乙内酰脲体系无氰电镀铜工艺的研究

发布时间：2018-11-05 07:46

【摘要】：金属铜具有良好的导电性、导热性和延展性,是防止渗氮、渗碳的优良镀层,在电镀中常作为金、银、镍等金属的打底层或中间层。氰化物电镀铜可以直接在钢铁、锌合金表面进行电镀而不生成置换层,且得到的镀层光亮、致密,但由于氰化物有剧毒,急需开发出一种可以替代氰化物镀铜的体系。本文通过对比不同的辅助配位剂,确定了以焦磷酸钾为辅助配位剂,以DMH为主配位剂的复合配位无氰电镀铜工艺。通过单因素实验,研究了镀液组分和工艺条件对镀液稳定性、阴极电流效率以及镀层外观、微观形貌等的影响,确定了优化的乙内酰脲体系无氰电镀铜工艺。实验结果表明,硫酸铜浓度、焦磷酸钾浓度、温度、搅拌强度等条件对镀层的外观及镀液的阴极电流效率、工作电流密度上限的影响较大。优化后的镀液组成及工艺条件分别为:硫酸铜25g·L~(-1),DMH 100 g·L~(-1),焦磷酸钾60 g·L~(-1),碳酸钾30~90 g·L~(-1):p H 9~10,温度50℃,搅拌速度600 rpm,阴极电流密度为1.5~4.0 A·dm-2。在此条件下,可以得到外观平整、光亮、致密的铜镀层。通过Hull槽实验筛选出了可用于本体系的添加剂,发现加入添加剂后镀层的外观得到改善,光亮电流密度范围明显变宽,但镀液的阴极电流效率有所降低。实验证明,镀液的稳定性、分散能力、覆盖能力优异,阴极电流效率达到80%,电沉积速度达到32μm·h~(-1);镀层与钢铁基体结合牢固,孔隙率较少。用SEM观察发现,镀层晶粒细小,细致均匀。循环伏安曲线、阴极极化曲线等电化学研究表明,DMH与焦磷酸钾复配体系中Cu~(2+)的电沉积过程为扩散控制的不可逆过程,Cu~(2+)的阴极传递系数α为0.8548,在含有25 g·L~(-1)的Cu~(2+)的镀液体系中,Cu~(2+)的扩散系数为3.79×10-9 cm2·s~(-1)。焦磷酸钾的加入增大了阴极极化,抑制了析氢反应的发生,提高了阴极电流效率;但添加剂的加入使镀液的阴极极化减小,这不符合电沉积的实际需求,需要再进行深入探索。
[Abstract]:Metal copper has good electrical conductivity, thermal conductivity and ductility. It is an excellent coating to prevent nitriding and carburization. It is often used as the bottom layer or intermediate layer of gold, silver, nickel and other metals in electroplating. Copper electroplating with cyanide can be carried out directly on the surface of iron and steel and zinc alloy without the formation of replacement layer, and the coating is bright and dense. However, because cyanide is highly toxic, it is urgent to develop a system that can replace cyanide copper plating. In this paper, by comparing different auxiliary coordination agents, the process of complex coordination without cyanide electroplating with potassium pyrophosphate as auxiliary coordination agent and DMH as coordination agent was determined. The effects of bath composition and process conditions on bath stability, cathodic current efficiency, coating appearance and micromorphology were studied by single factor experiments. The optimized cyanide free copper plating process was determined. The results show that the influence of copper sulfate concentration, potassium pyrophosphate concentration, temperature and stirring intensity on the appearance of the coating, cathodic current efficiency and working current density upper limit of the plating solution are significant. The optimized bath composition and process conditions are as follows: copper sulfate 25g L ~ (-1), DMH 100g L ~ (-1), potassium pyrophosphate 60g L ~ (-1), potassium carbonate 3090 g L ~ (-1): p H 910, temperature 50 鈩，

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