To tin or not to tin?

[o1d_dude]

Not trying to start a wet sanding vs dry sanding primer discussion here. Just trying to track down something I read once that discussed whether we should tin the ends of our wiring at the altimeter or terminal strips ends. In both cases we use compression/mechanical means to make the connections need for dual-deploy.

I seem to recall a compelling argument was made that we should NOT tin the ends of the wires as "loose" wiring allows a better connection because the wire can compress to maximize surface area in the contact.

Can anyone weigh in on this? I'm wiring up a few alts and was wondering...

 

[Handeman]

I just pulled my altimeter out of the av-bay for the first time in about 3 years. I had tinned the wires that were connected to the altimeter. They were flattened and had plenty of contact.

I believe the reason against tinning the stranded wire is that tinning causes the wires to be held rigid. When the wire bends and vibrates, it can cause the wire strands to snap at the point the solder ends.

This may be the case, but I don't believe that we have enough time under thrust to stress the wires to a breaking point. If this was in a car and you wanted it to last 100,000 miles, that might be different, but I don't think tinning the wires is going to hurt anything with the little bit of time our rockets actually spend in vibration loading.

 

[FredA]

Tinning is NOT recommended for compression connections.

 

[rharshberger]

I think moderator BobKrech made a post about not tinning, mainly in reference to the aerospace/Nasa type rockets, and that it becomes a point of failure for wiring because its unable to flex and eventually breaks.

Its probably not a big problem for our rockets, as some have said because they don't really spend all that long in flight. However if its a good idea for NASA then it's probably not a bad idea for the hobbyist. I can also see how not tinning would increase contact area, so that's the route I plan to go.

 

[Sooner Boomer]

There was a huge debate about this on sci.electronics.design. If you tin the wires, they will become stiff and if there is vibration present, they could fail over time. However, by tinning the wires, you have a more compact bundle which should not have any stray wires coming out, plus the entire bundle is essentially under compression (rather than just the thick part of the bundle). I've never seen wiring fail that was tinned, even in automotive applications one of the harshest environments).

 

[cerving]

If you tin the wires to get a larger contact surface and prevent loose strands from causing problems, AND zip tie the ends to the sled to provide strain-relief, I would think that would be the best of both worlds...

Personally, I solder the wires to the board and zip tie the ends, but that's with Eggtimers and I realize that's not an option with most altimeters. Solder is your friend... it doesn't come loose.

 

[jderimig]

The best practice is to use stranded wires and a crimped ferrules on the termination. Cheap, easy and reliable to the max.

 

[GDJ]

Depends on what you're doing, and what application the wires are being subjected to.

In my industry, tinning wires before crimping / using screw terminals is mandatory and proper, but there is the argument that the wires can break at the point of where the solder "wick" terminates inside the stranded wire, causing a stress riser and a point of break.

Best scenario: tin the very tips of the wire, but absolutely no more than that, and use enough solder to join the end of the wire where it has been cut. That's tricky, but doable.

 

[Zeroignite]

What about the relative increase of corrosion on untinned wires?

 

[GDJ]

What about the relative increase of corrosion on untinned wires?

From a trucks perspective, the difference is negligible. Unprotected joints just corrode fast, tinned or not. Best to use heat-shrinkable crimp connectors or solder the wires together and use heat shrink tube over the joint.

As for rockets, probably not a factor since one would be taking everything apart and inspecting everything at every launch. A teeny tiny dab of dielectric grease on the terminals or the tips of the bare wires would probably stop any corrosion.

 

[zanfar]

The best practice is to use stranded wires and a crimped ferrules on the termination. Cheap, easy and reliable to the max.

+1. This is especially important in the era of non-leaded solder and the increased problem with solder whiskers. Although the frequent inspection rocketry electronics get might mitigate this problem, I don't tin anything that isn't going to be insulated or shrink wrapped.