无电镀镍浸金处理电路板在NaHSO_3溶液中的腐蚀电化学行为与失效机制

Corrosion behavior and failure mechanism of electroless nickel immersion gold processing circuit boards in NaHSO_3 electrolyte solution

采用交流阻抗谱研究了无电镀镍浸金处理电路板在模拟电解质溶液(0.1mol·L-1NaHSO3)中的电化学腐蚀行为,并结合体视学显微镜、扫描电镜、X射线能谱分析等手段分析了试样表面腐蚀产物形貌、组成和镀层失效机制.无电镀镍浸金处理电路板在NaHSO3溶液中的耐蚀性较差,浸泡12h试样表面局部即发生变色,伴随有微裂纹的产生.电解液能够通过裂纹直接侵蚀Cu基底,并在微裂纹周围生成较多的枝晶状结晶产物,其主要组分为Cu2S.该结晶腐蚀产物的不断生成使局部区域中间Ni过渡层与Cu基底结合部位存在较大的横向剪切应力,最终造成Ni镀层的脱离与鼓泡现象.

Electrochemical impedance spectroscopy （EIS） was used to study the corrosion behavior of electroless nickel immer- sion gold processing printed circuit boards （PCB-ENIG） in a simulated electrolyte solution （0. 1 mol. L-1 NaHSO3 ） , and the mor- phology, composition of corrosion products as well as the failure mechanism of the plating layer were analyzed with the aid of stereo mi- croscopy and scanning electron microscopy （SEM） combined with energy dispersive spectrometry （EDS）. It is found that the corro- sion resistance of PCB-ENIG in NaHSO3 solution is relative poor. Partial discolor appears in PCB-ENIG just immersing for 12 h, along with micro-crack generation. The electrolyte can directly erode the Cu substrate through micro-cracks, forming dendritic crystal- line products around these micro-cracks, whose main composition should be Cu2 S. Continuous generation of these corrosion products results in large transverse shear stress between the Ni intermediate layer and Cu substrate, and eventually bubbling and shedding of the Ni plating layer occur.