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

Abstract

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)6Sn5/Ni and (Ni, Cu)3Sn4 was detected at the Sn3Ag0.5Cu/Ni interface. A (Ni, Cu)3Sn4 layer formed at the (Cu, Ni)6Sn5/Ni interface and once the (Ni, Cu)3Sn4 layer had formed, it grew at an exceptionally rapid rate by consuming the (Cu, Ni)6Sn5 layer. The (Cu, Ni)6Sn5 layer was much thicker than the (Ni, Cu)3Sn4 layer after reflowing, but the (Ni, Cu)3Sn4 layer thickened rapidly and would to be thicker than the (Cu, Ni)6Sn5 layer after prolonged aging. The (Ni, Cu)3Sn4 grains revealed an elongated, rod-like shape while the (Cu, Ni)6Sn5 IMC was Polyhedral shape, which was on the top of (Ni, Cu)3Sn4 phase. The thicknesses of total IMC and (Ni, Cu)3Sn4 increased linearly with square root of aging time, while the thickness of (Cu, Ni)6Sn5 did not increase significantly. The activation energies for the diffusion constants of the total interfacial IMC and (Ni, Cu)3Sn4 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.