Recent development of the LED Chip on Board (COB) module with LED flip chips has successfully demonstrated its advantage in having a lower thermal resistance and cheaper packaging costs over the conventional wire-bond LED COB. By lowering the thermal resistance, LED chips are able to perform with lower junction temperatures and have less thermal decay while thermal dissipation is enhanced. Meanwhile, lower thermal resistance also enables the feasibility to increase optical output through the higher driving current.
What is COB?
COB, is the abbreviation of Chip on Board in English. It is a method of circuit board manufacturing in which the integrated circuits are wired, bonded directly to the PCB, and covered by epoxy glue. Because the bare chip is directly exposed to the air, it is easy to be aged and oxidized in long term, so the chip and bonding wires are sealed with coating and simplifying the packaging structure of ultra-fine electronic components and improving the stability of the final display.
In the process of developing towards the MicroLED era, it is difficult for SMD encapsulation to breakthrough the bottleneck of narrower pixel pitch.
COB encapsulation technology has absolute advantage such as higher reliability, higher assembling efficiency and softer light output. It can be applied to any pitch of millimeters in theory.
What's Next? COB Flip-chip is the future of display!
As an upgraded version of COB, flip-chip COB is based on the advantages of COB ultra-small dot pitch, high reliability, and non-glaring surface light source. Further, improve the reliability, simplify the production process, better display effect, perfect near-screen experience and real chip-level spacing can be realized.
Flip-Chip is one of the chip packaging technologies. This packaging technology mainly differs from the previous method of chip packaging. In the past, the chip was placed on a substrate, and using the gold wire to connect chips and the junction point on the substrate. Whereas in the Flip Chip packaging technology, chips have to be connected with bump, and be flipped over to make the bump directly connect with the substrate.
Advantage of Flip Chip COB LED:
1. High Reliability and Stability. Flip-Chip COB LEDs do not require gold wires, and the probability of light failure caused by gold wire breaking is reduced by 90%, thus ensuring product stability. Compared with the gold wire, its electrical contact surface is expanded by more than 1000 times, the current density is increased by 10,000 times, and the chip thrust will increase to 2000g. So the reliability of the entire packaged device will be higher.
2. High Luminous Intensity with small luminous area. Flip Chip device volume can be reduced by up to 80%, and it can achieve greater luminous flux in the same size compared to regular LEDs.
3. High Heat Dissipation. Flip chip is soldered by direct contact between metal and metal and its high current dissipation capability is better than conventional packaging. The conventional packaging is cooled through sapphire and solid crystal silver glue, but the flip chip is cooled only through the metal channel, so the heat dissipation is faster than conventional packaging.