Wire bonding is the most common practice for LED packaging, such as COB. Flip Chip technology can promote small size, high power LED but yet provides better efficiency. Flip chip technology implied by its name“flip”, electrodes of LED chip directly contact with MCPCB substrate. This approach can provide advantages such as larger light-emitting areas, better heat dissipation, and skip wire bonding.
The emitting efficiency of LED is called external quantum efficiency of component. It is the product of component’s internal quantum efficiency and light extraction efficiency. The internal quantum efficiency of component, indeed, is the electronopto converting efficiency of component itself.
In the early development of chip, it was focus on increasing internal quantum efficiency. It was achieved by improving the quality of epitaxy and changing the structure of epitaxy. Then, it can prevent electric energy turn into heat, as the result, increasing emitting efficiency of LED indirectly. Through this approach, 90% of internal quantum efficiency theoretical value can be achieved. However, the internal quantum efficiency is reaching its theoretical value limit through this practice. With this limitation, to increase amount of light through enhancing internal quantum efficiency of chip is not possible. Therefore, to increase total amount light is now focus on improving light extraction efficiency of chip. There are some approaches been introduced and flip chip technology is one of them.
For some materials such as Sapphire substrate used in Gallium Nitride, their Anode and Cathode must be placed on the same side of chip component. When using traditional packaging technique, most of top side light emitting area will be blocked due to the electrodes and lose quite a bit of light. Sapphire substrate is transparent. If light can be emitted from the sapphire substrate side, amount of light will be increased dramatically. This is the reason why using flip chip technology can produce larger light emitting area. Reducing loss of light at electrodes areas through this technology, it can double amount of light than using traditional packaging. Moreover, the flip chip structure can directly contact heat dissipating structure of packaging through electrodes or bump. It can increase the heat dissipation effectness and improve total amount of light emitted by component.