Matching your COB to a heat sink is one of the most difficult parts of designing your own COB grow light. Unless the manufacturer of the heat sink actually specifies the wattage you can get away with running, you’re left to do the calculations yourself. Luckily, there are tons of heat sinks available now that come pre-drilled for your COB or board, and are rated, in plain English, for their power handling ability. You might see smaller pin-fins (120mm or so) that are rated for 50 watts of power, larger pin fins at 140-150mm rated for 75 watts, or even bigger sinks that are 160mm+ and rated for 100W.
That being said, you might be a glutton for punishment and have a burning desire to source your own heat sink, or figure out if the one you’ve got kicking around will work. Fortunately, like most things in the DIY LED world, we can figure this out with a little research and perseverence. Fair warning though, this is pretty dry stuff.
Tonight, I want to share a bizarre-looking heat sink I found that’s made specifically for the kind of COBs indoor LED gardeners love to use, like the Cree CXB3590 and CXB3070, as well as the Bridgelux Vero 29 and Vero 18 series.
Northern Grow Lights’ SST X Passive Heatsink (shown above) looks alien in comparison to a standard “finned” heat sink, but has some very interesting advantages over the classic design, according to their product page:
Pin heatsinks have a unique pin geometry that uses surrounding air streams for a very effective cooling. The round, aerodynamic pin design reduces resistance to surrounding airstreams that enter the pin array, while simultaneously increasing air turbulence. The omnidirectional pin configuration allows air to enter and exit the heat sink in any direction and exposes the heat sink to the fastest possible air speed. The superior airflow and the high emissivity of the anodized heatsink surface allows Pin heatsink to offer an exceptional cooling for your COB LED. Compared to other undersized Pin Heatsinks, our large pin heatsinks are rated to provide better cooling and ensure reliable LED operation and minimum Light Loss over time.
A heat sink with this small of a footprint that is rated for passive cooling (no powered fans) of a 100 watt LED is really quite impressive! I intend to get my hands on one of these to do some testing in a new build.