GPCP250SL Carbon Fibre Thermal Pad

FEHONDA  |  Product Datasheet Guide

GPCP250SL Carbon Fibre Thermal Pad

25.0 W/(m·K) through-plane in a flexible 0.5–5.0 mm pad, oriented carbon fibre, V-0, -50 to 150 °C

Specification

Key advantages

• 25.0 W/(m·K) through-plane, with the full 22.5 band published. The direction that actually moves heat across a joint, achieved by an oriented sheeting process rather than by filler loading alone.
• Flexible and compressible. Conforms to uneven surfaces, absorbs assembly tolerance, and damps vibration — which is exactly what a brittle graphite film cannot do.
• V-0 across the entire 0.5 to 5.0 mm range, not just at one tested thickness. That removes a compliance question for designs using more than one thickness.
• Compact thickness window, 0.5 to 5.0 mm. Matched to tight-clearance assemblies such as handheld devices, HUD modules and medical instruments.
• Two hardness grades, Shore 00 55 and 65. Enough choice to suit the assembly pressure without a custom formulation.
• One layer instead of two. Removing a graphite film and a gap pad removes an interface, and interfaces are where thermal resistance accumulates.
• RoHS and REACH compliant, with declarations available on request.
• Conductive filler brings shielding and grounding behaviour with it. Where a design needs both, that is a part count and assembly saving — but only if you actually need conductivity. See the cautions.

Recommended applications

A useful rule for all seven: this material earns its place where the interface is the bottleneck and you also need compliance. If the bottleneck is airflow or heat-sink area instead, a more expensive interface will not move the result much.

Why through-plane is the number that matters

The 25.0 W/(m·K) figure for GPCP250SL is measured through the thickness, which is the direction that matters for a part doing an interface job. Heat has to cross the joint from the component to the heat sink, not merely spread sideways within the pad.

This is worth stating plainly because the two directions are near-opposites, and because one of them is much harder to make. Calendering, the natural way to form a filled sheet, tends to lay fibres down flat — which gives a high in-plane figure and a poor through-plane one. Getting fibres to stand up across the bond line requires a deliberate alignment step: magnetic, electric, flow-field or shear-induced orientation. That is what the oriented sheeting process behind this product does, and it is why the through-plane figure, rather than a headline number in some other direction, is the one to design against.

If you are comparing suppliers, ask for the direction on the test report. A conductivity figure with no direction on it will be read as through-plane by most engineers, and discovering otherwise costs a redesign.

How 25.0 compares, and against what

This table reads every material in the same column, doing the same job.

Two things follow. First, 25.0 sits clearly above both a conventional pad and the weak axis of a graphite film, and even the lower bound of 22.5 is above both — which is the case for specifying it. Second, within the FEHONDA carbon-fibre family there is a higher figure available, so the honest positioning is this: GPCP250SL is the choice where the gap is moderate, the space is tight and the thermal budget is real but not extreme. Where the bond line has to be thick or the flux is at the top of the range, the 35.0 W/(m·K) model with its 0.3 to 12 mm range is the better fit.

Why thickness still decides the result

A high conductivity figure does not license a thick pad. The thermal resistance of the material layer itself is thickness divided by conductivity, so it rises with bond line no matter how good the material is. The table below is the idealised material resistance in °C·in²/W. Real measured values are higher, because they include contact resistance at both faces.

Read it in both directions, because both readings matter.

• Across a row: GPCP250SL is roughly eight times better than a 3.0 W/(m·K) pad at every thickness. That advantage is real and consistent.
• Down a column: going from 0.5 mm to 5.0 mm multiplies the resistance of the same material by about ten. A good material does not rescue a thick bond line.

The practical instruction is unchanged: measure the real stack under assembly pressure and choose the thinnest workable option. The 0.5 to 5.0 mm range suits compact assemblies — handheld devices, HUD modules, medical instruments — where the clearance is small and predictable. Where the gap is larger or uneven, the 0.3 to 12 mm range of the 35.0 W/(m·K) model is the more forgiving choice.

What it replaces

GPCP250SL sits in a specific gap in the market. Conventional filled pads are soft and conformable but typically stay below about 10 W/(m·K). Graphite films spread heat superbly across the plane but are brittle, effectively incompressible, and weak through their thickness. A metal spreader plate conducts well but adds weight and cannot absorb tolerance.

A carbon-fibre-filled silicone composite does all three jobs in one layer: high through-plane conductivity, real compressibility, and useful lateral spreading. That is the case for it.

Two cautions we would rather you heard from us

Both follow from the filler, and both are the kind of thing that surfaces late if nobody mentions them early.

Neither is a reason to avoid the material. Both are reasons to place it deliberately, and to tell your supplier what it will be touching.

Why FEHONDA

Large material suppliers are built for volume. That is fine if you want ten thousand of one part. It is a poor fit if you are developing, qualifying, or running a product where the thermal design is still moving. This is where a focused manufacturer is genuinely easier to work with.

• Fast sampling and short lead times. We turn prototype pieces around quickly, because we know a thermal decision usually sits on the critical path of a build.
• Small-batch orders accepted. You do not have to commit to production volume to get production-grade material. That matters for pilot runs, low-volume products and spare parts.
• High prototyping responsiveness. Send a revision, get a revised sample. Iterating thickness, hardness or shape during development is normal for us, not an exception we charge for.
• Sheet size custom within 100 x 100 mm. You order the size the assembly actually needs rather than trimming a standard sheet, which suits compact devices and keeps waste down.
• Custom manufacture to your drawing. Die-cut shapes from your CAD, thickness matched to your measured gap, hardness selected between Shore 00 55 and 65, and colour coding where a build needs several variants told apart on the line.
• A family to select within, and honest guidance across it. 25.0 W/(m·K) over 0.5 to 5.0 mm, or 35.0 W/(m·K) over 0.3 to 12 mm. We will tell you which one fits rather than steering you to the more expensive part.
• Engineering input before the quote. Tell us the gap range, the mounting pressure, the flatness and what the material will touch, and we will tell you whether this is the right part — including when it is not.
• RoHS and REACH declarations with supporting test reports, available on request rather than after a chase.

If you are a small or mid-sized team, the practical benefit is simple: you get to talk to the people making the material, and you can change your mind during development without renegotiating a minimum order.

Next step

Send us the drawing with the gap range, the mounting pressure, the flatness of the mating surfaces and what the material will be touching. We will come back with a recommendation on grade and thickness, samples and a lead time. If GPCP250SL is not the right part for your interface, we will say so and point you at the one that is.

Please submit your request via our custom service form to ensure a faster response.
 

Frequently asked questions

Is 25.0 W/(m·K) through the thickness or across the plane?

Through the thickness. That is the direction that matters for an interface part, because heat has to cross the joint to the heat sink rather than spread sideways within the pad. It is also the harder direction to achieve: calendering tends to lay fibres flat, so a high through-plane figure comes from a deliberate orientation step during manufacture. When comparing suppliers, always ask which direction a figure refers to — an unqualified number is usually read as through-plane, and that assumption sometimes fails.

What does the 22.5 to 27.5 range mean?

It is the performance band around the nominal 25.0 W/(m·K), reflecting lot-to-lot and thickness-to-thickness variation in a filled, oriented composite. It is a property range, not a manufacturing defect. If your thermal budget is tight, design to the lower bound of 22.5 and state that assumption in your calculation — and note that even the lower bound is above both a conventional filled pad and the weak axis of a graphite film.

Does the conductivity change with thickness?

Treat it as thickness-dependent. In an oriented composite the measured value depends on the thickness it was measured at, so ask for the figure at the thickness you intend to use rather than assuming the nominal carries across the whole 0.5 to 5.0 mm range. This is also why we ask for your gap range before quoting.

How does it differ from the 35.0 W/(m·K) model?

Conductivity and thickness range. GPCP250SL is 25.0 W/(m·K) over 0.5 to 5.0 mm; the other is 35.0 W/(m·K) over 0.3 to 12 mm. In practice GPCP250SL suits compact assemblies with moderate gaps and a predictable bond line, while the 35.0 model suits larger or uneven gaps and higher heat flux. If your measured gap is under 5 mm and the flux is moderate, GPCP250SL is usually the more economical choice.

Which hardness grade should I pick?

Shore 00 55 is the softer of the two and suits lower assembly pressure and uneven surfaces. Shore 00 65 is slightly firmer, holds its shape better under handling and resists extrusion under higher clamp load, but needs flatter mating surfaces. Both are on the Shore 00 scale, which is for soft materials. If the stack is flat and clamped firmly, 65 is a reasonable default; if the surfaces are imperfect or the pressure is low, choose 55.

What thickness should I order?

The one that matches your measured gap, as thin as the stack allows. Measure the real stack under assembly pressure and select from the 0.5 to 5.0 mm range against that. Bond line drives the result more than the conductivity figure does, and an over-thick pad adds thermal resistance no matter how good the material is.

Can I use it where I need electrical insulation?

No, not as supplied. Carbon-based fillers are conductive, and comparable carbon-filled silicone products are sold specifically for shielding and grounding. Where the interface is also a voltage barrier, use a composite TIM with a reinforced insulating layer, or add an insulating laminate. Tell us the voltage and clearance and we will recommend accordingly.

Does it replace a graphite film?

Sometimes. It replaces a graphite film where you also need to fill a gap, absorb tolerance, or avoid handling a brittle sheet that sheds conductive particles. It is not a straight replacement where your only problem is lateral spreading across a large flat area — graphite film has the much higher in-plane number there, in the order of 1,000 to 1,900 W/(m·K). The honest answer depends on which of those two problems you actually have.

Can I order a non-standard sheet size?

Yes. Sheet size is custom within 100 x 100 mm, which is one of the reasons small and mid-sized teams work with us. Send the drawing and we will quote the size, the shape and the quantity together.