Quad MC-E Heat Management Question

zinetti

Newly Enlightened
Joined
Nov 16, 2008
Messages
13
- 4 MC-E K Bin LEDs running at 2.8A - Internally wired in P, 4 wired in Series


Hey guys, i have been trying to determine what size heat sink i will need to have behind these to keep them at a safe temperature. I have run across a crude calculation of
- Rise in temp C per watt = 50 / sqrt(surface area in sq cm)
- I have a 50 sq in heat sink which shows to be around 2.7C/watt

At an ambient of 10c and an LED efficiency of 15% (guessing) the heat sink would be at around 219F, this sounds way too high but here's my math using the crude results from above of 2.7c/w.
- 10c ambient + 2.7 * 40w * 85% inefficiency ) = 102c

Can someone let me know
- What is a safe upper temperature for the heat sink nearest the LED - LED to Star board soldered - Arctic alumina star to heat sink
- What is efficiency of MC-E - How much of the ~40 watts will be turned into heat?
- How large of a heat sink will it take?
- What is the formula to determine heat sink size?
- For both static air and if you use a fan to move air across it - is the a formula taking into account cubic foot per minute?

Thank you for your help,
Jason
 
THERMAL PASTE between Star and sink, no Arctic
(this Arctic is really something that must have been glued into the ppls heads)

Arctic is "just" a very expensive Epoxy glue, mixed with metal particles for more heat transfer,
(possibly a very small layer of Epoxy instead of the Arctic has the same capabilities)
thermal paste easily moves way more heat away

then, as one uses stars and a large sink: use screws to attach the Star
--> removable
--> more force, so hopefully a slimmer layer of paste/Expoxy


the proper way of mounting a Star/Led:
* place with thermal paste on back
* move it around to make layer thinner, get air out, come to an almost-glued (but removable) position of Star/Led
* when Star: use screws into sink to fix them
* if Led (if screws not possible with star): now - after the paste placing - glue the thing in with Epoxy applied around it


no help with the size of Your sink, but an advise: massive ;)
I have an Osram 6-die emitter, mounted on a Pentium II heatsink (14*9*3 cm).
When the led is run at only 500 mA, it gets too hot to handle within a few mins!
I think, with moving air, 1 Pii sink for every MC-E might be enough - if You want them mounted "in the open".
... no scientific explanation, sorry.
 
Thanks Yellow for the mounting advice. I used the stove and some solder paste to mount them to the boards, worked great.

Jason
 
Top