Formation of Silver Layer with a Multiporous Structure from Silver Nanoparticles for Highly Efficient Electromagnetic Interference Shielding Materials

In this work, we describe a simple and effective strategy for the fabrication of a thin silver (Ag) layer with a multiporous structure, showing a high electromagnetic interference shielding effectiveness (EMI SE). The Ag layer with a multiporous structure was produced by a simple spray coating of conductive ink containing porous Ag nanoparticles synthesized using a simple chemical reduction method in a wet medium, followed by a low-energy sintering process to develop the Ag layer with an interconnected multiporous structure and average thickness of ∼5.5 μm. The produced Ag layer possessed a remarkable multiporous structure, which was composed of pores in Ag NPs and additional pores generated by coalescence of Ag NPs during the sintering process. Even the thin Ag layer exhibited a high EMI SE (62.3 dB, 99.9% shielding) owing to the multiporous structure, which was comparable to that of Ag foil with much lower Ag loading. This multiporous structure helped to increase the internal multiple reflections of electromagnetic waves. The substantial shielding effectiveness of the obtained multiporous Ag layer was demonstrated by measuring the EMI SE of the Ag layer coated PCB antenna. Our approach is a suitable and alternative EMI shielding method to replace present package-level EMI shielding materials such as Ag foil for a wide range of applications.