Some comments on William Westfield's post:

(I know the date of the post is 1992, but the author's comments seem to
follow my post from a few days ago.)

> But little does Dave realize that his HP plotter will not allow big
> ol'
> pens to be loaded into the pen carousel. "No Problem!", says Dave,
> "I'll use the old HP 7470A plotter. There is NO CAROUSEL anyway, just
> two pen holding bays (one on the left, one on the right) which are
> easily accessable; this plotter works with the cover raised, so there
> is
> plenty of clearance for my new pen, and the pen holder has a circular
> aperture which allows easy loading and removal of the pen into the
> newly reamed out pen adapter."
>
An HP7470A is not a flatbed plotter. I didn't think the grit wheels
which normally drive the X-axis of the paper would hold something as
thick and rigid as copper clad. I'd like to know how the guy in the
original post did it. There are also some tricks which can be used to
take care of "pen bashing". Plot to a file, strip off the "SP" (select
pen) commands.

>  After the miserable failure of the Sanford Sharpie in the etching
> tank,
>
Sharpie worked fine for me. Made dozens of boards. Some rather
intricate. Even did traces between pins. Anytime you use an etch resist
method, you're in a fight against time. The quicker you can etch the
exposed copper off, the better your results will be. A spray etch tank
is the best. Not having this luxury, I resorted to a hot water bath
supporting a tray of ferric chloride. I used a rocking back and forth
agitation method to speed the etching. My etch time was about 5-7
minutes for a medium size (6" x 6") board. The etched copper "residue"
can scratch the etch resist causing pitting and undesired etching. It
took several practice runs to get the technique right. Definitely (not
by a long shot) not commercial quality, but good enough for prototype
stuff. Probably wouldn't use this technique for say, stripline type work
or other dimension critical stuff. This process definitely involves a
lot of technique. One person's success is another's failure.

> And in the catagory of 'Best Pen to Withstand Etching of Copper Clad
> Circuit Board Using Ferric Chloride' the winner is....
>
> Manufacturer: Staedtler
> Model: Lumocolor 313 AV
> Ink color: Red
>
Noted and filed for future reference.

> Prior to etching, I did gently heat the
> boards with a heat gun to ensure that all the solvent was removed from
> the
> inks,
>
I would have thought letting the ink dry was a given....... Scouring the
boards with kitchen cleanser before plotting is also a must. After
scouring the boards and letting them dry, I would wipe each board off
with lacquer thinner and allow it to dry again. Then always handle the
board by the edges.

-Frank


Frank Richterkessing

FRANK.RICHTERKESSING@APPL.GE.COM