印刷电路板Cu/焊锡界面早期局部腐蚀的扫描微参比电极测量

Scanning Micro Reference Electrode Testing of Localized Corrosion at Cu/Solderingtin Interface in Early Stage

应用扫描微参比电极(SMRE)技术,对NaCl溶液中印刷电路板Cu/焊锡界面局部腐蚀早期表面微区电位分布进行了测量。结果表明,在0.5 mol/L NaCl溶液中,焊锡电极电位基本稳定在-0.47 V(SCE)附近,纯铜电极的电位稳定在-0.19V(SCE)附近,两者差别较大;Cu/焊锡浸入0.5 mol/L NaCl溶液中,前期局部腐蚀发生在Cu与焊锡接触的界面上,且腐蚀程度随时间逐渐达到最大;以后焊锡作为阳极腐蚀逐渐加剧,而铜作为阴极受到保护,腐蚀程度逐渐减弱,直至焊锡最终全面腐蚀。

The localized corrosion in the early stage of Cu/solderingtin interface was observed by scanning micro reference electrode （SMRE） technique. SMRE results showed that the corrosion of Cu/soldering tin didn＇ t occur immediately after immersed in 0.5 mol/L NaC1 solution. The localized corrosion took place after immersed for about half an hour. With the immersion time extended to four hours, the localized corrosion occured in the interface of Cu and soldering tin, and the degree of corrosion reached the maximum. When immersion time was between five and six hours, the corrosion of the interface and soldering tin became worse gradually. After seven hours, galvanic corrosion was even more remarkable. The soldering tin as an anode was corroded gradually and the copper as a cathode was protected.