Great way to splice wires

[Seymour Snerd]

I found these for sale in reasonable quantities at Sherco Auto Supply Sherco Auto Supply. They are at the bottom of the page and called "multilink;" all with part numbers starting with ML.

They are absolutely wonderful. You feed your wire in, give it a little crimp, then hit it with the heat gun. The adhesive lined tubing shrinks as usual and then a little while later the solder ring melts and a little drop of solder is pushed out the front by the shrinking action to tell you its' done.

Voila: soldered and sealed termination in one easy three-step-sequence. I tried pulling one off and basically couldn't without destroying it.

View attachment NSPA_Sealed_Crimp_Solder_brochure.pdf page 3.

I did some more work with these NSPA Multilink sealed crimp/solder terminals and a heat gun today and have a few negatives to report. Not deal killers, but definitely things to watch out for:

1. With the female 1/4" faston-style terminals, the solder can flow all the way forward through the crimp and into the terminal which can make it impossible to fully seat the male. One fix is to give the terminal a little "flick" just after you take the heat away; this causes any liquid solder to fly out the front (and splatter all over the place, so be careful). Another might be to take the heat away before the solder capsule has completely collapsed; there is probably more solder in the capsule than needed, and the shrinking plastic pumps it forward since it has no other place to go. But then how do you know if you have a good solder joint?
2. Compared to a plain uninsulated terminal, these things are long (~1") and stiff, which can be a problem in close quarters. On the other hand this means they are very well strain relieved and mechanically retained since about half of that 1" is just the heat shrink glued to the wire insulation.
3. Once again, if with a heat gun you heat them enough to completely melt the solder capsule, the heat shrink can pull back from the ends of the female terminal, leaving you with a not-fully insulated terminal. So I ended up taping the junction of the ones I plugged together. Likely using a small butane torch would localize the heat on the heatshrink tubing and prevent this; and that in fact is what the mfr. instructions say. I've been using a heat gun and you can't localize that heat at all. So this is probably my stupidity as in "follow the directions, dummy". Next time I'll use the torch and report back.

So, when I step back from these I wonder if it isn't actually simpler to work with plain bare metal crimp terminals: crimp, solder with a gun, slip on some heat shrink and roast. It's nearly as quick, it's compact, and it's cheap. And you see right out in the open what the solder joint is like, whereas with the capsule-based ones you kind of have to take it on faith that the crimped joint also got well-soldered. But then as Joey Dean points out above, with the multilink parts you get a water-proof seal and a really good strain-relief that would be difficult to achieve with heat-shrink tubing.

 

[Randy V]

I don't know this first hand, but I am told that the FAA frowns on soldered joints in wires due to the copper hardening at the solder point thereby causing a potential failure when that joint is subject to movement or vibration.

I have been using properly sized crimp connectors and heat shrink tubing for many years now and have no reason to change that. I can't seem to locate it right now as I am in the process of moving my shop, but I have an attachment for my heat gun that has a semi circular shield that you put the joint with heat shrink in. This focuses the heat ll the way around the joint. Works very well.

 

[EGLITOM]

SUpport Randy´s comment

Properly sized crimping of quality wires and than a heat shrink tube to protect and ad stability is the way to go. Have seen broken soldered connections again and again due to hardening and nonflexibility to cope with vibrations and bending.

TOM

 

[Bob]

Ah yes, solder splices!

I work in the defense industry and we have had trouble with these in the past. When done correctly and used in the right environment they work fine. But they don't like vibration or flexing near the shrink tube, they'll fail eveytime. And as you found getting them to close and melt correctly is a pain. The heat gun temp hss to be just right. I myself have never had much luck with them.

 

[Seymour Snerd]

..But they don't like vibration or flexing near the shrink tube, they'll fail eveytime. .

I'm a little puzzled by that, since a crimped splice using shrink tube would seem to have the same problem. That is, if the issue is flexing near the shrink tube (i.e. at the ends), does it really matter how the wires are joined at the center?

 

[Jack]

Alan,
I believe that he was referring to the solder failing at that end of the shrink tube
nearest the connection. Best to simply use quality crimp connectors, and heat shrink
to seal them. The crimp connectors won't fail if properly done.

 

[Seymour Snerd]

Alan,
I believe that he was referring to the solder failing at that end of the shrink tube
nearest the connection. Best to simply use quality crimp connectors, and heat shrink
to seal them. The crimp connectors won't fail if properly done.

Hmmm. I'd like to hear from "iggy" on that one, because the multi-link splices themselves are very stiff, so I doubt failure between the tube ends would be an issue. Possibly the use of stiff, adhesive heat shrink creates a stress riser at the end, in which case we have a problem with that kind of tubing, not with the solder joint. Bob? And Randy, yes I was taught the same thing about plain solder joints in the electronics industry in general, not just aviation. But it was in the context of a joint where there was no strain relief on the wire.

Just to make sure we're all talking about the same thing, here's a good (3 min.) video on the multi-link product:​

[ame]http://www.youtube.com/watch?v=Aj1yvPvxir8[/ame]​

(I just noticed that in the ring terminal example they use a heat gun, but one with a tiny nozzle. I gotta get me one of those.)​

FWIW part of my interest in the solder/crimp method is that over the years I have had many crimp connections fail, admittedly because they were not "properly done" either by someone else or myself. There's no non-destructrive visual inspection method for an insulated crimp connection so you're depending on proper use of a properly adjusted pair of the proper pliers (that's three "propers!"). There's the "tug test" of course but my arm's not well calibrated for that.

With the Multi-link solder joints (with the exception of the female faston variant) you can tell the soldering was successful right away, and that solder joint is operating on top of a crimped connection. Any problems with heat application (eg the issues I identified from using heat guns) are instantly visible.

So the only way the multi-link part is inherently worse is because of the hypothetical strain-relief/copper-hardening/stress-riser issue which to my observation is eliminated by the intrinsic stiffness of the adhesive shrink tube. Those of you who haven't seen one of these "in the flesh" might want to try one before permanently committing to the DIY crimp and shrink technique. And if you're talking about non-adhesive shrink tube then I'm definitely not buying the superiority of crimp/shrink for moisture ingress reasons.​

 

[Jack]

Adhesive shrink tube, yes!
I have no real objection to using properly soldered joints as lond as they can be isolated from severe vibrations at the connector. I definitely use soldered connections on heavy guage wire such as AWG 10 or larger. For most needs, the crimp connectors and heat shrink have served me well.

 

[Seymour Snerd]

I definitely use soldered connections on heavy guage wire such as AWG 10 or larger.

Good point. I'd forgotten about them. I suppose they escape the whole strain relief discussion since they're so thick, although I tend to wrap them pretty heavily in heatshrink anyway for fear of a short....

BTW I just found a really neat no-flame butane heating/soldering torch (Master Appliance Ultratorch UT40) that comes with the heat-shrink shroud Randy mentions but also a 4.7 mm ID heat tip, and there is an optional 1.5 mm (!) tip as well, for those who want micro-control of where the heat goes. No more clunky heat guns and extension cords for me!

 

[Jack]

That UT-40 seems the ticket! Everyone with a "40" should have this. Entire kit can
be found for under $100.