配位剂对MSA体系电镀锡–铟合金的影响及镀层的焊接可靠性

Effect of complexing agent on electroplating of Sn–In alloy in methanesulfonic acid electrolyte and welding reliability of the coating

在甲基磺酸(MSA)体系Sn-In合金镀液(含MSA 60 g/L、Sn^(2+)12 g/L、In^(3+)2.5 g/L、对苯二酚8 g/L、明胶0.5 g/L及聚乙二醇2000 15 g/L)中分别添加10 g/L的柠檬酸或葡萄糖酸作为配位剂,通过循环伏安法研究了两种配位剂对Sn、In共沉积的影响。结果表明二者均可实现Sn和In的共沉积。通过X射线光电子能谱(XPS)、X射线衍射(XRD)和扫描电镜(SEM)对比了在相同条件下从不同配位体系中所得Sn-In合金镀层的元素组成、相结构和表面形貌。与柠檬酸配位体系相比,葡萄糖酸配位体系所得Sn-In合金镀层的In原子分数更高,微观上更细致平整,外观上更光亮,与低温共晶Sn58Bi焊膏焊接时形成的金属间化合物(IMC)层比相同条件下裸铜板焊接所形成的IMC层更薄。

Electroplating of Sn-In alloy was carried out by adding 10 g/L of citric acid or gluconic acid as complexing agent to a methanesulfonic acid(MSA) based electrolyte comprising MSA 60 g/L,Sn^(2+)12 g/L,In^(3+)2.5 g/L,hydroquinone 8 g/L,gelatin 0.5 g/L,and polyethylene glycol 2000 15 g/L.The effects of the two complexing agents on the codeposition of Sn and In was studied by cyclic voltammetry.The results showed that the codeposition of Sn and In can be realized in the electrolyte containing citric acid or gluconic acid.The elemental composition,phase structure,and surface morphology of the Sn-In alloy coatings electroplated from different electrolytes under the same operation conditions were examined by X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),and scanning electron microscopy(SEM).As compared with the Sn-In alloy coating electroplated from the citric acid complexing electrolyte,the one electroplated form the gluconic acid complexing electrolyte had higher atomic fraction of In,finer and smoother micromorphology,and brighter appearance.The thickness of intermetallic compound(IMC) layer formed at interface between Sn-In alloy coating electroplated from the gluconic acid complexing electrolyte and low-temperature eutectic Sn58Bi solder paste was thinner than that formed by soldering on blank copper.