Electromagnetic interference shielding, or EMI shielding, is the process of reducing the electromagnetic field in a space by decreasing the field with barriers, or covers made of conductive or magnetic materials. Shielding is commonly applied to enclosures to isolate electrical devices from the outside world. Shielding is also used to isolate wires from the environment through which the cable runs. Shields can also be manufactured to block radio frequency electromagnetic radiation interference, which is also known as RFI shielding.
Electromagnetic radiation is made of coupled electric and magnetic fields. Within the conductor, the electric field produces forces on the charge. When an electric field is applied to the surface of an ideal conductor, it induces a current that causes displacement of the charge inside the conductor. This displaced charge cancels the applied field inside, which will in turn stop the current.
Shielding is used to reduce the coupling of radio waves and electromagnetic fields. While coupling can be both desirable and undesirable, in this case, coupling is the undesirable transfer of energy from one medium to another medium. EMI shielding will reduce this unwanted transfer of energy. The amount of reduction will depend upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic field. Materials commonly used for shielding include, brass, tin plated steel, nickel, silver and stainless steel.
EMI is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. This disturbance can obstruct, interrupt and degrade the performance of the circuit. The effect can be a simple degradation of data and can range up to a much more serious loss of the total data. Shielding is an effective and efficient solution to this problem.
EMI interference can be caused by either conduction or induction. With conduction, EMI is caused by the physical contact of conductors. Induction on the other hand, involves no physical contact with the conductors.
The use of high quality and reliable EMI and RFI shields increases efficiency. Shields can be manufactured exactly to your desired specifications to meet any manufacturing needs. One piece shielding, shielding with peel away tops or two piece shields consisting of a “fence and cover” combination are typical designs for shielding however, experienced manufacturers can work with you to develop your own custom shielding applications.