Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I don't think I've seen a method described on the list for applying
photoresist film with just a clothes iron, so here goes, apologies if
it's well known.

I start with a board which is of course clean, dry, and cold. The film
is also cold. 10 to 15 degrees C, winter in the shed temperature around
here. Coldness makes it less sticky, at least I feel it does anecdotally.

Plug in the workshop clothes iron and put it on basically the minimum
setting, you'll of course have to experiment to find your particular
comfort zone.

Put the board, copper up, on top of a nice thick piece of cardboard.

Doing the "tape on each side at one corner and pull apart trick" I
remove the entire bottom (inside curl) protective layer.

Now lay the film over the copper, it doesn't really stick cold (at least
mine doesn't) so you can quite easily smooth it on and reposition if
necessary, as you smooth it your body temperature may make the film just
sticky enough to hold in place.

Once the film is in position, flat, and without wrinkles and bubbles,
place a piece of clean paper (or two) over the top of the film & board,
and place the iron on that, covering the board (naturally, this method
is only really going to be good for sizes up to the plate of your
clothes iron, maybe a bit larger).

Apply some pressure, don't move the iron yet.

After say 20 seconds things should be getting warmed up under there,
slide the iron around gently, just like ironing your shirt, paying
special attention to the edges of the board, these are the problem
areas, roll the iron over the edges. Periodically lift the paper and
check the board visually, if it's looking a bit melted, then you've gone
too hot, clean it off (unless it's just an inconsequential spot), reduce
the iron temperature, start again.

Check the temperature with the palm of your hand, you want it nice and
warm, but not so hot that you can't hold it, sort of hot water from your
tap temperature. Once you think it's warm, that's it, slice the board
off (the overhanging film will have stuck it to the cardboard), cool it,
and away you go. If you find that the film isn't stuck to the board
totally, you know that you needed to warm it up more, or more evenly
(spread the iron around), the most likely places to have a problem are
the edges.

I also have an old wallpaper seam roller which I run over the board once
I've removed the iron, just to make sure I've really hit every area with
a bit of pressure especially the edges, but it's probably not really
necessary.

I can do boards quite reliably this way, faster than heating up the
laminator, making a carrier the right size, hinging and taping the film
onto it, feeding it through several times... my clothes iron hits it's
min setting (or a couple clicks above) within a few seconds, and I can
have the film attached in a minute.