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A. M. El‑Taher,A. F. Razzk 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
Preventing the formation of large platelets of Ag3Snintermetallic compounds (IMCs) during solidification of solder jointshas become a significant challenge in the design of Sn–Ag–Cu lead-free solder alloys. Large platelets of Ag3Snare generallyconsidered as undesirable as their presence can create solidification defects and causes mechanical property anisotropy. In the present work, the synergetic effects of adding 0.1 wt% of Fe, Co, Te and 2 wt% Bi to Sn–3.0Ag–0.7Cu (SAC 307)solder are studied in terms of the growth of large platelets Ag3SnIMCs and the resulting alloy’ creep resistance as well astheir thermal behavior. Although minor Fe, Co, Te and Bi alloying elements addition causes large increase in the degree ofundercooling from 3.4 to 22.3 °C with maintaining the pasty range and melting temperature at the same levels, the modifiedSAC307–FeTeCoBi alloy exhibits considerable increase in creep resistance (~ 10 times) and large fracture life-time thanSAC (307) solder at same stress levels and testing temperatures. This is attributed to the transition of Ag3SnIMCs from largeplatelets into fine needle-like morphology and formation of new (Cu,Co)6Sn5, FeSn2,SnTe IMCs and Bi particles, whichcould provide more obstacles for dislocation movement at the interphase boundaries.