Enhancement of optical performance of the light emitting diode packages with advanced thermal design of die-attaching layers

To guarantee long lifetime of light emitting diodes (LEDs), thermal reliability of LED packages should be secured with suitable die-attaching materials. Die-attaching materials are important for the interconnection between optical devices and substrates, as they not only provide electrical transmission but also the emission of thermal budget generated under the operation of the devices. In this study, the joints with different die-attaching materials were closely investigated in conjunction with the optical performance of LED packages. Thermal reliability of the joints was quantitatively analyzed by estimating the thermal resistances of the metallic and intermetallic layers incorporating the joints. The experimental results revealed that insertion of nano-Ag paste between eutectic Au-Sn and Ag finish significantly improved heat emission by effectively suppressing thermal resistance of eutectic Au-Sn layer. However, to ensure long-term reliability, complete removal of numerous nano-voids among Ag nanoparticles should be accomplished to prevent accumulation of thermal budget.