The convergence and miniaturization of the consumer electronic products such as cell phones and digital cameras has led to the vertical integration of packages i.e., 3-D packaging. Chip-stacking (3-D) is emerging as a powerful tool that satisfies such Integrated Circuit (IC) package requirements. 3-D technology looks to be the future of hand-held electronics; hence, making it an important research area. Stacked chips are peripherally interconnected through wires; this increases the package size and usually requires an extra “interposer” layer between the chips, causing substantial delays. Due to high package density and chip-stacking on top of each other, heat dissipation from the die becomes a concern. To overcome these thermal challenges and provide better inter-chip and chip-substrate electrical connection, Through Silicon Via (TSV) technology is being implemented in 3-D electronics. Electrical interconnection and heat dissipation improves with the number of TSVs. But, there is a trade-off; TSVs occupy the chip real estate, resulting in reduced silicon efficiency when compared to the baseline (no-TSV) scenario. Coefficient of thermal expansion (CTE) mismatch and reduced chip area causes thermal stresses and may lead to premature chip failures. This can be a major reliability issue. In this paper, a parametric study of the number of TSVs in a test vehicle (TV) consisting of 2 vertically stacked dies and TSVs (between the die and the substrate) has been performed using ANSYS WORKBENCH. A quarter symmetry model has been formulated to study the various cases as a function of number of TSVs. Each die has an area of 5.7mm2 with 0.1-mm thickness and 0.5W power rating. The TSV diameter is 50-μm each with a SiO2 insulation film of 25-μm thickness. Junction temperature and thermal resistance is determined to obtain the best case in terms of temperature distribution on the die. Furthermore, thermo-mechanical analysis is performed for all the TSV configurations and a guideline is proposed based on thermal and structural response.

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