On Wed, Dec 15, 2010 at 4:19 PM, Simao Cardoso <
simaocardoso@...> wrote:
>
> So about chemical vias (and skipping all mechanical methods) the ones
> that can be 'homebrewed' are palladium and carbon black. But is more
> difficult the copper plating bath itself. There is a really great method
> found by a great mind of homebrew PTH but he never shared it here. That
> Chinese machine Simon posted seems to be built around the same trick, it
> will take 75 to 90 min to plate a pcb but is fair simple to build. I
> really am the 'flag-boy' for palladium since it's much simpler to use
> than carbon black (all wet vs 2 times drying), and super trustful (i
> made thousands of boards with palladium without missing a hole) and
> longer bath life (years vs months). Posting recipes will be bad faith
> since i haven't homebrew experience in either. Both are fair simple,
> both have a similar to industrial degreaser conditioner, a ionic
> suspension for one or in surfactant in other for activation and a ion
> remover with copper as accelerator for palladium or a common simple
> micro etch for carbon black. Of course that during last year i tried to
> get everything needed for the palladium chemistry and still miss some
> stuff (sh∗t really happens...).
This sounds very interesting since you've had actual experience using
these types of chemistries. Would you mind telling how you used them
as far as how you got your experience with them? Posting the recipe
for anything is always informative even if homebrew people can't
always get the same ingredients needed. I've looked at a lot of
patent applications and the chemicals used are often very difficult to
find, so I know how it can be.
(snip)
> THE SIMPLEST method i know about (and wish to try one day) is the good
> simple plating setup from one person with also his sharing from 12 years
> ago about drilling holes above graphite powder. There is some reference
> from IPC about this but never disclose what can be used under the pcb.
> Graphite chemistry is just like carbon black but almost 1000 times more
> conductive per hole with one pass only, but can last one day only if
> additives are used. Using it on a CNC is dumb but a simple drill press
> with a deep pool for powder seems to worth the money to try it.
Are you talking about covering a board with graphite powder and then
drilling the holes, such that the powder falls in and coats the
hole-walls as they are drilled? It's not clear exactly what is going
on, as you also talk about "graphite chemistry". Please let us know a
little bit more about how this is done.
> >
> > Apart from the chemistry, you're still looking at the high-hundreds for a reverse-pulse-plating machine if you DIY it.
>
> Simon, i looked into your descriptions. Reverse pulse can be really good
> but neither do you seem to full understand it either is a
> simple/complete answer. I am also building my driver, also with a avr,
> but with very low RDSon FETs (and fet drivers), using 4 psu's and 8 fets
> (multiple anodes and cathodes) for a tricky chemistry (big expectations
> in it). But for example i never figure out which voltage is appropriate
> for the reverse pulse. You don't seem to realize it but it all goes
> around current densities on surface vesus hole. And the magic number is
> 3 (or higher) - 3 times shorter reverse pulse, 3 times much current. For
> _SLAPPING_ copper from surface and leave holes without touch, using same
> values for both is wasting energy. You need at least 3V for plate pcb's
> nicely, but since the common setup uses additives to require voltage
> increase as current increases (without them current goes exponential
> above ~0.7V) there isn't document proof on which voltage to use (or
> known which psu to buy). Commercial systems say 12-20V capable but thats
> crazy it will electrolise water. Ohh and i am having big trouble on this
> so the avr changes voltage and current limits at cheap switched mode
> psu's.
Thanks for the detail you've given on this. I figured using something
like an H-bridge with MOSFETs would do it but it sounds like it's more
involved if you have to use reverse voltages that are different than
the positive plating voltage. Have you had any success doing this
type of plating or has it not worked out very well? What are some of
the problems you've run into?
Thanks-
Larry