Re: PC board making

Ian, Joe,

Sounds like you have a procedure which works well for you. I'd like
to caution about the usage of the "double transparency" tho...

Normally, the emulsion side (the side the printed "ink" is on would
be placed in contact with the board material. This prevents error
from the parallax error which can occur when the image is away from
the board material. (by the thickness of the film)

A second possible problem would be putting the "double film"
copies "ink side out". This would tend to make for even poorer
results, as there are now two images, two film thicknesses apart. The
one which (correctly) is against the board will cause no problem, but
the other one , which is "floating" away from the surface may cause
a "ghosting" image if the light source is not a broad -source (rather
than single point of light).

In other words, for everything to turn out the right size and in the
right place, everything (light, film, board) need to be in a straight
line...

May not be important for many simple boards, but can be VERY
important for complex (or RF) boards...

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., "Joel Jacobs" <jj@n...> wrote:
> I think thats the same PCB material I used to make my stepper
drives. I got
> the board from www.oceanstateelectronics.com
> I used a floodlight style grow light from Lowes and it seemed to
work fine.
> It did have a bit of a learning curve, the boards were taking a
long time to
> etch and I thought they needed more exposer when in fact the
developer was
> getting weak. I ended up with 2 usable PCB's from 5 attempts. I'd
sure try
> again though - the parts that came out ok look really good. The
> pre-sensitized board is pretty resonable too. I hadn't thought
about
> doubling the transparencies, sounds like a great idea...
>
> Joel
>
> ----- Original Message -----
> From: Ian Wright <Ian@i...>
> To: <CAD_CAM_EDM_DRO@y...>
> Sent: Saturday, April 21, 2001 9:11 AM
> Subject: [CAD_CAM_EDM_DRO] PC board making
>
>
> > Hi,
> >
> > I struggled for a long time trying to make decent PC boards by
all sorts
> of
> > different techniques but I now have the problems cracked. I can
now make
> > good small boards every time.
> > What I do is draw the board out in Eagle, Corel draw or some other
> graphics
> > package and print out two copies onto clear overhead projector
film (I use
> a
> > normal inkjet printer). One of the copies I print in reverse
(just tell
> the
> > graphics prog to flip it) and I then tape these together with the
printed
> > surfaces touching. This doubles the density of the print and
seems almost
> as
> > good as a litho film for this purpose. I then use commercially
coated,
> light
> > sensitive PC board from the local surplus electronics shop. I
have found
> > that there are (at least) two distinct types of this board about
and you
> > need to understand the type you have. The one I use is a
fibreglass based
> > board which develops with Sodium Hydroxide. I sandwich the board
and the
> > double 'negative' between a sheet of glass and a piece of wooden
board and
> > expose it to the light from a 35mm projector for about 8 minutes.
It then
> > gets developed in ordinary Caustic Soda drain cleaner, washed in
water,
> and
> > etched in Ferric Chloride.
> > The board says you should use ultra-violet light for exposure but
I have
> > found that, if you give it a strong enough blast of ordinary
light from
> the
> > quartz halogen projector lamp, it works just as well. You could
probably
> get
> > a similar effect using a car headlight lamp with a bit longer
exposure. I
> > would always try a narrow 'test strip' cut from the edge of any
new type
> of
> > board to verify timings first. HTH,
> >
> > Ian
> > --
> > Ian W. Wright
> > Sheffield UK
> > www.iw63.freeserve.co.uk