Hi Frank.

I actually wrote one based on the design spec references to I/L clearances
and our own manufacturing requirements. The 2221 design spec states that a
recc. min trace to edge clearance of .0157 inches be maintained on I/L with
additional spacing on outerlayers based on fab and assembly considerations.

(Our considerations) (W/ IPC-A-600 allowance of .098 inches of edge nicks or
haloing as a guide)
We adjusted our figures for worst case (scored edge):  +/- .002 for A/W
registration.  +/- .002 for drill registration. If taking score you need up
to .0125 inches from center score for blade width and depth of cut and
another .003 inches for blade wander. (the score line can easily be up to
.025 in. wide.

So we set optimum safe distance on outers (from score centerline to nearest
feature) of .035 inches.  Routing allows you to decrease that by the score
adjustments.  Customers are notified when the supplied data violates that
and they may opt to allow a change or accept as it.  We record and file
their response for future reference.

This doesn't apply to heatsinks, ground shields or edge connectors of
course.  And better equipment begets tighter allowances so as we change
equipment we will adjust our house spec accordingly.


Hope this helps.

Steve MacDonald

----- Original Message -----
From: "Franklin D Asbell" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, August 04, 2003 09:42
Subject: [TN] Score to trace criteria


> Is anyone aware of written criteria dealing with scored edge to trace edge
> criteria??? design criteria??? specification tolerance, etc etc
>
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