Performance Testing of 3-W LED Mounted on ZnO Thin Film Coated Al as Heat Sink Using Dual Interface Method

In high-power electronic devices, thermal interface material (TIM) helps to conduct heat effectively from the chip to ambient by connect the discrete points of the two mating solid surfaces. This paper demonstrates the use of zinc oxide (ZnO) thin film as TIM prepared on Al substrate using RF sputtering. The total thermal resistance (R_th-tot) measured by dual interface method is lower for ZnO coated than for bare and thermal paste applied Al substrates. The thickness of ZnO thin film also influences the thermal resistance as R_th-tot decreases with increased thickness at high driving current. Junction temperature (TJ) is also reduced noticeably for ZnO coated substrates and ATJ between bare and 800-nm ZnO thin film coated substrate is 3.33°C as high for other combinations. The thermal resistance of ZnO interface (R_th-b-hs) is also calculated from the transient curve and observed low resistance with 800-nm ZnO thin film measured at 700 mA. The observed correlated color temperature values are low for ZnO thin film coated Al substrates measured at >350 mA. ZnO thin film is supported to enhance the luminosity of the given light emitting diode and suggested for the replacement of thermal paste based interface material.