The Study of Liquid Cooling Solution on 51.2T Switch

Al/ML application hyper-growth in recent years is rapidly driving the increased switching bandwidth in data centers, which brings the increased thermal challenge for high performance switches with traditional air cooling solutions. Thermal design power of the latest generation 51.2T ASIC called Tomahawk 5(TH5) from Broadcom is up to 763W. The required thermal performance for air-cooled heat sink represented by Rca should be within 0.05°C/W to maintain 105°C of maximum junction limit, which could be still achieved by the large size VC heat sink in 2U chassis, however it costs larger space for heat sink and higher fan power consumption.In this paper, liquid cooling as an alternative solution of traditional air cooling solution was studied to identify thermal feasibility and thermal improvement for 51.2T ASIC in 2U chassis. First, three different cold plate solutions were explored for thermal performance comparison with CFD simulation analysis. Second, thermal performance of the three different cold plates and air-cooled VC heat sink were compared through experiments, the experiment result presents that thermal performance of the best cold plate solution is about 40% better than the target thermal performance of 0.05°C/W. Furthermore, thermal simulation results have good agreement with the experimental results with 5.7% error, and it can be used as reference of cold plate liquid cooling design and simulation.