JP2004315872A - Tin-zinc alloy plating bath - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tin-zinc alloy plating bath which has a plating having a dense and smooth plating surface and has high safety. <P>SOLUTION: The tin-zinc alloy plating bath contains three components; (a) Sn<SP>2+</SP>, (b) Zn<SP>2+</SP>, and (c) polyoxyethylene alkyl ether. The tin-zinc alloy plating bath which forms a plating film having the dense and smooth plating surface, has the high safety, and does not give rise to environmental problems and pollution problems is constituted. The polyoxyethylene alkyl ether (c) is a nonionic surfactant, has a good adhesion property and contributes to the formation of the dense and smooth plating film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００９】
より好ましくは、ポリオキシエチレンアルキルエーテルのアルキル基［式（１）］がラウリル基［式（２）］であり、さらにｎ＝４〜１３であるのがよい。
【００１０】
【発明の実施の形態】
本発明のすず−亜鉛合金めっき浴（ａ）成分であるＳｎ^２＋は、硫酸第一すずをグルコン酸塩水溶液中（例えばグルコン酸ナトリウム）に溶解することにより得られる。
【００１１】
また、本発明の（ｂ）成分であるＺｎ^２＋は、硫酸亜鉛をグルコン酸塩（例えばグルコン酸ナトリウム）水溶液に溶解することにより得られる。
【００１２】
また、さらに本発明の（ｃ）成分であるポリオキシエチレンアルキルエーテルは非イオン性界面活性剤であり、密着性がよく緻密で平滑なめっき面を得ることができる。本発明において、この（ｃ）成分を欠くと満足のいくすず−亜鉛合金めっき皮膜が得られない。
【００１３】
この（ｃ）成分の好ましい具体例としては、下記一般式（２）で表される化合物を主成分とするものが挙げられる。
【化３】

【００１４】
［式中、ｎは４〜１３の整数とする。］
【００１５】
本発明のすず−亜鉛合金めっき浴は、常法にしたがい、グルコン酸塩（例えばグルコン酸ナトリウム）水溶液中に前記（ａ）（ｂ）（ｃ）成分を添加することにより調整される。具体的には、グルコン酸塩（例えばグルコン酸ナトリウム）水溶液中に、硫酸第一すずと硫酸亜鉛を加え十分に融解させた後（ｃ）成分であるポリオキシエチレンアルキルエーテルを添加することにより調整される。
【００１６】
また、本発明のすず−亜鉛合金めっき浴において用いられるグルコン酸塩（例えばグルコン酸ナトリウム）は、その浴中濃度として１０〜１００ｇ／Ｌが適当である。
【００１７】
本発明のすず−亜鉛合金めっき浴中のＳｎ^２＋濃度は２０〜２５ｇ／Ｌ程度とすることが適当である。また、合金浴中における（ａ）成分と（ｂ）成分の量は、目的とする合金組成に合わせて調整する必要があるが、すず−鉛合金めっきの代替えとする場合は、融点と皮膜特性（強度）から考えて亜鉛含有量５〜１０（ｗｔ％）が最適と考えられる。このとき、（ｂ）成分の濃度は２ｇ／Ｌが適当である。また、さらに、本発明のすず−亜鉛合金めっき浴中の（ｃ）成分の量は、密着性がよく、緻密で平滑なめっき面を得るのに十分な量の１〜５ｇ／Ｌであるとよい。
【００１８】
本発明のすず−亜鉛合金めっき浴には、上記した成分のほか、本発明の効果を損なわない範囲で光沢剤、酸化防止剤、湿潤剤等を必要に応じて添加することができる。
【００１９】
また、Ｓｎ^２＋の酸化防止剤として例えばカテコール、レゾルシン、ヒドロキノン等を利用することができる。
【００２０】
かくして得られる本発明のすず−亜鉛合金めっき浴を用いてめっきを行なう場合、例えばめっき浴の浴温は約１５〜２５（℃）程度が好ましく、また陰極電流密度は約１〜５Ａ／ｄｍ２ 程度が好ましい。またさらに、陽極としてはすず、すず−亜鉛合金あるいは不溶解性電極等を利用することができる。
【００２１】
以上のすず−亜鉛合金めっき浴から得られるすず−亜鉛合金めっき皮膜は、緻密で平滑な外観を有しており、すず−鉛合金めっきの代替えとして電子部品や半導体部品のめっき浴に利用することができる。
【００２２】
【実施例】
以下、実施例、試験例を挙げ、本発明を説明するが、本発明はこれら実施例−試験例に限定されるものではない。
【００２３】
実施例１
下記組成により、常法に従ってすず−亜鉛合金めっき浴を調整した。
（組成）
グルコン酸ナトリウム ：５０ｇ／Ｌ
硫酸第一すず ：３６ｇ／Ｌ
硫酸亜鉛−７水和物 ： ８ｇ／Ｌ
ポリオキシエチレンラウリルエーテル ： ２ｇ／Ｌ
【００２４】
試験例１
実施例１で得られためっき浴を利用し、下記の条件で２０×５０（ｍｍ）の銅板にめっきを行った。
【００２５】
（めっき条件）
陰極電流密度 ： ２Ａ／ｄｍ２
浴温 ： ２０℃
攪拌 ： スターラー攪拌
膜厚 ： ５ミクロン／１０分
【００２６】
実施例１のめっき浴を用いて加工しためっき済み銅板は、どれも均一で微細な結晶を持つめっき皮膜を有するものであった。
【００２７】
【発明の効果】
本発明のすず−亜鉛合金めっき浴により得られるすず−亜鉛合金めっき皮膜は、緻密で平滑なめっき面を有し、すず−鉛合金めっき浴の代替えとして、電子部品や半導体部品等のめっき浴として利用できる。また、低コストであり、さらに、有害な鉛化合物を含まないので、安全性、環境問題、公害防止等の面から有利である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tin-zinc alloy plating bath.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, tin-lead alloy plating baths having a low melting point of a deposited film have been widely used for plating of electronic parts and semiconductor parts.
[0003]
However, since these tin-lead alloy plating baths contain toxic lead, there have been many problems such as wastewater treatment, environmental protection, soil and groundwater pollution due to elution of lead from semiconductor waste and the like due to acid rain.
[0004]
[Problems to be solved by the invention]
Accordingly, there has been a demand for a plating bath which does not contain lead and which can be used for plating of electronic components and semiconductors as a substitute for a tin-lead alloy plating bath. On the other hand, the applicant has proposed a plating bath containing tin and a relatively expensive metal in Patent Documents 1 and 2. However, due to the severe economic environment and competition with foreign countries, there is a strong demand for further cost reduction, and there is a need for a plating process that can realize a process that is more competitive in terms of cost.
[Patent Document 1] JP-A-2000-355791 (paragraph numbers 0006 and 0007)
[Patent Document 2] JP-A-2002-60990 (paragraph number 0006)
[0005]
The present invention has been made in view of the above conventional problems, and one of its objects is to form a plating film having a dense and smooth plating surface while maintaining low cost, and high safety, An object of the present invention is to provide a tin plating bath which does not cause environmental problems and pollution problems. Another object of the present invention is to form a tin-zinc alloy which is inexpensive and has a dense and smooth plating surface, and which has high safety and does not cause environmental problems and pollution problems. It is to provide a plating bath.
[0006]
[Means for Solving the Problems]
The present inventor has focused on a tin-zinc alloy plating bath containing no lead as an alternative to the tin-lead alloy plating, and has been conducting research on this, and found that a plating bath containing a certain nonionic surfactant was added. As a result, the present inventors have found that an excellent finished surface film can be obtained, and that the present invention can be used as a substitute for a tin-lead alloy plating bath while maintaining body cost.
[0007]
That is, the present invention comprises a tin-zinc alloy plating bath containing the following three components (a), (b) and (c).
(A) Sn ²⁺
(B) Zn ²⁺
(C) polyoxyethylene alkyl ether
At this time, the alkyl group (R) [formula (1)] of the polyoxyethylene alkyl ether may be a lauryl group [formula (2)].
Embedded image

[0009]
More preferably, the alkyl group [Formula (1)] of the polyoxyethylene alkyl ether is a lauryl group [Formula (2)], and n = 4 to 13.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Sn ²⁺ which is a component of the tin-zinc alloy plating bath (a) of the present invention is obtained by dissolving stannous sulfate in an aqueous gluconate solution (for example, sodium gluconate).
[0011]
Further, Zn ^{2+ as the} component (b) of the present invention can be obtained by dissolving zinc sulfate in an aqueous solution of gluconate (for example, sodium gluconate).
[0012]
Further, the polyoxyethylene alkyl ether which is the component (c) of the present invention is a nonionic surfactant, and can provide a dense and smooth plated surface with good adhesion. In the present invention, if the component (c) is omitted, a satisfactory tin-zinc alloy plating film cannot be obtained.
[0013]
Preferred specific examples of the component (c) include those containing a compound represented by the following general formula (2) as a main component.
Embedded image

[0014]
[In the formula, n is an integer of 4 to 13. ]
[0015]
The tin-zinc alloy plating bath of the present invention is prepared by adding the components (a), (b) and (c) to an aqueous solution of gluconate (for example, sodium gluconate) according to a conventional method. Specifically, it is adjusted by adding stannous sulfate and zinc sulfate to an aqueous solution of a gluconate (eg, sodium gluconate) and sufficiently melting the mixture, and then adding the polyoxyethylene alkyl ether as the component (c). Is done.
[0016]
The concentration of gluconate (eg, sodium gluconate) used in the tin-zinc alloy plating bath of the present invention is suitably from 10 to 100 g / L in the bath.
[0017]
The Sn ²⁺ concentration in the tin-zinc alloy plating bath of the present invention is suitably about 20 to 25 g / L. In addition, the amounts of the components (a) and (b) in the alloy bath need to be adjusted according to the target alloy composition. However, when replacing the tin-lead alloy plating, the melting point and the film properties are required. Considering (strength), a zinc content of 5 to 10 (wt%) is considered to be optimal. At this time, the concentration of the component (b) is suitably 2 g / L. Further, the amount of the component (c) in the tin-zinc alloy plating bath of the present invention is 1 to 5 g / L, which is sufficient to obtain a dense and smooth plated surface with good adhesion. Good.
[0018]
To the tin-zinc alloy plating bath of the present invention, in addition to the above-described components, a brightener, an antioxidant, a wetting agent, and the like can be added as needed, as long as the effects of the present invention are not impaired.
[0019]
In addition, as a Sn ²⁺ antioxidant, for example, catechol, resorcin, hydroquinone and the like can be used.
[0020]
When plating is performed using the tin-zinc alloy plating bath of the present invention thus obtained, for example, the bath temperature of the plating bath is preferably about 15 to 25 (° C.), and the cathode current density is about 1 to 5 A / dm 2. Is preferred. Furthermore, tin, a tin-zinc alloy, an insoluble electrode, or the like can be used as the anode.
[0021]
The tin-zinc alloy plating film obtained from the above-described tin-zinc alloy plating bath has a dense and smooth appearance, and should be used in plating baths for electronic components and semiconductor components as a substitute for tin-lead alloy plating. Can be.
[0022]
【Example】
Hereinafter, the present invention will be described with reference to Examples and Test Examples, but the present invention is not limited to these Examples and Test Examples.
[0023]
Example 1
A tin-zinc alloy plating bath was prepared according to the following composition according to a conventional method.
(composition)
Sodium gluconate: 50 g / L
Stannous sulfate: 36g / L
Zinc sulfate-7 hydrate: 8 g / L
Polyoxyethylene lauryl ether: 2 g / L
[0024]
Test example 1
Using the plating bath obtained in Example 1, a 20 × 50 (mm) copper plate was plated under the following conditions.
[0025]
(Plating conditions)
Cathode current density: 2A / dm2
Bath temperature: 20 ° C
Stirring: Stirrer Stirring film thickness: 5 microns / 10 minutes
Each of the plated copper sheets processed using the plating bath of Example 1 had a plating film having uniform and fine crystals.
[0027]
【The invention's effect】
The tin-zinc alloy plating film obtained by the tin-zinc alloy plating bath of the present invention has a dense and smooth plating surface, and is used as a plating bath for electronic components and semiconductor components as an alternative to the tin-lead alloy plating bath. Available. In addition, since it is low in cost and does not contain harmful lead compounds, it is advantageous in terms of safety, environmental problems, pollution prevention, and the like.

Claims (3)

A tin-zinc alloy plating bath containing the following three components (a), (b) and (c).
(A) Sn ²⁺
(B) Zn ²⁺
(C) polyoxyethylene alkyl ether The tin-zinc alloy plating bath according to claim 1, wherein the alkyl group (R) [formula (1)] of the polyoxyethylene alkyl ether is a lauryl group [formula (2)].

The tin-zinc alloy plating bath according to claim 2, wherein the alkyl group [formula (1)] of the polyoxyethylene alkyl ether is a lauryl group [formula (2)], and wherein n = 4 to 13.