Interfacial reaction between Sn1Ag0.5Cu(Co) solder and Cu substrate with Au/Ni surface finish during reflow reaction

In order to clarify the effect of the addition of Co to SAC105 solder, the reaction between solder and Au/Ni surface finish has been investigated, and the joint strength was also evaluated by a ball shear test. After soldering, the interfacial reaction layer in the SAC105Co solder contained Co, and the chemical composition of intermetallic compounds (IMCs) were identified as (Cu,Ni,Co)6Sn5 and (Ni,Cu,Co)3Sn4 by energy-dispersive X-ray spectrometer (EDX), which significantly differed from that of SAC105 solder. After multiple reflows, the formation rate of the (Cu,Ni,Co)6Sn5 IMC for the Co-added solder slow compared with that of (Cu,Ni)6Sn5 IMC for SAC105 solder. Experimental results clearly indicate that adding small amounts (0.05 wt.%) of Co to SAC105 solder strongly affected the formation of the IMC at the interface. Furthermore, ball shear test results demonstrate that the SAC105 and SAC105Co solder joints have good joint reliability.