Interfacial reaction and IMCs growth behavior of Sn3Ag0.5Cu/Ni solder bump during aging at various temperatures

The interfacial reaction, morphology, and growth behavior of interfacial intermetallic compound (IMC) between the Sn-3Ag-0.5Cu (in wt%) solder and Ni substrate during reflow at 523 K for 300 s and aging at different temperatures for up to 360 h were investigated, and the growth kinetics of the interfacial Ni-Cu-Sn ternary IMC layers were monitored during the isothermal aging. The experimental results showed that a bi-layer of IMCs including (Cu, Ni)(6)Sn-5/Ni and (Ni, Cu)(3)Sn-4 was detected at the Sn3Ag0.5Cu/Ni interface. A (Ni, Cu)(3)Sn-4 layer formed at the (Cu, Ni)(6)Sn-5/Ni interface and once the (Ni, Cu)(3)Sn-4 layer had formed, it grew at an exceptionally rapid rate by consuming the (Cu, Ni)(6)Sn-5 layer. The (Cu, Ni)(6)Sn-5 layer was much thicker than the (Ni, Cu)(3)Sn-4 layer after reflowing, but the (Ni, Cu)(3)Sn-4 layer thickened rapidly and would to be thicker than the (Cu, Ni)(6)Sn-5 layer after prolonged aging. The (Ni, Cu)(3)Sn-4 grains revealed an elongated, rod-like shape while the (Cu, Ni)(6)Sn-5 IMC was Polyhedral shape, which was on the top of (Ni, Cu)(3)Sn-4 phase. The thicknesses of total IMC and (Ni, Cu)(3)Sn-4 increased linearly with square root of aging time, while the thickness of (Cu, Ni)(6)Sn-5 did not increase significantly. The activation energies for the diffusion constants of the total interfacial IMC and (Ni, Cu)(3)Sn-4 IMC layers were obtained by plotting the diffusion constants (D) as a function of the aging temperature (1/T), and were 91.43 and 89 KJmol(-1), respectively.