Flexible Thermoelectric Coolers Anyone?

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WildBoar
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Flexible Thermoelectric Coolers Anyone?

Post by WildBoar » Sun Jun 27, 2004 2:09 pm

Does anyone sell a thermoelectric cooler
(also called a Peltier module) that can
be wrapped around something that is roughly
the shape and size of a soup can. A flexible
heat sink to go with the module would help
a lot too.<p>I've seen a whole bunch of the flat, rigid
kind. My instincts tell me that someone
must be making flexible modules since entire
circuit boards can now be bent or molded to
fit almost any application.<p>Here's another thing my sixth sense is telling
me. Yes, they are available but they cost more
then most of us want to spend.<p>Anyone got the up to date info on these modules?
I sure don't!<p>WildBoar

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jwax
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Re: Flexible Thermoelectric Coolers Anyone?

Post by jwax » Sun Jun 27, 2004 3:09 pm

Had the same thought myself (back in the 80's) for chilling a can of pop or whatever beverage from a wrap-around Peltier, plugged into the cig lighter. I couldn't get the two major makers of the chips to sell me the un-mounted chips. The flexible substrate is no problem- lots of folks make flexible circuitry these days, and conductive epoxy to hold the chips in place would do it. Getting the chips is the tricky part.
Anybody have a source?
John

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sofaspud
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Re: Flexible Thermoelectric Coolers Anyone?

Post by sofaspud » Sun Jun 27, 2004 8:15 pm

I have never seen or heard of a flexible Peltier device. Everyday Practical Electronics magazine had a beverage can cooler project in their June 2004 issue. You might want to check that out.

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dacflyer
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Re: Flexible Thermoelectric Coolers Anyone?

Post by dacflyer » Mon Jun 28, 2004 3:36 am

is "Everyday Practical Electronics magazine"
another electronics magazine???<p>tell me more...

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Externet
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Re: Flexible Thermoelectric Coolers Anyone?

Post by Externet » Mon Jun 28, 2004 6:24 am

Oh, yes. Major publication:<p>http://www.epemag.wimborne.co.uk/
with forum too.<p>And in relation to flexible Peltier coolers, nope.
The military medical may have a chemical wrap of some sort as they have the heating pads.
Flexible circuit boards rarely carry power enough to deserve Peltier cooling on them.<p>Miguel.<p>[ June 28, 2004: Message edited by: Externet ]</p>
- Abolish the deciBel ! -

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sofaspud
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Re: Flexible Thermoelectric Coolers Anyone?

Post by sofaspud » Mon Jun 28, 2004 12:56 pm

Everyday Practical Electronics is a British publication. I have seen it before on the newstand at my local Barnes & Noble bookstore. EPE also has an online version found at http://www.epemag.com/, where that June 2004 issue can be downloaded for about $5.

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dacflyer
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Re: Flexible Thermoelectric Coolers Anyone?

Post by dacflyer » Mon Jun 28, 2004 1:58 pm

:( ( never mind :p

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haklesup
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Re: Flexible Thermoelectric Coolers Anyone?

Post by haklesup » Mon Jun 28, 2004 2:12 pm

Since the Peltier Junction requires a substantial chunk of silicon, it is difficult to assemble onto anything but a flat substrate. I imagine it is possible but you would need to be a major player to get the manufacturers to change anything just for you. A polyimide flex substrate (the typical type) generally does not have the current carrying ability. Furthermore, unpackaged silicon devices are generally not affixed to flex substrates as support for these attach methods would be rare. Normally a package surrounds the Si device and the interconnect is metal to metal using solder.<p>The substrate must be capable of delivering several amps to each point on the array with little or no voltage variation due to conductor resistance.<p>All that aside, a more attainable way to make a can cooler would be to mount a regular CPU type heatsink on the hot side and engineer some sort of can shaped heat sink optimized to take heat from a can to sit on top of the cold side. Wrap that in an attractive, insulative plastic case and you have a mass producable product.<p>In my experience, conductive epoxy and silver conductive paint have very high resistance of thousands of ohms per inch. even closely spaced, I always measured at least 100 ohms. Not good at all for an interconnect that needs to carry significant current (I^2*R heating can negate the cooling effect). Silicon devices usually use a Gold-Silicon alloy that melts at several hundred C (within hotplate range)to attach to the substrate.<p>If you want to make your own junctions try to find someone who sells scrap Si from Chip Fabs. Sometimes you can find these guys at rock and gem shows. Talk with them and they might have something you can try. It's a long shot but worth a few minutes googling at it. It's not out of the question to make a diffusion furnace if all you want is a crude junction in a thick piece of silicon.

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sofaspud
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Re: Flexible Thermoelectric Coolers Anyone?

Post by sofaspud » Mon Jun 28, 2004 5:44 pm

dacflyer,
True those overseas subs cost an arm & a leg, but you can get a year (12 issues) of the EPE online version for $10.99. Each issue is about a 5 meg d/l.

WildBoar
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Re: Flexible Thermoelectric Coolers Anyone?

Post by WildBoar » Mon Jun 28, 2004 9:12 pm

When I described the thing I wanted to cool
I really wasn't thinking about a can of soda.
The object I'm trying to cool is part of a
much larger device that costs many thousands
of dollars.<p>Yeah, you guys are right. Thermoelectric
coolers are big current hogs. I should have
realized that constructing a flexible cooler
is not like creating these milliamp gizmos
such as roll-up keyboards, etc.<p>Thanks to all for your replies. Haklesup,
your electronics knowledge is a cut above
average, to say the least! I always learn
something when I read your postings.<p>WildBoar

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jwax
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Re: Flexible Thermoelectric Coolers Anyone?

Post by jwax » Tue Jun 29, 2004 6:40 pm

Peltier junctions are not made of silicon-
They're doped bismuth telluride. Also, I don't know which silver epoxy you've tested, but it is available and used for power MOSFETS, IGBTS, etc.
And if it's high current flexible circuits that you want, let me know.
Like I said, if you find a source for Peltier chips, from Melcor, or Teca, or wherever, a flexible heat transfer panel can be made.
John

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haklesup
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Re: Flexible Thermoelectric Coolers Anyone?

Post by haklesup » Wed Jun 30, 2004 9:46 am

Thats right, and strike my last irrelevant paragraph.<p>Thats why this and these forums are so great. Since you can't beleive any single source of information on the web (this includes me ;) ) an average of answers like these threads usually reviels the core of truth.<p>I only tried 4-5 retail available epoxies so it may not have been [was not] a complete sampling. For a flat surface to surface connection like a die to substrate they may perform better than the application I was trying.

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Re: Flexible Thermoelectric Coolers Anyone?

Post by Deal » Wed Jun 30, 2004 1:05 pm

I have designed and fabricated thermoelectrics for medical devices. On East Coast US, I would recommend Melcor in New Jersey. Thermos are current hogs but can deliver heat/refrig control to small areas ( I also do freon refrigeration). Thermoelectrics been around decades and have been fashioned into motorcycle helments for cooling and most everything you can think of. Good luck with your cool ideas.

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Re: Flexible Thermoelectric Coolers Anyone?

Post by rshayes » Wed Jun 30, 2004 8:58 pm

Have you considered using a flexible heat pipe to conduct the heat to a rigid, and rigidly mounted, thermoelectric cooler?<p>A flexible heat pipe might be much easier and cheaper to design and build than a flexible thermoelectric cooler. It also relocates the weight of the thermoelectric cooler and its radiator to a different, and possibly less critical, location.<p>[ June 30, 2004: Message edited by: stephen ]</p>

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