"Ross Herbert" wrote in message
...
On Mon, 21 Sep 2009 09:41:18 +0100, "Arfa Daily"
wrote:

:
:"Ross Herbert" wrote in message
.. .
: On Fri, 18 Sep 2009 08:28:42 -0700 (PDT), GeneO
wrote:
:
: :Have been Googling the proper way to clean plated electrical contacts
: :but either get nothing if use " or a lot of nonrelevant hits without.
: :
: :Am interested in any suggestions esp how to remove the nonconductive
: xides.
: :
: :If a connector is too damaged would also be interested in what are
: :considered the best type replacement.
: :
: :Thanks
: :
: :Gene
:
:
: I don't think I have ever come across a "plated" electrical contact. In
my
: experience electrical contacts are always a solid material such as
brass
: (cheap
: and nasty - often used in electrical appliances) or a more exotic alloy
: material
: such as nickel-silver. The contact material used is dependant on the
: application
: (AC or DC and whether inductive) and the magnitude of the current being
: handled.
:
:
:I'm sure that you must have, Ross ?? I'd agree with you on 'solid brass
:contacts' in clunky mains power switches etc, but elsewhere, many
contacts
:seem to be plated rather than solid. For instance, I just put the word
:"plated" into the search pane on one component supplier's website, and it
:came back with 59 items, most of which were connectors with a variety of
lating materials quoted for their contacts, including gold, silver &
tin.
:Similarly, a quick look in a catalogue at switches, reveals many to have
:either gold or silver plated contacts. Also, many relays have contacts
:described variously as gold "plated", "covered", "overlayed" etc. It is
:these contacts that I find you have to be careful not to use any kind of
:abrasion on, for fear of going through the very thin layer of plating. I
:generally find that pulling a piece of dry cardboard through things like
:relay contacts, is enough to clean them. A tiny spot of cleaner/lubricant
:introduced to the contact gap, finishes the job off.
:
:Arfa
:

My experience has been mainly related to relays of both open and enclosed
types,
from miniature pcb mounted types for signal transmission to heavy duty
high
current capacity types. I will agree that particularly for the low level
signal
types the manufacturers often "enhance" the contact material by adding a
gold
"overlay". However, the actual relay contact will be made of some alloy
material
such as silver-palladium or other mixture. The contact is usually rivetted
or
welded to the spring leaf, which is probably a plated phosphor bronze
material,
while the gold overlay on the contact pips is simply to reduce contact
resistance due to oxidation through lack of a wetting current. A typical
relay
of this type, which I have on hand, is the Fujitsu FBR46. With such
relays, as
you have mentioned, you never use abrasive methods of cleaning or
burnishing but
with gold as an overlay this should not be necessary. The problem with any
"plated" contact is that once the plating material has been lost either
through
repeated operation or arcing etc, the base contact material is all that is
left.
In cases where no plating is used unless the contact material is one of
the
recognised traditional materials such as nickel-silver, silver-palladium
etc,
the electrical performance of the contact will be unreliable. Such a relay
used
for heavy current carrying capacity which I also have on hand is a Fuji
HH62
witha contact rating at 10A. In this case the contact material is simply a
"silver alloy" - probably made to Fuji specification. Such contacts can be
burnished and reconditioned using abrasive tools.

It may be that later contacts, manufactured for cheapness, do not use
traditional solid alloy contact material which is rivetted or welded to
the base
contact spring material, and by so doing they would, in my opinion, be
inferior
to the types which do.

OK. Understand what you're saying ...

Arfa