I just read an interesting article True or false? High-power LEDs don’t generate IR heat in the forward direction like a filament lamp that give something to think about on LED technology. I and you have for sure read that a high power LED emits no UV or IR and that any heat is created only in the PN junction and then transferred to a heat sink. Okay on the UV part; but the IR part? Read on.
Operating at less than full power, with substrate below 50°C, the top surfaces of the array were measured at well over 100°C and as high as 150°C. Instrumentation error? The black, high-emissivity dot, affixed to a surface which, per all industry conventional wisdom, could not possibly be over 50°C. Where does this lead us? Contrary to conventional wisdom or, better said, industry awareness, high power LED’s DO generate IR and the heating resulting from such.
Now that we know about it, does it even matter? The materials on top of LED arrays must withstand high temperatures. It also means that if the top surface of a high power LED array is too close to a temperature sensitive object bad things could happen. The effects described here are not easy to detect in 1-2 watt LEDs or 5mm small LEDs, but on high power LEDs (many watts) they can be noticed.