Graphite Thermal Interface Layers With Low Roughness and High Heat Transfer
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Solution Overview
Problem
Existing graphite-based thermal interface materials suffer from low thermal conductivity, high surface roughness, and poor mechanical strength due to high graphite filler concentrations, which hinder effective heat dissipation in high-processing-rate electronic devices like 5G devices.
Innovation Solution
The development of an anisotropic thermal interface device using aligned thermally anisotropic conductive composite layers with 45-95 weight percent graphite flakes and a binder containing branched siloxane, which enhances thermal conductivity while maintaining softness and low surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high graphite filler concentration is used to increase thermal conductivity, then through-plane thermal conductivity is improved, but surface roughness increases and mechanical strength decreases
Solution Approach 1:
The patent uses a composite material system combining graphite flakes with a siloxane binder (containing at least one hydroxyl group) to create a thermal interface material that achieves high thermal conductivity (25-45 W/mK) while maintaining adequate mechanical strength (tensile strength 50-130 kPa). The siloxane binder with hydroxyl groups forms strong interfacial bonding with graphite flakes, preventing material degradation even at high graphite concentrations (60-95 wt%).
Solution Approach 2:
The patent changes the chemical parameters of the binder by specifying siloxanes with at least one hydroxyl group per molecule, and controls the processing parameters (hot pressing temperature 100-200°C, pressure 1-10 MPa, time 1-10 minutes). This parameter optimization allows achieving high thermal conductivity while maintaining mechanical integrity and low surface roughness (Ra ≤ 10 μm).
2Temperature
If high graphite filler concentration is used to increase thermal conductivity, then through-plane thermal conductivity is improved, but surface roughness increases
Solution Approach 1:
The siloxane binder with hydroxyl groups creates a matrix that holds graphite flakes in a flat, aligned configuration, reducing surface asperities. The chemical bonding between siloxane hydroxyl groups and graphite surface oxygen groups creates a stable composite structure that maintains low surface roughness (Ra ≤ 10 μm) even with high graphite content for enhanced thermal conductivity.
Solution Approach 2:
The patent applies hot pressing treatment before final assembly to pre-align graphite flakes and densify the composite structure. This preliminary action (hot pressing at 100-200°C under 1-10 MPa for 1-10 minutes) flattens surface irregularities and establishes low surface roughness before the material is installed, ensuring optimal thermal contact without requiring additional post-processing.
3Temperature
If aligned thermally anisotropic conductive composite layers are used to achieve high thermal conductivity, then through-plane thermal conductivity is improved, but device complexity increases
Solution Approach 1:
The thermal interface material is segmented into multiple thin composite layers (each 10-100 μm thick) with aligned graphite flakes, rather than using a single thick layer. This segmentation allows heat to conduct efficiently through the plane of each layer while the layered structure itself remains simple to manufacture via hot pressing. The alignment of graphite flakes within each thin layer provides high in-plane thermal conductivity without requiring complex 3D structures.
Solution Approach 2:
The patent optimizes processing parameters (hot pressing temperature, pressure, and time) to achieve spontaneous alignment of graphite flakes during manufacturing, eliminating the need for complex post-manufacturing alignment processes. By controlling these parameters, the material self-organizes into the desired anisotropic structure with high thermal conductivity in the plane of the layers, simplifying the overall device fabrication process.
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 solution achieves a through-plane thermal conductivity of 25 to 45 W/mK, a Shore C hardness of 30 to 70, and a tensile strength of 50 to 130 KPa, effectively addressing the limitations of existing thermal interface materials by improving thermal conductivity and mechanical strength while reducing surface roughness.
Implementation Method 1
a binder including a branched siloxane
Implementation Method 2
a second, larger thermal conductivity in a second direction... the x-y planes of the flakes align in the second direction having the second, larger thermal conductivity
Data Source
AI summary
An anisotropic thermal interface device including plural aligned thermally anisotropic conductive composite layers. Each layer has a first thermal conductivity in a first direction and a second, larger thermal conductivity in a second direction. The aligned thermally anisotropic conductive composite layers extend substantially parallel to each other in the first direction and include 45-95 weight percent graphite flakes aligned in the second direction. The thermally anisotropic conductive composite layers have a binder including a branched siloxane. The thermally anisotropic conductive composite layers are adhered to adjacent thermally anisotropic conductive composite. The thermally anisotropic conductive composite layers have a second thermal conductivity of 25 to 45 W/mK. The anisotropic thermal interface device has an arithmetic average surface roughness of 5 to 20 μm and a tensile strength of 50 to 130 KPa.