Investigation on nano-reinforced solder paste after reflow soldering part 1: Effects of nano-reinforced solder paste on melting, hardness, spreading rate, and wetting quality
Abstract In this study, the effects of three distinctive contents of metal oxide [Iron Nickel Oxide (Fe2NiO4), Iron Oxide (Fe2O3), Nickel Oxide (NiO), and Indium Tin Oxide (ITO)] and carbon nanostructure [diamond (C)]-reinforced solder paste on melting behavior, hardness, spreading rate, and wetting angle after reflow soldering were differentiated. Each nanoparticle was mechanically mixed with SAC 305 solder paste to produce homogeneous nanocomposite solder alloys. Based on the results, the addition of nanoparticles slightly increased the melting point; except for the SAC 305-ITO and SAC 305-Diamond composite solder pastes. The SAC 305-ITO composite solder showed negligible effects, but the SAC 305-Diamond composite solder reduced the melting point. The SAC 305-Diamond composite solder exhibited a very high increment in solder hardness compared with other nanocomposite solder pastes. Reinforcement of 0.5 wt% diamond nanoparticles increased solder viscosity higher than other metal oxide nanoparticles. The flow rate of SAC 305-Diamond molten solder on Cu substrate decreased upon the nanoparticle addition during reflow soldering. The reduction in the spreading caused the enlargement in the wetting angle of solder paste. However, very low percentage of carbon nanostructure addition into molten solder alloys reduced the melting point and increased solder hardness with tolerable spreading rate and wetting quality, which enhanced solder reliability after reflow.