Terry Davey commented:


>I thought the use of good gold-plate connectors completely solved this
>problem. Can anyone else confirm or deny this?

Bellcore requires lubricant on gold plated connectors, too. This is in
TR-NWT-000078. The potential problem with gold is porosity, and also the
reduced friction wear from mating cycles benefited by application of
lubricants. See also TR-NWT-001217 Generic Requirements for Separable
Electrical Connectors Used in Telecommunications Hardware

>In my understanding fretting corrosion is associated only with "tinned"
>mating surfaces on connectors, accelerated by relative movement of the
>surfaces caused by vibration or thermal cycling.
>I believe that the corrosion mechanism is for microscopic "balls" of
>insulating black tin oxide (stannic) to form on the surface(s).

something like that, I agree.

>Lubricants
>reduce friction and exclude oxygen, preventing the oxidation.

And this is true for all metals, regardless of the fretting effect.

>My solution so far for high reliability telecomms systems has been to
>recommend gold-plate connectors, so if I'm right on this the expense of
>applying lubricant has to be traded off on the cost-saving on connectors.

Bellcore requires 30 microinches (.75 micron) of noble metal (50 is
preferred) plus there is a performance criteria requiring certain
connectors to be qualified for use. The lubricant is also required unless
the connector can be qualified without it. This applies to harware sold to
U.S. BOC's under contract terms requiring TR-NWT-000078 which is pretty
common.

My own experience with this was at Fujitsu, and I had the same attitude as
you express, but after seeing the results I do believe it is very
beneficial to use the Monsanto OS-138 lubricant. This is a synthetic oil
developed for lubrication of turbine engines, and is very inert and stable.
has a consistency like Karo syrup (bleve that would be treacle for you) at
room temp, you dilute it with naptha and spray/dip on a thin coat, solvent
evaporates leaving a protective layer which fills pores, etc.

Jerry Cupples
Interphase Corp
Dallas, TX 75234 USA