Filling Uniformity of AgNPs in EMI Shielding Patch Regulated by Surface Morphology

Silver nanoparticles (AgNPs) are extensively employed for electromagnetic interference (EMI) shielding owing to their remarkable conductivity, and are commonly incorporated into polymer matrices. Therefore, the uniformity of the AgNP distribution within the polymer matrix is a crucial factor that affects the EMI shielding performance. This study demonstrates the impact of the surface morphology of AgNPs on the uniformity of the filling in electromagnetic interference shielding patches. The AgNPs were synthesized through a liquid-phase reduction process, regulating the surface shape by thermal treatment at varying temperatures. The morphology transitioned from a flower-spherical shape to a coarse-strip shape when the heat treatment temperature increased from 20°C to 250°C. The morphological alteration of the AgNPs was ascribed to the interplay between their surface effects and sintering kinetics. The results indicated that after heat treatment at 100°C, AgNPs with a spherical surface morphology demonstrated remarkably superior filling uniformity. The EMI patch containing AgNPs subjected to heat treatment at 100°C demonstrated superior EMI shielding efficacy. Its efficacy was further validated in practical electronic equipment by applying surface electromagnetic radiation scanning techniques. These findings offer significant insights into the practical design of EMI shielding patches for real-world applications using the morphology-regulated filling uniformity method.