A study of the pressureless sintering process of silver nanoparticles for electromagnetic interference shielding applications

Herein, we describe a simple and effective method of fabricating a porous thin silver (Ag) layer, exhibiting an excellent electromagnetic interference (EMI) shielding performance. The porous sintered Ag layer was fabricated by a simple blade-coating method using Ag nanoparticle (NP) dispersions. As-coated Ag NPs layer was sintered at a low temperature under 180 °C without external pressure to prevent device failure due to excessive pressure or thermal energy. The pressurelessly sintered Ag layer possessed an inherent porous structure, which multiplied the internal reflection of the incident electromagnetic (EM) waves within the Ag layer. The porous sintered Ag layer exhibited a high average EMI shielding efficiency (SE) of 56.5 dB over a broad frequency range of 0.5-18 GHz, which means EM waves were blocked over 99.99%. The EMI shielding performance of the porous sintered Ag layer was superior to that of previously reported EMI shielding materials. The practical application was demonstrated by near-field SE mapping of the porous sintered Ag layer coated PCB antennas. This research suggests a suitable and alternative EMI shielding method to replace package-level EMI shielding materials for a wide range of applications.