(1) The production process of packaging enterprises is not perfect, and the inspection methods of incoming materials are backward, which are the direct causes of LED dead lights. Generally, LEDs are packaged in bracket rows, and the bracket rows are stamped from copper or iron materials by precision molds. Because copper is more expensive, the cost is high. In order to reduce the manufacturing cost, cold-rolled low carbon steel is mostly used in the market to stamp the LED bracket row. The iron bracket row should be silver-plated. Silver plating has two functions. Oxidation and rust, the second is to facilitate welding. The plating quality of the bracket row is very critical. It is related to the life of the LED. Because there is a period of time every year, the air humidity is high, and it is easy to cause embroidery of metal parts with poor electroplating, which makes the LED components fail. Even if the packaged LED is too thin, the adhesion is not strong because the silver plating layer is too thin, and the solder joint is separated from the bracket, resulting in a dead lamp phenomenon.

  (2) Each process in the packaging process should be carefully operated, and any negligence in any link is the cause of the dead light. In the spotting and die bonding process, too much or too little silver glue (for single solder joint chips) will not work. Too many spots will return to the gold pad of the chip, causing a short circuit. The same is true for the double-solder chip dot insulating glue, so the glue must be just right. The welding process is also very important. The four parameters of pressure, time, temperature and power of the gold wire ball welding machine must be properly coordinated. Except for the fixed time, the other three parameters are adjustable. The adjustment of the pressure should be moderate and the pressure should be large. It is easy to crush the chip, and if it is too small, it is easy to be soldered. The welding temperature is generally adjusted at 280 ℃. The adjustment of power refers to the adjustment of ultrasonic power. Too large or too small is not good, and moderate is the degree.

  3. The method of identifying the dead light of the virtual welding Use a lighter to heat the lead of the LED light to 200-300℃, remove the lighter, and connect the LED with the positive and negative poles of the 3V button battery. If the LED light can be lit at this time , but as the lead temperature decreases, the LED light changes from bright to non-bright, which proves that the LED light is soldered. The reason why the heating can be lit is that the principle of metal thermal expansion and cold contraction is used. When the LED lead is heated, the expansion and elongation are connected to the internal solder joint. At this time, when the power is turned on, the LED can emit light normally; as the temperature drops, the LED lead When the shrinkage returns to normal temperature, it is disconnected from the internal solder joints, and the LED light does not light up.

  There are many reasons for the occurrence of dead lights, and all aspects from packaging, application to use may lead to dead lights. From the selection of chips and brackets to the packaging of LEDs, the entire process must be operated in accordance with the IS02000 quality system. Only in this way can the quality of LED products be improved in an all-round way, and long life and high reliability can be achieved. In the circuit design of the application, choosing varistor and PPTC components to improve the protection circuit, increasing the number of parallel circuits, using constant current switching power supply, and adding temperature protection are all effective measures to improve the reliability of LED products.