Papers by Keyword: Interfacial Delamination

Abstract: Fan-out wafer-level package is a very promising packaging technology with good thermal and electrical performance. The fan-out wafer-level package exhibits beneficial features such as low profile, high I/O density, low cost, and efficient computing. The package experiences large temperature variations in the assembly phase which causes internal stresses. In particular, the mismatch between the coefficient of thermal expansion of the epoxy molding compound and the substrate due to the cool down phase of the cure process causes the internal stresses in the package. These internally induced stresses result to interfacial delamination. In this study, the interfacial delamination on a fan-out wafer-level package right after post mold cure of glass wafer was evaluated using the stress-based damage index through the finite element analysis in the ANSYS software package. The model was validated by comparing the simulation result of the glass wafer warpage to the existing experimental result from literature. From the warpage simulation of the glass wafer, the region on the package with high stress level was located and examined which may cause interfacial delamination. The maximum shear stress and principal stress at the epoxy molding compound and the Silicon chip interface was found to exceed the adhesion strength. This indicates that the interfacial delamination is inevitable. The information obtained from the stress analysis of molded wafer provides insight for the possible interfacial failure of fan-out wafer-level package in the individual package when subjected to thermomechanical loads.

Abstract: Theoretical formulas for effective elastic modulus and Poisson's ratio of honeycomb core materials were proposed considering the bending, axial and shear deformations of cell walls. Theoretical results obtained by the formulas showed orthotropic elasticity and large Poisson’s ratio, which were comparable to results by finite element analysis(FEA). Tensile test of honeycomb sandwich composite(HSC) plates was performed for analysis of their deformation behaviors and interlaminar stresses. Equivalent plate model using the theoretical results of honeycomb core layer show that interlaminar shear stress occurring due to large difference of Poisson’s ratio between skin and honeycomb core layers led to the delamination in HSC plate under tensile loading. Load-displacement behavior of HSC specimen simulated by equivalent plate model coincided fairly with that of detailed FEA model similar to experimental results.

Abstract: The strength characteristics as well as local deformation behaviors of honeycomb sandwich composite (HSC) structures under three-point bending loads were investigated in consideration of various failure modes such as skin layer yielding, interface-delamination as well as shear deformation and local buckling in the core layer. Various types of aluminum honeycomb core and skin layer were used for this study. Their finite-element simulation was performed to analyze stresses and deformation behaviors of honeycomb sandwich plates. The results were very comparable to the experimental ones. Consequently, thicker skin layer, smaller cell size of honeycomb core and less delamiantion had dominant effects on the improvement in strength and deformation behaviors of honeycomb sandwich plates.