Growth of star gooseberry-like nickel–phosphorus films on aluminium as thermal interface material for light-emitting diode application

Abstract

Electroless deposition of nickel–phosphorus (Ni–P) on aluminium alloy and the effects of deposition time (1 to 5 min) on the structural, morphological and thermal properties of the coatings are investigated. As the deposition time increases, it leads to growth of star gooseberry-like films. The deposition of Ni–P films has been confirmed by X-ray diffraction spectroscopy and field emission scanning electron microscopy. The prepared films are stacked with high power LED package and the thermal management performance are tested by applying various driving current and temperatures. The Ni–P films shows a better thermal management compared to bare Al substrates. As the deposition time increases up to 4 min, it show gradual increase in thermal conduction, but decreases upon further coating. Ni–P 4 min film, efficiently reduces the rise in junction temperature (Tj) at a driving current of 700 mA from 81.8 to 68.9 °C at 50 °C compared to other ambient condition. Also, the film has very low interface thermal resistance (Rth-int) of 1.09 W/K at 25 °C. The best thermal performance of Ni–P 4 min film is attributed by the high crystallinity, optimized thickness, smooth surface and star gooseberry-like morphology which are effectively acting as conductive pathways for directional thermal transport.