Most semiconductor devices are now packaged in an epoxy polymer composite, which includes silica powder filler for reducing the thermal expansion coefficient. However, increased heat output from near-future semiconductors will require higher thermal conductivity fillers such as aluminum nitride (AlN) powder, instead of silica. Dispersant chemistry is applied, in order to achieve a high volume percentage of AlN powder in epoxy without causing excessive viscosity before the epoxy monomer is crosslinked, thereby increasing the thermal conductivity of the composite. In the preliminary experiment, high solids loading, up to 57 vol%, was achieved with a wide particle size distribution, and the viscosity of that dispersion was 60 000 to 90 000 cps, resulting in easy flow by gravity alone at room temperature. The highest thermal conductivity of the composites measured by the hot-disk method was 3.39 W/mK, which is approximately 15 times higher than pure epoxy. The Agari and Uno model was a good fit to the experimental data. Electronic I-V curves obtained after encapsulation of testing devices indicated that the highly AlN-filled epoxy slip appeared to be feasible for use in the encapsulation of integrated circuit chips.