The coupling effects of thermal cycling and high current density on Sn58Bi solder joints
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Currently, one of the serious challenges in microelectronic devices is the miniaturization trend of packaging. As the decrease of joint dimension, electromigration (EM) and thermomechanical fatigue become critical issues for fine pitch packaging. The independent mechanisms of EM and thermomechanical fatigue are widely investigated and understood. However, the coupling effect of both conditions needs further exploration. The current study established the correlation between resistance and microstructure evolution of solder joint under the combination effect of thermal cycling and high current density and illustrated the different contributions of these two factors to the reliability of the joint through the comparison monopoly tests. The results revealed that cracks had more impact on resistance increase than phase segregation. The resistance evolution could be divided into three stages. First, the resistance mitigated due to the phase coarsening. Second, Joule heating effect made the resistance increase slowly. Third, EM led to the resistance increase rapidly. The high current density can help to improve the reliability of the solder joint under the coupling effect of thermal cycling and EM at the initial stage, but harmful to the consequence process.
KeywordsSolder Joint High Current Density Solder Matrix Phase Segregation Thermomechanical Fatigue
The authors acknowledge the support of this work from National Natural Science Foundation of China (Grant No. 51071006) and Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education (KZ200910005004).
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