Beyond Copper: How High Thermal Conductivity Diamond Enables Faster And More Reliable Semiconductor Cooling

Pure copper has been used as a semiconductor heat dissipation substrate for several decades, with a thermal conductivity of approximately 400 W/m·K. In the current era where AI GPUs exceed 1000W and SiC/GaN power modules have a heat flux density of over 1000 W/cm², the physical limit of copper has been reached: hotspots cannot be quickly spread out, the chip junction temperature rises, triggering frequency reduction, and a 10°C increase in temperature leads to a 50% decrease in reliability. The package also warps and detaches due to the mismatch in CTE (16.7 ppm/℃) with silicon (2.6)/SiC.
High thermal conductivity synthetic diamond (polycrystalline CVD 1500–2000 W/m·K, single crystal IIa 2200–2400 W/m·K) is 5–5.5 times that of copper, with a CTE of only 1–2 ppm/℃, achieving nearly zero thermal mismatch with the chip; it is also an electrical insulator, allowing for direct attachment of bare dies, and can withstand 1200°C and a density of 3.5 g/cm³ (copper 9). The CVD diamond heat sink reduces the GPU junction temperature by 15–25°C, releasing 10–22% of the computing power; the diamond-copper composite (Diamond/Cu, 40–60% volume fraction) achieves 600–1000 W/m·K, balancing cost and manufacturability, and has become the main production force for AI servers and automotive-grade SiC inverters.

Procurement decision: It's not about "whether to replace or not", but "how to configure".
Flagship HPC/RF GaN: Single crystal/multi-crystal CVD diamond heat sink + Ti/Pt/Au metallization, near-junction heat dissipation;
Mainstream AI servers/automotive-grade power: Diamond/Cu composite substrate, CTE adjusted to match SiC;
Vacuum chambers and carriers: Tungsten copper, molybdenum copper for electronic packaging, titanium alloy for wafer holders and vacuum furnace components.
The pitfalls of decentralized procurement are quite evident: A power semiconductor factory separately purchased CVD diamond, tungsten copper substrate, and TC4 carrier. The delivery schedules of the three were 2 weeks apart. The metalization on the diamond surface did not meet the standards, resulting in voids in AuSn soldering, and the entire batch was scrapped. Another factory bought pure copper IHS and outsourced diamond composite. The interface thermal resistance exceeded the standard, and the chips still experienced frequency reduction.