With the continued development of microelectronics and 5G communication technologies, electronic components are moving toward miniaturization and higher integration densities. Traditional electronic packaging materials-suffering from low thermal conductivity, poor heat dissipation efficiency, and relatively high coefficients of thermal expansion-may cause overheating in high-speed electronic devices, leading to damage or even failure, and thus cannot meet the demands of high-performance integrated circuits.
Diamond possesses excellent thermodynamic, structural, and electronic properties, with a thermal conductivity exceeding 2000 W/(m·K), making it an ideal heat-dissipation material. Copper, on the other hand, offers outstanding workability and thermal conductivity. The combination of the two yields diamond/copper composites with low density, high thermal conductivity, and tunable thermal expansion coefficients, making them one of the most attractive thermal management materials.
Currently, there are many methods for preparing diamond/copper composites, such as powder metallurgy, infiltration, and additive manufacturing. Among these, powder metallurgy has become one of the most commonly used approaches due to its simple processing route and the excellent properties of the resulting composites. In this method, copper powder and diamond particles are mixed uniformly by ball milling or other means, and then consolidated by sintering to produce composites with a homogeneous microstructure.
Commonly used sintering techniques include vacuum hot-pressing sintering, rapid hot-pressing sintering, and spark plasma sintering.
Vacuum hot-pressing sintering:
Metalized diamond particles are mixed with copper powder and then sintered in vacuum under applied pressure and temperature (solid-state or liquid-phase sintering).
Advantages: mature technology, widely available equipment.
Disadvantages: high sintering temperature (900–1000 °C), risk of diamond graphitization.
Rapid hot-pressing sintering:
An external heat source rapidly heats the die and powder while uniaxial pressure is applied, enabling rapid densification.
Advantages: (1) short sintering time, significantly reducing diamond exposure at high temperatures and effectively suppressing graphitization; (2) high relative density, reaching above 95 % and approaching theoretical density; (3) low cost and simple equipment structure; (4) flexible adjustment of sintering temperature, pressure, and holding time, suitable for process optimization.
Disadvantages: (1) external heating causes a temperature gradient at the die edges; (2) sample size is limited by the die dimensions.
Spark plasma sintering:
A pulsed electric current generates spark plasma between powder particles, enabling rapid heating and sintering.
Advantages: fast heating rate, short sintering time, reducing excessive interfacial reactions.
Disadvantages: expensive equipment, limited sample size.
The practical implementation of these sintering processes relies on the support of high-temperature sintering equipment.