We often encounter situations LED is not lit, packaging companies, application companies as well as units and individuals, are likely to encounter, and this is within the industry, said the phenomenon of dead lights. The reason is nothing more than two situations:
First, LED caused by excessive leakage current PN junction failure, the LED lights point off, this generally does not affect the other LED lights work;
Second, the internal LED lights off the connecting leads, resulting in LED lamp current without generating dead through, this situation will affect the normal operation of other LED lights, due to low voltage LED lights (red, yellow, orange LED operating voltage 1.8V-2.2V, blue, green and white LED working voltage 2.8-3.2V), are generally required to use the series and parallel to join, to accommodate different operating voltage, the greater the series of LED lights more influence, as long as one LED interior lights connection open, will result in a whole string of the series circuit of the LED is not lit, showing that this situation more serious than the first case to be.
LED lights are dead affect product quality, reliability of the key, how to reduce and eliminate dead lights, improve product quality and reliability, are packaged, enterprise applications key issues need to be addressed. Here is some of the reasons causing the death of the lamp to make some analysis to explore,
1, electrostatic damage to the LED chip, the LED chip PN junction failure, increased leakage current, into a resistor
Static electricity is a great harm of the devil, because the world countless electrostatic damage electronic components, resulting in tens of millions of dollars in economic losses. So to prevent electrostatic damage to electronic components, the electronics industry is a very important job, LED packaging, application of business must not be taken lightly. Any one part of problem, will cause damage to the LED, the LED performance deterioration or even failure. We know that the body (ESD) Static electricity can reach about three volts, enough to damage the LED chip can be breakdown in LED packaging production lines, grounding resistance of various types of equipment to meet the requirements, it is also very important, and generally require grounding resistance of 4 Ohm, some situations that require high grounding resistance even to reach ≤2 ohms.
These requirements are for people familiar with the electronics industry, the key is in the actual implementation is in place, whether there is record. According to my understanding of private enterprise in general, anti-static measures do not in place, which is what most companies can not find out the test recording ground resistance, even ground resistance testing is done once a year, or a few years time, or there is a problem When the check earth resistance, ground resistance testing does not know that this is a very important job, at least four times a year (once every quarter to test), some of the requirements of a high place, a month is necessary to make a ground resistance testing.
Soil resistance will change with the seasons and different, spring and summer rain, wet ground resistance soil easier to achieve, autumn and winter dry soil less water, ground resistance may exceed the prescribed value, it is recorded in order to preserve the original data, do to have documented in the future. In line with ISO2000 quality management system. Testing ground resistance can design their own table, ground resistance testing and packaging companies, LED application businesses have to do, as long as the name of a variety of devices to fill in the form, measure grounding resistance documented record of each device, test signatures can be archived.
LED body static electricity damage is great, work should wear anti-static clothing, equipped with electrostatic rings and static ring should be well grounded, there is a grounded wrist strap does not require anti-static effect is not good, it is recommended not to use the strap The kinds of products, if staff violate the rules, you should receive appropriate warning education, but also play the role of a notice of others. How much body with static electricity, and people wear clothes of different fabrics, and each person's physique, autumn and winter night we undress easily see clothes between the discharge phenomenon, which had three electrostatic discharge voltage kV.
The silicon carbide substrate chip ESD value of only 1,100 volts, ESD value of the sapphire substrate chip is even lower, only 500-600 volts.
A good chip or LED, if we hand pick (the body does not make any protective measures), the results can imagine, chip or LED will be subject to varying degrees of damage, sometimes a good device through our hands somehow bad, this is the fault of static electricity.
Packaging companies if you do not act in strict accordance with the ground rules at the expense of the enterprise itself, will result in decreased rate of qualified products to reduce the economic efficiency of enterprises, the same application LED business if equipment and personnel poorly grounded, then the LED will cause damage, rework the inevitable. In accordance with the requirements of the standard instruction manual LED, LED colloidal lead from not less than 3-5 mm, were bent pins or welding, but most applications do not have to do this business, but only separated by the thickness of a PCB board (≤ 2 mm) directly welded, this will cause damage or damage to the LED, because of high soldering temperatures have an impact on chip, chip features will deteriorate, reducing the luminous efficiency, and even damage to LED, this phenomenon is not uncommon. Some small businesses using manual welding, using a 40 watt ordinary soldering iron, soldering temperature can not be controlled, iron at temperatures above 300-400 ℃, high soldering temperature can also cause death lights, LED lead at high temperature coefficient of expansion than about 150 ℃ several times higher coefficient of expansion, internal gold pads because excessive expansion and contraction will pull the weld, causing the phenomenon of dead lights.