Thermal Adhesive

[raptor1956]

I'm working on an idea using some Peltier modules to cool and/or heat something inside an aluminum box and I'd like some ideas on the proper thermal adhesive to bond the Peltier module on one side to the aluminum box and on the other side to an aluminum heatsink.  The modules are 40mm x 40mm x 4mm.  If I used regular thermal paste I would need to affix the module using mechanical connections such as screws or nylon standoffs and I may need to use them anyway but if a thermal adhesive is usable it might make the other connections easier.  So, any recommendations?

I am now testing a second batch of modules after the first batch of 10 turned out to be not so good with 4 of 10 failing outright and pretty dismal cooling performance of the other ones.  This second batch is much better with none of the 5 modules DOA and much better cooling performance.  The module I'm testing now has the cold side at -4.4C with a layer of frost on it and a room temperature of 22C.  The hot side is running around 36C and is a finned heatsink with fan.  Both side of the module have thermal paste on them but the connection is just weight at this point -- no hard connection.


Brian

[MK]

Go to the manufacturers websites for top end peltier units and have a look at the recommended clamping forces, you need long stainless steel M3 or M4 screws holding the assembly together, make it so that the length of steel exposed between hot and cold face is a lot more than the peltier thickness.
Use a 40x40 stub of copper on the cold face to build out the spacing.
It is quite easy to end up 1-4 watts pupmed cold side for 40-60 watts dissipated hotside.

[Gyro]

+1  Peltier elements are fairly strong in compression, maximum clamping force specs are quite high (between flat surfaces). They are mechanically weak in tension and shear modes though.

[raptor1956]

What about thermal adhesive?  I can figure out a mechanical mounting system but knowing how well thermal paste works both thermally and mechanically could simplify the mechanical side a bit.  If the adhesive is strong enough to secure the peltier module from moving about then the mechanical mounting hardware would not need to be so precisely made.  If the adhesive is not very strong or if the thermal properties are in adequate then going with a good thermal paste and then having to design a more precise mounting system that both secures the module to both the hot and cold connections as well as limit heat transfer from hot to cold.


Brian

[Mr.B]

I have never used the following for Peltier modules, but I have used it to glue small heatsinks to LED drivers.
This may be what you are looking for:

Arctic Silver Thermal Adhesive is a two part permanent epoxy adhesive for thermal joints...
Made with 99.8% pure micronized silver. 62% to 65% silver content by weight. Superior thermal performance.

http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

[raptor1956]

I have never used the following for Peltier modules, but I have used it to glue small heatsinks to LED drivers.
This may be what you are looking for:

Arctic Silver Thermal Adhesive is a two part permanent epoxy adhesive for thermal joints...
Made with 99.8% pure micronized silver. 62% to 65% silver content by weight. Superior thermal performance.

http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

Thanks,


Brian

[DaJMasta]

I've used the Arctic Silver adhesive mentioned to good effect, but I don't know if I would for your application.... it just seems like something you'd want to be able to remove/swap/whatever and it may be annoying to work on whatever's under the heatsink (if it's on the top side of the board, for example, you wouldn't be able to access it because it's now stuck face down to the chassis).

You'll get marginally better thermal performance with a regular thermal adhesive (provided you've got flat surfaces to attach to), but that adhesive is actually pretty good as far as TIM goes.  Maybe adhesive to one side and regular paste on the other?  You'd still need the mounting hardware, but it would be removable and it's not going to go out of alignment with a peltier floating between to surfaces.

[MK]

A peltier on the hot side is working so hard I would not trust an adhesive to be a thin enough layer to work well. I always used long stainless screws and graphite, but the real answer is to look at your application and see how hard the peltier may or may not be working and work out which gives the outcome you want, you may need a much bigger heatsink on hotside to overcome the interface loss for instance, you cost it out for yourself.

[Gyro]

Did you do a web search? Try "TEC mounting"...

http://www.customthermoelectric.com/TECmounting.html

[raptor1956]

I am doing testing but at this point it is with thermal paste, not adhesive.  I still have more testing to do but it looks like a single module should be sufficient for the task.  I should also mention that I plan to run the module in both directions so that in addition to cooling I need to be able to use it for heating purposes as well.  I haven't begun testing on that but by the look of things heating is the easier of the two by a long mile.

The bigger challenge is in designing a cage of sorts to hold the item being cooled or heated.  The cage needs to transfer the heat in or out so it will need to make physical contact with the item.  I also need to monitor the temp to keep it within the desired range.

Anyway, I appreciate the feedback...


Brian