J
John
- Jan 1, 1970
- 0
Jon said:Is it possible to throw together some home made heat sink pads?
After reading your posts in this thread, I conclude that toilet paper would
serve your purpose.
Jon said:Is it possible to throw together some home made heat sink pads?
HAHA. What a looser. Someone disagree's with you and you get mad. Just
what I expect from an "expert".
The regular Dow Corning thermal grease must have some very small fill
particles. With just modest pressure, I've measured its added spacing at
below 100 microinches (0.1 mils), which is the limit of the micrometer I
had at hand. It flows out of the gap. Right, it's not a very good thermal
conductor, but it does squish out very thin... a sil-pad may be 50-100
times as thick!
Grease over flat, 0.5 mil hard anodize is about as good as it gets.
In other applications mica is used as a thermal *insulator* !!
After reading your posts in this thread, I conclude that toilet paper would
serve your purpose.
Quite !
Since when did sanding produce a smooth surface Mr Blow Hard ?
Trying to show your mettle, eh?
(Let me re-phrase that)
Trying to show your metal, eh?
Trying to show your meddle, eh?!
Heheheh :-]
kell said:Cut a piece off a mylar potato chip bag. Mylar doesn't melt easy.
You're only using 12 volts, so super-thin chip bag mylar is
perfect.
Assuming it really is mylar. A commonly used dielectric. I have
some mylar sheet I use for insulators, but it's thicker than chip
bags. I can tell you, that stuff doesn't melt easy.
Have you looked at aluminum nitride? It's almost as good as BeO but
it's not toxic. For high-voltage and high thermal density, I'd go for
a non-insulated copper heat spreader over an AlN insulator, all
greased... if you can stand the capacitance!
I think BeO has the best ratio of thermal conductivity to dielectric
constant, except for diamond. Or flowing distilled water.
That's not *sand paper* though is it ?
John said:Have you looked at aluminum nitride? It's almost as good as BeO but
it's not toxic. For high-voltage and high thermal density, I'd go for
a non-insulated copper heat spreader over an AlN insulator, all
greased... if you can stand the capacitance!
I think BeO has the best ratio of thermal conductivity to dielectric
constant, except for diamond. Or flowing distilled water.
Hey John,
these guys (http://hypertextbook.com/physics/thermal/conduction/)
report the conductivity of properly oriented graphite as about twice as
good as diamond. It sure would be fun to find a way to take advantage
of that.(*)
(*) Wrongly-oriented graphite, though, is terrible.
Rich said:Do you have any examples of this? I've seen mica used as an _electrical_
insulator in a high-temp environment, like in toasters and hair dryers
and stuff, but I doubt its intent is thermal insulation there.
As long as there isn't a metal burr to puncture the paper and the
device isn't tightened to the point where it can make a compression
cut it should work.
Some old mica windows from kerosene heaters can be cut to make
insulating pads - mica conducts heat well (still need silicone grease
because it isn't perfectly flat).
Mike Monett said:The polyethylene layer may mean food wrapping is a poor choice for
a heat sink insulator since it melts at such a low temperature.
However, Christmas wrapping may be more robust. I'm on my way to
WalMart to see if they still have any on sale
Rich said:I've still got a tube of DC-340 (or maybe 320 - I don't remember exactly)
that I lifted when I was in the USAF in the 1970's; I'll swear by the
stuff. Whenever I replace a MB/CPU/heatsink I wipe off the goo that comes
with the heatsink and use my good ol' trusty Dow Corning, that's how much
I trust it.
Eeyore said:Read Motorola's AN1040.
The best heat sink pad is Grafoil.
Hey John,
these guys (http://hypertextbook.com/physics/thermal/conduction/)
report the conductivity of properly oriented graphite as about twice as
good as diamond. It sure would be fun to find a way to take advantage
of that.(*)
(*) Wrongly-oriented graphite, though, is terrible.
The dielectric constant of water's pretty high though, right?
I also wonder about:
a) electroplaning/polishing, for ultra-ultra-flat, smooth surfaces
and
b) microplasmic or other anodic coating (denser than ordinary
anodize)