The cost of producing Chip On Board (C.O.B.) LEDs is coming down, which is making producing fixtures with COB LEDs a lot more viable. Advantages include: Higher quality. Since the entire PCB (including the LED portion) is all machine-produced at the same time, the end result will be more uniform in construction. Increased thermal dissipation. Better thermal management, because the LED is directly attached to the PCB, giving it more surface area to pass heat away from the LED die. Fewer solder joints. Less soldering means a lower risk of a loss in performance due to a bad solder joint. Larger LED surface area. Since we can better control the cooling, we can build larger LED emitters. Using a COB light engine allows us to use a single LED to produce a huge amount of light. A single source LED can be easily lensed to create a hard-edge source, or in other applications, can be installed in a reflector for a softer effect.
—From “Focus on Fundamentals” by Michael Graham, product development manager for Chauvet Professional, PLSN, Dec. 2012