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Thermal vias in thermal pad of IC?

Discussion in 'General Electronics Discussion' started by eem2am, Dec 4, 2013.

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  1. eem2am

    eem2am

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    Last edited by a moderator: Dec 4, 2013
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Normally we don't place vias into pads at all. During soldering, solder will penetrate into the hole and will be lost for soldering the pin to the pad.

    A thermal via would be counterproductive: as it is thermally isolated from the pad it will reduce the heat transfer away from the IC to the PCB.

    I advise to put the necessary vias outside the thermal pad.
     
  3. OLIVE2222

    OLIVE2222

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    You can place thermal pad under via knowing that solder paste are not placed on the whole thermal pad surface but is spread in 4 (in this case) the room between each solder paste "island" is used to place via's (this avoid the soldering penetration mentionned by Harald Kapp)

    check the PCB layout of the TI evaluation board here you will see that:

    http://www.ti.com/lit/ug/snvu179/snvu179.pdf
     
    Last edited: Dec 4, 2013
  4. eem2am

    eem2am

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    http://www.ti.com/lit/ug/snvu179/snvu179.pdf

    thanks....the article (above) doesn't show solder paste islands, but I see what you mean.
    There are definitely 4 vias under the LP8556 chip, as you say.
    I am stil not sure that they have made a complex solder paste mask for that thermal pad. I agree that it seems to make sense.
     
  5. OLIVE2222

    OLIVE2222

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  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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