In your message dated Monday 18, November 1996 you wrote : > > 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. Is the separation in the electroless copper layer or are these direct plated boards? If the evidence suggests cracking of the electroless layer then it could be due to too fast a plating rate causing coarse grains and brittle deposits which crack under thermal cycling. Electroless copper must be a fine grain system and the plating rate tightly controlled (typically <2.5 microns in 30 minutes). The stress of z-axis thermal expansion is greater at the surface layers than in the centre due to the laminate expanding more than the copper which is why failures will tend to occur on the outermost inner layers. Good luck, Paul Gould EMail [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************