We are redoing our specification and are wondering if anyone has design 
guidelines that take into account either aspect ratio (or drilled hole size) 
and choice of material into account.  For instance on a 0.125" board with a 
0.0135" hole( ratio 9.4), or a 0.093" board with a 0.0135"  mil hole(ratio 
6.9) do you specify to the designer use of a higher glass transition 
material that you do on the same hole size on a 0.062"        ( ratio4.6)? 
 An example would be polyimide for the 0.125 thickness, multifunctional for 
the 0.093 thickness and standard FR-4 for the 0.062 thickness or a chart 
that shows increasing thickness or aspect ratio versus what material should 
be used.  Anybody have any thoughts on this or comments?  Or is there any 
fabrication industry consensus?
          Thanks in advance for your inputs;
               [log in to unmask]  

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