Homebrew_PCBs

Hi guys,

i have tryed to use a water resistent photo emulsion made for
serigraphy, as etch resist in ferric cloride etchant, and it seems it
was a very bad investment.
I have seen in the archive that there are some emulsions that do work
as etch resist, and also adhere to the metal.
Can someone please tell me which emulsion works ?

i have user ulano 995wr (diazo sensitizer and Polyvinil-Acetate base)
and this one doen not work....it bubbles off in the etchant.(i guess e
very small amount of etchant is penetrating through, and makes the
emulsion loose contact to the metal)

thanks for any information on this,
Mihai

your question makes me think of this:
if you used a coated board (similar to the photo type) and use the printer to
print the 'developer' (or solvent) on, could that be an alternative?
something as
-clean the board
-apply the miracle coat (spray-brush-spin...)
-dry
-print the miracle ink
-wash (develop)
-fix - burn (or whatever)
-etch

is this absolutely crazy??? perhaps even a non epson printer would do.
and if a method like this worked for the solder mask? or the legend? they don't
need as high a resolution...



--- mihai_hagianu <mihai_hagianu@...> wrote:

>
> Hi guys,
>
> i have tryed to use a water resistent photo emulsion made for
> serigraphy, as etch resist in ferric cloride etchant, and it seems it
> was a very bad investment.
> I have seen in the archive that there are some emulsions that do work
> as etch resist, and also adhere to the metal.
> Can someone please tell me which emulsion works ?
>
> i have user ulano 995wr (diazo sensitizer and Polyvinil-Acetate base)
> and this one doen not work....it bubbles off in the etchant.(i guess e
> very small amount of etchant is penetrating through, and makes the
> emulsion loose contact to the metal)
>
> thanks for any information on this,
> Mihai

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On Tue Aug 8, 2006 8:44 pm (PDT), Herbert E. Plett wrote:

>2. Re: serigraphy photo emulsion as etch resist ?
> Posted by: "Herbert E. Plett" cachureos@... cachureos
> Date: Tue Aug 8, 2006 8:44 pm (PDT)
>
>your question makes me think of this:
>if you used a coated board (similar to the photo type) and use the printer to
>print the 'developer' (or solvent) on, could that be an alternative?
>[snip procedure]
>is this absolutely crazy???

No, nor new either: prior art in message 13667, Apr 21, 2006, 2:14 pm.

Perhaps all mihai_hagianu needs to do is to bake the developed
PVA image to make the colloid completely irreversible.
Colour is a good indicator - dark straw should be about right.

This definitely does work on a homebrew gelatin-dichromate
photoresist in acidulated ferric chloride etchant.


Regards, LenW

--- In Homebrew_PCBs@yahoogroups.com, Len Warner <yahoo@...> wrote:

>
> No, nor new either: prior art in message 13667, Apr 21, 2006, 2:14 pm.
>
> Perhaps all mihai_hagianu needs to do is to bake the developed
> PVA image to make the colloid completely irreversible.
> Colour is a good indicator - dark straw should be about right.
>
> This definitely does work on a homebrew gelatin-dichromate
> photoresist in acidulated ferric chloride etchant.
>
>
> Regards, LenW
>

Hello again,

I have tryed to bake the PVA image as you sugested, at 3 temperatures,
and there is no perceptible impruvement.

You mentioned Gelatin-Dichromate homebrew resist. Do you have any
information about that?


Also, is there any reference of what was the PCB photoresist before
the canned aerosols like positive 20 came along ?


What I need to do is to get an emulsion which works on ungalvanised
steel sheets as etch resist (electroetch or chemical etch or better both).

I have done some more testing with ulano 995 water resistent emulsion,
but it is not good. On (Zn)galvaized steel it forms a good image but
it does not stand against electroetch nor FeCl3. On ungalvanised black
steel, something from the emulsion reacts with the iron, and the
emulsion becomes insoluble withouth the UV , so it cannot be developed
anymore.

any ideeas would be welcome. I'll keep you posted with my progres
(slow up to now)

thank's
mihai