Homebrew PCBs

Leon Heller wrote:

>What are you printing the transparencies on?
>  
>
I'm using a Canon i560 to print on IBM inkjet transparencies. I've tried 
a few different types of easily-available transparencies (the sort of 
stuff that places like PC World stock) and haven't noticed much of a 
difference between the types. I've made a number of test boards 
containing designs with 8/8 rules -- in each case the results haven't 
been nearly good enough to be usable. Something is definitely badly 
wrong with my process! I struggle to fully develop the boards without 
mechanical assistance (generally rubbing at the boards with cotton buds) 
-- this invariably leaves contaminants on the board, which in turn 
causes etching problems. Etching is in any case very uneven. This seems 
to point to either bad artwork or insufficient exposure.

I expose the boards (6" x 4" DS FR4 stock) about two inches above two 
15W UV tubes for three minutes. I'm extremely nervous about 
over-exposure: perhaps too nervous!

I'd love to be able to make 8/8 double-sided boards at home; the reduced 
turnaround time would really help some projects. I suspect, however, 
that DIY PTH may be beyond my abilities. I'm getting ready to send 
artwork over to Olimex in order to get some proto boards made up, but I 
have my doubts: my requirements seem to be at the absolute limits of 
what they offer -- 8/8, lots of fine-pitch high pin count SMDs, and so 
forth -- so I'm not sure whether the results will be any good. Still, it 
doesn't cost much to find out!


Stuart