Homebrew PCBs

Tom thanks for sharing this with the group. That is a fascinating
story. I just blows me away when I hear how a common ingredient used
in every day life can be so significant in a high tech processes like
printed circuits, heck, lignin vanillin extract !!! It just shows how
little the scientists understand electrochemistry and surface
chemistry. Its true when people say its in an art not a science.

During my research into the carbon black method of making holes
conductive I never came across Eric Harnden's invention. As far as I'm
aware of there are four main (non-electroless) commercial processes
for plating holes. This article gives a quick overview;

http://nr.stic.gov.tw/ejournal/ProceedingA/v23n3/365-368.pdf

I suspect Eric Harnden's super activate palladium chloride catalyst
puts a very large amount of palladium inside the holes, so much so
that copper can electroplate directly across the surface. I believe
the palladium acts as a catalyst and dramatically speeds up
electroposition of copper. The surface resistivity due to the
palladium alone does not need to be low. The article above mentions
Radovsky in 1969 discovering palladium inside holes being directly
electroplated even with initial resistance of 80 Mohms. The carbon
black process I am using reaches surface resistance of around 10 Kohms
for a unit square. This too uses an essential ingredient found in most
home  kitchens, and that's eatable Gelatin derived from beef skin.
There is already a patent on using Gelatin with carbon black
dispersions. The trick with using carbon black is to modifying the
carbon surface chemistry so it improves electrodeposition of copper.
Many soluble organic dyes can adsorb on the carbon surface and also
act as a catalyst in helping electrodeposition of copper. Palladium
can also be loaded into the carbon to dramatically improve the
plating, and I think that's what done with Blackhole(tm).

At the moment I'm working on trying to improve the Gelatin / carbon
dispersion process. I've got holes plating, but there are too many
variables and it takes long dwell times (30+ minutes) in the solutions
to achieve reliable results. Its all just fun experimenting and
discovery for me. I know that no money will be made from it because
the ideas are already patented and I don't really want to get into the
PCB manufacturing business.


--- In Homebrew_PCBs@yahoogroups.com, "twb8899 <twb8899@y...>"
<twb8899@y...> wrote:
> Jan and the group,
> 
> I'll be glad to do a write up on making plated through holes. How 
> much detail does everyone want?  There are about 60 steps to the 
> whole process if you break it down. 
> 
> I could give an overview of the entire process and then in future 
> posts give more details on each step. The hard part of the process
is 
> knowing what to do when something goes wrong. So another part could 
> be a discussion on problem solving.
> 
> BTW, the activated solution mentioned is actually a super activated 
> palladium chloride catalyst. My shop was the first one in North 
> America to install this process in 1990. It was invented by Eric 
> Harnden who owns a company called Solution Technology in
California. 
> I worked with Eric in the early days right after he received his 
> patent for this process. We ran his solutions along side our 
> electroless copper tanks and found them to be superior. At that
point 
> we junked the electroless system and converted everything to the
new 
> process by early 1991. 
> 
> At first there was much resistance to using this new method because 
> the MIL SPEC at the time only allowed electroless copper. This kept 
> the new process out of the big shops but one by one they caught on 
> and now Eric has licensed the technology to all the big chemical 
> suppliers. The magic ingredient was lignin vanillin extract!! The 
> catalyst tank smelled like a milk shake! I'm sure that Eric Harnden 
> has made a fortune from his invention.
> 
> The idea behind this catalyst was to get such a low resistance 
> between the two board layers that the electrolytic copper would
plate 
> right over the catalyst layer. This eliminated the electroless
copper 
> part of the process and about thirty minutes of time per load.
> 
> I'll write up the basics stating at the beginning and post them
over 
> the next few days. 
> 
> Tom