Thermal Analysis of Eutectic Flip-Chip Light-Emitting Diodes Fabricated Using Copper-Coated Ceramic Substrate

Die attachment quality plays a remarkable role in producing highly reliable solid-state lighting fixtures by providing a dominant impact on thermal resistance. Color rendering, efficacy, and lifetime are strongly related to junction temperature. This paper investigated the effects of varying the thickness of sputter-coated copper on an Al₂O₃ ceramic substrate on the thermal resistance and luminous intensity of flip-chip light-emitting diode (LED) devices. Eutectic bonding was applied to provide excellent bonding strength and low void content between the chip and ceramic substrate. The thermal resistance dramatically decreased as the copper thickness was reduced because of a substantial reduction in the conduction impedance for heat dissipation from the junction to the ambient. The luminous intensity was improved by reducing the copper thickness as the driving current was increased from 50 to 700 mA. The results demonstrated that reducing the copper thickness effectively reduced the junction temperature and improved the performance of the eutectic flip-chip bonding LED devices.