Optimized designs require less electromagnetic interference (EMI) shielding and other materials, improving sustainability. Improved EMI performance extends system life and reduces e-waste, further enhancing sustainability. More sustainable shielding materials are being developed for use when shielding is required.
This article reviews the basics of EMI, examines common shielding materials to provide a baseline for comparing the performance of sustainable shielding options, and concludes with a glance at some materials under development.
EMI comprises electric (E) and magnetic (H) field components oscillating at right angles. The E field is measured in volts per meter (V/m) and results from charge distribution. The H field is measured in amperes per meter (A/m) and is generated by electric currents (Figure 1).
The E and H components respond differently, and it’s important to know which one is dominant to arrive at an optimal solution. For example, the E field components of EMI can be attenuated using high-conductivity shielding materials, while the H field components can be attenuated with high-permeability materials. In most electronic systems, the E field is dominant, and shielding materials with high conductivity are best.
Traditional shielding choices
Common examples of high-conductivity EMI shielding materials include:
- Copper is a highly effective shielding material across a wide frequency range. There are a variety of copper alloys used for shielding that cost less than pure copper.
- Copper alloy 770 is composed of copper, nickel, and zinc. It is more corrosion-resistant than pure copper and provides good shielding up to several GHz.
- Nickel is an affordable alternative and is best suited for lower-frequency applications.
Sustainable and tunable shielding
Mining, refining, and processing metals in an environmentally friendly and sustainable manner is challenging. As a result, numerous efforts are underway to develop alternatives that can minimize the metal content of the shield material.
In one case, carbon fibers are being used to produce conductive nonwoven shielding materials. The carbon fibers can be coated with metals like copper and nickel. Depending on the formulation, these materials offer a lightweight solution of 4 to 75 g/m² and tunable shielding effectiveness of up to 78 dB.
They are suited for shielding EMI from about 100 MHz to over 40 GHz. The level of EMI shielding can be tuned to meet application requirements by selecting the fiber type, metal coating, and areal weight used (Figure 2).
More sustainable possibilities
Biomass materials like wood, lignin, and cellulose are being investigated for use in EMI shields. Some of these materials can also provide antibacterial, fire-retardant, transparent, waterproofing, and mildew-resistant properties.
The performance of biomass multi-function EMI shielding materials can be tuned by adjusting their structure using various treatment or processing methods that can optimize the pore structure, shape, size, and distribution to vary the material’s absorption loss and multiple reflection attenuation.
Adding conductive fillers to biomass materials can create a conductive mesh structure. A layered structure that stacks different materials can enhance shielding effectiveness by improving impedance matching, absorption losses, and multiple reflection attenuation.
Several compositions and production processes are being considered for biomass EMI shielding materials (Figure 3). Some processes produce toxic gases that need to be minimized. Production of greenhouse gases is also a significant challenge that needs to be managed throughout the product life cycle of biomass-based EMI shielding materials.
Summary
Effective EMI shielding is needed to ensure the reliable operation of electronic systems. Traditional shielding materials based on metals provide good performance but can be lacking in sustainability. As a result, more sustainable alternatives have been and continue to be developed that provide good levels of shielding, are also tunable in terms of shielding performance, and can provide additional functionalities.
References
A comparative study on biocomposites for electromagnetic interference shielding applications: A green initiative for environmental sustainability, Journal of Materials Research and Technology
Advanced Functional Electromagnetic Shielding Materials: A Review Based on Micro-Nano Structure Interface Control of Biomass Cell Walls, Nano-Micro Letters
How to Prevent Electromagnetic Interference From Ruining Your Devices, TT Electronics
Progress in polymer nonwoven textile materials in electromagnetic interference shielding applications, Springer Nature
Review on Sustainable EMI Shielding Materials Developed from Biodegradable Waste: A Waste to Wealth Strategy, Mapana Journal of Sciences
Sustainable Lightweight Biochar-Based Composites with Electromagnetic Shielding Properties, ACS Publications
The Best PCB Design Guidelines for Reduced EMI, Highleap Electronic
The Three Most Popular Shielding Metals and What You Should Know About Them, Leader Tech
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