Erika...
            There is no "standard distance", Maybe a minimum based on where it is used,
   thickness requirements. connector constraints, voltage requirements, impedance 
  concerns,etc. Talk to the box man and see what he/she has designed into the final board
  thickness. Then talk to the fabricator to see if there are any concerns. 4- layers is not 
  cutting- edge technology. When you finalize the thickness, it should be on the master 
  fabrication drawing and should remain the same unless there is a technical requirement 
  change. Hope that helps.

  Regards,
  Bob Vanech
  BVAN Enterprise
  ----- Original Message ----- 
  From: Sanchez-Benavides, Erika 
  To: [log in to unmask] 
  Sent: Tuesday, May 30, 2006 4:41 PM
  Subject: [DC] Distance between external and internal layers 4Layer FR4


  Hi!


  What is the standard distance between External and internal layers
  for 4-layer board, FR4?

  Should I specify an specific distance in my notes?
   In any case, the key point is that whatever is specified now should not
  change later.

  How can I get this?

  Thanks in advance for your help.

  Erika

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