Crimping and Soldering Breaker Connectors

I see it done in many higher power commercial and industrial electronics and electrical applications so I have no problem with doing it as well. Usually its best where the wire or cable has adequate support to minimize bending and twisting near the crimped and soldered ends.

When done right its a good solid connection that lasts. When done wrong its just like when a solder or crimp is done wrong, it eventually fails for one reason or another.

In a corrosive environment (i.e., marine applications) soldering trumps crimping. For smaller connections, one might crimp to hold things together while soldering, but soldering is the preferred connection method on sea-going vessels.

Soldering is allowed by the NEC - IF the connection is *mechanically* and electrically secure *before* the solder is applied (Section 110.14(B).)

Conductors shall be spliced or joined with splicing devices identified for the use OR by brazing,welding,or soldering with a fusible metal alloy.Soldered splices shall first be spliced or joined so as to be MECHANICALLY and electrically secure without solder and then soldered.

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I've taken this line from the comment in post #1...

If you solder the cables, you effectively make it into a solid end on the flexible materials. This becomes a stress concentrator at the point where the solder ends and could be many mm inside the insulation.

It's a very good point having the solder extend inside the insulation. A stress concentrator should not be allowed unless cables are not adequately supported ya think. I would prefer the crimp and solder myself as a little added quality, making things better than what is commonly thought necessary has made many a reputation.

Having thought this through a little more in the last day, I now have a stronger view on the matter.

If the crimp is done properly, then soldering in addition is a VERY POOR suggestion. In addition to the issue of making the end of the conductor solid and effectively eliminating the design work done by the crimp product designers on their strain relief you are now introducing additional thermal and chemical issues to the process.

Soldering could introduce contaminant (solder) into the interface zone of the connector.

Soldering will introduce flux into the spaces between the conductors and inside the insulation. Due to the thermal profile, some of that flux will be in the active state and cannot be cleaned.

Soldering could lead to melting of the insulation and then some of that ending up on your connection interface.

Soldering introduces another metal group into the potential galvanic processes with real potential consequences.

What solder do you intend to use? If it's eutechtic lead/tin, then if operating temperatures get relatively high (but still less than 80C) then there are issues with lead oxidation. If it's one of the new "lead free" solders then you have concerns with "tin whiskers" that could dislodge into other circuits.

The thermal cycle of soldering may impact the integrity of the crimp itself (due to differential thermal expansion.)

I suppose what I'm leading to is that if you decide to "solder", then you really need to include the POTENTIAL FAILURE MODES that this additional process brings with it and the ASSOCIATED RISKS.

Background to this: 20 years auto industry involved in process and quality engineering and warranty analysis including wire crimp and soldering processes at the same plant.

You make some very strong points, but based on the assumption that the "crimp is done properly", which is fine in a factory environment where you have quality control procedures in place, and have the opportunity to control work practices. Out in the real world, one encounters very few people who understand how to crimp properly, what the appropriate tools are, and no idea how to inspect/test the results. What you wind up with are more bad crimps than good ones. My experience working on boats is that 90% of all electrical problems are connection-related, and in most cases, resulting from bad crimps (except in the cases where someone has just twisted two wires together and covered them with electrical tape). I do not recall ever having encountered a failed soldered connection on a boat, but I will admit my experiences are limited...

"Proper Crimping" is mentioned. I have seen many people mistakenly place the crimp crimp on the wrong side of the connector. The indentation should be on the seam side of the connector. Panduit has a website that spells this out.

I would go along with "Just an Engineer" on this. A correctly applied crimp is capable of handling the current the cable is rated for. We regularly work on 24Vdc with 200A continuous and other circuits at >1000A (1500Hp marine diesel start circuits) and we always use crimps, as does every ship yard. Remember that at 24V we are very intolerant of voltage drop.

Ref inspection:- for top grade application the tool, the crimp and the cables are matched, as is possible in manufacture. This gives a guaranteeable joint and this can be seen by the die marks in the crimp. Look at what is used in the HV overhead distribution systems.

Inspecting a soldered joint is not so easy in my opinion. It is difficult to see a dry joint and it is impossible to know what type of flux has been used. Furthermore, it is difficult to solder heavy cables, 50mm and up, without damaging the insulation.

We don't use a calibrated system as we cannot guarantee what cable we will be working with or the manufacturer of the crimps. I still cannot remember any failures in more than twenty years.

About the only plus with solder is that it can seal the insulation to the cable, thus reducing wicking of moisture in wet environments (as stated by Charlie Warner) but the downside is that if the wire has already been wet, as in repairs on board, then it is difficult to make a good solder joint without using a corrosive flux.

regards Chas

The best connection on larger wires is CAD welding (Thermite Based).

No crimp or solder to worry about.

Not cheap, but the best connection possible, even when joining dissimilar metals(like copper to steel).

-- Ole Sparky

FWIW

You are dealing with two issues: 1 the spec call out ; and 2 what ever you think is best. Guess which one wins out ( P.S. it's not what you think).

If the mass transist system is to be used in places like where I live then the crimp is used for mechanical/electrical connection and the solder is used to exclude the corrosive effects of salt/water from winter road maintaince.

That is why all the boater people like the soldered connection as well. Its the salt getting into the connector corrodding it to nothingness.

Having dealt with driving vehicles for upwards of 300,000 km and 15-20 years any electrical repair or addition (ie: trailer lights) are allways Western Union Spliced, soldered, and shrink tubed.

Right. No matter what technique you use to make a joint, cover it with shrink tube. Not just any shrink tube however- it should have the internal melt adhesive as well...

John,

I just got through installing a couple of 1250kw @ 6.6kv pumps.

The spec called for crimp. Crimp, properly done, will be just fine.

Cheers

Stu.