[sdiy] DIY PCBs

[marmot1 at magma.ca]

Hi Paul and list,
The generally preferred method is getting a PCB shop to make the boards for you.... particularly if many are 
required. If you must DIY, here's what works for me...

I make prototype PCB's by hand using a Lumocolor pen for etch resist (Lumocolor #313 or #317) and rub-on "etch 
resist transfers" for hard-to-draw stuff like IC pads.  The secret here is to clean the copper surface (before 
putting on the resist) with slightly damp scouring powder - very fine steel wool is too coarse and will gouge 
the copper and prevent the resist from going on smoothly. Wash the board very well with hot water after 
cleaning, and dry thoroughly before applying resist. To etch, I float the board copper side down in a plastic 
tray of ferric chloride etchant. Takes about 30 minutes. Handle etchant carefully - it corrodes many metals, 
including stainless steel... remove the etched PCB, wash in warm water for a minute, then dry with a paper 
towel and remove resist using methanol or acetone - again being careful about skin contact and fume inhalation 
and flammability. Then give the PCB a very thorough washing for several minutes in running warm water to remove 
all traces of (conductive) ferric chloride. Then dry, drill, solder...

Make the layout with the help of the computer, and print it out actual size (foil side). Tape it to the cleaned 
board, and use a needle or punch to make pinpricks where the pads go - then remove the paper, draw in pads and 
traces, and use rub-on transfers. It is easy to make mistakes - there is a product called "Press n' Peel Blue) 
which is a sheet you put through the printer, and then use a hot clothes iron to iron the layout onto the 
copperclad board. Supposedly it works well although it requires carefull ironing to ensure that all of the 
layout is transferred to the board. Using the pen method is tedious, but gives me  perfect results every time - 
no bridges, no hair-line breaks. Not so good if you need to make several identical PCB's though. I have made 
boards with up to 23 DIP's this way. Also got reasonable results (long time ago) making boards using spray-on 
photoresist (no longer available - hazardous). I made the layout on a Mylar or acetate sheet, placed it on top 
of the sensitized board, put a thick sheet of window glass on top and put it in the sun for 5 minutes. This was 
followed by treatment with  developer solution, then drying and etching. Haven't tried it with pre-sensitized 
boards. 
Regards, Mike