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Tinning a solid copper bar.

Discussion in 'Electronic Basics' started by eromlignod, May 29, 2007.

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  1. eromlignod

    eromlignod Guest

    Hi guys:

    I'd like to tin one side of a 5/16" square copper bar so that it can
    be soldered to a PCB. A soldering iron isn't doing the trick, even
    with lots of flux. Any ideas?

  2. Meat Plow

    Meat Plow Guest

    Propane torch
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  3. Solder pot.

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  4. Did you clean it thoroughly? You can use acid flux for this as long as you
    thoroughly wash it off afterwards. Then you just need enough heat - even a
    burner on the stove will do.



  5. Blake

    Blake Guest

    First clean it with Scotch Brite until it's, well, bright.

    Then coat it with plenty of flux paste to prevent oxidation when it heats

    Next, heat it up. Your iron probably doesn't have enough power. A common
    technique to to heat the bar on a hot plate to something below soldering
    temperature, and then use the iron to "put it over the top".

    And you know about the solder.
  6. Ross Herbert

    Ross Herbert Guest

    Believe me, soldering a solid copper bar of this size directly to a
    PCB is a no-no!! Even after you get the bar tinned (as suggested with
    a propane torch) then you have to somehow get an even greater amount
    of heat into it in order to get it soldered to the pcb. Since you
    can't use a propane torch for this operation without destroying the
    pcb, and a soldering iron won't do the job adequately, then what do
    you do?

    The only solution is to drill and tap the copper bar (after tinning
    all over to stop oxidation) and then use metal thread screws and
    washers (combination of flat and shakeproof) to attach it to the pcb.
    That is how one Swiss manufacturer of sine wave inverters does it and
    I can attest to the effectiveness of this method. This technique also
    makes for ease of repairs if you ever have to remove the copper bar
    from the pcb.
  7. Chris

    Chris Guest

    Absolutely. Also, if you get the bar hot enough to accept the solder
    (as opposed to "tacking" it on -- not a good high current connection),
    it will delaminate the PCB traces. Use pan heads and internal tooth
    lockwashers where helpful.

    By the way, tinning it first is a good idea, too. Clamp it down using
    a couple of pieces of mica or other thermal insulator to keep the vise
    from becoming just another heat sink. If a soldering gun doesn't
    provide enough heat, try a propane torch. Use external flux (and
    *don't* use plumbers' flux or acid flux!)

    Good luck
  8. Jasen

    Jasen Guest

    get the bar hot enough to melt solder (stick it on the stove or blast
    it with a blow-torch) then flux it and apply solder.

  9. Rich Grise

    Rich Grise Guest

    And when the hot copper cools and contracts, it warps the board.

    If mica is such a good thermal insulator, why do they use it for
    electrical insulation on heat sinks? Just lay it in a piece of firebrick.

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