采用电化学阻抗谱(EIS)和扫描Kelvin探针技术(SKP)研究了热风整平无铅喷锡处理印制电路板(PCB-HASL)在模拟电解质0.1 mol/L NaHSO₃以及不同pH值的0.1 mol/L NaHSO₃/Na₂SO₃溶液中的腐蚀行为与机理, 探讨了浸泡时间和pH值对其腐蚀机理转变的影响, 通过OM, SEM结合EDS对PCB-HASL表面上腐蚀产物形核和扩展行为进行了观察和分析. 结果表明, PCB-HASL试样在酸性NaHSO₃/Na₂SO₃溶液体系中的腐蚀形式类似点蚀, 浸泡前期腐蚀坑加速扩展, 腐蚀产物主要为Sn的氧化物和硫酸盐. NaHSO₃溶液能够活化PCB-HASL试样表面, 且腐蚀坑形核仅发生在浸泡初期. 而在中性或碱性NaHSO₃/Na₂SO₃溶液体系中, PCB-HASL试样表面腐蚀坑形成受到抑制, 电解质溶液通过氧化膜向电极界面的传输过程限制了电极反应速率.

With the innovation of electronic technology, integration and miniaturization become the future developing direction of printed circuit board (PCB). Meanwhile, the corrosion problems of PCB also stand out more clearly, and even trace amounts of corrosion products will have a serious impact on the reliability of PCB. Under the actual condition for use, like sulfur-containing industrial environment, due to the diurnal temperature variations or/and the temperature field fluctuations for PCB itself, condensation phenomenon is likely to occur. Furthermore, as a result of the moisture absorption effect of granular deposit or supersaturated humidity, a layer of electrolyte solution will be formed on the surface of PCB, causing electrochemical corrosion. In this work, electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP) techniques were used to study the corrosion behavior and mechanism of hot air solder leveling printed circuit boards (PCB-HASL) in a simulated electrolyte 0.1 mol/L NaHSO₃ and 0.1 mol/L NaHSO₃/Na₂SO₃ solutions with different pH values, and the influences of immersion time and pH value on the change of corrosion mechanism were discussed. Meanwhile, with the aids of OM, SEM combined with EDS, the nucleation and propagation processes of corrosion products on the surface of PCB-HASL were observed and analyzed. SEM and EDS results showed that the corrosion behavior of PCB-HASL in acid simulation solution was similar to pitting corrosion, and the corrosion pits were in a state of accelerated expansion at the early immersion stage. The corrosion products mainly consisted of oxides and sulfates of Sn. EIS and SKP analysis indicated that the PCB-HASL surface could be activated by NaHSO₃ solution and pitting nucleation process only occurred at the early immersion stage. In the neutral or alkaline solution system of NaHSO₃/Na₂SO₃, pitting corrosion couldn't occur, and the transmission of the electrolyte to the electrode interface through the oxide film was the control step of the corrosion reaction.