Nano Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia (USM), Pulau Penang 11800, Malaysia
For 3 W green light emitting diode (LED), the top surface of commercial heat sink was machined with two different shapes (hole and ‘V’ shaped) and the thermal performance was tested. The contact surface area of the heat sink was increased by machining process. The observed junction temperature (TJ) from transient cooling curve was high for ‘V’ shaped surface for all driving currents. Hole shaped surface of heat sink did not influence much on the TJ values. In addition, total thermal resistance (Rth-tot) was not affected by the hole shpaed surface compared to plain surface. Noticeable increases in TJ as well as Rth-tot were observed for ‘V’ shaped surface for all driving currents (100, 350 and 700 mA). The observed correlated color temperature (CCT) values were high for hole and ‘V’ shaped surfaces and the variation in CCTwith respect to time was high for all surfaces measured at 700 mA. Increased lux for modified surface at high driving current (700 mA) was also observed. Very small variation in color rendering index (CRI) values could be observed.