Interfacial characterization and thermal conductivity of diamond/Cu composites prepared by two HPHT techniques

With the aim of obtaining materials with high-thermal conductivities (TCs) for heat sink applications, diamond/Cu composites were produced via two different high-pressure-high-temperature (HPHT) techniques: powder metallurgy method (HPHT–PM) and infiltration method (HPHT–IM). The interfacial characteristics of composite materials are compared with respect to the sintering process and their effect on thermal properties is addressed. The HPHT–IM process is clearly more favorable than that of HPHT–PM and the obtained composites exhibited TCs as high as 717 W/mK for the former, but also as low as 200 W/mK for the latter. The advanced thermal property of HPHT–IM composites is attributed to a well-bonded interface layer with gradual and continuous element transition probably due to amorphous carbon detected by Raman spectra. EDS analysis indicate selective interfacial bonding between diamond {100} faces and Cu. Diamond skeleton with connected particles have been observed in this case, also resulting in enhanced interfacial bonding and thermal properties. The HPHT–PM composites with isolated diamond particles feature visible macro interfacial debonding, leading to rather low TC less than that of pure Cu.