Electroplating needs to be done when all the area to be plated is
electrically connected - usually when the copper foil is still on the board.  That means
etching has to occur AFTER the electroplating of the nickel, palladium, and
gold.  And, of the etchant choices, only alkaline does not attack nickel, so
that is required in the fabrication sequence.

Etching of circuits with gold traces is sometimes a problem.  The gold and
the copper have widely separated electrical potentials (would generate a good
voltage if they were battery materials).  So, the gold causes the copper to etch
rapidly near the edge of the traces. Rapid etch means that the nickel/gold
can be undercut.  If that overhang breaks off in a "sliver", there can be
shorted circuits in later assembly, or in the field during life.  Scratching the
circuitry would be a prime cause of slivers.

Electroless plating "encapsulates" the copper circuits, and there is no
possibility of slivers.

Denny Fritz
MacDermid

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