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Development of Thin Thermal Ground Planes for Electronic Cooling

Key featuresThermal Ground Plane Measurements
A novel thermal ground plane has been developed and experimental studies on thermal ground planes (TGPs) for thermal management have been carried out. 

TGP used in this paper features a copper casing, circular micropillars, and oxidized nanostructure copper foam wick structure, with water as the working fluid. By studying the effect on thermal performance by the number of layers of porous wick structure of TGP, surface modification for a nanostructure-owning property of the copper wick structure and topper casing of different wettability. It is found that TGP with double layers of nanostructured copper foam wick structure and hydrophilic casing shows the best thermal performance among all the tested samples. A novel finding is that a double-layer wick structure with the same thickness owns a better thermal performance than a single-layer or quadruple-layer. Nanostructured wick structure also shows significant improvement from this project. Hydrophilic topper casing is superior to superhydrophobic/ superhydrophilic/ hydrophilic topper casing in axial heat transfer of the TGP. 

Thermal management helps improve reliability and prevent premature failure and solve the barrier of energy-intensive electronics. Through the use of environmental-friendly materials, TGP improves energy efficiency for a sustainable digital world.

Traditional thermal management

TGP Application

Heat sinks

Traditional heat pipes

Fans

Supercomputers

Smart devices

Light emitting diodes (LEDs)

Flexible handy electronics

PLC

 

Key findings

  • Double-layer copper wick - works best in axial heat transfer compared to single/ quadruple-layer
  • Oxidized nanostructured copper wick - improves water-carrying performance thus thermal performance
  • Hydrophilic surface topper casing - works best compared to hydrophobic/ superhydrophilic/ superhydrophobic

Mechanism of TGP

Methodology

Thermal ground plane (TGP) can improve thermal management of the heat-spots of electronics, by heat-spreading through convection.

Thermal image of TGP

Wettability surface modification - nanotechnology

nanotechnology - before and after

Water wicked across nano-coating

  • By chemical treatments, the flower-like nanostructure can be formed with different wettability properties
  • With nanowires, water can be coated on the entire microscale fibre with a thin condensate layer with an adequate wicking length, increasing the number of nucleation sites and heat transfer area. The geometric parameters around the free meniscus surface increase the capillary pressure.
  • By changing the surface wettability of the topper casing and copper wick, the axial thermal resistance has been investigated

 

Choice of materials

  • Mainly copper and water
  • Sustainable and recyclable

 

Results

Effect of number of layers of wick

 Double layer copper wick60% thermal resistance

  • capillary effect while permeability
  • evaporating meniscus develop both
    on the top surface and inside the wick

 

Effect of oxidize nanostructure of wick

Wick with Oxidized nanostructure66% thermal resistance

  • improve water-carrying capacity
  • thin condensate layer
  • reduce the chance of dryout

 

Effect of wettability of topper casing

 Hydrophilic topper casing46% thermal resistance

  • without clogging
  • rejects water at an optimal rate

 

Conclusion

  • Vapor core size: 6 cm * 2 cm * 0.677 mm
  • Thermal resistance: 1.22 K/W at 19.9 W
  • Heat source temperature: 65.7 °C at 19.9 Whttps://i.imgur.com/G61hXMP.png

Conclusion to research and using TGP

Electronics - requirements

The story behind this project

This project is my undergraduate final year design project (FYDP). Due to COVID-19, my co-op internship project was suspended midway and this FYDP is a substitute to satisfy my graduation requirement, without groupmates and I have got only half of the time as a normal FYDP project does. I would like to thank the support of my teaching assistant Yinchuang Yang and my supervisor Prof Huihe Qiu for guiding me through this cutting-edge technology, researching and achieving these remarkable breakthrough results. And more, I have won several regional awards from professional societies for this project.

As this project requires intensive laboratory techniques, for example, nanostructure forming process, degassing, soldering, etc. The TGP is extremely fragile and can be broken during the fabrication process. Moreover, due to limited experience from researchers worldwide in this nanotechnology, a lot of trial and error was required. I applied my engineering knowledge as a problem-solver and I hope to continue improving the world in the future.

Fabrication process - broken samples(Some samples that are broken during the fabrication process)

I'm a mechanical engineering student in Hong Kong, studying in the Department of Mechanical and Aerospace Engineering of the Hong Kong University of Science and Technology (HKUST). Currently, I am working on research with nanotechnology and also I am working with the power industry. I am also keen on taking leadership roles regarding sustainability, females in STEM, and community services.
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