Thermal Analysis of a Package Substrate with Filling Via-Holes for COB LED Packaging

摘要

The heat flux of high-power light-emitting diodes (HP LEDs) is 3__4 times larger than that of conventional electronics devices such as central processing unit (CPU). Therefore, it is important for the design that the heat generated from a multi quantum well (MQW) be rapidly emit to the lighting module and the cooling system. In this research, we designed a package substrate with thermal via-holes fully filled with copper and partially filled with epoxy for COB (chip-onboard) packaging. They are compared with a metal core printed circuit board (MCPCB) with a thermally enhanced insulator and a conventional printed circuit board (PCB) without via-holes. The detailed thermal performance was analyzed using CFD (computational fluid dynamics) technology and was verified by using the thermal resistance and the heat distribution on the PCB where light emitting diode (LED) packaging without an encapsulating material was implemented. The equivalent thermal conductivity of the specified bonding pad areas including via-holes and FR-4 was extracted from the simulated result of the actual 3D model. The effects of the main factors of the high performance PCB (HP-PCB) with filled via-holes are discussed using the design of experiment (DOE) methodology. The package substrate with small copper fill via-holes beneath the bonding pad is superior to others. The thermal resistance and the junction temperature of the HP-PCB were founded to be lower over three times lower and 30 °C, respectively, than others. Also, the heat emission scheme was optimized in accordance with the number of via-holes and the array area.