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MATERIALS ENGINEERING
“Transient Liquid Phase Sintering in Tin-Bismuth Solder”
By
Yaohui Fan
Purdue MSE Ph.D. Preliminary Exam
Advisors: Professor Carol A. Handwerker and Professor John E. Blendell
ABSTRACT
Transient liquid phase sintering (TLPS) is a widely-used processing method for electronics packaging industry. Despite previous studies have provided the method for forming dense TLPS interconnects and the kinetics
of isothermal solidification, a commercially practical method to form dense TLPS interconnects and find the key variables to control it, is still incomplete. Among all the TLPS systems, Sn-Bi binary system has attracted huge research interest due to its low
eutectic temperature and relative low cost, which made it a promising solder material for low temperature soldering. Previous research has a deep focus on melting and solidification characteristics during heating, and microstructure development at low bismuth
composition. In this study, in order to understand the isothermal solidification and diffusion mechanism in Sn-Bi TLPS system, the solidification characteristics of Sn-Bi systems with a higher bismuth composition during cooling process will be studied. A useful
method, differential scanning calorimeter (DSC) is utilized. During TLPS, Sn-Bi eutectic composition melts first during heating, followed by rapid diffusion of Bi into pure Sn and precipitation of Sn solid solution in the system. Excess Bi precipitates out
in Sn solid solution upon cooling and finally form a fine precipitation structure. This review mainly focuses on TLPS in Sn-Bi system to acquire a deeper understanding in solidification and microstructure development.
Date: Monday, July 16, 2018
Time: 8:30 A.M.
Place: ARMS 1028