62Sn－36Pb－2Ag焊点的可靠性及热疲劳位错亚结构的演化分析

The Reliability Analysis and Thermal Fatigue Dislocation Substructure Evolution of 62Sn-36Pb-2Ag Solder Joints

采用热疲劳试验分析了表面封装焊点的可靠性。讨论了不同的元器件及基片镀层工艺对焊点可靠性的影响，初步探讨了热疲劳过程中位错亚结构的变化及焊点的失效机理。结果表明：金属间化合物对焊点失效有重要影响．镀Ａｕ焊点热疲劳裂纹萌生于ＡｕＳｎ４金属间化合物并在其中扩展，镀Ｎｉ／Ａｕ焊点热疲劳过程中位错在ＡｕＳｎ４粒子处塞积，引起ＡｕＳｎ４／β－Ｓｎ界面应力集中，导致热疲劳裂纹沿ＡｕＳｎ４／β－Ｓｎ界面萌生，萌生后的裂纹在β－Ｓｎ相中扩展，ＴＥＭ观察也证明β－Ｓｎ相中位错密度较高。

The reliabilrty of 62Sn-36Pb-2Ag surface mount solder joints has been analyzed by means of thermal fatigue tests.Meanwhile,the effect of different plated process for components and substrate on reliability is discussed,and the evolution of thermal fatigue dislocation substrucure and failure mechanism of solder joints have been studied tentatively. The results show that:intermetallic compounds influence the reliability of solder joints significantly,for solder joints of components and substrate plated with Au ,the thermal fatigue cracks initate and propagate in AuSn4 intermetallic compounds ;on the other hand, solder joints plated with Ni/Au ,cracks initiate at the AuSn4/β-Sn interface. TEM observation finds out that there is high density dislocation in β-Sn phase after crack initiation.