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