Ron,
In the future you could design the breakaway tab to break flush.
Our design uses four 0.036 holes spaced 0.050 apart and
inset from the board edge 0.015.  
The solid part of the tab is 0.100, slot edge to slot edge. (0.093 bit)
This works great if the non perferated side of the tab is connected
to scrap. When the board is broken out the tab is still with the scrap.
If you have board edges on both sides of the tab that need to be flush,
then someone has to break the tab off whichever board the tab ends up on
since only one perf will break.  Like a wishbone.
I believe a note will be required on existing designs.

---------------------------
John Laur
Rockwell Automation
Allen-Bradley Co Inc.                 
1201 South Second Street
Milwaukee, WI 53204
+1 414 382 2162 (fax)
+1 414 382 2393 (phone)

[log in to unmask]
---------------------------

> From [log in to unmask] Thu Jan 16 20:43:31 1997
> Resent-Date: Thu, 16 Jan 1997 20:28:01 -0800
> Old-Return-Path: <[log in to unmask]>
> From: Ron Oneal <[log in to unmask]>
> Reply-To: [log in to unmask]
> To: [log in to unmask]
> Subject: FAB
> Resent-From: [log in to unmask]
> 
> We design a number of circuit boards which are oddly shaped, and must
> use breakaway panels and tabs in order to facilitate assembly.  We use a
> router bit to create the void between the panel and the board itself,
> but leave a small breakoff tab for the connection.  Our previous
> fabrication vendor would smooth the rough burr left by these breakaway
> tabs, but boards from a new vendor are arriving with the rough burrs
> intact.
> 
> Question:  Is there an IPC specification that dictates the allowable
> height of these burrs, or do we need to specify on the drawing that the
> height be witnin "X" mm of the board edge??
> 
> Thanks
> 
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