2024-01-20
Science LED lamp bead damage possible cause
Science LED lamp bead damage possible cause
Causes of LED dead lights
The causes of LED dead lights are nothing more than two situations: first, LED leakage current caused by large PN junction failure, so that the LED light is not bright, this situation generally does not affect the work of other LED lights;
Second, the internal connection lead of the LED lamp is disconnected, resulting in no current passing through the LED and a dead lamp, which will affect the normal operation of other LED lights, because the LED lamp working voltage is low (red yellow orange LED working voltage 1.8V-2.2V, blue green white LED working voltage 2.8-3.2V). Generally, it is necessary to use string and parallel connection to adapt to different working voltages, the more LED lights in series, the greater the impact, as long as there is an open internal connection of the LED light, the whole series of LED lights in the series circuit will not be bright, which is more serious than the first case.
Second, the internal connection lead of the LED lamp is disconnected, resulting in no current passing through the LED and a dead lamp, which will affect the normal operation of other LED lights, because the LED lamp working voltage is low (red yellow orange LED working voltage 1.8V-2.2V, blue green white LED working voltage 2.8-3.2V). Generally, it is necessary to use string and parallel connection to adapt to different working voltages, the more LED lights in series, the greater the impact, as long as there is an open internal connection of the LED light, the whole series of LED lights in the series circuit will not be bright, which is more serious than the first case.
Analyze and discuss the causes of LED dead lights
LED dead light is the key to affect product quality and reliability, how to reduce and eliminate dead light, improve product quality and reliability, is the key issue that packaging and application enterprises need to solve. The following is some analysis of the causes of dead lights.
1, electrostatic damage to the LED chip
Static electricity causes damage to the LED chip, makes the PN junction of the LED chip fail, the leakage current increases, and becomes a resistance Static electricity is a devil of great harm, and the world is countless electronic components damaged by static electricity, causing tens of millions of dollars in economic losses. Therefore, to prevent electrostatic damage to electronic components, is a very important work in the electronics industry, LED packaging, application enterprises must not be taken lightly. Any problem in any link will cause damage to the LED, so that the LED performance deteriorates or even fails. We know that the human body (ESD) static electricity can reach about three thousand volts, enough to breakdown and damage the LED chip, in the LED packaging production line, the grounding resistance of all kinds of equipment is in line with the requirements, which is also very important, the general requirements of the grounding resistance of 4 ohms, some high requirements of the grounding resistance even to reach ≤2 ohms. These requirements are familiar to people in the electronics industry, and the key is whether they are in place and documented when they are actually implemented.
It is understood that the general private enterprises, anti-static measures are not in place, which is that most companies can not find the grounding resistance test record, even if the grounding resistance test is once a year, or several years, or when there is a problem to check the grounding resistance, but do not know that the grounding resistance test is a very important work, at least 4 times a year (quarterly test), Some places with high requirements must be tested once a month for ground resistance. Soil resistance will vary with the change of seasons, spring and summer rain, soil wet ground resistance is easier to achieve, autumn and winter dry soil moisture is less, grounding resistance may exceed the specified value, record is to preserve the original data, so that the future can be checked. Comply with ISO2000 quality control system. Test ground resistance can design their own form, ground resistance test packaging enterprises, LED application enterprises are to do, as long as the name of the various equipment filled in the form, the grounding resistance of the equipment is measured and recorded, the test person can sign the disk.
The damage of human static electricity to LED is also very great, work should wear anti-static clothing, with electrostatic ring, electrostatic ring should be grounded well, there is a need to ground electrostatic ring anti-static effect is not good, it is recommended not to use this product, if the staff violate the operating procedures, you should accept the corresponding warning education, but also play a role in notifying others. The amount of static electricity in the human body is related to the different fabrics people wear, and the physique of each person, and it is easy to see the discharge phenomenon between clothes on the night of autumn and winter, and the voltage of this electrostatic discharge is three thousand volts.
The ESD value of the silicon carbide substrate chip is only 1100 volts, and the ESD value of the sapphire substrate chip is even lower, only 500-600 volts. A good chip or LED, if we use the hand to take (the body does not do any protective measures), the result can be imagined, the chip or LED will be damaged to different degrees, sometimes a good device through our hands inexplicably bad, this is the trouble caused by static electricity. Packaging enterprises if not strictly in accordance with the grounding regulations, the loss is the enterprise itself, will cause the product pass rate to decline, reduce the economic benefits of the enterprise, the same application of LED if the equipment and personnel grounding will also cause LED damage, rework is inevitable. According to the requirements of the LED standard user manual, the lead distance of the LED colloid should be no less than 3-5 mm, for bending feet or welding, but most application companies do not do this, but only separated by the thickness of a PCB board (≤2 mm) directly welded, which will also cause damage or damage to the LED, because too high welding temperature will have an impact on the chip. Will make the chip characteristics bad, reduce the luminous efficiency, and even damage the LED, this phenomenon is not uncommon. Some small businesses use manual welding, the use of 40 watts of ordinary soldering iron, welding temperature can not be controlled, soldering iron temperature above 300-400 ° C, too high welding temperature will also cause dead lights, LED lead at high temperature expansion coefficient is several times higher than the expansion coefficient of about 150 ° C, the internal gold wire solder will be due to excessive thermal expansion and contraction of the welding point will be pulled apart, Cause dead lamp phenomenon.
It is understood that the general private enterprises, anti-static measures are not in place, which is that most companies can not find the grounding resistance test record, even if the grounding resistance test is once a year, or several years, or when there is a problem to check the grounding resistance, but do not know that the grounding resistance test is a very important work, at least 4 times a year (quarterly test), Some places with high requirements must be tested once a month for ground resistance. Soil resistance will vary with the change of seasons, spring and summer rain, soil wet ground resistance is easier to achieve, autumn and winter dry soil moisture is less, grounding resistance may exceed the specified value, record is to preserve the original data, so that the future can be checked. Comply with ISO2000 quality control system. Test ground resistance can design their own form, ground resistance test packaging enterprises, LED application enterprises are to do, as long as the name of the various equipment filled in the form, the grounding resistance of the equipment is measured and recorded, the test person can sign the disk.
The damage of human static electricity to LED is also very great, work should wear anti-static clothing, with electrostatic ring, electrostatic ring should be grounded well, there is a need to ground electrostatic ring anti-static effect is not good, it is recommended not to use this product, if the staff violate the operating procedures, you should accept the corresponding warning education, but also play a role in notifying others. The amount of static electricity in the human body is related to the different fabrics people wear, and the physique of each person, and it is easy to see the discharge phenomenon between clothes on the night of autumn and winter, and the voltage of this electrostatic discharge is three thousand volts.
The ESD value of the silicon carbide substrate chip is only 1100 volts, and the ESD value of the sapphire substrate chip is even lower, only 500-600 volts. A good chip or LED, if we use the hand to take (the body does not do any protective measures), the result can be imagined, the chip or LED will be damaged to different degrees, sometimes a good device through our hands inexplicably bad, this is the trouble caused by static electricity. Packaging enterprises if not strictly in accordance with the grounding regulations, the loss is the enterprise itself, will cause the product pass rate to decline, reduce the economic benefits of the enterprise, the same application of LED if the equipment and personnel grounding will also cause LED damage, rework is inevitable. According to the requirements of the LED standard user manual, the lead distance of the LED colloid should be no less than 3-5 mm, for bending feet or welding, but most application companies do not do this, but only separated by the thickness of a PCB board (≤2 mm) directly welded, which will also cause damage or damage to the LED, because too high welding temperature will have an impact on the chip. Will make the chip characteristics bad, reduce the luminous efficiency, and even damage the LED, this phenomenon is not uncommon. Some small businesses use manual welding, the use of 40 watts of ordinary soldering iron, welding temperature can not be controlled, soldering iron temperature above 300-400 ° C, too high welding temperature will also cause dead lights, LED lead at high temperature expansion coefficient is several times higher than the expansion coefficient of about 150 ° C, the internal gold wire solder will be due to excessive thermal expansion and contraction of the welding point will be pulled apart, Cause dead lamp phenomenon.
