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January 2000

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Subject:
From:
"Hiteshew, Michael" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 17 Jan 2000 11:24:12 -0500
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Matt,
        My recommendation would be to NOT depend on the plating in the
mounting holes to ensure your connection to ground. Once those holes are in
compression, there's no guarantee that they will be reliable; plated holes
in compression are known to crack. Bring your ground to the surface using
vias outside of the zone of the screw compression. More vias are better than
less since it will reduce ground impedance.
        Also give serious consideration to using at least one terminal lug
under one of the screws. Solder the attached wire into a plated hole to
ground. This will ensure a ground connection (via the wire -> lug -> screw
-> chassis path) even if corrosion builds up on the tin-lead surface
plating. Use redundant and reliable methods whenever possible. Once it's in
space, it's real hard to fix it.

 Michael Hiteshew
 Lockheed Martin Launching Systems
 [log in to unmask]
 (410) 682-1259

> ----------
> From:         Matthias Mansfeld[SMTP:[log in to unmask]]
> Reply To:     [log in to unmask]
> Sent:         Sunday, January 16, 2000 11:30 PM
> To:   [log in to unmask]
> Subject:      [TN] Recommended design for grounding holes (space
> applicatio
>
> Hello all,
>
> Please apologize my cross-posting in DC, TechNet and PCD List
>
> I have  a 8 layer PWB for a space application which will be fixed with
> screws in the housing. The screw holes must be used as grounding
> contacts.
>
> My question is: Is there any standard or good recommendation for the
> design of these holes? The GND potential is one of the inner layers,
> but it is no problem to route it to the outer layers, if necessary.

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