Modification of epoxy systems for electronic packaging materials, specially flip chip bonding materials, by introducing diallyl phthalate (DAP) and core-shell rubber (CSR) particles into epoxy systems have been investigated to improve the mechanical and water absorption properties. The cure behavior of CSR/DAP/epoxy/anhydride system was monitored by differential scanning calorimetry (DSC). Dynamic mechanical analyzer (DMA) was used to measure the glass transition temperature (Tg) of epoxy systems. CSR particles with the diameter of 150-200nm played an important role in improving the peel strengths of non-conductive pastes (NCPs) while maintaining the thermodynamic properties such as the glass transition temperature of epoxy systems. Furthermore, introducing DAP into epoxy networks have improved both the water absorption properties and peel strengths of epoxy systems, in which the loading percent of DAP was limited to about 10% to obtain the lowered water absorption properties in this study.