Why so very small amount of thermal compound?

Archived from groups: alt.comp.hardware.overclocking (More info?)

I have read posts that suggest minimal thermal compound. The Arctic Silver
instructions also suggest a very small amount.
http://www.arcticsilver.com/arctic_silver_instructions.htm

I understand this advice if the concern is that too much compound may
contaminate the pins and cause electrical problems. But, I don't understand
it if the concern is heat transfer.
I realize that the objective is to only fill the microscopic gaps between
the two surfaces.

After the heat sink is mounted, the force pushing the two surfaces together
is so high that any extra compound will be squeezed out of the sides. The
compound is a fluid after all. There will be no compound between the peaks
(only in the valleys). Is that not true?
Am I missing something?

Thanks,

Navid
14 answers Last reply
More about small amount thermal compound
  1. Archived from groups: alt.comp.hardware.overclocking (More info?)

    > After the heat sink is mounted, the force pushing the two surfaces together
    > is so high that any extra compound will be squeezed out of the sides. The
    > compound is a fluid after all. There will be no compound between the peaks
    > (only in the valleys). Is that not true?

    Well, the same theory could be applied to water under a car's tires, and
    yet cars DO hydroplane.

    You are right the force is great, but some small amount will remain.
  2. Archived from groups: alt.comp.hardware.overclocking (More info?)

    Navid wrote:
    > I have read posts that suggest minimal thermal compound. The Arctic Silver
    > instructions also suggest a very small amount.
    > http://www.arcticsilver.com/arctic_silver_instructions.htm
    >
    > I understand this advice if the concern is that too much compound may
    > contaminate the pins and cause electrical problems. But, I don't understand
    > it if the concern is heat transfer.
    > I realize that the objective is to only fill the microscopic gaps between
    > the two surfaces.
    >
    > After the heat sink is mounted, the force pushing the two surfaces together
    > is so high that any extra compound will be squeezed out of the sides. The
    > compound is a fluid after all. There will be no compound between the peaks
    > (only in the valleys). Is that not true?
    > Am I missing something?

    The force isn't as high as you think and the thermal compound doesn't flow
    as easily as you think.

    >
    > Thanks,
    >
    > Navid
    >
    >
    >
  3. Archived from groups: alt.comp.hardware.overclocking (More info?)

    > I understand this advice if the concern is that too much compound may
    > contaminate the pins and cause electrical problems. But, I don't understand
    > it if the concern is heat transfer.

    The thermal conductivity of any fluid or suspension, however
    well-designed, will never be as good as the thermal conductivity of a
    metal. This is due to the way in which heat flows - heat is a
    consequence of the random motion of atoms and is transmitted more
    efficiently if the atoms are bonded in a regular (dense) structure, with
    lots of (relatively) weak bonds to transmit the random vibrations along.

    Hence, you want to apply as little as possible, only filling the valleys
    between the surfaces (removing air which does not conduct heat well),
    but not adding any more layers (of less thermal conductivity than the
    heatsink) than is absolutely necessary between the chip and the sink.

    The ultimate 'thermal compound' would be liquid metal that gets poured
    between the chip and sink and forms a perfect seal upon cooling.
    However, this would destroy your chip...

    > I realize that the objective is to only fill the microscopic gaps between
    > the two surfaces.

    This is because the thermal conductivity of your Arctic Silver (or even
    generic thermal grease) is greater than that of air, so you remove all
    air pockets.

    > After the heat sink is mounted, the force pushing the two surfaces together
    > is so high that any extra compound will be squeezed out of the sides. The
    > compound is a fluid after all. There will be no compound between the peaks
    > (only in the valleys). Is that not true?

    There will always be a small amount of thermal compound between the
    peaks, however little, as it will be nigh-on impossible to remove all of
    it purely by pressure. However, the separation between the peaks will be
    much less than that between valleys, as the force is indeed rather large.
  4. Archived from groups: alt.comp.hardware.overclocking (More info?)

    "David Besack" <daveREMOVEbesack@mac.com> wrote in message
    news:cao72n$sfq$1@netnews.upenn.edu...
    >> After the heat sink is mounted, the force pushing the two surfaces
    >> together
    >> is so high that any extra compound will be squeezed out of the sides.
    >> The
    >> compound is a fluid after all. There will be no compound between the
    >> peaks
    >> (only in the valleys). Is that not true?
    >
    > Well, the same theory could be applied to water under a car's tires, and
    > yet cars DO hydroplane.
    >
    > You are right the force is great, but some small amount will remain.

    OK.
    So, the pressure is not enough to get rid of all the compound between the
    peaks, and a small layer remains.
    Thanks for correcting me.
  5. Archived from groups: alt.comp.hardware.overclocking (More info?)

    "Navid" <nospam@nospam.invalid> wrote in message
    news:SbLzc.52262$tH1.1954660@twister.southeast.rr.com...
    > I have read posts that suggest minimal thermal compound. The Arctic
    Silver
    > instructions also suggest a very small amount.
    > http://www.arcticsilver.com/arctic_silver_instructions.htm
    >
    > I understand this advice if the concern is that too much compound may
    > contaminate the pins and cause electrical problems. But, I don't
    understand
    > it if the concern is heat transfer.
    > I realize that the objective is to only fill the microscopic gaps between
    > the two surfaces.
    >
    > After the heat sink is mounted, the force pushing the two surfaces
    together
    > is so high that any extra compound will be squeezed out of the sides. The
    > compound is a fluid after all. There will be no compound between the
    peaks
    > (only in the valleys). Is that not true?
    > Am I missing something?

    A layer will always remain, impeding heat transfer.

    That said, you can glop on as much compound as you like, and the pressure of
    the heatsink will push out enough to always give you half-decent
    temperatures.

    Unless you're a mad overclocker who wants every single megahertz and every
    single 0.1 degree, you shouldn't worry about it. I certainly don't, and I
    overclock, AND I've never had heat issues.
  6. Archived from groups: alt.comp.hardware.overclocking (More info?)

    On Thu, 17 Jun 2004 01:17:45 -0400, "Mercury" <nobody@nospam.null>
    wrote:

    >
    >"Navid" <nospam@nospam.invalid> wrote in message
    >news:SbLzc.52262$tH1.1954660@twister.southeast.rr.com...
    >> I have read posts that suggest minimal thermal compound. The Arctic
    >Silver
    >> instructions also suggest a very small amount.
    >> http://www.arcticsilver.com/arctic_silver_instructions.htm

    >
    >A layer will always remain, impeding heat transfer.
    >
    >That said, you can glop on as much compound as you like, and the pressure of
    >the heatsink will push out enough to always give you half-decent
    >temperatures.
    >
    >Unless you're a mad overclocker who wants every single megahertz and every
    >single 0.1 degree, you shouldn't worry about it. I certainly don't, and I
    >overclock, AND I've never had heat issues.
    >


    A wonderful approach.

    The moron's guide to unending stupidity.

    ...of course, those with IQ's over 40 understand it's easier to just
    use less.

    but... the morons will always be with us.

    Let's have a hand for the moron. And let me say it's always been such
    a pleasure working with people like you.
  7. Archived from groups: alt.comp.hardware.overclocking (More info?)

    > A layer will always remain, impeding heat transfer.

    True, but it won't impede heat transfer as much as air will - that's why
    you apply the stuff in the first place. Adding too much could cause the
    stuff to glop out and bridge 2 pins. Some thermal compounds are
    conductive, so you have just b0rked your system by doing that. AS is
    slightly capacitive, so it could do nasty things to system stability if
    it were to flow across 2 pins, and others are electrically neutral (like
    their Ceramique compound) so you could smear your whole board in it and
    suffer no ill effects.

    Plus your syringe of AS will last longer if you use the tiny amounts
    prescribed.
  8. Archived from groups: alt.comp.hardware.overclocking (More info?)

    Lech Staniewicz wrote:

    >> A layer will always remain, impeding heat transfer.
    >
    >
    > True, but it won't impede heat transfer as much as air will

    Not necessarily true. With the proper amount there is contact with only the
    voids filled but with too much there is a layer of the thermal compound
    between the two surfaces, separating them. Where, before, with 'dry, you
    had contact with some air, too much has thermal compound between all of it
    and that layer can be worse than the smaller amount of air in the dry mating.

    See here:

    http://power.ece.uiuc.edu/Balog/images/How%20to%20keep%20your%20cool%20when%20working%20with%20power%20electronics.pdf

    The principles are the same for processor heatsinks.


    > - that's why
    > you apply the stuff in the first place. Adding too much could cause the
    > stuff to glop out and bridge 2 pins. Some thermal compounds are
    > conductive, so you have just b0rked your system by doing that. AS is
    > slightly capacitive, so it could do nasty things to system stability if
    > it were to flow across 2 pins, and others are electrically neutral (like
    > their Ceramique compound) so you could smear your whole board in it and
    > suffer no ill effects.
    >
    > Plus your syringe of AS will last longer if you use the tiny amounts
    > prescribed.
  9. Archived from groups: alt.comp.hardware.overclocking (More info?)

    <then@again.com> wrote in message
    news:uam2d0t4skmrdcr7k6qdp9er9ha6bctak8@4ax.com...
    >
    > Let's have a hand for the moron.
    >

    Maybe instead of calling me a moron you could explain what it is I said that
    you consider wrong.

    Obviously glopping on heatsink compound is wasteful and runs the risk of
    causing electrical problems.

    My point was that one shouldn't worry about getting the
    impossibly-ultra-thin layer that is mentined in the AS3 instructions.

    And it's not "easier to use less". I tried the "half-grain of rice", and I
    don't have the patience or dexterity to work with it. I put on enough to get
    a nice even layer using a credit card. Like buttering toast.

    If you don't like it, do it your own way, and don't me a moron.
  10. Archived from groups: alt.comp.hardware.overclocking (More info?)

    Navid wrote:

    > I have read posts that suggest minimal thermal compound. The Arctic Silver
    > instructions also suggest a very small amount.
    > http://www.arcticsilver.com/arctic_silver_instructions.htm
    >
    > I understand this advice if the concern is that too much compound may
    > contaminate the pins and cause electrical problems. But, I don't understand
    > it if the concern is heat transfer.
    > I realize that the objective is to only fill the microscopic gaps between
    > the two surfaces.
    >
    > After the heat sink is mounted, the force pushing the two surfaces together
    > is so high that any extra compound will be squeezed out of the sides. The
    > compound is a fluid after all. There will be no compound between the peaks
    > (only in the valleys). Is that not true?
    > Am I missing something?
    >
    > Thanks,
    >
    > Navid

    I've been following this thread and the responses have been long on
    (mostly accurate) theory but short on practice. You can *feel* when
    you've got it right!

    - apply a dob of compound to the CPU core or heatspreader, spread it
    thin with a blade (I prefer a boxcutter blade, but a credit card works),
    remove any excess on non-contact areas using a cotton bud
    - place the heatsink on top, apply medium pressure and work it in a
    circular motion until you can feel the peaks grating against each other
    - remove heatsink to inspect coverage, it will be slightly difficult to
    unstick if you have it right, much easier if you have too little or too
    much compound
    - again remove any excess on non-contact areas with the cotton bud, and
    use it to add a little compound to any bare contact areas
    - repeat until you feel grating but find no excess or bare contact areas
    upon heaksink removal
    - work heaksink in a circular motion again briefly before final clamping

    P2B
  11. Archived from groups: alt.comp.hardware.overclocking (More info?)

    "P2B" <p2b@sympatico.ca> wrote in message
    news:1GuAc.50665$7H1.1718287@news20.bellglobal.com...
    >
    >
    > Navid wrote:
    >
    >> I have read posts that suggest minimal thermal compound. The Arctic
    >> Silver
    >> instructions also suggest a very small amount.
    >> http://www.arcticsilver.com/arctic_silver_instructions.htm
    >>
    >> I understand this advice if the concern is that too much compound may
    >> contaminate the pins and cause electrical problems. But, I don't
    >> understand
    >> it if the concern is heat transfer.
    >> I realize that the objective is to only fill the microscopic gaps between
    >> the two surfaces.
    >>
    >> After the heat sink is mounted, the force pushing the two surfaces
    >> together
    >> is so high that any extra compound will be squeezed out of the sides.
    >> The
    >> compound is a fluid after all. There will be no compound between the
    >> peaks
    >> (only in the valleys). Is that not true?
    >> Am I missing something?
    >>
    >> Thanks,
    >>
    >> Navid
    >
    > I've been following this thread and the responses have been long on
    > (mostly accurate) theory but short on practice. You can *feel* when you've
    > got it right!
    >
    > - apply a dob of compound to the CPU core or heatspreader, spread it thin
    > with a blade (I prefer a boxcutter blade, but a credit card works), remove
    > any excess on non-contact areas using a cotton bud
    > - place the heatsink on top, apply medium pressure and work it in a
    > circular motion until you can feel the peaks grating against each other
    > - remove heatsink to inspect coverage, it will be slightly difficult to
    > unstick if you have it right, much easier if you have too little or too
    > much compound
    > - again remove any excess on non-contact areas with the cotton bud, and
    > use it to add a little compound to any bare contact areas
    > - repeat until you feel grating but find no excess or bare contact areas
    > upon heaksink removal
    > - work heaksink in a circular motion again briefly before final clamping
    >
    > P2B


    Thanks for everyone's replies.

    The main point that I thought was made was that the pressure between the two
    surfaces is not enough to spread the compound thin enough. That is why we
    should apply a very small amount.

    There is still a disconnect, in my understanding, between this and the
    Arctic Silver 5 instructions for Pentium 4. The instruction is to place a
    small amount of arctic silver 5 "without spreading it" and place the sink
    with a wiggle and mount.

    Now, if the pressure is not enough to spread the compound, then, how is this
    technique going to make the peaks touch? Is it because the compound amount
    is small, the contact area is small, hence, the pressure is higher (smaller
    area, same force -> higher pressure)?

    But, that makes no sense either. The purpose of this is to spread the
    compound, which will increase the contact area. Larger area, and we are
    back to the low pressure problem!

    I don't mean to get into a senseless debate here. I would like to hear
    opinions to help me understand. Thanks again.

    Navid
  12. Archived from groups: alt.comp.hardware.overclocking (More info?)

    Navid wrote:

    > "P2B" <p2b@sympatico.ca> wrote in message
    > news:1GuAc.50665$7H1.1718287@news20.bellglobal.com...
    >
    >>
    >>Navid wrote:
    >>
    >>
    >>>I have read posts that suggest minimal thermal compound. The Arctic
    >>>Silver
    >>>instructions also suggest a very small amount.
    >>>http://www.arcticsilver.com/arctic_silver_instructions.htm
    >>>
    >>>I understand this advice if the concern is that too much compound may
    >>>contaminate the pins and cause electrical problems. But, I don't
    >>>understand
    >>>it if the concern is heat transfer.
    >>>I realize that the objective is to only fill the microscopic gaps between
    >>>the two surfaces.
    >>>
    >>>After the heat sink is mounted, the force pushing the two surfaces
    >>>together
    >>>is so high that any extra compound will be squeezed out of the sides.
    >>>The
    >>>compound is a fluid after all. There will be no compound between the
    >>>peaks
    >>>(only in the valleys). Is that not true?
    >>>Am I missing something?
    >>>
    >>>Thanks,
    >>>
    >>>Navid
    >>
    >>I've been following this thread and the responses have been long on
    >>(mostly accurate) theory but short on practice. You can *feel* when you've
    >>got it right!
    >>
    >>- apply a dob of compound to the CPU core or heatspreader, spread it thin
    >>with a blade (I prefer a boxcutter blade, but a credit card works), remove
    >>any excess on non-contact areas using a cotton bud
    >>- place the heatsink on top, apply medium pressure and work it in a
    >>circular motion until you can feel the peaks grating against each other
    >>- remove heatsink to inspect coverage, it will be slightly difficult to
    >>unstick if you have it right, much easier if you have too little or too
    >>much compound
    >>- again remove any excess on non-contact areas with the cotton bud, and
    >>use it to add a little compound to any bare contact areas
    >>- repeat until you feel grating but find no excess or bare contact areas
    >>upon heaksink removal
    >>- work heaksink in a circular motion again briefly before final clamping
    >>
    >>P2B
    >
    >
    >
    > Thanks for everyone's replies.
    >
    > The main point that I thought was made was that the pressure between the two
    > surfaces is not enough to spread the compound thin enough. That is why we
    > should apply a very small amount.
    >
    > There is still a disconnect, in my understanding, between this and the
    > Arctic Silver 5 instructions for Pentium 4. The instruction is to place a
    > small amount of arctic silver 5 "without spreading it" and place the sink
    > with a wiggle and mount.
    >
    > Now, if the pressure is not enough to spread the compound, then, how is this
    > technique going to make the peaks touch? Is it because the compound amount
    > is small, the contact area is small, hence, the pressure is higher (smaller
    > area, same force -> higher pressure)?

    It's the shear stresses of the wiggling.

    >
    > But, that makes no sense either. The purpose of this is to spread the
    > compound, which will increase the contact area. Larger area, and we are
    > back to the low pressure problem!
    >
    > I don't mean to get into a senseless debate here. I would like to hear
    > opinions to help me understand. Thanks again.
    >
    > Navid
    >
    >
  13. Archived from groups: alt.comp.hardware.overclocking (More info?)

    Well, why not use a different thermal compound, and not worry about the
    Arctic Silver instructions? The application of thermal compound, the
    condition of the surfaces, the parallelness of the two surfaces have a
    greater affect on cooling than the thermal compound itself. For that
    matter, unsalted butter is nearly as good as Arctic Silver or any other
    thermal compound for heat transfer (except that it eventually goes rancid,
    attracts ants, and leaks away.)

    --
    Phil Weldon, pweldonatmindjumpdotcom
    For communication,
    replace "at" with the 'at sign'
    replace "mindjump" with "mindspring."
    replace "dot" with "."

    "Navid" <nospam@nospam.invalid> wrote in message
    news:mHAAc.57119$2o2.3053324@twister.southeast.rr.com...
    >
    > "P2B" <p2b@sympatico.ca> wrote in message
    > news:1GuAc.50665$7H1.1718287@news20.bellglobal.com...
    > >
    > >
    > > Navid wrote:
    > >
    > >> I have read posts that suggest minimal thermal compound. The Arctic
    > >> Silver
    > >> instructions also suggest a very small amount.
    > >> http://www.arcticsilver.com/arctic_silver_instructions.htm
    > >>
    > >> I understand this advice if the concern is that too much compound may
    > >> contaminate the pins and cause electrical problems. But, I don't
    > >> understand
    > >> it if the concern is heat transfer.
    > >> I realize that the objective is to only fill the microscopic gaps
    between
    > >> the two surfaces.
    > >>
    > >> After the heat sink is mounted, the force pushing the two surfaces
    > >> together
    > >> is so high that any extra compound will be squeezed out of the sides.
    > >> The
    > >> compound is a fluid after all. There will be no compound between the
    > >> peaks
    > >> (only in the valleys). Is that not true?
    > >> Am I missing something?
    > >>
    > >> Thanks,
    > >>
    > >> Navid
    > >
    > > I've been following this thread and the responses have been long on
    > > (mostly accurate) theory but short on practice. You can *feel* when
    you've
    > > got it right!
    > >
    > > - apply a dob of compound to the CPU core or heatspreader, spread it
    thin
    > > with a blade (I prefer a boxcutter blade, but a credit card works),
    remove
    > > any excess on non-contact areas using a cotton bud
    > > - place the heatsink on top, apply medium pressure and work it in a
    > > circular motion until you can feel the peaks grating against each other
    > > - remove heatsink to inspect coverage, it will be slightly difficult to
    > > unstick if you have it right, much easier if you have too little or too
    > > much compound
    > > - again remove any excess on non-contact areas with the cotton bud, and
    > > use it to add a little compound to any bare contact areas
    > > - repeat until you feel grating but find no excess or bare contact areas
    > > upon heaksink removal
    > > - work heaksink in a circular motion again briefly before final clamping
    > >
    > > P2B
    >
    >
    > Thanks for everyone's replies.
    >
    > The main point that I thought was made was that the pressure between the
    two
    > surfaces is not enough to spread the compound thin enough. That is why we
    > should apply a very small amount.
    >
    > There is still a disconnect, in my understanding, between this and the
    > Arctic Silver 5 instructions for Pentium 4. The instruction is to place a
    > small amount of arctic silver 5 "without spreading it" and place the sink
    > with a wiggle and mount.
    >
    > Now, if the pressure is not enough to spread the compound, then, how is
    this
    > technique going to make the peaks touch? Is it because the compound
    amount
    > is small, the contact area is small, hence, the pressure is higher
    (smaller
    > area, same force -> higher pressure)?
    >
    > But, that makes no sense either. The purpose of this is to spread the
    > compound, which will increase the contact area. Larger area, and we are
    > back to the low pressure problem!
    >
    > I don't mean to get into a senseless debate here. I would like to hear
    > opinions to help me understand. Thanks again.
    >
    > Navid
    >
    >
  14. Archived from groups: alt.comp.hardware.overclocking (More info?)

    Also of note is some thermal compounds like Ceramique- which I pretty
    much use exclusively for system building- is applied differently.
    You first smear a small amoutn, then buff on and then off the
    heatsink. This leaves an extremely thin layer. then slop on the
    BB-size dot (or line on some of the CPUs, like the AMD mobiles, as
    they have a longer die) and G-E-N-T-L-Y apply the heatsink. This is
    where CPU shims make a difference. For serious overclocking and
    water/pelt/phase change, I really encourage a shim. It prevents
    shearing of the thermal goop and ensures PRECISE alignment.

    Shin-etsu is another great compound and will outperform the Arctic
    Silver silver-based compounds.

    Having said that, I also have a 12ounce tube (only about 8 ounces now)
    of DOW thermal compound I use for work. It also works very well, and
    the tube is at least 15 years old.

    The bottom line is to apply a very thin even layer and then stick on
    your heatsink evenly OR apply as per the manufacturer's instructions.

    ==============
    Posted through www.HowToFixComputers.com/bb - free access to hardware troubleshooting newsgroups.
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