Thermal Performance of High Power LED on Boron Doped Aluminium Nitride Thin Film Coated Copper Substrates

Abstract

Aims: The paper is aim to study the thermal performance of Boron doped Aluminium Nitride (B-AlN) thin film coated over Copper (Cu) substrate to improve surface configuration of the interface between two materials with different synthesis parameters. Study Design: Synthesis of Boron doped AlN thin film by sputtering and post processed for various temperatures. The processed samples were characterized to study the behavior of B doping as well as the annealing temperature in changing the properties of B doped AlN thin film. The structural and surface properties were studied and reported. Place and Duration of Study: Nano Optoelectronic Research Laboratory, School of Physics, University Sains Malaysia, Penang 11800, Malaysia, between December 2013 and July 2014. Methodology: B-AlN thin films were prepared with five different gas ratios over Cu substrates by DC-RF coupled sputtering method and suggested for thin film based thermal interface material (TIM). 3W green LED package was tested with B-AlN thin films coated Cu substrates through thermal transient and surface analysis. The results are compared with the performance of bare Cu substrates. Results: The thin film prepared with gas ratio of Ar 7: N2 13 coated at 200°C showed the lowest thermal resistance Rth (53.27 K/W), board to ambient thermal resistance RthB-A (36.03 K/W) and the lowest junction temperature Tj(120.98°C) at higher driving current (700 mA). Surface analysis results show that the thin film mentioned above exhibits low in surface roughness (8 nm) and range of valley depth (30-80 nm), which contribute in thermal performance of LED. Conclusion: Overall, B-AlN films coated with gas ratio of Ar 7: N2 13 are more favorable in reducing both total thermal resistance and junction temperature (Tj) of LED.