Reasons for Dead Lamp in LED Bead Welding Process

In the process of production, we always encounter the phenomenon that one, one or several beads can't be lighted when we test some beads after sticking the board. In view of this phenomenon, this paper makes a summary:

Dead lamp in welding process

1. Common welding methods can be divided into electric soldering, heating platform welding and reflow welding.

A, soldering iron welding is the most common, such as sample making, maintenance, because most of the existing manufacturers in order to save costs, the purchase of soldering iron is mostly slightly unqualified products, mostly grounded badly, there is leakage. In the process of welding, this is equivalent to the leakage of soldering iron tip - welded LED - human body - earth form a loop. That is to say, it is tens of times - hundreds of times the voltage that the bulb bears, which is added to the top of the LED bulb, and burns it out instantaneously. Note: The situation of electrostatic tape connection will be more serious, because when the body is connected with the electrostatic tape, the resistance to form a circuit to the ground will be smaller, and the current from the body to the lamp beads will be larger. This is also the problem that many people say that there are still so many lamp beads damaged with electrostatic tape.

B. Dead lamp caused by welding of heating platform. Because of the continuous sample list of lamps and lanterns, most enterprises in order to meet the needs of small batches and sample list. Because of the advantages of low cost of equipment, simple structure and operation, heating platform has become the best production tool. However, due to the use environment (e.g. local temperature storage with fans). In the unsteady problem) and the control of welding operator's proficiency and welding speed have become the major problem of dead light. In addition, there is the grounding of heating platform equipment.

C. Reflow welding is generally the most reliable mode of production, suitable for mass production and processing. If improper operation, it will cause more serious dead light consequences, such as unreasonable temperature adjustment, poor machine grounding and so on.

2. Improper storage causes dead lights:

This kind of problem is the most common. Because of the lack of attention to moisture-proof after unpacking, the sealing glue of lamp beads is mostly made of silica gel, which has certain water absorption characteristics. After damp lamp beads sticking board, silica gel will expand and shrink after high temperature welding process. The deformation of gold wire, chip and bracket will cause the gold wire to move and break. It is suggested that the LED should be stored in a dry and ventilated environment with a storage temperature of - 40 -+100 C and a relative humidity of less than 85%. The LED should be used within three months of its original packaging condition to avoid the rust of the bracket. When the packaging bag of the LED is opened, it should be used as soon as possible and the storage temperature should be kept at this time. The relative humidity is below 60% at 5 - 30 C.

3. Chemical cleaning:

Do not use unknown chemical liquid to clean the LED, because it may damage the surface of the LED colloid and even cause colloid cracks. If necessary, clean the LED with alcohol cotton swab under normal temperature and ventilation environment. The best time is controlled in one minute of wind.

4. Deformation causes dead light:

Because part of the lamp board is deformed, the operator will go to shaping. Because the plate is deformed, the above lamp beads are also deformed together, breaking the gold wire and causing the lamp not to turn on. It is suggested that the plate with this type should be shaping before production. The longer one has been assembled and moved in production and may also cause deformation and breakage of gold wires. There is also stacking, the production process for convenience, the lamp board will be stacked at will, because of gravity, the lower lamp beads will be deformed by force, damage the gold wire.

5. Heat dissipation structure, power supply and lamp board do not match:

Due to the unreasonable design or selection of power supply, the power supply exceeds the maximum limit that LED can withstand (super current, instantaneous impact); irrational heat dissipation structure of lamps will cause dead light and premature light failure.

6. Plant Grounding:

It is necessary to check whether the factory's grounding wire is good or not.

7. Electrostatic:

Static electricity can cause the failure of LED function. It is suggested to prevent ESD from damaging the LED.

A. Operators must wear anti-static hand rings and gloves when testing and assembling LED.

B. Welding equipment and testing equipment, working table, storage rack, etc. must be well grounded.

C. Use ion blower to eliminate static electricity caused by friction during storage and assembly of LED.

D. Anti-static cartridge is used for LED cartridge and electrostatic bag is used for packaging.

E. Don't be fluky, just touch the LED.

The abnormal phenomena of LED damaged by ESD are as follows:

A. Reverse leakage, light will cause a decrease in brightness, serious lights do not turn on.

B. The forward voltage decreases. LED cannot emit light when driven by low current.

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