LED heat sink prep?

[eddiesylas]

I have done a lot of reading and am very lost in the details.... so not being a "tech" before I go any further, or even read any more I would like a little feedback. In brief:

Aluminum plate (finned) heat sink from Rapid.

1) Mask the flat LED mounting surface with polyester masking tape (to prevent anodizing and provide marking surface).
2) DIY Anodize the finned surfaces (black for best emmisivity).
3) Mark all drilled points on tape surface
4) Drill #4
5) Tap #4-40
6) Remove tape
7) Polish mounting surface using lapping method (for best conductivity):
400, 600, 800, 1000, 1500, 2000, 2500 grit

Is this overkill or good practice?

 

[insomniac2k2]

Are you doing all that prep just so that you can get a cool anodize? Or is this just for heat transfer? If for heat transfer, see below. Otherwise ignore below

Pretty hardcore IMO. There is no doubt that you will get better heat transfer than not doing it. I would not see that as necessary unless it was a very small build (heatsink) with a ton of LED's on it. That heat transfer is also only as good as the export method. If you pull heat off the LED fast and store it in a heatsink that isnt dissipating the heat quickly and thoroughly, it is rendered useless. Basically what im saying is that if you want to go crazy, make sure you have a lot of air volume to transfer that quickly transferred heat off the heatsink and away from your fixture.

 

[eddiesylas]

Yes I was reading about good heat transfer. But maybe I should be more specific for my build: (21) 3 Watt LEDS per 12x9 heat sink. Each heat sink will have one fan. Of course black anodized aluminum will look great too. But that being said how much heat transfer is really necessary? I just don't want to find out two years from now that I could have done it better and have it cost me.

 

[Softhammer]

Having built my own LEDs that have been performing flawlessly for two years and counting, that is absurd. WAY WAY overkill, you are cooling LEDs, not a Nuclear reactor!! Mount the LEDs with the silver or white epoxy and you will be rocking and rolling. To make soldering easier I epoxied all the LEDs on the heatsink and then set it on my electric stove on low to pre heat everything. The heat sinks work so well that it make a nice solder joint impossible without preheating or a monster soldering iron. I then put one computer cooling fan ($2 on Ebay) per heatsink. Barely gets warm.

 

[insomniac2k2]

I used to tool out on a lot of PC water, heatpipe, fan and passive cooling in the past. From what ive found, most of it is complete overkill. I just went at my fixture/heatsink with a very common approach this time. Hell, I even used thermal pads instead of epoxy. I can tell you these things dont even get close to luke warm before i get good heat transfer over to the heatsink. As long as your pulling the heat off the heatsink by any practical means, you shouldnt see any more than standard degredation.

In your case. Thats a big heatsink for 21 LED's. One fan is more than adequate to pull any necessary heat off. The bigger the fan, the better. Higher CFM and lower noise. Plus you get more coverage.

Will your heatsink be in an enclosure? You will get a bit more heat, if so. But all of the above still applies. You just need correctly directed air flow.

Dont just take my advice on it. Keep reading. I do not think that you will have any regrets either direction that you take. I can just tell you that I wouldnt worry too much about heat transfer. I would concentrate on correct air flow.

 

[Gorgok]

While a black anodized heat sink should theoretically emit heat better (through radiation) the amount of that actually taking place is insignificant in the larger scale.

It does look prettier to have it black though. But i would just anodize the whole thing.

 

[eddiesylas]

that is absurd. WAY WAY overkill, you are cooling LEDs, not a Nuclear reactor!!

:lmao: I work in nuclear power.

The input is really good. I like hearing the "simpler is better" approach too (especially pads instead of epoxy). The "learn the science, you hobbiest dummies!!!" gets kind of old.

But my real motivation today is having a busywork project. As long as it remains labor intensive and not wallet sucking...

I'll post back if I come across anything new, or make a decision.