  This paper presents a multi-scale modelling approach to investigate the
underpinning mechanisms of microstructure-sensitive damage of single crystal
Sn-3Ag-0.5Cu (wt%, SAC305) solder joints of a Ball Grid Array (BGA) board
assembly subject to thermal cycling. The multi-scale scheme couples board-scale
modelling at the continuum macro-scale and individual solder modelling at the
crystal micro-scale. Systematic studies of tin crystal orientation and its role
in fatigue damage have been compared to experimental observations.
Crystallographic orientation is examined with respect to damage development,
providing evidence-based optimal solder microstructural design for in-service
thermomechanical fatigue.
