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通过添加1％ 和2％(质量分数)的Bi提高SAC305焊接接头的性能,并研究Bi掺杂对SAC305?xBi/Cu焊接接头显微组织、热性能和力学性能的影响.Bi掺杂通过细化初始β-Sn和共晶相改善焊接接头的显微组织.当Bi含量低于2％ 时,Bi溶解到β-Sn基体中形成固溶体;而当Bi含量等于或高于2％时,β-Sn基体中形成Bi的沉淀相.β-Sn基体中的固溶强化和析出强化机制使合金的极限抗拉强度和硬度分别从35.7 MPa和12.6 HV提高到55.3 MPa和20.8 HV,但是伸长率从24.6％降至16.1％.含2％Bi焊接接头断口呈典型脆性断裂形貌.所有焊接接头的界面层由两个平行的IMC层组成:Cu6Sn5层和Cu3Sn层.与SAC305/Cu焊接接头相比,SAC305?xBi/Cu焊接接头的界面层更薄,剪切强度更高.因此,添加少量Bi可以细化SAC305/Cu焊接接头的显微组织,降低熔点并提高其力学性能.“,”This research sought to improve the properties of SAC305 solder joints by the addition of 1 and 2 wt.％Bi. The effects of bismuth doping on the microstructure, thermal properties, and mechanical performance of the SAC305?xBi/Cu solder joints were investigated. Bi-doping modified the microstructure of the solder joints by refining the primaryβ-Sn and eutectic phases. Bi-doping below 2 wt.％dissolved in theβ-Sn matrix and formed a solid solution, whereas Bi additions equal to or greater than 2 wt.％ formed Bi precipitates in the β-Sn matrix. Solid solution strengthening and precipitation strengthening mechanisms in theβ-Sn matrix increased the ultimate tensile strength and microhardness of the alloy from 35.7 MPa and 12.6 HV to 55.3 MPa and 20.8 HV, respectively, but elongation decreased from 24.6％ to 16.1％. The fracture surface of a solder joint containing 2 wt.％ Bi was typical of a brittle failure rather than a ductile failure. The interfacial layer of all solder joints comprised two parallel IMC layers:a layer of Cu6Sn5 and a layer of Cu3Sn. The interfacial layer was thinner and the shear strength was greater in SAC305?xBi/Cu joints than in SAC305/Cu solder joints. Therefore, small addition of Bi refined microstructure, reduced melting temperature and improved the mechanical performance of SAC305/Cu solder joints.