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Best way to desolder?

Discussion in 'Electronic Repair' started by meirman, Mar 6, 2005.

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  1. meirman

    meirman Guest

    What is the best way to desolder?

    I have tried solder wicks, single bulb solder suckers, pen-like solder
    suckers, solder suckers with integrated soldering irons, and I've
    tried heating the item and shaking off the solder.

    My current best method is heating the solder and blowing it off with a
    plastic soda straw. This sometimes leaves solder all over the place,
    and I have to use my fingernail or a chopstick to nudge the solder off
    places where it is shorting two connectors, or where it might fall and
    short something (which is everywhere).

    I ask now because I have, that I found in the trash years ago, about
    12 Western Electric circuit boards, obsolete now, each with up to 7
    6-pole double throw relays. Needless to say, Western Electric used
    high quality relays, but when I try to desolder them from the boards,
    I lose a lot of the connections (there are 20 of them), and often I
    lose one of the two connections that goes to the relay coil, and I've
    ruined the relay.

    I need a better way to get these relays disconnected from the circuit
    boards.

    Help?

    Meirman
     
  2. For removing PC mounted relays I'd use a SOLDAPULLT (tm) followed, if
    necessary, by a little solder wick.
     
  3. James Sweet

    James Sweet Guest

    Depends what you're trying to solder, aside from very expensive vacuum
    stations I've had the best luck with the Radio Shack desoldering iron (one
    of the few truly useful things they sell) for larger joints, and solder wick
    dipped in liquid flux for smaller stuff. The flux is really the key, it
    dries out quickly from solder wick which then works poorly.
     
  4. Cubzilla

    Cubzilla Guest

    ">
    Try sucking,
     
  5. Ken

    Ken Guest

    The only thing I would add to your suggestion is a web site:
    http://www.hvwtech.com/pages/products_view.asp?ProductID=444
    and the comment that desoldering takes some skill. My suggestion would
    be that he practice on some items that he doesn't need before attempting
    to desolder the real items he wants.
     
  6. worldcitizen

    worldcitizen Guest

    Something I've done in the past that works pretty good is to heat the
    solder joint with your iron, remove the iron and then imediatly brush
    the hot solder away with an old tooth brush. Works good and all that
    is left to do is remove all the solder you have brushed away. Try to
    brush in a direction so that the debris is easily removed. I've even
    been know to lay a peice of cloth next to the solder joint before
    brushing and let that catch the trash solder. Taping down a peice of
    paper works too. Use a hot iron and get in and out fast so that you
    don't damage the part. A not so hot iron will force you to stay longer
    on the joint before the solder melts and could damage the part. Good
    luck.
     
  7. b

    b Guest

    (snip)

    I use pieces of old 75 ohm coax cable, with the core removed so just
    the braid remains, dipped in flux. Works like a dream. usually need to
    use a hot iron (40w at least). Practise on some old junk first to get
    the hang of it.
    -Ben
     
  8. This would be solder wick.
     
  9. Back in the days when computer memory chips looked like sixteen-legged
    caterpillars and cost a fortune each, a friend of mine got his hands on
    a pile of circuit boards with dozens of the things soldered in.

    His solution was to grab a board by the corner with pliers and hold it
    in the flame of his kitchen stove until the solder turned all shiny. A
    quick flip to bang the edge of the board, upside down, on the edge of
    the stove, deposited all the chips -- and lots of solder splats -- on
    the vinyl flooring.

    Almost all the chips were good. He was happy; his wife was distinctly
    *not*.

    Isaac
     
  10. meirman

    meirman Guest

    In sci.electronics.repair on Mon, 07 Mar 2005 20:36:45 -0800 Isaac

    These are great boards btw. Very thick and they have half-inch high
    steel frames on three sides of them.
    This sounds great. One more reason I wish I had a gas stove.

    Thanks a lot, and thanks to all of you for a lot of good ideas.

    Also someone emailed me to suggest a heat gun applied to the solder
    side, pointing up, and gravity or pliers or a pry to the other side.

    Meirman
     
  11. meirman

    meirman Guest

    In sci.electronics.repair on Sun, 06 Mar 2005 21:51:47 GMT Ken
    Thanks to both of you.

    I looked at the webpage and then I looked at my solder suckers (I have
    two, bought at rummage sales I think.)

    Much to my surprise, one of them was a Soldapullt, although a
    different model from the one shown. Mine is 3 inches shorter, but the
    stroke is only 3/4 inch shorter. 2 1/2 inches instead of 3 1/4.

    But mine doesn't work at all, and from the web page I realized I must
    replace the o-ring.

    The other one is one of those imitations they mention, and I don't
    think it works very well based on how well it sucks on my finger --
    that's probably why they sold it.
    Is there a problem letting the soldeapullt touch the soldering iron
    tip -- Does that damage it? Should I make sure that I only touch the
    liquid solder?

    I don't think I'll be able to get a replacement tip for the one I
    have, although if it wears out, I'd be willing to buy a new model.

    Thanks again.

    Meirman
     
  12. meirman

    meirman Guest

    In sci.electronics.repair on Sun, 06 Mar 2005 18:41:12 GMT "James
    I actually have liquid flux. I bought a small bottle of it new but
    hadn't realized yet that I have a use for it. I'll try that as you
    suggest.

    Meirman
     
  13. meirman

    meirman Guest

    In sci.electronics.repair on Sun, 6 Mar 2005 21:42:16 -0000 "Cubzilla"
    ;) I've worried about that, but I think I've got it down to only
    blowing. .... You're not serious, are you?




    Meirman
     
  14. meirman

    meirman Guest

    In sci.electronics.repair on 7 Mar 2005 07:33:17 -0800 "worldcitizen"
    I'll try those things too. I actually have a lot of experience doing
    this, and it's worked pretty well, although slowly, and I knew there
    must be a better way.

    That's why I was surprised when I did so much damage to so many of the
    relays and ruined about 3 of them, out of 7 that I removed.

    Thanks to you and to all.


    Meirman
     
  15. Ken

    Ken Guest


    If you will go to the following:
    http://www.hvwtech.com/pages/products1a.asp?CatID=36&SubCatID=154
    you will see you can purchase a refurb kit which includes a replacement
    tip. (Even a local Radio Shack might have them) It is true that
    eventually the tip will become damaged, but it does not occur as quickly
    as one would expect. Place the tip as close to the component as you can
    and release the solder sucker vacuum when you see the solder flow around
    the component. Again, practice is the best method to learn how to
    effectively do this. When I hired a technician for my crew many years
    ago, I would have them practice on scrap PWBs for a week before working
    on real product. One can do a lot of damage quickly to an expensive
    circuit board if you don't have the process perfected. Certainly you
    won't need to practice that long, but some is advised in my opinion.
     
  16. jtaylor

    jtaylor Guest

    Propane torch. Heat & beat (the board against an edge).
     
  17. To remove leaded components from plated-thru holes
    nothing beats a desoldering iron with vacuum pump built into the handle.
    We use one made by Den-on Instruments in Japan called SC7000.
    It is somewhat expensive (around US$ 500)
    Units with the pump on the table and a hose in between lose much of
    their efficiency in my experience.

    Stein
     
  18. Takes too long to heat up to solder-melting temperature. Long before
    that, the components will be cooked.

    Isaac
     
  19.  
  20. Also someone emailed me to suggest a heat gun applied to the solder
    They'll be fine. With correct (high enough) heat, and proper working, most
    of the components will be in excellent condition.
    I've even seen surface mount IC's being installed with a regular heat gun..

    One must not fry the components. Just heat the solder (from the solder side
    only..), hit the board lightly, and the components will drop off the board.
    Well, unless their legs have been turned. In that case, it'll be a bit
    trickyer.
    And of course, one spot of the board must not be heated too long. That too
    will cook it up.
     
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