Nanocomposites and nanomaterials
The effect of CoPd nanoparticles on the morphology and shear strength of the Sn-3.0Ag-0.5Cu/Cu solders joint
Yakymovych A.S.1,2, Plevachuk Yu.O.2, Slabon A.3, Švec P.Sr.4,  Orovcik L.5, Bajana O.5
1 Department of Inorganic Chemistry – Functional Materials, Faculty of Chemistry, University of Vienna, Althanstr., 14, Vienna-1090, Austria. 
2 Department of Metal Physics, Faculty of Physics, Ivan Franko National University of Lviv, Kyrylo & Mephodiy str. 8, Lviv-79005, Ukraine.
E-mail: plevachuk@mail.lviv.ua
3 Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden
4 Department of Metal Physics, Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 84511 Bratislava, Slovakia
5 Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dubravska cesta 9, 84511 Bratislava, Slovakia

The development of commercial solder joints nowadays is focused on reinforcement of lead-free Sn-based solders with ceramic or metal nanoparticles (NPs). The effect of bimetallic CoPd NPs on the microstructure and the shear strength of the Cu/SAC305/Cu solder joint was studied. The nanocomposite Sn-3.0Ag-0.5Cu (SAC305) solders with 0.1, 0.3, 0.5, and 1.0 wt.% nanoCoPd were prepared through a paste mixing method. The employed bimetallic NPs were produced via a modified oleylamine method. The microstructural analysis of as-solidified Cu/solder/Cu joints was performed by scanning electron microscopy. The results showed that initial additions of CoPd NPs into the SAC305 solder promoted the growth of the interfacial planar-type Cu3Sn IMC layer; while the average thickness of the interfacial scallop-type Cu6Sn5 IMC layer slightly decreased. Further additions of nanosized CoPd NPs to the SAC305 solder paste lead to a significant increase of the average thickness of the Cu6Sn5 intermetallic compound layer up to 40%. Also, the shear strength measurements were performed to investigate a relationship between the microstructure and mechanical properties of the investigated solder joints. The results indicated a decrease in the shear strength of the SAC305 solder joint by addition of 0.1 wt.% CoPd NPs; while a difference in absolute values between solder joints with 0.3, 0.5, and 1.0 wt.% nanoCoPd was practically insignificant.