Soldering Paste Flux

Hardcoaler Apr 3, 2018

  1. Hardcoaler

    Hardcoaler TrainBoard Member

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    I've recently become aware of Soldering Paste Flux for electrical work. A small dab is applied to the joint prior to soldering to enhance solder flow. Do any of y'all use this sort of product? I use 60/40 Rosin Core Solder. Thanks for any advice and tips.
    [​IMG]
     
  2. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    I always use a flux of some sort when soldering, it makes the job so much easier by distributing the heat in the area of the join, creates good bonds and takes much less contact time with the iron.

    My go to flux is a liquid flux, which I dab on with a microbrush. A 4 oz bottle can last years, and creates much less mess than the pastes.
     
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  3. emaley

    emaley TrainBoard Supporter

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    Absolutely. I love it. You get better flow, better heat transfer, and less time with the iron on the joint, which means less likely that you melt stuff. Good stuff.

    Trey
     
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  4. KE4NYV

    KE4NYV TrainBoard Member

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    In most cases your rosin core solder has enough flux for the job. While on that subject, dump the 60/40 solder and get 63/37 eutectic. Much easier to work with since it has virtually no plastic state and is harder to form cold solder joints.
     
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  5. Hardcoaler

    Hardcoaler TrainBoard Member

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    Thank you for your confirmations and suggestions guys. I'm indebted to my friend for telling me about the stuff. I've been messing around with circuits for 45+ years and never knew about it!
     
  6. Greg Elmassian

    Greg Elmassian TrainBoard Member

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    You do not want to mix flux types, you state you use 60/40 rosin core solder, i.e. rosin type flux... but your green stuff is water soluble flux, a different compound... and also be careful, liquid fluxes can be any of 3 types, and the acid type of flux is bad for electrical connections.

    Pick a flux type and stick with it.

    Greg
     
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  7. trainman-ho

    trainman-ho TrainBoard Member

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    I always thought that the flux was to remove any contaminants from the pieces to be soldered.

    The acid in acid core solder is a week acid that will remain on the soldered joint. That is the grey flaky stuff found on some copper water pipe joints. And will cause poor connection in electrical circuits eventually.

    I use electronic solder which doesn't, as far as I know, have any flux in the core. The brand I use comes with a tube of flux with the name BernzOmatic on it. The solder is quite thin,and requires very little heat to make a good joint.

    It is best to make sure the pieces to be soldered are clean by lightly sanding any older or pre used pieces. Some people will apply a small thin amount of solder on the pieces to be soldered, push them together, and apply more heat until the solder flows together. This is called tinning and ensures a good connection both physical and electrical.

    Keep in mind that dissimilar metals when subjected to current flow (electricity) will produce corrosion, and on a molecular level the ends of a 3 foot piece wire are dissimilar. And corrosion is a very poor conductor.

    Most of this info has been gathered while working as a mechanic for too many years, and some of the assumptions may not be correct, but it works for me!

    Jim
     
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  8. Jimbo20

    Jimbo20 TrainBoard Member

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    Some more 'aggresive' fluxes when used in electronic applications must be washed off with a suitable electronic solvent after the joints are soldered otherwise in time reactions cause partial shorts to occur between close, but normally separated connections. Don't ask how I know!

    Jim
     
  9. trainman-ho

    trainman-ho TrainBoard Member

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    We all really learn by mistakes....ours = experience.....other's = education!!

    Jim
     
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  10. Kitbash

    Kitbash TrainBoard Supporter

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    I have been using "Bernzomatic" water solvable flux for electronics for years. Never had ONE problem in 14 years of use of the stuff. I use a very thin electronic grade solder along with a needle tip 35W Weller.
     
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  11. Hardcoaler

    Hardcoaler TrainBoard Member

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    Sometimes when I'm soldering two wires together, I can't get the ends to line up for solder application. As a "tip", I tape the wires to a small piece of scrap bathroom tile. The tile is impervious to the heat and solder, so is the perfect surface to work on. My trusty 8" x 2-1/2" piece of tile has been on duty for 35 years now.
     
  12. chadbag

    chadbag TrainBoard Member

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    I long used rosin core 63/37 solder IIRC. I recently switched to using solid solder and H&N Superior Flux (hnflux.com) and have had good results -- even when soldering wire to some "steel" power "bus" pieces in some Japanese trains. Some folks on another forum recommended the H&N flux and it works very well. I have the liquid and the and double strength liquid.

    I still have the rosin core solder and use it instead when I have a quick job and don't want to fish out the other stuff, but usually I now use my new H&N solder and rosin.
     
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  13. jdetray

    jdetray TrainBoard Member

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    Just laying two bare wires next to one another and applying solder is not ideal. It creates a weak solder joint.

    Best practice for soldering is to -- whenever possible -- first make a secure mechanical connection between the two parts. For soldering together two wires together, something like this is recommended before you apply any solder:
    [​IMG]
    The above is sometimes called a "Western Union splice." If you're like me, your splice will never look as neat as the diagram! The point is to connect the wires securely before you solder.

    The underlying concept is that unlike, say, soldering copper water pipes, electrical soldering is not intended to hold parts together. It's designed to provide a good, low resistance path for current flow.

    - Jeff

    P.S. > In keeping with the topic of this thread, I use Radio Shack paste flux that I bought years ago. It still seems to do the job.
     
    Last edited: Jul 10, 2019
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  14. Doug Gosha

    Doug Gosha TrainBoard Member

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    Thanks Jeff. Yeah, the Western Union splice. I have used it for years and years, from the beginning of my career. I always thought it was best. Other guys I knew would just twist the wires together, leaving them sticking out sideways, requiring them to then be folded over. Not as neat although you're right that in real life situations the Western Union splice usually didn't end up as neat as the diagrams either.

    Also, the Western Union splice is pretty much wedded to railroads.

    Doug
     
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  15. Hardcoaler

    Hardcoaler TrainBoard Member

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    Good advice Jeff -- I'll start doing that as best I can. It's hard because my vision isn't what it once was, or maybe it's that the wires have since gotten really small. :)
     
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  16. Doug Gosha

    Doug Gosha TrainBoard Member

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    Don't worry, Dan, I often cheat and just lay the wires together, too, if I don't have room to twist them together. My reduced dexterity is a considerable factor, too. Strength is not always a real issue in N scale stuff, anyway. :D

    Doug
     
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  17. wvgca

    wvgca TrainBoard Member

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    most rosin fluxes are soluble in alcohol, which can be used for a cleaning agent... some are soluble in water, those are clearly marked on the tin ..
     
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  18. Onizukachan

    Onizukachan TrainBoard Supporter

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    If you can’t manage a perfect western union splice, eyesight and dexterity have their limits, you can jsut twist one about the other as best you can.. Make sure the stripped sections overlap slightly the unstripped sections Inevitable you’ll wind up with some twist of the main wire around the second and vice versa for a good connection.
    We aren’t soldering 2ga here after all.
    I tried using paste flux (and still do on tiny 38 ga magnet wire) but think it makes a mess on stranded wire unless you stick the wire in before twisting then tin. Works fine for tinnin a tip to solder to a decoder though!
    I don’t use it for making wired rail joiners at all, just tinning with normal 95/5 or 80/20, whatever is to hand.


    I’ve had good results on small wires with the “modified” twist connection described above and a two step solder technique. Apply solder only until it first gets “ wet” in the middle then take away the iron and let it cool a few seconds. Trim any excess tails , Then go back and the cooled solder will reflow more evenly thru the braid when heat is reapplied...
    You can then add a touch more if you need a smooth outer surface, like to sleeve with heatshrink or to paint insulating paint over (black nail polish works great on magnet wires or multi strand 32 and even 36, for example.)
     
  19. Hardcoaler

    Hardcoaler TrainBoard Member

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    That's a good tip. I use the flux sparingly, but if I glob too much on, a cotton swap dipped in rubbing alcohol does indeed to well at cleaning things up. (y)
     

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