Blackening of LED display screens is a common phenomenon. Today, let's take a look at several main reasons for its blackening.
1. Sulfurization, chlorination, and bromination
The silver plating layer on the LED display bracket will generate silver sulfide when it comes into contact with sulfur-containing gas, and when it comes into contact with acidic nitrogen-containing chlorine and bromine gas, it will generate photosensitive silver halide, which will cause the light source to turn black and fail. Sulfur/chlorine/bromination of light sources can occur in every stage of the production, storage, aging, and use of LED light sources and lamps. After being diagnosed with sulfur/chlorine/bromination due to blackening of the light source, the customer needs to choose a specific sulfur removal plan based on the stage where sulfur/chlorine/bromination occurs. At present, the sulfur/chlorine/bromine detection projects launched by Jinjian 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, and reflow soldering workshop sulfur/chlorine/bromine. Due to the fact that gases containing sulfur, chlorine, and bromine can penetrate into the interior of the light source through gaps in silicone or brackets, Jinjian has also launched an airtightness inspection plan to further help customers improve their requirements for light source materials.
2. Oxidation
Silver easily reacts with oxygen in high temperature and humidity environments, producing black silver oxide. After confirming that the reason for the blackening of the light source is oxidation of the silver plating layer, Jin Jian will suggest that the customer further conduct air tightness checks on the light source and lamp to eliminate the pathway of moisture infiltration.
3. Carbonization
Based on experience, material defects in the six major raw materials of LED light sources (chips, brackets, solid crystal glue, bonding wires, fluorescent powder, and packaging glue) and process defects in the three major packaging processes (solid crystal, wiring, and gluing) can all lead to extremely high temperatures in the light source, causing local or overall blackening and carbonization of the light source. Unreasonable heat dissipation design of LED lamps, low thermal conductivity of heat dissipation materials, unreasonable power supply design, and too many reflow soldering defects can also cause carbonization of the light source. Therefore, when Jinjian preliminarily confirms that the reason for the blackening of the light source is carbonization, it will suggest that the customer follow the LED light source or lamp failure analysis route, dissect the light source/lamp, and identify the source of defects or high thermal resistance.
4. Chemical incompatibility
The blackening of LED light sources may also be caused by chemical contamination, and this blackening phenomenon often occurs in sealed lamps with little or no air flow.
When we encounter a situation where the LED display screen turns black, we can investigate the reasons one by one and make adjustments.
Post time: Dec-05-2023
