论文部分内容阅读
采用96.5Sn3.0Ag0.5Cu无铅焊料以及一种免清洗助焊剂NCF(焊后不清洗)和一种水溶性助焊剂WSF(焊后清洗和焊后不清洗)分别焊接了3组PCB试件,进行了电化学迁移测试,评价助焊剂焊后残留物的绝缘可靠性。试验结果表明:使用NCF焊接后的第一组试件和使用WSF焊接(焊接后清洗)的第三组试件可以满足标准要求;使用WSF焊接(焊接后未清洗)的第二组试件最终绝缘电阻值下降幅度最大,不符合标准要求,并且在高倍显微镜下观察试件发现有树枝晶生成,说明助焊剂残留物的存在使得试件在试验条件下发生了电化学迁移现象。分析探讨了电化学迁移发生的原因,认为电化学迁移与清洗工艺、助焊剂的成分、固体含量和酸度有关。
Three sets of PCB test pieces were welded using 96.5Sn3.0Ag0.5Cu lead-free solder and a no-clean flux NCF (not cleaned after welding) and a water-soluble flux WSF (not cleaned after welding and not cleaned after welding) , An electrochemical migration test was conducted to evaluate the insulation reliability of the flux residue after soldering. The test results show that the first group of specimens after welding with NCF and the third group of specimens using WSF welding (post-welding cleaning) can meet the standard requirements; the second group of specimens using WSF welding (not cleaned after welding) Insulation resistance decreased the most, does not meet the standard requirements, and observed under high magnification microscope specimens were observed dendrite formation, indicating that the presence of flux residues makes the specimen electrochemical migration occurred under the experimental conditions. The reasons for the electrochemical migration were analyzed and discussed. It is believed that the electrochemical migration is related to the cleaning process, flux composition, solid content and acidity.