The development of electromagnetic shielding technology has promoted the continuous development of the form of shielding materials, which is no longer limited to the single-layer metal plate mode, and the shielding effectiveness is also continuously improved. When using different shielding materials, it should be based on the shielding effectiveness and application of the materials.
1. Metal plate
The electronic equipment uses a metal flat panel as the chassis, which is both sturdy and durable, and has an electromagnetic shielding effect. Its electromagnetic shielding effectiveness is related to parameters such as the material properties of the metal plate, the properties of the electromagnetic field source, the distance between the electromagnetic field source and the metal plate, and the grounding condition of the shield.
2. Shielding film
Nowadays, many electronic devices use engineering plastics as the chassis. Due to the good processing performance of engineering plastics, the chassis is not only beautiful in appearance, but also low in cost and light in weight. However, engineering plastics have no electromagnetic protection properties. The shielding film is made by spraying, vacuum deposition, electroplating and pasting technology, covering a layer of conductive film on the surface of engineering plastics and organic media, thereby playing a flat shielding role. Generally, the thickness of the conductive film is less than 1/4 of the wavelength of electromagnetic waves propagating inside it.
The shielding of the meter head or the display can be realized by arranging a light-transmitting conductive material on the front of the meter head or the display. The light-transmitting conductive material is covered with a conductive film on the surface of the organic medium or glass to make it transmit light and have a certain shielding effect.
Three, metal wire mesh
When there is a need for ventilation, light transmission, water addition, measurement, etc., holes should be made on the equipment shell. In order to improve the electromagnetic shielding effect of the equipment, metal wire mesh holes should be used for shielding. Or used in the joints of electronic equipment shells to provide effective electromagnetic shielding. The shielding effectiveness SE (dB) of the holes is related to the frequency of electromagnetic waves, the size and number of the holes and other parameters.
In order to improve the shielding effectiveness of the holes, the following measures can be taken: cover the large-diameter holes with a metal wire mesh to make the wire mesh and the shielding contact well; change the large holes into small holes and adopt waveguide attenuator vents; The shielding glass with the metal wire mesh covering the hole is filled with a metal wire mesh containing rubber and other materials on the hole that needs to be sealed by water and air.