Hybrid solder joints: morphology and shear strength of Sn-3.0Ag-0.5Cu solder joints by adding ceramic nanoparticles through flux doping

The shear strength and microstructural evolution of as-cast SAC305 solder joints by addition of various ceramic nanoparticles have been investigated. In contrast to the most popular approach of adding the nano-sized inclusions directly to the SAC solder, the nano-sized Al2O3, SiO2, TiO2, and ZrO2 were added to the commercial flux to improve the standard SAC305/Cu joints. In this case, the solder joint was prepared from a sandwich Cu/flux + nanoceramic/SAC305/flux + nanoceramic/Cu. The nanocomposite fluxes with various content (0-1.0 wt%) ceramic nanoparticles (NPs) were employed in our study. The analysis of the microstructure and mechanical properties of the produced hybrid SAC305 solder joints showed several satisfactory modified results. For instance, the growth kinetics of the interfacial Cu-Sn IMC decreased by the addition of Al2O3, SiO2, and ZrO2 NPs into the flux. The shear stress tests displayed an increase of this mechanical property of the corresponded hybrid solder joints. In contrast, an addition of up to 0.5 wt% nano-TiO2 increased the growth kinetics of the interfacial Cu-Sn layer. Furthermore, a comparison analysis showed that the most beneficial influence was obtained by minor additions of SiO2 NPs into the SAC305 solder alloy.