流で２時間通電し、１．５×３６００×２のトータル１０８００Ｃ（クーロン）の電気量にてめっきを行った。
めっき後のアノード液１６、めっき液１３のＳｎ２＋イオン、銀イオン、銅イオンのイオン濃度を測定した。
隔膜１７としてはポリエチレン製の孔径０．０２μｍで膜厚１６μｍの微多孔膜セティーラ（登録商標／東燃タピルス株式会社製）、及び、ポリエチレン製の孔径０．０２〜０．０４μｍで膜厚２７μｍの微多孔膜のハイポア（登録商標／旭化成株式会社製）を使用した。比較例としてイオン透過性膜であるＣＭＸ（登録商標／株式会社徳山製）を使用した場合について実験した。結果を表１に示す。なお、本実施例におけるＳｎ２＋の理論析出量は、流したすべての電気量（１０８００Ｃ）をＳｎ２＋めっきに使用したと換算した場合、めっきされる錫は６．６４ｇとなり、純Ｓｎのアノード板からなる溶解性アノードから溶ける錫は、６．６４ｇとなるので、Ｓ２＋の１Ｃ（クーロン）当たりの膜の透過量（ｇ）はめっき前後のカソード浴におけるＳ２＋の濃度から、〔６．６４−（めっき前濃度−めっき後濃度）×０．５〕／１．５×３６００×２の式で算出される。
【００５１】
【表１】

Figure 2005023374
【００５２】
表１に示すように、孔径０．０２μｍで膜厚１６μｍのセティーラ（登録商標）を使用した場合は、めっき前からめっき後のアノード液からめっき液へのＳｎ２＋の透過量が１．９４×１０−４であり、孔径０．０２〜０．０４μｍで膜厚２７μｍのハイポア（登録商標）は１．０４×１０−４であるのに対して比較例であるイオン透過性膜であるＣＭＸ（登録商標）は３．４７×１０−５となり、本実施例の隔膜の透過性は比較例に対して３〜６倍程度高く、めっき液への錫イオンの透過性が非常に良いことを示している。
また、アノード液１６中のＳｎ２＋濃度が本実施例に係る隔膜１７を使用した場合に比較して比較例は、大幅に上昇し、更に、めっき液１３（カソード浴）中のＳｎ２＋濃度が低下していることからも、本実施例に係る隔膜１７はＳｎ２＋イオンのアノード液１６からめっき液１３への透過性が非常に良いことがわかる。
さらに、めっき液１３からアノード液１６への銀の透過量は実施例であるハイポアは０．０９ｇ／Ｌで比較例であるＣＭＸ（登録商標）に比較して非常に低く、また実施例のセティーラも０．４４ｇ／Ｌであまり差異がないことがわかる。
従って、本実施例に係る隔膜１７は、錫イオンの透過性が高いにも係わらず銀イオンの非透過性にも優れており、隔膜として非常に優れていることが判る。
また、隔膜１７で仕切りをしなかったものについては、溶解性陽極１１の周りに酸化銀と思われる黒い銀化合物の析出が見られた。
従って、隔膜を使用してアノード浴を覆うことによって、アノード浴に銀イオンが侵入して、陽極で錫イオンと置換して析出するのを抑えることができ、さらに、錫イオンは膜を透過してめっき浴中に進出するため、めっき液の安定性に寄与することができることになった。
【００５３】
〔実施例２〕
次に、アノード浴に界面活性剤を加えることによるＳｎ２＋のめっき液への溶出効果をみるための実験について以下に説明する。
実施例１と同じめっき装置１０を使用し、隔膜１７として、実施例１で使用したポリエチレン製の孔径０．０２μｍで膜厚１６μｍの微多孔膜セティーラ（登録商標）、及び、ポリエチレン製の孔径０．０２〜０．０４μｍで膜厚２７μｍの微多孔膜のハイポア（登録商標）を使用した。めっきの手順としては実施例１と略同じで、アノード浴内にメタンスルホン酸に追加して非イオン性で親水性の界面活性剤を添加した点、並びに実施例２−１及び２−４において、更に錯化剤のアセチルシステイン及びジチオジアニリンを添加した以外は、実施例１と略同じ方法で２時間のめっきをした。なお、親水性のノニオン系界面活性剤としてαナフトールポリエトキシレート（ＰＯＥＮ）を使用した。
１．５Ａ（０．３ｄｍ２ ×５．８Ａ／ｄｍ２ ）で２時間のめっき後、アノード液１６を取り出し、撹拌後、ＩＣＰ（高周波プラズマ誘導結合プラズマ発光分光分析法）用サンプルとした。
めっき後のアノード液１６のＳｎ２＋、銀イオンのイオン濃度をＩＣＰ法を用いて測定した。結果を表２に示す。
【００５４】
【表２】
Figure 2005023374
【００５５】
実施例２−１〜２−３に隔膜１７としてセティーラ（登録商標）を使用し、５４重量％の１５０ｍｌ／Ｌ（１．０５ｍｏｌ／Ｌ）のメタンスルホン酸にＰＯＥＮをアノードバッグ１５内に６．０ｇ／Ｌ、９．０ｇ／Ｌ、１２．０ｇ／Ｌ追加してめっきした結果を示す。実施例２−４〜２−６は隔膜１７としてハイポア（登録商標）を使用し、アノードバッグ１５内にＰＯＥＮの６．０ｇ／Ｌ、９．０ｇ／Ｌ、１２．０ｇ／Ｌをメタンスルホン酸１５０ｍｌ／Ｌに追加して入れてめっきした。
比較例１は、ＰＯＥＮを入れず水を入れた場合を示し、比較例２、３として、ＰＯＥＮをめっき液１３と同量の３．０ｇ／Ｌ入れた。
また、比較例４として隔膜を孔径０．０２〜０．０４μｍで膜厚１００μｍのハイポア１０Ｃ（登録商標）とし、ＰＯＥＮをアノードバッグ内に１２．０ｇ／Ｌ追加した結果を示す。
実施例２−１〜２−６に示すように、アノード液１６中にノニオン系の界面活性剤であるＰＯＥＮをめっき液１３中の３．０ｇ／Ｌよりも高濃度の６．０ｇ／Ｌ、９．０ｇ／Ｌ、１２．０ｇ／Ｌ入れて１．５Ａで２時間めっきすると、アノード液１６中のＳｎ２＋イオンはめっき前より２０．７９〜４７．１ｇ／Ｌ増加するのに対し、ＰＯＥＮを入れず水を追加した比較例１及びＰＯＥＮをめっき液１３と同量の３．０ｇ入れた比較例２、３ではめっき後のアノード液１６中のＳｎ２＋イオンが６８．５〜８４ｇ／Ｌ増加した。
【００５６】
このことから、ＰＯＥＮをめっき液より高濃度に入れた実施例２は比較例に比べて、めっき後のアノード液１６中のＳｎ２＋イオンの上昇が非常に低く、Ｓｎ２＋イオンが隔膜１７を透過してめっき液１３中に順調に移行しているのがわかる。
また、実施例２−１及び実施例２−４において、アノード浴に錯化剤のアセチルシステイン及びジチオジアニリンを添加したのは、銀イオンが陽極側へ移行してきた場合に、陽極性電極の錫と置換析出するのを避けるためであるが、実際には銀イオンの透過量は少なく、錯化剤を添加しない他の例でもＡｇの析出は見られなかったた。従って、錯化剤の効果は無かったといえる。
さらに隔膜１７を膜厚２７μｍのハイポア（登録商標）の代わりに、膜厚が１００μｍのハイポア１０Ｃ（登録商標）とした比較例４ではＰＯＥＮをアノードバッグ１５内に１２．０ｇ／Ｌ追加していながら、アノード液１６内のＳｎ２＋濃度が大幅に上昇しており、Ｓｎ２＋のめっき液１３への透過性が悪いことを示している。従って、隔膜の厚みも重要な要素を持つことが判る。
【００５７】
いずれも同じアノード板に同じ電気量を流して実験をしたこの結果から、実施例２の隔膜を使用して、アノード液中のＰＯＥＮ濃度をめっき浴中のＰＯＥＮ濃度より高くした場合には、アノード浴中のＳｎ２＋イオンがめっき浴中に順調に出ていることがわかった。
従って、従来、めっき液中の錫以外の銀イオンあるいは銅イオン等の金属イオン及びその錯体が錫イオンと置換して錫を９０％以上含有する溶解性陽極の周りに金属塩となって析出し、めっき液の安定性が悪くなったり、液質が劣化するのを防ぐためにアノード浴の周りを隔膜で覆うと、アノード浴からめっき浴への錫イオンの透過性が悪くなるという問題があったが、実施例の隔膜を使用し、アノード液中のＰＯＥＮ濃度をめっき液中のＰＯＥＮ濃度より高くしてめっきすることによって、アノード液中の錫イオンのめっき液への透過性を高めることができる事となった。
さらに、アノード液中の錫イオンがめっき液に出過ぎる場合には、アノード液とめっき液を隔膜で仕切った溶解性陽極の他に、更に周囲に隔膜を設けた不溶性陽極を設け、溶解性陽極への電流量を調整することによって、溶解性陽極からの錫イオンの溶出を調整してめっき液中の錫イオン濃度が上昇し過ぎるのを防止することができ、めっき液の安定性がよく、液質の劣化が少ない錫系合金の電解めっき方法を提供できることとなった。
【００５８】
前記実施の形態において、めっき液として錫−銀−銅を含有する３元系めっき液を用いたが、錫を必須として、錫−銀あるいは錫−銅、又は錫−ビスマスの２元系のめっき液とする場合、あるいは銀又は銅に代わってビスマスを用いた３元系のめっき液とする場合、また、めっき液の濃度を本発明の要旨を変更しない範囲で変更する場合も本発明の権利範囲に含まれる。
さらに、本発明は前記実施の形態及び実施例に限定されるものではなく、要旨を変えないで変更する場合も本発明の権利範囲に含まれる。例えば、第１の実施の形態では、２個の溶解性陽極を用いた場合について記載したが、溶解性陽極を１個あるいは３個以上にしてもよい。
また、上記実施例においては、隔膜を非イオン性の隔膜としたがイオン交換膜としてもよい。
【００５９】
【発明の効果】
請求項１〜１０記載の錫系合金の電解めっき方法は、錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にして溶解性陽極の周囲の液Ａと陰極の周囲の液Ｂを錫イオンを透過し易い隔膜、特に請求項１は１Ｃの電気量を通電させたときに、錫イオンを陽極側から陰極側へ５×１０−５〜５×１０−４ｇ通す隔膜を設けて仕切り、請求項２は他のめっき金属のイオンあるいは錯体より錫イオンを透過し易い隔膜を設けて仕切り、請求項３は、孔径０．０１〜０．０５μｍで膜厚５〜１００μｍの微多孔膜からなる隔膜で仕切っているので、溶解性陽極からの錫イオンは隔膜を通過して陰極液（めっき液）である液Ｂ中に入る事ができ、めっき液中の錫イオンを溶解性陽極で補給することができると共に、錫イオンよりイオン化傾向の小さい他のめっき金属のイオンあるいは錯体、例えば銀イオンや銅イオン及びその錯体が液Ａ中に入って錫イオンと置換して金属化合物となって、析出するのを防ぐことができる。
【００６０】
請求項４及び５記載の錫系合金の電解めっき方法は、液Ａに界面活性剤を添加しているので、錫イオンの液Ａから液Ｂへの透過性がよくなっている。特に、請求項５では、液Ａに液Ｂ中の界面活性剤より高濃度になるように界面活性剤を添加しているので、液Ａから液Ｂへの錫イオンの透過性が、更に高まっている。
請求項６及び７記載の錫系合金の電解めっき方法は、更に不溶性陽極を設け、不溶性陽極の周囲の液Ｃと液Ｂを他の隔膜で仕切っているので、液Ｂ中の陽イオン、例えば銀イオンがこの不溶性陽極に触れるのを防止している。特に請求項７では、めっき対象物にめっき金属をめっきさせるのに必要な電流を溶解性陽極と不溶性陽極の両方から流し、溶解性陽極には、めっきに必要分から化学溶解分を除いた錫を溶解するのに必要な電流量のみを流し、不溶性陽極に残りの電流量を流しているので、錫の溶けすぎを防ぐことができる。
【００６１】
請求項８記載の錫系合金の電解めっき方法は、液Ｂに孔径０．１〜０．３μｍの濾過膜を備えた循環回路を設け、液Ｂに低圧力をかけて濾過膜を通過させているため、液質の劣化の原因となる不純物、特に酸化第二錫や酸化銅、酸化銀を除去することができる。
請求項９記載の錫系合金の電解めっき方法は、液Ａのスルホン酸類の濃度を０．５〜１．５ｍｏｌにしているので、化学溶解による錫の過剰溶解を防ぐことができる。
【００６２】
請求項１０記載の錫系合金の電解めっき方法は、液Ｂを、水を主体とする媒体に、スルホン酸類、錫イオン、銅イオン及び銀イオンを含むめっき液であって、Ｓｎ２＋濃度が０．２５〜２ｍｏｌ／Ｌ、銀イオン濃度が０．０１〜０．１ｍｏｌ／Ｌ、銅イオン濃度が０．００２〜０．０２ｍｏｌ／Ｌに調整されているので、融点が低い錫−銀−銅合金めっきが生産性高くできる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態に係る錫系合金の電解めっき方法の説明図である。
【図２】本発明の第２の実施の形態に係る錫系合金の電解めっき方法の説明図である。
【図３】本発明の第３の実施の形態に係る錫系合金の電解めっき方法の説明図である。
【符号の説明】
１０、１０ａ、１０ｂ：めっき装置、１１：溶解性陽極、１２：めっき対象物、１３：めっき液、１４：めっき槽、１５：アノードバッグ、１６：アノード液、１７：隔膜、１８：撹拌子、１９：端子、２０：端子、２１：不溶性陽極、２２：液Ｃ、２３：隔膜、２４：濾過膜、２５：ポンプ、２６：循環回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for electrolytic plating of a tin-based alloy used for lead-free solder plating.
[0002]
[Prior art]
Conventionally, for components that require soldering, such as chip components, crystal oscillators, bumps, connector pins, lead frames, various hoop materials, package lead pins, printed circuit boards, etc. Tin plating and tin lead alloy plating have been performed. Pure tin plating has problems such as deterioration of solderability and generation of whisker-like crystal whiskers in the coating. In recent years, the use of lead has been refrained from the viewpoint of environmental protection, and lead-free plating has been desired.
[0003]
For example, a tin-silver alloy, a tin-bismuth alloy, a tin-copper alloy, and the like have been studied as a lead-free plating. Conventionally known lead-free plating films are 20 degrees higher than tin-lead plating films. Since the melting point is high, a lead-free plating film having a low melting point has been desired in order to reduce the energy cost at the time of joining and to reduce the amount of heating to other parts.
Further, it is desired that the solder material on the substrate side to be joined to the plating film is lead-free. For example, a tin-silver-copper alloy having a composition close to the eutectic point has been used as the solder material. It was. However, a plating film having a composition similar to that of the tin-silver-copper alloy has not yet been obtained due to the difficulty of the stability of the plating solution, and the bondability with the solder material using the tin-silver-copper alloy A good plating film was desired. As a tin-copper alloy plating, a plating bath containing a specific organic compound component and a plating method thereof, and further, a tin-silver-copper alloy plating bath and a plating method thereof are disclosed (for example, see Patent Document 1). .
[0004]
[Patent Document 1]
JP 2001-164396 A (3rd, 4th, 7th, 8th, 25th to 27th pages)
[0005]
[Problems to be solved by the invention]
However, the composition of the plating bath specifically disclosed in Patent Document 1 has a low concentration of each metal, and has a problem in terms of productivity when used for industrial plating. The tin-silver-copper alloy plating bath is superior to the tin-copper alloy plating bath in terms of solder wettability, liquid stability, and strength, but contains three types of metal ions and metal ion complexes. In addition, liquid preparation is difficult, especially in industrial scales, the amount of plating chemicals handled is large, and in order to use for a long time, solids may be generated during the plating process, and the liquid quality may change. As a result, there were problems such as unstable plating quality. In addition, when using a plating solution having a high concentration of metal ions, for example, when a soluble anode containing 90% or more of tin is used, silver ions are easily deposited as silver compounds or metal silver, When the stability of the liquid is degraded and an insoluble anode is used, Sn 2+ Is Sn 4+ There was a problem of making an insoluble precipitate and deteriorating the liquid quality.
[0006]
The present invention is a tin-based material capable of performing a stable plating process without causing a deterioration in quality, such as a solid matter occurring during the process or a change in liquid quality, even if a large amount of plating process is continuously performed. It is an object of the present invention to provide a method for electrolytic plating of an alloy.
[0007]
[Means for Solving the Problems]
The electrolytic plating method of a tin-based alloy according to the first invention that meets the above-described object is the method for electrolytic plating of a tin-based alloy using a soluble anode containing 90% or more of tin and using the object to be plated as a cathode. When the liquid A around the soluble anode and the liquid B around the cathode are energized with an electric quantity of 1 C (Coulomb), tin ions are transferred from the anode side to the cathode side by 5 × 10. -5 ~ 5x10 -4 It is partitioned by a diaphragm that passes through g.
Accordingly, tin ions from the soluble anode can pass through the diaphragm and enter the liquid B as the catholyte (plating solution), and the tin ions in the plating solution can be replenished by the soluble anode.
When an amount of electricity of 1 C (Coulomb) is energized, 5 × 10 tin ions flow from the anode side to the cathode side. -5 If the amount is less than g (approximately 8.4% with respect to the dissolved amount of tin ions), the tin ions in the plating solution will be excessively reduced, making it difficult to keep the tin concentration in the plating solution constant. 5 × 10 -4 A diaphragm that passes more than g (about 84% with respect to the dissolved amount of tin ions) is not suitable because the permeability of silver ions increases.
[0008]
The tin-based alloy electrolytic plating method according to the second invention uses a soluble anode containing 90% or more of tin, and the tin-based alloy electrolytic plating method uses a plating object as a cathode. The surrounding liquid A and the surrounding liquid B of the cathode are partitioned by a diaphragm that allows permeation of tin ions more easily than ions or complexes of other plating metals.
Accordingly, tin ions in the plating solution can be replenished with the soluble anode, and ions or complexes of other plating metals having a lower ionization tendency than tin ions in the solution B, which is the plating solution, such as silver ions and copper ions. Can be prevented from entering the liquid A and substituting for tin ions to form a metal compound.
[0009]
A tin-based alloy electroplating method according to a third aspect of the present invention is a tin-based alloy electroplating method using a soluble anode containing 90% or more of tin and using a plating object as a cathode. The surrounding liquid A and the surrounding liquid B of the cathode are partitioned by a diaphragm made of a microporous film having a pore diameter of 0.01 to 0.05 μm and a film thickness of 5 to 100 μm.
Accordingly, tin ions having a small diameter can be transferred from the liquid A to the liquid B, but other plating metals in the liquid B, in particular, complexes thereof, for example, complexes of silver ions and copper ions, pass through the diaphragm and enter the liquid A. Intrusion can be prevented.
When the pore diameter and film thickness are outside the above ranges, the permeability of tin ions becomes very bad, and the permeability of silver ions, copper ions and their complexes, which are plating metals other than tin ions, is disadvantageous.
[0010]
The tin-based alloy electroplating method according to the fourth invention is the tin-based alloy electroplating method according to the first to third inventions, wherein the liquid A is a surfactant, particularly preferably water-soluble and nonionic. The surfactant is added.
Accordingly, the permeability of tin ions from the liquid A to the liquid B is improved.
The tin-based alloy electrolytic plating method according to a fifth aspect of the present invention is the tin-based alloy electrolytic plating method according to the fourth aspect of the present invention, wherein the liquid A has a higher concentration than the surfactant in the liquid B. An activator is added.
Accordingly, the permeability of tin ions from the liquid A to the liquid B is further increased.
[0011]
The tin-based alloy electrolytic plating method according to a sixth aspect of the present invention is the tin-based alloy electrolytic plating method according to the first to fifth aspects of the present invention, further comprising an insoluble anode, and the liquid C around the insoluble anode and the liquid B is separated by another diaphragm.
By providing an insoluble anode in addition to the soluble anode and adjusting the amount of current to the soluble anode, it is possible to prevent an excessive increase in the tin ion concentration in the liquid B due to excessive elution of tin ions from the soluble anode. it can. In addition, since the liquid C and the liquid B around the insoluble anode are separated by separate diaphragms, the cations in the liquid B, such as silver ions, are prevented from touching the insoluble anode.
Here, the diaphragm that separates the liquid A and the liquid B has good permeability of tin ions, and a plating metal ion other than tin ions and a complex thereof, for example, a film with poor permeability of silver ions and the complex is necessary. . The diaphragm that separates the liquid B and the liquid C may be good or bad as long as the permeability of other plating metal ions and their complexes is poor. The same diaphragm may be used, or different diaphragms may be used.
[0012]
A tin-based alloy electrolytic plating method according to a seventh aspect of the present invention is the tin-based alloy electrolytic plating method according to the sixth aspect of the present invention, wherein the electric current necessary for plating the plating object on the plating object is the soluble anode. And the insoluble anode.
In general, in a tin-based alloy electrolytic plating method, a current necessary for plating a plating target with a plating metal is passed through a soluble anode containing 90% or more of tin.
At this time, the soluble anode containing 90% or more of tin dissolves tin by the amount of current passed, but the soluble anode containing 90% or more of tin is also chemically dissolved by the liquid around the anode containing acid. To do. Therefore, if the current required for plating the plating metal is applied only to the soluble anode, the soluble anode is chemically dissolved, and the amount of current that causes the plating metal other than tin to be deposited on the cathode is dissolved. Tin melts too much and Sn 2+ The concentration rises too much and the ion balance of the liquid is lost. Furthermore, if a current is passed only through the insoluble anode, Sn 2+ Is oxidized to Sn 4+ And Sn 4+ Becomes a tin oxide and precipitates, which causes a problem of deteriorating liquid quality.
Therefore, for the soluble anode, only the amount of current required to dissolve tin, which is the amount required for plating, is removed, and the remaining amount of current is supplied to the insoluble anode. Therefore, the above-mentioned problem can be solved by supplying a current necessary for plating the plating metal.
[0013]
The tin-based alloy electroplating method according to an eighth invention is the tin-based alloy electroplating method according to the first to seventh inventions, wherein the liquid B is provided with a filtration membrane having a pore diameter of 0.1 to 0.3 μm. A circulation circuit is provided, and the liquid B is subjected to a low pressure to pass through the filtration membrane to remove impurities.
Impurities that cause deterioration of the liquid quality, especially stannic oxide, copper oxide, and silver oxide, are removed by applying low pressure to the liquid B and passing through a filtration membrane having a pore diameter of 0.1 to 0.3 μm. Can do.
[0014]
A tin-based alloy electroplating method according to a ninth invention is the tin-based alloy electroplating method according to the first to eighth inventions, wherein the liquid A contains sulfonic acids having a concentration of 0.5 to 1.5 mol. is doing.
Since the concentration of the sulfonic acids in the liquid A is 0.5 to 1.5 mol, the solubility of tin is maintained by the applied current, but chemical dissolution can be prevented and excessive dissolution of tin can be prevented.
[0015]
The tin-based alloy electroplating method according to a tenth invention is the tin-based alloy electroplating method according to the first to ninth inventions, wherein the liquid B is added to a medium mainly comprising water, sulfonic acids, tin. A plating solution containing ions, copper ions and silver ions, and Sn 2+ The concentration is adjusted to 0.21 to 2 mol / L, the silver ion concentration is adjusted to 0.01 to 0.1 mol / L, and the copper ion concentration is adjusted to 0.002 to 0.02 mol / L.
Tin ions in the plating solution are Sn 2+ And Sn 4+ But Sn 4+ Is further oxidized to SnO 2 It is Sn that is involved in the plating. 2+ It is estimated that. Therefore, Sn 2+ The concentration of.
Thereby, tin-silver-copper alloy plating having a low melting point can be made highly productive, and more preferably Sn. 2+ By setting the concentration to 0.3 to 1 mol / L, the silver ion concentration to 0.02 to 0.05 mol / L, and the copper ion concentration to 0.003 to 0.01 mol / L, a tin-silver-copper eutectic crystal A tin-silver-copper alloy plating having a melting point close to the point can be made highly productive.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
FIG. 1 is an explanatory diagram of a tin-based alloy electrolytic plating method according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram of a tin-based alloy electrolytic plating method according to the second embodiment of the present invention. FIG. 3 is an explanatory diagram of a tin-based alloy electrolytic plating method according to the third embodiment of the present invention.
[0017]
As shown in FIG. 1, a plating apparatus 10 used in the tin-based alloy electrolytic plating method according to the first embodiment of the present invention includes two soluble anodes 11 containing 90% or more of tin, a cathode, A plating object 12 to be formed, a plating solution 13 containing an example of a plating metal component dissolved in sulfonic acids (an example of a solution B around the cathode), a plating tank 14 for containing the plating solution 13, and a plating solution 13 as required. It has a stirring bar 18 for stirring.
Further, around each soluble anode 11, an anode bag 15, which is a commercially available bag that covers the soluble anode 11 and removes impurities (particularly tin oxide), and an anolyte 16 around the anode (liquid A A diaphragm 17 is provided to partition an example) from the plating solution 13, and the anolyte 16 is filled with a sulfonic acid solution in order to maintain the ion state of tin ions. The concentration of this sulfonic acid solution is 0.5 to 1.5 mol / L, which is a concentration at which the tin ionized by the electric current dissolves and maintains an ionic state, but hardly dissolves chemically.
Further, the anolyte 16 has a higher concentration of nonionic and hydrophilic surfactant than the surfactant in the plating solution 13 in order to increase the permeability of tin ions from the anolyte 16 to the plating solution 13. Is added.
[0018]
In the method for plating a tin-based alloy according to the first embodiment of the present invention, first, the inside of the plating tank 14 is filled with the plating solution 13, the stirrer 18 for stirring the plating solution 13 is added, and the soluble anode 11 is placed in the anode bag. 15, covered with a diaphragm 17, and placed in the plating tank 14. The diaphragm 17 is made of a nonionic microporous film made of a synthetic resin having good permeability of tin ions but having poor permeability of other plating metal ions and complexes thereof, for example, silver complexes. Next, the terminal 19 of the soluble anode 11 and the terminal 20 of the cathode are connected, the anolyte 16 is placed in the anode bag 15, and an electric current is applied to plate the tin of the soluble anode and the plating metal in the plating solution 13. The object 12 (cathode) is plated.
Here, the two soluble anodes 11 are provided symmetrically with respect to one cathode as the plating object 12 by plating on both surfaces of the plating object 12 by providing the anodes on both sides of the cathode. Because.
[0019]
For example, the plating solution 13 contains tin, silver, and copper as essential components as a sulfonic acid and a metal component in a medium mainly composed of water.
The metal component is present as a metal ion in the plating solution 13, and the plating solution 13 is obtained by mixing a plating mother solution mainly composed of water and sulfonic acids and a metal compound, which is preferable for the stability of the metal ion. It is preferable to add an organic complexing agent to make it exist as a metal ion and a complex of metal ions.
[0020]
Specific examples of tin compounds include tin salts of organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, p-phenolsulfonic acid, tin sulfate, tin oxide, tin nitrate, tin chloride, bromide Tin, tin iodide, tin phosphate, tin pyrophosphate, tin acetate, tin formate, tin citrate, tin gluconate, tin tartrate, tin lactate, tin succinate, tin sulfamate, tin borofluoride, tin silicofluoride, etc. These stannous compounds are mentioned. These tin compounds can be used individually by 1 type or in mixture of 2 or more types.
[0021]
As the copper compound, copper salt of the above sulfonic acid, copper sulfate, copper oxide, copper sulfate, copper chloride, copper bromide, copper iodide, copper phosphate, copper pyrophosphate, copper acetate, copper formate, copper citrate, Examples include copper gluconate, copper tartrate, copper lactate, copper succinate, copper sulfamate, copper borofluoride, copper silicofluoride and the like. These copper compounds can be used individually by 1 type or in mixture of 2 or more types.
[0022]
Examples of silver compounds include silver, silver sulfate, silver oxide, silver nitrate, silver chloride, silver bromide, silver iodide, silver phosphate, silver pyrophosphate, silver acetate, silver formate, silver citrate, and gluconic acid. Examples thereof include silver, silver tartrate, silver lactate, silver succinate, silver sulfamate, silver borofluoride, and silver silicofluoride. These silver compounds can be used individually by 1 type or in mixture of 2 or more types.
[0023]
Any sulfonic acid can be used as long as it can dissolve the above-mentioned metal component, and examples thereof include aliphatic sulfonic acids such as methanesulfonic acid and ethanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid. It is done. Of these, aliphatic sulfonic acids are preferred, and methanesulfonic acid is particularly preferred from the standpoints of solubility of metal salts and ease of wastewater treatment.
These sulfonic acids are contained in the plating solution 13 in an amount of preferably 50 to 500 g / L, more preferably 100 to 300 g / L.
[0024]
In the plating solution 13, the metal component is an example of a strong acid ion. For example, a sulfonic acid ion is used as a counter anion and is dissolved in a medium mainly composed of water in the form of a metal ion and metal ion complex. 2+ And Sn 4+ Copper ion is Cu + Or Cu 2+ Silver ion is Ag + Exist as. The amount of each metal in the plating solution 13 is Sn. 2+ 0.21-2 mol / L, preferably 0.25-1 mol / L, 0.01-0.1 mol / L as silver, preferably 0.02-0.05 mol / L, 0.002-0 as copper 0.02 mol / L, preferably 0.003 to 0.01 mol / L. Here, it is Sn that tin ions are involved in plating. 2+ Therefore, Sn 2+ Regulate the amount of
Moreover, if the composition of the tin-silver-copper ternary plating solution produced is regulated by the amount of tin, silver, and copper, the composition of the plating film formed using the plating solution is also regulated. The composition of tin, silver, and copper is determined so that the melting point of the plating film to be produced is as low as possible. Furthermore, you may contain a trace amount metal element in the range which does not impair the effect of lowering | hanging melting | fusing point of a film | membrane. Examples of the trace metal include nickel, cobalt, gold, bismuth, lead, palladium, antimony, zinc, iron, germanium, indium and the like, and the content is preferably less than the content of copper.
[0025]
In addition, a sulfonic acid salt soluble in the plating mother liquid, an organic acid and a salt thereof, an inorganic acid and a salt thereof can be blended together with sulfonic acids within a range that does not hinder the performance of the plating solution 13 from being deteriorated. Examples of the inorganic acid include sulfuric acid, phosphoric acid, condensed phosphoric acid, nitric acid, hydrofluoric acid, and borohydrofluoric acid. Examples of the organic acid include sulfamic acid, carboxylic acid, and phosphonic acid. The salt of each acid described above may be a soluble salt, such as an alkali metal salt such as Na salt or K salt, an alkaline earth metal salt such as Ca salt, an alkylamine salt such as diethylamine salt, an ammonium salt, or the like. Can be used.
[0026]
The plating solution 13 preferably contains a specific organic complexing agent as an additive.
Preferred organic complexing agents are thiol compounds (compounds having an SH group in the molecule), thiourea compounds and aromatic amino compounds.
As the thiourea compound, any compound having a thiourea skeleton can be used. As the aromatic amino compound, any compound having an amino group directly in the aromatic ring can be used. These organic complexing agents are preferably higher in solubility in the plating mother solution from the viewpoint of producing a stable plating solution. The solubility is preferably 3 g / L or more, more preferably 5 g / L or more, and particularly preferably 10 g / L. That's it. Moreover, since the complexing ability tends to decrease when the complexing agent molecule is too large, the molecular weight is preferably 2000 or less, more preferably 1000 or less, and particularly preferably 80 to 500.
[0027]
Specific examples of the thiol compound include aliphatic thiol compounds such as butanethiol and pentanethiol, aromatic thiol compounds such as thiophenol, toluenethiol, and o-aminothiophenol, mercaptoacetic acid, mercaptosuccinic acid, mercaptolactic acid, and the like. Mercapto group-containing carboxylic acids, mercapto group-containing amino acids such as cysteine, and mercapto group-containing amino acid derivatives such as acetylcysteine. Of these, mercapto group-containing carboxylic acids or mercapto group-containing amino acids and derivatives thereof are preferred from the viewpoints of solubility in water, performance as a complexing agent, and low odor, and acetylcysteine is particularly preferred. A compound having a disulfide bond may be used and reduced in a plating bath to generate a thiol compound.
[0028]
Specific examples of the thiourea compound include thiourea, dimethylthiourea, trimethylthiourea, N, N′-diisopropylthiourea, acetylthiourea, allylthiourea, 1,3-diphenylthiourea, and thiosemicarbazide. .
[0029]
Specific examples of the aromatic amino compound include aniline compounds such as aniline, methylaniline, and methoxyaniline, and compounds having two aniline rings in the molecule such as 2,2′-dithiodianiline. In particular, 2,2′-dithiodianiline is preferred.
The compounding amount of the organic complexing agent in the plating solution 13 is preferably 1 to 100 g / L, more preferably 1 to 30 g / L, and still more preferably 2 to 20 g / L. These organic complexing agents may be used in combination. Preferably, a mercaptan compound and an aromatic amino compound are used in combination, and acetylcysteine and 2,2′-dithiodianiline are used in combination.
[0030]
In the plating solution 13, a surfactant can be blended in addition to the above components.
The surfactant is used for improving the appearance, denseness, smoothness, adhesion, uniform electrodeposition and the like of the plating film. In the present embodiment, the surfactant is used in addition to methanesulfonic acid in the anolyte 16 and Sn in the anolyte 16 is used. 2+ It functions to increase the permeability of ions to the plating solution 13. Here, the amount of the surfactant added to the anolyte 16 is added so as to be higher than the concentration of the surfactant in the plating solution 13. The surfactant added to the anolyte 16 is preferably the same as the surfactant in the plating solution 13.
The surfactant is a nonionic and hydrophilic surfactant, specifically, for example, C1-C20 alkanol, phenol, naphthol, bisphenol, C1-C25 alkylphenol, arylalkylphenol, C1-C25 alkylnaphthol, C1- C25 alkoxylated phosphoric acid (salt), sorbitan ester, styrenated phenol, polyalkylene glycol, C1-C30 aliphatic amine, C1-C22 aliphatic amide, etc. were selected from ethylene oxide (EO) and propylene oxide (PO) Examples include alkylene oxide compounds obtained by addition condensation of 2 to 300 mol of at least one alkylene oxide.
[0031]
Among these, alkylene oxide compounds are preferable. Specifically, for example, polyoxyethylene α-naphthol ether, polyoxyethylene β-naphthol ether, ethylene oxide propylene oxide block copolymer, polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, Examples thereof include polyoxyethylene alkylamino ether, polyoxyethylene fatty acid ester, polyoxyethylene polyhydric alcohol ether, polyethylene glycol, and polypropylene glycol.
The blending amount of the surfactant used in the plating solution 13 is preferably 0.1 to 50 g / L, more preferably 2 to 10 g / L, and the blending amount of the surfactant used in the anolyte 16. The concentration is higher than that used in the plating solution 13 and is 3 to 15 g / L, preferably 5 to 12 g / L.
[0032]
The plating solution 13 can contain an aldehyde compound as a brightening agent on the surface of the plating film.
Specific examples of the aldehyde compound include 1-naphthaldehyde, 2-naphthaldehyde, o-chlorobenzaldehyde, m-chlorobenzaldehyde, p-chlorobenzaldehyde, 2,4-dichlorobenzaldehyde, acetaldehyde, propionaldehyde, salicylaldehyde, Examples include 2-thiophenaldehyde, 3-thiophenaldehyde, o-anisaldehyde, m-anisaldehyde, p-anisaldehyde, salicylaldehyde allyl ether, 2-oxy-3-methoxybenzaldehyde and the like.
As a compounding quantity when using an aldehyde compound, Preferably it is 0.001-10 g / L, More preferably, it is 0.05-0.5 g / L.
In addition to the above components, the plating solution 13 may contain various additives such as known antioxidants, pH adjusters, and buffering agents depending on the purpose.
[0033]
Next, an example of a method for producing the plating solution 13 will be described. In the production of the plating solution 13, it is necessary to dissolve each of the above components in a mixture of water and sulfonic acids, but it has been found that the plating solution 13 is stabilized by specifying the dissolution order. In the production of the conventional binary plating solution, there was no particular restriction as to the order of dissolving each metal component and additive in water, but in the production of the tin-silver-copper ternary plating solution, The order of dissolution is important.
Since the tin-silver-copper ternary plating solution has a high metal concentration, uneven adjustment tends to occur particularly when a large amount of plating solution is adjusted on an industrial scale.
In addition, among the components in the plating solution, the metal component is not very soluble in water, so the metal component must be mixed in the presence of a certain amount of sulfonic acid.
Therefore, first, a groundwater is prepared with 30% by weight or more of water contained in the plating solution 13 and 50% by weight or more of the sulfonic acids contained in the plating solution 13, and a metal component is added to the groundwater. Are preferably mixed.
[0034]
The plating solution 13 containing tin-silver-copper used in the present embodiment is a lead-free plating solution, and the plating film formed by electroplating this is a conventional tin-lead alloy. The solder joint strength is comparable to the coating film. Therefore, the plating solution 13 can form a plating film having excellent solderability when the electronic component is the plating object 12.
There are no particular restrictions on the electronic parts used as the plating object 12, but chip parts, terminal parts, press parts, crystal oscillators, bumps, connectors, connector pins, lead frames, various hoop materials, package lead pins, pin grids. Examples include arrays, ball grid arrays, printed circuit boards, switches, resistors, variable resistors, capacitors, filters, inductors, thermistors, crystal resonators, and the like. Although there is no restriction | limiting in particular about the thickness of a plating film, 1-20 micrometers is preferable.
[0035]
The tin-based alloy electroplating method according to the first embodiment of the present invention can employ a conventional method, for example, any plating method such as a high-speed plating method, a rack method, or a barrel method can be employed without limitation. can do. The current density of electrolytic plating is 0.01-100 A / dm by these plating methods. 2 It can be.
In this embodiment, particularly 0.01 to 50 A / dm 2 In the case of the high-speed plating method, usually 3 to 50 A / dm. 2 , Especially 5-40A / dm 2 In the case of the rack method, usually 0.5 to 5 A / dm 2 , Especially 1-4A / dm 2 In the case of the barrel method, usually 0.01 to 1 A / dm 2 , Especially 0.05-0.5A / dm 2 It is. The plating temperature may be 10 to 50 ° C., particularly 15 to 40 ° C., and may be unstirred, or may be agitated such as cathode rocking, stirring with a stirrer, or liquid flow with a pump.
Further, the appearance of plating is glossy, semi-glossy, and matte. When a bright plating is obtained, a brightening agent is usually added to the plating solution. Further, when obtaining bright plating, it is preferable to use a chopper power supply waveform as the current waveform, and when obtaining semi-gloss plating, usually a direct current waveform is preferably used.
[0036]
The soluble anode 11 is a soluble anode containing 90% or more of tin, and one or more metals selected from nickel, cobalt, gold, bismuth, lead, palladium, antimony, zinc, iron, and indium May be included. By using the soluble anode 11, the metal ions corresponding to the metal constituting the soluble anode 11 can be replenished to the plating solution as plating metal ions. The cathode current efficiency is usually 80 to 99%.
[0037]
Moreover, the tin ion concentration, the silver ion concentration, and the copper ion concentration in the plating solution 13 can be easily managed in appropriate ranges. In this case, in order to be able to stably obtain the desired good coating film composition ratio and film physical properties, tin, copper, and silver ion concentrations in the plating bath are determined by volume analysis, optical analysis, Analyze the plating bath using one or more analysis methods selected from analysis methods such as electrical analysis, thermal analysis, X-ray analysis, colorimetric analysis, gravimetric analysis, etc. It is preferable to replenish in the plating bath.
[0038]
The main metal ions in these plating baths, tin ions, copper ions, and silver ions, are blended in appropriate concentrations in advance to give the desired plating film alloy composition ratio and film properties, but the amount of plating treatment is large. As it is consumed, the metal ion concentration in the plating bath varies. Along with this, the consumed metal ions can be maintained at a preset concentration by dissolution from the anode and / or replenishment with a concentrated metal salt solution from the outside of the plating bath.
[0039]
In volumetric analysis, there are redox titration method, chelate titration method, precipitation titration method and the like. Optical analysis includes colorimetric analysis, atomic absorption analysis, inductively coupled plasma emission analysis, and the like. Electroanalysis includes polarography, coulometric analysis, potentiometry, and the like. Thermal analysis includes differential thermal analysis and differential scanning calorimetry. X-ray analysis includes X-ray diffraction measurement method, fluorescent X-ray analysis method and the like.
[0040]
Before supplying tin ions, silver ions, and copper ions, which are main metal ions, to the plating solution 13, the concentration of the metal ions in the plating solution 13 is selected from one or more of the above analysis methods. Analyze and measure in combination with the method, calculate the excess and deficiency, elute the metal ions from the anode, or / or select from a concentrated solution, powder, paste, solid of the metal salt from the outside One or more types can be replenished.
[0041]
In particular, it is preferable to use in combination so as not to bring impurities into the plating solution 13. In this case, the concentrated solution, powder, paste, and solid of the metal salt may be replenished with a metal that supplies each metal ion alone or in combination. In addition, supply with metal salt powder, paste, and solid requires sufficient stirring, and supply with a concentrated solution is particularly preferable.
[0042]
The plating film obtained by the tin-based alloy electrolytic plating method according to the present embodiment has a silver content of 2.6 to 3.4% by weight and a copper content of 0.4 to 0.7% by weight. The balance is tin, and a plating film having a low melting point close to the eutectic point of the alloy is obtained. Above all, the bondability with the solder paste using tin-silver-copper alloy is good, the composition is similar, so the bonding strength (soldering strength) is high and the melting point is low, so it is necessary for soldering The amount of heat can be reduced.
[0043]
Next, a tin-based alloy electrolytic plating method according to a second embodiment of the present invention will be described below with reference to a plating apparatus 10a shown in FIG.
In the present embodiment, as shown in FIG. 2, one of the two soluble anodes 11 of the first embodiment described above is an insoluble anode 21 provided with a diaphragm 23 around the plating anode 13. Except that the silver ions from the electrode are prevented from touching the insoluble anode 21 and the amount of current flowing through the soluble anode 11 is substantially matched to the equivalent current of tin plated on the plating object 12. Since it is substantially the same as that of the first embodiment and the procedure of the plating method is the same, detailed description thereof is omitted. Here, the diaphragm 23 covering the insoluble anode 21 may be the same as the diaphragm 17 covering the soluble anode 11 as long as it prevents silver ions from touching the insoluble anode 21 and allows current to flow. Alternatively, different diaphragms may be used.
As the insoluble anode 21, a commonly used insoluble anode such as platinum, platinum-plated titanium, or carbon is used, and the liquid C22 around the insoluble anode 21 is only methanesulfonic acid.
In the second embodiment, a nonionic hydrophilic surfactant may be added to the anolyte 16 together with methanesulfonic acid.
[0044]
When the soluble anode 11 is covered with the diaphragm 17 and the entry of silver ions from the plating object 12 is suppressed, when a necessary amount of current is passed, Sn in the plating solution 13 is passed. 2+ The concentration is, for example, plating of 6000 lead frames (plating objects) (referred to as 6000Fr), and Sn in the plating solution 13 2+ The concentration was calculated by ICP measurement method to 33.7 g / L and increased to 39.7 g / L at 15000 Fr. The plating solution 13 had turbidity that seemed to be tin oxide.
Further, when 1.53 F of electric current was applied to the soluble anode 11 and plating was performed, 85.8 g of tin on the soluble anode 11 side was dissolved and reduced, whereas 80.22 g of tin in the plating film was reduced. Met.
In other words, 5.58 g of the dissolved tin is not used for plating, and excess Sn 2+ It is presumed that it was dissolved in the plating solution 13. This is because, when a current of 1.53 F is passed, tin is dissolved by the amount of current that is passed, but tin is also dissolved by chemical dissolution, and furthermore, tin is only by the amount of current for plating a plating metal other than tin. Since it melt | dissolves excessively, it is thought that 5.58g became the surplus tin among melt | dissolved tin.
Therefore, the amount of current that flows to the soluble anode 11 side is 1.478F, which is the amount of current required to dissolve tin obtained by removing the chemical dissolution from the amount to be plated, and the remaining 0.052F is the diaphragm. The surplus Sn is caused to flow by flowing the current required for plating from both the soluble anode and the insoluble anode. 2+ We were able to suppress the occurrence of
[0045]
Furthermore, a tin-based alloy electrolytic plating method according to a third embodiment of the present invention will be described below with reference to a plating apparatus 10b shown in FIG.
As shown in FIG. 3, the plating apparatus 10b used in the present embodiment is a cellulose non-woven fabric made of polyethylene having a pore diameter of 0.1 to 0.3 μm in the plating solution 13 of the plating apparatus 10 used in the first embodiment. A circulation circuit 26 having a coated filtration membrane 24 is provided, and the plating solution 13 is passed through the filtration membrane 24 by applying a low water head pressure of 10.0 to 12.0 m with a pump 25. As a result, impurities that are solids in the plating solution 13, such as stannic oxide, copper oxide, and silver oxide, can be removed by filtration, and deterioration of the liquid quality can be prevented. In order to see the effect of the filter membrane 24, the liquid becomes clouded by 46000Fr plating, Sn 4+ Was used, and a filtration membrane 24 manufactured by ADVANTEC Co., Ltd. in which a 0.2 μm non-woven fabric made of polyethylene was coated with cellulose was used, and a water head pressure of 10.0-12. An experiment was made to pass through the filtration membrane 24 at a low pressure of 0 m.
For the pressure adjustment, the motor that rotates the pump was an inverter motor, and was adjusted to the minimum frequency at which the furnace liquid emerges. The minimum frequency was a water head pressure of 11.6 m, a flow rate of 130 L / min, and 37 Hz.
[0046]
The liquid becomes cloudy and Sn 4+ When the unprocessed plating solution 13 with 51.9 g / L passes through the filtration membrane 24 for 12 hours, Sn 4+ Became 2.1 g / L and became transparent.
Further, as a comparative example, the white turbid plating solution was treated with activated carbon by the same plating of 46000 Fr. In the activated carbon treatment, the liquid remained cloudy and further became blackish by activated carbon. Next, a commercial flocculant (floc) treatment for lead-free plating was performed, but the liquid did not become cloudy.
[0047]
Next, 46000Fr plating causes the liquid to become cloudy and Sn 4+ The same untreated plating solution with a 51.9 g / L was applied to a 0.2 μm non-woven fabric made of polyethylene and coated with cellulose, and flowed at a frequency of 37 Hz and a flow rate of 833 mL / min for 12 hours. The turbidity of was not removed. Using the same filtration membrane, the result of flowing for 12 hours at a frequency of 40 Hz and a flow rate of 600 mL / min is Sn 4+ Was 25 g / L. Furthermore, as a result of flowing through the same filter membrane at a frequency of 50 Hz and a flow rate of 5 mL / min, the liquid was clear.
Further, when the circulation circuit 26 was used from the beginning of plating, the plating solution 13 was always transparent without becoming cloudy.
[0048]
From the above results, the plating solution 13 in which impurities are generated is regenerated by filtering the plating solution 13 at a low pressure by using a filtration membrane 24 in which a 0.1 to 0.3 μm polyethylene non-woven fabric is coated with cellulose. It has been found that the use of the filter membrane 24 during plating prevents deterioration of the liquid.
In this embodiment, the case where the circulation circuit 26 is provided in the plating apparatus 10 described in the first embodiment has been described. However, the circulation circuit 26 is provided in the plating apparatus 10a described in the second embodiment. May be.
[0049]
【Example】
Subsequently, in the tin-based alloy electroplating method of the present invention, an experiment for observing the diaphragm effect, and Sn by adding a surfactant to the anode bath 2+ An experiment for seeing the elution effect on the plating solution will be described below.
First, the plating apparatus 10 was used, and the plating solution 13 thrown into the plating tank 14 was adjusted as follows.
One-third of the water necessary for adjusting the plating solution was placed in a stirring vessel, and the entire volume of a 54 wt% methanesulfonic acid aqueous solution was further placed as the groundwater.
Next, add the entire volume of the required amount of silver oxide while stirring and confirm that the film is completely black and clear, then immediately add the entire volume of cupric hydroxide and completely dissolve it. As an agent, acetylcysteine, which is an example of a mercaptan compound, was added, and after dissolution confirmation, 2,2′-dithiodianiline, which is an example of an aromatic amino compound, was added as another complexing agent.
When it became a light water-colored gel-like liquid, stannous methanesulfonate was quickly added to make it yellow and transparent. Next, 2/3 of the necessary water was added to the plating solution 13, and finally α-naphthol polyethoxylate (EO 10 mol) 3 g / L, which is an example of a surfactant, was added to complete the adjustment of the plating solution 13. The concentration of methanesulfonic acid in the plating solution 13 is 2.64 mol / L, Sn 2+ The concentration was adjusted to 0.25 to 2 mol / L, the silver ion concentration was adjusted to 0.01 to 0.1 mol / L, and the copper ion concentration was adjusted to 0.002 to 0.02 mol / L.
[0050]
[Example 1]
First, an experiment for observing the diaphragm effect in the electrolytic plating method of the tin-based alloy of the present invention will be described. In this experiment, the experiment was conducted without adding a surfactant to the anode bath.
In the above-described plating apparatus 10, two pure Sn anode plates (cuboid ingots) are prepared as the soluble anode 11 containing 90% or more of tin, and 0.3 dm as the plating object 12 as the cathode. 3 A copper test piece was prepared. A 500 mL beaker is used for the plating tank 14, and a stirrer 18 for filling the plating solution 13 adjusted as described above and stirring the plating solution 13 is placed therein.
Two soluble anodes 11 are each wrapped in an anode bag 15, further covered with a diaphragm 17, and placed in a plating tank 14. Two wires were taken out from the rectifier + side and fixed to the terminals 19 of the respective soluble anodes 11 with clips. On the other hand, one wire was taken out from the rectifier side and fixed to the terminal 20 of the plating object 12 in the same manner. In the anode bag 15, 80 ml (1.05 mol / L) of 54% by weight of methanesulfonic acid was put into the anolyte 16 and the current density was 5.8 A / dm. 2 The current waveform was a direct current waveform, current was applied at a current of 1.5 A for 2 hours, and plating was carried out with a total amount of electricity of 10800 C (Coulomb) of 1.5 × 3600 × 2.
Anolyte 16 after plating, Sn of plating solution 13 2+ The ion concentrations of ions, silver ions, and copper ions were measured.
The diaphragm 17 is a microporous membrane setilla (registered trademark / manufactured by Tonen Tapils Co., Ltd.) having a pore size of 0.02 μm and a thickness of 16 μm made of polyethylene, and a fine pore having a pore size of 0.02 to 0.04 μm and a thickness of 27 μm made of polyethylene A porous membrane hypo (registered trademark / manufactured by Asahi Kasei Corporation) was used. As a comparative example, an experiment was conducted using CMX (registered trademark / manufactured by Tokuyama Corporation), which is an ion permeable membrane. The results are shown in Table 1. In addition, Sn in a present Example 2+ The theoretical amount of precipitation of Sn is the total amount of electricity (10800C) that was allowed to flow 2+ When converted to use for plating, the amount of tin to be plated is 6.64 g, and the amount of tin dissolved from the soluble anode made of pure Sn anode plate is 6.64 g. 2+ The permeation amount (g) of the membrane per 1 C (Coulomb) of S is S in the cathode bath before and after plating. 2+ From the concentration of [6.64- (concentration before plating−concentration after plating) × 0.5] /1.5×3600×2.
[0051]
[Table 1]
Figure 2005023374
[0052]
As shown in Table 1, when Cetilla (registered trademark) having a pore diameter of 0.02 μm and a film thickness of 16 μm was used, Sn from the anolyte after plating to the plating solution after plating was used. 2+ Is 1.94 × 10 -4 Hypore (registered trademark) having a pore diameter of 0.02 to 0.04 μm and a film thickness of 27 μm is 1.04 × 10 6. -4 In contrast, CMX (registered trademark), which is an ion-permeable membrane as a comparative example, is 3.47 × 10. -5 Thus, the permeability of the diaphragm of this example is about 3 to 6 times higher than that of the comparative example, indicating that the permeability of tin ions to the plating solution is very good.
In addition, Sn in the anolyte 16 2+ Compared with the case where the diaphragm 17 according to the present embodiment is used, the concentration of the comparative example is significantly increased, and Sn in the plating solution 13 (cathode bath) is further increased. 2+ The diaphragm 17 according to the present example is Sn because the concentration is decreased. 2+ It can be seen that the permeability of ions from the anolyte 16 to the plating solution 13 is very good.
Further, the permeation amount of silver from the plating solution 13 to the anolyte 16 is 0.09 g / L in Example, which is very low compared to CMX (registered trademark) as a comparative example. It can be seen that there is not much difference at 0.44 g / L.
Therefore, it can be seen that the diaphragm 17 according to the present example is excellent in silver ion non-permeability although the tin ion permeability is high, and is very excellent as a diaphragm.
Moreover, about what was not partitioned by the diaphragm 17, precipitation of the black silver compound considered to be silver oxide around the soluble anode 11 was seen.
Therefore, by covering the anode bath using a diaphragm, it is possible to prevent silver ions from entering the anode bath and substituting and depositing tin ions at the anode, and further, the tin ions permeate the membrane. As a result, it has been possible to contribute to the stability of the plating solution.
[0053]
[Example 2]
Next, Sn by adding a surfactant to the anode bath 2+ An experiment for seeing the elution effect on the plating solution will be described below.
Using the same plating apparatus 10 as in Example 1, as the diaphragm 17, a microporous membrane setilla (registered trademark) having a polyethylene pore diameter of 0.02 μm and a film thickness of 16 μm used in Example 1 and a polyethylene pore diameter of 0 A micropore Hypore (registered trademark) having a thickness of 0.02 to 0.04 μm and a thickness of 27 μm was used. The plating procedure was substantially the same as in Example 1, except that a nonionic hydrophilic surfactant was added to the anode bath in addition to methanesulfonic acid, and in Examples 2-1 and 2-4. Further, plating was carried out for 2 hours in substantially the same manner as in Example 1 except that acetylcysteine and dithiodianiline as complexing agents were added. In addition, α-naphthol polyethoxylate (POEN) was used as a hydrophilic nonionic surfactant.
1.5A (0.3 dm 2 × 5.8 A / dm 2 ), The anolyte 16 was taken out, stirred, and used as a sample for ICP (high-frequency plasma inductively coupled plasma emission spectroscopy).
Sn of anolyte 16 after plating 2+ The ion concentration of silver ions was measured using the ICP method. The results are shown in Table 2.
[0054]
[Table 2]
Figure 2005023374
[0055]
In Examples 2-1 to 2-3, SETILA (registered trademark) was used as the diaphragm 17, and POEN was added to 54% by weight of 150 ml / L (1.05 mol / L) methanesulfonic acid in the anode bag 15. The results of plating by adding 0 g / L, 9.0 g / L, and 12.0 g / L are shown. In Examples 2-4 to 2-6, Hypore (registered trademark) was used as the diaphragm 17, and 6.0 g / L, 9.0 g / L, and 12.0 g / L of POEN were added to the anode bag 15 in methanesulfonic acid. It was added and plated at 150 ml / L.
Comparative Example 1 shows a case where water was added without adding POEN. As Comparative Examples 2 and 3, POEN was added in an amount of 3.0 g / L in the same amount as the plating solution 13.
Further, as Comparative Example 4, a result is shown in which the diaphragm was made into Hypore 10C (registered trademark) having a pore diameter of 0.02 to 0.04 μm and a film thickness of 100 μm, and POEN was added to the anode bag by 12.0 g / L.
As shown in Examples 2-1 to 2-6, POEN which is a nonionic surfactant in the anolyte 16 is 6.0 g / L having a concentration higher than 3.0 g / L in the plating solution 13; After adding 9.0 g / L, 12.0 g / L and plating at 1.5 A for 2 hours, Sn in the anolyte 16 2+ Ion increased from 20.79 to 47.1 g / L before plating, whereas Comparative Example 1 in which POEN was not added and water was added, and Comparative Example 2 in which POEN was added in the same amount as the plating solution 13, 3, Sn in the anolyte 16 after plating 2+ The ion increased by 68.5 to 84 g / L.
[0056]
From this fact, Example 2 in which POEN was added at a higher concentration than the plating solution had Sn in the anolyte 16 after plating compared to the comparative example. 2+ The rise of ions is very low, Sn 2+ It can be seen that ions permeate the diaphragm 17 and smoothly migrate into the plating solution 13.
In Examples 2-1 and 2-4, the complexing agents acetylcysteine and dithiodianiline were added to the anode bath when the silver ions migrated to the anode side. In order to avoid substitutional precipitation with tin, the amount of silver ion permeation was actually small, and no Ag precipitation was observed in other examples where no complexing agent was added. Therefore, it can be said that there was no effect of the complexing agent.
Further, in the comparative example 4 in which the diaphragm 17 is replaced with a Hypore 10C (registered trademark) having a film thickness of 100 μm instead of the Hypore (registered trademark) having a film thickness of 27 μm, POEN is added to the anode bag 15 at 12.0 g / L. Sn in the anolyte 16 2+ Concentration has increased significantly, Sn 2+ This indicates that the permeability to the plating solution 13 is poor. Therefore, it can be seen that the thickness of the diaphragm also has an important factor.
[0057]
In both cases, the same amount of electricity was applied to the same anode plate and the experiment was conducted. As a result, when the POEN concentration in the anolyte was made higher than the POEN concentration in the plating bath using the diaphragm of Example 2, the anode Sn in the bath 2+ It was found that ions were smoothly emitted in the plating bath.
Therefore, conventionally, metal ions such as silver ions or copper ions other than tin in the plating solution and their complexes are substituted with tin ions and deposited as a metal salt around a soluble anode containing 90% or more of tin. When the periphery of the anode bath is covered with a diaphragm in order to prevent the plating solution from deteriorating or the liquid quality from deteriorating, there is a problem that the permeability of tin ions from the anode bath to the plating bath is deteriorated. However, the permeability of tin ions in the anolyte to the plating solution can be increased by using the diaphragm of the example and plating with the POEN concentration in the anolyte higher than the POEN concentration in the plating solution. It became a thing.
Furthermore, in the case where tin ions in the anolyte are excessively discharged into the plating solution, in addition to the soluble anode in which the anolyte and plating solution are separated by a diaphragm, an insoluble anode having a diaphragm in the surrounding area is further provided to the soluble anode. By adjusting the amount of current, the elution of tin ions from the soluble anode can be adjusted to prevent the tin ion concentration in the plating solution from rising excessively, and the stability of the plating solution is good. Therefore, it is possible to provide a method for electrolytic plating of a tin-based alloy with little deterioration in quality.
[0058]
In the above embodiment, a ternary plating solution containing tin-silver-copper is used as the plating solution. However, tin is essential, and a tin-silver or tin-copper or tin-bismuth binary plating is used. The right of the present invention is also applicable to the case of using a ternary plating solution using bismuth instead of silver or copper, or to changing the concentration of the plating solution within the range not changing the gist of the present invention. Included in the range.
Furthermore, the present invention is not limited to the above-described embodiments and examples, and modifications without changing the gist are also included in the scope of rights of the present invention. For example, in the first embodiment, the case where two soluble anodes are used is described, but one or three or more soluble anodes may be used.
Moreover, in the said Example, although the diaphragm was made into the nonionic diaphragm, it is good also as an ion exchange membrane.
[0059]
【The invention's effect】
The electrolytic plating method for a tin-based alloy according to claims 1 to 10 uses a soluble anode containing 90% or more of tin, and uses a plating object as a cathode and a liquid A around the soluble anode and a surrounding of the cathode. The liquid B is a diaphragm that can easily transmit tin ions. In particular, when a 1C electricity is applied, tin ions are transferred from the anode side to the cathode side by 5 × 10 5. -5 ~ 5x10 -4 The partition is provided with a diaphragm through which g is passed. Claim 2 is provided with a diaphragm that allows tin ions to permeate more easily than ions or complexes of other plating metals. Claim 3 is a film having a pore diameter of 0.01 to 0.05 .mu.m and a film thickness of 5. Since it is partitioned by a diaphragm made of a microporous film of ˜100 μm, tin ions from the soluble anode can pass through the diaphragm and enter the liquid B as the catholyte (plating solution), and the tin in the plating solution Ions can be replenished with a soluble anode, and ions or complexes of other plating metals that have a lower ionization tendency than tin ions, such as silver ions, copper ions, and complexes thereof enter liquid A to replace tin ions. Thus, it can be prevented that it becomes a metal compound and precipitates.
[0060]
In the tin-based alloy electroplating method according to claims 4 and 5, since the surfactant is added to the liquid A, the permeability of the tin ion from the liquid A to the liquid B is improved. In particular, in claim 5, since the surfactant is added to the liquid A so as to have a higher concentration than the surfactant in the liquid B, the permeability of tin ions from the liquid A to the liquid B is further increased. ing.
In the method of electroplating a tin-based alloy according to claims 6 and 7, an insoluble anode is further provided, and the liquid C and liquid B around the insoluble anode are separated by another diaphragm, so that a cation in the liquid B, for example, Silver ions are prevented from touching the insoluble anode. In particular, in claim 7, a current necessary for plating a plating object with a plating metal is supplied from both a soluble anode and an insoluble anode, and tin that is obtained by removing the chemical dissolved component from the component necessary for plating is applied to the soluble anode. Since only the amount of current necessary for melting is supplied and the remaining amount of current is supplied to the insoluble anode, it is possible to prevent the tin from being excessively melted.
[0061]
The electrolytic plating method for a tin-based alloy according to claim 8 is provided with a circulation circuit provided with a filtration membrane having a pore diameter of 0.1 to 0.3 μm in the liquid B, and a low pressure is applied to the liquid B to pass through the filtration membrane. Therefore, impurities that cause deterioration of the liquid quality, particularly stannic oxide, copper oxide, and silver oxide can be removed.
In the tin-based alloy electrolytic plating method according to the ninth aspect, since the concentration of the sulfonic acids in the liquid A is 0.5 to 1.5 mol, excessive dissolution of tin due to chemical dissolution can be prevented.
[0062]
The tin-based alloy electroplating method according to claim 10, wherein the solution B is a plating solution containing sulfonic acids, tin ions, copper ions and silver ions in a medium mainly composed of water, and Sn. 2+ Since the concentration is adjusted to 0.25 to 2 mol / L, the silver ion concentration is 0.01 to 0.1 mol / L, and the copper ion concentration is 0.002 to 0.02 mol / L, tin-silver having a low melting point -Highly productive copper alloy plating.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a tin-based alloy electrolytic plating method according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of a tin-based alloy electrolytic plating method according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram of a tin-based alloy electroplating method according to a third embodiment of the present invention.
[Explanation of symbols]
10, 10a, 10b: plating apparatus, 11: soluble anode, 12: object to be plated, 13: plating solution, 14: plating tank, 15: anode bag, 16: anode solution, 17: diaphragm, 18: stirrer, 19: terminal, 20: terminal, 21: insoluble anode, 22: liquid C, 23: diaphragm, 24: filtration membrane, 25: pump, 26: circulation circuit

Claims (10)

錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にした錫系合金の電解めっき方法において、前記溶解性陽極の周囲の液Ａと前記陰極の周囲の液Ｂを、１Ｃの電気量を通電させたときに、錫イオンを陽極側から陰極側へ５×１０−５〜５×１０−４ｇ通す隔膜で仕切ることを特徴とする錫系合金の電解めっき方法。In a tin-based alloy electroplating method using a soluble anode containing 90% or more of tin and using an object to be plated as a cathode, the liquid A around the soluble anode and the liquid B around the cathode are 1C. A tin-based alloy electroplating method characterized by partitioning a tin ion with a diaphragm that passes 5 × 10 −5 to 5 × 10 −4 g from the anode side to the cathode side when the amount of electricity is applied. 錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にした錫系合金の電解めっき方法において、前記溶解性陽極の周囲の液Ａと前記陰極の周囲の液Ｂを、他のめっき金属のイオンあるいは錯体より錫イオンを透過し易い隔膜で仕切ることを特徴とする錫系合金の電解めっき方法。In the electrolytic plating method of a tin-based alloy using a soluble anode containing 90% or more of tin and using the object to be plated as a cathode, the liquid A around the soluble anode and the liquid B around the cathode A method for electroplating a tin-based alloy, characterized in that it is partitioned by a diaphragm that allows permeation of tin ions more easily than ions or complexes of plating metals. 錫を９０％以上含有する溶解性陽極を使用し、めっき対象物を陰極にした錫系合金の電解めっき方法において、前記溶解性陽極の周囲の液Ａと前記陰極の周囲の液Ｂを、孔径０．０１〜０．０５μｍで膜厚５〜１００μｍの微多孔膜からなる隔膜で仕切ることを特徴とする錫系合金の電解めっき方法。In a tin-based alloy electrolytic plating method using a soluble anode containing 90% or more of tin and using a plating object as a cathode, the liquid A around the soluble anode and the liquid B around the cathode A tin-based alloy electroplating method characterized by partitioning with a diaphragm comprising a microporous membrane having a thickness of 0.01 to 0.05 µm and a thickness of 5 to 100 µm. 請求項１〜３のいずれか１項に記載の錫系合金の電解めっき方法において、前記液Ａに界面活性剤を添加したことを特徴とする錫系合金の電解めっき方法。The tin-based alloy electrolytic plating method according to any one of claims 1 to 3, wherein a surfactant is added to the liquid A. 請求項４に記載の錫系合金の電解めっき方法において、前記液Ａに添加する界面活性剤は、前記液Ｂ中の界面活性剤より高濃度であることを特徴とする錫系合金の電解めっき方法。5. The tin-based alloy electroplating method according to claim 4, wherein the surfactant added to the liquid A has a higher concentration than the surfactant in the liquid B. Method. 請求項１〜５のいずれか１項に記載の錫系合金の電解めっき方法において、更に不溶性陽極を設け、前記不溶性陽極の周囲の液Ｃと前記液Ｂを他の隔膜で仕切ったことを特徴とする錫系合金の電解めっき方法。6. The tin-based alloy electroplating method according to claim 1, further comprising an insoluble anode, wherein the liquid C and the liquid B around the insoluble anode are partitioned by another diaphragm. A method for electrolytic plating of a tin-based alloy. 請求項６記載の錫系合金の電解めっき方法において、前記めっき対象物にめっき金属をめっきさせるのに必要な電流を前記溶解性陽極と前記不溶性陽極の両方から流していることを特徴とする錫系合金の電解めっき方法。7. The tin-based alloy electroplating method according to claim 6, wherein a current necessary for plating the plating object with a plating metal is supplied from both the soluble anode and the insoluble anode. Electrolytic plating method for aluminum alloys. 請求項１〜７のいずれか１項に記載の錫系合金の電解めっき方法において、前記液Ｂに、孔径０．１〜０．３μｍの濾過膜を備えた循環回路を設け、前記液Ｂに低圧力をかけて前記濾過膜を通過させ、不純物を除去することを特徴とする錫系合金の電解めっき方法。The electrolytic plating method for a tin-based alloy according to any one of claims 1 to 7, wherein the liquid B is provided with a circulation circuit including a filtration membrane having a pore diameter of 0.1 to 0.3 µm. A tin-based alloy electroplating method, wherein impurities are removed by applying a low pressure through the filtration membrane. 請求項１〜８のいずれか１項に記載の錫系合金の電解めっき方法において、前記液Ａは０．５〜１．５ｍｏｌ濃度のスルホン酸類を有していることを特徴とする錫系合金の電解めっき方法。The tin-based alloy electroplating method according to any one of claims 1 to 8, wherein the liquid A contains sulfonic acids having a concentration of 0.5 to 1.5 mol. Electrolytic plating method. 請求項１〜９のいずれか１項に記載の錫系合金の電解めっき方法において、前記液Ｂは水を主体とする媒体に、スルホン酸類、錫イオン、銅イオン及び銀イオンを含むめっき液であって、Ｓｎ２＋濃度が０．２１〜２ｍｏｌ／Ｌ、銀イオン濃度が０．０１〜０．１ｍｏｌ／Ｌ、銅イオン濃度が０．００２〜０．０２ｍｏｌ／Ｌに調整されていることを特徴とする錫系合金の電解めっき方法。10. The method for electroplating a tin-based alloy according to claim 1, wherein the liquid B is a plating liquid containing sulfonic acids, tin ions, copper ions, and silver ions in a medium mainly composed of water. The Sn 2+ concentration is adjusted to 0.21 to 2 mol / L, the silver ion concentration is adjusted to 0.01 to 0.1 mol / L, and the copper ion concentration is adjusted to 0.002 to 0.02 mol / L. A method for electrolytic plating of a tin-based alloy.
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JP2007100113A (en) * 2005-09-30 2007-04-19 Meiko:Kk Copper plating method and apparatus for electrolytically removing chlorine ion, which is used in the method
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