Since I do a lot of circuit board salvage I end up with a good supply of great components with short leads. When I use these components in my experiments and builds I must either deal with the short leads or add an extension. This is usually done by tinning the component lead and the extension and then holding them parallel while heating the solder and allowing it to bridge them. This works fine but there is always the danger when soldering the component to the board that heat transfer up the lead will damage or unsolder the splice.
Tonight I decided to explore the possibility of spot welding extensions to short leaded components. The spot welds would not be susceptible to melting like the solder splices. I had a rough idea how to build a simple spot welder so I gathered some resources:
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The 33000 uF capacitor is capable of 60 volts so It should be able to store up to 60 Joules of energy. U = 1/2 C V^2. I am going to use the copper strapping to bring the energy from the capacitor to a point where I can sandwich the short component lead and the proposed extension between it and a copper point. The contactor in the picture will be used to close the circuit and apply the energy in the capacitor to the circuit. Hopefully enough of this energy will get concentrated in the splice and fuse the two leads together. The mouse trap is the starting point for making a spring loaded copper point which will apply the pressure through a copper point to the weld point. The 12 AWG wire in the foreground will be the copper pressure point.
Here is the experiment built to the point where I will be able to test for proof of concept. The capacitor will be charged and then the contactor will be energized which will close the circuit and hopefully weld the two wires together. The first big problem was positioning the two wires to be welded between the lower copper plate and the upper electrode. Finally, by flattening both wires I was able to get them positioned. I charged the capacitor to 5 volts and energized the contactor. No weld. I tried again at 10 volts and still no weld. Next I upped the voltage to 30 volts and tried it once more. This time I got a nice pop and a splatter of small molten particles exiting the site of the weld. The two wires had been welded together but it was a very poor weld and was easily broken with a slight bend.
I repeated this process of fighting with the wires until they were positioned and then closing the contactor. After several failed attempts to get a good weld I realized that the metallurgy of the standard component leads and extensions were not suited to spot welding. I went and got some high nickel and chrome content wire that is used in dentistry and intended for spot welding and tried that. Now I was getting much better welds but this metal which is very similar to the metal used to spot weld battery packs together would not make good lead extensions for components as it is not very ductile and is difficult if not impossible to solder.
Here is a picture of my artistic creation using the dental orthodontic wire and the resistor with a piece of the dental wire welded to it. I was not able to weld any of the conventional tinned extension wire satisfactorily to the resistor.
As you can see from the blast marks on the copper contact point the energy was getting to the proper point. At the 30 volts of charge that I was using there was about 15 Joules of energy available. The copper in the component leads would melt too much and the arc would blow it out of the point of contact. It doesn't look like this will work.
If anyone has any other ideas on how to successfully add extension leads to short leaded components let me know or if there are some spot welding techniques for working with copper I will continue to experiment.
Thanks
John
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