We use a small hand held router to "cut" the tang off. To snap the boards
apart from the carrier seemed a bit to harsh on the PCB.
Dan Lorinser
BFGoodrich Aerospace

>>> Robert Cronin <[log in to unmask]> Jan 20, 1997  3:16 pm >>>
I read the responses to the inquiry from Ron Oneal on breakaway tab
remnants. We use the same specifications that John Laur had mentioned
(four 0.036 in. holes spaced 0.050 in. apart). 

  My question has do with the other side of the breakaway holes facing
into the board. I have not found any specific recommendations on how
close traces should be to these breakaway holes. We have a board
(0.062 in. thick) that has a trace that is 0.079 inches away from these
four breakaway holes, and we occassionally have a board scrapped out
due to trace damage during breakaway (our last lot of 40 boards had 1
board scrapped for this). The board is double sided and has a high
expense at this point. Occassionally a very small piece of fiberglass will
tear away with the breakaway portion and damage a trace.

 We have discussed what would be a reasonable trace spacing from the
 breakaway holes to prevent this occassional scrap from happening. The
initial figure of 0.200 inch spacing was deemed way to much by the
design community. Another suggestion of two times the board thickness
(0.124 inches in this case) was proposed. 

1) Has anyone else seen similiar damage of this sort during breakaway ?
  2) Is there anyone who has experience with a miminum trace spacing
from
   breakaway holes that works well ?
3) Is there an accepted standard or Rule of Thumb (such as two times
the
   board thickness) that anyone has used without incident in moderate  
    volumes (200 plus a month)?

Thank You in advance for any comments.
Bob Cronin
Eastman Kodak

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