LED dead light causes of the chip

29 views admin 2024-03-15

Big data shows that the causes of LED dead lights may be more than 100 kinds, limited to time, today we only take LED light source as an example, from the LED light source one of the five raw materials - chip, introduce some of the causes that may lead to dead lights.

The antistatic index of LED lamp bead depends on the LED light-emitting chip itself, and the packaging material is expected to be basically unrelated to the packaging process, or the influencing factors are very small and subtle; LED lights are more prone to electrostatic damage, which is related to the distance between the two pins, the LED chip bare crystal of the two electrode spacing is very small, generally within one hundred microns, and the LED pin is about two millimeters, when the electrostatic charge to transfer, the greater the spacing, the easier to form a large potential difference, that is, high voltage. Therefore, after sealing LED lights, electrostatic damage accidents are often more likely.

LED epitaxial sheet in the high temperature crystallization process, the substrate, MOCVD reaction cavity residual sediment, peripheral gas and Mo source will introduce impurities, these impurities will penetrate into the epitaxial layer, prevent gallium nitride crystal nucleation, form a variety of epitaxial defects, and finally form a small pit on the surface of the epitaxial layer. These will also seriously affect the crystal quality and properties of epitaxial film materials.

Electrode processing is a key process for the production of LED chips, including cleaning, evaporation, yellow light, chemical etching, fusion, grinding, will come into contact with a lot of chemical cleaning agents, if the chip cleaning is not clean enough, it will make harmful chemical residues. These harmful chemicals will have an electrochemical reaction with the electrode when the LED is powered on, resulting in dead lights, light decay, dark light, black and other phenomena. Therefore, the identification of chip chemical residues is crucial for LED packaging plants.

The damage of the LED chip will directly lead to the failure of the LED, so it is important to improve the reliability of the LED chip. The chip is sometimes held in place with a spring clamp during evaporation, resulting in a clamp mark. If the development of yellow light is incomplete and the mask is broken, there will be residual metal in the luminous region. In the process of grain in the front section, each process such as cleaning, evaporation, yellow light, chemical etching, fusion, grinding and other operations must use tweezers, flower baskets, vehicles, etc., so there will be grain electrode scratching.

The influence of the chip electrode on the welding spot: the evaporation of the chip electrode itself is not secure, resulting in the electrode falling off or damage after the welding line; Poor weldability of chip electrode itself will lead to virtual welding of welding ball. Improper chip storage can lead to electrode surface oxidation, surface contamination, etc. Slight contamination of the bonding surface may affect the diffusion of metal atoms between the two, resulting in failure or virtual welding.

The chip of the new structure process is incompatible with the light source material

The new structure of the LED chip electrode has a layer of aluminum, its role is to form a layer of mirrors in the electrode to improve the chip light efficiency, and secondly, it can reduce the use of gold in the evaporation electrode to a certain extent to reduce the cost. However, aluminum is a relatively active metal, once the packaging factory incoming material control is not strict, the use of excessive chlorine glue, the aluminum reflection layer in the gold electrode will react with the chlorine in the glue, resulting in corrosion.