Microstructure investigation of copper-tin intermetallics and the influence of layer thickness on shear strength : low-tin solders are recommended in applications where high temperatures encourage intermetallic buildup

Abstract

This study focuses on the behavior of the intermetallic layer forming at the interface between tin-bearing solders and a copper substrate. Scanning electron microscopy was used to reveal the morphology of this environment. Point analyses of energy dispersive x-rays identified the individual phases while elemental line scans yielded the tin and copper partition extent across the boundary zone, providing information about the diffusive interpenetration and phase growth. Transmission electron microscopy yielded electron diffraction patterns for the microstructures of the Cu 3 Sn and Cu 6 Sn 5 phases