Effect of ultrasonic vibration on the interfacial IMC three-dimensional morphology and mechanical properties of Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu halogen free solder joints
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Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu halogen free solder joints were fabricated by an ultrasonic vibration (USV)-assisted soldering process. The effects of the USV power on the three-dimensional (3-D) morphology of the intermetallic compounds (IMC) and mechanical properties of the halogen free solder joints were characterized systematically. Results showed that the root-mean-square roughness (Rrms) and the mean spacing of adjacent peaks of the profile (λave) of the interfacial IMC were linearly correlated with shear strength of the halogen free solder joints. It was more comprehensive to adopt the λave and Rrms evaluation parameters to characterize the relationship between the interfacial IMC 3-D morphology and shear strength of the halogen free solder joints. With increasing USV power, the eutectic microstructure of the solder seam was refined, and the proportion of eutectic microstructure in the solder seam and microhardness increased. When the USV power increased to 130 W, the Rrms and average thickness of the interfacial IMC decreased (decreases of 37.6% and 56.4%, respectively) and the corresponding λave and shear strength of the solder joint increased (increases of 68.7% and 45.8%, respectively). With increasing USV power, the fracture mechanism of the halogen free solder joint changed from brittle fracture to the ductile–brittle mixed fracture, and the fracture pathway transferred from the interfacial transition zone consisting of the solder seam and the interfacial IMC layer to the solder seam.
This work was financially supported by the National Natural Science Foundation of China under Grant No. U1604132, the Plan for Scientific Innovation Talent of Henan Province under Grant No. 154200510022, the National Science and Technology International Cooperation of China under Grant No. 2014DFR50820 and the Collaborative Innovation Center of Non-ferrous Metals, Henan Province, China.
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Conflict of interest
All of the authors declare that they have no financial and personal relationships with other people or organizations.