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Magnetic Shielding

Electromagnetic interference, sometimes abbreviated as EMI, can prevent sensitive electronic products from functioning properly, if not irreversibly damage them. Fortunately, magnetic shielding is one of many preemptive measures that can be taken to eliminate this risk and properly protect your devices. Magnetic shielding defines any component that uses highly permeable magnetic alloys to isolate machinery from external magnetic fields. Any product that is used to protect electronics from outgoing or incoming emissions of electromagnetic frequencies can fall under the category of magnetic shielding. Magnetic shielding is typically used in environments where the magnetic field is below 100 KHz.

Magnetic shielding protects devices from electromagnetic interference by drawing the magnetic field toward it and then absorbing it, rather than simply blocking the magnetic field. Magnetic shields are therefore typically designed as a closed container that completely encompasses the device that it is meant to protect. Some varieties of magnetic shields are multi-layered, which prevents any single layer from being oversaturated by electromagnetic frequencies and thus rendering them unable to absorb any frequency that is stronger. The earth’s magnetic field is one example of an external magnetic frequency that can interfere with certain devices. Other examples include thunderstorms, or electric cables that are not properly grounded. There are numerous security applications in commercial and industrial settings that require the application of magnetic shielding. Applications that require magnetic shielding include TV studios, closed circuits, or home videos. Magnetic shields can also be found in stereo systems, TV sets, mobile phones, and even in sets of windows, vents, and walls. Magnetic shielding can either be solid, or made from perforated metal. If the enclosure should be fabricated from perforated metal, it should be noted that both the proximity and size of the holes must be smaller in order to effectively hinder electromagnetic waves.

Another measure that can be taken is coating the interior of an electronic device. EMI coating must be spray-coated, and can be utilized in a variety of areas, enclosures, and insulators. There are various types of EMI coatings to choose from. These include “metal inks” that contain nickel, chromium, or copper alloys. Applications that utilize EMI spray coatings include mobile phone housings, circuit board housings, and central processing units. EMI coatings can be sprayed to coat wire insulation. One problem that could arise is “cross-talk” within certain devices such as circuit boards, CPUs, and laptops, that involve multiple components working together within and tight enclosed space. Thererfore, Spray-coating wire insulation with EMI coating is important for the prevention of “cross-talk” within a device.

Electromagnetic interference can affect data presented on a display such as a radar screen. Therefore, commercial and military equipment such as aircraft carriers use magnetic shielding extensively to ensure that their readings are correct. Within an aircraft, there are various sensitive components that are in close proximity to each other because of limited space. Therefore, the primary functions of these components, such as a radar tube, are highly susceptible to being interfered with by the functions of other components, such as the tachometers. Radars are utilized to notify its users of a shift in velocity or altitude of other aircrafts, and are heavily relied upon in unfamiliar or low-visibility conditions. If the readings of the radar are not accurate, it could be incredibly dangerous for others involved. Therefore, radars use magnetic shielding to prevent other signals from altering the information it provides.

Popular materials that are used to fabricate magnetic shielding enclosures include metals with high magnetic permeability, and conductive rubbers such as silicone or nitrile. Other metals that are popular to use are aluminum, steel, nickel, and copper. However, industries have highly recommended the use of Mu-Metal®, which is an alloy that consists of molybdenum, copper, iron, and nickel. Mu-Metal® is recommended for low intensity fields that require high shielding efficiency, high initial permeability, and high attenuation is required. Its fabrication involves putting the metal material through a heat treatment process known as annealing. Annealing involves heating raw material to a certain temperature to weaken its grain structure, thus making the material easier for manufacturers to form it into a desired shape. Once the metal is manipulated into the desired configuration, it is allowed to cool. In order for the product to maintain its shape and grain structure, the metal must be cooled at a consistent rate. Sometimes, controlled atmospheric annealing is applied. In this process, metal is exposed to gases such as hydrogen or nitrogen in order to prevent the side effects of annealing such as scale or oxidation.

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