摘要
The collapse-free joints were successfully built under a low reflowing temperature of 185 °C via using the Sn–Ag–Cu(-Ni)/Sn–Bi hybrid solders. Such a structure with middle and low melting points solders could prevent the infrastructure of 3D packages from collapse caused by overweight of stacked dies on substrates. Furthermore, a low bonding temperature could reduce the consumption of thermal budget during chip fabrication. By introducing Ni-doped Sn–Ag–Cu solder, the potential harm micro-Ag Sn particles adjacent to the interfacial Cu Sn layer in Sn–Ag–Cu/Sn–Bi/Cu joints were suppressed. Also, the microstructure of the hybrid joints was investigated in detail as well.