Residual strain and whiskers growth in Sn layer

Whiskers (long single crystal filaments of micro/submicrometer diameter) growth on Sn coating is a major technological threat for electronic/electrical devices. Despite numerous studies during the last 70 years, quantitative modelling is not yet achieved. One major identified driving force is the presence of compressive stress and/or stress gradients within the Sn layer. Several industrial solid state soldering processes (f.e. Press-Fit) generates residual stress of unknown magnitude. The purpose of this proposal is to quantify, using 2D and 3D microLaue diffraction techniques, the residual strain fields around well controlled deformed areas. Two technologically relevant microstructures of Sn thin films will be studied. A better understanding of the role of stress and its threshold to nucleate whiskers is therefore expected.