Connecting non-solderable wires

[HANKMARS]

I will be using resistance wire which will not accept lead/tin solder. On prototype I would use a loop to loop sort of configuration when one of the wires were solder-able. This would tightly trap the resistance wire but is unsuitable for practical use. I desire to have a positive hold at these connections. How have you seen these connections made up resulting in secure, rugged results?

 

[Harald Kapp]

Haven't actually seen this in connection with "non-solderable" wires, but I would go for screw terminals or cage clamps.

 

[Bluejets]

Crimp link.

 

[duke37]

I used to use chromel/alumel thermocouples, there could not be soldered with tin/lead solder so the ends were 'tinned' with silver solder (Easyflow) which would take normal solder very well.

 

[Bluejets]

Thermocouples are supposed to use dedicated material type terminations to suit the thermocouple type otherwise the readings will be off.

 

[Harald Kapp]

Thermocouples are supposed to use dedicated material type terminations

Plus a cold junction compensation.
But theermocouples are not an issue here, as the op asked about resistance wire. On another forum aluminum solder is suggested.

 

[duke37]

Thermocouples are supposed to use dedicated material type terminations to suit the thermocouple type otherwise the readings will be off.

There will be temperature errors if the junction is not at a uniform temperature. We used compensation cable (copper/constantan?) to extend the couple by several meters and this worked well. The cold junction was at the measuring meter/computer.
The main problem was making a neat thermocouple junction. This was done with a gas/oxygen flame. I became quite good at this and could make a junction no wider than the two wires side by side so any hole would be small and not have a great effect on the thermal flow.

 

[HANKMARS]

Haven't actually seen this in connection with "non-solderable" wires, but I would go for screw terminals or cage clamps.

I did a short search for screw terminals but decided cost prohibitive. Plus weight and rigidness were a negative. Have not searched cage clamps yet.

 

[HANKMARS]

There will be temperature errors if the junction is not at a uniform temperature. We used compensation cable (copper/constantan?) to extend the couple by several meters and this worked well. The cold junction was at the measuring meter/computer.
The main problem was making a neat thermocouple junction. This was done with a gas/oxygen flame. I became quite good at this and could make a junction no wider than the two wires side by side so any hole would be small and not have a great effect on the thermal flow.

Very nice solution but does not fit this application. Thank you for your response.

 

[HANKMARS]

I used to use chromel/alumel thermocouples, there could not be soldered with tin/lead solder so the ends were 'tinned' with silver solder (Easyflow) which would take normal solder very well.

This may very well be the best solution. I assume Easyflow silver solder will have a somewhat higher melting point. Or I can make a silver solution and deposit the silver on the wire by electrolysis. The wire is KANTHAL A-1 FeCrAl alloy. Ferrictic iron-chromium-aluminium alloy. For use up to 2550º F (1400º C). A bit of overkill seeings how I do not wish to exceed 115º F. I will try to post the heat shrinkable connectors that I have purchased.

 

[HANKMARS]

Crimp link.

I considered crimp links and would fill voids with tin/lead solder but am concerned with wire pulling out. A loop to loop primary connection with a crimp connector filled with solder might keep joint from failing completely but may also result in sporadic conduction.

 

[Ylli]

A properly sized crimp will make an airtight and secure connection. No 'solder fill' required.

 

[HANKMARS]

A properly sized crimp will make an airtight and secure connection. No 'solder fill' required.

OK. These are solid wires, not stranded, but still quite possible I imagine.

 

[HANKMARS]

I will be using resistance wire which will not accept lead/tin solder. On prototype I would use a loop to loop sort of configuration when one of the wires were solder-able. This would tightly trap the resistance wire but is unsuitable for practical use. I desire to have a positive hold at these connections. How have you seen these connections made up resulting in secure, rugged results?

I have not tried these yet but am optimistic.

 

[Ylli]

I thought you said the resistance wire was not solderable. These form the connection via soldering.

 

[Harald Kapp]

These form the connection via soldering.

Right. A crimp looks different and requires a special crimp tool. Crimping works on stranded wire only. Solid wire is not suitable for crimping, see e.g. here.

 

[HANKMARS]

I thought you said the resistance wire was not solderable. These form the connection via soldering.

Yes they do. My initial thot was that the mere "snugness" of the connector would be enough to maintain acceptable electrical conductivity. Another reader mentioned silver solder tinning. I will be trying that suggestion soon. The reader mentioned that the silver tinned wire readily accepted tin/lead solder, which does sound correct. And if that all rings true, I will have solved this problem of mine with the help of active readers. Thank you all for your participation. I will let you know the outcome.

 

[duke37]

If the resistance wire gets hot, then tin/lead solder would probably fail. Electric elements are often spot welded. You could use Easyflow for the entire connection.

 

[HANKMARS]

If the resistance wire gets hot, then tin/lead solder would probably fail. Electric elements are often spot welded. You could use Easyflow for the entire connection.

Hopefully, maximum temp will be 115º F. Will I be able to use Easyflow with soldering iron? My cheapo adjustable iron adjustment knob implies that it can reach 450º F.

 

[Bluejets]

I can foresee this ending in a complete mess.
Just use a crimplink or a ceramic terminal block and be done with it.