Methods of Heat Dissipation for

Laptops using MEMS Devices

Tyler Baker

May 31, 2016 ME 141A

Agenda

● Background

● Three Unique Methods○ Impingement

○ Heat Exchangers and Sinks

○ Liquid Cooling

● Other Promising Technologies

● Conclusions

Background

● As the demand for more, and more powerful laptop computers increases, so does the problem of heat

Experimental Investigation of the Thermal Performance of Piezoelectric Fans S. M. Wait, et al.

Heat Transfer Engineering 2004

● Devices need to cool quickly, efficiently, and quietly...

● ...but most importantly, a cooling device needs to be small

Impingement● Investigated the effects of different flow regimes

determined by height, h

● Stagnation - Needs to be avoided (for large jets)

● Laminar - Ideal

● Transition

● Turbulent

● High heat transfer rates depended on diameter, spacing of

jets, and location of jets

● heat transfer rate of 420 W/cm2

● Problem of high pressure loss

● Bifurcation

3-D visualization of flow in microscale jet impingement systems E. N.

Wang, et al. International Journal of Thermal Sciences 2010

Direct Liquid Jet-Impingement Cooling with Micronsized Nozzle Array

and Distributed Return Architecture T. Brunschwiler, et al. IEEE 2006

Heat Exchangers and Sinks

● Cooligy’s closed loop Liquid Cooling System

● Microheat exchangers with high surface to

volume ratio microstructures (HSVRM)

significantly enhance heat transfer

● Heat is sinked into the HSVRM

● Closed loop system attained a heat transfer

rate of 420 W/cm2

● High pumping requirements for microchannels

● Hydraulic diameters between 318 and 564 μm

tested

● Analytical models derived for microchannel heat

exchangers

● Pressure and flowrate dominated by channel

width, wc

Liquid Cooling

System for

Advanced

Microelectronics

M. Datta, et al.

ECS 2007

Single-Phase flow and

Heat Transport and

Pumping

Considerations in

Microchannel Heat

Sinks S. V. Garimella, et

al. Heat Transfer

Engineering 2004

Liquid Cooling● control electrodes regulates

wettability through use of an

electric field (Pamula et al.)

● Three mechanisms for flow

control

● thermal sensor feedback

control

● Flow-rate feedback control

● Electrothermocapillary

control

Development of a chip-integrated micro cooling device J. Darabi, et al. Microelectrics Journal 2003

● Device using electrohydrodynamics to pump a thin film

over a heated surface

● Self-contained design

● Opening should be approximately 50 μm and have a

length of 10 mm when HFE-7100 (C4F

9OCH

3) is used as

the fluid (best results)

● 35 W/cm2

Other Promising Technologies

● Gas molecules are ionized; forms a flow of air

● Corona-driven flow ensures greater flow

closer to the walls

● Effective for cooling

● Requires high voltages

● Not ideal for laptops

● Bridge-type micro-thermoelectric coolers (μ-TECs)

● Bridge-type shown to have better heat transfer characteristics compared to column-type

● Peltier Effect ● Transfers heat from center of the device

outwards at the cost of electrical energy

Corona Driven air propulsion for cooling of electronics F. Yang, et al. Millpress 2003

Development of low-cost

micro-thermoelectric

coolers utilizing MEMS

technology I. Huang, et al.

Elsevier 2008

Conclusions● Impingement

● Requires source of fluid

● High heat transfer rates (420 W/cm2)

● not self-contained

● Avoids high pressure losses with bifurcation, but pressure is still a problem

● Heat Exchangers and Sinks

● High heat transfer rates (500 W/cm2)

● Requires entire system (Cooligy)

● Large pressure drops

● Pumping requirements

● Liquid Cooling Using Electric Fields

● Low heat transfer rates (35 W/cm2)

● Highly controllable

● Can be attached to an existing device

● Self-contained

● Other Technologies

● Corona driven flow optimizes flow profile, but requires high voltage (kV range)

● μ-TECs are well understood and already have a place in cooling technologies

● Bridge-type is better option

References1. 3-D visualization of flow in microscale jet impingement systems E. N. Wang, et al. International Journal of Thermal Sciences 2010

2. Direct Liquid Jet-Impingement Cooling with Micronsized Nozzle Array and Distributed Return Architecture T. Brunschwiler, et al. IEEE 2006

3. Development of a chip-integrated micro cooling device J. Darabi, et al. Microelectrics Journal 2003

4. MEMS-enabled thermal management of high-heat-flux devices EDIFICE: embedded droplet impingement for integrated cooling of electronics C. H. Amon, et al.

Experimental Thermal and Fluid Science 2001

5. Liquid Cooling System for Advanced Microelectronics M. Datta, et al. ECS 2007

6. Corona Driven air propulsion for cooling of electronics F. Yang, et al. Millpress 2003

7. Closed-Loop Cooling Technologies for Microprocessors C. Upadhya, et al. (Cooligy, Inc.) IEEE 2003

8. Cooling of Integrated Circuits Using Droplet-Based Microfluidics V. K. Pamula, et al. ACM 2003

9. Single-Phase flow and Heat Transport and Pumping Considerations in Microchannel Heat Sinks S. V. Garimella, et al. Heat Transfer Engineering 2004

10. Development of low-cost micro-thermoelectric coolers utilizing MEMS technology I. Huang, et al. Elsevier 2008

11. Experimental Investigation of the Thermal Performance of Piezoelectric Fans S. M. Wait, et al. Heat Transfer Engineering 2004