Assessing thermal and microstructural parameters of the Sn-40wt%Bi-2wt%Ag solder alloy

Abstract

New legislations have been continuously launched by the European Union (EU) in order to avoid the usage of hazardous substances on microelectronics. Other important countries like Japan and China have already adopted such restrictions. The specific element to be evaluated in the present proposal is lead (Pb), which is considered one of the six substances with higher toxic potential. The usage of lead-based or lead-containing materials in processes like soldering tends to be completely banned. As a consequence, development and understanding of alternative alloys become essential priority for industry on microelectronics. The control of structure and intermetallics are pointed as critical parameters considering soldered parts. Such kind of control is already possible basically by assessing cooling rate level during solidification of soldered parts. Sn-Bi-Ag appears as one of the promising alternatives due to the probable benefits of adding on the properties of the commercial Sn-Ag. The present study aims to use facilities on directional solidification with a view to better comprehend the effects of solidification thermal variables on the as-cast structure of a Sn-Bi-Ag solder alloy, including formation of primary phases, eutectics and intermetallics. (AU)