Why can’t I solder?

[Nocoolname]

Hi folks, looking for some guidance and advice from those who have experience of succesfully assembling lighting kits. 
 

Despite practicing I just can’t seem to get the hang of soldering, in particular, wires to connecting points such as on battery holders and switches. 
 

I can just about solder wires together and have followed the guidance I’ve been able to find, such as tinning the target parts, but it’s just not working for soldering wires to connection parts and I’m struggling to understand where I am going wrong. 
 

I can struggle a bit with keeping my hands perfectly still and have struggled to create the right jig to support parts while I hold the iron and solder. 
 

I thought I had cracked it earlier, finally finishing up a lighting kit by attaching the connecting wires to the battery holder after several attempts. But as well as being really difficult to lay down the solder didn’t hold and the wires eventually broke off. On a second kit I was working that had a pre-wired battery holder it all unravelled when trying to solder wires to a switch. The solder either beads and falls off or just won’t melt at all. Holding the iron to the target part to heat and the solder to the part does nothing. If I’m lucky I’ll get a few clumps of solder beads that stay together for a while but are not robust. 
 

Am I missing some key kit? Is it just my technique and if so, is there anywhere I can get some good instruction (I’ve tried to follow the few useful videos I could find (and tolerate) on YouTube). 
 

Would really appreciate guidance and advice from anyone with good experience of such matters.

 

Thanks 

 

Nocool

[szeregowy]

Hi @Nocoolname

 

My only experience is with audio/dmx and multipin cables, but I guess you can relate it to lighting kit as well.

Firstly it is important that the soldering station or iron hit the correct temperature, if it's too cold the solder won't melt. Another important thing is to have the right soldering tip for the job. If you are working with small soldering contacts or very thin cables in a restricted space then it may be helpful to have a tip that is suited for that kind of job. Otherwise you will not be able to be precise.

Set of 'helping hands' might come useful if you don't have one. And of course a lot will depend on the size (gauge) and quality of the cables that you're working on, but it is also important to have a decent quality solder.

 

Quote

I thought I had cracked it earlier, finally finishing up a lighting kit by attaching the connecting wires to the battery holder after several attempts. But as well as being really difficult to lay down the solder didn’t hold and the wires eventually broke off.

One of the reasons why the connection failed may be that the soldering contacts were dry. Try tinning the prepped cables and before you solder them to the battery put a little bit of solder on the battery contacts as well. Then hold the cable at the correct connection point, add a bit more solder and this should be enough for a very good hold.

 

 

Quote

On a second kit I was working that had a pre-wired battery holder it all unravelled when trying to solder wires to a switch. The solder either beads and falls off or just won’t melt at all. Holding the iron to the target part to heat and the solder to the part does nothing. If I’m lucky I’ll get a few clumps of solder beads that stay together for a while but are not robust. 

Same thing again. Try to split the soldering into three parts.

1. Prep and tin the cable

2. Add some solder on the battery connection point

3. Hold the prepped cable to the connection point and add a bit more solder (and heat)

Be careful not to heat up too much as you run a risk of melting something (super annoying when soldering small midi connectors)

 

This is just my experience with all sorts of audio cables, but I hope that it make some sense.

 

PS. Practice with some old cables, as soldering is all about muscle memory. The more you do it the easier it gets.

[speedy]

Flux. I can't see if you are using flux, which will encourage the solder to flow in its melted form. Also as mentioned above the quality of the solder. In my old work we went to lead free solder and it didn't go down well. So they returned to leaded solder and the grumbles went away.

 

As mentioned above, practice just like airbrushing. But get some flux..........

[Nocoolname]

Thanks both. I think I was using cheap plain lead free solder that came with my old soldering iron years ago. I’ve been out and picked up a reel of LF with a rosin flux core to try first before reaching for flux paste also. I still have the battery holders that failed to solder along with a ton of switches with connection points so will use these to practice on. I’m also going to see if I can buy pre-wired switches just in case, or at least to get these two builds over the line. I’ve plenty more lighting kits to come so if I don’t apply what I learn to the immediate few I will get the chance with future kits. 

[Andrew Jones]

As has already been said "flux" , I was useless at soldering until I realised you need plenty of flux .  I've also find that you need a small amout of solder on the tip of your iron to help the heat to transfer and ensure a successful bond .

[Nocoolname]

1 hour ago, Andrew Jones said:

As has already been said "flux" , I was useless at soldering until I realised you need plenty of flux .  I've also find that you need a small amout of solder on the tip of your iron to help the heat to transfer and ensure a successful bond .

Thanks. I did get a hang of tinning the tip but everything afterwards went sideways. I take note of ‘flux, flux and more flux’ and will pick up a pack of flux paste in the week. I need a break from this after a long day yesterday that came to nought so I’m off to the beach tomorrow instead and will dive back into this Thursday and Friday with a lot of cleaning of the parts then practice with flux and solder. Cheers for now!

[jenko]

And if you don't  get the hang of it (which you will) just shout out "for flux sake" and turn to the Bakers fluid. 👍

[Casey]

+1 for flux

 

Metals naturally form oxide layer, which prevents molten solder to bind to it it - it feels like if you are trying to stick something to a non stick pan.

 

When you add flux and heat it, it corrodes the metal and then the solder is able to 'flow' and bind with the heated and de-oxidized metal. And you want to keep flux on the metal while soldering since it also acts as a preventive barrier not letting the oxygen to reach it. 

 

Without it, it's an exercise in frustration. With it, it becomes easy.

 

Applies to jewelry making too

Edited July 8 by Casey

[jenko]

Bakers fluid ( commercial name) is zinc chloride. Made by dissolving zinc in hydrochloric acid. Hydrogen is given off.  The residue is zinc chloride.

Edited July 8 by jenko

[jenko]

error

Edited July 8 by jenko

[jenko]

10 minutes ago, Casey said:

 

 

Applies to jewelry making too

Are we talking borax here.

Dick😁

[dnl42]

FWIW, I've only ever used flux for mechanical soldering, like brass to brass in this Beaverette, which also used solid solder.

For electronics wire-to-wire and through-hole components, I've only used rosin-core solder without other flux. If you do use flux, make sure it's for electronics. Plumbing flux or any acid is a huge NO for electronics! To be clear, I've never soldered surface-mount components, which uses a solder paste. I've built quite a number of electronic devices, from kits early on to my own designs for years now. I also prefer leaded solder--I've never been happy working with lead-free.

 

As mentioned, make sure the tip temperature is correct for the solder, the tip is tinned, to-be-soldered areas are clean, and any wires are tinned. For wire-to-wire joints, twisting the wires is a good practice to make sure there's a mechanical bond in addition to the solder. Also, clamp the wires with a 3rd-hand to hold the wires still. For through-hole components, you can also bend the leads so the component is held in place for soldering. Once the solder has flowed, make sure nothing moves until the solder has cooled. Soldered joints should be bright and shiny. Grainy or dull soldered joints indicate a cold joint, which will fail electrically and/or mechanically. 

 

BTW, if you're going to do things with LEDs, a Velleman LED Buddy (amazon.co.uk, amazon.com)  is a useful device--it also provides soldering practice!

 

HTH

-- 

dnl

[szeregowy]

Personally I only use lead free solder and no flux, but that's down to personal preference. Never had any issues with joints whether that is for XLR cable, socapex or bigger multipin systems. Just for the reference the solder that I tend to use is this one https://cpc.farnell.com/duratool/d03342/solder-wire-lead-free-0-7mm-250g/dp/SD02294

 

Do what works for you of course, if you have better experience with flux then use it. But as @dnl42 mentioned, make sure that is flux for electronics.

 

Good luck.

[Nocoolname]

Thanks @szeregowy @speedy @Andrew Jones @jenko @Casey and @dnl42 for the advice. Quick question about flux - is there any specific type I need, any specific ingredient or formula? For instance I’ve found a pot of water soluble, lead free, non acid and zinc chloride free paste at my local Screwfix. Would this suffice? Thanks folks!

[szeregowy]

34 minutes ago, Nocoolname said:

Thanks @szeregowy @speedy @Andrew Jones @jenko @Casey and @dnl42 for the advice. Quick question about flux - is there any specific type I need, any specific ingredient or formula? For instance I’ve found a pot of water soluble, lead free, non acid and zinc chloride free paste at my local Screwfix. Would this suffice? Thanks folks!

Check the description and make sure that it's not for plumbing.

 

I'm not a fan of Amazon, but they seems to have one https://www.amazon.co.uk/Soldering-Electronics-Professional-Appliance-Electrical/dp/B0DXF12QBN?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A3HLEJQ6TPDQBM

[Nocoolname]

59 minutes ago, szeregowy said:

Check the description and make sure that it's not for plumbing.

 

I'm not a fan of Amazon, but they seems to have one https://www.amazon.co.uk/Soldering-Electronics-Professional-Appliance-Electrical/dp/B0DXF12QBN?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A3HLEJQ6TPDQBM

Thanks for that. Yea I’m not a fan of Amazon either but I’ve popped that in the basket just in case. There’s a good old fashioned proper independent hardware store in town that generally cater for every aspect of DIY so I’m going to pop there first and see if they have an equivalent to this. If not, I’ll go the Amazon route. Thanks again!

[szeregowy]

8 minutes ago, Nocoolname said:

Thanks for that. Yea I’m not a fan of Amazon either but I’ve popped that in the basket just in case. There’s a good old fashioned proper independent hardware store in town that generally cater for every aspect of DIY so I’m going to pop there first and see if they have an equivalent to this. If not, I’ll go the Amazon route. Thanks again!

That's a very good way of supporting your local shop.

Soldering is like making models, at the beginning you will make a mess, but with time you will get better... in not getting your hands or fingers burned 😉 Enjoy!

[Nocoolname]

25 minutes ago, szeregowy said:

That's a very good way of supporting your local shop.

Soldering is like making models, at the beginning you will make a mess, but with time you will get better... in not getting your hands or fingers burned 😉 Enjoy!

Like model making it’s ’re-learning’ after a gap that’s a real pain. I did actually manage to do some good soldering about 7 years ago, unfortunately the part I used to solder was unsuitable, but the bond itself was good. I somehow lost the knowledge and the knack, like other aspects of model making. I really hate getting old and addled. 😡

[szeregowy]

12 minutes ago, Nocoolname said:

I did actually manage to do some good soldering about 7 years ago, unfortunately the part I used to solder was unsuitable, but the bond itself was good. I somehow lost the knowledge and the knack, like other aspects of model making.

Skills will come back sooner than you think. 👍

[Nocoolname]

Quick update on the soldering front…

 

I bought the flux paste as suggested above along with solder with a rosin core. I also had to get a new iron, the basics one I bought was garbage that simply stopped working. I followed a lot of videos about how to solder with flux, from cleaning and tinning the tip to the right way to solder wires to connectors. 
 

Took a fair bit of trial and error, including with the amount of flux paste to use. The outcome is a case of good news and bad news. The good news is that my soldering improved significantly following the advice above. The soldered connections I made were robust and stable and there was a real visible difference in the quality. The bad news is actually down to the quality of the battery holder I was trying to solder the wires to. It’s a cylindrical holder for 3xAAA, specifically chosen so it could fit inside the model. Unfortunately the plastic had a tendency to melt where the metal connectors were attached causing them to ping off, this was despite my only touching the metal momentarily. 
 

So, the soldering I’m starting to get a hang of and I’m going to follow up by finishing the wiring on my BOP kit tomorrow. But for my other model I now have to try and find better quality cylindrical battery holders where the plastic doesn’t melt as easily. I’ll try and share pictures when I get the chance but thanks for all of your advice and support so far. 
 

Cheers

 

Nocool

[szeregowy]

3 hours ago, Nocoolname said:

Quick update on the soldering front…

 

I bought the flux paste as suggested above along with solder with a rosin core. I also had to get a new iron, the basics one I bought was garbage that simply stopped working. I followed a lot of videos about how to solder with flux, from cleaning and tinning the tip to the right way to solder wires to connectors. 
 

Took a fair bit of trial and error, including with the amount of flux paste to use. The outcome is a case of good news and bad news. The good news is that my soldering improved significantly following the advice above. The soldered connections I made were robust and stable and there was a real visible difference in the quality. The bad news is actually down to the quality of the battery holder I was trying to solder the wires to. It’s a cylindrical holder for 3xAAA, specifically chosen so it could fit inside the model. Unfortunately the plastic had a tendency to melt where the metal connectors were attached causing them to ping off, this was despite my only touching the metal momentarily. 
 

So, the soldering I’m starting to get a hang of and I’m going to follow up by finishing the wiring on my BOP kit tomorrow. But for my other model I now have to try and find better quality cylindrical battery holders where the plastic doesn’t melt as easily. I’ll try and share pictures when I get the chance but thanks for all of your advice and support so far. 
 

Cheers

 

Nocool

Very positive update then. The issue with the battery holder is not because of your soldering technique. It's more down to the overall quality of the battery holder.

 

[jenko]

6 hours ago, Nocoolname said:

Quick update on the soldering front…

 

I bought the flux paste as suggested above along with solder with a rosin core. I also had to get a new iron, the basics one I bought was garbage that simply stopped working. I followed a lot of videos about how to solder with flux, from cleaning and tinning the tip to the right way to solder wires to connectors. 
 

Took a fair bit of trial and error, including with the amount of flux paste to use. The outcome is a case of good news and bad news. The good news is that my soldering improved significantly following the advice above. The soldered connections I made were robust and stable and there was a real visible difference in the quality. The bad news is actually down to the quality of the battery holder I was trying to solder the wires to. It’s a cylindrical holder for 3xAAA, specifically chosen so it could fit inside the model. Unfortunately the plastic had a tendency to melt where the metal connectors were attached causing them to ping off, this was despite my only touching the metal momentarily. 
 

So, the soldering I’m starting to get a hang of and I’m going to follow up by finishing the wiring on my BOP kit tomorrow. But for my other model I now have to try and find better quality cylindrical battery holders where the plastic doesn’t melt as easily. I’ll try and share pictures when I get the chance but thanks for all of your advice and support so far. 
 

Cheers

 

Nocool

 

Have a look at the firms that supply the model railway people. Plenty of good cheap firms out there selling quality gear.

 

Dick

[Nocoolname]

On 7/17/2025 at 10:38 PM, jenko said:

 

Have a look at the firms that supply the model railway people. Plenty of good cheap firms out there selling quality gear.

 

Dick

Thanks for the tips. I did just as you suggested and found an alternative 3xAAA battery holder that is a little bit larger but should hopefully still fit with some jiggery pokery. And crucially this one is pre-wired so if it works on a successful test the only thing I have to solder will be the connecting wires.