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D2pak mounting

Discussion in 'Electronic Design' started by Martin Riddle, Nov 17, 2009.

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  1. Yea, that the concept I was thinking, problem is it’s a 7 pin device.
    1-gate 5-source and pad as Drain.
    I want to mount the pad on a buss bar( er clamp) and use screws into a
    second bussbar from the source pins.
    The question is whether the pad can conduct to the bussbar when its
    clamped or do I need to flow solder, then it becomes a 2 piece Buss bar,
    which I'd rather not do.

  2. Joerg

    Joerg Guest

    Wow, impressive. What is that thing doing?

    Note that John's DPAK devices seem to have the drain additionally piped
    out at pin 2. Most FETs have that pin snipped so then there is only the
    bus bar contact. Meaning you'll have to deal with dissimilar metal
    issues, corrosion, etc.

    Can't use TO220?
  3. But are they heat spreaders or Bussbars? Where is the bulk of the
    current flowing, thru the pins or the heat spreaders?

  4. That’s the look of it, 4 oz copper, maybe 8. I have to shunt 1-2KA for
    100us or so.
    Yea and Stake the hell out of D and S with Vias. Too bad I don’t see
    anything good in a TO-277 package, That I could work with.
    The D packs are cheaper than the 277's. Takeup less space. And the Rdson
    will be lower for a half dozen or so devices.
  5. TheM

    TheM Guest

    How does that affect reliability of the devices? Soldering them directly
    to the big massive copper bus must involve slow heat-up and cool-down
    time, not to mention pretty high device temp in between.

    Fried any fets that way?

  6. I envisioned soldering the devices to copper foil, then clamping them to
    the heat sink.
    This may work, I have to go thru the numbers on electrical resistance.

  7. TheM

    TheM Guest

    Sounds nasty and not elegant.

  8. No.
  9. TheM

    TheM Guest

    Well, I think copper foil that's sufficiently thin to avoid problems with
    overheating is going to warp, keeping it flat will be a problem.

    Yes, a better solution is what I'd like to see, too.
    These parts are not easy to cool.

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