Study on the variation in thermal resistance and junction temperature of GaN based LEDs using thermal transient measurement

Proper heat management in solid state lighting (SSL) is vital to enhance its efficiency and reliability. The ease of heat flow through the LED package was described in terms of the thermal resistance, R_th. In this study white and green LEDs were used to investigate the variation in junction temperature and junction-to-ambient thermal resistance, R_thJA. It was reported that the green LED always shows higher junction temperature and thermal resistance compared to the white LED. This is due to current crowding effect at the p-n junction of the green LED. At 700mA, the R_thJA of green LED was increased about 3KW compare with white LED. Furthermore, the die attach quality also influences the temperature rise and thermal resistance of the LED packages. Due to poor die attach, the R_thJA rises about 7K/W when compared with good die attach sample.