Fabrication And Characterization Of Flip-Chip Power Light Emitting Diode With Different Number Of Au Stud Bumps

Light emitting diodes (LED) with low power consumption, long life time,small size and fast response are going to be the mainstream device in the solid-statelighting applications. When LED used as lighting devices, it has to exhibit high-poweroperation to achieve the required brightness. At the meanwhile, how to dissipate heatgenerated from LED is a very important issue for the real applications. In thisresearch, using thermosonic bonding technology, the chip LED and the sub-mount arebonded to produce a Flip-Chip power LED with high thermal conductivity Au bumps(291W/mK). The PLED usually exhibits an area of larger than1mm2, its powerconsumption is greater than1watt, therefore the Flip-Chip LED structure here weproposed can let the heat sink rapidly to improve the heat dissipation problem andenhance the luminous efficiency.Four different LED electrode patterns are prepared for Flip-Chip bonding, afterthe whole Flip-Chip LED fabrication process are accomplished, IV and LIcharacteristics, integration sphere measurement and thermal image analysis etc., areadopted to analyze their experimental results. The data showed that Flip-Chip LEDshave the luminous efficiency22.7%higher than non Flip-Chip LED at350mA, theFlip-Chip LED with reflector’s luminous efficiency is42.6%higher than theFlip-Chip LED without reflector. Thermal characteristics show that the Au bumpnumber is proportional to the thermal dissipation ability, but with a saturation at theAu bump reach the number of20~24. Thus, even through the entire Flip-Chip LEDwith28~36Au bumps, due to the bonder can’t provide enough bonding force, resultin a poor Flip-Chip LED electrical and thermal characteristics.