Thin micro-cold plate for hot-spot aware chip cooling

This work proposes a non-invasive and hot spot aware cooling approach by stacking a micro-cold plate at the backside of a chip. With trends such as 3D stacking and hotspot generation, microelectronics face major cooling challenges to ensure chip performance and reliability. It makes the liquid microchannel solutions more adapted than conventional air cooling for both space and heat removal. One approach is to concentrate the cooling in the vicinity of the heat sources to help to judiciously use the pumping power and contribute to keep the cooling solution thin and easily integrated. An experimental micro-cold plate has been fabricated through wafer level produced microchannels, capped with die-to-wafer pick-and-place operation. The microchannels from the cooling die are formed by Si DRIE and the die is capped with a Si wafer attached by SiNR adhesive on one side. An epoxy adhesive is then bonded to a thermal test chip with metallic lines as heaters and temperature sensors for a total stack thickness of 1.5 mm. It has then been characterized on a dedicated test bench. A cooling resistance of 3.5 °C/W is achieved with an electric power of only 1.2 W, showing a coefficient of performance of 5770 in respect of an hydraulic power of 2.6 mW and with a 609 W/cm
²
heat flux. Finally, such micro-cold plate could be used as an “add-on solution” in applications where space and pumping power are limited, independently of the chip thickness or the possibility of etching its back surface.