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. It
is NO pads-only design (because of much SMD stuff, they prefered
solder mask as the smaller disadvantage against microvia technology or
filled blind vias..)

- Standard like in consumer electronic: Just plated through and
connected to the GND plane, ourer pads at least as big as the screw
head?

- non plated with or without nonfunctional pads in the inner layers
(don't reach to the inner hole diameter), outer pads as big as the
screw head and with separate vias in the neighbourhood connected to
GND?

- for each of the above mentioned designs: outer pad to the housing
side only, to the screw head side only or on both sides?

Thanks a lot in advance, regards
Matthias Mansfeld
-----------------------------------------------
Matthias Mansfeld Elektronik
* Printed Circuit Board Design and Assembly
Am Langhoelzl 11, D-85540 Haar, GERMANY
Phone: +49-89-4620 0937, Fax: +49-89-4620 0938
E-Mail: [log in to unmask]
Internet: http://www.mansfeld-elektronik.de

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