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This paper aims to measure and simulate the warpages of 3D through-silicon via (TSV) die-stacked dynamic-random-access-memory (DRAM) packages during the manufacturing process. The related die stresses and keep-out zone (KOZ) for the stacked dies in the packages at room temperature are further calculated with the validated simulation model. The out-of-plane deformations (or warpages) of the packages from the full-field shadow moiré are documented under temperature loading and found consistent with those from finite-element method (FEM). The results of the stresses and KOZs at the proximity of a single TSV for each die in the package at room temperature are presented. It is found that the sizes of KOZs in four-die stacked DRAM packages with and without epoxy molding compound (EMC) at room temperature are dominated by the horizontal pMOS transistors and more than double the size in wafer-level die. The sizes of KOZs at each die are similar in this four-die stacked DRAM package, even though the stresses at each die are apparently different. [ABSTRACT FROM AUTHOR]

Microstructural characterization of deformation-induced martensite in its early stage of formation has been performed in an ultrafine-grained (UFG) medium Mn advanced high strength steel (AHSS). By using field emission scanning electron microscope (FESEM) and electron backscattered diffraction (EBSD), the nucleation site of deformation-induced martensite has been studied. Grain sizes, Schmid factors and aspect ratios of the parent austenite grains of deformation-induced martensite were measured in order to know their influence on the formation of deformation-induced martensite. Orientation relationship between deformation-induced martensite and its parent austenite has also been analyzed. Discussion on the effect of microstructural parameters on the formation of deformation-induced martensite in AHSS is given. [ABSTRACT FROM AUTHOR]

To explore the mechanical behavior and microstructure evolution of nanostructured bainite under deformation at high strain rates (> 10 3 s − 1 ), split Hopkinson pressure bar experiments were conducted. It was found that nanometer-sized twinning occurred in both blocky austenite and film austenite. In the former case, the intersections of different twin variants brought about strain-induced α’-martensite, while in the latter case, the lamellar twinned structures were occasionally accompanied by a small amount of ε martensite. It is concluded that twinning occurs first in blocky austenite, enhancing the initial work-hardening; subsequent twinning takes place in film austenite, promoting further straining. [ABSTRACT FROM AUTHOR]