@One Meter Sunshine Hello, our company has profound experience in EMI Cable products. We are the end supplier of various unmanned aerial vehicle video transmission lines and mass-produce EMIproducts. The samples provided to customers, after comparison by the customers and the market, the EMI shielding effect of our company is extremely excellent. I will contact you later to provide you with samples.
Why is our EMI effect good?
Electromagnetic Compatibility (EMC) abbreviation, refers to that an electronic device neither interferes with other devices nor is affected by other devices. Electromagnetic compatibility, like the safety we are familiar with, is one of the most important indicators of product quality. Safety involves personal and property, while electromagnetic compatibility involves personal and environmental protection. Electromagnetic waves interact with electronic components, causing interference phenomena, known asEMI (Electromagnetic Interference). For example, the common "snowflakes" on TV screens indicate that the received signal is interfered. Shielding is the metallic isolation between two spatial regions to control the induction and radiation of electric fields, magnetic fields, and electromagnetic waves from one region to another. Specifically, it is to surround the interference sources of components, circuits, assemblies, cables or the entire system with a shielding body to prevent the interference electromagnetic field from spreading outward; surround the receiving circuits, equipment or systems with a shielding body to prevent them from being affected by external electromagnetic fields. Because the shielding body plays the role of absorbing energy (eddy current loss), reflecting energy (interface reflection of electromagnetic waves on the shielding body) and counteracting energy (reverse electromagnetic field generated on the shielding layer by electromagnetic induction, which can counteract part of the interference electromagnetic waves) for the external interference electromagnetic waves and internal electromagnetic waves, the shielding body has the function of weakening interference,
(1) When the frequency of the interfering electromagnetic field is high, the eddy current generated in the metal material with low resistivity is utilized to form a counteracting effect on the incoming electromagnetic wave, thereby achieving the shielding effect.
(2) When the frequency of the interfering electromagnetic wave is low, materials with high magnetic permeability should be used to limit the magnetic force lines within the shielding body and prevent them from diffusing to the shielded space.
(3) In some cases, if good shielding effects against both high-frequency and low-frequency electromagnetic fields are required, multi-layer shielding bodies composed of different metal materials are often used.
Many people do not understand the principle of electromagnetic shielding and think that as long as a metal box is made and then the box is grounded, it can play the role of electromagnetic shielding. Under the guidance of this concept, the result is failure. Because electromagnetic shielding has nothing to do with whether the shielding body is grounded or not. There are only two factors that truly affect the shielding effectiveness of the shielding body: One is that the entire surface of the shielding body must be electrically conductive and continuous, and the other is that there cannot be conductors that directly penetrate the shielding body. There are many electrically non-continuous points on the shielding body, and the most important type is the non-conductive gap formed at the junction of different parts of the shielding body. These non-conductive gaps cause electromagnetic leakage, just as fluid leaks from the gap on the container. One solution to this leakage is to fill the gap with conductive elastic material to eliminate the non-conductive points. This is like filling the gap of a fluid container with rubber. This elastic conductive filling material is the electromagnetic sealing gasket. In many literatures, the electromagnetic shielding body is compared to a liquid sealing container. It seems that only when the gap is sealed with conductive elastic material to the extent of no leakage of water can electromagnetic wave leakage be prevented. In fact, this is not accurate because whether the gap or hole leaks electromagnetic waves depends on the size of the gap or hole relative to the wavelength of the electromagnetic wave. When the wavelength is much longer than the opening size, there will be no obvious leakage of electromagnetic shielding mechanism.
a. When the electromagnetic wave reaches the surface of the shielding body, due to the impedance discontinuity at the interface between air and metal, reflection of the incident wave occurs. This reflection does not require the shielding material to have a certain thickness, only requires the discontinuity at the interface:
b. The energy that enters the shielding body without being reflected off the surface and propagates forward within the body is attenuated by the shielding material. That is, the so-called absorption;
C. The remaining energy that has not been attenuated within the shielding body, when reaching the other surface of the material and encountering the interface with impedance discontinuity of metal-air, will form a reflection again and return to the shielding body. This reflection may have multiple reflections at the interface of the two metals. In conclusion, the attenuation of the electromagnetic field by the electromagnetic shielding body is mainly based on the reflection and absorption of electromagnetic waves.
Nowadays, there are many national and international standards regarding the radiation and conducted emission limits of products. Some also stipulate the minimum sensitivity requirements for various interferences. Usually, there are different standards for different types of electronic devices. Although meeting these standards is necessary for a product to succeed in the market, compliance with these standards is voluntary. However, in some countries, what is provided are specifications rather than standards. Therefore, for selling products in these countries, compliance with the standards is mandatory. Some specifications not only stipulate the standards but also give the authorities the power to confiscate non-compliant products. Application scope 3C products such as laptops, GPS, ADSL and mobile phones will generate noise due to high-frequency electromagnetic wave interference, affecting communication quality. Moreover, if the human body is exposed to strong electromagnetic fields for a long time, it may be prone to cancerous lesions. Therefore, anti-electromagnetic interference is an essential and imperative process. Conductive paint, EMI conductive paint spraying technology has the characteristics of high conductivity, high electromagnetic shielding efficiency, and simple spraying operation (just like surface spray painting, only a thin layer of conductive paint needs to be sprayed inside the plastic shell), and is widely used in the EMI shielding of electronic equipment such as communication products (mobile phones), computers (laptops), portable electronic products, consumer electronics, network hardware (servers, etc.), medical instruments, household electronic products, aerospace and defense. It is suitable for shielding of various plastic products (PC, PC + ABS, ABS, etc.). Spraying conductive paint solves the limitations of space, operation and cost pressure caused by making metal shielding covers. Due to the extremely simple operation of conductive paint spraying, plastic metallization has received increasing attention and promotion. It has gradually replaced the previous processes of pasting tin foil, copper paper and making metal shielding covers.
Our products are executed strictly in accordance with the standard process from the beginning to the end. The inner mold of the product is externally covered with multiple shielding layers, evenly distributed braiding, circumferential welding on the shielding layer, and strictly sealed, with good effect. The disadvantage is that the scrap rate is much higher than that of ordinary products.
Why can the shielding layer shield electromagnetic waves??
Because
1. Electromagnetic waves are composed of changing electric fields and changing magnetic fields. Changing magnetic fields generate electric fields, and changing electric fields generate magnetic fields. Both are indispensable; otherwise, they cannot propagate
2. The material of the shielding layer is conductive metal. When the electric field in the air is formed around the metal mesh, due to the short-circuit effect of the conductive metal, the formation of the electric field is disrupted (ideally, the resistance of the conductive medium is zero, and the electric field is completely short-circuited and disappears).
3. Based on the above two points, when the electromagnetic wave reaches the shielding layer area, the electric field disappears and cannot continue to generate a magnetic field, thereby cutting off the continuous propagation of the electromagnetic wave
4. If the shielding layer is a closed system, the electromagnetic wave cannot enter the closed system, thus forming a shielding effect. If the shielding layer is not a closed system, due to the diffraction effect of the electromagnetic wave, some electromagnetic waves still bypass the metal mesh and enter. At this time, the shielding effect is very poor,
5. In fact, if the metal mesh is not grounded, when the electric field reaches this area, it can still form an electric field to the ground, forming a new electromagnetic wave. Therefore, when the shielding layer is grounded, the shielding effect is better
Look forward to in-depth communication with you. Thank you!
