Homebrew PCBs

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.

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. 
> 
>

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. 
> > 
> >

twb8899  wrote:
> 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"...

What is the phosphorous for?
I've found that hard-drawn copper shim etches much more difficult
in FeCl than the copper on circuit boards. Why? (i've tried cleaning
any preservatives off first)

Russell wrote:
> twb8899  wrote:
> 
>>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"...
> 
> 
> What is the phosphorous for?
> I've found that hard-drawn copper shim etches much more difficult
> in FeCl than the copper on circuit boards. Why? (i've tried cleaning
> any preservatives off first)
> 


I've read that grain structure has an effect copper etching speed. The copper on 
PCBs  is made from electroplated foil over stainless steel drums is then hot 
rolled to the epoxy sheet. My guess is they want softest copper.

The phosphorous in copper anodes is to produce correct erosion of the anodes. I 
think its quite complicated, but when using a typical PCB plating bath 
containing brightening additives, and high acid/copper ratio then if you use 
normal copper anode they tend to erode with loose film of copper particles. The 
bath soon builds up a sediment of copper power. However with using copper with 
0.05% phosphorous (anodes for acid copper plating) then a dark, almost black, 
film develops over the anodes and does not produce powdery copper. The anodes 
are "bagged" with a polypropylene fabric to minimize solution flow and upsetting 
the delicate black film on the copper anodes.

When I first started doing experiments with copper plating I used much lower 
acid/copper ratio (no additives) as this was described in most old texts. Using 
plain copper anodes didn't produce even a tenth as much power as they did with 
the PCB bath above. Some copper powder was released but not enough be a big 
problem. The PCB plating bath is superior to standard plating bath because of 
the improved "throwing power" as Tom explained. Without additives you will have 
a hard time trying to get uniform plating. Also without additives, the deposts 
get very rough with increasing plating thickness.