JP3937373B2 - Self-catalyzed electroless silver plating solution - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、自己触媒型の無電解銀めっき液、及び無電解銀めっき方法に関する。
【０００２】
【従来の技術】
銀めっきは、古くから装飾分野、電子産業分野などにおいて広く利用されている。従来用いられている銀めっき液は、殆どが銀のキレート剤として、シアンイオンを含有するものであるが、シアン化合物には強い毒性があり、排水処理、薬品管理、作業時の安全管理等において、取り扱いに注意が必要である。このためシアン化合物を含まない、非シアン型の銀めっき液が要望されている。
【０００３】
非シアン型の銀めっき液は、銀が貴金属であることから、浴中で分解し沈殿を生じ易く、めっき液の安定性に課題がある。さらに、銅等の素材に対して置換し易いため、密着性のある皮膜が得られ難いという欠点もある。
【０００４】
近年では、幾つかの非シアン銀めっき液が提案されている。例えば、電解めっきを例に挙げると、特公平５−７５８３７号公報には、有機スルホン酸銀、硝酸銀、塩化銀等の銀化合物とヨウ化カリウムを含むめっき液に、スルファニル酸誘導体を配合しためっき液が報告されている。しかしながら、このめっき液は、液の安定性や電導性を維持するためにヨウ化カリウムを大量に配合する必要があり、従来のシアン浴に比べて非常にコストが高くなるという欠点がある。
【０００５】
また、特開平７−１６６３９１号公報では、有機スルホン酸銀塩、コハク酸イミド又はその誘導体、緩衝剤等を含むめっき液に、界面活性剤を配合した電解銀めっき液が報告されている。このめっき液によれば、光沢皮膜を形成することが可能であるが、主キレート成分がめっき液中で不安定で適応できるｐＨが狭く、加水分解等が生じやすく、浴寿命が短いという欠点がある。
【０００６】
またこれら電解めっき液では、非導電体上へめっきを行う場合には、無電解めっき処理等を施して導電性を付与した後、電解銀めっきを行う必要があり、経済的、時間的に不利な点は否めない。
【０００７】
自己触媒型無電解銀めっき液についても幾つかの報告がなされている。例えば、特開平０５−２８７５４３号公報には、チオ硫酸塩、チオシアン酸塩、亜硫酸塩等をキレート剤として用い、水素化ホウ素カリウムを還元剤とした自己触媒型無電解銀めっき液が報告されている。しかしながら、チオ硫酸塩、亜硫酸塩等は空気等で酸化されやすく不安定である。しかも、形成される錯体は光に対して敏感であり、安定した溶液を得ることは困難である。
【０００８】
また、特開昭６１−１５９８６号公報には、アンモニアやエチレンジアミン等の窒素化合物をキレート剤とした自己触媒型無電解銀めっき液が報告されている。しかしながら、窒素系化合物は爆発性を有する窒化銀を形成するおそれがあり、しかもアンモニアやエチレンジアミン等は臭気の問題から、作業環境にも注意を払う必要がある。
【０００９】
【発明が解決しようとする課題】
本発明の主な目的は、シアン化合物、窒素系化合物などを含有しない非シアン、非アンモニアタイプの自己触媒型無電解銀めっき液であって、めっき液の安定性が良く、良好な物性の銀めっき皮膜を形成できる無電解銀めっき液を提供することである。
【００１０】
【課題を解決するための手段】
本発明者は、上記の如き従来技術の問題点を解決するために、鋭意研究を重ねてきた。その結果、分子内に２個のモノスルフィド基を有する水溶性含硫黄有機化合物をキレート剤として用いることによって、シアン、アンモニア等を用いることなく、安定性が良好で、優れた物性を有する銀めっき皮膜を形成できる非シアン非アンモニアタイプの自己触媒型無電解銀めっき液が得られることを見出し、ここに本発明を完成するに至った。
【００１１】
即ち、本発明は、以下の自己触媒性無電解銀めっき液、無電解銀めっき方法、及び銀めっき処理品を提供するものである。
１．（ｉ）水溶性銀塩、（ii）分子内に２個のモノスルフィド基を有する水溶性含硫黄有機化合物、及び（iii）還元剤、を含有する水溶液からなる自己触媒型無電解銀めっき液。
２．水溶性銀塩が、硫酸銀、硝酸銀、及び過塩素酸銀から選ばれた少なくとも１種である上記項１に記載の無電解銀めっき液。
３．分子内に２個のモノスルフィド基を有する水溶性含硫黄有機化合物が、分子内に水酸基、カルボキシル基、スルホン酸基、アミノ基、ホスホン基及びメルカプト基から選ばれた少なくとも一種の水溶性基を有し、２個のモノスルフィド基の間に炭素数２〜８個の２価の炭化水素基が存在する化合物、及び該化合物の塩から選ばれた少なくとも一種である上記項１又は２に記載の無電解銀めっき液。
４．還元剤が、水溶性アルデヒド化合物、水溶性ヒドラジン誘導体、水素化ホウ素化合物、次亜リン酸化合物、亜リン酸化合物、及びアスコルビン酸化合物から選ばれた少なくとも１種である上記項１〜３のいずれかに記載の無電解銀めっき液。
５．（ｉ）水溶性銀塩を、銀金属量として、０．２〜１０ｇ／ｌ、（ii）分子内に２個のモノスルフィド基を有する水溶性含硫黄有機化合物を、銀イオン量に対して、等モル〜２０倍モル、及び（iii）還元剤を、水溶性銀塩に対して、等グラム当量〜２０倍グラム当量、含有する水溶液からなる上記項１〜４のいずれかに記載の無電解銀めっき液。
６．上記項１〜５のいずれかに記載の無電解銀めっき液を、ｐＨ１〜１４、液温０〜８０℃として、該銀めっき液に被めっき物を浸漬することを特徴とする無電解銀めっき方法。
７．無電解銀めっき液が、ｐＨ６〜１３、液温１０〜６０℃である上記項６に記載の無電解銀めっき方法。
８．上記項６又は７の方法で銀めっき皮膜が形成された銀めっき処理品。
【００１２】
【発明の実施の形態】
本発明の自己触媒型無電解銀めっき液は、（ｉ）水溶性銀塩、（ii）分子内に２個のモノスルフィド基を有する水溶性含硫黄有機化合物、及び（iii）還元剤、を含有する水溶液からなるものである。
【００１３】
本発明のめっき液に配合する水溶性銀塩としては、めっき液に可溶性であって、所定の濃度の水溶液が得られるもので有れば特に限定されないが、特に硫酸銀、硝酸銀、過塩素酸銀等の無機銀塩が溶解性が良好である点で好ましい。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。
【００１４】
水溶性銀塩の配合量は、銀金属量として、０．２〜１０ｇ／ｌの程度とすることが好ましく、０．５〜５ｇ／ｌ程度とすることがより好ましい。
【００１５】
銀金属量が、上記範囲に有る場合には、適度な析出速度を有し、しかも、良好な安定性を有するめっき液となり、しかもめっき液の無駄な持ち出しを減少させることができる。
【００１６】
本発明では、銀のキレート剤成分として、分子内に２個のモノスルフィド基を有する水溶性含硫黄有機化合物を用いる。該水溶性含硫黄有機化合物を配合することによって、浴中の銀イオンが十分に錯化されて、めっき浴の安定性が良好になる。該含硫黄有機化合物は、分子内に２個のモノスルフィド基を有すると共に、分子内に水酸基、カルボキシル基、スルホン酸基、アミノ基、ホスホン基及びメルカオプト基から選ばれた少なくとも一種の水溶性基を有し、２個のモノスルフィド基の間に炭素数２〜８個の２価の炭化水素基が存在する化合物、該化合物のアルカリ金属塩、アンモニウム塩等が好ましい。水溶性基は、分子内に一個以上存在すれば良いが、二個以上存在することが好ましい。該水溶性含硫黄有機化合物は、一種単独又は２種以上混合して用いることができる。
【００１７】
該水溶性含硫黄有機化合物の好ましい例としては、下記一般式で表される化合物、その塩等を挙げることができる。
【００１８】
Ｘ−Ｒ1−Ｓ−Ｒ2−Ｓ−Ｒ3−Ｙ
（式中、Ｒ1及びＲ2は、同一又は異なって、それぞれ、炭素数１〜５の直鎖又は分岐鎖状のアルキレン基、Ｒ3は、炭素数２〜８の直鎖又は分岐鎖状のアルキレン基、Ｘ及びＹは、同一又は異なって、水酸基、カルボキシル基、スルホン酸基、アミノ基、ホスホン基又はメルカプト基である。）
該水溶性含硫黄有機化合物の具体例としては、１，２−ビス(２−ヒドロキシエチルチオ)エタン、２，２’−(エチレンジチオ)ジエタンチオール、１，４−ビス(２−ヒドロキシエチルチオ)ブタン、３，３’−(プロピレンジチオ)ジプロピオン酸、これらの化合物の塩（アルカリ金属塩、アンモニウム塩等）等を挙げることができる。
【００１９】
該水溶性含硫黄有機化合物は、一種単独又は２種以上混合して用いることができる。
【００２０】
該水溶性含硫黄有機化合物の配合量は、めっき浴中の銀イオンに対して、等モル以上とすることが好ましく、２倍モル以上とすることがより好ましい。該水溶性含硫黄有機化合物の配合量が少なすぎると、銀が十分に錯化されないため、めっき浴が不安定となり、液の分解が生じ易くなる。配合量の上限については、使用する含硫黄有機化合物の溶解度までとすることが可能であり、配合量が多いほどめっき液の安定性は向上するが、大過剰に配合すると、めっき析出速度が低下して、所定の析出銀量を得るために長時間が必要となる。また持ち出しの増大により、経済的にも好ましくない。このため、通常、銀イオンに対して２０倍モル程度までの配合量とすることが好ましい。
【００２１】
以上より、水溶性含硫黄有機化合物の配合量は、めっき浴中の銀イオンに対して、等モル〜２０倍モルとすることが好ましく、２倍モル〜２０倍モルとすることがより好ましい。
【００２２】
還元剤としては、めっき液中の水溶性銀塩を金属銀に還元する能力を有し、且つ水溶性の化合物を用いることができる。この様な還元剤としては、ホルマリン、グリオキシル酸、ヒドロキシベンズアルデヒド、還元糖類（ブドウ糖、蔗糖等）等の水溶性アルデヒド化合物；水加ヒドラジン、セミカルバジド等の水溶性ヒドラジン誘導体；水素化ホウ素ナトリウム、ジメチルアミンボラン等の水素化ホウ素化合物；次亜リン酸、次亜リン酸塩等の次亜リン酸化合物；亜リン酸、亜リン酸塩等の亜リン酸化合物；アスコルビン酸、アスコルビン酸塩等のアスコルビン酸化合物等が挙げられる。還元剤は、一種単独又は２種以上混合して用いることができる。
【００２３】
還元剤の配合量は、水溶性銀塩に対して等グラム当量以上とすることが好ましい。配合量が少なすぎると、めっき液中に水溶性銀塩が未反応のまま存在するために経済的に好ましくない。還元剤の配合量の上限は、使用する還元剤の溶解度までとすることができるが、大量に還元剤を配合すると、めっき液の安定性に悪影響を及ぼし、しかも経済的に好ましくない。このため、還元剤の配合量は水溶性銀塩に対して２０倍グラム当量程度以下とすることが望ましい。
【００２４】
本発明の無電解銀めっき液には、更に、必要に応じて、上記した各成分の働きに悪影響を及ぼさない限り、各種の添加剤を配合することができる。
【００２５】
本発明の無電解銀めっき液は、上記した各成分を水に溶解したものであり、好ましくは、水溶性銀塩及び水溶性含硫黄化合物を溶解した水溶液中に、還元剤を添加する方法によって調製することができる。
【００２６】
本発明の無電解銀めっき液は、液温０〜８０℃程度の範囲で用いることが好ましい。めっき液の温度が低い場合には、銀の析出速度が遅く所定の銀析出量を得るために長時間が必要となる。また液温が高過ぎると、自己分解反応による還元剤の損失や、浴安定性の低下を引き起こし易い。本発明めっき液は、特に、１０〜６０℃程度で用いることが好ましく、この温度範囲とすることによって、めっき液の安定性が良好となり、適度な析出速度を有するものとなる。
【００２７】
めっき液のｐＨは１〜１４程度とすることが適当である。ｐＨが低過ぎる場合には自己分解反応による還元剤の損失や、還元剤自身が水溶性銀塩を還元できる電位に達しない場合があり、一方、ｐＨが高過ぎる場合には、還元剤の還元性が強くなりすぎて、めっき液が分解する恐れがある。特に、めっき液のｐＨを６〜１３程度とすることによって、めっき液の安定性が良好で、しかも適度な析出速度を有するものとなる。めっき液のｐＨ調整は、通常、ｐＨを下げる場合には、水溶性銀塩のアニオン部分と同種のアニオン部分を有する酸、例えば、水溶性銀塩として硫酸銀を用いる場合には硫酸、水溶性銀塩として硝酸銀を用いる場合には硝酸を用いて行えばよく、ｐＨを上げる場合には、アルカリ金属水酸化物、アンモニア等を用いて行えばよい。
【００２８】
本発明の無電解銀めっき液を用いてめっき処理を行うには、上記した液温、及びｐＨ値に調節しためっき液中に被めっき物を浸漬すればよい。
【００２９】
本発明の無電解銀めっき液により無電解銀めっき皮膜を形成できる被めっき物の材質については特に限定はなく、金属材料やその他の各種の導電性材料、非導電性材料を被めっき物とすることができる。
【００３０】
金属材料を被めっき物とする場合には、通常、常法に従って脱脂処理等の前処理を行った後、被めっき物を直接めっき液中に浸漬すればよい。
【００３１】
セラミックス、プラスチックス等の非金属材料にめっき処理を行うには、脱脂処理等の前処理を行った後、被めっき物を活性化処理し、その後めっき液に浸漬すればよい。活性化処理は、常法に従えばよく、例えば、パラジウム触媒（キャタリスト−アクセラレーター法、センシタイズ−アクチベーター法等）、酸性塩化第１スズ溶液、特開平１０−３１８８号公報に記載の銀触媒又は銅触媒等を用いて、公知の条件に従って、活性化処理を行えばよい。
【００３２】
以上の方法で、無電解銀めっき皮膜が形成された材料は、従来から銀めっき皮膜が適用されている各種分野において用いることができる。例えば、電磁波シールド、セラミックコンデンサー、抗菌材料等の用途に有効に用いることができる。
【００３３】
【発明の効果】
本発明の無電解銀めっき液は、有害なシアン化合物やアンモニア等の窒素系化合物を含んでおらず、安全で取り扱い易いめっき液である。そして、該めっき液は、安定性が良好で、適度な析出速度を有し、形成される銀めっき皮膜は、密着性、耐食性、耐磨耗性等の皮膜物性、電気的特性などが良好である。
【００３４】
【実施例】
以下に、実施例を示して本発明をさらに詳細に説明する。
（実施例１）
硝酸銀０．１７ｇ／ｌ、１，２−ビス（２−ヒドロキシエチルチオ）エタン１０ｇ／ｌ、及び水加ヒドラジン８ｇ／ｌを含有する水溶液からなる無電解銀めっき液を調製し、これを水酸化カリウムを用いてｐＨ１０に調整した。
【００３５】
アルミナセラミック試験片（５×５ｃｍ）を被めっき物として用い、これをＰｄ触媒（商標名：キャタリストＣ、奥野製薬工業(株)製）５０ｍｌ／ｌ及び３５％塩酸１５０ｍｌ／ｌを含有する触媒液中に２５℃で３分間浸漬し、次いで、１０％硫酸水溶液中に３５℃で３分間浸漬した後、上記無電解銀めっき液に浸漬し、３５℃で１時間無電解銀めっきを行った。その結果、厚さ１．２μｍの平滑で無光沢の緻密な銀めっき皮膜が析出し、銀めっき皮膜の表面には、外観ムラは認められなかった。さらに、めっき液を室温で４週間放置後、同様のめっき試験を行ったが、良好なめっき性能を示し、ｐＨの変動、沈殿などは認められなかった。
（実施例２）
硫酸銀０．３１ｇ／ｌ、１，４−ビス（２−ヒドロキシエチルチオ）ブタン１５ｇ／ｌ、及びホルムアルデヒド４ｇ／ｌを含有する水溶液からなる無電解銀めっき液を調製し、これを水酸化ナトリウムを用いてｐＨ１１に調整した。
【００３６】
あらかじめ脱脂を行った圧延銅板（５×５ｃｍ、厚さ０．２ｍｍ）を被めっき物として用い、これを上記無電解銀めっき液に浸漬し、５０℃で１時間無電解銀めっきを行った。その結果、厚さ３μｍの平滑で無光沢の緻密な皮膜が析出し、銀めっき皮膜の表面には、外観ムラは認められなかった。さらに、めっき液を室温で４週間放置後、同様のめっき試験を行ったが、良好なめっき性能を示し、ｐＨの変動、沈殿などは認められなかった。
（実施例３）
硝酸銀０．３４ｇ／ｌ、２，２’−（エチレンジチオ）ジエタンチオール２０ｇ／ｌ、及び次亜リン酸ナトリウム１０ｇ／ｌを含有する水溶液からなる無電解銀めっき液を調製し、これを水酸化ナトリウムを用いてｐＨ１０．５に調整した。
【００３７】
エポキシ樹脂試験片（５×５ｃｍ、厚さ１．８ｍｍ）を被めっき物として用い、これを塩化第一スズ２水和物３０ｇ／ｌ及び３５％塩酸２０ｍｌ／ｌを含有する酸性塩化第一スズ溶液に２５℃で３分間浸漬した後、上記無電解銀めっき液に浸漬し、５０℃で１時間無電解銀めっきを行った。その結果、厚さ２．８μｍの平滑で無光沢の緻密な皮膜が析出し、銀めっき皮膜の表面には、外観ムラは認められなかった。さらに、めっき液を室温で４週間放置後、同様のめっき試験を行ったが、良好なめっき性能を示し、ｐＨの変動、沈殿などは認められなかった。
（比較例１）
硝酸銀０．５ｇ／ｌ、エチレンジアミン１．０８ｇ／ｌ、ロッセル塩（酒石酸ナトリウムカリウム４水和物）３．７８ｇ／ｌ、及び３，５−ジヨードチロシン０．１８ｇ／ｌを含有し、水酸化ナトリウムを使用してｐＨ１１．０とした無電解銀めっき液を調製した。
【００３８】
実施例１と同様にして活性化したアルミナセラミック試験片（５×５ｃｍ、厚さ０．２ｍｍ）を被めっき物として用い、これを上記めっき液に浸漬し、３０℃で１時間無電解銀めっきを行った。その結果、厚さ０．４μｍの平滑で無光沢の皮膜が析出したが、めっき皮膜は試験片全体に析出することなく、所々無めっきの部分があった。さらにめっき液からはエチレンジアミン臭が立ちこめ、局所排気設備を必要とした。
【００３９】
また、めっき液を室温で４週間放置後、同様の試験を行ったが、ｐＨの変動がみられ、めっき槽の底に金属銀の沈殿が確認された。
（比較例２）
硝酸銀３．５ｇにアンモニア水を沈殿が溶解するまで加え、さらにブドウ糖４５ｇ／ｌを加えて、水で１リットルとして、めっき液（銀鏡反応液）を調製した。
【００４０】
このめっき液に、実施例１と同様にして活性化したアルミナセラミック試験片を浸漬し、２５℃で無電解めっきを行った。
【００４１】
試験片浸漬後、約５分後にめっき液は懸濁し始め、約１０分後にめっき槽全面にめっきが析出した。めっき皮膜は試験片全体に析出したが、膜厚はめっき液が分解したため測定不可能であった。
【００４２】
以上の結果から判るように、本発明の自己触媒型無電解銀めっき液を使用することにより、安定でしかも均一な銀めっき皮膜を形成することができる。また、本発明のめっき液は、長期に亘って安定しためっき性能を発揮できる。しかも、本発明めっき液は、非アンモニア系であるため、アンモニアの飛散による臭気の問題や、環境対策に配慮する必要もなく、また爆発性の窒化銀を生ずることもない。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an autocatalytic electroless silver plating solution and an electroless silver plating method.
[0002]
[Prior art]
Silver plating has been widely used in the decoration field, the electronics industry field, and the like for a long time. Most silver plating solutions used in the past contain cyan ions as a silver chelating agent. However, cyanide compounds are highly toxic and can be used in wastewater treatment, chemical management, safety management during work, etc. Care must be taken in handling. Therefore, a non-cyan type silver plating solution that does not contain a cyanide compound is desired.
[0003]
The non-cyan type silver plating solution has a problem in stability of the plating solution because silver is a noble metal and is easily decomposed in a bath to cause precipitation. Furthermore, since it is easy to substitute for materials such as copper, there is also a drawback that it is difficult to obtain an adhesive film.
[0004]
In recent years, several non-cyan silver plating solutions have been proposed. For example, taking electroplating as an example, Japanese Patent Publication No. 5-75837 discloses plating in which a sulfanilic acid derivative is blended with a plating solution containing a silver compound such as organic silver sulfonate, silver nitrate, silver chloride and potassium iodide. Liquid has been reported. However, this plating solution has a drawback in that it needs to contain a large amount of potassium iodide in order to maintain the stability and conductivity of the solution, and the cost is very high compared to a conventional cyan bath.
[0005]
Japanese Patent Application Laid-Open No. 7-166391 reports an electrolytic silver plating solution in which a surfactant is added to a plating solution containing an organic sulfonic acid silver salt, succinimide or a derivative thereof, a buffering agent, and the like. According to this plating solution, it is possible to form a gloss film, but the main chelate component is unstable and adaptable in the plating solution, has a narrow pH, is prone to hydrolysis, and has a shortcoming in that the bath life is short. is there.
[0006]
In addition, in the case of plating on a non-conductor with these electrolytic plating solutions, it is necessary to perform electroless silver plating after applying electroless plating treatment or the like to provide conductivity, which is disadvantageous economically and in time. I cannot deny that.
[0007]
Several reports have been made on self-catalyzed electroless silver plating solutions. For example, Japanese Patent Laid-Open No. 05-287543 reports an autocatalytic electroless silver plating solution using thiosulfate, thiocyanate, sulfite or the like as a chelating agent and potassium borohydride as a reducing agent. Yes. However, thiosulfate, sulfite and the like are easily oxidized by air or the like and are unstable. In addition, the complex formed is sensitive to light and it is difficult to obtain a stable solution.
[0008]
Japanese Patent Laid-Open No. 61-15986 reports a self-catalyzed electroless silver plating solution using a nitrogen compound such as ammonia or ethylenediamine as a chelating agent. However, nitrogen-based compounds may form explosive silver nitride, and ammonia, ethylenediamine, and the like need to pay attention to the working environment due to odor problems.
[0009]
[Problems to be solved by the invention]
The main object of the present invention is a non-cyanide, non-ammonia type self-catalyzed electroless silver plating solution that does not contain a cyanide compound, a nitrogen-based compound, etc. An electroless silver plating solution capable of forming a plating film is provided.
[0010]
[Means for Solving the Problems]
The present inventor has intensively studied to solve the problems of the prior art as described above. As a result, by using a water-soluble sulfur-containing organic compound having two monosulfide groups in the molecule as a chelating agent, silver plating having good stability and excellent physical properties without using cyan, ammonia, etc. The present inventors have found that a non-cyanide non-ammonia type autocatalytic electroless silver plating solution capable of forming a film can be obtained, and the present invention has been completed here.
[0011]
That is, the present invention provides the following autocatalytic electroless silver plating solution, electroless silver plating method, and silver-plated product.
1. An autocatalytic electroless silver plating solution comprising an aqueous solution containing (i) a water-soluble silver salt, (ii) a water-soluble sulfur-containing organic compound having two monosulfide groups in the molecule, and (iii) a reducing agent. .
2. Item 2. The electroless silver plating solution according to Item 1, wherein the water-soluble silver salt is at least one selected from silver sulfate, silver nitrate, and silver perchlorate.
3. A water-soluble sulfur-containing organic compound having two monosulfide groups in the molecule contains at least one water-soluble group selected from a hydroxyl group, a carboxyl group, a sulfonic acid group, an amino group, a phosphone group, and a mercapto group in the molecule. The compound according to Item 1 or 2, which is at least one selected from a compound having a divalent hydrocarbon group having 2 to 8 carbon atoms between two monosulfide groups, and a salt of the compound Electroless silver plating solution.
4). Any of the above items 1 to 3, wherein the reducing agent is at least one selected from a water-soluble aldehyde compound, a water-soluble hydrazine derivative, a borohydride compound, a hypophosphorous acid compound, a phosphorous acid compound, and an ascorbic acid compound. An electroless silver plating solution according to any one of the above.
5). (I) The water-soluble silver salt is 0.2 to 10 g / l in terms of the amount of silver metal, and (ii) the water-soluble sulfur-containing organic compound having two monosulfide groups in the molecule is based on the amount of silver ions. 5 to 20 times mol, and (iii) the reducing agent according to any one of the above items 1 to 4, comprising an aqueous solution containing an equivalent gram equivalent to 20 times gram equivalent of a water-soluble silver salt. Electrolytic silver plating solution.
6). The electroless silver plating solution according to any one of the above items 1 to 5, wherein the electroless silver plating solution has a pH of 1 to 14 and a solution temperature of 0 to 80 ° C, and an object to be plated is immersed in the silver plating solution. Method.
7). The electroless silver plating method according to item 6, wherein the electroless silver plating solution has a pH of 6 to 13 and a solution temperature of 10 to 60 ° C.
8). A silver-plated product in which a silver plating film is formed by the method of item 6 or 7 above.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The self-catalyzed electroless silver plating solution of the present invention comprises (i) a water-soluble silver salt, (ii) a water-soluble sulfur-containing organic compound having two monosulfide groups in the molecule, and (iii) a reducing agent. It consists of the aqueous solution to contain.
[0013]
The water-soluble silver salt to be blended in the plating solution of the present invention is not particularly limited as long as it is soluble in the plating solution and can obtain an aqueous solution having a predetermined concentration, but in particular, silver sulfate, silver nitrate, perchloric acid Inorganic silver salts such as silver are preferred in terms of good solubility. A silver compound can be used individually by 1 type or in mixture of 2 or more types.
[0014]
The blending amount of the water-soluble silver salt is preferably about 0.2 to 10 g / l, more preferably about 0.5 to 5 g / l as the amount of silver metal.
[0015]
When the amount of silver metal is in the above range, the plating solution has an appropriate deposition rate and good stability, and wasteful removal of the plating solution can be reduced.
[0016]
In the present invention, a water-soluble sulfur-containing organic compound having two monosulfide groups in the molecule is used as the silver chelating agent component. By compounding the water-soluble sulfur-containing organic compound, silver ions in the bath are sufficiently complexed, and the stability of the plating bath is improved. The sulfur-containing organic compound has two monosulfide groups in the molecule, and at least one water-soluble group selected from a hydroxyl group, a carboxyl group, a sulfonic acid group, an amino group, a phosphone group, and a mercapto group in the molecule. A compound in which a divalent hydrocarbon group having 2 to 8 carbon atoms is present between two monosulfide groups, an alkali metal salt, an ammonium salt, or the like of the compound is preferable. One or more water-soluble groups may be present in the molecule, but two or more water-soluble groups are preferably present. These water-soluble sulfur-containing organic compounds can be used singly or in combination of two or more.
[0017]
Preferable examples of the water-soluble sulfur-containing organic compound include compounds represented by the following general formula and salts thereof.
[0018]
X—R 1 —S—R 2 —S—R 3 —Y
(In the formula, R 1 and R 2 are the same or different and are each a linear or branched alkylene group having 1 to 5 carbon atoms, and R 3 is a linear or branched chain group having 2 to 8 carbon atoms. And the alkylene group, X and Y are the same or different and are a hydroxyl group, a carboxyl group, a sulfonic acid group, an amino group, a phosphone group or a mercapto group.
Specific examples of the water-soluble sulfur-containing organic compound include 1,2-bis (2-hydroxyethylthio) ethane, 2,2 ′-(ethylenedithio) diethanethiol, 1,4-bis (2-hydroxyethyl). Thio) butane, 3,3 ′-(propylenedithio) dipropionic acid, salts of these compounds (alkali metal salts, ammonium salts, etc.), and the like.
[0019]
These water-soluble sulfur-containing organic compounds can be used singly or in combination of two or more.
[0020]
The blending amount of the water-soluble sulfur-containing organic compound is preferably equimolar or more, more preferably 2-fold molar or more with respect to silver ions in the plating bath. If the amount of the water-soluble sulfur-containing organic compound is too small, the silver is not sufficiently complexed, so that the plating bath becomes unstable and the solution is liable to decompose. The upper limit of the blending amount can be up to the solubility of the sulfur-containing organic compound used. The larger the blending amount, the more stable the plating solution will be. Thus, a long time is required to obtain a predetermined amount of precipitated silver. Moreover, it is not preferable economically due to an increase in carry-out. For this reason, it is usually preferable to use a blending amount of up to about 20 moles with respect to silver ions.
[0021]
From the above, the blending amount of the water-soluble sulfur-containing organic compound is preferably equimolar to 20-fold mol, more preferably 2-fold mol to 20-fold mol, with respect to the silver ions in the plating bath.
[0022]
As the reducing agent, a water-soluble compound having the ability to reduce the water-soluble silver salt in the plating solution to metallic silver can be used. Examples of such reducing agents include water-soluble aldehyde compounds such as formalin, glyoxylic acid, hydroxybenzaldehyde, and reducing sugars (such as glucose and sucrose); water-soluble hydrazine derivatives such as hydrated hydrazine and semicarbazide; sodium borohydride and dimethylamine. Boron hydride compounds such as borane; hypophosphorous acid compounds such as hypophosphorous acid and hypophosphite; phosphorous acid compounds such as phosphorous acid and phosphite; ascorbine such as ascorbic acid and ascorbate An acid compound etc. are mentioned. A reducing agent can be used individually by 1 type or in mixture of 2 or more types.
[0023]
The blending amount of the reducing agent is preferably equal to or greater than an equivalent gram with respect to the water-soluble silver salt. If the blending amount is too small, the water-soluble silver salt is present in the plating solution in an unreacted manner, which is not economically preferable. The upper limit of the amount of the reducing agent can be up to the solubility of the reducing agent to be used. However, if a large amount of the reducing agent is added, the stability of the plating solution is adversely affected and economically undesirable. For this reason, it is desirable that the compounding amount of the reducing agent is about 20 times gram equivalent or less with respect to the water-soluble silver salt.
[0024]
In the electroless silver plating solution of the present invention, various additives can be further blended as necessary as long as they do not adversely affect the function of each component described above.
[0025]
The electroless silver plating solution of the present invention is obtained by dissolving the above-described components in water, and preferably by a method of adding a reducing agent to an aqueous solution in which a water-soluble silver salt and a water-soluble sulfur-containing compound are dissolved. Can be prepared.
[0026]
The electroless silver plating solution of the present invention is preferably used in the range of a solution temperature of about 0 to 80 ° C. When the temperature of the plating solution is low, the silver deposition rate is slow and a long time is required to obtain a predetermined silver deposition amount. On the other hand, if the liquid temperature is too high, it tends to cause a loss of the reducing agent due to the self-decomposition reaction and a decrease in bath stability. The plating solution of the present invention is particularly preferably used at a temperature of about 10 to 60 ° C. By setting the temperature within this temperature range, the stability of the plating solution is improved and an appropriate deposition rate is obtained.
[0027]
The pH of the plating solution is suitably about 1-14. If the pH is too low, there may be a loss of the reducing agent due to the autolysis reaction, or the reducing agent itself may not reach a potential at which the water-soluble silver salt can be reduced, while if the pH is too high, the reducing agent will be reduced. There is a risk that the plating solution may be decomposed due to excessive strength. In particular, when the pH of the plating solution is about 6 to 13, the stability of the plating solution is good and the deposition rate is moderate. The pH of the plating solution is usually adjusted to lower the pH by using an acid having the same anion part as that of the water-soluble silver salt, for example, sulfuric acid or water-soluble when silver sulfate is used as the water-soluble silver salt. When silver nitrate is used as the silver salt, nitric acid may be used, and when the pH is raised, alkali metal hydroxide, ammonia or the like may be used.
[0028]
In order to perform the plating treatment using the electroless silver plating solution of the present invention, an object to be plated may be immersed in a plating solution adjusted to the above-described solution temperature and pH value.
[0029]
There is no particular limitation on the material of the object to be plated that can form an electroless silver plating film with the electroless silver plating solution of the present invention, and a metal material, other various conductive materials, and non-conductive materials are used as the object to be plated. be able to.
[0030]
When a metal material is to be plated, it is usually sufficient to immerse the plating object directly in a plating solution after performing a pretreatment such as a degreasing process according to a conventional method.
[0031]
In order to perform a plating process on non-metallic materials such as ceramics and plastics, a pretreatment such as a degreasing process is performed, the object to be plated is activated, and then immersed in a plating solution. The activation treatment may be carried out in accordance with a conventional method. For example, a palladium catalyst (catalyst-accelerator method, sensitizing-activator method, etc.), an acidic stannous chloride solution, silver described in JP-A-10-3188 What is necessary is just to perform an activation process according to well-known conditions using a catalyst or a copper catalyst.
[0032]
The material on which the electroless silver plating film is formed by the above method can be used in various fields to which a silver plating film is conventionally applied. For example, it can be effectively used for applications such as electromagnetic shielding, ceramic capacitors, antibacterial materials, and the like.
[0033]
【The invention's effect】
The electroless silver plating solution of the present invention does not contain harmful cyanide compounds or nitrogenous compounds such as ammonia, and is a plating solution that is safe and easy to handle. The plating solution has good stability and an appropriate deposition rate. The formed silver plating film has good film properties such as adhesion, corrosion resistance, and wear resistance, and electrical characteristics. is there.
[0034]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
An electroless silver plating solution comprising an aqueous solution containing 0.17 g / l of silver nitrate, 10 g / l of 1,2-bis (2-hydroxyethylthio) ethane, and 8 g / l of hydrated hydrazine was prepared, and this was hydroxylated. The pH was adjusted to 10 using potassium.
[0035]
An alumina ceramic test piece (5 × 5 cm) was used as an object to be plated, and this was a catalyst containing Pd catalyst (trade name: Catalyst C, manufactured by Okuno Pharmaceutical Co., Ltd.) 50 ml / l and 35% hydrochloric acid 150 ml / l. It was immersed in the solution at 25 ° C. for 3 minutes, then immersed in a 10% aqueous sulfuric acid solution at 35 ° C. for 3 minutes, then immersed in the above electroless silver plating solution and subjected to electroless silver plating at 35 ° C. for 1 hour. . As a result, a smooth and matte dense silver plating film having a thickness of 1.2 μm was deposited, and no uneven appearance was observed on the surface of the silver plating film. Further, the plating solution was allowed to stand at room temperature for 4 weeks, and then the same plating test was performed. However, the plating solution showed good plating performance, and no pH variation or precipitation was observed.
(Example 2)
An electroless silver plating solution comprising an aqueous solution containing 0.31 g / l of silver sulfate, 15 g / l of 1,4-bis (2-hydroxyethylthio) butane, and 4 g / l of formaldehyde was prepared. To adjust the pH to 11.
[0036]
A previously degreased rolled copper plate (5 × 5 cm, thickness 0.2 mm) was used as an object to be plated, which was immersed in the electroless silver plating solution and subjected to electroless silver plating at 50 ° C. for 1 hour. As a result, a smooth and matte dense film having a thickness of 3 μm was deposited, and no uneven appearance was observed on the surface of the silver plating film. Further, the plating solution was allowed to stand at room temperature for 4 weeks, and then the same plating test was performed. However, the plating solution showed good plating performance, and no pH variation or precipitation was observed.
(Example 3)
An electroless silver plating solution consisting of an aqueous solution containing 0.34 g / l of silver nitrate, 20 g / l of 2,2 ′-(ethylenedithio) diethanethiol, and 10 g / l of sodium hypophosphite is prepared. The pH was adjusted to 10.5 using sodium oxide.
[0037]
An epoxy resin test piece (5 × 5 cm, thickness 1.8 mm) is used as the object to be plated, and this is an acidic stannous chloride containing 30 g / l stannous chloride dihydrate and 20 ml / l 35% hydrochloric acid. After being immersed in the solution at 25 ° C. for 3 minutes, it was immersed in the electroless silver plating solution and subjected to electroless silver plating at 50 ° C. for 1 hour. As a result, a smooth and matte dense film having a thickness of 2.8 μm was deposited, and no uneven appearance was observed on the surface of the silver plating film. Further, the plating solution was allowed to stand at room temperature for 4 weeks, and then the same plating test was performed. However, the plating solution showed good plating performance, and no pH variation or precipitation was observed.
(Comparative Example 1)
Contains 0.5 g / l of silver nitrate, 1.08 g / l of ethylenediamine, 3.78 g / l of Roselle salt (sodium potassium tartrate tetrahydrate), and 0.18 g / l of 3,5-diiodotyrosine. An electroless silver plating solution adjusted to pH 11.0 using sodium was prepared.
[0038]
An alumina ceramic test piece (5 × 5 cm, thickness 0.2 mm) activated in the same manner as in Example 1 was used as an object to be plated, which was immersed in the above plating solution and electroless silver plated at 30 ° C. for 1 hour. Went. As a result, a smooth and matte film having a thickness of 0.4 μm was deposited, but the plated film did not deposit on the entire test piece, and there were portions that were not plated. Furthermore, the plating solution gave off an ethylenediamine odor and required local exhaust equipment.
[0039]
Further, after the plating solution was allowed to stand at room temperature for 4 weeks, the same test was performed, but a change in pH was observed and precipitation of metallic silver was confirmed at the bottom of the plating tank.
(Comparative Example 2)
Ammonia water was added to 3.5 g of silver nitrate until the precipitate was dissolved, and 45 g / l of glucose was further added to make 1 liter of water to prepare a plating solution (silver mirror reaction solution).
[0040]
An alumina ceramic test piece activated in the same manner as in Example 1 was immersed in this plating solution, and electroless plating was performed at 25 ° C.
[0041]
After immersion of the test piece, the plating solution started to suspend after about 5 minutes, and after about 10 minutes, plating was deposited on the entire surface of the plating tank. The plating film was deposited on the entire test piece, but the film thickness was not measurable because the plating solution was decomposed.
[0042]
As can be seen from the above results, a stable and uniform silver plating film can be formed by using the autocatalytic electroless silver plating solution of the present invention. Moreover, the plating solution of the present invention can exhibit stable plating performance over a long period of time. In addition, since the plating solution of the present invention is non-ammonia, there is no need to consider odor problems due to scattering of ammonia and environmental measures, and no explosive silver nitride is produced.
Claims (7)
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| JP17866598A JP3937373B2 (en) | 1998-06-25 | 1998-06-25 | Self-catalyzed electroless silver plating solution |
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| JP17866598A JP3937373B2 (en) | 1998-06-25 | 1998-06-25 | Self-catalyzed electroless silver plating solution |
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| WO2013061773A1 (en) | 2011-10-27 | 2013-05-02 | 上村工業株式会社 | Reducing electroless silver plating solution and reducing electroless silver plating method |
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| JP4660800B2 (en) * | 2000-06-21 | 2011-03-30 | 石原薬品株式会社 | Electroless gold plating bath |
| JP4609705B2 (en) * | 2005-01-27 | 2011-01-12 | 石原薬品株式会社 | Silver plating bath for copper-based materials |
| KR101731675B1 (en) * | 2014-07-10 | 2017-05-02 | 삼성에스디아이 주식회사 | Electro-conductive carbon-ball, composition for forming solar cell comprising the same and method for preparing the same |
-
1998
- 1998-06-25 JP JP17866598A patent/JP3937373B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013061773A1 (en) | 2011-10-27 | 2013-05-02 | 上村工業株式会社 | Reducing electroless silver plating solution and reducing electroless silver plating method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000008174A (en) | 2000-01-11 |
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