Homebrew PCBs

I think it really has to do with the balancing chemistries. , or the
organics. The Flash I'm using has no cyanide, I was under the impression
that the blackhole method was purley an electroless process , including the
copper flash.

** Big side note here ... I'm not a chemist, and I cant get in to many
details beyond the basics, or what I have specific instructions for.
I was under the impresion that the balncers were most attracted to the areas
with the greates potential for conductivity. And thus the higher thier
consentration in the solution, the more profound the hole plating vs the
foil~ would be. as the foil surface en mass is of higher potential. I have
noted that I start to see color change in the holes before the foil begins
to pinken. < is that a word? So I'm assumin I happen to have enough organic
content to effectivley hamper the plating on the urface of the foil until
after the hole walls bein to fall in to balance with the foil surface.
I've also seen that I do not need to flip and rotate the board 1/2 thru
plating for uniformity like I did with the acid copper. But this may be due
to anode placement. vs board size, so to many variable to state that as
fact. Caswell sataes it like this:

"
FLASH COPPER produces a fine grained. smooth. dense and ductile copper
deposit. which is nonporus and has excellent bonding properties. The
throwing  and covering power of the non-cyanide process is superior to
cyanide processes. This is especially evident in barrel plating. It has
uniform low current density distribution with excellent micro-throw
The grain is smaller than cyanide copper. which increases the density of the
deposit. This density provides excellent heat treat stop off and masking
properties. The fine-grained FLASH COPPER deposit under nickel chrome
improves the overall corrosion resistance and helps to throw the nickel
farther into the low current density areas.
FLASH COPPER produces a softer and more ductile deposit than cyanide or acid
copper. The soft deposit imparts improved adhesion and corrosion resistance
and greatly improved resistance to thermal shock.
It has a high deposit purity and hence no out-gassing with subsequeut
brazing. soldering or vacuum operations.
FLASH COPPER is simple and inexpensive to use because it replenishes the
copper in solution by dissolving the copper anode and here again it is a
unique product with only one maintenance additive.
"


After speaking with Ron at TnT , he sugested that alot of customers who use
thier process skip the flash step, and go directly to pattern plating with
thier Acid copper product, I'd asume they have acid worked out well enough
to market it with the ink , or we'd be seeing a change in procedure. But
with that siad, Caswells flash is performing very well and for a complete
kit setup cost under $200 I'd like to see more people try this method to
verify my results. Caswell sells a product called "silvaspray" made for
plating plastics and works very well with the flash copper product, I'd
suspect - it to could be used for hole plating. I'll probably try it out
when I start running out of the TnT  ink.

... thoughts to promote either a solid tin / SnPb plate, or acid copper
plate over the flash. I'm tempted to try a few boards without eitther to see
if it holds up , If the solder from the assembly process would cover it. I'm
preparing a plot for a negative I'll run tonigh, In the morning I'll see how
it deveolps, and if this film can tent well enough I'll give it a go

JT


----- Original Message ----- 
From: "Adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, April 02, 2004 6:36 PM
Subject: Re: [Homebrew_PCBs] Plating Holes (was: plated tin as the etch
resist)


>
> Ok, thanks for your response. I thought you might have had made a grand
> discovery in getting through holes to place reliably over carbon coated
> holes. As I said earlier, I'm using carbon black to coat the holes and I
am
> experiencing the same problems as many did in who tried to make
> carbon/graphite process commercially viable, such as MacDermid. The
current
> process by MacDermid is called BLACKHOLE SP, and is well established in
> industry. They claim BLACKHOLE SP to be suitable for even the most high
> tech PCBs, 16+ layers, 0.1 mm hole diameters, et. The early attempts by
> these companies had problems getting the copper to plate on relatively
thin
> layer of carbon/graphite. From my experiments of plating carbon coated
> holes, I've found the chemistry of the plating solution to play a huge
part
> in obtaining successful copper coverage. For example, I found acid sulfate
> bright tin bath plates the holes much more reliable than acid copper bath.
> I also found small amounts of chloride in the acid copper bath have a
> detrimental effect, with > 300ppm of Cl- will completely inhibit any hole
> wall plating. I am wondering if the alkaline bath you use is the answer to
> getting the holes plated with good reliability. I'm not up to speed with
my
> electrochemistry but I believe the reason holes are difficult to plate in
> is that the carbon has a higher overpotential for deposition of copper
than
> copper on copper does. In other words you need higher cell voltage to
plate
> on carbon than on copper. Overpotentials depend on many things and pH is
> one of them. The carbon surface resistively is relatively high (about
10e+6
> times more resistance of a unit square) compared to the copper foil
surface
> resistively. During plating a voltage drop develops at the boundary were
> copper meets the carbon. The result is a forward growth of copper over the
> carbon surface during the plating cycle. The copper growth emanates at the
> hole ends and eventually meets half way inside the hole completing the
> coverage. Its the rate of this copper growth front the determines how good
> the process is running. If the growth rate is too slow (or nonexistent)
> then too much copper will be deposited on copper cladding, and not enough
> inside the holes. Worse still is the voiding inside the holes due to
> patches of extremely thin coatings of carbon. This is the fundamental
problem.
>
> There a number of alkaline copper plating chemistries that could be
tested.
> The good news is we don't need high speed, smooth bright finishes, since
> the aim is to "flash plate". The acid copper bath will take care of the
> remaining copper. Industrial alkaline copper uses cyanide , which I prefer
> not to use. Another possibility is copper sulfate + ammonia hydroxide +
> ammonium sulfate with around pH 8 so it doesn't smell.
>
> Like you, I am doing this as a hobby so I don't get the time needed to do
> thorough experiments. I did most of my carbon hole work when I had a part
> time job in which I had the time to built a home lab just to explore this
> process. I've had a about 1 year break from it now, but these discussions
> have got me thinking about it again. It might be time to dust out the lab.
>
> Adam
>
>
>
>
> Jeremy Taylor wrote:
> > Hard to say - and subjective at best. but IMO yes.
> > We can discuss this more tomorrow, I've been trying to take some pics ,
but
> > man is it difficult to even get the holes...
>
>
>
>
>
>
>
> >
> >
> >
> > http://www.soundclick.com/jtsound
> > ----- Original Message ----- 
> > From: "Adam Seychell" <adam_seychell@...>
> > To: <Homebrew_PCBs@yahoogroups.com>
> > Sent: Thursday, April 01, 2004 11:09 PM
> > Subject: Re: [Homebrew_PCBs] plated tin as the etch resist
> >
> >
> >
> >>
> >>Jeremy Taylor wrote:
> >>
> >>>My last post must been sent just prior to yours.
> >>>
> >>>I actually ended up completely closing up some holes with the acid
> >
> > copper.
> >
> >>Does that mean the alkaline plate was more capable of completely
> >>covering the holes walls with copper than compared to acid copper
> >>plating ? Which bath was better ?
> >>
> >>
> >>
> >>>It' definitely a more aggressive plate.
> >>
> >>yes, the acid copper is fast, almost 100% coulombetric
> >>efficient, good throwing power and easy to maintain and setup.
> >>This is why I suspect you have chosen alkaline plating because it
> >>performed better when plating on the ink surface.
> >>
> >>Regards,
> >>
> >>Adam
> >>
> >>
> >>
> >>Be sure to visit the group home and check for new Bookmarks and files:
> >>http://groups.yahoo.com/group/Homebrew_PCBs
> >>Yahoo! Groups Links
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
> >
> >
> > Be sure to visit the group home and check for new Bookmarks and files:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>