Nowadays, there are thousands of reasons for the death of LED lamp beads. So today, Xiaobian has started with several major raw materials for LED lamp beads. In this issue, the reasons for possible dead lights are introduced from the chip:
1. Chip epitaxial defect LED epitaxial wafer In the process of high temperature crystal growth, the substrate, the residual deposit in the MOCVD reaction chamber, the peripheral gas and the Mo source will introduce impurities, which will penetrate into the epitaxial layer and prevent the gallium nitride crystal from forming. The nucleus forms various epitaxial defects and eventually forms tiny pits on the surface of the epitaxial layer, which also seriously affects the crystal quality and performance of the epitaxial film material.
2, damage to the chip Damage to the LED chip will directly lead to LED failure, so it is important to improve the reliability of the LED chip. In the evaporation process, it is sometimes necessary to fix the chip with a spring clip, so that a pinch is generated. If the yellow light operation is incomplete and the mask has holes, there will be residual metal in the light-emitting area. In the pre-stage process, various processes such as cleaning, evaporation, yellow light, chemical etching, fusion, grinding, etc. must use tweezers and flower baskets, carriers, etc., so there will be scratches of the die electrodes.
3, the new structure of the chip and the light source material is not compatible with the new structure of the LED chip electrode has a layer of aluminum, its role is to form a mirror in the electrode to improve the chip light extraction efficiency, and secondly can reduce evaporation to some extent The amount of gold used in the electrode reduces the cost. However, aluminum is a relatively active metal. Once the packaging plant is not well controlled, the aluminum reflective layer in the gold electrode reacts with the chlorine in the glue to cause corrosion.
4, chip anti-static ability is poor LED lamp beads anti-static indicators depending on the LED light-emitting chip itself, and packaging materials are expected to have nothing to do with the packaging process, or the influencing factors are small, very subtle; LED lights are more susceptible to electrostatic damage, this It is related to the distance between the two pins. The distance between the two electrodes of the bare chip of the LED chip is very small, generally less than one hundred micrometers, and the LED pin is about two millimeters. When the electrostatic charge is to be transferred, the spacing is larger. The easier it is to form a large potential difference, that is, a high voltage. Therefore, it is often more prone to electrostatic damage accidents after being sealed into LED lights.
5, the impact of the chip electrode on the solder joint: the chip electrode itself is not reliable evaporation, resulting in the electrode behind the wire off or damage; chip electrode itself can be poor solderability, will lead to solder ball solder joint; improper storage of the chip will 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 solder joints.
6, chip chemical residual electrode processing is the key process of making LED chips, including cleaning, evaporation, yellow light, chemical etching, fusion, grinding, will contact a lot of chemical cleaning agents, if the chip cleaning is not clean enough, it will cause harmful chemicals Residue of matter. These harmful chemicals react electrochemically with the electrodes when the LEDs are energized, resulting in dead lights, light decay, darkness, blackening, and the like. Therefore, identifying chip chemical residues is critical to LED packaging plants.
This is a way for LED lamp bead chips to die.