Holistic Understanding of Best Engineering Practice to Extend Cooling Limit of Next Generations of GPU

The thermal design power (TDP) and power density of microelectronics is increasing abruptly. The ever-increasing trend of localization of power is the result of heterogeneous integration of different silicon dies on a single package. Air cooling is no longer sufficient to meet these challenging requirements. An aggressive cooling solution is needed to keep up with the surge in electronics power density. The paper explains the history of indirect two-phase liquid cooling using refrigerants. IBM has disclosed several patents where they used refrigerant or liquid nitrogen to cool high density electronic circuit packages. The paper also explains the deployment of extended cooling using indirect liquid cooling and immersion cooling in the late 1980 where Fujitsu and Cray deployed immersion cooling for their system and IBM deployed indirect liquid cooling for their Z series products. This work presents comprehensive analysis of single-phase liquid cooling of high-power electronic packages using cold plate. A customized test vehicle is used for the thermal evaluation of the performance of the indirect liquid cooling solutions. The TTV was tested with a uniform power map of 500W, and the liquid cooling solution was used by attaching the cold plate to the silicon die. The coolant used in the experiment is PG-25, maintained at the constant temperature using a chiller, and flow rate was varied from 0.5LPM to 1.5LPM. The result shows a Rhs of 0.015°C/Wat lLPM flow rate. Furthermore, the paper also compares the current performance of single-phase liquid cooling with micro fluidic cooling, two-phase liquid cooling, and immersion cooling. The comparison shows the better performance of indirect liquid cooling compared to immersion liquid. In addition, there are other critical concerns like reliability, cost, contamination, and use of optical devices need to be addressed before implementing immersion cooling in large scale data centers.