Aha! Thank you. I almost didn't get to chemical until sending my question, then the light bulb started to glow. Now all is clear.
Thanks for the information about hole activation, too. Some day, I'll give it a try. I've done some plating, but never PCB holes.
Donald.
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----- Original Message -----
> From: "Simao Cardoso" <simaocardoso@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Wednesday, December 15, 2010 4:19:22 PM
> Subject: Re: [Homebrew_PCBs] Quimical VIAs
>
> Simon Gornall wrote:
>
>
>
> >
> > (BTW: What on earth does 'quimical' mean ?)
> >
> It should be a typo for 'chemical' since in both Portuguese and
> Spanish
> chemistry is spelled as 'química' (quimica for non-utf8 users), and
> Vicent seems Spanish name. I am Portuguese and didn't even realize
> the
> typo until you did ;)
>
>
> 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...).
>
> I moved and am living away from where i have all my tools and stuff
> and
> so not much progress on this, but for construct it the acrylic glass
> with solvent is amazing, even if you cut the acrylic with 1 mm
> breaches,
> multiple passes of solvent fill the holes. I tried both store
> expensive
> solvent (it says dichloromethane and nitroethane) and pure
> dichloromethane cheap from eBay. With 100eur for a 3 sq meter 5mm
> thick
> sheet is fair cheap to build (there is two types and only one works
> with
> the solvent).
>
>
> 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.
>
> >
> > 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.
>
> And thats all for quimical vias :D
> Simao
>
> >
> >
> > >
> > > Anyway, some of this "inventions" can work with more o less
> result, but I'm
> > > convinced the way is to go to a quimical or electrolytical plated
> process.
> > > Is there anything affordable for the hobbyier?
> > >
> > > 2010/12/15 Donald H Locker <dhlocker@...>
> > >
> > > >
> > > >
> > > > I have no personal experience. I think a plated-through-holes
> (PTH) process
> > > > is usually a bit beyond the hobbyist level, but is the only way
> of achieving
> > > > no-bulge vias. All other methods (eyelets, fine-gauge wire)
> leave
> > > > protrusions on the surface that prevent flat mounting of
> components.
> > > >
> > > > It _might_ be possible to put down a pad with a slot in the
> copper
> > > > (extending radially from the hole) just wide enough to lay a
> fine gauge wire
> > > > in and bridge the pad's slot and the wire with solder, producing
> a
> > > > nearly-flat surface, but I wouldn't want to do many of those.
> Never mind.
> > > > 1oz copper is about 0.0013 inches thick, while 30AWG wire is
> 0.010 inch
> > > > diameter - that's about a 0.009 inch ridge on the board.
> > > >
> > > > Donald.
> > > > --
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> > > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
>
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