电-力耦合作用下Cu/Sn-3.0Ag-0.5Cu/Cu微焊点的拉伸力学性能和断裂行为

对比研究三明治结构线形Cu/Sn-3.0Ag-0.5Cu/Cu微焊点在拉伸、电-拉伸和电迁移后电-拉伸三种加载模式下的力学行为和断裂特性,并基于电流引发的焦耳热效应和电迁移效应,从电流对原子和空位扩散、空位浓度及位错滑移与攀移的影响等方面,探讨电-力耦合载荷对焊点拉伸断裂行为的影响。结果表明,焊点在电-拉伸时应力-应变曲线呈现快速变形、线性变形和加速断裂三阶段,其中快速变形阶段是以焦耳热引起的热弹性变形为主,而拉伸和电迁移后电-拉伸时应力-应变曲线只存在线性变形和加速断裂阶段;电迁移后电-拉伸时焊点断裂强度和断裂应变最小而等效模量最大,拉伸加载时焊点断裂强度和断裂应变最大而等效模量最小;电-拉伸时β-Sn相趋于沿电、力加载方向排列;三种加载模式下焊点断裂均发生在钎料体内,呈韧性断裂。

Mechanical Performance and Fracture Behavior of Microscale Cu/Sn-3.0Ag-0.5Cu/Cu Joints under Electro-tensile Coupled Loads

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.