High thermally conductive and high reliability under-fill

The miniaturization of flip-chip package is examined in many manufacturers. A thermal conductivity of underfill material has been regarded as important. Silica is contained in conventional under-fill as filler. Thermal conductivity of under-fill which contains silica filler is around 0.4W/mK. More than 1 W/mK of thermal conductivity is required for high thermally conductive under-fill. However, it is difficult to confirm if thermal conductivities are more than 1W/mK when silica is chosen as filler, since thermal conductivity of silica is about 1.3 W/mK. The various kinds of aluminum nitride were examined. High thermally conductive under-fill has been developed. It is filled with fine particle size aluminum nitride which will provide high thermal conductivity and good fluidity. And this under-fill realized over 2W/mK of thermal conductivity by control of loading level of the aluminum nitride filler. Also, this product satisfies the basic requirements for the under-fill, such as the JEDEC level 3 preconditioning test and temperature cycle test