New approach for measuring the surface tension of SnAgCu305 molten alloy

The aim of the research is to improve the exactness of the measurement of the surface tension of the molten SnAgCu soldering alloy at different temperatures. The method used for surface tension measurement of molten alloys is of pendant drop type. The weak point of this method is the exactness of the curvature radius measurement, but mostly the exactness of the first order derivative of the droplet profile function depending on the droplet height measured from its apex. The authors propose a modeling approach of the droplet profile by analytical function of the class C2. Based on the analytical profile function were calculated the curvature of the droplet and subsequently the surface tension. The paper will present the main data and results obtained during the first part of the researches regarding implementation the method for temperature in the range of soldering process. There were measured the surface tension of a SnAgCu 305 alloy obtained in a laboratory of UPB at temperature ranging from 225 to 265°C. The expanded measurement uncertainty of the results, with 95% degree of confidence, was estimated based on multi-convolutional approach of uniform probability density functions. The main result of the paper consists in finding of a simple way of simulating of the symetric shape profile with analytical function. Based on the first and second order derivatives of the simulated profile function were calculated the surface tension. An other important result consists in improving the quality of the test results based on measurement uncertainty estimation.