Homebrew_PCBs

Has anyone got a homebrew set up working for printing component
location overlays? Any tips and gotcha's ?

Been toying with the idea of making a small screen printing set up
but
no point in re-inventing the wheel if you've been there before!

AWEM

On Fri, 23 Sep 2005 00:08:58 +0200, Andrew Mawson <andrew@...>
wrote:

> Has anyone got a homebrew set up working for printing component
> location overlays? Any tips and gotcha's ?
> Been toying with the idea of making a small screen printing set up
> but
> no point in re-inventing the wheel if you've been there before!
> AWEM
>

i do toner transfer it.

wonder if colored toner would work in a bw printer and if it'd look even
better.

recenty experience adhesion problems on some board materials, greatly
puzzled and annoyed by it.


ST

> Has anyone got a homebrew set up working for
> printing component
> location overlays? Any tips and gotcha's ?
>
> Been toying with the idea of making a small screen
> printing set up
> but
> no point in re-inventing the wheel if you've been
> there before!
>
> AWEM
>
>

Its rare that I will add the overlay, but I do have
the capability of doing so.

Here are a few things I found.

1. Use orange screen, as it reduces ghosting due to
reflections as compared to white. (I still mostly use
white, as its what I bought at the start)
2. One might get better results using sheet emulsion,
but I have found that manually coating the screen
works pretty well. The key is to only make one pass
with the emulsion on front side, and then on the back
side. If you make multiple passes, the emulsion gets
too thick, and you loose resolution.
3. Be sure to refrigerate your emulsion... most of
them have a short shelf life, and when they go bad,
you run into big problems.
4. Don't be cheap when it comes to emulsion remover.
While one can use bleach and scrubbing, the commercial
removers work wonders, and I think are a lot easier on
the screens.
5. A Stouffer gauge is a good investment, even for
making PCB's. Spending $US18 for a strip of plastic
seems insance, but it will save you tons of scrap
screens, pcb's, and time... The 21 step is what was
recommended to me, and its amazing.
6. Wash out your screen when you are done... if you
wait around... it becomes pretty much permanent
7. scrap pcb's work well for registration
8. Water soluble inks make for ease of cleanup, but
are not as robust as some of the solvent based inks
9. I use student grade art supplies, as most of the
time, they are a lot safer than the industrial inks
and solvents.
10. Currently, I make my films using ink jet printed
transparencies. The black is not as opaque as would be
nice for optimum resolution, so I am thinking of
getting some ortho film or something like it.
11. Wood screening frames warp... but I have yet to
find a good source of aluminum ones. A warped frame
makes it a challenge to get decent resolution.

Silkscreening just overlays is a ton of extra messing
around for not a lot of value imho. However, you can
also make up soldermask, solder stencils, and
enclosure screens at the same time. The net result is
you save a lot of time and increase reliability via
reflowing the boards vs hand soldering, so imho its
usually worthwhile.

Ron

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Thanks Ron the informative reply.

Silkscreening a one off PCB is like I figured, lots of messing around. I
suspect it would add another hour to two of labor.

I bought some silkscreen emulsion once, in a futile attempt to use it as
a liquid photoresist for etching PCBs. First, I could not get thin even
coatings, and 2nd the cured emulsion is not resistant to etchants
(swells and lifts of copper). Just letting others no it ain't work.

Adam


ron amundson wrote:

>>Has anyone got a homebrew set up working for
>>printing component
>>location overlays? Any tips and gotcha's ?
>>
>>Been toying with the idea of making a small screen
>>printing set up
>>but
>>no point in re-inventing the wheel if you've been
>>there before!
>>
>>AWEM
>>
>>
>
> Its rare that I will add the overlay, but I do have
> the capability of doing so.
>
> Here are a few things I found.
>
> 1. Use orange screen, as it reduces ghosting due to
> reflections as compared to white. (I still mostly use
> white, as its what I bought at the start)
> 2. One might get better results using sheet emulsion,
> but I have found that manually coating the screen
> works pretty well. The key is to only make one pass
> with the emulsion on front side, and then on the back
> side. If you make multiple passes, the emulsion gets
> too thick, and you loose resolution.
> 3. Be sure to refrigerate your emulsion... most of
> them have a short shelf life, and when they go bad,
> you run into big problems.
> 4. Don't be cheap when it comes to emulsion remover.
> While one can use bleach and scrubbing, the commercial
> removers work wonders, and I think are a lot easier on
> the screens.
> 5. A Stouffer gauge is a good investment, even for
> making PCB's. Spending $US18 for a strip of plastic
> seems insance, but it will save you tons of scrap
> screens, pcb's, and time... The 21 step is what was
> recommended to me, and its amazing.
> 6. Wash out your screen when you are done... if you
> wait around... it becomes pretty much permanent
> 7. scrap pcb's work well for registration
> 8. Water soluble inks make for ease of cleanup, but
> are not as robust as some of the solvent based inks
> 9. I use student grade art supplies, as most of the
> time, they are a lot safer than the industrial inks
> and solvents.
> 10. Currently, I make my films using ink jet printed
> transparencies. The black is not as opaque as would be
> nice for optimum resolution, so I am thinking of
> getting some ortho film or something like it.
> 11. Wood screening frames warp... but I have yet to
> find a good source of aluminum ones. A warped frame
> makes it a challenge to get decent resolution.
>
> Silkscreening just overlays is a ton of extra messing
> around for not a lot of value imho. However, you can
> also make up soldermask, solder stencils, and
> enclosure screens at the same time. The net result is
> you save a lot of time and increase reliability via
> reflowing the boards vs hand soldering, so imho its
> usually worthwhile.
>
> Ron

Adam - What emulsion did you try and what was your etchant? I seem
to recall a discussion on this topic recently but I'm not sure any
conclusions came of it.

Ron - Thanks for all the info on screening.


Regards, Bob


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

> Thanks Ron the informative reply.
>
> Silkscreening a one off PCB is like I figured, lots of messing

around. I

> suspect it would add another hour to two of labor.
>
> I bought some silkscreen emulsion once, in a futile attempt to use

it as

> a liquid photoresist for etching PCBs. First, I could not get thin

even

> coatings, and 2nd the cured emulsion is not resistant to etchants
> (swells and lifts of copper). Just letting others no it ain't work.
>
> Adam
>

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.

Adam

Bob_xyz wrote:

> Adam - What emulsion did you try and what was your etchant? I seem
> to recall a discussion on this topic recently but I'm not sure any
> conclusions came of it.
>
> Ron - Thanks for all the info on screening.
>
>
> Regards, Bob
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Adam Seychell
> <a_seychell@y...> wrote:
>
>>Thanks Ron the informative reply.
>>
>>Silkscreening a one off PCB is like I figured, lots of messing
>
> around. I
>
>>suspect it would add another hour to two of labor.
>>
>>I bought some silkscreen emulsion once, in a futile attempt to use
>
> it as
>
>>a liquid photoresist for etching PCBs. First, I could not get thin
>
> even
>
>>coatings, and 2nd the cured emulsion is not resistant to etchants
>>(swells and lifts of copper). Just letting others no it ain't work.
>>
>>Adam
>>
>
>
>
>
>
>
>
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