Hi Gary,
 
If they're punching through an existing TAB, you will probably be ok.   
However, from Dieter's quote out of the IPC-2222: 
"Rejections can occur when the edge defect is greater than 50% of the  
clearance to edge spacing. Brittle material or heavier glass weights  increase 
this risk."
 
I find that statement very telling.  Your clearances from the edge of  the 
board are not that great.  You'll need to know the thickness  of the boards 
& the glass content of the material to determine your  clearance needs.  

Cherie
 
 
In a message dated 2/26/2013 7:20:18 A.M. Pacific Standard Time,  
[log in to unmask] writes:

Our Asia  Pacific CM is requesting permission to use punching tools to 
singulate boards  from panels.

My experience with punching tool sets is that their cost  outweighs the 
benefits, but this CM states they can make the tool sets at a  beneficial cost.

Our initial reaction is that it's okay, as long as  components are not 
stressed by the punching action of the male die onto the  female die, and as 
long as the exterior board profile dimensions match the  Gerbers.

Earlier today I posted about edge spacing, and was also  curious whether 
minimum edge spacing would matter in the world of punched-out  boards.

We saw the CM's panel design, and it was a combination of mouse  bite and 
v-score that really didn't look essentially different from what we  see 
without punching tools.

There doesn't seem to be any IPC guidance  regarding punching tool accuracy 
or designing panels for punch.  Any  comments welcome.


TIA and Best Regards,

Gary M. Koven,  C.I.D.
InVue Security Products

Charlotte, NC, USA
Board Of  Directors, RTP  Chapter

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