In the application of LED high-power plastic packaging and chip factory contact engineers have learned that the chip (especially the high-power chip) in the use of the process, often problems, we share with you the reasons and solutions!
1. The voltage will drop and the brightness will drop abruptly during the test:
The engineer told us that this is because one kind of electrode is in ohmic contact with the luminescent material, but due to the high resistance of the contact, it is mainly caused by a low concentration of the material substrate or an electrode defect. Another reason is that in the case of non-ohmic contacts, chip electrodes are subjected to extrusion or pinching when the first layer of electrodes is evaporated during the manufacturing process. In addition, the forward pressure drop may also be caused during the packaging process. The main reason is that the silver paste is not cured sufficiently, and the contact resistance or the contact resistance is unstable due to the contamination of the support or the chip electrode.
2. In the process of testing, because the forward voltage is reduced, the current passing through the chip is small, which indicates a dark spot. There is also a phenomenon of low light that the light emission efficiency of the chip itself is low, and the forward voltage drop is normal.
Engineers summed up the following reasons: difficult to weld (mainly hit non-stick, the electrode off, break through the electrode), hit non-stick (mainly because the surface of the electrode is oxidized or glued), contact with the luminescent material is not strong and thick wire bond The layer is not strong, in which the thick layer is mainly peeled off, and the punching electrode is usually related to the chip material. The material is brittle and the material with low strength is easy to break through the electrode. Generally GAALAS materials (such as high red, infrared chips) are better than GAP materials. Easily penetrating electrode], pressure welding debugging should be adjusted from the welding temperature, ultrasonic power, ultrasonic time, pressure, the size of the gold ball, stent positioning and so on.
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