Technetters,
        We have experienced a strange problem on a recent lot of assembled PWB's.  We are experiencing conductor cracks  between a surface mount land and its associated via.  The pad is  .030" wide with a .010" trace attached going about .30" to a standard via hole.  The mounting pad is a part of a quad flat pack (32 pins).  THe failure always occurs in the upper right hand pad.  There is dry film solder mask on the board.  Mask clearance around the pads is .003".  Board substrate is GIN material with a constraining core of copper.  What makes this strange, is this pattern is used on other designs all fab'ed from the same lot of material and assembled with similair parts and identical processes.
        The cracking occurs at the solder fillet/mask interface.  Solder fillets appear normal.  The breaks are clean.  Tooling artwork was checked and no problems detected.  The problem manifests itself when the PWB is put under vibration albiet low levels.
        Any and all help would be greatly appreciated.

                                Thanks,
                                George Kotecki

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