Effects of diamond nanoparticles reinforcement into lead-free Sn–3.0Ag–0.5Cu solder pastes on microstructure and mechanical properties after reflow soldering process

• Diamond nanoparticles were added into Sn–3.0Ag–0.5Cu solder by mechanical mixing to form nanocomposite solder paste.
• Nanoparticles in the solder transported with flux to the surface during reflow.
• The addition of nanoparticles into solder paste significantly reduced the intermetallic compound thickness.
• The plain solder hardness increased by 77.5% with the addition of 0.5 wt.% diamond nanoparticles.

This paper presents the effects of diamond nanoparticles reinforcement on lead-free SAC 305 solder paste after the reflow soldering process. Different diamond nanoparticles amounts (0.5, 1.5, and 2.5 wt.%) were mechanically mixed with SAC 305 to produce a new form of nanocomposite solder paste. The characteristics of the nanocomposite solder, such as melting point, morphology and thickness of the intermetallic compound (IMC), agglomeration of diamond nanoparticles, and hardness, were investigated. The experimental results revealed that the addition of diamond nanoparticles slightly decreases the melting point but significantly reduces the IMC thickness. The morphologies of the nano-reinforced solder paste showed the agglomeration of nanoparticles on the surface of the solder paste with increasing diamond nanoparticles percentage. The addition of 0.5 wt.% diamond nanoparticles was well embedded in the solder matrix after the reflow soldering process. The hardness of the nano-reinforced solder paste was evaluated via nanoindentation technique. The addition of 0.5 wt.% diamond nanoparticles improved the hardness of SAC 305 by 77.5%. Increasing the nanoparticles amount by 1.5 and 2.5 wt.% in SAC 305 enhanced the hardness of SAC 305–0.5 wt.% by 6.3% and 17.8%, respectively.

FESEM micrographs of cross-sectional view of Sn–3.0 wt.% Ag–0.5 wt.% Cu–x wt.% diamond nanoparticles on copper substrate after reflow soldering process: (a) x = 0; (b) x = 0.5; (c) x = 1.5 and (d) x = 2.5.Figure optionsDownload as PowerPoint slide