Study On The Properties Of Sb And In For Sn-15Bi Solid Solution Solder And Solder Joint

With the continuous development of microelectronics industry and the implementation of lead-free,Sn-Bi solder has good wettability and good performance,which makes it have broad application prospects.Interconnect solder joints play an important role in mechanical structure support and electrical connection in electronic packaging system.However,due to the development trend of miniaturization and integration,the size and spacing of solder joints are continuously reduced,which brings increasingly severe challenges to solder joints.Therefore,it is of great significance to study the reliability of solder joints.In this thesis,the effects of Sb and In elements on the microstructure and mechanical properties of Sn-15Bi solder were studied.It was found that the tensile strength and hardness of Sn-15Bi-x Sb solder gradually increased with the increase of Sb content,while the elongation gradually decreased.The tensile strength,elongation and hardness of Sn-15Bi-x In solder decrease gradually with the increase of In element content.During isothermal aging,the precipitation strengthening caused by the precipitation of fine Bi particles makes the hardness of Sn-15Bi-x Sb solder and Sn-15Bi-x In solder gradually increase with the extension of aging time.Secondly,the changes in the micro-interface and shear properties of Sn-15Bi-x Sb/Cu and Sn-15Bi-x In/Cu solder joints with different Sb and In contents before and after isothermal aging were studied,and in-depth analysis was carried out on the metallurgical reaction at the interface of solder joints,the growth of interfacial compounds,fracture mode and shear strength.It was found that the composition of interfacial compounds in Sn-15Bi-x Sb/Cu solder joints was Cu₆（Sn,Sb）₅,and the growth rate of interfacial compounds gradually decreased with the increase of Sb content during isothermal aging,and the shear strength of the corresponding solder joint is higher,and the brittle fracture of the solder joint occurs in the compound layer.When the content of In element is less than5wt.%,the composition of intermetallic compounds in Sn-15Bi-x Sb/Cu solder joints does not change,but when the content of In element reaches 5wt.%,the composition of intermetallic compounds is Cu₆（Sn,In）₅.The addition of In element reduces the resistance of diffusion of Cu-Sn reaction atoms at the interface,promotes the growth of intermetallic compounds at the interface,and the shear strength of solder joints gradually decreases with the increase of In content,and the fracture mode gradually changes from ductile fracture to brittle fracture.Finally,the microstructure and interface behavior changes of Cu/Sn-15Bi/Cu,Cu/Sn-15Bi-5In/Cu and Cu/Sn-15Bi-3Sb/Cu linear solder joints were studied at room temperature（25℃）and current density of 1×10⁴A/cm²for 8 days.Bi atoms in Cu/Sn-15Bi/Cu solder joints migrate and aggregate to anode under the action of electromigration driving force,but no Bi-rich layer is formed.The addition of 5wt.%In improves the solid solubility of Bi in Sn,and the migration of Bi atoms in solder joints is inhibited.However,the addition of 3wt.%Sb leads to the increase of solder joint temperature,which promotes the migration of Bi and Cu atoms.More obvious Bi migration and polarity effect are observed,which reduces the reliability of solder joint electromigration.