Homebrew_PCBs

Hi all, It's me again. I've been busy for a couple of months now, but
I accidentally have perfected the cheap photo etching method I posted
a few months ago.

So here we go:
The emulsion is way past expiration date. And that's a good thing! For
some reason, it becomes less viscous when it expires. It's thick as
cooking oil now, before that it was as thick as good latex-based wall
paint. This allows for two things: a thin layer and quicker drying.

The thin layer allows for thinner tracks too. I went down to 0.01" and
had minimal trouble. I'm working with 0805 SMDs with no problem at all.

Also I now expose to sunlight. I asked the pros about how they do this
and they all said you need either 2 - 3kW special lamps with special
timers, or the cheap (and more efficient) sunlight for "about 3 or 4
minutes". It works GREAT. not even the finest line cuts when
developing (that was my problem before).

But, the expired emulsion leaves a nasty residue, as if it's still
stuck to copper. No problem. Fine steel wool makes it go away. Even
pushing (relatively) hard to the thin tracks, the artwork stays.

I'm really happy with the results.

Have you tried using the screen cleaner solvent that's specifically
made for removing the photo emulsion from silkscreens? I have no idea
what chemicals are in it. If it can remove cured emulsion from a
screen, it should certainly work on a PCB.


Regards, Bob

--- In Homebrew_PCBs@yahoogroups.com, "hjf2k2" <drgenio@h...> wrote:
<snip>
>
> But, the expired emulsion leaves a nasty residue, as if it's still
> stuck to copper. No problem. Fine steel wool makes it go away. Even
> pushing (relatively) hard to the thin tracks, the artwork stays.
>
> I'm really happy with the results.

sorry, I didn't express myself clearly. the residue is there after
developing but before going into ferric chloride.

to finally remove the emulsion, i do use screen cleaner. but it seems
to attack copper. i was told to use bleach or sodium hydroxide which
can remove the emulsion and won't attack copper... but I'm not so sure
about that. I use paint thinner and a little more work, and it goes
away, and thinner surely doesn't attack copper.

regards,
hernan

--- In Homebrew_PCBs@yahoogroups.com, "Bob_xyz" <bob_barr@h...> wrote:
> Have you tried using the screen cleaner solvent that's specifically
> made for removing the photo emulsion from silkscreens? I have no idea
> what chemicals are in it. If it can remove cured emulsion from a
> screen, it should certainly work on a PCB.
>
>
> Regards, Bob
>
> --- In Homebrew_PCBs@yahoogroups.com, "hjf2k2" <drgenio@h...> wrote:
> <snip>
> >
> > But, the expired emulsion leaves a nasty residue, as if it's still
> > stuck to copper. No problem. Fine steel wool makes it go away. Even
> > pushing (relatively) hard to the thin tracks, the artwork stays.
> >
> > I'm really happy with the results.

Thanks for the clarification. I had misunderstood what you were
saying. I'm a bit surprised that screen cleaner attacks copper since
it's used to clean aluminimum-framed screens. I suppose that it
could weaken the bond between the copper and the laminate though.


Regards, Bob

--- In Homebrew_PCBs@yahoogroups.com, "hjf2k2" <drgenio@h...> wrote:
> sorry, I didn't express myself clearly. the residue is there after
> developing but before going into ferric chloride.
>
> to finally remove the emulsion, i do use screen cleaner. but it
seems
> to attack copper. i was told to use bleach or sodium hydroxide
which
> can remove the emulsion and won't attack copper... but I'm not so
sure
> about that. I use paint thinner and a little more work, and it goes
> away, and thinner surely doesn't attack copper.
>
> regards,
> hernan
>

maybe the aluminum protects itself, like it does on air?

I don't know how does it affect copper, but it does. copper gets kind
of dull and some colors appear. The cleaner smells like pool water,
and it's supposedly "ecological", that is, it can go down the drain.
For what I have found out, it's made in USA. I don't have the bottle
here, I'll check the label tomorrow.

--- In Homebrew_PCBs@yahoogroups.com, "Bob_xyz" <bob_barr@h...> wrote:
> Thanks for the clarification. I had misunderstood what you were
> saying. I'm a bit surprised that screen cleaner attacks copper since
> it's used to clean aluminimum-framed screens. I suppose that it
> could weaken the bond between the copper and the laminate though.
>
>
> Regards, Bob
>
> --- In Homebrew_PCBs@yahoogroups.com, "hjf2k2" <drgenio@h...> wrote:
> > sorry, I didn't express myself clearly. the residue is there after
> > developing but before going into ferric chloride.
> >
> > to finally remove the emulsion, i do use screen cleaner. but it
> seems
> > to attack copper. i was told to use bleach or sodium hydroxide
> which
> > can remove the emulsion and won't attack copper... but I'm not so
> sure
> > about that. I use paint thinner and a little more work, and it goes
> > away, and thinner surely doesn't attack copper.
> >
> > regards,
> > hernan
> >

Clarification....

>sorry, I didn't express myself clearly. the residue is there after
>developing but before going into ferric chloride.

The conventional process uses sodium hydroxide or something similar
here. You apparently have to resort to steel wool...Not good.

>to finally remove the emulsion, i do use screen cleaner. but it seems
>to attack copper. i was told to use bleach or sodium hydroxide which
>can remove the emulsion and won't attack copper... but I'm not so sure
>about that. I use paint thinner and a little more work, and it goes
>away, and thinner surely doesn't attack copper.

The conventional process normally uses acetone here. You apparently use
what you can get. I suspect recommendations to use bleach or sodium
hydroxide were aimed at the previous step above where "unfriendly to
copper" doesn't matter since ferric chloride would be the next step.

hjf2k2 wrote:

> Hi all, It's me again. I've been busy for a couple of months now, but
> I accidentally have perfected the cheap photo etching method I posted
> a few months ago.
> [deleted]

Hi,
What type of screen emulsion did you use. It sounds like its not water
based like the one I tried to use. I recently posted a reply to Bob
about my failure using the screen emulsion. I'm not up to date with
photocure screen emulsions, but I'd image not all are the same.

"Hi Bob, it was a long time ago, but from what I remember the emulsion
was nothing special, just common silk screen emulsion. Color was red and
smelled a bit like PVA glue. After coating, drying, exposing and
developing, the emulsion became quite solid and difficult to remove.
However it would "swell" slightly in etchant, and I think somehow a
microscopic amount of etchant would reach to the copper surface, causing
the bond to break and it lifts off. Unlike photoresists, these emulsions
don't seem to be completely impermeable to aqueous solutions."

Well I don't know, I'm using chemicals for serigraphy "for
professional use only", more precisely, bichromate-sensitivized vinyl
dispersion, used for TEXTILE printing. that is, for making originals
to print t-shirts. this emulsion it's for water-based inks.

The sodium hydroxide will remove all of the emulsion, while what I
want to remove is a little "veil" that stays there after rinsing.

--- In Homebrew_PCBs@yahoogroups.com, "derekhawkins"
<derekhawkins@y...> wrote:

> Clarification....
>
> >sorry, I didn't express myself clearly. the residue is there after
> >developing but before going into ferric chloride.
>
> The conventional process uses sodium hydroxide or something similar
> here. You apparently have to resort to steel wool...Not good.
>
> >to finally remove the emulsion, i do use screen cleaner. but it seems
> >to attack copper. i was told to use bleach or sodium hydroxide which
> >can remove the emulsion and won't attack copper... but I'm not so sure
> >about that. I use paint thinner and a little more work, and it goes
> >away, and thinner surely doesn't attack copper.
>
> The conventional process normally uses acetone here. You apparently use
> what you can get. I suspect recommendations to use bleach or sodium
> hydroxide were aimed at the previous step above where "unfriendly to
> copper" doesn't matter since ferric chloride would be the next step.

hey there. I posted pictures on the files area. It's water based
emulsion, the MSDS states that it is a "vinyl dispersion", a fancy
name for white paper glue. It's purple in color,
bichromate-sensitivized. Bichromate is illegal in many countries.

I tried using diazo-sensitivized ink, color green, but it wont stick
to the copper as this one.

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:

> hjf2k2 wrote:
>
> > Hi all, It's me again. I've been busy for a couple of months now, but
> > I accidentally have perfected the cheap photo etching method I posted
> > a few months ago.
> > [deleted]
>
> Hi,
> What type of screen emulsion did you use. It sounds like its not water
> based like the one I tried to use. I recently posted a reply to Bob
> about my failure using the screen emulsion. I'm not up to date with
> photocure screen emulsions, but I'd image not all are the same.
>
> "Hi Bob, it was a long time ago, but from what I remember the emulsion
> was nothing special, just common silk screen emulsion. Color was red and
> smelled a bit like PVA glue. After coating, drying, exposing and
> developing, the emulsion became quite solid and difficult to remove.
> However it would "swell" slightly in etchant, and I think somehow a
> microscopic amount of etchant would reach to the copper surface, causing
> the bond to break and it lifts off. Unlike photoresists, these emulsions
> don't seem to be completely impermeable to aqueous solutions."

>Well I don't know, I'm using chemicals for serigraphy "for
>professional use only", more precisely, bichromate-sensitivized vinyl
>dispersion, used for TEXTILE printing.

Is this the emulsion you have been referring to or an excerpt from
your resume? I'm confused.

--- In Homebrew_PCBs@yahoogroups.com, "derekhawkins"
<derekhawkins@y...> wrote:

> >Well I don't know, I'm using chemicals for serigraphy "for
> >professional use only", more precisely, bichromate-sensitivized vinyl
> >dispersion, used for TEXTILE printing.
>
> Is this the emulsion you have been referring to or an excerpt from
> your resume? I'm confused.

I don't get it.

--- In Homebrew_PCBs@yahoogroups.com, "hjf2k2" <drgenio@h...> wrote:

> --- In Homebrew_PCBs@yahoogroups.com, "derekhawkins"
> <derekhawkins@y...> wrote:
> > >Well I don't know, I'm using chemicals for serigraphy "for
> > >professional use only", more precisely, bichromate-sensitivized

vinyl

> > >dispersion, used for TEXTILE printing.
> >
> > Is this the emulsion you have been referring to or an excerpt from
> > your resume? I'm confused.
>
> I don't get it.

Where is the cheap (and assumed readily available) in your photo-
etching process besides the use of sunlight? What's the cost and
availability of this emulsion you're using bearing in mind that the
rest of us may be non-professional average Joes?