Solid-State Microrefrigeration in Conjunction With Liquid Cooling

Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hot spots could alleviate the design requirement for the whole package. Combination of solid-state and liquid cooling will allow removal of both hot spots and background heating. In this paper, we analyze the performance of thin film $Bi2Te3$ microcooler and the 3D SiGe-based microrefrigerator, and optimize the maximum cooling and cooling power density in the presence of a liquid flow. Liquid flow and heat transfer coefficient will change the background temperature of the chip but they also affect the performance of the solid-state coolers used to remove hot spots. Both Peltier cooling at interfaces and Joule heating inside the device could be affected by the fluid flow. We analyze conventional Peltier coolers as well as 3D coolers. We study the impact of various parameters such as thermoelectric leg thickness, thermal interface resistances, and geometry factor on the overall system performance. We find that the cooling of a conventional Peltier cooler is significantly reduced in the presence of fluid flow. On the other hand, 3D SiGe cooler can be effective to remove high power density hot spots up to $500W/cm2$⁠. 3D microrefrigerators can have a significant impact if the thermoelectric figure-of-merit, $ZT$⁠, could reach 0.5 for a material grown on silicon substrate. It is interesting to note that there is an optimum microrefrigerator active region thickness that gives the maximum localized cooling. For liquid heat transfer coefficient between 5000 and $20,000Wm−2K−1$⁠, the optimum is found to be between $10μm$ and $20μm$⁠.