Michael Ross via EV wrote:
I have to give Jay big yay for the perfect answer. Solder loses any ability
to create a useful joint when it liquifies, hence the need for some very
solid mechanical joining means. The failure modes are truly bad with power
involved.
Agreed; a good answer.
Solder is mechanically weak, and has a low melting point. It's fine for
little low-power stuff, when there is negligible shock and vibration. It
is, after all, how 99.9% of all electronic connections are made on
circuit boards. :-)
But, it's a poor choice for high power, things that get hot, or where
there is mechanical stress.
Crimping to make gas-tight fused connection is the only acceptable joint.
Well, to play devil's advocate... It is *possible* to make excellent
reliable strong high-power solder joints. It's just harder to do.
Soldered copper water pipes are one obvious example. Hams have used this
for high-power RF antenna work for decades. Other examples are
silver-soldering and brazing. Both use stronger, higher-temperature
"solders". You'll find them used in all sorts of high power electrical
work, like attaching wires to commutator bars in a motor, or big lugs
onto transformer windings.
But most people just use a good crimper instead. It's easier. If the
person doing the work is unskilled, a good crimper can make up for it.
Note: There are lots of BAD crimpers out there, too. Cheap,
hardware-store toys, and "hammer crimpers" that don't produce good
crimps. If forced to use one of these, it is a good idea to *also*
solder the connection. The crimp provides at least some mechanical
support, and the solder provides the electrical conductivity and keeps
out corrosion.
On stiffening the wire from wicking: This depends strongly on how you
solder it. I have a solder pot. To solder a big lug on a cable, I put
flux on the wire, put it in the terminal, crimp it, then dip it in the
solder pot for 2-3 seconds. That's all it takes. There is no time for
solder to wick up the wire.
In any case, you don't want the wire coming out of a crimp to be
unsupported. It will still break strands (soldered or not) if allowed to
flex at the crimp. You must have some kind of anti-bending support or
strain relief. This is usually provided by the shell of the connector,
or the crimp terminal itself may have an insulation grip.
--
Imagination is your preview of life’s coming attractions. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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