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soldering ICs to prepunched circuit board

Discussion in 'Electronic Basics' started by Ed, Jan 20, 2004.

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  1. Ed

    Ed Guest

    Hello all, I've purchased a piece of circuit board from Radio Shack, and
    am having a hard time soldering an IC (ULN2068B motor driver) chip to
    it. The rest of the circuit is passive, and that's not a problem. It's
    not my soldering skills. I'm guessing that the momentary heat is
    killing the IC. Radio Shack makes some IC 'sockets' which you can
    first solder on, then insert the chip... but the pins are < 1/4" long,
    and once through the plastic board, there's no 'meat' to work with. Any
    suggestions?

    Thanks,
    Ed
     
  2. As long as the socket pins are visible in the holes, you should be
    able to solder them in place. What would you do with longer pins,
    except cut them off after soldering? The trick is to hold the socket
    in place somehow, till you solder two opposite corner pins to hold it
    in place while you solder the others.
     
  3. Garrett Mace

    Garrett Mace Guest

    somehow == masking tape
     
  4. Steve

    Steve Guest

    I just slightly bend the pins on opposite corners to hold them in place
    until I can get some solder on them and the rest..

    Steve
     
  5. I usually solder all sockets in first, with the board laying flat on
    top of them. Otherwise, I put some small object on the table that
    will prop the board up slightly through pressure on the socket till I
    get it tacked down.
     
  6. Garrett Mace

    Garrett Mace Guest

    somehow == masking tape
    Unnecessarily difficult. If you don't have enough sockets to make a stable
    setup, at some point you tip the board with the soldering iron or your
    finger and everything falls out. Or, if you have lots of sockets, you have
    to hold everything in with fingers and do some sleight-of-hand to get it all
    on the tabletop in one piece. I messed around with that tactic for a while,
    and found that a simple strap of masking tape across the socket lets you
    solder all of them at once, and clamp the board in a vise where it's not
    going to flip or skitter across the table at the slightest nudge. It also is
    a good way to immobilize SMD parts before you get those first few critical
    pins tacked down.
     
  7. Rich Webb

    Rich Webb Guest

    Did you thoroughly clean the board before you started soldering? The
    solder core helps some, by reacting with the oxide layer, but it's hard
    to get a good "wetting" action on copper oxide and so you may be having
    to leave the iron against the chip for too long. It's not like soldering
    to a tin-plated pad. Try some fine (1600, 2000) grit wet/dry sandpaper
    in water. Polish until it shines and then dry with a lint-free wipe.
     
  8. Ed

    Ed Guest

    Thanks for the reply. I guess I mis-stated my problem - I'm trying to
    solder a piece of wire onto the bottom of the lead. Maybe I'm a bad
    solderer, but I can't get the wire to make a good enough physical
    contact with the pin that I feel comfortable tacking it down with a bit
    of solder.

    Basically, I have the socket on top of the board, then underneath, a
    small lead of wire wrapped around one of the pins, which I then solder
    for permanence. Then the other end of the wire lead goes to a
    transistor, etc.

    How do y'all attach wires to the sockets?

    *John Popelish* uttered the words:
     
  9. Rileyesi

    Rileyesi Guest

    This may help (or may not!)

    There are two types of IC sockets: a solder type and a wire wrap type. The
    solder type of sockets have short pins that are designed to go through a PBC
    like the pins of an IC would. They stick out of the solder side of the PCB
    just enought to let you solder them in place. These are typically used in PCBs
    that have traces or some type of copper on them.

    The wire wrap type has longer pins that sitck out farther from the PCB enabling
    you to wrap a wire to them using a tool called a (now get this!) a wire wrap
    tool! When used correctly, and with the correct wire (which is very thin), you
    can "stitch" todether a circuit using a board called a punch board or a perf
    board. This is a board that usually has no copper on it at all. You put your
    resistors, caps, diodes, IC sockets, etc. into the perf board and then make the
    circuit connections using a wire wrap tool and the correct wire.

    The wire for this is thin. I bought a wire wrap tool and a pack of three
    colors of wire (the colors come in handy when de-bugging the circuit) from
    Radio Shack for a total of about $12.

    If done correctly, the wire wrap technique needs no solder.

    Hope this helps.
     
  10. Those circuit boards are pretty cheesy - the holes are fairly large and
    the pads will lift off if heated only a little too much.

    assuming that every part is CLEAN...
    The trick is to heat the pad and the pin and the wire at the same time.
    Maybe your wire is kinda big ?
    Make sure the wire is pre-tinned. You can try to hook the wire around the
    pin. Or, before soldering, stick it into the hole alongside the pin. THis
    will help the solder to wick into the hole.
    Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
     
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