Hans,
I looked at the picture of your UV exposure setup. I just wanted to comment
that I would never use the round bulb. Use the florescent tubes and your
results will be better. I have found that the round bulb tends to give more
exposure in the center than at the outer edges. Even more apparent with
larger boards. This is the reason all exposure units sold on the market use
the florescent tube. You can compensate somewhat by having the bulb not so
close, but this just increases your exposure time. The other bad thing about
the round bulb is the heat. This will actually get in the way of your
process, depending upon what type of photo etch you are using. I am trying
to recall if it was a problem caused to the developer or if it was a
consistency problem in the exposure. Nevertheless, I found it to be a
problem several years back. If you modify your design to use the florescent
bulbs, you will notice a marked difference in detail as well as less
exposure time needed.
-Mike
----- Original Message -----
From: "Hans Wedemeyer" <hans@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, May 18, 2003 7:41 AM
Subject: Re: [Homebrew_PCBs] How I make my PCBs
> Leon,
> good advice except for Easy-PC....
> I spent full price on that program and found I wasted my money.
> Here's what I think of Easy-PC
> http://hans-w.com/ezpcbugs.html
>
> I moved on to EAGLE and have been happy with it. It's STABLE does not
> blow up cause me to lose work=time=money.
>
> A limited version of EAGLE is available for Free, it is limited to two
> sided board and size check it out at
> http://www.cadsoftusa.com
> EAGLE has a VAST library of part and users add parts all the time.
> Compared EAGLE parts Library to to Easy-PC several 1000 to 1
>
> I put Easy-PC up for sale on eBay but none wanted it. In fact I put my
> entire collection of Numberone product in the same auction
> Filter program, Easy-PC for DOS and for Windows and the digital
> simulator Pulsar. INo one reached my minimum Price of $200 ! It's still
> here in a box onthe floor, I think I'll use the disks and CD's for
> target practice sometime...
>
> Here's one thing that is not (was not)( they may have fixed it by now)
> possible to do with Easy-PC for Wndows, in a situation where top and
> bottom layers have parallel tracks sections that overlap, and a whole
> bunch of closely spaced via's or other pads, it is not possible to put
> the cursor on the trace/pad that I want for move/edit. It just snaps to
> the nearest and of course that is not handy at all ! I can turn snap off
> but that is not what it's all about.
> EAGLE allows ANY pad/trace on any layer to be individually selected even
> if they are overlapping.
>
> Pulsonix used to look like Easy-PC, I think they are the same bunch...
> Although Pulsonix used to give the schematic editor away for free, the
> PCB layout part is high $$$$ ! That's much like saying "this car is
> free, but the special wheel cost $20,000 each "
>
> I'll get off my soap boix now...
>
> I make double side board all the time. I used to do it the way you
> mentioned, and even wrote a program for my CNC mill to compensate for
> alignment problems.
> I found a better way by printing on transparencies and then aligning
> them visually, then stapling them together. Then slide the board in
> between the transparencies and sandwich the whole lot between two plates
> of glass, and place the sandwich between two lamps
> http://hans-w.com/setupforexposure.jpg
> and
> http://hans-w.com/twolampexposure.jpg
> Credit for this sandwich idea goes to
> http://www.electricstuff.co.uk/pcbs.html
>
> Alignment between top and bottom is good. Perhaps the greatest problem
> I've run into is the HP LaserJet making different print sizes when I
> mirror the one side.
> I used to worry about getting the printed side of the transparency close
> to the PCB, after testing with 5 mil lines I decided there is NO need to
> mirror. Using the exposure as I how in my photo it allows me to do 5 mil
> lines all day everyday.
>
> Thanks for all the tips.
> Best Regards
> Hans Wedemeyer
>
>
> Leon Heller wrote:
>
> > I've been making my own PCBs at home for about 40 years, starting by
> > painting the pattern onto single-sided PCB material using a fine
> > paintbrush and cellulose paint, with ferric chloride or ammonium
> > persulphate etchant. I used 0.1" graph paper for designing the layout
> > then marked the holes with a centre punch through the paper onto the
> > copper surface. I even made a couple of double-sided PCBs using this
> > technique, by masking off one side, etching the other side, drilling
> > it,
> > and using the drill holes as a guide when painting on the resist on
> > the
> > second side. I then masked off the first side with tape to etch the
> > second side.
> >
> > When low-cost CAD software became available (I used Easy-PC from
> > Number
> > One Systems for years) I progressed to printing 2:1 artwork on a dot
> > matrix printer. I then got a local litho platemaking company to
> > produce
> > a 1:1 positive transparency that I used with a home-made UV exposure
> > unit and resist-coated PCB material. When I got an ink jet printer I
> > found that I could get reasonable results by printing 1:1 artwork onto
> >
> > tracing paper.
> >
> > I now use an old LaserJet IIIp I picked up very cheaply to print 1:1
> > onto LaserStar film and expose the PCBs in a home-made UV exposure
> > unit.
> > I sometimes use tracing paper (nice and cheap), but find that I get
> > better results from the LaserStar film. The CAD software I use is
> > Pulsonix, a professional package out of the same stable as Easy-PC. I
> > regularly use 12/12 design rules, occasionally going down to 10 mils
> > if
> > I need to route tracks between IC pads. Rather than conventional
> > positive-resist FR4 PCB material, I usually use something called
> > FPC-16
> > which consists of a sandwich of compressed paper between thin layers
> > of
> > fibreglass. It's cheaper than FR4 and much easier to cut and drill.
> > It's
> > available from Mega Electronics, as is the LaserStar film.
> >
> > Etching is in ferric chloride. I place the etchant in a small plastic
> > food container inside a larger container half-filled with hot water
> > and
> > continuously agitate the etchant manually by rocking the container.
> > Etching typically takes 5-10 minutes.
> >
> > I'm quite pleased with the results. I intend to experiment with
> > double-sided boards by making a UV exposure unit that can expose both
> > sides of the PCB simultaneously. With a better printer and vacuum on
> > the
> > UV exposure unit I think I could get 8 mil tracks quite reliably. I've
> >
> > heard of other people managing it at home.
> >
> > Here is an example of one of my PCBs:
> >
> > http://www.geocities.com/leon_heller/pcb.html
> >
> > I often use the Pulsonix copper pour facility for this type of board,
> > as
> > it makes the routing easier. Cross-hatching is better with a laser
> > printer, as they don't tend to print large black areas very well.
> >
> > Links:
> >
> > Mega Electronics: http://www.megaelect.demon.co.uk/
> > Number One Systems: http://www.numberone.com/
> > Pulsonix: http://www.pulsonix.com/
> >
> > Leon
> > --
> > Leon Heller, G1HSM
> > leon_heller@...
> > http://www.geocities.com/leon_heller
> >
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