Roland,
You're correct about using the methods I mentioned earlier for micro
wave strip lines. I used to have a commercial shop and used much of
the same equipment I now have to make strip line and other RF
circuits. These were for McDonnell F/A-18 parts and equipment. I
closed that plant several years ago but kept most of the smaller
equipment for my home based shop.
I built my spray developer and spray etcher from scratch and use them
all the time. They are a simple design and kind of based on the Kepro
stuff. When Kepro shut down I bought quite a bit of the manufacturing
equipment they used to make their products. I'm now thinking about
making the etchers myself and offering them for sale. Biggest problem
is getting the cost down. The Kepro units were way too expensive and
could probably be offered for a more attractive price with some
engineering changes.
This new spray etcher is in the works but it's still to early to say
much about it except that the prototype works great. If we can get the
cost just right it will be available later this summer. If anyone is
interested in a product like this contact me by email and I'll forward
photographs and more information when we are ready to go.
Tom
--- In
Homebrew_PCBs@yahoogroups.com, "Roland F. Harriston"
<rolohar@...> wrote:
>
> 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
> > >
> >
> >
>