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    LED lamp beads often face some dead light phenomenon solutions

    Source: Time:2019-02-19 15:47:54 frequency:

    We often encounter LED lamp beads that are not bright, packaging companies, application companies, and the units and individuals that use them. It is possible to encounter this, this is the phenomenon of dead lights that people in the industry say.
    We often encounter LED lamp beads that are not bright, packaging companies, application companies, and the units and individuals that use them.
    It is possible to encounter this, this is the phenomenon of dead lights that people in the industry say.

      The reason is nothing more than two cases: First, the LED leakage current is too large, causing the PN junction to fail, so that the LED light is not bright, this situation generally does not affect the work of other LED lights;
      
      Second, the internal connection lead of the LED lamp is disconnected, causing no current to pass through the LED and generating a dead light. This situation will affect the normal operation of other LED lamps, because the operating voltage of the LED lamp is low (red yellow orange LED working voltage) 2.0V—2.6V, blue green white LED working voltage 3.0—3.6V), generally need to be connected in series and parallel to adapt to different working voltages. The more LED lights in series, the greater the impact, as long as there is one LED. The internal wiring of the lamp is open, which will cause the entire string of LEDs of the series circuit to be off, which is more serious than the first case. LED dead lights are the key to affect product quality and reliability. How to reduce and eliminate dead lights and improve product quality and reliability is a key issue that packaging and application companies need to solve.
      
      Here are some analysis of some of the causes of the dead lights:
     
      1. Static electricity damages the LED chip, causing the PN junction of the LED chip to fail, and the leakage current is increased. It becomes a resistor. The static electricity is a very harmful devil. The number of electronic components damaged by static electricity all over the world is caused by countless numbers. Tens of millions of dollars in economic losses. Therefore, it is an important task in the electronics industry to prevent static electricity from damaging electronic components. LED packaging and application companies should not be taken lightly. Any problem in one link will cause damage to the LED, making the LED performance deteriorate or even fail. A good chip or LED, if we take it by hand (the body does not take any protective measures), the result can be imagined, the chip or LED will be damaged to varying degrees, sometimes a good device passes our hands It’s inexplicably broken, this is the fault of static electricity.
     
      In this regard, Shenzhen Xingchen Weiye Photoelectric Co., Ltd. is doing very well, it is worth learning.
      
      2. Some small enterprises use manual soldering, using 40 watt ordinary soldering iron, the soldering temperature can not be controlled, the soldering iron temperature is above 300-400 °C, too high soldering temperature will also cause dead light, LED lead expansion coefficient at high temperature is 150 The expansion coefficient around °C is several times higher, and the internal gold wire solder joint will open the solder joint due to excessive thermal expansion and contraction, resulting in a dead light phenomenon.

      3. Analysis of the cause of the dead light caused by the open connection of the internal connection of the LED lamp
     
      4. The production process of the packaging enterprise is not complete, and the incoming inspection method is backward, which is the direct cause of the LED dead light.
     
      5. Generally, LEDs are packaged in brackets. The brackets are made of copper or iron metal materials and stamped by precision molds. Because copper is expensive, the cost is naturally high, and it is affected by fierce competition factors in the market. In order to reduce manufacturing costs, Most of the market adopts cold-rolled low-carbon steel to bring stamped LED brackets. The iron brackets are silver-plated. Silver plating has two functions. One is to prevent oxidation and rust, the other is to facilitate welding, and the plating quality of the brackets. Very critical, it is related to the life of LED, the treatment before plating should be strictly in accordance with the operating procedures, derusting, degreasing, phosphating and other processes should be meticulous, the current should be controlled during plating, the thickness of the silver plating layer should be controlled, The coating is too thick and costly, too thin to affect quality. Because the general LED packaging companies do not have the ability to check the plating quality of the bracket row, this gives some electroplating companies the opportunity to make the electroplated bracket silver plating thinner and reduce the cost. The general packaging enterprise IQC is the bracket row. The inspection method is lacking, and there is no instrument for detecting the thickness and fastness of the plating layer of the stent, so it is easier to get away with it. Even if the packaged LED is too thin due to the silver plating layer, the adhesion is not strong, and the solder joint is separated from the bracket, causing a dead light phenomenon. This is the well-used lamp that we encountered is not bright, in fact, the internal solder joint is separated from the bracket.
       
       The general quality requirements of the products of Star Weiye Optoelectronics Co., Ltd. are very strict. The quality of the company's procurement of raw materials must be in place. The LED lamp beads and LED light bars are guaranteed to be used for more than two years. Corporate CEOs must have this attitude, because we ourselves are consumers and we must make products from the perspective of consumers. In order to be recognized, companies will become stronger and bigger.
     
    6 Every process in the packaging process must be carefully operated. Any negligence in any link is the cause of the dead light.
     
    7. In the point and solid crystal process, silver glue (for a single solder joint chip) is much less and less, and more glue will return to the chip gold pad, causing a short circuit, and the chip is less sticky. The double-solder chip is also the same as the point-insulating glue. When more points are added, the insulating glue will return to the gold pad of the chip, causing the solder joint to cause a dead light. The point is less and the stick is not sticky, so the dispensing must be just right, neither too much nor too little.
      
      8. The welding process is also very important. The four parameters of the pressure, time, temperature and power of the gold wire ball welder should be just right. In addition to the fixed time, the other three parameters are adjustable, and the pressure adjustment should be moderate. Pressure is easy to crush the chip, too small is easy to solder. The welding temperature is generally adjusted at 280 °C. The adjustment of the power refers to the adjustment of the ultrasonic power. Too big or too small is not good. It is moderate. In short, the adjustment of various parameters of the gold wire ball welder is good. The material is tested by ≥6 g with a spring torque tester. Every day, the parameters of the gold ball welder are tested and corrected to ensure that the welding parameters are in the best condition. In addition, the arc of the welding wire is also required. The arc height of the single soldering chip is 1.5-2 chip thickness, and the arc height of the double soldering chip is 2-3 chip thickness. The height of the arc also causes the quality of the LED, and the arc height is high. Too low is likely to cause a dead light phenomenon during welding. If the arc height is too large, the current impact resistance is poor.
     
      9. Method for identifying dead soldering dead lights
     
    10. Use the lighter to heat the LED lead to 200-300 °C, remove the lighter, and connect the LED with the positive and negative electrodes with a 3 volt button battery. If the LED light can be lit at this time, but with the lead The temperature reduction LED light changes from bright to off, which proves that the LED light is a virtual solder. The reason why the heating can be ignited is to use the principle of thermal expansion and contraction of the metal. When the LED lead is heated, the expansion elongation is connected to the internal solder joint. At this time, the LED is turned on normally, and the LED leads to shrink normally with the temperature drop. Return to the normal temperature state, disconnected from the internal solder joints, the LED light will not light up, this method is tried and tested. The two soldered dead lights are soldered to a metal strip, soaked with concentrated sulfuric acid to dissolve the external colloid of the LED, and the colloid is completely dissolved and taken out, and the welding condition of each solder joint is observed under a magnifying glass or a microscope. It is possible to find out whether it is a welding or a second welding problem. It is the parameter setting of the gold ball ball welder, or other reasons, in order to improve the method and process to prevent the phenomenon of the virtual welding from happening again.
     
      11. Users who use LED products will also encounter the phenomenon of dead lights. This is the phenomenon of dead lights after using LED products for a period of time. There are two reasons for dead lights. Open circuit dead lights are poor soldering quality, or bracket plating There is a problem with the quality, and the LED chip leakage current will also cause the LED light to not light. Nowadays, many LED products do not have antistatic protection in order to reduce the cost, so it is easy to cause damage to the chip by induced static electricity. In the rainy day, it is easy for the power supply line to induce high-voltage static electricity, and the spikes superimposed on the power supply line will cause LED products to suffer different degrees of damage.
     
    In short, there are many reasons for the death of lights, can not be listed one by one, from the packaging, application, to the use of various links may have a dead light phenomenon.

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