Effects of Ni nanoparticles addition on the microstructure, electrical and mechanical properties of Sn-Ag-Cu alloy

The effects of Ni nanoparticles addition on the microstructure, electrical resistivity and mechanical properties such as elastic/shear moduli, microhardness and creep of Sn-3.0Ag-0.5Cu (SAC305; in wt.%) electronic interconnect materials have been investigated. Microstructure analysis of Sn-3.0Ag-0.5Cu-0.5 Ni nanoparticles (in wt.%) solder revealed that adding Ni nanoparticles has promoted the formation and growth of (Cu, Ni)-Sn intermetallic compound (IMC) in the bulk phase of the samples and the structure of composite material resulted refined. This finer structure and (Cu, Ni)-Sn IMCs in a composite solder resulted in improved mechanical and electrical properties with respect to the Sn-3Ag-0.5Cu reference alloy. Indeed, a comparison between the reference alloy and composite material doped with 0.5 wt.% Ni nanoparticles indicates that the improvement in elastic and shear modulus was 8% and 11.2%, respectively, whereas the microhardness value was increased about 16.7%. Moreover, in the electronic interconnect systems on organic solderability preservative (OSP)-Cu pad, a scallop-shaped Cu6Sn5 IMC was detected at their interfaces at early stage reaction. Increasing the reaction time, the growth of the Cu6Sn5 and the formation of a very thin Cu3Sn IMC layer was observed. However, in Sn-3.0Ag-0.5Cu-0.5 Ni nanoparticles composite material, a very stable (Cu, Ni)-Sn IMC grew at the interface between composite solder and (OSP)-Cu pad in absence of Cu3Sn IMC. In addition, a relatively fine Ag3Sn and (Cu, Ni)-Sn IMC appeared to be evenly dispersed in β-Sn matrix and the fine microstructure surely affect the overall properties of solder joints.