Tailored Dielectric Properties of High-k Polymer Composites via Nanoparticle Surface Modification for Embedded Passives Applications

Novel materials for embedded passive applications are in great and urgent demands, for which high dielectric constant (k), low dielectric loss and process compatibility with the printed circuit boards (PCBs) are the most important prerequisites. Dramatic increase of dielectric constant near the percolation threshold observed by our earlier work in the conductor-insulator percolative system arouses interest of developing these composites as dielectric materials. This material option represents advantageous characteristics over the conventional polymer-ceramic composite. Specifically, the polymer-conductive filler composite demonstrates an ultra-high k with balanced mechanical properties including the adhesion strength. However, the relatively high dielectric loss and narrow processing window have plagued the metal/polymer composites from real applications. In this study, surface modification of nanoparticles with organic molecules was employed to change the surface chemistry of nanoparticles and thus interaction between nanoparticles and polymer matrix. Fully characterization of the surface modified nanoparticle (SMN) by FT-IR, HRTEM, EDS, DSC, TGA et al. methods demonstrated that a thin layer was successfully coated on the surface of the nanoparticles via surface modification of the nanoparticles. The effect of surface modification of nanoparticles on the dielectric and electrical behaviors of SMN/polymer nanocomposites was investigated as well. The surface coating layer on the nanoparticles was demonstrated to be able to decrease the dielectric loss, enhance the dielectric breakdown strength and expand the processing window. This improvement in the performance of the polymer nanocomposites can be attributed to the interparticle electrical barrier layer formed via surface modification of nanoparticles which prevents the metal cores from direct contact. Different surface modification conditions such as surface modification agent type and concentration, solvent media - etc., may play complex roles to the degree of surface modification which impact the changes of k and dielectric loss tangent values of SMN/polymer composites dramatically. Therefore, surface modification of nanoparticles is believed to be an effective approach to adjust the electrical features at the nanoparticle surface and the interface between the nanoparticle and the polymer matrix, and thus tailor the corresponding properly of interest of nanocomposites.