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Hand Soldering

Discussion in 'Electronic Basics' started by [email protected], Oct 28, 2007.

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  1. Guest

    I'm a EE student at Cornell working on a research project. We have to
    do a significant amount of hand soldering for the project. Which chip
    packages are hand solderable? I need to know what I can purchase
    from, say, DigiKey and actually solder. Examples of packages I'm
    interested in are:
    * DIP
    * SIP
    * SOT
    * SOIC
    * SSOP
    * TSSOP
    * QFN
    * TDFN

    I know it depends on equipment and skill. I've done some soldering
    before, but not much. We have medium quality soldering irons (not
    tiny tips) and basic magnification (no microscopes).

    Thanks,
    -J
     
  2. Marra

    Marra Guest

    Given a small enough tip you can solder pretty much anything.

    www.ckp-railways.talktalk.net/pcbcad28.htm
     
  3. John Larkin

    John Larkin Guest

    They're all hand solderable. The real indicator of difficulty is lead
    pitch. 50 mils is easy; 20 mils takes more care and skill, and careful
    post-inspection for solder bridges. Since you're not likely to want to
    spend a lot of time practicing, try to use dip or larger-pitch parts
    for now.

    The leadless parts are a bitch, and bga's are impossible to hand
    solder.

    What are you building?

    John
     
  4. Randy Day

    Randy Day Guest

    TDFN has all pins under the device.

    Attaching any of the rest to a PCB can be
    done by hand with a soldering iron and a
    light touch, but if you're *removing*
    parts? Only the first four.

    You might get the rest off a board with
    lots of solder wick, but you'll likely
    take a few traces with it...
     
  5. Rich Webb

    Rich Webb Guest

    As John says, 20 mil (0.5 mm) pitch is quite do-able by hand with a
    modicum of care. An Optivisor (a.k.a. geek helmet ;-) is useful. A
    medium tip is also fine; better, actually, for "wave tip" soldering,
    where a bead of solder is drawn across the package leads.

    Some useful tutorials at
    http://www.sparkfun.com/commerce/hdr.php?p=tutorials

    If you don't have access to a rework station (I've become a True
    Believer for hot air), a ChipQuik starter kit might be a good
    investment if you do work with the many-legged SMT devices.
    Good advice...
     

  6. (This is only needed for small pitch)

    You can do all of them. The easiest way I've found(although I'm by far an
    expert at it) is to pre-solder the pads and remove as much solder from the
    pads as possible(use wick). Then just put the IC on the pads and heat the
    leads(use flux). It sticks pretty well and I have yet to have any pins not
    make good contact. I suppose its not the best method but seems to work well.
    Trying to solder the pins after the fact is a mess IMO and takes about 10x
    longer for very low pitch.

    I imagine you could also use hot air or some other method but this, IMO,
    seems the easiest if you don't have something better. You can check for
    mechanical connection by using a continuity tester. If any pins don't stick
    then you can always add a little solder to the tip and reheat the pin.

    You would be supprised what you can solder. When I first tried SMT I was
    nervious but its actually not all that difficult once you get the hang of
    it.
     
  7. Rich Webb

    Rich Webb Guest

    ChipQuik really works for this, although I haven't personally used it
    on larger than 48 pin LQFP devices (and I prefer hot air now, having
    gotten the necessary gizmo). It's even possible to re-use the removed
    device (after cleaning) if it turns out that the problem was elsewhere
    in the circuit (like THAT ever happens).

    Not recommended for more than occasional use, since it's relatively
    expensive (in the neighborhood of US$5 per foot) and a quad pack
    probably takes 2" to 4".

    Usual disclaimer: just a customer who buys too many gadgets...
     
  8. John G

    John G Guest

    A related question from someone who only does the odd (sometimes Very
    Odd) repair these days.

    Can RHoS certified components (Resistors etc) be succesfully soldered
    with ordinary old solder and reasonable Weller Iron?
    John G.
     
  9. DJ Delorie

    DJ Delorie Guest

    I've done all of these by hand, although I tend to use solder paste
    and a hotplate for most SMT work these days, especially the "FN"
    packages, where the connections are under the chip. Also, even with
    the iron, for SMT resistors and capacitors I find it much easier to
    apply a dab of solder paste to each pad, put the part on it, and then
    melt the paste with the iron; than to try to use wire solder for that
    task.

    A fine tip on the iron and some form of magnifier (I also use an
    optivisor) is key to doing small parts by hand.

    As for size, I've hand soldered (with an iron) down to 01005 caps
    (0.016" x 0.008"), and 0.4mm (16 mil) pitch ICs. It's not fast,
    though. For most boards, using a stencil, solder paste, and a cheap
    hotplate or electric skillet will be much faster and easier.
     
  10. Randy Day

    Randy Day Guest

    Absolutely. Standard solder works just
    fine. You just can't call it RoHS and
    sell it in Europe...
     
  11. John Fields

    John Fields Guest

    ---
    For prototype surface mount packages I flux everything up first,
    then I use a times ten visor to line up the chip as best I can in X
    and Y. Then, when everything looks good, I tack down one corner.

    If, after that, everything still looks good I tack down the
    diagonally opposite corner so that all of the pins fall on their
    respective traces.

    I don't do RoHS and I get my PCB's plated Sn63 SMOBC, so a touch of
    the iron on the pin over the fluxed trace melts the plating and
    solders the pin to the pad/trace.
     
  12. John G

    John G Guest

    Thanks. I do not sell things anywhere, only do repairs and gadget type
    things, often for disabled clients thru a Sydney Australia charity
    called Technical Aid to the Disabled.

    John G.
     
  13. john jardine

    john jardine Guest

    If you get a kick out of watchmaking, egg implantation, keyhole gynaecology
    and have suitable kit, then all the types are approachable.
    For normal humans, DIP, SIP.
    The remainder are spawn of the devil, not meant to be touched by human hand
    and an utter pain the arse.
     
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