EMI shielding is an enclosure, coating or transmitted signal which protects electronic equipment from ambient electromagnetic interference. EMI, or electromagnetic interference, is the magnetic field which is created by electrical currents; EMI can travel along wires, electrical circuits and conductors, while radio frequency interference (RFI) is radiated electromagnetic "noise" which travels through the air as radio waves. Both EMI and RFI cause the same effect.
EMI enclosures, RF absorbers, EMI coating, EMI gaskets and EMI filters are used as magnetic shielding and RFI shielding to guard sensitive electronic equipment. EMI and RFI are created, by widely varying degrees, by everything which conducts electrical energy, including electrical wires, electrical appliances, computers and all electronic equipment. Signal-bearing electronic devices such as mobile phones give off RFI. Normal electrical currents are disrupted when moderate to high levels of EMI or RFI are introduced; un-channelled electromagnetic signals and radio frequency waves can act as "noise", magnetically altering normal flow of electrical currents and impeding the flow of electrical energy.
With circuit boards and CPUs, most problematic EMI comes from electromagnetic cross-talk between different components on the same board as EMI travels across wires and conductive materials. Shielding sensitive electronic equipment from electromagnetic interference (and shielding high EMI-emitting equipment from contaminating other equipment) can be achieved by enclosing equipment in a conductive EMI absorbing material (EMI enclosure) or by coating equipment or equipment enclosures with EMI coating. EMI enclosures and EMI shields are also called magnetic shields, and may be made from metals with high magnetic permeability, which is the ability to absorb magnetic energy. Metals such as nickel, copper, steel and aluminum are commonly used, although the industry standard electromagnetic shielding material is Mu-Metal®, an alloy of nickel, iron, copper and molybdenum. Many industries depend on EMI shielding products to protect communication systems, such as hospitals, telecommunication, stage production, sound production and many others.
EMI enclosures, or "faraday cages" surround the equipment which needs to be shielded, absorbing harmful EMI and RFI. EMI enclosures are generally constructed from aluminum, stainless steel, nickel or copper alloys. Enclosures and shields built to block EMI need not be solid; perforated metals are often sufficient, as long as the surface's holes are smaller and closer together than the electromagnetic waves it is meant to block. Microwave doors are a good example of this. EMI coating allows for more flexible applications, as it may be spray-coated to the inside of plastic housings or the outsides of wires and regular enclosures. "Metal inks" containing copper, nickel or chromium alloys may be sprayed on to virtually any housing or material to create the effect of EMI shielding. EMI gaskets create more robust EMF protection by preventing the leakage of EMI in or out of an enclosure through seams or gaps. Gaskets are made from electrically conductive rubber materials and are often combined with EMI shielding metals. As electronic equipment advances and electromagnetic and radio frequencies become higher and stronger, EMI gaskets are used for more robust protection.
An alternative to enclosures, coatings and gaskets is the EMI filter, a passive electronic device which suppresses the electromagnetic interference generated by surrounding electronics. EMI filters are used to block electromagnetic interference which is conducted through power lines and signals (not RFI). Usually attached or integrated into the power source or switch which is to be shielded, EMI filters shunt high EMI frequencies, allowing normal low frequencies to pass; as with all types of EMI shielding, EMI filters work to both block incoming EMI and outgoing EMI. EMI filters can be an effective way to manage the EMI created on a specific power source or power line, although EMI shielding such as coating, enclosures and gaskets are still necessary to provide full protection from RFI, or electromagnetic interference conducted by radio waves.
Surface Mount Magnetic Shields - Spira Manufacturing Corporation
Magnetic Shields - Magnetic Shield Corporation
Magnetic Shields - Magnetic Shield Corporation
Magnetic Shields - Magnetic Shield Corporation
Expanded Metal Electromagnetic Shielding - Dexmet Corporation
MuMETAL Magnetic Shield Cans - Magnetic Shield Corporation
EMI/RFI shielding involves creating a layer around electrical and electronic components to prevent them from emitting harmful magnetic radiations. Things that need electricity to operate tend to give out electromagnetic radiation (EMR), as electricity passes through a medium it creates electromagnetic waves. There are applications where EMR is desired, but many common household electronic devices and appliances produce EMR, which is unwelcome, as the can pose a risk to human health. In such a case, magnetic shielding techniques, such as EMI shielding (electromagnetic shielding) and RFI shielding (radio frequency shielding), are employed to prevent exposure to radiation.
EMI/RFI shielding solutions are widely used across industries; one of the biggest reasons for their wide adoption is that electromagnetic waves and radio frequency signals hamper other similar electronic devices from working. A simple example: When the radio is switched on and there is a call on a nearby cell phone, you can hear noise coming out of the radio. This happens because the receiver in the radio also captures some of the cell phone signal. While this specific interference is not a huge problem, similar interactions in other equipment can lead to the appliance or device malfunctioning.
In today's world where gadgets have almost overcome our lives, there are millions, probably billions of signals scattering around in any given point of time. And that is the mother of all RFI and EMI problems. However, providing magnetic shielding the components can help deal with the issue.
A number of materials are used to make create EMI coating, including aluminum and zinc, which are used to create barriers in electronics enclosures (such as cabinets, doors, plates, etc.). Polycarbonate is also used to filter out EMR and electrical noise.
There are several advantages of EMI/RFI shielding; the most obvious being they save electronic devices from failing. However, there are several alternative methods competing for attention--shielding materials like foils, plastics with a conductive layer, fabrics with conductive coating, and metallic inner shields. These are pitted against the most common shielding method--conductive painting. There is also another contender-- vacuum metallization, which has been coming to the forefront lately.
All these techniques are used since they come with advantages and disadvantages depending on the application, one of them is recyclability. EMI shielding compounds are highly recyclable, which is not possible with conductive coatings. At the same time, the former requires complex designs but the latter has simple designs. Shielding permanence is an integral property in EMI shielding compounds whereas conductive coatings is scratch prone, which may cause a shield to fail and may delaminate during thermal cycling, as well as other adhesion issues.
In any case, both these methods offer great protection against EMR. Industries are increasingly adopting EMI/RFI shielding methods to comply with electromagnetic radiation norms being implemented by governments across the world. With EMR posing severe health risks, strict regulations being formulated to reduce exposure, and manufacturers in the various industrial sectors, including electronics, appliances, telecommunication, and medical, have been forced to provide robust protection against EMR unless they risk conflicting with regulatory standards.
Electromagnetic interference (EMI) and radio frequency interference (RFI) are inherently associated with electronic components, devices, and appliances. Both create problems in the working of these devices, and they can cause severe disruptions in their operations, eventually leading to mechanical failure. To prevent this, two techniques, EMI shielding and RFI shielding, are applied.
EMI is a byproduct of electromagnetic radiation, which travels and spreads through free space or through a physical medium (such as an electric wire) in the form of electromagnetic waves. Electromagnetic waves from one source can interact and influence waves from another, creating an "interference." This interference is sometimes desirable and sometimes undesirable. When it is unwanted, EMI shielding and RFI shielding are needed to prevent the release of such radiations. Both the techniques decrease this undesirable transfer of energy. However, the amount of reduction is dependent on several factors, including materials used for the shielding, frequency of the EMI, the size of the application on which the shielding is being applied, etc. Brass, tin plated steel, nickel, silver, and stainless steel are some of the most commonly used shielding materials.
Advantages of EMI/RFI Shielding
Obviously, the primary benefit and aim of EMI/RFI shielding is the reduction of electromagnetic interference, which in turn prevents interruption, obstruction, performance degradation or even malfunctioning of electronic devices and appliances. The efficiency of electronic devices can be greatly improved with high quality and reliable EMI and RFI shields. These shields can be made to meet specific manufacturing needs. Generally, shields are available in one piece, or with peel-off tops or a combination of two-piece shields comprising a ‘fence and cover;' however, manufacturers can also produce custom shields.
In a majority of scenarios, EMI/RFI shielding is created using a type spray, often made from acrylic-based materials. This type of shielding is used in plastic electronics housings. If the spray is combined with highly pure metals, such as nickel, silver, and copper, the shields can help to cut or fully block EMI and RFI interferences. Shielding agents can be bought in the forms of paints and brush on coatings too.
EMI/RFI Shielding is beneficial and critical to numerous industries, including telecommunication and healthcare. For instance, if a radio transmission from a telecommunication setup is similar in frequency to a signal receiving by a recipient, there can be huge inference. This can be prevented using EMI/RFI. In the healthcare industry, electronic devices, such as PDAs or cell phones, can hamper the operations of medical equipment such as MRI or ECG machines. Here, it becomes critical to shield components. That is why the FDA mandates that hospital machinery must meet it guidelines to prevent them from being affected by outsider inferences. Such protection is only made possible through radiation shielding.
As the world is becoming more gadget-savvy, the need for shielding is only increasing. With governments across the world focusing on regulation aimed at reducing electromagnetic emissions, manufacturers need to invest and research more on EMI shielding and RFI shielding to remain compliant.
EMI shielding, or electromagnetic interference shielding, is a commonly used mechanism to reduce electromagnetic radiation from electronic devices and components, and for EMF protection (electromagnetic frequency protection). The process involves creating a barrier surrounding electronics and cables with conductive or magnetic materials to protect them from outward magnetic interferences, or prevent the release of magnetic emissions of electromagnetic frequencies (EMFs).
Electromagnetism is caused when electrically charged particles move through a circuit. Electromagnetic radiation is a form of energy, which exhibit in different forms, such as radio waves, microwaves, X-rays and gamma rays. We commonly experience EMI when we use different household electronics side by side-for instance, when the radio is switched on and at the same time we pick up a cell phone call, there is noise in the radio reception. This happens because the radio is also picking up some of the cell phone signal. EMI is an undesirable outcome, because it hampers the working of devices, preventing proper communication, also creating several other issues. To solve these problems, we have what is called EMI shielding.
Why EMI shielding matters
EMI is very common; it causes extensive disturbance in the working of electronic operations and can cause electronic devices to fail. The Federal Communication Commission's Interference Handbook discusses the effects of electromagnetic interference on household electronics and appliances.
The most common form of electromagnetic interference occurs in the radio frequency range from 104 to 1012 Hz of the electromagnetic spectrum. This type of EMI can come from common household items such as computer circuits, radio transmitters, electric motors, and even fluorescent lamps.
With the advancement of technology, devices are getting smaller and its electronic components are more intricate and sensitive. This is contributing to the rise in device failures due to EMI or "noise." Managing this noise has become an even bigger challenge due to the small size of the mechanical parts and faster operating speeds of these components. As the frequencies emitted from the devices scale to a higher range (more than 10GHz), it proportionally decreases wavelengths, which penetrates very small openings in casings and containers and making it more difficult to manage.
This, actually, raises more concern and makes it more important to shield these devices and components with magnetic shielding, wire shielding, or radiation shielding.
EMI shielding requires different materials and different approaches. To block escaping radiation from wires, they can be coated with a metallic foil or braid shield. The sound driver in an audio system usually has an inner metallic casing to prevent EMI from the driver so that it does not interact with other electronic appliances. Similarly, purpose-made conductive paints are also used to block EMF from escaping network terminals. Using electronic components, such as capacitors and ferrules, and by grounding wires of electronic connections of electronic devices, help filter out electromagnetic interferences.
Regulatory requirement for EMR of devices are also being made stringent across the globe, requiring manufacturers of electronic devices and appliances to put enough EMI shielding mechanisms to prevent both emissions and susceptibility to such radiation.
With the demand for electronic devices and appliances increasing day by day, the debate surrounding the effects of electromagnetic radiation (EMR) from these utilities, as well as from telecommunication installations and electric transmission lines, is only heating up. Let's face it-electromagnetic waves not only hamper the operations of electrical and electronic components, the radiation poses a health hazard. In such a scenario, EMI shielding or electromagnetic interference shielding can potentially protect humans from this hazard.
How EMR is affecting health?
Acute exposure to EMR causes immediate burns, but chronic or occupational contact with the radiation can take time to physically manifest. High-power but extremely low radio frequencies have been known to induce effects in the human body that is perceivable, creating an irritating tingling sensation. Similarly, exposure to shortwave radio frequencies can cause human tissues, such as blood vessels and muscle, to heat up, as they are good electrical conductors.
Researches also believe that electromagnetic fields from cell phones may pose an increased risk of glioma and acoustic neuroma. The World Health Organization (WHO) designates mobile phone signals as "possibly carcinogenic," and similar classification came from the International Agency for Research on Cancer (IARC) in 2011. However, there is inconclusive data to rule that this is actually a fact. Despite this, it is undeniable that there are risks associated with cell phones, especially radiation released by the fixed telecommunication infrastructures such as mobile base stations and their antennas. Similar concerns arise from power transmission lines, which are another prolific source of EMR.
There are also health concerns about millimeter waves, used in scanners for airport security. These scanners operate above microwave band to SAR exposure regulations. Radiation levels in the millimeter wavelength are characterized by high microwave band, which is close to infrared wavelengths. Infrared wavelengths bigger than 750 nm can affect the lens of the eye.
The solution to EMR is EMI Shielding (electromagnetic shielding) and RFI shielding (radio frequency shielding). Both of these techniques involve creating a barrier surrounding electrical cables, components, and circuits to prevent the release of electromagnetic emissions. The process employs several methods, including foils and conductive fabrics, metallic inner shields, and plastics with a conductive coating. There are also conductive paints, which is a common technique of creating a conductive surface coating in plastics. Another method is the vacuum metallization, which is becoming more widely used.
EMI/RFI shielding can work in a number areas, including marine electronic equipment, medical devices (example: x-ray, MRI machines), radios, computers, mobile phones, and process control equipment.
While these techniques go a long way to ensure that no EMR escapes from electronic components and appliances, there are still prevailing concerns about radiation from mobile towers and other telecommunication installations, power lines etc., as they are not easy to shield. With governments around the world putting an emphasis on EMF protection, the need for radiation shielding is only increasing. When we couple this with the health risks posed by EMR, the need becomes a burning necessity.
EMI shielding is a necessary part of the industrial world, protecting objects from magnetic and electrical interference. There are many ways to shield products, from panels to a thin coating that provides EMI shielding with just a few coats.
Master Bond has created a new conductive coating system that offers EMI shielding, temperature resistance, and easy application. Of all the EMI shielding companies in the world, Master Bond has created one of the first innovative products in some time.
Master Bond MB600S is manufactured using one component - sodium silicate. The coating is silver and fully conductive, offering effective shielding and temperature resistance up to 700 degrees Fahrenheit. The coating is easy to apply, making it versatile and effective on any possible object.
The coating is completely aqueous-based, and is formulated for applications where any form of EMI or RFI shielding is necessary. As a water-based coating, it is non-toxic and easy to handle. The coating is effective at shielding with a range of 95-105 dB, from 100 MHz to 2 GHz. For above 2 GHz, the shielding decreases to 60-80 dB. It is possible to apply the coating by brushing or spraying. Spraying the coating makes it more effective than brushing.
It takes about 48 hours for the coating to set and become an effective shield. It can resist a variety of temperatures from 0 degrees to 700 degrees Fahrenheit.
Any company looking for an effective brush or spray on EMI shield will appreciate the versatility and protection that the Master Bond MB600S can bring.
- A room in which no acoustical reflections or echoes exist. The
floor, walls and ceilings of these rooms are lined with a metallic substance
to prevent the passage of electromagnetic waves.
- An electrical signal's reduction in concentration as the signal passes through media. Attenuation is measured in decibels.
- A round-wire spring with inclining (canted) elliptical coils that, when compressed, deflect independently. Whenever any part of the coil is deflected, the whole spring responds, allowing consistent loading at each point of contact.
- A mandatory mark for about 70% of the products sold on the European Free Trade Association (EFTA) and European Union (EU) markets. CE Marking is sometimes called "CE Mark" and referred to as the "Trade Passport to Europe " for non-EU products.
- A shielded enclosure containing inner and outer walls isolated from one another, except at the point of filter penetration
- The ability of electronic equipment to be operated without EMI.
- The release of electrical energy usually caused by the shift of electrons from one object to another as the objects come into contact with and separate from one another. ESD is also known as triboelectric charge.
- Shielding that prevents the failure of electronic equipment from interference associated with electrostatic discharge.
release from electronic equipment of electromagnetic waves that have
the potential to create EMI.
- The removal of certain unwanted signal components through attenuation while allowing the passage of the remaining signal components.
- The complete opposition offered by a circuit to the flow of current at a certain frequency that is a combination of resistance (R) and reactance (X). Impedance is measured in ohms; the quality of the conductor is better the lower the ohmic value.
- Measurement reflecting filtering ability. Insertion loss represents the difference in power reception prior to and after the use of a filter.
- The movement of electromagnetic energy in the form of particles, rays or waves.
- Low frequencies of electromagnetic radiation used for communications.
- Interference in a specific frequency range used for radio communication. Unlike EMI, RFI is not conducted through circuits or power lines, but through "free" air space as radio waves. EMI and RFI are often used interchangeably; the term EMI/RFI shielding covers all interference caused by electromagnetic radiation.
- The ability of a shield component to prevent the passage of electromagnetic radiation. Shielding effectiveness is expressed as a ratio of electromagnetic signals with and without the shield component.
- The propensity of high frequency current to travel close to the outside of an electric conductor rather than through its cross section. At high frequencies, the effective resistance of a wire is increased by skin effect.
- A radiating element that is created by a slot in the conducting surface or in a waveguide's wall.
- In a vacuum, the condensation of thin material coatings on cool surfaces.
- Media that controls the passage of electromagnetic energy and signals.