Sequential interfacial intermetallic compound formation of Cu6Sn5 and Ni3Sn4 between Sn-Ag-Cu solder and ENEPIG substrate during a reflow process

▶ Discontinuous polygonal-shape (Cu,Ni)6Sn5 IMCs formed at the Sn-3.0Ag-0.5Cu solder/ENEPIG interface during initial reflowing. ▶ Preferential consumption of Cu atoms within the solder. ▶ Continuous Ni diffusion from the Ni(P) layer. ▶ Sequentially variation of the interfacial IMCs: discontinuous (Cu,Ni)6Sn5-(Cu,Ni)6Sn5 and (Ni,Cu)3Sn4-embedded (Cu,Ni)6Sn5 in (Ni,Cu)3Sn4.