Investigation on Thermal Characterization of Eutectic Flip-Chip UV-LEDs With Different Bonding Voidage

Flip-chip ultraviolet light-emitting diode (FC UV-LED) fabricated by direct AuSn eutectic package is of high interest in Research and Development due to its excellent thermal performance and good reliability. However, the voids in eutectic bonding layer due to the lack of AuSn filled have a big influence on the thermal management and optical performance of FC UV-LEDs, and it is believed that the eutectic voids can affect the thermal-conduction resistance (the following unified called thermal resistance) and the junction temperature of FC UV-LEDs. In this paper, modeling and thermal simulation using finite element analysis is developed by considering the geometrical model of eutectic FC UV-LEDs with 3%, 10%, 20%, and 30% bonding voidage. Meanwhile, to validate the simulation, the thermal parameters of FC UV-LEDs are determined and measured using thermal transient tester, and it is found that UV-LED with 3% voidage shows lowest thermal resistance and junction temperature compared with the other samples in both simulation and experiment. Moreover, the optical performance of UV-LEDs is evaluated via the photoelectric analysis system, and the results confirm that the lowest thermal resistance leads to the lowest junction temperature but the highest light output power.