How to prevent LED large screen dead light phenomenon
We often encounter LED display is not bright, the packaging business, application enterprises and the use of units and individuals, are likely to encounter, this is the industry that the phenomenon of dead lights. And LED large-screen dead lights and static electricity has a close relationship, perhaps you should seriously understand some.
What is the LED dead light is going on?
A: LED leakage current is too large cause PN junction failure, so that LED lights do not light, this situation generally does not affect the work of other LED lights;
2: LED lights connected to the internal lead disconnect, resulting in LED current through the dead lamp, this situation will affect the normal operation of other LED lights.
The reason is because the LED lamp operating voltage is low (red orange orange LED voltage 1.8V-2.2V, blue and green LED operating voltage 2.8-3.2V), generally have to use string, parallel to connect to adapt to different operating voltage, The greater the impact of the LED lights in series.
As long as there is a LED light inside the internal wiring open, will cause the series circuit of the whole string of LED lights do not shine, showing that this situation is more serious than the first case.
Static as LED dead light stealth killer
Electrostatic damage to the LED chip, the LED chip PN junction failure, leakage current increases, into a resistance.
Static electricity is a great harm to the devil, the world because of static electricity damage to countless electronic components, resulting in tens of millions of dollars in economic losses.
So to prevent static damage to electronic components, the electronics industry is a very important work, LED packaging, the application of enterprises do not take it lightly.
Any part of the problem, will cause damage to the LED, LED performance deterioration or even failure.
We know that the human body (ESD) static can reach about three thousand volts, enough to break the LED chip damage in the LED packaging production line, all kinds of equipment grounding resistance is in line with the requirements, which is very important, generally require grounding resistance of 4 Ohm, some demanding high ground resistance even to achieve ≤ 2 ohms.
These requirements are familiar to the people of the electronics industry, whether the key is in place in the actual implementation, whether there is a record.
General private enterprises, anti-static measures are not in place, which is the majority of enterprises can not find the grounding resistance test records, even if the grounding resistance test is once a year, or once a year, or when the problem check Grounding resistance, do not know the grounding resistance test This is a very important work, at least 4 times a year (quarterly test once), some demanding places, every month to make a grounding resistance test.
Soil resistance will vary with the seasons, spring and summer rain, soil wet grounding resistance easier to achieve, autumn and winter dry soil moisture, grounding resistance may exceed the specified value, for the record is to save the original data, do To be informed in the future.
Conform to ISO2000 quality management system. Test grounding resistance can design their own form, grounding resistance test packaging enterprises, LED application companies have to do, as long as the various equipment name to fill in the form, measured the grounding resistance of the equipment recorded, test people can be signed signature.
The human body static damage to the LED is also great, work should wear anti-static clothing, with static ring, static ring should be well grounded, there is no need to ground the static ring static effect is not good, it is recommended not to use with The kind of product, if the staff in violation of operating procedures, should receive the appropriate warning education, but also play a role in informing others.
How much of the body with static electricity, and people wear different fabric clothes, and their physical fitness, autumn and winter night we underestimate the clothes is easy to see the discharge between the phenomenon, this electrostatic discharge voltage there are three thousand volts.
While the silicon carbide substrate chip ESD value of only 1100 volts, sapphire substrate chip ESD value is even lower, only 500-600 volts.
A good chip or LED, if we get by hand (the body did not make any protective measures), the results can be imagined, the chip or LED will be subject to varying degrees of damage, and sometimes a good device through our hands On the inexplicable bad, this is the accident caused by static electricity.
If the enterprise does not strictly follow the grounding procedures, the loss of the enterprise itself, will result in product qualification rate decline, reduce the economic efficiency of enterprises, the same application of LED enterprises if the equipment and personnel grounding will cause damage to the LED, rework It is inevitable.
In accordance with the requirements of the LED standard manual, LED lead from the colloid should be no less than 3-5 mm, bending or welding, but most of the application companies have not done this, but only separated by a PCB thickness (≤ 2 Mm) on the direct welding, which will cause damage to the LED or damage, because the high welding temperature will have an impact on the chip, will make the chip characteristics deteriorate, reduce the luminous efficiency, and even damage the LED, this phenomenon is not uncommon.
Some small businesses using manual welding, the use of 40-watt ordinary soldering iron, welding temperature can not control the soldering iron temperature above 300-400 ℃, too high welding temperature will cause dead lights, LED lead at high temperature expansion coefficient at about 150 ℃ The expansion coefficient of several times higher, the internal gold solder joints will be too large because of the thermal expansion and contraction will be opened, resulting in the phenomenon of dead lights.