When applying graphite sheets, why do some projects result in a temperature drop of over 10 degrees, while others show almost no change?

In recent years, the term "thermal conductive graphite sheets" has become increasingly common in the electronics, power supply, and new energy circles. Mobile phones and tablets are getting thinner and thinner, but they are generating more and more heat; The power of vehicle controllers and energy storage BMS has increased, but the structural space has been continuously squeezed; When making high-temperature aging tests for boards and power modules, they always get stuck at the 80°C or 90°C edge.

Many engineers have heard similar statements: "Add a high thermal conductivity graphite sheet, and the temperature can drop by as much as 10 degrees at once." But when they actually got involved in the projects themselves, the experience was very polarized:

Some projects:

After replacing the graphite sheet, the peak temperature did indeed drop significantly, and the high-temperature aging process was completed in one go;

Some other projects:

A large number of graphite sheets were applied, but the temperature hardly changed at all. They even wondered —

"Is the graphite sheet just a waste of money?"

Both are using graphite sheets, but why is the effect so much different?

Is the problem with the material itself, or with the application method?

Ⅰ. First, let's clarify: What exactly is the thermal graphite sheet doing?

Let's make the core point clear first:

The graphite sheet is not a "magic that can cool itself", but rather helps you create a faster and longer path for the heat.

In typical board cards / power modules / vehicle controllers, the general path of heat is:

Thermal devices (chips, MOS, IC, etc.)

→ Intermediate heat-conducting materials (graphite sheets, heat-conducting pads, copper-aluminum components, etc.)

→ Metal casings / heat dissipation plates / cold plates

→ Air or other cooling sources

The value of thermal graphite sheets mainly lies in the following two aspects:

1. Excellent in- heat conduction

The "in- thermal conductivity" of the current mainstream artificial graphite sheets varies roughly from several hundred to several thousand W/m·K. Some high-end models can reach a level close to 2000 W/m·K under specific testing conditions (referring specifically to the heat conduction performance in the direction, and there may be differences among different products).

This means: It can quickly spread out the local hotspots.

2. Thin, lightweight, cuttable, and conformable

The thickness can be as thin as several tens of micrometers or even thinner. It can be placed between the device and the casing, or between the back of the board and the metal part.

3. Almost no space occupation and not much weight increase.

Simple understanding:

The chip is very small and the heat is very concentrated; The graphite sheet is very thin and can have a large area, helping to spread the heat more widely and handing it over to a larger "heat dissipation surface" for processing. But there is a prerequisite for this - the "heat path" laid out by you must be unobstructed.

II. Why do some projects show significant cooling effects while others remain almost unchanged?

The performance of graphite sheets can be influenced by four factors: material, route, connection, and edge.

1. "Material": The selection of materials in the first step determines the upper limit.

There are many misunderstandings in the industry, stemming from a statement:

"Since they are all graphite sheets, just buy a cheaper one and try it first."

In fact, the thermal conductive graphite sheets from different manufacturers vary greatly:

In- thermal conductivity: Some can reach several hundred W/m·K, while others can achieve over a thousand or even higher.

Thickness: Some are 0.1–0.2 mm, while others can be as thin as several micrometers.

The flexibility, whether it has an insulating layer, and whether it comes with a self-adhesive backing, all vary.

If the project itself:

Power is not low.

The heat flux is very high.

The structural space is also very limited.

However, I chose a graphite sheet with average thermal conductivity and a relatively thick thickness.

The cooling effect it can bring is quite limited on its own.

On the contrary, if during the scheme evaluation stage, based on power and space constraints,

I selected the material with higher in- thermal conductivity, thinner thickness, and better adhesion, even "applying a single graphite sheet", the effect might be completely different.

So, the first step of self-check:

What is the thermal conductivity and thickness of this graphite sheet I'm using? Does it match my power and space conditions?

2. "Pathway": The hot path should connect from the "hot spot" to the "heat dissipation surface".

The second common issue is that the hot path has not been established.

A typical situation is:

The engineer placed the graphite sheet on top of the chip. Or it may cover a small area of the board card.

However, the graphite sheets did not cross over to come into contact with the metal casing / heat dissipation plate / cooling plate.

This usage merely adds an additional "middle layer" to the hotspot.

The heat still circulates locally and cannot escape from that small area.

As a result, there is no noticeable temperature difference.

In contrast, a well-designed solution typically looks like this:

The graphite sheets start from the hot spot and extend onto the cooler and larger metal components.

The coverage path is continuous and is not "cut off" in the middle.

It avoided being limited to just areas that "stick well but do not dissipate heat".

The second step of self-check:

Is this piece of graphite sheet not only covering the hot spot but also truly "grabbing" the heat dissipation surface?

Or is it only stuck in the "convenient sticking" areas?

3. "Adhesive": The quality of adhesion determines whether your efforts were in vain.

Heat conduction is most prone to failure when there are gaps in the middle.

Even if the graphite sheet itself has excellent thermal conductivity:

If the surfaces of the components, boards, and enclosures are not flat,

There are hollow areas, bulges and curled edges in the middle of the graphite sheet.

The pressing force was insufficient and the assembly tolerances were not properly controlled.

The interface thermal resistance will be extremely high, and the advantages of the graphite sheet will be largely lost.

The common "failure" is like this:

During the proofing stage, it was manually laminated, and the prototype performed very well.

As soon as we got on the production line, there were deviations in the alignment method, pressure and position.

After conducting a round of temperature tests, it was found that the results were completely different from those of the prototype.

The third step of self-check:

Did the graphite sheets truly "stick" the device to the casing,

or were they merely "attached" in a way that only seemed like they were attached?

4. "Boundary": Who does the graphite sheet transfer the heat to at the end?

The final step is the boundary condition.

The function of the graphite sheet is to help spread the heat over a small area;

But after spreading, there must be a place to remove the heat:

For example, large-area metal shells, metal frameworks, heat sinks, cold plates, etc.

Or in areas where forced air cooling and natural convection conditions are relatively good.

If the final message received is:

A structural component with poor heat conductivity and still generating heat itself.

Or a small plastic piece,

And with almost no airflow inside,

Then this situation would occur:

"The heat has spread a little, but the overall environment is too hot.

It seems as if the temperature has not dropped much at all."

The fourth step of self-check:

Is the end point of the graphite sheet a "reliable heat dissipation surface"?

III. "Self-Inspection Checklist for Engineers"

If you currently have a project that "has graphite sheets attached but shows no effect", you can go through the following four points:

1. Material grade

Is there a mismatch between the thermal conductivity, thickness, project power and space constraints?

2. Thermal path design

Did the graphite sheets connect all the way from the hot spot to the metal housing / heat dissipation component?

Are there any "breakpoints" in the middle?

3. Adhesive quality

Is the surface flatness of the device / housing and the compression structure properly designed?

After the fitting, are there any gaps, edges that are lifted up, or position deviations?

4. Boundary conditions

Can the internal airflow and shell temperature conditions of the entire machine allow this area to truly "cool down"?

In the end, it was the metal heat dissipation surface that was connected, or was some "overwhelmed" part that was connected?

Often, it's not that "the graphite sheets are useless", but rather that one or two of these four aspects were not handled properly.

Ⅳ. Why are some manufacturers more suitable for "bringing them in from the very beginning"?

What was mentioned earlier is the general principle.

Returning to the practical level, many companies now choose to bring material + solution-type suppliers into the project for early review, rather than conducting a bunch of tests on materials in isolation.

Take an industry representative as an example: Jiangxi Dasen Technology Co., Ltd. (DSN)

It possesses the following capabilities:

1. In the material aspect, it can cover different grades of thermal conductive graphite sheets.

For different scenarios such as consumer electronics, power supplies, and new energy, it provides graphite sheet products with various thermal conductivities, thicknesses, and flexible grades;

For projects with different sensitivities to power, space, and cost,

it can make a trade-off between "adequate" and "higher performance", rather than a one-size-fits-all approach.

2. In the solution aspect, it can discuss "how to handle heat" together.

Many engineers have reported that when communicating with such manufacturers, it is not a simple matter of reporting a size and then being done.

But they will discuss:

The location of the heat source, the general power situation;

Which metal parts / shells can be connected;

Which places are suitable for applying graphite sheets, and which places applying them are ineffective;

Whether adhesive, insulation layers, or stack structures need to be used, and what is the more reasonable way to do it.

This is actually the "material, path, connection, and edge" four matters mentioned earlier,

with a team that has been doing graphite sheets + thermal management for a long time, helping you dig out the problems in advance.

3. In the mass production aspect, it can handle requirements ranging from small batches to large volumes.

According to public information, Jiangxi Dasen's monthly production capacity of artificial graphite alone has reached approximately 700,000 square meters, and it has also passed multiple quality and environmental-related system certifications.

This means:

It's not just about providing you with a small number of verification samples. Instead, after your project is completed, we can still undertake subsequent batch deliveries.

In terms of dimensions, precision, tolerance, yield, and delivery time, we have relatively mature management experience.

V. Make Graphite Sheets Truly Useful

Returning to the question at the beginning of the article:

When applying graphite sheets, why do some projects reduce temperatures by 10 degrees, while others hardly change?

Now, it can be summarized in one sentence:

The material selection should be appropriate (for the material), the heat path should be unobstructed (for the path), the adhesion should be solid (for the connection), and finally, there should be a reliable heat dissipation surface to help remove the heat (for the edge).

If all these four steps are done correctly, thermal graphite sheets in high-power, space-constrained products do have the potential to help you lower the "high-temperature aging not lasting, peak temperature too high" problem by one step.

If you currently have such a project:

boards, power supplies, automotive electronics, energy storage BMS;

the power is not small, and the hotspots remain at 80–100°C for a long time; the space is limited, and you don't want to immediately modify the mold or redo the structure;

Then you can definitely consider:

First, organize the power, structure illustration, and allowable thickness range, and talk to a supplier like Jiangxi Dasen, which not only produces thermal graphite sheets but also provides thermal management technical support, to see if a more reasonable graphite sheet solution can be adopted, to open up a "heat path" for your project.