Making Cool High-Brightness LEDs

Okay. You are probably more interested in reading about OLEDs than LEDs. OLEDs are the thin displays that look way better than LCDs and are used in high-end mobile phones and will be here “any day now” in HDTVs. LEDs are those little thingies that make power indicators light up.

But right now, LEDs are a whole lot more important to the HDTV industry than OLEDs. Way more important. The notebook computer industry has already shifted to LEDs for backlights for their LCD screens, and HDTV makers are following close behind. LEDs use less power to produce the same amount of light as fluorescent tubes, have better color performance, and don’t have use the environmentally hazardous mercury that complicates waste disposal and recycling. Oh, and the LED backlights make it possible to create impossibly thin LCD televisions.

But the problem is that you need very bright LEDs for those thin edge-lit panels. And high brightness LEDs get hot. And when an LED gets hot, its light output is reduced. So heat management is a critical issue for LCD HDTV backlights. The LED manufacturers are working with new substrates as alternatives to the standard sapphire substrates used to make LEDs. These alternatives have better heat dissipation, so the LED chips can run cooler. According to a report in DIGITIMES, Formosa Epitaxy is one of the leaders in using copper-tungsten substrates, and has started production in small volumes. For now, most of the product is used as illumination for pico projectors, but the company projects that the new substrate could account for 20% to 30% of its high-brightness LED production for 2011.

So not all the technology advances are in the obvious parts of an HDTV. Sometimes an improvement in a small part can make a big difference in the overall system.