About LED electrostatic protection

    In recent years, the production technology of LED display screen is becoming mature in China, and the application field is becoming widespread and popular. However, at present, most LED display screen manufacturers are not fully equipped to produce such products, which brings hidden dangers to LED display screen products and even affects the entire market. How to standardize production, and how to produce LED display products with low attenuation and long life in the real sense? This paper discusses the harm and protection methods of static electricity in the production process of LED display screen from the perspective of static electricity protection.

    From the microscopic point of view, according to the theory of atomic physics, the matter is in the state of electric balance when it is electrically neutral. The gain and loss of electrons generated by the contact of different substances and electrons will cause the matter to lose its electric balance and generate electrostatic phenomena. On the macro level, the reasons are as follows: friction between objects generates heat and excites electron transfer; Contact and separation between objects produce electron transfer; The unbalanced distribution of surface charge caused by electromagnetic induction; The combined effect of friction and electromagnetic induction.

     Electrostatic voltage is generated by the contact and separation of different kinds of substances. This effect is known as friction electrification, and the voltage generated depends on the characteristics of the materials that rub against each other. In the actual production process of LED display screen, static electricity is mainly generated by direct contact and indirect contact between human body and relevant components. Therefore, according to the characteristics of the industry, we can take some targeted electrostatic prevention measures.

    If anti-static is ignored in any link of production, it will cause electronic equipment failure or even damage.

     When semiconductor devices are placed separately or installed in the circuit, even if they are not powered on, static electricity may cause permanent damage to these devices. As we all know, LED is a semiconductor product. If the voltage between two or more pins of LED exceeds the breakdown strength of the component medium, the component will be damaged. The thinner the oxide layer, the greater the sensitivity of LED and drive IC to static electricity. For example, the solder is not full, the solder itself has quality problems, and so on, which will cause serious leakage path, thus causing destructive damage.

    Another fault is caused when the temperature of the node exceeds the melting point of semiconductor silicon (1415 ℃). The pulse energy of static electricity can generate local heat, so the failure of directly breakdown the lamp tube and IC occurs. This fault occurs even if the voltage is lower than the breakdown voltage of the medium. A typical example is that LED is a diode composed of PN junction. The breakdown between the emitter and the base will sharply reduce the current gain. After the LED itself or the IC in the drive circuit are affected by static electricity, functional damage may not occur immediately. These potentially damaged components are usually shown during use, so the impact on the life of the display screen is fatal.

    Grounding is to directly discharge static electricity to the ground through wire connection, which is the most direct and effective anti-static measures. For conductors, the grounding method is usually used. We require the grounding of manually used tools, anti-static bracelets with grounding, and the grounding of worktable.

    (1) During production, workers are required to wear grounding electrostatic bracelet. Especially in the process of leg cutting, plug-in, debugging and post-welding, the quality personnel must conduct the static test of the bracelet at least once every two hours and keep the test record.

    (2) During welding, the electric soldering iron should be anti-static low-voltage thermostatic soldering iron as far as possible, and maintain good grounding.

    (3) During assembly, use low-voltage DC electric screwdriver (commonly known as electric screwdriver) with grounding wire as much as possible.

    (4) Ensure that the production pulling platform, rubber filling platform and aging rack are effectively grounded.

    (5) We require that the production environment should be grounded with copper wires, such as floors, walls, and ceilings used in some occasions. Anti-static materials should be used. Generally, even ordinary plasterboard and lime paint walls can be used, but it is prohibited to use plastic ceiling and ordinary wallpaper or plastic wallpaper.

    (1) The lightning rod of the plant building is generally welded with the reinforced concrete of the building and properly grounded. When a lightning strike occurs, the grounding point and even the ground of the whole building will become the discharge point of high voltage and strong current. It is generally believed that there will be "step voltage" within 20M of the discharge grounding point, that is, it is no longer an ideal zero potential within this range. In addition, because the zero line of three-phase power supply cannot be absolutely balanced, there will also be unbalanced current generated and flowing into the grounding point of the zero line, so the embedding point of anti-static ground wire should be 20 meters away from the building and equipment ground.

    (2) Embedding method: In order to ensure the reliability of grounding, at least three points should be grounded, that is, the pit with a depth of more than 1.5m should be dug every 5m, the iron pipe or angle iron with a depth of more than 2m should be driven into the pit (that is, the angle iron should be inserted more than 2m underground), and then the three points should be welded together with a 3mm thick copper bar, and the 16m2 insulated copper core wire should be welded to the indoor main line.

    (3) Apply appropriate amount of charcoal powder and industrial salt in the pit to increase the soil conductivity. After landfilling, measure the grounding resistance with a grounding resistance tester. The grounding resistance should be less than 4 Ω, and it should be tested at least once a year.