Choosing the thermal material for an accelerator is not about picking the highest conductivity number. It is about matching the stack to the power level, the bond line and the mechanical load. This guide covers the mainstream accelerators of 2026 and the three architectures that cover almost every design.
Accelerator power reference (2026)
| Accelerator | TDP (W) | Package | Typical cooling stack |
|---|---|---|---|
| NVIDIA H100 | 700 | SXM5 | Cold plate + 180 W/m·K pad |
| NVIDIA H200 | 700 | SXM5 | Cold plate + 180 W/m·K pad |
| NVIDIA B200 | 1000 | SXM6 | Cold plate + 180 W/m·K pad + 1200 W/m·K plate |
| AMD MI300X | 750 | OAM | Cold plate + 180 W/m·K pad |
| Ascend 910B | 400 | HCCS | Cold plate + 100 W/m·K pad or better |
| Cambricon MLU590 | 350 | Custom | Cold plate + 100 W/m·K pad or better |
Numbers indicate the package class rather than a vendor specification. Use them to bracket the design, then confirm against the current datasheet.
Three cooling architectures
A. Direct die-to-cold-plate (below ~500 W)
Where package flatness and clamping are well controlled, a thin high-conductivity pad or a bonded interface is enough. Keep the bond line under 0.5 mm and validate the mounting pressure.
B. Pad plus cold plate (500-800 W)
A 0.3-0.7 mm, 180 W/m·K pad absorbs stack-up variation while keeping bulk resistance low. This is the workhorse configuration for 700 W-class accelerators, and it is stable over thermal cycling because the interface is solid.
C. Pad plus spreader sandwich (above ~800 W)
Above roughly 800 W the die-level hot spot starts to matter more than the average. A 1200 W/m·K graphene plate between the pad and the cold plate carries heat through to the cold plate, so the coolant does not have to absorb a local peak.
Why the interface temperature gap matters
Accelerator clocks are thermally throttled by the hottest point on the die, not by the average. Reducing the interface gap by a few degrees can be the difference between sustained boost and periodic throttling. In practice the largest wins come from three things: closing the bond line, eliminating pump-out, and spreading the hot spot before it reaches the cold plate.
Qualification checklist
- Thermal resistance measured at the real mounting pressure, not at a laboratory optimum.
- Aged resistance after thermal cycling and high-temperature soak.
- Compression and rebound data for the gap range in the actual stack.
- Outgassing and electrical properties if the material sits near optics or high-voltage traces.
- A sample tested in your own fixture, with your own cold plate.