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  • TI Thinks Resolved

TAS5624A: Heatsink mounting recommendation : Maximum torque force that IC can sustain

Part Number: TAS5624A

My customer facing some market feedback due to D-amp IC broken.

This D-amp IC broken caused by mechanical heatsink vibration which make some IC pin break.

Customer would like to understand how much kg/f can stand for screw torque or maximum load (kg) withstand when the heatsink mounted on top of the IC.

Customer wants to study to improve vibration to avoid broken pin IC with strengthen the screw torque of the heatsink.

Please provide heatsink mounting data(screw torque) /recommendation for HTSSOP or similar IC package.

Thanks.

Best regards,

Chin

  • Hi Chin,
    We are looking into this and Adam will get back to you later.
  • Chin,

    On our EVMs we use M3 screws and 60-80 Newton Centimeters of torque to tighten the screws. This is only a rough estimation as we have not mechanically tested the heatsinks, PCBs, or devices.

    We use 60-80 Ncm because it is the minimal number that gives us good thermal performance.

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Hi Adam,

    Thanks for your reply.

    I will inform customer to control the torque force at range 60-80 Ncm for optimum thermal performance.

    Just to confirm that TI doesn't have measured/simulated data for maximum torque, am I right?

    Thanks.

    Best regards,

    Chin

  • In reply to Wee Keat Chin:

    Chin,

    We only have this recommended value from our own experience. We have not tested a maximum value.

    Regards,

    -Adam
  • In reply to Adam Sidelsky:

    Hi Adam,

    Sorry to trouble you again.

    My customer has additional questions. Please refer to attachments for details of failure.

    TAS5624A IC pin lead broken .xlsxTAS5624A IC pin lead broken .pdf

    1) Customer wants to know what is the maximum displacement of pin lead when overstress happens?

    Is it possible to simulate ? Could you please consult your IC package designer?

    2) Is it possible the vibration of IC or heatsink at resonance frequency caused the IC pin lead broken?

     Customer actually has other model using same IC but different size of heatsink and didn't encounter the problem so far.

     So customer suspect the IC vibrate at resonance frequency and overtress condition causing the pin lead broken.

    3) From the part spec, the height between pins and IC mold body is ranges 0.05 – 0.15. May I know the design purpose ? Is it for soldering or coplanity consideration ?

    Thanks.

    Best regards,

    Chin

  • In reply to Wee Keat Chin:

    Chin,

    I am not sure if we can answer these questions but let me ask.

    Regards,

    -Adam
  • In reply to Wee Keat Chin:

    Chin,

    1. Unfortunately this isn't something we can simulate. We only torque the heatsink enough to maintain thermal contact at the pressures I mentioned above.

    2. I don't think vibration is the cause.

    3. My thought is this is tolerance. If the pins are a small amount below the mold body, we can guarantee that they will be level with the PCB including any tolerance variation.

    Regards,

    -Adam
  • In reply to Adam Sidelsky:

    Hi Adam,

    Thanks for your reply.

    i) Based on your explanation, since there has no data for the pin lead displacement due to stress from top, does it mean that this parameter is not a consideration during IC package design?

    ii) If vibration is not the cause, could you suggest any possibility that could lead to such failure? Customer needs to find out the root cause.

      [The Damp IC is still functioning despite of the broken of pin lead and failure only happened to the specific model with different heatsink and heatsink bracket]

    Please give some hints.

    Thanks.

    Best regards,

    Chin

  • In reply to Wee Keat Chin:

    Chin,

    In the following picture, is the pink piece a thermal pad? Please let me know the Thermal pad part number.

    Once mounted in position, does the heatsink touch the PCB? Or is it only touching the top of the DAMP?

    Also, what is the screw model number or type?

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Hi Adam,

    Besides touching the top of DAMP, the heatsink touches the PCB through heatsink bracket.

    Please check attachments for the assembly of heatsink, thermal pad and screw drawing and datasheet.

    D-AMp Heat Sink construction.pptx

    Do inform if you need more info.

    Thanks.

    Best regards,

    Chin

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