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Does fluxless solder exist? If so, help me

  1. Oct 5, 2012 #1
    Hi guys,
    I have been commanded by my superior to find a "fluxless solder." I can't find anything like this except for vague allusions to tin-gold alloys, but once I investigate them further, I hit a dead end.

    Basically, we want to solder wires on a surface that will be inside a UHV chamber.

    Thanks in advance
  2. jcsd
  3. Oct 5, 2012 #2


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    Sure fluxless solder exists but it is unlikely you will be able to solder with it unless you apply flux to the pieces you are soldering. Solder used for plumbing these days contains no lead and is solid wire, therefore containing no flux. Flux is applied to the pipe fittings with a brush and they are put together, heated and when hot enough to flow solder, the molten solder is drawn into the joint. I have attempted to solder pipes without flux and it is completely pointless to attempt it. I have also tried soldering pipes with a flux core solder and it works, but not as well. Don't do it for plumbing since you will likely end up with lead solder which is not legal for plumbing.
  4. Oct 5, 2012 #3

    Simon Bridge

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    Welcome to PF;
    - you go to a hardware store or a plumbing supplies and you ask for it. You get a stick of some metal alloy and a tin of flux.

    But you may mean that you have to solder the wires without using flux at all.

    Flux basically cleans the surfaces to be joined (removes oxides and inhibits further oxidation). Since you will be soldering in vaccuo(?), oxidation may not be a problem. What you use will depend on the exact method.

    Why didn't you just ask your superior what is usually used?
  5. Oct 5, 2012 #4


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    Google solid core solder. It is very common.
  6. Oct 5, 2012 #5


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    An electronics store will also have small reels of fluxless solder for use with 25 watt soldering irons. Usefull for circuit boards and small wire. check out somebody such as Radio shack or similar. If you clean you wires completely and depending upon their makeup - silver alloy wire does not need flux most times but tin it and the connection ( coat with solder ) before soldering the wire to the connection
  7. Oct 5, 2012 #6
    The flux sold in hardware store for soldering plumbing contains acid.
    In the old days if acid flux was used for a kit, the warranty was void.
    A technician at work used acid type flux and the flux shorted 115 volt terminals spaced maybe 3/8" apart.
  8. Oct 6, 2012 #7


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    It's not good enough to first solder using flux, then remove all traces of excess flux before placing into the chamber?
  9. Oct 6, 2012 #8
    For UHV work you shouldnt use any solder. Their vapor pressures are too high.

    Use clean crimps.
  10. Oct 6, 2012 #9

    Simon Bridge

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    @Ochreyes: solved the problem?
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