Thermal Analysis of High-Power Multichip COB Light-Emitting Diodes With Different Chip Sizes

This paper demonstrates the thermal analysis of high-power light-emitting diodes (LEDs) with various chip sizes, in the same chip-on-board (COB) package and with the same total chip size and input power. The 4-, 9-, 25-, and 100-chip multichip COB LEDs with chip-side lengths of 1500, 1000, 600, and 300 μm were used. The simulation results indicate that the maximal junction temperature of the multichip COB LEDs increased as the number of chips in the multichip COB LED decreased. In addition, with the same input power, the difference between the maximal and minimal junction temperatures of the multichip COB LED increased as the number of chips in multichip COB LEDs increased. That is, if the multichip COB LED contains a few number of large chips, the output power of each chip will drop but uniform owing to the high junction temperature and low temperature difference. Oppositely, if the multichip COB LED contains a lot of small chips, the output power of the chips at the corners will be higher than other chips, but the output power of each chip will be nonuniform owing to the nonuniform junction temperature distribution.