应变率效应对无铅焊锡接点跌落冲击力学行为的影响

Influence of Strain Rate Effect on Behavior of Solder Joints Under Drop Impact Loadings

采用应变率相关的Johnson-Cook材料模型和率无关的弹塑性模型分别计算了跌落/冲击载荷下焊锡接点的应力及应变,研究应变率对焊锡接点力学行为的影响,预测了焊锡接点的破坏情况,并与动态4点弯曲实验结果进行了比较.结果表明:焊锡材料的应变率效应对电路板的挠度几乎没有影响,但对焊锡接点的应力及应变有较大影响;不考虑应变率效应的弹塑性模型低估焊锡接点的应力值而高估等效塑性应变值;采用率相关的Johnson-Cook模型能更好地预测焊锡接点的力学行为,能较真实地预测焊锡接点的破坏情况.

The strain rate dependent Johnson-Cook material model and the rate independent elastic-plastic model of lead-free solders are used to investigate the influence of strain rate effect on the mechanical behavior of solder joints under drop impact loadings. Failure of the solder joints is predicted and the results are compared with the experimental observations. The strain rate effect of lead-free solders has no influence on the deflection of the PCB during the drop impact but has significant influence on the stress and strain in solder joints. The rate independent elastic-plastic solder material model always underestimates the stress and overestimates the strain of the solder joints. The material model that takes the strain rate effect into account can predict more realistic behavior of the solder joints.