Effects of Phosphorus Addition on the Corrosion Resistance of Sn–0.7Cu Lead-Free Solder Alloy

The corrosion behavior of Sn–0.7Cu–xP (x = 0, 0.1, 0.3, 0.5) solder alloy in the aggressive environment was investigated by potentiodynamic polarization and weight loss method. Scanning electron microscope (SEM) was used to observe the morphology of Sn–0.7Cu–xP solder alloys and X-ray diffraction (XRD) was applied to characterize the phases formed on the surface after corrosion. The results indicate that phosphorus (P) can enhance the corrosion resistance of Sn–0.7Cu solder alloy whether in acidic or in alkaline solution, and its corrosion resistance increases with increasing P. The corrosion resistance of the solder alloy is better in alkaline solution compared to that in acidic solution. The morphology observation also shows that the incorporation of P into Sn–0.7Cu alloy can obviously decrease the damage extent of the solder alloys. XRD analysis reveals that the corrosion products both in acidic and alkaline solution are Sn oxides.