Synchrotron X-ray Microdiffraction Study of Whisker Growth in Sn Films

A prototype three-dimensional x-ray crystal microscope is installed on beamline 34-ID at the Advanced Photon Source, Argonne National Lab, and has begun operation. The microscope has a routine spatial resolution of approximately 0.5 x 0.5 x 1.0 um$^{3}$. With scanning technique, spatially resolved microdiffraction measurements can be made in two or three dimensions. Properties that can be measured include the local crystalline phase, local texture (orientation), and the local strain tensors. One of its applications is to study the whiskers in Sn films, which is an example of anomalous grain growth and an area of long-standing interest to the application of Pb-free solder in electronic manufacturing. Recent measurements illustrated the ability of this newly developed crystal microscope to characterize the local orientation and strain of whiskers and near whisker regions. Research supported by the DOE, Division of Materials Sciences under contract with ORNL, operated by UT-Battelle, LLC. UNICAT is supported by ORNL, UIUC-MRL, NIST, and UOP Inc.