An innovative process to fabricate copper/diamond composite films for thermal management applications

Diamond dispersed copper matrix (Cu/D) composite films with strong interfacial bonding were produced by tape casting and hot pressing without carbide forming additives. The tape casting process offers an original solution to obtain laminated materials with accurate thickness control, smooth surface finish, material net-shaping, scalability, and low cost. This study presents an innovative process of copper submicronic particles deposition onto diamond reinforcements prior to densification by hot pressing. Copper particles act as chemical bonding agents between the copper matrix and the diamond reinforcements during hot pressing, thus offering an alternative solution to traditionnal carbide-forming materials in order to get efficient interfacial bonding and heat-transfer in Cu/D composites. It allows high thermal performances with low content of diamond, thus enhancing the cost-effectiveness of the materials. Microstructural study of composites by scanning electron microscopy (SEM) was correlated with thermal conductivity and thermal expansion coefficient measurements. The as-fabricated films exhibit a thermal conductivity of 455 W m ^-1 K ^-1 associated to a coefficient of thermal expansion of 12 × 10 ^-6 °C ^-1 and a density of 6.6 g cm ^-3 with a diamond volume fraction of 40%, which represents a strong enhancement relative to pure copper properties (λ _Cu = 400 W m ^-1 K ^-1, α _Cu = 17 × 10 ^-6 °C ^-1, ρ _Cu = 8.95 g cm ^-3). The as-fabricated composite films might be useful as heat-spreading layers for thermal management of power electronic modules.