Research On Failure Mechanism And Behavior Of SnAgCu Solder Joints Under Current Aging And Thermal Cycling Coupling With Current

The BGA technology is a commonly used micro-interconnect method.With the introduction of lead-free,the Sn Pb used in BGA solder balls is gradually replaced by lead-free solder.A commonly used solder is Sn-3.0Ag-0.5Cu.The performance of lead-free solder will change in the course of service.Its performance decline will affect the reliability of the chip,and lead to the failure of the product.Under the service condition,thermal mismatch will lead to a great deal of thermal stress in the position of the solder joints,while the material migration phenomenon caused by current will lead to holes in the solder joints and other problems.Thermo-electric often leads to a significant reduction in the failure time of the solder joints.Many reliability problems are related to the morphology evolution of the solder joints under the impact of thermal and current.Therefore,it is of great significance to study the micro morphology evolution of solder joints and analyze the evolution mechanism for solving the problem of the failure and improving the reliability of the package.This paper analyzes the mechanism of recrystallization phenomenon and IMC morphological evolution of IMC in the solder by studying the morphology evolution behavior of SAC305 under thermal cycling and thermo-electric conditions.And in order to further analyze the function of current with EBSD technology,the organization evolution of the solder under electromigration is studied.The current distribution inside the solder joints is analyzed by finite element method.Firstly,under the condition of thermal cycle,the sudden position of geometry in the solder joints will be prone to recrystallization.The thickness of IMC at the interface position of the solder joints will gradually be thicken with increase of the cycles and change from scallop to layer.Secondly,the current,which is 1.15×10~3 A/cm~2,will cause the generation of joule heat and aggravate the occurrence of recrystallization in the solder joints under the condition of thermal-electric.The morphological evolution of IMC in the solder joints will appear polarization phenomenon.Finally,there is no obvious recrystallization phenomenon with the extension of the test time in the solder joint under the condition of the single current which was 6.2 A.The change of the crystal boundary angle appears in the local position,and the morphological evolution of IMC in the solder joints is affected by the migration speed of copper atoms and the grain orientation of the solder joints.The average thickness of the IMC is increased by 3.5μm after 588 h.The simulation results show that the power-on mode and the height of the solder joints will affect the current distribution of the local position in the solder joints.The current density approaches 10~4 A/cm~2 at local position.