Design of a GaN-Based Flip Chip Light Emitting Diode (FC-LED) with au Bumps & Thermal Analysis with Different Sizes and Adhesive Materials for Performance Considerations

Abstract

Flip chip (FC) light emitting diodes (LEDs) are considered to be more promising in solid state lighting as compared to wire bonded LEDs. For solid-state lighting, thermal management is a very critical factor to enhance the device’s performance. In the Flip Chip Light Emitting Diode (LED), the active region is the main source of heat generation. This heat is to be conducted through different layers to the heat sink. The adhesive layer and bump assembly cause heat dissipation because of their low conductivity values and poor transparency and hence cause degradation in performance of FC-LEDs. In this paper, thermal analysis of flip chip LED is done to find out how material, size of die and bumps affect the thermal performance of FC-LED. A flip chip LED structure is modeled on a GaN substrate. Different material properties of silicon, gold, and aluminum have been studied to perform the thermal analysis and to see the effects of different die sizes, bump sizes, and adhesive materials. Thermal analysis of the high-power FC LED by using the Finite Element Method is done on Ansys Software. The FC structure and its meshing design are presented.Temperature variation with different sizes of bump, chip-die and different adhesives (silver filled epoxy, Au-Sn, Pb-Sn) on flip chip LED is discussed. The result shows that thermal heat is directly proportional to the size of the bump and the type of adhesive material selected also affects the performance of FC-LEDto some extent.