PCB化学镀镍层改性对置换镀金的影响

Effect of modification of electrolessly plated nickel coating on immersion gold plating thereon for PCB

分别采用盐酸-氯化铜溶液、硫酸-双氧水溶液和硫酸高铈溶液对化学镀Ni层或Pd层进行改性,再置换镀Au。研究了改性溶液组成和工艺条件对Au层厚度(镀金速率)的影响,得到较佳的改性工艺条件为:温度50℃,时间4 min。对比了采用不同溶液改性Ni层时置换镀Au层的微观形貌和晶体结构。结果表明,表面改性不会对Ni层造成腐蚀,对Au层晶面择优取向的影响也不大,但对Au层的平均晶粒尺寸有一定的影响。采用盐酸-氯化铜溶液或硫酸高铈溶液改性能够显著提高置换镀Au的速率。

Prior to immersion gold plating,the electrolessly plated Ni coating or Pd coating was modified with a solution composed of chloric acid and copper(Ⅱ)chloride,a solution composed sulfuric acid and hydrogen peroxide,or a cerium(Ⅳ)sulfate solution.The effects of the solution composition,temperature,and time for the modification on the thickness of Au coating(i.e.Au deposition rate)were studied.The optimized modification temperature and time were 50℃and 4 min,respectively.The micromorphologies and phase structure of Au coating deposited on the Ni coating modified with different solutions were compared.The results showed that the surface modification of Ni coating had not only no corrosive attack to itself,but also no impact on the preferred orientation of Au coating,while had certain influence on the average grain size of Au coating.The deposition of gold during immersion plating could be increased significantly if the Ni coating was modified with the solution composed of chloric acid and copper(Ⅱ)chloride or the cerium(Ⅳ)sulfate solution.