soldering iron

Use lead/tin solder. Lead free is the spawn of the devil :)

The other problems that you may be having

i) The (large) size of the tracks on the PCB are acting as a heatsink and taking away the heat faster than you are applying it with the iron, especially if you are using a low power soldering iron.

ii) The wire you are trying to solder is oxidised and the solder will not stick to it unless you clean off the oxidisation layer.

iii) You haven't "tinned" the wire. Apply solder to the wire before trying to solder it to the PCB.

iv) You are not using flux. Electrical solder often has a (rosin) flux inbuilt. Plumbing solder does not have flux (you apply flux to the pipes separately) . You can buy flux suited for electronic soldering.

There are a number of reasons you may have problems soldering and a few more details about what is happening will help.

To get you started I would suggest the following;

For PCB work generally a 18 - 25Watt iron is more than adequate. Use Lead/tin solder, lead free is only required for commercial work, lead/tin solder is still widely available. Use Rosin cored solder this contains the necessary flux to keep soldered area clean by preventing oxidisation. Flux can be applied separately but use appropriate flux for electrical work, do not use any acid based fluxes such as used in plumbing.

For soldering a through wire component to a PCB the technique is fairly straightforward. Insert the wire into the PCB paint on flux if the solder does not already contain flux. Apply the tip of the soldering iron to the joint for a count of 1-2-3 then apply the solder whilst keeping the iron steady in place. The solder should melt and form around the joint. Remove the solder then the iron, the resulting joint should be shiny and appear like a little volcano around the wire. A dull or blob like appearance is what is called a dry joint and is not soldered.

Some things that may be causing problems;

Is the tip of the soldering iron clean or is it oxidised? When heated the tip should have a shiny layer of solder on it known as “tinning”. If not then it needs to be cleaned and re-tinned as it will never solder in a month of Sundays. What ever you do do not use any abrasives like files, emery cloth or sand paper on the tip, modern irons have tips made of copper and coated in an iron carbide layer if you abrade through that layer the tip will soon get pitted and become useless. If the oxidisation is fairly light dipping it hot into tip cleaner and quickly applying solder repeating the process several times will re-tin the tip. If you feel the tip needs more mechanical cleaning then a small brass wire brush can be used but under no circumstances use a steel wire brush.

Once you have a clean tinned tip the next task is keeping it in that condition. Most soldering stands come with a small replaceable sponge which should be wet when in use. Get into the habit of every time you lift the iron to wipe the tip on the sponge and observe that it leaves a shiny tinned tip. If not then repeat the tinning process. Normal soldering should replenish the tinning but if the iron is left on for long periods and not being used the tinning can oxidise.

As already mentioned in the technique holding the iron steady on the work is essential the iron is simply a source of heat and in order for the solder to take to the joint the materials being heated need to attain the melting point of the solder moving the iron about breaks this transfer of heat. Depending on the material thickness you might require a higher wattage iron. Higher wattage does not equate to a hotter iron it just means the iron has a greater ability to replenish the heat sinking into the materials being soldered.

The components being soldered should be clean and any oxidisation is removed mechanically before soldering, be careful with PCBs as the tracks are quite thin and easily abraded away.

If you can give more details of what is happening then more specific advice can be given.

What metal(s) are the wires made of? Have you been able to tin these wires?

Has the PCB been lacquered? Have you been able to tin the PCB?

Unless your soldering iron is temperature-regulated, pondering if it gets hot enough is not a good use of your time!

I've used the same Weller WP60 - a 60W regulated iron - for 50+ years; from thermionic valve sockets to 40 pins per inch surface mount.

Always with multicore tin/lead solder.

PA

Am 15/03/2024 um 16:30 schrieb alan_m:

It's not legal to buy. Where would you find it? I have never since 2000 ish.

In message <ut3rvm$2rhsk$ snipped-for-privacy@dont-email.me, Ottavio Caruso snipped-for-privacy@yahoo.com writes

Have you tried Googling? It certainly doesn't seem to be illegal per se, although some of its uses are.

Still readily available

eg.

It's available just about everywhere, I recently bought some on Amazon UK.

well, CPC sell it.

leaded solder has always remained legal for critical components, repairs, and D-i-Y and hobby use. Its not especially legal for plumbing, but compared with the lead free s*it, it does at least work...

60/40 solder

It is 100% legal to buy. The use of lead/tin solder was only banned for new production, but specifically excluded from the ban for repair of existing equipment and some critical uses (such as aircraft, where lead-free solder is consider too unreliable). It is also not banned for purely mechanical purposes, only for electrical/electronic items.

Here's one selection:

It is an old 30W Hilka with a gradually tapering wedge shaped tip.

It is flux cored but I have not got lead-tin yet.

The tip is tinned

Interesting, I inherited the iron from my dad and did clean it with wet and dry paper before tinning it.

Again I did not realise this and have never used a wet sponge.. I have a new soldering stand with crocodile clip arms and a lit magnifying glass, it does have a sponge so I will use it.

I was managing to melt the solder onto the wire poking through the board but it did not adhere well to the pcb track. Adding solder made the blob large enough to bridge tracks.

I'm not new to soldering but had not used this lead free solder before, plus my sight is somewhat impaired since I last did it years ago.

Well you seem to be doing most things right and if solder is taking to the wire but not the track on the PCB then that suggests to me that the track is either oxidised or as sometimes happens a lacquer has been applied to protect the PCB from possible moisture. Either way you will need to clean the track to expose bright copper but be very careful as the copper track is very thin and over abrasion will destroy it, a fibre glass pen is probably the gentler way to do it. Rosin flux is not an aggressive flux so will not clean surfaces it works by suspending forming oxides within the liquid.