Why Does Applying Graphite Sheets Cool Some Projects by Over 10°C? While Others Show Almost No Change?

In recent years, the term "thermal conductive graphite sheet" has become increasingly common in electronics, power supply, and new energy circles:

- Smartphones and tablets are getting thinner, yet generating more heat;

- On-board controllers and energy storage BMS systems boast higher power, but their structural space is constantly being compressed;

- High-temperature aging tests for boards and power modules often hit a bottleneck around 80°C to 90°C.

Many engineers have heard claims like: "Stick a high thermal conductivity graphite sheet, and the temperature will drop by over 10°C instantly." However, real-world project experiences are highly polarized:

- Some projects: After installing graphite sheets, the peak temperature drops significantly, and high-temperature aging tests pass smoothly;

- Other projects: Even with multiple graphite sheets applied, the temperature barely changes, leading to doubts like, "Are graphite sheets just a gimmick?"

Why is there such a huge difference in effectiveness when applying graphite sheets? Does the problem lie in the material itself or its usage?

I. First, Understand: What Exactly Do Thermal Conductive Graphite Sheets Do?

Let’s break down the core function in one sentence:

Graphite sheets aren't "magic cooling devices"—they simply create a faster, longer path for heat to dissipate.

In a typical board/power module/on-board controller, the general heat transfer path is: Heat-generating components (chips, MOSFETs, ICs, etc.) → Intermediate thermal conductive materials (graphite sheets, thermal pads, copper/aluminum parts, etc.) → Metal housing/heat sink/cold plate → Air or other cold sources

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

1. Exceptional in- thermal conductivity

Mainstream artificial graphite sheets today have in- thermal conductivity ranging from several hundred to over 1,000 W/m·K, with some high-end models reaching nearly 2,000 W/m·K under specific test conditions (this refers specifically to planar thermal performance, which varies by product). This means they can quickly spread local hotspots over a larger area.

2. Thin, lightweight, die-cuttable, and easy to attach

With thicknesses as low as tens of micrometers or even thinner, they can fit between components and housings, or between the back of boards and metal parts—taking up almost no space and adding negligible weight.

To put it simply:

Chips are small, so heat concentrates easily; graphite sheets are thin and can be made large, helping to spread heat over a wider area for more efficient dissipation through larger cooling surfaces.

However, this relies on one crucial premise:

The "heat path" you create with the graphite sheet must be unobstructed.

II. Why Do Some Projects See Significant Cooling While Others Don't?

The effectiveness of graphite sheets depends on four key factors: Material, Path, Contact, and Boundary (abbreviated as "Cai, Lu, Jie, Bian" in Chinese).

1. "Material": Selection Determines the Upper Limit from the Start

A common misunderstanding in the industry comes from the phrase: "All graphite sheets are the same—just buy a cheap one and test it." In reality, graphite sheets from different manufacturers vary greatly:

- In- thermal conductivity: From several hundred W/m·K to over 1,000 W/m·K or higher;

- Thickness: From 0.1–0.2 mm to just tens of micrometers;

- Flexibility, presence of an insulating layer, and self-adhesive backing also differ.

If a project has:

- High power,

- High heat flux density,

- Tight structural space,

but uses a graphite sheet with average thermal conductivity and excessive thickness, its cooling effect will inevitably be limited.

Conversely, if during scheme evaluation, you select a graphite sheet with higher in- thermal conductivity, thinner thickness, and better fit based on power and space constraints, the same "single sheet" can deliver drastically different results.

First self-check:What is the thermal conductivity and thickness of the graphite sheet I’m using? Does it match my project’s power and space requirements?

2. "Path": The Heat Path Must Connect "Hotspots" to "Cooling Surfaces"

A second common issue is an unbroken heat path. A typical scenario:Engineers attach graphite sheets directly above chips or cover a small area of the board, but the sheets do not extend to contact the metal housing/heat sink/cold plate.

This usage merely adds a "sandwich layer" over the hotspot—heat remains trapped locally and cannot escape the small area, resulting in almost no visible temperature drop.

In contrast, effective designs usually:

Extend graphite sheets from the hotspot to a cooler, larger-area metal component;

Ensure a continuous coverage path without "breaks";

Avoid attaching only to "convenient but non-cooling" areas.

Second self-check:Does my graphite sheet both cover the hotspot and truly "connect to" a cooling surface? Or is it only attached where it’s easy to apply?

3. "Contact": Bond Quality Determines Success or Failure

Heat transfer hates "gaps." Even if a graphite sheet has excellent thermal conductivity:

If the surfaces of components, boards, or housings are uneven;

If the graphite sheet is suspended, bulging, or warped at the edges;

If the compression force is insufficient or assembly tolerances are poorly controlled,

the interface thermal resistance will be extremely high, and the graphite sheet’s advantages will be largely negated.

A common "failure case":

Hand-pressed samples perform well during prototyping;

Once in mass production, deviations in bonding methods, pressure, or positioning lead to drastically different temperature test results compared to prototypes.

Third self-check:Is the graphite sheet truly "tight" between the component and housing, or just "stuck on and seemingly attached"?

4. "Boundary": Who Ultimately Takes Over the Heat from the Graphite Sheet?

The final link is boundary conditions. Graphite sheets spread heat from small areas, but the heat must eventually be dissipated by:

Large-area metal housings, metal frames, heat sinks, cold plates, etc.;

Areas with good forced air cooling or natural convection.

If the heat is ultimately transferred to:

A poorly conductive structural part that itself generates heat;

A small plastic component;

An internal area with almost no air flow,

the result will be: "Heat spreads a bit, but the overall environment is too hot—there’s almost no noticeable temperature drop."

Fourth self-check:Does the end of the graphite sheet connect to a "reliable cooling surface"?

III. A Self-Check List for Engineers

If you have a project where "graphite sheets are applied but show no effect," go through these four steps:

Material grade

Does the thermal conductivity and thickness of the graphite sheet match the project’s power and space constraints?

Heat path design

Does the graphite sheet connect the hot spot to the metal housing/heat sink without "breaks"?

Bond quality

Are the surface flatness of components/housings and compression structure properly designed? Is there any suspension, warping, or positional deviation after bonding?

Boundary conditions

Do the air flow and housing temperature inside the device allow the area to truly "cool down"? Is the final connection to a metal cooling surface or a "overburdened" part?

In most cases, graphite sheets aren’t "useless"—one or two of these four steps are usually not properly executed.

IV. Why Involve Suppliers "From the Very Beginning" for Some Projects?

The above covers general principles. For practical implementation, many companies now choose to involve material + solution suppliers early in projects rather than testing materials in isolation.

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

It offers three key capabilities:

Material range covering different grades of thermal conductive graphite sheets.

For consumer electronics, power supplies, new energy, and other scenarios, it provides graphite sheets with various thermal conductivity, thickness, and flexibility grades. For projects with different power, space, and cost sensitivities, it balances "sufficiency" and "high performance" instead of a one-size-fits-all approach.

Solution support to jointly optimize "heat paths"Many engineers report that communicating with such suppliers involves more than just quoting dimensions—they collaborate to discuss:

Heat source location and approximate power;

Accessible metal components/housings;

Suitable and unsuitable areas for graphite sheet application;

Need for adhesive/insulating layers and optimal lamination structures.

This addresses the four key factors ("Material, Path, Contact, Boundary") mentioned earlier, with a team experienced in graphite sheets and thermal management helping to identify potential issues in advance.

Mass production capacity from small to large batches

According to public information, DSN’s monthly production capacity for artificial graphite alone reaches approximately 700,000 square meters, with multiple quality and environmental management system certifications. This means:

It can meet both small-batch verification and large-scale mass production needs as projects scale;

It has mature experience in dimensional accuracy, tolerances, yield rates, and lead times.

V. Making Graphite Sheets "Truly Useful"

Returning to the initial question: Why does applying graphite sheets cool some projects by over 10°C while others show almost no change?

The answer can be summarized in one sentence:

Choose the right material, ensure an unobstructed heat path, achieve tight contact, and connect to a reliable cooling surface.

If these four steps are properly executed, thermal conductive graphite sheets can effectively reduce temperatures in high-power, space-constrained products—resolving issues like "failed high-temperature aging tests" and "excessively high peak temperatures."

If you currently have a project involving:

Boards, power supplies, on-board electronics, or energy storage BMS;

Moderate to high power with hot spots consistently ranging from 80–100°C;

Limited space, with no immediate plans to modify molds or restructure;

Consider: First, compile details such as power specifications, structural diagrams, and allowable thickness ranges.

Then consult a supplier like Jiangxi Dasen that offers both thermal conductive graphite sheets and thermal management technical support. 

A more optimized graphite sheet solution may open up an additional "heat path" for your project.