Study on the structure and thermal properties of graphite/copper laminated composites assembled by Ti-containing active filler metals

The development of high-power and small-sized electronic components requires the emergence of heat management materials with high heat flux. Hence, Ti-containing filler was used to braze graphite film/Cu high heat flux composites. The microstructure and forming mechanism of joints were studied, the influence of temperature on joint formation was analyzed, and the influence of graphite volume fraction on the thermal properties of the composites were discussed. The results show that the main microstructure of graphite/copper joints are Cu(s,s), Ti6Sn5 and CuTi2. As the brazing temperature increases, the carbide layer (TiC) that affects the connection gradually thickens, from <0.5 mu m at 800 degrees C to 3 mu m at 850 degrees C, which deeply improve heat transfer of composite materials. The tensile properties of composites also increase with increasing temperature, maximum tensile strength 31.94 MPa can be obtained at 850 degrees C. Furthermore, the composites are proved to possess high heat flux during process of heat transfer, and the transfer rate was 1.77 times that of Cu, 3.72 times of Al. The temperature rise test carry out in hot bench intuitively demonstrating that the composites have faster heating rate. Al used 197 s to raise from 25 degrees C to 50.5 degrees C, Cu used 140 s, while 76.92 % graphite-contained composites only took 75 s in the same volume and experimental condition.