Troubleshooting Soldering: My Experience with a 25W Iron

[Wrichik Basu]

I have a 25W soldering iron. I am trying to learn this art from Youtube. From the videos, it seems that soldering is not much difficult. But in practice, it just doesn't work out for me.

For example, consider this video among a few thousands on this topic. You can see how easily the solder sticks to the twisted wires once the iron is touched. But in my case, the solder just doesn't stick! Sometimes, even the other end of the wire gets hot, but the solder won't stick. I have tried with wires of different thicknesses (from single wires to thick ones meant for carrying 18A, all copper), using solder wires with and without lead from different companies, and even used the flux paste (which is advertised to give a smooth and uniform solder), but with no success.

Solder, however, melts if I directly touch it to the soldering bit. But not on any wire.

I have tried cleaning the bit on a sponge, and then on steel wires to remove any residual solder. But with no effect.

Should I buy a higher power soldering iron? Something like https://www.amazon.com/dp/B07HM1DMLN/?tag=pfamazon01-20 or maybe https://www.amazon.com/dp/B07HM34RFZ/?tag=pfamazon01-20? Or is it something else that I am missing?

 

[Rive]

I have a 25W soldering iron.

That's OK for some small SMD work, but that's all. For general DIY electronics soldering buy a 75W or similar, what can maintain a stable temperature around 340-360 C degree (being able to set the required temperature and changing the tip according to the job is an extra).
Check if your solder is a classic Pb containing version with rosin inside.

Ps.: about the linked soldering irons: none of those are recommended (well, they are OK for wires at most...) We prefer to keep the line voltage further away from the electronics and our hands... Spend a bit more and buy a soldering station which supports changeable tips and temperature adjustment.
Check if spare tips are really available: some cheap stations from unknown manufacturers are so clearly just 'one-shot' types, that unlikely to have spare components even just a few years later.

Ps2.: you might consider buying a second hand Weller. They are around for some decades already and they will be available for some more for sure...

 

[NascentOxygen]

The solder wire needs to have a rosin core, you can confirm this by the presence of smoke when you melt a new length of solder. The copper wire needs to show bare clean copper without an oxide layer, you can ensure this on your practice wire by first scraping the copper wire with very fine sandpaper. Soldering is a process involving the formation of an alloy between lead and copper, and you need to complete this while there is still smoke coming off the joint. Absence of smoke means the flux has all evaporated and the molten lead will be forming lead oxide which is a grainy contaminant spoiling the integrity of the solder joint, both electrically and mechanically.

Solder is not hot glue, you can't carry a molten blob around on the end of the soldering iron expecting to dab it wherever you'd like it to stick—it won't. I use a 25W iron, it's perfect for electronics projects.

 

[Borek]

and even used the flux paste

Flux is a must, without it your chances of soldering copper are pretty slim.

 

[Wrichik Basu]

Ps.: about the linked soldering irons: none of those are recommended (well, they are OK for wires at most...) We prefer to keep the line voltage further away from the electronics and our hands... Spend a bit more and buy a soldering station which supports changeable tips and temperature adjustment.
Check if spare tips are really available: some cheap stations from unknown manufacturers are so clearly just 'one-shot' types, that unlikely to have spare components even just a few years later.

Soldering stations are costly as per Amazon. The one I can afford at this moment is this one. It is not a famous brand, but maybe later I will be able to buy a better one. The ones that I linked are by a company which is well-known in my country. There are spare bits available, like this one.

The solder wire needs to have a rosin core, you can confirm this by the presence of smoke when you melt a new length of solder.

Yes, the ones I have used till now have a rosin core.

The copper wire needs to have bare clean copper without an oxide layer, you can ensure this on your practice wire by first scraping the copper wire with very fine sandpaper.

Will look into that.

Solder is not hot glue, you can't carry a molten blob around on the end of the soldering iron expecting to dab it wherever you'd like it to stick—it won't.

I have never done that. I have touched the iron to the wire, the wire has been heated up, and then I touched the solder to the wire so that it will melt and spread evenly. But the last thing has never happened.

 

[Wrichik Basu]

Flux is a must, without it your chances of soldering copper are pretty slim.

One small question - how do you correctly apply the flux? I take a brush and apply the flux on the wire joints first before touching the soldering iron. Is that the correct way?

 

[Tom.G]

25W should be adequate for finer wires, say 22AWG (0.6mm). When a problem occurs, either the wire is not hot enough or it is oxidized (tarnished).

An oxidized tip prevents heat transfer to the wire.

If solder melts when applied to the wire but does not stick, then the wire is oxidized and needs cleaning. This can also occur if flux is not used. The flux dissolves the oxidation and allows contact between the wire and solder.

• The wire should be shiny, not tarnished.
• Wipe the tip on a damp sponge to remove oxidation that occurs when exposed to the air.
• Apply a SMALL amount of molten solder on it.
  • The tip should have a thin coating of shiny solder on it, if not, apply some flux and solder. This is called 'tinning' the tip. Repeat the two steps above and this one until the tip is shiny.
  • Again wipe the tip on a damp sponge and apply a SMALL amount of molten solder on it.
• There must be some flux on the wire, or at least on the solder on the iron tip.
• Apply the tip to the wire where the small amount of solder is. Be sure the tip is contacting the wire to get the wire hot.
• Often some slight scrubbing motion of the tip on the wire is needed to get thru any oxidation on the wire.
• When the wire shows signs of accepting the solder, apply more solder as needed to the wire next to where it contacts the tip. Do NOT apply the additional solder directly to the tip and expect it to transfer to the wire, it won't.

Remove the tip from the joint but do not move or disturb the joint until the solder solidifies. This is needed because as the solder cools, it cools to slightly below its melting temperature before actually solidifying. If it is disturbed at this super-cooled stage it will flash-freeze to a granular consistency that is mechanically very weak. Upon solidifying the solder should have a smooth, shiny surface.

Hope this helps.

Cheers,
Tom

 

[Wrichik Basu]

If solder melts when applied to the wire but does not stick

No, it just doesn't melt. It melts if I touch it to the bit directly. But not when I touch it to the wire, even if I wait sufficiently long for the wire to get hot. This happens even if there is flux.

 

[Rive]

Soldering stations are costly as per Amazon. The one I can afford at this moment is this one.

I would rather try a second hand Weller then.

Te ones that I linked

For wires they might be OK, but for electronics - just no. What would you use it for?

No, it just doesn't melt. It melts if I touch it to the bit directly. But not when I touch it to the wire, even if I wait sufficiently long for the wire to get hot. This happens even if there is flux.

Insufficient temperature or power.

 

[Wrichik Basu]

I would rather try a second hand Weller then.

I don't have a source for buying second hand things. Ebay India is closed. Amazon is not selling used Weller. The minimum price of a new one is INR 10,000, which is just not possible.

For wires they might be OK, but for electronics - just no. What would you use it for?

First use will be wires. The next will be to solder components on a general purpose PCB, like https://www.amazon.com/gp/product/B07J4549V7/?tag=pfamazon01-20.

 

[dlgoff]

It melts if I touch it to the bit directly. But not when I touch it to the wire, ...

First, flux the wire well, then the iron's tip (I stick the iron's tip directly into flux container). Now put the iron's tip on the wire and immediately run the solder into the wire and tip simultaneously. 25 watts is what I use.

 

[Rive]

I don't have a source for buying second hand things. Ebay India is closed.

Difficult. I can only say what I would buy and why: this one is an absolute cheapo (so you can save some funds for something decent), but should be able to do the job - at least for a few years, I think. The others you found are the same class, but has long metal fronts what makes them a bit more difficult to use for smaller work. It also comes with spare and variation of tips.

You should understand that none of these (!) soldering irons can be recommended for any sensitive work in electronics. It is better to keep the line voltage further away from the tip/your hand and the temperature in sensitive check - so on long term I still suggest to keep your eyes open for soldering stations.

By the way, the guy on the video is using a 40W station - but at maximal temperature if I see it correctly. For that type it should be ~ 450 degree C or above. That's just cruel.

 

[Wrichik Basu]

You should understand that none of these (!) soldering irons can be recommended for any sensitive work in electronics. It is better to keep the line voltage further away from the tip/your hand and the temperature in sensitive check - so on long term I still suggest to keep your eyes open for soldering stations.

Yes, I absolutely understand that. Thanks for the advise, I will surely keep those points in mind.

 

[Tom.G]

No, it just doesn't melt. It melts if I touch it to the bit directly. But not when I touch it to the wire, even if I wait sufficiently long for the wire to get hot. This happens even if there is flux.

• The tip should have a thin coating of shiny solder on it, if not, apply some flux and solder. This is called 'tinning' the tip. Repeat the two steps above and this one until the tip is shiny.

Does the tip have a shiny coat of solder, or is the tip grey or black? If it is grey or black that is oxidation and there will be little heat transfer to the wire.

Cheers,
Tom

EDIT:
Can you post a photo of the tip?

 

[Wrichik Basu]

Can you post a photo of the tip?

I won't boast that these are good pictures, but should help you identify whether the tip is shiny or not.

 

[Tom.G]

OK, the first photo shows a shiny tip. The second photo looks like not shiny.

I think your best bet is to find someone locally that can spend a half hour giving you hands-on experience.

Or if you can get to Southern California, USA, I would be glad to help! But it would be cheaper if you can find a local repair shop that is willing for a nominal fee.

Cheers,
Tom

 

[Tom.G]

After sleeping on the problem, another possibility is that the solder you have is not compatibile with the wires you are using. "Solder" has a somewhat generic definition of "...a metal or metallic alloy used when melted to join metallic surfaces...". You may have something other than the usual Tin-Lead (Sn-Pb) solder normally used in electrical work.

Of course a similar situation could apply to the flux.

If/when you find someone to assist you in person, be sure to have available your Iron, Solder, Flux, and some of the wire you are having trouble with. It could be more than one problem.

Please keep us updated as to your progress, we too would like to know the answer!

Cheers,
Tom

 

[Wrichik Basu]

After sleeping on the problem, another possibility is that the solder you have is not compatibile with the wires you are using. "Solder" has a somewhat generic definition of "...a metal or metallic alloy used when melted to join metallic surfaces...". You may have something other than the usual Tin-Lead (Sn-Pb) solder normally used in electrical work.

Some months back, a person came to our house for servicing the stabilizer to our air conditioner. His solder and flux paste were nearly over, so I gave him what I had, and he could complete the work properly. (The work included soldering wires to a PCB) I also know that he was using a 25W soldering iron, similar to what I have. And the wires were quite thick, rated 20A.

I think your best bet is to find someone locally that can spend a half hour giving you hands-on experience.

That would have been the best thing, but I have been trying to find such a person for nearly the past four years, without any luck. All the shops who service appliances like mixer grinder and televisions have people who use soldering almost everyday, but their workshops are located too far away for me to actually pay a visit. Some others are reluctant to allow me to enter their workshops (maybe they are scared that I will get to know that they use low quality spare parts while they take the price of branded ones).

Please keep us updated as to your progress, we too would like to know the answer!

Sure, I will let you know what happens. And thanks for helping out this far.

 

[Stephen Tashi]

No, it just doesn't melt. It melts if I touch it to the bit directly. But not when I touch it to the wire, even if I wait sufficiently long for the wire to get hot. This happens even if there is flux.

You can try keeping the tip of the soldering iron on the wire and applying the the solder so it touches both the tip of the iron and the wire. As the solder melts, it will help in transferring heat from the iron to the wire. Keep the tip of the iron on the wire until the solder flows over the wire. If you remove the iron too soon, you will get a "blob" of solder instead of a coating of solder.

It helps to press the tip of the soldering iron firmly against the wire. This transfers heat to the wire better.

 

[Wrichik Basu]

You can try keeping the tip of the soldering iron on the wire and applying the the solder so it touches both the tip of the iron and the wire. As the solder melts, it will help in transferring heat from the iron to the wire. Keep the tip of the iron on the wire until the solder flows over the wire. If you remove the iron too soon, you will get a "blob" of solder instead of a coating of solder.

It helps to press the tip of the soldering iron firmly against the wire. This transfers heat to the wire better.

Will try that and let you know whether it works. Thanks for the advice.

 

[davenn]

Will try that and let you know whether it works. Thanks for the advice.

OK something obvious that no one else has mentioned

Are you absolutely sure that it is bare copper wire ?
That is, I am wondering if it is enamelled wire, which would be hell to try
solder to ? There are some enamels that will burn off with the heat of a
soldering iron others that wont

The soldering iron you linked to should be idea for most home electronics
it has a good temperature range and the 350 - 400C would be where you would use it most
other than for small delicate components

IF you are using proper rosin flux cored solder, you DONT need any other flux
In 50 years of doing soldering at home and at various job, I have never had the need
to use additional flux the cored flux has never failed me

your iron tips look OK
would like to see a photo of the wire ends you were trying to soldercheers
Dave

 

[yungman]

I have a 25W soldering iron. I am trying to learn this art from Youtube. From the videos, it seems that soldering is not much difficult. But in practice, it just doesn't work out for me.

.....

Should I buy a higher power soldering iron? Something like https://www.amazon.com/dp/B07HM1DMLN/?tag=pfamazon01-20 or maybe https://www.amazon.com/dp/B07HM34RFZ/?tag=pfamazon01-20? Or is it something else that I am missing?

I think 25W is way way too low power. People don't realize how important is the solder iron in soldering. I would not get anything below 60W unless you go into really expensive ones like Metcal etc. I don't know whether you are planning to use it a lot in the future or just learn for the fun if it. If you plan to learn electronic and do more soldering, don't be cheap.

I am OCD in soldering iron. I am born cheap, I bought almost all test equipment used like I bought an old 350MHz Tektronics analog scope for $400, BUT when comes to soldering iron, I go for the best and really makes a difference. I do a lot of SMD work and I need two irons. I used a Metcal MX500 and a Weller WTCPT with Weller as the main one because it's supposed to be higher power. The Weller broke and I had to move the Metcal as first iron and use the crappy Chinese Aoyue as second. WHAT A DIFFERENCE with the Metcal. It brought smile to me face using it. In fact I just spent $400 buying a Thermatronics 9000 that is interchangeable parts with Metcal MX500. What a difference now that I got the best on both side.

OK, enough of my OCD. It's very important to have higher soldering iron. You need speed to do good soldering. If the solder stay on the iron for more than 3 or 4 sec, the flux will evaporate and the solder is useless, you will get cold solder. To avoid heating the solder for long time, you need powerful soldering iron. In your case, you put a little solder on the tip, heat the wire on one side and feed the solder on the other side of the wire, the solder should melt on the wire and tin the wire. If you have a small iron, you cannot do that and you'll get cold solder

I don't know the simple solder irons, I only use solder stations. My suggestion is even if you want to go cheap, buy Weller. Never buy those Chinese Aoyue those just to save a penny. Weller WAS the industry standard brand before SMD stuffs, then Weller got replaced by Metcal. Weller should know what they are doing. I have a high power soldering iron for really heavy duty soldering, it works, no complain. I wasted over $100 on the stupid Aoyue station with desoldering and fume absorber, it's a total waste of money. It supposed to be like 60W, but it just didn't melt the solder and it's slow. It's not just the power, it's how fast it can deliver the power. Even if you have high power iron, if the the delivery of power is slow, the moment you touch a big wire, the tip cools down and cannot recover.

Sorry about the long post. I am very picky on the soldering iron, to me, it's like the knife set for the chef, everything else can go cheap, but the soldering iron has to be top notch. My two soldering irons cost more than all the other test equipment combined.

 

[yungman]

I was looking on ebay, most of the soldering iron from Weller are 40W or below. I found a used Weller WTCPT like the one I have. I don't know whether you trust used stuffs. New ones are going to be over $120 if you can even get it.

https://www.ebay.com/itm/Weller-PU1...567541&hash=item23c87cc388:g:2r8AAOSw0L9dp8sW

I don't know how high it will bit up to, but for less than $50, I would take a chance if I were to buy it. This was the industry standard in the pass until SMD components become popular. The iron pencil is just too huge for SMD work and Metcal came out with a new technology using RF to heat the iron instead of heater coil. That makes the iron pencil like 1/3 the size and heat recovery much much faster. But you can see the WTCPT is still popular as people still are biting on it. They last for decades. My first one lasted 30 years and was my fault that I broke it. The current one turn out to be the blown fuse. But since I start using the Metcal, I would never go back anymore.

If you are close to Santa Clara Ca. I can give it to you free. There might be something wrong as I have to replace with a bigger fuse. Make sure you don't leave it on unattended, if it smoke, dump it. I tested if for a while, it works ok. But I just bought the Thermatronics, I have no need for that anymore.

 

[davenn]

I think 25W is way way too low power.

As has been said, no it isn't for general small electronics 25 - 30 watt is ideal

If heavier work needs to be done, then yes, 40W + is needed, heavy wires , large circuit groundplanes etc

 

[yungman]

As has been said, no it isn't for general small electronics 25 - 30 watt is ideal

If heavier work needs to be done, then yes, 40W + is needed, heavy wires , large circuit groundplanes etc

I don't think so.

 

[Rive]

As has been said, no it isn't for general small electronics 25 - 30 watt is ideal

If you have the experience then 30W is acceptable, but for beginners that (paired with some cheap iron) often brings an uphill battle.
Especially if the temperature is set at some fixed point (usually somewhere above 400C). The stable, adjustable temperature almost as important I think as the available power. Beginners are easier to catch up to task if they can get a bit higher temperature than the necessary - but still without oxidizing the solder in moments.

I don't think so.

Your Weller won't work any more seriously than 20W average.

 

[yungman]

If you have the experience then 30W is acceptable, but for beginners that (paired with some cheap iron) often brings an uphill battle.
Especially if the temperature is set at some fixed point (usually somewhere above 400C). The stable, adjustable temperature almost as important I think as the available power. Beginners are easier to catch up to task if they can get a bit higher temperature than the necessary - but still without oxidizing the solder in moments.Your Weller won't work any more seriously than 20W average.

From my years of experience in soldering, high temp and powerful iron is the KEY for good soldering(with good technique). Even with SMD as small as 0402, I use 800deg tips all the way and use the biggest tip possible for the job so the extra mass will help keeping the temperature. Nothing is worst than it takes a few seconds or more to even melt the solder. A small and low temperature iron requires heating stuff for a long time to bring it to melt the solder, the flux will all be burnt away and create cold solder joint. People need to learn and practice to do soldering fast. If I have to heat things for a few seconds to melt solder, I always touch up and refloat with new solder to make sure the solder joint looks shinny to ensure it's a good solder. You keep heating and heating using a small iron, the solder joint will likely look dull, that's the tell tale sign of cold solder that will present problem in the future.

Keeping stable temperature and recovery is very important. My suspicion why my Aoyue is so bad is because even if I set to higher temperature of 450deg , the moment the tip touch the wire or other things, the temperature drops and recovery is very slow. The result is it won't melt the solder. It uses a ceramic rod heating element placing inside the hollow cavity of the solder tip, I bet the heat transfer is bad. Once the tip touch any surface, temperature drops and it's too slow to transfer heat from the ceramic rod to the tip to bring the temperature back to spec.

Soldering is NOT as easy as it looks, takes practice and practice. I taught technicians how to solder, you'll be surprised how many people that work in the field don't know how to solder. Particular now a days soldering SMD parts, it's a skill to solder. With good technique, one can solder SMD much faster than through hole components. I use a lot of SMD in my design at home, I try not to use through hole parts if I can help it. Reworking on SMD pcb is a lot easier than through holes.

As for my Weller WTCPT, it's spec for 60W, I don't know what is the average. It's a strong iron for pcb work. Heat recovery is much better than the Aoyue that is 70W. What is the average power of the 25W soldering iron?

 

[Rive]

I use 800deg tips all the way

Then at the company I'm working you would not be allowed to use the equipment at all and most likely you would get yourself fired in the middle of the probation period.

Overheating the PCB/components is one of the biggest taboos, especially in SMD soldering. If you can't do the job at acceptable temperatures you better get a https://uk.farnell.com/weller/whp-200-eu/preheating-plate-200w-230v-eu/dp/2629057.

 

[yungman]

Then at the company I'm working you would not be allowed to use the equipment at all and most likely you would get yourself fired in the middle of the probation period.

Overheating the PCB/components is one of the biggest taboos, especially in SMD soldering. If you can't do the job at acceptable temperatures you better get a https://uk.farnell.com/weller/whp-200-eu/preheating-plate-200w-230v-eu/dp/2629057.

What company are you working for? I worked for more than 30 years as a technician, an engineer and manager of engineer in quite a few companies, never have any issue.

It's the technique and the speed. I never ever have problem with SMD parts. I am still building a lot of boards for my amplifiers with a lot of SMD parts, never have a problem peeling traces. Actually if you have a weak iron and has to stay on the pcb for a long time, you rip traces and pads out.

As a manager, I would fire someone that keep giving me boards with cold solder joints.

 

[tech99]

I am wondering if the wire you are trying to solder is enamelled? Goes it have an insulating varnish? Try scraping the surface with a knife.

 

[Rive]

What company are you working for?

Strict. We are developing and testing/reworking our own boards for our own industrial equipment. While scrapped components are somewhat acceptable, scrapped PCBs are painful since that means scrapping a bunch of other component and cost too. Actually I was the one who finally managed to establish some decent soldering culture here, and since that there are barely any boards got wrecked and product quality shoot up.

In short, the starting point was: 350-360C is preferred, but anything above 380C is forbidden: if you still can't finish the job in seconds, then ask. Anything with not rosin based flux is forbidden.

Not too complicated but surprisingly successful in guiding the new guys, should they be technicians or fresh engineers.

 

[yungman]

Even I was and engineer and Manager of EE, I did a lot of work building boards at crunch time as I was faster than the technicians. I am doing more soldering and building boards since I retired as I don't have people to boss around, I am the designer and assembler and all at home. I was contracting at home for over a year and half working at home so I have to build all the boards of my designs using TSSOP and 0402 parts.

I am retired, but I am very active in designing high end audiophile power amps that mixed power electronics components with SMD on one board. Attached are what I am working on, I spent like 3 hours a day building and testing stuffs. I build in higher quantity for comparisons. You can see those

1)IPS boards are all SMD with a few through parts.

2) Old power amp boards L that I am at the process of pulling out parts to reuse. It's mixed SMD and large transistors on one board. What make it very difficult for soldering is I have to use 2oz copper for high current purpose. Try soldering SMD parts on 2oz copper.

3) Scrapted boards are boards in various stages of pulling out parts. Those transistors, capacitors and a lot of stuffs are expensive. I even recycle SMD parts.

4) Boards to recycle are piles of boards either obsoleted or parts been pulled and ready to go to recycle.

I do a lot of soldering and rework now that I am retired and no one to boss around and dump the dirty work on anymore like when I was at work. It's all on me. Particular I fab boards in China as it's a lot cheaper. There quality is much lower, they don't hold up to soldering heat anywhere close to the boards made in USA. This make it so much more critical in soldering. I have absolutely no problem using what I described.

I don't want to debate this any more, to each their own, we just agree to disagree. I walked the mile...many miles on this, it works for me and serve me well.

 

[davenn]

I am wondering if the wire you are trying to solder is enamelled? Goes it have an insulating varnish? Try scraping the surface with a knife.

.

Yeah, I commented about that some posts back

the OP hasn't responded
It seems the OP @Wrichik Basu has gone AWOL

 

[Wrichik Basu]

would like to see a photo of the wire ends you were trying to solder

.

Yeah, I commented about that some posts back

the OP hasn't responded
It seems the OP @Wrichik Basu has gone AWOL

Yeah yeah, sorry for the delayed reply. I was busy in some college work...

Here is a photo of the type of wires that I generally use. This one is the thickest one available locally.

 

[Wrichik Basu]

Some months back, I found a diode bridge that I had made when I was young (idea was to convert 220V AC to 220V DC). I was laughing at my own stupid ideas, but then decided to test my soldering "skills" on that. The wires were a bit tarnished, but they were too twisted for me to rub them with a sand paper. I kind of dipped the joints into flux. The result was this:

This was perhaps expected. A good and smooth solder requires a good joint first. The joints, in this case, were wires twisted together in almost any fashion. I can't even think of such joints nowadays.