Spherical aluminum nitride fillers for heat-conducting plastic packages

It is necessary for encapsulants to have not only a suitable coefficient of thermal expansion (CTE) compatible to IC devices and a low dielectric constant to reduce the device propagation delay, but also a high thermal conductivity to dissipate large amounts of heat from power-hungry, high-speed IC and high-density packages. Fillers such as silica have been mixed with polymers to improve their properties. Aluminum nitride (AIN) is considered as an alternative one, because it has a higher theoretical thermal conductivity of similar to 320 W/mK(1), a compatible CTE with silicon chips and a low dielectric constant. Commercial AIN fillers are angular in shape, because they are prepared via grinding coarse AIN powders synthesized by direct nitridation of aluminum metal and classification. The angular AIN are not expected to have high fluidity when mixed with polymers and hence low packing density. Recently, we successfully obtained single-crystalline spherical AIN fillers. Furthermore, polymer composites filled with the spherical AIN showed excellent thermal conductivity (> 8 W/mK) as encapsulants; for dissipating the heat generated in electronic devices.