Experimental and numerical study of 3D stacked dies under forced air cooling and water immersion cooling

Abstract

3D stacked die structure is a promising architecture to realize small feature size and enhance electronic performance. However, thermal performance in 3D stacked die has aroused extensive attention for its high density integration. In this paper, a stacked dummy die structure integrated with polyimide heater inside is presented to investigate the thermal behavior of 3D stacked dies. One-dimensional thermal resistance network is built and calculated to analyze thermal resistance distribution of the stacked dies. Under natural convection, the thermal resistance of convective heat transfer greatly influences total thermal resistance and limits heat dissipation ability of stacked dies. To significantly reduce the thermal resistance of convective heat transfer, forced air cooling and water immersion cooling have been applied in the stacked die structure. Experiment and numerical simulation have been conducted in this work. In the experiment, forced air cooling and water immersion cooling systems are set up to cool down the stacked die structure. The temperature dependence of the stacked die structure is obtained by thermocouples. The measured thermal resistances between junction and ambient environment of the stacked die structure decrease to 7.6°C/W under forced air cooling and to 0.6°C/W under water immersion cooling, respectively. Then heat dissipation abilities of forced convection cooling for the stacked die structure are analyzed. Simulation models are built for experimental validation and further thermal analysis. Temperature influences on the internal structure of the stacked dies with different power map are discussed. The simulation results can well capture the experimental results with 5.8% variation under forced air cooling and with 7.4% variation under water immersion cooling when total power of 3W is applied.