Introduction
What is EMI shielding?
EMI shielding means using materials or technologies to prevent electromagnetic waves from penetrating or interfering with a specific space or device. Electromagnetic waves are a form of energy that travels through space and can be created by electronics, power lines, or natural phenomena (such as lightning). These electromagnetic waves may cause electromagnetic interference (EMI) to other electronic devices, causing unwanted signals or noise, which may degrade the device's performance or cause malfunction.
The goal of EMI shielding is to create a barrier between the noise source and the area or device to be protected (victim). These barriers are made using materials with high electrical conductivity or high magnetic permeability to reflect or absorb radio waves.
Electromagnetic wave shielding is used in various fields such as aerospace, military, medical, and home appliances. In aerospace, for example, they are used to protect critical avionics and communication systems from lightning strikes, solar flares, or other electromagnetic interference. In the field of medical devices, they are used to prevent interference from other electronic devices or to protect patients from the harmful effects of electromagnetic waves.
EMI shielding plays an important role in the proper functioning of electronic devices and systems. Electromagnetic shielding allows a wide range of applications to operate safely and reliably while protecting people and equipment from the potential hazards of electromagnetic waves.
Purpose of shielding
The purpose of electromagnetic shielding is to protect electronics and systems from the harmful effects of electromagnetic waves.
Electromagnetic waves can interfere with electronic devices in many ways, causing them to deteriorate, malfunction, or fail. This interference can occur in various ways, such as electromagnetic induction, electrostatic coupling, or electromagnetic radiation. The purpose of shielding is to ensure the proper functioning of electronic devices and systems against such interference.
In the case of sensitive medical equipment, for example, electromagnetic interference can endanger patients if they give inaccurate readings. Similarly, for avionics, electromagnetic interference can interfere with communication systems and navigation equipment, creating potentially hazardous situations.
The importance of shielding
In modern electronic devices, electromagnetic wave shielding is very important. As electronic devices and systems proliferate in all areas, the risk of electromagnetic interference has increased dramatically. As a result, the need for effective electromagnetic shielding is more important than ever.
One of the key benefits of electromagnetic shielding is that it can improve the performance and reliability of electronic devices and systems. By avoiding electromagnetic interference, you can reduce the risk of malfunction, improve signal quality and increase the life of electronic components.
Electromagnetic shielding is also important for safety reasons. In some cases, electromagnetic interference can cause potentially hazardous situations, such as medical or avionics. Effective electromagnetic shielding can reduce the risk of these hazards and ensure the safety of people and equipment.
Principle of EMI shielding
Electromagnetic interference
Electromagnetic interference (EMI) is a problem caused by one electronic device or system generating electromagnetic waves that interfere with other devices or systems. EMI can cause various problems, including signal degradation, data loss, and even complete failure of electronic devices and systems. This is where the principle of electromagnetic shielding comes into play.
The principles of electromagnetic shielding are based on the properties of radio waves and how they interact with matter. Electromagnetic waves can be reflected, absorbed, or transmitted depending on the material’s properties. The goal of electromagnetic shielding is to create a barrier that prevents radio waves from penetrating or interfering with a particular space or device.
There are several ways to achieve electromagnetic shielding, including using conductive and magnetic materials, or a combination of both. Conductive materials such as copper or aluminum can be used to create shields that reflect electromagnetic waves. Magnetic materials such as iron or nickel can be used to absorb or divert electromagnetic waves.
In addition to using conductive or magnetic materials, other design principles can be used to increase the effectiveness of electromagnetic shielding. Shielding can be achieved, for example, using a Faraday cage which is an enclosed conductive structure that blocks electromagnetic fields.
The effectiveness of electromagnetic wave shielding depends on various factors, such as the frequency and strength of the electromagnetic wave and the characteristics of the material used for shielding. In some cases, multiple shielding layers may be required to achieve the desired level of protection.
Electromagnetic compatibility
Electromagnetic compatibility (EMC) is the ability of electronic devices and systems to function properly in the presence of electromagnetic interference (EMI) from other devices or sources.
EMC can be achieved through a combination of design principles, including proper grounding and shielding. To achieve EMC, it is essential to design electronic devices and systems with shielding in advance. This includes ensuring that all components are properly grounded and that shielding materials are in place to prevent EMI from interfering with the device or system's performance. The effect of EMI on signal quality and data transmission can also be reduced by using appropriate filtering.
EMI shielding material
Conductive material
Conductive materials are commonly used for electromagnetic shielding due to their ability to reflect or absorb electromagnetic waves. Conductive materials are materials in which electrons can move freely and are very effective at conducting electricity and absorbing electromagnetic energy. Conductive materials commonly used for electromagnetic shielding include:
- Metals: Metals such as copper, aluminum, and silver are commonly used for electromagnetic shielding because of their high conductivity. These materials can be used as thin foil sheets, mesh, or other shapes.
- Conductive Polymer: Conductive polymer is a type of plastic material that contains conductive materials such as carbon or metal particles. These materials can be molded into a variety of shapes.
- Conductive coating: A conductive coating is a type of paint or spray that contains a conductive material such as silver or carbon. These coatings can be applied to various surfaces to provide effective electromagnetic shielding.
- Conductive fabric: Conductive fabric is a type of fabric that is plated with a conductive material such as copper, nickel, or silver. These materials can be used to make electromagnetic shielding gaskets, conductive tapes, and other shielding products.
The effectiveness of conductive materials for electromagnetic shielding depends on many factors, such as the type and thickness of the material, the frequency and strength of the electromagnetic waves, and the design of the shielding system. Generally, thicker and more conductive materials provide better shielding but can be heavier and more expensive.
When designing an electromagnetic shielding system, it is important to consider the specific requirements of the application and select the appropriate materials and design principles to achieve the desired level of shielding. Conductive materials are very effective in shielding electromagnetic waves and are used in various fields.
Magnetic material
Magnetic materials are another type of material commonly used for electromagnetic shielding. These materials work by absorbing or redirecting the magnetic fields rather than the electrical fields of electromagnetic waves.
Magnetic materials commonly used for electromagnetic shielding include:
- Ferrite: Ferrite is a type of ceramic material containing iron oxide and other metal oxides. This material has high permeability, which allows it to absorb magnetic fields and reduce its strength of that. Ferrite is commonly used in electronic devices such as transformers and inductors to reduce electromagnetic interference.
- Nickel-iron alloys: Mu-metal and permalloy are trade names for magnetic alloys used in electronics and industry. Mu-metal is generally 80% nickel, 15% iron, and small amounts of copper, molybdenum, etc. Permalloy contains 78-80% of nickel, and the rest contains iron and trace amounts of metals (PC type). These alloys have excellent magnetic shielding properties and are useful for transformer cores due to their low coercive force.
- Soft magnetic materials: Soft magnetic materials such as iron, cobalt, and nickel alloys have high magnetic permeability and are commonly used for magnetic shielding applications. These materials can be fabricated into various shapes, such as sheets or cylinders, and can be effective for shielding against low-frequency magnetic fields.
Generally, thicker materials with higher magnetic permeability and higher saturation flux density provide better magnetic shielding.
EMI shielding technology
Reflection
Reflection is a shielding technique that does not absorb radio waves but reflects them at an angle equal to the angle of incidence. This technology is commonly used to shield high frequencies and can be implemented using materials with high conductivity, such as copper or aluminum. The Faraday cage is a typical example of a reflection technique. However, it is important to consider when designing that electromagnetic waves reflected in unintended directions can cause new interference.
Absorption
Absorption is a technique that converts radio wave energy into another form, such as thermal energy or electrical current.
When the radiated electromagnetic wave meets an electromagnetic absorber, some of it is reflected, and most of it is transmitted. Radio waves of a certain frequency are converted into thermal energy in the absorber. The intensity of radio waves is weakened by the amount of energy converted in this way, and the material that plays this role is called a microwave absorber. Absorbers with this role include pyramid absorbers, ferrite tiles, ferrite rubber sheets, etc. When attached to the Faraday cage inside, they reduce diffused reflection of internal radio waves.
EMI shielding test and certification
Electromagnetic shielding regulations
To ensure the effectiveness of electromagnetic shielding, various standards have been established to guide the testing and certification of electromagnetic shielding materials and products. These standards allow the performance of different electromagnetic shielding materials and products to be evaluated and compared.
One such standard is the US military standard MIL-STD-285 for testing the shielding effectiveness of materials used in electronic enclosures. MIL-STD-285 specifies test procedures and measurement methods for evaluating the shielding effectiveness of materials over a range of frequencies. Another standard is IEEE Standard 299. It specifies test methods, measurement procedures, and data analysis techniques for evaluating the shielding effectiveness of enclosures over a range of frequencies.
In addition, various regulatory bodies such as the International Electrotechnical Commission (IEC), the US Federal Communications Commission (FCC), and the European Union (EU) have established regulations and standards for electromagnetic wave shielding for wireless communication and medical devices.
Testing and certification in accordance with electromagnetic shielding standards is critical to ensuring the safety, reliability and effectiveness of electromagnetic shielding materials and products.
EMI shielding test method
To ensure the effectiveness of electromagnetic shielding, various test methods have been developed to evaluate the shielding performance of materials and products. These test methods also include measuring the amount of electromagnetic waves that pass through a shielding material or product.
One commonly used test method is the shielding effectiveness test (SET), which measures the attenuation of electromagnetic field strength on a shielding material or product relative to the inside and outside. SET is performed by placing a shielding material or product between a noise source and an antenna (receiver) and measuring the electromagnetic field strength on both sides of the shielding material or product. The shielding effectiveness is then measured as the ratio of the electromagnetic field strength on the unshielded side to the field strength on the shielded side.
Testing and certification of electromagnetic shielding materials and products according to established standards and test methods are critical to ensuring the safety, reliability, and effectiveness of these materials and products in various applications. These test results provide useful information for product development and quality control and help customers make informed decisions when selecting electromagnetic shielding materials and products.
Certification and Compliance
Compliance with certified and established standards is an important aspect in the testing and certification of electromagnetic shielding materials and products. The purpose of certification is to ensure that materials and products meet established standards for electromagnetic shielding effectiveness and safety.
A number of national and international standards have been developed to regulate electromagnetic shielding materials and products for various applications. For example, the International Electrotechnical Commission (IEC) has developed standards for electromagnetic shielding materials and products used in electronic equipment and medical devices, and the American Society for Testing and Materials (ASTM) has developed standards for electromagnetic wave shielding used in aerospace, automotive, and military applications.
To comply with these standards and be certified, electromagnetic shielding materials and products must undergo strict testing according to established test methods. Independent certification bodies then evaluate the test results to determine whether materials and products meet established standards for electromagnetic shielding effectiveness and safety.
Certification and compliance with established standards not only ensure the safety and effectiveness of electromagnetic shielding materials and products but also help manufacturers gain the trust and confidence of their customers. Certification and compliance can also provide a competitive advantage in the marketplace by proving that a manufacturer's products meet the highest quality standards for electromagnetic shielding.
Conclusion
Electromagnetic shielding plays an important role in protecting electronic devices, equipment, and systems from the harmful effects of electromagnetic interference (EMI). EMI can cause failure, malfunction, or damage to electronic devices and systems, so shielding these systems is essential. Electromagnetic shielding is a key element of modern technology and will continue to grow in importance as electronic devices and systems become more pervasive in our daily lives.
The future of electromagnetic shielding
Here are some future trends that could shape how electromagnetic shielding is used.
One is the development of new materials that provide better shielding performance at higher frequencies. As electronic devices become smaller and more powerful, the need for materials capable of blocking high-frequency electromagnetic waves is growing. Researchers are exploring nanomaterials such as carbon nanotubes and graphene as potential solutions.
Another trend is the integration of electromagnetic shielding into the electronic device and system designs. Designers are considering shielding requirements early in the design process, rather than applying shielding as an afterthought. This allows for the development of more efficient and effective shielding solutions tailored to the specific requirements of a device or system. Semiconductor packaging using EMC techniques is already commercialized.
Additive manufacturing technologies such as 3D printing are also future trends in electromagnetic shielding. These technologies allow you to create complex geometries and incorporate multiple materials into a single part. This allows you to develop more efficient and effective shielding solutions tailored to the specific needs of your application.
Finally, the development of new testing and certification methods is a future trend in electromagnetic shielding. As new materials and technologies are developed, new test methods must be developed to ensure that these solutions meet established standards for electromagnetic shielding effectiveness and safety.
In conclusion, the need for effective electromagnetic shielding solutions will continue to grow as technology advances, such as the development of new materials, the integration of shielding technologies into the design process, and the development of new testing and certification methods.