Electrically Insulating yet Excellent EMI Shielding FeSiAl/CNF Composite Film with Thermal Conductivity for Electronic Packaging Applications

Electrical conductivity is typically prioritized when designing and fabricating high-performance electromagnetic interference (EMI) shielding materials. Achieving electrically insulating yet high-performance EMI shielding presents a significant challenge in the field of advanced electronic packaging due to the essence of the conflict between electric insulation and EMI shielding. Herein, we innovatively design and propose a flaky FeSiAl/cellulose nanofiber composite film (FFSA/CNF) with a markedly aligned structure, which achieves an insulation resistivity of up to 10⁹ Ω·cm while providing broadband EMI shielding efficiency of 60 dB with a thickness of 220 μm. The mechanism of electrically insulating EMI shielding is systematically investigated based on the contact resistance between FFSA, localized eddy current losses, and strong magnetic loss of FFSA. Moreover, the FFSA/CNF film with densely stacked and oriented FFSA possesses a high thermal conductivity of 4.74 W/m·K. Interestingly, it exhibits a tunable and intelligent characteristic for EM attenuation by varying the aqueous FFSA/CNF composite film. In addition, the outstanding near-field shielding performance of FFSA/CNF is demonstrated in simulated electronic chips, which have the potential to be applied in the electronic packaging field. This study provides insights for design and development in both electrically insulating and high-performance EMI shielding materials.