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Research Papers

Thermal Management of On-Chip Hot Spot

[+] Author and Article Information
Avram Bar-Cohen, Peng Wang

Department of Mechanical Engineering,  University of Maryland at College Park, College Park, MD 20742abc@umd.edu

J. Heat Transfer 134(5), 051017 (Apr 13, 2012) (11 pages) doi:10.1115/1.4005708 History: Received July 20, 2010; Revised February 02, 2011; Published April 11, 2012; Online April 13, 2012

The rapid emergence of nanoelectronics, with the consequent rise in transistor density and switching speed, has led to a steep increase in microprocessor chip heat flux and growing concern over the emergence of on-chip hot spots. The application of on-chip high flux cooling techniques is today a primary driver for innovation in the electronics industry. In this paper, the physical phenomena underpinning the most promising on-chip thermal management approaches for hot spot remediation, along with basic modeling equations and typical results are described. Attention is devoted to thermoelectric micro-coolers and two-phase microgap coolers. The advantages and disadvantages of these on-chip cooling solutions for high heat flux hot spots are evaluated and compared.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Hot spot temperature rise as a function of hot spot size for various silicon chip thickness [8]

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Figure 2

Schematic of minicontact enhanced TEC for hot spot remediation [5-6]

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Figure 3

Effect of minicontact size on TEC-induced temperature profile. Bismuth telluride element thickness is 20 μm, silicon chip thickness is 500 μm, the hot spot size is 400 μm × 400 μm with a heat flux of 1250 W/cm2 , the electrical contact resistivity is 1 × 10−7 Ω cm2 , and the thermal contact resistance is 1 × 10−7 K cm2 /W [5].

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Figure 4

Effect of thermoelectric element thickness on the hot spot cooling performance. Bismuth telluride element thickness tTE is 20 μm, 50 μm, and 100 μm, respectively, silicon chip thickness is 500 μm, and the hot spot size is 400 μm × 400 μm with a heat flux of 1250 W/cm2 , the electrical contact resistivity is 1 × 10−7 Ω cm2 , and the thermal contact resistance is 1 × 10−7 K cm2 /W [5].

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Figure 5

Influence of thermal contact resistance on hot spot cooling. Bismuth telluride leg thickness is 20 μm, silicon chip thickness is 500 μm, and the hot spot size is 400 μm × 400 μm with a heat flux of 1250 W/cm2 , the electrical contact resistivity is 1 × 10−7 Ω cm2 [5].

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Figure 6

Variation of measured maximum spot cooling with copper minicontact size. Thermion miniaturized TEC has 200 μm-thick elements and silicon chip thickness is 500 μm [5].

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Figure 7

Schematic of silicon thermoelectric microcooler. The arrows indicate the direction for electric current [4].

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Figure 8

Hot spot cooling as a function of boron doping concentration for various electrical contact resistivity. Microcooler size is 600 μm × 600 μm, silicon chip thickness is 100 μm, and the hot spot size is 70 μm × 70 μm with a heat flux of 680 W/cm2 [4].

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Figure 9

In-plane silicon thermoelectric hot spot cooling as a function of microcooler size and chip thicknesses. Silicon chip thickness is 100 μm, and the hot spot size is 70 μm × 70 μm with a heat flux of 680 W/cm2 [4].

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Figure 10

Schematic of Si/SiGe superlattice microcooler integrated on the backside silicon ship for hot spot cooling (The arrows indicate the direction for electric current) [15]

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Figure 11

Temperature profile on the bottom of silicon chip. The hot spot size is 70 μm × 70 μm with a heat flux of 680 W/cm2 , the chip thickness is 50 μm, and SiGe/Si microcooler size is 150 μm × 150 μm [15].

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Figure 12

Hot spot heat flux distribution (a) without microcooler and (b) with microcooler powered with 0.6 A. The hot size is 70 μm × 70 μm with a heat flux of 680 W/cm2 , silicon chip thickness is 50 μm, and SiGe/Si microcooler size is 150 μm × 150 μm [15].

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Figure 13

Cross section of the electronic test package with a Bi2 Te3 -based superlattice TEC attached to the underside of the integrated heat spreader [7]

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Figure 14

Measured hot spot temperature on the chip as a function of current through the thermoelectric cooler (TEC). The hot spot size is 400 μm × 400 μm with a heat flux of 1250 W/cm2 [7].

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Figure 15

Structure of microgap cooler for on-chip hot spot cooling [19]

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Figure 16

Average heat transfer coefficient in 210 μm gap cooler: (a) variation with heat flux and (b) variation with exit quality [19]

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Figure 17

Taitel and Dukler two-phase flow regime map for FC-72 flowing in a 110 μm microgap channel [G = 133.3 kg/m2 s, Dh  = 0.218 mm, q″ = 16.8 kW/m2 ] [19]

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Figure 18

Characteristic heat transfer coefficient curve in microgap channel [20]

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Figure 19

Microgap size effect on the two-phase heat transfer coefficient [19]

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Figure 20

Three-dimensional temperature profile for microgap cooling of 10 mm × 10 mm × 0.5 mm chip with a background heat flux of 100 W/cm2 . The circular hot spot (dhotspot  = 400 μm) has a heat flux of 2 kW/cm2 , the effective heat transfer coefficient applied on the chip surface is 10 kW/m2 K [26].

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