Dr. Bongtae Han is an Associate Professor of the Mechanical Engineering Department of the University of Maryland at College Park, directing the Laboratory for Opto-Mechanics and Multi-layer Systems.  He received his Ph.D. degree in Engineering Mechanics from Virginia Polytechnic Institute & State University in 1991.  He joined the faculty of the University of Maryland in August 1999.  His previous professional career includes Assistant Professor at Clemson University (1996-1999) and Advisory Engineer at IBM Microelectronics (1992-1996).  His research interest is centered on mechanical design of microelectronics devices for optimum reliability and development of photomechanics methods for micromechanics. 

Dr. Han is responsible for development of Portable Engineering Moiré Interferometer, and holds a related patent.  He co-authored a textbook entitled "High Sensitivity Moiré: Experimental Analysis for Mechanics and Materials", Springer-Verlag, 1994.  He edited two books and has published over 70 journal and conference papers in the field of microelectronics and experimental mechanics.  He served as an Executive Board Member and the Chairman of the Electronic Packaging Division of the SEM.  He currently serves as an Associate Technical Editor for Experimental Mechanics.  Notable distinctions include IBM Excellence Award for Outstanding Technical Achievements in 1994 and Brewer Award for Outstanding Experimental Stress Analyst, SEM, 2001.  He holds a membership of SEM, ASME, IEEE, SPIE and IMAPS.

microscopic MOIRÉ INTERFEROMETRY for thermal deformation analysis of microelectronics circuit

B. Han, Department of Mechanical Engineering, University of Maryland, College Park, MD 20742

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ABSTRACT

Microscopic moiré interferometry is used to document thermo-mechanical deformations of microstructures in a surface laminar circuit (SLC) substrate.  Two specimens are analyzed; a bare SLC substrate and a flip chip package assembly with the same SLC substrate.  The specimens are subjected to a uniform thermal loading of ∆T = 70°C and the microscopic displacement fields are documented at the identical region of interest in the substrate.  The nano-scale displacement sensitivity and the microscopic spatial resolution obtained from the experiments provide a faithful account of the complex deformation of the surface laminar layer and the embedded microstructures.  The high modulus of underfill produces a strong coupling between the chip and the surface laminar layer, which produces a DNP-dependent shear deformation of the layer.  The effect of the underfill on the deformation of the microstructure is investigated and its implications on the package reliability are discussed.

Key words: Microscopic moiré interferometry, Surface laminar circuit, Flip chip, Underfill, Metal via.

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