Larry and Bill have hit the nails on the heads. For crimping, it's
important to achieve a gas-tight connection, by essentially cold-welding
enough Cu of the wire to the Cu or alloy of the crimp device. Too much
of the wrong other materials present, or insufficient crimping force,
may produce weaker, less reliable joints, or rectifying junctions.
Environmental effects can take their toll over time too, so the
application and level of reliability needed should be considered.
For good crimps, the materials should be clean, of course, or typically
protected by thin plating like Sn or Ag or Ni. Some of the plating is
displaced during deformation, and the fresh, clean Cu underneath becomes
intimately bonded to that of the crimp device. Too little deformation
won't provide as much fresh Cu to bond, while too much will damage and
weaken the wire strands. The best crimps can be made with both the wire
and crimp made of bare copper, and thoroughly cleaned just before
crimping. This isn't very practical for routine use, so plated crimps
are much more common, while the wire can be had in all sorts of varieties.
Even tarnished bare Cu wire and crimps can work, as long as the crimping
action exposes enough good copper to bond, rather than just squeezing
them together, possibly forming a copper oxide rectifier (remember
those?). This doesn't matter much in power connections, but may
especially in small-signal applications. Consider the lowly wire-nut, an
insulated helical cone of spring steel, threaded onto two or more wires
that are simply in contact, say in AC power branch circuits. These work
just fine, if properly applied, left mostly undisturbed, and protected
from the elements.
Ed
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
