Woodruff School of Mechanical Engineering

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The Role of Elastic and Plastic Anisotropy on Damage Nucleation in Lead-Free Solder Joints


Dr. Thomas Bieler


Chemical Engineering and Materials Science, Michigan State University


Tuesday, January 19, 2010 at 3:00:00 PM


Love Building, Room 183




Because failures in lead-free solder joints do not occur only in the most highly shear strained regions, reliability prediction is challenging. As most SAC solder balls are single or tri-crystals, anisotropic properties of Sn are more important than in polycrystalline Pb-Sn solder joints, where average properties can be used in system level models. Unlike Pb, Sn has strongly anisotropic thermal expansion, elastic, and plastic deformation characteristics, leading to complex internal stress and strain evolution with thermal cycling, making every joint a special case. As Sn is always above half of its melting temperature, microstructural evolution occurs differently in different joints. Thus, statistical characterization of the most problematic grain orientations and loading histories need to be experimentally characterized, analyzed, and computationally simulated to develop


Tom Bieler earned a B.A. in Applied Mechanics, at UC San Diego in 1978, a M.S. in Ceramic Engineering at University of Washington in 1980, focusing on numerical heat transfer, worked for 5 years at Sandia National Laboratories in Livermore CA in the Experimental Mechanics Department, and completed his Ph.D. at UC Davis in 1989, where he examined high strain rate superplasticity under the guidance of Prof. Amiya K. Mukherjee. He has been at Michigan State University since then, where he has focused on hot deformation, texture and microstructure evolution, and damage nucleation in Ti alloys, high purity Nb, and lead-free solder.