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Finding a good soldering iron....

Discussion in 'General Electronics Discussion' started by Lee Aufdemkampe, Mar 22, 2017.

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  1. Lee Aufdemkampe

    Lee Aufdemkampe

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    Mar 22, 2017
    I have tried several soldering irons recently and they all fail to pull the solder into the wires. Instead the partially melted solder just sits there on top of my connection. I admit that these irons are rather inexpensive so I figure I'll have to step up a level or so but would appreciate some guidance. The irons I have now are just not hot enough!
     
  2. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    I don't think its a question of heat. If your iron is a simple plug in iron they run pretty hot. Too hot for my tastes actually. What you need is to apply flux to your wires and solder connections. Flux is an acid (safe to handle) that cleans all the oils and dirt off the wire. The solder will flow right into the wire. You can get flux pens which are good for board work and tins of flux which are nice for tinning wires. Really the only benefit to a nice iron is precise temperature control for working around heat sensitive components. I like to run my irons a little cool, that keeps the solder on the tip of the iron so it won't drip off.

    This is my personal iron. Pretty happy with it.

    http://www.velleman.co.uk/contents/en-uk/p557_vtssc40n.html
     
    Last edited: Mar 22, 2017
  3. duke37

    duke37

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    Jan 9, 2011
    Flux can be acid and is used for plumbing. Keep acid flux well away from electronic compoments, it will cause long term corrosion problems. I have seen transistors with no leads.:(

    Cleanliness is essential to get solder to run. The solder tends to run towards the heat so heat the component and feed cored solder onto the component as soon as it is hot. You only need anough solder on the iron to get a good thermal connection.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I hate the expression "solder flows toward the heat".

    Solder isn't possessed of some heat-seeking anti-gravity magic.

    Solder flows on surfaces it can "wet", when it is hot enough to remain molten, and within the constraints of gravity, its viscosity and shape of its meniscus.

    Sure, that's not as simple, but it's right.

    If solder flows toward heat, all you would need to desolder something would be a hot iron. It would just draw the solder away. But as we know, if to surfaces are hot enough to keep solder in a liquid state, solder will be drawn up into a relatively cooler place. Solder wick is a perfect example. Another example is soldering a TO220 heatsink tab to a PCB.

    What we need to teach us that the surfaces to be soldered need to be "wetable" by solder (I.e. tinned, or gold plated, silver plated, copper, brass, ... All the metals you can solder), they need to be clean (no excessive oxide, solder mask, oils, etc), hot enough, and the solder needs a reason to be there.

    Some parts are simple, the whole joint need to be hot enough, of the right type of materials and sufficiently clean (generally so the flux can clean up and keep clean the surfaces before they are covered in solder).

    The part that isn't so simple is making the solder "want" to go there. Unless it's being wicked up, it won't go uphill far against gravity, no matter how hot the joint is.

    One simple trick is to use a little bit of solder on the tip to assist with heat transfer, then use the solder to "paint it" where you want it. Rather than applying the solder to the joint near the tip and just waiting for it to spread itself around the joint, you simply paint it on around the joint. The flux is where you want it, and you know the joint is hot enough because it is melting the solder.

    Done this way the solder will wick into most joints rather than flowing over them. It's also a lot faster.
     
    Last edited: Mar 22, 2017
  5. shrtrnd

    shrtrnd

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    Jan 15, 2010
    To me, because you said you used several soldering irons and have the same problem:
    1) Are the soldering iron tips clean? Do they need to be cleaned and re-tinned for better transfer of heat?
    2) You didn't specify the gauge of the wire you're trying to solder, or what you're trying to solder the wire to.
    *steve* gave you a pretty good tutorial on the issues. Most soldering irons are fine for simple work. IF you are
    trying to solder a heavy gauge wire and/or a large contact area, you need a higher wattage iron.
    I do electronics work, and have relatively low-wattage irons for that.
    Those low-wattage irons are useless when I try to solder 10 gauge grounding cables on my cars. I have to
    use a higher wattage iron for that kind of work.
    Can you give us a little information about what it is that you're having a hard time soldering?
    Is this simple bench repair work, or are you trying to solder ground planes on a 1000 watt power supplies?
     
  6. Externet

    Externet

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    Aug 24, 2009
    All soldering irons work. Some better for some uses, some better for others. Skills and experience are more questionable than the item itself.
    $1 irons or hundred$ irons have a place. Focus on your skills.

    To solder properly, the pad, the pin and the solder should be at the same heat level. It is not matter of just melting solder.

    ---->
     
  7. duke37

    duke37

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    Jan 9, 2011
    The op had trouble with a blob of solder on the top of a presumably cold component. If the solder is applied to a cooler part and it melts, then it should migrate towards hotter areas where the viscosity and surface tension are more suitable.

    Perhaps one factor is that he may be using lead free solder with a high melting point rather than 60Sn/40Pb eutectic.
     
  8. Chemelec

    Chemelec

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    Jul 12, 2016
  9. Audioguru

    Audioguru

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    Sep 24, 2016
    No. 60/40 solder is for plumbing and it remains pasty so it can be molded while it cools. I hate trying to connect electronic things with 60/40 solder because if the joint is moved a little while it is cooling then it forms a bad connection. 63/37 solder is eutectic for electronics and a good connection is made immediately
     
  10. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
  11. Audioguru

    Audioguru

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    Sep 24, 2016
    I have some Name brand 60/40 solder and it is horrible. 63/37 solder is much better. Look up eutectic solder in Google.
     
    (*steve*) likes this.
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I 100% agree with this.

    You can do perfectly good solder joints with 60/40 solder, but the difference between it and 63/37 is like night and day.
     
    hevans1944 likes this.
  13. Audioguru

    Audioguru

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    Sep 24, 2016
    My 63/37 solder has a flux core so I have never needed and I have never used separate flux except when I soldered together some copper water pipes with a butane torch, 60/40 solder and acid flux from a can.

    I have never seen a Fry's store so I looked it up. They sell many products. I buy electronic parts from a store that sells electronic parts, not products. Fry's sells the 63/37 flux core solder that I recently bought at an electronic parts store.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What brand are you using @Audioguru?

    I'm currently using Kester.
     
  15. Chemelec

    Chemelec

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    Jul 12, 2016
    Personally I Like the Kester 331 Solder.
    This is a 63/37 with a Water Based Flux.
    Just wash the Assembled board under a Warm or Hot Water To to remove all the flux residue.
     
    hevans1944 likes this.
  16. duke37

    duke37

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    Jan 9, 2011
    60Sn/40Pb is very close to the eutectic. It may contain a smidgeon of other metals such as copper. What is the accuracy of your analysis?

    60Pb/40Sn is the pasty plumber's solder.

    I use Multicore solder, not sure if it is Savbit (with copper), the label has gone.
     
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    High.

    It really does make a significant difference.
     
  18. Audioguru

    Audioguru

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    For years I used Ersin 63/37 multicore (British?) and it worked very well and I liked the aroma of its flux. I was running out so I bought Kester 60/40 but I do not like its behaviour. Now I have MG Chemicals 63/37 rosin core but its flux does not work as well as the Ersin.
     
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Maybe I should send you some of the kester I'm using :)
     
  20. Audioguru

    Audioguru

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    Sep 24, 2016
    Thanks for your offer but you are on the other side of the world (between Beijing and Ronne Ice Shelf?) from me.
    It looks like you are in Australia, MATE!;)
     
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