The hobby jewelry people like copper disks (aka blanks), so they are cheap and plentiful. I got these from Amazon, but there are lots of sources, all sorts of diameters and gages.
I'm thinking about heat sinking some small parts with these.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
If they cost more than a "penny", you paid too much ;-)
Yeah, just use the penny.
Pennies haven't been made of copper for yonks.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
But they can still be found. ...for a penny. ;-)
Discreet device copper heat sinks are cheap. Already fashioned. Well worth the quite low price considering the benefit. They radiate far better than a slab would.
They're not very flat, either.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Yes... use an old penny would have been a better prompt.
No need to bite it or look at the date... I can tell.
Measure the thermal resistance junction to air for a modern penny and a real copper one. Betcha you can't tell the difference in any practical sense. If you live near a railroad, you can make 'em thinner ;-)
I don't want to radiate, I want to conduct heat from the top of a very small part, through an insulating gap-pad, into a metal cover. A 3/16 diameter disk will increase the transfer area into the pad by about
20:1.A 1/4" disk would be more like 30:1.
The parts here have a surface area around 1e-6 square meters. That small an area wouldn't conduct much heat into an insulator. The copper spreads the heat.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
My Father figured out by weight when copper was up you could take in 100 pe nnies and get about $1.34 or something like that. But he had forgotten that they are mostly zinc now.
When he retired he definitely had too much tome on his hands. you should ha ve seen the collection of tools he amassed. We ad about every tool you coul d think of except for a plasma cutter and a set of acetylene torches, and i f one happened by at a good price we would have had it I guarantee.
But that would e nice if you could take in $ 10,000 worth of pennies and ge t $ 13,400 for it. That would be worth the freight. But like Rome before it fell, we use base metals in our coins.
Funny, I thought copper was already a base metal, so they got a base base m etal...
Better stack gold and silver, and arms, and non-perishable food. The surviv alist "nut jobs" may be right ! (stacking means buying the real thing and p utting it in a safe, not on paper)
But wouldn't aluminum work ? Or is the thermal mass of copper an advantage in your application ?
I don't know what you'd call cheap but AliExpress has them in all kinds of sizes and gauges too. I just picked one at random - 10 pieces of 15x15x0.8mm for $0.89 with free shipping.
I know many of you balk at the idea of using a Chinese product. But how bad could a sheet of "pure" copper be for heatsinking?
It's more like $0.02/cent nowadays, and even the zinc ones are worth more by material. 'Course, when metal prices peaked back in 2006ish, Congress was quick to make melting coin illegal again.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:
My Father figured out by weight when copper was up you could take in 100 pennies and get about $1.34 or something like that. But he had forgotten that they are mostly zinc now.
When he retired he definitely had too much tome on his hands. you should have seen the collection of tools he amassed. We ad about every tool you could think of except for a plasma cutter and a set of acetylene torches, and if one happened by at a good price we would have had it I guarantee.
But that would e nice if you could take in $ 10,000 worth of pennies and get $ 13,400 for it. That would be worth the freight. But like Rome before it fell, we use base metals in our coins.
Funny, I thought copper was already a base metal, so they got a base base metal...
Better stack gold and silver, and arms, and non-perishable food. The survivalist "nut jobs" may be right ! (stacking means buying the real thing and putting it in a safe, not on paper)
But wouldn't aluminum work ? Or is the thermal mass of copper an advantage in your application ?
Then it is perfect and that is called conduction cooling.
Better to mill the metal cover to be just a few tens of mils above the chips you wish to dissapate best and the gap pad gets compressed at those locations and conducts better as the cross sectional thickness of the pad is reduced and you no longer have yet another series element in the chain.
It was never not illegal. One cannot legally deface currecny and melting down a pile of coin is multiple counts thereof.
I wonder what alloy are they. Very small amounts of impurities can make a very large difference to the thermal and electrical conductivity.
e.g.:
If I care enough about conductivity to use copper instead of aluminium then I use offcuts of highly conductive copper busbar from a place that builds electrical switchboards. Of course one should expect to have to pay for these. If I don't need high conductivity but do need it to be solderable then I might use any old copper plumbing pipe etc.
I guess you have seen these:
Perhaps it was even you that pointed them out to me. If it matters, they might have less capacitance than a big copper disc with gap pad dielectric.
I'm not sure that they are relevant in your situation, but perhaps you could put the heat-generating component soldered to the PCB at one end of the therma-bridge, and solder a powerpeg thermal connector at the other end of the therma-bridge.
powerpeg thermal connectors:
One concern is to control the down-force on the part. Another is to make sure the heat conduction surface makes a good, parallel contact to the part. Those things are easier to deal with if the gap-pad is thick, so its compression and compliance define the force and allow for a bit of tilt correction.
The part is a BGA, and I don't know exactly how far above the surface of the board they will finally be, in production. I'm thinking a mm or even 2 mm of gap pad would be nice and springy.
The bracelet-earring-dangley copper things are cute and cheap; there must be a use for them.
People sell rectangles and other shapes too
If these were sold as electronic parts, they would cost 10x as much. I'm always impressed by how much extruded heat sinks cost; I can tool up my own extrusion and run off a truckload for less than I'd pay Wakefield.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I guess the isotopes of copper are similar in China. Heat conduction goes down fast with impurities, so the jewelry-bracelet stuff wouldn't conduct heat (or electricity) as well as conductor-grade OFHC, but that wouldn't affect me much now.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Copper plumbing pipes are pure copper and just as conductive as any bus bar ever was.
Slide one inside the other, cut to length, and smash flat, solder ends to lock them together, drill holes, apply PEM studs (google image "copper PEM stud").
The bars are not too much in single and surley less in bulk...
Or buy a rack enclosure. They usually come with one. Don't populate the rack with anything highly consumptive unless you replace it (and use it) though.
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