Micropillar Thermal Ground Plane for Thin Device Heat Spreading
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Solution Overview
Problem
Mobile systems such as smartphones and wearable electronics face challenges in controlling skin temperatures due to thermal resistance issues with thin metal heat spreaders, which are ineffective in transferring heat over large areas efficiently.
Innovation Solution
A flexible thermal ground plane (TGP) with a micro-wicking structure and nano-wicking structure coupled with a micromesh, featuring a top and bottom layer hermetically sealed by thermo-compression bonding, and pillars and mesh layers for enhanced thermal conductivity and heat transfer through evaporation-vapor transport-condensation-liquid return paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thin metal heat spreaders are used, then device thickness is reduced, but thermal resistance increases and heat transfer efficiency deteriorates
Solution Approach 1:
The patent employs phase change of working fluid (evaporation at heat source, condensation at heat sink) to transfer heat through the thin TGP structure. The vapor transport phase carries thermal energy across the device, enabling efficient heat transfer despite the thin form factor.
Solution Approach 2:
The TGP incorporates porous wicking structures that facilitate capillary transport of the working fluid through the thin layer. These porous materials enable liquid circulation and phase change processes essential for maintaining low thermal resistance in the thin device structure.
2Adaptability or versatility
If thin layer thickness is used, then device flexibility is improved, but thermal conductivity decreases
Solution Approach 1:
Phase change heat transfer mechanisms compensate for the reduced thermal conductivity inherent in thin structures. The latent heat of vaporization and condensation provides intensive heat transfer that overcomes the limitations of thin layer thermal conduction while maintaining flexibility.
Solution Approach 2:
The patent uses fluid-based heat transport (vapor and liquid phases of working fluid) to transfer thermal energy through the thin flexible structure. This hydraulic/pneumatic heat transfer mechanism is more effective than solid conduction in thin layers and preserves device flexibility.
3Reliability
If hermetic sealing is implemented, then device reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses flexible thin film layers that can be hermetically sealed through edge bonding or welding techniques. This approach achieves reliable sealing while maintaining a simple planar structure that is easier to manufacture than rigid hermetic enclosures with multiple components.
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
The TGP achieves effective thermal conductivities higher than copper, reducing thermal resistance and improving heat spreading, with thermal resistances dropping from 7 K/W to 2 K/W at increased power levels, and effective thermal conductivity reaching up to 4,000 to 7,000 W/mK.
Implementation Method 1
a micro-wicking structure and a nano-wicking structure
Implementation Method 2
heat transfer through evaporation-vapor transport-condensation-liquid return paths
Implementation Method 3
heat transfer through evaporation-vapor transport-condensation-liquid return paths
Implementation Method 4
the top layer and the bottom layer are hermetically sealed together by thermo-compression bonding
Data Source
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AI summary
A thermal ground plane (TGP) is disclosed. A TGP may include a first planar substrate member configured to enclose a working fluid; a second planar substrate member configured to enclose the working fluid; a plurality of wicking structures disposed on the first planar substrate; and one or more planar spacers disposed on the second planar substrate. The first planar substrate and the second planar substrate are may be hermetically sealed.