Thermal resistance of high power LED on surface modified heat sink

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 (T J) 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 T J values. In addition, total thermal resistance (R th-tot) was not affected by the hole shpaed surface compared to plain surface. Noticeable increases in T J as well as R th-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 CCT with 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. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.