Physics / mechanism
Synthetic diamond has the highest thermal conductivity of any bulk material at room temperature: 1,000–2,200 W/m·K depending on isotopic purity and crystal quality, versus 400 W/m·K for copper. Heat spreaders exploit this by sitting between a high-flux source (laser diode bar, GaN-on-SiC MMIC, power module) and a conventional heat sink, flattening hotspots before they degrade junction temperature. Key parameters: thermal boundary resistance (Kapitza resistance at diamond/device interface, typically 5–30 m²K/GW), grain size in CVD polycrystalline material (larger = higher conductivity), and wafer diameter (100 mm now commercial). Element Six, II-VI/Coherent, and Applied Diamond are the main CVD suppliers. Single-crystal plates hit the top of the conductivity range; polycrystalline is cheaper but caps around 1,500 W/m·K.
Competitive landscape
The primary competitor is CVD diamond’s cost: $50–500/cm² depending on grade, versus copper-molybdenum composites ($5/cm²), aluminium nitride ceramics ($10/cm²), or pyrolytic graphite sheets (~$2/cm²). For photonics and RF, the real comparison is GaN-on-diamond substrates (diamond as growth substrate, not just spreader) versus GaN-on-SiC. Emerging competition comes from high-purity SiC heat spreaders and boron arsenide (BAs, ~1,300 W/m·K, still lab-scale). Diamond wins on peak flux density tolerance but loses on cost, machinability, and supply chain maturity.
| Material | Thermal conductivity (W/m·K) | Cost (relative) |
|---|---|---|
| CVD diamond | 1,000–2,200 | Very high |
| AlN ceramic | 170–220 | Low |
| Cu-Mo composite | 160–200 | Low–medium |
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.