Homebrew PCBs

boombox666 wrote:

> 
> Speaking of those solder filled tubes for via's, would it be possible
> to take some ordinary solder and electroplate a layer of copper on
> this? I regenerate my sodium persulphate with a platinum and copper
> electrode, and the copper electrode is encrusted with copper, so it
> does not plate evenly. You need some chemicals called brighteners. Any
> idea what those are for copper?

Electric regeneration of sodium persulphate etchant is really possible?
You do it like this?
http://www.electro-tech-online.com/general-electronics-chat/32177-new-pcb-etching-soultion.html#post668383

>From all etchant descriptions i ever read, this one really pleases me.
But no more info anywhere. Any academic paper about this. Or any other
information that can sustain the web post. From this group i got what
convinced me to forget it. CuCl initiated with a peace of metal copper
in acid and peroxide and regenerated with air, is the best thing around,
but don't let me do things like i want to.
So the regeneration of sodium persulfate is possible? It works like the
post? Can you give me further info? 


About rivets, true plating chemistry can be more simple to use than
rivets/eyelets, soldered wires, conductive ink or mechanic activation
(drilling pcb above a conductive powder and letting drill spread it on
the hole wall). The chemistry may seem crazy difficult as theory but
using it is just simple as dip in a few baths one after the other and
thousand's of holes are plated in less than 1 hour, with no work. 

Brightener and other additives are used in any plating system. My
readings are only about pcb applications so there goes what i know:

Brightener, catalyst, leveler and suppressor additives work on the
copper plating of trough holes, because end quality and the chemical
complexity required to plate enough copper on the higher resistant
activated hole wall, than on the more conductive pcb copper surface
(throwing power). 

The thing works like this, after hole activation by means of dipping the
board in any the many palladium, conductive polymer or carbon/graphite
chemistries. The hole still have relative resistance, about 100ohm per
hole in the best chemistries, its them copper plated, but it still
difficult on the copper plating. Plating (slow) at low current can give
enough throwing power for an homebrew.
The first comercial chemistry in the direct plating field used the
palladium activation from a electroless chemistry, but instead the
electroless plating it used an copper electroplating with a suppressor
(PEG) mixed in. Because it 'flows' with the electric current and
deposits more in the higher conductive places, making those spots more
resistive and so distributes the current trough all the immersed
surface. 

Further direct plating chemistries changed to low sulphuric acid and
high copper to increase throwing power. But with it the problems starts.
The copper anode faces difficult to soluble problems, because of it,
catalyst is added (HCl or NaCl). But then copper dissolves in big
chunks, phosphoric containing anodes are used to maintain a 'oxide' like
equally resistive across surface. Anode bags of fine propylene fabric
used to keep copper chunks in electric contact to anode. But still the
electric current in Cl containing bath is difficult to control. To get
>3V potencial between anode and cathode to archive quality plating a
leveler is added, working with the Cl ions in a more proportional
voltage vs current setup.

In the hazard electroless chemistry after enough copper been deposit in
the holes it can go to a eletroplating bath up to desired copper thick.
Holes have same low resistance than surface so can be used normal copper
plating (easier to use high sulphuric acid and low copper).

Copper electroplating Brighter is a copper chelating agent like in metal
poisoning meds for example. DMPS is the most used molecule. It makes the
plated particles smaller in size, so it will look brighter and should be
used because the higher quality of the plated surface. I think it works
by acting as a 'transportation agent', one ion at time. Older patents
refer the use of thiourea, but it is plated with copper and increases
plated metal resistance, and should not be used at all, actual manuals
even refer maximum nitrogen values. Adding sugar to the sulfuric plating
bath is written across the web but it only reacts with sulfuric acid
decreasing sulfuric acid content in the bath.

Additives explained! Or at least how i got to understand them... 




PS
There are simpler setups than the ones explained above. To the people
interested, and to not make this look so scary:

To avoid the complexity of the low acid plating setup with chemical
control, there are electronic control setups (simple for an electronics
homebrew). The better one I now found is just like an ideia i have
abandoned in the past: insoluble material to make electric contact to
pure copper scrap,  liquid flow by means of a pump with filter, (pump
from anode to cathode) flow from cathode to anode, but it only work by
adding an inorganic additive considered an efficiency killer in normal
setup. The redox of the metal additive in contact with the copper makes
the all thing great. I will dig a bit more before posting. But its not
cheaper or easier to build. And is used in via filling. Filling the
holes in minutes with few copper plated on pcb surface.


The activation chemistries are explained here
http://nr.stpi.org.tw/ejournal/proceedingA/v23n3/365-368.pdf
http://books.google.com/books?id=g9Q8RekeKaAC&pg=SA30-PA1&lpg=SA30-PA1

More significant palladium Patents to an homebrew:
Direct plating system, Okabayashi 1991-93  (SOLUTION TECHNOLOGY SYSTEMS
Redlands CA)
US4933010 Sensitizing activator composition for chemical plating
US5071517 Method for directly electroplating a dielectric substrate and
plated substrate so produced
US5268088 Simplified method for direct electroplating of acrylic or
epoxy containing dielectric substrates
US5262042 Simplified method for direct electroplating of dielectric
substrates

Neopact 1994 (Atotech)
Pd/PVP nanoparticles which is even more advanced and easier stuff but no
enough info 
US6325910 Palladium colloid solution and its utilization

I have used a very simple chemistry that looks like this:
cleaner/conditioner 65�C --- etanolamine 3g/L; polyethylene glycol
trimethylnonyl ether (non ionic surfactant/wetting) 1.5g/L; (with a bit
of vanillin and NaCl predip)
pre-dip ---- NaCL 250g/L; HCl <1%
Activator ---- NaCl 250g/L; SnCl 25g/l; PdCl 0.2g/L; HCl <1%
Accelerator 40�C ---- K2CO3 220g/L; NaOH 10g/L; CuSO4 0,2g/L; H2SO4 <1%
(can be done with NaHCO3/Na2CO3/K2CO3/NaOH/KOH, copper mandatory)

I finally can know explain it but its written on the patents anyway. For
all the chemistry types about 45 patents have to be read.

Other (great) example is Adam Sheychell Homebrew carbon black setup,
with gelatin as a wetting agent, carbon paste and vinegar as activator,
and a food dye that i don't know what it makes, but it should be a
fixer.  
http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/150
Is not much like the patents. The hole resistance may end high, making
things difficult in the copper plating, but is a big proof that this is
not difficult for an homebrew. Although this one is not that easier to
run.

For the copper plating setup one may read:
http://books.google.com/books?id=g9Q8RekeKaAC&pg=SA29-PA6&lpg=SA29-PA6


Commercially speaking: from many, many suppliers, in Holland you can
find ENTHONE,  their Direct Metallization System ENVISION HDI is
thiophene conductive polymer based. But their Electroless Copper
Processing (activator only, ENVISION  2061 Clean-Condition / 2095
Pre-dip / 2105 Activation / 2110  Accelerator) is paladium tin based
similar to the one above. 
Same for FLORIDA CIRTECH OMEGA II PROCESS. Same for ELECTROCHEMICALS
(electroless activator only, Cleaner/Conditioner ML-373; Pre-Dip PD-472;
Catalyst C-473; Accelerator A-676). 
Rohm&Haas Cunductron/Crimson are a bit different. The original STS set
is sold by OSTECH now. The APT ABC set only has a fake web page. But
many others around, mega and bungard are *resellers*.

http://www.enthone.com/pwb/index.aspx
http://www.floridacirtech.com/Databases/pdfs/OMEGA%20II%20VERTICAL.pdf 
http://www.os-tech.com/chemistry.htm 
http://www.electrochemicals.com/ecframe.html


Big mail but full of info, no?