During the production process, we will always encounter the phenomenon that one, one string, or several strings of lamp beads cannot be lit when testing after mounting the board. To summarize this phenomenon:
7 major reasons why the LED lamp bead is dead during the welding process. webp.jpg
1. Common welding methods can be divided into electric soldering iron welding, heating platform welding and reflow soldering, etc.:
A, electric soldering iron welding is the most common, such as sample making and maintenance. In order to save costs, most of the electric soldering irons purchased by existing manufacturers are substandard and low-quality products. Most of them are poorly grounded and have leakage. During the welding process, this is equivalent to forming a circuit between the leaking soldering iron tip - the LED to be welded - the human body - and the earth. That is to say, the voltage equal to dozens to hundreds of times that the lamp bead withstands is applied to the LED lamp bead, burning it out instantly.
B. Dead lights caused by welding of heating platforms. Due to the constant flow of lamp sample orders, most companies have to meet the needs of small batches and sample orders. Due to the advantages of low equipment cost, simple structure and operation, heating platforms have become the best production tools. However, due to the use environment (for example: the temperature in places with fans cannot be constant) and the welding operator's proficiency and welding speed control have become major problems causing dead lights. In addition, there is the grounding of the equipment of the heating platform.
C, reflow soldering. Generally, this soldering method is the most reliable production method and is suitable for mass production and processing. If improperly operated, it will cause more serious dead light consequences, such as unreasonable temperature adjustment, poor machine grounding, etc.
2. Improper storage causes dead lights:
This kind of problem is the most common, due to not paying attention to moisture-proofing after opening the package, and because the sealing glue of the lamp beads is mostly made of silica gel material, which has certain water-absorbing properties. After the damp lamp beads are attached to the board, the silica gel will expand and contract with heat during the high-temperature welding process. The gold wire, chip, and bracket will deform, causing the gold wire to shift and break, and the light spot will not light up. Therefore, it is recommended that the LED be stored in a dry and ventilated environment, and the storage temperature is -40℃- +100℃, the relative humidity is below 85%; it is better to use the LED within 3 months in its original packaging condition to avoid the bracket from rusting; when the LED packaging bag is opened, it must be used as soon as possible. At this time, the storage temperature is 5℃-30℃, and the relative humidity is below 60%.
3. Chemical cleaning:
Do not use unknown chemical liquids to clean LEDs, because that may damage the surface of the LED colloid and even cause colloid cracks. If necessary, please use an alcohol cotton swab to clean it in a room temperature and ventilated environment. It is best to control the time to complete in one minute.
4, deformation causes dead lights:
Because some of the lamp panels are deformed, the operator will reshape them. As the board deforms, the lamp beads on it will also deform at the same time, breaking the gold wire and causing the lamp to not light up. It is recommended that this type of board be reshaped before production. Longer ones may also cause deformation and breakage of the gold wire during production, assembly and movement. There is also the problem of stacking. In order to facilitate the production process, the lamp panels are randomly stacked. Due to gravity, the lower lamp beads will be deformed due to force and damage the gold wire.
5. The heat dissipation structure, power supply and lamp panel do not match:
Due to unreasonable power supply design or selection, the power supply exceeds the maximum limit that the LED can withstand (overcurrent, instantaneous impact); the unreasonable heat dissipation structure of the lamp will cause dead lights and premature light.
< div>6. Factory grounding:
It is necessary to check whether the factory's general grounding wire is good.
7. Static electricity:
Static electricity can cause LED function failure. It is recommended to prevent ESD from damaging the LED.
A. Workers must wear anti-static bracelets and anti-static gloves when testing and assembling LEDs.
B. Welding equipment and testing equipment, work tables, storage racks, etc. must be well grounded.
C. Use an ion blower to eliminate static electricity generated by friction during LED storage and assembly.
D. The box containing the LED is an anti-static box, and the packaging bag is an electrostatic bag.
E. Don’t take chances and touch the LED casually.
The abnormal phenomena that will occur in LEDs damaged by ESD are:
A. Reverse leakage. In mild cases, the brightness will decrease, and in severe cases, the light will not light up.
B. The forward voltage value becomes smaller. The LED cannot emit light when driven at low current.
C, poor welding causes the lamp to not light up.
ANNA