<p>Processor energy density is exceeding the capabilities of conventional air-cooling technology, but two-phase cooling has the potential to manage these resulting heat fluxes at reliable temperatures and higher electrical efficiency.&nbsp; When two-phase cooling is used in tandem with overclocking, data center footprints are reduced as individual chip processing power can be set at limits well beyond the manufacturer’s Thermal Design Power (TDP) or nominal operating condition.&nbsp; This study examines how Liquid Nitrogen (LN2) can be used with Additive Manufacturing (AM) and overclocking to increase the computational performance of a commercially available GPU.&nbsp; AM facilitated the implementation of baffled venting used to effectively remove spent vapor in a way that was not possible with conventional manufacturing techniques.&nbsp; The cold plate was also designed to fit within the confines of a conventional PCI-E double slot form factor with the intent of the final package comparable in size to air-cooled thermal solutions. With the incoming cooling temperature being the ambient reference, the thermal resistance of the cold plate from the die-to-ambient was measured at 0.13 K/W.&nbsp; Including ancillary components on the motherboard, the total board power was 140W where pressure drop across the cold plate was found to be approximately 28 kPa.&nbsp; At this pressure drop, partial Power Usage Effectiveness (pPUE) was measured to be as low as 1.01 as opposed to the 1.06 measured using the high-powered motherboards stock cooling system.&nbsp; The cryogenic LN2 maintained chip temperatures of approximately -120°C for hours of reliable operation.&nbsp; One of the main difficulties in using cryogenics for electronics cooling is frost/condensate formation near sensitive components.&nbsp; By submersion of the board in dielectric fluid (density of approximately 1600 kg/m^3) in tandem with an upward-facing board, frost/condensate that formed and detached would be forced upward and away from the motherboard via buoyancy.&nbsp; A control scheme was developed with an upstream solenoid valve to distribute coolant to the cold plate only when it was needed.&nbsp; Higher flow rates produced more stable operating temperatures even though more cycling of the upstream solenoid valve was needed.&nbsp; Lower flow rates, while producing larger temperature swings, would increase the long-term reliability of the upstream solenoid valves through reduced switching.&nbsp; Neither the higher or lower flow rate scenario resulted in increased coolant usage over extended periods of time offering end-users flexibility in how they want to distribute the coolant to the GPUs with no impact on overall coolant costs.&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;</p>

Cooling of High Powered GPUs Using Liquid Nitrogen Cold Plates Made With Additive Manufacturing

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2021/volume/85505

ASME 2021 International Electronic Packaging Technical Conference and Exhibition (InterPACK2021)

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