So what if thermal compound spreads?

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.

On Mon, 12 Apr 2004 10:11:12 -0400, "jeffc" wrote:

snip

You'll always get a little but if you are squeezing a lot out it
indicates you've applied far too much, meaning the layer of paste
between the processor die/heatspreader and heatsink is too thick.

The pressure from the heatsink clamps won't allow a "layer" to be formed.
Metal will be pressed against metal wherever possible, and there's nothing
you could do to stop it if you tried.


Almost, but they all have a film strength, will keep the 'sink suspended
above the CPU. However there are no truely, perfectly flat 'sinks so
applying too little can be just as bad as too much.. the portion of the
CPU with the thermal diode in it could be in closer contact to the
heatsink than other regions, so the temp reported isn't so accurate
anymore.

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.

jeffc wrote:
"Paul Hopwood" wrote in message
...

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?

You'll always get a little but if you are squeezing a lot out it
indicates you've applied far too much, meaning the layer of paste
between the processor die/heatspreader and heatsink is too thick.


The pressure from the heatsink clamps won't allow a "layer" to be formed.
Metal will be pressed against metal wherever possible, and there's nothing
you could do to stop it if you tried.



And I don't think anybody has mentioned that the compound gets less
viscous when it heats up, and so is squeezed out more easily then.

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.

"Matt" wrote in message
...
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?


Dielectric was 'dialectric' - like dialectic !

In article , says...

"QBall" wrote in message
...

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

Thick? Like viscosity? Then you have bad paste for this application.

No. THick as in distance from one face to the other.


--
Conor

If you're not on somebody's **** list, you're not doing anything
worthwhile.