I have been having a problem with oxide skips when using a brown oxide on
polyimide.  Identical panels made on epoxy and on polyimide and run through
oxide at the same time display different characteristics.  On the polyimide,
 the oxide skips on the edge and part of the conductors on some small
conductors and may completley skip on some fine (0.005 inch) conductors. the
surface of ground planes and large lands are unaffected , but sometimes the
edge of the copper on the ground plane will not coat.  Full sheets coat very
well and the epoxy-glass panels have no skips on the conductors or the edge
of the conductors.  I have experience this condition in a previous case in
which those panels containing foil with a zinc plating on the laminate side
would exhibit oxide skips while those with the brass would not.  I though
that the zinc was not used any more since Yates is no longer here and brass
gave a better peel strength than zinc on polyimide boards.  Any comment would
be appreciated.   

Phil Hinton 
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