Influence of bismuth on microstructure, thermal properties, mechanical performance, and interfacial behavior of SAC305−xBi/Cu solder joints
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.
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万方数据
维普
