An alternative thermal approach to evaluate the wettability of solder alloys

作者：Santos Washington L R; Silva Bismarck L; Bertelli Felipe; Spinelli Jose E; Cheung Noe; Garcia Amauri

来源：Applied Thermal Engineering, 2016, 107: 431-440.

DOI：10.1016/j.applthermaleng.2016.06.177

• Zn-Sn solder alloys
• Solidification
• Wettability
• Interfacial heat transfer coefficient

The aim of the work is to propose an alternative method to qualitatively evaluate the wettability of different alloys of a particular alloy system. The technique is based on a thermal approach supported by experimental/theoretical methodologies involving a directional solidification procedure and numerical simulations based on the solution of the inverse heat conduction problem (IHCP). The wettability strongly affects the heat ability to flow across the alloy/substrate interface during solidification, which is construed as a heat transfer coefficient (h(g)). Particularly, for the alloys used in soldering processes, the wettability plays an important role in the integrity of solder junctions, being a fundamental parameter for selecting the most appropriate solder composition. The experiments were carried out with high temperature Zn-Sn solder alloys (10, 20, 30 and 40 wt%Sn) in a solidification device in which heat is extracted only through a water-cooled steel bottom. Experimental thermal profiles collected during solidification are used as input data to solve the IHCP and determine expressions hg vs. time for each alloy examined, permitting a tendency of wettability to be established. In order to validate the wetting behavior indicated by the hg values, alloy/substrate contact angles (theta) were measured on a steel substrate using a goniometer. It is shown that both hg and theta indicate improvements in wettability with the decrease in the alloy Sn content.

• 出版日期2016-8-25