Hi folks,
I think I've finally perfected my toner-transfer method. I've just done a
double-sided PCB - no faults, except for the broken track I had to wire-jump
after the ∗£$#ing drill packed up and sent shards of tungsten carbide all
over the board. I don't really feel like repeating the gory details here, but
suffice it to say I'm in the market for a new PCB drill (see other message).
Anyway, here's how I did it:
Cleaning
========
1) Spray some 99% Isopropyl onto a scouring pad (Scotchbrite). I used one of
the combined sponge/scouring pad things. Rub in a circular motion until
the board is shiny, adding more IPA as necessary.
2) Put some IPA on a piece of kitchen paper and wipe the board clean. Repeat
with clean paper until the paper remains clean after wiping.
Transfer prep
=============
3) Take both transfers, and place them with the toner sides together. Place
the bundle on top of a light-box and align them. Use a magnifying glass
if you feel really pessimistic, but it's not (usually) required.
4) Use two small pieces of double-sided tape on the corners to hold the
transfers together. You should end up with a pouch that's open on three
sides.
5) Insert the PCB blank into the pouch and use the lightbox to align it.
Transferring
============
6) Iron one side for two minutes, using as much pressure as you can apply
without breaking the iron. Move the iron around to make sure the board
gets heated evenly.
7) Flip the board over and iron the other side for around a minute.
8) Put the board into a sink full of warm water (with dish soap added - the
"Fairy" branded stuff seems to work well). If the board is hot enough, it
will sizzle as it hits the surface of the water.
9) Leave the board for about 10 minutes to allow the water to soak into the
paper. Peel it off slowly from the corners. Leave the board for another
five minutes, then rub off any leftover paper with your fingers.
10) Use a dry toothbrush to remove the white clay that sticks between the
tracks. If you can't see the clay coating, dry the board with a paper
towel and it will become more visible. Make sure you get the coating out
of the holes in the pads, unless you enjoy trying to get a drill bit
absolutely central in a solid copper pad. The white clay IS etch
resistant.
11) Dry the board, check it carefully and put it in your etch tank. I use
ferric chloride in a homemade heated bubble-etch tank. The heating
doesn't seem to do much to the etch time, but the bubbles really speed up
the etching process.
I'm planning to try and make a fuser-based toner-transfer laminator, just as
soon as I find a decent geared motor, a shaft adapter and a suitable base
board. Oh, and a triac. And a temperature sensor that goes up to 160C (I
don't have any data on the LJ fuser's thermistor).
Later.
--
Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem@... | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.me.uk/ | 48xCD, ARCINv6c IDE, SCSI
... Blessed are the Greeks