Mechanical performance and fracture behavior of microscale Cu/Sn-3.0Ag-0.5Cu/Cu joints under electro-tensile coupled loads

Abstract

Mechanical performance and fracture behavior of microscale line-type Cu/Sn-3.0Ag-0.5Cu/Cu joints under electro-tensile coupled loads are investigated, comparing with those in tests under tensile load and under electro-tensile coupled loads following electromigration test. The focus is placed on clarifying the effect of electro-tensile coupled loads with a current density of 1.0×104 A/cm2 on the tensile fracture behavior of joints, and the effect of electro-tensile coupled loads is explained based on Joule heating and electromigraion effect induced by electric current, in terms of the influence of electric current on the diffusion of atoms and vacancies, the change of vacancy concentration, and dislocation slipping and climbing. Results show that the stress-strain curves of solder joints under electro-tensile coupled loads exhibit three distinct stages, i.e., fast deformation stage at the beginning of loading, linear deformation stage, and the accelerating fracture stage. The fast deformation stage is dominated by thermo-elastic deformation induced by Joule heating. It is worth noting that only the linear deformation stage and accelerating fracture stage exist in joints under either tensile load or electro-tensile coupled loads following electromigration test. Furthermore, the fracture strength and strain is the lowest, and the equivalent modulus is the highest in joints under electro-tensile coupled loads following electromigration test, while it is reverse in joints under tensile load. Moreover, the orientation of β-Sn phase tends to rearrange along the direction of electric current and tensile load, and the fracture occurs in the middle of solder joints with a ductile fracture mode regardless loading conditions.