PERFORMANCE OF HIGH POWER LIGHT EMITTING DIODE FOR VARIOUS ZINC OXIDE FILM THICKNESS AS THERMAL INTERFACE MATERIAL

Oxide ceramic materials have attractive features either as filler or substrate materials in electronic packaging. Consequently, ZnO thin film for various thicknesses was prepared over Al substrates by RF sputtering and used as heat sink for high power LED. The thermal transient curve of device under test (DUT) was recorded for five boundary conditions. Rise in junction temperature (TJ) was measured and observed low value (54.4°C) for 200 nm ZnO thin films at 350 mA. The difference in junction temperature rise (ΔTJ) was observed as 7.46 °C at 700 mA when compared to bare Al substrates. The total thermal resistance (Rth-tot) of the DUT was low for 200 nm ZnO thin film coated Al substrates. AFM images were used to evaluate the surface roughness factors and their influence on thermal resistance. As expected, the surface roughness, grain size and peak-valley distance were strongly influenced the heat flow