Embedded Passive Heat Pipes in Electronic Assemblies for Stable Cooling
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Solution Overview
Problem
Current heat transfer systems for electronic assemblies, such as those using annealed pyrolytic graphite (APG) composites and heat pipes, face degradation over time due to thermal cycling and have limitations in through-plane conductivity, leading to inefficient thermal transport and reliability issues, especially when exposed to the environment or requiring complex geometries and clamps.
Innovation Solution
The integration of a 3D printed heat sink body with elongate, passive heat pipes that are removably fastened within the heat sink body and chassis, providing concealed heat transport and weight relief recesses to enhance thermal conductivity while minimizing exposure and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If annealed pyrolytic graphite (APG) composite structures are used for heat transport, then in-plane thermal conductivity is high (800-1000 W/m-K at EOL), but through-plane conductivity is much lower due to orthotropic properties and thermal cycling degradation occurs over time
Solution Approach 1:
The patent changes the thermal transport mechanism from solid conduction through APG to phase-change-based heat pipe transport. Heat pipes maintain consistent thermal performance by utilizing vaporization and condensation cycles, which are not degraded by thermal cycling in the same way solid composites are. This parameter change from solid-state conduction to two-phase flow enables stable thermal conductivity over time.
Solution Approach 2:
The patent employs composite structures combining heat pipe technology with heat sink materials. The heat pipe itself is a composite system containing working fluid, wick structure, and shell material. This composite approach allows the system to leverage the high thermal conductivity of the heat pipe vapor space (>10,000 W/m-K) while maintaining structural integrity and resistance to thermal cycling degradation.
2Temperature
If heat pipes are exposed to external environment for heat dissipation, then heat removal is effective, but corrosion occurs and complex geometries are required
Solution Approach 1:
The patent nests the heat pipes within the heat sink body, placing them in recesses or passageways of the heat sink structure. This nested configuration protects the heat pipes from direct exposure to corrosive environmental elements while maintaining their heat dissipation function. The heat sink body acts as a protective enclosure, eliminating the need for complex external geometries or additional corrosion protection measures.
3Shape
If clamps are used to secure heat pipes, then heat pipe positioning is achieved, but heat pipe deformation occurs and integration complexity increases
Solution Approach 1:
The patent merges the heat pipe mounting function into the heat sink body structure itself. The heat sink incorporates integrated mounting features such as recesses, passageways, or attachment mechanisms that are part of the heat sink's basic structure. This eliminates the need for separate clamps or external mounting hardware, reducing integration complexity and eliminating heat pipe deformation risks associated with clamp loads.
4Temperature
If dedicated heat spreaders or heat sinks are added to reduce thermal gradients, then conductive transport between heat sources and heat sink improves, but device complexity and integration difficulty increase
Solution Approach 1:
The patent combines the heat spreader and heat sink functions into a single integrated heat sink body. The heat sink is designed with internal structures, recesses, and passageways that perform both heat spreading and heat dissipation functions. This merging eliminates the need for separate heat spreader components and their associated mounting hardware, reducing device complexity while maintaining effective thermal gradient reduction through the heat pipe conduction paths.
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 design effectively reduces thermal gradients and improves thermal transport efficiency, outperforming APG composite designs by a factor of five and reducing temperatures by 10° to 15° C, while simplifying integration and reducing assembly time, and maintaining robustness and reworkability.
Implementation Method 1
Each elongate, passive heat pipe is received within a respective one of the heat pipe receiving passageways and is fastened to at least one end to the heat sink body
Implementation Method 2
improving conductive transport
Implementation Method 3
a heat sink body mounted to the printed circuit substrate
Data Source
AI summary
An electronic assembly may include a chassis, and electronic modules mounted within the chassis. Each electronic module may include a printed circuit substrate, heat-generating electronic components mounted on the printed circuit substrate, and a heat sink body mounted to the printed circuit substrate and having a plurality of heat pipe receiving passageways extending between opposing side edges and overlying corresponding heat-generating components. A respective elongate, passive, heat pipe may extend within each heat pipe receiving passageway and be removably fastened to at least one end to the heat sink body for enhanced conductive heat transport.