Materials that block or absorb radio frequency (RF) energy include:
Metals: Metals, such as aluminum and copper, are good conductors of electricity and are often used as RF shielding materials due to their high conductivity.
Ferrites: Ferrites are magnetic materials that are commonly used in RF absorbers and filters. They absorb RF energy and convert it into heat.
Conductive polymers: Conductive polymers, such as carbon-loaded polyethylene, are materials that can be used for RF shielding. They are often used as coatings or films to cover electronic components.
Mu-Metal: Mu-Metal is an alloy of nickel, iron, and other metals that has high magnetic permeability. It is commonly used as an RF shielding material in electronic devices.
Graphite: Graphite is a conductive material that is often used as a filler material in RF shielding applications.
Carbon composites: Carbon composites, such as carbon-fiber reinforced plastic, are materials that can be used for RF shielding. They are lightweight, flexible, and have high electrical conductivity.
Shielding materials are shown in Table 1 below. Some materials work better than others for shielding at certain frequencies due to materials property regarding its absorption loss and its reflection loss. There are two types of material classifications regarding shielding effectiveness / shielding: 1) ferrous and 2) non-ferrous. The concept is as simple as this: a ferrous material is one which does include some trace amounts of iron (ferrite) whereas a non-ferrous material is one that does not.
Material | A | R |
Silver | 1.05 | 1.05 |
Copper | 1 | 1 |
Gold | 0.7 | 0.7 |
Aluminum | 0.61 | 0.61 |
Brass | 0.26 | 0.26 |
Bronze | 0.18 | 0.18 |
Tin | 0.15 | 0.15 |
Lead | 0.08 | 0.08 |
Nickel | 120 | 0.000033 |
Stainless Steel | 10 | 0.000004 |
Steel | 100 | 0.00001 |
Mumetal (at 1 kHz) | 900 | 0.000001 |
Superpermalloy (at 1 kHz) | 3000 | 0.0000003 |
In general, the effectiveness of a material as an RF shield or absorber depends on its conductivity, magnetic permeability, and loss tangent. The material should have low electrical resistance and high magnetic permeability to effectively block or absorb RF energy.
The trend is the smaller the Reflection Loss the better the material for shielding effectiveness, and the larger the absorption loss the better the material for shielding effectiveness. The tabular data also indicate that reflection loss is the primary contributor to shielding effectiveness at low frequencies for either ferrous or non-ferrous shielding materials.
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