fj12ryder wrote:
"Mere oxygen turns copper dark over time." But doesn't that "patina" actually protect the underlying copper? As opposed to iron oxide, rust, which just flakes off. There are other issues involved I'm sure, but the fact that copper turns dark doesn't indicate the copper is damaged.
Sort of, the problem is that there is not only Oxygen in the air, there is MOISTURE in that same air (it IS the same air that we breathe).
Oxygen and moisture together create a thin oxidation layer on the surface of the copper wire. That in it's self isn't a big issue, the problem is that oxidized layer has considerable resistance. Not to mention, that layer does not stop at the point the wire is covered, it keeps CREEPING, right under the cover.. Partly due to the moisture in the air which gets wicked up the wire strands..
Oxidization of copper also severely weakens the copper, basically over time as it oxidizes the strands get weak and start breaking.
Now, for adding insult to injury, toss some road salt or salt water spray into the mix and watch that unprotected copper wire rot before your eyes!
That is one of the reasons marine grade wire is pretinned..
Yes, crimping "packs" the wires together tightly, but often not enough to prevent moisture and oxygen from creeping into the crimp.
There is also an issue with over crimping and under crimping. It is extremely easy to crush the wires making the wire BRITTLE just before the crimp and that results in strands simply breaking off all on their own, add in vibration and that crimp will fail..
Under crimped and the wires tend to simply pull loose and you will also have a very high resistance connection..
Name of the game is making a very low resistance connection which is also mechanically strong and well protected from air and moisture in the air.. Solder CAN do all of that, but it has been maligned by those that really don't understand how to properly solder..
By the way, ALL of the components like resistors, transitors, ICs, capacitors and such in "Avionics" equipment are ALL SOLDERED to the circuit boards, those parts are not "crimped" to the boards..
So, if "vibration" is the supposed reason as to why crimps are used in connectors perhaps you could explain why important electronic parts in airplane radios and systems are only soldered to the board and not crimped?
