: Sn-Pb commercial solder is used as a solder in electronic connections due to its appropriate mechanical properties and good wetting and reliability. However, the lead in this solder is toxic and causes irreparable damage to humans and the environment. Numerous alternatives for Sn-Pb solder have been introduced, one of which is the Sn-0.7Cu eutectic alloy. Due to lower production costs of Sn-0.7Cu than other lead-free solders, acceptable wetting and electrical conductivity, and high creep resistance, it is an attractive alloy for replacing Sn-Pb solder. In contrast, its low tensile strength compared to Sn-Pb solder has limited its application. Nowadays, with increasing miniaturization of electronic devices, electronic packaging systems must have a higher current density, better performance, longer lifespan and, at the same time, they should be smaller in size. Synthesis of Sn-0.7Cu matrix nanocomposite solder is one of the approaches to resolve improper mechanical properties. In this research, Sn-0.7Cu lead-free nanocomposite solder was synthesized by adding 0.5 and 1 percent silica nanoparticles through angular accumulative extrusion. The results of the characterization of samples containing 0.5% and 1% nanoparticles indicated a 22% and 12% increase in the tensile strength of as-synthesized nanocomposites respectively. After reflow of the lead free nanocomposite solders, increase of 9 and 17% in shear strength, 41 and 44% of the tensile strength and 14 and 32% of microhardness were achieved for the nanocomposite reinforced with 0.5 and 1 percent nanoparticles compared to the monolithic sample, respectively. Also, adding nanoparticle resulted in the smaller wetting angle, finer microstructure, and the suppress of the growth of intermetallic compounds at the solder-substrate interface of the naocomposite samples compared to the monolithic one. Although amorphous ceramic nanoparticles have been added to the solder matrix, no significant change was observed in the electrical conductivity of the nanocomposite solder. Keywords: Lead-free solder, nanocomposite, angular accumulative extrusion method, nanoparticles, intermetallic compounds, mechanical properties
