Kinetics of the polymorphic phase transformation of Cu6Sn5

Cu6Sn5 is a critical intermetallic compound in soldering and three-dimensional integrated circuit packaging technology and exists in at least five different crystal structures in the solid state, with a polymorphic phase transformation from hexagonal to monoclinic structures occurring on cooling. The kinetics of polymorphic transformations in Sn-rich Cu6Sn5 and Cu-rich Cu6Sn5 is systematically investigated in this study. This includes the generation of continuous cooling transformation diagrams as well as time temperature transformation diagrams. Techniques used include variable temperature synchrotron powder X-ray diffraction and differential scanning calorimetry. The findings have important implications for the manufacture of solder joints and their in-service performance. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.