Two-Phase Cooling Apparatus With Variable Aspect Ratio Wicking
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Solution Overview
Problem
Existing cooling systems for semiconductor devices face challenges in efficiently managing heat in confined spaces with high thermal conductivity and resistance to environmental stresses, particularly in achieving high capillary forces while minimizing viscous losses.
Innovation Solution
The development of two-phase cooling devices featuring microfabricated metal substrates with etched microstructures forming a wicking structure, an intermediate substrate, and a vapor chamber, which utilizes capillary forces to transport thermal energy across different regions, including an evaporator, adiabatic, and condenser regions, with optimized aspect ratios and structural configurations to enhance heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wicking structure uses higher aspect ratio microstructures to increase capillary force, then the heat transfer rate improves, but the viscous losses in liquid flow increase
Solution Approach 1:
The wicking structure employs microstructures with varying aspect ratios distributed across different regions of the thermal ground plane. Regions with higher heat flux demands utilize higher aspect ratio structures to maximize capillary force and heat transfer, while regions with lower demands use lower aspect ratio structures to minimize viscous losses. This spatial variation of structural properties optimizes the overall heat transfer performance while controlling energy losses.
Solution Approach 2:
The invention changes the geometric parameters of the wicking microstructures, specifically the aspect ratio (height-to-width ratio), to control capillary pressure and liquid flow characteristics. By adjusting this parameter across different operational regions, the system achieves high capillary forces where needed while maintaining acceptable flow conditions elsewhere, thus balancing heat transfer enhancement against viscous loss minimization.
2Length of moving object
If the thermal ground plane is made thinner to conform to confined spaces, then the device compactness improves, but the heat transfer capability decreases
Solution Approach 1:
The invention transitions from relying solely on the planar dimension for heat transfer to utilizing the vertical dimension through high aspect ratio microstructures. These vertical channels and pores enable efficient capillary-driven liquid transport and phase change heat transfer within a thin profile, effectively adding a third dimension to the heat transfer mechanism while maintaining device compactness.
Solution Approach 2:
The thermal ground plane utilizes two-phase (liquid-vapor) heat transfer through evaporation and condensation cycles within the microstructured wicking material. This phase change mechanism provides high heat transfer coefficients that compensate for the reduced thickness, enabling thin designs to achieve heat transfer capabilities comparable to or exceeding thicker conventional designs.
3Productivity
If the wicking structure is designed for high capillary force to support large pressure differences, then the heat transfer performance improves, but the liquid flow resistance increases
Solution Approach 1:
The wicking structure employs microstructures with varying aspect ratios distributed across different regions of the thermal ground plane. Regions with higher heat flux demands utilize higher aspect ratio structures to maximize capillary force and heat transfer, while regions with lower demands use lower aspect ratio structures to minimize viscous losses. This spatial variation of structural properties optimizes the overall heat transfer performance while controlling energy losses.
Solution Approach 2:
The invention changes the geometric parameters of the wicking microstructures, specifically the aspect ratio (height-to-width ratio), to control capillary pressure and liquid flow characteristics. By adjusting this parameter across different operational regions, the system achieves high capillary forces where needed while maintaining acceptable flow conditions elsewhere, thus balancing heat transfer enhancement against viscous loss minimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables higher heat transfer rates, thinner thermal ground planes, and improved resistance to gravitational effects, while maintaining stability and minimizing viscous losses, thus outperforming earlier cooling technologies.
Implementation Method 1
the fluid may be driven by capillary forces within the wicking structure
Implementation Method 2
the working fluid adsorbs or rejects heat by changing phases between liquid and vapor
Implementation Method 3
configured for high capillary force in the wicking structure, to support large pressure differences between the liquid and vapor phases
Data Source
AI summary
The present application discloses two-phase cooling devices that may include at least three substrates: a metal with a wicking structure, an intermediate substrate and a backplane. A fluid may be contained within the wicking structure and vapor cavity for transporting thermal energy from one region of the thermal ground plane to another region of the thermal ground plane, wherein the fluid may be driven by capillary forces within the wicking structure. The intermediate substrate may form narrow channels within the wicking structure, providing high capillary forces to support large pressure differences between the liquid and vapor phases, while minimizing viscous losses of the liquid flowing in the wicking structure.