Interfacial reactions between Sn–3.0Ag–0.5Cu solder and Cu–xZn (x=0–35wt%) or Cu–xZn–yNi (x=20 and 25wt%, y=15 and 10wt%) substrates

Abstract The interfacial reactions of Sn–3.0Ag–0.5Cu (SAC 305) solder on Cu– x Zn ( x = 0 wt%, 10 wt%, 15 wt%, 30 wt%, and 35 wt%) substrates and Cu– x Zn– y Ni ( x = 20 wt% and 25 wt%, y = 10 wt% and 15 wt%) were investigated after soldering and isothermal aging. SAC 305 solder was reacted with Cu– x Zn and Cu– x Zn– y Ni substrates by dipping Cu– x Zn or Cu– x Zn– y Ni wires into molten solder at 250 °C for 90 s. After soldering, Cu 6 Sn 5 -based intermetallic compound (IMC) formed at the solder interfaces. After aging at 150 °C, a bi-layer structure of Cu 6 Sn 5 /Cu 3 Sn formed, and microvoids were observed in the Cu 3 Sn layer at the SAC/Cu solder interfaces. For SAC/Cu–Zn samples, Cu 6 (Sn, Zn) 5 was the predominant reaction product, and formation of Cu 3 Sn was not observed. Interfacial IMC growth was delayed as the Zn concentration increased. In addition, the Cu(Zn, Sn) phase formed at the Cu 6 (Sn, Zn) 5 /Cu–Zn interfaces in the Cu– x Zn substrates with a high Zn concentration (30 wt% and 35 wt%). In the case of the Cu– x Zn– y Ni samples, the major interfacial IMC was (Cu, Ni) 6 (Sn, Zn) 5 phase. The Ni atoms from the Cu– x Zn–Ni substrates participated in the interfacial reaction at the SAC/Cu– x Zn– y Ni interfaces and resulting in the formation of a thick and layered IMC phase, comparing to those at the SAC/Cu–Zn interfaces. Although the effect of Ni addition to the Cu–Zn substrates exhibited delayed IMC growth, the Zn concentration in the Cu– x Zn– y Ni substrates influenced the IMC growth behavior more than the Ni concentration.