Medium temperature heat transfer adhesive - Page 1
Forum section: electronics / general

author: TimB100
author_rank: Contributor
timestamp: October 25, 2016, 09:20:50 am
content: Hi,Hi I have an need to transfer heat from copper tube to an aluminium heat sink. Imaging a grove in an aluminium block with a small dia copper tube set into it. I want an adhesive that will hold it in place and provide a very good heat transfer between the copper and the ali.Temperature range is 0 - 180oCI have tried an aluminium solder to braze the copper in place but there is adhesion issues onto the copper.Any ideas?Thanks! Tim

author: BradC
author_rank: Super Contributor
timestamp: October 25, 2016, 09:49:26 am
content: Aluminium solder is predominantly zinc and should adhere to the copper spectacularly, you just need to get the copper hot enough to melt the aluminium. The trick is to tin the copper to get the bond, then you can reheat it at a lower temperature to melt the "solder" and get it on the aluminium. It's actually quite tricky stuff to work with, and getting the oxides off the ally to get a good bond there is the really tricky part.

author: TimB100
author_rank: Contributor
timestamp: October 25, 2016, 10:13:46 am
content: Thanks BradI agree now its a technique issue and perhaps I need better solder / and flux etc.I'm going to go back to it.Cheers Tim

author: BradC
author_rank: Super Contributor
timestamp: October 25, 2016, 12:44:00 pm
content: Quote from: TimB100 on October 25, 2016, 10:13:46 amTry some fluoride based brazing flux on the copper. You'll want the copper at a dull red heat to activate the flux. I've done this sort of thing without flux, but I did it with a TIG, so lots of localized heat and a completely inert atmosphere. Copper oxidizes fairly rapidly at high temperatures. Don't go too hot or you'll boil the zinc. Let the copper melt the solder rather than direct heat on the solder. There is special flux to use with the aluminium, but most of the ally "solder" uses a technique where you cover the surface with molten "solder" and use a stainless brush to break up the oxides on the surface allowing adhesion. It bypasses the requirement for flux because the solder displaces the oxygen anyway.Your other option might be an oxy (acetylene, propylene or propane) in a reducing environment (more gas than oxygen). That or a big blowtorch and lots of flux with a stainless wire brush to clean up the resulting mess.

author: Ian.M
author_rank: Super Contributor
timestamp: October 25, 2016, 01:21:40 pm
content: I'd be suspicious of the reliability of the zinc based Aluminium solder at elevated temperature. DO NOT use any lead containing solder when pre-tinning the copper as the combination of trace lead contamination and AlZn intermetallicsis likely to result in premature failure.Seehttps://en.wikipedia.org/wiki/Zinc_pest

author: grifftech
author_rank: Frequent Contributor
timestamp: October 26, 2016, 02:33:46 pm
content: get the aluminium copper plated.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 26, 2016, 08:39:56 pm
content: I know there are thermal epoxies. But I do not know if they withstand 180 Celsius.http://multimedia.3m.com/mws/media/142914O/3mtm-thermally-conductive-epoxy-adhesive-tc-2707.pdf