湿热环境下倒装焊无铅焊点的可靠性

对板上倒装芯片底充胶进行吸湿实验,并结合有限元分析软件研究了底充胶在湿敏感元件实验标准MSL—1条件下吸湿和热循环阶段的解吸附过程,测定了湿热环境对Sn3.8Ag0.7Cu焊料焊点可靠性的影响,并用蠕变变形预测了无铅焊点的疲劳寿命。结果表明:在湿热环境下,底充胶材料内部残留的湿气提高了焊点的应力水平。当分别采用累积蠕变应变和累积蠕变应变能量密度寿命预测模型时,无铅焊点的寿命只有1740和1866次循环周期。

Reliability of lead-free solder joint for FCOB in hygrothermal environment

By moisture absorption test and using a commercial FEA software, moisture absorption in moisture sensitive component test criterion MSL—1 (85 ℃, RH 85% and 168 h) and desorption in thermal cycle stage of the underfill of flip chip on board (FCOB) was investigated. Then, effects of hygrothermal environment on reliability of lead-free flip chip Sn3.8Ag0.7Cu solder joint were determined. Based on creep deformation, the fatigue life of lead-free solder joint was predicted. The results show that the residual moisture within underfill materials enhances the stress level in solder joint. Therefore, when the life prediction model of based on the accumulated creep strain and accumulated creep strain energy density were implemented, the life values of lead-free solder joint are 1 740 cycles and 1 866 cycles, respectively.