Richard,

"BlackHole" refers to a patented technique of using carbon black solution to
create the initial conductivity in plated-through-holes.   MacDermid holds
the patents, having bought the original technology from Olin, and then
introducing improvements.  BlackHole is a "direct metallization" technique
for this conductivity, replacing the electroless copper process.

Direct metallization processes are:

1. Easily conveyorized in horizontal process equipment
2. Use little, if any, hazardous chemistry - especially chelated copper that
may be difficult to waste treat
3. Operate fast - processing takes a matter of minutes, compared to perhaps
90 minutes for the entire electroless plating line.

In contrast to electroless copper, direct metallization cannot be inspected
for complete hole coverage - this occurs only after copper electroplate.   A
good study of direct metallization was done by the EPA in 1997 as part of
their "Making Holes Conductive" effort.  This should be available thru EHS
committees of the IPC or thru EPA direct.   Direct metallization is
particularly popular in Europe where environmental pressure is even higher
than in the US.

I suggest contact off line for the differences between "BlackHole" and other
direct metallizations.

Dennis Fritz
MacDermid, Inc
203-575-5740