Hybrid solid-state/liquid cooling

Hyprid solid-state/liquid cooling

In collaboration with Profs. Joshi and Fedorov at Georgia Tech

According to the road map of electronic components, it is projected that the average power dissipation in high performance chips will increase over the next decade to more than 100 W/cm^2. Furthermore, close packaging of high power density microelectronic components generates high heat flux localized area called hotspots. Heat flux at these localized hotspots could be more than 5 times higher than the average over the entire chip, which makes the heat flux distribution very non-uniform.

Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hotspots could alleviate the design requirement for the whole package. Along the past decades, many cooling techniques have been developed for cooling down the chip background. Liquid cooling techniques are the most widespread ones for this purpose. On the other hand, solid-state cooling utilizing thermoelectric refrigeration has been proven to be an efficient cooling technique for selectively removing hotspots. Combination of solid-state and liquid cooling appears then as a promising hybrid technique that will exploit the advantages of individual techniques and will allow removal of both hot spots and background heating.

In collaboration with The Interconnect Focus Center at the Georgia Institute of Technology, we are developing a prototype of the hybrid cooling system. The scheme utilizes single-phase convection inside the microchannels fabricated on the backside of the chip to remove the background heat flux. The solid-state thermoelectric coolers (TEC) made of SiGe superlattices are fabricated where the hotspots are located in order to cool down the localized hotspots of sub-millimeter square in size.

Our group focuses on the design and fabrication of the solid-state thermoelectric micro-coolers. Small heaters of different sizes were designed and fabricated to mimic the effect of both the chip background (large heaters) and the hotspots (small heaters) for test chips. The SiGe superlattice micro-coolers are measured to perform the hotspot cooling with the cooling power density larger than 400 W/cm^2. The figures below show the schematic of the hybrid cooling device, and the thermoreflectance images of the solid-state micro-refrigerators at different bias currents.


Figure 1 Schematic structure of hybrid solid-state/liquid cooling device.


Figure 2 Thermoreflectance images of 2 of the developed solid-state microocoolers at different bias currents.

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