Preparation of core-shell structured SiO2@Ag spheres and their role in improving micro-sized Ag flake filled electrically conductive adhesive for LED packaging

In this study, core-shell structured SiO2@Ag sub micro-sized spheres were prepared and used to improve the performance of the micro-sized silver flakes filled electrically conductive adhesive (ECA). The silica cores with an average diameter of 400 nm were prepared by hydrolysis and polycondensation of tetraethoxysilane using a modified Stober process. The synthesis of compact silver shells on silica spheres was achieved by electroless plating, which involves three steps: (1) sensitization of silica cores, (2) activation of silica cores, and (3) preparation of core-shell structured SiO2@Ag sub micro-sized spheres. Finally, different amounts of SiO2@Ag sub micro-sized spheres were introduced into the silver flakes filled ECA to study the effect of SiO2@Ag sub micro-sized spheres on the performance of the ECA. The results show that a small quantity of the SiO2@Ag spheres substituting for micro-sized silver flakes in the same mass can improve both the electrical and mechanical properties of the ECA.