Thermosonic Flip Lighting Led Thermal Analysis

LED solid state lighting(SSL) has a good prospects, but there are some bottlenecks, the one is that efficiency of light emitting is not enough for general lighting, the other is too much heat generated by higher power which effect the efficiency and life of LED. Flipchip's applying is good for improvement of efficiency of light emitting of LED and especially for thermal management. Here aiming at thermal management technique, the micro structure of bonding interface was tested, and heat field of downward package was simulated by FEM, on which the effect of bonding interface, quantity of bumps and its layout has been studied for better solution on chip thermal management.1. By using SEM and TEM the microscale phenomenal was studied, the results show that thickness of Au/Ag atomic diffusion interface was about 200nm, and interface is made of an unlimited solid solution of Au/Ag; thickness of Au/Al interface was about 500nm, and an inter-metallic compound (e.g. Au4Al) was formed. Ultrasonic vibration occurs high acceleration which is about several ten thousands times as acceleration of gravity. Strong mechanical effect activates dislocations at metal crystal lattice during bonding process, which formed the solder and increased atomic diffusion.2. LED lighting thermal analyzing need heat transfer theory and finite element method. Base the theory and method the theoretics model was conducted.3. The stimulating model of LED light was set up. The physics properties will change after thermosonic bonding, of which the effect was studied to the thermal management of LED.4. The effect of the layout, the number and defect of bumps of LED Flipchip to thermal management of LED light was analyzed by using FEM simulation. The results show that better effect of thermal management can get after optimizing layout of bumps, and also show that the more bump number used the better thermal management can get, but there is a best optimal number as there are some other limiting factors such as Structure and cost. The study shows that bumps defect will badly affect thermal management of LED light, especially effect of the bumps defect at corner.5. The thermal conductibility of glue used in LED packaging is the lowest; this paper respectively studied the effect of conductibility changing and glue thickness changing to thermal management of LED light, the results show that the relations between them are basically linear.