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Research Papers

# Solid-State Microrefrigeration in Conjunction With Liquid Cooling

[+] Author and Article Information
Younes Ezzahri1

Department of Electrical Engineering, University of California, Santa Cruz, Santa Cruz, CA 95064younes@soe.ucsc.edu

Ali Shakouri

Department of Electrical Engineering, University of California, Santa Cruz, Santa Cruz, CA 95064ali@soe.ucsc.edu

1

Present address: Institut Pprime, CNRS-Université de Poitiers-ENSMA, Département Fluides, Thermique, Combustion, ENSIP-Bâtiment de mécanique, 40, avenue du Recteur Pineau, F 86022 Poitiers, Cedex, France.

J. Electron. Packag 132(3), 031002 (Sep 08, 2010) (8 pages) doi:10.1115/1.4001853 History: Received November 05, 2009; Revised April 20, 2010; Published September 08, 2010

## Abstract

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 $500 W/cm2$. 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 $20,000 W m−2 K−1$, the optimum is found to be between $10 μm$ and $20 μm$.

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## Figures

Figure 1

Schematic diagram of a TEC and the corresponding thermal network model

Figure 2

Schematic diagram of the 3D SiGe-based microrefrigerator (a) and its corresponding thermal quadrupole circuit (b)

Figure 3

Temperature variation at the cold side of the 3D SiGe-based microrefrigerator (a) and the conventional Bi2Te3 thin film TEC (b)

Figure 4

Variation of the minimum TC (a) and the maximum CPD (b) of the conventional TEC as a function of roc

Figure 5

Variation of the maximum cooling and the maximum CPD for the conventional TEC ((a) and (b)) and for the 3D microrefrigerator ((c) and (d)) as a function of the thermoelectric layer thickness

Figure 6

Variation of the maximum cooling of the 3D SiGe microrefrigerator as a function of the thermoelectric layer thickness for ZT=0.1 (a) and ZT=0.5 (b) of the active thermoelectric layer. HF is fixed to 104 W m−2 K−1.

Figure 7

Variation of the maximum CPD of the 3D SiGe microrefrigerator as a function of the thermoelectric layer thickness for ZT=0.1 (a) and ZT=0.5 (b) of the active thermoelectric layer. HF is fixed to 104 W m−2 K−1.

Figure 8

Variation of the maximum cooling (a) and the maximum CPD (b) of the 3D SiGe microrefrigerator as a function of the thermoelectric layer thickness for different values of ZT and the thermal load QH. HF and roc are fixed to 104 W m−2 K−1 and 10−7 Ω cm2, respectively.

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