In recent years, LED display production technology matures in our country, a wide range of applications and universal become a trend. However, at present, most LED display manufacturers are not yet fully equipped with the true ability to produce such products, thereby bringing hidden dangers to LED display products and even affecting the entire market. How to standardize production, how to produce a true sense of the low attenuation, long life LED display products? This article only from the perspective of the production of LED display ESD protection, discuss the dangers of the process of static electricity and its protection methods.
Static electricity causes:
From the microscopic point of view, according to the theory of atomic physics, when the material is neutral, the material is in the state of electrical balance, and due to the electronic gains and losses caused by the contact of different substances, the material loses the electrical balance and generates the electrostatic phenomenon.
From a macro point of view, the reasons are: friction between objects heat, stimulate electron transfer; contact and separation between objects to produce electron transfer; electromagnetic induction caused by the uneven distribution of surface charge; friction and electromagnetic induction of the combined effect.
Electrostatic voltage is generated by the contact and separation of different kinds of materials. This effect is known as triboelectric charging and the resulting voltage depends on the properties of the material itself that rub against each other. As the LED display in the actual production process is mainly the human body and related components in direct contact with indirect contact static electricity. So according to the characteristics of the industry we can do some targeted anti-static measures.
Static electricity in the LED display during the production of hazards:
If neglected in any aspect of the production of anti-static, it will cause the electronic equipment failure or even damage it.
When a semiconductor device is placed alone or into a circuit, permanent damage to these devices can be caused by static electricity even if power is not applied. It is well-known that LEDs are semiconductor products that can damage components if the voltage between two or more pins of the LED exceeds the breakdown strength of the component media. The thinner the oxide layer, the more sensitive the LED and the driver IC are to the static electricity. For example, the solder is not full, the quality of the solder itself is a problem, and so on, which causes a serious leakage path and causes destructive destruction.
Another failure is due to node temperature exceeds the melting point of semiconductor silicon (1415 ℃) caused. Electrostatic pulse energy can generate local heating, resulting in breakdown of the lamp and the IC directly. This failure can occur even if the voltage is lower than the breakdown voltage of the medium. A typical example is that LEDs are diodes made of PN junctions and the breakdown of the emitter and base causes the current gain to drop dramatically. The LEDs themselves or the various ICs in the driver circuit may not exhibit functional damage immediately after being affected by static electricity. The potentially damaged components are usually not shown during use, so the lifetime of the display is affected It is fatal.
Static electricity in LED production protection measures:
Ground is the direct discharge of static electricity through the wire connection to the earth, which is the most direct and effective anti-static measures, for the conductor is usually used in the grounding method, we require manual tools to ground, with anti-static wrist strap grounding, and work Table ground and so on.
(1) Workers are required to wear grounded electrostatic wristbands during production. Especially in the cut feet, plug-ins, commissioning and post-welding process, and be monitored, quality personnel must do at least once every two hours wrist bracelet static test, make a test record.
(2) When soldering, the electric iron should adopt anti-static low-voltage thermostat iron as much as possible and maintain good grounding.
(3) In the assembly process, as far as possible the use of a ground wire low-voltage DC electric screwdriver (commonly known as electric screwdriver).
(4) to ensure the production of pull table, filling stations, aging shelves and other effective grounding.
(5) We require the production environment to be laid copper grounding, such as floors, walls, and some occasions such as the use of ceilings, should use anti-static materials. Normally, even normal gypsum plasterboard and lime-coated wall surfaces are acceptable, but plastic ceilings and normal wallpaper or plastic wallpaper are forbidden.
Second, the laying of anti-static ground
(1) Lightning rods for building buildings are generally properly grounded to reinforced concrete buildings. When a lightning strike occurs, the grounding point and even the floor of the entire building will be the discharge point for high-voltage current. It is generally believed that there will be a "step voltage" in the range of 20M at the discharge grounding point, that is, it is no longer ideal zero potential within this range. In addition, zero-phase three-phase power supply because it is impossible to balance and there will be unbalanced current generated and flowed into the zero line grounding point, so the anti-static ground embedding point should be 20 meters away from buildings and equipment.
(2) Buried Method: In order to ensure the grounding is reliable, there should be at least three points of grounding, that is to dig a pit of 1.5m deep every 5m, and more than 2m of iron pipe or angle iron into the pit (that is, the angle iron should be inserted into the ground below 2m) , And then 3mm thick copper row welding these three together, with 16m2 insulated copper wire on the introduction of indoor wiring for the trunk.
(3) Put appropriate amount of charcoal powder and industrial salt in the pit to increase the conductivity of the soil. Measure the ground resistance after the landfill. The grounding resistance should be less than 4Ω and be tested at least once a year.
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