Transient liquid phase bonding (TLPB) of Cu to Cu using Sn interconnect solder reinforced by submicron Al particles

As an intermediate layer of transient liquid bonding, Sn interconnect solder is widely used in 3D chip stack interconnection due to its lower cost and excellent wettability. This study focuses on the effect of submicron Al particles on the interfacial microstructure and properties of Sn interconnect solder. Adding submicron Al particles efficiently restrained the growth of interfacial IMC and improved the wettability and mechanical properties of Sn interconnect solder, but it has little effect on the melting characteristics. When the 0.3 wt% submicron Al particles are added into Sn interconnect solder, the spreading area, shear strength and microhardness were improved by 69.5 %, 45.6 % and 20 %, respectively. Based on the content optimization of Al particles, the microstructure evolution and bonding strength of Sn-0.3Al interconnect solder as transient liquid bonding intermediate layer at different bonding times were studied. It was found that the growth rate of IMC and the number of voids in Sn-0.3Al TLPB joints were lower than those in the Sn TLPB joints. The bonding strength of TLPB joints increased with the increase of bonding time, and the bonding strength of Sn-0.3Al TLPB joints was always higher than that of TLPB joints without submicron Al.