Has anyone built a 4 layer mulitlayer PCB utilizing  Rogers RO4003/4350 
materials for two layers and 
FR4 for the other 2 
Questions :  what type of stack up did you use
  we are imagining  0.020 RO double side material FR4 prepreg and 0.020 FR4 
double side
  for a finished of aprox 0.062

What happens to flammability rating if you hybrid 94VO rated FR4 with non rated 
RO4003
Can we still expect UL approval if we utilize FR4 and RO4350 which is 94VO rated

Also what sort of cost saving is to be expected by utilizing FR4 for the non 
critical layers.


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