Jim,  I've seen the same "anamoly" in multilayer boards.  The areas in question were the same on every board, but did not seen to spread or propagate during our (limited) temp cycling.  We felt it was delamination due to thermal stress from a particularly hot component (PTH installation) adjacent to a large buried ground plane.  However, neither our cross-sections or those of our board supplier showed any evidence of actual delamination or disbond in the cross-sections, ie no areas of separation.  The cross sections did (in our opinion) have some areas which appeared to be resin starved, but we couldn't reject them on that.  The boards did not fail during our testing but we were still concerned about long time reliability.  We ended up scrapping the boards and remaking them in a higher Tg laminate.  The "anamoly" went away ...

Sheila @ Tracor AES

----------
From:  PELCHAT_JM[SMTP:[log in to unmask]]
Sent:  Friday, August 14, 1998 9:15 AM
To:  [log in to unmask]
Subject:  [TN] Wavy board surface - NOT delamination?

        We have a 12 layer board with a heavy ground layer that had
        three edge BNC type connectors installed using a mini wave.

        The circuitry tracing away from the connectors is surrounded by
        vias.  There is a distinct lightening of the board material I
        have typically associated with measling.  This lightening
        however, doesn't have any fiber crosshatching I am used to
        seeing with measling, not does it look like classic
        delamination.  I have documented the event as delamination for
        lack of a better description.

        The opposing consensus is that it is "merely" soldermask
        discoloration.  Without classic delamination or measling
        features, I don't feel I have a leg to stand on to call it
        anything other than that. (Don't worry though - both sides feel
        the Customer needs to review the board no matter WHAT the defect
        is).

        Does anyone have any opinions?

        Jan Pelchat

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