Wettability of Sn-8Zn-3Bi lead-free solder alloy on copper substrate was evaluated via measuring the contact angle of the solder and the substrate. The measured contact angle then compared to the contact angle of the traditional and widely used eutectic Sn-37Pb solder alloy. Experiment to study the effect of temperature, flux, and surface roughness of the substrate on contact angle were also carried out. The results show that contact angle of Sn-8Zn-3Bi on copper substrate decreased as temperature increases. The minimum value of contact angle obtained was approximately 23° for Sn-8Zn-3Bi. At the same experimental conditions, contact angle of Sn-8Zn-3Bi is higher than that of Sn-37Pb. When three types of fluxes were used, at 230°C, contact angle of Sn-8Zn-3Bi has the smallest value with the MHS37 flux, 25°, and it has the largest value with the zinc chloride flux, 47°. Surface roughness of the substrate shows little influence on contact angle of Sn-8Zn-3Bi on copper, the contact angle changes a few degrees as the roughness changed
