JP3994295B2 - Method for preventing discoloration of copper or copper alloy material and copper or copper alloy material - Google Patents
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
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- H05K3/22—Secondary treatment of printed circuits
Description
【０００１】
【発明の属する技術分野】
本発明は、銅または銅合金材の変色防止方法に関するものである。特には、リードフレームやプリント配線板などの銅または銅合金素材の変色防止方法に関するものである。
【０００２】
【従来の技術】
近年、リードフレーム等の電子部品材料には高速部分銀めっきが行われることが多い。例えば、金製のボンディングワイヤーを使用してのボンディングに際しては、その接合性の向上のためにリードフレームのボンディング部分に高速部分銀めっきが施される。この高速部分銀めっきは、通常以下のようにして行われる。先ず、リードフレーム等の電子部品材料に用いられる基材を脱脂及び酸洗後、被覆される銀めっき被膜と基材との密着性を良くするため、銅ストライクめっきが施される。次に、銅ストライクめっきが施された基材は、水洗後基材を銀めっき液に浸漬した時に銀の置換析出を防止するための前処理を行った後、必要部分のみに高速電気銀めっきを行う。
【０００３】
ここで、銀の置換析出を防止するための前処理は、被めっき基材を銀置換析出防止液中に浸漬することによって実施されるのが普通であるが、このような前処理が必要な理由は次の通りである。
即ち、高速電気銀めっき液は銀濃度が高いため、これにより銀より卑な金属から成る基材を浸漬すると浸漬しただけで銀が大量に置換析出してしまう。この置換析出層は基材に対する密着性が極めて悪く、この上に銀を電気めっきしても密着性は改善されずにめっき被膜の剥がれ乃至は加熱時の膨れや変色を生じる原因となるので、上記置換析出層を極力抑えるべく前記前処理を施すことが必要となるのである。
なお、前処理で使用する処理液はこのような銀の置換防止剤を含有しており、基材表面に薄い置換防止被膜を形成することにより銀の置換を防止するもので、銀の置換防止剤としては例えば、チオカルボン酸もしくはその塩、２，２’−ジピリジル等の含窒素複素環化合物、２−チオバルビツル酸等のチオウレイレン基を環内に含む化合物等が用いられる。
電子部品材料として用いられる基材の部分的な電気銀めっきは上述のような要領で行われるが、この高速部分銀めっきを実施した場合、種々の理由により、前記基材の銀めっき不要部分にも銀がめっきされたり銀の析出が起きたりすることが多い。このような銀の異常析出部を放置しておくと、銀のマイグレーションが起こる可能性があり、電子材料の信頼性が低下する。従って、このような銀の異常析出部は、銀の剥離液を用いて選択的に溶解除去される。
【０００４】
このようにして製造された電子部品材料において、その運搬や貯蔵等を行っている際、異常析出部の銀を剥離した後に露出した銅または銅合金基材表面若しくは銅ストライクめっき処理を施した銅めっき面が変色するという問題点があることが認識されるようになった。なお、この変色は、特に銀を剥離した後に露出した銅または銅合金の露出面が運搬や貯蔵等のために重ねられた部位で著しかった。
この変色の原因については未だ明瞭な結論が出ていないが、変色部に酸化銅が生成していることが確認されていることから、
ａ）銀を剥離した直後なので該部分の銅または銅合金が活性である、
ｂ）銀と銅または銅合金との間に電位差が発生して銅または銅合金表面が活性となる、
等の理由によって銀を剥離した銅または銅合金の露出面部分が酸化されることが変色の原因であると考えられる。
何れにしろ、この銅または銅合金の酸化変色は、モールディング性、はんだ付け性等のアセンブリ特性に悪影響を与え、電子材料の信頼性を低下させることから大きな問題となるものであった。
【０００５】
この問題を解決するために、本出願人は先に、銀めっき不要部分に付着した銀を剥離した後の銀剥離面の銅の変色を防止するための処理液として、５−メチル−１Ｈ−ベンゾトリアゾール、５，６−ジメチル−１Ｈ−ベンゾトリアゾール及び２−メルカプトピリミジンから選ばれる１種または２種以上を含有する無機酸及び／または有機酸の酸性溶液からなり、更に必要に応じてｐＨ緩衝剤をも含有する銅変色防止液を提案した（特開平４−１６０１７３号）。
しかしながら、その後の検討により、上記銅変色防止液は通常環境化での変色防止効果には大変優れているものの、処理面の耐熱性がそれほど良好ではなく、例えば大気中で２８０℃程度に３０分間ほど加熱されると変色防止液で処理済みのものであっても銅または銅合金の露出面部分に剥離しやすい酸化被膜が形成されがちであることが明らかとなった。
【０００６】
このため、本出願人はさらに、“分子内に窒素又は硫黄あるいはこれら両方を含んでいて銅のインヒビターとして働く複素環状化合物”を含有する溶液に銅よりも貴な金属又はその塩を添加して成る、銅又は銅合金の変色防止液を提案した（特願平８−１２２３４３号）。この変色防止液を用いると、「銅よりも貴な金属」（代表的には銀）の置換被膜層が１０〜１０００Å程度の厚さで均一に薄く形成されるため銅又は銅合金は運搬・貯蔵環境から保護され変色が防止され、しかもこの「銅よりも貴な金属」の置換層被膜は耐熱性に富むため比較的高温の環境下に置かれた場合でも自身の酸化及び銅又は銅合金面の酸化を防止することができ酸化膜の剥離といった不都合を来すことはなかった。
ところが、上記の変色防止処理を行った場合には、変色防止処理直後の耐熱性は上がるものの、数ヶ月の放置後には著しく耐熱性が低下することが指摘された。
【０００７】
【発明が解決しようとする課題】
本発明は、耐変色性に優れると同時に、長期間の保存の後も耐熱性の低下がないような変色防止処理表面を得るための銅又は銅合金材の変色防止手段を確立することを目的とした。
【０００８】
【課題を解決するための手段】
本発明者は、上記目的を達成すべく鋭意研究を行った結果、銅または銅合金材の耐熱性低下は、高速部分銀めっきの前に行う銀置換防止剤、銀めっきの添加剤、銀剥離剤等に含まれる有機物が、最終工程まで残留することに起因することがわかった。即ち、銅または銅合金材の表面に吸着した有機被膜の大部分は高速部分銀めっき、不要部の銀剥離処理で除去されるが、銀めっきや銀剥離の条件によっては一部銅面に残留し、その上に銅変色防止被膜が形成されることになる。
そこで、銅の変色防止処理工程の前に残留する有機被膜を酸，アルカリで洗浄することにより、良好な銅変色防止被膜が形成され、良好な耐熱性、耐食性を示すことが明らかになった。
【０００９】
本発明は、この知見に基づいて、
１．銅または銅合金の表面に残留する銅変色防止機能を有する被膜以外の有機被膜を実質的に除去し、銅変色防止機能を有する被膜を表面に形成することを特徴とする銅または銅合金材の変色防止方法
２．銅または銅合金材に対して酸洗浄またはアルカリ洗浄を行った後、変色防止処理を行うことを特徴とする請求項１記載の銅または銅合金材の変色防止方法
３．銀置換防止処理とそれに引き続く銀めっきを行った銅または銅合金材に対して、残留する有機被膜を酸またはアルカリで洗浄・除去し、その後変色防止処理を行うことを特徴とする銅または銅合金材の変色防止方法
４．銅または銅合金材に対して、銅のインヒビターに銅よりも貴な金属またはその塩を添加して成る変色防止液による変色防止処理を施す前または後に酸洗浄またはアルカリ洗浄を行うことを特徴とする請求項１記載の銅または銅合金材の変色防止方法
５．銀置換防止処理とそれに引き続く銀めっきを行った銅または銅合金材に対して、銅のインヒビターに銅よりも貴な金属またはその塩を添加して成る変色防止液による変色防止処理を施す前または後に酸洗浄またはアルカリ洗浄を行うことを特徴とする請求項１記載の銅または銅合金材の変色防止方法
６．銅または銅合金の表面に残留する銅変色防止機能を有する被膜以外の有機被膜が実質的に除去され、銅変色防止機能を有する被膜が表面に形成されていることを特徴とする銅または銅合金材
を提供するものである。
【００１０】
【発明の実施の形態】
本発明における変色防止処理を施される基材としての「銅または銅合金材」とは、銅あるいは銅合金のみからなる無垢の材料はもちろんのこと、鉄または鉄合金、ニッケルまたはニッケル合金等といった金属に銅ストライクめっき処理を施したものなど、銅あるいは銅合金の表面が存在する材料の全てを包含するものである。
【００１１】
銅または銅合金材は、その表面に残留する銅変色防止機能を有する被膜以外の有機被膜を実質的に除去され、銅変色防止機能を有する被膜を表面に形成される。
表面に残留する銅変色防止機能を有する被膜以外の有機被膜を除去するために変色防止工程の前に酸洗浄またはアルカリ洗浄を行う。通常、銀置換防止処理とそれに引き続く銀めっきを行った後、酸洗浄またはアルカリ洗浄を行うが、酸洗浄またはアルカリ洗浄工程は、銀めっきの後、さらに銀剥離工程の後に行っても良いし、あるいは銀剥離工程の前に行っても構わない。
酸洗浄またはアルカリ洗浄は、主成分として、酸またはアルカリを０．１％以上、５０％以下、好ましくは１〜１０％含有する水溶液によって行えば良い。
酸としては、無機酸、有機酸のいずれも使用することが可能であり、例えば、塩酸、硫酸、リン酸、ホウ酸、スルホン酸、酢酸、クエン酸などが代表的に挙げられる。
アルカリとしては、水酸化カリウム、水酸化ナトリウム、シアン化カリウム、シアン化ナトリウム等の無機アルカリ、アミン等の有機アルカリが代表的に挙げられる。
酸またはアルカリ濃度が低すぎると効果がなく、濃度が高すぎると素材のエッチングが激しすぎるため好ましくない。
【００１２】
なお、洗浄液には必要に応じて、ｐＨ緩衝剤として、無機酸、有機酸またはその塩などを１〜５００ｇ／Ｌ、好ましくは１０〜１００ｇ／Ｌ添加しても良い。ｐＨ緩衝剤の濃度が低すぎると、ｐＨ緩衝能が低く、濃度が高すぎてもそれ以上の効果が期待できないため好ましくない。
【００１３】
また、必要に応じてアニオン系、カチオン系、ノニオン系界面活性剤のいずれかまたはその混合物を１μｇ／Ｌ〜１０ｇ／Ｌ、好ましくは１０μｇ／Ｌ〜１ｇ／Ｌ添加しても良い。界面活性剤の濃度が低すぎると、界面活性能が低く、濃度が高すぎてもそれ以上の効果が期待できないため好ましくない。
【００１４】
洗浄液のｐＨは特に限定されない。
洗浄液の液温は５〜８０℃、好ましくは１０〜５０℃とすべきである。液温が低すぎると洗浄能力が低く、液温が高すぎてもそれ以上の効果が期待できず、また、設備の腐食につながるため好ましくない。
【００１５】
酸洗浄またはアルカリ洗浄の方法は、銅または銅合金材を洗浄液に浸漬するかまたは、銅または銅合金材に洗浄液を散布（シャワー、スプレー等）することによって行えば良い。
【００１６】
酸洗浄またはアルカリ洗浄処理を行った銅または銅合金材は、その後、変色防止処理が施される。変色防止処理は、銅変色防止液に浸漬するかまたは銅変色防止液を銅または銅合金に散布（シャワー、スプレー等）することによって行う。銅変色防止液は、一般的なベンゾトリアゾール系の変色防止剤を含むもの等の他、特願平８−１２２３４３号に記載した“分子内に窒素又は硫黄あるいはこれら両方を含んでいて銅のインヒビターとして働く複素環状化合物”を含有する溶液に銅よりも貴な金属又はその塩を添加して成るもの、など公知の銅変色防止液のいずれを用いても構わない。
【００１７】
なお、銅または銅合金材に対して、「銅のインヒビターに銅よりも貴な金属またはその塩を添加して成る変色防止液」を用いる変色防止処理を施す場合には、酸洗浄またはアルカリ洗浄はその変色防止処理の後に行っても良い。これは、「銅のインヒビターに銅よりも貴な金属またはその塩を添加して成る変色防止液」を用いた変色防止処理を施した場合には表面に「銅よりも貴な金属」の置換被膜層が形成されることによって変色防止機能が付与されるが、この変色防止機能を有する置換被膜層は、通常の有機化合物による銅変色防止被膜とは異なり、酸洗浄またはアルカリ洗浄によっても銅または銅合金基材上に残留し銅変色防止機能を発揮することが可能だからである。
【００１８】
本発明の銅または銅合金材の変色防止方法においては、主に銀置換防止剤などに含まれ、基材表面に残留していた有機物被膜が酸洗浄またはアルカリ洗浄によって洗浄除去されるとともに変色防止処理によって良好な銅変色防止機能を有する被膜が形成されるため、不要有機物の残留に起因する耐熱性、耐食性の低下などを抑制することができる。
【００１９】
【実施例】
以下、実施例によって本発明を説明するが、本発明の範囲は実施例によって限定されるものではない。
厚さ０．１μmの銅ストライクめっきを施した「２５ｍｍ幅×４０ｍｍ×０．２ｍｍ厚」の銅合金（Cu:97.77%-Sn:2.0%-Ni:0.2%-P:0.03%）製基材を純水で水洗した後、銀置換防止剤である２−チオバルビツル酸を１００ｍｇ／Ｌ含むとともに、ｐＨが１０に調整された銀置換防止液に液温３０℃で１０秒間浸漬し、続いて純水水流で洗浄した。
その後、
ＫＡｇ（ＣＮ）2：１３０ｇ／Ｌ
Ｋ2ＨＰＯ4 ：１００ｇ／Ｌ
を含むとともにｐＨが８．５に調整された高速電気銀めっき液に浸漬して電流密度７０Ａ／ｄｍ2で１０秒間銀めっきを行った。
その後、銀めっきした基材を純水で洗浄してから、中央部（７ｍｍ×６ｍｍ）を除く他の部位の銀めっき層を市販の銀剥離液を用いて溶解除去し、再度純水で水洗した後、表１に記載の洗浄液に浸漬するかまたは表１に記載の洗浄液を基材表面に散布（シャワー）する処理を行った。
【００２０】
【表１】
さらに、純水で水洗した後、表１に記載の変色防止液に基材を１０秒間浸漬する変色防止処理を行った。
なお、変色防止剤として銅インヒビターに銅よりも貴な金属を添加して成る変色防止液を用いた場合については、該変色防止処理の前に酸洗浄を行った場合（実施例５）だけでなく該変色防止処理の後に酸洗浄を行った場合（実施例７）も併せて示した。
【００２２】
このような処理を行った各基材について、「３０分間加熱後、テープによるピールテストで銅酸化被膜が完全に剥離する温度」を調べて耐熱性の評価を行った。
なお、変色防止処理を行った後１２ヶ月放置した後に同じ試験を行い、長期間保管後の耐熱性を評価した。
また、変色防止処理を行った各基材を煮沸純水中に１０分間浸漬し、銅ストライクめっき部（剥離液によって銀めっき層を除去した部位）の変色を目視により判定し、耐変色性の評価を行った。ここで、「煮沸純水中に１０分間浸漬する」という前記熱処理は、大気中に放置した場合の加速試験として通常に行われている処理である。
【００２３】
なお、比較例として、酸洗浄またはアルカリ洗浄を行わずに実施例１，５，６と同じ変色防止処理を行った場合について、同様の試験を行い、その結果を評価した。これらの結果を表２に示す。
【００２４】
【表２】
表１、２に示した結果から、本発明に係る変色防止方法を施した場合には、非常に良好な耐熱性、耐変色性を示すと同時に、１２ヶ月放置後の耐熱性は変色防止処理直後と同じ高い耐熱性を示した。
これに対して、比較例では、同じ変色防止を用いて剤理を行った場合でも酸洗浄またはアルカリ洗浄を行った場合に比べて耐熱性が低く、また、１２ヶ月放置後の耐熱性は低下するという問題があった。
【００２６】
【発明の効果】
本発明の銅または銅合金材の変色防止方法を施すことにより表面に残留する不要有機被膜が実質的に除去され、銅変色防止被膜が表面に形成された銅または銅合金材は、非常に良好な耐熱性、耐変色性を示すと同時に、長期間保管後でも変色防止処理直後と同じ高い耐熱性を示す。従って、高速部分銀めっきが施された電子部品材料（例えばリードフレーム）等の信頼性向上に大きく寄与し得るなど、産業上有用な効果がもたらされる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for preventing discoloration of a copper or copper alloy material. In particular, the present invention relates to a method for preventing discoloration of copper or a copper alloy material such as a lead frame or a printed wiring board.
[0002]
[Prior art]
In recent years, high-speed partial silver plating is often performed on electronic component materials such as lead frames. For example, when bonding using a gold bonding wire, high-speed partial silver plating is applied to the bonding portion of the lead frame in order to improve the bonding property. This high-speed partial silver plating is usually performed as follows. First, after degreasing and pickling a base material used for an electronic component material such as a lead frame, copper strike plating is performed in order to improve the adhesion between the silver plating film to be coated and the base material. Next, the substrate subjected to copper strike plating is subjected to pretreatment to prevent silver substitution deposition when the substrate is immersed in a silver plating solution after washing, and then only high-speed electrosilver plating is applied to necessary portions. I do.
[0003]
Here, the pretreatment for preventing silver substitutional precipitation is usually carried out by immersing the substrate to be plated in a silver substitutional precipitation preventing liquid, but such a pretreatment is necessary. The reason is as follows.
That is, since the high-speed electrosilver plating solution has a high silver concentration, when a base made of a metal lower than silver is immersed, a large amount of silver is deposited and deposited just by immersion. This substitutional deposited layer has extremely poor adhesion to the substrate, and even if electroplating silver on this, the adhesion is not improved, causing peeling of the plating film or causing swelling and discoloration during heating, It is necessary to perform the pretreatment in order to suppress the substitutional precipitation layer as much as possible.
The treatment liquid used in the pretreatment contains such a silver substitution inhibitor, and prevents silver substitution by forming a thin substitution prevention film on the substrate surface. Examples of the agent include thiocarboxylic acids or salts thereof, nitrogen-containing heterocyclic compounds such as 2,2′-dipyridyl, and compounds containing a thioureylene group such as 2-thiobarbituric acid in the ring.
The partial electrosilver plating of the base material used as an electronic component material is performed as described above. However, when this high-speed partial silver plating is performed, for various reasons, the silver plating is not necessary on the base material. In many cases, silver is plated or silver is deposited. If such an abnormally precipitated portion of silver is left unattended, silver migration may occur, and the reliability of the electronic material is lowered. Accordingly, such an abnormally precipitated portion of silver is selectively dissolved and removed using a silver stripping solution.
[0004]
In the electronic component material manufactured in this way, when transporting or storing the copper, the copper or copper alloy substrate surface exposed after peeling off the silver in the abnormally precipitated portion or copper strike plating treatment It has been recognized that there is a problem that the plating surface is discolored. This discoloration was particularly remarkable at the site where the exposed surfaces of copper or copper alloy exposed after peeling off the silver were stacked for transportation or storage.
Although there is still no clear conclusion about the cause of this discoloration, it has been confirmed that copper oxide is generated in the discoloration part,
a) The copper or copper alloy in the part is active because it is immediately after peeling off the silver.
b) A potential difference occurs between silver and copper or a copper alloy, and the copper or copper alloy surface becomes active.
For example, the exposed surface portion of copper or copper alloy from which silver has been peeled is considered to be a cause of discoloration.
In any case, this oxidative discoloration of copper or copper alloy has been a serious problem because it adversely affects assembly characteristics such as molding properties and solderability and lowers the reliability of electronic materials.
[0005]
In order to solve this problem, the present applicant firstly used 5-methyl-1H- as a treatment liquid for preventing the discoloration of copper on the silver peeling surface after peeling the silver adhering to the silver plating unnecessary portion. It consists of an acidic solution of an inorganic acid and / or an organic acid containing one or more selected from benzotriazole, 5,6-dimethyl-1H-benzotriazole and 2-mercaptopyrimidine, and if necessary, pH buffering A copper discoloration preventing liquid that also contains an agent was proposed (Japanese Patent Laid-Open No. 4-160173).
However, as a result of subsequent studies, the copper discoloration preventing liquid is very excellent in the effect of preventing discoloration under normal environment, but the heat resistance of the treated surface is not so good, for example, in the atmosphere at about 280 ° C. for 30 minutes. It was revealed that an oxide film that tends to be peeled off tends to be formed on the exposed surface portion of copper or copper alloy even if it has been treated with the anti-discoloring liquid when heated to such an extent.
[0006]
For this reason, the applicant further added a metal or a salt thereof more precious than copper to a solution containing “a heterocyclic compound containing nitrogen or sulfur or both in the molecule and acting as an inhibitor of copper”. A copper or copper alloy discoloration prevention liquid was proposed (Japanese Patent Application No. 8-122343). By using this anti-discoloring solution, the replacement coating layer of “metal more precious than copper” (typically silver) is formed uniformly thin with a thickness of about 10 to 1000 mm, so that copper or copper alloy can be transported and Protected from the storage environment, prevented from discoloration, and this “metal noble than copper” replacement layer coating is highly heat resistant, so that it can oxidize itself and copper or copper alloys even when placed in a relatively high temperature environment The surface could be prevented from being oxidized, and there was no inconvenience such as peeling of the oxide film.
However, it has been pointed out that when the above-described discoloration prevention treatment is performed, the heat resistance immediately after the discoloration prevention treatment is increased, but the heat resistance is remarkably lowered after being left for several months.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to establish a means for preventing discoloration of copper or a copper alloy material for obtaining a discoloration-preventing surface that is excellent in discoloration resistance and has no deterioration in heat resistance even after long-term storage. It was.
[0008]
[Means for Solving the Problems]
As a result of diligent research to achieve the above object, the present inventor has found that the heat resistance of copper or copper alloy material is reduced before the high-speed partial silver plating, such as silver substitution inhibitor, silver plating additive, silver peeling It was found that the organic matter contained in the agent and the like was caused by remaining until the final step. That is, most of the organic film adsorbed on the surface of copper or copper alloy material is removed by high-speed partial silver plating and unnecessary part of the silver stripping process, but some of the organic film remains on the copper surface depending on the conditions of silver plating and silver stripping. And a copper discoloration prevention film is formed on it.
Thus, it has been clarified that by washing the organic film remaining before the copper discoloration preventing treatment step with an acid or alkali, a good copper discoloration preventing film is formed and exhibits good heat resistance and corrosion resistance.
[0009]
The present invention is based on this finding.
1. An organic film other than a film having a copper discoloration preventing function remaining on the surface of copper or a copper alloy is substantially removed, and a film having a copper discoloration preventing function is formed on the surface. 1. Method for preventing discoloration 2. The method for preventing discoloration of copper or copper alloy material according to claim 1, wherein the copper or copper alloy material is subjected to acid washing or alkali washing and then subjected to discoloration prevention treatment. A copper or copper alloy characterized by subjecting a copper or copper alloy material subjected to silver replacement prevention treatment and subsequent silver plating to washing / removing the remaining organic film with an acid or alkali, and then performing discoloration prevention treatment 3. Material discoloration prevention method The copper or copper alloy material is subjected to acid cleaning or alkali cleaning before or after being subjected to a discoloration prevention treatment with a discoloration prevention liquid obtained by adding a metal or a salt more noble than copper to a copper inhibitor. 4. A method for preventing discoloration of copper or a copper alloy material according to claim 1. Before applying a color change prevention treatment to a copper or copper alloy material subjected to silver substitution prevention treatment and subsequent silver plating by a color change prevention solution comprising a copper inhibitor added with a metal noble than copper or a salt thereof, or 5. A method for preventing discoloration of copper or copper alloy material according to claim 1, wherein acid cleaning or alkali cleaning is performed later. An organic coating other than a coating having a copper discoloration prevention function remaining on the surface of copper or a copper alloy is substantially removed, and a coating having a copper discoloration prevention function is formed on the surface. The material is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The “copper or copper alloy material” as the base material subjected to the discoloration prevention treatment in the present invention is not only a pure material consisting of copper or copper alloy, but also iron or iron alloy, nickel or nickel alloy, etc. It includes all materials having a copper or copper alloy surface, such as a metal subjected to copper strike plating.
[0011]
The organic film other than the film having a copper discoloration preventing function remaining on the surface of the copper or copper alloy material is substantially removed, and a film having a copper discoloration preventing function is formed on the surface.
In order to remove the organic film other than the film having a copper discoloration preventing function remaining on the surface, acid cleaning or alkali cleaning is performed before the discoloration preventing step. Usually, after performing silver replacement prevention treatment and subsequent silver plating, acid cleaning or alkali cleaning is performed, but the acid cleaning or alkali cleaning step may be performed after the silver plating and further after the silver peeling step, Or you may carry out before a silver peeling process.
The acid cleaning or alkali cleaning may be performed with an aqueous solution containing 0.1% or more and 50% or less, preferably 1 to 10% of acid or alkali as a main component.
As the acid, any of an inorganic acid and an organic acid can be used. For example, hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, sulfonic acid, acetic acid, citric acid and the like are representatively mentioned.
Typical examples of the alkali include inorganic alkalis such as potassium hydroxide, sodium hydroxide, potassium cyanide and sodium cyanide, and organic alkalis such as amines.
If the acid or alkali concentration is too low, there is no effect, and if the concentration is too high, etching of the material is too intense, which is not preferable.
[0012]
If necessary, the cleaning liquid may contain 1 to 500 g / L, preferably 10 to 100 g / L of an inorganic acid, an organic acid, or a salt thereof as a pH buffering agent. If the concentration of the pH buffering agent is too low, the pH buffering ability is low, and if the concentration is too high, no further effect can be expected.
[0013]
Further, if necessary, any one of anionic, cationic and nonionic surfactants or a mixture thereof may be added at 1 μg / L to 10 g / L, preferably 10 μg / L to 1 g / L. If the concentration of the surfactant is too low, the surfactant activity is low, and if the concentration is too high, no further effect can be expected, which is not preferable.
[0014]
The pH of the cleaning liquid is not particularly limited.
The temperature of the cleaning liquid should be 5 to 80 ° C, preferably 10 to 50 ° C. If the liquid temperature is too low, the cleaning ability is low, and if the liquid temperature is too high, no further effect can be expected, and this also leads to corrosion of the equipment.
[0015]
The acid cleaning or alkali cleaning method may be performed by immersing copper or a copper alloy material in a cleaning solution or by spraying a cleaning solution (shower, spray, etc.) on the copper or copper alloy material.
[0016]
The copper or copper alloy material that has been subjected to the acid cleaning or alkali cleaning treatment is then subjected to a discoloration prevention treatment. The discoloration preventing treatment is performed by immersing in a copper discoloration preventing liquid or by spraying (discharging, etc.) the copper discoloration preventing liquid onto copper or a copper alloy. The copper discoloration preventing liquid includes those containing a general benzotriazole-based discoloration preventing agent, etc., as described in Japanese Patent Application No. 8-122343, “a copper inhibitor containing nitrogen or sulfur in the molecule or both of them. Any known copper discoloration-preventing solution such as a solution obtained by adding a metal noble than copper or a salt thereof to a solution containing a heterocyclic compound that functions as “a heterocyclic compound” may be used.
[0017]
In addition, in the case of subjecting copper or a copper alloy material to a discoloration prevention treatment using “a discoloration prevention liquid obtained by adding a metal or a salt noble of copper to a copper inhibitor”, acid washing or alkali washing May be performed after the discoloration prevention treatment. This is because when the anti-discoloration treatment using “a discoloration prevention solution made by adding a metal or its salt noble than copper to a copper inhibitor” is performed, the surface is replaced with a “metal noble than copper”. The discoloration prevention function is imparted by the formation of the coating layer, but the replacement coating layer having this discoloration prevention function is different from a copper discoloration prevention film by a normal organic compound, and copper or This is because it can remain on the copper alloy substrate and exhibit a copper discoloration preventing function.
[0018]
In the method for preventing discoloration of the copper or copper alloy material of the present invention, the organic coating contained mainly in the silver substitution inhibitor and the like and remaining on the substrate surface is washed and removed by acid washing or alkali washing, and discoloration prevention is performed. Since a film having a good copper discoloration preventing function is formed by the treatment, it is possible to suppress a decrease in heat resistance, corrosion resistance, and the like due to residual unnecessary organic substances.
[0019]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, the scope of the present invention is not limited by an Example.
Base material made of copper alloy (Cu: 97.77% -Sn: 2.0% -Ni: 0.2% -P: 0.03%) with a thickness of 0.1μm and copper strike plating of 25μm width × 40mm × 0.2mm thickness After washing with pure water, it was immersed for 10 seconds at a liquid temperature of 30 ° C. in a silver replacement prevention solution containing 100 mg / L of 2-thiobarbituric acid, which is a silver replacement inhibitor, and having a pH adjusted to 10. Washed with a stream of water.
afterwards,
KAg (CN) 2 : 130 g / L
K 2 HPO 4 : 100 g / L
And silver plating was performed for 10 seconds at a current density of 70 A / dm 2 by dipping in a high-speed electrosilver plating solution having a pH adjusted to 8.5.
Then, after washing the silver-plated base material with pure water, the silver plating layer of the other part except the central part (7 mm × 6 mm) is dissolved and removed using a commercially available silver remover, and washed again with pure water. After that, the substrate was immersed in the cleaning liquid shown in Table 1 or sprayed (showered) on the surface of the substrate with the cleaning liquid shown in Table 1.
[0020]
[Table 1]
Further, after washing with pure water, a discoloration preventing treatment was performed in which the substrate was immersed in the discoloration preventing liquid shown in Table 1 for 10 seconds.
In the case of using a discoloration preventing liquid obtained by adding a metal nobler than copper to a copper inhibitor as a discoloration preventing agent, only when the acid cleaning was performed before the discoloration preventing treatment (Example 5). In addition, the case (Example 7) where acid washing was performed after the discoloration prevention treatment was also shown.
[0022]
About each base material which performed such a process, "the temperature which a copper oxide film peels completely by the peel test with a tape after heating for 30 minutes" was investigated, and heat resistance was evaluated.
In addition, after performing the discoloration prevention treatment, the same test was performed after leaving for 12 months, and the heat resistance after long-term storage was evaluated.
In addition, each base material that has been subjected to discoloration prevention treatment is immersed in boiling pure water for 10 minutes, and the discoloration of the copper strike plating part (the part from which the silver plating layer has been removed by the stripping solution) is visually determined to prevent discoloration resistance Evaluation was performed. Here, the heat treatment of “immersing in boiling pure water for 10 minutes” is a treatment that is normally performed as an acceleration test when left in the atmosphere.
[0023]
As a comparative example, the same test was performed for the case where the same discoloration prevention treatment as in Examples 1, 5, and 6 was performed without performing acid cleaning or alkali cleaning, and the results were evaluated. These results are shown in Table 2.
[0024]
[Table 2]
From the results shown in Tables 1 and 2, when the method for preventing discoloration according to the present invention is applied, it exhibits very good heat resistance and discoloration resistance. It showed the same high heat resistance as immediately after.
On the other hand, in the comparative example, the heat resistance is lower even when the chemical treatment is performed using the same discoloration prevention, and the heat resistance after being left for 12 months is lower than when the acid cleaning or the alkali cleaning is performed. There was a problem to do.
[0026]
【The invention's effect】
The copper or copper alloy material in which the unnecessary organic coating remaining on the surface is substantially removed by applying the method for preventing discoloration of the copper or copper alloy material of the present invention and the copper discoloration preventing coating is formed on the surface is very good. In addition to exhibiting excellent heat resistance and discoloration resistance, it exhibits the same high heat resistance as that immediately after discoloration prevention treatment even after long-term storage. Therefore, an industrially useful effect is brought about, such as being able to greatly contribute to improving the reliability of electronic component materials (for example, lead frames) subjected to high-speed partial silver plating.
Claims (6)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36660497A JP3994295B2 (en) | 1997-12-26 | 1997-12-26 | Method for preventing discoloration of copper or copper alloy material and copper or copper alloy material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36660497A JP3994295B2 (en) | 1997-12-26 | 1997-12-26 | Method for preventing discoloration of copper or copper alloy material and copper or copper alloy material |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11193482A JPH11193482A (en) | 1999-07-21 |
| JP3994295B2 true JP3994295B2 (en) | 2007-10-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP36660497A Expired - Fee Related JP3994295B2 (en) | 1997-12-26 | 1997-12-26 | Method for preventing discoloration of copper or copper alloy material and copper or copper alloy material |
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| JP4553870B2 (en) * | 2006-06-05 | 2010-09-29 | 株式会社メイクリーンお仏壇本舗 | Oil cleaning method |
| CN113373485A (en) * | 2021-04-19 | 2021-09-10 | 辉门环新（安庆）粉末冶金有限公司 | Powder metallurgy copper plating process |
| CN115161647B (en) * | 2022-07-13 | 2023-07-21 | 江苏富乐华半导体科技股份有限公司 | Method for improving oxidation of copper surface of copper-clad ceramic substrate after welding |
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