Industry news

2016August

A comprehensive interpretation of the reasons for the natural damage of LED ligh

From: www.szbako.com Data:08/08/2016

from the point of view that causes necrosis of the LED bulb is nothing less than the following two types:
, LED leakage current caused by the failure of the LED PN junction lights, is not bright, this situation generally does not affect the other LED lights work;
second, the internal connection wire of LED lights off, cause LED has no current through the dead lights, this situation 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 working voltage 2.8-3.2V), usually used in series and parallel to join, to adapt to different operating voltages. LED lamp series 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 and application of enterprises need to solve the key issues. The following are some of the reasons for the death of a number of reasons for the analysis of. Next detailed interpretation:
1, static on the LED chip damage, make LED chip of PN junction failure, leakage current increases, become a resistor electrostatic harm is great, the world because of the numerous electrostatic damage electronic components, resulting in several tens of millions of dollars in economic losses. So to prevent electrostatic damage to electronic components, electronic industry, an important work, LED packaging and application of enterprises must not be taken lightly. Any link out of the problem, will cause damage to the LED, so that the performance of LED worse or even failure. We know that human body static (ESD) can reach 3000 volts or so, can be led chip breakdown, in LED packaging production line, the equipment of various types of ground resistance whether it meets the requirements, this is also very important, the general requirements for the grounding resistance is a 4 ohm, and some demanding the grounding resistance even to reach less than or equal to 2 ohm. These requirements are familiar to people in the electronics industry, Guan Jian is in the actual implementation is in place, whether there is a record. According to general understanding of private enterprises, anti electrostatic measures do not place, this is the majority of enterprises do not check to ground resistance test records, even to do contact resistance test is also a year a, or a few years, or a problem with the check grounding resistance, not knowing the ground resistance test which is a very important work, at least four times a year (testing every quarter), where some of the requirements of high per month to grounding resistance test for. Soil resistance with the change of seasons and different, spring and summer rain, soil wetting contact resistance is easy to reach, autumn and winter dry soil moisture less, grounding resistance is probably exceeds a specified value, record is to preserve the original data, do well documented in the future. ISO2000 quality control system. Testing and measurement of grounding resistance can be designed table, ground resistance test packaging companies, led enterprise application to do, as long as the name of various equipment fill in this form in measured the equipment grounding resistance documented test signature can save. Human body electrostatic damage to the LED is also great, work should wear anti electrostatic clothing, equipped with electrostatic ring, good electrostatic ring should be grounded, a don't need grounding electrostatic ring anti electrostatic effect is not good, not recommended for use with the kinds of products, if the staff in violation of the operating rules, accept the respective warning education, as well as to notice of others. Human body electrostatic, and people wear different clothes, fabrics, and every man's physique, autumn and winter night we undressed it was easy to see discharge phenomenon between the clothes, the electrostatic discharge voltage have 3000 volts. The silicon carbide substrate chip ESD value of only 1100 volts, sapphire substrate chip ESD value is lower, only 500-600 volts. A good chips, or LED, if we use hand to take (a body without any protective measures), the result it can be imagined, LED chips, or will be subject to varying degrees of damage, sometimes a good device through our hands on the inexplicable bad, this is electrostatic provoked disaster. Packaging companies if not strictly on the ground rules for work, the loss is their own business will cause products pass rate of decline, reduce the economic efficiency of enterprises, the same application of led enterprises if equipment and personnel bad grounding will cause such damage, rework is unavoidable. In accordance with such standards manual requirements that lead led from the gel should be not less than 5 mm, to kink or welding, but most enterprise applications do not this, and only separated by a piece of PCB board thickness (less than or equal to 2 mm) is directly welded, which will cause damage or damage to the LED, because of the high welding temperature will have an impact on the chip, and will become bad chip characteristics, reduce the luminous efficiency, even damage the LED. This phenomenon not uncommon. Some small businesses to use manual welding, using a 40 Watt ordinary iron, beyond the control of welding temperature, solder iron temperature in more than 300 to 400 DEG C, high welding temperature will cause dead lights, LED lead at high temperature expansion coefficient than in about 150 DEG C expansion coefficient high several times, the internal wire solder joints will because of thermal expansion and contraction welding point opened, resulting in dead lights phenomenon.
2, LED lamp inside line to analyze the causes of death light solder joint open circuit phenomenon are as follows:
2.1 packaging production process is not complete, incoming inspection means backward, is caused by the direct cause of LED death lights generally use the support row package LED, stent row is used copper or iron metal materials by stamping and precision molds, because copper is expensive, cost is high, due to fierce market competition factors, in order to reduce manufacturing costs, the market mostly adopts cold rolled low carbon steel stamping LED stent can bring, iron bracket row to the silver, silver has two functions, one is to prevent rust, two is convenient for welding, plating the quality of support platoon is critical, it is related to the life of LED, in the treatment before plating should be in strict accordance with the operating rules, derusting, degreasing, phosphating processes should be strict in demands, electric To control the current plating, silver plating layer thickness to be controlled, the coating is too thick, too thin, too thin to affect the quality of the coating. Because LED encapsulation enterprises in general do not have the checking bracket electroplating quality. This gives some electroplating enterprises exploit, the plating bracket row of silver plating layer thinning, reduce costs, general packaging companies IQC to support row inspection of the lack of means, did not detect stent coating thickness and the fastness of the instrument, therefore easy to muddle through. Some stents in the warehouse after a few months on the rust, do not say that the use of visible plating quality is poor. With such a bracket out of the product is sure to use not long, do not say 3-5 million hours, 10 thousand hours into a problem. The reason is very simple every year have southerly days for a period of time, in such weather, the air humidity is big, very easy to cause the differential plating metal parts rust, the LED component failure. Even if the package of the LED is also due to the silver plating layer is too thin adhesion, solder joints and stents from the dead light phenomenon. This is the use we encountered a good light is not bright, in fact, the solder joints and the stent is out of the.
2.2 encapsulation process in each procedure must be careful operation, a part of any negligence are caused by dead lights at the point, solid crystal process, silver glue (for single chip solder joints) much more and less are not that much glue will return to the gold chip pad, caused by a short circuit, less chip and glue rickety. Double joint chip insulating glue is the same, the insulating glue chip the gold pad on the back, causing welding the weld resulting in dead lights. A little sticky chip is not strong, so the glue must be just perfect, neither more nor less. Welding process is also critical, with gold wire bonder with pressure, time, temperature, and the power of the four parameters must be just right, in addition to the fixed time, three other parameters are adjustable, pressure regulation should be moderate, pressure crushes easily chip, too small to weld. Welding temperature regulation in 280 DEG C for good, power regulation is that the ultrasonic power regulation, too big, too little is not good, to moderate, in short, regulation of the parameters of the gold wire ball welding machine, to the welded material and spring torque test meter detection is more than or equal to 6 grams, which is qualified.

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