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Home made heat sink pads

J

Jon Slaughter

Jan 1, 1970
0
Is it possible to throw together some home made heat sink pads? I saw the
silicone was a decent thermal conductor and was thinking about using it. I
just need something that will let me electrically isolate the output of some
voltage regulators. I don't think they will ever get to hot but I'd like to
attach a heat sink to them just incase but I have no pads around.

Thanks,
Jon
 

neon

Oct 21, 2006
1,325
Joined
Oct 21, 2006
Messages
1,325
MICA is very good insulator for electronics.see MOUSER for parts.
 
J

John Larkin

Jan 1, 1970
0
Is it possible to throw together some home made heat sink pads? I saw the
silicone was a decent thermal conductor and was thinking about using it. I
just need something that will let me electrically isolate the output of some
voltage regulators. I don't think they will ever get to hot but I'd like to
attach a heat sink to them just incase but I have no pads around.

Thanks,
Jon

Silicone is a terrible heat conductor. Filled silicone is slightly
less terrible.

One trick is to add a little sand (very little) to epoxy and epoxy the
transistors to a heatsink. The sand grains enforce an insulating
spacing. This is thermally mediocre, similar to a sil-pad, but useful
for low power stuff. (Cataphote makes precision glass balls to do this
more scientifically. It's just a screen-graded version of their
retroreflector beads.) You can also use thread or monofilament as an
epoxy spacer. I suppose sand in grease might work too.

There's a new, relatively expensive, pink kitchen wrap stuff, maybe
from Reynolds. It seems pretty tough. A layer of this, with some
grease (vaseline?) on each side, wouldn't be bad; just make sure there
are no metal spurs or such that might cut through. Thicker plastic,
like maybe some household packaging stuff, maybe mylar sheet from a
greeting card or some such, would be tougher, but keep in mind that
thermal resistance increases directly with thickness.

It would be interesting to compile a list of the thetas of household
materials, like yogurt covers or milk carton stock or whatever. Auto
supplies (shims, gaskets) would be interesting too.

The best insulator is of course none; float the heat sink and use a
dab of grease under the semi.

John
 
J

Jon Slaughter

Jan 1, 1970
0
Eeyore said:
Not very practical no.



No it isn't.

Try doing a search for silicone heat sink pad's and you might be supprised.
 
J

Jon Slaughter

Jan 1, 1970
0
John Larkin said:
Silicone is a terrible heat conductor. Filled silicone is slightly
less terrible.

Well, When I did some searches I found many silicone based heat sink pads.
While it might not be the best from what I found on the internet it might be
good enough for my applications. Here I'm talking about a thickness of less
than a mm.
One trick is to add a little sand (very little) to epoxy and epoxy the
transistors to a heatsink. The sand grains enforce an insulating
spacing. This is thermally mediocre, similar to a sil-pad, but useful
for low power stuff. (Cataphote makes precision glass balls to do this
more scientifically. It's just a screen-graded version of their
retroreflector beads.) You can also use thread or monofilament as an
epoxy spacer. I suppose sand in grease might work too.

Well, wouldn't a thin piece of hard plastic with many small holes in it
work? (say, soemthing from a soda bottle with many 2-3 mm holes drilled in
it along with some thermal grease?
There's a new, relatively expensive, pink kitchen wrap stuff, maybe
from Reynolds. It seems pretty tough. A layer of this, with some
grease (vaseline?) on each side, wouldn't be bad; just make sure there
are no metal spurs or such that might cut through. Thicker plastic,
like maybe some household packaging stuff, maybe mylar sheet from a
greeting card or some such, would be tougher, but keep in mind that
thermal resistance increases directly with thickness.

It would be interesting to compile a list of the thetas of household
materials, like yogurt covers or milk carton stock or whatever. Auto
supplies (shims, gaskets) would be interesting too.

Yeah. I tried searching for some possibilities that I could put together
quickly and silicone was the only thing that I could find that might work.

http://sound.westhost.com/heatsinks.htm

There are "Sil-Pads" with Fair+ thermal insulation it has 1 - 1.5 thermal
resistance while it says mica is 0.75 to 1.0.

So as far as I can tell you guys are wrong about the silicone. I'm not sure
if the sil-pads are "standard" silicone or not but it seems so.

On another site I saw that 1mm of silicone offers about 1kV of protection.
Since I just need ~12V I could get away with a pretty thin covering. Just
enough to prevent shorting. I doubt the components themselfs would get about
100 C but I wanted to mount them to the chasis just incase they did get to
hot.

Thanks,
Jon
 
A

Andy

Jan 1, 1970
0
Jon said:
Is it possible to throw together some home made heat sink pads? I saw the
silicone was a decent thermal conductor and was thinking about using it. I
just need something that will let me electrically isolate the output of some
voltage regulators. I don't think they will ever get to hot but I'd like to
attach a heat sink to them just incase but I have no pads around.

Thanks,
Jon

Out of curiosity: why do you want them home-made? What would be wrong
with using some commercially-available insulators? They are not
expensive. (Ex. made from some "Boron nitride loaded silicon Elastomer")

Thanks.

-- Andy
 
J

John Larkin

Jan 1, 1970
0
Try doing a search for silicone heat sink pad's and you might be supprised.

Factor in the effect of gross lies on the part of the silicone pad
vendors, compounded by measurements done at huge contact pressures.

Try actually using and measuring this stuff.

John
 
Jon said:
Well, When I did some searches I found many silicone based heat sink pads.
While it might not be the best from what I found on the internet it might be
good enough for my applications. Here I'm talking about a thickness of less
than a mm.

But perhaps you don't understand that 1mm is HORRIBLE ?
Well, wouldn't a thin piece of hard plastic with many small holes in it
work? (say, soemthing from a soda bottle with many 2-3 mm holes drilled in
it along with some thermal grease?

What's the thermal conductivity of polystyrene though, and in thick
layers? Numbers matter.

The see-thru windows commonly used in envelopes are mylar, and I've
recently measured some: thicknesses ranged from 0.8 to 2 mils.
Metallic wrapping "paper" is super-thin aluminized mylar, which might
also do in a pinch. Thetas? Dunno.

Yeah. I tried searching for some possibilities that I could put together
quickly and silicone was the only thing that I could find that might work.

http://sound.westhost.com/heatsinks.htm

There are "Sil-Pads" with Fair+ thermal insulation it has 1 - 1.5 thermal
resistance while it says mica is 0.75 to 1.0.

So as far as I can tell you guys are wrong about the silicone.

<snip>

You've already received advice to the contrary from experts ... real
experts. Dismiss it if you will, but, if so, why bother asking?

Best wishes,
James Arthur
 
J

Jon Slaughter

Jan 1, 1970
0
But perhaps you don't understand that 1mm is HORRIBLE ?

1mm is for 1kV+. The data seems to show that its not much worse than mica.
What's the thermal conductivity of polystyrene though, and in thick
layers? Numbers matter.

I didn't say they didn't. But the numbers I've seen on the internet suggest
something very different than what is suggested here. I've not seen anyone
here post any numbers but just say "Your wrong". If the site is wrong then
prove it but just don't say stupid shit without backing it up. Theres to
many "wanna-be's" here and many cannot be trusted. (Not all, there are some
good engineers here but most are not)
The see-thru windows commonly used in envelopes are mylar, and I've
recently measured some: thicknesses ranged from 0.8 to 2 mils.
Metallic wrapping "paper" is super-thin aluminized mylar, which might
also do in a pinch. Thetas? Dunno.

I dunno either, which is why I asked. I cannot seem to find any real
information on this subject on the net and you guys say what I have found is
wrong. I don't really know who to believe.
<snip>

You've already received advice to the contrary from experts ... real
experts. Dismiss it if you will, but, if so, why bother asking?

real experts? How do I know they are real experts? Do you really expect me
to take it on faith that everyone in this NG is an expert? I'm sorry. If
you want to prove you are an expert than back up what you say with data and
references. Don't just say "There wrong and I'm right" because when you do
that you look more like a cooke.

If you expect me to take everything you guys say on faith then I'm sorry. It
won't happen. I'll listen to what you guys have to say but in the end if it
doesn't add up then I'll come to my own conclusions(and if I'm wrong then
I'm wrong... atleast I'll find out for myself instead of trying to be a
mindless drone like you seem to want me to be).

Anyone can claim to be an expert and many people do it. I'm not saying there
are not experts in here or those who have replied are not experts but all I
know is that there is some contradictions between what people are telling me
and hence someone is wrong. Right now the score is against John and Eeyore
because I've found many different sites claiming that silicone works. Its
possible that all these sites are ran by the same idiot or that all of them
are created by idiots but I would imagine the odds of that happening is
pretty slim.

I think the issue you need to get over is that you don't have to take what
people anyone says on faith. Its ok to be hard headed or skeptical because
else you will be conned. Lots of people try to be experts but few are. Many
people try to impress others by acting smart but few are actually smart. Is
this happening here? I don't know. I just know that someone's wrong and it
would be nice to know if silicone is actually worth using or not so I'll
know. Probably the only way it will really get resolved is for me to test it
out on my own and see. Ofcourse thats much more work than I'd want to do
but...


Anyways, I've heard to many "You can't do this or that" type of BS from
newsgroups like this and then when you do it it works. Some people try
something once and it doesn't work and they conclude that it can't work and
then try and convince others it can't work. Those people are usually easy
to spot because they go ape shit when you don't believe them 100%.


Jon
 
J

John Larkin

Jan 1, 1970
0
1mm is for 1kV+. The data seems to show that its not much worse than mica.


I didn't say they didn't. But the numbers I've seen on the internet suggest
something very different than what is suggested here. I've not seen anyone
here post any numbers but just say "Your wrong". If the site is wrong then
prove it but just don't say stupid shit without backing it up. Theres to
many "wanna-be's" here and many cannot be trusted. (Not all, there are some
good engineers here but most are not)


I dunno either, which is why I asked. I cannot seem to find any real
information on this subject on the net and you guys say what I have found is
wrong. I don't really know who to believe.


real experts? How do I know they are real experts? Do you really expect me
to take it on faith that everyone in this NG is an expert? I'm sorry. If
you want to prove you are an expert than back up what you say with data and
references. Don't just say "There wrong and I'm right" because when you do
that you look more like a cooke.

If you expect me to take everything you guys say on faith then I'm sorry. It
won't happen. I'll listen to what you guys have to say but in the end if it
doesn't add up then I'll come to my own conclusions(and if I'm wrong then
I'm wrong... atleast I'll find out for myself instead of trying to be a
mindless drone like you seem to want me to be).

Anyone can claim to be an expert and many people do it. I'm not saying there
are not experts in here or those who have replied are not experts but all I
know is that there is some contradictions between what people are telling me
and hence someone is wrong. Right now the score is against John and Eeyore
because I've found many different sites claiming that silicone works. Its
possible that all these sites are ran by the same idiot or that all of them
are created by idiots but I would imagine the odds of that happening is
pretty slim.

I think the issue you need to get over is that you don't have to take what
people anyone says on faith. Its ok to be hard headed or skeptical because
else you will be conned. Lots of people try to be experts but few are. Many
people try to impress others by acting smart but few are actually smart. Is
this happening here? I don't know. I just know that someone's wrong and it
would be nice to know if silicone is actually worth using or not so I'll
know. Probably the only way it will really get resolved is for me to test it
out on my own and see. Ofcourse thats much more work than I'd want to do
but...


Since you don't want to hear things you don't want to hear, that's
what you'll have to do. So don't whine about how much work it's going
to be. Silicone pads are OK where a largish thermal resistance is
tolerable, as for low power densities and small heatsinks; I use them
myself in such applications. But you started this thread by asking for
materials you might have around the house, which was actually an
interesting question. Have you forgotten the title of this thread?
Anyways, I've heard to many "You can't do this or that" type of BS from
newsgroups like this and then when you do it it works. Some people try
something once and it doesn't work and they conclude that it can't work and
then try and convince others it can't work. Those people are usually easy
to spot because they go ape shit when you don't believe them 100%.


Jon

Look at my web site. Look at the power amp pics I posted to a.b.s.e.
Wanna see my water-cooled, 2400 volt, 20 kilowatt pulser?

http://www.highlandtechnology.com/DSS/T220DS.html

The critical semiconductors are clamp mounted to a machined-flat,
gold-plated, water cooled copper block.

If you newbie into an established ng and ask questions and don't get
the answers you expected, and insist that people who are trying to be
helpful "prove" that they are right, well, foad. And have a nice day.

John
 
Jon said:
I think the issue you need to get over is that you don't have to take what
people anyone says on faith.

No, of course you oughtn't take things on faith--you're right to be
skeptical. On the other hand, it's clear you don't know enough about
the topic to appreciate the sagacity of those whose advice you've
already rejected--real engineers, not salesmen, but experienced *users*
of these things who've made *real* measurements of real products.
Its ok to be hard headed or skeptical because
else you will be conned. Lots of people try to be experts but few are.

Yes, which is why it's worth listening to an actual expert when you
finally encounter him. If 99% of people are fools and you reject 100%
of them, you'll be 100% right 99% of the time, but 100% wrong when it
really counts. I offered my endorsement; it's that's not enough, check
the archives.
Many
people try to impress others by acting smart but few are actually smart. Is
this happening here? I don't know. I just know that someone's wrong and it
would be nice to know if silicone is actually worth using or not so I'll
know.

That's the problem with polling as a way of resolving conflicting
information--reality is not a popularity contest.
Probably the only way it will really get resolved is for me to test it
out on my own and see. Ofcourse thats much more work than I'd want to do
but...

Others have already done that hard work--made those tests and
measurements over the years--and posted their results here. Those are
the results you've already dismissed. If you yourself don't know
enough to recognize truth and wisdom when you encounter it, then yes,
you'll have to rediscover it for yourself. We've all had that dilemma.

Best wishes,
James Arthur
 
B

Barry Lennox

Jan 1, 1970
0
Is it possible to throw together some home made heat sink pads? I saw the
silicone was a decent thermal conductor and was thinking about using it. I
just need something that will let me electrically isolate the output of some
voltage regulators. I don't think they will ever get to hot but I'd like to
attach a heat sink to them just incase but I have no pads around.

Some additives to epoxy improve the theta, ie slate or aluminium
powder. I guess the same might work with grease, and some sort of
woven cloth to act as a spacer.

Some quick trials would soon show up what works, sounds messy though.
 
R

Rich Grise

Jan 1, 1970
0
So as far as I can tell you guys are wrong about the silicone. I'm not
sure if the sil-pads are "standard" silicone or not but it seems so.

Well, they're not. Sil-pads suck as heat sink insulators.

What the hell is wrong with mica and heat goop?
http://www.google.com/search?q=mica+insulators

Or, like John Larkin suggested, don't use any insulation at all, but
just float the heat sink?

Good Luck!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Anyone can claim to be an expert and many people do it. I'm not saying
there are not experts in here or those who have replied are not experts
but all I know is that there is some contradictions between what people
are telling me and hence someone is wrong. Right now the score is against
John and Eeyore because I've found many different sites claiming that
silicone works. Its possible that all these sites are ran by the same
idiot or that all of them are created by idiots but I would imagine the
odds of that happening is pretty slim.

Bitch, bitch, bitch.

So, go someplace where people will tell you what you want to hear.

Good Luck!
Rich
 
J

Jon Slaughter

Jan 1, 1970
0
Since you don't want to hear things you don't want to hear, that's
what you'll have to do. So don't whine about how much work it's going
to be. Silicone pads are OK where a largish thermal resistance is
tolerable, as for low power densities and small heatsinks; I use them
myself in such applications. But you started this thread by asking for
materials you might have around the house, which was actually an
interesting question. Have you forgotten the title of this thread?


hmm... your starting to sound like your getting mad because I don't take
everything you say on faith. hmm. I wonder what that means?

I asked if anyone knew of heat sink pads that could be made from common
materials. I mentioned silicone and immediately you and Eeyore jumped on
that saying that it was crap. I have web sites that disagree with you. Now,
instead of proving with reason that the sites are wrong I get insulted into
trying to believe you are right. Now maybe most people will roll over and
play dead but I won't. Do you really expect me to believe you when you
reason through "muscle" instead of logic and observation?
Look at my web site. Look at the power amp pics I posted to a.b.s.e.
Wanna see my water-cooled, 2400 volt, 20 kilowatt pulser?

http://www.highlandtechnology.com/DSS/T220DS.html

The critical semiconductors are clamp mounted to a machined-flat,
gold-plated, water cooled copper block.

If you newbie into an established ng and ask questions and don't get
the answers you expected, and insist that people who are trying to be
helpful "prove" that they are right, well, foad. And have a nice day.

omg, I guess that proves beyond any reasonable doubt that you are an expert
in heat sink pads of all kinds of materials?
 
J

Jon Slaughter

Jan 1, 1970
0
Barry Lennox said:
Some additives to epoxy improve the theta, ie slate or aluminium
powder. I guess the same might work with grease, and some sort of
woven cloth to act as a spacer.

Some quick trials would soon show up what works, sounds messy though.

yeah. I suppose I could just test some stuff and see. Maybe burn up a few
regulators and see which ones go out first. Just not really something I'm
intersted in doing and I figured someone would know.
 
P

Phil Allison

Jan 1, 1970
0
"Jon Slaughter"
1mm is for 1kV+.


** Typical silicone pads ( eg from Berquist) have thicknesses of 0.2mm and
quote breakdown voltages in the range of 3 to 6 kV.

The data seems to show that its not much worse than mica.


** Where high device power levels are involved, it is much worse than using
thin ( ie 0.002 inch) mica and good thermal compound. For low and moderate
device power levels, sil pads work fine.

Neither mica nor silicone are technically good thermal conductors, mica is
in fact far poorer than silicone - but mic wins as a thermally conductive
insulator because it is possible to use such thin layers of it.



........ Phil
 
J

Jon Slaughter

Jan 1, 1970
0
Rich Grise said:
Well, they're not. Sil-pads suck as heat sink insulators.

and? Did I say I needed something that was good? You know, what sucks is a
relative issue. You seem to have overlooked that. I enver said I needed the
best method or even a good one. Just something that "works". Now a piece of
shit could work AFAIK. I didn't clarify what I was good or not so all in
all you have no clue what I actually want.
What the hell is wrong with mica and heat goop?
http://www.google.com/search?q=mica+insulators

um, I have none around and that wasn't my question. If I had the shit don't
you think I would have used it?
Or, like John Larkin suggested, don't use any insulation at all, but
just float the heat sink?


Because the there is possible contact with the heat sink and the ground. It
doesn't matter though. I didn't ask for that and I don't have to explain
those details as they have nothing to do with my original question which you
seem not to have read.
 
J

John Larkin

Jan 1, 1970
0
I asked if anyone knew of heat sink pads that could be made from common
materials. I mentioned silicone and immediately you and Eeyore jumped on
that saying that it was crap. I have web sites that disagree with you. Now,
instead of proving with reason that the sites are wrong I get insulted into
trying to believe you are right. Now maybe most people will roll over and
play dead but I won't. Do you really expect me to believe you when you
reason through "muscle" instead of logic and observation?

What I expect you to do is go away and don't come back.

John
 
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