• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 101 subscribers
  • Views 584 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AM5708: Heat sink force on package

Martin Seeger
Expert 5411 points
Part Number: AM5708

Dear Team,

our customer uses the AM5708BCBDJEAS. It is cooled with a gap filler and a heat sink.

Do you have any spec of the maximum force which is allowed to be applied on the top of the CPU?

Thanks and best regards
Martin

  • 0
    TI__Mastermind 46460 points

    Martin,

    Please see the referenced E2E below for other devices in this family that have 0.8mm ball pitch.  I will research the answer for 0.65mm pitch for the AM570x family of devices.

    Tom

    https://e2e.ti.com/support/processors/f/791/p/615253/2284868#2284868

  • 0 in reply to Tom Johnson 16214
    TI__Mastermind 46460 points

    Martin,

    We do not have precise modeling for this pressure at 0.65mm pitch with this ball alloy.  We will request that this be modeled but that will take time.  Until that is available, I recommend that you use the table provided in the referenced discussion and derate the values by 50%.  That should make sure that you are using a reasonable max pressure with margin.

    Tom

  • 0 in reply to Tom Johnson 16214
    TI__Mastermind 46460 points

    Martin,

    I responded too soon.  We do have a table for 0.65mm pitch, SAC305.  See below:

    Below are the steps to apply these numbers:

    PROCEDURE FOR LIFETIME ESTIMATION
    1.  Determine pressure distribution at package substrate level due to the specific heat sink assembly scheme from measurement or using numerical simulation.
    2.  Select the max averaged pressure over one ball pitch as the pressure/load for life prediction to determine concentration factor (CF):

    CF = Maximum pressure/load on a ball pitch / Average pressure/load per ball pitch across the package

    3.  Select the appropriate force (BF) at the intersection of the applicable time column and equivalent temperature row over the designed life of the device from the table above
    4.  Determine total allowed force

    Total force (TF) = (BF / CF) * n

    where n is the number of BGA balls

    Tom