Computer motherboard shielding cover, how to choose magnetic shielding materials according to different performance + 15 years of experience

Xiaoshuo, who is responsible for the production of hardware for computer motherboard shields, said that there are three types of magnetic shielding: magnetostatic shielding, low-frequency electromagnetic shielding, and high-frequency electromagnetic shielding. In terms of production and practicality, different shielding materials are selected according to different situations. Let's take a look at the specific selection of materials: Magnetostatic shielding: In order to concentrate the stray magnetic field on the shield shell, the shield should have as high a permeability as possible. All soft magnetic materials with high magnetic permeability, such as electromagnetic pure iron, ductile iron, permalloy, silicon steel, soft ferrite, etc., can be used in principle. The design should be selected according to the requirements of the magnetic screen, price, shell strength, processing performance, etc., after comprehensive consideration. Low-frequency electromagnetic shielding: In addition to shielding static magnetism, it also needs to shield changing electromagnetic fields. Such as power frequency electromagnetic field. In addition to requiring high magnetic permeability, high electrical conductivity is also required. The ideal material is Permalloy. Considering the price and processing factors, electromagnetic pure iron is suitable for the large shielding cover. When the nickel content of permalloy is higher than 40%, the magnetic permeability and electrical conductivity are very good. In addition, iron-aluminum alloys containing 15% to 16% aluminum are also commonly used magnetic screen materials. High-frequency electromagnetic shielding: To shield electromagnetic waves as the main purpose, the principle of shielding is Lenz's law. The induced electromagnetic field in the shielding case is used to offset the external electromagnetic interference. Good conductors should be used to make the shielding case, such as aluminum and copper. Material selection requirements during production: The material of the shielding cover is generally 0.2mm thick stainless steel and nickel silver as materials, among which nickel silver is a kind of metal shielding material that is easy to be tinned. The design of the suction cup should be considered when using SMT patches. The shielding frame generally adopts Cu-C7521-H [general material], Cu-C7521-OH [soft material, for deep drawing] (nickel-nickel-nickel-nickel-zinc alloy (Copper-Nickel-ZincAlloy), Nickel Silver), tu003d0.2, 0.3mm ; The shielding cover is generally made of stainless steel SUS304R-1/2H [bending processing], SUS304R-1/4H [for deep drawing], tu003d0.15, 0.2mm, tin-plated steel strip (tinplate), etc.; used for welding on PCB The nickel silver and tinplate can be used for the above, and it is recommended to use nickel silver. This is mainly because the nickel silver is better in terms of welding, heat dissipation and steam. Tips for use: The tray where the shielding cover is placed has too much active space, and it is easy to swing during patching, resulting in failure to pick up. The material must be placed in the tray. There is about 1.0mm of moving space. If it is too large, it will cause the material to swing, and the material is too small to take the material. It may not be available. The size of the reclaiming point of the shielding cover should be appropriate. The reclaiming point should be in the middle of the material as much as possible. The size of the reclaiming point is preferably Φ6.0mm. The larger the reclaiming point, the higher the stability of the patch and the higher the efficiency. Hardware, 15 years of computer motherboard shielding, 20,000+ sets of customized stamping die production experience, monthly 100+ sets of mold processing capacity, hundreds of precision processing production equipment, daily production capacity of 3 million punches, silk-like stamping accuracy up to 0.01mm , The raw materials are imported and the original national standard factory, and 16 quality inspections are strictly controlled.