Anisotropic Thermal Conduit for CTE Mismatch Management
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Solution Overview
Problem
Current heat spreader designs face challenges due to coefficient of thermal expansion (CTE) mismatches between high conductivity metals and low thermally conductive materials, leading to degraded thermal performance, increased electrical parasitics, and added complexity and cost.
Innovation Solution
Embedding anisotropic thermal materials like Thermal Pyrolytic Graphite (TPG) inside metal tube walls allows for high and low thermal conductivities in a desired configuration, enabling intimate transitions from heat sources to heat sinks while using low CTE materials externally, reducing weight and design complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intermediate heat spreader transitions are added between low CTE materials and high conductivity metals, then CTE mismatch is managed, but design complexity and thermal performance degrade
Solution Approach 1:
The patent applies composite materials by creating a tubular structure with anisotropic thermal conductivity material (such as pyrolytic graphite) embedded within a metal tube. This composite structure provides both low CTE externally (from the metal tube) and high thermal conductivity internally (from the anisotropic material), eliminating the need for multiple intermediate transitions while managing CTE mismatch between heat source and heat sink.
2Reliability
If multiple intermediate heat spreader transitions are used, then CTE mismatch is managed, but thermal performance degrades
Solution Approach 1:
The composite tubular structure with anisotropic thermal conductivity material provides a direct thermal pathway from heat source to heat sink, eliminating multiple thermal interfaces that cause thermal resistance. The high thermal conductivity of the anisotropic material in specific directions enables efficient heat transfer while the composite structure manages CTE mismatch.
3Loss of energy
If high thermal conductivity materials are used, then thermal performance improves, but CTE mismatch increases
Solution Approach 1:
The patent applies local quality by orienting the anisotropic thermal conductivity material such that its high conductivity direction aligns with the heat flow path from heat source to heat sink, while the low conductivity direction provides CTE management. This directional property allows the material to simultaneously provide high thermal performance and manage expansion differences.
Solution Approach 2:
The composite structure combines materials with different thermal and mechanical properties, allowing the system to achieve both high thermal conductivity where needed and appropriate CTE characteristics at the interfaces with heat source and heat sink.
4Reliability
If additional heat spreader interfaces are added, then CTE mismatch is managed, but electrical parasitics increase
Solution Approach 1:
The composite tubular structure provides a direct transition path that eliminates multiple intermediate interfaces, thereby reducing electrical parasitics associated with additional connections while still managing CTE mismatch through the inherent properties of the composite material structure.
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 approach enhances thermal performance by controlling heat flow in multiple directions, reducing the number of transitions and enabling new packaging concepts, while maintaining mechanical strength and allowing for liquid cooling systems.
Implementation Method 1
the anisotropic thermal material has a basal plane perpendicular to the longitudinal axis of the tube and conducts heat radially outwardly from the longitudinal axis of the tube
Implementation Method 2
TPG material exhibits very anisotropic thermal conductivity such that, within the basal plane, the thermal conductivity can be ∼1600 W/m-°K (4x of copper) and perpendicular to the basal plane is ∼10 W/m-°K (1/40 of copper)
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
An anisotropic thermal conduit having an outer cylindrical tube; and an anisotropic thermal material disposed with the outer cylindrical tube.