Not really, no. Most laser module housings are anodized, and that doesn't hurt the heat transfer either.
Starting out with a flat surface (on both surfaces) and using a little thermal compound will handle all but the most extreme heat loads, regardless of anodizing.
Adam
Senior Member
Oops...no matter ....I don't mind swimming against the tide on this one !
Cheers
PS. From an IR point of view silver is just as black as black!
PPS. "thermal compound" has much the same conductivity as "concrete!" but since it is "thin", (although not quite as thin as anodizing) most people prefer to ignore this, despite it having a similar effect in heat, as "dirty optics" do in light
Last edited by catalanjo; 07-26-2016 at 08:58.
The point of the thermal compound is to fill microscopic voids between the surfaces, since while the paste has a relatively low thermal conductivity compared to metal, it's relatively high compared to air.
Good point about the IR reflectivity. I was referring specifically to visible light, but I grant you that IR is a different animal.
Believe it or not, there are aluminum anodizing processes that produce a conductive coating, rather than an insulating one. That really helps with heat transfer. But the other key thing is that unlike paint or powder coat, the anodizing is very thin, so even in cases where they don't use the two-step chromate process (to obtain a conductive coat), the resulting layer still has a minimal effect on the heat transfer rate. (Which, as I pointed out, is why so many laser modules are anodized even though they have to conduct all their heat through the base to the optical plate they are mounted on.)
Adam
Senior Member
What about thermal grease? The white solidifying compound is too expensive for things like big heatsinks on the bottom of a baseplate.
I think you'd be fine with whatever you have. I actually had a couple tubes of some cheap Chinese knock-off of the original "Arctic Silver" paste that I used back when I was experimenting with high power 445 diodes. (Except the Chinese version I found was "Antarctic Silver"!) Stuff cost me under a buck per tube, and I think I used maybe 2 tubes total on the projector build. (Which ultimately was abandoned for other reasons. But heat was never a problem.)
Basically the stuff I had was cheap thermal paste with some metal dust in it. Probably not even real silver. Worked fine though, and was still tacky a couple months later when I took it apart. And to be honest, I probably would have been OK without it, but I had the stuff sitting on the shelf so I used it.
I haven't used thermal grease in a long, long time. (Long before I started playing with lasers) But it should be OK too. The key is to use a *thin* layer. You're just trying to fill microscopic voids with the stuff. But if you use too much, you make a sandwich with the grease being the "filling", and that's not good.
Adam
Senior Member
@ "Believe it or not, there are aluminum anodizing processes that produce a conductive coating, rather than an insulating one. That really helps with heat transfer." .... better than the aluminium itself? ... I am all ears
@ " use too much, you make a sandwich with the grease being the "filling", and that's not good."
...will also give you a nasty stomach problem if you happen to eat it !
Cheers
Ha!
Well, I don't know anyone who has intentionally eaten any thermal grease, but at the very least I would imagine it would make a pretty good laxative...
As for the conductivity of the 2-step anodizing, no, it's not as good as bare aluminum. But it's not bad... Look up hexavalent and trivalent chromate conversion coatings for more info.
Adam
Jr. Woodchuckington Janitor III, Esq.
it tastes like chicken.Originally Posted by buffo
Ha!
Well, I don't know anyone who has intentionally eaten any thermal grease, but at the very least I would imagine it would make a pretty good laxative...
Adam
suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.
Adam
Senior Member
Hexavalent chromium will do a number on your stomach as well. I've seen it eat a titanium processing tank.Ha!
Well, I don't know anyone who has intentionally eaten any thermal grease, but at the very least I would imagine it would make a pretty good laxative...
As for the conductivity of the 2-step anodizing, no, it's not as good as bare aluminum. But it's not bad... Look up hexavalent and trivalent chromate conversion coatings for more info.
Adam
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