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1996

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From:
"Walker, Don" <[log in to unmask]>
Date:
Mon, 16 Sep 96 15:23:56
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Dave,
     It depends.  Is this a via or a component mounting hole?  How much
current is expected to pass thru the spokes?  Is this a connection for
the ground pin of a chip, and if so, are there any expected noise problems?
How wide are your spokes?
     If this is a via then termal isolation from the ground plane is probably
not an issue.  If you are concerned about a loss in current carrying capacity
then just add up the combined widths of the remaining spokes and check it
against the IPC-I-00005 chart (Conductor thickness and width for internal
and external layers -- IPC-D-275, fig 3-4, p.10).
     If this is a ground connection for a chip, and this is a noisy component
(ie: fast switching/high current), AND there are sensative circuits on the
board, then you may want to consider either making a low impedance repair
to the ground connection OR increasing the impedance on the power supply
side of the chip.  Without going into great detail, you usually want to
funnel the noise into the ground plane instead of into the power plane.
     So, anyway, if the current is ok, and this is not a noise issue, you
are probably fine.

[log in to unmask]
Don Walker

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