Thermal Cycle Failure of SnPb Solder Joint for Flip Chip Package and Effects of Underfill Material
倒装焊SnPb焊点热循环失效和底充胶的影响

The thermal cycle lifetim es of Sn Pb solder joints for flip chip package were determined experim entally. With vis- coplastic and viscoelastic materials representing the mechanical behavior of Sn Pb solder and underfill,respectively,the stress/ strain responses of Sn Pb solder joints under thermal cycling with finite element method are simulated.Based on the calculated plastic strain ranges and the experim ental therm al cycle lifetim es,the material constants in Coffin- Manson empirical equation were then obtained.The results show that,the plastic strain ranges of solder joints with underfill decrease distinctly and the thermal cycle lifetim es are approxim ately2 0 times larger than that in the case without underfill.Moreover,the influences of solder joint height on solder joint reliability are weakened for the flip chip package with underfill.