We often encounter the situation is not bright LED, packaging enterprises, the use of enterprises and the use of units and individuals, are likely to encounter, this is the industry said the dead lights phenomenon. The reason is nothing more than two cases:
First, the LED leakage caused by large leakage of PN junction failure, so that the LED lamp is not lit, this situation will not affect the work of other LED lights;
Second, the internal connection wire of LED lights off, causing LED caused death no current through the lamp, this will affect the normal work of other LED lamp, LED lamp is due to low working voltage (red and yellow orange LED working voltage of 1.8V - 2.2V, blue green and white LED voltage of 2.8 - 3.2V), general are used in series and parallel to join, to adapt to different working voltage, LED lamp series the more the greater the impact, as long as there is a LED lamp inside line open, will cause the whole series of LED series circuit of the lamp is not lit, the situation is more serious than the first case.
LED dead light is the impact of product quality, reliability of Guan Jian, how to reduce and eliminate dead lights, improve product quality and reliability, packaging, application companies need to address the key issues. Here are some of the reasons for the death of light to do some analysis,
1 electrostatic damage to the LED chip, so that the LED chip PN junction failure, leakage current increases, into a resistor
Static electricity is a great harm to the devil, the world because of the number of static damage to electronic components, resulting in tens of millions of dollars in economic losses. Therefore, to prevent static damage to electronic components, is a very important work in the electronics industry, LED packaging, application companies do not take lightly. Any link problems, will cause damage to the LED, so that LED performance deterioration or even failure. We know that the human body electrostatic (ESD) can reach about three thousand volts, enough LED chip breakdown, in LED packaging production line, all kinds of the grounding resistance of the equipment meets the requirements, it is also very important, general requirements for the grounding resistance of 4 ohms, and some demanding occasions even to the grounding resistance reach less than or equal to 2 ohms.
These requirements are familiar to the electronics industry, Guan Jian is in the actual implementation is in place, whether there is a record. According to the general understanding of private enterprises, anti-static measures do not place, this is the majority of enterprises can not find the test record of grounding resistance, even if the ground resistance test is once a year, or a few times a year, or when there is a problem to check the grounding resistance, grounding is not known the resistance test is a very important work, at least 4 times a year (every quarter of a test), some of the requirements of high places, per month to make a ground resistance test.
The soil resistance changes with the seasons of spring, summer rain, soil moisture and ground resistance is easy to reach, the autumn and winter dry soil less water, the grounding resistance is likely to exceed the prescribed value, the record is in order to preserve the original data, do the days after the well documented. Comply with ISO2000 quality management system. The test of grounding resistance can design form, grounding resistance test, LED application package business enterprises have to do, as long as the various device name fill in the form, measure the equipment grounding resistance test record, signature can be archived.
Damage to the LED human body is great, work should wear anti-static clothing, with electrostatic ring, electrostatic ring should be well grounded, there is a need of electrostatic grounding ring anti-static effect is not good, it is recommended not to use with this product, if the staff in violation of the rules, it should be accept the corresponding warning education, but also to notice others' effect. The human body electrostatic, different fabric clothing and each with people wearing the physique, autumn and winter night we take off our clothes is very easy to see the discharge phenomenon between the clothes, the voltage is three thousand volts electrostatic discharge.
The silicon carbide substrate chip ESD value of only 1100 volts, sapphire substrate chip ESD value is lower, only 500 - 600 volts. A good chip or LED, if we use the hand to take (the body without any protective measures), the result of the chip or LED as can be imagined, will be subject to different degrees of damage, sometimes a good device through our hand is rather baffling bad, this is the electrostatic blame.
The package if the enterprises do not strictly according to the grounding procedures, at the expense of the enterprise itself, will cause the qualified rate of products decreased, reducing the economic benefits of the enterprise, the same enterprise application of LED equipment and personnel if bad grounding would cause damage for LED rework can hardly be avoided. The manual in accordance with the LED standards, LED lead from the gel should be not less than 3 - 5 mm, by bending or welding, but most companies do not have to do this, but just a piece of PCB plate thickness (less than 2 mm) is directly welded, it may cause damage or damage to LED, because of the high temperature will affect the chip will make the chip characteristics worse, low luminous efficiency, even damage the LED, this phenomenon It is often seen. Some small enterprises adopt manual welding, using 40 Watt ordinary iron, welding temperature control, soldering temperature was above 300 and 400 C, the high temperature welding will cause death lamp, LED lead coefficient ratio at about 150 DEG C. the expansion coefficient of several times higher in high temperature, the internal wire joint because the expansion and contraction of the welding point opened, causing death light phenomenon.
Analysis of the cause of dead light phenomenon in the open circuit of 2.LED lamp
2.1 packaging enterprise production process is not