The purpose of this paper is to investigate the effects of zinc (Zn) nanoparticles on the interfacial intermetallic compounds (IMCs) between Sn‐3.8Ag‐0.7Cu (SAC) solder and Cu substrate during multiple reflow.
The nanocomposite solders were prepared by manually mixing of SAC solder paste with varying amounts of Zn nanoparticles. The solder pastes were reflowed on a hotplate at 250°C for 45 s for up to six times. The actual Zn content after reflow was analyzed by inductively coupled plasma‐optical emission spectroscopy (ICP‐OES). The wetting behavior of the solders was characterized by analyzing the contact angles and spreading rates according to the Japanese Industrial Standard (JIS 23198‐3, 2003). The interfacial microstructure of the solder joints were investigated by field emission scanning electron microscope (FESEM) and energy dispersive X‐ray spectroscopy (EDAX).
It was found that upon the addition of 0.3 wt% Zn nanoparticles to the SAC solder, the growth of interfacial intermetallic compound (IMC) layers was retarded to a minimum value. Excessive amount of Zn nanoparticles (0.8 wt%) induced an additional IMC layer (Cu5Zn8) which increased the total IMC thickness and raising the reliability issue.
It is concluded that Zn nanoparticles undergo melting/reaction during reflow and impart their effect on the IMCs through alloying effects.
