COB Die Bonding Placement and Reliability
Die Bonding Placement: COB die bonding involves placing RGB chips in a straight line. The lens above the chip is a smooth curved surface. The lens has excellent light refraction, resulting in more uniform color mixing and a more even light spot when the three colors of light pass through it. This leads to a better visual effect and more realistic display. SMD full-color displays lack this characteristic because the top of the SMD chip is flat, resulting in less effective refraction and inferior color matching compared to COB.
The light distribution curves show that COB full-color displays have good consistency across the three colors, while SMD full-color displays have poor consistency. There is a significant separation between the red and blue/green light curves, resulting in a worse overall effect compared to COB full-color displays.
Reliability and Low Thermal Resistance: The system thermal resistance of traditional SMD packaging applications is: chip-die adhesive-solder joint-solder paste-copper foil-insulator-aluminum material, while the system thermal resistance of COB packaging is: chip-die adhesive-aluminum material. Clearly, the system thermal resistance of COB packaging is much lower than that of traditional SMD packaging, which significantly improves the lifespan of LEDs.
Furthermore, Auleda's COB dispensing chips are directly fixed to the PCB board, resulting in a large heat dissipation area. This prevents the chip junction temperature from rising too high, leading to better light decay and more stable product quality. In contrast, SMD chips are fixed in a cup, not in direct contact with the PCB board, resulting in a smaller heat dissipation area and poorer heat dissipation performance. This leads to a rise in chip junction temperature and greater light decay. These factors are precisely the bottlenecks in the development of SMD full-color technology.
Waterproof, moisture-proof, and UV-resistant: COB uses a lens encapsulation method with adhesive dispensing on the board, so it performs well in terms of waterproof, moisture-proof, and UV-resistant properties when used outdoors. SMD, on the other hand, generally uses PPA material for the bracket, which is inferior in terms of waterproof, moisture-proof, and UV-resistant properties. If the waterproof and moisture-proof issues are not properly addressed, quality problems such as failure, dimming, and rapid degradation can easily occur.
