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Soldering question for the more experienced

Discussion in 'Misc Electronics' started by MattB, Dec 1, 2003.

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  1. MattB

    MattB Guest

    Hi, I've got a project that I'm working on and I'm having some trouble
    with a solder joint. I'm adding an optical output to a Minidisc deck. It's a
    low-cost deck and the output exists on the pricier models in this line. So
    the circuitry is there, just no Toslink transmitter. I located a transmitter
    and proceeded to try to solder it to the PCB. The holes were already there
    and they were filled with solder. My plan was to just heat the existing
    solder to insert the part. That wasn't working very well, so I ended up
    cleaning out a couple of the holes with a sucker and tried to solder the
    part in with new solder (flux filled "for electronics" solder).
    The problem is, the new solder doesn't stick to the board, just the post
    of the transmitter, making a lollipop-shaped stick with the lump of solder
    at the top. It doesn't make a good connection. I figured I just needed to
    buy some flux and clean that part of the board with it. The problem is, they
    have no flux at my local RS (back by the guns in the local hardware store).
    So I ask you experts, is this the right solution? Is there something
    else I should do? Where can I order some flux from inexpensively in the USA?
    Anything special to look for with flux for electronics projects?

  2. It sounds like the pads are not being heated properly. When soldering, it
    is important to use a small tip that can touch both the lead and the pad
    simultaneously. A small bead of solder on the iron tip is also a requirement to
    conduct heat to both items properly. Also, I recommend a 700 degree (F) tip for
    most solder jobs.
    Check my page and the soldering tutorial- not really an exhaustive one, but


    Chip Shults
    My robotics, space and CGI web page -
  3. Don Bruder

    Don Bruder Guest

    You're "cold-soldering", it sounds like to me. Heat the lead/pad, not
    the solder. Done correctly, the solder will flow to where it's needed.
    Done incorrectly, the result is much like what you describe: A solder
    "lolipop" on the end of a component-lead stick.

    It's also possible that there is no copper on the "back" side of the
    board for the solder to grab - The actual connection may be either on
    the other side of the board, or partway through, on an internal layer of
    traces. You are aware that some electronic goods use boards with many
    different layers, aren't you? 11 layers are the most I've ever
    personally seen (And lord, what a pain to try to either solder or
    desolder) on a single board, but there's no theoretical limit to how
    many *COULD* be stacked up like a Dagwood sandwich.
  4. Ken Taylor

    Ken Taylor Guest


    Like Chip and Don said, but also, DON'T USE FLUX FROM THE STORE! It's highly
    acidic and will eat the board away. Just use the flux/resin-cored solder,
    and use a good soldering technique, as you're being advised. Good luck.

  5. MattB

    MattB Guest

    Thanks to all you guys. I'll try the methods mentioned and see how it goes.
    I think it's just a single layer board, there's not really that much to it.

  6. I think your main problem is that the soldering iron you're using
    can't heat up the PC board enough, just the component leg. Get a
    higher power soldering iron.

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  7. Ross Mac

    Ross Mac Guest

    Matt, if this is a single sided board than how could you have solder in the
    holes?....What you need to do is to is heat the board and the wires at the
    same time, then add the solder to the board. It should crawl up the wire and
    form a fillet.......good luck, Ross
  8. Ken Taylor

    Ken Taylor Guest


    Check out any/all of these to verify your soldering technique:



  9. Ross Mac

    Ross Mac Guest

  10. Ken Taylor

    Ken Taylor Guest

    A pictures worth 842 words (damn inflation.....)

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