December 2012 Issue
Focus on Fundamentals

Chip On Board (COB) Technology

Michael Graham, product development manager for Chauvet ProfessionalFor several years now, the entertainment lighting industry has been inundated with LED technology. Even though over the past eight years we have seen a diametric shift from any bi-pin style lamp bases towards LEDs, I still say that we are just scratching the surface of the possibilities. But I do think that LEDs are beginning to transcend their infancy. I finally feel like the “Baby On Board” sign can be replaced with “Chip On Board.”

We see a lot of things come and go in the lighting industry. We have watched over the years as fixtures have become more efficient, smaller, faster, quieter, and lighter in weight. A good friend of mine once told me that the lighting industry is a lot like the fashion industry. Designers like what they like. They all want to use the latest and greatest gear. I guess that makes shows like LDI our fashion week.

The latest fashion rage in lighting is the Chip On Board (COB) LED technology. You see it at tradeshows, you read about it in blogs, and manufacturers tout it as the newest advance in LED technology. And, yes, COB LEDs are absolutely awesome at producing light. But the technology itself is by no means new. All it refers to is the fact that the semiconductor (in our case, an LED) is directly mounted on and electrically interconnected to its circuit board. This process was originally designed to make manufacturing of PCBs (printed circuit boards) faster, easier and more reliable. Without COB technology, we would still be walking around with a boom box on our shoulders instead of a smartphone on our belts.

Chauvet Nexus 4x4Advantages of developing devices Chip On Board LEDs are:

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.

Over the past few years, we have seen these same light sources used more and more for wash lights and arrays. An example of the COB LED being used in an array configuration is the Nexus 4x4 from Chauvet Professional. This fixture uses a total of 16 COB LEDs in a 4-by-4 layout. Instead of using a lens, it has a reflector that is roughly the size of a PAR 38 lamp and has about the same effect.

Being able to use a COB for this kind of application has major advantages. Because the actual LED is part of the PCB, we are able to have a lot more powerful LED in a much smaller space. The tri-color LEDs installed in the Nexus 4x4 are capable of running at 20 watts each. With a standard SMD (surface mounted device) LED, it would not be possible to use that much power in such a small space.

COB LEDs are also finding their way into many other entertainment fixtures, such as ellipsoidal reflector spot lights, Fresnel lights, PAR-style LED lights and effect lights. It is a great fit because of its light characteristics. Having a fairly flat field and the ability to be easily lensed, COB LEDs work really well when installed into fixtures that require good optics.

In the ellipsoidal reflector spot lights and in Fresnel lights, it is most common to see a single COB LED being used to replace the incandescent light source traditionally used there. The COB can be a good source for this, since the light level and quality look similar to the more conventional source it is replacing. Using a single warm or cool LED allows for easy replacement of the older, power-hungry incandescent light sources. With regards to the PAR style lights, since COB LEDs are also built in the color-changing variety, you can still mix any color you like without the blender sounds that scrollers make.

Outside of entertainment, you will see COB LEDs mounted in high bay lights, powering LED projectors, lighting up the outsides of buildings, airport runway applications, and even in medical applications. So the next time you are sitting in the dentist chair, look up, and ponder whether the light source that is blinding you is a COB LED. At least it will take your mind off the drilling.

Are COB LEDs the next big thing? It all comes down to the economics of it all. You get all of the benefits that we have come to demand from the LED fixtures, such as low cost of operation, long life of the product, less maintenance, and all of this with a really good reproduction of the incandescent or discharge lamp that they are replacing. The cost of producing COB LEDs is coming down, which is making producing fixtures with COB LEDs a lot more viable. With that being said, we are also going to see more of these COB-powered products replacing older, less efficient LED fixtures as time goes on.

It is all pretty amazing that, in such a short time, the lighting industry has changed so much. I feel like it was not so long ago that I was changing out a bunch of old fixtures with the asbestos-covered power cables for some brand-new Source Four ellipsoidals. Going from having 96 channels of dimming to filling an entire universe of DMX, to working with a single static fixture that takes 53 channels to operate it, it all seems like a blur. Watching and working on the constant evolution of the entertainment and architectural lighting industry has been amazing. So, when people ask me if I think COB LEDs are the future, all I can say is that, for right now, it looks that way.

Michael Graham, product development manager for Chauvet Professional, has also designed and installed entertainment and architectural lighting systems.

 


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