Experimental Study on the Effects of Eutectic Voids on the Thermal Performance Within Flip-Chip Ultraviolet Light-Emitting Diodes

In this paper, the effects of eutectic voids in bonding area on the thermal resistance and light output power of flip-chip ultraviolet light-emitting diode (UV-LED) devices have been studied by experiments in detail. It has been demonstrated that the eutectic voids effectively influenced the thermal resistance, the junction temperature, and the light output power of the UV-LEDs. The UV-LEDs with lower eutectic voidage exhibited a superior thermal performance based on the thermal resistance analysis. The thermal resistance was greatly reduced by 48% and the junction temperature by 3.5 °C as the driving current was 800 mA when the eutectic voidage decreased from 30% to 3%. As a consequence, a maximal enhancement of 13.3% of light output power was obtained when the LED was driven by a current of 1500 mA. These results confirmed that a better performance of eutectic flip-chip UV-LED can be obtained with lower eutectic voidage for the reason that the thermal resistance and junction temperature can be decreased effectively.