Homebrew PCBs

What I am thinking about:

 Forget about the "silk screen". which in most modern "silk screening" 
operations is actually a screen made of stainless steel, and can have a 
rather fine "mesh".

 Obtain the emulsion only, and apply it directly to the copper clad 
printed circuit material, NOT to a screen.

 Do imaging.

 Develop the emulsion.

 Etch the board.

This is not really "silk screening" per se. It is using the silk screen 
emulsion instead of Kodak KPR or any of the other now-unavailable photo 
resist materials.

The challenges are: Obtaining the emulsion.  Assuring that the emulsion 
will withstand the etch process.  Also, how well the emulsion will 
adhere to the
copper.

It seems to me that a long time ago, I was able to obtain a 
photosensitive material that was designed for "silk" screen work that 
was a polymer, sold in a roll.
This material was applied to the wire or "silk" mesh, imaged and 
developed. I got the material at a graphics art supply store. I never 
really used it because
at that time Kodak KPR and competing emulsions were readily available 
and the KPR process was more familiar to me.

The new trick would be to apply this "silk" screen emulsion directly to 
a copper surface.

Not "silk" screening.

But then, we already have readily available dry film resist materials 
(sheets), and  PC  board stock that is already  coated with dry  film  
resist.
 
Roland F. Harriston, P.D.
*******************




David wrote:
>  
>
> Silk screen emulsion is UV sensitive, when exposed it becomes very 
> hard,(i.e. To block the printing inks) the unexposed area is simply 
> washed off, ready for etching. I think I will give it a go, and give 
> feedback when i've run a few tests! Many thanks to all who have so far 
> offered suggestions
> David
>
> --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "tda7000" <Tda7000@...> wrote:
> >
> > That would all depend on whether the silk screen emulsion stuff was 
> UV sensitive and reacted the same way as normal UV resist, to actually 
> stay on or wash off according to the pattern.
> >
> > --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "David" <dgh2259@> wrote:
> > >
> > > Leon / Andrew,
> > >
> > > Sorry, I dont think i made myself clear, I was suggesting the 
> emulsion used in silk screen printing to be put directly onto the PCB 
> using Craig's spinning method, not through a mesh, oven dry it, then 
> expose using UV and circuit pattern on a transparency or tracing paper 
> as normal, the exposed area would remain and the circuit washed off 
> with water ready for etching, if that makes sense! I was also 
> wondering if the resist would stand up to the etching chemicals? the 
> main reason is, this type of emulsion is a lot cheaper and easier to 
> get than the dedicated PCB stuff!
> > >
> > > David
> >
>
> 



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