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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