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研究了表面封装电路中 ６２Ｓｎ－３６Ｐｈ－２Ａｇ焊点的微观组成及－５５～１２５℃热疲劳过程中裂纹的萌生与扩展情况，初步探讨了微观组织变化与焊点热疲劳失效的关系。结果表明：焊点组成主要为先共晶β－Ｓｎ， α－Ｐｂ＋β－Ｓｎ共晶，ＡｕＳｎ４及Ａｇ３Ｓｎ金属间化合物。热疲劳过程中，焊点显微组织发生不均匀粗化，疲劳裂纹萌生于不均匀粗化区的 ＡｕＳｎ４金属间化合物与基体组织的界面或 α－Ｐｂ与 β－Ｓｎ的相界，并沿富Ｓｎ的β相晶界扩展。
The micro-composition of 62Sn-36Ph-2Ag solder joints in the surface mount circuit and the initiation and propagation of cracks during thermal fatigue at -55 ~ 125 ℃ were investigated. The relationship between the microstructure and the thermal fatigue failure of the solder joints was discussed. The results show that the solder joints mainly consist of eutectic β-Sn, α-Pb + β-Sn eutectic, AuSn4 and Ag3Sn intermetallic compounds. In the process of thermal fatigue, the microstructure of the weld spot is unevenly roughened, and the fatigue crack initiation occurs at the interface between the AuSn4 intermetallic compound and the matrix structure in the uneven roughening zone or the phase boundary between α-Pb and β-Sn, The β phase boundary of Sn expands.