Static and Dynamic Surface Tension of Molten Eutectic Solder under Various Oxygen Concentrations

Abstract

The static and dynamic surface tensions of the molten eutectic solder were measured for various oxygen concentrations in the environment. When the oxygen concentration was more than 0.025%, an oxide film might be formed on the surface of the eutectic solder, and the surface tension tended to increase with the maximum droplet diameter. The dynamic surface tension was measured by the capillary jet method proposed by the authors in the previous reports. The measured results for oxygen concentrations under 0.025% showed that the surface tension changes during a relaxation time of several milliseconds. As the oxygen concentration increases, the rate of oxygen adsorption to the surface increases, while the time necessary to reach the equilibrium state increases as the increase of amount of saturated adsorption. As a result of these contradictory effects, it was shown that the relaxation time of eutectic solder is maximized at around 0.018% oxygen concentration.