Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

To date component placement silk screens have been limited to black
using toner transfer. With colour laser printers you should be able to
toner transfer a vivid yellow.

Toner transfer has a couple of issues when nice readable paterns are
required.

1. It is difficult to get a complete image due to the differing
heights of the copper and the missing copper.

2. You need a very good paper that releases well and does not leave
any paper fibres or clay behind.

Direct printing to the PCB using an inkjet printer and then toner
dusting could provide a better screen print.

Using direct printing the process requires baking the pigment ink such
that it goes brown. If you direct print the solder mask a black toner
will not be of much value. Yellow would be the colour to use and the
printing industry may even have a white toner they use as a base coat
for their photographic processes on transparent material.(To be confirmed)

A printer other than a pigment ink Epson may also be successful. This
will depend on the binding characteristics of the toner once wetted
and then dried. Taking this thought one stage further, a water/alcohol
mix may be usable through a dye print head if the toner stays bound
to itself and the PCB once dry.

Although it would be better if the toner did not blow away once the
ink has dried, the method may not depend on any adhesion once dry.
Just keep the PCB horizontal and carefully get it up to temperature in
the next stage.

Once the PCB has been dusted the toner needs to be flowed. Ideally
this should be done using heat but no pressure. I don't know if it can
be done without pressure as the plastic particles in the toner need to
get together if the final result is to be strong.

I suspect having most of the ink liquid evaporated before applying the
higher melting heat would be best to stop boiling the ink as this will
move the toner. I would then evenly raise the temperature of the PCB
to prevent stress and then locally heat the toner to melting point. An
oven or heat gun are the tools to try here but over temperature will
likely burn the plastic and loose the vivid yellow/white that the
toner promises.

Those with direct printing ability may like to give it a try and
report back.


Warren