Thermal pad or Thermal paste?

The assumption being that heatsink to CPU surfaces must be
flat. However a better interface is formed with maximum
pressure between those surfaces that transfer most heat.
Almost all heat is transferred from CPU to heatsink in
center. That is where two surfaces typically have most
pressure - so that maximum amount of heatsink is in direct
contact with CPU where the heat is transferring.

~misfit~ wrote:
Thanks for that. I've been watching this thread and also thought the
same thing about dies not being completely flat. What's the use of
having a totally flat HS base if the die is concave or convex?
--
~misfit~

Okay, it seems that to w_tom a temperature improvement of 9 degrees C is
of little consequence.

Perhaps I'm the living dead I should be dead, by all rights! Having
worked (unsafely, I might add!) with many carcinogens and toxic solvents for
the better part of 14yrs....

-
We Live For The One We Die For The One stood up at show-n-tell, in
, and said:

Its safe then, your not dead are you

or are you :0


On Fri, 5 Sep 2003 21:59:56 -0500, "Strontium"
wrote:


-
David Maynard stood up at show-n-tell, in ,
and said:

Arthur Hagen wrote:
"AnthonyR" wrote in message
...

What do you mean the chemist didn't have alcohol?


Vin said that the chemists said they didn't have *isopropyl*
alcohol (isopropanol). Alcohol is at least a dozen different
things, from methanol
to glycerin.

(Also note that when he said chemist, he almost certainly meant
what
we call
a drugstore here in the US.)


Do you not have rubbing alcohol in your house? here in the states
every
house has a bottle, its used to clean wounds and stuff.


We sure don't have a bottle. Is it mandatory?


What do you use for scraped knee's?


Iodine tinctures, witch hazel, hydrogen peroxide, antibacterial
salves and lotions, or a whole lot of other stuff. Including other
alcohols. Using isopropanol as rubbing alcohol might be a regional
thing, because I'm used
to ethanol.

Denatured Alcohol vs. Isopropanol

Denatured Alcohol is ethyl alcohol, or ethanol, containing traces of
benzene. While ethenol, in it's natural form, is a source of
combustible fuel, it contains trace amounts of water making it less
efficient for burning than in it's denatured form. Introducing
Benzene during the distillation process drives out the water
contained in ethanol creating a very pure and potent fuel source -
denatured alcohol.
NOTE: Ethanol is the alcohol consumed in alcoholic beverages.
However, once denatured, ethanol becomes toxic and can cause
blindness or death if consumed.

You are confusing this with Methanol (wood alcohol). Denatured
alcohol (benzene dirtied ethanol) will not cause blindness. Death?
Perhaps, if enough is consumed. More than likely, though, cancer as
well as a multitude of other health problems.. Having worked with
Benzenes for many years, I think I can attest to this.


snip

--
Strontium

"It's no surprise, to me. I am my own worst enemy. `Cause every
now, and then, I kick the livin' **** `outta me." - Lit

Vin wrote:

But my case to cpu temperature delta has gone out of whack!

I haven't followed the whole thread, but we should know whether you
upset the contact between the HS and CPU somehow, maybe by bumping or
removing the HS.

Strontium wrote:
Perhaps I'm the living dead I should be dead, by all rights!
Having worked (unsafely, I might add!) with many carcinogens and
toxic solvents for the better part of 14yrs....

Whagh, our amanuensis (lab assistent) managed 30 yrs already, and still
breathing ;-) I feel a bit queer after sniffing a bit lot of Acrylonitryl
one time, but i think it's normal, hehehe

Thomas

AN is some nasty stuff! Just don't get it on your skin I worked for
Monsanto (after they spun off into Solutia)....the makers of AN used for
Wear-dated carpet. A catalyst, in the reaction, and byproduct is liquid
HCN. I loved going to work, knowing I was going to be handling liquid HCN
(they sampled the liquid HCN tanks once a week for GC and color)...was kinda
neat! AN, depending on it's grade can contain lethal amounts of HCN.
Smells like bleach (as pure HCN does, also). Just don't take too big of a
whiff hehehe.
-
Thomas stood up at show-n-tell, in 7wM6b.36380$tK5.4322954@zonnet-reader-1,
and said:

Strontium wrote:
Perhaps I'm the living dead I should be dead, by all rights!
Having worked (unsafely, I might add!) with many carcinogens and
toxic solvents for the better part of 14yrs....

Whagh, our amanuensis (lab assistent) managed 30 yrs already, and
still breathing ;-) I feel a bit queer after sniffing a bit lot of
Acrylonitryl one time, but i think it's normal, hehehe

Thomas

--
Strontium

"It's no surprise, to me. I am my own worst enemy. `Cause every
now, and then, I kick the livin' **** `outta me." - Lit

w_tom wrote:
The assumption being that heatsink to CPU surfaces must be
flat. However a better interface is formed with maximum
pressure between those surfaces that transfer most heat.
Almost all heat is transferred from CPU to heatsink in
center.

Center of what? The heatsink? Well, close since the heatsink is typically much
larger than the CPU die, or even the IHS, but it's also not (usually) precisely
in the 'center'. The heatsink is often offset due to usually extending on over
the socket hinge cam section. Center of the CPU die? as in the case of an Athlon
XP? No. It depends on the die layout and what portions are being used at any
point in time.

That is where two surfaces typically have most
pressure - so that maximum amount of heatsink is in direct
contact with CPU where the heat is transferring.

The P4 IHS is flat to within 50 um. The Athlon die is essentially 'flat'. Where
is the point of "most pressure?"

The celeron PGA IHS is slightly concave with maximum height on the edges. But
then it not only has to contact the heatsink but the CPU die, down there
underneath in the center.


~misfit~ wrote:

Thanks for that. I've been watching this thread and also thought the
same thing about dies not being completely flat. What's the use of
having a totally flat HS base if the die is concave or convex?
--
~misfit~

Do the entire thermal circuit. Calculate the numbers. 9
degrees is not a serious improvement. Exception is
overclocking which means no valid numerical specifications are
available anyway. Therefore no reliable calculations can be
performed.

9 degrees must be well below what any CPU and heatsink
assembly does in a system running in a 100 degree room. Any
properly constructed system works just fine in a 100 degree F
room.

But when overclocking, then one no longer has any idea of
the heat produced by CPU, a what temperature makes internal
CPU electronic timings unstable, and other parameters. These
are not parameters that damage hardware. These are parameters
that determine CPU stability. Since no calculations can be
performed, then even those trivial 9 degrees might be
significant.

First running that system without thermal compound will
demonstrate how effective that CPU/heatsink interface really
is. More that thermal compound reduces CPU temperature, then
the more inferior that heatsink really was. Just another way
of finding which heatsinks have superior surface machining -
before improving heatsink performance with a least amount of
thermal compound.

If 9 degree C is of significance to a standard clocked
system, then the system has far more serious problems; not
thermal problems. And testing a heatsink without thermal
compound can go a long way to verifying the real integrity of
that heatsink - something that any overclocker should want to
learn.

"Degree C per watt" is an overall number. The heatsink
without and with thermal compound tests but one aspect of that
overall heatsink performance.

Matt wrote:
Okay, it seems that to w_tom a temperature improvement of 9
degrees C is of little consequence.

We provide the simplest instructions to those who follow
instructions without knowing the full story. Experience
without understanding the underlying theoretical science means
such people are ripe for junk science reasoning. Even I would
tell the naive hobbyist to use thermal compound because many
don't want to even bother to learn the whys and why nots.
Intel and AMD do same. They tell hobbyists to use thermal
compound regardless of whether it is really necessary.

But, for example, one Intel engineering paper demonstrated
no advantage to using thermal compound on higher heat
generating semiconductors. Correct. High heat semiconductors
demonstrated no significant advantage over a bare heatsink to
CPU interface. Intel went on to discuss other superior
concepts beyond the scope of this discussion. But if a
hobbyist does not even know if his heatsink is machined; if he
only buys on price, then why tell him any of this. Better to
have him use thermal compound.

Not everyone uses thermal compound. In a previous
discussion, one found no thermal compound on his Intel CPU /
heatsink assembly direct from the factory. Not a problem. It
is rather hit or miss as to whether to apply thermal
compound. Many of our custom designs did not use it because
complications from thermal compound caused other reliability
problems. Semiconductors come both ways - with and without -
because thermal compound only provides a small additional
advantage.

These advantages become glaringly obvious once theoretical
numbers confirm what the product does.

There is a difference between theoretical science and
applied science. If both are not used, then failures are a
probability. What is unique in previous posts? Both
theoretical and applied science were used. As a result, a
number of points were made:
1) that thermal compound must be applied so sparingly that CPU
makes mostly a direct contact with heatsink. So little
thermal compound that it does not spread much into the outer
half of CPU.
2) if heatsink is properly machined, then heatsink can be
applied to CPU without any thermal compound. If properly
machined, then thermal compound would only result in single
digit temperature decreases.
3) many heatsinks are sold even without the essential "degree
C per watt" number. Many don't even know how good their
heatsink really is OR how much better it would be if properly
mated to CPU. That test first without thermal compound, then
with goes a long way to learning how good a heatsink really
is.
4) Arctic Silver is overhyped. Most thermal compounds do for
dimes what Arctic Silver does for dollars. But then Arctic
Silver also does not make numerical specifications easily
available - which should be the first indicator that Arctic
Silver is hiding something. Products sold without numerical
specs should be routinely suspect. Arctic Silver is mostly
sold on hype - engineering specs be damned when your customers
too often fear the numbers.

David Maynard wrote:
w_tom wrote:
Intel and AMD do not demand that everyone use thermal
compound. They say to ill informed hobbyists to install

Following installation instructions is not "ill informed."

thermal compound because experience has demonstrated that
"degree C per watt" is too complex for some assemblers. For
those with some experience, any heatsink without the "degree C
per watt" parameter is suspect - at best.

But then, since thermal compound is so cheap (tens of times
less than what the overhyped Arctic Silver costs), then why
not provide thermal compound so that the bad CPU installation
does not cause permanent failure. Thermal compound is good
compensation for the ill informed computer system assembler.

And where are these 'good installers'? Not at Dell, or Compaq, or HP, or any
other manufacturer because they all use some kind of thermal interface material.

In one Intel paper for engineers, the negative effects of
thermal compound are discussed. But that paper is beyond
scope of this discussion.

Useless since you don't say which one it is and there are many papers discussing
the 'negative effects' of thermal compound, as well as thermal pads, graphite
sheet, and tape, and all the other interface materials. Nothing is 'perfect' and
they all have 'negative effects'. They also have different 'advantages'. That's
what engineering is about: selecting the best solution for the specifications
and conditions one has to work with in the real world.

A properly machine heatsink without
thermal compound will only cause single digit temperature
decrease on CPU ... IF heatsink is properly machined. If
thermal compound results in better temperature decreases, then
one must ask how improperly a heatsink was applied OR how poor
the heatsink really is.

Alpha PAL PAL8942M81. Expulsion0 .23 deg C/W, Induction
0.26 deg C/W. Comes with thermal grease and installation instructions spell out
to apply it. There is no 'exception' mentioned for 'if you're a good installer'.

Now you show me one of your readily available 'proper' CPU heatsinks that comes
without thermal compound and explicitly says you don't need it because it's so
wonderful.

If you dispute this, then the theoretical numbers can be
posted, obviously, OR examples provided from scientifically
controlled experiments.

Having already disputed it THIS was the time for you to post something
supporting your claims.

In the meantime, decades of
experience says that thermal compound results in only single
digit temperature reduction if the heatsink is properly
machined. This is science that was old even thirty years
ago.

What "decades of experience" shows is that virtually everyone uses some form of
thermal interface material with virtually every heatsink application involving
significant power, from CPUs to stereo power output transistors. Crack open your
PSU and you'll find thermal interface material between the power transistors and
their heatsinks. Pop the can off your P4 and you'll find thermal interface
material between it and the CPU die. The stuff is everywhere.

Why promote the hype of Arctic Silver, et al? They
already sell a product that is grossly profitable.

Where in the world you come up with the notion I 'promote' Arctic silver, or any
other product for that matter, is a complete mystery.

Instead
promote the well proven science.

There's a difference between theoretical and applied science.