Simulation analysis on surface morphology and hysteresis characteristics of molten Sn–3.0Ag–0.5Cu sitting on the inclined Ni substrate

To investigate interface properties of molten Sn–3.0Ag–0.5Cu solder melting on the inclined Ni substrate at 540 K, wetting experiments are performed and the numerical simulation is carried out by Surface Evolver. Profile curves of the droplets are fitted with empirical equation, which are proposed to obtain preferable contact angles. The spreading behavior of the droplets is analyzed. It is indicated that the contact line hardly moves at the very beginning; the rear point of triple line moves forward along the substrate subsequently, but the front point of triple line is still pinned on the substrate. Correspondingly, the advancing contact angle gradually increases to the peak value, and then declines with the migration of the front point of triple line. The spreading process is simulated to demonstrate the contact angle hysteresis. Interface microstructure is observed to clarify the effect of reactions on the spreading behavior, and the distribution of intermetallic compounds including Ni3Sn4 and (Cu,Ni)6Sn5 are identified.