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Do you use "flux" when soldering?

Discussion in 'Pickups & Electronics [BG]' started by Chrisk-K, Mar 25, 2011.


  1. Chrisk-K

    Chrisk-K

    Joined:
    Jan 20, 2010
    Location:
    Maryland, USA
    I recently read about soldering flux. It's supposed to help achieve clean soldering joints. I've never used it. I can solder but am not very good at it. Am I supposed to use "flux"? You apply a little bit of flux before soldering, right?
     
  2. Rob22315

    Rob22315

    Joined:
    Oct 23, 2010
    Location:
    Alexandria Virginia
    If you are using solder for electronics, the flux is embedded in the solder. The stuff that smokes when you solder is the flux. Brush on solder is for plumbing and stained glass.
     
  3. Coop Soup

    Coop Soup

    Joined:
    Aug 24, 2005
    Location:
    Minneapolis
    There is some flux in solder, but having a liquid flux really helps achieve a cleaner joint. I used to solder for a living (electronics repair) and you should always use liquid flux to achieve professional results.
     
  4. murphy

    murphy

    Joined:
    May 5, 2004
    Location:
    Toronto, Canada
    How do you apply it and to what?
     
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  6. Bongolation

    Bongolation

    Joined:
    Nov 9, 2001
    Location:
    California
    I'm also an ex-pro handwiring tech, forty hours a week doing boutique audio P2P.

    I always used extra flux.

    With SMT, it's impossible to solder without flux as the flux's wicking effect is the only way the solder can move where it has to.

    Flux is freakin' magic. Watch a guy do copper pipes sometime. ;)
     
  7. Jazzdogg

    Jazzdogg Less barking, more wagging! Supporting Member

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    Location:
    San Diego, CA
  8. Bongolation

    Bongolation

    Joined:
    Nov 9, 2001
    Location:
    California
    You apply it however you can to both surfaces being soldered together.

    When I'm doing PCB repair or rewiring instruments, I dab some paste flux on with a toothpick. As soon as the heat gets near, it will melt and spread where it needs to.

    On some extremely Hi-Z circuits, such as the bleeder resistors in condenser microphones -- which can run as high as 3GOhms [!] -- boards will have to be defluxed and conformally-coated, but for everyday stuff it's not an issue.
     
  9. Hawaii Islander

    Hawaii Islander

    Joined:
    Aug 11, 2007
    Location:
    Big Island
    +1

    We used separate flux rather than relying on incore solder in the U.S. Air Force.
     
  10. fhm555

    fhm555 So FOS my eyes are brown Supporting Member

    Joined:
    Feb 16, 2011
    Flux gets my vote. I've always used a rosin paste for electrical work and it works great. Heat the exposed end of a wire just a bit, stick the hot end in your paste flux and tinning becomes a snap. Use a toothpick to apply it the back of pots, terminals, etc. I've built hundreds of sub C, AA, AAA, and 2/3 A battery packs and it's almost impossible to get a good joint between a bar and a small dry cell quick enough to avoid venting the cell without using flux. It's also a good idea to keep some desolder braid handy.
     
  11. James Judson

    James Judson

    Joined:
    Jul 16, 2009
    Use the solder with flux in it. There is no reason to use more flux unless your making up for poor solder skills. Me???? Electronic Technician since 1967 (thats when I built my first guitar amp).
     
  12. Bongolation

    Bongolation

    Joined:
    Nov 9, 2001
    Location:
    California
    You need to update your skill set. SMT soldering relies on added flux to work, and it won't without it.
     
  13. Batmensch

    Batmensch

    Joined:
    Jul 4, 2010
    Location:
    Chester, Pa.,USA
    I use paste flux, and it makes it so much easier. One thing you're not supposed to do is to spend too long heating up your work, or you could damage it. For me, the flux helps with that, it's pretty much touch the iron to the work, and ZAP!, it's done.
     
  14. Batmensch

    Batmensch

    Joined:
    Jul 4, 2010
    Location:
    Chester, Pa.,USA
    And my Dad was an electronics engineer since WW2, and he always used flux. That's where I learned it from.
     
  15. murphy

    murphy

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    May 5, 2004
    Location:
    Toronto, Canada
    Great info people.Should be stickied.
     
  16. aborgman

    aborgman Supporting Member

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    Jun 12, 2007
    Location:
    Ypsilanti, MI 48197

    Yeah, this.
     
  17. Ric5

    Ric5 Supporting Member

    Joined:
    Jan 29, 2008
    Location:
    Colorado
    I use paste flux ... without it sometimes the lead will not adhere to a surface.
     
  18. aborgman

    aborgman Supporting Member

    Joined:
    Jun 12, 2007
    Location:
    Ypsilanti, MI 48197
    I use flux all the time...

    Now I've only been building amps for about 15 years but...

    BS Computer Engineering - University of Michigan

    Senior Component Design Engineer - Intel

    Chief Electrical Engineer - Precision Devices, Inc.

    Electronics Technician Senior - University of Michigan Department of Aerospace Engineering.


    SMT - you ain't doing it without solder paste or flux.

    Anything that is easy to over temperature damage and not easily heatsinkable (see batteries) - you ain't doing it without flux.

    ...and even given a flux cored solder you'll get a cleaner joint using additional flux - plus what if you have to reflow a joint? Flux core solder ain't helping.
     
  19. gjbassist

    gjbassist Supporting Member

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    Sep 7, 2005
    Location:
    Kansas City, MO
    I have had problems getting solder to stick to the back of pots. Will using flux help?
     
  20. UncleFluffy

    UncleFluffy

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    Mar 8, 2009
    Location:
    California
    Disclosures:
    Head Tinkerer, The Flufflab
    I don't tend to use it for regular through-hole PCB soldering.
    SMTs can be done without it (using the excess solder then solder sucker technique) but it does make things easier.
    Bigger lumps of metal - such as pot backs - will benefit from flux.
     
  21. Clark Dark

    Clark Dark

    Joined:
    Mar 3, 2005
    Location:
    on groove maneuvers
    after reading all this advice about how it should be used you're still asking questions ?? get the flux outta here :D
     

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