GRAPHENE HEAT SINK: THERMAL MANAGEMENT APPLIED TO AUTOMOBILE TO TABLET COMPUTER

For most PCB, high signal frequency is very common, so the heat generated inside PCB will be larger, which leads to the problem of plane heat management is more and more important. Engineers have been trying to solve heat management problems with various types of heat sinks, heat dissipation substrates, and different forms of heat sinks (such as aluminum, copper, etc.); at the same time, the electronic industry is still looking for solutions that take less space, are more effective, and are more economical. MS company combines carbon nanotechnology with graphene with very high thermal conductivity, and has made a breakthrough in the plane thermal management technology with nanometer thickness. This technology can provide heating management solutions for driverless cars, tablet computers and other personal devices.

Graphene is a kind of allotrope (carbon) of carbon. It is a two-dimensional carbon nano material with honeycomb lattice formed by carbon atoms and SP 2 hybrid orbital. It is the basic structural element of many other forms of carbon, such as graphite, diamond, charcoal, carbon nanotubes and fullerenes. Graphene is one millionth thinner than a sheet of paper; because it is so thin, it can be considered a two-dimensional structure. Graphene's flat honeycomb pattern gives it many unusual features, including being the most powerful material in the world. Its strength comes from the continuous hexagon structure and the strong bond between carbon atoms. This strong bond has great toughness, can twist, stretch, and bend to a certain extent without fracture, which means that graphene is bendable and extensible.

Graphene's revolutionary material properties include:

* The strongest material ever;

* The thinnest material known in science;

* High toughness and excellent light transmittance;

* The most impervious material on earth;

* Record-breaking thermal and electrical conductivity;

* And incredibly energy efficient.

With the advent of autopilot, more computing power, console, vehicular Internet, wireless network and sensor array will be used. This will lead to greater consumption of CPU power. The superposition of various new applications will significantly increase heat. The application of new graphene film in automobile will be expanded.

Therefore, the demand for heat dissipation has increased accordingly. The size of console and other related computer / electronic systems will be enlarged by using traditional aluminum fins, while the plane heat management scheme using new graphene film fins is not only thinner in thickness, but also more effective in heat dissipation.

Figure 1: Radiation structure of a new graphene film radiator

Graphene is very suitable for flat heat management and electronic packaging applications. It can be dispersed in the solution of spraying ink and coating, and mixed with polymer, so as to substantially enhance its thermal characteristics. With this in mind, graphene composite films are made by using graphene's unique thermal conductivity and carbon nanoparticles, as well as diamond powder particles, which can greatly enhance its thermal performance. In addition, diamond powder particles can reduce the conductivity of graphene, which will not cause any electromagnetic interference (EMI) problems to PCB and electronic components.

The patented graphene composite film engineering method is to integrate graphene and diamond powder particles into a mesh structure, allowing uninterrupted heat conduction. In addition, carbon nanoparticles (with a thermal radiation divergence of 0.98) are filled in the pores of the structural grid to increase the thermal radiation efficiency. Graphene film heat sink with very high thermal conductivity in X and Y plane, combined with the effective conversion of infrared thermal radiation of carbon nanoparticles in Z plane, can transfer heat in 3D form. The thermal conductivity of graphene film is limited in X and Y plane, and the new graphene composite film has excellent thermal diffusivity in Z plane. Therefore, the plane thermal management performance of graphene composite film is much better than that of graphite heat sink, because it can not only heat in X and Y plane, but also in Z plane.

The high polarizability of these nanomaterials enables them to be evenly distributed on the surface of the film, thus maximizing the cooling effect of thermal radiation. The nanostructure of graphene film strengthens its electrical insulation characteristics, so it can withstand high voltage of 2KV. The heat radiation layer has a high level of heat radiation ability through infrared radiation, so even in the confined space, it also increases the heat emission. According to the requirements of the product, metal layer can be added under the film to accelerate the thermal emission of the nanostructure layer and promote greater thermal radiation.

The thickness of graphene film heat sink is 25 μm ~ 210 μm, which is very thin compared with the traditional heat sink. The graphene film heat sink can contain a layer of graphene from several microns to dozens of microns, plus a layer of aluminum or copper of dozens of microns, or only one layer of graphene. This light and thin film is suitable for smart phones, iPads, tablets and other portable devices, as well as small components such as ICs, led and DDR memory.

Graphene film is usually adhered to the surface of the heat source, or the top or bottom of PCB. The graphene film can also be added to the front or back of the shell of various mobile phones, or on the top or bottom of the heat source. The film will not interfere with the antenna performance, so it can also be added to the antenna area if necessary. Of course, the actual arrangement will depend on the layout of the device and the location of the heat source.

Figure 2: Graphene film can be applied to the top and bottom of PCB

Figure 3: Adding graphene film on the existing aluminum heat sink can improve the heat dissipation, or directly using graphene film instead of aluminum heat sink