As electronic devices become smaller and more powerful, heat generation rises sharply. Reliable heat dissipation is now essential not only for stable operation, but also for long service life. That is why high-performance thermal-management and packaging materials remain a major focus in both research and manufacturing.
Diamond offers exceptional thermal conductivity, while copper delivers excellent thermal and electrical transport together with relatively mature processing routes. When the two are combined in a diamond/copper composite, the result is a strong candidate for next-generation heat spreaders and electronic packaging materials.
The interface is the critical challenge. Diamond and copper do not wet each other easily and show little direct chemical interaction, so untreated bonding is weak. At the same time, their thermal expansion coefficients differ dramatically: diamond is about 2.3 x 10-6/K, while copper is about 16.5 x 10-6/K. That mismatch introduces thermal stress during cooling and can lead to interfacial debonding if the interface is not engineered carefully.
For that reason, interface design is essential. A common strategy is to introduce carbide-forming elements such as Cr, Mo, W, Si, B, Ti, or Zr as a buffer layer. Other practical routes include matrix alloying, metallization of the diamond surface, and process optimization aimed at reducing interfacial defects.
Main preparation routes
1. High-temperature high-pressure sintering (HTHP): delivers excellent density and strong performance, but equipment cost and energy consumption are high.
2. Vacuum hot-press sintering (VHPS): lowers side reactions and uses lower temperatures, but bonding pressure and throughput are more limited.
3. Spark plasma sintering (SPS): offers fast heating and good efficiency, though component size and ultimate conductivity still depend heavily on composition and interface quality.
4. Melt infiltration: fills a diamond preform with molten metal by capillary action or applied pressure and is well suited to dense structures.
For diamond/copper systems, copper powder quality matters just as much as process selection. The powder should provide high purity, strong dispersion, good activity, and high intrinsic thermal conductivity so the final composite can reach the required density, strength, and heat-transfer performance.
Typical copper-powder requirements
Cu content: above 99.9%
Oxygen content: below 0.5%
Carbon content: below 0.3%
Tap density: above 2.5 g/cm3
Specific surface area: below 2 m2/g
Average particle size by SEM: 0.8-1.3 um
