Industry news

2016August

May cause

From: www.szbako.com Data:09/08/2016

LED

dead lights in the LED lighting industry often appear, seriously affect the quality and reliability of the product, but also the problems of the manufacturers concerned. LED dead light is caused by what reason? How to avoid the phenomenon of LED dead lights is the focus of this paper.

LED

LED dead dead lights cause light no more than two reasons: first, through the LED leakage caused by failure of the LED light point PN junction, not bright, this situation generally does not affect the other LED lights work;

second, internal LED lamp connecting lead wire is disconnected, resulting in LED no current through the resulting dead lights, 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 working voltage 2.8-3.2V), usually used in series and parallel to join, to adapt to different working voltage, LED the more light series more 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 more seriously than the first one More. Analysis of

of LED die

due to the lamps LED dead lights is key influence product quality and reliability, how to reduce and eliminate dead lights, improve the quality and reliability of its products is encapsulation, application of enterprise needs to solve the key problem. The following are some of the reasons for the death of a number of reasons for the analysis of.

1, electrostatic on the LED chip caused 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.

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.

2, LED lamp inside line open circuit causes death light solder joint analysis of the phenomenon of the production process of

2.1 package enterprises 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, due to copper more 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 two for one is to prevent rust, two is convenient welding, plating quality support the row 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, Electroplating to control the current, silver plated 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 package in the process of every working 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 & Ge; 6 grams, which is qualified.

every year to the gold wire ball welding machine parameters into the detection and correction, to ensure that the welding parameters in the best condition. Also welding line arc is also required. Single chip solder joints of camber is 1.5-2 chip thickness, double chip solder joints, the camber is 2-3 chip thickness, radian level will cause quality problems led, arc height is too low, easy to cause the welding when the lights die phenomenon, the camber is too large, current anti impact.

3, identification of weld die however, even China Electronics Fair exhibits, in the use of LED products users will encounter the phenomenon of dead lights, this is a period of time a product LED, dead light phenomena, dead lights have two reasons, open circuit dead lights is the welding quality is not good, or plating rack of quality problems, LED chip leakage current increases will cause led lamp does not light. Now a lot of LED products in order to reduce the cost is not anti static protection, it is easy to appear the phenomenon of induction electrostatic damage to the chip. Rainy days of thunder prone to power supply circuit of high voltage electrostatic induction, and power lines superimposed spike pulse, will make the LED products are subject to different degrees of damage.

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