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

[RickOKC]

I wanna solder /connect two 18ga wires together but apparently I'm missing something important. I've watched videos & read instructions so I have learned to:

* hold the soldering iron against the bottom the wires
* let it heat 'em up
* hold the solder on top of the wires and let it melt down through.

My "practice" result: Nuthin'. :mad:

I'm using thin (fine) 60/40 rosin core flux. Is the cheap, $15, 25w/750 deg soldering iron just a "hello kitty piece of junk"? Do I need to upgrade to something stouter? :_confused

[bigblock8396375]

If it's melting the solder,you might be having a contamination problem. Try paste flux on the wire.Hope this helps.

[pbkid]

yup, either paste flux, or dirty wires.

try to wire brush the copper wires.

i assume you are referencing multi-strand wiring when you say 18ga? not solid core?

[Grif]

If the solder just rolls off the wires, then they arent getting hot enough. Yes, they need to be really hot. Sounds like you might need a hotter iron. The iron will melt the solder WAY quicker than the wires will heat up enough for the solder to stick.

My technique is to heat the hell out of the wires first then touch the solder only to the wires, not the iron. If the solder melts by only touching the wires, then it most likley will stick. But that sounds like what yer doing.

Contamination may be an issue, but usually the solder itself has enuff flux to do the job. When in doubt, cut back more wire, strip again, and rough up the surface by scraping the bare ends with a knife, it may help. I've also had some pretty crappy solder at times too, so that may be at play here.

[RickOKC]

Thanks for the replies/help!!! In no particular order...

Yes, I'm trying to solder multi-strand wire, not solid. So far I have been unable to get the solder to melt at all unless I touch the wire directly to the iron. I'm trying to use the method where I make the heat from the wire melt the solder and not touch the iron directly.

I've been practicing before I go on to my real project so I'm using brand new wire with freshly stripped insulation. It's shiny & new - so does that rule out contamination?

Does this all point back to having a wienie iron that just isn't hot enough? Should I get something heartier or just bail out and use a paste flux? How would I know if I bought a crappy solder (374 deg F melting point)?

[VX KAT]

Is the cheap, $15, 25w/750 deg soldering iron just a "hello kitty piece of junk"? Do I need to upgrade to something stouter? :_confused
hmm, I've got the Hello Kitty edition of the iron and I've had no problems at all...:_confused....and really like the pink handle, don't you?

[Grif]

IMHO, yes your iron is not hot enough to heat the wires. The wires are dissipating the heat faster than the iron can keep up. You can try separating the strands of the cable to give them less mass so they will heat up easier, but then you end up soldering a few strands at a time then using a mass of solder to "glue" the solder joints together. I've used that in a pinch, but its not a good idea, more time consuming, and more likely to fail over time.

Just get a decent iron. In a pinch a butane micro torch will also give you plenty more heat but harder to control.

I dont think flux is gonna help much. Better solder may be a good idea.

[Triathlete]

Or you can get some solder splices.:yesy:

[Grif]

Or crimp connectors.

http://rsk.imageg.net/graphics/product_images/pRS1C-2266050w345.jpg

[Hiredgoon]

Oh how I hate crimp connectors.

18AWG is not particularly robust wire, you should have no problem heating it enough for this to work with pretty much any cheap-o soldering iron.

It's possible that the wires are contaminated, but dipping them in flux won't have much more effect than the 60/40 you're using, which already has a rosin flux core.

I tend to only use flux when soldering copper pipe, as it really is useful when soldering with a torch. In my experience a torch--even the little creme-brulee making ones--are a little too hard to control and I just wind up melting the insulation and burning my fingers.

I use a solid-core silver solder myself for all the electrics that I am working with, and I've noticed that it adheres a little better. I find the flux core is prone to sort of envelop the little bead of solder and make it want to slide off of my work; that could be what's happening.

As well, as you're new to this, don't forget to slip the shrink wrap sleeve over one of the ends of wire BEFORE you do your soldering, or you'll be doing it all over again. It's the most common mistake I see when I'm teaching new students.

[Grif]

Oh how I hate crimp connectors.

18AWG is not particularly robust wire, you should have no problem heating it enough for this to work with pretty much any cheap-o soldering iron.

It's possible that the wires are contaminated, but dipping them in flux won't have much more effect than the 60/40 you're using, which already has a rosin flux core.

I tend to only use flux when soldering copper pipe, as it really is useful when soldering with a torch. In my experience a torch--even the little creme-brulee making ones--are a little too hard to control and I just wind up melting the insulation and burning my fingers.

I use a solid-core silver solder myself for all the electrics that I am working with, and I've noticed that it adheres a little better. I find the flux core is prone to sort of envelop the little bead of solder and make it want to slide off of my work; that could be what's happening.

As well, as you're new to this, don't forget to slip the shrink wrap sleeve over one of the ends of wire BEFORE you do your soldering, or you'll be doing it all over again. It's the most common mistake I see when I'm teaching new students.

Agreed on all points.

I've been lucky enough to inherit some old school lead solder from my father (RIP). That stuff works the treat.

[SlowPro48]

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.

[tom4bren]

One last point - What is the quality of the wire?

Good copper wire is easy to solder. Cheap wire can have a lot of other metals (especially aluminum) that can really dork up your soldering efforts. I recently tried to solder some cheapo jumper cable wires together & actually burned the wire before the solder could adhere.

I don't agree that a butane torch is hard to control when soldering. Unless I'm working in a really tight area, I actually prefer to use one. When in tight areas though, I have a nice butane soldering iron that works really well.

If the wire you are using is a good quality copper, then the solder and flux you can get from the plumbing department at Lowes/Home Depot works quite well. I've always had better luck with flux paste rather than relying on the 'stuff' they have in the core of the solder.

[samneil2000]

I like to put the iron beneath the wires and then introduce the solder from above. Might need another set of hands if the wire isn't fixed though.

[RickOKC]

Hmmm, I have no idea if I've been practicing with low quality wire.

Thanks again for all the tips. I'm going to try again tonight.

[eblank]

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.

[Marlin]

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.

[SlowPro48]

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...

[Marlin]

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

[RickOKC]

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! :laughy:

[tom4bren]

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.

[SlowPro48]

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.

[RickOKC]

:) 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.