Immersion cooling and monolithic packaging for the thermal management of high-power density electronics

Gebrael, Tarek

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https://hdl.handle.net/2142/117546 Copy

Description

Title

Immersion cooling and monolithic packaging for the thermal management of high-power density electronics

Author(s)

Gebrael, Tarek

Issue Date

2022-11-10

Director of Research (if dissertation) or Advisor (if thesis)

Miljkovic, Nenad

Doctoral Committee Chair(s)

Miljkovic, Nenad

Committee Member(s)

• Alleyne, Andrew G
• Braun, Paul V
• Pilawa-Podgurski, Robert

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• electronics
• GaN
• cooling
• packaging
• immersion
• water
• coating

Abstract

With the advancement of electrical systems comes a dire need for developing new thermal management techniques that can dissipate the ever-increasing heat generated by high-power density electronics. As we are increasingly depending on big data, connectivity, autonomous systems, electric infrastructures, and transport enabled by renewable energy, the amount of heat we are generating per unit volume is simultaneously, and considerably, increasing. The continuation of this power densification, and the resulting performance improvement, strongly depends on the development of cooling solutions capable of dissipating the generated heat while keeping the temperature of the electronics in a range suited for their optimal performance. Furthermore, the move towards reducing carbon footprint and achieving energy security necessitates efforts to reduce the power needed to operate those cooling systems. This dissertation focuses on developing electronics packaging and cooling techniques that enhance the thermal management efficiency by increasing the heat transfer coefficient, increasing the heat spreading surface area, increasing the surface area for uniform cooling, and shortening the distance between the heat-generating elements and the cooling solution. In summary, we introduced two board-level monolithic packages made of Aluminum Nitride / Parylene C and Copper / Parylene C respectively, to insulate electronics submerged in water and enhance heat spreading. Both methods leverage the high heat transfer coefficient and the uniform cooling that water immersion cooling can achieve, and they enlarge the heat transfer area from the hotspot size to a larger spreading surface area. Moreover, both packaging techniques eliminate the need for thermal interface materials (TIM), create low-resistance thermal paths from the device junction to the coolant, and bring the electronic device junction and the heat spreader to a close proximity. We start by investigating Aluminum Nitride / Parylene C packages that reduce the leakage current in water while enabling heat spreading and high-performance water immersion cooling. Short-term and long-term leakage current measurements, as well as a thermal analysis were performed to assess the viability of implementing the packages with functional electronics. Next, we explore the fabrication of conformal copper coatings that can be used as heat spreaders, heat shields, and heat routers. The coatings were characterized electrically, thermally, and thermo-mechanically. A heat spreading analysis was devised to guide the design and implementation of the coatings in electrical systems. Finally, we present a reduced order model to accurately quantify the thermal performance of the copper coatings in different configurations and cooling media. The results of the model are compared with those from finite volume method simulations and experiments.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Tarek Gebrael

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