Homebrew PCBs

On Mon, 2009-06-22 at 10:34 +0000, aurangzebhaque wrote:
> I wonder if it is possible to use the photo sensitive Emulsion used in
> the silk screen making process directly on the blank PCB copper
> surface. I realize that in the silk screen process there is the silk
> mesh in which the emulsion gets trapped and then hardens to form the
> "screen". The idea that I would like to test is whether:
> 

I also think about it, not to use the 'emulsion' but to buy the
'sensiblizer' which is said to be benzenophenone, the same thing used in
dry films and i think also in LPI and dry film soldermask. 
I know an 'how to' full of pictures with the process. But is Brazilian.
All Portuguese/Spanish speakers will be fine others...

http://br.geocities.com/jaosan13/DicasCustomizacao/PhotoetchEmulsaoFotosensivel.html 

Some curious things there is that i talks about the emulsion (without
sensiblizer) that can be replaced with white hood glue (PVA - water
soluble also), and the not exposed emulsion he uses is washed with
simple water.

If you are willing to try, get the benzenophenone, and emulsion, or
acrylic resin (widely avaiable) or even de PVA glue. The acrylic resin
should behave like the dry film, develop with Na2CO3 and strip with
NaOH. But is my guess.

The silkscreen method use this emulsion to make the silkscreen, and
apply almost anything on the board with it. Acrylic based, epoxy based
(soldermask), oil based, even asphalt! But yes you can use it directly.
if you can do an uniform thick layer.



> 1. Will the emulsion initially stick to the copper surface?
> 2. Will a screen be formed on the copper surface as it does in the
> case of the silk screening process?
> 
> Any comments most appreciated.
> 
> Thanks and regards
> 
> Aurangzeb

>