With the rapid advancement of technology, diamond has been hailed as a ‘supermaterial’ due to its exceptional acoustic, optical, electrical and thermal properties, demonstrating vast application potential across numerous fields. As the hardest
substance in nature, diamond not only possesses a wide bandgap and a broad range of optical transparency, but also exhibits chemical inertness towards most substances, enabling it to operate stably under extreme conditions such as high temperatures, high pressures and high frequencies.
In terms of thermal properties, diamond is truly in a class of its own, boasting the highest thermal conductivity found in nature. At room temperature, the thermal conductivity of diamond reaches as high as 2,000–2,200 W/mK, which is 4
times that of silicon carbide (SiC), 13 times that of silicon (Si), 43 times that of gallium arsenide (GaAs), and 4–5 times that of copper and silver. In modern high-power electronic and optoelectronic devices (such as 5G applications, high-speed computing or high-power semiconductor chips), the
substantial amount of heat generated within an extremely small area poses a severe challenge to heat dissipation. To rapidly resolve cooling issues, heat sinks or thermal coatings made from highly thermally conductive materials need to be deployed at the heat-generating end (such as radiators, fans,
and heat sinks). Thanks to its extremely high thermal conductivity, extremely low coefficient of thermal expansion and insulating properties at room temperature, diamond has become an ideal choice in the field of thermal management.
Diamond is used in thermal management applications primarily in two forms: firstly, as diamond films; and secondly, as a thermally conductive filler. At present, thermally conductive diamond fillers are mainly used in two areas: metal-based diamond composites and thermally conductive interface materials.
Metal-based diamond composites
With diamond acting as the reinforcing phase, its extremely high thermal conductivity (ranging from 600 to 2,200 W/m·K at room temperature) enables metal-based diamond composites to exhibit outstanding thermal conductivity. For example, when the volume fraction of diamond in a diamond/copper composite is 35 per cent, its thermal conductivity can reach as high as 602 W/m·K. This high thermal conductivity makes the material particularly well-suited for applications requiring efficient heat dissipation, such as electronic packaging and high-power electronic devices. Furthermore, when combined with a metallic matrix (such as copper or aluminium), diamond’s low coefficient of thermal expansion (approximately 2.3 × 10⁻⁶ K⁻¹) effectively reduces the composite’s coefficient of thermal expansion, minimising dimensional changes in the material during temperature fluctuations and thereby enhancing the stability and reliability of the equipment.
Diamond Thermal Conductive Gel
As with other thermal conductive gels, the performance of diamond thermal conductive gel depends to a large extent on the maturity and precision of the preparation process. Factors such as the particle size of the filler, the volume fraction of the filler, and the modification process all have a significant impact on the gel’s overall thermal conductivity.
Particle size control: The particle size of diamond particles must not be too small (less than 10 micrometres), otherwise it will be difficult to form effective thermal conduction chains.
Filling volume fraction: The filling volume fraction must be moderate; if too low, the contact area will be insufficient, making it difficult to form effective thermal conduction chains; if too high, the gel will be unable to fully wet the surface of the diamond particles, resulting in voids that impair thermal conductivity.
Modification treatment: Modification is an essential step for diamond thermal conductive gel fillers; otherwise, particles with high surface activity are prone to agglomeration and cannot be uniformly dispersed in the organic polymer resin, leading to a decline in gel performance
