Influence of Solder Layer Thickness on the Interfacial Reaction in Ni/Sn/Cu System

In this paper, we reported a study on the effect of solder volume on the intermetallic layer morphology and thickness in the Ni/Sn/Cu system wi th 10μm, 20μm, 40μm Sn layer. The content of Cu and Ni in the solder increased wi th the reducing of solder volume. In the aging process, the IMCs at Cu/Sn boundary remained stable with nearly constant thickness in 10μm and 20μm Sn layer diffusion couples, of which the scallop-shaped IMCs at Sn/Ni side transformed into rod-shaped, and tended to connect mutually after 24 hours aging, while in 40μm the IMC layer continued to grow at a fast rate, and the IMCs of (Cu, Ni) 6 Sn 5 at Sn/Ni boundary transformed rapidly into planar after 96h aging. Lower volume of solder may lead to increasing density of (Cu, Ni) 6 Sn 5 rods and formation of Kirkendall voids at Cu/ IMC interface, which is a reliability concern. For the addi tion of Ni prevents the formation of Cu 3 Sn, no visible Cu 3 Sn was detected at the Sn/Ni boundary.