Why won't solder stick to wires with my 25W soldering iron?

[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.

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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

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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.

 

[Rive]

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:

It is hard to 'repair' a tarnished wire. I suggest to give up on them at the start: most of the time it is just better to cut it shorter and strip it again.
This 'result' won't give a good example. I can tell that the soldering iron is burning hot (the insulation of the wire on the top got burned), the flux is burnt as well - but for a tarnished wire (and oxidized component legs) it is not really about your skill.

Try to tin the wire on the photo in #34 and post a picture of that.

 

[Wrichik Basu]

Try to tin the wire on the photo in #34 and post a picture of that.

I tried to tin that one, but it was too thick for my 25W soldering iron to handle. So I picked up a thinner wire of the same quality. After trying a few times, this is the best I got today:

I won't say that it is good when compared to something done by a professional. There is some cold solder near the bottom, which I couldn't prevent even after putting flux paste. Perhaps more practice is needed on my side.

In addition, here is a better picture of the tip of the soldering iron (the pictures posted previously in this thread were perhaps of not a good quality):

 

[Rive]

After trying a few times, this is the best I got today:

As long it is just an occasional soldering what does not matter much (low voltage, low current, no responsibility), then it is passable.
However: the insulation is still damaged, long up from the stripped part: the surface is uneven, the flux is burnt brown. Won't pass anywhere where it really matters.
I don't think this will be much better later on. To heat up the wire at 25W you really need the high temperature, but with a high temperature iron it is really difficult to spare the insulation and the flux.

Link the process on a 4mm² wire with an old and battered Weller WSP-80 80W soldering iron @360°C (!).
Still not perfect, but the flux kept fresh (yellow), the surface is nice shinny and the insulation is intact.
Could have been faster but the magnifying glass was in the way.
I still suggest to get a better soldering iron.

 

[Wrichik Basu]

I still suggest to get a better soldering iron.

Yeah absolutely, I know that I won't be able to go far with this 25W. I will be buying a better one next month or so.

In your video, the wire brilliantly absorbs the solder. In my case, the solder doesn't melt unless I touch it near the tip of the iron. Temperature issue, of course.

By the way, I tried using this iron on a faulty pcb that I had. It could desolder the joints, and re-solder them as well (except the joints of the IC). Maybe those joints required lower temperature, so this iron could do it.