Recently, as 3-D stacking and high integration are required in semiconductor packaging technology, it is critical to develop higher performance packaging materials. Insulation ability and mechanical properties of passivation layer should be enhanced to prevent device from electrical short and malfunction. In this study, low dielectric, residual stress, and the coefficient of thermal expansion polyimide/surface modified silica nanoparticle composites for wafer level packaging are synthesized and investigated. Silica nanoparticles of which surface modified with amine functional group increased the distance between polymer chains to form a free space, thereby lowering the dielectric constant. Also, they acted as a cross-linker and showed the effect of improving the mechanical properties of polyimide. Consequently, synthesized composites are potential candidate for high performance packaging material.