Resistance soldering anyone?

[mariushm]

I was thinking how hard would it be to make some kind of laser soldering machine by re-purposing a bluray laser diode and realized it would be pretty hard to control the temperature with a home made machine.

Browsing the Youtube videos and admiring the laser soldering machine "hardware porn" I stumbled onto a resistance soldering video for an American Beauty soldering machine that uses some tweezer system to solder using resistance:

http://www.youtube.com/watch?feature...&v=sn63FOWqesk

This thing is expensive at 479$ but other than the tweezers it seems to be just a 100 watt transformer with voltage control.

I've found even some pdf files where people showed how they made one using a car battery charger (12v 5-10 amps) and some foot pedal and regular carbon rods.

edit: the document i mention is here: https://cdn.badcaps-static.com/pdfs/...ee11818840.pdf

Now my questions are these...

* has any of you worked with something like this? Are they as easy as they seem to be?

* how safe are to use with some of these smaller diameter holes on PCBs? And especially how safe is to warm up the pins of capacitors or resistors and so on?
They say the heat is very centralized unlike regular soldering techniques but it seems to me there's a higher chance to accidentally raise the heat to some ridiculous temperatures.

I'm especially puzzled a bit about how it would produce quality soldering because all I've learned so far says both metal parts should be heated and then fed solder to create a good welding but using this method I'd only heat both surfaces if I somehow press one onto the other with the tweezers.

Seems a bit hard to put pressure under magnifying glass and at the same time be careful about how much it heats and so on.

Thanks in advance for any clarification you more experienced guys can give me.

[Evil Lurker]

Re: Resistance soldering anyone?

I personally think I could do better with a regular iron for thru hole or hot air for SMD work.

[severach]

Re: Resistance soldering anyone?

Resistance soldering is usually avoided for electronics because the current could pass through the board or part leads and damage semiconductors. It works fine for high current devices where a little current can't hurt anything or jewelry where stray heat from an iron would damage the finish. Soldering the resistor would be fine so long as the semiconductors were unpopulated.

I don't like it because it's an expensive device that does much less for electronics than a lower cost hot air gun. I can desolder and resolder a 128 PQFP with hot air. I would need to use one to see how well the tip maintains its ability to conduct in a dirty solder environment.

All the Youtube examples I've seen so far are with high current tolerant applications or unpopulated boards and in all those examples hot air assist would have been my first choice.

Not that resistance soldering is bad but I wouldn't get one until the need arises.

[Agent24]

Re: Resistance soldering anyone?

Without reading the links this sounds like one of those "cold heat" irons.
Basically a miniature spot welder I think, and not good for PCB work at all.

Even if you ignore the fact that the voltage can kill your parts, the joint will be crap (think: cold heat = cold joint)

Good article here: http://www.epemag.wimborne.co.uk/cold-soldering.htm
Or the conclusion if you're lazy: http://www.epemag.wimborne.co.uk/cold-soldering2.htm


No, I say keep your traditional iron, and if you want to spend money, spend it on a better iron.

If you want to do SMD without hot air, research 'drag soldering'