Thermalright sp-97 question (for Asus A7V8X-X)

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Hello,

I recently got a Thermalright SP-97. I noticed it is very heavy (585g
without the fan).

Before I install it, I was wondering if this is too heavy?

It comes with a backplate to go behind the mobo to help with weight
dissipation. But it just seems so heavy... I'm looking for some
reassurance that my mobo (Asus A7V8X-X) won't crack 6 months later
from weight of this heatsink.
2 answers Last reply
More about thermalright question asus a7v8x
  1. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    In article <6c38b64b.0409042141.5c2cc0e2@posting.google.com>,
    genericaudioperson@hotmail.com (xy) wrote:

    > Hello,
    >
    > I recently got a Thermalright SP-97. I noticed it is very heavy (585g
    > without the fan).
    >
    > Before I install it, I was wondering if this is too heavy?
    >
    > It comes with a backplate to go behind the mobo to help with weight
    > dissipation. But it just seems so heavy... I'm looking for some
    > reassurance that my mobo (Asus A7V8X-X) won't crack 6 months later
    > from weight of this heatsink.

    Raw data for the Athlon can be found in the Barton datasheet:

    http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26237.PDF

    Table 20. Mechanical Loading
    Location Dynamic (MAX) Static (MAX) Units Note
    Die Surface 100 30 lbf 1
    Die Edge 10 10 lbf 2

    Die edge is if the heatsink is accidently inclined by 2 degrees.
    Static force is the force of the spring loaded screws that hold the
    heatsink down. The mass of the heatsink is a bit more than a pound,
    and the max static force allowed is thirty pounds of force. The
    dynamic force is that force applied to the processor die, when the
    computer chassis receives a shock.

    Force is applied to the heatsink for a number of reasons. There is
    a bare minimum needed to just keep the heatsink in place. Additional
    force is needed to meet the minimum force needed to make the thermal
    interface material work. Note that, the boxed processor solutions have
    an amount of force applied to make thermal tape or phase change material
    work, and grease needs much less force than that.

    As for the rest of my research, I chose Intel's web site, as the
    AMD search engine is a PITA.

    Page 16 of this document, mentions shock and how the dynamic force
    is related to heatsink mass:

    ftp://download.intel.com/design/Pentium4/guides/30056401.pdf

    "The heatsink mass can also add additional dynamic compressive load
    to the package during a mechanical shock event. Amplification factors
    due to the impact force during shock must be taken into account in
    dynamic load calculations. The total combination of dynamic and static
    compressive load should not then exceed the processor datasheet
    compressive dynamic load specification during a vertical shock. For
    example, with a 0.454 kg [1 lb mass] heatsink, an acceleration of 50G
    during an 11 ms shock with an amplification factor of 2 results in
    approximately a 445 N [100 lbf] dynamic load on the processor package.
    If a 445 N [100 lbf] static load is also applied on the heatsink for
    thermal performance of the thermal interface material and/or for
    mechanical reasons, the processor package sees 890 N [200 lbf]. The
    calculation for the thermal solution of interest should be compared
    to the processor datasheet specification."

    Roughly translated, this means your heavier than allowed heatsink
    should be treated more gently than its less heavy counterpart. I expect
    the silicon die of the processor will get damaged, before the printed
    circuit board will. Fiberglass is very strong, and flexure of the PCB
    is more likely to bust solder joints under the BGA chips, than damage
    the FR-4 itself. The 11 ms shock sounds like a standard value that
    comes from a shaker table used for engineering testing.

    If the heatsink comes with a backing plate, that helps reduce bend near
    the socket solder joints. Ideally, the mass of the heatsink should be
    tied into the motherboard tray (but those really aren't that strong
    anyway - mine isn't).

    This document is a slide set that discusses some of the issues.
    Treat this as general reading material.

    ftp://download.intel.com/design/Pentium4/guides/29072801.pdf

    When Thermalright designed the heatsink, they should be aware of
    the 30lbF limit on fastening the heatsink to the motherboard. The
    100lbF limit you can help, by treating the computer with more
    respect. If moving the computer (and this is good advice no matter
    how your computer is constructed) consider how violent the transport
    company is - if going UPS remove the disk drive, all plug-in circuit
    cards, the power supply (due to its mass, it could tear the
    screws out of the case, the heatsink (if it has any amount of copper
    in it - due to mass). This doesn't leave much, other than the
    motherboard and the case itself :-) A little less kicking of the
    computer with your shoes helps too :-))

    If you want to do more research, a good search term (include the quotes)

    "heatsink design considerations"

    There is an AMD document here:
    http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/23794.pdf

    It says the clip load target is 16lbf, which in your case would equal
    4lbf per screw. I doubt Thermalright provides any design data for
    you to look at.

    HTH,
    Paul
  2. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    thanks Paul,

    I don't plan to ship or transport it. the computer will stay put.
    since it has a backplate, do you think i'm ok?

    it's not trauma from a bump or fall i'm worried about. it's the
    constant weight over time finally making something overflex or break
    that i'm worried about (including solder points).
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