Synthesis of MgO Thin Film on Aluminum and Copper Substrates as Thermal Interface Materials

In this paper, RF sputtered magnesium oxide (MgO) thin films (225 nm) on Aluminum (Al6061) grade and Copper substrates were used as thermal interface materials for high-power LED. X-ray diffraction spectra showed the presence of polycrystalline MgO with (200) and (220) oriented cubic MgO (c-MgO) phase as preferred. Thermal conductivity measurement showed an improvement from 17.26 to 22.63 W/mK for Al6061 substrates and from 15.04 to 20.18 W/mK for Cu substrates, respectively. An impressive decrease in junction temperature ( ${T}_{j}$ ) was recorded for MgO thin films interfaced LED on both substrates, especially 2 h annealed MgO on Cu and Al6061 showed a noticeable difference in junction temperatures ${\Delta } {T}_{j}$ of 32.91 °C and 23.08 °C, respectively. Consequently, the difference in total thermal resistance ( $\Delta {R}_{\textit {th-tot}}$ ) of 5.15 and 3.69 K/W were recorded for MgO film coated Cu and Al6061 substrates, respectively, when compared to their values of bare substrates measured at 700 mA. From surface analysis by atomic force microscope, smooth surfaces for annealed MgO thin films were evidenced when compared to the unannealed films and bare substrates, which was making the LED package with low junction temperature and thermal resistance. Overall, MgO thin film synthesized over Cu substrates showed good performance on reducing ${T}_{j}$ and ${R}_{\textsf {th}}$ of LED at higher driving currents when compared to that of LED on MgO coated Al6061 substrates.