Hi all,

Recently I have had some discusions regarding breaking up large (greater than
1" circle) conductive areas.  Both Mil-Std-275 and IPC-D-275 recommend doing
this to prevent blistering.  During prototyping of several military, RF PWAs we
found that the 'breaking up' of the ground planes adversely affected perfor-
mance.  In discussing this with one of our fab suppliers to determine what
compromises we could make to improve electrical performance, I learned that
'breaking up' the ground plane was no longer necessary due to improvements in
processes and materials.  I was told that there were problems in the late 70s 
and early 80s but not any more.  

Are the specs cited out of date with respect to this issue and current processes?  Should I be concerned about not breaking up large conductive areas?  If yes,
how large is too large?  That is, is a 1" circle still a valid threshold?  

This is more of a general question but the design specifics are - 6 layer MLB,
11"x 9"x .063", SMOBC, layers 1, 4 and 6 are ground planes with layer 5 a 
controlled impedence layer.  Largest area not broken up by holes is approx. 8 
square inches.

Thanks to all for your comments and opinions.

Jeff  

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