Not Just a Heat Spreader: Diamond Enables 100x Better Cooling with 55x Less Water Flow for AI Data Centers
It turns out that substrating AI chips with single-crystal diamond not only solves hotspots.
It also fundamentally changes how AI data centers can be cooled.
Diamond, and only diamond, redistributes the thermal resistance stack through the total system yielding a cooling surface sufficiently hot enough to be able to trigger phase change at near-atmospheric pressure.
Just a few years ago there was discussion about air vs liquid cooling for AI data centers. In a few years, the idea of pumping massive volumes of water through GPU racks and buildings to only then cool that loop with evaporation may look equally quaint.
It is well known how diamond as a chip substrate conducts heat 15x better than silicon and thus solves hotspots plaguing today’s high-power AI chips. What is less well known is how this is unlocking a far more powerful way to cool high-power AI chips.
- Coldplates are today's state-of-the-art — but physically limited to roughly 1 kW per chip and requiring large, heavy water infrastructure throughout the rack.
- Microchannels are promising but plagued by flow instability, clogging, and water quality requirements that have prevented commercial adoption.
- Evaporative cooling is commonplace for buildings and facilities because it is so powerful.
The reason evaporative cooling has not worked with chips directly is simple: their backside surface is not hot enough.
Diamond – and only diamond – redistributes the thermal resistance through the chip to the extent that it yields a cooling surface hot enough for phase change at near-atmospheric pressure.
Spray boiling and other thin-film water evaporation techniques at 500–2,000 W/cm² versus flowing water at 10–100 W/cm² means 10–100× higher cooling performance. Water flow at 13 mL/min for evaporative versus 7100 mL/min coldplate for the same 1kW chip means dramatically, up to 55x less water.
Diamond + two-phase water cooling allows much higher power than either coldplates or microchannels and a simpler fluid loop with less water.
Read more in DF Tech Note 2604-01.