Robert Cronin wrote:
> 
> 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

Bob, Just a suggestion for your production people would be to switch
from actually breaking parts out of panel to using pnumatic shears to
cut the board out. I have used this methode in a past life with a great
deal of success.

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