4 reasons why LED lamp beads turn black
The blackening of LED lamp beads is a common problem encountered by LED manufacturers. Tongjia has done a series of tests and found that the blackening of LED lamp beads is only an appearance. Carbonization, oxidation, vulcanization, chlorination, bromination, and chemical incompatibility can all lead to the phenomenon of blackening of LED lamp beads. Here is a brief introduction:
1. Carbonization
Material defects of the six major raw materials of LED lamp beads (chips, brackets, die-bonding glue, bonding wires, phosphors, encapsulation glue) and process defects of the three major packaging processes (die-bonding, wire bonding, glue filling) may cause The LED lamp beads generate extremely high temperatures, causing the LED lamp beads to turn black locally or as a whole, and the light source to carbonize. Unreasonable heat dissipation design of LED lamps, low thermal conductivity of heat dissipation materials, unreasonable power supply design, and too many defects in reflow soldering will also cause carbonization of the light source.
2. Oxidation
In a high temperature and high humidity environment, silver will easily react with oxygen to form black silver oxide. After Tongjia has confirmed that the reason for the blackening of the LED lamp bead is the oxidation of the silver-plated layer, it will recommend the customer to further check the air tightness of the light source and the lamp to eliminate the way of moisture penetration.
3. Sulfurization, chlorination, bromination
The silver-plated layer on the LED lamp bead bracket will generate silver sulfide when it comes into contact with sulfur-containing gas. When it contacts with acidic nitrogen-containing chlorine and bromine gas, it will generate light-sensitive silver halide, which will cause the light source to become black and fail. Light source sulfur/chlorine/bromination may occur in every link of production, storage, aging and use of LED lamp beads and lamps. Therefore, after the blackening of LED lamp beads is determined to be sulfur/chlorine/bromination, it is recommended that customers choose a specific sulfur removal scheme according to the occurrence of sulfur/chlorine/bromination. Sulfur/chlorine/bromine testing items include: lamp sulfur/chlorine/bromine (including built-in power supply), lamp sulfur/chlorine/bromine (excluding external power supply), power supply sulfur/chlorine/bromine, auxiliary material sulfur/chlorine/ Bromine, packaging workshop sulfur/chlorine/bromine, lighting workshop sulfur/chlorine/bromine, reflow soldering workshop sulfur/chlorine/bromine.
4. Chemical incompatibility
Blackening of LED lamp beads can also be caused by chemical contamination, which is often seen in sealed lamps with little or no air flow. Therefore, the blackening of LED lamp beads is determined to be caused by chemical compatibility problems. It is recommended that customers conduct chemical incompatibility investigations on the materials used in the lamps to find materials that are incompatible with the light source.
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