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The BLACKHOLE processes is fast, cheaper and safer to run than conventional
electroless copper. This is expected since its aim is to replace the
electroless copper line in the PCB fabrication plant. The low toxicity is the
reason I choose to develop a carbon black processes myself at home. However
the chemistry of BLACKHOLE is a trade secret and your not going to replicate
the same results at home. BLACKHOLE SP is the latest process from MacDermid
and performs many times better than the process explained below. Of course
the hobbyist doesn't need the reliability of a multimillion dollar plant
producing a hundreds of panels a day. Its taken me about 6 months of fiddling
around with carbon black dispersions, conditioning solutions and circuit
board material to get a working process suitable for home use. Basically my
process can be written down as follows;

1) drill PCB
2) clean copper surface with week solution of detergent/NaOH and 600 emery
paper.
3) rinse well with tap water
4) immerse in a "hole wall conditioner" 1 min
5) rinse well with with tap water
6) immerse in "carbon dispersion" 1 min
7) sponge off excess dispersion with sponge, so all holes are fully empty.
8) hot air dry
9) repeat steps 4 to 8
10) immerse in "activator" for 1 minute
11) rinse well with with tap water
12) microetch in a conventional non-chloride etching solution
13) spray rinse with with tap water to remove all traces of carbon on copper
surface.
14) air dry (optional)


Bath compositions/conditions;

hole wall conditioner:
5 to 10 g/l gelatine
0.04 to 0.06 g/l CuSO4.5H20 (as a biocide)
temperature between 26???C and 32???C
agitation: unnecessary


carbon dispersion:
2 to 4% (w/w) of non-ionic surfactant based
conductive carbon black dispersion paste*
6 to 10 g/l acetic acid
room temperature
agitation: unnecessary


activator:
1 g/l of dye D&C Green No.5 , C.I 61570.
room temperature
agitation: not known

non-chloride etchant:
100 to 200 g/l ammonium persulfate
or
1% hydrogen peroxide
10% sulfuric acid.
both baths may be used at room temperature.


* The carbon black dispersion paste is FLEXOBRITE BLACK 258/86 manufactured
by Degussa Coatings & Colorants.

You will have to phone around and get a 500g sample for aqueous based
non-ionic surfactant conductive carbon black dispersion. Many of the colorant
manufactures will have these. 500g will last you forever. There is still a
whole range of information I left out, either because I haven't worked it out
yet or I missed it. The D&C Green No5 is available from food, drug & cosmetic
dye suppliers, either as a sample or in small volume (1 kg). Good luck

Adam





j_hallows wrote: