Viscoplastic Creep Characterization of Novel Sn–0.7Cu-0.2Ni–xAl Lead-Free Solders for Electronics Applications

Document Type : Original Article

Authors

1 Physics Department, Faculty of Science, Zagazig Univ., Zagazig, Egypt.

2 Modern Academy of Engineering and Technology, Basic Science Department, Cairo, Egypt

Abstract

In this study, the effects of adding 0.1-0.2wt.%Al on microstructure and creep properties of Sn–0.7Cu-0.2Ni (SCN) alloys were investigated. The presence of Ni in SCN alloy inhibits the polymorphic transition of Cu6Sn5 IMC particles and forms a more stable (Cu,Ni)6Sn5 IMC particles. After Al-microalloying, the Sn–0.7Cu-0.2Ni–xAl alloys exhibit heterogeneous-structure with an additional fine Al3Ni2 and Al2Cu IMC phases and coarse (Cu,Ni)6Sn5 IMCs. Adding of 0.1%Al to SCN solder is the most effective in softening while the creep rate and yield strength is slightly maintained down to the SCN solder level. Hence, the desirable creep property was attained in SCN-0.1 wt.%Al solder could play a significant role in drop impact performance enrichment in electronic devices. The creep deformation at stresses of 8.8–23.4 MPa is characterized by a stress exponents of 4.4-5.0 and activation energy of 46.8-53.9 kJ.mol-1 close to that for pipe-diffusion of Sn, which are typical of dislocation creep mechanism.

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