arctic alumina failed on one of my lights
I'm not sure why, it doesn't seem like it should have been stressed very much. I don't remember the history of the arctic alumina, there is a possibility it aged before I used it. It just peeled off in a sheet.
Is anyone using an alternative adhesive? I'm thinking about just bolting down the star and using heat sink compound, but that's a lot of work.
In my experience, poor adhesion is usually traceable to a surface that is not clean enough or too smooth. Epoxy based adhesives need a somewhat rough surface to properly bond to. Of course that is counter to the best surface for heat transfer in metal to metal junctions. Structural adhesives do have limited shelf life to achieve their design strength. My first couple lights used screws and thermal compound and it is certainly more work. I do think it a better method though I am lazy and switched to arctic silver adhesive a couple years ago.
How about thermal adhesive tape? That's how the L-flex boards are supplied, and I've used it on emitters and heatsinks. No long term data yet.
I'm going to mess around with some homebrew AAA.
I have a few different epoxies, and picked up a sack of powdered aluminum from a rock polishing store.
We'll see how it turns out.
Got the stuff called "Linde B" from this webstore.............
The Linde A is a smaller micron, but from what I've read, the Linde B works fine.
We will see...................
Look, whatever happens, don't fight the mountain.
Be careful with Linde powder, either A or B.
1 - don't inhale the fine stuff ... very bad for the lungs. Wear a respirator and if possible work outdoors with a fan blowing behind you in the direction the wind is blowing.
2 - don't mail it to anybody or else the DEA and/or Homeland Security will be all over you before you can say "It's not Cocaine/Anthrax" Don't ask how I know this is a bad idea
I've made my own Arctic Alumina using Linde. It's cheap but kind of a hassle. It does work pretty well. Best place to buy AA (IMHO): http://www.sidewindercomputers.com/araltherad.html
They used have a buy 5 for a cheaper price deal, but their current price isn't bad. If you live in the US they ship priority mail for a very reasonable price.
With regards to Arctic Alumina strength over time:
Clean all surfaces with alcohol or acetone first. Wear gloves when handling parts to keep finger oils off surfaces.
Light sanding with a fine sandpaper doesn't hurt as described by Vancbiker, clean up afterwards. I usually use number 500 grit sandpaper or finer. You can sometimes find the really fine stuff with a plastic backing at hobby stores or websites. You can rinse it off and use over and over.
Where possible add another layer of epoxy over optics or star boards to backup the AA. I use reflectors in a lot of my lights. I AA down the stars. AA down the reflector. Then cover everything with a 1/4 inch of epoxy. That makes sure nothing is ever going to move and it provides a bit of additional thermal path for the star. This has proven to be a very robust mounting system, at least for me.
Thanks, using epoxy on top is a good idea
+1 everything that firstname.lastname@example.org said but aluminium powder is also very explosive. There was a story on the news not too long ago in the UK when a man opened a tin of the stuff and it exploded in his face. He is now blind.
Sorry to put a damper on the idea unterhausen, but have a read of this http://www.jtbaker.com/msds/englishhtml/a2712.htm
I use Arctic Silver 5 and screws or pressure from the face plate pushing down on the optics.
Last edited by yetibetty; 04-09-2011 at 08:01 AM.
I think unterhausen is talking about using aluminum oxide powder (linde), not aluminum. I'm pretty sure it is not explosive.
But you are right aluminum dust can be explosive. I found an article online (don't remember where) about the dangers of using the same sander for sanding iron and then aluminum some time later. The iron turns to rust and iron oxide and aluminum are the components used to make thermite. And sanding aluminum heats everything up till suddenly fwoop! boom!
My first thought was that I didn't clean well enough. But it still would have worked if I had used your epoxy idea. I think I'm going to go that way before I make any radical changes.