Homebrew PCBs

John,
That is a nice board. At the end of your page, you mention that you 
think the tracks ended up 25 mils rather than 20 because of the 
extra toner. That is exactly what I am talking about that used to 
cause me trouble. I think you have the right idea by not applying 
too much pressure. I still apply a good bit of pressure but I make 
sure my toner is thin from the printer. The board where I learned 
the most about toner thickness, pressure, etc. was on a board with a 
C8051F018 SMT with .5 mm lead spacing. The pads and traces to the 
chip were 12 mils wide with 8 mil spacing believe it or not. After 
lots of experiments with toner spreading, I reduced the width to 8 
mils, leaving 12 mil spacing. When I ironed it, it spread to about 
what I originally needed, I think. This was using a Lexmark Optra S 
1650 printer. I believe that if I were to do it again with the 
printer I am using now (Xerox Phaser 6250), I would not have the 
trouble, particularly if I do as you mention and NOT press so hard.

For one just learning, I would definitely try to stay with trace 
separation of 20 mils or more but with practice (and use of Toluol 
from the hardware store to remove toner if it doesn't go on well so 
you can start over), very fine traces are possible.

NOTE: Toluol causes all kinds of cancer, etc., according to the 
label. Be careful! It is wonderful for washing the toner off the 
boards, however. A little in a tin pan is all that is needed. I use 
a paper towel held in tweezers to wash the board. What do you other 
guys do to remove the toner either for a redo or just after etching?

--- In Homebrew_PCBs@yahoogroups.com, whoop@b... wrote:
>
> 
> On 31 Dec 2005, at 17:19, kennytrussell wrote:
> 
> > I agree with all of Stefan's comments completely. I will add to 
my
> > comments that the ironing-on process is the most difficult to get
> > consistent. Particularly, I have had trouble around the edges.
> 
> I am finding the iron toner process so easy and predictable I am  
> wondering why some of you find it a problem. I am using Epson 
photo  
> quality paper, S041061 and after a 2 minute soak it comes off  
> completely, leaving no residue or paper. I found it better than 
the  
> cheap glossy I tried. I just did my first double sided board 
which  
> was also OK.
> 
> I move the iron around making sure I get the edges done. I don't 
use  
> much downward force, just enough to keep intimate contact with 
the  
> board.
> 
> My first board efforts, making some LED clocks, are at http:// 
> www.jsdesign.co.uk/charlie/
> 
> John
>