JP4296733B2

JP4296733B2 - Sn-plated ultrafine copper wire, stranded wire using the same, and method for producing Sn-plated ultrafine copper wire

Info

Publication number: JP4296733B2
Application number: JP2001260053A
Authority: JP
Inventors: 貴朗市川; 裕幸阿久津
Original assignee: Hitachi Cable Ltd
Current assignee: Hitachi Cable Ltd
Priority date: 2001-08-29
Filing date: 2001-08-29
Publication date: 2009-07-15
Anticipated expiration: 2021-08-29
Also published as: JP2003073760A

Description

【０００１】
【発明の属する技術分野】
本発明は、Ｓｎめっき極細銅線及びそれを用いた撚線並びにＳｎめっき極細銅線の製造方法に係り、特に、電子機器のケーブル用導体として用いられるＳｎめっき極細銅線及びそれを用いた撚線並びにＳｎめっき極細銅線の製造方法に関するものである。
【０００２】
【従来の技術】
近年、電子機器の小型・軽量化の要求が高まっていることから、電子機器のケーブル用導体においては、線径が０．１ｍｍ以下の極細銅線が主流となりつつある。この極細銅線の１つに、表面にＳｎめっきを有するＳｎめっき極細銅線がある。
【０００３】
Ｓｎめっき極細銅線の従来の製造方法として、ｄｉｐ法（溶融めっき法）と電気めっき法の二つが主に挙げられる。
【０００４】
溶融めっき法は、極細銅線の表面をフラックス又は還元ガスを用いて活性化した後、その極細銅線を純Ｓｎめっき液中に浸漬し、極細銅線の外周に溶融Ｓｎめっき層を形成するものである。また、電気めっき法は、表面を活性化した極細銅線を純Ｓｎめっき液中に浸漬すると共に、極細銅線と純Ｓｎめっき液との間に電圧を印加して、極細銅線の外周に電気Ｓｎめっき層を形成するものである。
【０００５】
これらのめっき法の内、溶融めっき法の方が簡便で、経済性に優れていることから、Ｓｎめっき極細銅線の製造には、一般的に、溶融めっき法が用いられている。
【０００６】
【発明が解決しようとする課題】
ところで、得られたＳｎめっき極細銅線を複数本撚り合わせて撚線を製造する際、撚線時に、Ｓｎめっき極細銅線同士が摺動することで、各線の表面でＳｎめっきカスが発生する。このＳｎめっきカスが、撚線製造時に用いる治具であるニップルに堆積することで、撚線に断線が生じるおそれがあり、撚線性が良好でないという問題があった。
【０００７】
また、極細銅線のＣｕとＳｎめっき層のＳｎが反応し、それらの界面にＳｎ−Ｃｕ系金属間化合物が形成されるが、Ｓｎめっき層の層厚が十分でないと、Ｓｎめっき層全体がＳｎ−Ｃｕ系金属間化合物層となってしまう。このＳｎ−Ｃｕ系金属間化合物は、ハンダ濡れ性が良好でないため、結果的に、撚線のハンダ付性が悪くなるという問題があった。
【０００８】
以上の事情を考慮して創案された本発明の目的は、撚線性およびハンダ付性が良好なＳｎめっき極細銅線及びそれを用いた撚線並びにＳｎめっき極細銅線の製造方法を提供することにある。
【０００９】
【課題を解決するための手段】
上記目的を達成すべく本発明に係るＳｎめっき極細銅線は、線径が０．１ｍｍ以下のＳｎめっき極細銅線において、銅又は銅合金からなる極細銅線の外周に、Ｓｎ−０．２〜７．０ｍａｓｓ％Ｃｕ系めっき層を、０．０５μｍ以上の層厚で形成し、そのＣｕ系めっき層中に、直径が２μｍ以下のＳｎ−Ｃｕ系金属間化合物を均一分散させたものである。
【００１０】
以上の構成によれば、めっき層の層硬度が十分に高いＳｎめっき極細銅線が得られる。
【００１１】
一方、本発明に係るＳｎめっき極細銅線を用いた撚線は、線径が０．１ｍｍ以下で、銅又は銅合金からなる極細銅線の外周に、Ｓｎ−０．２〜７．０ｍａｓｓ％Ｃｕ系めっき層を０．０５μｍ以上の層厚で形成し、そのＣｕ系めっき層中に、直径が２μｍ以下のＳｎ−Ｃｕ系金属間化合物を均一分散させたＳｎめっき極細銅線を、複数本撚り合わせて形成したものである。
【００１２】
以上の構成によれば、撚線が容易で、ハンダ付け性が良好なＳｎめっき極細銅線を用いた撚線（Ｓｎめっき極細銅撚線）が得られる。
【００１３】
また、本発明に係るＳｎめっき極細銅線の製造方法は、銅又は銅合金からなる線径が０．１ｍｍ以下の極細銅線の外周に、溶融Ｓｎめっき層を形成するＳｎめっき極細銅線の製造方法において、めっき浴槽内にＣｕ濃度が０．２〜７．０ｍａｓｓ％の溶融Ｓｎ−Ｃｕ系めっき浴を形成すると共に、溶融Ｓｎ−Ｃｕ系めっき浴の、２５０〜３５０℃の温度範囲における温度分布を±５℃以内に調整し、その溶融Ｓｎ−Ｃｕ系めっき浴中に上記極細銅線を浸漬し、極細銅線の外周に、０．０５μｍ以上の層厚であり、かつ直径が２μｍ以下のＳｎ−Ｃｕ系金属間化合物を均一分散する溶融Ｓｎ−Ｃｕ系めっき層を形成するものである。
【００１４】
以上の方法によれば、撚線性およびハンダ付性が良好なめっき極細銅線を得ることができる。
【００１５】
【発明の実施の形態】
以下、本発明の好適一実施の形態を添付図面に基いて説明する。
【００１６】
第１の実施の形態に係るＳｎめっき極細銅線の断面図を図１に、第２の実施の形態に係るＳｎめっき極細銅線の断面図を図２に示す。ここで、図２（ｂ）は、図２（ａ）の要部Ａの拡大図である。
【００１７】
図１に示すように、第１の実施の形態に係るＳｎめっき極細銅線１１は、線径が０．１ｍｍ以下のＳｎめっき極細銅線であり、軟質銅或いは硬質銅よりなる銅又は銅合金からなる極細銅線１２の外周に、Ｓｎ−０．２〜７．０ｍａｓｓ％Ｃｕ系めっき層（以下、Ｓｎ−Ｃｕ系めっき層と示す）１３を、０．０５μｍ以上、好ましくは０．５μｍ以上の層厚で形成したものである。
【００１８】
また、図２（ａ），図２（ｂ）に示すように、第２の実施の形態に係るＳｎめっき極細銅線２１は、軟質銅或いは硬質銅よりなる銅又は銅合金からなる極細銅線１２の外周に、層中に直径が２μｍ以下、好ましくは１μｍ以下のＳｎ−Ｃｕ系金属間化合物２４が均一分散したＳｎ−Ｃｕ系めっき層２３を、０．０５μｍ以上、好ましくは０．５μｍ以上の層厚で形成したものである。
【００１９】
一方、本実施の形態に係るＳｎめっき極細銅線を用いた撚線３１は、図３に示すように、Ｓｎめっき極細銅線１１，２１を複数本（図３中では７本を図示）撚り合わせて形成したものである。ここで言う撚線は、撚線導体及び撚線導体を用いた電線・ケーブルの総称である。
【００２０】
次に、本実施の形態の作用を説明する。
【００２１】
極細銅線１２の外周にＳｎ−Ｃｕ系めっき層１３，２３を形成することで、従来のＳｎめっき極細銅線の純Ｓｎめっき層と比べて層硬度が十分に高いＳｎめっき極細銅線１１，２１が得られる。この銅線１１，２１は、Ｓｎ−Ｃｕ系めっき層１３，２３の層硬度が高いことから、この銅線１１，２１を用いて撚線を製造する際、撚線の素線同士が摺動して生じるＳｎめっきカスの量が少なくなる。特に、Ｓｎめっき極細銅線２１の場合、Ｓｎめっきカスの量が非常に少なくなる。その結果、本実施の形態に係るＳｎめっき極細銅線１１，２１を撚線する時に、断線が生じるおそれがなくなり、従来のＳｎめっき極細銅線と比較して、撚線性が向上する。
【００２２】
また、撚線時に発生するＳｎめっきカスの量が少ないことから、銅線１１，２１を用いて得られた撚線は、Ｓｎ−Ｃｕ系めっき層１３，２３の表面が平滑又は略平滑で、表面状態が良好となる。このため、これらの撚線のハンダ濡れ性は、従来のＳｎめっき極細銅線を用いて得られた撚線のそれよりも、良好となる。その結果、本実施の形態に係るＳｎめっき極細銅線１１，２１を用いて得られた撚線においては、良好なハンダ付性が得られる。
【００２３】
Ｓｎめっき極細銅線１１，２１において、Ｓｎ−Ｃｕ系めっき層１３，２３の層厚を、０．０５μｍ以上、好ましくは０．５μｍ以上と規定したのは、以下の理由によるものである。
【００２４】
一般に、銅線にＳｎめっきを施す場合、銅線表面のＣｕとＳｎめっき層のＳｎが反応し、それらの界面に、Ｃｕ₃ＳｎやＣｕ₆Ｓｎ₅のＳｎ−Ｃｕ系金属間化合物層が形成される。ここで、Ｓｎめっき層の層厚が０．０５μｍ未満であると、Ｓｎめっき層自体がＳｎ−Ｃｕ系金属間化合物層となってしまう。このＳｎ−Ｃｕ系金属間化合物は、硬くて脆いと共に、ハンダ濡れ性が良好でないことから、Ｓｎめっき層自体がＳｎ−Ｃｕ系金属間化合物層になると、めっき導体（Ｓｎめっき極細銅線）の機械的特性、例えば屈曲特性が低下すると共に、Ｓｎめっき極細銅線と各種電子部品のハンダ付け時に不具合が生じてしまう。
【００２５】
また、Ｓｎめっき極細銅線１１，２１において、Ｓｎ−Ｃｕ系めっき層１３，２３のＣｕ濃度を、０．２〜７．０ｍａｓｓ％と規定したのは、Ｃｕ濃度が０．２ｍａｓｓ％未満だと、Ｓｎ−Ｃｕ系めっき層１３，２３の硬度が、純Ｓｎめっき層とあまり変わらないためである。また、Ｃｕ濃度が７．０ｍａｓｓ％を超えると、Ｓｎ−Ｃｕ系めっき層１３，２３自体がＳｎ−Ｃｕ系金属間化合物層になり易くなるためである。
【００２６】
Ｓｎめっき極細銅線２１において、Ｓｎ−Ｃｕ系めっき層２３中に均一分散させるＳｎ−Ｃｕ系金属間化合物（Ｃｕ₃ＳｎやＣｕ₆Ｓｎ₅）２４の直径を２μｍ以下、好ましくは１μｍ以下と規定したのは、以下の理由によるものである。
【００２７】
金属間化合物２４の晶出サイズを２μｍ以下、好ましくは１μｍ以下に規定したのは、２μｍを超えるとＳｎ−Ｃｕ系めっき層２３の表面の平滑性が損なわれるためであり、また、Ｓｎ−Ｃｕ系めっき層２３の層厚の調整を行うために絞りダイスを用いる場合、金属間化合物２４がダイス部に堆積し、Ｓｎめっき極細銅線２１の断線の原因となるためである。
【００２８】
次に、本発明に係るＳｎめっき極細銅線の製造方法を、図４に基いて説明する。
【００２９】
図４に示すように、先ず、極細銅線１２を送出ボビン４１から送出すると共に還元炉４２内を走行させ、極細銅線１２に還元処理を施し、表面の酸化層の除去を行う。
【００３０】
次に、酸化層の除去後の極細銅線１２を、ガイドプーリ４３ａ，４３ｂ間において、浸漬棒４６によりめっき浴槽４４内の溶融Ｓｎ−Ｃｕ系めっき浴４５中に浸漬させる。この時、溶融Ｓｎ−Ｃｕ系めっき浴４５のＣｕ濃度を０．２〜７．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴４５の、２５０〜３５０℃の温度範囲における温度分布を±５℃以内に予め調整しておく。このため、めっき浴槽４４は、少なくともめっき浴４５の温度を測定する多数の温度センサ（図示せず）と、温度センサからの信号が入力される調節装置（図示せず）と、調節装置からの信号によりめっき浴を攪拌する攪拌装置（図示せず）を備えている。
【００３１】
めっき浴浸漬後の極細銅線１２の外周にはＳｎ−Ｃｕ系めっき液が不均一に付着しているため、この極細導線１２を、絞りダイス４７に挿通させ、極細導線１２の外周に付着するＳｎ−Ｃｕ系めっき液の量を均一にし、Ｓｎ−Ｃｕ系めっき層の層厚が０．０５μｍ以上、好ましくは０．５μｍ以上となるように調整する。
【００３２】
その後、極細導線１２の外周に付着したＳｎ−Ｃｕ系めっき液が冷却（空冷）されて凝固することで、極細銅線１２の外周に溶融Ｓｎ−Ｃｕ系めっき層１３，２３を有するＳｎめっき極細銅線１１，２１が得られ、この銅線１１，２１が巻取ボビン４９に巻き取られる。Ｓｎ−Ｃｕ系めっき液を冷却させて凝固させる際、冷却装置４８により、極細銅線１２に冷却空気（図示せず）を吹き付け、強制的に冷却を行ってもよい。これによって、空冷による冷却を行った時と比較して、Ｓｎ−Ｃｕ系めっき層１３，２３に対する極細銅線１２のＣｕ拡散が抑制されることから、Ｓｎめっき極細銅線１１，２１のハンダ濡れ性が更に向上し、延いては、ハンダ付け性が向上する。
【００３３】
ここで、極細銅線１２をめっき浴槽４４内の溶融Ｓｎ−Ｃｕ系めっき浴４５中に浸漬させる際、銅の溶解度が飽和に達しているめっき浴４５の浴温度を低下させると、それに伴って銅の溶解度が低下する。その結果、溶解しきれなくなった余剰の銅が金属間化合物（例えば、Ｃｕ₆Ｓｎ₅）の形で晶出するようになる。この時、後述する温度条件でめっき浴４５の温度分布の調整を行うことによって、めっき浴４５中に晶出する金属間化合物のサイズを２μｍ以下に制御することができ、このＳｎ−Ｃｕ系めっき浴４５中に極細銅線１２を浸漬することで、Ｓｎ−Ｃｕ系めっき層２３中に、直径が２μｍ以下、好ましくは１μｍ以下のＳｎ−Ｃｕ系金属間化合物２４が均一分散したＳｎめっき極細銅線２１を得ることができる。
【００３４】
溶融Ｓｎ−Ｃｕ系めっき浴４５の、２５０〜３５０℃の温度範囲における温度分布を±５℃以内、好ましくは±３℃以内に調整すると規定したのは、温度分布が±５℃を超えると、めっき浴４５の最も温度が低い部分に粗大な金属間化合物が晶出し、この粗大な金属間化合物がＳｎ−Ｃｕ系めっき層１３，２３に分散することで、Ｓｎめっき極細銅線１１，２１の断線原因となるためである。
【００３５】
【実施例】
（実施例１）
直径がφ０．０３ｍｍの極細銅線をめっき浴槽内の溶融Ｓｎ−Ｃｕ系めっき浴中に浸漬させた後、極細銅線の表面に冷却空気を吹き付け、めっき層厚が０．７μｍ、０．８μｍ、０．７μｍのＳｎめっき極細銅線を作製する（試料１〜３）。この時、溶融Ｓｎ−Ｃｕ系めっき浴のＣｕ濃度は、それぞれ０．５ｍａｓｓ％、０．７ｍａｓｓ％、１．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴の温度分布は、一律３３０℃±５℃以内に調整した。
【００３６】
（実施例２）
直径がφ０．０３ｍｍの極細銅線をめっき浴槽内の溶融Ｓｎ−Ｃｕ系めっき浴中に浸漬させた後、極細銅線の表面に冷却空気を吹き付け、めっき層厚が共に０．８μｍで、かつ、めっき層中に直径が１．０μｍ以下の微細な金属間化合物が均一分散したＳｎめっき極細銅線を作製する（試料４，５）。この時、溶融Ｓｎ−Ｃｕ系めっき浴のＣｕ濃度は、それぞれ３．０ｍａｓｓ％、５．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴の温度分布は、一律３１０℃±５℃以内に調整した。
【００３７】
（実施例３）
直径がφ０．０３ｍｍの極細銅線をめっき浴槽内の溶融Ｓｎ−Ｃｕ系めっき浴中に浸漬させた後、極細銅線を自然冷却（空冷）し、めっき層厚が０．５μｍ以上のＳｎめっき極細銅線を作製する（試料６）。この時、溶融Ｓｎ−Ｃｕ系めっき浴のＣｕ濃度は、３．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴の温度分布は、３３０℃±５℃以内に調整した。
【００３８】
（比較例１）
直径がφ０．０３ｍｍの極細銅線をめっき浴槽内の溶融Ｓｎ−Ｃｕ系めっき浴中に浸漬させた後、極細銅線の表面に冷却空気を吹き付け、めっき層厚が０．７μｍ、０．８μｍのＳｎめっき極細銅線を作製する（試料７，８）。この時、溶融Ｓｎ−Ｃｕ系めっき浴のＣｕ濃度は、それぞれ０．１ｍａｓｓ％、１０．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴の温度分布は、一律３５０℃±５℃以内に調整した。
【００３９】
（比較例２）
直径がφ０．０３ｍｍの極細銅線をめっき浴槽内の溶融Ｓｎ−Ｃｕ系めっき浴中に浸漬させた後、極細銅線の表面に空気を吹き付け、めっき層厚が０．０４μｍ、０．０３μｍのＳｎめっき極細銅線を作製する（試料９，１０）。この時、溶融Ｓｎ−Ｃｕ系めっき浴のＣｕ濃度は、それぞれ１．０ｍａｓｓ％、３．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴の温度分布は、一律３５０℃±５℃以内に調整した。
【００４０】
（比較例３）
直径がφ０．０３ｍｍの極細銅線をめっき浴槽内の溶融Ｓｎ−Ｃｕ系めっき浴中に浸漬させた後、極細銅線の表面に空気を吹き付け、めっき層厚が０．８μｍのＳｎめっき極細銅線を作製する（試料１１）。この時、溶融Ｓｎ−Ｃｕ系めっき浴のＣｕ濃度は、５．０ｍａｓｓ％に、また、溶融Ｓｎ−Ｃｕ系めっき浴の温度分布は、２４０℃±５℃以内に調整した。
【００４１】
試料１〜１１の諸元（Ｓｎ−Ｃｕ系めっき層のＣｕ濃度（mass％）、めっき浴温度（℃）、Ｓｎ−Ｃｕ系めっき層の層厚（μｍ）、冷却過程）を表１に示す。ここで、Ｓｎ−Ｃｕ系めっき層の層厚の測定は、コクール法（JIS8610-8619）により行った。
【００４２】
【表１】

【００４３】
次に、各試料の表面状態の評価を行った。その評価結果を表２に示す。ここで、表面状態の評価は、電子顕微鏡（ＳＥＭ）を用いて行った。
【００４４】
【表２】

【００４５】
表２に示すように、試料１〜７の表面状態はいずれも良好であった。また、試料１〜３，７の試料は、Ｓｎ−Ｃｕ系めっき層の表面が平滑であったが、試料４〜６のＳｎ−Ｃｕ系めっき層の表面には、直径１μｍ以下の微細な金属間化合物（Ｃｕ₆Ｓｎ₅）が認められた。
【００４６】
これに対して、試料８，１１の表面状態はいずれも不良であった。これは、試料８については、Ｓｎ−Ｃｕ系めっき層のＣｕ濃度が規定範囲よりも高く、試料１１については、めっき浴温度が規定範囲よりも低いことから、めっき浴中に溶解できない余剰の銅が金属間化合物として晶出し、Ｓｎ−Ｃｕ系めっき層に、直径約３μｍの粗大な針状金属間化合物（Ｃｕ₆Ｓｎ₅）が分散していることに起因する。
【００４７】
また、試料９，１０の表面状態はいずれも不良であった。これは、Ｓｎ−Ｃｕ系めっき層の層厚が規定範囲よりも薄いことから、Ｓｎめっき極細銅線の表面全体に、極細銅線表面のＣｕとＳｎが反応して形成される金属間化合物層が露出し、Ｓｎめっき極細銅線の表面が凹凸であることに起因する。
【００４８】
次に、各試料を、７本ずつ、ピッチ３．３ｍｍで同心撚りして、１０，０００ｍの長さの撚線を製造する。この時の、各撚線の表面状態、めっきカスの発生状況、ハンダ付性の評価を行った。その評価結果を表３に示す。ここで、めっきカスの発生状況は、撚線機のニップル部に堆積するめっきカスの量で評価を行った。また、ハンダ付性は、撚線を共晶ハンダ浴に浸漬させた際の、濡れ面積の大小で評価を行った。
【００４９】
【表３】

【００５０】
表３に示すように、試料１〜６を用いた撚線の表面状態はいずれも良好であった。また、めっきカスの発生は、撚線作業上、問題がなかった。即ち、撚線工程中、めっきカスによる断線はなかった。特に、試料３〜６は、撚線時に発生するめっきカスの量が非常に少なかった。さらに、ハンダ付性は、試料６を用いた撚線がやや良である以外は、大変良好又は良好であった。
【００５１】
これに対して、試料７を用いた撚線は、撚線の表面状態は良好（平滑）であり、また、ハンダ付性も大変良好であるものの、撚線時にめっきカスが多量に発生し、断線が生じた。これは、試料７のＳｎ−Ｃｕ系めっき層のＣｕ濃度が規定範囲よりも低いことから、Ｓｎ−Ｃｕ系めっき層の硬度が純Ｓｎめっき層の硬度とあまり変わりがなく、硬度不足であったことに起因する。
【００５２】
また、試料８〜１１を用いた撚線は、撚線時に発生するめっきカスの量は非常に少なかったものの、撚線の表面に微細な亀裂が認められ、表面状態が不良であった。この亀裂は、金属間化合物（又は金属間化合物層）とＳｎ−Ｃｕ系めっき層の界面に生じていた。つまり、試料８〜１１においては、Ｓｎ−Ｃｕ系めっき層に分散する金属間化合物が粗大である（試料８，１１）又はＳｎ−Ｃｕ系めっき層に金属間化合物層が露出している（試料９，１０）ことから、撚線時に各試料の表面に負荷された曲げ歪みを、Ｓｎ−Ｃｕ系めっき層が吸収できず、亀裂が生じたと考えられる。さらに、試料８〜１１を用いた撚線は、Ｓｎ−Ｃｕ系めっき層に分散する金属間化合物が粗大であったり、Ｓｎ−Ｃｕ系めっき層に金属間化合物層が露出しているため、ハンダ付性が悪かった。
【００５３】
以上、本発明の実施の形態は、上述した実施の形態に限定されるものではなく、他にも種々のものが想定されることは言うまでもない。
【００５４】
【発明の効果】
以上要するに本発明によれば、次のような優れた効果を発揮する。
（１）めっき層の層硬度が十分に高いＳｎめっき極細銅線が得られる。
（２）撚線が容易で、ハンダ付け性が良好なＳｎめっき極細銅撚線が得られる。
（３）撚線性およびハンダ付性が良好なめっき極細銅線を得ることができる。
【図面の簡単な説明】
【図１】第１の実施の形態に係るＳｎめっき極細銅線の断面図である。
【図２】第２の実施の形態に係るＳｎめっき極細銅線の断面図である。
【図３】本発明に係るＳｎめっき極細銅線を用いた撚線の断面図である。
【図４】Ｓｎめっき極細銅線の製造装置の概略図である。
【符号の説明】
１１，２１Ｓｎめっき極細銅線
１２極細銅線
１３，２３Ｓｎ−Ｃｕ系めっき層（Sn-0.2〜7.0mass％Cu系めっき層）
２４Ｓｎ−Ｃｕ系金属間化合物
３１撚線
４４めっき浴槽
４５溶融Ｓｎ−Ｃｕ系めっき浴[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an Sn-plated ultrafine copper wire, a stranded wire using the same, and a method for producing an Sn-plated ultrafine copper wire, and in particular, an Sn-plated ultrafine copper wire used as a cable conductor for electronic equipment and a stranded wire using the same. The present invention relates to a method for producing a wire and an Sn-plated ultrafine copper wire.
[0002]
[Prior art]
In recent years, demands for reducing the size and weight of electronic devices have increased, and therefore, ultrafine copper wires having a wire diameter of 0.1 mm or less are becoming mainstream in cable conductors for electronic devices. One of these ultrafine copper wires is an Sn plated ultrafine copper wire having Sn plating on the surface.
[0003]
Two conventional methods for producing Sn-plated ultrafine copper wires are mainly dip method (hot dip plating method) and electroplating method.
[0004]
In the hot dipping method, the surface of the extra fine copper wire is activated using a flux or a reducing gas, and then the extra fine copper wire is immersed in a pure Sn plating solution to form a molten Sn plating layer on the outer periphery of the extra fine copper wire. Is. In addition, the electroplating method immerses an ultrafine copper wire whose surface has been activated in a pure Sn plating solution and applies a voltage between the ultrafine copper wire and the pure Sn plating solution to the outer periphery of the ultrafine copper wire. An electric Sn plating layer is formed.
[0005]
Of these plating methods, the hot dipping method is simpler and more economical, so the hot dipping method is generally used for the production of Sn-plated ultrafine copper wires.
[0006]
[Problems to be solved by the invention]
By the way, when producing a stranded wire by twisting a plurality of obtained Sn-plated ultrafine copper wires, the Sn-plated debris is generated on the surface of each wire as the Sn-plated ultrafine copper wires slide during the stranded wire. . When this Sn plating residue accumulates on the nipple which is a jig used at the time of manufacture of a twisted wire, there is a possibility that the twisted wire may be broken, and there is a problem that the twistability is not good.
[0007]
In addition, Cu of the ultrafine copper wire reacts with Sn of the Sn plating layer, and an Sn—Cu intermetallic compound is formed at the interface between them. If the Sn plating layer is not thick enough, the entire Sn plating layer It will become a Sn-Cu type intermetallic compound layer. Since this Sn—Cu-based intermetallic compound has poor solder wettability, there is a problem that the solderability of the stranded wire is deteriorated as a result.
[0008]
The object of the present invention, which was created in view of the above circumstances, is to provide a Sn-plated ultrafine copper wire with good twistability and solderability, a stranded wire using the same, and a method for producing a Sn-plated ultrafine copper wire. It is in.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the Sn-plated ultrafine copper wire according to the present invention is an Sn-plated ultrafine copper wire having a wire diameter of 0.1 mm or less, and Sn-0.2 on the outer periphery of the ultrafine copper wire made of copper or a copper alloy. A 7.0 mass% Cu-based plating layer is formed with a layer thickness of 0.05 μm or more, and a Sn—Cu-based intermetallic compound having a diameter of 2 μm or less is uniformly dispersed in the Cu-based plating layer. .
[0010]
According to the above configuration, an Sn-plated ultrafine copper wire having a sufficiently high layer hardness can be obtained.
[0011]
On the other hand, the twisted wire using the Sn-plated ultrafine copper wire according to the present invention has a wire diameter of 0.1 mm or less, and Sn-0.2 to 7.0 mass% on the outer periphery of the ultrafine copper wire made of copper or a copper alloy. A Cu-based plating layer is formed with a layer thickness of 0.05 μm or more, and a plurality of Sn-plated ultrafine copper wires in which a Sn—Cu-based intermetallic compound having a diameter of 2 μm or less is uniformly dispersed in the Cu-based plating layer It is formed by twisting together.
[0012]
According to the above configuration, a stranded wire (Sn-plated ultrafine copper stranded wire) using an Sn-plated ultrafine copper wire that is easy to twist and has good solderability can be obtained.
[0013]
Moreover, the manufacturing method of the Sn plating ultrafine copper wire which concerns on this invention is the Sn plating ultrafine copper wire which forms a molten Sn plating layer on the outer periphery of the ultrafine copper wire whose diameter is 0.1 mm or less which consists of copper or a copper alloy. In the manufacturing method, a molten Sn—Cu plating bath having a Cu concentration of 0.2 to 7.0 mass% is formed in the plating bath, and the temperature of the molten Sn—Cu plating bath in a temperature range of 250 to 350 ° C. The distribution is adjusted to within ± 5 ° C., and the ultrafine copper wire is immersed in the molten Sn—Cu plating bath. The outer periphery of the ultrafine copper wire has a layer thickness of 0.05 μm or more and a diameter of 2 μm or less. A molten Sn—Cu-based plating layer that uniformly disperses the Sn—Cu-based intermetallic compound is formed.
[0014]
According to the above method, it is possible to obtain a plated ultrafine copper wire having good stranded wire property and solderability.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.
[0016]
FIG. 1 shows a cross-sectional view of the Sn-plated ultrafine copper wire according to the first embodiment, and FIG. 2 shows a cross-sectional view of the Sn-plated ultrafine copper wire according to the second embodiment. Here, FIG.2 (b) is an enlarged view of the principal part A of Fig.2 (a).
[0017]
As shown in FIG. 1, the Sn-plated ultrafine copper wire 11 according to the first embodiment is an Sn-plated ultrafine copper wire having a wire diameter of 0.1 mm or less, and is made of soft copper or hard copper or copper alloy An Sn-0.2 to 7.0 mass% Cu-based plating layer (hereinafter referred to as Sn-Cu-based plating layer) 13 is 0.05 μm or more, preferably 0.5 μm or more on the outer periphery of the ultrafine copper wire 12 made of It was formed with a layer thickness of.
[0018]
As shown in FIGS. 2A and 2B, the Sn-plated ultrafine copper wire 21 according to the second embodiment is an ultrafine copper wire made of soft copper or copper or a copper alloy made of hard copper. The Sn—Cu-based plating layer 23 in which the Sn—Cu-based intermetallic compound 24 having a diameter of 2 μm or less, preferably 1 μm or less is uniformly dispersed on the outer periphery of 12 is 0.05 μm or more, preferably 0.5 μm or more. It was formed with a layer thickness of.
[0019]
On the other hand, the stranded wire 31 using the Sn-plated ultrafine copper wire according to the present embodiment, as shown in FIG. 3, twists a plurality of Sn-plated ultrafine copper wires 11 and 21 (seven are shown in FIG. 3). They are formed together. The stranded wire mentioned here is a general term for electric wires and cables using stranded wire conductors and stranded wire conductors.
[0020]
Next, the operation of the present embodiment will be described.
[0021]
By forming the Sn—Cu-based plating layers 13 and 23 on the outer periphery of the ultrafine copper wire 12, the Sn-plated ultrafine copper wire 11 having sufficiently higher layer hardness than the pure Sn plating layer of the conventional Sn-plated ultrafine copper wire, 21 is obtained. Since the copper wires 11 and 21 have high layer hardness of the Sn—Cu plating layers 13 and 23, when the stranded wires are manufactured using the copper wires 11 and 21, the strands of the stranded wires slide with each other. The amount of Sn plating residue generated as a result is reduced. In particular, in the case of the Sn-plated extra fine copper wire 21, the amount of Sn plating residue is very small. As a result, there is no risk of disconnection when the Sn-plated ultrafine copper wires 11 and 21 according to the present embodiment are twisted, and the twistability is improved as compared with the conventional Sn-plated ultrafine copper wires.
[0022]
Further, since the amount of Sn plating residue generated at the time of stranded wire is small, the stranded wire obtained using copper wires 11 and 21 has a smooth or substantially smooth surface of the Sn-Cu-based plating layers 13 and 23. The surface condition becomes good. For this reason, the solder wettability of these stranded wires is better than that of stranded wires obtained by using conventional Sn-plated ultrafine copper wires. As a result, good solderability is obtained in the stranded wire obtained using the Sn-plated ultrafine copper wires 11 and 21 according to the present embodiment.
[0023]
The reason why the thicknesses of the Sn—Cu plating layers 13 and 23 in the Sn-plated ultrafine copper wires 11 and 21 are set to 0.05 μm or more, preferably 0.5 μm or more is as follows.
[0024]
In general, when Sn plating is applied to a copper wire, Cu on the surface of the copper wire reacts with Sn in the Sn plating layer, and an Sn—Cu based intermetallic compound layer of Cu ₃ Sn or Cu ₆ Sn ₅ is formed at the interface between them. Is done. Here, when the layer thickness of the Sn plating layer is less than 0.05 μm, the Sn plating layer itself becomes a Sn—Cu-based intermetallic compound layer. Since this Sn—Cu based intermetallic compound is hard and brittle and the solder wettability is not good, when the Sn plating layer itself becomes a Sn—Cu based intermetallic compound layer, the plated conductor (Sn plated ultrafine copper wire) Mechanical properties such as bending properties are degraded, and problems occur when soldering Sn-plated ultrafine copper wires and various electronic components.
[0025]
In addition, in the Sn-plated ultrafine copper wires 11 and 21, the Cu concentration of the Sn-Cu-based plating layers 13 and 23 is defined as 0.2 to 7.0 mass% when the Cu concentration is less than 0.2 mass%. This is because the hardness of the Sn—Cu plating layers 13 and 23 is not so different from that of the pure Sn plating layer. Further, if the Cu concentration exceeds 7.0 mass%, the Sn—Cu based plating layers 13 and 23 themselves are likely to become Sn—Cu based intermetallic compound layers.
[0026]
In the Sn-plated ultrafine copper wire 21, the diameter of the Sn—Cu based intermetallic compound (Cu ₃ Sn or Cu ₆ Sn ₅ ) 24 uniformly dispersed in the Sn—Cu based plating layer 23 is defined as 2 μm or less, preferably 1 μm or less. The reason is as follows.
[0027]
The reason why the crystallization size of the intermetallic compound 24 is specified to be 2 μm or less, preferably 1 μm or less is that if it exceeds 2 μm, the smoothness of the surface of the Sn—Cu-based plating layer 23 is impaired, and Sn—Cu This is because when a drawing die is used to adjust the layer thickness of the system plating layer 23, the intermetallic compound 24 is deposited on the die portion, causing disconnection of the Sn-plated ultrafine copper wire 21.
[0028]
Next, the manufacturing method of the Sn plating extra fine copper wire which concerns on this invention is demonstrated based on FIG.
[0029]
As shown in FIG. 4, first, the ultrafine copper wire 12 is sent out from the delivery bobbin 41 and travels in the reduction furnace 42, and the ultrafine copper wire 12 is subjected to reduction treatment to remove the oxide layer on the surface.
[0030]
Next, the ultrafine copper wire 12 after the removal of the oxide layer is immersed in the molten Sn—Cu plating bath 45 in the plating bath 44 by the immersion rod 46 between the guide pulleys 43a and 43b. At this time, the Cu concentration of the molten Sn—Cu plating bath 45 is set to 0.2 to 7.0 mass%, and the temperature distribution of the molten Sn—Cu plating bath 45 in the temperature range of 250 to 350 ° C. is ± 5. Adjust in advance to within ° C. Therefore, the plating bath 44 includes at least a number of temperature sensors (not shown) for measuring the temperature of the plating bath 45, an adjustment device (not shown) to which a signal from the temperature sensor is input, and an adjustment device. A stirring device (not shown) for stirring the plating bath by a signal is provided.
[0031]
Since the Sn—Cu-based plating solution is unevenly attached to the outer periphery of the ultrafine copper wire 12 after immersion in the plating bath, the ultrafine conductor wire 12 is inserted into the drawing die 47 and attached to the outer periphery of the ultrafine conductor wire 12. The amount of the Sn—Cu plating solution is made uniform, and the thickness of the Sn—Cu plating layer is adjusted to be 0.05 μm or more, preferably 0.5 μm or more.
[0032]
Thereafter, the Sn—Cu plating solution adhering to the outer periphery of the ultrafine conductive wire 12 is cooled (air-cooled) and solidified, so that the Sn plating ultrafine having the molten Sn—Cu plating layers 13 and 23 on the outer periphery of the ultrafine copper wire 12 is obtained. Copper wires 11 and 21 are obtained, and the copper wires 11 and 21 are wound around the winding bobbin 49. When the Sn—Cu plating solution is cooled and solidified, the cooling device 48 may blow cooling air (not shown) onto the ultrafine copper wire 12 to forcibly cool the Sn—Cu plating solution. This suppresses Cu diffusion of the ultrafine copper wire 12 with respect to the Sn—Cu-based plating layers 13 and 23 as compared to when cooling by air cooling, so that the solder wetting of the Sn plated ultrafine copper wires 11 and 21 is suppressed. In addition, the solderability is further improved.
[0033]
Here, when the ultrafine copper wire 12 is immersed in the molten Sn-Cu-based plating bath 45 in the plating bath 44, when the bath temperature of the plating bath 45 in which the solubility of copper has reached saturation is lowered, it is accompanied accordingly. Copper solubility is reduced. As a result, surplus copper that cannot be dissolved is crystallized in the form of an intermetallic compound (for example, Cu ₆ Sn ₅ ). At this time, by adjusting the temperature distribution of the plating bath 45 under the temperature conditions described later, the size of the intermetallic compound crystallized in the plating bath 45 can be controlled to 2 μm or less. This Sn—Cu-based plating By immersing the ultrafine copper wire 12 in the bath 45, the Sn-plated ultrafine copper in which the Sn—Cu intermetallic compound 24 having a diameter of 2 μm or less, preferably 1 μm or less, is uniformly dispersed in the Sn—Cu plating layer 23. Line 21 can be obtained.
[0034]
The temperature distribution in the temperature range of 250 to 350 ° C. of the molten Sn—Cu plating bath 45 is regulated to be within ± 5 ° C., preferably within ± 3 ° C. When the temperature distribution exceeds ± 5 ° C., A coarse intermetallic compound crystallizes in the lowest temperature portion of the plating bath 45, and the coarse intermetallic compound is dispersed in the Sn—Cu-based plating layers 13 and 23. This is to cause disconnection.
[0035]
【Example】
Example 1
After immersing an ultrafine copper wire with a diameter of φ0.03 mm in a molten Sn—Cu plating bath in the plating bath, cooling air is blown onto the surface of the ultrafine copper wire, and the plating layer thickness is 0.7 μm, 0.8 μm. A 0.7 μm thick Sn-plated ultrafine copper wire is prepared (Samples 1 to 3). At this time, the Cu concentration of the molten Sn—Cu plating bath is 0.5 mass%, 0.7 mass%, and 1.0 mass%, respectively, and the temperature distribution of the molten Sn—Cu plating bath is uniformly 330 ° C. ± The temperature was adjusted within 5 ° C.
[0036]
(Example 2)
After immersing an ultrafine copper wire having a diameter of φ0.03 mm in a molten Sn—Cu plating bath in the plating bath, spraying cooling air on the surface of the ultrafine copper wire, the plating layer thickness is both 0.8 μm, and Then, an Sn-plated ultrafine copper wire in which a fine intermetallic compound having a diameter of 1.0 μm or less is uniformly dispersed in the plating layer is prepared (Samples 4 and 5). At this time, the Cu concentration of the molten Sn—Cu plating bath is adjusted to 3.0 mass% and 5.0 mass%, respectively, and the temperature distribution of the molten Sn—Cu plating bath is uniformly adjusted within 310 ° C. ± 5 ° C. did.
[0037]
(Example 3)
After immersing an ultrafine copper wire with a diameter of φ0.03 mm in a molten Sn—Cu plating bath in the plating bath, the ultrafine copper wire is naturally cooled (air-cooled), and Sn plating with a plating layer thickness of 0.5 μm or more is performed. An ultrafine copper wire is prepared (Sample 6). At this time, the Cu concentration of the molten Sn—Cu plating bath was adjusted to 3.0 mass%, and the temperature distribution of the molten Sn—Cu plating bath was adjusted to within 330 ° C. ± 5 ° C.
[0038]
(Comparative Example 1)
After immersing an ultrafine copper wire with a diameter of φ0.03 mm in a molten Sn—Cu plating bath in the plating bath, cooling air is blown onto the surface of the ultrafine copper wire, and the plating layer thickness is 0.7 μm, 0.8 μm. The Sn-plated ultrafine copper wire is prepared (Samples 7 and 8). At this time, the Cu concentration of the molten Sn—Cu plating bath is adjusted to 0.1 mass% and 10.0 mass%, respectively, and the temperature distribution of the molten Sn—Cu plating bath is adjusted to within 350 ° C. ± 5 ° C. did.
[0039]
(Comparative Example 2)
After immersing an ultrafine copper wire having a diameter of φ0.03 mm in a molten Sn—Cu plating bath in the plating bath, air is blown onto the surface of the ultrafine copper wire, and the plating layer thickness is 0.04 μm and 0.03 μm. An Sn-plated ultrafine copper wire is prepared (Samples 9 and 10). At this time, the Cu concentration of the molten Sn—Cu plating bath is adjusted to 1.0 mass% and 3.0 mass%, respectively, and the temperature distribution of the molten Sn—Cu plating bath is adjusted to within 350 ° C. ± 5 ° C. did.
[0040]
(Comparative Example 3)
After immersing an ultrafine copper wire with a diameter of φ0.03 mm in a molten Sn—Cu plating bath in the plating bath, air is blown onto the surface of the ultrafine copper wire, and the Sn plating ultrafine copper with a plating layer thickness of 0.8 μm A wire is prepared (sample 11). At this time, the Cu concentration of the molten Sn—Cu plating bath was adjusted to 5.0 mass%, and the temperature distribution of the molten Sn—Cu plating bath was adjusted to 240 ° C. ± 5 ° C. or less.
[0041]
Table 1 shows the specifications of Samples 1 to 11 (Cu concentration (mass%) of Sn—Cu plating layer, plating bath temperature (° C.), layer thickness (μm) of Sn—Cu plating layer, cooling process)). . Here, the measurement of the layer thickness of the Sn—Cu based plating layer was performed by the Kocourt method (JIS8610-8619).
[0042]
[Table 1]

[0043]
Next, the surface state of each sample was evaluated. The evaluation results are shown in Table 2. Here, the evaluation of the surface state was performed using an electron microscope (SEM).
[0044]
[Table 2]

[0045]
As shown in Table 2, the surface states of Samples 1 to 7 were all good. Samples 1 to 3 and 7 had a smooth surface of the Sn—Cu plating layer, but the surface of the Sn—Cu plating layer of Samples 4 to 6 was a fine metal having a diameter of 1 μm or less. An intermetallic compound (Cu ₆ Sn ₅ ) was observed.
[0046]
On the other hand, the surface states of Samples 8 and 11 were both poor. This is because, for sample 8, the Cu concentration of the Sn—Cu-based plating layer is higher than the specified range, and for sample 11, the plating bath temperature is lower than the specified range, so that excess copper that cannot be dissolved in the plating bath. This results from crystallization as an intermetallic compound, and a coarse acicular intermetallic compound (Cu ₆ Sn ₅ ) having a diameter of about 3 μm is dispersed in the Sn—Cu-based plating layer.
[0047]
Further, the surface states of Samples 9 and 10 were both poor. This is because the layer thickness of the Sn—Cu-based plating layer is thinner than the specified range, so that the intermetallic compound layer formed by the reaction of Cu and Sn on the surface of the ultrafine copper wire with the entire surface of the Sn-plated ultrafine copper wire. This is because the surface of the Sn-plated ultrafine copper wire is uneven.
[0048]
Next, 7 pieces of each sample are concentrically twisted at a pitch of 3.3 mm to produce a stranded wire having a length of 10,000 m. At this time, the surface state of each stranded wire, the state of occurrence of plating residue, and the solderability were evaluated. The evaluation results are shown in Table 3. Here, the state of occurrence of plating residue was evaluated by the amount of plating residue deposited on the nipple portion of the twisting machine. The solderability was evaluated based on the wet area when the stranded wire was immersed in a eutectic solder bath.
[0049]
[Table 3]

[0050]
As shown in Table 3, the surface states of the stranded wires using Samples 1 to 6 were all good. Moreover, the generation of plating residue has no problem in the stranded wire work. That is, there was no disconnection due to plating residue during the stranded wire process. In particular, Samples 3 to 6 had a very small amount of plating residue generated during stranded wire. Furthermore, the solderability was very good or good except that the stranded wire using the sample 6 was slightly good.
[0051]
On the other hand, the stranded wire using the sample 7 has a good surface state of the stranded wire (smooth) and a very good solderability, but a large amount of plating residue is generated during the stranded wire, Disconnection occurred. This is because the Cu concentration of the Sn—Cu plating layer of Sample 7 is lower than the specified range, so the hardness of the Sn—Cu plating layer is not much different from the hardness of the pure Sn plating layer, and the hardness is insufficient. Due to that.
[0052]
Moreover, although the amount of the plating residue which generate | occur | produces at the time of a twisted wire was very small, the fine crack was recognized on the surface of the twisted wire, and the surface state was unsatisfactory for the twisted wire using the samples 8-11. This crack was generated at the interface between the intermetallic compound (or intermetallic compound layer) and the Sn—Cu-based plating layer. That is, in Samples 8 to 11, the intermetallic compound dispersed in the Sn—Cu based plating layer is coarse (Samples 8 and 11), or the intermetallic compound layer is exposed in the Sn—Cu based plating layer (Sample 9, 10), it is considered that the bending strain applied to the surface of each sample at the time of stranded wire could not be absorbed by the Sn—Cu-based plating layer, and a crack occurred. Furthermore, the stranded wires using Samples 8 to 11 are soldered because the intermetallic compound dispersed in the Sn—Cu based plating layer is coarse or the intermetallic compound layer is exposed in the Sn—Cu based plating layer. It was bad.
[0053]
As mentioned above, it cannot be overemphasized that embodiment of this invention is not limited to embodiment mentioned above, and various things are assumed in addition.
[0054]
【The invention's effect】
In short, according to the present invention, the following excellent effects are exhibited.
(1) An Sn-plated ultrafine copper wire having a sufficiently high layer hardness can be obtained.
(2) An Sn-plated ultrafine copper stranded wire that is easy to twist and has good solderability can be obtained.
(3) It is possible to obtain a plated ultrafine copper wire having good twisting properties and solderability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an Sn-plated ultrafine copper wire according to a first embodiment.
FIG. 2 is a cross-sectional view of an Sn-plated ultrafine copper wire according to a second embodiment.
FIG. 3 is a cross-sectional view of a stranded wire using an Sn-plated ultrafine copper wire according to the present invention.
FIG. 4 is a schematic view of an apparatus for producing an Sn-plated ultrafine copper wire.
[Explanation of symbols]
11, 21 Sn-plated extra-fine copper wire 12

Extra-fine copper wire

13, 23 Sn-Cu-based plating layer (Sn-0.2 to 7.0 mass% Cu-based plating layer)
24 Sn-Cu-based intermetallic compound 31 Stranded wire 44 Plating bath 45 Molten Sn-Cu-based plating bath

Claims

Sn-0.2 to 7.0 mass% Cu-based plating layer on the outer periphery of an ultrafine copper wire made of copper or a copper alloy in a Sn-plated ultrafine copper wire having a wire diameter of 0.1 mm or less, a layer of 0.05 μm or more A Sn- plated ultrafine copper wire , which is formed with a thickness and in which a Sn-Cu intermetallic compound having a diameter of 2 μm or less is uniformly dispersed in the Cu-based plating layer .

A stranded wire using an Sn-plated ultrafine copper wire, which is formed by twisting a plurality of Sn-plated ultrafine copper wires according to claim 1 .

In the manufacturing method of the Sn plating ultrafine copper wire which forms a molten Sn plating layer in the outer periphery of the ultrafine copper wire whose wire diameter which consists of copper or a copper alloy is 0.1 mm or less, Cu density | concentration is 0.2-7 in a plating bath A 0.0 mass% molten Sn—Cu plating bath is formed, and the temperature distribution of the molten Sn—Cu plating bath in the temperature range of 250 to 350 ° C. is adjusted to within ± 5 ° C. Molten Sn-Cu that immerses the ultrafine copper wire in the plating bath and uniformly disperses the Sn-Cu intermetallic compound having a layer thickness of 0.05 μm or more and a diameter of 2 μm or less on the outer periphery of the ultrafine copper wire A method for producing an Sn-plated ultrafine copper wire, comprising forming a system plating layer.

The production of Sn-plated ultrafine copper wire according to claim 3, wherein a molten Sn-Cu plating layer having a thickness of 0.05 µm or more is formed on the outer periphery of the ultrafine copper wire, and then the molten Sn-Cu plating layer is forcibly cooled. Method.