High Thermal Conductivity, Pitch-Based Carbon Fiber/Copper Composites

In our modern world everything is empowered by electronics. There are increasing requirements for high-power-density, miniaturization and high integration of electronic systems. Thermal management has become the key packaging bottleneck to achieve those goals. Kuprion Inc. developed a break-through solution in very large thermal vias for printed circuit boards (PCBs) and CTE-matched heat spreaders and heat sinks by combining commercial coal-derived pitchbased carbon fibers with its unique ActiveCopper material to form a metal composite that can exceed the thermal conductivity of copper. In addition, it allows to tune its thermal expansion over a wide range (3-17 ppm) to match that of PCBs and semiconductor materials. Coal-Pitchbased carbon fibers possess very high thermal conductivities of up to 1100 W/m*K, low CTE (1.6 – 2.1 ppm/K longitudinal), low electric resistivity (1.5 – 25 x 10-6 Om), and low density (1.8 – 2.2 g/cc). These unique properties are combined with Kuprion’s ActiveCopper enabling the design of composites that exceed the thermal conductivity of copper. The new composite is characterized by high electrical conductivity, low processing temperature (180 – 240 C), and high operating temperature (>350 C). With up to 43% v/v carbon fibers, the material incorporates a large volume of coal-derived materials and converts it into valuable products for today’s electronics such as thermal vias, heat spreaders, thermal ground planes, heat sink, etc. Large thermal vias exceeding 3-4 mm solve today’s electronics thermal management problems by enabling direct die bonding and conducting the heat through the board to the other side for increased heat dissipation. Initial modeling showed the ability to achieve a heat transfer coefficient exceeding 3000 W/cm2*K. Thanks to the ease of processing, such a composite can be used in a wide range of applications for efficient heat dissipation. The market size is expected to be in the tens of thousands of tons annually once fully utilized. In Phase I, Kuprion Inc. will (1) investigate different compositions of carbon-copper composites incorporating up to 43% v/v of pitch-based carbon fibers to exceed the thermal conductivity of copper, (2) demonstrate easy fabrication of heat spreader and thermal coin samples using injection molding, (3) measure thermal performance, and (4) demonstrate easy fabrication of 3-4 mm large thermal vias. The studies will incorporate transition metal additives to promote bonding between the carbon fibers and the copper matrix to push thermal performance beyond that of copper.