US How conduction cooling works
Conduction cooling moves heat out of a computer through solid materials rather than through moving air. Thermal pads, heat spreaders and heat pipes carry heat from the processor, memory and storage into the metal chassis, which then passes it on to whatever the computer is bolted to, or to the surrounding air.
Heat always flows from hot to cold, and solids such as copper and aluminum conduct it far better than air does. A conduction-cooled design makes that path as short and as continuous as possible: from the silicon die, through a thin thermal interface material, into a spreader or heat pipe, and then into a thick chassis wall.
Ordinary fanless computers still rely on air flowing past their fins. A conduction-cooled design goes further, coupling the hot components directly to the chassis and the chassis to a cold plate, wall or frame. In cold environments it works especially well, because the large temperature difference pulls heat away efficiently.
The parts of a conduction path
Every joint in the path adds thermal resistance, so the design is about keeping each step short, flat and well clamped.
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Thermal interface material. Pads, putty or phase-change material fill the microscopic gaps between a chip and the metal above it, where trapped air would otherwise insulate.
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Heat spreader. A copper or aluminum block that takes heat from a small, hot die and spreads it over a larger area.
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Heat pipes. Sealed copper tubes that move heat quickly along their length, used where the hot component sits away from the chassis wall.
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Chassis. A thick, machined metal enclosure that acts as the heatsink, often with fins on the outside for the final transfer to air.
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Mounting interface. A flat, clean contact with a cold plate, bulkhead or vehicle frame, sometimes with a thermal pad, so the structure can take heat away.
Conduction cooling compared with other methods
| Method | How heat leaves | Sealing | Moving parts | Typical use |
|---|---|---|---|---|
| Forced air | Fans blow air over heatsinks and out of vents | Difficult | Fans | Office PCs, servers, high-power GPU systems |
| Passive convection | Fins on the case shed heat to still air | Easy | None | Fanless industrial and embedded PCs |
| Conduction cooled | Solid path into the chassis and mounting surface | Easy | None | Rugged, military, vehicle and cold-store systems |
| Liquid cold plate | Coolant carries heat from a plate to a remote radiator | Easy at the computer | Pump | High-power sealed electronics, some military platforms |
Most fanless computers use a mix of conduction and convection: conduction carries heat to the case, and convection removes it from the fins. A fully conduction-cooled system relies more on the surface it is mounted to, which is why the installation matters as much as the computer. Our guide to active vs passive cooling compares the options in more depth.
Why sealed systems use conduction cooling
Conduction cooling is chosen where air cannot be trusted to do the job, or where it would bring problems in with it.
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Sealed operation. No vents for dust, moisture or frost to enter.
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No fans to fail. Nothing to wear out or ice up.
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Uses the structure. Walls, frames and cold plates become the heatsink.
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Quiet and reliable. Silent, solid-state operation for long lifecycles.
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Vibration tolerance. With no fan bearings and with components clamped to metal, conduction-cooled designs suit vehicles and aircraft.
Conduction-cooled boards in military systems
In defense electronics, conduction cooling also applies to plug-in boards. Conduction-cooled boards in VPX and CompactPCI systems have a metal frame that carries heat to the board edges, where wedge locks clamp them to the cooled walls of the chassis. Standards such as IEEE 1101.2 and VITA 48.2 define the mechanics so that boards from different suppliers fit the same chassis.
The same thinking appears in sealed rugged mission computers, where the processor and storage are bonded to the enclosure and the enclosure is bolted to a cooled structure in the vehicle or airframe.
Designing for the mounting surface
Because a conduction-cooled computer sheds heat into what it is fixed to, the installation needs the same attention as the electronics. Mount it on a flat, bare metal surface where possible, keep paint and gaps out of the contact area, and allow for the temperature of that surface, not just the room. A hot bulkhead or a sun-heated panel reduces the margin, and the processor may throttle to stay within limits.
Heat pipes are often the link that makes this work in compact designs; our explainer on how heat pipes work covers them. In cold stores the opposite issue arises: a cold chassis can collect condensation when it is moved into warmer air, which our condensation guide explains how to avoid.
Quick answers on conduction cooling
Conduction cooling: common questions
What is the difference between conduction and convection cooling?
Solid path versus moving air. Conduction moves heat through solid materials, while convection carries it away in air or liquid. Most fanless computers use both.
Does a conduction-cooled computer need a fan?
No. Heat leaves through the chassis and mounting surface, so there are no fans or vents, and the enclosure can be sealed.
What is a cold plate?
A cooled metal plate the computer is bolted to. It may be cooled by the vehicle structure, by air on its far side or by liquid, and it draws heat out of the chassis.
What is a wedge lock?
A clamp that holds a board edge to a cooled wall. Wedge locks expand when tightened, pressing conduction-cooled boards against the chassis rails so heat can flow out.
Can conduction cooling handle high-power processors?
Up to a point. It suits low and mid-power processors well. High-power CPUs and GPUs usually need large finned enclosures, liquid cooling or fans.
The cold-chain case study runs a conduction-cooled Bedrock R8000 in a refrigerated warehouse. We integrate and validate every fanless and conduction-cooled system as standard, including checking the thermal design against the mounting and ambient conditions on site.