The "Invisible Heat Radiator" of The High-Power Era: How Graphite Sheets Enable Heat To Disappear Faster?

With the rapid development of high-power density, lightweight and thin electronic products and highly integrated modules, heat is no longer merely a matter of "temperature increase" - it can lead to frequency drop, noise increase, lifespan reduction, even safety risks. To remove heat from chips, apart from fans, heat sinks, and heat dissipation devices, the key lies in quickly spreading and evenly distributing the heat, preventing local hotspots from getting out of control.

Among various heat dissipation materials, graphite sheets have become the most common "invisible heat diffusers" in mobile phones, laptops, vehicle electronics, and communication equipment. Especially the high conductivity artificial graphite sheets (commonly known as pyrolytic graphite sheets, etc.), their in- heat conduction capacity usually reaches several hundred to several thousand W/(m·K), and have obvious advantages in terms of lightness, flexibility, and modularity, and are becoming the "standard components" in thermal management solutions.

01 "High Thermal Conductivity Graphite Sheets: From Structure to Performance"

Graphite is a typical layered material: within the same layer, there are strong covalent bonds, while between layers, there are weaker van der Waals forces. This structure directly leads to one result - heat spreads quickly in the direction and slowly in the thickness direction.

The core value of graphite sheets for heat dissipation is not like copper, which "transfers heat to a distant place", but more like "a highway for heat + a spreader":

High thermal conductivity: quickly spreads the hot spot heat, reducing the peak temperature;

Light and flexible: suitable for irregular spaces, conforming to curved surfaces;

It also has electromagnetic shielding/conductive properties (depending on the material system): in some terminal structures, it can "serve multiple purposes with one sheet".

However, graphite sheets are not "effective once attached", and their effect is strongly bound to the application method:

If the graphite sheet does not fit tightly with the heat source, there is an air layer at the interface, and the heat diffusion ability will be severely weakened;

If the heat is not further conducted (for example, to the middle frame, VC, or heat sink), the graphite sheet is only "spreading heat" and it is difficult to achieve real cooling.

Therefore, the engineering value of graphite sheets = material performance × structural design × interface process.

02 "Complexification and Systematization: Graphite Sheets No Longer Work Alone"

In the face of higher power consumption and more complex stacking structures, a single graphite sheet often needs to collaborate with other materials to form a "thermal path system". Common routes can be roughly divided into two categories:

(1) "Graphite Sheet + Polymer/Adhesive System": Solving Adhesion and Reliability

In mobile phones, wearables, TWS devices, and lightweight laptops, graphite sheets are often installed in the form of "back adhesive + release film". At this time, the key variable affecting heat dissipation has become: adhesive layer thickness, thermal resistance, temperature resistance, bonding reliability, rebound, and warpage control.

To reduce interface thermal resistance, common practices include:

Choosing a more suitable conductive pressure-sensitive adhesive/structural adhesive system;

Improving the real contact area of the interface through surface treatment/microstructure design;

Using multi-layer stacking (such as combination of graphite sheets with PI, foam, copper foil, etc.) to balance strength and assembly tolerance.

A small reminder: Many "poor graphite sheet effects" problems actually stem from the adhesive layer and the bonding process, rather than the graphite sheet itself.

(2) "Graphite sheet + metal/thermal equalization device": Transform "heat distribution" into "heat conduction"

As power consumption continues to increase, merely relying on graphite sheets for heat distribution is insufficient. Heat needs to be conducted to a larger heat dissipation structure:

Collaboration between graphite sheets and VC thermal equalization plates/thermal pipes: The graphite sheets are responsible for quickly spreading the hotspots, while the VC is responsible for transporting the heat to a larger area;

Collaboration between graphite sheets and aluminum/magnesium alloy frames and heat sinks: Through structural components, secondary diffusion and convective heat exchange are achieved;

In automotive and communication equipment, graphite sheets are also often combined with thermal pads, thermal gels, and phase change materials to construct a stable heat path.

At the same time, the "weak points" of graphite sheets should also be recognized:

Thermal conductivity in the thickness direction is weak: It is more suitable as a heat diffusion layer rather than a vertical heat conduction main channel;

Prone to be affected by assembly stress: Bending, compression, and warping will change the contact thermal resistance;

Environmental adaptability: Under humid heat, salt spray, and long-term thermal cycling conditions, higher requirements are imposed on adhesive and interlayer structure.

03 "Selection and Implementation: Three Steps to Use Graphite Sheets 'Correctly'"

In actual projects, instead of merely asking "What is the thermal conductivity?", it is better to select based on the thermal path:

Step 1: Define the objective - Do you need to "spread heat" or "conduct heat outwards"?

High temperature difference, hot surface: Prioritize high in- thermal conductivity and reasonable area laying;

High core temperature, significant frequency drop: It is necessary to conduct heat to the VC/central frame/heat sink. The graphite sheet is just one part of it.

Step 2: Match the structure - Thickness, size, stacking and assembly tolerance are all determined together.

Thin and light space: Focus on thickness, rebound, and the compressibility of the back adhesive;

Special-shaped structure: Focus on die-cutting accuracy, opening position, assembly efficiency and consistency.

Step 3: Make the interface the "main character" - Thermal resistance often fails due to the adhesive layer and bonding.

Too thick adhesive layer, bubbles, warping, insufficient bonding pressure, all may turn "high thermal conductivity materials" into "high thermal resistance structures"