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Soldering D-PAK Mosfet? (TO-252)

Discussion in 'Electronic Basics' started by Hammy, Apr 23, 2008.

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  1. Hammy

    Hammy Guest

    I'm using Fairchilds FCD5N60 in a D-PAK (TO-252).

    Data sheet

    The D-PAK I'm using has a small drain tab that extends above the
    plastic case; the bottom portion of the drain tab is recessed into the
    plastic case Like a T0-220 .

    I am unsure on how to solder the drain.

    1. Are you supposed to just solder the metal tab that extends
    above the plastic case?

    2. Are you supposed to lay solder down on the whole drain
    footprint? This includes the metal Drain that is recessed into the
    plastic case. If so wouldn't this potentially damage the case?

    I just soldered the tab part that extends above the case to a small
    piece of PCB for testing the FET in my circuit. There is a no contact
    between the drain, (the part of the drain that's recessed into the
    plastic case) and the copper PCB. I pushed down to try and get contact
    while soldering but either I wasn't pushing hard enough or it's not
    supposed to touch the PCB. Is there supposed to be a gap for air flow
    and the copper that the tab is soldered to acting as the heatsink.

  2. Eeyore

    Eeyore Guest

    You would normally apply solder paste underneath the tab and reflow solder

  3. huh? The drain needs as much cooling as it needs. If you only solder a very
    small bridge between the tab and the copper then heat must flow through that
    bridge... do you think thats a good idea? If you were not suppose to solder
    the whole thing then why would they have it exposed?

    You really need to think of why the did what the did and what is the purpose
    and then it should be quite clear what to do.
  4. Hammy

    Hammy Guest

    I see I printed out a footprint and all became clear.I'm going to have
    to put some solder on the drain pad lay the D-PAK on it and heat the
    tab and push when the solder starts to flow.

  5. Hammy

    Hammy Guest

    Thanks John.
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