Composite Heat Spreader Using Adhesive-Free Graphite Layers
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Solution Overview
Problem
Current heat spreaders face challenges in achieving high in-plane thermal conductivity and sufficient thickness for effective thermal management in electronic devices, particularly in high heat environments, where existing materials like pyrolytic graphite and graphitized polyimide films are limited by thickness and surface area, and adhesives can interfere with thermal properties.
Innovation Solution
A composite heat spreader is created by combining sheets of compressed exfoliated graphite and synthetic graphite, such as pyrolytic graphite or graphitized polyimide, without adhesives, to achieve an in-plane thermal conductivity of over 600 W/m*K and a thickness of greater than 50 microns, utilizing calendering or burnishing to join the elements and optimize thermal conductivity for specific applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pyrolytic graphite or graphitized polyimide films are used as heat spreaders, then in-plane thermal conductivity is improved, but thickness and surface area are limited
Solution Approach 1:
The heat spreader is divided into multiple layers: a first element made of compressed exfoliated graphite particles and a second element made of synthetic graphite (pyrolytic graphite or graphitized polyimide). This segmentation allows each layer to contribute different properties, with the exfoliated graphite providing thickness and flexibility while the synthetic graphite provides high thermal conductivity.
Solution Approach 2:
The patent creates a composite structure by combining exfoliated graphite particles with synthetic graphite materials. This composite approach enables the heat spreader to achieve both high thermal conductivity (from the synthetic graphite) and sufficient thickness (from the compressed exfoliated graphite particles) without the limitations of using single materials.
2Strength
If adhesives are used to join heat spreader elements, then structural integrity is improved, but thermal properties are interfered with
Solution Approach 1:
The patent removes adhesives from the construction process entirely. Instead of using adhesive layers to join the heat spreader elements, it relies on the natural adhesion properties of the exfoliated graphite particles and the bonding capability of the synthetic graphite material, thereby eliminating the thermal barrier that adhesives would create.
Solution Approach 2:
The exfoliated graphite particles act as an intermediary between the synthetic graphite layers, providing both structural bonding and thermal conduction pathways. These particles naturally bond the layers together through van der Waals forces while maintaining excellent thermal contact, replacing the need for adhesive mediators.
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 composite heat spreader effectively manages heat in electronic devices by providing high thermal conductivity and capacity, preventing heat from overwhelming the spreader and ensuring even heat distribution, thus enhancing device performance and reliability.
Implementation Method 1
The formation of graphite particles which have been expanded to have a final thickness or 'c' dimension which is as much as about 80 times or more the original 'c' direction dimension into integrated flexible sheets by compression, without the use of any binding material, is believed to be possible due to the mechanical interlocking, or cohesion, which is achieved between the voluminously expanded graphite particles.
Implementation Method 2
The formation of graphite particles which have been expanded to have a final thickness or 'c' dimension which is as much as about 80 times or more the original 'c' direction dimension into integrated flexible sheets by compression, without the use of any binding material, is believed to be possible due to the mechanical interlocking, or cohesion, which is achieved between the voluminously expanded graphite particles.
Implementation Method 3
a heat spreader having an in-plane thermal conductivity of at least about 600 W/m*K... each synthetic graphite layer includes at least one sheet selected from either pyrolytic graphite or sheets of graphitized polyimide film
Data Source
AI summary
A composite heat spreader (10) having an in-plane thermal conductivity of greater than 600 W/m*K and a thickness of greater than 50 microns, the composite heat spreader including a first element (20) which includes at least one sheet of compressed particles of exfoliated graphite having a density of at least about 1.4 grams/cc; and a second element (30) which includes at least one sheet of synthetic graphite having a density of at least 1.8 grams/cc and an in-plane thermal conductivity of at least 700 W/m*K, where the first element and the second element are joined into a composite sheet without the use of adhesives.