Shielding is present in cables to protect them from electromagnetic interference. Common types of shielding are foil, braid, etc. Shielding is used in communication cables, medium and high voltage power cables.
The most popular types of cable shielding
Foil shielding is a shield that provides moderate protection against electromagnetic interference. It is a very thin layer of aluminum that is attached to polyester for added strength. While not the strongest protection against EMI, aluminum foil shielding is beneficial for many applications. It is lighter, allowing smaller cable diameters to be used. This type of shielding is ideal for protection against low-frequency electromagnetic interference. With this shielding, coverage approaches 95-100%.
Braided shielding consists of metal conductors connected in a cross-cut pattern, hence the name braid. This metal braided shield is made of bare copper or tinned copper. Other metals, such as steel, are also possible. It is a flexible and robust shield that provides a reliable level of protection against high frequency electromagnetic interference. However, due to the shield construction, coverage rates only range from 40% to 95%. 40% to 96% coverage is the most common. Braided shielding is typically more expensive than foil. It is also more difficult to terminate.
Other types of cable shielding
Foil/braided shielding is a combination of foil and braided shielding. The two types of shielding are combined to improve coverage and effectiveness. Like braided shielding, it is strong and flexible, but slightly lighter in weight.
Tape shielding, or shielding tape, is a lightweight shield wrapped around the cable conductor. This shielding is made from a variety of materials, usually a combination of copper, aluminum and bronze with polyester or polyester film. Polyester and polyester film are similar materials, as the latter is simply a brand of polyester. The shield also has a line of exclusion.
Tape shielding has similar properties to foil shielding and provides approximately 100% complete coverage. While tape shielding is primarily part of the standard cable construction created by manufacturers, it can also be DIY. A significant difference between foil shielding and tapes is that the former is always aluminum.
Spiral shielding is the braided analog. This type of shield is made of copper. The shield is called spiral because the strands are wound in a spiral shape around the conductor. The coverage is approximately 95%.
The factor that distinguishes spiral shielding from braiding is that the spiral is more flexible. In addition, termination is easier.
Copper and aluminum for shielding
While some other metals are popular, copper and aluminum are commonly used as shielding materials. Aluminum is used for foil shielding, while copper is commonly used for woven shielding.
While copper and aluminum are often judged by their electrical conductivity, conductivity is not important when it comes to preventing electromagnetic interference. One factor that should be considered is that copper is easier to weld than aluminum. However, when choosing a shield, the type of shield is more important than the material used to make it. Therefore, feel free to choose your shielding based on its type.
