| Abstract Scope |
This study explores the interfacial reactions between FeCoNiCr and FeCoNiMn medium-entropy alloys and pure Sn or SAC305 solders at 250oC, with FeCoNiCrMn high-entropy alloy included for comparison. A stable (Fe,Cr,Co)Sn2 IMC layer formed in the Sn/FeCoNiCrMn system. In contrast, Sn/FeCoNiCr and Sn/FeCoNiMn systems showed severe IMC spalling. In the FeCoNiCr case, (Fe,Cr,Co)Sn2 spalled into the solder, attributed to the repulsive Cr-Sn interaction and formation of large (Co,Ni)Sn3 from substrate dissolution. The FeCoNiMn system exhibited a finer, more stable interface, as Mn enhanced element dissolution and suppressed spalling. Reactions with SAC305 solder resulted in finer (Fe,Co,Cu)Sn2 particles due to Cu doping, which stabilized IMCs and promoted nucleation. These findings emphasize the critical role of element selection, particularly Cr, Mn, and Cu, in controlling IMC morphology and interfacial stability, which is essential for improving solder joint reliability in advanced electronic packaging using MEA and HEA substrates. |