Controlling heat transfer in electronic packaging using thermal switches and high power thermal buffers

Advances in electronic devices and vehicle electrification have resulted in increased power density (power-to-volume ratio) and specific power (power-to-mass ratio). The temporally and spatially irregular heat generation from high-power devices causes temperature spikes and gradients, leading to reduced device reliability and bulky thermal management systems. Controlling heat transfer is a key challenge of electronic packaging. Thermal devices able to actively control heat transfer in space and time are desired for advanced thermal management. We focus on two thermal devices – a thermal switch and a thermal buffer – that can provide spatial and temporal control of heat transfer. In an analogy with electrical circuits, a thermal switch is a device to bridge or break a heat transfer pathway between a heat source and heat rejection system. A thermal buffer with a large thermal capacitance can absorb large amounts of heat and suppress temperature swings of electronics in transient operation. This dissertation reports the development of a high contrast thermal switch and a high cooling capacity thermal buffer designed to control heat transfer in electronic packaging. The main contributions of this work are: (i) Design of a millimeter-scale liquid metal droplet thermal switch with high ON/OFF switching ratios > 70; (ii) Control of heat transfer from one or two gallium nitride (GaN) devices using the thermal switch; (iii) Integration of a solid copper (Cu) thermal switch with a 3 kW DC/AC power converter to isothermalize silicon carbide (SiC) modules; (iv) Development of a composite phase change material (PCM) thermal buffer with high cooling capacity and large energy density; and (v) Stabilization of GaN device temperatures under transient heat loads using the PCM thermal buffer heat sink. This work investigates the fundamentals of steady and transient heat transfer in electronic packaging controlled by the thermal switch and thermal buffer, and demonstrates opportunities for applications and further research into thermal management systems of power electronics.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Yang, Tianyu

Contributors dc:contributor

• King, William Paul
• Miljkovic, Nenad
• Braun, Paul
• Sinha, Sanjiv

• Mechanical science

Statement dc:rights

• Copyright 2021 Tianyu Yang

Language dc:language

en, eng

Handle dc:identifier

http://hdl.handle.net/2142/113847

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F113847