So what if thermal compound spreads?

On Mon, 12 Apr 2004 12:19:51 +0100, Conor wrote:

In article ymoec.80914$Pk3.59130@pd7tw1no, says...

Please start with this: In what way does 3 contradict 2?

How can you have capacitive properties if a compound is not conductive?

Precisely.

Actually, you can have a "capacitive property" without being conductive. Do
some research on dielectric constant. Every substance has one. Even a
vacum has one. Some substances with high dialectric constants, such as
silicones, have such high resistances they are effectively non-conductive
(you won't read any resistance with a standard ohmmeter), yet they do
increase the capacitance between between conductors. So there are 2 points

1. Everything has a capacitive property. It is called the dielectric
constant. It is not directly related to conductance or resistance.

2. Everything is also to some degree conductive. When the resistance (the
inverse of conductance) is high enough we can't practically measure it we
call that substance non-conductive.

http://www.rfcafe.com/references/ele..._strengths.htm
JT

On Mon, 12 Apr 2004 10:47:11 +0100, Piotr Makley wrote:

Conor wrote:

Hmmm greasy finger goop, damn boy if you worked in my place
and used your bare hands you'd be getting a **** round the
back of your head...

Why is that? Is it because you buy into the hype of the
anti-static wristband manufacturers lies?

And yes I know all about static damage...


I don't think he is referring to damage by static. I think there
is something "bad" about even a trace of grease like that from a
finger. I don't know why this is though.

Can anyone enlighten me (gently)?

Short term, skin oils are a poor heat conductor, so interfere with heat
transfer from cpu to heatsink. Long term most peoples skin oils are acidic
or salty enough to cause corrosion, which is also not a good thing to have
between a cpu and a heatsink

JT

On Mon, 12 Apr 2004 13:19:12 GMT, JT wrote:

On Mon, 12 Apr 2004 10:47:11 +0100, Piotr Makley wrote:

Conor wrote:

Hmmm greasy finger goop, damn boy if you worked in my place
and used your bare hands you'd be getting a **** round the
back of your head...

Why is that? Is it because you buy into the hype of the
anti-static wristband manufacturers lies?

And yes I know all about static damage...


I don't think he is referring to damage by static. I think there
is something "bad" about even a trace of grease like that from a
finger. I don't know why this is though.

Can anyone enlighten me (gently)?

Short term, skin oils are a poor heat conductor, so interfere with heat
transfer from cpu to heatsink. Long term most peoples skin oils are acidic
or salty enough to cause corrosion, which is also not a good thing to have
between a cpu and a heatsink

JT

Nonsense. NOBODY has enough oil on their fingers to significantly cause
corrosion or degrade the cooling efficiency. Now maybe if someone had
just finished picking their nose or painting a fence...

"JT" wrote in message
s.com...
On Mon, 12 Apr 2004 10:47:11 +0100, Piotr Makley wrote:

Conor wrote:

Hmmm greasy finger goop, damn boy if you worked in my place
and used your bare hands you'd be getting a **** round the
back of your head...

Why is that? Is it because you buy into the hype of the
anti-static wristband manufacturers lies?

And yes I know all about static damage...


I don't think he is referring to damage by static. I think there
is something "bad" about even a trace of grease like that from a
finger. I don't know why this is though.

Can anyone enlighten me (gently)?

Short term, skin oils are a poor heat conductor, so interfere with heat
transfer from cpu to heatsink. Long term most peoples skin oils are acidic
or salty enough to cause corrosion, which is also not a good thing to have
between a cpu and a heatsink


Everything depends on the amount of skin-oil.
If you've recently washed your hands, very little will be deposited.
Some people barely secrete any oil, others have greasy skin.
Ultimately, the tiny amounts involved are unlikely to find their way onto
the sink because they'll be trapped under a layer of goop on the finger.



JT

On Mon, 12 Apr 2004 12:31:22 +0000 (UTC), "QBall"
wrote:


"kony" wrote in message
.. .
On Mon, 12 Apr 2004 09:26:44 +0000 (UTC), "QBall"
wrote:

And it's so thick, there's no metal-metal contact.

Metal to metal eh? Obviously you're only talking about CPUs with a heat
spreader on them. It makes a much greater difference how thick the
compound is when there's a spreader, because the retention force per sq.
mm is so much lower.

It's difficult enough to rub the goop away with a finger - try it for
yourself.

Well that's just a sign that your heatsink compound is too thick.


Hehem .... I'm the guy who's been saying that it should be applied so it's
invisible.

Not APPLIED too thick, rather too viscous.

Rubbing it off the point of invisibility takes a little application of
effort and could no way be achieved by squeezing with a sink clip.
You've gotten the complete wrong end of the stick, sir !

An assumption that seems to be based around using overly viscous compound.

If it
can't even be rubbed with a finger it's not going to be getting into the
crevasses very well either until it heats up,


This is a problem with crappy, coarse goops like Ceramique.
For the CPU, a fine goop like AS3 should be used.

It's not even worth taking the time to consider. There's at most 4C
difference between any of 'em, and if the system is THAT close to
instability the time should've been spent on heatsink or chassis cooling
issues.

QBall wrote:
"Johannes H Andersen" wrote in message
...


Matt wrote:

Conor wrote:

In article ,
says...


CrackerJack wrote:


What exactly is the problem if too much cpu compound is put on the
core and it gets squashed out onto the surrounding area?

Apart from looking messy, is there any real problem with this?

I propose this answer:

1) If the compound is not too viscous, and the heatsink is clamped on
with some force, and you apply enough compound, the thickness of the
layer of compound does not depend on the amount applied, which is to

say

that the excess gets squeezed out.

2) Thermal compounds are not electrically conductive.

3) Some thermal compounds (notably those containing silver compounds)
have capacitative properties that can be problemmatic if compound gets
between the chip's leads.

4) If you use a compound that doesn't have the problemmatic

capacitative

properties and is not too viscous, in general it won't hurt to use too

much.


1) WRONG
2) WRONG
3) If 3 is true then 2) is wrong. You've just proved that yourself.
4) WRONG.


Your reply is practically content-free.

Please start with this: In what way does 3 contradict 2?

Apart from the above, the word you're looking for is 'dielectric'. Look
up any elementary physics text book.



Hehe ..... LOL
The contemporary edukation system has a lot to answer for.
Bad spelling is so freaking irritating.


What was misspelled?

Conor wrote:
In article ymoec.80914$Pk3.59130@pd7tw1no, says...


Please start with this: In what way does 3 contradict 2?

How can you have capacitive properties if a compound is not conductive?


Precisely.


Taken as a rhetorical question, it is precisely (if I may use your term)
WRONG.

Placing a sheet of glass, rubber, or wood between the plates of a
parallel-plate capacitor increases the capacitance by a factor of
something like 5.

I invite your arguments regarding each of the other points.

Piotr Makley wrote:
"QBall" wrote:

Anyway, the addition of a
microscopic quantity of skin oil makes no difference
whatsoever.


But why do people seem to worry about it?

The Arctic Silver people preserve their products' mystique by requiring
the user to jump through hoops that are about as relevant as the phase
of the moon and how you hold your mouth. That way the user feels guilty
if he doesn't achieve the promised super-duper temperature improvement.

One of their instructions that I took seriously is that excess compound
between chip leads can cause capacitance problems. Next time I will buy
a low-capacitance (low dielectric) thermal compound.

Johannes H Andersen wrote:

Matt wrote:

Conor wrote:

In article ,
says...


CrackerJack wrote:


What exactly is the problem if too much cpu compound is put on the
core and it gets squashed out onto the surrounding area?

Apart from looking messy, is there any real problem with this?

I propose this answer:

1) If the compound is not too viscous, and the heatsink is clamped on
with some force, and you apply enough compound, the thickness of the
layer of compound does not depend on the amount applied, which is to say
that the excess gets squeezed out.

2) Thermal compounds are not electrically conductive.

3) Some thermal compounds (notably those containing silver compounds)
have capacitative properties that can be problemmatic if compound gets
between the chip's leads.

4) If you use a compound that doesn't have the problemmatic capacitative
properties and is not too viscous, in general it won't hurt to use too much.



1) WRONG
2) WRONG
3) If 3 is true then 2) is wrong. You've just proved that yourself.
4) WRONG.


Your reply is practically content-free.

Please start with this: In what way does 3 contradict 2?


Apart from the above, the word you're looking for is 'dielectric'. Look
up any elementary physics text book.

Yes. Thank you. One could in the forgoing substitute "dielectric
constant" for "capacitative properties".

"CrackerJack" wrote in message =
...
What exactly is the problem if too much cpu compound is put on the=20
core and it gets squashed out onto the surrounding area?
=20
Apart from looking messy, is there any real problem with this?

Is there any "real" problem? No.

Is the heat transfer less efficient? Yes.

By how much? Not very.

There is a point past which application thickness doesn't matter. For =
example, putting on a layer 1mm thick and 2mm or 3mm or more will give =
you the same amount between the heatsink and the core; the excess is =
squished out. Essentially, past a point, it can't possibly get any =
worse.

However, below a certain thickness (at which I could only guess), the =
thickness of the paste as applied will affect the thickness of the paste =
(and hence the thermal conductivity) once the heatsink is on. This point =
is only reached when no compound squishes out i.e. what you put on is =
what ends up between the HS and CPU. Here less is better.

Personally, I never worry about it. Unless it's dripping off the CPU, =
it'll be fine.

However, do heed the warnings that have been given. A silver-based =
compound, such as Arctic Silver, can cause problems if it comes in =
contact with the CPU bridges. No such problems exist with ceramic-based =
compounds, such as Ceramique.