Industry news

2016February

Comprehensive interpretation of the death of LED lights a variety of reasons for

From: www.szbako.com Data:17/02/2016

  often encounter LED does not light the situation, packaging enterprises, applications and the use of units and individuals, are likely to come across, this is the industry’s people say dead light phenomenon. The reason is nothing more than two kinds of situations: first, through the LED leakage 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, causing LED caused death no current through the lamp, the normal work of the a LED lamp will affect the other, because the LED lamp low 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 working voltage, LED lamp series and 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 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.
 
1, electrostatic on chip LED damage, make LED chip of PN junction failure, leakage current increases, becomes a static resistance is a harm great devil, all over the world because of the numerous electrostatic damage electronic components, resulting in 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 the human body static (ESD) can reach 3000 volts or so, can be led chip breakdown, in LED packaging production line, equipment grounding resistance whether it meets the requirements, this is also very important, general requirements for the grounding resistance is a 4 ohm, and some demanding the grounding resistance even to reach & Le; 2 ohms. 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 and even do contact resistance test is also a year once, or a few years, or have a problem check a 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 of such damage 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, such as fruit staff in violation of operation 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.
 
and 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 (& le; 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.
 
  analysis of the cause of death of
2, LED lamp light phenomenon of internal wiring of solder joint open
2.1 package; the 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 precision die stamping, because copper is more expensive, the cost is naturally 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 rack 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 And other procedures should be meticulous, electroplating to control the good current, silver plated layer thickness to control, the coating is too thick, too thin, too thin to affect quality. 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.
 
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