Homebrew PCBs

Adam's comments are correct concerning the use of a sulfuric acid 
based copper plating system. It will work even better if 
a "brightner" chemistry is added to the tank. This helps to level out 
the plating and increase the "throwing power" which is very important 
when plating in the holes. Do a search on "throwing power" to learn 
more about this. 

When plating large flat areas the center of the panel will receive 
the minimum amount of plating while the edges and corners will get 
the most. Brightner chemistry helps to level this out and also 
increase the efficiency through the holes. What is needed is a 1:1 
thickness ratio between the hole wall and surface thickness and this 
is almost never achived but you can get very close. 

The copper anodes should contain a small amount of phosphorus to 
plate properly in an acid copper tank. These anodes will be 
marked "CU-PHOS". If setting up a small system you could get small 
titanium anode baskets or make your own from titanium mesh and fill 
it with copper anode balls. Try and purchase a small quantity of 
these balls from a friendly PCB shop to keep the cost down. Another 
way is to get the PCB shop to sell you their used up copper slab 
anodes. The slab anodes wear down to a pointy stub so you just chop 
these up and put them in anode baskets. 

An air sparger and small oil free air pump is also needed. Acid 
copper tanks should always be air agitated for best results. You can 
get away without the air but the plating current has to be cut way 
back and it takes forever to plate even .001". When everything is 
just right you should be able to plate .001" in about 30 minutes.

Tom

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell 
<adam_seychell@y...> wrote:
> If I were you I'd first get a good copper plating apparatus setup. 
> Acetic is a terrible electrolyte for plating (I assume you have 
copper 
> acetate in there to carry the copper ions !!). For now, use 
standard 
> acid copper plating recipes, not special PCB formulations as they 
> require a bit more control. You'll have to check in references, but 
I 
> think a good start will be;
> 
> 140-180 g/l copper sulfate pentahydrate.
> 40-60 g/l sulfuric acid.
> 
> also see http://www.pfonline.com/articles/pfd0014.html
> 
> Once you can copper plate onto copper successfully then do your 
> experiments with the carbon holes.
> 
> I got most of my chemicals for experimenting by contacting the 
> chemical suppliers and asking for free samples. I have probably 
done 
> this for 5 or 6 different products. The cheap and common chemicals 
are 
> usually not available as free samples. 98% Sulfuric is dirt cheap, 
so 
> just buy 10 liters (18kg) and be done with it.
> 
> dsv1486 wrote:
> > Ok I have just joined this group and was reading the various 
topics. 
> > One that has intrigued me was the plating through the circuit 
board 
> > hole method using carbon. I have wanted to do this for quite some 
> > time. I have experimented with a graphite spray that sells at 
> > Canadian tire, (I live in Edmonton Alberta Canada). I would pre 
drill 
> > the CB and then basically spray a puddle on the board and use a 
> > squeegee to fill all of the holes. Then use an air knife to clear 
the 
> > holes leaving a residue. Then let dry and sand the leftover 
graphite 
> > from the board. I would then electroplate with acetic acid 
(vinegar). 
> > However the issue was the length of time to plate. The graphite 
was 
> > suspended in a weak binder, perhaps a urethane or other type 
> > of "plastic coating". It seemed that only long times in the 
acetic 
> > acid bath would allow plating of copper onto the graphite. I am 
> > thinking that I should have used a strong sulfuric or 
hydrochloric to 
> > break down the surface layer and then plate. However I have not 
tried 
> > this yet. The carbon method mentioned here in the files section 
seems 
> > better so I would like to know, can I use crushed carbon for this 
> > method or perhaps using a candle's carbon to coat the holes as it 
is 
> > very difficult to get chemicals here in small quantities. Does 
anyone 
> > have any ideas as to how this could be done simply? I know it is 
a 
> > complex process using palladium or the other ones mentioned, 
hoverer 
> > I have the time to use a slow process and it would only be for 
hobby 
> > purposes. 
> > 
> >