Preparation of high thermal conductivity shaped diamond/copper composites by isostatic pressing

•Pressureless sintering with cold/hot isostatic pressing is employed.•Thermal conductivity reached 620 W/mK, which is 57 % higher than that of pure copper.•Hot isostatic pressing is employed to eliminate the closed holes and gaps between diamond and copper.•Open pores in copper skeleton closed post high-temperature pressureless sintering.