Homebrew PCBs

I just joined this group today and noticed that no one has mentioned
the Sharpie Industrial pens in the message archive. 

IT HAS TO BE THE *INDUSTRIAL* VERSION. THIS CONTAINS THE MAGIC INK.
(See link at end of message.)

A couple of years ago I accidentally discovered the Sharpie Industrial
pens are a supreme etch-resist pen, unlike any other, and I have tried
a lot.


Pen Performance as stated by Sanford:

Resists acids, processing chemicals, and cleansers

Ink stays permanent under most chemical washes, extreme heat and steam
up to 500°F.

Waterproof, resistant to many solvents, smear proof.

Specially formulated for industrial, laboratory and commercial use.

Permanent on metal, foil, glass, photographic film, plastic and most
hard-to-mark surfaces.


Yeah Baby! This is one special ink.

A single stroke is all that is required to create the finest track.
Ferric chloride will not touch this ink nor pit the masked area like
other pens allow.

I created a pen holder from one of the pen caps for my HP7475A plotter
and can create circuit boards for most of my projects.

A few important hints:

Use a CAD package that outputs HPGL. Eagle and Pulsonix will do this
as well as some others.

Set the pen speed as low as it will go and plot to file. If the Cad
package doesn't allow you to set pen speed, set the default pen speed
manually by adding the pen speed command after the initialization
string at the beginning of the file. There are special shareware
Notepad replacement programs that will edit in ASCII that can be used
if the file is larger than 64K.

When converting the HP pen claw to hold the new pen, use many loops of
an ordinary rubber band to secure the pen into the claw. The pen will
still slip upward in the holder so glue a piece of 220 grit sandpaper
with solvent-based contact cement or good quality (the thicker stuff)
double-sided carpet tape to the inner surface of the pen claw. I tried
to use epoxy putty to form a perfect
holder but the increased mass delayed the pen rise enough to produce
"icicles" at the pickup points. Just use the rubber band and a
sandpaper friction pad, it works.

Do a test plot of the board outline onto a sheet of paper, first. Then
tape the prepared PCB board to the paper on top of the first plot. I
used clear box packing tape.

The "paper" loading can be hairy. The plotter will load and
fling the
paper back and forth a few times at full traverse speed. Just nurse it
through. If I can do it, you can do it. The pen should not be loaded.

Pen height will need to be adjusted. I forgot to mention above under
building the pen holder to use the pen cap as the holder. Rip off the
pocket clip and cut off the shut end of the cap with a razor knife
until enough has been removed. Secure the pen cap into the plotter
claw as noted above. Insert the pen until it clicks into the cap and
set the pen height as needed by test-running. Now when you're done
plotting, remove the pen and recap it with another cap. Your pen
height adjustment will remain set with the cap/holder.


http://www.sharpie.com/sanford/consumer/sharpie/pr
oductcatalog/tipfamilydetail.jhtml?attributeId=SNA
TT40202¤tType=SNTYPE004