Effect of Cu6Sn5 nanoparticles addition on properties of Sn3.0Ag0.5Cu solder joints

The ever-increasing packaging density of electronic products has led to a dramatic reduction in the dimensions of solder joints, which further results in a surge in current density and harsher operating environments. The reliability of lead-free solders is facing more and more challenges during service. In this study, Cu6Sn5 nanoparticles (NPs) were added to Sn3.0Ag0.5Cu (SAC305) solder paste to improve its mechanical strength and service reliability. We designed an ultrasound-assisted method to prepare Cu6Sn5 NPs and studied the effect of energy input on the crystallinity and size of Cu6Sn5 NPs. Cu6Sn5 NPs with an average diameter of 19.1 nm were prepared in ultrasonic bath for 15 min. The addition of Cu6Sn5 NPs could improve the solderability of the composite solder paste while having little effect on the melting point. Since the adsorption of Cu6Sn5 NPs at the interface reduced the interfacial energy, the addition of Cu6Sn5 NPs could also inhibit the growth of the interfacial IMC layer. When the mass fraction of Cu6Sn5 NPs was 0.6 wt%, the shear strengths of the solder joints increased by 13.5% to 53.8 MPa. In general, the composite solder joints prepared by adding Cu6Sn5 NPs have better solderability and shear strength, which can improve the reliability of SAC305 in harsh operating environments.