Performance Analysis of Electromagnetic Interference Shielding Based on Carbon Nanomaterials Used in AMS/RF IC Design

Introduction

Since each day there is more and more commercial, military, and scientific electronic devices and communication instruments, electromagnetic interference (EMI) shielding of radio frequency is a more serious concern in actual society. Motivated by environmental questions and by a wide variety of technological applications, the need for materials with high efficiency to mitigate and/or reduce electromagnetic interferences (EMI) has become a mainstream field of research. EMI shielding implies the reflection and/or absorption of electromagnetic radiation by a material, which in a system or device acts as a shield against the penetration of the radiation through the shield. Around the world, EMI shielding of both electronics and radiation source are required to provide an effective performance of devices and systems. EMI modifies the incoming and/or outward signals to ICs, and therefore, the design of the polymeric housing to protect or reduce the electromagnetic interference is strategic to guarantee the operation of AMS/RF ICs. Most metals are by far the most useful materials for EMI shielding. The polymer-based composites are popular in electronic appliance housings due to their lightweight, low cost, high strength and easy processing. However, most polymeric materials are transparent to EM radiation and provide no shielding against electromagnetic interference. In the search of solutions with lightweight for guarantying EMI shielding for avionic electronics, laptop computers, aircraft and many other devices, the polymer-matrix composites containing carbon nanomaterials as electrical fillers, are the better option developed until now. Compared to conventional metal-based EMI shielding materials, carbon-nanotube-polymer composites have gained popularity recently due to their lightweight, resistance to corrosion, flexibility, and processing advantages. These excellent technical shielding materials are ideal for coating ICs found in laptops, cell phones, aircraft electronics, etc. Shielding electromagnetic waves with frequencies between 30 MHz and 1 GHz is of greatest importance because these waves can interfere with broadcast communications. A shielding effectiveness of 10 and 20 dB means that 90% to 99% of the electromagnetic waves have been attenuated. Three mechanisms have been reported to be involved in EMI shielding, namely: reflection, absorption and multiple-reflection. In polymer composites, shielding mechanisms are more complex because the huge surface area generates different mechanisms of reflection, absorption, and multiple-reflections on electromagnetic waves that are applied to the material used as barrier. This chapter presents a comprehensive performance analysis of electromagnetic interference shielding based on composite materials used as barriers and based on polymers and carbon nanomaterials such as graphite, black carbon, carbon nanotubes and graphene that can be used in AMS/RF IC Design.