Browsing by Subject "materials science, characterization & testing"
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Item Numerical Simulation And Analytical Solution For Plane Waves Focused By A Parabolic Reflector(2013-07) Tsai, Y. T.; Haberman, M. R.; Zhu, J.; Tsai, Y. T.; Haberman, M. R.; Zhu, J.A transient analytical solution is presented to predict the pressure responses along the axis of a parabolic reflector for normally incident plane waves. The solution was derived using geometrical acoustics and the Kirchhoff-Helmholtz integral. Results of the analytical solution were compared to the numerical simulation results, and good agreements were obtained. The numerical simulation visualizes the wave field in air to give a better understanding of propagation of the reflected waves.Item Stress-Induced Delamination Of Through Silicon Via Structures(2011-09) Ryu, S. K.; Lu, K. H.; Im, J.; Huang, R.; Ho, P. S.; Ryu, S. K.; Lu, K. H.; Im, J.; Huang, R.; Ho, P. S.Continuous scaling of on-chip wiring structures has brought significant challenges for materials and processes beyond the 32 nm technology node in microelectronics. Recently three-dimensional (3-D) integration with through-silicon-vias (TSVs) has emerged as an effective solution to meet the future interconnect requirement. Thermo-mechanical reliability is a key concern for the development of TSV structures used in die stacking as 3-D interconnects. This paper examines the effect of thermal stresses on interfacial reliability of TSV structures. First, the three-dimensional distribution of the thermal stress near the TSV and the wafer surface is analyzed. Using a linear superposition method, a semi-analytic solution is developed for a simplified structure consisting of a single TSV embedded in a silicon (Si) wafer. The solution is verified for relatively thick wafers by comparing to numerical results obtained by finite element analysis (FEA). Results from the stress analysis suggest interfacial delamination as a potential failure mechanism for the TSV structure. Analytical solutions for various TSV designs are then obtained for the steady-state energy release rate as an upper bound for the interfacial fracture driving force, while the effect of crack length is evaluated numerically by FEA. Based on these results, the effects of TSV designs and via material properties on the interfacial reliability are elucidated. Finally, potential failure mechanisms for TSV pop-up due to interfacial fracture are discussed.Item Using Air-Coupled Sensors To Measure Depth Of A Surface-Breaking Crack In Concrete(2009-03) Kee, S. H.; Zhu, J. Y.; Kee, S. H.; Zhu, J. Y.Previous studies show that surface wave transmission ratio across a surface breaking crack in concrete can be used as an indicator of the crack depth. However, due to inconsistent sensor coupling condition on rough concrete surface, reliable measurement of the transmission ratio is still a challenging task. In this study, the air-coupled sensing method is proposed as a solution to this problem. Without direct contact between sensors and the testing surface, the air-coupled sensing not only allows rapid testing speed, but also enables more consistent signal measurement owing to removal of sensor coupling variation. The latter feature is especially valuable to wave transmission measurement. This paper first presents results from a numerical analysis (FEM model). Based on the results, a simplified algorithm is proposed for surface wave transmission ratio calculation. A calibration curve between the transmission ratio and normalized crack depth (actual crack depth/wavelength) is obtained. Experimental study using the air-coupled sensing method verifies the validity of the curve.