Analysis of Interface Stress of Sn3.5Ag0.75Cu Solder under Temperature Cycle QFP Device

Using elastoplastic finite element method study the interface stress distribution of Sn3.5Ag0.75Cu lead-free solder at different temperatures and different strain rate. Numerical analysis results show that: when strain-rate is identical, as the temperature rises, the interface stress increased rapidly of Sn3.5Ag0.75Cu lead-free solder and the substrate binding sites, from 11 ℃ when 2.6MPa rose to 90 ℃ in 49.7MPa, so the temperature is very large have effects of the interface stress of the lead-free solder and the substrate binding sites; when the temperature is constant, as the strain rate increases, Sn3.5Ag0.75Cu lead-free solder and the substrate binding sites of the interface stress showed a slight increase, from 0.005% / S when the 49.47MPa rose to 0.005% / S when the 50.08MPa, so strain rate on lead-free solder and the substrate binding sites of the interface stress effect is very small, indicating Sn3 .5Ag0.75Cu lead-free solder has strong rate-independent nature.