A guide to resistance soldering basics, how resistance soldering works, choosing a resistance solderer, about DIY resistance solderers, and about making solder joints.
This is the resource page for anyone interested in soldering.
There are four sections to this page. The first gives you tips and hints, the second shows free books on resistance soldering, the third contains an extensive collection of video tutorials on resistance soldering and the last an index of our complete series on resistance soldering.
Advantages Of Resistance Soldering Over Conventional Soldering
- Pinpoint, localized heat allows making joints without affecting other nearby joints.
- Near instantaneous and cooling prevents collateral damage.
- Solder feeder wires to track without melting plastic ties.
- Reduces solder cleanup requirements.
- Will heat a larger work than a conventional soldering iron of the same power.
How Resistance Soldering Works
Resistance solderers take advantage of a material’s resistance to electrical current flow.
An incandescent light bulb does the same thing. The filament in the bulb has a certain resistance to electrical current flow. When voltage is applied to the light bulb, current flows through the filament. It gets hot. The heated filament throws off light and heat.
If you substitute for the filament two pieces of brass with some solder between them, just like the filament, the brass will get hot. The solder will melt and a joint will be made.
By using probes with carbon tips, we can focus the path of the current to a very small area. When the resistance soldering iron is turned on, the pinpointed area gets very hot very fast. In two or three seconds, the solder melts and power is turned off. The heated spot cools rapidly and the area around it stays coo,. So the solder joints near it stay unchanged. And that is why this method is particularly useful when making joints in close proximity to each other or where you need to avoid overheating the surrounding materials.
In short, with a resistance soldering iron you can make a soldered joint that would be impossible to make by any other method.
Choosing A Resistance Solderer
If you are a dedicated brass modeler, you really should have a resistance soldering iron on your bench. Most are so expensive that they are quite likely to scare you off.
No doubt, many people see how much a resistance soldering iron can do for them that they consider a big investment as well worth the money.
Others go the DIY route and hack microwave transformers, battery chargers and what not to make their own.
HACKS CAN BE DANGEROUS. If you are going to go DIY, go safely.
In any case, if you are like many of us, budget conscious, look at DIY.
In any case, you must be aware that a resistance soldering iron is a spot welder. And it can burn holes in your brass. The more power, the more likely it is to burn holes.
As a hobby modeler you want to work in the range of 30 to 60 watts. Typical voltages will be 2.5 to 6 volts AC.
You will see videos on the web of guys using resistance solderers at such high power that the probe tips and metal turn red. THAT IS BAD.
And these people even create arcs by removing the probe before power is off. Arcs damage the brass.
You want your metal hot, but not red. Hot is normal. Red it NOT.
You want a soldering iron and neither a spot nor arc welder.
3 volts at 10 amps is sufficient for etched kit builders and other fine scale work. For heavier jobs you may want to move up to 4.5 or 6 volts at 10 amps.
About DIY Resistance Solderers
Commercial resistance soldering machines have no performance advantages over a properly made DIY unit. The may look nicer, but that is about it.
You can find on the web many pages and videos describing how to make a resistance soldering unit. Most start with modifying a microwave transformer. We consider that hacking and dangerous.
We recommend that you use a professionally made transformer that is made in accordance with published safety standards. They are available from several well established European transformer manufacturers.
And our network has had a transformer made for us. You can get either the transformer or complete DIY resistance soldering iron kit here.
About Making Solder Joints
They key to good joints is cleanliness.
Clean soldering probe tips.
Clean and organized work area.
Oxidation Free Metals
You can solder copper based materials. They include copper, brass and bronze. Oxidation occurs on their surfaces rapidly. This oxidation prevents solder from bonding (its an ionic bond) to the metal.
The books shown here are excellent reference books that beginners and experts alike will find useful. They are highly recommended. Try at least one now. Click on the image.
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Resistance Soldering Tutorial Library
About DIY Resistance Soldering Irons –
Why Resistance Soldering Instead Of Conductive Soldering –
How to build your own DIY resistance soldering unit. –
How To Make And Use Resistance Soldering Pickle –
Resistance Soldering Frequently Asked Questions –
How To Make Resistance Soldering Iron Tools –
Resistance Soldering Tips And Hints –