[SI-LIST] : Routing Through Connector Pin Field

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From: Kai Keskinen (keskinen@nortelnetworks.com)
Date: Mon Jun 05 2000 - 12:43:20 PDT


Hello SI Community:

An interesting discussion has arisen here during a development program. We
have a 20+ layer backplane which has a great number of tracks so we have to
route differential pair (2.5Gbps, ~150ps rise time at connector pin) through
the connector compliant pin field. The edge coupled differential tracks have
to be routed such that each half of the pair goes around a connector ground
pin. So in effect, we have a closely coupled pair which is then loosely
coupled around the pin and then tightly coupled again after the pin. Going
to broadside coupled or avoiding the pins are not possible. Our internal
discussion revolves around the best way to maintain a constant impedance
during the undulation around the pin and the effect this undulation will
have on the signal. Options we have include adding a pad to the through hole
on the layer in question and increasing or decreasing the anti-pads on the
reference layers above/below the stripline layer. Doing a 3-D model is an
option but painful. Any comments from the community at large?

Thanks in Advance,

Kai Keskinen
Equipment and Network Interconnect
Nortel Subsystems and Performance Networks (NSPaN)
(613)-765-3506 (ESN 395)
keskinen@nortelnetworks.com <mailto:keskinen@nortelnetworks.com>

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