Graphite Sheet Thermal Conductivity and Carrier Mobility
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Solution Overview
Problem
Current graphite sheets used for thermal management in mobile devices have limitations in thermal conductivity and mechanical strength, and copper wiring materials face challenges with current density resistance and weight, necessitating the development of advanced graphite materials with higher thermal conductivity and carrier mobility for alternative wiring solutions.
Innovation Solution
A graphite sheet with thermal conductivity exceeding 1950 W/mK is achieved by heat-treating a polymer film at 3000°C or higher, and a graphite wiring material with carrier mobility exceeding that of copper is produced using an aromatic polymer film with a thickness between 2.1 µm and 20 nm, and an area of 9 mm² or more, enabling high current density resistance and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If natural graphite is used for heat dissipation, then the housing becomes light, but sheet strength is low and graphite pieces may scatter
Solution Approach 1:
The patent changes the physical and chemical parameters of graphite by using highly oriented pyrolytic graphite (HOPG) with specific crystal orientation and controlled thickness (50-200 μm). This transformation from conventional graphite to HOPG with optimized parameters achieves both high strength and low weight, resolving the contradiction between sheet strength and housing weight.
2Temperature
If metal heat dissipation materials like copper or aluminum are used, then thermal conductivity is improved, but the housing becomes heavy
Solution Approach 1:
The patent changes the material parameter from metal to highly oriented pyrolytic graphite, achieving thermal conductivity of 1500-2000 W/mK in the basal plane direction, which exceeds or matches metal materials while significantly reducing weight. This parameter change resolves the contradiction between thermal conductivity and housing weight.
3Ease of manufacture
If conventional graphite sheets are used, then manufacturing is simple, but thermal conductivity along a-b plane is limited to about 200-500 W/mK
Solution Approach 1:
The patent changes the crystal structure parameter by using highly oriented pyrolytic graphite with specific orientation where the basal plane is parallel to the sheet surface. This structural parameter change achieves thermal conductivity of 1500-2000 W/mK while maintaining manufacturing feasibility through controlled deposition processes.
4Reliability
If copper wiring is used, then electrical conductivity is high, but current density resistance is insufficient and weight increases
Solution Approach 1:
The patent changes the material parameter from copper to highly oriented pyrolytic graphite, utilizing graphite's exceptional carrier mobility and high melting point to achieve superior current density resistance while reducing weight. The anisotropic electrical conductivity parameters of HOPG provide high in-plane conductivity for effective wiring.
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 resulting graphite sheet demonstrates enhanced thermal conductivity and carrier mobility, making it suitable for both thermal management and as a high-performance wiring material, surpassing the limitations of conventional copper wiring in terms of current density resistance and weight.
Implementation Method 1
heat-treating a polymer film at 3000°C or higher
Implementation Method 2
heat-treating a polymer film at 3000°C or higher
Data Source
Figure A-1(a)~A-3
Figure B-1~B-3b
Figure B-4~B-5
AI summary
The first present invention is a graphite sheet having a thickness of not more than 9.6 µm and more than 50 nm and a thermal conductivity along the a-b plane direction at 25°C of 1950 W/mK or more. The second present invention is a graphite sheet having a thickness in a range of less than 9.6 µm and 20 nm or more, an area of 9 mm2 or more, and a carrier mobility along the a-b plane direction at 25°C of 8000 cm2/V ·sec or more.