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neat SMD heatsink

Discussion in 'Electronic Design' started by [email protected], May 2, 2013.

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  1. Guest

    Probably old hat, but new to me:
    http://media.digikey.com/Photos/Assmann Photos/V-1100-SMD^A-L.JPG

    Solders down on the board straddling the device, and sucks out the
    heat. Cooool.

    / /
    / / / / /
    ------. / .------'
    |.-----------.|
    || / || /
    || / || /
    || / || /
    ||/ ||/
    `' `'

    ___________
    _/________ /|
    / /|//
    /_________/ // D-PAK
    | |//
    '//-//-//-'
    // //



    Handy.
    (Popularity prediction: should attract fans.)
     
  2. Guest

    They're not perfect, but I've got a 6-layer board, packed, 85c worst-
    case ambient, still air, and about a watt that needs dumping. A
    little air-borne copper really helps.
    Looks like yours has more surface area. I considered the (larger)
    D2PAK heatsinks, but was skeptical of leaving a gap--that's
    potentially hard to solder. Adds theta too. The little fellow I
    picked was good enough, so I stopped there.
     
  3. Guest

    I'm using the layers, but that's my margin of safety. A great deal of
    the difficulty has been that it's unknown, and pretty well the worst
    case scenario (very small box, low clearances, sealed, plastic, small
    air space, possibly horizontally mounted). It has to work, first
    time, and I don't get to test it.

    Not much room for copper pours on the bottom--that's paved with
    parts. The top side too, mostly. The inner layers are fully engaged
    as heat-spreaders--that helps. I calculate the thermal resistance of
    vias is surprisingly high--you need a lot of 'em.
    Nice pictures!
    The copper patch looks like 0.5x.3"? That's not much area at all--the
    semi mfr references I've been reading would've put that patch at
    around 60C/W Your 30C rise is surprising.

    I can stand 40C rise, exactly what AAVID says the heatsink provides
    alone. The modest top-copper + middle layer spreading adds the margin
    that should make it solid. The refs I've been reading say inner-layer
    spreading gains about 30%.
    That experiment of yours is a pretty good sales pitch for a FLIR.
     
  4. Anyone know a good current FLIR for this sort of thing? The ones I have
    seen are all for long-range stuff like looking at buildings. Or do you
    have to buy a special lens for it?

    There is a new cheap type available, but it is no good for closeup work.

    <http://uk.farnell.com/fluke/fluke-vt02/thermometer-visual-ir-10-to-250/dp/2254306>

    The "Technical Data Sheet" is useless, too:

    <http://www.farnell.com/datasheets/1682887.pdf>
     
  5. impressive ascii art job there.
     
  6. Guest

    The photo I linked showed the part inverted, so I figured a diagram
    would make it all clear.

    (The more I try to explain technical things in words, the more I
    appreciate the value of pictures.)
     
  7. I use quarter inch male spade lugs. They are plated copper so they
    take solder really well, and hence couple the thermals really well. They
    are about 1mm thick.

    Instead of solder, I use silver filled conductive epoxy. The same
    thing they use to attach the chip die to the back side of the thermal
    interface surface! Stay away from the pins!
     
  8. Oh they tell you that. For the visual camera!

    11,025 (which seems suspect to me).

    Like I said, useless.

    I got one in earlier in the week, out of curiousity (everything is "sale
    or return" from Farnell in the UK). It resolved my steaming coffee cup
    quite impressively. But no chance at seeing small parts.
     
  9. Dunno, could be.

    Actually just a pinpoint measurement together with a visual picture
    would be pretty useful for occasional use. So you could point it at each
    suspect part in turn and get a reading.
     
  10. Guest

    sorta like this? http://www.cheap-thermocam.com/

    -Lasse
     
  11. Nice, and a slow scan would be perfectly feasible for looking at circuit
    boards. But again it looks like it is not good for small parts.
     
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