Speaker: Dr. Chris Gourlay
Affiliation: Department of Materials, Imperial College London, UK
Date and time: Friday, February 28, 2020, 1 – 2 PM
Location: Galbraith Building, 35 St George St, Room 248
 
 
Abstract: Most segments of the electronics industry have now transitioned successfully to Pb-free solders and, in common thermal cycling tests, the developed Sn-Ag-Cu and Sn-Cu-Ni solders can outperform the Sn-37Pb used previously.  However, the operating conditions and requirements of electronics are changing which is driving the continuous need for improved solder joints.  For example, solder joints are required that can operate reliably at higher temperature, cycling through larger temperature ranges whilst enduring higher current densities, steeper temperature gradients and impact loading.
Research is tackling these challenges by developing new solder alloys and methods to control and optimise solder microstructures.  Of particular importance for the latter are tin grain orientations, the number of tin grains per joint, and the lengthscale of intermetallic compounds.
This talk will overview synchrotron imaging research that probes microstructure development during solder joint solidification.  The understanding from these in situ experiments is then used to develop methods to control microstructure formation, with a focus on controlling the tin nucleation process and the growth orientation of tin dendrites.  Finally, next generation solder alloys that contain relatively concentrated additions of Bi, Sb and/or In will be discussed, with a focus on how these additions alter microstructure development.
 
Biography: Chris Gourlay read metallurgy at the University of Oxford, UK, (MEng, 2002) and the University of Queensland (PhD, 2007), where he worked within the Australian Cooperative. Research Centre for Cast Metals Manufacturing (the CAST CRC).  He was then a Postdoctoral Research Fellow in the Australian Research Council’s CoE for design in light metals (2007-08).  He joined the Materials Department at Imperial College in 2008 on a RAEng/EPSRC Research Fellowship and was made Lecturer in 2012, Senior Lecturer in 2014 and Reader in 2016.  His research focuses on alloy solidification and its application in electronic soldering and structural castings with interests including: mushy-zone mechanics; X-ray imaging of solidification phenomena; nucleation; eutectics; intermetallic crystal growth; Pb-free soldering; and High-pressure die casting.