Study on reactive wetting of Sn0.7Cu-xZn lead-free solders on Cu substrate

The reactive wetting properties of Sn_0.7Cu-xZn (x=0,0.2,0.5,1.0) lead-free solder on Cu substrate were investigated by using the wetting balance test under the condition of air and N2 environment respectively. Even tiny addition of Zn could lead the surface tension of solders to increase greatly comparing to the original Sn_0.7Cu solder due to the and oxidation of Zn in air, but in the N2 atmosphere, the effect of Zn on the surface tension of solder is small. And since the first IMC could affect the wetting property according to the reactive wetting theory, the effect of IMC formation on wetting was discussed based on the recent reactive-wetting theory. Using the CALPHAD (Thermo calc software) method, the first IMC that forms during wetting reaction were analyzed. And with the Zn content increasing, the IMC formed during wetting test changed from Cu6Sn5 into y-CuZn both from EDX analysis and CALPHAD method