I am a hobbyist doing some research into the carbon black method for making
double sided PTH boards at home. My research so far has mainly been
reading the numerous patents and journals on the subject, plus countless
hours spent in my lab (an old tin shed) trying different chemistry and
processes. I'm at the point where through hole conductivity due to carbon is
below 2000 ohms for a single 1.5mm diameter hole. This proved to
be sufficient for void free plating in acid copper (200g/l H2SO4, 60g/l
CuSO4). What makes carbon process most attractive for me is the low toxicity
and costs.

From what I understand this is a relatively new area in PCB manufacture (<
12 years) and technical information is difficult to come by. This has been
the reason for my own pain staking research. Theory of colloid suspensions
and surface interaction is way out of my league, and so its all been a trial
and error. If anyone is interested I can post the details of what I've
discovered so far. For me, I'd be interested discussing with anyone the
details of the carbon dispersion process. There are many questions, such as
how long to  the dispersions last before carbon particles aggregate and
become ineffective ? I've learned that the conditioner is a critical step
before the carbon dip, since it is responsible for getting the carbon to
stick to the surface. 0.3% (wt) gelatin showed to be very effective for
this. What formulations are typical used for conditioners ?

regards,

Adam Seychell

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