化学镍金工艺中金剥落问题的探讨

Study on gold-peeling of electroless nickel immersion gold

化学镍金工艺能够有效的保护导电和焊接表面而被广泛的应用于PCB行业。然而,针对该工艺的品质保证绝非易事。化学镍金工艺受药水等因素的影响,在品质上容易会出现甩金、渗镀等不良问题。本文利用SEM、EDS分析手段对化学镍金工艺中的甩金问题进行了分析探讨。结果发现:甩金处镍层被腐蚀而形成空洞,EDS分析发现镍层中含有铜元素。这很有可能是金缸受到污染,镀液中存在一定含量的Cu2+,镍层与Cu2+发生自发的置换反应置换出铜而沉积在镍层上面,从而腐蚀镍层形成大量孔洞,使之与金层的结合力下降,导致化学镍金后甩金。

Electroless nickel/immersion gold（ENIG） technology is widely used in printed circuit board（PCB）,providing a protective,conductive and solderable surface.However,it is not easy to control the quality assurance of the process.For ENIG the problem of gold peeling easily occurs influenced by chemical medicine.Therefore,in this paper,the problem of gold peeling was studied by SEM and EDS.The results showed that Nickel has been corrupted,and emerged many pinholes.Cu element is found in nickel plating.This is most likely contaminated by chemical medicine in gold tank.When there is a certain content of Cu2＋,Cu2＋ and Ni will spontaneously occur displacement response,and deposit on top of Ni.The binding force of Ni and gold is significantly reduced,which occurred gold peeling.