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IMAGES ARE STILL TO ADD.

The only 'dangerous' products used are:

FERRIC CHLORIDE

Synonyms: Iron chloride hexahydrate; ferric trichloride hexahydrate
Molecular Weight: 270.30
Chemical Formula: FeCl3 6H2O

Appearance: dark brown. May cause liver and kidney damage. May cause blood abnormalities. May cause adverse reproductive effects. Harmful if swallowed.

Warning! May cause respiratory and digestive tract irritation. Causes eye and skin irritation and possible burns.
Target Organs: Blood, kidneys, liver.


Potential Health Effects
Eye: Contact produces irritation, tearing, and burning pain. Causes eye irritation and possible burns.
Skin: May be absorbed through the skin. Causes skin irritation and possible burns.
Ingestion: May cause irritation of the digestive tract. May cause severe irritation of the mouth and throat. May cause low blood pressure, rapid heartbeat, skin discoloration, and possible coma.
Inhalation: May cause respiratory tract irritation.
Chronic: Prolonged or repeated exposure may cause adverse reproductive effects. May cause liver and kidney damage. Repeated exposure may increase iron levels in the liver, spleen and lymphatic system. Damage may occur in the spleen and liver.

LASER PRINTER TONER (Styrene Acrylate Copolymer + Iron Oxide)

Inhalation: Minimal respiratory tract irritation may occur with exposure to large amounts of dust.

Chronic: Prolonged inhalation of excessive amounts of any dust may cause lung damage. Use of toner as intended does not result in inhalation of excessive amounts of dust.

Please do not harm yourself with the hot iron, or with the photographic paper... I don't know how you can harm yourself with the paper, but people is getting everyday smarter...

After many tries, I managed to get to a reproducible technique to have a high quality printed circuit board using only a laser printer, a carefully chosen paper and the usual ferric chloride.

The tests have been conducted with a test routing with a clearance of 0.2 mm; the layout in Protel appears much more defined than here... I don't know why :(

(For testing I have ignored the need of a double layer PCB due to net P1-11; this is only a useless test PCB, after all... more info on double layers later!)

Here is the sequence:

1) Set up the printer NOT to save toner, and to the maximum possible resolution

2) Prepare your PCB final template... and convert any color or grayscale to BLACK. Try to print at the upper end of the sheet, not in the center; doing so, you will maximize the paper use, cutting away the template and reinserting the sheet...

3) Take the precious photographic paper out; after trying normal paper, trasparent sheets, very thin oiled paper and some kinds of photo papers, I settled for the Canon Glossy Photo Paper GP-401, suitable for inkjet prints, weight 190g/m², thickness 225 μm; reasonably cheap, too...

4) Print, being extra careful not to bend/jam/stain the paper in the process (ok, just print using an average laser printer; I use a cheap Samsung ML1210)

5) Thoroughly clean the copper PCB with a very fine sandpaper; it must be shining, and it will not remain so for much, because of oxidation... do not wait 12 hours before going on!

6) position the template FACE DOWN on the board, and with the pre-heaten iron (set it to MAX) apply an uniform pressure for 10 seconds

7) Interpone a thin cloth between the iron and the paper, and continue ironing with a firm pressure for 2-3 minutes

8) Switch off the iron, and WAIT UNTIL EVERYTHING COOLS DOWN TO ROOM TEMPERATURE (It doesn't matter what temperature a room is, it's always room temperature :) ). Not a degree more! If you feel more confortable, leave a weight on (but be cautious, at the beginning it will be ferociously hot! Do not use as a weight anything that could burn/melt/explode/scream...)

9) GENTLY pull out the paper, SLOWLY, starting from a corner and peeking at the result (In any case you could not resist peeking, at this stage)

10) If everything worked the way it is expected, the toner will be completely transferred on the copper, TOGETHER with the thin glossy finish of the paper. The trick is that is not the toner that 'transfers', but it sticks enough to the copper to tear apart the paper glossy finish from the substrate. You cannot obtain this result with normal paper, or by any other means. The result will be a WHITE piece of paper with your template 'engraved'... and the same template sticking mirrored on the copper (you will not see the black toner but the whitish paper finish!) - ** SEE ADDENDUM! **

10a) If the toner somewhere does not transfer COMPLETELY, you will see it clearly on the paper, "black on white". Check if the trace is missing or only lighter than the others, without the glossy finish... in the latter case you you could probably go on anyway... the toner is highly protective. Otherwise restart from point 1...

11) Put the board into ferric chloride as usual... If it is not "usual", take a tour to any site that talks about it (for example this one).

12) At the end of the copper removal, the toner will be still there, and difficult to remove; I used the same sandpaper cited above, lightily and with GREAT CARE, to obtain a shining look.

13) If you REALLY need a 0.2 mm clearance (I used it just for testing purposes), thoroughly check for shorts; in case of troubles, use a precision knife (knives are sharp... standard disclaimer applies) to clean traces. I had to do it in one point.

I will add images of the process as soon as possible...

ADDENDUM (07/12/2005)... I found that the whitish paper glossy finish transferred on the copper board slightly reduces during etching the precision of the toner tracks! So, VERY CAREFULLY, use the finest sandpaper you can find to remove the paper finish from the toner tracks. You'll want to end up with a nice BLACK layout on shiny copper, before putting the board into the ferric chloride. The results are astonishing (better than photoengraving!)

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