What is the structure of a blocking net?
Date:2025-12-03
The shielding mesh structure of LCD screens is not a single layer, but a "layered composite system" designed to achieve the best electromagnetic shielding effect. The core design concept is to construct a continuous, complete, and reliably grounded conductive enclosed space.
The following diagram systematically illustrates the layered composition, key materials, and electrical connection logic of this composite structure:
Detailed analysis of each layer structure
1. Basic shielding layer
This is the main body of the shielding system, directly covering the main electromagnetic radiation source.
Screen back panel shielding layer: usually a whole piece of aluminum foil or conductive cloth with conductive backing adhesive, tightly attached to the interior of the metal back panel of the LCD module. For scenarios with severe interference, customized tinplate shielding covers will be used.
Chip level shielding cover: On the driver board (T-Con board) or power chip, a common independent nickel steel alloy shielding cover is directly soldered onto the PCB, completely enclosing the high-frequency chip.
2. Interface and gap processing layer
This is the difficulty and key of shielding design, used to block "leakage points".
Cable interface wrapping: Use copper foil tape or open conductive cloth cover to tightly wrap the interface of LVDS/EDP flexible cable (FPC) and overlap it with the backplate shielding layer.
Frame gap filling: Use strip-shaped conductive foam or conductive rubber between the module frame and the device metal shell to ensure structural assembly tolerance and achieve conductive contact.
3. Auxiliary grounding and connection layer
This is the lifeline to ensure shielding effectiveness.
Grounding medium: At the contact point between the shielding layer and the equipment grounding point, use high compressibility conductive foam or beryllium copper alloy spring to ensure minimal resistance under screw fastening.
Electrical connection point: The shielding layer is ultimately crimped or soldered to the grounding wire (GND) of the equipment motherboard through the above-mentioned medium, forming a discharge path for static electricity and interference energy.
Core design points and misconceptions
1. Continuity priority: Each shielding material must be overlapped and overlapped to ensure that there are no gaps or breakpoints. A gap can lead to a significant decrease in shielding effectiveness.
2. Grounding is the soul: If the shielding layer is not connected to the system ground through a low impedance path, it is not only ineffective, but sometimes it can also become a radiating antenna, exacerbating interference.
3. Integrity requirement: During maintenance, no shielding material should be discarded or damaged at will. Even if the screen can display the missing information, it may still result in the failure of EMC testing or other functional abnormalities of the entire machine (such as touch failure, Wi Fi disconnection).
4. Material adaptability: It needs to be selected comprehensively based on interference frequency, installation space, and cost. Copper foil is commonly used for high-frequency interference, while aluminum foil is sufficient for low-frequency interference; Use ultra-thin conductive cloth for narrow spaces and thick foam for large gaps.
Simply put, the shielding mesh structure of a LCD screen is a precision system engineering that covers the "surface", blocks the "lines", and then grounds the "points", with the goal of building a complete "Faraday cage".
If you want to understand the specific form of shielding nets in specific devices (such as laptops, industrial displays), or typical fault phenomena after shielding failure, I can provide more specific case studies.
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