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Heat Sink Compound for DRV8432

John Cole
Intellectual 340 points
Other Parts Discussed in Thread: DRV8412

Hey TI,

A question about heat-sink compounds for the DRV8432.  In the documentation, we noted that connecting the heat sink to ground is recommended.  We found that connecting it to ground in our application greatly improves the stability of our whole system (at very high loads and temps, we noticed our system crashing; when we connected the sink to ground, this problem went away).

So we're looking for a thermally conductive, and electrically conductive thermal paste.

Two questions:

- Are we going about this right?  We want to ground that top pad, so we're looking to mount the heat sink to ground on the PCB.  Is this the proper way to do this, or is there a better way to ground the heat sink?

- Do you have any recommended thermal compound that's electrically conductive and stable.  The two recommended in the datasheet are:

Ceramique Arctic Silver - http://www.arcticsilver.com/ceramique.htm - This says specifically it's an electric insulator.

Timtronics 413 - http://www.timtronics.com/PDF/nonsilicone/Blue%20Ice%20414.pdf - This says that it's volume resistivity is 2.8 x 10^12.  

Are there any TI-recommended options for this?

Thanks folks!

  • 0
    TI__Mastermind 26065 points

    Hi John

    The PowerPAD and GND are not connected inside the parts. And the PowerPAD will not play roles to branch the GND current. So the improving should come from the additional function of filter and shielding after the PowerPAD and heat-sink is connected to GND. In this case, you don't have to have a strong conductivity between heat-sink and PowerPAD. Just make sure they are mounted directly and firmly with thin thermal paste.

    Or you can add a grounded copper layer directly contact to PowerPAD, then put thermal compound between heat-sink and copper layer.

    Another way is that pure soft copper sheet itself can be used to instead of thermal paste. It is good conductor also.

    Thanks.

    Wilson.

    Motor Application Team

  • 0 in reply to Wilson Zuo
    Intellectual 340 points

    Wilson,

    I just want to make sure we're on the same page here, I might be confusing the message:  the DRV8412 has a "Power Pad" on the bottom that's soldered to the PCB for heat disipation.

    We're working with the DRV8432, which has a "heat slug" on the top of it for disipating heat through a heatsink.  

    Thanks,

    John

  • 0 in reply to John Cole
    TI__Mastermind 26065 points

    Hi John

    Yes. I mean DRV8432. Please refer to the following drawing.

     

    Also, you can just ground via mechanical screw structure. if you feel the thermal agent will isolate the "heat slug" of DRV8432, you can use copper sheet instead. copper will give you also the mechanical mounting margin and good heat and electric conductivity.

    Thanks

    Wilson