Effect of Amount of Cu on the Intermetallic Layer Thickness Between Sn-Cu Solders and Cu Substrates

In the present study, Sn-Cu solders were synthesized using pure tin with varying weight percentage of nanosized copper particles (0 wt.%, 0.25 wt.%, 0.43 wt.%, 0.86 wt.%, and 1.35 wt.%) by a powder metallurgy route incorporating microwave-assisted sintering. Intermetallic compound (IMC) layer formation between Sn-Cu solders and Cu substrates was investigated following a reflow process. Isothermal aging studies were also conducted on selected Sn-Cu solders at 150°C for up to 4 weeks. Results revealed that the average IMC layer thickness decreases with the addition of nanocopper up to 0.43 wt.%. Beyond 0.43 wt.% Cu addition, the IMC layer thickness started to increase, and the maximum IMC layer thickness was found for Sn with 1.35 wt.% Cu addition. An attempt was made in this study to correlate the effect of nanocopper additions and aging time on the IMC layer thicknesses.