Homebrew PCBs

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