Two Phase Cooling Technologies: Stacking of multiple functional dice promises significant performance advantages for the next generation of computing and communication systems. However, increased power densities per chip footprint area results in challenging thermal problems. Technical challenges remain when designing systems to address the largest expected heat fluxes, which may be in excess of 1kW/cm2, with local hotspots exceeding 5kW/cm2. Two phase cooling has been identified as a potential solution for cooling of such modules. A key challenge to implementation of two phase cooling in 3D systems is the inevitable non-uniformity of power consumption within individual tiers, which gives rise to localized hotspots. Hotspots are problematic in two phase cooling systems, as the local variation in heat flux can cause flow oscillations and flow by-pass with reduction in the local heat transfer coefficient (a) Typical two phase force heat sink with no hotspot cooler, (b) “Fluid to fluid, spot to spreader” heat sink with separate background and hotspot cooler.
3D Stackable Evaporative Cooler (3D STAECOOL) Heat Sink: STAECOOL is inspired by the F2/S2 (Fluid to fluid, spot to spreader) hybrid heat-sink design. The thermal design seeks to achieve removal of very large (in excess of 500 W/cm2) background heat fluxes over a large 1cm1cm chip area, as well as extreme (in excess of 2 kW/cm2) hotspot heat fluxes over small 200 μm x 200 μm areas using two phase flow. This design combines a micro pin–fin heat sink for background cooling and localized, ultrathin micro gaps for hotspot cooling.
Green C, Kottke P, Han X, et al., “A Review of Two-Phase Forced Cooling in Three-Dimensional Stacked Electronics: Technology Integration”, ASME. J. Electron. Packag. 2015;137(4):040802-040802-9. doi:10.1115/1.4031481.