In-situ alloying of Sn-3.5Ag solder during reflow through Zn nanoparticle addition and its effects on interfacial intermetallic layers

Driven by the necessity to improve the reliability of lead free electronic products and by the trend towards miniaturization, researchers are putting intense efforts to improve the properties of Sn based solders. The present work investigates the effects of Zn nanoparticle addition to Sn-3.5Ag (SA) alloy through paste mixing on the interfacial structure between solder and copper substrate during reflow. Results show that the addition of Zn nanoparticles does not alter the morphology of the interfacial intermetallic compounds although they substantially suppress their growth. Zn nanoparticles are seen to be most efficient compared with Co and Ni nanoparticles in suppressing the growth of Cu3Sn layers. It is suggested that Zn nanoparticles exert their influence through an in-situ dissolution and alloying effect.