Hi Darrel,

Think of any oxide layer as an insulator - poor carrier of current.
As long as the bolts use a star washer that punches through the
oxide when turned down, you're *probably* okey.  Depends upon alot
of things though - how thick the oxide layer is, if the bolts
are going into floating pems (not the best connection to ground
anyway), torque on the bolts, etc ...

Don't know about OSP or other options for copper finishing.

Darrel Therriault wrote:
>
> Technet,
>
> My Mechanical Engineers just brought something to my attention that I would
> like to get some opinions/advise/info from the TechNet expertise.
>
> We have recently switched from HASL to OSP (Entek 106 I believe) finish for
> our boards.  We run a ground plane around the perimeter of boards and
> backplanes to help with EMI shielding and grounding in general.
>
> Their concern is with the change to OSP finish, we are seeing bare copper
> now that is tarnishing/oxidizing and is this still an acceptable grounding
> contact where it bolts to the chassis or contacts a cardcage?
>
> Other Questions :
>
> 1.   When the board is processed (IR) does the OSP get removed or does it
> remain, and
>      is it conductive or an insulator?
>
> 2.   What are the options for having the ground perimeter copper finished
> so it won't
>      oxidize and will provide a conductive surface for acceptable
> ground/EMI contact?
>
> I would appreciate any comments/opinions/advise.
>
> Thanks..........DT

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