无铅焊点在电迁移与高低温冲击下的失效机理

研究了Cu/Sn-3.0Ag-0.5Cu/Cu焊点接头在电迁移与高低温冲击双重耦合作用下的失效机理。结果表明,在高低温冲击条件下,由于铜柱、钎料合金及镶样用环氧树脂的热膨胀系数不匹配,因此,焊点接头在高低温冲击过程中无法自由伸缩,在热疲劳的作用下,焊接接头易于在界面处形成裂纹,且随着时间的延长裂纹会发生扩展,造成焊点接头的有效横截面积减小,使得焊点接头的电阻增大、焦耳热增加,进而导致焊点接头发生熔化而失效。

Failure mechanism of the lead-free solder joints during the coupling effect between electromigration and high and low temperature impact

Failure mechanism of the Cu/Sn-3.0Ag-0.5Cu/Cu solder joints was investigated during the coupling effect between electromigration and high and low temperature impact.Results indicate that under the high and low temperature impact condition,because of the mismatch of coefficients of thermal expansion of copper,solder alloy and epoxy resin,solder joints cannot stretch and contract freely during the high and low temperature impact cycles,thus,cracks tend to form and propagate at the solder/Cu rod interface under the function of thermal fatigue.The propagation of the cracks leads to the reduce of the effective cross sectional area of solder joints,and that lead to the increment of the solder joints resistance,eventually a lot of joule heat is created which lead to the melting failure of solder joints.