The surface oxidations of molten Sn(Ag, Ni, In, Cu) alloys are studied. We conclude that the microstructure (phase and density) of the surface oxide layer is the key factor for the surface oxidation formation. Also, we found that the microstructure (phase and density) of the Sn surface oxide layer is highly influenced by the additives in the solder alloys, which can be roughly anticipated from the additives' electromagnetic field values and Gibbs free energies of oxide formation. The detailed effect (either retarding or enhancing) of the additives on the surface oxidation is discussed in this paper.
