Design and Fabrication of Full Board Direct Liquid Cooling Heat Sink for Densely Packed FPGA Processing Boards

In recent years, thermal management of FPGAs has attracted extensive scientific attention. However, the majority of proposed cooling solutions remain in research phase with prototypes not addressing the dynamic thermal needs of the full hardware configuration. In this work we present the design and fabrication of a full-board, direct liquid cooling, heat sink for densely packed FPGA-based processing boards. The liquid cooling heat sink design forms part of the high power consuming Gemini Line Replaceable Unit (LRU) processing board, developed for the Square Kilometre Array (SKA) low-frequency aperture array correlator and beam former (CBF). To test the cooling capabilities, in-house developed “heater-firmware” is used to generate 121 watt inside the FPGA and another 85 watt in peripheral heat sources. The presented results show that this direct liquid cooling solution is an efficient thermal design, not only suitable for large quantity production, but also for integration into a dense implementation of 12 Xilinx Ultrascale+ FPGA LRU boards in a standard sub-rack of 178x483x415mm. This configuration enables a processing capacity of 3.4 TMAC/s, while maintaining the die temperature of all FPGAs at a $60.6^{\circ}\mathrm{C}$ level with a water supply temperature of $33^{\circ}\mathrm{C}$.