PCB success!

[R.G. Keen]

>How much does Press-N-Peel cost per board (100x160 mm)? 
It costs about $1 to $2 per letter size sheet, which can be several
boards.
>Where can you buy it? 
Do a web search on "Techniks" and "Press-N-Peel", or look on the 
sci.electronics FAQ.


>It isn't available at my electronics supplier.
That's right.

>Didn't somebody say that some touching up was necessary with that method?

Depends on what you want it to do. I have literally gone from schematic 
to etched board in under one hour. I payment for that, there is some
care involved.

Like every technique, there are some limitations.

The practical resolution on the method seems to be about 10 mils,
although I have had moderate success with 8 mil lines in characters.

The practical trace width limit, for me, with my techniques, seems
to be about 12-15 mil traces. Using 15 mil traces, I typically would have
one or two touchups on a 100mm by 160mm board. I consider this amount
of touchup a very fair trade for not having to either wait for film
generation or for the chemical steps in exposing and processing photo
films, and for not needing an exposure frame or UV light source, or for
worrying about the sun and the time of day. And I don't wind up with 
useless copper clad material if I get the exposure wrong. I have
literally gone from schematic to etched board in under one hour.

If I foul up the ironing, I just wipe off the copper with solvent and
iron another one. Presensitized boards are either useful or worthless
after they are exposed, no middle ground.

Using 30 mil traces an no lines between IC pads, the yield is virtually
100%, no touchup required. 

Your results will vary depending on how well you control the ironing.
If you have access to an office laminator, you can tinker with the
temperature and speed and get 100% perfect every time. If you use a
household iron (I do) there are some errors, but then I didn't have to
buy either chemicals or a laminator.

The toner tends to spread out a bit when it's ironed on, so features
get a bit larger than printed. This means that shorts are much more
likely to result than opens, the reverse of many other methods.

This is not the method that will end photo methods - it's just
incredibly easy, fast, and has a very acceptable error rate, especially
for one-off boards where very tight trace spacing is not critical. It's 
so easy that I think that any discussion of PCB making that does not 
include it, even with its limitations, is shortsighted. This is not
just my experience. I provide toner sheets to a number of first time
and novice electronics builders. I have a large number of these people
who send email indicating working results the first time they try.

It's not perfect, just good.