James,
I think you have an oxidation/corrosion problem. There are dissimilar metals (solder, housing, screws, ect.)
involved that will create ground problems when they contact each other in humid conditions.
The best advise I have is don't use screws for grounding. You need to solder the housing to the ground plane.
Run the ground plane to the rest of the chassis through a connector (gold to gold). Then use specially designed
grounding straps to connect with the chassis. Other wise there will be permanent problems.
David A. Douthit
Manager
LoCanm LLC
"Marsico, James" wrote:
> This specific application doesn't warrant a Teflon substrate, I think it is
> FR-4. Let me clarify one thing, It's assumed that the material is cold
> flowing, causing ground interruptions (this is an RF Engineer's assumption).
> The fact is that, after time in service, the main complaint from the test
> guys is electrical problems associated with a degenerated ground. It could
> be associated with moisture entering the housing causing the tin-lead
> plating on the ground plane, which is in direct contact to the housing via
> screws, to become slightly oxidized. This is not a hermetically sealed
> housing. In fact, there is a hole in it to allow for a pot adjustment.
> Which leads to another question... are there bulk-mounted pots available,
> mounted directly to the housing wall, which would eliminate the hole?
>
> Jim Marsico
> Senior Engineer
> Production Engineering
> EDO Electronics Systems Group
> [log in to unmask] <mailto:[log in to unmask]>
> 631-595-5879
>
> -----Original Message-----
> From: Crepeau, Phil [SMTP:[log in to unmask]]
> Sent: Tuesday, December 09, 2003 4:47 PM
> To: [log in to unmask]
> Subject: Re: [TN] GOOD RF GROUND
>
> hi,
>
> is the fastener loosening up because the laminate is teflon based
> (which is common in rf applications)?
>
> phil
>
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