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, "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
>