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采用试验观测和数值模拟相结合的方法研究表面贴装板级封装焊点在热疲劳过程中的裂纹萌生及扩展规律。结果表明,在热疲劳过程中,焊点上存在着3个典型的热疲劳裂纹萌生位置,其中器件与钎料的交角附近区域最容易发生裂纹萌生。这与数值模拟分析得到的焊点在热疲劳过程中所产生的非弹性应变分布规律基本一致。无铅钎料焊点相对于锡铅钎料焊点具有相对较长的热疲劳寿命;焊盘尺寸较小时,热疲劳裂纹扩展速度相对较大。这与焊点中的等效非弹性应变数值具有较好的一致性。
The combination of experimental observation and numerical simulation is used to study the law of crack initiation and propagation during the thermal fatigue of surface mount board-level package solder joints. The results show that there are three typical thermal fatigue crack initiation sites on the solder joint during the thermal fatigue test, and the crack initiation is most likely to occur in the vicinity of the contact angle between the device and the solder. This is consistent with the distribution of inelastic strain produced by thermal fatigue in the solder joints obtained by numerical simulation. Lead-free solder joints have a relatively long thermal fatigue life compared to solder joints of tin-lead solder; when the pad size is small, the thermal fatigue crack growth rate is relatively large. This has a good agreement with the equivalent inelastic strain in the solder joint.