A multi-scale approach to microstructure-sensitive thermal fatigue in solder joints.

• A multi-scale modelling approach has been presented to investigate the underpinning mechanisms of microstructure-sensitive damage of single crystal Sn-3Ag-0.5Cu solder joints of a ball grid array board assembly subject to thermal cycling. • Systematic studies of β-Sn crystal orientation and its role in thermal fatigue damage development within solder joints have been shown and compared to experimental observations and analysis. • It provides evidence-based optimization for solder microstructural design under in-service thermomechanical fatigue. 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. [Display omitted] [ABSTRACT FROM AUTHOR]