Effect of Addition of Al to Sn-Zn Solder Alloys

Abstract

Conventional solders consist of Lead, that was found to be toxic and carcinogenic. Hence, restrictions were put on its use by the industrially developed nations. To counter the use of Lead, active research was pursued into the development of Lead-free solders. In our project, we fabricated alloys of composition 3:15:82, 7:43:50 and 10:80:10 (in terms of Aluminium, Zinc and Tin respectively), under furnace cooled and air-cooled conditions. The use of Aluminium was made so as to increase the resistance of the solder to atmospheric corrosion, and also to improve the wettability of the samples. Optical micrographs were obtained for each sample so as to analyze their microstructures. For a deeper understanding, SEM images of each sample were obtained, and EDX analysis was performed side-by-side so as to understand the elemental composition of different phases present in the sample. DSC and TG tests were conducted to determine the melting point of the solder alloy, and the weight gain in the alloy on oxidation respectively. The wettability of each sample was also analyzed. We recorded and plotted down the trends in each case. We then tried to evaluate the most effective solder composition on the basis of the above tests. The near-eutectic composition was considered so as to avoid the formation of a pasty phase that will cause disruption in electrical work.