| Abstract Scope |
The interfacial reactions between pure Sn and Cu-Fe alloy (C194) substrates were investigated under multiple reflow cycles at 240, 250, and 270 °C, each conducted for 3 min over 1 to 5 cycles. The results revealed that two types of intermetallic compounds (IMCs), (Cu, Fe)6Sn5 and (Cu, Fe)3Sn, consistently formed under all conditions. As the reflow cycle numbers increased, the IMC layers became denser. However, only the (Cu, Fe)6Sn5 layer exhibited significant growth in thickness, whereas the (Cu, Fe)3Sn phase remained discontinuous, with minimal variation in thickness. Kinetic analysis yielded n-values of 0.39, 0.31, and 0.29 at the respective temperatures, all close to 0.33, indicating that the IMC growth mechanism was controlled by grain boundary diffusion. This behavior is attributed to Fe atoms in the C194 alloy acting as heterogeneous nucleation sites, which promote IMC grain refinement and facilitate grain boundary diffusion. |