Jesse Willis wrote:
>
> ... What I did was swing by my local art store and pick up
> an Eberhard Faber DESiGN Art Marker, Broad Nib 311 Colorless
> Blender (only about 2 dollars). With this, you simply photocopy
> the circuit you wish, and then take lay the photocopy face down
> on the PCB. Run the marker over the -back- of the photocopy, and
> the image transfers to the copper. Might be more trouble than
> it is worth, though, unless you have a laser printer or copier
> and are only making small circuits. (But boy can you make them
> small!)
> I'll be sure to check up on that photo-etching thing, though.
> I wasn't aware that they sold anything like that. Thanks for
> the heads up!

There's more than a few threads on PCB photoetching in the archives, and
in the alt-BEAM archives as well. Here's some advice I offered:

http://groups.yahoo.com/group/beam/message/10105

If you look for messages with the same subject around this time you'll
get the full picture. Also, David Perry discusses the MG Chemical system
(same one I use) at:

http://groups.yahoo.com/group/beam/message/6772

Finally, a number of BEAMers have had success printing (laser printer)
onto plastic film (for overhead projectors) and then ironing the image
onto the circuit board. Jim Mullins also offered a suggestion for
improving the quality of a printed image at:

http://groups.yahoo.com/group/alt-beam/message/8403

> ... When etching, do NOT let the PCB settle on the bottom of the
> basin. Have it facing down, but floating at the top of the etchant.
> Otherwise, a vacuum seal will form and no etchant will get through.
> I learned this by experience. ...

"Conventional wisdom" says, invert he board, or the exposed copper will
get covered up with the ferric precipitate that forms during the
reaction. This effectively blocks the copper from the etchant and stops
the etching process.

However, many professionals recommend that the etched side should be
face up, so you can monitor the etching process. If you gently agitate
the solution, or push your circuit board around with a small plastic rod
(e.g., a swizzle stick), this will flush off the precipitate. MG
chemicals recommends using a foam brush to gently brush the surface
clean (that's the way I do it).

Finally, you get the best etching results if your ferric chloride
solution is warm. This speeds up the etching process and avoids
undercutting at the edges of traces. Ideal etching temperature is 50
degrees (C) ... 120 F, but don't go above 57 C (135 F) or your solution
will start to fume (hydrochloric acid -- very corrosive). I have a
shallow glass etching tray with a handles sticking out the end. To heat
the etchant, I suspend this tray in a container (Rubbermaid) of hot
water, using a couple of flat sticks under the handles. I marked the
water container with a permanent marker to indicate the height of the
water before the tray is suspended in it. This lets me fill the
container to exactly the right height, and not worry about spilling
water when I place the etching tray in it. I use water heated to 55 C --
it cools down slightly when the heavy glass tray is placed in it. This
speeds up the etching dramatically.

Remember, be safe, be consistant, and don't get discouraged if your
first few efforts fail. Use your notes and make minor changes. Start
small until you get the technique exactly right.

Bruce