JP2004238658A - Surface treatment agent for silver and silver alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment agent for silver and a silver alloy, which prevents rust occurrence on the surfaces of silver and the silver alloy and gives adequate solderability to the surface, to provide a surface treatment method, and to provide a method for manufacturing a printed wiring board. <P>SOLUTION: The surface treatment agent for silver and the silver alloy essentially comprises at least one selected from imidazole compounds shown by the formulas in the Fig. 1 and Fig. 2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

（式中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４及びＲ_５は同一あるいは異なって水素原子、炭素原子１〜２０の直鎖状又は分岐状のアルキル基又はハロゲン原子を表す。ｎは０〜８の整数を表す。）
【００１５】
【化４】

（式中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４及びＲ_５は同一あるいは異なって炭素原子１〜２０の直鎖状又は分岐状のアルキル基又はハロゲン原子を表す。ｎは０〜８の整数を表す。）
（２）銅イオンを含有することを特徴とする前記（１）に記載の銀及び銀合金の表面処理剤。
（３）銅イオン及びハロゲンイオンを含有することを特徴とする前記（１）に記載の銀及び銀合金の表面処理剤。
（４）銅イオン及び又は鉄イオンとコンプレクサン化合物を含有することを特徴とする前記（１）に記載の銀及び銀合金の表面処理剤。
（５）前記（１）〜（４）の何れかに記載の表面処理剤が水溶液であって、該水溶液に接触させることを特徴とする銀及び銀合金の表面処理方法。
（６）前記（５）に記載の表面処理方法により耐食処理を行った後、はんだ付けを行うことを特徴とする銀めっき処理されたプリント配線板の製造方法である。
【００１６】
【発明の実施の形態】
本発明の実施において使用されるイミダゾール化合物は、化３及び又は化４で示されるものである。
化３で示される２−アリールイミダゾール化合物として、例えば、２−フェニルイミダゾール、２−トルイルイミダゾール、２−（４−クロロフェニル）イミダゾール、２−フェニル−４−ベンジルイミダゾール、２−フェニル−４−ベンジル−５−メチルイミダゾール、２，４−ジフェニルイミダゾール、２−（４−クロロフェニル）−４−フェニルイミダゾール、２−（２，４−ジクロロフェニル）−４−フェニルイミダゾール、２−フェニル−４−（４−ブロモフェニル）イミダゾール、２，４，５−トリフェニルイミダゾール等が挙げられる。
【００１７】
化４で示される２−アラルキルベンズイミダゾール化合物として、２−ベンジルベンズイミダゾール、２−（２−フェニルエチル）ベンズイミダゾール、２−（５−フェニルペンチル）ベンズイミダゾール、２−（３−フェニルプロピル）−５−メチルベンズイミダゾール、２−（４−クロロベンジル）ベンズイミダゾール、２−（２−メチル−４−クロロベンジル）ベンズイミダゾール、２−（２，４−ジクロロベンジル）ベンズイミダゾール、２−（３，４−ジクロロベンジル）ベンズイミダゾール等が挙げられる。
これらのイミダゾール化合物の添加量は、表面処理剤に対して０．０５〜１０重量％、好ましくは０．１〜５重量％の範囲である。
【００１８】
本発明の表面処理剤には、イミダゾール化合物の皮膜形成速度の促進のために、銅イオン、ハロゲンイオン、コンプレクサン化合物及び鉄イオンを添加することによって、所望の成膜速度に調整する事ができる。
【００１９】
本発明の実施において使用される代表的な銅化合物としては、酢酸銅、塩化銅、臭化銅、水酸化銅、リン酸銅、硫酸銅、硝酸銅等が挙げられ、それらの添加量は、表面処理剤に対して０．００１〜１０重量％、好ましくは、０．０１〜５重量％の範囲である。
銅イオンを添加することにより、銀及び銀合金の表面へのイミダゾール化合物の化成皮膜形成速度を著しく速めることができる。
【００２０】
本発明の実施において、鉄イオンを供給するのに好適な鉄化合物の代表的なものとして、塩化鉄、臭化鉄、硝酸鉄、硫酸鉄、過塩素酸鉄、硫酸アンモニウム鉄、クエン酸鉄アンモニウム、蓚酸鉄アンモニウム、クエン酸鉄、２−エチルヘキサン鉄、フマル酸鉄、乳酸鉄、蓚酸鉄等が挙げられる。鉄化合物は表面処理剤に対して、０．０００１〜５重量％の割合、好ましくは０．００１〜１重量％の割合で添加すればよい。
【００２１】
本発明の実施において、ハロゲンイオンはイミダゾール化合物の化成皮膜を銀及び銀合金の表面に均一に形成させる効果がある。ハロゲンイオン源は、特に規制されるものはなく、塩化アンモニウムなどのハロゲン化アンモニウム塩、臭化カリウム等のハロゲン化カリウム塩、ヨウ化ナトリウム等のハロゲン化ナトリウム塩、塩化銅などのハロゲン化銅塩などを用いることができる。ハロゲン化塩の添加量は、表面処理剤に対して０．００１〜１０重量％の割合、好ましくは、０．００５〜５重量％である。
【００２２】
本発明の実施において使用されるコンプレクサン化合物の代表的なものとしては、イミノ二酢酸（ＩＤＡ）、ニトリロ三酢酸（ＮＴＡ）、エチレンジアミン四酢酸（ＥＤＴＡ）、ジエチレントリアミン五酢酸（ＤＴＰＡ）、トリエチレンテトラミン六酢酸（ＴＴＨＡ）、１，２−ジアミノシクロヘキサン四酢酸（ＣｙＤＴＡ）、グリコールエーテルジアミン四酢酸（ＧＥＤＴＡ）、Ｎ，Ｎ−ビス（２−ヒドロキシベンジル）エチレンジアミン二酢酸（ＨＢＥＤ）、エチレンジアミン二プロピオン酸（ＥＤＤＰ）、エチレンジアミン二酢酸（ＥＤＤＡ）、ジアミノプロパノール四酢酸（ＤＴＰＡ−ＯＨ）、ヘキサメチレンジアミン四酢酸（ＨＤＴＡ）、ヒドロキシエチルイミノ二酢酸（ＨＩＤＡ）、ヒドロキシエチルエチレンジアミン四酢酸（ＥＤＴＡ−ＯＨ）、ジアミノプロパン四酢酸（Ｍｅｔｈｙｌ−ＥＤＴＡ）、ニトリロ三プロピオン酸（ＮＴＰ）、エチレンジアミンテトラキスメチレンホスホン酸（ＥＤＴＰＯ）、ニトリロトリスメチレンホスホン酸（ＮＴＰＯ）等とこれらの塩類が挙げられる。
前記コンプレクサン化合物は、上記から選ばれる２種類以上を併用してもよい。コンプレクサン化合物の添加量は、鉄イオン（モル濃度）又は銅イオン（モル濃度）あるいは鉄イオンと銅イオンの合計（モル濃度）に対して、１〜１０倍モルの割合、好ましくは１〜５倍モルの割合で表面処理剤に添加すればよい。
【００２３】
イミダゾール化合物を水溶液化するに当っては、有機酸又は無機酸を用いたり、少量の有機溶媒を併用することもできる。この際、用いられる有機酸としては、ギ酸、酢酸、プロピオン酸、酪酸、ヘプタン酸、カプリル酸、カプリン酸、ラウリル酸、グリコール酸、乳酸、アクリル酸、安息香酸、パラニトロ安息香酸、パラトルエンスルホン酸、サリチル酸、ピクリン酸、シュウ酸、コハク酸、マレイン酸、フマール酸、酒石酸、アジピン酸等であり、無機酸としては、塩酸、燐酸、硫酸、硝酸等である。酸濃度は水溶液に対して０．０１〜４０重量％、好ましくは０．２〜２０重量％の範囲である。
【００２４】
また、この際に用いられる有機溶媒としては、メタノール、エタノール、イソプロピルアルコールなどの低級アルコール類や、アセトン、Ｎ，Ｎ−ジメチルホルムアミド等の水と混和させることができるものである。
ｐＨ緩衝剤として、前記の有機酸又は無機酸の他に、アンモニアあるいはアミン類、水酸化ナトリウム、炭酸ナトリウム等のアルカリ塩類を添加してもよい。
【００２５】
本発明の表面処理剤は、液温１０〜７０℃、接触時間１秒〜１０分間の条件で、銀又は銀合金と接触させればよい。また、その接触方法としては、浸漬、噴霧又は塗布するなど、何れの方法によることもできる。
【００２６】
【作用】
上記した処理方法によれば、銀及び銀合金の表面に化３又は化４で示されるイミダゾール化合物を主体とする化成皮膜が形成される。この化成皮膜は、銀及び銀合金の表面を長期間保護すると共に、後工程のはんだ付け時のはんだ付け性を良好なものとすることができる。
【００２７】
【実施例】
以下、本発明を実施例及び比較例によって具体的に説明するが、本発明はこれらに限定されるものではない。
なお、実施例及び比較例で使用したイミダゾール化合物ならびに評価試験方法は次のとおりである。
【００２８】
［イミダゾール化合物］
・２、４−ジフェニルイミダゾール：特開平７−２４３０５３号公報に記載の方法により合成した。
・２−（２，４−ジクロロベンジル）−ベンズイミダゾール：特開平７−５４１６９号公報に記載の方法に準拠して合成した。
・２−メルカプトベンズイミダゾール（和光純薬工業社製、試薬）
・２−オクチル−５−メチルベンズイミダゾール：特開平４−９９２８５号公報に記載されている方法により合成した。
・２−ウンデシル−４−メチルイミダゾール：日本化学雑誌，８９巻，７８０頁（１９６８年）に記載の方法により合成した。
・２−（４−クロロベンジル）ベンズイミダゾール：特開平７−５４１６９号公報に記載の方法により合成した。
【００２９】
［耐食試験］
プリント配線板（ガラスエポキシ樹脂製片面銅張積層板、銅箔厚さ３５μｍ、基板サイズ：縦６０ｍｍ×横５０ｍｍ×厚さ１．６ｍｍ）の銅表面を予め銀めっきし、所定の液温に保持した表面処理剤に所定時間浸漬し、次いで水洗、乾燥して厚さ約０．０２〜０．３μｍの化成皮膜を形成させた試験基板を作成した。
得られた試験基板を、温度２５℃／相対湿度８０％に設定した密閉容器中に放置し、ガス濃度が１ｐｐｍの硫化水素雰囲気下で２４時間曝露し、銀めっき表面の変色を目視にて観察した。この変色の度合いから防食効果を評価し、表面の変色が無かったものを○（良好）、表面が黒色に変色したものを×（不良）と判定した。
【００３０】
［はんだ付け性試験］
プリント配線板（ガラスエポキシ樹脂製片面銅張積層板、銅箔厚さ３５μｍ、基板サイズ：縦５０ｍｍ、横５０ｍｍ、厚さ１．６ｍｍ、回路パターン：導体幅０．８０ｍｍ、長さ２０ｍｍ、導体間隔１．０ｍｍ、導体部１０本）の銅表面を予め銀めっきし、所定の液温に保持した表面処理剤に所定時間浸漬し、次いで水洗、乾燥して厚さ約０．０２〜０．３０μｍの化成皮膜を形成させた試験基板を作成した。
前記の耐食試験の方法で硫化水素ガスを曝露させた試験基板を、赤外線リフロー装置（製品名：ＭＵＬＴＩ−ＰＲＯ ３０６、Ｖｉｔｒｏｎｉｃｓ社製）を用いて、ピーク温度が２５０℃であるリフロー加熱を１回行った。その後、開口幅１．２０ｍｍ、厚み１５０μｍのメタルマスクを使用して、導体の中央部にクリームはんだを印刷し、前記条件でリフロー加熱を行い、はんだ付けを行った。該試験基板について、導体上に濡れ広がったはんだの長さを測定した。また、硫化水素ガスを曝露させない試験基板についても同様にして、はんだ付けを行い、はんだの長さを測定した。
はんだ付け性の評価については、はんだの長さが長い程、はんだ付け性が良好なものと判定した。
なお、クリームはんだは、錫−銀−銅（組成：９５．６５／３．０／０．５重量％）系無鉛クリームはんだ（商品名：Ｍ７０５−２２１ＢＭ５−４２−１１、千住金属工業（株）製）を使用した。
【００３１】
〔実施例１〕
水に対して、２、４−ジフェニルイミダゾールを０．２５重量％、酢酸を９．０重量％の濃度で溶解させ、アンモニア水でｐＨ４．０に調整した表面処理剤を調製した。該表面処理剤に、予め銀めっきした試験基板を４０℃で６０秒間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３２】
〔実施例２〕
水に対して、２、４−ジフェニルイミダゾールを０．２５重量％、酢酸を９．０重量％、塩化鉄（ＩＩＩ）・六水和物を０．０４３重量％（Ｆｅイオン＝１５０ｐｐｍ）、酢酸銅一水和物を０．０１６重量％（Ｃｕイオン＝５０ｐｐｍ）、エチレンジアミン四酢酸・二ナトリウム・二水和物を１重量％の濃度で溶解させ、アンモニア水でｐＨ４．０に調整した表面処理剤を調製した。該表面処理剤に、予め銀めっきした試験基板を４０℃で２分間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３３】
〔実施例３〕
水に対して、２−（２，４−ジクロロベンジル）−ベンズイミダゾールを０．１５重量％、酢酸を２０重量％、酢酸銅を０．０５重量％の濃度で溶解させ、アンモニア水でｐＨ３．５に調整した表面処理剤を調製した。該表面処理剤に、予め銀めっきした試験基板を４０℃で５分間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３４】
〔比較例１〕
メタノールに対して、２−メルカプトベンズイミダゾールを０．２５重量％の濃度で溶解させた表面処理剤を調製し、該表面処理剤に予め銀めっきした試験基板を室温で３０秒間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３５】
〔比較例２〕
水に対して、２−オクチル−５−メチルベンズイミダゾールを０．２５重量％、酢酸を５．０重量％、塩化銅を０．０５重量％の濃度で溶解させ、アンモニア水でｐＨ３．０に調整した表面処理剤を調製した。該表面処理剤に、予め銀めっきした試験基板を４０℃で６０秒間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３６】
〔比較例３〕
水に対して、２−ウンデシル−４−メチルイミダゾールを１．０重量％、酢酸を１．５重量％、塩化銅を０．０５重量を％の濃度で溶解させ、アンモニア水でｐＨ４．３に調整した表面処理剤を調製した。該表面処理剤に、予め銀めっきした試験基板を４０℃で６０秒間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３７】
〔比較例４〕
水に対して、２−（４−クロロベンジル）ベンズイミダゾールを０．１重量％、酢酸を３．５重量％、塩化銅を０．０５重量％の濃度で溶解させ、アンモニア水でｐＨ２．６に調整した表面処理剤を調製した。該表面処理剤に、予め銀めっきした試験基板を４０℃で６０秒間浸漬した後、取り出して水洗、水切り後、乾燥して防食処理を行った。
得られた試験基板を、耐食試験及びはんだ付け性試験に供した。これらの試験結果は、表１に示したとおりであった。
【００３８】
【表１】

【００３９】
表１に示した試験結果によれば、本発明の表面処理剤はプリント配線板に施した銀めっきの表面の防食効果に優れ、また銀めっきの表面にはんだ付けを行った場合には、はんだ付け性が良好なものと認められる。
【００４０】
【発明の効果】
本発明によれば、銀及び銀合金の表面を防食することができ、銀及び銀合金の表面のはんだ付け性を良好なものとすることができるので、産業上利用価値の高いものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface treatment agent for silver and a silver alloy, a surface treatment method, and a method for producing a printed wiring board. More specifically, the surface of silver and a silver alloy is subjected to a rust-proof treatment, and the surface of the silver and silver alloy is soldered. The surface treatment agent of the present invention is intended to improve the attachment property, and is also suitable as a treatment for sealing a pinhole of a silver plating film.
[0002]
[Prior art]
Since silver is a good conductor of electricity and heat, silver plating is widely performed on terminal surfaces of electronic components. For example, a silver plating layer is provided on a copper pattern of a printed wiring board, and a connector or lead frame, which is a connection part for electronic equipment, is provided with a copper or nickel base plating on a surface of brass or phosphor bronze, and further over the surface. Is silver plated.
However, silver plating films are easily corroded, and silver is chemically reacted with sulfur-based compounds even when left in air containing a small amount of sulfur-based compound gas such as mercaptans, sulfur dioxide, and hydrogen sulfide. There is a problem that it is corroded and turns brown or blue-black, causing an increase in the electrical resistance value of the silver-plated surface and a decrease in solderability, and further impairing the appearance of the silver-plated surface.
[0003]
In order to solve such problems, various surface treatment agents containing an imidazole compound have been studied.
[0004]
For example, Patent Literature 1 discloses a heat-resistant pre-flux that prevents rust on a copper or copper alloy circuit portion of a printed wiring board, improves wettability, spreadability, and solderability of a low-melting cream solder; Surface treatment agents containing various benzimidazole compounds as rust inhibitors such as zinc and the like have been proposed.
Patent Literature 2 discloses a benzimidazole compound for performing electroplating of a noble metal such as gold, silver, rhodium, and palladium by sealing a pinhole in which a noble metal plating film is generated and suppressing corrosion of the film. It has been proposed to use nitrogen-containing cyclic compounds such as
Patent Document 3 exemplifies undecyl imidazole, 2- (p-chlorobenzyl) benzimidazole, and the like as metal discoloration inhibitors. These discoloration inhibitors are added to a plating solution, or these discoloration inhibitors are added after plating. A method for preventing discoloration of metal by treating with a solution containing
However, these imidazole compounds have insufficient rust-preventing effects on silver and silver alloys.
[0005]
In Patent Document 4, as a method for enhancing the solderability of the surface, the surface before soldering is subjected to displacement plating of silver using a solution containing a soluble source of silver ions and an acid, an oxidizing agent and an imidazole compound, and A method of directly soldering the silver plating has been proposed. However, the immersion silver plating film obtained from the imidazole-containing plating bath has an effect that the brightness is greater, smoother, and more adherent than the immersion silver coating film plated from the imidazole-free bath. There is no mention of silver corrosion protection.
[0006]
Patent Document 5 discloses, as a means for improving the solderability of copper and a copper alloy, a surface treatment of copper and a copper alloy which is brought into contact with an aqueous solution containing silver ions and then brought into contact with an aqueous solution containing various imidazole compounds. A method is disclosed.
However, there is no description about silver corrosion prevention, which is different from the technical idea of the present invention.
[0007]
[Patent Document 1]
JP-A-5-287563 (page 14)
[0008]
[Patent Document 2]
JP-A-5-31492 (pages 2-3)
[0009]
[Patent Document 3]
JP-A-8-255968 (page 8)
[0010]
[Patent Document 4]
JP-A-10-8262 (page 4)
[0011]
[Patent Document 5]
JP-A-2002-105662 (pages 3 and 4)
[0012]
[Problems to be solved by the invention]
The present invention has been made in view of such a problem, and a surface treatment agent for silver and a silver alloy, which prevents rust on the surface of silver and a silver alloy and improves the solderability of the surface. It is an object to provide a processing method and a method for manufacturing a printed wiring board.
[0013]
[Means for Solving the Problems]
The present inventors have conducted various tests in order to solve the above-mentioned problems, and as a result, by performing anticorrosion treatment on the surface of silver and silver alloy with a surface treatment agent containing a specific imidazole as an essential component, It has been found that the object of the present invention can be achieved, and the present invention has been completed.
That is, the present invention provides (1) a surface treating agent for silver and silver alloys, which comprises, as an essential component, at least one selected from imidazole compounds represented by Chemical Formula 3 or Chemical Formula 4.
[0014]
Embedded image

(Wherein, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are the same or different and each represent a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms or a halogen atom. N is 0 Represents an integer of to 8)
[0015]
Embedded image

(In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are the same or different and represent a linear or branched alkyl group having 1 to 20 carbon atoms or a halogen atom. Represents an integer.)
(2) The surface treating agent for silver and silver alloy according to the above (1), which contains a copper ion.
(3) The surface treating agent for silver and silver alloys according to the above (1), comprising a copper ion and a halogen ion.
(4) The surface treating agent for silver and silver alloys according to (1), which contains a copper ion and / or iron ion and a complexan compound.
(5) A surface treatment method for silver and silver alloys, wherein the surface treatment agent according to any one of the above (1) to (4) is an aqueous solution, and is brought into contact with the aqueous solution.
(6) A method of manufacturing a silver-plated printed wiring board, which comprises performing a corrosion-resistant treatment by the surface treatment method described in the above (5), and then performing soldering.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The imidazole compound used in the practice of the present invention is represented by Chemical Formula 3 and / or Chemical Formula 4.
Examples of the 2-arylimidazole compound represented by Chemical Formula 3 include, for example, 2-phenylimidazole, 2-toluylimidazole, 2- (4-chlorophenyl) imidazole, 2-phenyl-4-benzylimidazole, 2-phenyl-4-benzyl- 5-methylimidazole, 2,4-diphenylimidazole, 2- (4-chlorophenyl) -4-phenylimidazole, 2- (2,4-dichlorophenyl) -4-phenylimidazole, 2-phenyl-4- (4-bromo Phenyl) imidazole, 2,4,5-triphenylimidazole and the like.
[0017]
As 2-aralkylbenzimidazole compounds represented by Chemical formula 4, 2-benzylbenzimidazole, 2- (2-phenylethyl) benzimidazole, 2- (5-phenylpentyl) benzimidazole, 2- (3-phenylpropyl)- 5-methylbenzimidazole, 2- (4-chlorobenzyl) benzimidazole, 2- (2-methyl-4-chlorobenzyl) benzimidazole, 2- (2,4-dichlorobenzyl) benzimidazole, 2- (3 4-dichlorobenzyl) benzimidazole and the like.
The addition amount of these imidazole compounds is in the range of 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the surface treatment agent.
[0018]
The surface treatment agent of the present invention can be adjusted to a desired film formation rate by adding a copper ion, a halogen ion, a complexan compound and an iron ion in order to accelerate the film formation rate of the imidazole compound. .
[0019]
Typical copper compounds used in the practice of the present invention include copper acetate, copper chloride, copper bromide, copper hydroxide, copper phosphate, copper sulfate, copper nitrate, and the like, and the added amount thereof is It is in the range of 0.001 to 10% by weight, preferably 0.01 to 5% by weight, based on the surface treatment agent.
By adding copper ions, the rate of forming a chemical conversion film of an imidazole compound on the surface of silver or a silver alloy can be remarkably increased.
[0020]
In the practice of the present invention, typical iron compounds suitable for supplying iron ions include iron chloride, iron bromide, iron nitrate, iron sulfate, iron perchlorate, iron ammonium sulfate, iron ammonium citrate, Examples thereof include iron ammonium oxalate, iron citrate, iron 2-ethylhexane, iron fumarate, iron lactate, and iron oxalate. The iron compound may be added at a ratio of 0.0001 to 5% by weight, preferably 0.001 to 1% by weight, based on the surface treatment agent.
[0021]
In the practice of the present invention, halogen ions have an effect of forming a chemical conversion film of an imidazole compound uniformly on the surface of silver and a silver alloy. There are no particular restrictions on the halogen ion source, and ammonium halide salts such as ammonium chloride, potassium halide salts such as potassium bromide, sodium halide salts such as sodium iodide, and copper halide salts such as copper chloride. Etc. can be used. The amount of the halide salt to be added is 0.001 to 10% by weight, preferably 0.005 to 5% by weight, based on the surface treating agent.
[0022]
Representative of the complexan compounds used in the practice of the present invention include iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetramine Hexacetic acid (TTHA), 1,2-diaminocyclohexanetetraacetic acid (CyDTA), glycol etherdiaminetetraacetic acid (GEDTA), N, N-bis (2-hydroxybenzyl) ethylenediaminediacetic acid (HBED), ethylenediaminedipropionic acid ( EDDP), ethylenediaminediacetic acid (EDDA), diaminopropanoltetraacetic acid (DTPA-OH), hexamethylenediaminetetraacetic acid (HDTA), hydroxyethyliminodiacetic acid (HIDA), hydroxyethylethylenediaminetetraacetic acid ( DTA-OH), diaminopropane tetraacetic acid (Methyl-EDTA), nitrilotriacetic propionic acid (NTP), ethylene diamine tetrakis methylene phosphonic acid (EDTPO), these salts can be mentioned and the like nitrilotris methylene phosphonic acid (NTPO).
As the complexan compound, two or more kinds selected from the above may be used in combination. The added amount of the complexan compound is 1 to 10 times mol, preferably 1 to 5 times, relative to iron ion (molar concentration) or copper ion (molar concentration) or the total (molar concentration) of iron ion and copper ion. What is necessary is just to add to a surface treating agent in the ratio of 2 times mol.
[0023]
In converting the imidazole compound into an aqueous solution, an organic acid or an inorganic acid can be used, or a small amount of an organic solvent can be used in combination. In this case, as the organic acid used, formic acid, acetic acid, propionic acid, butyric acid, heptanoic acid, caprylic acid, capric acid, lauric acid, glycolic acid, lactic acid, acrylic acid, benzoic acid, paranitrobenzoic acid, paratoluenesulfonic acid , Salicylic acid, picric acid, oxalic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, adipic acid and the like, and inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid and the like. The acid concentration is in the range of 0.01 to 40% by weight, preferably 0.2 to 20% by weight, based on the aqueous solution.
[0024]
The organic solvent used at this time is a solvent that can be mixed with lower alcohols such as methanol, ethanol and isopropyl alcohol, and water such as acetone and N, N-dimethylformamide.
As the pH buffer, ammonia or an alkali salt such as an amine, sodium hydroxide, or sodium carbonate may be added in addition to the organic acid or the inorganic acid.
[0025]
The surface treatment agent of the present invention may be brought into contact with silver or a silver alloy under the conditions of a liquid temperature of 10 to 70 ° C and a contact time of 1 second to 10 minutes. In addition, any method such as immersion, spraying, or coating can be used as the contact method.
[0026]
[Action]
According to the above-described treatment method, a chemical conversion film mainly containing an imidazole compound represented by Chemical Formula 3 or Chemical Formula 4 is formed on the surface of silver and a silver alloy. This chemical conversion film can protect the surface of silver and silver alloy for a long period of time and can improve the solderability at the time of soldering in a later step.
[0027]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
In addition, the imidazole compound used in the Example and the comparative example and the evaluation test method are as follows.
[0028]
[Imidazole compound]
-2,4-diphenylimidazole: synthesized according to the method described in JP-A-7-243053.
-2- (2,4-dichlorobenzyl) -benzimidazole: synthesized according to the method described in JP-A-7-54169.
・ 2-mercaptobenzimidazole (Wako Pure Chemical Industries, Ltd., reagent)
-2-octyl-5-methylbenzimidazole: synthesized by the method described in JP-A-4-99285.
-2-undecyl-4-methylimidazole: synthesized by the method described in Nippon Kagaku Magazine, Vol. 89, p. 780 (1968).
-2- (4-chlorobenzyl) benzimidazole: synthesized according to the method described in JP-A-7-54169.
[0029]
[Corrosion resistance test]
The copper surface of a printed wiring board (single-sided copper-clad laminate made of glass epoxy resin, copper foil thickness 35 μm, board size: length 60 mm × width 50 mm × thickness 1.6 mm) is previously silver-plated and maintained at a predetermined liquid temperature. The test substrate was immersed in the surface treatment agent for a predetermined time, then washed with water and dried to form a chemical conversion film having a thickness of about 0.02 to 0.3 μm.
The obtained test substrate was left in a closed container set at a temperature of 25 ° C. and a relative humidity of 80%, exposed to a hydrogen sulfide atmosphere having a gas concentration of 1 ppm for 24 hours, and visually observed for discoloration of the silver plating surface. did. The anticorrosion effect was evaluated from the degree of the discoloration, and those without surface discoloration were evaluated as ○ (good), and those with discolored black surface were evaluated as x (poor).
[0030]
[Solderability test]
Printed wiring board (single-sided copper-clad laminate made of glass epoxy resin, copper foil thickness 35 μm, board size: 50 mm long, 50 mm wide, 1.6 mm thick, circuit pattern: conductor width 0.80 mm, length 20 mm, conductor spacing The copper surface of 1.0 mm, 10 conductor portions) was previously silver-plated, immersed in a surface treatment agent maintained at a predetermined liquid temperature for a predetermined time, then washed with water and dried to a thickness of about 0.02 to 0.30 μm. A test substrate on which a chemical conversion film was formed was prepared.
The test substrate exposed to the hydrogen sulfide gas by the method of the corrosion resistance test was subjected to one reflow heating at a peak temperature of 250 ° C. using an infrared reflow device (product name: MULTI-PRO 306, manufactured by Vitronics). went. Thereafter, using a metal mask having an opening width of 1.20 mm and a thickness of 150 μm, cream solder was printed at the center of the conductor, and reflow heating was performed under the above conditions to perform soldering. For the test substrate, the length of the solder spread on the conductor was measured. In addition, soldering was performed in the same manner on the test substrate to which the hydrogen sulfide gas was not exposed, and the length of the solder was measured.
Regarding the evaluation of solderability, it was determined that the longer the length of the solder, the better the solderability.
The cream solder is a tin-silver-copper (composition: 95.65 / 3.0 / 0.5% by weight) lead-free cream solder (trade name: M705-221BM5-42-11, Senju Metal Industry Co., Ltd.) Manufactured).
[0031]
[Example 1]
A surface treatment agent was prepared by dissolving 2,4-diphenylimidazole in water at a concentration of 0.25% by weight and acetic acid at a concentration of 9.0% by weight in water, and adjusting the pH to 4.0 with aqueous ammonia. A test substrate preliminarily silver-plated was immersed in the surface treatment agent at 40 ° C. for 60 seconds, taken out, washed with water, drained, and dried to perform an anticorrosion treatment.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0032]
[Example 2]
Based on water, 0.24% by weight of 2,4-diphenylimidazole, 9.0% by weight of acetic acid, 0.043% by weight of iron (III) chloride hexahydrate (150 ppm of Fe ion), acetic acid Surface treatment in which copper monohydrate is dissolved at a concentration of 0.016% by weight (Cu ion = 50 ppm) and ethylenediaminetetraacetic acid disodium dihydrate at a concentration of 1% by weight and adjusted to pH 4.0 with aqueous ammonia. An agent was prepared. A test substrate preliminarily silver-plated was immersed in the surface treatment agent at 40 ° C. for 2 minutes, taken out, washed with water, drained, and dried to perform an anticorrosion treatment.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0033]
[Example 3]
In water, 0.15% by weight of 2- (2,4-dichlorobenzyl) -benzimidazole, 20% by weight of acetic acid, and 0.05% by weight of copper acetate are dissolved, and the pH is adjusted to 3.0 with ammonia water. The surface treatment agent adjusted to 5 was prepared. A test substrate, which had been previously silver-plated, was immersed in the surface treatment agent at 40 ° C. for 5 minutes, taken out, washed with water, drained, and dried to perform an anticorrosion treatment.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0034]
[Comparative Example 1]
A surface treatment agent in which 2-mercaptobenzimidazole was dissolved at a concentration of 0.25% by weight in methanol was prepared, and a test substrate preliminarily silver-plated in the surface treatment agent was immersed at room temperature for 30 seconds, and then taken out. After washing with water, draining, and drying, anticorrosion treatment was performed.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0035]
[Comparative Example 2]
In water, 0.25% by weight of 2-octyl-5-methylbenzimidazole, 5.0% by weight of acetic acid and 0.05% by weight of copper chloride are dissolved, and the pH is adjusted to 3.0 with aqueous ammonia. The adjusted surface treatment agent was prepared. A test substrate preliminarily silver-plated was immersed in the surface treatment agent at 40 ° C. for 60 seconds, taken out, washed with water, drained, and dried to perform an anticorrosion treatment.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0036]
[Comparative Example 3]
1.0% by weight of 2-undecyl-4-methylimidazole, 1.5% by weight of acetic acid, and 0.05% by weight of copper chloride are dissolved in water, and the pH is adjusted to 4.3 with aqueous ammonia. The adjusted surface treatment agent was prepared. A test substrate preliminarily silver-plated was immersed in the surface treatment agent at 40 ° C. for 60 seconds, taken out, washed with water, drained, and dried to perform an anticorrosion treatment.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0037]
[Comparative Example 4]
0.1% by weight of 2- (4-chlorobenzyl) benzimidazole, 3.5% by weight of acetic acid, and 0.05% by weight of copper chloride are dissolved in water, and pH 2.6 with ammonia water. Was prepared. A test substrate preliminarily silver-plated was immersed in the surface treatment agent at 40 ° C. for 60 seconds, taken out, washed with water, drained, and dried to perform an anticorrosion treatment.
The obtained test board was subjected to a corrosion resistance test and a solderability test. These test results were as shown in Table 1.
[0038]
[Table 1]

[0039]
According to the test results shown in Table 1, the surface treating agent of the present invention is excellent in the anticorrosion effect on the surface of silver plating applied to a printed wiring board, and when soldering is performed on the surface of silver plating, It is recognized that the attachment property is good.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, since the surface of silver and a silver alloy can be prevented from corrosion and the solderability of the surface of silver and a silver alloy can be made favorable, it is a thing with high industrial value.

Claims (6)

A surface treating agent for silver and silver alloys, comprising as an essential component at least one selected from the imidazole compounds represented by Chemical Formula 1 or Chemical Formula 2.

(Wherein, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are the same or different and each represent a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms or a halogen atom. N is 0 Represents an integer of to 8)

(Wherein, R ₁ and R ₂ are the same or different and represent a linear or branched alkyl group having 1 to 20 carbon atoms or a halogen atom. R ₃ and R ₄ are the same or different and represent a hydrogen atom or a carbon atom Represents a linear or branched alkyl group or a halogen atom of 1 to 20. n represents an integer of 1 to 8.) The surface treating agent for silver and silver alloys according to claim 1, which contains copper ions. 2. The silver and silver alloy surface treating agent according to claim 1, comprising a copper ion and a halogen ion. 2. The silver and silver alloy surface treating agent according to claim 1, comprising a copper ion and / or iron ion and a complexan compound. A surface treatment method for silver and a silver alloy, wherein the surface treatment agent according to any one of claims 1 to 4 is an aqueous solution, and is brought into contact with the aqueous solution. A method for manufacturing a printed wiring board, comprising performing a soldering process after performing a surface treatment by the surface treatment method according to claim 5.