As published in Readout October 2003

PCB TRACK COPYING

Dear EPE,

I've been playing with my p.c.b. etching kit and I think I've come up with
a near-foolproof method for transferring a p.c.b. master from an issue of
EPE onto a copper-plated p.c.b. blank using Press-n-Peel (PnP),
though the method could probably be adapted for other "toner transfer"
p.c.b. etching systems.

First of all, scan the p.c.b. image into IrfanView (from
www.irfanview.com), making sure it's as straight as possible. Scan
it in "256 Greyscales" mode at either 300dpi or 600dpi. When IrfanView has
finished loading the scanned image, zoom out until all of the p.c.b.
pattern is visible. Open the Image menu, then select Enhance Colours. Move
the Contrast slider all the way to the right and click OK.

This should have left you with a near-flawless black and white image. Save
it to disk and edit it in Paintshop Pro, Paint or whatever graphics editing
program you usually use. The objective in this case is to get a p.c.b.
image in black and white with no filled in pads or short-circuited tracks.
Save the image and load it into IrfanView again.

Next, select Print from the File menu. Select your printer and set its
resolution to match the resolution of the scanned image (300 or 600 dpi).
Click OK. In the next window, select "Original size (from image DPI)". Make
sure your printer is loaded with blank paper, then click the Print button.
When the image has printed, cut a piece of PnP toner-transfer material to
match the image, but oversize it by half an inch (13mm) on each side.

Remove a label from a sheet of laser printer labels (or tear a bit off).
Use the label to stick down the PnP. Make sure the label is affixed to the
leading edge - the side the printer starts loading from. Reload the paper.
If your printer uses an oiled cleaning pad or roller to keep the fuser pads
clean, remove it temporarily. Print the image again using the same settings
as before.

When the transfer has printed, cut it off of the paper sheet with a sharp
pair of scissors or craft knife. Cut a piece of p.c.b. laminate to size,
leaving a 5mm or so border. Set a normal clothes iron to "No steam,
Cotton/Linen". Put on a pair of rubber gloves and clean the p.c.b. with a
green scouring pad and some washing-up liquid. When properly cleaned, the
board will be a bright copper colour with no signs of dirt or grime on it.
Water should form a solid "sheet" on the board instead of beading up.

Make sure the surface of the PnP is clean (no dust) and place it on the
p.c.b. blank. Heat one corner of the PnP for around five seconds to melt
the toner and stick the PnP down. Place a sheet of paper on top of the PnP
and start ironing down the transfer. This should take around 30 seconds
- make sure you don't stay in one place for too long and don't apply too
much pressure. Ideally the weight of the iron should be doing most of the
work.

After the 30 seconds are up, remove the iron and the sheet of paper and put
the board and PnP under cold running water for a few seconds to "set" the
toner. Dry the board and use a craft knife to lift the corner of the PnP
sheet. Keep pulling the PnP back carefully. If some of the PnP hasn't fused
to the board, put the sheet of paper back on top and iron that area for an
additional 30 seconds.

Cool the board and remove the PnP again. Generally, if the PnP didn't fuse
the second time, either the iron isn't hot enough or there's some dirt on
the PnP or the board. Touch up with a sharp tool, such as a craft knife,
and an etch-resist pen.

Etch the board as normal, then clean off the PnP and toner with a scouring
pad and washing up liquid, or you can use acetone, which is quicker.

Philip Pemberton, via email

Thank you Philip, that sounds extremely useful. I'll put your advice into
our PIC Tricks folder on our ftp site (even though it's not strictly
speaking "PICing"!).