All electronic devices produce unwanted signals that cause disturbances. Electromagnetic interferences (EMI) occur when an external electromagnetic field negatively affects the operation of an electronic device. To prevent the incoming or outgoing of these electromagnetic interferences, EMI shields are used. EM shielding (electromagnetic shielding) is the practice of using conductive or magnetic materials to prevent the electromagnetic interference signals from causing disturbances. EMI/RFI shielding helps in limiting the unwanted signals by covering the casings of the electrical device.
EMI shielding is the use of conductive coatings or housings to absorb electromagnetic radiation to protect a device from EMI, or it may prevent a device from producing EMI. To protect all electronic components from EMI/RFI, manufacturers use shielding in the construction of electronic devices. There are many different kinds of EMI shielding, which are appropriate for different kinds of devices. For shielding, a conductive material is applied to electronic enclosures in the form of a spray or metallic screen to absorb electromagnetic interference. The concept of shielding is based on the principle of the Faraday cage. Design engineers use this concept to ensure that a circuit has been designed to prevent EMI/RFI disruption by shielding. Besides using acrylic paints, metallic mesh shields can also be used inside a particular device to protect one component from affecting another.
Manufacturers or design engineers use several techniques and materials for EMC Shielding. One of the most popular techniques is using an EMI shielding gasket that fits directly into electronic housings or compartments to help negate any interference. EMI shield also comes in the form of coatings that uses paint mixed with conductive metals that form a shield. When designing an electromagnetic interference (EMI) shielded enclosure for a circuit board, it is important to maintain a balance between cost and performance. Also, galvanic compatibility, conductivity, material thickness, enclosure geometry, application frequencies, and other factors determine what material the shielded enclosure will be constructed from.
Popular Metals Used in RFI Shielding
When it comes to electromagnetic compatibility (EMC), the material choice has a significant impact on project cost and application performance. Let’s take look at the most common metals used for RFI / EMI shielding.
- Copper
Another feasible material is copper which is also highly conductive, capable of blocking Radio waves and magnetic. As a reliable metal for EMI shielding, copper is being used in hospital MRI facilities and in basic computer equipment for shielding purposes. It is also a versatile metal that can be easily fabricated along with its alloys brass, phosphorous bronze, and beryllium copper.
- Pre-Tin Plated Steel
The most popular material choice for EMI/RFI shielding is pre-tin plated steel and copper alloys. It is a cost-effective solution that works well in the lower GHz range. The tin plating is corrosion resistant to prevents rusting.
- Aluminum
Aluminum is also a great material that offers high conductivity and a cost-effective shielding solution. It has non-ferrous properties and is a great choice for a number of applications due to its high conductivity. However, this meal may form into an oxide over time due to oxidation properties.