Effects of copper content in Sn-based solder on the intermetallic phase formation and growth during soldering

Abstract

This research has studied the effects of copper contents in the Sn-based solder (i.e. Sn-0.7Cu, Sn-1.0Cu, and Sn-3.0Cu) on the intermetallic phase formation and the growth during soldering. In the experiments, reflow soldering was performed at 350 °C with the Cu substrate by using three solders for various soldering times of 10, 20, 40, 60, 120, 240 and 480 s. XRD data have shown that the η-Cu6Sn5 and ε-Cu3Sn phases with hexagonal crystal structure were present between the solder and the substrate. The presence of ε-Cu3Sn phase was found only when the substrate was soldered for at least 240 s. The Cu content in solder had significant effects on the intermetallic growth with long term soldering time. In addition, the diffusion coefficient was correlated to the Cu content in the solder.