Wednesday, December 29, 2010

【 Weak current College 】 led display production process of electrostatic protection 】

In recent years, led display production technology in China is becoming a mature, widely spread in the area of application and become a trend. But most of the led display manufacturer is not fully equipped with the production of these products really capabilities to led display products brings risks, as well as the impact on the entire market. How standardized production, how to produce a truly low attenuation, long-life led display products? this article only from led display production process of electrostatic protection perspective, discusses the process of electrostatic harm and protection methods.
Static electricity causes:
From microscopic, according to atomic physics theory, electrically neutral substance in electrical balance status, due to the different material e contact produces electronic material, so that the loss of balance, generate static electricity.
From a macro sense, reason: body heat, friction between excited electron transfer; objects between contact and the electronic transfer; separation of electromagnetic induction caused surface charge distribution of imbalances; friction and synthetic effects of electromagnetic induction.
Voltage is determined by the different types of material touching and separation. This effect is well-known friction electrification, the voltage depends on the frictional characteristics of the material itself. Because of the led screen in the actual production process is the human body and the related components of direct contact and indirect contact generate static. So according to the characteristics of the industry we can do some targeted electrostatic prevention measures.
Electrostatic in led display production hazards
If any of the links in the production of static-free neglect, it will cause electronic equipment failure or even make them damage.
When the Microsemi place or mount circuit separately, even without power, due to static electricity can also cause permanent damage to these devices. Familiar, LED is the semiconductor product, if LED by two pins or more pins than a component of the voltage between the media of the breakdown strength, will damage the components. More thin oxide layer, the LED and driven IC on the sensitivity of, for example, solder, solder of quality problems, and so on, would have severe leakage path, resulting in devastating destruction.
Another failure is due to the node's temperature exceeds the melting point of semiconductor Silicon (1415 ℃). Static pulse energy can produce localised heating, direct breakdown lamp and IC. Even if the voltage is lower than the medium's breakdown voltage, also happens to fail. A typical example is the LED is composed of a pn junction diode, the emitter and base of breakdown makes current gain dramatically. LED itself or the driver circuit in electrostatic IC is in, or may not immediately appear functional damage to those affected by the potential damage of the element is typically used in the process will be demonstrated, on the display of life are fatal.
Static led production of protective measures
1. grounding
Grounding is directly connected via the electrostatic discharge wire to the Earth, this is the most antistatic measures directly the most effective, the conductor is usually used to ground, we require artificial use tool grounding, grounding antistatic bracelets and work table surface to ground.
(1) in the production process, require workers must wear a grounded antistatic bracelets. Especially in the cut feet, plug-ins, debugging, and after welding process, and for monitoring, quality personnel must be at least every two hours to do a hand ring static testing, test records.
(2) in the welding, soldering should, whenever possible, use low temperature soldering iron and anti-static, and maintain a good grounding.
(3) in the Assembly process, where possible, use a grounding line of low-voltage direct-current electric screwdriver (commonly known as electric group).
(4) to ensure that production La terrace, gluing, aging aircraft effective grounding.
(5) we call production environment to do layout copper grounding, such as floors, walls, and ceilings for certain occasions, should use anti-static material. Generally, even if common plasterboard and lime coating walls can also be, but the prohibition of the use of plastic ceiling and wall paper or plastic wallpaper.
Antistatic ground burial:
(1) building of the lightning rod General and buildings reinforced concrete welded together properly grounded, when lightning occurs, take place and the whole surface of the building will become a high current of discharge points. General considers that the relief grounding 20M scope there will be "stepped voltage", that is, in this context is no longer an ideal zero potential. In addition, three-phase power supply of the zero line as impossible absolute balance will have unbalanced currents generated and flows into the zero line by location, so the anti-static grounding wire installation point from the buildings and equipment and 20 metres away.
(2) laying method: in order to guarantee reliable grounding, caused by the least point above ground, that is, every 5m digging deep pit above 1.5m will 2m above an iron or iron bar into the pit (i.e. the angle steel insert underground 2m above), then use 3mm thick copper will this three welded together, with 16 m2 insulated copper wire welding laboratory for trunk on introduction.
(3) impose proper charcoal pits powder and industrial salt, in order to increase the conductivity of the soil, landfill after Earth resistance testers, grounding resistance should be less than 4 Ω, and testing at least once.
The second component of stockpiling .LED display handling
Electrostatic sensitive components in storage and during transport will be exposed to a static area, use the static method can weaken the external effects of static electricity on electronic components, the most common method is to use electrostatic shielding bags and anti-static plastic box for protection. Also anti-static clothing on the body's electrostatic shielding effect with certain.
So we called turnover handling process, workers must wear gloves, cordless, anti-static and wear anti-static clothing, and anti-static shoes and so on, should use anti-static material box, PCB anti-static material rack, stainless steel and other specialized equipment transporting cart, try to avoid working in direct contact with the human body.
To illustrate: as anti-static clothing, special synthetic fibers woven into the fabric, under normal circumstances no rubbing friction generate static. but it is not a static screenShort suits, it cannot eliminate them other material produced by electrostatic. it should be properly dressed inside only a shirt or underwear, wearing anti-static clothing-winter wear more of chemical fiber, hair, clothing, and other such wear anti-static clothing to no great use.
Therefore, in the storage and handling procedures, shall control the ambient temperature and humidity, wear antistatic bracelets, proper wear static clothing-raise staff awareness of antistatic. Do hands and product "insulation," prevent sweat contamination of products, is very necessary.
3. Regulation of temperature and relative humidity
SMT electronic job especially for temperature and humidity are high demands, General temperature control in 18 ~ 28 ° c, is too high or too low will affect the normal operation of equipment and precision; relative humidity should be 50% ~ 85%, too low then the prone to static electricity, the excessive condensation device easy to paste water increases, so should strengthen its monitoring and control, anti-static, autumn and winter when the relative humidity is low, free humidifier or wet resolved butuo manner.
IV. monitoring and recording
Antistatic measures have to be responsible for implementation and formation system, and do the implementation work, otherwise all hardware facilities of inputs may no practical effect.
(1) personnel: by two common management, test, document, in most cases require two people to meet, and to prevent the movement of persons for the discontinued.
(2) tests and record: done every day, electrostatic protection work should complete the following tests and record:
A. electrostatic test point---electrostatic field.
B. electric iron head grounding and soldering iron tip temperature measurement.
C. small Tin stove grounding and Tin oven temperature measurement.
D. testing equipment grounding measurement.
E. electrostatic hand ring earthing test.
F. indoor temperature, relative humidity measurement and regulation.
(3) check the workspace staff dress and anti-static requirements for implementation.
(4) the conditions under which should be in the factory and the Assembly line with electrostatic Tester measuring conditions under voltage, the voltage should generally be less than 100V, special circumstances should be less than 25V.
V. training and literacy
Should be anti-static knowledge, measures for staff training, let everyone get if we cannot get to raise staff awareness of anti-static, executed from top to bottom, anti-static requirements to form a good habit. Example: to enter the shop you are replacing an anti-static clothing, wear antistatic shoes, required wear antistatic ring and gloves to contact components, holding PCB or sensitive devices to hold edge, avoid contact with their leader and lug, consciously abide by and implement anti-static system and provisions.
In fact, anti-static should be to prevent and suppress static charge build-up of production, and rapid, safe, and effective elimination of electrostatic charge as a basic principle. But many measures against static electricity for a set of system engineering, a link of omissions may occur "thousand Bank collapse-nest", cautious.
Led display monitor's manufacturing process is avery precise and subtle process, every link must not be overlooked. Led display monitor's electrostatic protection work is led display important link of the production, the industry's understanding of the electrostatic protection is still not sufficiently deep, much less meet the professional needs of led panel production, but also require more professionals continue to study, discuss.

No comments:

Post a Comment