Electron Backscatter Diffraction (EBSD)
OIM orientation (left) and phase (right) maps from a tin-based lead free solder alloy joined to copper showing intermetallic compound formation.
A Tin-Copper interface.
OIM orientation map showing microstructural evolution of lead-free solder during thermal cycling.
Grain boundary sliding occurred in pure tin during cooling after 200 hr grain growth anneal at 150| |C (large ledges). Shrinkage of lower (red) grain was greater than surrounding grains due to highly anisotropic expansion coefficient. The initially small grain size is evident by differential expansion and grain boundary sliding that was retained on the surface after grain growth occurred.
A. U. Telang, T. R. Bieler, J. P. Lucas, K. N. Subramanian, L. P. Lehman, Y. Xing, E. J. Cotts (2004). “Grain Boundary Character and Grain Growth in Bulk Tin and Bulk Lead-free Solder Alloys” J Electronic Materials 33: 1412-1423.
OIM orientation maps from thermomechanically cycled Tin-Silver-Copper solder balls with internal cracks observed in some cases.
Maps of the orientation of the c-axis of Sn for a row of eleven cross sectioned SnAgCu solder balls in a thermomechanically cycled package. The orientations of the c axis are indicated by color, with purple corresponding to the c-axis perpendicular to component and board, and orange-red corresponding to the c-axis nearly parallel to component and board. Cracks were observed in four of the samples’ optical micrographs, these samples are labeled ‘crack’.
T. R. Bieler, H. Jiang, L. P. Lehman, T. Kirkpatrick, and E. J. Cotts (2006). “Influence of Sn Grain Size and Orientation on the Thermomechanical Response and Reliability of Pb-free Solder Joints”. Proceedings of ECTC