Soldering - inability to avoid cold joints

[JHZR2]

Have you tried an alligator clip?

Kind of past that now. The wrap and the bad joint was enough to give the same resistance as the other lead, and it charges the battery fine (they only charge at up to 10v, 3A).

It’s more for the skill building and some other things that I know I need to solder.

 

[JHZR2]

That lug looks like it's designed to be clamped around the wire. Is that way still possible? What you're doing seems destined for failure.

You should have seen the original connection. Just the wire laid on the lug, a blob of solder. The wire fell off and the pad of solder was just a perfectly flat smooth surface.

OP seems to be asking future as well. Lifetime investment but reall a super skill improvement. I have a Hakko 936, I paid $80 new in 2009. Now they have some real watt beast China knock offs for less.

FTR I trained at China Lake NWC. I was a certified solder process examiner for many years

Exactly!

Years ago I could not get some half inch copper plumbing pipes to solder no matter how many times I tried. I just happened to buy some new soldering paste as a last resort. Instant success! The old paste in my plumbing kit had turned a dark brown, the new paste was light amber colour.
It's was like the old paste had turned into solder repellant.

Interesting! So fluxes may have a shelf life?

I know the flux would melt and flow. Saw that happen easily.

 

[Pablo]

You should have seen the original connection. Just the wire laid on the lug, a blob of solder. The wire fell off and the pad of solder was just a perfectly flat smooth surface.


Exactly!


Interesting! So fluxes may have a shelf life?

I know the flux would melt and flow. Saw that happen easily.

I edited my post a bit.

I can't vouch for any of these

https://www.amazon.com/s?k=hakko+93...71&ref=nb_sb_ss_p13n-expert-pd-ops-ranker_5_9

 

[Kestas]

60-40 should be okay for your work. I will throw a few things to watch out for.
The two mating surfaces must be nothing less than perfectly clean. Flux will not clean tarnish.
Both parts must be at temperature for the solder to wet. If one acts like a heat sink it'll be impossible to wet it. I have problems soldering wires to chasses when I restore old radios because the chassis acts as a big heat sink. (I'm guessing this may be your problem)
I've used old flux before... like decades old, so I doubt that is a problem.

 

[TooManyWheels]

Kind of past that now. The wrap and the bad joint was enough to give the same resistance as the other lead, and it charges the battery fine (they only charge at up to 10v, 3A).

It’s more for the skill building and some other things that I know I need to solder.

General priciples - I apologize if these are too simplistic.

Clean soldering tip! Tinned. Make sure the solder is appropriate (i.e. no plumbing solder for electronics). The tinning on the tip is the first heat pathway to the joint.

Setting up the fixturing of the parts is usually the most complicated part of the job, and can be an art in itself. As said ealier, you don't want them to move.

There must be physical contact between the parts. Since you often can't touch them all at the same time with the tip, heat needs to flow between them. In my experience, the flux is very helpful in facilitating heat flow.

Never use the tip to "dip" solder onto the work. This seldom works.

Do use the tip to try to evenly heat all the parts. The solder follows the heat. No heat, no solder flow. After fixturing, heat flow should be your primary area of focus. Note - this would also apply to soldering plumbing copper with a torch.

Once solder is where it needs to be, do not disturb the joint.

It's best practice to clean off the visible flux, and is usually required for professional electrical joints.

 

[zzyzzx]

Light sanding on the contact solder area may help too.

I was going to suggest sanding the solder gun tip.

 

[JHZR2]

I edited my post a bit.

I can't vouch for any of these

https://www.amazon.com/s?k=hakko+936+soldering+station&crid=2AOPMDITMA122&sprefix=Hakko+936,aps,371&ref=nb_sb_ss_p13n-expert-pd-ops-ranker_5_9

Those are all 65-75W it seems. I can’t heat this enough with 140.

Heat sink, I get it, but still want to figure how much heat I really need….

 

[Pablo]

Those are all 65-75W it seems. I can’t heat this enough with 140.

Heat sink, I get it, but still want to figure how much heat I really need….

There is more to soldering than raw wattage rating but yeah some look weak

https://a.co/d/03yGPdeD

Soldering demands high heat fast to a fairly fine point and little temperature drop while transferring the heat. Solder guns are slow and not particularly heat concentrated

 

[Chris142]

Is the contact in a metal vice? That is a good sized heatsink.

First thing i noticed too. They make a tool to hold wires for soldering

 

[Chris142]

This is a better choice than that big vise

 

[Touring5]

....

Interesting! So fluxes may have a shelf life?

I know the flux would melt and flow. Saw that happen easily.

Yes. I was going to reply in agreement.

A couple of years ago I was working with some 1" copper & fittings and kept getting crummy joints, despite thorough brush and flux prep. I was using run-of-the-mill Oatey flux that I'd had for years. Just for giggles I bought a new tin and as soon as I applied it I saw a huge difference. Where the flux was on the old, oxidized pipe (past the cleaned area) it turned bright and shiny when hit with my torch. The old stuff didn't. All subsequent joints were excellent.

I mentioned it to a plumber and he said he hadn't seen that, but he never used 25+ year old flux

 

[martinq]

I'm only going to use solder that's 63/37 unless there's a **** good reason. Would not touch 60/40.

 

[Pablo]

I'm only going to use solder that's 63/37 unless there's a **** good reason. Would not touch 60/40.

Yes eutectic. I neglected to mention this!!

 

[DemoFly]

Are the newest ones that bad. Reading the reviews it looks like the quality has gone down the drain now but mine is an older one.

I don't know. I've never had any success with them new or old. I can't stand them. They heat up fast and transfer no heat to the joint. I don't get it. I like weller products, and my main iron is a weller. But those guns are a joke.

 

[Chris142]

A small torch would be a better option at this point?

 

[supton]

I can't tell from the terminal but I think it might be a crimp of some sort? once the wire is wrapped around or "crimped" even in some poor way, what I would have done is something like this:

For small gauge wire, often I can balance a large spool of solder on it. Leaving the soldering surface floating. Yeah I have to chase it a bit but no heatsinking.

Alternatively, clamp the wire back aways from the joint. The longer you solder, the more the insulation will heat, so you need to move fast. A hot iron is needed.

Those old soldering guns, I'm starting to wonder if they work as well as the wattage indicates. I've had too many issues with them. A really old soldering iron is something I ought to find some day, and I bet it'd work like a charm here. Big thermal mass.


Finally, I hated the idea of a digital soldering station, but finally on a lark tried one of the newer direct heating irons. Oh my, totally worth it, first time it reduced power and dropped temp because I had forgotten about it was a solid reminder that stuff happens in the hobby den, and the fact it responds very quickly to any heat flow out of it means it does well when asked to do a big job. Cheap China made controller and handle, but I did buy a genuine Hakko tip, and need to get a smaller one, but very happy with its power output (my soldering ability, not so much).

Finally... Chinese solder? If you can get good results on other soldering works then I'm just wrong, but, while I buy plenty of stuff from there, I'm just not sure I'd want to mess with anything that isn't Kester. Radioshack was ok but it's been worth finding old Kester rosin core stuff. 60/40 seems to work ok (although it's RS so who knows if it's really that) but 63/37 IMO is better.

 

[TnT_M]

We have a nicer RC car that the kids like to play with at the park. Traxxas or something.

The nickel metal hydride battery charge connector positive lead fell off of the interface plug at some point. When I looked at how it came apart, the way they had made it was just laying a piece of wire on a brass terminal, and somehow getting a giant blob of solder that kind of stuck until it didn’t.

Years ago, I had tried to do some other soldering work, and I couldn’t get anything to solder correctly. I was told that my soldering iron was two weak and I needed more heat. So I got a real soldering gun, a Weller brand.

So today, I tried to reflow the solder and get it to stick again onto the terminal, and I could never get anything hot enough to work. So then I drilled a hole through the brass terminal, and cut and wrapped the wire around, hoping that a hot tinned iron end would allow me to get the wires hot enough to flow some additional solder and get the whole thing to be solidly in place.

I could never get hot enough, even though the wire itself was too hot through the insulation to hold comfortably.

In the end, I took the oversize wire ( probably 10 gauge) and I cut 3/4 of the strands from it, wrapped it around the terminal, and then try to get back to flow.

The result was this:

View attachment 346143

I’m running a Weller 140W gun. Fortunately resistance checked out and so I’m leaving it. Stuffing the terminal back in the connector gives strain relief and it’s solid enough I guess.

I think it’s me not the tools. But I couldn’t heat the work enough. Yet the wire got unbearably hot.

What gives? How can I be so bad at soldering?

I’d like to be able to reflow parts on circuit boards and replace capacitors and whatnot. But I can’t even get a wire to solder.

Batting 1000 this weekend.

my son does lots of RC stuff and bought a veyr nice soldering iron. It makes all the differnce in the world. Soldering guns are a PITA! If you add "helping hands" to your mix it will also help the process.