摘要:
基于蠕变模型采用有限元法对WLCSP30器件Sn3.9Ag0.6Cu焊点可靠性及疲劳寿命进行预测.研究发现WLCSP器件整体的最大应力集中在阵列最拐角焊点的上表面处,该部位可能成为焊点裂纹的发源地,试验结果也验证了模拟结果的正确性.对焊点应力-应变分析,发现焊点部位出现明显的蠕变应变和蠕变应变能累积现象,结合焊点疲劳寿命方程,预测焊点疲劳寿命,发现基于蠕变应变能密度的计算结果和试验结果较吻合,但是基于蠕变应变的预测结果和试验结果相差较大,因此基于蠕变应变的疲劳寿命预测方程需要进一步的研究.
Abstract:
Based on creep model,the fatigue life of Sn3.9Ag0.6Cu-soldered joints in WLCSP device is predicted using finite element method.It is found that the stress concentrates on the top surface of the outermost soldered joints,and this location could be the origin of micro-crack,which is in well agreement with the experimental results.After the stress-strain analysis,the accumulated increase of creep strain and creep strain energy density was found in the soldered joints,respectively.Two life prediction equations,comparing with the experimental results,were employed to analyze the fatigue life of SnAgCusoldered joints under thermal cycling test.It is seen that the calculated life with creep strain energy based fatigue life prediction equation coincides well with that of the experimental data,and the life calculated by creep strain based equation is significantly higher than that of the experimental result,therefore,the creep strain equation needs to be further studied.
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