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
> 
> 
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

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com