Every new generation of electronic products integrates smaller dimensions with advanced technical abilities. This results in unavoidable heat generation because the electrical resistance of the products is focused on smaller and smaller areas. If heat is not efficiently managed, these spots can become increasingly hot.
Heat dissipation materials that were formerly used, such as metals like copper combined with a smart airflow or even water-cooling systems, are not as easily applied because of the small dimensions of electronic products.
Researchers have evaluated a range of carbon-based materials to solve this challenge. Standard graphite materials have a dramatically lower thermal conductivity of 117 W/mK to 165 W/mK compared to copper at 350 W/mK to 400 W/mK. Graphene or diamond exhibits a significantly higher thermal conductivity, higher than that of any other material used.
Diamond is not flexible and is very hard, which makes it challenging to apply on heat generation components such as the power supply, micro controller, integrated circuits and others. In contrast, graphene is highly flexible, which makes it simple to apply to the various components of the electronic product.
1. Graphene Structure and Thermal Conductivity
Graphene consists of a hexagonal, two-dimensional structure established on carbon-carbon sp2-hybrid orbitals. In an optimal example, this also creates a large crystal lattice. In this type of construction, the average free path of phonons is around 775 nm higher compared to graphite with high thermal conductivity.
The thermal conductivity of graphene as a result of this composition can reach up to 2500 W/mK. The vibration of the crystal lattice is the main cause of graphene’s heat conduction. The synchronized harmonic modulation of the crystal structure with the phonon vibration results in heat being conducted outside of the structure.
Along with this, the electrons can move freely due to the sp2-hybrid orbitals. This type of construction at room temperature will cause the electrons to have a speed that is 1/300 of the speed of light, dramatically higher than in configurations that lack the sp2-hybrid orbitals.
In these sp2-hybrid orbitals, electron mobility can reach up to 15000 cm2/Vs, greater than the electron mobility in all metals at room temperature.
To conclude, graphene exhibits a significantly high thermal conductivity due to the interaction between electrons and phonons.
2. Preparation of Graphene Thermal Film
The preparation techniques for graphene thermal film commonly include spin coating, vacuum filtration and spraying. The thickness of the graphene film created by the vacuum filtration technique is comparatively thin and is challenging to use independently in the area of heat conduction.
The spraying technique produces a graphene film with low density and poor uniformity. The spin coating technique provides an even application of the (oxidized) graphene solution to the substrate. The solvent of the (oxidized) graphene solution is evaporated at a specific temperature to produce the desired film.
The spin coating technique creates a graphene film with high uniformity and is appropriate for large-scale production. Figure 1 details the preparation stages of a standard graphene thermal film.
Figure 1. Typical preparation for the production of thermal dissipation films. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.
3. Application of Graphene Thermal Film
The Sixth Element (Changzhou) Materials Technology Co Ltd. is a leading manufacturer of reduced graphene oxide, graphene oxides and high-quality graphene.
The Sixth Element (Changzhou) Materials Technology Co Ltd. supply graphene oxides that are highly suitable for the manufacture of heat dissipation films based on graphene.
To establish the manufacture of heat dissipation films based on graphene, Changzhou Fuxi Technology Co Ltd. was founded in 2014 through a collaboration between The Sixth Element (Changzhou) Materials Technology Co Ltd. and Jiangsu Warwick Century Electronics Group Co Ltd.
The Sixth Element (Changzhou) and Changzhou Fuxi Technology worked together to produce a highly oriented thermal conductive graphene-based film with an in-plane thermal conductivity between 1000 W/mK to 1500 W/mK, reliant on thickness.
The film can be manufactured in thicknesses between 30 µm to 400 µm. A key advantage of the film is that it can maintain thermal conductivity while being bent by 180° more than 105 times.
Figure 2. Thermal conductive graphene film – ready for die-cutting. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.
Leading smartphone manufacturers have been attracted to this graphene based thermal conductive film. Huawei was the first producer to adopt the film in 2018, employing this type of technology in its range of Mate20 smartphones.
Huawei demonstrated that compared to widely used cooling systems, the working temperature at full power is drastically reduced. The technology continued to be used by Huawei in the subsequent smartphone generations, for example, the Mate30pro, Mate30, MateP40 series and more. Along with this, the technology is also employed in the Matepad Pro 5G tablet from Huawei.
Changzhou Fuxi Technology and The Sixth Element (Changzhou) continue to invest in additional production capacities to meet the rising demand.
Along with smartphones, this material could potentially be used in applications such as folding screens, wearable devices and similar consumer products that integrate a high processing power with small dimensions (mainly thickness).
This information has been sourced, reviewed and adapted from materials provided by The Sixth Element (Changzhou) Materials Technology Co.,Ltd.
For more information on this source, please visit The Sixth Element (Changzhou) Materials Technology Co.,Ltd.