Al,

IPC-D-275 does NOT allow for internal copper planes to go to the edge of a
printed circuit board. If a design, such as RF, requires the plane to extend
to the edge, then the design dictates, due to functionality.

To answer your question concerning exposed copper edges. Two things must be
considered. The first is a product safety requirement. Power conductors on
the edge of a board present a safety problem. The second consideration is
that for many years the military accepted exposed copper on the edges of
lands, where the board was reflowed. The reasoning was that solder, in a
plated through hole,  is not intended to flow past the land and on to the
vertical surface, on the outer perimeter of the land. IPC-D-275 and
IPC-RB-276 also allow this occurance, for the same reasons.

Regards,

Gary Ferrari
Tech Circuits