Effects of Co nanoparticle addition to Sn–3.8Ag–0.7Cu solder on interfacial structure after reflow and ageing

Effects of Co nanoparticle additions to Sn–3.8Ag–0.7Cu on the structure of solder/copper interface have been studied after reflow and high temperature ageing (150 °C, up to 1008 h). Results show that the Co nanoparticles substantially suppress the growth of Cu3Sn but enhance Cu6Sn5 growth. Cobalt nanoparticles reduce interdiffusion coefficient in Cu3Sn. It is suggested that the Co nanoparticles undergo surface dissolution during reflow and exert their influence, at least partially, through alloying effect.

Research highlights
► This work presents data on the effects of Co nanoparticles on the interfacial intermetallic compounds in between lead-free solder and copper substrate.
► The work shows that the addition Co nanoparticles suppresses the growth of Cu3Sn but enhances the growth of Cu6Sn5.
► It is suggested that Co nanoparticles undergo dissolution during reflow and impart then influence through alloying effect.