Sounds like you have interplane separation.  It is a separation of the
  plated copper on the hole wall from the edge of the inner layer.  Dr.
  Alan Poskanzer wrote an article in Plating and Surface Finishing for
  March 1990 that you might want to read.  It's title is IP Separation: Its
  Causes and Cures.  The magazine is by the American Electroplaters
  Society.  Since we are on the subject, I'd like to piggyback on this and
  ask:  Is anyone seeing post separation of the Tg 170 range materials and
  if so do you have a root cause?

   ----------
  From: [log in to unmask]
  To: [log in to unmask]
  Subject: Interconnect Failure
  Date: Monday, November 18, 1996 8:17AM


  RECENTLY WE FIND INNER LAYER OPEN COMPLAINT IN EIGHT LAYER BOARDS FOR ONE
  PARTICULAR PART NUMBER. ON MICRO SECTIONING WE FIND NO INTER CONNECTION
  BETWEEN HOLE COPPER AND INNER LAYER (SEVENTH LAYER).
    THE CONSTRUCTION 1,2,7 & 8 ARE SIGNAL LAYERS REST ARE GROUND LAYERS.
    TWO TO SEVEN ( INNER LAYERS HAVE ONE OUNCE BASE COPPER) ONE AND EIGHTTH
  LAYER
  HALF OUNCE BASE COPPER.
     COPPER INSIDE THE HOLES IS >25 MICRONS. WE DONT FIND ANY WEDGE VOID OR
  PINK RING.

    THE CUSTOMER BAKES THE BOARD BEFORE ASSEMBLY AND ALL BOARDS PASSED
  ELECTRICAL TESTING. BUT AFTER ASSEMBLY THE CUSTOMER REPORTS INNER LAYER
  OPEN.

  CAN ANYONE THROW LIGHT ON THE ABOVE PROBLEM?

  Thanks in advance


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