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

Abstract

Oxide ceramic materials have attractive features ei ther 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 si nk for high power LED. The thermal transient curve of device under test (DUT) was recorded for five boundary conditions. Rise in junction temperature (T J) was measured and observed low value (54.4°C) for 200 nm ZnO thin films at 350 mA. The difference in juncti on temperature rise (ΔTJ) was observed as 7.46 °C at 700 mA when compared to bare Al substrates. The total thermal resistance (R th-tot ) of the DUT was low for 200 nm ZnO thin film coated Al substrates. AFM imag es were used to evaluate the surface roughness fact ors and their influence on thermal resistance. As expected, the surface roughn ess, grain size and peak-valley distance were stron gly influenced the heat flow. Index Terms: ZnO thin film, thermal interface material, LED, th ermal resistance, surface roughness