Using 8020 extruded aluminum as a heatsink - Page 1
Forum section: electronics / projects

author: fivefish
author_rank: Frequent Contributor
timestamp: August 03, 2015, 02:00:33 am
content: Heatsinks... they're so expensive once you get beyond the small size.So I thought about using an 8020 extruded aluminum.Crazy idea? Anybody tried it? Of course, we don't know the C/W rating. That's something that can be measured after the fact.It's about 2.9lbs for a 2 foot section of a 3"x0.75"...Here's what I'm thinking.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 03, 2015, 02:59:03 am
content: It's probably heavy enough to carry heat across the width, but I wouldn't expect its heat dissipation capability is much better than a solid block of the same dimensions.And (brand name) 80/20 is pretty expensive, too(Isn't it written with a slash? 8020 sounds like an exotic aluminum alloy.)Tim

author: TheMG
author_rank: Frequent Contributor
timestamp: August 03, 2015, 03:54:55 am
content: There's a treasure trove of large heatsinks to be found in e-waste, especially old commercial electronic equipment.Heck, I'd even give you some from my extensive collection, but the shipping costs from my location are probably quite high.

author: Gyro
author_rank: Super Contributor
timestamp: August 03, 2015, 05:38:42 pm
content: The other thing to check is that the mounting surface of the extrusion is sufficiently flat (ie. no curvature). This is something that is controlled on commercial heatsinks, but not necessarily on extrusions intended for other uses.This may or may not be an issue in practice depending on dissipation requirements - there probably wouldn't be any danger of package distortion with single hole fixing devices on a convex surface, just poor heat transfer.

author: SeanB
author_rank: Super Contributor
timestamp: August 03, 2015, 08:24:11 pm
content: I have used extrusions originally meant for demountable partitioning as heatsinks, you just have to assume it will be as effective as the same size non finned heatsink. Your mounting though will either need to be flat, or you will have to mill it flat or file it flat. I got around 4C/W of dissipation out of a 5cm offcut, which was perfect for the TO220 package I screwed to it with a sheet metal screw. I just needed better than bare, and this worked.Thicker extrusions will need some preparation, as they are all going to have uneven surfaces, though your regular heatsinks are in any case extrusions cut to length. Theyy might ne milled for the more expensive ones, but most are not and in many cases ( PC power supplies) they barely debur the holes.

author: ajb
author_rank: Super Contributor
timestamp: August 03, 2015, 09:11:20 pm
content: Quote from: Gyro on August 03, 2015, 05:38:42 pmAnd even commercial heatsink extrusions may not be sufficiently flat over a large enough area. Controlling the curvature of an extrusion is hard, especially on a complex asymmetrical shape like a heatsink. I just looked at some 1"x1" 80/20 out of curiosity, though,and the closed sides seem pretty darn flat--certainly flat enough for one or two TO220 devices. However I suspect it wouldn't perform nearly as well as a similar size purpose-made heatsink extrusion because the thin areas around the holes through the 80/20 will limit the rate of heat propagation from the mounting point of the device to the distant areas of the heatsink. You may get similar results to the 8/20 for less money by using a simple U-channel.