Homebrew PCBs

twb8899:

Your technique is probably the most "professional"
that I've read about on this forum.

Negative acting resist may have an edge over
the positive stuff, and may produce better products.

I don't know if "Resiston" or any of the laminated resist
materials are still being made, but this stuff worked really good.
But one needs to have a dry film laminating setup to use it.

I recall the excellent results that Kodak KPR resists
could produce, but alas, the Feds said it was too
nasty and Kodak moved away from it, although I
think some version of KPR is still being made for
the microcircuit fab industry, but not generally
available to the public.

A lot of microstripline work used to be done using
the photo plotter methods you described, but I've been divorced
from that area for so long, I don't know what they
are using now. It might be interesting to set up a
plotter using an LED "pen" in a dark box to plot
on sheets of litho film and then develop the film
in AB litho developer.  I think such a setup could
produce some really high contrast PC artwork.

Having done "tape-up" artwork as large as 10X,
and having it reduced to Actual on a big copy
camera, I have a feeling for the accuracy one can
obtain from the methods you described.

Good Show!

Roland F. Harriston






twb8899 wrote:
>
>
> I use photo plotted film negatives with negative acting dry film photo
> resist. Expose with 1 kW mercury vapor bulb for 17 seconds. Etching is
> with ferric chloride at 110 degrees F in a small spray etcher. I use
> negative acting resist because it's lower cost and exposes much faster
> than positive types. Almost never have any rejects using this method.
> My production is 10 to 50 boards per lot with nearly 100% yield every
> time.
>
> Find a supplier in your area with a photo plotter to make your films.
> If that's not available plot the design at 2:1 scale with black ink on
> white paper and have a printing shop shoot a negative film at 50%
> reduction on their camera. You will have a high accuracy master film
> that will last for years.
>
> Do some research on D-min and D-max concerning photo films. It's the
> measure of density in the clear and black areas of the film. The
> biggest problem with laser and ink jet printing is not enough D-max or
> very dense black areas. Shine a lamp through the black areas of your
> film and look at it with a maginfier. This is what your photoresist is
> seeing and it's usually not dense enough for a proper exposure.
>
> Tom
>
> --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "lcdpublishing"
> <lcdpublishing@...> wrote:
> >
> > Hi guys,
> >
> > I have almost given up on direct ink-jet resist and on "plotting"
> > with Staedtler pens using the CNC machine, and I am about to abandon
> > toner transfer. Only problem with toner transfer is the "scaling"
> > issues either through the printer or from the paper not being stable
> > which causes problem with CNC drilling.
> >
> > Anyway, I ordered up some negative type resist chemical, the
> > developer, a lamp, and an exposure frame. I am not expecting this
> > to go "perfectly" either, but am hoping to have a bit less
> > frustration in other areas.
> >
> > I am thinking the best accuracy I can get when printing is to use an
> > ink jet printer (I have Epson R220 and Epson CX6600). I have a PDF
> > editor program that allows me to edit trace colors and back ground
> > colors so that I can make negatives so that shouldn't be a problem.
> >
> > The first "problem" I suspect I will run into is getting enough
> > density on the transparency to make sure the "black" areas are dense
> > enough to block out the UV exposure lamp where needed. Has anyone
> > run into this issue and how do you deal with it?
> >
> > Any other pointers would be greatly appreciated as well as this is
> > my first time for "photo-processing".
> >
> > Thanks
> >
> > Chris
> >
>
>