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Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Hi, I was wondering how I would go about heatsinking these high power surface mount LED's in the pictures below.
I had one running off of a 12v battery during a power-cut last night and I noticed with-in 5 minutes they get too hot to touch. They are 2.2v each and 400mA max so I used a high wattage 30 ohm resistor in series to limit current. It was drawing around 385mA with the 30 ohm resistor.
What sort of heatsink do I need and how would I mount one of them to it? The one I had running is soldered to the underside of a piece of strip-board with copper traces but obviously that is not enough too keep them relatively cool.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Do you have a part number or a datasheet? Datasheets often give mounting tips. High power LEDs are most often mounted on aluminum substrate circuit boards, and bare boards are cheaply available on dealextreme and other similar sites. I could not find anything smaller than a 100-pack , and they are probably made for a different kind of LED, so this is not an ideal solution. You could also try soldering it directly to some thin copper sheet, just be careful not to overheat it.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Wolfram wrote ...
Do you have a part number or a datasheet? Datasheets often give mounting tips. High power LEDs are most often mounted on aluminum substrate circuit boards, and bare boards are cheaply available on dealextreme and other similar sites. I could not find anything smaller than a 100-pack , and they are probably made for a different kind of LED, so this is not an ideal solution. You could also try soldering it directly to some thin copper sheet, just be careful not to overheat it.
Thanks, I did look in the data-sheet but could not find anything.
VLMK71 series from Vishay.
What about a small aluminium heatsink, can I solder the larger solder pad directly onto that? Also is thermal paste needed?
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Good luck soldering to aluminium. I know it can be done with some special solder and flux, but it's not something you can do with regular solder.
You wouldn't need thermal compound if it was soldered to the heatsink, just make sure the biggest terminal on the underside of the LED is the one soldered to the heatsink as this is the terminal that heat is dissipated through.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
Another option for cooling surface mount LED's is to mount it on a two-sided standard FR4 board and use a bunch of vias to conduct heat from the LED side to the other side, where you can put a heatsink. For best performance it will be a thin board with thick copper and large copper areas on both sides. You want to do this for the larger pad because you can see this is the one the die is mounted on.
It's not as high performance as the metal core PCB's but you can have it built in any PCB house pretty cheaply.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
Adapt something from here Thermal vias in thin FR4 work well - sweat the pcb to a copper heatsink. I've also done it using double sided Kapton flex pcb, also sweated to a copper heatsink. If you need to mount a lot of LEDs, its not hard to get MCPCB made especially.
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Heatsinking 1W surface mount LED's
