Microstructure and thermal conductivity of diamond/copper composite prepared by spark plasma sintering

Diamond/copper composites (DCCs) are widely used in heat dissipation of electronic integrated devices on account of their combination of high thermal conductivity (TC) and low coefficient of thermal expansion (CTE). In this study, DCCs were fabricated by spark plasma sintering (SPS) technology. The effects of sintering parameters on the TC of the DCCs were explored. It was found that the TC of the DCCs first increased and then decreased with increasing sintering temperature. As the sintering pressure increased, the TC exhibited a trend of first increasing and then decreasing. With the extension of holding time, the TC exhibited a trend of first increasing and then decreasing. In addition, the effects of the process parameters on the forming process of the DCCs were analyzed from a microscopic perspective, and it was found that the main interface defect of DCCs is the interface gap between copper and diamond. Finally, the main mechanism by which SPS enhances the TC of DCCs was investigated, and it was found that pulsed current can purify and activate diamond and copper particles; in addition, under the action of electric field, copper particles can actively coat the surface of diamond particles. Under the conditions of a sintering temperature of 900 °C, a sintering pressure of 50 MPa and a holding time of 10 min, the TC of the composite reached 552 W/(m·K), and its CTE was 9.02 × 10−6/°C, which meets the usage requirements of highly integrated electronic devices.