How to solder

I’m currently working on a project that involves soldering these +12V and GND wires (on the right) to this DC barrel plug (on the left), and I’m rather new to soldering. I’ve only previously soldered on two occasions and they’ve both come out quite trash looking.
I only have this cheap soldering kit, as shown below, and a tub of flux I haven’t touched. I also notice every time I’m done soldering, the iron tip is dirty and covered in solder and other crap, so I sand it down to clean it.

I’m looking for proper advice on what I should actually be doing in order to solder and clean the iron correctly.

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A flux pen, or gel syringe is a good way to get accurate flux where you need it.

For the cleaning, a wet sponge while the iron is hot is the easiest, just drag the tip across relatively quickly and it will do a lot to clean it. Another option that is quite nice and maintence free compared to keeping a sponge wet is a ball of brass wool, just stab it with the soldering iron and in generally scrape the tip clean, again while hot.

Despite the gnashing teeth and wailing, lead solder is far better than lead free for DIY stuff. It is just easier to work with, flows better, leaves better joints.

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As a general rule, is it better to heat the target and apply the solder to it? (like heating the pad of the PCB, or the wires to be soldered)

Rather than using the tip as a trowel and heating the solder to the tip, then scraping it on to a cold target like glue?

I’ve heard of solder wire with flux inside.
Does it run through the centre like a reversed with (opposite of plastic outside, metal inside)
Or is the flux distributed evenly along/inside the solder?

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Oh yeah flux core solder, I never even considered there was solid for small scale home gamers. Yeah flux core is pretty much all we get here. Definitely recommended, though get a flux for the parts to be soldered too as well.

And yes, heat the parts to be soldered with the iron and flow the solder on to them rather than the tip if possible.

Also clean and then wet the tip of the iron with fresh solder before starting.

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Well, I’ll wait a few weeks for those items to be delivered in: flux pen, brass wool, crimping tool, solder sponges and flux core solder. Cheers Guys

If you are getting the brass wool you probably don’t need the sponges, but they are probably not much extra just in case they are separate orders, saves the shipping another thing.

nah its fine, they’re both like £2, it’s ebay anyway so it’s all free shipping

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A cheap soldering iron is totally fine for what you’re trying to do here.
That tub of flux should remain untouched because
A: You normally don’t need any additional flux (electronics solder contains plenty of flux already).
And B: That stuff is hot garbage. It usually contains quite a lot of acid which will corrode your solder joints over time. The only thing it’s good for is cleaning your tip, but ONLY if everything else fails.

That’s normal. It’s just flux residues that burn on the tip, but you should clean your tip every time you take the soldering iron out of the stand.

NEVER sand your soldering tips! They have a thin metal coating that prevents the solder from dissolving the copper core. Once that coating is gone, the tip will start dissolving and/or oxidizing and get destroyed pretty quickly.

In order to clean the tip, just wet the sponge included with your soldering kit with some water (it should only be damp, not dripping wet) and wipe the tip accross it.

Here’s a step by step guide on soldering:

  1. Clean your tip.
  2. Add a little fresh solder to the tip to assist the heat transfer. Don’t add a big blob and try and “smear” it onto the solder joint.
  3. Put the tip to the joint and give it a second to heat up.
  4. Add some solder (not too much, you don’t want big blobs) and give it a couple of seconds to flow over the whole joint.
  5. Remove the tip and let it cool.

Since you’re trying to solder wires to a jack, you could either put the wires through the holes in the contacts and solder them in one go or coat the wires and contacts first and then melt the solder on the contacts and add the wire. It mostly comes down to preference.

Now for some general tips and tricks:

  • Work quickly, the longer you heat your joints, the worse they will look (wire insulation melting, etc.). As a rule of thumb 5 - 10 seconds is the maximum amount of time you should take.
  • Always clean your tip and add a little fresh solder before using it. A clean tip melts your solder a lot quicker.
  • Keep a bit of solder on the tip before you put the iron back in the stand to prevent tip oxidation.
  • Practice on some wire scraps until you get the hang of it.

You already have everything you need. You don’t need a flux pen unless you’re working with SMD components, there is a sponge on your soldering stand waiting to be used, it just needs some cleaning, and you already have flux core solder, so there’s nothing stopping you.

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Cheers. I’ve already sanded my soldering tip quite heavily so… LOL :sweat_smile:

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If it develops some cavities, you now know why.

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as you got a bunch of stuff, I would say have a go and just practice on random stuff you might be able to solder?

And as you have a solder-removing thing, maybe try un soldering them and re-soldering?

#WhatCouldGoWrong?

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Basic solder guide:

  1. Piece of scrap wood or dense cardboard to protect your table from dripping flux or solder. This also works nicely as a “keep out zone” so you don’t bump into things with the soldering iron.

  2. Clean Tip = Good Tip, don’t use the soldering tip to shrink heatshrink!

  3. Heat the parts, then add the solder to them.

  4. Flux is your friend. The puff of smoke you get when heating solder is what makes the solder flow in place.
    A Fluxpen (when working with electronics, a “no-clean”-flux is preferable) can help with tricky/dirty joints.


When working with Litz, tin the wire first. Makes your job way easier.

As the connector is also quite chunky, hold it with pliers or a third hand, it will get quite toasty! I would also start with the big section (1) and then do the small contact (2).


It may help to pre-tin the contact surfaces before soldering the cable to it.

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Solder one (1) short wire to each of the joints: black and yellow, then solder the rest of the wires to that short section. With your skill level, soldering that much thick wire into a small space is asking for trouble. Lots of trouble, as these wires are for 12V PSU power and they can handle a lot of Amps. If you wanna know what it can do when you get it wrong, look up the NZXT Riser cable saga on the Gamers Nexus YT channel.

yeah. hahaha, I’ve figured out the pinout for these wiring connections anyway so that shouldn’t be a problem. You’re right about the wires being chonky for the plug connector. I’m thinking I just buy a terminal connector and then solder those two up to that and then solder it on to the barell plug connector. Or I just rip out most of the ATX wires and yeet it with only one +12V and one GND. That just seems stupid to me.

Also if I replace my soldering iron tip with one that has a smaller shaft diameter, would that still work? (it’s not working like it used to, prob cos I sanded it down, the solder gathers up in a sticky ball, rather than spreading like an inviscid liquid)

The plan for this project btw is to assemble a 300W PicoPSU setup that connects to a HP common slot server PSU, and so I can have the EPS, PCIe and PicoPSU power connectors all coming off the HP server PSU, with the Pico powering just the motherboard.
And you may ask why? FOR FUN :grin:

You should try and find one with the right diameter, otherwise the thermal resistance will greatly increase.
Since you’re already buying a new tip, I would go for a chisel shaped one (~4 mm wide). Those pencil tips included with most soldering irons are completely useless in my opinion.

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Should I be using a third hand? I know it’s been suggested, I’m trying to hold the two pieces together with my hands whilst keeping the iron stationary on my table. Keeps shifting around too much.

No, those are fine. For SMD work :wink:

@amarvir02 don’t bother with crimp/terminal connectors, better do it right and use the method I described. For a short section (5cm/2") it doesn’t matter too much it’s a single wire, especially if it’s a few sizes up from the wire you’re soldering it on.

I’ve done quite a lot of SMD work (including fine pitch packages) and I always use chisel tips (very small ones, but still chisel shaped). I just don’t like pecil tips.

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Certainly helps. Otherwise you might run out of hands and/or burn yourself.
In a pinch, some heavy pliers can also work to keep your parts in place.

Just in case it wasn’t mentioned.

There is never enough Flux. Flux is your friend. Flux is love.

The main Things Flux helps you with is with lowering melting temperature a bit.
The solders surface-tension, flow behavior and it slows oxidation.

If you put solder on the tip, you will first see it melting and smokeing.
Possibly some bubly liquid brownish substance running around and the solder will be shiny.

The longer you leave it on the tip, looking at it, the less shiny it becomes, the less smoke and bubles come of off it, until it is crusty, dark and utterly fucked. That solder, is not nice to work with anymore.
That would be a time to clean the tip and use new solder.

The bubles and brown liquid are Flux that is usually contained in most solder* for the common use-case. There is solder without flux, don’t use that.

Another thing to observe is that solder can become sticky and spicky, following the Tip of the iron around and leave spikes on solderjoints.

That is also an observable indicator of not enough Flux.
More heat makes Flux go away faster, so either you took way to long doing the joint, or you are way too hot on the iron.
EIDT: Not enough flux anyhow. Hence, use more flux!

Don’t breathe Flux fumes in. Not really healthy.

Good luck and much success

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