Industry new

Electromagnetic field shielding magnetic material

To determine what material should be used to make the shield, you need to know what the material's shielding effectiveness is and what the material is. According to the shielding mechanism, shielding can be divided into three categories: electric field shielding, magnetic field shielding and electromagnetic field shielding.
The electric field shielding is to reduce the coupling voltage of the disturbance electric field to the sensitive circuit. A conductive metal shield is disposed between the disturbance source and the sensitive circuit, and the metal shield is grounded. As long as the metal shield can be well grounded, the coupling voltage of the disturbance electric field to the sensitive circuit can be made very small. The electric field shielding is mainly based on reflection, so the thickness of the shielding body does not have to be too large, and a thin layer of shielding can be used or a thin conductive layer can be plated on the plastic.
Magnetic shielding has low frequency and high frequency. Low-frequency magnetic field shielding uses a material with high magnetic permeability to form a low-reluctance path, so that most of the magnetic field is concentrated in the shielding body. Therefore, the higher the magnetic permeability of the shield, the greater the thickness, the smaller the magnetic resistance, and the better the effect of magnetic shielding. When the magnetic field frequency is high, the magnetic permeability of the high permeability material decreases, and the magnetic loss increases. Instead, the turbulent magnetic field generated by the high conductivity material should be used to cancel out the disturbance magnetic field to achieve shielding. The shield used to shield the magnetic field does not need to be grounded.
Electromagnetic field shielding generally uses a highly conductive material as a shield and grounds the shield. It uses the reverse magnetic field of the eddy current generated by the high conductivity material to cancel out the harassment magnetic field, and the electric field shielding is realized because the shield body is grounded. As the frequency increases, the wavelength becomes close to the size of the aperture on the shield. Therefore, in addition to using high conductivity materials, the key to electromagnetic shielding is to control the leakage of the aperture of the shield.
The conductivity and magnetic permeability of the shielding material were measured by the relative conductivity σr and the relative permeability μr respectively. Table 1 lists the σr and μr values of commonly used shielding materials [1].
Thus, in order to improve the shielding effectiveness, high conductivity materials can be aluminum, copper, or aluminum copper plating, and when the requirements are higher, silver can be replated. High permeability materials can be made of stainless steel or iron, while the thickness of the material can be appropriately increased.

PREVIOUS：The Characteristics and Application of NormalNEXT：Electromagnetic stainless steel static, dynam