Earthing. Why crimp and not solder?

[ptp170]

This one has tickled my curosity again since seeing Dave's speaker box tear down.  I've done a couple of searches on here and on Google and haven't really come up with an answer.

Why does one crimp an earthing connector and not solder it??

TIA

Chris

[ludzinc]

A proper crimp is a cold weld, and more reliable that a soldered joint.

That said, a soldered joint is waaaay better that a crappy crimp!

The problem with a soldered joint is that the wire is made inflexible (where the solder wicks up the wire), and any movement of the cable will fatigue the joint and lead to cracking, and worse case breaking of the wire.

Yes, it's an extreme condition that will see a soldered joint fail, but a proper crimp will last in the same situation.

Also, just soldering onto the frame as per the White Van Speaker teardown, is just a poor, mechanically weak way to do it.

[ptp170]

Thanks ludzinc.  Thought it may have been something like that but also thought it might be something to do with the flux in the joint.

Cheers for clearing that up for me 

[mikeselectricstuff]

Because soldering is easier to do badly in production. It's hard to mess up a crimp done with the right tool.

[ptp170]

It's about creating consistancy then as well 

[ciccio]

Safety regulations require that safety ground conductor (and also all mains carrying conductors) be connected both electrically and mechanically (the electrical connection is not allowed to be subject to mechanical stress).  Crimping the wire with an eyelet or a faston terminal connected to metal frame with adequate precautions assures both electrical (crimping the conductor) and mechanical (crimping the insulation) compliance.
You could solder the wire to the eyelet, but you should at least turn the wire inside the soldering hole and make something similar to a knot, and this before soldering. It's complicated and time consuming.
This is done on some products I've seen, but I'm not sure that this will comply with all standards.
I'm pretty sure that soldering the wire to the frame is NOT compliant.
Best regards

[ptp170]

That soldering direct to the frame looked as dodgy as hell anyway.  I've seen Dave comment in some previous videos that soldering to an earthing lug was a no-no in his books also.  Think it may have been the Hakko ripoff or the hot air rework station video?

[N TYPE]

If you want a really top dog connection you can always crimp a lug onto the wire and then feed solder into the crimp connection... then you get the best of both worlds

[KJDS]

If you want a really top dog connection you can always crimp a lug onto the wire and then feed solder into the crimp connection... then you get the best of both worlds

That's fine unless solder wicks up the wire away from the crimp, in which case it leaves the wire brittle.

[David Hess]

The problem with a soldered joint is that the wire is made inflexible (where the solder wicks up the wire), and any movement of the cable will fatigue the joint and lead to cracking, and worse case breaking of the wire.

They make special tools (antiwicking tweezers?) to prevent this.  It is an issue when tinning leads as well.

If you want a really top dog connection you can always crimp a lug onto the wire and then feed solder into the crimp connection... then you get the best of both worlds

If I use a crimp connection this is what I do although the wicking problem noted above is an issue.

I agree with ciccio.  It is just cheaper to do it with only a crimp.  Lots of older test equipment used a positive mechanical connection which was then soldered.

[nanofrog]

If you want a really top dog connection you can always crimp a lug onto the wire and then feed solder into the crimp connection... then you get the best of both worlds

Generally speaking, not recommended IME.

The heat anneals the copper terminal, which reduces mechanical strength.  Solder wicking up the wire and reduce flexibility is also an issue. Either is bad, but combined, is a huge no-no. Do keep in mind though, I'm posting this from an aerospace background, where vibration is a significant consideration (similar for automotive applications).

As per the anti-wicking tweezers, you'd have to crimp first, then solder if you actually want to generate a cold weld between the wire and terminal. Don't see them working well in that situation.

[David Hess]

As per the anti-wicking tweezers, you'd have to crimp first, then solder if you actually want to generate a cold weld between the wire and terminal. Don't see them working well in that situation.

I am sorry if I was not clear.  That is the order I use; crimp and then solder.  Of course if the crimp is done properly then I agree that soldering is usually irrelevant and just provides an opportunity for other problems.  For other than production work, I always suspect bad crimps unless soldered but I have occasionally found bad crimps in production work anyway although usually when they were the cause of failure.

The heat anneals the copper terminal, which reduces mechanical strength.

Do copper and copper alloys anneal at such a low temperature?  I have had to use a torch in the past for this.

Most of the terminals I have used were soft copper but the star ones are hard (kovar?) for obvious reasons.  If the heat from soldering to a hard terminal was a problem, then I would have expected this to be an issue with the ones intended to be soldered to.

[Monkeh]

If you solder a crimp you may as well just have soldered in the first place. The crimp no longer serves a function and the joint is now weakened at the transition from flexible copper to solder.

[SeanB]

Speaking from avionics that is why all your multiplug connections are crimped, not soldered, unless it is inside equipment. The crimp connections stand up to vibration very well. often still having good crimp strength when vibration has actually worn the pin and socket side of the connector to the point where the pin has broken due to wear and the socket has worn through and split into pieces. Major fun to repair after a few years when you have to replace an entire wiring loom section because the small amount of extra cable left to enable you to remove the connector and box has shrunk down to the point where it no longer will reach.

Pilot comes in complaining tail is "twitchy", and you open the panel to get to the control box, undo the connector and the pins all fall out onto the afterburner shield.

[T3sl4co1l]

I don't think the admonition against soldering a crimp is so much to do with that, as disturbing the joint.  Filling it with another metal introduces a different expansion rate material, and also adds a galvanic corrosion concern (though you'd be hard pressed to solder with something that will actually encourage copper to corrode, any corrosion is unsightly at the very least).

Supposedly, pure copper does in fact anneal (at least partially) at lower temperatures than alloys, but I think I'd still be surprised if much changed at soldering temperatures.  That's in terms of stress holding the joint together (hard to measure externally, though you could set up a "typical process" example test) and crystalline / microstructure change (which can be determined with a destructive test).

As an interesting side note, there are materials where you're required to compromise: the best way to solder large Litz cables (say, 10AWG down to #4-0 and the like) is to crimp the (fresh, cold, still enameled) wires in a lug, then submerge the lug in a solder pot until the bubbling stops.  This is only possible with solderable enamels, of course (but, if you've purchased ten thousand strands of unsolderable polyimide, one hopes you've already thought about what you're doing).  Almost certainly, such a joint is not "cold welded", but personally, I can't think how else you'd do it without expensive and hazardous chemicals, so this would be one of those exceptions.

Tim

[nanofrog]

Do copper and copper alloys anneal at such a low temperature?  I have had to use a torch in the past for this.

Yes. You can anneal copper at 700F/371C.

To fully anneal you will need more time, say on the order of ~30min, but even the short time of a solder joint can in fact relax some of the work hardening that's been performed in a terminal (crimped or not), even if just a small amount.

Regarding solder terminals, alloys can be used to shift the temperatures upward of course. But the differences in their mechanical design from crimp terminals is what really distinguishes them, as they don't rely on work hardening for their mechanical properties (i.e. machining used to produce them instead of stamping).

[coppice]

Speaking from avionics that is why all your multiplug connections are crimped, not soldered, unless it is inside equipment. The crimp connections stand up to vibration very well. often still having good crimp strength when vibration has actually worn the pin and socket side of the connector to the point where the pin has broken due to wear and the socket has worn through and split into pieces. Major fun to repair after a few years when you have to replace an entire wiring loom section because the small amount of extra cable left to enable you to remove the connector and box has shrunk down to the point where it no longer will reach.

Pilot comes in complaining tail is "twitchy", and you open the panel to get to the control box, undo the connector and the pins all fall out onto the afterburner shield.

Throughout military electronics solder is only used when some form of crimp is not practical. Crimp always beats solder for reliability by orders of magnitude. As you said, this is especially true where there is strong vibration. However, I'm puzzled by your tale of connectors wearing away. That happens a lot when inappropriate connectors are used - e.g. ones with flat mating surfaces, which vibrate laterally until all the metal has gone. However, the time tested military connectors hardly ever fail like this.

[hamster_nz]

Somewhat related link, from NASA, on how to do it:

http://workmanship.nasa.gov/lib/insp/2%20books/links/sections/201%20General%20Requirements.html

Crimping is an efficient and highly reliable method to assemble and terminate conductors, and typically provides a stronger, more reliable termination method than that achieved by soldering..

[huggy]

This one has tickled my curosity again since seeing Dave's speaker box tear down.  I've done a couple of searches on here and on Google and haven't really come up with an answer.

Why does one crimp an earthing connector and not solder it??

TIA

Chris

I would solder the wire that was already crimped tight to start with, then use a bolt for attachment of the crimp connection.

[con-f-use]

Why does one crimp an earthing connector and not solder it??

As was said: crimping is mechanically more stable and can take corrosion better. You want your earth connection to be as unbreakable and last as long as can be.  Otherwise people die.

[Tandy]

Also don't be tempted to tin the ends of multistrand before crimping you will end up with probably the worst of both worlds. The solder is soft, so may deform in time loosening the connection.

[lpc32]

Speaking of which, can anyone suggest a cheap but decent terminal crimper from CN/HK sources (eBay or other stores)?

[coppice]

I would solder the wire that was already crimped tight to start with, then use a bolt for attachment of the crimp connection.

So you crimp and get a robust connection. Then you add solder, which will wick up the multi-strand wire. Even if you use a tool to limit wicking, you will get some. Now you have a fragile connection, that will break with very few bends or with some long term vibration. Why would you ruin a good crimp?

[G7PSK]

I think that the reason crimping is considered better than soldering is due to tin erosion of copper. Tin in solder erodes or dissolves into copper causing embrittlement, copper age hardens which means that in order to anneal it you need to quench immediately after heating it in order to maintain the crystalline structure, it will revert back to the hardened state over a period of time any way but will be softer in the meantime. Heating from soldering will not anneal copper but will speed the age hardening. The faster you cool from anneal heat the more of the soft crystalline state is preserved. Since the ROHS regulations have been introduced the tin problem is worse than before.

[SeanB]

Throughout military electronics solder is only used when some form of crimp is not practical. Crimp always beats solder for reliability by orders of magnitude. As you said, this is especially true where there is strong vibration. However, I'm puzzled by your tale of connectors wearing away. That happens a lot when inappropriate connectors are used - e.g. ones with flat mating surfaces, which vibrate laterally until all the metal has gone. However, the time tested military connectors hardly ever fail like this.

Right connectors, right sockets, right crimp tooling just right next to a great big afterburner shell, which does tend to create a lot of vibration in operation. If you are using a burner that will go through 20kl of fuel per hour ( note you will not get an hour at full taps with any tank on the plane, it will run dry fast) it tends to vibrate a lot. Was a known issue with high hour count airframes, where you would also have issues with cracking of the airframes as well. wiring looms were very well supported there as well, well laced, sleeved and with a lot of loom clamps. Would have been nicer located elsewhere, but that was where the actuators had to be.