Soldering - inability to avoid cold joints

JHZR2

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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:

IMG_8554.webp


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.
 
Is the contact in a metal vice? That is a good sized heatsink. Flux might help, although flux core solder has always worked well enough for me (tin-lead, not the RoHS junk). But take the contact out of the vice so it can heat up too.

Light sanding on the contact solder area may help too.
 
Is the contact in a metal vice? That is a good sized heatsink. Flux might help, although flux core solder has always worked well enough for me (tin-lead, not the RoHS junk). But take the contact out of the vice so it can heat up too.

Light sanding on the contact solder area may help too.
Have to hold it somehow. The vice being a heat sink didn’t tbeough my head but when soldering I only had 1-2mm of contact. What choice did I have? I can’t hold it.
 
Have to hold it somehow. The vice being a heat sink didn’t tbeough my head but when soldering I only had 1-2mm of contact. What choice did I have? I can’t hold it.
A pair of hemostats to hold the wire, and if need be, the vice can hold the hemostats. You need to minimize the heat sink.
And make sure the materials involved are compatible with solder. If they are just copper coated steel, it will be tough to get a bond.
 
What solder did you use. The lead free stuff it total 💩💩 so i only use leaded solder and i took too long shelving the weak 100w harbor freight solder gun for a far better 200w weller dual heat one and i haven't had cold joint issues ever again.
 
What solder did you use. The lead free stuff it total 💩💩 so i only use leaded solder and i took too long shelving the weak 100w harbor freight solder gun for a far better 200w weller dual heat one and i haven't had cold joint issues ever again.
I first tried what came in the kit. Then I figured I should use some leaded thin wire.

IMG_8566.webp

Weller guns need the nuts that hold the tip on re-tightened frequently.

Did that at the start and partway.

Weller guns are terrible. For gauge that big you’re better off with a pencil tipped torch.
Recommendations???
 
Solder station
Stations with nice variable wattage are great but a bit of an investment for infrequent usage. I say to just buy a stronger 300w gun for the thicker wire.

The 200/300w weller has been good to me. The 100w hf is only good for thin high gauge wire anything lower gauge the weller is what I'd use which is most of what I do so I should have gotten that from the beginning. I paid 40 something for it and to my surprise it's around 80 now. The 100w took way too long to heat up thicker wire reliably to not cold joint.
 
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Stations with nice variable wattage are great but a bit of an investment for infrequent usage. I say to just buy a stronger 300w gun for the thicker wire.

The 200/300w weller has been good to me. The 100w hf is only good for thin high gauge wire anything lower gauge the weller is what I'd use which is most of what I do so I should have gotten that from the beginning. I paid 40 something for it and to my surprise it's almost 70 now. The 100w took way too long to heat up thicker wire reliably to not cold joint.
OP seems to be asking future use as well. Lifetime investment but really a super skill improvement game changer with a very short learning curve. 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.

CLEAN CLEAN CLEAN to new metal!

Good flux

NO MOVEMENT of parts.

Both sides hot fast, minimal dwell time. Solder bridge, feed a little solder then done.
 
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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.
 
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