原位研究 PCB-ENIG 在吸附薄液膜下的大气腐蚀行为

摘要

通过阴极极化曲线、交流阻抗谱以及 SEM、XPS，原位研究了相对湿度对无电镀镍金印制电路板(PCB-ENIG)在吸附薄液膜下的影响机制。结果表明：PCB-ENIG 板在薄液膜下的阴极过程主要包括 O2、腐蚀产物和 H2O 的还原过程。阴极电流密度随相对湿度的增加而增加，并且均小于溶液中阴极电流密度，表明扩散过程并不是阴极氧化还原过程的控制步骤。极化电位较负时，75%和85%相对湿度下的阴极极化电流密度逐渐减小。随着腐蚀产物的增加，试验后期腐蚀过程由阳极过程控制。%The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.