The Study of Thermal Resistance Measurement of Multichip LED

The high-power light-emitting diode (LED) lighting is especially essential in the high-temperature applications such as the street and automotive lighting. However, >70% of electrical power is converted into heat due to the low electrical-optical conversion efficiency. Because of the characteristics of semiconductor, the electrical property of LEDs sensitively varies with the operating temperature. These deviations affect the measurement of light and electricity. In this paper, the steady-state thermal measurement techniques developed by the National Institute of Standards and Technology are used to study the thermal resistances of multichip LEDs. The experimental results show that the measurements of thermal resistances with different connections are constant at the same power dissipation. The simulation results show that the detail of thermal interaction between powered and unpowered chips and confirm the experiment results.