添加Mg对Sn-9Zn-3Bi钎料显微组织及性能的影响OA

Alloying is a crucial approach for developing new solders.To investigate the effects of Mg addition on the microstructure,melting point,wettability,oxidation resistance,hardness,and intermetallic compound(IMC)layer formation at the Sn-9Zn-3Bi/Cu joint interface,Sn-9Zn-3Bi lead-free solder was selected as the base material and was alloyed with trace amounts of Mg.Results showed that as the Mg content increased,the melting point of the Sn-9Zn-3Bi solder decreased,while its spreading area on the Cu substrate initially increased and then decreased.Notably,the addition of Mg significantly improved the solder's oxidation resistance.Microstructural analysis revealed that the solder primarily consists of β-Sn phases,granular Bi-rich phases,short needle-like β-Sn/Zn-rich eutectic phases,and coarse needle-shaped Zn-rich phases.As the Mg content increased,the microstructure underwent a transition from refinement to coarsening,resulting in a corresponding increase followed by a decrease in hardness.Although the introduction of Mg did not alter the type of IMC layer at the joint interface,the thickness of the IMC layer first decreased and then increased with increasing Mg content.When the Mg mass fraction reaches 0.05%,the solder achieved an optimal balance among all performance parameters.