Pure copper has a thermal conductivity of approximately 400 W/m·K, while the copper/diamond composite material showcased at the Taiwan Semiconductor Show reaches approximately 800 W/m·K, which helps to dissipate heat more quickly and reduce localized hot spots. They also reduce warpage: silicon has a thermal expansion coefficient of approximately 3 ppm/K, copper approximately 17 ppm/K, while copper/diamond can be tuned to closer to 6–10 ppm/K.
Currently, only ElementSix (a De Beers subsidiary) publicly offers copper/diamond composite materials with a conductivity in the 800 W/m·K range. ElementSix, launching in January 2025, focuses on AI/HPC and 2.5/3D advanced packaging. A key challenge with this material lies in the copper/diamond interface. Copper and diamond naturally do not bond well, so titanium, chromium, molybdenum, or tungsten are often added to form a carbide bonding layer. However, too much carbide can impair thermal conductivity, making interface thickness control crucial. Compared to simple copper alloying, the industry is using physical vapor deposition or chemical vapor deposition to pre-coat diamond particles for more precise control.
