I spent the last 2 months investigating the possibilities of directly
depositing toner on copper clad boards. Some of my tests can be seen
at <
http://www.pbase.com/mark10970/galleries>. While I can claim some
success, including clean 2 mil traces, results were inconsistent. My
final thoughts are:
It can be done. I spoke with someone who is actually using this
process in a commercial venture making boards for (mostly) hobbyists.
I'm not mentioning his name because I'm not sure he wants to be
identified, but he can chime in if he wants to. AFAIK he's the first
to attempt this method in a serious way. He uses a proprietary method
of externally charging the boards as they ride on a custom table
beneath (I think) the printer.
The built in HV Transfer supply has a feedback mechanism to
compensate for humidity caused leakage. Because of this, the voltage
is constantly changing and is impossible to control. I ended up using
an external supply and found that 2400 volts worked best for me. DO
NOT play with this stuff if you're not familiar with high voltage
safety requirements!!! It can kill you!! It might be possible to
modify the internal transfer supply directly, but it is fed from a
pwm signal from the processor, so I didn't bother. High voltage
supplies are pretty cheap - see eBay.
Get a service manual for your printer! <
http://www.smpcshop.com/> is
a good source - mine cost about $10 USD. It has all the schematics as
well as a lot of useful information.
I found that the transfer charge did not distribute evenly across the
rubber transfer roller so that larger boards had uneven density. The
boards are charged from the rear so that the pcb acts as a high
voltage capacitor, further complicating things. Thinner boards work
much better than thicker ones. Perhaps directly charging the board
with a conductive roller might be better.
Make sure the edges and corners of the board are smooth - I gently
filed the corners. This will protect the drum form mechanical damage.
I really stripped down the printer so that the board was only in the
"printer" for an inch or so. This made for a very straight path.
A special thanks to Robert <
listgroups08@... > for all the
technical data on many of these issues. His long, detailed
explanations were insightful and invaluable in this endeavor.
My main interest lies in using the boards for swarm robotics, not in
pcb production. I have decided to abandon this approach and go to
direct inkjet printing on boards as described by several people on
this group. It seems easier, more reproducible, and less dangerous!
Additionally, I am thinking that it should be possible to deposit
conductive ink on the boards directly. I read a short summary of some
work wherein they used a silver nitrate (?) solution to draw traces
then ran a solution of Ascorbic acid (vitamin C) through the printer
to convert it to silver. Lots of interesting things can be tried,
without the high voltage.
If anyone has any questions, I will be happy to answer them.
Mark