Scott,

Try IPC-2221 and IPC-2222.  These replace the old IPC-D-275.

Good Luck,

Phil Nutting
Manufacturing Engineer
Kaiser Systems, Inc.

-----Original Message-----
From: Scott A. Bowles [mailto:[log in to unmask]]
Sent: Tuesday, September 12, 2000 6:02 PM
To: [log in to unmask]
Subject: [TN] PTH clearance/spacing to conductor


Scenario: We have a customer, that by design has eliminated the pads for
nonfunctional plated through holes on internal layers because of spacing
issues.  The spacing between the edge of the hole to the edge of the trace
is
0.007".  If we drill the hole oversize by 0.005" to allow for plating, the
spacing is then reduced to 0.0045".  There is also etchback of approximately
0.0005" that further reduces the spacing to 0.004".  Now this is before
taking into account for any layer shift, drill misregistration, etc., that
standard manufacturing allowances are supposed to cover.

Questions to all:
Is there an IPC design specification that states how close the edge of a
plated through hole should be to a trace on an internal layer?  What is the
minimum spacing that you would design between a plated through hole to a
trace, on an internal layer for a Class 2 board, realizing that performance
and reliability is of major concern?

Thanks for any input,
Scott

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