In this study, Mo nanoparticles were used as a reinforcing material into the Sn-3.8Ag-0.7Cu (SAC)
solder on the nickel (Ni) substrate electrodeposited on polycrystalline copper (Cu) sheets. The Mo nanoparticles
were characterized by transmission electron microscopy (TEM) and X-ray diffractometer (XRD). The
composite solder pastes were prepared by manual mixing of Mo nanopartic1es with the SAC solder paste. Ni
layer was electrodeposited on polycrystalline Cu substrate by using the Watts bath. The solder paste was placed
on the substrate by following the Japanese Industrial Standard (nS) and reflowed up to six times at 250°C for 45
seconds. After first reflow, elemental compositions of the nanocomposite solders were analyzed by inductively
coupled plasma-optical emission spectrometer (ICP-OES). The spreading rate and wetting angle of the solder
were determined after first reflow. Microstructural investigations at the solder joints were carried out by using
high resolution field emission scanning electron microscope (FESEM) and energy dispersive X-ray (EDX).
Results reveal that after reflow only a fraction of Mo nanoparticles were retained inside the solder matrix. Mo
nanoparticles are effective in suppressing the growth of total IMC layer and scallops during reflow. The
retardation of IMC thickness and scallop diameter is suggested due to the discrete particle effect of Me
nanoparticles