Research On Creep Behavior Of Flip-chip Sn-3Ag-0.5Cu Solder Under Large Current Action

With a comprehensive total ban on leaded solder electronic field production anduse of America and other industrialized countries, relevant research on lead-freesolder flourished in the twenty-first century. Due to its good mechanical properties,Sn-Ag-Cu lead-free solder is considered one of the best Sn-Pb solder alternatives.Since Sn-Ag-Cu lead-free solder performance under specific package is notmuch, this dissertation selected Sn-3.0Ag-0.5Cu lead-free solder and studied the creepbehavior in Flip-chip packaging structure. The main contents of this dissertation areas following.Under343K,363K and383k temperature, studied the Sn-3.0Ag-0.5Cu creeplaws creep and organizational structure evolution in power-heat-stress couplingfield by experiments by high precision creep equipment. Obtained that within thescope of the current stress and temperature, creep index was2.30, the creep activationenergy was53.60KJ.mol-1and established the creep constitutive equation. In adding alarge current and reaching electromigration threshold condition, the current slowedcreep flip chip bump and bump’s fracture was mainly due to the intermetalliccompound interface morphology control. It reflected the huge difference between theadiabatic creep samples. When discussing the creep mechanism, it needed to considerfactors other aspects, such as sample size and the specific package type, the reactionwith the substrate solder plating metal, the proliferation and growth of intermetalliccompounds. Creep characteristic cannot be characterized by itself under differentpackaging structure.In the unpowered stress-the thermal coupling conditions, the Sn-3.0Ag-0.5Cusamples were made according to ASTM standards and were tested the stress-straincurve obtained under the condition358K,373K,398K with tensile machine. Aftercalculated the yield strength, comparatively studied tensile creep behavior of high-temperature Sn-3.0Ag-0.5Cu lead-free solder and analyzed the fracture mode bymicrostructure observation. The results showed that the creep rate of Sn-3.0Ag-0.5Cusignificantly enhances when unpowered, and its fracture failure mode is ductilefracture.