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Thread: Soldering fail. Ok... what am I doing wrong?

  1. #16
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    I am by no means an expert in this area but with the little i've done I found that cleaning the iron with a wire brush or file makes a huge difference. Maybe you already were doing that but I didn't see mention of it.

  2. #17
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    Hmmm, some good advice given below (above for those that old school setup your threads with newest at the bottom), seeming that I teach soldering here at the Naval Nuclear Power School. I rarely solder anything at home. I prefer crimp on connectors as they are far superior in longevity and strength. They have a lower resistance at the connection, therefore generate less heat. They are also almost dummy proof, and can't have unseen internal flaws. Where vibration is involved, such as a vehicle, terminal lugs are 100% the way to go, hence the fact that virtually every connection in your car is via terminal lug of some type vice soldered. JMTC as a soldering instructor. If you really want to do it, get some eutectic alloy (60/40 tin lead) and a Pace unit. Its like comparing a Harbor Freight 90A flux welder to a Millermatic. You can be the best welder in the world, and not do anything useful with the crappy HF welder.

    I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them.
    Thomas Jefferson

  3. #18
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    Haha! TomDude that's beastly - using inorganic acid flux from the plumbing aisle for electronics! I hope you're not in the satellite business! I'm no electronics repair expert so maybe Marlin can confirm or dispel this - but I've heard it's better to stick with rosin or some other organic-based flux (i.e., less acidic) when soldering electrical stuff. Corrosion and circuit boards generally don't mix well...

  4. #19
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    X10, we only use rma flux, rosin, mildly activated. Anything stronger will eat the connection.

  5. #20
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    Quote Originally Posted by SlowPro48 View Post
    A 25 watt iron is PLENTY big for joining 18 ga wire. If you've got a new iron, you need to tin the tip before you can effectively solder with it. Let the iron get really hot, wipe the tip off with a moist cellulose sponge then coat the tip with solder and wipe the excess off with the sponge. It should have a thin layer of solder all over it and is now ready for use. The tips on the cheaper irons are sometimes hard to tin for some reason. It sometimes helps to rough them up with some emery cloth first but I've run across cheap chinese tips that will not tin completely no matter how much flux and solder you throw at them. And 60/40 rosin core is perfect for your purpose.

    One thing I've found that speeds up the soldering process is to let the iron get good and hot then just touch it briefly with the solder to put a small drop of molten solder on the tip. Then place the wires in this drop, using it to transfer the heat. If you just place a dry tip on the wire there's not much surface area contacting the wire thus not much heat transfer. The goal is to transfer as much heat as quickly as possible. Quick heat transfer aids in localized heating so you don't end up holding the iron on the wire for 30 seconds heating six inches of wire and messing up your insulation (and causing your shrink wrap to shrink too soon!) . Using this method (very hot iron and drop of solder to transfer heat) it should only take a couple seconds to heat the joint enough to touch the solder to the wire and it will instantly flow. Hope this helps.
    Woo hoo! I think that did it!

    I tinned the tip - most bled off so maybe that's due to being a cheap iron. Then I melted a drop of solder directly to the tip and put it on the underside of my wires. After that, while keeping the iron on the underside of the wires, touching the solder on top FINALLY allowed it to bleed down through the strands.

    Thank you - after several more practice runs, I think I'll feel confident enough to tackle my real project upside down under the VX. I see what you're saying about the shrink wrap, too - wow is that ever sensitive and shrinky!


  6. #21
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    Quote Originally Posted by SlowPro48 View Post
    Haha! TomDude that's beastly - using inorganic acid flux from the plumbing aisle for electronics! I hope you're not in the satellite business! I'm no electronics repair expert so maybe Marlin can confirm or dispel this - but I've heard it's better to stick with rosin or some other organic-based flux (i.e., less acidic) when soldering electrical stuff. Corrosion and circuit boards generally don't mix well...
    True ... but most of my soldering is just connecting some wires together or fixing jewelry or stained glass stuff that broke. Soldering on a circuit card is another matter entirely. It's been so long since I've done any of that, I don't even have a temp controlled soldering iron anymore.
    [SIGPIC][/SIGPIC]

    Put a smiley after you say that Bub.

  7. #22
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    Tom, yeah I've never done enough electronics work to justify one of those variable temp irons - my soldering tool collection is rather sparse too. A 40 year old Sears 25W chisel tip for wires and a 15W/25W conical tip from The Shack for the occasional fried resistor/diode/transistor, etc., some 60/40 rosin core and a roll of Chemwick. The chisel tip works better for wire joints since it has a lot more surface area available and can dump the heat more quickly. Plus it's much easier to balance some molten solder on the flat of a chisel tip than on a cone!

    Rick, you said "finally" but it really shouldn't take very long for the solder to flow after you hit it with a hot, wet iron. Think of the end of the iron as a repository of heat - you let the temp build up and then you have a certain mass at a certain temp and (in the short duration it should take to solder 18ga wire) it's almost irrelevant whether the iron is 25W or 40W - all that matters is the temp differential, the mass of the hot body, and how well the heat can be conducted. You can't do anything about the mass of your tip so to minimize heating time (maximize heat transfer) you work with the other two variables - let the iron get good and hot, i.e., give it enough time to heat up initially and let it recover between joints - this will maximize temp. As for maximizing conduction, you already know about using a dab of molten solder to help transfer heat. There's not much difference in the temp of a 40W iron and a 25W iron it's just that, given the same mass, the 40W iron will recover and be ready to solder the next joint more quickly.

    Now, if you've got a small iron that doesn't store enough heat to solder 18ga wire then you're relying on the output of the element itself and yeah that will take a while. Need a bigger iron if that's the case. But I doubt it. Never seen a 25W iron that wasn't physically big enough to solder 18ga. The bigger the wire, the more heat it sucks up thus the bigger the iron required. Bigger irons have more mass to re-heat so need more power to get back up to temp in a reasonable timeframe and once up to temp they dissipate more heat so need more power to maintain temp.

    Yeah, I know blah blah blah - OK I'm done.

  8. #23
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    By "finally", I meant "I finally learned how to do this after all my previous attempts had failed!" Like you said, the actual process doesn't take very long. Thanks for mentioning that I may need to pause between joints to let the iron recover.

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