Sintering Behavior and Thermal Properties of Cu-Graphite Materials by a Spark Plasma Sintering Method

Abstract

The use of heat dissipation materials in various field such as power semiconductor device, LED and microelectronic system. Therefore, there is a need for heat dissipation materials using copper (Cu) and graphite (Gr). These materials have high thermal conductivity. In particular, graphite has high thermal stability with a low coefficient of thermal expansion. This study was conducted to enhance the thermal properties of Cu for use in heat dissipation materials, using a spark plasma sintering method. Cu-Gr powders were mixed by a shaking mixer and fabricated with volume fractions of 7:3, 6:4, 5:5, 4:6 and 3:7. The spark plasma sintering method is a uniaxial pressurization process, which can control the direction of Gr. The Cu-Gr powders were sintered at a temperature of 850 oC at a heating rate of 30 oC/min and a sintering pressure of 40MPa. Consequently, as the Gr contents were increased, the relative densities of the Cu-Gr composites decreased from 99.25 to 94.85%. Gr has high resistance to high-temperature deformation, which contributed to a decrease in shrinkage and relative density. The highest thermal conductivity was measured at 539.7 W/ m·K for a Cu-Gr volume ratio of 5:5. The thermal conductivity of the directionally controlled Gr was measured to be about 20-30 W/m·K higher than the uncontrolled sample. Furthermore, the TDP (Thermal distortion parameter), for which a lower value indicates better thermal stability, was systematically investigated.