Thermal Resistance Analysis of High Power Light Emitting Diode Using Aluminum Nitride Thin Film-Coated Copper Substrates as Heat Sink

Abstract

AlN thin film was coated over Cu substrate (575 mm2) with 400 nm thickness using DC sputtering for thermal interface material (TIM) application. Aluminum Nitride (AlN)-coated Cu substrate (AlN/Cu) was used as a heat sink for 3-W green light emitting diode (LED). The thermal transient curve was recorded for given LED attached with bare Cu and AlN-coated Cu substrate at three different driving currents. LED attached on AlN/Cu showed the reduced raise in junction temperature (TJ) by 2.59 °C at 700 mA. The LED/TIM/AlN/Cu boundary condition was not supported to reduce the TJ. The total thermal resistance (Rth-tot) was reduced for AlN-coated Cu substrate at 350 mA. The thermal resistance between metal core printed circuit board and Cu substrate (Rth-b-hs) was also observed as low for AlN-coated Cu substrates compared with other boundary conditions measured at 700 mA. The observed results were supported for the use of AlN thin film as TIM in high power LEDs.