Why crimp an extension over soldering an extension? Ignoring any weatherproofing, a crimp can get corrosion while the connection inside a solder joint will not. I have a project going on now that requires exactly this and it never occured to me that a crimp butt splice is better than interlacing stranded wire and making a solid connection???
I worked in a wire manufacturing house in another life. I know more about correctly crimping contacts than I ever wanted to. I've also soldered a shit ton and know it's weaknesses. I've had audio shops solder contacts and have them fall apart in my hand. Why an audio shop would solder a fine conductor large gauge wire when is was in a compression contact is beyond me. They tend to not be the smartest people. Here today gone tomorrow type of businesses, I digress.
If you shouldn't solder 750 kcmil than you shouldn't solder 12 gauge. The principal is exactly the same. The only time to solder is when the connector forces you to and SMB PCBs etc.
I could make a post that would take me hours to write over why crimping is better than soldering. But I'll make it brief unless I end up having more time at work today. A quick google I came up with this:
ABYC (E-11.16.3.7), “Solder shall not be the sole means of mechanical connection in any circuit”. Further, crimping provides a solid mechanical connection resistant to “cold joints” breaking under fatigue, and removes strain.
Crimping will make a better electrical connection. You can google cut aways of the contacts comparing solder vs. crimp.
It is difficult to verify how far up the wire solder has traveled under the insulation. The issue here is vibration. The solder makes the physical connection weaker and in a vibration environment: aviation, navel, automotive, etc. crimping is superior.
Flux residues can cause corrosion. No Flux solder sucks.
http://www.pinrepair.com/connect/
The crimp method is the most popular because:
- There is no need for soldering; therefore, installation time is reduced.
- It takes an experienced technician about 15 seconds to install a crimp-crimp connector, thereby greatly reducing the time required to create cable assemblies. This is very important in today's cabling market where time is of the essence and fewer technicians are being asked to maintain more and more equipment. Digital video, computer and network cabling is almost universally crimped today.
- Crimped connections, done correctly, are superior to soldered connections.
- A good crimped connection deforms the metal sufficiently past the yield point, but not too much, so that the "spring back" keeps the connection secure, even under thermal cycling (the coefficient of expansion of the two metals might be different) and vibration.
- A good crimp connection is gas tight and won't wick: it is sometimes referred to as a "cold weld".
- Like the solder method, it can be used on solid or stranded conductors, and provides a good mechanical and electrical connection.
Disadvantages of solder method:
- It takes more time to terminate than other methods.
- "Cold" solder joints can cause problems if the connector is not soldered properly to the cable, observing solder flow through the contact solder hole.
- Soldered joints between contact and center conductor can work harden if subjected to excessive vibration during use and develop micro-cracks followed by solder fatigue.
- Soldering can be inconsistent and subject to failure as a result of mechanical or temperature stresses.
- Care must be taken to control heat applied during the soldering process and not allow solder to wick or distort the cable dielectric
If a connection is solely soldered there'd be no mechanical connection, nothing to physically hold the connection in place other than the solder itself functioning as a metal "glue" which was not solder's intent.
Lead(Solder) is not as good a conductor as copper. The resistance of copper is 13 times less than lead so why introduce it into the circuit if not necessary? The crimp will be a copper connector and a copper wire and
the crimp pressure with seal out air and moisture creating a low resistance connection
NASA-STD-8739.4 Crimps
NASA-STD-8739.3 Solder
The main difference you will see from these two doc's is that soldering is preferred for SMD. Cabling and interconnections is nearly 99% crimped. The main benefit from crimping is reputability and there is less room for error.
Do what you want obviously, but I crimp and my connections don't fail. You can always heat shrink tube over your crimped contact if you are really concerned. They make heat shrink with glue inside too. Again, a proper crimp is air/gas tight aka cold weld.