Integrated Microfluidic Cooling of Heterogeneous HBM-GPU Package with Die Height Difference

System-level thermal management of heterogeneously integrated HBM-GPU module with step height variance is analyzed in this paper. Heterogeneous integration of high-powered chiplets with different functionalities and die sizes motivates the development of advanced cooling solutions that are compatible with multi-die configurations. By exploiting computational fluid dynamics (CFD) - heat transfer (HT) analysis, we propose top-side single-phase microfluidic cooling solutions that compensate for multi-die thickness mismatch, including a flat-microchannel pin-finned heat sink (F-MPFHS) with structural silicon and a backward-facing step microchannel pin-finned heat sink (BFS-MPFHS). The thermal performances are benchmarked with a conventional forced air-cooled heat sink with structural silicon. The HBM-GPU module is modeled up to 35 W from the HBM and 2000 W from the GPU. Thermal-hydraulic indexes, including thermal resistance, pressure drop, and coefficient of performance (COP), are evaluated. The temperature of the HBM-GPU can be maintained below 387 K at the highest flow rate of 0.15 LPM with pumping power of 169 mW and 117 mW for F-MPFHS and BFS-MPFHS, respectively. A 45% higher COP is calculated for BFS-MPFHS with a step height of 235 μm, owing to a 31% lower pressure drop with a 7.4% lower thermal resistance compared to F-MPFHS. A performance-cost trade-off relation between the design solutions is revealed, as BFS-MPFHS requires a relatively complex fabrication process despite its higher COP. The thermal impacts of GPU power scaling, the number of DRAM stacks (8-, 12-, and 16-stack), and step height variations are further investigated.