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Trouble with solder

Discussion in 'General Electronics Discussion' started by 8bit, Jun 9, 2015.

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  1. 8bit

    8bit

    97
    3
    Oct 30, 2013
    I am trying to solder onto the outer casing of a small 9v motor but the solder just rolls off it. The designer of the device I am trying to build suggests scuffing/scratching the outer case which should solve the problem but I still can't get the solder to stick. Has anyone got any suggestions, maybe different solder?
     
  2. duke37

    duke37

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    Jan 9, 2011
    You will not be able to solder to aluminium or chromium due to the persistent oxide layer.
    You may be able to spot weld a wire with suitable equipment. What is the material?
    Iron/steel can be difficult but an acid flux helps.
     
  3. hevans1944

    hevans1944 Hop - AC8NS

    4,543
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    Jun 21, 2012
    If it's an aluminum casing, you will never be able to get the solder to stick. Best thing you could do then is to fasten a steel band-clamp around the casing, after soldering a wire to the band-clamp. Make sure the area under the clamp is clean and perhaps apply a dab of lubricant to keep it clean. The clamp will push the lubricant aside to create a metal-to-metal contact as the band is tightened. Don't over-tighten it; snug so the band doesn't rotate is all you need.

    It is just barely possible that you are not heating the casing hot enough (because your soldering iron is too low wattage), or you are not using enough flux to "wet" the surface of the casing, which probably acts as a good heat sink... all that is assuming the casing IS solderable. See previous comment on aluminum. If the casing is solderable, you still run the risk of damaging the internal components of the motor by heating it while applying solder. I would try the band clamp method first.
     
    8bit likes this.
  4. 8bit

    8bit

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    Oct 30, 2013
    Thanks for the replies. Not aware of the actual material the casing is made from. Bought them from Ebay and posted from China. :s
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    It could even be nickel or zinc plated which is also difficult

    The other main issue ( that wasn't commented on) is ( even if the metal was solderable) is the mass of metal may not have been getting hot enough for solder to flow
    if the OP didn't have a soldering iron of high enough wattage

    Dave
     
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  6. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    Scratch the surface, use a HOT iron and make sure the iron has a large mass so the casing will get hot too. It must get HOT HOT.
     
    8bit likes this.
  7. Hypatia's Protege

    Hypatia's Protege

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    Jun 10, 2015
    Contrary to common belief aluminum can be soldered - however you will need to 'clean' and solder the metal under an 'inert' atmosphere (Note: CO2 and N2 qualify as 'inert' for these purposes) -- Be advised, however, that 'retail' He is unacceptable owing to the 'common' practice of adulterating same with O2 (in an apparent attempt to thwart 'huffers' anoxic aspirations:rolleyes:)

    If, on the other hand, you are using ROHS compliant solder, please be advised that expectation of favorable results on any surface is wildly optimistic!;)

    Best Regards and good luck!:)
    HP
     
    8bit likes this.
  8. 8bit

    8bit

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    Oct 30, 2013
    Thanks for all the info, I'll try a more powerful iron. :)
     
  9. Hypatia's Protege

    Hypatia's Protege

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    Jun 10, 2015
    If the casing is aluminum you'll need to take measures to remove the oxide under conditions preclusive of its reformation (as per post #7) --- A high-powered 'iron' may indeed be useful considering Al's 'high degree' of thermal conductivity...

    Best regards and, again, best of luck!:)
    HP
     
  10. hevans1944

    hevans1944 Hop - AC8NS

    4,543
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    Jun 21, 2012
    And perhaps you should buy a few spare motors too, for use after you melt the plastic-insulated parts of the motor if you don't like the idea of using a band-clamp instead. If you have access to an AC heli-arc TiG welder, and a friend who knows how to use one, it takes only a few seconds to weld a copper wire to an aluminum case with minimal heating of the case. I buy helium (He) from a reputable welding supply store that does not "dilute" it with anything, although some folks prefer a helium-nitrogen custom mix. Offer the friend a few bucks to replace the gas used. Maybe buy him a package of "stingers" for his torch... you can never have too many of those laying around.

    Hop
     
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  11. Hypatia's Protege

    Hypatia's Protege

    8
    2
    Jun 10, 2015

    Sound advice indeed!:) --- How truly the practical approach always reigns supreme!:cool:

    Best regards
    HP
     
    Last edited: Jun 10, 2015
  12. 8bit

    8bit

    97
    3
    Oct 30, 2013
    Thanks.

    I made some headway and managed to solder my first component onto the motor. A little messy but it's on there. Only two more to go! :)

    Just to add I am only a beginner at all this and my equipment it quite basic and limited. I am not a hardcore enthusiast but I like to dabble from time to time. What I am trying to construct at the moment is a small solar bot, or BEAM bot I think they are called.
     
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