JP3831842B2 - Electroless gold plating solution - Google Patents

Electroless gold plating solution Download PDF

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JP3831842B2
JP3831842B2 JP2002082882A JP2002082882A JP3831842B2 JP 3831842 B2 JP3831842 B2 JP 3831842B2 JP 2002082882 A JP2002082882 A JP 2002082882A JP 2002082882 A JP2002082882 A JP 2002082882A JP 3831842 B2 JP3831842 B2 JP 3831842B2
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plating solution
gold
gold plating
electroless
nickel
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JP2003277942A (en
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輝明 下地
薫 内藤
克茂 岩松
喜美子 工藤
直美 村瀬
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奥野製薬工業株式会社
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Description

【0001】
【発明の属する技術分野】
本発明は、無電解金めっき液に関する。
【0002】
【従来の技術】
プリント配線板、電子部品等を製造する際に、最終工程の一つとして、無電解金めっき処理が行われている。これは、主として、プリント配線板の銅回路表面の酸化防止や、電子部品の接続面のはんだ接合性を向上させることを目的とするものであり、この処理によって、プリント配線板と実装される電子部品との間で良好な半田接合強度が確保されている。
【0003】
近年、各種電子部品に対して高い信頼性が要求されており、プリント配線板と電子部品との接合強度に関しては、はんだの剪断強度と同程度以上の高い強度が必要とされている。
【0004】
通常、プリント配線板、電子部品等に無電解金めっき皮膜を形成する場合には、回路材料である銅金属中への金めっき皮膜の拡散を防止すること等を目的として、銅金属上に無電解ニッケルめっき皮膜を形成した後、無電解金めっきを行うことが一般的である。この場合、無電解金めっき液としては、一般的に置換型のめっき液が用いられているが、置換型のめっき液を用いると、ニッケルめっき皮膜との置換反応によって金めっき皮膜が形成されるために、ニッケルめっき皮膜に腐食が生じて、ニッケル皮膜表面が、ポーラスな状態となることが避けられない。
【0005】
一般に、無電解金めっき上のハンダ接合強度は、無電解ニッケルめっき皮膜の表面状態の影響を大きく受け、ポーラスな状態の無電解ニッケル皮膜では、ハンダと無電解ニッケル皮膜との間に良好な金属間結合を形成することが難しく、その結果、ハンダ接続強度の低下を招くという大きな問題点がある。
【0006】
【発明が解決しようとする課題】
本発明は、上記した従来技術の現状に鑑みてなされたものであり、その主な目的は、無電解ニッケルめっき皮膜上に良好な金めっき皮膜を形成し得る無電解金めっき液であって、ニッケルめっき皮膜の腐食を最小限に抑制することが可能な新規なめっき液を提供することである。
【0007】
【課題を解決するための手段】
本発明者は、上記した目的を達成すべく研究を重ねた結果、特定の還元剤、腐食抑制剤、安定剤等を配合した無電解金めっき液によれば、無電解ニッケルめっき皮膜上に無電解金めっき皮膜を形成する際に、ニッケルめっき皮膜の腐食を最小限に抑制した上で、良好な金めっき皮膜を形成することが可能となることを見出し、ここに本発明を完成するに至った。
【0008】
即ち、本発明は、下記の無電解金めっき液を提供するものである。
1.(i)水溶性金化合物、
(ii)錯化剤、
(iii)酸化数2〜4のカルコゲン元素を含む酸及びその塩からなる群から選ばれた少なくとも一種の成分、
(iv)ヒドラジン及びその誘導体からなる群から選ばれた少なくとも一種の成分、並びに
(v)分子内に2個以上のイミノ基を含み、置換基を有することのあるエチレン基を該イミノ基の窒素原子間に有する化合物、
を含有することを特徴とする無電解金めっき液。
2. 水溶性金化合物がシアン化金錯塩であり、錯化剤が、エチレンジアミン誘導体である上記項1に記載の無電解金めっき液。
【0009】
【発明の実施の形態】
本発明の無電解金めっき液は、(i)水溶性金化合物、(ii)錯化剤、(iii)酸化数2〜4のカルコゲン元素を含む酸及びその塩からなる群から選ばれた少なくとも一種の成分、(iv)ヒドラジン及びその誘導体からなる群から選ばれた少なくとも一種の成分、並びに(v)分子内に2個以上のイミノ基を含み、置換基を有することのあるエチレン基を該イミノ基の窒素原子間に有する化合物、を含有するものである。以下、本発明の無電解金めっき液で用いられる各成分について説明する。
(i)水溶性金化合物:
本発明の無電解金めっき液では、金化合物として、水溶性の金化合物であれば特に限定なく使用できるが、特に、シアン化金錯塩を用いることが好ましい。
【0010】
シアン化金錯塩の具体例としては、シアン化金カリウム、シアン化金ナトリウム等を挙げることができる。水溶性金化合物は、一種単独又は二種以上混合して用いることができる。
【0011】
本発明の無電解金めっき液中における水溶性金化合物の濃度については、特に限定的ではないが、金化合物の濃度が低すぎると、金めっきの析出速度が遅くなって、所定の金めっき皮膜を形成するために長時間を要することになる。一方、金化合物の濃度が高すぎる場合には、めっき液からの金化合物の持ち出し量が多くなってコスト高となるので好ましくない。この様な点から、通常、無電解金めっき液中の水溶性金化合物の濃度は、0.001〜0.1mol/l程度とすることが好ましく、0.002〜0.05mol/l程度とすることがより好ましい。
(ii)錯化剤:
本発明の無電解金めっき液では、金の析出は、下地金属との置換反応と還元剤による還元反応の二種類の反応によるものと考えられる。このため、ニッケルめっき皮膜上にめっき処理を行う際合には、反応の初期においてニッケルめっき皮膜上に金皮膜の置換反応が生じて、めっき液中にニッケルが溶解する。
【0012】
本発明めっき液に配合する錯化剤は、このようなニッケルの溶解反応を円滑に進行させ、さらに、溶解したニッケルイオンをめっき液中で可溶化させる働きをするものである。
【0013】
本発明めっき液では、錯化剤としては、めっき液中でニッケルイオンを安定に可溶化させることができるものであれば、特に限定なく使用できるが、特に、エチレンジアミン誘導体を用いることが好ましい。本発明において有効に使用できるエチレンジアミン誘導体の具体例としては、エチレンジアミン四酢酸、N−ヒドロキシエチルエチレンジアミン−N,N’,N’−三酢酸(バーセノール)、ジエチレントリアミン五酢酸、N,N,N’,N’−テトラヒドロキシエチルエチレンジアミン(クォードロール)、エチレンジアミンテトラメチレンホスホン酸等のエチレンジアミン又はジエチレントリアミンの窒素原子上に、ヒドロキシアルキル基、カルボキシアルキル基、スルホン酸基等から選ばれた置換基を3〜5個程度有する誘導体、これらの誘導体のナトリウム塩、カリウム塩等のアルカリ金属塩、アンモニウム塩等の塩を挙げることができる。
【0014】
本発明のめっき液では、錯化剤は、一種単独又は二種以上混合して用いることができる。
【0015】
本発明めっき液における錯化剤の濃度については、特に限定的ではないが、錯化剤濃度が低すぎると、溶解したニッケルイオンを金めっき液中に安定に可溶化させることが困難となって、水酸化ニッケル等の沈殿を生じ易くなる。一方、錯化剤濃度が高すぎると、無電解ニッケル皮膜からのニッケルの溶解が過剰となって、無電解ニッケル皮膜の腐食を引き起こし易くなる。これらの点から、錯化剤濃度は、0.001〜1mol/l程度とすることが好ましく、0.002〜0.1mol/l程度とすることがより好ましい。
(iii)酸化数2〜4のカルコゲン元素を含む酸及びその塩からなる群から選ばれた少なくとも一種の成分:
これらの成分は、めっき液中に含まれる水溶性金塩に対する還元剤として有効な成分である。この様な特定の還元剤を用いることによって、適度な析出速度を有し、且つ安定性に優れた無電解金めっき液が得られる。
【0016】
酸化数2〜4のカルコゲン元素を含む酸及びその塩としては、本発明のめっき液に可溶な化合物であれば特に限定なく使用できる。その具体例としては、スルホキシル酸、亜硫酸、チオ硫酸、二亜チオン酸、亜セレン酸、亜テルル酸等の酸、これらの酸のナトリウム塩、カリウム塩等のアルカリ金属塩、アンモニウム塩等を挙げることができ、更に、ホルムアルデヒドナトリウムスルホキシレート(ロンガリット)等の上記酸又は塩の誘導体も用いることができる。上記還元剤は、一種単独又は二種以上混合して用いることができる。
【0017】
本発明めっき液中における上記還元剤の濃度は、特に限定的ではないが、0.001〜1mol/l程度とすることが好ましく、0.002〜0.5mol/l程度とすることがより好ましい。還元剤濃度が低すぎると、金イオンの還元速度が遅くなって所定の金めっき皮膜を形成するために長時間を要することになり、一方還元剤濃度が高すぎると、めっき液の分解が生じやすくなるので、いずれも好ましくない。
(iv)ヒドラジン及びその誘導体からなる群から選ばれた少なくとも一種の成分:
これらの成分は、ニッケルめっき皮膜の腐食を抑制するために有効な成分(以下「腐食抑制剤」という)である。
【0018】
ヒドラジン誘導体としては、例えば、ピラゾール類、トリアゾール類、チアジアゾール類、マレイン酸ヒドラジド等を用いることができる。これらの内で、ピラゾール類としては、ピラゾールの他に、5−アミノ−3−メチルピラゾール等のピラゾール誘導体を用いることができ、トリアゾール類としては、1,2,4−トリアゾール等のトリアゾールの他に、3−アミノ−1,2,4−トリアゾール等のトリアゾール誘導体等を用いることができ、チアジアゾール類としては、2−アミノ−5−エチル−1,3,4−チアジアゾール等のチアジアゾール誘導体を用いることができる。
【0019】
本発明では、ヒドラジン及び上記したヒドラジン誘導体は、一種単独又は二種以上混合して用いることができる。
【0020】
本発明めっき液中における腐食抑制剤の濃度については、特に限定的ではないが、腐食抑制剤の濃度が低すぎると、ニッケルめっき皮膜の腐食を抑制する効果が不足して、ニッケルめっき皮膜の腐食が発生しやすくなり、一方、高すぎる場合には、無電解金めっき皮膜の初期析出が阻害されて、十分な膜厚の金めっき皮膜を形成することが困難になる。この様な点から、腐食抑制剤の濃度は、0.001〜1mol/l程度とすることが好ましく、0.002〜0.1mol/l程度とすることがより好ましい。
(v)分子内に2個以上のイミノ基を含み、置換基を有することのあるエチレン基を該イミノ基の窒素原子間に有する化合物:
この化合物は、めっき液の安定化剤として作用するものである。このような化合物(以下、「安定化剤」という)の好ましい例としては、下記一般式
【0021】
【化1】
【0022】
(式中、R1及びR2は、同一または異なって、低級アルキル基を示し、R3〜R6は、同一または異なって、低級アルキル基または水素原子を示す。nは1〜4の整数である。)で表される化合物を挙げることができる。
【0023】
上記一般式において、低級アルキル基としては、メチル、エチル、n−プロピル、イソプロピル、n−ブチル、イソブチル、tert−ブチル等の炭素数1〜4程度の直鎖状又は分岐鎖状のアルキル基を例示できる。
【0024】
この様な化合物の具体例としてはN,N’−ジメチルエチレンジアミン、N,N’−ジエチルエチレンジアミン、N,N’’−ジメチルジエチレントリアミン、N,N’−ジメチル−1,2−ジアミノプロパン等を挙げることができる。これらの化合物は、一種単独または二種以上混合して用いることができる。
【0025】
安定化剤の濃度については、特に限定的ではないが、低すぎる場合にはめっき液の安定性が不足して分解が生じやすくなり、一方、高すぎる場合には上記した腐食抑制剤による腐食抑制効果が妨げられて、ニッケルめっき皮膜の腐食が生じやすくなる。これらの点から、安定化剤の濃度は、0.001〜10mmol/l程度とするとが好ましく、0.002〜1mol/l程度とすることがより好ましい。
【0026】
本発明の無電解金めっき液には、さらに、めっき液の特性に悪影響を及ぼさない限り、上記した成分の他に、他の金属塩、有機化合物などが含まれていてもよい。
無電解めっき方法
本発明の無電解金めっき液を用いるめっき方法は、通常の無電解めっきの処理方法と同様でよい。一般的には、該無電解金めっき液中に被めっき物を浸漬し、めっき液の温度を所定の温度範囲とすることによって、被めっき物の表面に無電解金めっき皮膜を形成することができる。この場合、必要に応じて、めっき液を攪拌してもよい。
【0027】
無電解金めっき液の液温については、低すぎると析出反応が緩慢となって金めっき皮膜の未析出や外観不良等が発生し易くなるので、通常、40℃程度以上とすればよいが、液温が高すぎるとめっき液の分解が生じ易くなり、更に、水の蒸発が激しすぎるために、めっき液中に含まれる成分の濃度維持が困難となる。このため、めっき液の液温は、60〜100℃程度とすることが好ましい。
【0028】
めっき液のpHについては、低すぎるとめっき液中のシアンイオンが大気中に放出されてめっき液の安定性が低下し、作業環境も悪化する。一方、pHが高すぎると、還元剤の還元電位が高すぎてめっき液の安定性が低下する。
【0029】
これらの点から、めっき液のpHは3〜12程度とすることが好ましく、5〜10程度とすることがより好ましい。
【0030】
被めっき物の種類については、特に限定はなく、金属材料の他、プラスチック材料、セラミック材料など各種の材質の材料を被めっき物とすることができる。この場合、被めっき物の種類に応じて、必要に応じて、公知の方法に従って、適宜、触媒付与などを行えばよい。本発明の無電解金めっき液は、ニッケルめっき皮膜上に金めっき皮膜を形成する際に、ニッケルめっき皮膜の腐食を最小限に抑えることができるという特徴を有するものである。従って、無電解ニッケルめっき皮膜が形成された物品を被めっき物とする場合に、特に、本発明の無電解金めっき液を有効に使用することができる。この様な被めっき物の内で、形成された無電解金めっき皮膜上にハンダ付けを行う物品、例えば、プリント配線板、電子部品等を被めっき物とする場合には、下地として形成するニッケル皮膜の腐食を抑制でき、ニッケル皮膜の腐食に伴うハンダ接続強度の低下を防止できる点で、本発明の無電解金めっき液の効果が特に有効に発揮される。
【0031】
【発明の効果】
本発明の無電解金めっき液は、安定性が良好であって、均一で良好な外観の金めっき皮膜を形成することができ、さらに、ニッケル上に無電解金めっき皮膜を形成する場合に、ニッケルの腐食が非常に少ないという優れた特徴を有するものである。
【0032】
従って、本発明の無電解金めっき液を用いることにより、無電解ニッケルめっき皮膜が形成されたプリント配線板、電子部品等を被めっき物とする場合には、特に、ニッケルめっき皮膜の腐食を抑制して、ハンダ接合強度の低下を防止できるという優れた効果が発揮される。
【0033】
【実施例】
以下、実施例を挙げて本発明をさらに詳細に説明する。
【0034】
実施例1
パッド径0.5mmのBGA搭載用の銅回路を有する5×10cmの独立回路基板について、該銅回路上に厚さ約5μmの無電解ニッケルめっき皮膜(含リン率5〜8%)を形成した基板を被めっき物として用いた。
【0035】
この被めっき物を、下記表1に示す無電解金めっき液中に10分間浸漬して無電解金めっき皮膜を形成した。
【0036】
形成された金めっき皮膜について、下記の方法で析出速度、外観、ハンダ接合強、浴安定性及びニッケル皮膜腐食状態を評価した。結果を下記表2に示す。
*析出速度:
蛍光X線膜厚測定装置を用いて膜厚を測定し、10分間当たりの析出速度を求めた。
*外観:
目視により色調および未析出の有無を調べた。
*ハンダ接合強度:
パッド径0.5mmのBGA搭載用パターンに、直径0.63mmの共晶はんだボールをリフロー装置を用いて搭載し、常温はんだボールプル試験器を用いて、ハンダボールを機械で挟んで垂直に引っ張り上げる方法によってはんだの接続強度を測定した。
*浴安定性:
金濃度及び各種成分の濃度を測定し、補給操作を行いながら、繰り返し無電解金めっきを行い、2ターン終了後、めっき液を0.2μmのメンブランフィルターで濾過した。その後、フィルター上に残った濾過物について、蛍光X線分析装置を用いて金の有無を調べた。濾過物中に金の存在が認められなかった場合には、浴安定性を安定と評価し、濾過物中に金の存在が認められた場合には、浴安定性を不安定と評価した。
*ニッケル皮膜腐食状態:
無電解金めっきを行った後、金剥離剤にて金めっき皮膜を剥離し、走査型電子顕微鏡でニッケルめっき皮膜の表面状態を観察し、下記の基準で評価した。
【0037】
○:良好、△:一部腐食あり、×:腐食が多数発生
【0038】
【表1】
【0039】
【表2】
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electroless gold plating solution.
[0002]
[Prior art]
When manufacturing printed wiring boards, electronic components and the like, electroless gold plating is performed as one of the final steps. This is mainly for the purpose of preventing oxidation of the copper circuit surface of the printed wiring board and improving the solderability of the connection surface of the electronic component. Good solder joint strength is ensured between the parts.
[0003]
In recent years, high reliability is required for various electronic components, and the bonding strength between the printed wiring board and the electronic component is required to be as high as or higher than the shear strength of solder.
[0004]
Normally, when an electroless gold plating film is formed on a printed wiring board, electronic parts, etc., there is no effect on the copper metal in order to prevent the gold plating film from diffusing into the copper metal as a circuit material. In general, electroless gold plating is performed after forming an electrolytic nickel plating film. In this case, a substitution-type plating solution is generally used as the electroless gold plating solution, but when a substitution-type plating solution is used, a gold plating film is formed by a substitution reaction with the nickel plating film. For this reason, it is inevitable that the nickel plating film is corroded and the nickel film surface is in a porous state.
[0005]
In general, the solder joint strength on electroless gold plating is greatly affected by the surface condition of the electroless nickel plating film, and in the case of a porous electroless nickel film, a good metal is present between the solder and the electroless nickel film. It is difficult to form an inter-bond, and as a result, there is a serious problem that the solder connection strength is lowered.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the current state of the prior art described above, and its main purpose is an electroless gold plating solution capable of forming a good gold plating film on the electroless nickel plating film, To provide a novel plating solution capable of minimizing corrosion of a nickel plating film.
[0007]
[Means for Solving the Problems]
As a result of repeated studies to achieve the above-described object, the present inventor has found that an electroless gold plating solution containing a specific reducing agent, corrosion inhibitor, stabilizer, etc. When forming an electrolytic gold plating film, it was found that it was possible to form a good gold plating film while minimizing the corrosion of the nickel plating film, and the present invention was completed here. It was.
[0008]
That is, the present invention provides the following electroless gold plating solution.
1. (I) a water-soluble gold compound,
(Ii) complexing agents,
(Iii) at least one component selected from the group consisting of an acid containing a chalcogen element having an oxidation number of 2 to 4 and a salt thereof;
(Iv) at least one component selected from the group consisting of hydrazine and derivatives thereof; and (v) an ethylene group which contains two or more imino groups in the molecule and may have a substituent, A compound having between atoms,
An electroless gold plating solution comprising:
2. Item 2. The electroless gold plating solution according to Item 1, wherein the water-soluble gold compound is a gold cyanide complex salt and the complexing agent is an ethylenediamine derivative.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The electroless gold plating solution of the present invention is at least selected from the group consisting of (i) a water-soluble gold compound, (ii) a complexing agent, (iii) an acid containing a chalcogen element having an oxidation number of 2 to 4, and a salt thereof. One component, (iv) at least one component selected from the group consisting of hydrazine and derivatives thereof, and (v) an ethylene group containing two or more imino groups in the molecule and having a substituent. The compound which has between the nitrogen atoms of an imino group is contained. Hereinafter, each component used in the electroless gold plating solution of the present invention will be described.
(I) Water-soluble gold compound:
In the electroless gold plating solution of the present invention, any gold compound can be used as long as it is a water-soluble gold compound, but it is particularly preferable to use a gold cyanide complex salt.
[0010]
Specific examples of the gold cyanide complex salt include potassium gold cyanide and sodium gold cyanide. The water-soluble gold compound can be used singly or in combination of two or more.
[0011]
The concentration of the water-soluble gold compound in the electroless gold plating solution of the present invention is not particularly limited, but if the concentration of the gold compound is too low, the deposition rate of the gold plating becomes slow, and the predetermined gold plating film It takes a long time to form. On the other hand, when the concentration of the gold compound is too high, the amount of the gold compound taken out from the plating solution is increased, resulting in an increase in cost. From such a point, normally, the concentration of the water-soluble gold compound in the electroless gold plating solution is preferably about 0.001 to 0.1 mol / l, and about 0.002 to 0.05 mol / l. More preferably.
(Ii) Complexing agent:
In the electroless gold plating solution of the present invention, gold deposition is considered to be caused by two kinds of reactions, a substitution reaction with a base metal and a reduction reaction with a reducing agent. For this reason, when the plating treatment is performed on the nickel plating film, a substitution reaction of the gold film occurs on the nickel plating film in the initial stage of the reaction, and nickel is dissolved in the plating solution.
[0012]
The complexing agent blended in the plating solution of the present invention functions to smoothly advance such nickel dissolution reaction and solubilize the dissolved nickel ions in the plating solution.
[0013]
In the plating solution of the present invention, the complexing agent can be used without particular limitation as long as it can stably solubilize nickel ions in the plating solution, but it is particularly preferable to use an ethylenediamine derivative. Specific examples of ethylenediamine derivatives that can be used effectively in the present invention include ethylenediaminetetraacetic acid, N-hydroxyethylethylenediamine-N, N ′, N′-triacetic acid (Versenol), diethylenetriaminepentaacetic acid, N, N, N ′, N'-tetrahydroxyethylethylenediamine (quadrol), ethylenediamine such as ethylenediaminetetramethylene phosphonic acid, or a substituent selected from hydroxyalkyl group, carboxyalkyl group, sulfonic acid group, etc. on the nitrogen atom of diethylenetriamine is used for 3-5 Derivatives having about one unit, alkali metal salts such as sodium salts and potassium salts of these derivatives, and salts such as ammonium salts can be mentioned.
[0014]
In the plating solution of the present invention, complexing agents can be used singly or in combination of two or more.
[0015]
The concentration of the complexing agent in the plating solution of the present invention is not particularly limited, but if the complexing agent concentration is too low, it becomes difficult to stably solubilize the dissolved nickel ions in the gold plating solution. , Precipitation of nickel hydroxide and the like is likely to occur. On the other hand, if the concentration of the complexing agent is too high, the dissolution of nickel from the electroless nickel film becomes excessive, and corrosion of the electroless nickel film tends to occur. From these points, the complexing agent concentration is preferably about 0.001 to 1 mol / l, and more preferably about 0.002 to 0.1 mol / l.
(Iii) At least one component selected from the group consisting of an acid containing a chalcogen element having an oxidation number of 2 to 4 and a salt thereof:
These components are effective components as a reducing agent for the water-soluble gold salt contained in the plating solution. By using such a specific reducing agent, an electroless gold plating solution having an appropriate deposition rate and excellent stability can be obtained.
[0016]
Any acid and salt thereof containing a chalcogen element having an oxidation number of 2 to 4 can be used without particular limitation as long as it is a compound soluble in the plating solution of the present invention. Specific examples thereof include acids such as sulfoxylic acid, sulfurous acid, thiosulfuric acid, dithionic acid, selenious acid and telluric acid, alkali metal salts such as sodium salts and potassium salts of these acids, ammonium salts, and the like. Furthermore, derivatives of the above acids or salts such as sodium formaldehyde sulfoxylate (Rongalite) can also be used. The said reducing agent can be used individually by 1 type or in mixture of 2 or more types.
[0017]
The concentration of the reducing agent in the plating solution of the present invention is not particularly limited, but is preferably about 0.001 to 1 mol / l, more preferably about 0.002 to 0.5 mol / l. . If the reducing agent concentration is too low, the reduction rate of gold ions will be slow and it will take a long time to form the prescribed gold plating film, while if the reducing agent concentration is too high, the plating solution will decompose. Since it becomes easy, neither is preferable.
(Iv) At least one component selected from the group consisting of hydrazine and its derivatives:
These components are effective components for suppressing the corrosion of the nickel plating film (hereinafter referred to as “corrosion inhibitor”).
[0018]
As the hydrazine derivative, for example, pyrazoles, triazoles, thiadiazoles, maleic hydrazide and the like can be used. Among these, as pyrazoles, in addition to pyrazole, pyrazole derivatives such as 5-amino-3-methylpyrazole can be used, and as triazoles, other than triazole such as 1,2,4-triazole, etc. In addition, triazole derivatives such as 3-amino-1,2,4-triazole can be used, and thiadiazole derivatives such as 2-amino-5-ethyl-1,3,4-thiadiazole are used as thiadiazoles. be able to.
[0019]
In the present invention, hydrazine and the hydrazine derivatives described above can be used singly or in combination of two or more.
[0020]
The concentration of the corrosion inhibitor in the plating solution of the present invention is not particularly limited, but if the concentration of the corrosion inhibitor is too low, the effect of suppressing the corrosion of the nickel plating film is insufficient, and the corrosion of the nickel plating film On the other hand, when it is too high, initial deposition of the electroless gold plating film is hindered, and it becomes difficult to form a gold plating film having a sufficient film thickness. From such points, the concentration of the corrosion inhibitor is preferably about 0.001 to 1 mol / l, and more preferably about 0.002 to 0.1 mol / l.
(V) A compound containing two or more imino groups in the molecule and having an ethylene group which may have a substituent between nitrogen atoms of the imino group:
This compound acts as a stabilizer for the plating solution. Preferred examples of such a compound (hereinafter referred to as “stabilizer”) include the following general formula:
[Chemical 1]
[0022]
(Wherein R 1 and R 2 are the same or different and represent a lower alkyl group, and R 3 to R 6 are the same or different and represent a lower alkyl group or a hydrogen atom. N is an integer of 1 to 4) The compound represented by this can be mentioned.
[0023]
In the above general formula, the lower alkyl group is a linear or branched alkyl group having about 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl and the like. It can be illustrated.
[0024]
Specific examples of such compounds include N, N′-dimethylethylenediamine, N, N′-diethylethylenediamine, N, N ″ -dimethyldiethylenetriamine, N, N′-dimethyl-1,2-diaminopropane and the like. be able to. These compounds can be used individually by 1 type or in mixture of 2 or more types.
[0025]
The concentration of the stabilizer is not particularly limited, but if it is too low, the plating solution is not stable enough to cause decomposition, whereas if it is too high, the above-described corrosion inhibitor is used to suppress corrosion. The effect is hindered, and corrosion of the nickel plating film tends to occur. From these points, the concentration of the stabilizer is preferably about 0.001 to 10 mmol / l, and more preferably about 0.002 to 1 mol / l.
[0026]
In addition to the above-described components, the electroless gold plating solution of the present invention may further contain other metal salts and organic compounds as long as the properties of the plating solution are not adversely affected.
Electroless plating method :
The plating method using the electroless gold plating solution of the present invention may be the same as a normal electroless plating treatment method. In general, an electroless gold plating film can be formed on the surface of an object to be plated by immersing the object to be plated in the electroless gold plating solution and setting the temperature of the plating solution to a predetermined temperature range. it can. In this case, the plating solution may be stirred as necessary.
[0027]
About the liquid temperature of the electroless gold plating solution, if it is too low, the precipitation reaction becomes slow and the gold plating film is not easily deposited and the appearance is poor. If the solution temperature is too high, decomposition of the plating solution is likely to occur, and furthermore, since the evaporation of water is too intense, it is difficult to maintain the concentration of the components contained in the plating solution. For this reason, it is preferable that the liquid temperature of a plating solution shall be about 60-100 degreeC.
[0028]
If the pH of the plating solution is too low, cyan ions in the plating solution are released into the atmosphere, the stability of the plating solution is lowered, and the working environment is also deteriorated. On the other hand, if the pH is too high, the reduction potential of the reducing agent is too high and the stability of the plating solution is lowered.
[0029]
From these points, the pH of the plating solution is preferably about 3 to 12, more preferably about 5 to 10.
[0030]
The type of the object to be plated is not particularly limited, and various materials such as a plastic material and a ceramic material can be used as the object to be plated in addition to the metal material. In this case, according to the kind of to-be-plated thing, what is necessary is just to perform catalyst provision etc. suitably according to a well-known method as needed. The electroless gold plating solution of the present invention has a feature that corrosion of the nickel plating film can be minimized when the gold plating film is formed on the nickel plating film. Therefore, when the article on which the electroless nickel plating film is formed is to be plated, the electroless gold plating solution of the present invention can be used effectively. Among such objects to be plated, nickel to be formed as a base when an article to be soldered on the formed electroless gold plating film, for example, a printed wiring board, an electronic component or the like is to be plated. The effect of the electroless gold plating solution of the present invention is particularly effectively exhibited in that the corrosion of the film can be suppressed and the decrease in the solder connection strength accompanying the corrosion of the nickel film can be prevented.
[0031]
【The invention's effect】
The electroless gold plating solution of the present invention has a good stability, can form a uniform and good appearance gold plating film, and when forming an electroless gold plating film on nickel, It has an excellent feature that nickel corrosion is very low.
[0032]
Therefore, by using the electroless gold plating solution of the present invention, especially when the printed wiring board, electronic parts, etc., on which the electroless nickel plating film is formed are to be plated, the corrosion of the nickel plating film is suppressed. And the outstanding effect that the fall of solder joint strength can be prevented is exhibited.
[0033]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0034]
Example 1
About a 5 × 10 cm independent circuit board having a copper circuit for mounting a BGA with a pad diameter of 0.5 mm, an electroless nickel plating film (phosphorus content 5 to 8%) having a thickness of about 5 μm was formed on the copper circuit. The substrate was used as an object to be plated.
[0035]
This object to be plated was immersed in an electroless gold plating solution shown in Table 1 for 10 minutes to form an electroless gold plating film.
[0036]
About the formed gold plating film, the following methods evaluated the deposition rate, appearance, solder joint strength, bath stability, and nickel film corrosion state. The results are shown in Table 2 below.
* Deposition rate:
The film thickness was measured using a fluorescent X-ray film thickness measuring apparatus, and the deposition rate per 10 minutes was determined.
*appearance:
The color tone and the presence / absence of undeposited were examined visually.
* Solder joint strength:
Eutectic solder balls with a diameter of 0.63 mm are mounted on a BGA mounting pattern with a pad diameter of 0.5 mm using a reflow device, and the solder balls are pulled vertically by using a room temperature solder ball pull tester. The connection strength of the solder was measured by the method.
* Bath stability:
The gold concentration and the concentrations of various components were measured, and electroless gold plating was repeated while performing the replenishment operation. After completing two turns, the plating solution was filtered through a 0.2 μm membrane filter. Thereafter, the filtrate remaining on the filter was examined for the presence of gold using a fluorescent X-ray analyzer. When the presence of gold was not observed in the filtrate, the bath stability was evaluated as stable. When the presence of gold was observed in the filtrate, the bath stability was evaluated as unstable.
* Nickel film corrosion state:
After performing electroless gold plating, the gold plating film was peeled off with a gold release agent, and the surface state of the nickel plating film was observed with a scanning electron microscope and evaluated according to the following criteria.
[0037]
○: Good, △: Partially corroded, ×: Many corrosion occurred.
[Table 1]
[0039]
[Table 2]

Claims (2)

  1. (i)水溶性金化合物、
    (ii)錯化剤、
    (iii)酸化数2〜4のカルコゲン元素を含む酸及びその塩からなる群から選ばれた少なくとも一種の成分、
    (iv)ヒドラジン及びその誘導体からなる群から選ばれた少なくとも一種の成分、並びに
    (v)N,N’−ジメチルエチレンジアミン、N,N’−ジエチルエチレンジアミン、N,N’’−ジメチルジエチレントリアミン及びN,N’−ジメチル−1,2−ジアミノプロパンからなる群から選ばれた少なくとも一種の化合物
    を含有することを特徴とする無電解金めっき液。
    (I) a water-soluble gold compound,
    (Ii) complexing agents,
    (Iii) at least one component selected from the group consisting of an acid containing a chalcogen element having an oxidation number of 2 to 4 and a salt thereof;
    (Iv) at least one component selected from the group consisting of hydrazine and its derivatives, and (v) N, N′-dimethylethylenediamine, N, N′-diethylethylenediamine, N, N ″ -dimethyldiethylenetriamine and N, At least one compound selected from the group consisting of N′-dimethyl-1,2-diaminopropane ,
    An electroless gold plating solution comprising:
  2. 水溶性金化合物がシアン化金錯塩であり、錯化剤が、エチレンジアミン誘導体である請求項1に記載の無電解金めっき液。The electroless gold plating solution according to claim 1, wherein the water-soluble gold compound is a gold cyanide complex salt and the complexing agent is an ethylenediamine derivative.
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AU2003301573A1 (en) * 2002-10-22 2004-05-13 Nihon Koujundo Kagaku Co., Ltd. Substitution type electroless gold plating bath
JP5526458B2 (en) 2006-12-06 2014-06-18 上村工業株式会社 Electroless gold plating bath and electroless gold plating method
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JP5526440B2 (en) * 2007-01-17 2014-06-18 奥野製薬工業株式会社 Printed wiring board formed using reduced deposition type electroless gold plating solution for palladium film
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KR101483599B1 (en) 2008-07-04 2015-01-16 롬 앤드 하스 일렉트로닉 머트어리얼즈 엘엘씨 An electroless gold plating solution
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